KR0143703B1 - Thermosensitive recording material - Google Patents

Abstract

The present invention relates to a thermosensitive recording having a thermosensitive recording layer comprising modified polyvinyl alcohol containing 2.5 to 8 mol% of carboxyl group-containing monomer units, having a saponification degree of 50 to 65 mol% and a viscosity average degree of polymerization of 50 to 500. A material, a dispersant comprising a modified polyvinyl alcohol according to claim 1 for the thermosensitive dye or coloring agent which can cause the thermosensitive dye to develop upon heating and a thermosensitive which can cause the thermosensitive dye to develop upon heating A process for the preparation of an aqueous dispersion comprising dispersing a dye or colorant in an aqueous medium with the dispersant of the modified polyvinyl alcohol according to claim 1. The aqueous dispersion obtained, which has excellent applicability to the surface of the base paper in the manufacture of the thermosensitive recording paper and contains the dispersoid of the thermosensitive raw material and the coloring agent dispersed in the fine particles, generates a highly sensitive thermosensitive recording material. can do.

Description

Thermosensitive recording material

The present invention relates to a heat-sensitive recording material.

The present invention also relates to a dispersant having a good dispersibility for dispersing a thermosensitive dye and a coloring agent and suitable for producing a thermosensitive recording material.

The invention further relates to a process for the preparation of an aqueous dispersion having a dispersoid of granular thermosensitive dyes or colorants.

The thermosensitive recording material includes a paper, a plastic film, or a paper to which a metal is attached, on which a thermosensitive recording layer forms a color by thermal energy, chemical change or physical change and provides a recorded image. Is provided. The thermosensitive recording material has the advantage of providing a recorded image by simply dimming it, eliminating the need for complicated processing such as developing and sticking, and producing a relatively inexpensive recording system without causing noise during recording. Therefore, such materials have been widely used as recording materials for electronic calculators, word processors, telex machines, fax machines and various calculators.

Such thermosensitive recording materials are generally colorless or light-color leuco dyes and acids which react with the leuco dyes upon heating to form colors. Organic acid or phenol].

In recent years, in the field of facsimile and the like, where the printing speed is increasing year by year, there has been a demand for a thermosensitive recording material which can provide a more transparent image and adapt to high speed printing. In terms of recorded images, there is a need for a thermosensitive recording material capable of providing precise and flawless images, as well as for text and drawings.

As a result, there is a strong demand for a thermosensitive recording material having a thermosensitive recording layer which cannot observe the color of the tissue of the substrate because the thermosensitive dye and the coloring agent having a particle diameter of 1 mu or less are uniformly dispersed and present in the thin layer with high density.

Known dispersants for thermosensitive dyes and colorants include alkali metal salts or esters of low molecular weight partially saponified polyvinyl alcohol, low molecular weight sulfonic acid group modified polyvinyl alcohol and α-olefin-maleic anhydride copolymers. . However, such dispersants may not exhibit sufficient performance.

Low molecular weight partially saponified polyvinyl alcohols have insufficient dispersibility to disperse thermosensitive dyes and coloring agents and cannot stably disperse them to particle sizes below 1 micron.

Low molecular weight sulfonic acid modified polyvinyl alcohol has some dispersibility, but makes the tissue color of the substrate quite visible.

Maleic anhydride copolymers, when used in paint liquids, often lack cohesion with the binders contained in the paint liquids, often causing agglomeration of dispersed particles or increasing the viscosity of the paint liquid. There is a problem that makes this quite visible.

Accordingly, it is an object of the present invention to provide a thermosensitive recording material which can make the tissue color of a substrate invisible and provide a clean image even at high speed printing.

It is still another object of the present invention to provide a dispersant having excellent dispersibility for dispersing granular thermosensitive dyes and coloring agents and suitable for producing a thermosensitive recording material.

It is another object of the present invention to provide a method for preparing an aqueous dispersion having a dispersoid of granular thermosensitive dyes or colorants.

As a result of intensive research to solve the above-described problems, the inventor of the present invention includes 2.5 to 8 mol% of carboxyl group-containing monomer units, 40 to 65 mol% of saponification degree, and 50 to 500 viscosity average polymerization degree. A thermosensitive recording material having a thermosensitive recording layer comprising phosphorus-modified polyvinyl alcohol, comprising the above-mentioned modified polyvinyl alcohol for thermosensitive dyes or colorants which can cause the thermal dye to develop upon heating The present invention has been found to provide a process for preparing an aqueous dispersion comprising dispersing a dispersant and a thermosensitive dye or colorant which can cause the heat sensitive raw material to develop upon heating in an aqueous medium together with the dispersant of the modified polyvinyl alcohol mentioned above. Was completed.

