JP2019195933A - Heat sensitive substrate and printed article with identification code - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-sensitive base material having an improved anti-counterfeit property, and a printed matter provided with an identification code using the same. A heat-sensitive base material 10 for printing an identification code includes a base material 11, a thermal layer 12 for thermally printing an identification code, and a hiding layer 13, and a protective layer covering at least a part of the hiding layer 13. 14 is further included. In the heat-sensitive base material 10, the concealing layer 13 and the protective layer 14 contain the same resin as a main component. The protective layer 14 contains wax in addition to the resin. The wax is contained in the protective layer 14 in a ratio of 9% or more and less than 30% with respect to the weight of the resin. [Selection diagram] Figure 1

Description

  The present invention relates to a heat-sensitive substrate for thermal printing an identification code, and a printed matter with an identification code using the same.

  Conventionally, a printed matter to which an identification code such as a one-dimensional code or a two-dimensional code is attached is known. As such printed matter, for example, in Patent Document 1, a base material, an infrared absorbing color forming layer formed on the base material, a concealing layer covering the infrared absorptive color forming layer, and a protection covering the concealing layer. An optical reading form comprising a layer is disclosed.

  Further, in Patent Document 2, as a printed matter with an identification code, a support, a heat-sensitive / pressure-sensitive recording layer for recording information provided on the support, and a heat-sensitive / pressure-sensitive recording layer are provided. An information recording medium including a picture print layer and a heat-resistant protective layer provided on the picture print layer is disclosed. In addition, Patent Document 3 discloses a printed matter including a base material, an infrared absorption pattern layer provided on the base material, and an OP clear layer covering the infrared absorption pattern layer.

JP 2013-1077 A Japanese Patent Laid-Open No. 7-96656 JP-A-9-31382

  By the way, for example, the optical reading form of Patent Document 1 includes a concealing layer printed with infrared non-absorbing ink so as to cover the identification code in order to prevent the identification code from being copied using a copying machine.

  However, Patent Document 1 mentions that an infrared non-absorbing ink is used as a hiding layer, but there is no mention of a specific material, and a description that UV mat OP varnish may be used as a protective layer. There is only.

  Therefore, in the optical reading form of Patent Document 1, the identification code is exposed when the concealing layer is removed by water, eraser, etc., and there is a problem that the printed matter with the regular identification code can be easily duplicated. .

  Patent Document 2 discloses that a polymer binder such as polyvinyl alcohol, vinyl chloride resin, vinyl acetate resin or the like is used as the pattern printing layer. Examples of the material for the protective layer include polyvinyl alcohol, hydroxycellulose, carboxymethylrose, and the like. Polyvinyl alcohol, hydroxycellulose, carboxymethylrose and the like are water-soluble resins and have a problem of low water resistance. Vinyl chloride resin, vinyl acetate resin, and the like are resins that are softened by the plasticizer used in the eraser, and are likely to be removed by continuing rubbing with the eraser.

  Further, in Patent Document 3, there is a description that the OP clear layer can use the resin constituting the vehicle, but consideration is given to whether it can withstand water resistance when it is rubbed with something like an eraser. Absent.

  Accordingly, there has been a demand for a heat-sensitive substrate that has water resistance, is difficult to be removed by an eraser, has improved anti-counterfeiting properties, and a printed matter including an identification code using the same.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a heat-sensitive substrate having improved anti-counterfeiting properties and a printed matter including an identification code using the same.

The heat-sensitive substrate according to the first aspect of the present invention is
A heat-sensitive substrate for printing an identification code having a substrate, a thermal layer for thermally printing the identification code, and a concealing layer,
A protective layer covering at least part of the concealing layer;
The concealing portion and the protective layer include the same resin as a main component,
The protective layer further includes a wax,
The wax is contained in the protective layer in a ratio of 9% or more and less than 30% based on the weight of the resin.
It is characterized by that.

The printed matter according to the second aspect of the present invention is:
The identification code is thermally printed on the heat-sensitive substrate according to the first aspect,
It is characterized by that.

  ADVANTAGE OF THE INVENTION According to this invention, a printed matter provided with the thermosensitive base material which has the forgery prevention property improved, and the identification code using the same can be provided.

It is sectional drawing which shows the outline | summary of the thermosensitive base material which concerns on embodiment. It is sectional drawing which shows the outline | summary of the printed matter which concerns on embodiment. FIG. 3A is a plan view of an identification code printed on a printed material according to the embodiment. FIG. 3B is a plan view showing an identification code and a concealing layer and a protective layer provided on the identification code. FIG. 3C is a plan view showing an identification code and a concealing layer and a protective layer provided on the identification code. Read the ink component for forming the concealing layer in Examples 1 to 3 and Comparative Examples 1 to 5, the ink component for forming the protective layer, the ratio of the solid content of the wax to the solid content of the resin binder, and the QR code. It is a figure which shows the frequency | count of reciprocation of an eraser when evaluation was completed, and evaluation.

