WO2008062662A1

WO2008062662A1 - Method for producing glass substrate for information recording medium, glass substrate for information recording medium, and information recording medium

Info

Publication number: WO2008062662A1
Application number: PCT/JP2007/071540
Authority: WO
Inventors: Yukitoshi Nakatsuji; Kenichi Sasaki
Original assignee: Konica Minolta Opto, Inc.
Priority date: 2006-11-21
Filing date: 2007-11-06
Publication date: 2008-05-29

Abstract

Disclosed is a method for producing a glass substrate for information recording medium at low cost, wherein a stable chemical strengthening treatment can be performed by conveying a glass substrate in such a manner that the temperature decrease from the time when the glass substrate is taken out of a preheating vessel to the time when the glass substrate is immersed into a chemical strengthening treatment liquid is suppressed to 10˚C or less, thereby minimizing variations of temperature of the glass substrate at the time when it is immersed into the chemical strengthening treatment liquid. Also disclosed are a glass substrate for information recording medium, and an information recording medium.

Description

Specification

Method for manufacturing glass substrate for information recording medium, glass substrate for information recording medium, and information recording medium

Technical field

The present invention relates to a method for producing a glass substrate for an information recording medium used for an information recording medium having a recording layer utilizing properties such as magnetism, light, and magnetomagnetism, and an information recording medium produced by the production method. The present invention relates to a glass substrate and an information recording medium.

Background art

Among information recording media having a recording layer using properties such as magnetism, light, and magnetomagnetism, there is a magnetic disk as a representative one. Conventionally, aluminum substrates have been widely used as magnetic disk substrates. However, in recent years, with the demand for higher recording density, glass substrates that can reduce the flying height of the magnetic head have been found to have better surface smoothness and fewer surface defects than aluminum substrates. The proportion used for magnetic disk substrates is increasing.

[0003] In such a method of manufacturing a glass substrate for information recording media such as a magnetic disk, the impact resistance and vibration resistance of a glass substrate are improved, and the substrate is prevented from being damaged by impact or vibration. In general, the substrate is strengthened by applying a chemical strengthening treatment to the surface of the glass substrate.

[0004] In chemical strengthening treatment, a glass substrate is usually immersed in a heated chemical strengthening treatment solution, and alkali metal ions such as lithium ions and sodium ions, which are components of the glass substrate, are ionized from these ions. This is performed by an ion exchange method in which an alkali metal ion such as sodium ion or potassium ion having a large radius is substituted.

[0005] In order to prevent cracking of the glass substrate due to thermal shock when the glass substrate is immersed in a heated chemical strengthening treatment solution, the glass substrate is heated to a predetermined temperature in advance before being immersed in the chemical strengthening treatment solution. A method of providing a preheating step is known. Further, in order to increase the flatness of the glass substrate, a method has been proposed in which the preheating temperature is at least 100 ° C. lower than the strain point of the glass (see, for example, Patent Document 1). Patent Document 1: JP-A-7-29170

Disclosure of the invention

Problems to be solved by the invention

[0006] However, after the glass substrate is heated to a predetermined temperature in the preheating tank, the temperature of the glass substrate decreases while the glass substrate is taken out of the preheating tank and transported to be immersed in the chemical strengthening treatment liquid. The temperature that decreases at this time depends on many factors such as the ambient temperature at which the material is transported and the flow of air, so in the actual process, the temperature of the glass substrate at the time of immersion in the chemical strengthening solution is In general, it varied widely.

[0007] As described above, the chemical strengthening treatment is performed by ion exchange between the glass substrate and the chemical strengthening treatment liquid. The ion exchange speed, the amount of ions exchanged, The depth of penetration into the glass substrate greatly depends on the temperature of the glass substrate and the chemical strengthening solution. For this reason, if the temperature of the glass substrate at the time of immersion in the chemical strengthening treatment liquid varies, there is a problem that the chemical strengthening treatment cannot be performed stably.

[0008] Further, in order to suppress the variation in the temperature of the glass substrate at the time of being immersed in the chemical strengthening treatment liquid, when trying to strictly control many factors such as the temperature of the atmosphere in which the conveyance is performed and the air flow, For this purpose, a large amount of cost and labor are required, which causes a problem of increasing the cost of the glass substrate.

[0009] The present invention has been made in view of the technical problems as described above, and an object of the present invention is to provide information recording that can perform stable chemical strengthening treatment and can be manufactured at low cost. The object is to provide a method for producing a glass substrate for a medium, a glass substrate for an information recording medium, and an information recording medium.

