JPH0648024A - Rewritable thermal recording medium - Google Patents

Abstract

PURPOSE:To extend a transparency creating temperature range and thereby improve the transparency of a recording layer by providing a recording layer which contains an organic low molecule, an alicyclic dicarboxylate compound and an aliphatic dicarboxylate compound in a resin material, on a support. CONSTITUTION:A recording layer in which an organic low molecule substance such as higher alcohol, an alicyclic dicarboxylate compound and an aliphatic dicarboxylate compound are blended in a resin material, is laminated on a support of transparent plastic film, to manufacture a rewritable thermosensitive recording medium. In concrete, an anchor layer 2, an optical reflective metal (aluminum) layer 3, an adhesive layer 4, a recording layer 5 and a protecting layer 6 are sequentially laminated on a support of transparent polyester sheet to manufacture a thermal recording medium. This thermal recording medium allows the heating temperature of a heating means such as a thermal head to be set within a transparency creating temperature range at high speed. Thus it is possible to form a transparent image on a white background or an opaque image on a transparent background easily.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rewritable thermosensitive recording medium provided with a recording layer whose transparency reversibly changes depending on temperature, and particularly, the transparency temperature range thereof is dramatically expanded. The present invention relates to a heat-sensitive recording medium which can be improved in transparency of a recording layer and has a high contrast between an image portion and a non-image portion.

[0002]

2. Description of the Related Art As a thermal recording medium of this type, Japanese Patent Laid-Open No. 55-154198 and US Pat.
As described in Japanese Patent Publication No. 3, a recording layer containing a thermoplastic resin such as polyvinyl chloride and an organic low molecular weight substance such as a higher fatty acid dispersed in the resin as a main component is provided on a support. The structure is known.

This heat-sensitive recording medium is constructed by skillfully utilizing the property that the light absorption characteristic (light scattering property) of the recording layer reversibly changes depending on temperature. That is, this recording layer has a specific temperature T near room temperature.
_It has two state transition temperatures T ₁ and T ₂ (provided that T ₁ <T ₂ ) at a temperature higher than ₀ , and becomes cloudy when the recording layer is heated to T ₂ or higher and held and then cooled to T ₀ or lower. When the recording layer in the cloudy state is heated to T ₁ or more and less than T ₂ and then cooled to T ₀ or less, the light scattering property is decreased while the light scattering property increases to the maximum light shielding state. It becomes transparent. Moreover, the maximum light-shielding state and the transparent state of the recording layer can be stably maintained under a temperature condition of T ₀ or less, and these states can be reversibly changed. When set to, the recording medium can be used as a rewritable recording medium that can be differentiated from the other state.

Since the recording layer can be made transparent in the temperature range from T ₁ to T ₂ , this temperature range is referred to as a transparentization temperature range.

By the way, in the conventional thermal recording medium of this kind, the transparentization temperature range is very narrow, about 2 to 4 ° C., and therefore, a part or the whole of the recording layer in the cloudy state is T ₁ or more and T ₂ or more. There is a problem in that it is extremely difficult to control the temperature when it is made transparent by heating it below the temperature.

Therefore, in Japanese Patent Laid-Open No. 1363/1990, at least one of higher fatty acids having 16 or more carbon atoms and aliphatic saturated dicarboxylic acid and its derivative are contained in the organic low molecular weight substance dispersed in the resin base material. In addition, in Japanese Patent Laid-Open No. 3-2089, the number of carbon atoms in the organic low molecular weight substance is 1
A means for expanding the above-mentioned clearing temperature range by applying at least one kind of higher fatty acid having 6 or more and at least one kind of saturated aliphatic dicarboxylic acid having 20 or more carbon atoms has been proposed.

[0007]

By applying these means, it is certainly possible to slightly expand the transparentization temperature range.

However, as is clear from the embodiment disclosed in Japanese Patent Laid-Open No. 3-2089, the transparentizing temperature range expanded by these means is still narrow at about 20 ° C. at the maximum, and rewriting is repeated. When a thermosetting resin is used as the resin base material to improve resistance, the clearing temperature range is 8 as shown in the comparative example described below.
There is a problem that the temperature is narrowed to about 0 ° C., and due to this, there are problems as described below. That is, in this type of thermal recording medium, it is theoretically possible to form an image in a transparent state on the basis of a white background (that is, a cloudy state) by using a heating means such as a thermal head. Since the temperature range is still narrow and it is practically difficult to set the heating temperature of the thermal head or the like at a high speed within the above temperature range, it is usually difficult to sense heat between the heating rollers that are set to an appropriate temperature within the above-mentioned clearing temperature range. After inserting the recording medium to make the recording layer uniformly transparent, T ₂
A method of forming an image in a cloudy state on the basis of a transparent background (that is, a transparent state) by selectively making the cloudy by using a heating means such as a thermal head heated as described above is adopted.

Therefore, the recorded image formed by such a method is a black-and-white inverted image (so-called negative pattern) as compared with a normal image original composed of a black image on a white base. There is a fatal problem that the applicable range of the thermal recording medium of some kinds is limited to a special field.

When the transparent temperature range is expanded by the means disclosed in the above publications, it is clear from the results of the examples described in the publications that the ratio of the aliphatic saturated dicarboxylic acid to the higher fatty acid is mixed. When is low, the temperature range to which it is expanded becomes small.

