WO2005047367A1

WO2005047367A1 - Polyimide precursor, method for producing polyimide precursor, method for producing polyimide precursor solution in organic solvent, method for producing cast film, and method for producing polyimide film

Info

Publication number: WO2005047367A1
Application number: PCT/JP2004/006414
Authority: WO
Inventors: Masatoshi Hasegawa; Junichi Ishii
Original assignee: Sony Chemicals Corp.
Priority date: 2003-11-13
Filing date: 2004-05-06
Publication date: 2005-05-26

Abstract

A polyimide precursor, which has a recurring structure unit represented by the following unit structure formula (1a) or unit structure formula (1b); and a polyimide produced by the imidation of the polyimide precursor. The control of the percentage of the silylation in the process of the formation of the polyimide precursor makes the reaction system less prone to formation of a salt and results in the preparation of a uniform and viscous polyimide precursor solution in an organic solvent. The above polyimide can combine the two desirable characteristics of a low dielectric constant and a low linear thermal expansion coefficient.

Description

TECHNICAL FIELD The present invention relates to a polyimide precursor, a method for producing a polyimide precursor, a method for producing a polyimide precursor organic solvent solution, a method for producing a cast film, and a method for producing a polyimide film.

The present invention provides a practically useful polyimide film having a low dielectric constant, a low coefficient of linear thermal expansion, a high glass transition temperature, high transparency, sufficient toughness and film forming processability, and a solution film having excellent solution storage stability. The present invention relates to a method for producing a precursor. Background art

Generally, polyimide is easily obtained by equimolar reaction of an aromatic tetracarboxylic dianhydride such as pyromellitic anhydride with an aromatic diamine such as diaminodiphenyl ether in an aprotic polar solvent such as dimethylacetamide. The polyimide precursor having a high degree of polymerization is formed into a film or the like and cured by heating. Since such wholly aromatic polyimides have excellent properties such as excellent heat resistance, chemical resistance, radiation resistance, electrical insulation, and mechanical properties, they can be used as substrates for flexible printed wiring circuits, substrates for tape automation bonding, At present, it is widely used in various electronic devices such as protective films for semiconductor devices and interlayer insulating films for integrated circuits.

In recent years, in particular, increasing the operation speed of microprocessors and shortening the rise time of clock signals have become important issues in the information processing and communication fields. It is necessary to lower the rate.

In order to lower the dielectric constant of polyimide, it is effective to introduce a fluorine group into the polyimide structure (Macromolecules, 24, 5001 (1991)), High Perform.Polym., 15, 47 ( 2003), 2,2-bis (3,4-carboxyphene) ) The fluorinated polyimide film obtained from hexafluoropropanoic acid dianhydride and 2,2'-bis (trifluoromethyl) benzidine has a very low dielectric constant of 2.8, estimated from the average refractive index. Indicates a value.

Reducing T electrons by replacing aromatic units with alicyclic units, thereby hindering intramolecular conjugation and formation of charge-transfer complexes (Macromolecules, 32, 4933 (1999)) is also effective in lowering the dielectric constant. is there. As is known from Reactive & Functional Polymers, 30, 61 (1996), non-aromatic compounds obtained from 1,2,3,4-cyclobutanetetracarponic dianhydride and 4,4'-methylenebis (cyclohexylamine). The aromatic polyimide film has an extremely low dielectric constant of 2.6, which is estimated from the average refractive index.

On the other hand, when a polyimide film is laminated on a metal substrate such as copper as an interlayer insulating film, mismatches in the coefficients of linear thermal expansion generate residual stress, causing serious problems such as coiling, film peeling and cracking. It is known to cause. In order to avoid this problem, it is necessary to make the coefficient of linear thermal expansion of the polyimide film close to that of the metal substrate, that is, to reduce the thermal expansion of the polyimide film. Most of the currently known polyimides have a linear thermal expansion coefficient of 40-90 ppm / K, much higher than the copper substrate 18 ppra / K. Recently, as the density of electronic circuits has increased, the necessity for multilayer wiring boards has been increasing. However, residual stress in multilayer boards has significantly reduced device reliability.

In general, it is known that a polyimide must have a low thermal expansion coefficient if its main chain structure is linear, but its internal rotation is constrained and it is rigid (Pomer, 28, 2282 (1987) ). At present, polyimide formed from 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride and paraphenylenediamine is the best known low thermal expansion polyimide material. This polyimide film is known to exhibit a very low linear thermal expansion coefficient of 3 to 10 ppm / K, depending on the film thickness and fabrication conditions (Polyimides: Fundamentals and Applications, Marcel Dekker, New York). York, 1996, p 207)).

However, it has low dielectric constant and low thermal expansion coefficient at the same time, and has solder heat resistance It is not easy to obtain a polyimide that retains its properties in terms of molecular design. In order to achieve this, low dielectric constant polymer materials and inorganic materials other than polyimide are also being studied, but the required characteristics in terms of dielectric constant, coefficient of linear thermal expansion, heat resistance and toughness are not sufficiently satisfied. Is the current situation.

In recent years, with the trend of multi-layer wiring boards in electronic devices, attempts have been made to make the interlayer insulating film itself photosensitive, for example, to make through holes for wiring in the insulating layer. I have. In this case, since it is necessary to suppress light absorption by the polyimide insulating film itself, it is desirable that the polyimide film itself has high transparency in the entire range of ultraviolet and visible light.

In general, the introduction of a fluorine group into a polyimide structure weakens the intermolecular interaction and tends to hinder the spontaneous molecular orientation during imidization, which is a factor of low thermal expansion. Introduction of a fluorine group is disadvantageous in terms of cost. As described above, a typical example is obtained from 2,2-bis (3,4-carboxyphenyl) hexafluoropropanoic acid dianhydride and 2,2'-bis (trifluoromethyl) benzidine. Although the fluorinated polyimide film has a low dielectric constant as described above, it has a very high linear thermal expansion coefficient of 64 ppm / K and does not exhibit low thermal expansion characteristics (Hi Perform. Polym., 15 , 47 (2 003)). Further, transparency is insufficient.

In addition, the polyimide film obtained from pyromellitic dianhydride and 2,2'-bis (trifluoromethyl) benzidine has a very low linear thermal expansion coefficient due to the linear and rigid main chain. (Macromol ecules, 26, 419 (1993)) However, the film is colored and has a problem in transparency. This is because the use of aromatic monomers for both acid dianhydride and diamine caused intramolecular conjugation and charge transfer interaction (Polym. J., 29, 69 (1997)).

The introduction of alicyclic structural units into the polyimide skeleton reduces the number of electrons, is effective in lowering the dielectric constant and making the film transparent. However, the introduction of alicyclic structural units generally has a problem that the linearity and rigidity of the polyimide main chain skeleton are reduced, and the linear thermal expansion coefficient is increased.

For example, 4,4'-methylenebis (cyclohexylamino) represented by the following chemical formula (3) When an alicyclic diamine with high flexibility as in (1) is used, polymerization proceeds easily with various acid dianhydrides to produce a polyimide precursor with a high degree of polymerization, but the polyimide film obtained by the ring closure reaction Do not exhibit low thermal expansion properties.

For example, a polyimide film obtained from 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride and 4,4'-methylenebis (cyclohexylamine) has high transparency and low dielectric constant as described above. However, it has a very high linear thermal expansion coefficient of 7 O ppm / K and does not exhibit low thermal expansion characteristics.

Similarly, polyimide films obtained from pyromellitic dianhydride and 4,4'-methylenebis (cyclohexylamine) do not show low thermal expansion characteristics. This is due to the fact that in these polyimides, the in-plane orientation of the polymer chains is not promoted during thermal imidization due to the bent structure of the main chain skeleton.

Although polyimides using various aliphatic diamines have been reported so far, there have been no reports on semi-aliphatic polyimide films exhibiting a linear thermal expansion coefficient lower than 25 ppm / K. This means that the polyimide produced from alicyclic diamine is inevitably reduced in the linearity and rigidity of the main chain skeleton.

The only alicyclic diamine that maintains linearity and rigidity is trans-1,4-diaminocyclohexane.

However, in order to simultaneously satisfy the required characteristics, that is, low dielectric constant and low thermal expansion characteristics, if a polyimide precursor is to be polymerized from highly linear acid dianhydride and trans-1,4-diaminocyclohexane, the synthesis will be difficult. Face serious problems. That is, the aliphatic diamine differs greatly from the known aromatic diamine. In this case, due to its high basicity, salt formation occurs with the low molecular weight amic acid formed in the early stage of the polymerization reaction.

If a flexible alicyclic diamine such as 4,4'-methylenebis (cyclohexylamine) is used, the salt formed will dissolve slightly in the polymerization solvent and can be stirred for a long time at room temperature. The polymerization reaction can be easily advanced by a known method. In contrast, when trans-1,4-diaminocyclohexane is used, the formed salt is very strong and the solubility in the polymerization solvent is almost zero, and the polymerization reaction is often hindered.

In order to satisfy the above-mentioned required characteristics, an alicyclic acid dianhydride having a rigid structure is preferable, but the number of alicyclic acid dianhydrides known so far is limited.

From the viewpoint of molecular design described above, 1,2,3,4-cyclobutanetetracarboxylic dianhydride as an alicyclic dianhydride and trans 1,4-diaminocyclohexane as an alicyclic diamine It is expected that the all alicyclic polyimide represented by the unit structural formula (2a) described below achieves all the above-mentioned required characteristics. This system is also advantageous in terms of cost because it does not contain fluorine.