The modified polyvinyl alcohol (hereafter termed polyvinyl alcohol, often referred to as PVA) used in the present invention should contain 2.5 to 8 mole percent units of carboxyl group containing monomers and a degree of saponification of 40 to 65 mole percent. And the polyvinyl alcohol has a viscosity average polymerization degree of 50 to 500.

The content of the carboxyl group-containing monomer unit needs to be 2.5 to 8 mol%, preferably 3 to 6 mol%. If the degree of modification by the carboxyl group is less than 2.5 mole percent, the printed portion of the thermosensitive recording material has a low color density and the PVA has a low dispersibility for dispersing the thermosensitive dye and the colorant, so that the dispersion after the aqueous dispersion is prepared. Aggregates. When the modification degree exceeds 8 mol%, the unprinted portion of the thermosensitive recording material has low whiteness, and the aqueous dispersion prepared using PVA has very low whiteness.

There is no particular limitation on the form of the carboxyl group-containing monomer unit, but examples thereof include fumaric acid, maleic acid, itaconic acid, maleic anhydride, phthalic anhydride, trimellitic anhydride and itaconic anhydride. Of these monomeric units, dibasic acids are preferred, and itaconic acid is particularly preferred.

The modified PVA needs to have a saponification degree of 40 to 65 mol%, preferably 45 to 60 mol%, more preferably 50 to 60 mol%. If the degree of saponification is less than 40 mol%, the dispersibility of dispersing the thermosensitive dye and the coloring agent decreases, and the aqueous dispersion prepared using PVA agglomerates the dispersion fill after preparation, so that it is possible to use a thermosensitive recording material that can be used. It cannot be obtained. When the saponification degree exceeds 65 mol%, the obtained thermosensitive recording material, in addition to lowering the color density of the printed portion, the aqueous acid solution prepared using PVA has a high viscosity and is difficult to handle, thus increasing the concentration of the dispersion. Can't increase

The viscosity average degree of polymerization (hereinafter simply referred to as degree of polymerization) of the modified PVA should be in the range of 50 to 500 and preferably in the range of 100 to 300. If the degree of polymerization is less than 50, the PVA cannot disperse the fine particles, and after preparation of the aqueous dispersion, the dispersion is aggregated, and thus a thermosensitive recording material that can be used cannot be obtained. When the degree of polymerization exceeds 500, the obtained thermosensitive recording material lowers the color density of the printed portion, and the aqueous dispersion prepared using PVA can increase the concentration of the dispersion because the viscosity is too high to be easily handled. none.

The carboxyl group modified PVA is not particularly limited and may be prepared by any method. For example, one of the carboxylic acids mentioned above is post-reacted with polyvinyl alcohol or saponified copolymers of vinyl acetate with ethylenically unsaturated and carboxylic acids. Specific examples of such a method are described in Japanese Patent Publication No. 21112/1980 and Japanese Patent Laid-Open Nos. 91995/1978, 28389/1979, and 28390/1979.

The carboxyl groups in the PVA of the present invention may exist in the form of alkali metal salts such as COONa or in the form of COOH. When the carboxyl group-containing monomer is a dibasic acid, one of the two carboxylic acids present in the monomer may form a lactone ring.

The carboxyl group modified polyvinyl alcohol used in the present invention can be modified using a chain transfer agent. Any ethylenically unsaturated monomer can be copolymerized with the vinyl ester as long as it can be copolymerized with the vinyl ester. Examples of such monomers include α-olefins; Ethylene, propylene, n-butene, isobutene and 1-hexadecene]; Carboxylic acid-containing monomers such as (meth) acrylic acid, fumaric acid, crotonic acid, maleic acid, maleic anhydride and salts thereof; (Meth) acrylic acid esters such as methyl (meth) acrylate, m-butyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-ethylhexyl (meth) acrylate and stearyl ( Meth) acrylate]; Other esters such as dimethyl fumarate, dimethyl itaconate, dimethyl maleate, monomethyl maleate and methyl glotonate; vinyl ethers such as methyl vinyl ether, butyl vinyl ether, lauryl vinyl ether and stearyl Vinyl ethers; sulfonic acid group-containing monomers [e.g., sulfonic acid, arylsulfonic acid, metallylsulfonic acid, 2-acrylamide-2-methylpropanesulfonic acid and salts thereof]; amido group-containing monomers [e.g. ( Meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-methylol (meth) acrylamide, Nt-butoxy (meth) acrylamide, Nt-octyl (meth) acrylamide and N-vinylpyrroli DON] quaternary ammonium salt-containing monomers such as vinylhydroxysilane and 3-trimethoxysilyl (meth) acrylamide] and acetyl group-containing monomers such as allyl acetate, dimethylallyl acetate and isopropenyl acetate this All.