On the other hand, as the blending ratio of the aliphatic saturated dicarboxylic acid to the higher fatty acid increases, the clarification temperature range broadens, but on the other hand, the blending ratio of the higher fatty acid decreases as the aliphatic saturated dicarboxylic acid increases. The white turbidity of the recording layer also tends to decrease (see Table 2 of JP-A-3-2089), and the contrast between the white turbid portion and the transparent portion (corresponding to the image portion and the non-image portion) is sufficient. There was a problem that could not be removed.

Under such a technical background, the present inventors have already proposed a thermosensitive recording medium which can dramatically expand the above-mentioned transparentization temperature range and which is unlikely to reduce the contrast between the image portion and the non-image portion. (See Japanese Patent Application No. 3-304690).

The present invention relates to the improvement of the invention described in the specification of Japanese Patent Application No. 3-304690, and its object is to increase the transparency temperature range and improve the transparency of the recording layer. Another object of the present invention is to provide a thermosensitive recording medium which can further enhance the contrast between the image portion and the non-image portion.

[0014]

That is, the invention according to claim 1 is based on a resin base material and an organic low molecular weight substance dispersed in the resin base material as main components, and its transparency is reversible depending on temperature. Assuming a rewritable heat-sensitive recording medium having a recording layer that changes to, an alicyclic dicarboxylic acid compound and an aliphatic dicarboxylic acid compound are added to an organic low molecular weight substance dispersed in a resin matrix. It is characterized by.

In such a technical means, as the resin base material forming a part of the recording layer, organic low molecular weight substances, alicyclic dicarboxylic acid compounds and aliphatic dicarboxylic acid compounds described below and their refractive indices are Thermoplastic resins having good transparency and good mechanical strength and film forming ability, which are close to each other and are not compatible with each other, and specific examples thereof include polyester resins such as saturated copolyesters;
Polyvinyl chloride resin; vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-acrylate copolymer, etc. Polymers; polyvinylidene chloride resins; vinylidene chloride-vinyl chloride copolymers, vinylidene chloride-acrylonitrile copolymers and other vinylidene chloride copolymers; polyamide resins; silicone resins; polyacrylates or polymethacrylate resins or copolymers thereof There are coalesces and the like, and these can be applied alone or as a mixture of two or more kinds.

Further, it is composed of a hydroxyl-modified vinyl chloride-vinyl acetate copolymer and an isocyanate compound, and the refractive index of the organic low molecular weight substance, the alicyclic dicarboxylic acid compound and the aliphatic dicarboxylic acid compound are close to each other, and they are similar to each other. A thermosetting resin that is not compatible with and has good transparency can also be applied.

Here, the above hydroxyl-modified vinyl chloride-
The vinyl acetate copolymer means a vinyl chloride-vinyl acetate copolymer in which a hydroxyl group (-OH) is introduced in an amount of about 0.5 to 10% by weight, and for example, vinyl chloride-vinyl acetate-vinyl alcohol copolymer. Polymer and vinyl chloride
Examples thereof include vinyl chloride-vinyl acetate-hydroxyl group-containing alkyl acrylate copolymers such as vinyl acetate-hydroxyalkyl acrylate copolymers. On the other hand,
The isocyanate compound that reacts with the hydroxyl group of the hydroxyl-modified vinyl chloride-vinyl acetate copolymer to form the thermosetting resin that is the resin matrix has an isocyanate group (-N = C = O), and is generally An isocyanate compound widely used as a cross-linking agent can be applied, for example, toluylene diisocyanate, dimer of 2,4 toluylene diisocyanate, naphthylene-1,5-diisocyanate, o-toluylene diisocyanate. , Diphenylmethane diisocyanate, triphenylmethane triisocyanate, tris- (p-isocyanatophenyl) thiophosphite, polymethylene polyphenyl isocyanate, polyfunctional aromatic isocyanate, aromatic polyisocyanate, polyfunctional aliphatic Isocyanate, hexamethylene diisocyanate Diisocyanate, trimethylhexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, and the like.

Next, the organic low molecular weight substance dispersed in the resin base material contains at least one atom of oxygen, sulfur, nitrogen and halogen, has a carbon number of 10 to 40 and a molecular weight of 100 to 100. 700 and a melting point of 50-
Organic compounds in the range of 150 ° C. may be mentioned, and specific examples thereof include higher alcohols such as alkanols, carkanediols, halogenalkanols and halogenalkanediols; higher aliphatic amines; alkanes, alkenes, alkynes and halogen-substituted products thereof. Cyclic compounds such as cycloalkanes, cycloalkenes, cycloalkynes; saturated carboxylic acids, unsaturated monocarboxylic acids, dicarboxylic acids or their esters, amides, ammonium salts; saturated or unsaturated halogen fatty acids or their esters, amides , Ammonium salts; acrylic carboxylic acids or their esters, amides, ammonium salts; halogenallyl carboxylic acids or their esters, amides, ammonium salts; thioalcohols or their carboxylic acid esters;
There are thiocarboxylic acids or their esters, amides, ammonium salts and the like, and these can be used alone or in combination of two or more kinds.