Means for solving the problem

In order to solve the above problems, the present invention has the following features.

[0011] 1. In a method for manufacturing a glass substrate for an information recording medium, the method includes a step of chemically strengthening the glass substrate by immersing the glass substrate in a heated chemical strengthening treatment liquid. Prior to, the glass substrate is brought to a predetermined temperature in a preheating tank. A preheating step for heating;

A conveyance step of taking out the glass substrate from the preheating tank and immersing it in the chemical strengthening treatment liquid,

In the transporting step, the glass substrate is transported so that the temperature drop of the glass substrate is 10 ° C or less after the glass substrate is taken out of the preheating tank and immersed in the chemical strengthening treatment liquid. A process for producing a glass substrate for an information recording medium, which is a process.

[0012] 2. When the temperature of the glass substrate when immersed in the chemical strengthening treatment liquid is TS (° C) and the temperature of the chemical strengthening treatment liquid is TL (° C), TL-50 ° C 2. The method for producing a glass substrate for an information recording medium according to 1 above, wherein ≤TS≤TL + 50 ° C is satisfied.

3.When the temperature of the glass substrate when immersed in the chemical strengthening treatment liquid is TS (° C) and the temperature of the chemical strengthening treatment liquid is TL (° C), TL-30 ° C≤TS≤ 2. The method for producing a glass substrate for an information recording medium according to 1 above, wherein TL + 30 ° C. is satisfied

[0013] 4. The transporting step is a step of transporting the glass substrate in an atmosphere heated to a temperature of 50 ° C or higher and lower than a heating temperature of the glass substrate in the preheating step. The method for producing a glass substrate for an information recording medium as described in any one of 1 to 3 above.

[0014] 5. A glass substrate for information recording medium manufactured by the method for manufacturing a glass substrate for information recording medium according to any one of 1 to 4 above.

[0015] 6. An information recording medium characterized in that at least a recording layer is formed on the glass substrate for information recording medium described in 5 above!

[0016] 7. The information recording medium as described in 6 above, wherein the recording layer is a magnetic layer.

The invention's effect

[0017] According to the present invention, the glass substrate is transported so that the temperature drop of the glass substrate after the glass substrate is taken out of the preheating tank and immersed in the chemical strengthening treatment liquid is within 10 ° C. Of the temperature of the glass substrate at the time of being immersed in the chemical strengthening solution. Provide a method for manufacturing a glass substrate for information recording media, a glass substrate for information recording media, and an information recording medium that can be manufactured at low cost, capable of performing stable chemical strengthening treatment with minimal adhesion can do.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail.

[0019] (Method for producing glass substrate for information recording medium)

A glass substrate for an information recording medium is generally manufactured through processes such as a blank material manufacturing process, an inner and outer peripheral processing process, a polishing 1 ”-polishing process, a chemical strengthening process, and a cleaning process. The blank material production process is a process for forming a blank material that is the basis of a glass substrate for an information recording medium. There are a method for producing molten glass by press molding, and a method for producing by cutting sheet-like glass. Are known. The inner and outer peripheral machining process is a process of drilling the central hole, grinding to ensure the shape and dimensional accuracy of the inner and outer circumferences, and polishing the inner and outer circumferences. The grinding / polishing step is a step of performing grinding and polishing to satisfy the flatness and surface roughness of the surface on which the recording layer is formed. Usually, it is often performed in several stages, such as rough grinding, fine grinding, primary polishing, and secondary polishing. The chemical strengthening step is a step of strengthening the glass substrate by immersing the glass substrate in a heated chemical strengthening treatment solution. The cleaning step is a step of removing foreign matters such as abrasives and chemical strengthening treatment liquid remaining on the surface of the glass substrate.

[0020] The method for producing a glass substrate for an information recording medium of the present invention is characterized by a chemical strengthening step among these steps. In the present invention, the chemical strengthening step may be performed after the polishing polishing step is completed, or the polishing strengthening / polishing step may be performed after the chemical strengthening step is performed first. Alternatively, the chemical strengthening process can be performed when the polishing polishing process reaches a certain stage, and then the remaining steps of the polishing | J 'polishing process can be performed.

[0021] It should be noted that the method for producing a glass substrate for an information recording medium of the present invention may include various processes other than those described above. For example, it has an annealing process to alleviate internal distortion of the glass substrate, a dealkali treatment process to prevent the precipitation of alkali metal ions from the glass substrate, and various inspection / evaluation processes! Also good!

