JP6139142B2 - Reversible thermosensitive recording material and reversible thermosensitive recording medium - Google Patents

Description

  The present invention relates to a reversible thermosensitive recording material capable of developing color and decoloring depending on the difference in heating temperature and cooling rate after heating, and further, reversible thermosensitive material in which the reversible thermosensitive recording material is laminated on a substrate such as a card. The present invention relates to a recording medium.

  The reversible thermosensitive recording material includes a reversible thermosensitive recording layer containing a leuco dye and a developer / decolorizer on a support, and the reversible thermosensitive recording layer is heated to reversibly develop and decolorize the dye. This makes it possible to rewrite information on the reversible thermosensitive recording layer.

  A reversible thermosensitive recording material containing a leuco dye and a developer color reducing agent is used in various recording media, such as a prepaid card or an IC card in which a reversible thermosensitive recording material is laminated on a substrate such as PET-G. In a recording medium, it is used for displaying rewritable information on a card. In prepaid cards and IC cards, a protective layer formed of a thermosetting resin or an ultraviolet curable resin is provided on the reversible thermosensitive recording layer in order to protect the reversible thermosensitive recording layer provided on the card support. ing.

In a reversible thermosensitive material or a reversible thermosensitive recording medium having a reversible thermosensitive recording layer, heat is transmitted to the reversible thermosensitive recording layer and information is rewritten when the protective layer is heated by a thermal head of a printing press.
However, when the protective layer is repeatedly heated, problems such as peeling of the protective layer and the reversible thermosensitive recording layer and / or blurring of characters due to scratches generated on the protective layer have occurred.
Further, in the printing machine, the rewriting of the card is repeatedly performed, so that the thermal head is contaminated due to the components of the protective layer and scratches, and it is necessary to frequently perform maintenance and inspection.

Regarding the scratches on the protective layer, the heat resistance of the resin component forming the protective layer is improved and the hardness is increased to prevent the scratches. However, when the hardness of the protective layer is increased, there is a problem in that the bending strength of the reversible thermosensitive recording medium is lowered and the reversible thermosensitive recording medium is easily damaged.
It is known that the adhesion between the protective layer and the reversible thermosensitive recording layer can be improved by providing an anchor layer between the protective layer and the reversible thermosensitive recording layer (see Patent Document 1).

    Patent Document 1: Japanese Patent Laid-Open No. 1-133781

  An object of the present invention is to provide a reversible thermosensitive recording material with improved printing durability and a reversible thermosensitive recording medium with improved printing durability and bending strength.

The present inventors paid attention to an anchor layer provided to improve the adhesion between the reversible thermosensitive recording layer and the protective layer, and conducted extensive research. As a result, the types of resins forming the anchor layer and the anchors were investigated. It has been found that the film thickness of the layer affects the printing durability and the bending strength of the protective layer of the reversible thermosensitive recording material.
As described above, Patent Document 1 discloses providing an anchor layer in order to improve the adhesion between the reversible thermosensitive recording layer and the protective layer. The anchor layer is a reversible recording medium. There is no description suggesting that it is involved in the bending strength and the durability of the protective layer.

Furthermore, the present inventors have found that silicone oil contained as a lubricant in the protective layer contributes to the contamination of the thermal head, and have studied a protective layer that does not contain silicone oil. However, if silicone oil is not included in the protective layer, the thermal head slips, resulting in a problem that the protective layer is easily damaged and the printing durability is lowered.
In addition, when urethane acrylate was used as the protective layer, we faced the problem that it could not withstand 300 times of rewriting.
However, as a result of further investigation, (1) the resin component of the anchor layer is a compound having an isocyanate group, a glass transition temperature of more than 40 ° C. and 90 ° C. or less, and a hydroxyl value of less than 150 mgKOH / g. A resin condensed with a compound having a hydroxyl group, adjusting the film thickness, and (2) a resin for the protective layer containing an acrylate having a pentaerythritol group or a dipentaerythritol group and a urethane acrylate, and containing tetrafluoroethylene It has been found that the printing durability of the protective layer is improved by containing the resin and silica and adjusting the film thickness of the protective layer, and the present invention has been completed.