  Hereinafter, the thermal substrate 10 according to the present embodiment and the printed matter 20 having an identification code formed using the thermal substrate 10 will be described with reference to the drawings.

(Thermosensitive substrate)
As shown in FIG. 1, the heat-sensitive substrate 10 includes a substrate 11, a thermal layer 12, a concealing layer 13, and a protective layer 14. As will be described in detail later, the printed matter 20 having the identification code 12a as shown in FIG. 2 is formed by printing the identification code 12a on the thermal layer 12 of the heat-sensitive substrate 10.

  The substrate 11 is a paper such as high-quality paper, recycled paper, paper, or a label, or a resin film such as a polyester film or a polypropylene film. A thermal layer 12 is provided on one surface of the substrate 11 (the upper surface shown in FIG. 1). In addition, as the base material 11, if the thermal layer 12 can be formed on the base material 11, the paper or resin film which consists of arbitrary materials can be used.

  As shown in FIG. 1, the thermal layer 12 is provided on one surface of the substrate 11. The thermal layer 12 is a layer in which, for example, an infrared leuco dye (electron donor) and an acidic substance (electron acceptor) are dispersed as solid fine particles in a resin binder. When the thermal layer 12 is heated with a thermal head, the fine particles are melted, and both components of the leuco dye and the acidic substance react with each other to develop a color. The colored portion absorbs infrared light, and the non-colored portion transmits or reflects infrared light. The thermal layer 12 may be formed of other materials as long as the printed portion absorbs infrared light and the portion not thermally printed has the property of transmitting or reflecting infrared light.

  The shielding layer 13 is provided on the thermal layer 12. The masking layer 13 is a layer containing a urethane-modified copolymer polyester and a color pigment. The masking layer 13 absorbs visible light and transmits infrared light having a wavelength used by the reader of the identification code. This makes it difficult for the identification code formed on the thermal layer 12 to be visually recognized, and prevents the identification code from being duplicated.

  The urethane-modified copolymer polyester contained in the masking layer 13 is a urethane-modified copolymer polyester having an aromatic polyester as a basic skeleton, a urethane-modified copolymer polyester containing an ester repeating unit and a urethane repeating unit in the skeleton, and the like. . Examples of such urethane-modified copolyesters include Byron (registered trademark) UR series manufactured by Toyobo Co., Ltd. As will be described later, the present embodiment is characterized in that the concealing layer 13 and the protective layer 14 contain the same resin.

  The hiding layer 13 contains a color pigment, thereby absorbing visible light and transmitting infrared light having a wavelength used by the reader of the identification code. The shielding layer 13 is preferably visually black.

  In addition, a well-known pigment can be used as a coloring pigment. Examples of the color pigment include Microlith Yellow3G-K / KP, Microlith Yellow2R-K / KP, Microlith Yellow3R-K / KP, “Microlith Brown2R-K, Microlith Brown5R-” manufactured by BASF Japan Ltd. K / KP, Microlith ScalletR-K / KP, Microlith RedBR-K / KP, Microlith Red4C-K, Microlith Magenta174-K, Microlith VioletB-K / KP, Microlith BlueA3R-K / KP, Microlith Examples include Blue4G-K / KP, Microlith GreenG-K / KP, and IK yellow, IK red, IK blue, and IK green manufactured by Fuji Dye Co., Ltd.

  The concealing layer 13 is provided so as to cover at least a part of the region where the identification code is thermally printed so that at least a part of the identification code formed on the thermal layer 12 can be covered. Moreover, the concealment layer 13 may cover the entire identification code or only a part thereof. Specifically, as shown in FIG. 3B, if only a part of the identification code 12 a is covered, it becomes easier for the user of the printed matter 20 with the identification code to recognize where the identification code is on the printed matter 20. In addition, although there is no limitation on the area where the concealing layer 13 covers the identification code, when the identification code covers only a part of the identification code, the copied identification code cannot be read even if the identification code is copied by a copying machine or the like. It is preferable to provide the concealing layer 13 so that

  For example, when the identification code is a QR code (registered trademark, hereinafter omitted), if the area of the portion hidden by the concealment layer 13 is too small, the QR code copied by the copier may be readable. Therefore, the concealing layer 13 is preferably present in an area of 20% or more, 30% or more, 40% or more, or 50% or more of the portion on which the identification code is printed, and is 100% or less, 80% or less, Or it is suitable to exist in an area of 60% or less. Further, the concealment layer 13 may be formed so as to conceal the QR code position detection pattern, the quiet zone, and the like so that the QR code cannot be read. The same applies to two-dimensional codes other than QR codes and one-dimensional codes.