[0022] (Chemical strengthening process) In the chemical strengthening process, by immersing the glass substrate in a heated chemical strengthening treatment solution, alkali metal ions such as lithium ions and sodium ions, which are components of the glass substrate, have a larger ion radius than these ions. It is carried out by an ion exchange method in which it replaces the alkali metal ions such as sodium ions and potassium ions. The surface of the glass substrate is strengthened by generating compressive stress in the ion-exchanged region due to the strain caused by the difference in ion radius.

[0023] Chemical strengthening treatment liquids include molten salts such as potassium nitrate (KNO), sodium nitrate (NaNO), carbonated potassium (KCO), and mixtures thereof (for example, a mixture of potassium nitrate and sodium nitrate, potassium nitrate and A melt of potassium carbonate or the like) can be used. Further, another metal salt or the like may be mixed.

[0024] The heating temperature of the chemical strengthening treatment liquid needs to be higher than the temperature at which the above components melt. For example, when potassium nitrate is used as the chemical strengthening treatment solution, it may be heated to a temperature higher than 334 ° C., which is the melting point, and when it is used, it may be heated to a temperature higher than 306 ° C., which is the melting point.

[0025] On the other hand, if the heating temperature of the chemical strengthening treatment liquid is too high, the temperature of the glass substrate is excessively increased, which may cause deformation of the glass substrate. For this reason, the heating temperature of the chemical strengthening treatment liquid is preferably lower than the glass transition temperature of the glass substrate (hereinafter referred to as “Tg”). More preferred.

[0026] Sharpening 1 ”· When the chemical strengthening process is performed after the polishing process is completed, the thickness of the region strengthened by ion exchange (hereinafter referred to as“ strengthening layer ”) and the degree of strengthening are determined according to the hardness of the glass substrate. In addition to mechanical strength, it directly affects various performances as a glass substrate for information recording media, such as surface roughness and the amount of alkali metal ions deposited after the recording layer is formed on the substrate. .

[0027] In addition, even if the polishing step is further performed after the chemical strengthening step, the thickness of the reinforcing layer and the degree of strengthening are largely dependent on the conditions of the subsequent grinding and polishing. As a result, the performance of the finally obtained glass substrate for information recording media is greatly affected.

[0028] The thickness of the reinforcing layer and the degree of strengthening depend on the temperature of the glass substrate and the chemical strengthening treatment liquid, and the immersion. It depends on time. Since it is very difficult to easily measure the thickness of the reinforcing layer and the degree of strengthening during the manufacturing process, in the actual process, the temperature of the glass substrate and the chemical strengthening treatment liquid, and the immersion time By managing this, the chemical strengthening process is stabilized. In other words, in manufacturing a glass substrate for information recording media, it is important to perform stable chemical strengthening treatment, and for that purpose, temperature control between the glass substrate and the chemical strengthening treatment solution is a very important point. .

[0029] From the viewpoint of providing the necessary hardness, strength, and surface roughness as a glass substrate for information recording media, the thickness of the reinforcing layer is determined by performing the chemical strengthening step after the polishing and polishing steps are completed. In the case of 5 H m to 200 11 m, the range of 10 μm to 500 m is preferable when the polishing step is further performed after the chemical strengthening step. The immersion time required to obtain such a reinforcing layer thickness is usually about 0.5 to 20 hours.

[0030] (Preheating process, conveying process)

In the present invention, the temperature of the glass substrate at the time of being immersed in the chemical strengthening treatment liquid is stabilized, and the glass substrate is cracked or microcracked by thermal shock when immersed in the heated chemical strengthening treatment liquid. In order to prevent the occurrence of this, a preheating step of heating the glass substrate to a predetermined temperature in a preheating tank is performed prior to immersion in the chemical strengthening treatment solution.

[0031] From the viewpoint of minimizing the temperature change of the chemical strengthening treatment liquid, the temperature of the glass substrate when immersed in the chemical strengthening treatment liquid is TS (° C), and the temperature of the chemical strengthening treatment liquid is TL (° When C), TL—50 ° C≤TS≤TL + 50 ° C is preferable S, TL—30 ° C≤TS≤TL + 30 ° C is more preferable! TS force STL—Lower than 50 ° C! / When higher than TL + 50 ° C, the temperature of chemical strengthening treatment liquid by immersion of glass substrate is large, so chemical strengthening treatment liquid Temperature control becomes difficult, and chemical strengthening treatment tends to be unstable.

As the preheating tank, a known electric furnace or the like can be used as long as it can heat the glass substrate to a predetermined temperature.