However, in this system, a serious problem is encountered at the stage of producing a polyimide precursor. That is, as described above, the formation of a strong salt completely prevents the polymerization reaction. This is the main reason that there have been no reports of this system so far.

In addition, the polyimide obtained from pyromellitic dianhydride and trans-1,4-diaminocyclohexane has a linear and rigid molecular structure in the main chain skeleton. There is expected. The use of inexpensive pyromellitic dianhydride is advantageous in terms of cost.

However, due to the above-mentioned problem of polymerization reactivity, a combination of pyromellitic dianhydride and trans-1,4-diaminocyclohexane and 1,2,3,4-cyclobutanetetracarboxylic dianhydride Trans-1, 4-Zia It is extremely difficult to synthesize a high molecular weight polyimide precursor from a combination of minocyclohexane. This is the main reason why there have been no reports of this system so far.

After salt formation at the early stage of the polymerization reaction, as described in JP-A-2002-16-11136 and High Perform. Polym., 13, S93 (2001), the polymerization It is known that a polyimide precursor having a high degree of polymerization can be obtained by heating at a temperature of, for example, 120 ° C. for a short time.

However, in the polymerization reaction system of pyromellitic dianhydride and trans 1,4-diaminocyclohexane, the salt formed is extremely strong and the salt does not dissolve at any temperature conditions, so it is difficult to apply this method. .

As a method for avoiding salt formation when using an aliphatic diamine, an interfacial polymerization method is disclosed in High Perform. Polym., 10, 11 (1998). In this method, tetracarboxylic dianhydride and alcohol are first reacted to form a diester of tetracarboxylic acid, which is then chlorinated and dissolved in an oil layer, and this is mixed with an aliphatic diamine dissolved in an aqueous alkaline solution at an oil / water interface. To obtain an alkyl ester of a polyamic acid.

However, in this polymerization method, the production process is complicated, and it is difficult to obtain a polyimide precursor having a high degree of polymerization, and also the variation in molecular weight among batches becomes large. Furthermore, chlorine is generated in the interfacial polymerization method, which is not preferable for use in electronic materials.

In addition, a rigid polyimide based on pyromellitic dianhydride and trans-1,4-diaminocyclohexane may cause serious problems in the film forming process. That is, after the polyimide precursor film is cast, cracking of the film occurs during the thermal imidization process. This is because, in a rigid system, the degree of entanglement between polymer chains is low, so that the toughness of the film is originally low.In addition, the reverse reaction of the polymerization reaction passes through around 200 ° C during the imidization of polyamic acid. When the molecular weight decreases, the film toughness further decreases, and the film cannot withstand the film shrinkage during the imidization reaction. A method for producing a polyimide precursor by reacting pyromellitic dianhydride with 1,4-diaminocyclohexane is known (Jourina lof Polymer Science: part A, Vol. 31, 235-2351, (1993)). However, in general, cis-form and trans-form are mixed in 1,4-diaminocyclohexane, and cis-form 1,4-diaminocyclohexane increases the thermal expansion coefficient of the polyimide film due to its bent structure.

As another method, a method of using silylated diamine for polyimide synthesis is known. However, in this method, it is necessary to silylate diamine with a halogen-containing silylating agent, and then to purify the silylated diamine. Also, the produced polyimide precursor has low dielectric constant and low thermal expansion characteristics. The two required characteristics were not satisfied at the same time.

In addition to the above-mentioned problems in controlling the characteristics of the polyimide film and manufacturing the polyimide precursor, there are still some serious problems in the film formation process.

One of the problems is the storage stability of the polyimide precursor solution. A common polyimide precursor synthesized from an acid dianhydride and diamine by a known method is polyamic acid, but it is known that the weight average molecular weight decreases due to a reverse reaction of a polymerization reaction during storage of the solution. ing. The change with time in the solution viscosity due to this is a serious problem in controlling the film thickness during the film forming process by spin coating or the like.

In order to stabilize the viscosity of the polyamic acid solution, a method of storing the solution at a low temperature or heating the solution to intentionally lower the molecular weight to suppress the subsequent change in the solution viscosity has been adopted. In particular, the latter measure for avoiding the change in viscosity may make the polyimide film brittle.

If a linear and rigid polyimide system is selected for low thermal expansion, the main chain skeleton of the precursor is also relatively rigid, and non-uniformity such as gelation and liquid crystal formation during storage of the precursor solution will occur. It often occurs, and it may be difficult to produce good quality polyimide films. In such a case, the addition of salts such as lithium chloride increases the storage stability, but is preferable for electronic materials. And the use of salts should be avoided.

In addition, in such a rigid system, a more serious problem occurs in most cases in the film forming process. That is, after the polyimide precursor film is cast, cracking of the film occurs during the thermal imidization process. This is because in a rigid system, the degree of entanglement between polymer chains is low, so that the film originally has poor toughness.In addition, when the reverse reaction of the polymerization reaction passes around 200 ° C during the thermal imidization of polyamic acid, The film toughness further decreases with a decrease in molecular weight, and the film cannot withstand film shrinkage during the imidization reaction.

Also, a method for producing a polyimide precursor by reacting 1,2,3,4-cyclobutanecarboxylic anhydride with 1,4-cyclohexanediamine is known. However, in general, cis-form and trans-form are mixed in 1,4-cyclohexanediamine, and the cis-form 1,4-cyclohexanediamine increases the thermal expansion coefficient of the polyimide film due to its bent structure.

Non-patent documents among the related technical documents of the present invention are shown below.

"Macromolecules J, (USA), American Chemical Society, 1991, 24, ρ 5001

"High Performance Polymers", (UK), Institute of Physics; 2003, Volume 15, p47

"Macromolecules", (USA), American Chemical Society, 1989, No. 32, p. 4933

"Reactive & Functional Polymers", (Netherlands), Elsevier 'Science, 1996, Volume 30, p. 61

"Polymer", (Netherlands), Elsevier's Science (E1 sevier Science), 198 7, volume 28, p 22 8 2

"Macromolecules", (USA), American Chemical Society, 1996, 29, p 7897

"High Performance Polymers", (UK), Institute of Physics, 2001, Vol. 13, Volume S93

"High Performance Polymers", (UK), Institute of Physics, 1999, 1998, vol. 10, p. 11

Polyimides: Fundamentals and Applications, (USA), Marcel Dekker Inc., 1996, ρ207

"Macromolecules", (USA), American Chemical Society ^ 1993, 26, p. 419

"Polymer Journal", The Society of Polymer Science, Japan, 1999, Vol. 29, p. 69

Among the related technical documents of the present invention, the patent documents are Japanese Patent Application Laid-Open No. 2002-0216136, Japanese Patent Application Laid-Open No. 2002-3237666, and Japanese Patent Application

Japanese Patent No. 27768, Japanese Patent Application Laid-Open No. 64-63070 and Japanese Patent Application Laid-Open No. 2-294

No. 330 publication.

The present invention provides a practically useful polyimide film having low dielectric constant, low coefficient of linear thermal expansion, high glass transition temperature, high transparency, sufficient toughness and film forming processability, and a solution storage stability that is excellent. It is intended to provide a method for producing a precursor. Disclosure of the invention

In view of the above problems, the present inventors have determined that using the selected silylating agent Trans, 1,4-diaminocyclohexane silylated in a wide range of silylation rates, and equimolar amounts of 1,2,3,4-cyclobutanetetracarboxylic dianhydride or equimolar pyromellitic dianhydride By conducting the polymerization reaction in a limited organic solvent, we succeeded in obtaining an all-alicyclic polyimide precursor solution having excellent storage stability and a high degree of polymerization, and completed the first and second inventions. I got it.

Furthermore, they found that the all-alicyclic polyimide film produced by subjecting the cast film to an imidization reaction under limited conditions can achieve all of the above-mentioned required characteristics, and completed the first and second inventions. Was.

Figure 1 is a diagram showing an example of the steric structure of 1,4-diaminocyclohexane, which is a diamine monomer. The polyimide film represented by the unit structural formulas (2a) and (2b) described below exhibits low thermal expansion characteristics. In order to achieve this, both amino groups of 1,4-diaminocyclohexane must be in an equatorial configuration, that is, the steric structure of 1,4-diaminocyclohexane is trans as shown in Figure 1. .

The trans configuration at the monomer stage is retained in the polyimide precursor and polyimide skeleton. The use of cis 1,4-diaminocyclohexane during the polymerization may cause a sharp increase in the linear thermal expansion coefficient of the polyimide film due to its bent structure.

As disclosed in JP-B-51-48198, 1,4-diaminocyclohexane obtained by hydrogenation of parafudinylenediamine is usually obtained as a cis / trans mixture, but this is used as it is. When subjected to polymerization, the polymerization proceeds without any problem under known reaction conditions.

In addition, when the diamine component is copolymerized not only with trans 1,4-diaminocyclohexane alone but also with another flexible aliphatic diamine, the polymerization proceeds without any problem under known reaction conditions. However, the use of the above mixture instead of trans 1,4-diaminocyclohexane alone may cause a rapid increase in the linear thermal expansion coefficient of the obtained polyimide film and a decrease in the glass temperature. Should be avoided.