On the other hand, the alicyclic dicarboxylic acid compound added to the organic low molecular weight substance dispersed in the resin base material is compatible with the above organic low molecular weight substance and compatible with the resin base material. Examples of such compounds include 1,1-cyclopropanedicarboxylic acid (mp140 ° C.), 1,2-ciscyclopropanedicarboxylic acid (mp139 ° C.), 1,2-transcyclopropanedicarboxylic acid (mp175 ° C.), etc. Propane dicarboxylic acids; 1,1-cyclobutanedicarboxylic acid (mp157 ° C), 1,2-ciscyclobutanedicarboxylic acid (mp138 ° C), 1,2-transcyclobutanedicarboxylic acid (mp137 ° C), 1,3-ciscyclobutanedicarboxylic acid (Mp143 ° C), 1,3-transcyclobutanedicarboxylic acid (mp171 ° C), etc. Bon acids; 1,1-cyclopentane dicarboxylic acid (mp184 ℃), 1,2- cis-cyclopentane dicarboxylic acid (mp140 ℃), 1,2- trans-cyclopentane dicarboxylic acid (mp181 ℃), 1,
3-cis cyclopentane dicarboxylic acid (mp121
C), 1,3-trans cyclopentane dicarboxylic acid (mp 188 C) and the like cyclopentane dicarboxylic acids;
1,2-ciscyclohexanedicarboxylic acid (mp170
° C), 1,2-transcyclohexanedicarboxylic acid (mp310 ° C), 1,3-ciscyclohexanedicarboxylic acid (mp187 ° C), 1,3-transcyclohexanedicarboxylic acid (mp148 ° C), 1,4-ciscyclohexanedicarboxylic acid (Mp192 ° C.), cyclohexanedicarboxylic acids such as 1,4-transcyclohexanedicarboxylic acid (mp221 ° C.), and the like.

The invention according to claim 2 applies one or more alicyclic dicarboxylic acid compounds selected from these material groups.

That is, the invention according to claim 2 is claim 1
Assuming the heat-sensitive recording medium according to the above, the alicyclic dicarboxylic acid compound is 1,2-ciscyclopropanedicarboxylic acid, 1,2-transcyclopropanedicarboxylic acid,
1,2-ciscyclobutanedicarboxylic acid, 1,2-transcyclobutanedicarboxylic acid, 1,2-ciscyclopentanedicarboxylic acid, 1,2-transcyclopentanedicarboxylic acid, 1,3-ciscyclobutanedicarboxylic acid, 1,3 -Transcyclobutanedicarboxylic acid, 1,
3-cis cyclopentane dicarboxylic acid, 1,3-trans cyclopentane dicarboxylic acid, 1,2-cis cyclohexane dicarboxylic acid, 1,2-trans cyclohexane dicarboxylic acid, 1,3-cis cyclohexane dicarboxylic acid, 1,3-trans Cyclohexanedicarboxylic acid,
1 selected from 1,4-ciscyclohexanedicarboxylic acid, 1,4-transcyclohexanedicarboxylic acid, 1,1-cyclopropanedicarboxylic acid, 1,1-cyclobutanedicarboxylic acid, and 1,1-cyclopentanedicarboxylic acid It is characterized by being composed of one or more alicyclic dicarboxylic acids. When a mixture of a cis-type alicyclic dicarboxylic acid compound and a trans-type alicyclic dicarboxylic acid compound is applied, the same type of cis-type alicyclic dicarboxylic acid compound and trans-type alicyclic dicarboxylic acid compound are used. An acid compound may be applied, or different types of cis-type alicyclic dicarboxylic acid compounds and trans-type alicyclic dicarboxylic acid compounds may be applied.

As the aliphatic dicarboxylic acid compound which is added to the organic low molecular weight substance in the resin matrix together with the alicyclic dicarboxylic acid compound to improve the transparency of the recording layer, succinic acid, glutaric acid and adipic acid are used. , Pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, heptadecanedioic acid,
Octadecanedioic acid, nonadecanedioic acid, eicosanedioic acid,
Heneicosandioic acid, docosandioic acid, tricosandioic acid,
Examples thereof include tetracosanedioic acid, pentacosanedioic acid, and hexacosanedioic acid.

The above resin material, organic low molecular weight substance,
For alicyclic dicarboxylic acid compounds and aliphatic dicarboxylic acid compounds, methyl ethyl ketone, methyl isobutyl ketone, chloroform, ethanol, benzene,
An organic low-molecular substance, an alicyclic dicarboxylic acid, which is dissolved in an organic solution of toluene, tetrahydrofuran, carbon tetrachloride, etc. and is applied on the support described below and dried, or is uniformly compatible Acid compounds and aliphatic dicarboxylic acid compounds are finely dispersed in a solution in which the above resin material is dissolved to obtain a dispersion liquid, and the dispersion liquid is coated on a support and dried to be temperature-dependent. The recording layer whose transparency changes reversibly is formed.

In this case, the alicyclic dicarboxylic acid compound is added to the organic low molecular weight substance dispersed in the resin base material, and the addition of the alicyclic dicarboxylic acid compound allows the organic low molecular weight substance and the alicyclic dicarboxylic acid compound to be added. The eutectic temperature of the formula dicarboxylic acid compound and the aliphatic dicarboxylic acid compound when heated is higher than that of the organic low molecular weight substance alone, and the degree of increase is higher than those of JP-A-2-1363 and JP-A-2-1363. 3-2089
Since it is larger than the conventional method described in the publication, the transparentization temperature range can be dramatically expanded.

Although the transparency of the recording layer composed of the resin base material or the organic low molecular weight substance may be slightly deteriorated due to the addition of the alicyclic dicarboxylic acid compound, it is possible that Since the aliphatic dicarboxylic acid compound that improves the transparency of the recording layer is added together with the alicyclic dicarboxylic acid compound, the transparency of the recording layer does not decrease.

Therefore, the transparency temperature range can be dramatically expanded, the transparency of the recording layer can be improved, and a high contrast between the image portion and the non-image portion can be achieved.