[0033] Further, the present invention includes a transporting step in which the glass substrate is taken out of the preheating tank and immersed in the chemical strengthening treatment liquid. Usually, in this transfer process, the glass substrate that has been preheated between the time when the glass substrate is taken out of the preheating tank and immersed in the chemical strengthening treatment liquid is used. The temperature will decrease. Therefore, in order to keep the temperature of the glass substrate when immersed in the chemical strengthening treatment liquid within the above range, the preheating temperature in the preheating tank is set higher than the temperature of the glass substrate when immersed in the chemical strengthening treatment liquid. It is necessary to set

[0034] In the present invention, the preheating temperature is preferably close to the temperature of the chemical strengthening treatment solution! /, Preferably in the range of 300 ° C to 400 ° C, preferably 330 ° C to 380 ° C. More preferably. This is because preheating at a temperature significantly different from the temperature of the actual chemical strengthening treatment liquid causes a sudden temperature change of the chemical strengthening treatment liquid when a large amount of glass substrate is immersed and chemically strengthened. This is because the state of the strengthening process becomes unstable, and it becomes difficult to uniformly control the thickness of the strengthening layer and the value of the compressive stress generated.

[0035] Under the condition that the temperature of the glass substrate is greatly decreased from the time when the glass substrate is taken out of the preheating tank to the time when the glass substrate is immersed in the chemical strengthening treatment liquid, the temperature decrease in the transport process affects the influence of the ambient temperature, air flow, etc. Because it receives a large amount, the amount of variation in temperature drop when the process is repeated increases. In addition, if the preheating temperature in the preheating tank is too high, the temperature of the glass substrate may approach Tg and the glass substrate may be deformed. In the present invention, the temperature drop of the glass substrate from the time the glass substrate is taken out of the preheating tank to the time when it is immersed in the chemical strengthening treatment liquid is set to 10 ° C or less, and the influence of the ambient temperature, air flow, etc. in the transfer process By making it less susceptible to heat, the temperature variation of the glass substrate at the time of immersion in the chemical strengthening solution is minimized.

[0036] When the glass substrate is removed from the preheating tank, the temperature of the glass substrate decreases with time. Therefore, it is necessary to complete the transfer process within a time shorter than the time when the temperature drop of the glass substrate reaches 10 ° C. The temperature drop per unit time is affected by the ambient temperature at which the glass substrate is transported in the transport process. In order to reduce the temperature drop per unit time and to increase the time that can be spent on the transport process, it is preferable that the ambient temperature is high. On the other hand, if the ambient temperature is too high, the glass substrate tends to be deformed. From these viewpoints, it is preferable to transport the glass substrate in an atmosphere heated to 50 ° C. or higher and lower than the glass substrate heating temperature in the preheating step.

[0037] (Glass substrate) The glass substrate that can be used in the present invention is not particularly limited as long as it is a glass substrate that can be ion-exchanged by being immersed in a chemical strengthening treatment solution. Examples thereof include aluminosilicate glass, soda lime glass, soda aluminosilicate glass, aluminoporosilicate glass, and polosilicate glass. Of these, aluminosilicate glass is particularly preferred because of its excellent impact resistance and vibration resistance.

[0038] There is no limitation on the size of the glass substrate. For example, glass substrates of various sizes such as 2.5 inches, 1.8 inches, 1 inch, and 0.8 inches can be used. There is no limitation on the thickness of the glass substrate. For example, glass substrates having various thicknesses such as 2 mm, lmm, and 0.63 mm can be used.

[0039] (Information recording medium)

An information recording medium can be obtained by forming at least a recording layer on a glass substrate for information recording medium obtained by the method of the present invention. The recording layer is not particularly limited, and various recording layers utilizing properties such as magnetism, light, and magnetomagnetism can be used. However, the recording layer is particularly useful for manufacturing an information recording medium (magnetic disk) using the magnetic layer as a recording layer. Is preferred.

[0040] The magnetic material used for the magnetic layer is not particularly limited, and a known material can be appropriately selected and used. For example, a force S such as CoPt, CoCr, CoNi, CoNiCr, CoCrTa, CoPtCr, CoNiPt, CoNiCrPt, CoNiCrTa, CoCrPtTa, CoCrPtSiO containing Co as a main component can be cited. In addition, the magnetic layer can be divided into non-magnetic films (for example, Cr, CrMo, CrV, etc.) to reduce noise.

[0041] As the magnetic layer, in addition to the above Co-based materials, ferrite-based and iron-rare earth-based materials, SiO

It is also possible to use a durailleur having a structure in which magnetic particles such as Fe, Co, CoFe, and CoNiPt are dispersed in a nonmagnetic film made of BN or the like. The magnetic layer may be either an in-plane type or a vertical type.