The reversible thermosensitive recording material of the present invention comprises a reversible thermosensitive recording layer containing a reversible thermosensitive composition provided on a support, a compound having an isocyanate group and a hydroxyl group provided on the reversible thermosensitive recording layer. A compound having an anchor layer made of a resin condensed with a compound having a protective layer provided on the anchor layer, and the compound having a hydroxyl group has a glass transition temperature of more than 40 ° C. and 90 ° C. or less. The hydroxyl value is less than 150 mgKOH / g, the thickness of the anchor layer is more than 0.2 μm and less than 2.5 μm, and the protective layer contains urethane acrylate and an acrylate having a pentaerythritol group or a dipentaerythritol group. It contains 3 to 11 parts by weight of tetrafluoroethylene resin and 12 to 17 parts by weight of silica with respect to 100 parts by weight of UV curable resin, and the layer thickness is 7μm less der than 4μm is, and characterized in that it does not contain a silicone oil.
The reversible thermosensitive recording medium of the present invention is characterized in that a substrate is laminated on the support of the reversible thermosensitive recording material.

The reversible thermosensitive recording material of the present invention has an effect that the surface of the protective layer is hardly scratched even when heating by a thermal head is repeated, and printing is dark.
The reversible thermosensitive recording medium of the present invention is less likely to be damaged because it has a bending strength in addition to the effect that the surface of the protective layer is hardly scratched and the printing is dark.

It is a schematic diagram which shows an example of the reversible thermosensitive recording medium of this invention.

Hereinafter, the present invention will be described in detail based on embodiments.
The reversible thermosensitive recording material of the present embodiment comprises a reversible thermosensitive recording layer containing a reversible thermosensitive composition provided on a support, a compound having an isocyanate group and a hydroxyl group provided on the reversible thermosensitive recording layer. And a protective layer provided on the anchor layer, wherein the compound having a hydroxyl group has a glass transition temperature of more than 40 ° C., 90 ° C. The hydroxyl value is less than 150 mgKOH / g, and the thickness of the anchor layer is more than 0.2 μm and less than 2.5 μm. Further, the protective layer is composed of 3 to 11 parts by weight of a tetrafluoroethylene resin and 12 to 17 parts by weight of silica with respect to 100 parts by weight of an ultraviolet curable resin containing urethane acrylate and an acrylate having a pentaerythritol group or a dipentaerythritol group. Part is contained, and the layer thickness is 4 μm or more and less than 7 μm.

  As the support, a synthetic resin sheet or synthetic paper such as polyethylene terephthalate (PET), polyacetate, polystyrene (PS), epoxy resin, polyvinyl chloride (PVC), and polycarbonate (PC) can be used. The thickness of the support is usually about 20 to 300 μm.

  A reversible thermosensitive recording layer is a resin layer containing a reversible thermosensitive composition that can form a relatively colored state due to the difference in heating temperature and cooling rate after heating. It is a layer that repeats. The reversible thermosensitive composition is composed of a leuco dye and a developer / color reducing agent. As the leuco dye and the developing / subtracting color reducing agent, conventionally known materials used in the reversible thermosensitive composition can be used.

  Examples of leuco dyes include crystal violet lactone, 3-indolino-3-p-dimethylaminophenyl-6-dimethylaminophthalide, 3-diethylamino-7-chlorofluorane, 2- (2-chlorophenylamine) -diethylaminofluoride. Oran, 2- (2-fluorophenylamino) -6-diethylaminofluor) lane, 2- (2-fluorophenylamino) -6-di-n-butylaminofluorane, 3-diethylamino-7-cyclohexylaminofluorane 3-diethylamino-5-methyl-7-t-butylfluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-p-butylanilinofluorane, 3-cyclohexylamino-6-chlorofluorane, 2-anilino 3-methyl-6- (N-ethyl-p-toluidino) -fluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-pyrrolidino-7-cyclohexylaminofluorane, 3-N-methylcyclohexyl Examples include amino-6-methyl-7-anilinofluorane and 3-N-ethylpentylamino-6-methyl-7-anilinofluorane.