The addition ratio of the alicyclic dicarboxylic acid compound is set to 2% by weight to 30% by weight with respect to the total amount of the alicyclic dicarboxylic acid compound, the organic low molecular weight substance and the aliphatic dicarboxylic acid compound. It is desirable to do.
If it is 2% by weight or less, the addition action of the alicyclic dicarboxylic acid compound is insufficient, and the transparency temperature range cannot be sufficiently expanded. On the other hand, if it exceeds 30% by weight, the transparency temperature range is significantly expanded. This is because the white turbidity of the recording layer decreases with an increase in the proportion of the cyclic dicarboxylic acid compound.

The invention according to claim 3 is based on such a technical basis.

That is, the invention according to claim 3 is claim 1
Or, on the premise of the heat-sensitive recording medium according to 2, the mixing ratio of the alicyclic dicarboxylic acid compound is 2% by weight to 30 based on the total amount of the alicyclic dicarboxylic acid compound, the organic low molecular weight substance and the aliphatic dicarboxylic acid compound. It is characterized by being set to weight%.

The compounding ratio of the organic low molecular weight substance to which the alicyclic dicarboxylic acid compound and the aliphatic dicarboxylic acid compound are added and the resin base material is 1: 2 by weight.
It is set to 1: 6.

As described above, in this technical means, the above-mentioned JP-A-2-1363 and JP-A-3-2089 are used.
It has an advantage that the transparentization temperature range can be drastically expanded as compared with the conventional means disclosed in Japanese Patent Laid-Open Publication No. H09-242, and the alicyclic dicarboxylic acid compound content is from 2% by weight to 30% by weight.
Even if the amount is as small as about 10% by weight, it functions sufficiently, so that the white turbidity of the recording layer does not easily decrease, and the transparency of the recording layer can be prevented from decreasing due to the action of the aliphatic dicarboxylic acid compound.

Here, for the purpose of improving the optical properties of the recording layer, a dye, an ultraviolet absorber or an infrared absorber may be added to the recording layer in the same manner as in the conventional case, and the plasticity and surface slippage of the recording layer may be added. For the purpose of improving the property, a plasticizer, a surface active agent, etc. may be added as in the conventional case.

Further, in order to improve the printability and the repeated rewriting resistance, a protective layer made of a fluorine-based resin or a silicone-based resin may be provided on the recording layer as in the conventional case. In this case, instead of the fluorine-based resin such as an organic material to be applied is dissolved or dispersed in an organic solvent, terminal or side chain acryloyl group (-OOC-CH = CH ₂₎ or methacryloyl group (-OOC-CH Alternatively, an acrylic resin obtained by irradiating an aqueous emulsion containing an acrylic oligomer having ═CHCH ₃ ) as a main component with ultraviolet rays or an electron beam to cure may be applied. By applying such an aqueous material as the material for the protective layer, there is no risk that oligomers, aqueous solvents, etc. will penetrate into the recording layer during the formation of the protective layer, as compared with the case where the above organic material is applied. Therefore, there is an advantage that the initial dispersion state of the organic low molecular weight substance in the recording layer can be maintained before and after the formation of the protective layer.

Here, as the acrylic oligomer, those modified with urethane, polyester, polyether, epoxy, silicone or the like as shown below can be applied. Hereinafter, each will be described.

(1) Polyurethane Acrylate Polyurethane acrylate means polyol (polyester type and polyether type), diisocyanate,
A polymer (oligomer) obtained by reacting an acrylate or a methacrylate having a hydroxyl group,
For example, the following compounds may be mentioned.

[0036]

[Chemical 1] (2) Polyester acrylate Polyester acrylate is a polymer (oligomer) obtained by introducing an acryloyl group or a methacryloyl group into a polyester synthesized from a polyhydric alcohol and a polybasic acid.
Then, for example, the following compounds are applicable.

[0037]

[Chemical 2] (3) Epoxy acrylate Epoxy acrylate is a polymer (oligomer) synthesized by reacting an epoxy resin with acrylic acid or methacrylic acid, for example, bisphenol A as shown below.
Type, F type, S type, phenol novolac type, alicyclic epoxy acrylate or epoxy methacrylate.

[0038]

[Chemical 3] (4) Silicone Resin Acrylate Silicone resin acrylate is a polymer (oligomer) obtained by introducing an acryloyl group or a methacryloyl group into polysiloxane, and the following compounds can be applied, for example.

[0039]

[Chemical 4] Here, the above-mentioned hydroxyl-modified vinyl chloride-vinyl acetate copolymer and an isocyanate compound are used as the resin base material of the recording layer, and the organic low-molecular substance and the alicyclic dicarboxylic acid compound and the aliphatic dicarboxylic acid compound are combined. When a thermosetting resin with good transparency that has a similar refractive index and is not compatible with these is applied, this thermosetting resin has excellent heat resistance and mechanical strength and is suitable for substrates such as plastic sheets and paper. Since the adhesiveness is also good, thermal deterioration of the recording layer is less likely to occur compared to when a thermoplastic resin is applied to the resin base material, and the initial dispersion state of the organic low molecular weight substance in the recording layer can be maintained for a long time. It will be possible. Therefore, there is an advantage that the white turbidity can be prevented from lowering due to the heat deterioration of the recording layer, the rewriting resistance thereof can be improved, and the formation of the protective layer can be omitted.

However, when a thermosetting resin is applied as the resin base material of the recording layer, the clearing temperature is higher than that when a thermoplastic resin is applied, as is clear from the results of the comparative examples described below. This has the adverse effect of narrowing the range.