Figure 2 shows the 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride monomer An example of the configuration of the acid dianhydride is shown. 1,2,3,4-Cyclobutanetetracarboxylic dianhydride is particularly preferable to have the anti configuration shown in FIG. The use of syn-type 1,2,3,4-cyclobutanetetracarboxylic dianhydride may lead to an increase in linear thermal expansion coefficient due to its bent structure.

A first invention made based on such findings is to produce an intermediate product by reacting trans 1,4-diaminocyclohexane with a silylating agent, and then forming the intermediate product with 1, 2, 3 A method for producing a polyimide precursor, which comprises reacting 1,4-cyclobutanetetracarboxylic dianhydride to produce an all-alicyclic polyimide precursor having a repeating structural unit represented by the following structural formula (la): .

-Structural formula (1a)

(In the above-mentioned unit structural formula (la), R is H or a silyl group, and in the polyimide precursor, one or both of the substituents R in one unit structural formula are a silyl group. Has at least one unit structure)

The first invention is a method for producing a polyimide precursor, wherein a non-halogenated silylating agent having no octogen atom in its chemical structure is used as the silylating agent.

The first invention is directed to a polyimide precursor using either or both of Ν, Ο-bis (trimethylsilyl) trifluoroacetamide and Ν, Ο-bis (trimethylsilyl) acetoamide as the non-halogenated silylating agent. Manufacturing method.

In the first invention, R in the unit structural formula (la) is H or Si (CH ₃ ) ₃ , and the trans 1,4-diaminocyclohexane and the silylating agent are present at a predetermined ratio. A method for producing a polyimide precursor to be reacted, wherein, among Rs contained in the entire chemical structure, the number of Rs composed of _three Si (CH ₃ ) groups is the number of Rs composed of A and H Is B, the silylation agent is reacted with the trans 1,4-diaminocyclohexane at a rate such that the silylation rate represented by the following formula (1) becomes 0.4 or more and 0.9 or less. This is a method for producing a polyimide precursor to be produced.

Silylation rate = AZ (A + B) …… Formula (1)

In the first invention, trans 1,4-diaminocyclohexane and a silylating agent are reacted in a polymerization solvent to produce an intermediate product, and then 1,2,3,4-cyclobutane is added to the polymerization solvent. A tetracarboxylic dianhydride is added, the intermediate product is reacted with the 1,2,3,4-cyclobutanetetracarboxylic dianhydride, and a polyimide precursor is dispersed or dissolved in the polymerization solvent. This is a method for producing a polyimide precursor organic solvent solution for producing the obtained polyimide precursor organic solvent solution. The first invention is a method for producing a polyimide film, comprising applying a polyimide precursor organic solvent solution to an object to be coated, forming a cast film, and then imidizing the polyimide precursor in the cast film. The solvent has an affinity for the trans 1,4-diaminocyclohexane, the silylating agent, the 1,2,3,4-cyclobutanetetracarboxylic dianhydride, and the intermediate product. A polyimide film that contains a high-boiling-point solvent, has a high affinity for the polymerization solvent, and has a lower boiling point than the polymerization solvent, is brought into contact with the cast film, and after the cast film is washed, the imidization is performed. Is a manufacturing method.

The first invention is a method for producing a polyimide film using hexamethylphosphoramide as the high boiling point solvent and using alcohol as the cleaning solution. The first invention is a completely alicyclic compound wherein the repeating structural unit is represented by the unit structural formula (1a), and the substituent R in the unit structural formula (la) is H or Si (CH ₃ ) ₃ group. A polyimide precursor, having at least one unit structure in which one or both of the substituents R in one unit structural formula are Si (CH ₃ ) ₃ groups, and having an intrinsic viscosity of 1 0 d 1 or more.

The first invention is a polyimide precursor, wherein the stereostructure of each 1,4-cyclohexane residue in the unit structural formula (la) is a trans configuration. The first invention, the total chemical structure, the total number of Si (CH ₃₎ consists of ₃ groups substituents R A, When B the total number of substituents R consisting of hydrogen, table by the following mathematical formula (1) A polyimide precursor having a silylation rate of 0.4 or more and 0.9 or less.

Silylation rate = AZ (A + B) …… Formula (1)

In the first invention, the repeating structural unit is represented by the following structural formula (2a), and the steric structure of each 1,4-cyclohexane residue in the following structural formula (2a) is in a trans configuration. A polyimide characterized by the following.

-Unit structural formula (2a)

The first invention is a polyimide film containing the above polyimide as a main component. The second invention is to produce an intermediate product by reacting trans 1,4-diaminocyclohexane with a silylating agent, and then reacting the intermediate product with pyromellitic dianhydride, and repeating the process. This is a method for producing a polyimide precursor in which a structural unit is represented by the following unit structural formula (lb).

-Unit structural formula (lb)

(In the unit structural formula (lb), R is H or a silyl group, and in the polyimide precursor, one or both of the substituents R in one unit structural formula are a silyl group. Has at least one unit structure)

The second invention is a method for producing a polyimide precursor, wherein a non-perogenating silylating agent having no halogen atom in its chemical structure is used as the silylating agent. The second invention is directed to a polyimide precursor using one or both of Ν, Ο-bis (trimethylsilyl) trifluoroacetamide and Ν, Ο-bis (trimethylsilyl) acetoamide as the non-halogenated silylating agent. Manufacturing method.

A second invention is a method for producing a polyimide precursor in which the trans 1,4-diaminocyclohexane and the silylating agent are reacted at a predetermined ratio, wherein R is contained in the entire chemical structure. When the number of R consisting of a silyl group is Α, and the number of R consisting of Β is Β, the silylation rate of the polyimide precursor represented by the following formula (1) is 0.9 or more and 1.0 or less. Wherein the trans 1,4-diaminocyclohexane and the silylating agent are reacted to produce a polyimide precursor.

Silylation rate = ΑΖ (Α + Β) ...... Formula (1)

The second invention is a method for producing a polyimide precursor, comprising reacting the trans 1,4-diaminocyclohexane with the silylating agent at a predetermined ratio, wherein the trans 1,4-diaminocyclohexane before the reaction is prepared. Assuming that the number of all amino groups of hexane is c and the number of all silyl groups of the intermediate product is d, the silylation rate of the intermediate product represented by the following formula (2) is 0.9 or more 1 A method for producing a polyimide precursor, comprising reacting the trans 1,4-diaminocyclohexane with the silylating agent at a ratio that falls within a range of 0.0 or less.

Silylation rate = d / c… formula (2)

In the second invention, trans 1,4-diaminocyclohexane is reacted with a silylating agent in a polymerization solvent to produce an intermediate product, and then pyromellitic dianhydride is added to the polymerization solvent. And reacting the intermediate product with the pyromellitic dianhydride to produce a solution of a polyimide precursor in which the polyimide precursor is dispersed or dissolved in the polymerization solvent. Is a manufacturing method.

In a second aspect, the polyimide precursor organic solvent solution is applied to an object to be coated, a cast film is formed, and then the polyimide precursor in the cast film is removed. A method for producing a polyimide film to be imidized, wherein the polymerization solvent includes the trans 1,4-diaminocyclohexane, the silylating agent, the pyromellitic dianhydride, and the intermediate product. A high-boiling-point solvent having a high affinity for the polymerization solvent, a cleaning solution having a high affinity for the polymerization solvent and a boiling point lower than the polymerization solvent is brought into contact with the cast film, and after washing the cast film, the imide This is a method for producing a polyimide film to be converted.

A second invention is a method for producing a polyimide film using hexamethylphosphoramide as the high boiling point solvent and using alcohol as the cleaning solution. A second invention is a completely alicyclic polyimide wherein the repeating structural unit is represented by the above-mentioned unit structural formula (lb), and the substituent R in the above-mentioned unit structural formula (lb) is H or Si (CH ₃ ) _3. A precursor, having at least one unit structure in which one or both of the substituents R in one unit structural formula are Si (CH ₃ ) ₃ groups, and having an intrinsic viscosity of 2. It is a polyimide precursor of 0 dL / g or more.

A second invention is a polyimide precursor, wherein the stereostructure of each 1,4-cyclohexane residue in the above-mentioned unit structural formula (lb) is in a trans configuration.

The second invention is, in all the chemical structure, the total number of Si (CH ₃₎ consists of ₃ groups substituents R A, When B the total number of substituents R consisting of hydrogen, table by the following mathematical formula (1) The polyimide precursor has a silylation rate of 0 to 0.9 inclusive.

Silylation rate = AZ (A + B) …… Formula (1)

In the second invention, the repeating structural unit is represented by the following structural formula (2b), and the steric structure of each 1,4-cyclohexane residue in the following structural formula (2b) is in a trans configuration. It is a polyimide characterized by having. Unit structural formula (2b)

A second invention is a polyimide film containing the above polyimide as a main component. In the first and second inventions, the silylation rate of the polyimide precursor is not determined from the number of Si (CH ₃ ) 3 groups and hydrogen contained only in one structural unit, It is determined from the number of substituents R consisting of _three Si (CH ₃ ) groups contained in the whole body molecule and the number of substituents R consisting of hydrogen. Brief Description of Drawings

FIG. 1 is a diagram showing a steric structure of 1,4-diaminocyclohexane.

FIG. 2 is a diagram showing the molecular structure of 4,4′-methylenebis (cyclohexylamine).

FIG. 3 is a view showing an infrared absorption spectrum of the polyimide precursor film of the first invention.