  The masking layer 13 is formed by printing using ink for forming the masking layer 13 described later. The hiding layer 13 may be formed by printing once using the ink for forming the hiding layer 13, or may be printed twice or three times or more to increase the density of the printing portion. it can.

  The masking layer 13 is a polygon, a circle or an ellipse, a character, a pattern, or the like drawn with regular or irregular lines or points. In this case, it is preferable that the identification code positioned under the concealing layer 13 be printed so that it is difficult to visually read the identification code. The concealing layer 13 shown in FIG. 1 is drawn with regular or irregular lines or dots. Note that the masking layer 13 is not limited to being drawn with lines or dots.

  When the masking layer 13 is drawn with a line or a point, the side length of one cell of the code part of the two-dimensional code (corresponding to the colored portion of the thermal layer 12), the diameter of the line constituting the masking layer, or the minimum diameter of the point Are preferably about the same in order to make it difficult to read visually. Here, the two-dimensional code includes a code portion corresponding to the coloring portion of the thermal layer 12 and a blank portion. Specifically, the ratio of the diameter of the line constituting the concealing layer 13 or the minimum diameter of the points to the side length of one cell of the code part of the two-dimensional code (diameter of the concealing layer / side length of the two-dimensional code) is: It is preferably 0.5 or more, 0.7 or more, or 0.9 or more, and preferably 2.0 or less, 1.5 or less, or 1.2 or less.

  Further, the ratio of the area of the margin part of the identification code to the area of the entire identification code (the area of the margin part of the identification code / the area of the identification code: the margin ratio of the identification code), and there is no concealing layer on the identification code The difference between the ratio of the portion to the entire area of the identification code (the area of the portion where the concealment layer does not exist on the identification code / the area of the identification code: the nonexistence ratio of the concealment layer) is preferably about the same. Specifically, the difference (the margin ratio of the identification code−the nonexistence ratio of the hiding layer) is preferably 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less.

  As shown in FIG. 1, the protective layer 14 is provided on the concealing layer 13 so as to cover the concealing layer 13. By providing the protective layer 14 on the concealing layer 13, peeling of the concealing layer 13 is prevented and duplication of the identification code provided under the concealing layer 13 is prevented. Moreover, the area in which the protective layer 14 is provided is arbitrary, and the protective layer 14 may cover the entire concealing layer 13 as shown in FIG. Furthermore, the protective layer 14 may cover only a part of the concealing layer 13 as shown in FIG. In addition, the protective layer 14 may be provided so as to cover the entire thermal layer 12.

  Further, the shape of the protective layer 14 when viewed in plan is arbitrary. As shown in FIGS. 1 and 3B, the protective layer 14 may be formed as a solid layer, or may be a polygon, a circle or an ellipse, a character, a pattern, or the like.

  The protective layer 14 includes urethane-modified copolymer polyester and wax. When the protective layer 14 contains wax, the slipperiness on the surface of the protective layer 14 is improved, and the wear resistance is improved. However, if the ratio of the wax contained is too high, the protective layer 14 is softened and the wear resistance is lowered. On the other hand, if the ratio of the wax contained is too low, the slipperiness of the surface of the protective layer 14 is not good. Accordingly, in the protective layer 14, the ratio of the weight of the wax to the weight of the urethane-modified copolymer polyester is preferably 9% or more and less than 30%.

  The urethane-modified copolymer polyester includes a urethane-modified copolymer polyester having an aromatic polyester as a basic skeleton, a urethane-modified copolymer polyester having an ester repeating unit and a urethane repeating unit in the skeleton. Examples of such urethane-modified copolyesters include Byron (registered trademark) UR series manufactured by Toyobo Co., Ltd.

  In particular, in this embodiment, the hiding layer 13 and the protective layer 14 contain the same urethane-modified copolymer polyester as a main component. Thereby, the adhesiveness of the interface of the concealment layer 13 and the protective layer 14 improves, and the concealment layer 13 and the protective layer 14 become strong with respect to peeling, and wear resistance improves. Further, such a concealing layer 13 has good printability in gravure printing.

  In addition, as the wax, plant wax such as candelilla wax, carnauba wax, rice wax, petroleum wax such as paraffin wax, microcrystalline wax, petrolatum, synthetic hydrocarbon wax such as Fischer-Tropsch wax, polyethylene wax, Modified waxes such as montan wax derivatives, paraffin wax derivatives, and microcrystalline wax derivatives can be used.