As a method for forming the magnetic film, a known method can be used. Examples include sputtering, electroless plating, and spin coating.

[0043] The magnetic disk may be further provided with an underlayer, a protective layer, a lubricating layer, and the like as necessary. Any of these layers can be used by appropriately selecting a known material. Examples of the material for the underlayer include Cr, Mo, Ta, Ti, W, V, B, Al, and Ni. Protective layer material Examples thereof include Cr, Cr alloy, C, Zr 0 ₂ and SiO ^. As the lubricating layer, for example, a liquid lubricant made of perfluoropolyether (PFPE) or the like is applied and heat-treated as necessary.

Example

[0044] (Example 1)

Aluminosilicate glass with a Tg of 480 ° C was used as the glass material, and a blank was produced by press-molding the molten glass. A glass substrate having an outer diameter of 65 mm, an inner diameter of 20 mm, and a thickness of 0.635 mm was obtained through an inner and outer peripheral machining process and a grinding / polishing process. The surface roughness was finished so that the arithmetic average height Ra (JIS B0601: 2001) force SO. The flatness was less than 1.5 111 on both sides. The flatness was measured by measuring interference fringes using a flat master finished to a level of 0.1 m or less.

[0045] A mixed molten salt of potassium nitrate (KNO) and sodium nitrate (NaNO) was prepared as a chemical strengthening treatment solution. The mixing ratio was 1: 1 by mass ratio. The temperature of the chemical strengthening solution was 40 ° C.

[0046] The temperature of the preheating tank was set to 409 ° C. In addition, the atmospheric temperature in the transfer process was set to 150 ° C. Ten glass substrates were set in one carrier and put into a preheating tank for preheating. After 30 minutes, the glass substrate together with the carrier was taken out of the preheating tank, and immersed in the chemical strengthening solution after 25 seconds. When the temperature of the glass substrate being transported was measured 20 times in advance using the same glass substrate in advance, the temperature of the glass substrate after 25 seconds was in the range of 399 ° C to 401 ° C, and the temperature decreased due to transportation. Ranged from 8 to 10 ° C.

[0047] After immersion for 2 hours, the glass substrate was taken out together with the carrier, the remaining chemical strengthening treatment liquid was washed by an ultrasonic cleaner, and the glass substrate was taken out from the carrier.

[0048] The glass substrate was replaced and the same process was repeated 20 times to obtain 200 processed substrates. A total of 20 glass substrates were extracted from each carrier, and the flatness was measured. The flatness was measured by measuring interference fringes in the same manner as the substrate before the chemical strengthening treatment. If the flatness is smaller than 5 m, which is preferable, there will be a problem in terms of performance as a magnetic disk. Here, the evaluation criteria are

Less than lm '. © The surface accuracy is very high and the recording and playback characteristics are very good. [0049] 1-2 ^ 111: 〇 The surface accuracy is practically satisfactory, and sufficient recording / reproduction characteristics can be obtained. [0050] 2-5 ^ 111: Δ surface accuracy is insufficient and recording / reproduction characteristics are slightly There is a risk of decline

[0051] 5 111 or more: X Clearly, the surface accuracy is insufficient and sufficient recording / reproduction characteristics cannot be exhibited.

It was.

[0052] Next, for the same 20 glass substrates, the thickness of the ion-exchanged reinforcing layer was measured. The thickness of the reinforcing layer was measured by using a polarimeter SF-2C manufactured by Shinko Seiki Co., Ltd., immersed in a refractive liquid close to glass, and holding the substrate vertically. The thickness was measured. The stability of the reinforcing layer was evaluated by the standard deviation (σ) of the thickness of the reinforcing layer of the 20 glass substrates measured. If the standard deviation is less than 2 m, the chemical strengthening process is considered to have very high stability, which has almost no effect on practical performance. However, when the standard deviation is 2 m or more, the effects on the performance such as the hardness and mechanical strength of the glass substrate increase. Here, the evaluation criteria are

未満 Less than δΐη: ◎ The stability of the reinforcing layer is very high, and the recording / reproduction characteristics are very good.

[0053] 1. 5-2 _β χη: 〇 Stability with no problem in practical use and sufficient recording / reproduction characteristics.

[0054] 2 111 or more: 明らかに Apparently the stability of the reinforcing layer is insufficient and sufficient recording / reproducing characteristics cannot be exhibited.

It was.

[0055] Further, the annular bending strength of the same 20 glass substrates was measured. The annular bending strength is a measure of the occurrence of fine cracks in the glass substrate called microcracks, and was performed using a testing machine called an annular bending tester.