The modified PVA may be included in the thermosensitive recording layer of the thermosensitive recording material in an amount not particularly limited. However, the modified PVA is preferably 3 to 30 parts by weight, more preferably 5 to 20 parts by weight, and most preferably 7 to 16 parts by weight based on 100 parts by weight, which is a sum of the thermosensitive material and the color developer. to be.

In the preparation of an aqueous dispersion of a thermosensitive raw material or colorant according to the invention, the thermosensitive dye or colorant is dispersed using a dispersant of the above modified PVA. The dispersant may be used in any amount, but is preferably 3 to 30 parts by weight, more preferably 5 to 20 parts by weight, and most preferably 7 to 5 parts by weight based on 100 parts by weight of the total amount of the thermosensitive raw material or the coloring agent. It can be used in an amount of 16 parts by weight. In general, it is preferable to prepare an aqueous dispersion of the thermosensitive raw material and the coloring agent separately and then mix the two dispersions. The processed aqueous dispersion preferably has a dispersoid concentration of 20 to 70% by weight, more preferably 40 to 60% by weight.

The dispersion process of the thermosensitive raw material or color developer is carried out in a sand mill containing a plurality of glass beads having an average particle diameter of 0.2 to 3 mm (preferably 0.3 to 0.8 mm). The dispersion process is completed in 1 hour to 1 week (preferably 3 hours to 4 days, especially 1 to 4 days in order to obtain a fine dispersion having an average particle diameter of 0.45 μm or less).

In the case of using the dispersant of the present invention, the dispersion of the dye or the coloring agent having a particle diameter in the range of 0.1 to 1 μm (preferably 0.3 to 0.8 μm, more preferably 0.2 to 0.6 μm, most preferably 0.2 to 0.45 μm) Aqueous dispersions with quality can be provided.

Any thermosensitive dye used in conventional pressure sensitive or thermosensitive paper can be used in the present invention, specific examples of which are triarylmethane compounds [eg, 3,3-bis (p-dimethylaminophenyl) -6- Dimethylanimophthalide (Crystal Violet Lactone), 3- (p-dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-phenylindol-3-yl) phthalide and 3,3-bis- (9-ethylcarbazol-3-yl-5-dimethylaminophthalide]; diphenylmethane compounds [eg 4,4 '-Bisdimethylaminobenzhydrin benzyl ether and N-halophenylleucoauramin]: xanthan compounds [eg rhodamine B-anilinolactam, 3-diethylamino-7-benzylaminofluorane, 3- Diethylamino-7-butylaminofluorane, 3-diethylamino-7- (chloroanilino) fluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-piperidino- 6-methyl-7-anilinofluorane, 3-ethyl-tolyl Amino-6-methyl-7-anilinofluorane, 3-cyclohexyl-methylamino-6-methyl-7-anilinofluroran, 3-diethylamino-6-chloro-7- (β-ethoxy Methyl) aminofluorane, 3-diethylamino-6-chloro-7- (γ-chloropropyl) aminofluoran, 3- (N-ethyl-N-isoamyl-6-methyl-7-phenylaminofluorane And 3-dibutylamino-6-methyl-7-aniliofluorane]: thiazine-based compounds such as benzoyl leuco methylene blue and p-nitrobenzoyl leuco methylene blue] and spiro compounds such as 3-methyl-spiro -Dinaphtopyran, 3-ethyl-spiro-Dinaphtopyran, 3-benzyl-spiro-Dinaphtopyran, 3-methylnaphtho- (3-methoxy-benzo) -spiro-pyran] Silver may be used alone or in combination of two or more of these thermosensitive dyes are appropriately selected depending on the intended use of the thermosensitive recording material.