FIG. 4 is a diagram showing an infrared absorption spectrum of the polyimide film of the first invention.

FIG. 5 is a diagram showing an infrared absorption spectrum of the polyimide precursor film of the second invention.

FIG. 6 is a diagram showing an infrared absorption spectrum of the polyimide film of the second invention. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail.

As described above, the polymerization system of 1,2,3,4-cyclobutanetetracarboxylic dianhydride and trans 1,4-diaminocyclohexane, and the polymerization of pyromellitic dianhydride and trans 1,4-diaminocyclo Strong in the early stage of the reaction in the polymerization system with xane A salt is formed, and it is difficult to promote polymerization under any solvent and temperature conditions. Thus, the use of a silylation method to avoid salt formation has led to a solution to the problem of producing polyimide precursors.

To explain the first and second inventions, first, trans 1,4-diaminocycloaliphatic diamine, which is a hexane, is dissolved in a limited polymerization solvent, and an appropriate amount of N, 0-bis (trimethylsilyl) is added thereto. Trifluoroacetamide or N, 0-bis (trimethylsilyl) acetamide is added dropwise to carry out silylation to produce an intermediate product consisting of silylated alicyclic diamine.

Then, without isolating the silylated alicyclic diamine, the solution is equimolar 1,2,3,4-cyclobutanetetracarboxylic dianhydride powder or equimolar pyromellitic dianhydride. Add the tetracarboxylic dianhydride powder slowly and stir at room temperature for 1-2 hours to obtain a viscous, clear and homogeneous solution.

The trans 1,4-diaminocyclohexane used in the first and second aspects of the present invention completely completes coloring components by repeating recrystallization with n-hexane before silylation or reaction with carboxylic dianhydride. It is preferable to use after removing. Otherwise, coloring of the obtained polyimide film may be caused.

A commonly known silylation method is disclosed in Proceedings of the 49th Symposium on Polymers, p 191 (2000). In this silylation method, a representative silylation agent is used. The presence of a hydrogen chloride acceptor such as triethylamine using conventional trimethylsilyl chloride, silylating the aliphatic diamine, isolating and purifying it by distillation, and subjecting it to the polymerization reaction with acid dianhydride Things.

Here, hydrogen chloride generated by the reaction between trimethylsilyl chloride and aliphatic diamine is partially added to not only triethylamine as an acceptor but also aliphatic diamine as a polymerization reaction component to form a hydrochloride. Since the hydrochloride of aliphatic diamine not only loses polymerization reactivity but also precipitates due to a decrease in solubility, it is necessary to carry out polymerization by adding an acid dianhydride to the reaction solution without isolating the silylated diamine. Is because the molar balance is broken Impossible.

This is why the isolation and purification steps of silylated diamines are generally required. In addition, silylated diamine easily reacts with a small amount of moisture in the air and is decomposed, so that equipment such as a glove box is required in some cases, and the isolation / production process becomes complicated.

However, the step of producing the polyimide precursor in the first and second inventions does not include such a step of isolating and purifying the silylated diamine. When a non-halogenated silylating agent having no halogen atom in its chemical structure is used as a silylating agent, hydrogen chloride can be used as a by-product when silylating trans 1,4-diaminocyclohexane, which is an alicyclic diamine. Does not generate hydrogen halide.

For example, when one or both of N, 0-bis (trimethylsilyl) trifluoroacetamide and Ν, Ο-bis (trimethylsilyl) acetamide are used as a non-halogenated silylating agent, the alicyclic diamine is silylated. After silylation in reaction with the agent, only acetoamides that are harmless to the polymerization reaction are generated as by-products, and do not generate hydrogen chloride as a by-product. This is because the molar balance is maintained even when the substance is added. It should be noted that acetoamides as by-products have no problem at all since the polyimide precursor is volatilized with a solvent during a thermal imidization reaction after the production of the polyimide precursor.

In addition, since hydrogen chloride is not generated when trans 1,4-diaminocyclohexane, which is an alicyclic diamine, is silylated, a neutralizing agent such as a tertiary amine is not used in the present invention. Therefore, no salts remain in the formed polyimide film.

First, the first invention will be described. The key to the success of the polymerization reaction in the all-alicyclic polyimide precursor represented by the unit structural formula (1a) is control of the silylation rate X. The silylation rate X of the alicyclic diamine and the silylation rate X of the polyimide precursor can be controlled by adjusting the amount of the silylating agent added. When an alicyclic diamine is reacted with a silylating agent, the hydrogen of the amino group of the alicyclic diamine is replaced by a silyl group (S i (CH ₃ ) ₃ group). Assuming that the number of amino groups substituted with a silyl group is a and the number of amino groups not substituted with a silyl group is b, among the amino groups of all intermediate products formed in the polymerization solvent, The silylation rate X (average silylation rate of all intermediate products) is represented by the following formula (2).

x = a / (a + b) ... Formula (2)

Since one alicyclic diamine reacts with one carboxylic dianhydride to form one structural unit, the carboxylic acid dianhydride in an amount equal to or more than the molar amount of the intermediate product is added to the polymerization solvent. However, when all the intermediate products are reacted with carboxylic dianhydride, the silylation rate X of the polyimide precursor generated in the polymerization solvent is equal to the silylation rate X of the intermediate product.

The silylation rate of the intermediate product can be adjusted by the amounts of the alicyclic diamine and the silylating agent added to the polymerization solvent. Since alicyclic diamines have two amino groups in the chemical structure, if the silylating agent has S silyl groups per mole, then silylation using c moles of alicyclic diamines In order to obtain an intermediate product having a ratio X and a polyimide precursor, 2 c · XZ s mol of the silylating agent may be reacted with the alicyclic diamine.

For example, a compound having two silyl groups in one molecule such as N, 0-bis (trimethylsilyl) trifluoroacetamide ゃ N, 0_bis (trimethylsilyl) acetamide is used as a silylating agent. In order to make the silylation rate of the polyimide precursor from 0.4 to 0.9, the silylating agent may be added in an amount of from 0.4 to 0.9 mol.

The silylation rate X of the intermediate product is preferably in the range of 0.4 or more and 0.9 or less, and when the silylation rate is in this range, the intermediate product is reacted with the carboxylic dianhydride. After this, a clear, viscous and homogeneous polymerization solution is obtained.

If X is less than 0.4, salt formation occurs during polymerization with carboxylic dianhydride, and the polymerization does not proceed. When X exceeds 0.9, a uniform polymerization solution cannot be obtained, It is difficult to obtain a polyimide precursor having a high degree of polymerization. This is because, when the silylation rate is very high, the solubility of the polyimide precursor in the polymerization solvent is extremely reduced due to hydrogen bonding between the polyimide precursor chains, and the polyimide precursor becomes one before the polymerization reaction sufficiently proceeds. This is due to the partial precipitation.

When X is in the range of 0.4 or more and 0.9 or less, the polyimide precursor has a moderately strong propyloxy group, which strongly solvates with the polymerization solvent and results in an increase in the solubility of the produced polymer. Has become. Until now, silylation was generally thought to dramatically increase the solubility of the polyimide precursor.However, in the first invention, the silylation rate of the polyimide precursor was rather controlled to 0.4 or more and 0.9 or less. Control led to the solution of the polymerization problem.

In the first invention and the second invention described later, selection of a polymerization solvent is extremely important. Hexamethylphosphoramide alone, or a mixture of hexamethylphosphoramide and N, N-dimethylacetoamide, or a mixture of hexamethylphosphoramide and N-methyl-2-pyrrolidone A mixed solvent of is preferred. If the polymerization solvent is not appropriate, alicyclic diamine and tetracarboxylic dianhydride, intermediate product and tetracarboxylic dianhydride, alicyclic diamine and pyromellitic dianhydride, intermediate product and pyromellitic acid Polymerization may not proceed at all due to salt formation during polymerization with the anhydride, or even if a partial polymerization reaction occurs, a uniform polymerization solution may not be obtained due to precipitation, gelation, etc., and film formation may not be possible. It is not necessary to use any polymer dissolution promoter often added during the polymerization of polyamide or the like, that is, metal salts such as lithium bromide and lithium chloride in the polymerization systems according to the first and second inventions. These metal salts should not be used, since traces of metal ions remaining in the polyimide film significantly reduce the reliability of electronic devices.

In the first invention, although the polymerization does not proceed as described above when the silylation rate X represented by the above formula (1) is out of the range of 0.4 or more and 0.9 or less, the dissolution of the above salts There is almost no accelerating effect, and the addition of salts cannot improve the polymerization reactivity. Antioxidants, fillers, silane coupling agents, photosensitizers, photopolymerization initiators, sensitizers, etc. are added as necessary to the polyimide films obtained in the first invention and the second invention described below. Things can be mixed.

The polyimide precursor solution applied to the substrate to be applied is dried in a forced circulation hot air dryer or vacuum dryer at a temperature of 40 ° C or more and 120 ° C or less. It becomes.

In this case, if the temperature is lower than 40 ° C, not only long time is required for drying, but also a large amount of solvent remains in the film, and bubbles are easily generated due to rapid evaporation of the solvent at the time of imidization, so that a good polyimide film is obtained. Not preferred. On the other hand, drying at a temperature higher than 120 ° C tends to make the cast film brittle, which is not preferable for obtaining a tough polyimide film.