[0056] Specifically, the glass substrate is placed on the support base 23, the outer periphery of the glass substrate is supported in an annular shape, and the iron ball is placed on the inner periphery of the hole in the center of the glass substrate. A pressure fracture test was performed by applying force to the inner periphery of the glass substrate from above. This method is hard This is the same as the method commonly used in the industry as a strength test for disk recording media.

[0057] If the breaking strength is 150 N or more, the yield due to breakage such as cracking or chipping of the glass substrate will be good. Below that, the strength is insufficient, and the yield deteriorates due to breakage, chipping, etc. of the glass substrate. Here, the evaluation criteria are

170N or more: Excellent recording reliability with very high strength reliability.

[0058] 150-170N: 〇 This strength is practically satisfactory, and sufficient recording / reproduction characteristics can be obtained.

[0059] 120-150N: Δ Although the strength is somewhat high, the process may be damaged.

[0060] 120N or less: X The strengthened state is insufficient, and the risk of breakage due to insufficient practical strength is high.

It was.

The evaluation results of Example 1 are shown in Table 1. The average value of the thickness of the strengthening layer was 85 m, and the standard deviation of 20 glass substrates was 1.5 111, confirming that there was no practical problem with the stability of the chemical strengthening process. The average value of the flatness was also good at 1. 8 111. In addition, the average bending strength was 181.4 N, which was very good.

[0062] [Table 1]

(Example 2)

Unlike Example 1, the temperature of the preheating tank was set to 405 ° C. Ten glass substrates produced in the same manner as in Example 1 were set in one carrier and put into a preheating tank for preheating. Half an hour Thereafter, the glass substrate together with the carrier was taken out from the preheating tank, and immersed in a chemical strengthening treatment solution after 10 seconds. When the temperature of the glass substrate being transferred was measured 20 times in advance using the same glass substrate, the temperature of the glass substrate after 10 seconds was in the range of 399.5 ° C to 40.5 ° C. The temperature drop ranged from 4.5 to 5.5 ° C.

[0064] After immersion for 2 hours, the glass substrate was taken out together with the carrier, the remaining chemical strengthening treatment liquid was washed by an ultrasonic cleaner, and the glass substrate was taken out from the carrier. The other conditions are the same as in Example 1.

[0065] The same process was repeated 20 times with the glass substrate replaced, and 200 processed substrates were obtained. A total of 20 glass substrates were extracted from each carrier, and the flatness, the thickness of the reinforcing layer, and the annular bending strength were measured in the same manner as in Example 1.

[0066] The evaluation results of Example 2 are shown in Table 1. The average thickness of the reinforcing layer was 87 m, and the standard deviation of 20 glass substrates was 1.3 111, confirming that the chemical strengthening process is very stable. The average flatness was 1.9 111, which was good. Also, the average value of the ring bending strength was very good at 178.5N.

[0067] (Example 3)

A glass substrate was produced in the same manner as in Examples 1 and 2 using an aluminopolysilicate glass having a Tg of 495 ° C as the glass material.

[0068] As a chemical strengthening treatment solution, a mixed solution of potassium nitrate (KNO) and sodium nitrate (NaNO) is used.

3 3 Prepared molten salt. The mixing ratio was 2: 1 by mass. The temperature of the chemical strengthening treatment liquid was 350 ° C.

[0069] The temperature of the preheating tank was set to 350 ° C. Ten glass substrates produced in the same manner as in Examples 1 and 2 were set in one carrier and put into a preheating tank for preheating. After 30 minutes, the glass substrate together with the carrier was taken out of the preheating tank, and immersed in the chemical strengthening solution after 22 seconds. When the temperature of the glass substrate being transported was measured 20 times in advance using the same glass substrate in advance, the temperature of the glass substrate after 2 seconds was in the range of 343 ° C to 345 ° C, and the temperature drop due to transportation was It was in the range of 5-7 ° C.

[0070] After immersion for 2 hours, the glass substrate was taken out together with the carrier, the remaining chemical strengthening treatment liquid was washed by an ultrasonic cleaner, and the glass substrate was taken out from the carrier. Other conditions are real Same as Example 1 and 2.

[0071] The same process was repeated 20 times with the glass substrate replaced, and 200 processed substrates were obtained. A total of 20 glass substrates were extracted from each carrier, and the flatness, the thickness of the reinforcing layer, and the annular bending strength were measured in the same manner as in Examples 1 and 2.