  In this embodiment, the abrasion resistance of the protective layer 14 can be improved because the protective layer 14 contains wax. In order to improve the wear resistance of the protective layer, for example, silicone oil may be added to the protective layer. However, the silicone oil added to the protective layer is not fixed well in the coating film (protective layer) and is easily removed by the eraser. Accordingly, the silicone oil is removed and the wear resistance is easily lowered. On the other hand, when wax is added to the protective layer 14, the wax is well fixed in the coating film (protective layer), so that it is not easily removed by the eraser and the wear resistance can be maintained longer.

  In particular, the hiding layer 13 and the protective layer 14 contain the same urethane-modified copolymer polyester as a main component, so that the protective layer 14 and the hiding layer 13 can be prevented from being easily removed by the eraser. .

  A general plastic eraser is made of a polyvinyl chloride resin and includes a plasticizer for polyvinyl chloride (for example, a phthalic acid plasticizer such as dioctyl phthalate (DOP), diisononyl phthalate (DINP)). Conventionally, the concealing layer includes a vinyl chloride / vinyl acetate copolymer as a resin binder. However, the vinyl chloride / vinyl acetate copolymer has a problem that it is softened and easily removed by contact with the plasticizer contained in the eraser. On the other hand, since the urethane-modified copolyester as in this embodiment is difficult to be softened by the plasticizer contained in the eraser, it can be suppressed that the resin is softened by rubbing the eraser.

  Moreover, in this embodiment, the concealing layer 13 and the protective layer 14 contain urethane-modified copolymer polyester as a main component. Since the urethane-modified copolymer polyester is not water-soluble, the hiding layer 13 and the protective layer 14 containing the urethane-modified copolymer polyester can also have water resistance.

  Thus, since the concealing layer 13 and the protective layer 14 of this embodiment have water resistance and are not easily removed by the eraser, it is possible to provide the heat-sensitive substrate 10 having improved anti-counterfeiting properties.

  In general, considering the printability of the masking layer, the masking layer uses a resin suitable for a pigment for coloring (for example, vinyl chloride / vinyl acetate modified resin), and the protective layer uses a thermal printer. A heat-resistant resin (polyurethane or the like) is used in consideration of heat at the time of printing. On the other hand, in the heat-sensitive substrate 10 of the present embodiment, not only the wear resistance is improved by using the urethane-modified copolymer polyester in the concealing layer 13 and the protective layer 14, but also the gravure printing of the concealing layer 13 is performed. Good printability is also obtained.

(Printed matter with identification code)
The printed matter 20 with an identification code of the present invention is obtained by thermally printing the identification code on the heat-sensitive substrate 10 including the base layer 11, the thermal layer 12, the hiding layer 13, and the protective structure 14.

  Examples of the identification code include a one-dimensional code and a two-dimensional code. Specific examples of the one-dimensional code include barcodes such as CODE39, CODE128, JAN, and ITF. Specific examples of the two-dimensional code include QR code, PDF417, data matrix, CP code, MaxiCode. Etc. In the present embodiment, a QR code will be described as an example.

  Since the code part of the identification code and the concealing layer both absorb visible light and are visually the same color, when the identification code is thermally printed on the heat-sensitive substrate of the present invention, the identification code Duplication by a copying machine and visual duplication can be prevented. On the other hand, in the infrared light near 850 nm mainly used by the identification code reader, the code portion of the identification code absorbs light while the concealing layer transmits light. The reader can read the code.

  FIG. 3A is a plan view showing the identification code 12a. FIG. 3A is a plan view of a part of the printed matter 20 (identification code 12a). 3A also corresponds to a schematic diagram of how the printed material 20 is seen when read with a reader (infrared light), and FIG. 3B is a printed material when viewed visually (visible light). It also corresponds to a schematic view of 20 appearances. As shown in FIG. 3B, in the case of visual observation, the concealing layer 13 conceals a part of the identification code 12a. However, when reading using a reader, the concealing layer 13 transmits infrared light. Therefore, the identification code 12a is not concealed by the concealment layer 13, and the identification code 12a can be read.

  As described above, the concealing layer 13 and the protective layer 14 of the present embodiment have water resistance and are not easily removed by the eraser. Therefore, the heat-sensitive substrate 10 has improved anti-counterfeiting properties. Therefore, the printed matter 20 using this also has an improved anti-counterfeit property.

(Ink for forming the hiding layer)
The masking layer 13 is formed by printing using a mixed color ink containing a resin binder, a color pigment, and a solvent. The ink for forming the hiding layer 13 is a so-called solvent-based ink. The mixed color ink is, for example, a mixed color black ink exhibiting black. The mixed color black ink is prepared by mixing three color pigments of cyan, magenta, and yellow. These pigments of each color do not absorb infrared light in the wavelength region used by the identification code reader, and therefore do not absorb infrared light even when mixed, but exhibit black in the visible light region.