However, in this technical means, the transparentization temperature range can be dramatically expanded as compared with the conventional method. Therefore, even if the transparentization temperature range is narrowed due to the application of the thermosetting resin, the transparent method of the conventional method is used. The temperature is still higher than the temperature range, so that it does not affect the characteristics of the thermal recording medium.

The invention according to claim 4 is based on such a technical basis, and on the premise of the heat-sensitive recording medium according to claim 1, 2 or 3, the resin base material is a hydroxyl-modified vinyl chloride-acetic acid. It is characterized by comprising a thermosetting resin composed of a vinyl copolymer and an isocyanate compound.

Further, in this technical means, the same support as the conventional one can be applied as it is to the support for the recording layer and the like, and for example, a transparent plastic film or sheet, a colorant such as a dye or a pigment is mixed. A plastic film or sheet, a plastic film or sheet on which a colored layer composed of paint or ink containing a dye or pigment is laminated, and a light-reflecting metal layer of aluminum, tin, silver, magnesium, chromium, nickel or the like. The provided plastic film, sheet or paper can be used. Specific examples of the plastic film or sheet include materials such as polyethylene terephthalate, polyethylene naphthalate, polycarbonate, and polyparabanic acid, which are excellent in heat resistance, transparency, and mechanical strength.

When a light-reflecting metal layer is formed on the above-mentioned plastic film, sheet, paper or the like, in order to strengthen the adhesive force between this light-reflecting metal layer and the recording layer formed thereon. An adhesive layer composed of an adhesive is interposed, and as the adhesive, a conventionally applied polyester resin, acrylic polyol resin, vinyl chloride-vinyl acetate copolymer resin having a phosphoric acid ester group, or the like can be applied. In addition to these materials, a thermoplastic polyparabanic acid resin represented by the following structural formula, which is excellent in heat resistance, solvent resistance, and adhesion to a metal, may be applied. That is, when this polyparabanic acid resin is applied, since this resin has almost no heat shrinkage effect when forming the adhesive layer, cracks and pinholes are not formed in the light-reflecting metal layer, and the reflection density is reduced. Can be prevented, and
This resin is dissolved in an organic solvent such as tetrahydrofuran,
Since it has a property that it is difficult to swell, there is almost no possibility that the organic solvent for forming the recording layer will penetrate into the adhesive layer, and it is possible to further prevent the reduction of the reflection density in the light-reflecting metal layer. Since it has excellent adhesion to a metal, it has an advantage that the peeling phenomenon of the adhesive layer from the light-reflecting metal layer can be prevented.

[0045]

[Chemical 5]

[0046]

According to the inventions according to claims 1 and 2, the alicyclic dicarboxylic acid compound and the aliphatic dicarboxylic acid compound are added to the organic low molecular weight substance dispersed in the resin base material. Organic low molecular weight substance by the addition of the formula dicarboxylic acid compound, the temperature at which the alicyclic dicarboxylic acid compound and the aliphatic dicarboxylic acid compound are eutectic when heated is higher than that of the organic low molecular weight substance alone, and, Since the degree of increase is larger than that of the conventional method described in JP-A-3-2089, it is possible to dramatically expand the transparentization temperature range, and the addition of the aliphatic dicarboxylic acid compound makes the recording layer. Transparency is improved, and high contrast between the image portion and the non-image portion can be achieved.

On the other hand, according to the invention of claim 3, the addition ratio of the alicyclic dicarboxylic acid compound is 2% by weight based on the total amount of the alicyclic dicarboxylic acid compound, the organic low molecular weight substance and the aliphatic dicarboxylic acid compound. % To 30% by weight, and the transparentization temperature range is sufficiently expanded even if the addition ratio of the alicyclic dicarboxylic acid compound is low as compared with the conventional method described in JP-A-3-2089. Therefore, it is possible to prevent a decrease in the white turbidity of the recording layer due to the lower addition ratio of the alicyclic dicarboxylic acid compound.

Further, according to the invention of claim 4, the resin base material is composed of a thermosetting resin comprising a hydroxyl-modified vinyl chloride-vinyl acetate copolymer and an isocyanate compound, and the thermosetting resin is Since it has excellent heat resistance and mechanical strength, and also has good adhesiveness to a support such as a plastic sheet or paper, thermal deterioration of the recording layer is less likely to occur than when a thermoplastic resin is applied to the resin base material. Therefore, since it is possible to prevent the white turbidity from being lowered due to the heat deterioration of the recording layer, it is possible to improve the repeated rewriting resistance and it is possible to omit the formation of the protective layer.

[0049]

EXAMPLES Examples of the present invention will be described in detail below.

The parts and percentages of the blending components described in Examples and Comparative Examples are all parts by weight and% by weight.

[Example 1] A thermosensitive recording medium according to this example, as shown in Fig. 1, is a support 1 made of a transparent polyester sheet, an anchor layer 2 provided on the support 1, and an anchor layer 2 provided on the support 1. Light-reflecting metal layer 3 provided on anchor layer 2 and adhesive layer 4 provided on this light-reflecting metal layer 3.
The recording layer 5 provided on the adhesive layer 4 and the protective layer 6 provided on the recording layer 5 form a main part.

The thermosensitive recording medium is manufactured through the following steps.