  As the color reducing agent, (N- (p-hydroxyphenyl) -N′-n-octadecylthiourea, N- (p-hydroxyphenyl) -N′-n-octadecylurea, N- (p-hydroxyphenyl) -N'-n-octadecylthioamide, 4'-octadecananilide, 2-octadecylterephthalic acid, N-octadecyl (p-hydroxyphenyl) amide, N- (p-hydroxybenzoyl) -N-octadecanoylamine, N- [3- (p-Hydroxyphenyl) propiono] -N′-octadecanohydrate, N-[(p-hydroxyphenyl) methyl] -n-octadecylamide, N-[(p-hydroxyphenyl) methyl]- n-octadecylurea, N-[(p-hydroxyphenyl) methyl] -N′-n-octadecyloxamide, etc. Can be mentioned.

  The resin used for the reversible thermosensitive recording layer is preferably a thermosetting resin with good transparency and good film forming properties, such as polyvinyl chloride, vinyl chloride copolymer, vinylidene chloride copolymer, polyester, polyamide. Or resin, such as polyacrylate, can be mentioned.

  In the present invention, the resin forming the anchor layer is a polymer in which a compound having an isocyanate group and a compound having a hydroxyl group are condensed via a urethane bond. Examples of the compound having an isocyanate group include hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), and isophorone diisocyanate (IPDI).

The compound having a hydroxyl group is a resin having two or more hydroxyl groups in the molecule and capable of reacting with an isocyanate group to form a urethane bond. For example, there are polyether polyol, polyester polyol, polycarbonate polyol, polycapron lactone polyol and the like.
The compound having a hydroxyl group preferably has a glass transition temperature of more than 40 ° C. and 90 ° C. or less. More preferably, it is 60 degreeC or more and 90 degrees C or less. When the glass transition temperature is 40 ° C. or lower, the anchor layer becomes too soft, and the protective layer is easily damaged by printing. On the other hand, if the glass transition temperature exceeds 90 ° C., the anchor layer becomes too hard and the bending strength of the reversible thermosensitive recording material is lost, such being undesirable.

  The compound having a hydroxyl group preferably satisfies the condition that the hydroxyl value is less than 150 mgKOH / g. Preferably, it is the range of 3 mgKOH / g or more and 100 mgKOH / g or less. When the hydroxyl value is 150 mgKOH / g or more, the print density tends to decrease.

The thickness of the anchor layer affects the printing durability of the reversible thermosensitive recording material and the bending strength of the reversible thermosensitive recording medium. The thickness of the anchor layer is preferably more than 0.2 μm and less than 2.5 μm.
When the thickness of the anchor layer is increased, the printing durability is improved, but the printing density is reduced, and the bending strength of the reversible thermosensitive recording medium is deteriorated. That is, when the thickness is 0.2 μm or less, the printing durability is lowered, and when it is 2.5 μm or more, the printing density is decreased and the bending strength of the reversible thermosensitive recording medium is deteriorated. More preferably, it is the range of 0.3 micrometer or more and 2.0 micrometers or less.

The protective layer is a resin layer mainly composed of an ultraviolet curable resin containing urethane acrylate and an acrylate having a pentaerythritol group or a dipentaerythritol group. Further, the resin layer is formed in four parts per 100 parts by weight of the ultraviolet curable resin. It contains 3 to 11 parts by weight of a fluoroethylene resin and 12 to 17 parts by weight of silica.
Examples of the acrylate having a pentaerythritol group or a dipentaerythritol group include pentaerythritol triacrylate, pentaerythritol tetraacrylate, and dipentaerythritol hexaacrylate.
The thickness of the protective layer is preferably in the range of 4 μm or more and less than 7 μm. When the thickness is 4 μm or less, the printing durability is lowered and the thermal head is likely to be stained. When the thickness is 7 μm or more, the erasability of information recorded on the reversible thermosensitive recording layer is deteriorated, which is not preferable. The thickness of the protective layer is more preferably 4 μm or more and 6 μm or less.