  The color mixture ink contains urethane-modified copolymer polyester as a resin binder. The urethane-modified copolymer polyester includes a urethane-modified copolymer polyester having an aromatic polyester as a basic skeleton, a urethane-modified copolymer polyester having an ester repeating unit and a urethane repeating unit in the skeleton. Examples of such urethane-modified copolyesters include Byron (registered trademark) UR series manufactured by Toyobo Co., Ltd. The urethane-modified copolymer polyester is suitable because it has excellent pigment dispersibility.

  The content of the resin binder in the color mixture ink for printing the concealing layer 13 is 1.0% by weight or more, 2.0% by weight or more or 3% by solid content so that an appropriate viscosity and fixability can be obtained. It is preferably 0.0% by weight or more, and more preferably 15.0% by weight or less, 10.0% by weight or less, or 8.0% by weight or less.

  As the colored pigment contained in the mixed color ink for printing the concealing layer 13, a pigment supported on a resin can be used. For example, as the coloring pigment, Microlith Yellow3G-K / KP, Microlith Yellow2R-K / KP, Microlith Yellow3R-K / KP, Microlith Brown2R-K, Microlith Brown5R-K / manufactured by BASF Japan Ltd. KP, Microlith ScalletR-K / KP, Microlith RedBR-K / KP, Microlith Red4C-K, Microlith Magenta174-K, Microlith VioletB-K / KP, Microlith BlueA3R-K / KP, Microlith Blue4G- Examples thereof include K / KP, Microlith Green G-K / KP, and the like, IK yellow, IK red, IK blue, and IK green manufactured by Fuji Dye Co., Ltd.

  The content of the color pigment in the mixed color ink for printing the hiding layer 13 is 1.0% by weight or more, 3.0% by weight or more, or 5.0% by weight or more so that an appropriate viscosity and coloring can be obtained. Preferably, it is also 30.0% by weight or less, 20.0% by weight or less, or 10.0% by weight or less.

  Solvents used in the color mixture ink include hydrocarbon solvents (for example, toluene, xylene, hexane, cyclohexane, etc.), ester solvents (for example, ethyl acetate, butyl acetate, etc.), alcohol solvents (for example, isopropyl alcohol, Butanol) and ketone solvents (for example, methyl ethyl ketone, methyl isobutyl ketone, etc.).

  The content of the solvent in the mixed color ink for printing the concealing layer 13 is 40.0% by weight or more, 45.0% by weight or more, or 50.0% by weight or more so as to obtain an appropriate viscosity. Is preferably 85.0% by weight or less, or 80.0% by weight or less.

  The masking layer 13 can be printed by a known method such as gravure printing, offset printing, flexographic printing, silk screen printing, or the like. When the above-described mixed color ink is used, the concealing layer is preferably printed by gravure printing.

  In general, considering the printability of the hiding layer, the hiding layer often uses a resin suitable for a pigment for coloring (for example, a vinyl chloride / vinyl acetate modified resin). However, when the urethane-modified copolymer polyester is used as the ink for forming the concealing layer 13 as in this embodiment, not only the wear resistance of the concealing layer 13 is improved, but also good in gravure printing. Printability is also obtained.

(Ink for forming the protective layer)
The protective layer 14 is formed by printing using an ink containing a resin binder, a wax, and a solvent. The ink for forming the protective layer 14 is a so-called solvent-based ink.

  The ink for forming the protective layer 14 contains urethane-modified copolymer polyester as a resin binder. The urethane-modified copolymer polyester includes a urethane-modified copolymer polyester having an aromatic polyester as a basic skeleton, a urethane-modified copolymer polyester having an ester repeating unit and a urethane repeating unit in the skeleton. Examples of such urethane-modified copolyesters include Byron (registered trademark) UR series manufactured by Toyobo Co., Ltd.

  The content of the resin binder in the ink for printing the protective layer 14 is 1.0% by weight or more, 2.0% by weight or more, or 3% by solid content so that an appropriate viscosity and fixability can be obtained. It is preferably 0% by weight or more, and preferably 25% by weight or less, 20% by weight or less, or 15.0% by weight or less.

  In addition, as the wax, plant wax such as candelilla wax, carnauba wax, rice wax, petroleum wax such as paraffin wax, microcrystalline wax, petrolatum, synthetic hydrocarbon wax such as Fischer-Tropsch wax, polyethylene wax, Modified waxes such as montan wax derivatives, paraffin wax derivatives, and microcrystalline wax derivatives can be used.

  In the ink forming the protective layer 14, the ratio of the solid content (parts by weight) of the wax to the solid content (parts by weight) of the resin binder is preferably 9% or more and less than 30%. By adding wax in the ink forming the protective layer 14, the wear resistance can be improved, but if the addition rate is low, the wear resistance is low, and if the addition rate is too high, the wear resistance is reduced. It is to do.