In a known method, a polyimide film is produced by heating a cast film on a substrate to a temperature of 200 ° C or more and 400 ° C or less to imidize a polyimide precursor in the cast film. When a polyimide precursor cast film represented by the above-mentioned unit structural formula (la) is thermally imidized according to a known method, the film is severely ruptured and blackened regardless of whether it is in a nitrogen atmosphere or in a vacuum, and the polyimide It becomes difficult to manufacture the membrane. This is because hexamethylphosphoramide used as a solvent is very difficult to volatilize, so it tends to stay in the film during imidization, causing thermal decomposition of hexamethylphosphoramide itself and some reaction with the polyimide precursor. It is thought that it is.

By dipping the cast film of the polyimide precursor of the first and second inventions in water, it is possible to almost completely extract and remove water-soluble residual solvents such as hexamethylphosphoramide. However, immersion in water causes a decrease in the adhesive strength between the substrate and the film, causing not only peeling but also severe contraction of the film. This large film shrinkage causes the polyimide film to crack during imidization, making it difficult to form the polyimide film on the substrate.

As a result of intensive research, the cast film was immersed in a cleaning solution composed of alcohols such as methanol, and the cleaning solution was brought into contact with the cast film to perform cleaning. It was found that shrinkage and peeling from the substrate were suppressed, and at the same time, it was possible to almost completely extract and remove residual solvents such as hexamethylphosphoramide, which led to the solution of problems during film formation.

The alcohol constituting the cleaning solution is not limited to methanol, but may be ethanol, butanol, propanol, or the like. These alcohols may be used alone or as a mixture of two or more.

The polyimide precursor film (cast film) formed on the substrate in this manner is heated at a temperature of 200 ° C or more and 400 ° C or less, preferably 300 ° C or more and 350 ° C under reduced pressure (a condition where the pressure is lower than the atmospheric pressure). A tough polyimide film can be obtained by heat treatment at a temperature of less than or equal to ° C.

If the temperature at which the cast film is heated is lower than 300 ° C, imidization may not be completed, and if it is higher than 350 ° C, coloring of the polyimide film occurs. The step of imidizing the polyimide precursor in the cast film is not limited to heat treatment, and the imidation reaction involves reacting the polyimide precursor film with a dehydrating reagent such as a mixture of acetic anhydride and a tertiary amine. It can also be done chemically.

Since the polyimide according to the first invention has a wholly alicyclic structure, it has poor long-term thermal stability as compared with a wholly aromatic polyimide containing no alicyclic structure, but has a glass transition temperature and a thermal decomposition temperature in nitrogen. Both are 400 ° C or higher, and the short-term heat resistance such as solder heat resistance is sufficiently high, and there is no problem in application to the above-mentioned industrial fields.

In addition, the polyimide of the first invention represented by the unit structural formula (2a) not only has a low dielectric constant at 1 MHz of 2.7 or less, but also has a low linear thermal expansion coefficient of 25 ppm or less. It also has high transparency and toughness.

Next, the second invention will be described. In order to obtain a high polymerization degree semi-aromatic polyimide precursor represented by the unit structural formula (lb) described later, the silylation ratio X is adjusted to 0.9 or more and 1.0 or less by adjusting the amount of the silylating agent added. It is preferable to carry out the polymerization within the range of. If X is less than 0.9, salt formation occurs during polymerization and the reaction solution is not uniform. The thus obtained polyimide precursor solution is dropped into an acidic aqueous solution, alcohol, or the like, or, after casting, the polyimide precursor film is immersed in these, so that silyl groups are easily eliminated. At this time, it is possible to obtain a polyimide precursor having a silylation ratio X of 0 to 1.0 by adjusting the acid or alcohol concentration and the reaction time.

When polymerizing the polyimide precursor of the unit structural formula (lb), it is important to set the monomer concentration in addition to the points to be considered such as the polymerization solvent and additives. The monomer concentration for obtaining a uniform and high polymerization degree polyimide precursor solution is preferably from 10 to 13% by weight. When the polymerization is carried out at a monomer concentration of 10% by weight or less, the intrinsic viscosity of the obtained polyimide precursor is much lower than the intrinsic viscosity of 2.0 OdL / g, and the finally obtained polyimide film becomes extremely brittle and cracks in the film. Etc. may occur. If the content is 13% by weight or more, the polyimide precursor solution tends to gel and the storage stability may be reduced.

When the polymerization is carried out in the above monomer concentration range, a polyimide precursor solution having a uniform and high polymerization degree can be obtained.However, after 24 to 48 hours at room temperature after the polymerization, some gel components are generated. It becomes uneven and hinders the production of high quality polyimide film. This is due to strong intermolecular hydrogen bonding between amide groups based on the rigid structure of this polyimide precursor. To avoid this, after the polymerization is completed, the storage stability can be significantly improved by subjecting this solution to heat treatment at 100 ° C. for 10 minutes or more and 20 minutes or less.

The polyimide precursor solution applied on the substrate is dried in a forced circulation hot air dryer or a vacuum dryer at a temperature in the range of 50 ° C to 100 ° C. In this case, if the temperature is lower than 50 ° C, not only long time is required for drying, but also the cast film (polyimide precursor film) becomes cloudy due to the formation of liquid crystal, and a large amount of solvent remains in the film. Bubbles are easily generated by evaporation, which is not preferable for obtaining a high quality polyimide film. Further, if the drying is performed at a temperature exceeding 100 ° C., the cast film (polyimide precursor film) is fragile and tends to crack or peel off, which is not preferable for obtaining a high quality polyimide film. In a known method, a polyimide film is produced by directly heating a cast film on a substrate at a temperature of 200 ° C. or more and 400 ° C. or less, but a polyimide precursor represented by the unit structural formula (lb) according to the second invention When the cast film is thermally imidized according to a known method, the film is severely ruptured and blackened regardless of whether it is in a nitrogen atmosphere or in a vacuum, and it becomes difficult to produce a polyimide film. This is because hexamethylphosphoramide used as a solvent is very difficult to volatilize, so it is likely to stay in the membrane during imidization, causing thermal decomposition of hexamethylphosphoramide itself and the decomposition of polyimide precursor. It is considered that some reaction was caused. As described above, also in the second invention, by immersing the cast film in alcohols, shrinkage of the film and peeling from the substrate can be suppressed, and the residual solvent can be removed. The same alcohol as used in the first invention can be used for washing.

By subjecting the polyimide precursor film thus formed on the substrate to a heat treatment under reduced pressure at a temperature of 200 ° C to 400 ° C, preferably 250 ° C to 350 ° C, a tough polyimide film is obtained. can get. If the temperature is lower than 200 ° C, imidization may not be completed. If the temperature is higher than 350 ° C, the polyimide film may be colored. The imidization reaction can also be performed chemically by reacting the film of the polyimide precursor with a dehydrating reagent such as a mixture of acetic anhydride and a tertiary amine.

Since the polyimide according to the second invention has an alicyclic structure, it has poor long-term thermal stability as compared with a wholly aromatic polyimide containing no alicyclic structure, but has a glass transition temperature, nitrogen and air. Both thermal decomposition temperatures are 400 ° C or higher, and short-term heat resistance such as solder heat resistance is sufficiently high, and there is no problem in application to the above-mentioned industrial fields.

In addition, the polyimide of the second invention represented by the above unit structural formula (2b) has not only a low dielectric constant of 3.0 MHz or less at a frequency of 1 MHz but also a linear thermal expansion coefficient of 20 ppm / K or less. In addition, it is characterized by having high transparency and sufficient toughness for use as an insulating film in electronic substrates.

【Example】 Hereinafter, the first and second inventions will be specifically described, but the invention is not limited thereto. Each embodiment of the first invention is distinguished by adding a suffix a, and each embodiment of the second invention is distinguished by adding a suffix b.

[First invention]

Put recrystallized and purified trans-1,4-diaminocyclohexane 5.710 g (0.05 mol) in a well-dried sealed reaction vessel with a stirrer, and fully dehydrate hexane methylphosphoramide and Ν, Ν- After dissolving in 150 mL of a polymerization solvent consisting of a mixed solvent of dimethylacetamide (3: 1 by volume), N, 0_bis (trimethylsilyl) trifluoroacetamide with a syringe is used as a silylating agent. 025 mol) was slowly added dropwise and stirred at room temperature for 1 hour to perform silylation (silylation rate X = 0.5).

To this solution, 9,806 g (0.05 mol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride powder was gradually added, followed by stirring at room temperature for 24 hours. The resulting polyimide precursor solution did not precipitate or gel at all even when left at room temperature for 2 weeks, and showed extremely high solution storage stability with almost no change in viscosity. The intrinsic viscosity measured at 30 ° C in the same solvent as in the polymerization was as high as 4.3 dL / g, indicating that an extremely high-polymer polyimide precursor was obtained.

The polyimide precursor solution (cast film) obtained by applying the polyimide precursor solution to a glass substrate to be coated and drying at 60 ° C. for 2 to 4 hours is added to methanol, which is a washing solution, for 4 hours. Dipping for ~ 24 hours completely removed the residual solvent.

This was heated on a substrate under reduced pressure at 340 ° C for 3 hours to obtain an imidized product, thereby obtaining a transparent and tough all-alicyclic polyimide film having a thickness of 10 m.