  The reversible thermosensitive recording material can be produced by sequentially coating the resin forming each layer on a support with a wire bar and drying.

The reversible thermosensitive recording material may be used as a reversible thermosensitive recording medium by further laminating a base material of PET-G, PET, PVC, paper or the like alone or in combination on the lower layer of the support of the reversible thermosensitive recording material. Lamination of the support and the substrate may be performed by hot pressing, lamination, or the like.
Further, as shown in FIG. 1, an IC chip 3 and an antenna 4 may be mounted on the base material 2 under the reversible thermosensitive recording material 1.
Note that the thickness of the reversible thermosensitive recording medium may be set within a range defined in JIS X6301.

  As described above, the reversible thermosensitive recording material in which the compound forming the anchor layer satisfies the glass transition temperature condition and the hydroxyl value condition described above, and the thickness of the anchor layer satisfies the above-described condition is high in printing, Even if the heating by the head is repeated, the surface of the protective layer is hardly damaged.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.
[Test on the effect of resin component and layer thickness forming the anchor layer on the protective layer]
The following materials (1) to (4) are mixed with a paint shaker for 18 hours to form a paint, coated on a support (Mitsubishi Resin W-400J) with a wire bar, and dried at 100 ° C. for 2 minutes. Thus, a reversible thermosensitive recording layer having a dry film thickness of 11 μm was formed.

(1) Thermosetting polyacrylic resin (DIC-made WBU-1218): 25 parts by weight (2) Leuco dye (Yamamoto Kasei Blue63): 10 parts by weight (3) Reducing colorant (N- [3- (p- Hydroxyphenyl) propiono] -N′-n-docosanohydrazide): 40 parts by weight (4) XDI curing agent (Mitsui Chemicals Takenate 500): 25 parts by weight

  80 parts by weight of the compound having a hydroxyl group shown in Table 1 and 20 parts by weight of an XDI curing agent (D-110 manufactured by Mitsui Chemicals) are mixed, and coated on the reversible thermosensitive recording layer with a wire bar at 100 ° C. An anchor layer having a dry film thickness of 0.2 to 2.5 μm was formed by drying for 1 minute.

  The following materials (5) to (8) are mixed and coated on the anchor layer with a wire bar, dried at 100 ° C. for 1 minute to form a protective layer with a dry film thickness of 5 μm, and reversible thermosensitive A recording material was prepared.

(5) UV curable urethane acrylate resin (Unidic C7-164 manufactured by DIC): 88 parts by weight (6) Silica (Cycilia 436 manufactured by Fuji Silysia): 6 parts by weight (7) Polytetrafluoroethylene (manufactured by Kitamura KTL- 4N): 5 parts by weight (8) Silicone oil (AD-8719D manufactured by Fujikura Kasei): 1 part by weight

  Using the card obtained by laminating a PET-G sheet (500 μm) and PET (100 μm) so that the produced reversible thermosensitive recording material is the uppermost layer, bonding them with a hot press, and die-cutting. The evaluation of the degree of damage to the protective layer by the printing machine, the pencil hardness test, the evaluation of the printing density, and the bending strength of the reversible thermosensitive recording medium were carried out. The results are shown in Table 2.

Evaluation of the degree of damage by the printing machine was performed by repeating erasing and printing 60 times with a printing machine TH-TCP (manufactured by Okura Engineering Co., Ltd.), and measuring the depth of the scratch on the surface.
The pencil hardness was determined by measuring the surface hardness based on the pencil scratch value test method specified in JIS K 5600 5.4.
The printing density was printed by a printing machine TH-TCP (manufactured by Okura Engineering), and the printing density was measured by a Macbeth densitometer. The printing density is indicated by a circle mark of 0.9 or more and a cross mark of less than 0.9. In the visual judgment, 0.9 is used as a reference based on the knowledge that the visibility deteriorates when the print density is less than 0.9.
The bending strength of the reversible thermosensitive recording medium was evaluated based on “JIS6305-15.8 Dynamic bending strength”. A case where no abnormality was found in the protective layer was indicated by a circle, and a case where a crack occurred was indicated by a cross.