  Solvents include hydrocarbon solvents (eg, toluene, xylene, hexane, cyclohexane, etc.), ester solvents (eg, ethyl acetate, butyl acetate, etc.), alcohol solvents (eg, isopropyl alcohol, butanol, etc.), ketones Examples of the solvent include methyl ethyl ketone and methyl isobutyl ketone.

  The content of the solvent in the ink for forming the protective layer 14 is preferably 40.0% by weight or more or 45.0% by weight or more, so that an appropriate viscosity can be obtained. It is preferable that it is less than or equal to 80.0% by weight.

  The protective layer 14 can be printed by a known method such as gravure printing, offset printing, flexographic printing, silk screen printing, or the like, but the protective layer is preferably printed by gravure printing.

  In the present embodiment, the ink for forming the concealing layer 13 and the ink for forming the protective layer 14 are both solvent-based inks. For this reason, the concealment layer 13 and the protective layer 14 can be formed by carrying out gravure printing on winding roll paper.

  In order to provide the hiding layer and / or the protective layer with water resistance and improve wear resistance, it is also possible to form these layers using ultraviolet curable ink or electron beam curable ink. However, when printing ultraviolet curable ink or electron beam curable ink on take-up roll paper, a high-speed printing offset rotary press is used. Therefore, there is a problem that a large amount of paper is required to adjust the printing position and color tone, and the cost increases. In particular, a thermal paper capable of thermal printing in which the colored portion absorbs infrared light and the non-colored portion transmits or reflects infrared light is more expensive than ordinary paper and further increases the cost. There is a problem. On the other hand, in the present embodiment, gravure printing can be performed on the take-up roll paper at a low speed when adjusting the printing position and color tone, thereby preventing an increase in cost.

(Example 1)
As the heat-sensitive substrate, white thermal paper (manufactured by Oji Imaging Media Co., Ltd.) that exhibits a black color that absorbs infrared light when colored is used. On the thermal paper, the bar coater No. Ink 4 having the following composition was applied using No. 4 and dried in an oven at 70 ° C. for 1 minute to form a coating film having a thickness of 1 μm. Thereby, a concealing layer was formed. The thickness was measured using a digital micrometer M-30 (Sony Magnescale Co., Ltd.).

<Ink for forming the hiding layer>
Urethane modified copolymer polyester UR-8200
(Toyobo 30% solid content) 13.3 parts by weight Micro Resled BR-K (BASF Japan) 2.8 parts by weight Microlith Blue 4G-K (BASF Japan) 2.6 parts by weight Microlith Yellow 3G-K (BASF Japan) 2.6 parts by weight Methyl ethyl ketone 75.3 parts by weight Toluene 3.4 parts by weight

  Subsequently, a bar coater No. was formed on the concealing layer so as to cover the entire concealing layer. Ink 4 having the following composition was applied using No. 4 and dried in an oven at 70 ° C. for 1 minute to form a coating film having a thickness of 1 μm. Thereby, a protective layer was formed.

<Ink for forming the protective layer>
Urethane modified copolymer polyester UR-8200
(Toyobo solid content 30%) 42.6 parts by weight Polyethylene wax Slip aid SL-551
(Elementis Japan KK solid content 18.5%) 6.9 parts by weight Methyl ethyl ketone 30.0 parts by weight Toluene 10.7 parts by weight Ethyl acetate 9.8 parts by weight

  QR code (data: 56789, version 1, correction level: standard M, 6 dots / cell, 300 dpi) using thermal printer PX430 (Phoenix) on thermal paper on which a concealing layer and a protective layer are formed. Printed with energy 14.

  Subsequently, a rubbing test was carried out by rubbing the portion on which the QR code was printed with a plastic eraser several times. The rubbing test was performed by reciprocating an eraser (dragonfly mono PE-03A, dragonfly pencil) on a test sample (a heat-sensitive substrate having a hiding layer and a protective layer). The eraser was held by hand, and the strength with which the eraser was pressed against the test sample was strong enough to erase characters written with pencil on general paper.

  After rubbing, a copy machine was used to copy the portion on which the QR code was printed. A bizhub C754e manufactured by Konica Minolta Co., Ltd. was used as the copying machine, the copying conditions were full color, the original image quality was text / photo, and the density was set to an intermediate setting. Next, the QR code replicated by the copy machine was read by a reading device (BHT-845QW, manufactured by Denso Wave Co., Ltd.), and whether or not reading was possible was confirmed. In addition, the evaluation was good (◯) when the QR code replicated when the eraser was reciprocated 500 times or more was good (◯), and the one that was able to read the QR code less than 500 times was bad ( X).