The physical properties of the film are as follows: Dielectric constant = 1. IX Dielectric constant estimated from the square of the average refractive index 2.65 (corresponding to 1MHz), Linear thermal expansion coefficient 25ppm / K (Average value between 100 ° C and 200 ° C) ), And glass transition temperature 423 ° C, cutoff wavelength 240nm, 5% weight loss temperature in nitrogen atmosphere (heating rate 10 ° C / min) 437, 398 ° C in air. All the characteristics could be satisfied. The synthesized polyimide precursor film and 3 and 4 show the infrared absorption spectra of the polyimide film and the polyimide film, respectively. The peak tables of the polyimide precursor film and the polyimide film are shown in Tables 1a and 2a below.

The vertical axes in FIGS. 3 and 4 indicate transmittance (%), respectively, and the horizontal axes indicate wave numbers (cm ¹ ). Table 1a: Peak table of the polyimide precursor film formed in Example 1a

No. Wave number (transmittance%) No. Wave number (transmittance%) No. Wave number (transmittance%)

15 3308.22 3ί „Θ> 3990,24 ·: 44.9> 2941,7

2864, 55 <48-4 5 * 2 et 08 * ΘΘί: c * ί95Θ.2ί (75, 7

17 pla 88 ku 21,9) j 1637 = 71 <15,3 9 1548.98-

1452: 53 <53,8) lis 1292. 2 <41 »5 '125 38.1)

13; 1ί1ί »18 et al. I = 2> i 989, 57 <63, 1> 982.7 '::

16 6Θ5.7S <54.i> Table 2a: Example la Peak table of polyimide film formed in a

1: '"' ■

Ma _ · ί »-ι 7ί, 8) .c ■ 3; 28? _Λ )

ID76.12 (?

43 2364 = 4 (p _: ~ 7 ヽ. Ϊ́ 6: 17 Θ C! 3 ".-'·.

^r 'Λ Ku i''' 3 «) 1456.39 ·: 68» 9) 9z 1369.53 <ii.8>

1338, 72 <36.4) i i * 1387, 85 ku 1 * 1275.06 66, x

• j; * a 32 = 4) 145 1093.74 ':: ic: * 1Θ47.4

: L 974, 14 ^! :: 7 7) 175 'Θ6, et al. 3 (7b »b 18 ϊ 887.34 76.8)

1 Q »810. iS <7Q, 4> ·

'· Above, ·-, -i ·', Qf 21:: tsu, J 68.9 «63.5? 6 · «8): 488. Θ3 <65» 2> In the above tables la and 2a, the unit of wave number is cm- ¹ and the unit of transmittance is%.

A recrystallized trans-1,4-diaminocyclohexane 5.710 g (0.05 mol) was placed in a well-dried closed reaction vessel with a stirrer, and polymerized from Ν, Ν-dimethylacetoamide, which was sufficiently dehydrated. Dissolved in 150 mL of solvent. Without silylation of diamine, 9.806 g (0.05 mol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride powder was gradually added, followed by stirring at room temperature. However, a strong salt is formed at the beginning of the polymerization, and even if the stirring is continued at room temperature for several weeks to one month, the polymerization proceeds at all. Did not go.

In addition to N, N-dimethylacetamide, 溶媒, Ν-dimethylformamide, Ν-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, dimethylsulfoxide, Polymerization was attempted using a-butyrolactone, diglyme, m-cresol, acetamide mixed solvent, hexamethylphosphoramide / N-methyl-2-pyrrolidone mixed solvent, and tetrahydrofuran / methanol mixed solvent. Polymerization did not proceed at all.

Polymerization was attempted in these solvent systems at a solute concentration of 1 to 15% by weight in a temperature range of room temperature to 150 ° C, but no polymerization was observed. Further, tertiary amines such as pyridine and triethylamine or inorganic salts such as lithium chloride were also used, but the effect of adding these was not seen at all and the polymerization did not proceed at all.

(Example 2a)

Put 5.710 g (0.05 mol) of purified trans-1,4-diaminocyclohexane in a well-dried closed reaction vessel equipped with a stirrer, and fully dehydrate hexanemethylphosphoramide and Ν.重合, 混合 -dimethylacetamide mixed solvent (3: 1 by volume) Polymerization solvent 1 After dissolving in 50 niL, use a syringe to prepare Ν, Ο-bis (trimethylsilyl) trifluoroacetamide silylating agent 14. Ιπι L (0.05 mol) was slowly added dropwise, and the mixture was stirred at room temperature for 1 hour to perform silylation (silylation rate X = 1.0).

To this solution, 9,806 g (0.05 mol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride powder was gradually added, and the mixture was stirred at room temperature. In this method, although a polyimide precursor organic solvent solution was obtained, a part of the polyimide precursor was precipitated in the solution, and a uniform solution was not obtained even if stirring was continued for several weeks. This is because all the carboxy groups in the polyimide precursor are silylated, so that they are difficult to solvate and partially precipitate during polymerization due to hydrogen bonds between polymer chains. If the silylation ratio X is lower than 0.4, a strong salt Formed and polymerization did not proceed.

Example 3 a>

Recrystallized and put 5.710 g (0.05 mol) of purified trans-1,4-diaminocyclohexane in a well-dried closed reaction vessel equipped with a stirrer, and thoroughly dehydrated Ν, Ν-dimethylacetamide Is dissolved in 150 mL of a polymerization solvent consisting of The silylation (silylation rate X = 0.5) was performed by stirring.

To this solution, 9,806 g (0.05 mol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride powder was gradually added, followed by stirring at room temperature. In this method, although a polyimide precursor organic solvent solution was obtained, a part of the polyimide precursor in the solution was precipitated, and a viscous and uniform solution was obtained even if stirring was continued for one month. What This is because the partially silylated polyimide precursor had poor solubility in Ν, Ν-dimethylacetamide and partially precipitated during polymerization. When hexamethylphosphoramide was not contained as a polymerization solvent, a viscous and uniform solution could not be obtained at any silylation rate regardless of whether lithium chloride was added or not.

Example 4 a>

A solution of the polyimide precursor polymerized in Example 1a was applied to a glass substrate and dried at 60 ° C. for 2 hours to obtain a polyimide precursor film. This was thermally imidized on a substrate at 340 ° C. for 3 hours under reduced pressure without removing the residual solvent, whereby a polyimide film was obtained.

However, the obtained polyimide film was partially blackened, and the film was partially broken. This is because hexamethylphosphoramide used as a solvent is very difficult to volatilize, so it tends to stay in the film during imidization, causing thermal decomposition of hexamethylphosphoramide itself and some reaction with the polyimide precursor. Probably because it was caused.

(Comparative Example 2a) 10.518 g (0.05 mol) of an alicyclic amine consisting of 4,4'-methylenebis (cyclohexylamine) was placed in a well-dried closed reaction vessel equipped with a stirrer, and N, N-dimethylacetamide was sufficiently dehydrated. After dissolving in 200 mL of a polymerization solvent consisting of 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 9.806 g (0.05 mol) of carboxylic acid dianhydride powder is gradually added, and the mixture is stirred at room temperature for 24 hours. did. In this system, polymerization proceeded easily by a known method without silylation of alicyclic diamine.

The polyimide film obtained by thermally imidizing the substrate at 300 ° C for 1 hour under reduced pressure has a dielectric constant of 1. The dielectric constant estimated from the square of the IX average refractive index is 2.6, which is a low dielectric constant. However, the coefficient of linear thermal expansion was 70 ppm / K, indicating no low thermal expansion characteristics. This is because the spontaneous in-plane orientation during thermal imidization was inhibited by the bent structure of the alicyclic diamine used.

(Comparative Example 3a)

5.710 g (0.05 mol) of alicyclic amine consisting of 1,4-diaminocyclohexane (trans / cis mixture) was placed in a well-dried closed reaction vessel equipped with a stirrer, and sufficiently dried N, N-dimethylacetamide After dissolving in 150 mL of a polymerization solvent consisting of 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 9.806 g (0.05 mol) of carboxylic acid dianhydride powder was gradually added, and the solution was added at room temperature. Stirred for 4 hours. In this system, polymerization proceeded easily by a known method without silylation of alicyclic diamine. The polyimide film obtained by thermally imidizing the substrate at 340 ° C for 1 hour under reduced pressure was brittle, but the dielectric constant was 1. The dielectric constant estimated from the square of the IX average refractive index was 2.6. And low dielectric constant. However, the coefficient of linear thermal expansion was 60ppm / K, indicating no low thermal expansion characteristics. This is because spontaneous in-plane orientation during thermal imidization was inhibited because the alicyclic diamine used contained cis 1,4-diaminocyclohexane having a bent structure.

'(Comparative Example 4a)

5.407 g (0.05 mol) of aromatic diamine consisting of paraphenylenediamine was placed in a well-dried closed reaction vessel equipped with a stirrer, and sufficiently dried N, N-dimethyl was added. After dissolving 200 mU of a polymerization solvent composed of rusacetamide, powder of carboxylic dianhydride composed of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride 14.71 lg

(0.05 mol) was added slowly, and the mixture was stirred at room temperature for 3 hours. In this system, polymerization proceeded easily by a known method without silylation of diamine. The polyimide film obtained by thermal imidization at 350 ° C for 1 hour under reduced pressure on the substrate showed a low linear thermal expansion coefficient of 6.0 PPm / K, but the dielectric constant was 1.1 x the average refractive index. The dielectric constant estimated from the square of was 3.5, indicating no low dielectric constant. This is due to the use of aromatic monomers.