  In Experimental Examples 1 to 6 and Comparative Examples 1 to 7, the thickness of the protective layer is the same as that of the resin forming the protective layer (dry film thickness 5 μm), and the protective layer is changed by changing the resin component and the layer thickness forming the anchor layer. Printing durability (evaluation of scratch condition), pencil hardness test, printing density evaluation, and bending strength of a reversible thermosensitive recording medium were examined.

From Table 2, it can be seen that when the glass transition temperature of the compound having a hydroxyl group exceeds 40 ° C., the printing durability and the pencil hardness of the protective layer are improved. However, when the temperature exceeds 90 ° C., cracks occur in the reversible thermosensitive recording medium (see Experimental Examples 1 to 4 and Comparative Example 7).
Further, it can be seen that even when the glass transition temperature exceeds 40 ° C. and is in the following range of 90 ° C., the printing density decreases as the thickness of the anchor layer increases (see Experimental Example 6 and Comparative Example 6). Further, it can be seen that when the thickness of the anchor layer is 2.5 μm, the reversible thermosensitive recording medium is cracked (Comparative Example 6).

  The hydroxyl value is less than 150 mgKOH / g, preferably in the range of 3 mgKOH / g or more and 100 mgKOH / g or less. When the hydroxyl value is less than 150 mgKOH / g, the anchor layer is considered to have a cushioning role between the protective layer and the reversible thermosensitive recording layer.

  From the above, the glass transition temperature of the compound having a hydroxyl group is 60 ° C. or more and 90 ° C. or less, the hydroxyl value is less than 150 mgKOH / g, and the thickness of the anchor layer is more than 0.2 μm and less than 2.5 μm. When the conditions are satisfied, it can be seen that even if printing is repeated, the protective layer is hardly damaged and printing can be performed without fading.

[Test of resin component forming protective layer and printing durability, head dirt, bending strength of reversible thermosensitive recording medium]
The following materials (a) to (d) are mixed with a paint shaker for 18 hours to form a paint, coated on a support (Mitsubishi Resin W-400J) with a wire bar, and dried at 100 ° C. for 2 minutes. Thus, a reversible thermosensitive recording layer having a dry film thickness of 11 μm was formed.

(A) Thermosetting polyacrylic resin (WBU-1218 manufactured by DIC): 25 parts by weight (b) Leuco dye (Blue 63 manufactured by Yamamoto Kasei): 10 parts by weight (c) Reducing colorant (N- [3- (p- Hydroxyphenyl) propiono] -N′-n-docosanohydrazide): 40 parts by weight (d) XDI curing agent (Takenate 500 manufactured by Mitsui Chemicals): 25 parts by weight

  80 parts by weight of the compound having a hydroxyl group shown in Table 3 and XDI curing agent (D-110N, manufactured by Mitsui Chemicals): 20 parts by weight are mixed and coated on the reversible thermosensitive recording layer with a wire bar at 100 ° C. An anchor layer having a dry film thickness of 0.5 μm was formed by drying for 1 minute.

The following materials (e) to (j) are mixed in the proportions shown in Table 4, diluted with toluene (the solid content concentration is adjusted to 20%), coated on the anchor layer with a wire bar, and 100 After drying at a temperature of 1 ° C. for 1 minute, ultraviolet ray irradiation (160 W / cm, 30 m / min, 1 pass) was performed to cure, and a protective layer having a surface dry film thickness of 5 μm was formed to prepare a reversible thermosensitive recording material.
In addition, 100 parts by weight of DIC Unidic C7-164 was used only for the protective layer of Comparative Example 18.
Moreover, the blending ratio of (g) to (j) is a ratio with respect to 100 parts by weight which is the sum of (e) and (f).