(Example 2)
Example 1 is the same as Example 1 except that the ink for forming the protective layer was changed as follows. Specifically, for the ink for forming the protective layer, the ratio of the solid content of the polyethylene wax to the solid content of the urethane-modified copolymer polyester of the protective layer was 18%.
<Ink for forming the protective layer>
Urethane modified copolymer polyester UR-8200
(Toyobo solid content 30%) 40.0 parts by weight Polyethylene wax Slip aid SL-551
(Elementis Japan KK solid content 18.5%) 11.7 parts by weight Methyl ethyl ketone 28.0 parts by weight Toluene 10.3 parts by weight Ethyl acetate 10.0 parts by weight

(Example 3)
Example 1 is the same as Example 1 except that the ink for forming the protective layer was changed as follows. Specifically, for the ink for forming the protective layer, the ratio of the solid content of the polyethylene wax to the solid content of the urethane-modified copolymer polyester of the protective layer was 25%.
<Ink for forming the protective layer>
Urethane modified copolymer polyester UR-8200
(Toyobo solid content 30%) 38.6 parts by weight Polyethylene wax Slip aid SL-551
(Elementis Japan KK solid content 18.5%) 15.7 parts by weight Methyl ethyl ketone 27.1 parts by weight Toluene 9.7 parts by weight Ethyl acetate 8.9 parts by weight

(Comparative Example 1)
In Comparative Example 1, the composition of the ink for forming the hiding layer was changed as follows, and the protective layer was not formed. Other than that was the same as Example 1.
<Ink for forming the hiding layer>
Urethane modified copolymer polyester UR-8200
(Toyobo 30% solid content) 13.2 parts by weight Micro Resled BR-K (BASF Japan) 2.7 parts by weight Microlith Blue 4G-K (BASF Japan) 2.6 parts by weight Microlith Yellow 3G-K (BASF Japan) 2.6 parts by weight Polyethylene wax Slip aid SL-551
(Elementis Japan KK solid content 18.5%) 2.2 parts by weight Methyl ethyl ketone 70.0 parts by weight Toluene 6.7 parts by weight

(Comparative Example 2)
Example 1 is the same as Example 1 except that the ink for forming the protective layer was changed as follows. Specifically, for the ink for forming the protective layer, the ratio of the solid content of the polyethylene wax to the solid content of the urethane-modified copolymer polyester of the protective layer was 5%.
<Ink for forming the protective layer>
Urethane modified copolymer polyester UR-8200
(Toyobo solid content 30%) 48.0 parts by weight Polyethylene wax Slip aid SL-551
(Elementis Japan KK solid content 18.5%) 3.9 parts by weight Methyl ethyl ketone 28.1 parts by weight Toluene 10.0 parts by weight Ethyl acetate 10.0 parts by weight

(Comparative Example 3)
Example 1 is the same as Example 1 except that the ink for forming the protective layer was changed as follows. Specifically, for the ink for forming the protective layer, the ratio of the solid content of the polyethylene wax to the solid content of the urethane-modified copolymer polyester of the protective layer was 8%.
<Ink for forming the protective layer>
Urethane modified copolymer polyester UR-8200
(Toyobo solid content 30%) 46.0 parts by weight Polyethylene wax Slip aid SL-551
(Elementis Japan KK solid content 18.5%) 5.9 parts by weight Methyl ethyl ketone 28.1 parts by weight Toluene 10.0 parts by weight Ethyl acetate 10.0 parts by weight

(Comparative Example 4)
Example 1 is the same as Example 1 except that the ink for forming the protective layer was changed as follows. Specifically, for the ink for forming the protective layer, the ratio of the solid content of the polyethylene wax to the solid content of the urethane-modified copolymer polyester of the protective layer was 30%.
<Ink for forming the protective layer>
Urethane modified copolymer polyester UR-8200
(Toyobo solid content 30%) 37.5 parts by weight Polyethylene wax Slip aid SL-551
(Elementis Japan KK solid content 18.5%) 18.3 parts by weight Methyl ethyl ketone 26.3 parts by weight Toluene 9.4 parts by weight Ethyl acetate 8.5 parts by weight

(Comparative Example 5)
Example 1 is the same as Example 1 except that the ink for forming the masking layer was changed as follows. Specifically, the resin contained in the concealing layer was a urethane-modified copolymer polyester and a vinyl chloride / vinyl acetate modified resin.
<Ink for forming the hiding layer>
Vinyl chloride / vinyl acetate modified resin Solvein A
(Nisshin Chemical Co., Ltd.) 4.9 parts by weight Urethane-modified copolymer polyester UR-8200
(Toyobo 30% solid content) 6.1 parts by weight Micro Resled BR-K (BASF Japan) 2.1 parts by weight Microlith Blue 4G-K (BASF Japan) 1.8 parts by weight Microlith Yellow 3G-K (BASF Japan) 1.8 parts by weight Methyl ethyl ketone 60.0 parts by weight Toluene 23.3 parts by weight