[0072] The evaluation results of Example 3 are shown in Table 1. The average thickness of the reinforcing layer was 25 m, and the standard deviation of 20 glass substrates was 1. O ^ m, confirming that the chemical strengthening process is very stable. The average flatness was 1. O ^ m, which was very good. The average value of the ring bending strength was 194.2N, which was very good.

[0073] (Example 4)

Unlike Example 3, the temperature of the preheating tank was set to 330 ° C. Ten glass substrates produced in the same manner as in Example 3 were set in one carrier and put into a preheating tank for preheating.

[0074] The chemical strengthening treatment liquid was the same potassium nitrate (KNO) and sodium nitrate (NaNO) as in Example 3.

3 3

) Mixed molten salt was used. The mixing ratio was 2: 1 by mass. The temperature of the chemical strengthening treatment liquid was also set to 350 ° C. as in Example 3.

[0075] 30 minutes after the start of preheating, the glass substrate together with the carrier was taken out of the preheating tank and immersed in the chemical strengthening treatment solution after 25 seconds. When the temperature of the glass substrate being transferred was measured 20 times in advance using the same glass substrate in advance, the temperature of the glass substrate after 25 seconds was 34.5 ° C-3

It was in the range of 26 ° C, and the temperature drop due to conveyance was in the range of 4 to 5.5 ° C.

[0076] After immersion for 2 hours, the glass substrate was taken out together with the carrier, the remaining chemical strengthening treatment liquid was washed by an ultrasonic cleaner, and the glass substrate was taken out from the carrier. The other conditions are the same as in Example 3.

[0077] The same process was repeated 20 times with the glass substrate replaced, and 200 processed substrates were obtained. A total of 20 glass substrates were extracted from each carrier, and the flatness, the thickness of the reinforcing layer and the annular bending strength were measured in the same manner as in Example 3.

[0078] The evaluation results of Example 4 are shown in Table 1. The average value of the thickness of the reinforcing layer was 31 m, and the standard deviation of 20 glass substrates was 1.5 111, confirming that the stability of the chemical strengthening process has no practical problem. The flatness was also good at 1.6 111. The ring bending strength was also very good, with an average of 187.3 N. [0079] (Example 5)

Unlike Examples 3 and 4, the temperature of the preheating tank was set to 375 ° C. Ten glass substrates produced in the same manner as in Examples 3 and 4 were set in one carrier and put into a preheating tank for preheating.

[0080] The chemical strengthening treatment liquid was the same potassium nitrate (KNO) and sodium nitrate (NaN) as in Examples 3 and 4.

A mixed molten salt of O 2) was used. The mixing ratio was 2: 1 by mass. The temperature of the chemical strengthening treatment liquid was also set to 350 ° C. as in Examples 3 and 4.

[0081] 30 minutes after the start of preheating, the glass substrate together with the carrier was taken out of the preheating tank, and immersed in the chemical strengthening treatment solution 20 seconds later. When the temperature of the glass substrate being transported was measured 20 times in advance using the same glass substrate in advance, the temperature of the glass substrate after 20 seconds was in the range of 367.5 ° C to 369 ° C. The decrease was in the range of 6 to 7.5 ° C.

[0082] After immersion for 2 hours, the glass substrate was taken out together with the carrier, the remaining chemical strengthening treatment liquid was washed by an ultrasonic cleaner, and the glass substrate was taken out from the carrier. The other conditions are the same as in Examples 3 and 4.

[0083] The same process was repeated 20 times with the glass substrate replaced, and 200 processed substrates were obtained. A total of 20 glass substrates were extracted from each carrier, and the flatness, the thickness of the reinforcing layer and the annular bending strength were measured in the same manner as in Examples 3 and 4.

[0084] The evaluation results of Example 5 are shown in Table 1. The average thickness of the reinforcing layer was 33 m, and the standard deviation of 20 glass substrates was 1. l ^ m, confirming that the stability of the chemical strengthening process was very high. The average flatness was 0.9 m, which was very good. The average bending strength of the ring was very good at 198.1 N.

[0085] (Comparative Examples 1 and 2)

For comparison with Examples, Comparative Examples 1 and 2 were produced using a glass substrate of aluminosilicate glass having the same Tg of 480 ° C. as in Example 1. As the chemical strengthening treatment liquid, a mixed molten salt having a mass ratio of potassium nitrate (KNO) and sodium nitrate (NaNO) of 1: 1 as in Example 1 was used. The temperature of the chemical strengthening treatment liquid was also set to 400 ° C. as in Example 1.