(E) UV curable urethane-acrylate resin: V-4018 made by DIC
(F) UV curable pentaerythritol tetraacrylate resin: PE-4A manufactured by Kyoeisha Chemical Co., Ltd.
(G) Silica: Cicilia 436 manufactured by Fuji Silysia
(H) Polytetrafluoroethylene (indicated as PTFE in Table 3): Kitamura KTL-4N
(I) Silicone oil: AD8719D manufactured by Fujikura Kasei
(J) Photopolymerization initiator (Irgacure 184 manufactured by BASF)

  A reversible thermosensitive recording medium obtained by laminating a PET-G sheet (500 μm) and PET (125 μm) so that the produced reversible thermosensitive recording material is the uppermost layer, bonding them with a hot press, and die cutting. (Hereinafter, referred to as a card), the protective layer was evaluated in four items: printing durability, head contamination, erasability, and cracking due to bending of the card. The results are shown in Table 4.

In addition, printing durability, head stains, erasability, and cracks due to card bending were evaluated as follows.
For printing durability, using a printing machine TH-TCP (manufactured by Okura Engineering Co., Ltd.), printing and erasing were repeated 300 times. When the reversible thermosensitive recording layer was exposed, x, and when it was not exposed, ○ evaluated.

  The head stain was evaluated as x when the characters were faint in the 300th printing for printing durability, and evaluated as o when the characters were printed normally.

  The erasability of the place where there was no surface roughness and no printing on the protective layer after printing and erasing once using a printing machine TH-TCP (manufactured by Okura Engineering). The difference in surface roughness was used as an index. The case where the difference between the surface roughness Ra value of the printed part and the surface roughness Ra value of the unprinted part is 0.03 or less is indicated by ◯, and the case where it exceeds 0.03 is indicated by ×. When the surface roughness Ra value exceeds 0.03, if the light is reflected on the card and tilted obliquely and the surface is observed, the trace of the thermal head will be seen and the appearance will deteriorate. The surface roughness Ra value was measured based on JIS X6305.2 “5.3 Surface roughness of magnetic stripe”.

  Cracks due to card bending were tested in accordance with JIS X6305-1 “5.8 Dynamic Bending Force (Bending Characteristics)”, and a case where there was no abnormality was indicated by a circle, and a case where a crack was present was indicated by a cross.

From Table 4, it can be seen that when all of the following conditions (1) to (7) are not satisfied, the evaluation value of any of printing durability, head contamination, erasability, and cracking due to card bending is inferior.
(1) The glass transition temperature of the compound having a hydroxyl group of the anchor layer is more than 40 ° C. and 90 ° C. or less,
(2) The hydroxyl value of the compound having a hydroxyl group of the anchor layer is less than 150 mgKOH / g,
(3) The resin of the protective layer contains an acrylate having a pentaerythritol group or a dipentaerythritol group and a urethane acrylate,
(4) The resin of the protective layer contains 3 to 11 parts by weight of a tetrafluoroethylene resin with respect to 100 parts by weight of the ultraviolet curable resin,
(5) 12 to 17 parts by weight of silica is contained in the protective layer resin;
(6) The thickness of the protective layer is 4 μm or more and less than 7 μm, and (7) The protective layer does not contain silicone oil.

Claims (2)

A reversible thermosensitive recording layer containing a reversible thermosensitive composition provided on a support, and a resin obtained by condensing a compound having an isocyanate group and a compound having a hydroxyl group provided on the reversible thermosensitive recording layer. A laminate having an anchor layer and a protective layer provided on the anchor layer,
Compounds having a pre-Symbol hydroxyl, glass transition temperature exceeds 40 ° C., and at 90 ° C. or less, the hydroxyl value is less than 150 mgKOH / g,
Thickness before Symbol anchor layer is greater than 0.2 [mu] m, less than 2.5 [mu] m,
Before Symbol protective layer is 3 to 11 parts by weight of polytetrafluoroethylene resin with respect to 100 parts by weight of ultraviolet curing resin containing acrylate having a urethane acrylate and pentaerythritol group or a dipentaerythritol group and silica 12-17 parts by weight and contained, the layer thickness is 4μm or more, der less than 7μm is, and does not contain silicone oil, the reversible thermosensitive recording material. A reversible thermosensitive recording medium comprising a substrate laminated on the support of the reversible thermosensitive recording material according to claim 1 .

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