That is, an anchor layer composition having the following composition was coated on a support 1 made of a transparent polyester sheet having a thickness of 150 μm with a wire bar, dried at 100 ° C. for 5 minutes, and heat-cured to dry. An anchor layer 2 having a thickness of 1.5 μm is formed, aluminum is vacuum-deposited on the anchor layer 2 to provide a light-reflecting metal layer 3 having a thickness of 500 Å, and then the light-reflecting metal layer is formed. The composition for the adhesive layer having the following composition was similarly applied onto 3 using a wire bar and dried at 90 ° C. for 5 minutes to give a dry film thickness of 0.5 μm.
m adhesive layer 4 was formed.

Next, the following composition for a recording layer, which was uniformly dissolved, was applied onto the adhesive layer 4 with a wire bar,
A recording layer 5 having a dry film thickness of 9 μm is formed by drying at 100 ° C. for 5 minutes, and a composition for a protective layer having the following composition is coated on the recording layer 5 with a wire bar, and at 90 ° C. for 3 minutes. After drying, the support 1 was placed on a conveyor and moved at a speed of 10 m / min, and a height of 10
High-pressure mercury lamp (80W / cm, ozone condensing type) from the m position
Then, the composition for a protective layer was photocured to form a protective layer 6 having a cured film thickness of 2.5 μm to obtain a thermosensitive recording medium.

(Composition for anchor layer) Polyester resin (manufactured by Toyobo Co., Ltd., trade name: Byron # 200) 10 parts Isocyanate 0.1 part (curing agent manufactured by Asahi Kasei Co., Ltd., trade name Duranate 24A-100) Triethylenediamine (curing accelerator) 0.01 parts Toluene 45 parts 2-Butanone 45 parts (Composition for adhesive layer) Polyparabanic acid tree (Nitto Chemical Co., Ltd. trade name PPA-D) 10 parts

[Chemical 6] Acetone 80 parts Dioxane 10 parts (Composition for recording layer) Behenic acid (7 parts) Eicosane diacid (1 part) 1,4-Ciscyclohexanedicarboxylic acid (0.7 parts) 1,4-transcyclohexanedicarboxylic acid (0 .3 parts) 100 parts in total in the ratio in parentheses Vinyl chloride-vinyl acetate-vinyl alcohol copolymer 300 parts (Sekisui Chemical Co., Ltd. trade name Eslec A) Isocyanate 30 parts (Asahi Kasei curing agent trade name Duranate 24A-100) Triethylenediamine (curing accelerator) 3 parts Toluene 300 parts Tetrahydrofuran 1200 parts (composition for protective layer) Polyfunctional polyester acrylate 100 parts Emulsion (solid content 40% by weight) (trade name M- manufactured by Toagosei Co., Ltd.) 8060 emulsion) Lubricant (special polymer silicone resin solution, solid) Min. 50 wt% 5 parts BYK-Japan Japan trade name BYK-301) Photoinitiator 2 parts (Nippon Ciba Geigy trade name IRGACURE 651) [Examples 2 to 10] For the recording layer applied in Example 1 Among the compositions, only behenic acid, eicosane diacid, and alicyclic dicarboxylic sun compound (provided that 1,4-ciscyclohexanedicarboxylic acid: 1,4-transcyclohexanedicarboxylic acid = 7: 3) are shown in the table below. Example 1 except that the composition for recording layer changed to the composition shown in 1 was applied.
The thermal recording medium according to the present invention is substantially the same.

[0056]

[Table 1] [Comparative Example 1] A recording layer composition having the following composition was applied with a wire bar onto a polyester film having a film thickness of 50 µm and aluminum was vapor-deposited, and the composition was heated and dried to a thickness of about 15 µm.
Was formed on the recording layer, and the intermediate layer composition having the following composition was coated on the recording layer with a wire bar and dried by heating to form an intermediate layer having a thickness of about 1 μm.

Then, a butyl acetate solution of a urethane acrylate type ultraviolet curable resin is applied to this intermediate layer with a wire bar, dried by heating and irradiated with ultraviolet rays for 5 seconds by an 80 W / cm ultraviolet lamp to have a thickness of about 10. A protective layer having a thickness of 2 μm was formed to obtain a thermal recording medium.

(Composition for recording layer) Behenic acid 50 parts Eicosane diacid 50 parts Vinyl chloride-vinyl acetate copolymer 250 parts Di (2-ethyl-hexyl) phthalate 30 parts Tetrahydrofuran 2000 parts (Composition for intermediate layer) ) Polyamide resin 10 parts Methyl alcohol 90 parts [Comparative Example 2] The thermosensitive recording medium is substantially the same as that of Comparative Example 1 except that the following recording layer composition is applied.

Behenic acid 50 parts Eicosane diacid (aliphatic saturated dicarboxylic acid) 50 parts Vinyl chloride-vinyl acetate-vinyl alcohol copolymer 300 parts (Sekisui Chemical Co., Ltd. trade name Eslec A) Isocyanate 30 parts (Asahi Kasei Co., Ltd. Hardening agent Trade name: Duranate 24A-100) Triethylenediamine (curing accelerator) 3 parts Toluene 300 parts Tetrahydrofuran 1200 parts [Comparative Example 3] Thermosensitive recording according to Example 1 except that the following recording layer composition was applied. It is almost the same as the medium.

(Composition for Recording Layer) Behenic acid (9 parts) 1,4-ciscyclohexanedicarboxylic acid (0.8 parts) 1,4-transcyclohexanedicarboxylic acid (0.2 parts) Total 100 parts Vinyl chloride-vinyl acetate-vinyl alcohol copolymer 300 parts (Sekisui Chemical Co., Ltd. trade name S-REC A) Isocyanate 30 parts (Asahi Kasei curing agent trade name Duranate 24A-100) Triethylenediamine (curing accelerator) ) 3 parts Toluene 300 parts Tetrahydrofuran 1200 parts [Comparative Example 4] A thermosensitive recording medium according to Comparative Example 3 except that a recording layer composition in which only the ratio of behenic acid and cyclohexanedicarboxylic acid was changed as follows was applied. It is almost the same.