  In FIG. 4, the ink component for forming the protective layer, the ink component for forming the concealing layer, and the solid content of the urethane-modified copolymer polyester of the protective layer in Examples 1 to 3 and Comparative Examples 1 to 5 The ratio (%) of the solid content of polyethylene wax to the number of times, the number of times the eraser was rubbed when the QR code was read (one reciprocation is shown as one time), and evaluation are shown. The ratio (%) of the solid content of the polyethylene wax to the solid content of the urethane-modified copolymer polyester of the protective layer was calculated from the weight parts shown in FIG. 4 and the solid content (%) in each material. In addition, in FIG. 4, about the comparative example 1, the ratio (%) of the solid content of the polyethylene wax with respect to the solid content of the urethane-modified copolymer polyester in a concealment layer is shown.

  In Examples 1 to 3, the QR code was read 500 times or more as shown in FIG. By continuing rubbing with an eraser, the thickness of the coating became thinner in the order of the protective layer and the concealing layer. However, in Examples 1 and 2, the protective layer and the concealing layer remained even after 500 round trips, and the QR code could not be read. In Example 3 as well, the QR code was finally read after 500 reciprocations. Therefore, in Examples 1 to 3, the adhesion between the hiding layer and the protective layer was good. In Examples 1 to 3, the wear resistance was also good.

  In contrast, in Comparative Example 1, wax was added to the concealing layer in the same proportion as the protective layer of Example 1, but no protective layer was provided. For this reason, the wear resistance of the hiding layer was low, and the QR code could be read when the eraser was reciprocated 100 times. Therefore, it was found that it is necessary to provide a protective layer so that the concealing layer is not easily removed.

  Next, Comparative Example 2 and Comparative Example 3 are obtained by reducing the ratio of wax in the protective layer. In Comparative Example 2, the QR code could be read when the eraser was reciprocated 300 times, and in Comparative Example 3, the eraser was reciprocated 400 times. In Comparative Example 2 and Comparative Example 3, it is considered that the wear resistance of the protective layer was lowered because the ratio of the wax contained was 5% or 8%, respectively, which was low compared to each Example.

  Further, in Comparative Example 4, the ratio of the wax in the protective layer is higher than those in Examples 1 to 3. In Comparative Example 4, the QR code could be read when the eraser was reciprocated 400 times. In Comparative Example 4, it is considered that the wear resistance of the protective layer was lowered because the percentage of wax contained was 30%, which was higher than in each Example.

  According to the above Comparative Examples 2 to 4, the ratio (%) of the solid content (parts by weight) of the polyethylene wax to the solid content (parts by weight) of the urethane-modified copolymer polyester of the protective layer is 9% or more, 30 Less than% is preferred.

  In Comparative Example 5, the components of the protective layer are the same as those of Example 1, but the resin component of the hiding layer is different from that of Example 1. According to Comparative Example 5, the wear resistance is lowered by making the resin component different, and it is understood that the urethane-modified copolymer polyester that is the resin component of Example 1 is effective in improving the wear resistance. It was.

  It was also found that the concealing layer contains the same resin as the protective layer as a main component, thereby improving the adhesion and improving the wear resistance. In addition, since the urethane modified copolymer polyester employ | adopted as resin in this embodiment has high water resistance, the protective layer and concealing layer of this embodiment are also equipped with favorable water resistance.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the specific embodiments, and the present invention includes the invention described in the claims and the equivalent scope thereof. included.

  DESCRIPTION OF SYMBOLS 10 ... Thermosensitive base material, 11 ... Base material, 12 ... Thermal layer, 12a ... Identification code, 13 ... Concealing layer, 14 ... Protective layer, 20 ... Printed matter

Claims (5)

A heat-sensitive substrate for printing an identification code having a substrate, a thermal layer for thermally printing the identification code, and a concealing layer,
A protective layer covering at least part of the concealing layer;
The concealing portion and the protective layer include the same resin as a main component,
The protective layer further includes a wax,
The wax is contained in the protective layer in a ratio of 9% or more and less than 30% based on the weight of the resin.
A heat-sensitive substrate characterized by that. The resin contained in the concealing layer and the protective layer is a urethane-modified copolymer polyester,
The heat-sensitive substrate according to claim 1. The wax is selected from vegetable wax, petroleum wax, synthetic hydrocarbon wax or modified wax,
The heat-sensitive substrate according to claim 1 or 2, wherein The wax is polyethylene wax,
The heat-sensitive substrate according to claim 1 or 2, wherein The identification code is thermally printed on the heat-sensitive substrate according to any one of claims 1 to 4.
Printed matter characterized by that.

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