[Second invention]

The analysis value in each case was determined by the following method.

The 0.5 wt% polyimide precursor solution was measured at 30 ° C. using an Ostwald viscometer.

The dynamic viscoelasticity was measured from the loss peak at a frequency of 0.1 mm and a heating rate of 5 ° CZ.

<5% weight loss temperature>

The thermogravimetric change of the polyimide film was measured using a thermobalance, and the temperature at which the weight was reduced by 5% was determined.

According to thermomechanical analysis, the linear thermal expansion coefficient was calculated as an average value in the range of 100 to 200 ° C from the elongation of the test piece at a load of 0.5 gZ film thickness l_im and a heating rate of 5 ° CZ. I asked.

<Cut-off wavelength (transparency)>

The visible / ultraviolet transmittance from 200 nm to 100 nm was measured with a spectrophotometer. The wavelength (cutoff wavelength) 'at which the transmittance is 1% or less was used as the index of transparency. The shorter the cutoff wavelength, the better the transparency.

<Birefringence> The refractive index _{in the} direction parallel to the polyimide film (n _in ) and _{in the} direction perpendicular to the polyimide film (n. _Ut ) was measured with an Atsube refractometer (using a sodium lamp, wavelength 589 mn), and the birefringence (Δ _{_{n = n in -. n ut}} ) was determined.

Based on the average refractive index [n _av = (2 nm + n out) Z3] of the polyimide film, the dielectric constant (ε) at 1 MHz was calculated by the following equation.

ε = 1.1 X n av ² (1 kHz)

(Example 1b)

Put 5.710 g (0.05 mol) of re-transformed and purified trans-1,4-diaminocyclohexane in a well-dried closed reaction vessel equipped with a stirrer, and fully dehydrate hexane methylphosphoramide and Ν, Ν- After dissolving in 130 mL of a mixed solvent of dimethylacetamide (volume ratio 3: 1), 15.OmL (0.05 mol) of N, 0_bis (trimethylsilyl) trifluoroacetamide was slowly added dropwise with a syringe. The mixture was stirred at room temperature for 1 hour to perform silylation (silylation rate X = 1.0).

To this solution, 10.906 g (0.05 mol) of pyromellitic dianhydride powder was gradually added and stirred at room temperature for 2 hours to obtain a uniform and viscous polyimide precursor solution (polyimide precursor organic solvent solution). This was heated at 100 ° C for 20 minutes to increase the storage stability. The intrinsic viscosity of the polyimide precursor measured at 30 ° C in the same solvent as in the polymerization was 3.9 dL / g, which was an extremely high polymer.

A polyimide precursor solution is applied to a glass substrate and vacuum-dried at 60 ° C for 2 to 4 hours.The transparent and high-quality polyimide precursor film is immersed in 1-butanol for 2 hours to remove residual solvent. Removed completely. This is thermally imidized as it is on a substrate under reduced pressure at 300 ° C for 1 hour, peeled off from the substrate, and then heat-treated at 305 ° C for 1 hour to give a 10 m-thick uncolored transparent semi-finished film. An aromatic polyimide film was obtained. The physical properties of the film are: dielectric constant 2.91, coefficient of linear thermal expansion llppm / K, glass transition temperature 442: 5% weight loss temperature in nitrogen atmosphere (heating rate 10 ° C / min) 435 ° C, 425 in air ° C and cutoff wavelength of 320, all of the desired characteristics could be satisfied. Since the birefringence △ n was 0.1771, which was a very high value, Polyimide chains are highly oriented in the plane, which is the reason for the low thermal expansion characteristics. The infrared absorption spectra of the obtained polyimide precursor thin film and polyimide thin film are shown in FIGS. 5 and 6, respectively. The peak tables of the polyimide precursor thin film and polyimide thin film are shown in Tables 1b and 2b below. Table 1b: Peak table of the polyimide precursor of the present invention

Table 2b: Peak table of the polyimide of the present invention

(Comparative example l b)

Put 5.710 g (0.05 mol) of recrystallized and purified trans-1,4-diaminocyclohexane in a well-dried closed reaction vessel with a stirrer, and sufficiently dry 脱水, Ν-dimethylacetamide Dissolved in 130 mL. Do not silylate diamine Then, 10.906 g (0.05 mol) of pyromellitic dianhydride powder was gradually added thereto, followed by stirring at room temperature.

However, a strong salt was formed at the beginning of the polymerization, and the polymerization did not proceed at all even if stirring was continued at room temperature for several weeks to one month. Other than Ν, Ν-dimethylacetamide, 溶媒, Ν-dimethylformamide, Ν-methyl-2-pyrrolidone,

3-dimethyl-2-imidazolidinone, dimethyl sulfoxide, _Τ -butyrolactone, diglyme, m-cresol, hexamethylphosphoramide, hexamethylphosphoramide / N, N-dimethylacetamide Polymerization was attempted using a mixed solvent, hexamethylphosphoramide / N-methyl-2-pyrrolidone mixed solvent, and tetrahydrofuran / methanol mixture solvent, but no polymerization proceeded in any solvent system. .

Polymerization was attempted in these solvent systems in a solute concentration range of 1 to 15% by weight and a temperature range of room temperature to 150 ° C. Furthermore, tertiary amines such as pyridine-triethylamine or inorganic salts such as lithium chloride were also used, but the effect of adding these was not observed at all and the polymerization did not proceed at all.

(Example 2b)

Recrystallized in a well-dried closed reaction vessel with a stirrer

Add 5.710 g (0.05 mol) of 4-diaminocyclohexane, dissolve in 30 mL of fully dehydrated N, N-dimethylacetoamide, and use a syringe to add N, 0_bis (trimethylsilyl) trifluoro. A silylating agent composed of oloacetamide (15.0 OmL (0.05 mol)) was slowly added dropwise, and the mixture was stirred at room temperature for 1 hour to perform silylation (silylation rate X = 1.0). To this solution, 10.906 g (0.05 mol) of pyromellitic dianhydride powder was gradually added, followed by stirring at room temperature.

In this method, although a polyimide precursor solution was obtained, a part of the polyimide precursor precipitated in the solution, and a viscous and uniform solution was not obtained even if stirring was continued for one month. This is due to the poor solubility of the silylated polyimide precursor in N, N-dimethylacetoamide and partial precipitation during the polymerization. is there. When hexamethylphosphoramide was not contained as a polymerization solvent, a viscous and uniform solution could not be obtained at any silylation rate regardless of whether or not lithium chloride was added.

(Example 3b)

A solution of the polyimide precursor polymerized in Example 1b was applied to a glass substrate, and vacuum-dried at 60 ° C. for 2 hours to obtain a transparent and high-quality polyimide precursor film. This was thermally imidized at 300 ° C. for 1 hour under reduced pressure on the substrate without going through the step of removing the residual solvent.

In this method, the obtained polyimide film was partially blackened, and the film was partially broken. This is because hexamethylphosphoramide used as a solvent is very difficult to volatilize, so it tends to stay in the membrane during imidization, causing thermal decomposition of hexamethylphosphoramide itself and some reaction with the polyimide precursor. Probably because it was caused.

(Comparative Example 2b)

Put 4,4'-methylenebis (cyclohexylamine) 10.518 g (0.05 mol) in a well-dried closed reaction vessel equipped with a stirrer, and sufficiently dry 脱水, Ν-dimethylacetamide in 80 mL. After dissolution, 10.906 g (0.05 mol) of pyromellitic dianhydride powder was gradually added, followed by stirring at room temperature for 24 hours. In this system, polymerization proceeded easily by a known method without silylation of alicyclic diamine. However, the polyimide film obtained by thermally imidizing the substrate at 300 ° C for 1 hour under reduced pressure had a linear thermal expansion coefficient of 70 ppm / K and did not show low thermal expansion characteristics. This is because the spontaneous in-plane orientation during thermal imidization was inhibited by the bent structure of the alicyclic diamine used.

(Comparative Example 3b)

1,4-Diaminocyclohexane in a well-dried closed reaction vessel with stirrer

(Trans / cis mixture) 5. Add 710 g (0.05 mol), fully dehydrated 30, Ν-dimethylacetamide (1 30 mU), dissolve, and pyromellitic dianhydride powder 10.906 g (0. (05 mol) was added slowly and the mixture was stirred at room temperature for 24 hours. Alicyclic in this system Polymerization proceeded easily in a known manner without silylation of the formula diamine. However, the polyimide film obtained by thermally imidizing the substrate at 300 ° C for 1 hour under reduced pressure was extremely fragile.

This is because the diamine component contained cis-1,4-diaminocyclohexane with low reactivity. The polyimide film had a linear thermal expansion coefficient of 60 ppm / K and did not exhibit low thermal expansion characteristics. This is because spontaneous in-plane orientation during thermal imidization was inhibited because the alicyclic diamine used contained cis 4-diaminocyclohexane having a bent structure.

(Comparative Example 4b)

Put 5.407 g (0.05 mol) of paraphenylenediamine in a well-dried closed reaction vessel with a stirrer, dissolve in 200 mL of fully dehydrated Ν, Ν-dimethylacetamide, and then add 3,3 ', 4 , 4'-biphenyltetracarboxylic dianhydride powder 14.71 lg

(0.05 mol) was added slowly, and the mixture was stirred at room temperature for 3 hours. In this system, polymerization proceeded easily by a known method without silylation of diamine.