The coloring agent used in the present invention is preferably selected from phenol derivatives and aromatic carboxylic acid derivatives, in particular bisphenol. Specific examples thereof include phenols such as p-octylphenol, p-tert-butylphenol, p-phenylphenol, 1,1-bis (p-hydroxyphenyl) propane, and 1,1-bis (p-hydroxy). Hydroxyphenyl) pentane, 2,2-bis (p-hydroxyphenyl) propane, 1,1-bis (p-hydroxyphenyl) hexane, 2,2-bis (p-hydroxyphenyl) hexane, 1,1 Bis (p-hydroxyphenyl-2-ethyl-hexane, 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane and dihydroxydiphenyl ether]; and aromatic carboxylic acid derivatives such as p-hydroxybenzoic acid, ethyl p-hydroxybenzoate, butyl p-hydroxybenzoate, 3,5-di-tert-butyl salicylic acid, 3,5-α-methylbenzyl salicylic acid and Polyvalent metal salts of such carboxylic acids].

In the present invention, it is preferable to use an aqueous binder for the thermosensitive recording layer. Examples of binders that can be used for this purpose include cellulose derivatives: starch, starch derivatives, hydroxymethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose and ethylcellulose; Water soluble polymers such as polyvinyl alcohol, poly (sodium acrylate), polyvinylpyrrolidone, acrylamide / acrylic acid ester copolymers, acrylamide / acrylic acid ester / methacrylic acid terpolymers, styrene / maleic anhydride copolymers Alkali metal salts and alkali metal salts of isobutylene / maleic anhydride copolymer; Polyacrylamide, sodium alginate, gelatin and casein; Emulsions such as polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic acid ester, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene / vinyl acetate copolymer; And latexes such as styrene / butadiene copolymer and styrene / butadiene / acrylic acid ester.

The aqueous binder is preferably added in an amount of 1 to 20 parts by weight, based on 100 parts by weight, which is a sum of the dye and the coloring agent.

In the present invention, the thermosensitive recording layer is used in addition to the thermosensitive fuel and coloring agent to prevent color development under auxiliary pressures such as fillers, surfactants, thermocomposites (or lubricants) and pressures, which are usually used for low temperature thermosensitive recording materials. Anti-pigmentation agents] can be incorporated.

In the present invention, the thermosensitive recording layer is, for example, air-knife coating, plate coating, embossing, roll coating, spraying, dipping, bar coating It may be formed by one of the known methods such as bar coating and extrusion coating.

In the present invention, no substrate can be used as the substrate for the thermosensitive recording material. For example, it selects suitably from various paper, a synthetic paper, and a synthetic resin film. However, it is preferable to use paper.

The thermosensitive recording material of the present invention provides a printing portion which is excellent in color development and a non-printing portion which is hard to be fogged (colored on a substrate). The thermosensitive recording material of the present invention excellent in high speed printability and excellent in image resolution can be suitably used in fields requiring high speed printing such as facsimile.

The dispersant of the present invention having excellent dispersibility for dispersing the thermosensitive dye and the coloring agent can provide a low viscosity aqueous dispersion having a high concentration of the dispersoid of the granular thermosensitive dye or the coloring agent. The aqueous dispersion obtained which has excellent adaptability to the surface of the base paper in the manufacture of the thermosensitive recording paper and which contains the dispersoid of the coloring agent and the thermosensitive dye dispersed in the fine particles can produce the thermosensitive recording material having very high resolution. have.

EXAMPLE

Other features of the invention will be apparent from the description of the following exemplary embodiments which are given to illustrate the invention and are not intended to be suggested thereby. In the following examples and control examples, parts and percentages refer to parts by weight and percentages unless otherwise indicated. In the following description, the viscosity value is measured by using a Brookfield viscometer manufactured by Tokyo Keiki Co., Ltd. at 30 ° C. with a rotor speed of 12 rpm.

Example 1

(1) Preparation of Paint Liquid (Dispersion of Thermosensitive Dye and Coloring Agent)

A. Preparation of Aqueous Dispersion of Thermosensitive Dye

Leuco Dye (S-205, Yamama Kagaku K.K.) 20%

10% aqueous solution 20% of PVA (4mole% itaconic acid modified by copolymerization; polymerization degree: 500; saponification degree: 46mole%) modified by carboxyl group

59.9% of water

Anti-foaming material (SURFYNOL 440, Nisshin Chemical Co., Ltd.) 0.1%

B. Preparation of Aqueous Dispersion of Coloring Agent

Bisphenol A20%

20% 10% aqueous solution of PVA modified by carboxyl group (same as used above)

59.9% of water

Anti-foaming material (SURFYNOL 440, Nisshin Chemical Co., Ltd.) 0.1%

C. Aqueous Dispersions of Pigments (Fillers)

Stearylamide 10%

Calcium Carbonate 20%

30% 5% aqueous solution of PVA modified by carboxyl group (same as used above)

40% of water

The aqueous mixtures A, B and C described above are prepared separately and prestirred for 15 minutes.