Behenic acid (9 parts) 1,4-ciscyclohexanedicarboxylic acid (0.6 parts) 1,4-transcyclohexanedicarboxylic acid (0.4 parts) 100 parts in total in parentheses [Comparative Example 5 ] The thermal recording medium of Comparative Example 3 is substantially the same as the thermal recording medium of Comparative Example 3 except that a recording layer composition in which only the ratio of behenic acid and cyclohexanedicarboxylic acid is changed as follows is applied.

Behenic acid (9 parts) 1,4-ciscyclohexanedicarboxylic acid (1 part) 1,4-transcyclohexanedicarboxylic acid (0 part) 100 parts in total in parentheses "Comparative test" (1) Transparent Temperature Range Next, thermal recording media according to Examples 1 to 10 and Comparative Examples 1 to 1
For the heat-sensitive recording medium according to No. 5, a comparison test as described below was conducted in order to compare the transparentization temperature ranges.

The recording layers of the thermosensitive recording media according to the examples and comparative examples obtained as described above were all formed in a cloudy state.

First, each of the obtained heat-sensitive recording media was heated stepwise from 65 ° C. once and cooled to room temperature, and then the reflection thereof was performed by an optical reflection densitometer (Macbeth optical densitometer RD-514). Each density (optical density) was measured.

The light reflected from the light-reflecting metal layer made of aluminum was measured for the thermosensitive recording media according to each of the examples and the comparative examples.

The temperature at which the reflection density exceeded 1.0 was recorded as the clearing temperature, and the clearing temperature range and clearing temperature range were measured from these data.

The results are shown in Table 2 below.

(2) Maximum transparency and maximum white turbidity Further, the maximum transparency and the maximum white turbidity of the thermal recording media according to each of the examples and the comparative examples were measured, and the contrasts of the image portion and the non-image portion were compared. .

A card reader / writer KU-400 manufactured by Kyushu Matsushita Electric was used as an evaluation machine, and printing conditions were:
0.5 mj / dot (white turbid state), erasing condition: 0.2 m
It was performed at j / dot (transparent state). The results are also shown in Table 2.

(3) Repeated rewriting resistance test Further, the repeated rewriting resistance test was conducted on the thermosensitive recording medium according to Example 7. The printing density (white turbidity) and the erasing density (transparency) were measured by the Macbeth optical densitometer RD-514 every 10 times under the same printing and erasing conditions using the above evaluation machine.

The results are shown in FIG.

[0072]

[Table 2] "Evaluation" (1) Clarification temperature range In Table 2, a thermosensitive recording medium according to Comparative Example 1 in which a thermoplastic resin was applied as a resin base material (clarification temperature range 19 ° C)
As is clear from the comparison between the thermosensitive recording medium (transparent temperature range 8 ° C.) according to Comparative Example 2 to which the thermosetting resin is applied,
It can be confirmed that when the thermosetting resin is applied as the resin base material, the transparentization temperature width (width of the transparentization temperature range) becomes narrower than that of the thermoplastic resin. However, regarding the thermosensitive recording medium according to each example in which the alicyclic dicarboxylic acid compound is added in the organic low molecule of the recording layer, the thermosetting resin is applied as the resin base material in spite of that. It was confirmed that the transparency temperature range showed a large value of 41 ° C. to 72 ° C. and that the characteristics of the recording medium were not affected.

Next, the heat-sensitive recording medium according to each of Examples and Comparative Examples 3 to 5 to which the alicyclic dicarboxylic acid compound was applied and Comparative Examples 1 to 1 to which the aliphatic dicarboxylic acid compound was applied.
As is clear from the comparison with the heat-sensitive recording medium according to No. 2, by using an alicyclic dicarboxylic acid compound instead of the conventional aliphatic dicarboxylic acid compound as an additive for expanding the transparency temperature range, the clearing temperature range can be improved. It was also confirmed that the number would dramatically increase. Therefore, it is easy to set the heating temperature of the thermal head etc. within the above transparency temperature range at a high speed by expanding the transparency temperature range. Therefore, compare the images in the transparent state based on the white background (that is, the cloudy state). It was confirmed that it can be easily formed.

(2) Maximum Transparency and Maximum White Turbidity Further, the maximum white turbidity (0.15 to 0.25) of each of the thermal recording media of Examples and Comparative Examples 3 to 5 and Comparative Examples 1 to 1 were obtained.
The maximum white turbidity (0.40 to 0.4
As is clear from the comparison with 2), the decrease in the white turbidity is large in the thermal recording media according to Comparative Examples 1 and 2. This is because the addition ratio of the aliphatic dicarboxylic acid compound to behenic acid, which is an organic low molecular weight substance, is larger than that in each of the examples and the comparative examples 3 to 5 to which the alicyclic dicarboxylic acid compound is applied, and the organic low amount is reduced accordingly. This is because the blending ratio of the molecular substance has decreased.

Next, the maximum transparency (1.72 to 1.97) of the thermal recording medium according to each of the examples to which the alicyclic dicarboxylic acid compound and the aliphatic dicarboxylic acid compound were applied, and the alicyclic dicarboxylic acid compound Maximum transparency (1.14 to 1.25) of the thermal recording media according to Comparative Examples 3 to 5 to which only
As is clear from the comparison with the above, it can be confirmed that the thermal recording media according to the examples also have excellent transparency.