The polyimide film obtained by thermal imidization at 350 ° (: 1 hour under reduced pressure on the substrate showed an extremely low coefficient of linear thermal expansion of 6. Oppm / K, but a dielectric constant of 3 .5, showing no low dielectric constant, and the polyimide film was markedly colored.

This is because the use of aromatic monomers in both the acid dianhydride component and the diamine component caused intramolecular conjugation and charge transfer interaction. Similarly, a polyimide film having a rod-like structure obtained from pyromellitic dianhydride and paraphenylenediamine showed only low thermal expansion characteristics, but could not achieve low dielectric constant and high transparency. This is also due to the use of aromatic monomers for both the acid dianhydride component and the diamine component. Industrial applicability

According to the present invention, a polyimide film having a low dielectric constant, a low coefficient of linear thermal expansion, a high glass transition temperature, high transparency, sufficient toughness, and film forming processability can be produced. Further, according to the production method of the present invention, the dispersibility in a polymerization solvent is A high polyimide precursor is obtained, and a solution of such a polyimide precursor in an organic solvent has excellent solution storage stability. Further, the production method of the present invention does not require an extra purification step, so that the production cost of polyimide is lower than in the past.

Claims

The scope of the claims

After reacting 1 · trans 1,4-diaminocyclohexane with a silylating agent to produce an intermediate product, the intermediate product is combined with 1,2,3,4-cyclobutanetetracarboxylic dianhydride To produce an all-alicyclic polyimide precursor having a repeating structural unit represented by the following structural formula (la).

2. The method for producing a polyimide precursor according to claim 1, wherein a non-halogenated silylating agent having no halogen atom in a chemical structure is used as the silylating agent.

3. The polyimide precursor according to claim 2, wherein one or both of Ν, Ο-bis (trimethylsilyl) trifluoroacetamide and Ν, 0_bis (trimethylsilyl) acetamide are used as the non-halogenated silylating agent. Production method.

4. In the unit structural formula (la), R is H or Si (CH ₃ ) ₃ group, and the trans 1,4-diaminocyclohexane and the silylating agent are reacted at a predetermined ratio. The method for producing a polyimide precursor according to any one of claims 1 to 3, wherein

Assuming that the number of 1 ^ consisting of 51 ((11 ₃ ) ₃ groups is eight and the number of R consisting of H is B among R contained in the entire chemical structure, the silylation represented by the following formula (1) The silylating agent and the trans 1,1 A method for producing a polyimide precursor in which 4-diaminocyclohexane is reacted. Silylation rate = AZ (A + B) …… Formula (1)

5. Trans 1,4-diaminocyclohexane and a silylating agent are reacted in a polymerization solvent to produce an intermediate product, and then 1,2,3,4-cyclobutanetetracarboxylic acid is added to the polymerization solvent. Adding a dianhydride, reacting the intermediate product with the 1,2,3,4-cyclobutanetetracarboxylic dianhydride, and dispersing or dissolving the polyimide precursor in the polymerization solvent. A method for producing a polyimide precursor organic solvent solution for producing a body organic solvent solution.

6. A method for producing a polyimide film, comprising applying the polyimide precursor organic solvent solution according to claim 5 to an object to be coated, forming a cast film, and then imidizing the polyimide precursor in the cast film.

In the polymerization solvent, the trans 1,4-diaminocyclohexane, the silylating agent, the 1,2,3,4-cyclobutanetetracarboxylic dianhydride, and the intermediate product High affinity solvent containing high boiling point solvent,

A method for producing a polyimide film, comprising: bringing a cleaning liquid having a high affinity with the polymerization solvent and having a boiling point lower than that of the polymerization solvent into contact with the cast film; washing the cast film;

7. Using hexamethylphosphoramide as the high boiling solvent,

7. The method for producing a polyimide film according to claim 6, wherein alcohol is used as the cleaning liquid.

8. The repeating structural unit is represented by the unit structural formula (la), and the substituent R in the unit structural formula (la) is an all-alicyclic polyimide precursor in which H or Si (CH ₃ ) _{3 is a} group. hand,

A polyimide having at least one unit structure in which one or both of the substituents R in one unit structural formula is a Si (CH ₃ ) 3 group, and having an intrinsic viscosity of 1.O dl Zg or more precursor.

9. The polyimide precursor according to claim 8, wherein the stereostructure of each 1,4-cyclohexane residue in the unit structural formula (la) is a trans configuration.

10. In the entire chemical structure, if the total number of substituents R consisting of Si (CH ₃ ) ₃ groups is A, and the total number of substituents R consisting of hydrogen is B,

10. The polyimide precursor according to claim 8, wherein a silylation rate of the polyimide precursor represented by the following formula (1) is in a range of 0.4 or more and 0.9 or less.

Silylation rate = AZ (A + B) …… Formula (1)

1 1. The repeating structural unit is represented by the following unit structural formula (2a), and the steric structure of each 1,4-cyclohexane residue in the following unit structural formula (2a) is in a trans configuration. Characteristic polyimide.

-Unit structural formula (2a)

1 2. A polyimide film comprising the polyimide according to claim 11 as a main component.

1 3. Trans 1,4-diaminocyclohexane and a silylating agent are reacted to form an intermediate product, and then the intermediate product is reacted with pyromellitic dianhydride to form a repeating structural unit. A method for producing a polyimide precursor for producing a polyimide precursor represented by the following unit structural formula (lb).

-Unit structural formula (lb)

(In the unit structural formula (lb) ′, R is H or a silyl group, and the polyimide precursor is a compound in which one or both of the substituents R in one unit structural formula are a silyl group. Has at least one unit structure)

14. The production of a polyimide precursor according to claim 13, wherein a non-halogenated silylating agent containing no halogen atom in a chemical structure is used as the silylating agent. Method.

15. The polyimide precursor according to claim 14, wherein one or both of N, 0-bis (trimethylsilyl) trifluoroacetamide and Ν, 0_bis (trimethylsilyl) acetamide are used as the non-halogenated silylating agent. Production method.

16. The process for producing a polyimide precursor according to any one of claims 13 to 15, wherein the trans 1,4-diaminocyclohexane and the silylating agent are reacted at a predetermined ratio. So,

Assuming that the number of R consisting of a silyl group is Α and the number of R consisting of Η is Β among the Rs contained in the entire chemical structure, the silylation rate of the polyimide precursor represented by the following formula (1) is A method for producing a polyimide precursor, wherein the trans 1,4-diaminocyclohexane is reacted with the silylating agent so that the ratio is 0.9 or more and 1.0 or less.

Silylation rate = ΑΖ (Α + Β) …… Formula (1)

17. The method for producing a polyimide precursor according to any one of claims 13 to 16, wherein the trans 1,4-diaminocyclohexane and the silylating agent are reacted at a predetermined ratio. So,

When the number of all amino groups of the trans 1,4-diaminocyclohexane before the reaction is c, and the number of silyl groups of all the intermediate products is d,

The trans 1,4-diaminocyclohexane and the silylating agent in such a ratio that the silylation rate of the intermediate product represented by the following formula (2) is in the range of 0.9 or more and 1.0 or less. And a method for producing a polyimide precursor.

Silylation rate = dZc …… Equation (2)

1 8. Trans 1,4-diaminocyclohexane and a silylating agent are reacted in a polymerization solvent to produce an intermediate product, and then pyromellitic dianhydride is added to the polymerization solvent. A method for producing a polyimide precursor organic solvent solution, comprising reacting an intermediate product with the pyromellitic dianhydride to produce a solution of a polyimide precursor in which the polyimide precursor is dispersed or dissolved in the polymerization solvent. Law.

19. A method for producing a polyimide film, comprising: applying the polyimide precursor organic solvent solution according to claim 18 to an object to be coated; forming a cast film; and imidizing the polyimide precursor in the cast film. hand,

The polymerization solvent contains the trans 1,4-diaminocyclohexane, the silylating agent, the pyromellitic dianhydride, and a high boiling solvent having high affinity for the intermediate product. Let

20. Using hexamethylphosphoramide as the high boiling solvent,

The method for producing a polyimide film according to claim 19, wherein an alcohol is used as the cleaning liquid.

2 1. The repeating unit is represented by the above-mentioned unit structural formula (lb), and the substituent R in the above-mentioned unit structural formula (lb) is H or Si (CH ₃ ) ₃ , an all-alicyclic polyimide precursor Body

One or more of the substituents R in one unit structural formula have at least one unit structure in which one or both are Si (CH ₃ ) 3 groups, and have an intrinsic viscosity of 2.0 dL / g or more. A certain polyimide precursor.

22. The polyimide precursor according to claim 21, wherein the stereostructure of each 1,4-cyclohexane residue in the unit structural formula (Ib) is a trans configuration.

2 3. the total chemical structure, Si (CH ₃₎ consists of ₃ groups the total number of substituents' groups R A, When B the total number of hydrogen or Ranaru substituent R,

23. The polyimide precursor according to claim 21, wherein the silylation rate of the polyimide precursor represented by the following formula (1) is in a range of 0 to 0.9.

Silylation rate = AZ (A + B) …… Formula (1)

24. The repeating structural unit is represented by the following structural formula (2b), and each 1,4-cyclohexane residue in the structural formula (2b) is in a trans configuration. Polyimide.

Unit structural formula (2b)

2 5. Polyimide film containing polyimide as a main component according to claim 24