Aqueous mixtures A and B were transferred into sand mills (batch-type, desk-top sand mills manufactured by Kansai Paint Co.) and then 300 cc of glass beads (0.5 mm diameter soda quartz). Glass). Dispersion is carried out for 6 hours at high rotational speed (2,170 rpm).

The aqueous mixture is dispersed C for 2 minutes in a homogenizer (10,000 rpm).

The aqueous dispersion A of the thermosensitive dye is evaluated according to the following method.

Dispersion Particle Diameter

Six hours after the start of dispersion, the particle diameter is measured using a laser diffraction particle size analyzer (SALD-1000, manufactured by Sihmadzu Corp.).

[Viscosity of Aqueous Dispersion]

The dispersion for 6 hours is completed, the aqueous dispersion is allowed to stand for about 1 hour and the viscosity is tested at 30 ° C.

[Whiteness of Aqueous Dispersion]

The dispersion for 6 hours is completed and the aqueous dispersion is allowed to stand for about 1 hour, then the whiteness is tested using a colorimeter (Z-1001DP, manufactured by Nippon Denshoku Kogyo Co., Ltd.). A whiteness value of 0 means completely white, and discoloration increases with the absolute value of a negative value.

(2) Production of thermosensitive recording paper

The coating liquid for the thermosensitive recording layer was stirred with 1 part of aqueous dispersion A, 4 parts of aqueous dispersion B, 2 parts of aqueous dispersion C and 2 parts of 10% aqueous solution of polyvinyl alcohol (polymerization degree: 1,750, saponification degree: 98.6 mole%). Prepared by mixing. The coating liquid is applied in an amount of 6 g / m 2 (based on a solid state) on a base paper (wood-free paper having a weight of 52 g / m 2) using a wire bar coater, and at 10 ° C. at 10 ° C. After drying for minutes, super calender [line pressure: 30 kg / cm; Roll diameter: upper part (metal): 20 cm, lower part (rubber): 30 cm] to obtain a thermosensitive recording paper.

The thermosensitive recording paper thus obtained was evaluated by the following method.

[Color Density of Printed Part on Thermosensitive Recording Paper]

After printing on paper using a printing machine for a thermosensitive facsimile (RIFAX 300, manufactured by Ricoh Co.), the color density of the printed portion was measured by a Macbeth color density tester (RD-514, manufactured by Macbeth Co.) Measure using

[Color Density of Unprinted Part of Thermosensitive Recording Paper]

The same Macbed tester as described above is used to measure the color density of the unprinted portion.

Macbed densities of 0 and 1.82 mean full white and full black, respectively. Table 1 shows the evaluation results of the aqueous dispersion A and the thermosensitive recording material described above for the thermosensitive raw material.

[Examples 2 to 11]

Example 1 was repeated except that the ataconic acid modified polyvinyl alcohol as shown in Table 1 was used instead of the itaconic acid / modified polyvinyl alcohol used in Example 1, and the coating liquid (the Dispersion). Thereafter, the thermosensitive recording material is produced in the same manner using the obtained coating liquid. The results are shown in Table 1.

[Comparative Examples 1 to 8]

Example 1 was repeated except that various polyvinyl alcohols as shown in Table 1 were used instead of the itaconic acid-modified polyvinyl alcohol used in Example 1, the coating liquid (dispersion of the thermosensitive raw material and the coloring agent). To prepare. Thereafter, the thermosensitive recording material is produced in the same manner using the obtained coating liquid. The results are shown in Table 1.

It is apparent that numerous processes and modifications can be made to the invention in light of the above teaching. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described in the invention.

Claims (3)

A thermosensitive recording material having a thermosensitive recording layer comprising a modified polyvinyl alcohol containing 2.5 to 8 mol% of carboxyl group-containing monomer units, 40 to 65 mol% of saponification degree, and 50 to 500 viscosity average polymerization degree. A dispersant comprising a modified polyvinyl alcohol according to claim 1 for use in a thermosensitive dye or colorant which can cause the thermosensitive dye to develop upon heating. A process for preparing an aqueous dispersion comprising dispersing a thermosensitive dye or colorant which can cause the thermosensitive dye to develop upon heating in an aqueous medium together with the dispersant of the modified polyvinyl alcohol according to claim 1.