[0086] In Comparative Example 1, the temperature of the preheating tank was set to 420 ° C. When the temperature of the glass substrate being transferred was measured 20 times in advance using the same glass substrate in advance, the temperature of the glass substrate after 50 seconds was in the range of 395 ° C to 405 ° C, and the temperature drop during transfer was In the range of 15-25 ° C I got it.

[0087] In Comparative Example 2, the temperature of the preheating tank was set to 450 ° C. When the temperature of the glass substrate being transferred was measured 20 times in advance using the same glass substrate in advance, the temperature of the glass substrate after 150 seconds was in the range of 380 ° C to 420 ° C, and the temperature drop during transfer was It was in the range of 30-70 ° C.

[0088] Ten glass substrates produced in the same manner as in Example 1 were set in one carrier, put into a preheating tank, and preheated. After 30 minutes, the glass substrate together with the carrier was taken out from the preheating tank and immersed in the chemical strengthening treatment solution after 50 seconds in Comparative Example 1 and after 150 seconds in Comparative Example 2. After immersion for 2 hours, the glass substrate was taken out together with the carrier, the remaining chemical strengthening solution was washed by an ultrasonic cleaner, and the glass substrate was taken out from the carrier. Other conditions are the same as in Example 1.

[0089] The glass substrate was replaced under the conditions of Comparative Examples 1 and 2, and the same process was repeated 20 times to obtain 200 processed substrates. A total of 20 glass substrates were extracted from each carrier, and the flatness, the thickness of the reinforcing layer and the annular bending strength were measured.

[0090] The evaluation results of Comparative Examples 1 and 2 are also shown in Table 1. The average thickness of the reinforcing layer is Comparative Example 1 with a force of 8 am, Comparative Example 2 is 82 μm, and the standard deviation of 20 glass substrates is Comparative Example 1 with 3 · 1 ^ m and Comparative Example 2 with 3.8 m. Yes, the stability of the chemical strengthening process was not satisfactory. The average flatness was 2.3 111 in Comparative Example 1, insufficient surface accuracy, and 5.6 m in Comparative Example 2, which was a problematic level. In addition, the average value of the annular bending strength was 135.3N in Comparative Example 1, which could be damaged in the process, and in Comparative Example 2, the strength was clearly insufficient at 106.9N.

[0091] As described above, from the results shown in Table 1, the superiority of Example 15 of the present invention over Comparative Example 12 was confirmed.

[0092] As described above, according to the present invention, the temperature drop of the glass substrate from when the glass substrate is taken out of the preheating tank to when it is immersed in the chemical strengthening treatment liquid is within 10 ° C. By transporting the glass substrate to the glass substrate, the temperature variation of the glass substrate at the time of being immersed in the chemical strengthening treatment liquid can be minimized, and a stable chemical strengthening treatment can be performed at low cost. Method for producing a glass substrate for an information recording medium, information recording A glass substrate for media and an information recording medium can be provided.

Claims

The scope of the claims

[1] In the method for manufacturing a glass substrate for an information recording medium including a step of chemically strengthening the glass substrate by immersing the glass substrate in a heated chemical strengthening treatment liquid, prior to the immersion in the chemical strengthening treatment liquid, A preheating step of heating the glass substrate to a predetermined temperature in a preheating tank;

[2] When the temperature of the glass substrate when immersed in the chemical strengthening treatment solution is TS (° C) and the temperature of the chemical strengthening treatment solution is TL (° C), TL—50 ° C≤TS 2. The method for producing a glass substrate for an information recording medium according to claim 1, wherein ≤TL + 50 ° C is satisfied.

[3] When the temperature of the glass substrate at the time of immersion in the chemical strengthening treatment liquid is TS (° C) and the temperature of the chemical strengthening treatment liquid is TL (° C), TL—30 ° C≤TS 2. The method for producing a glass substrate for an information recording medium according to claim 1, wherein ≤TL + 30 ° C is satisfied.

[4] The transporting step is a step of transporting the glass substrate in an atmosphere heated to a temperature of 50 ° C. or higher and lower than the heating temperature of the glass substrate in the preheating step. 4. The method for producing a glass substrate for an information recording medium according to any one of items 1 to 3 of the above range.

[5] An information recording medium glass substrate produced by the method for producing an information recording medium glass substrate according to any one of claims 1 to 4.

[6] An information recording medium, wherein at least a recording layer is formed on the glass substrate for information recording medium according to claim 5.

7. The information recording according to claim 6, wherein the recording layer is a magnetic layer.

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O SUO / LOOZdT / lDd 6 V Z99Z90 / 800Z OAV