Therefore, since it was possible to prevent the white turbidity from decreasing and the transparency to be improved, it was confirmed that a high contrast between the image portion and the non-image portion can be achieved in the thermal recording medium according to the example.

(3) Repeated rewriting resistance test As shown in FIG. 2, even if the number of times of printing is repeated, the change in print density (white turbidity) and erase density (transparency) is small, and the erase density (transparency) is small. Since there is no difference in transparency in the non-image area where is not printed and the initial transparent state is maintained, it was confirmed that the repeated rewriting resistance was also improved.

[0078]

According to the invention of claims 1 and 2, when an organic low molecular weight substance, an alicyclic dicarboxylic acid compound and an aliphatic dicarboxylic acid compound are heated by the addition of an alicyclic dicarboxylic acid compound, The melting temperature is higher than that of the organic low molecular weight substance alone, and the degree of increase is larger than that of the conventional method, so that the transparentization temperature range can be dramatically expanded, and the aliphatic dicarboxylic acid The addition of the acid compound also improves the transparency of the recording layer, and makes it possible to achieve high contrast between the image area and the non-image area.

On the other hand, according to the invention of claim 3, the alicyclic dicarboxylic acid compound can be sufficiently expanded even if the addition ratio of the alicyclic dicarboxylic acid compound is lower than that in the conventional method. The decrease in the ratio of addition of the acid compound makes it possible to prevent the white turbidity of the recording layer from decreasing.

Therefore, since it becomes easy to set the heating temperature of the heating means such as the thermal head at a high speed within the transparentization temperature range, it is possible to form a transparent image on the background of a white background (white turbid state), or It is also possible without difficulty to form a cloudy image on the background of (transparent state), which has the effect of expanding the applicable range of this type of thermal recording medium, and also reduces the contrast between the image part and the non-image part. Since it is difficult, the recording image quality can be improved.

Further, according to the invention of claim 4, the resin base material is composed of a thermosetting resin comprising a hydroxyl-modified vinyl chloride-vinyl acetate copolymer and an isocyanate compound, and the thermosetting resin is Since it has excellent heat resistance and mechanical strength and also has good adhesiveness to a support such as a plastic sheet or paper, thermal deterioration of the recording layer is less likely to occur as compared with the case where a thermoplastic resin is applied to the resin base material.

Therefore, since it is possible to prevent the white turbidity from being lowered due to the thermal deterioration of the recording layer, it is possible to improve the resistance against repeated rewriting, and it is possible to omit the formation of the protective layer.

[Brief description of drawings]

FIG. 1 is a structural cross-sectional view of a thermosensitive recording medium according to an example.

FIG. 2 is a graph showing the relationship between the number of prints, the print density, and the erase density of the thermosensitive recording medium according to Example 7.

[Explanation of symbols]

 1 Support 2 Anchor Layer 3 Light Reflective Metal Layer 4 Adhesive Layer 5 Recording Layer 6 Protective Layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuji Nakato 1-5-1, Taito, Taito-ku, Tokyo Toppan Printing Co., Ltd.

Claims (4)

[Claims] 1. A rewritable thermosensitive recording medium comprising a resin base material and an organic low molecular weight substance dispersed in the resin base material as a main component, and a recording layer whose transparency reversibly changes depending on temperature. 2. A rewritable heat-sensitive recording medium, wherein the alicyclic dicarboxylic acid compound and the aliphatic dicarboxylic acid compound are added to the organic low-molecular substance dispersed in the resin base material. 2. The alicyclic dicarboxylic acid compound is 1, 2
-Cis cyclopropane dicarboxylic acid, 1,2-trans cyclopropane dicarboxylic acid, 1,2-cis cyclobutane dicarboxylic acid, 1,2-trans cyclobutane dicarboxylic acid, 1,2-cis cyclopentane dicarboxylic acid,
1,2-transcyclopentanedicarboxylic acid, 1,3
-Ciscyclobutanedicarboxylic acid, 1,3-transcyclobutanedicarboxylic acid, 1,3-ciscyclopentanedicarboxylic acid, 1,3-transcyclopentanedicarboxylic acid, 1,2-ciscyclohexanedicarboxylic acid,
1,2-transcyclohexanedicarboxylic acid, 1,3
-Ciscyclohexanedicarboxylic acid, 1,3-transcyclohexanedicarboxylic acid, 1,4-ciscyclohexanedicarboxylic acid, 1,4-transcyclohexanedicarboxylic acid, 1,1-cyclopropanedicarboxylic acid,
The 1,1-cyclobutanedicarboxylic acid and 1,1-cyclopentanedicarboxylic acid, which is composed of one or more kinds of alicyclic dicarboxylic acids selected from the group consisting of alicyclic dicarboxylic acids. Rewritable thermal recording medium. 3. The addition ratio of the alicyclic dicarboxylic acid compound is 2% by weight based on the total amount of the alicyclic dicarboxylic acid compound, the organic low molecular weight substance and the aliphatic dicarboxylic acid compound.
The rewritable thermosensitive recording medium according to claim 1 or 2, wherein the rewritable thermal recording medium is set to -30% by weight. 4. The resin base material is composed of a thermosetting resin comprising a hydroxyl-modified vinyl chloride-vinyl acetate copolymer and an isocyanate compound. Rewritable thermal recording medium.