JPH0257795B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording material. Conventionally, as a heat-sensitive recording material, a sensitive layer formed by dispersing a diazo compound and a coupling agent in a binder resin on a base material of paper or plastic film, and a base agent that becomes alkaline or releases an alkaline substance when heated are used. It is already known that a base agent layer dispersed in a binder resin and an overcoat layer are sequentially laminated. The above-mentioned conventional heat-sensitive recording materials are generally used in a recording method in which thermal printing is followed by optical fixation, and are widely used because recording is easy and the recording apparatus is simple. The outermost layer of conventional heat-sensitive recording materials is provided with an overcoat layer as described above, and the overcoat layer is made of a binder selected in consideration of its adhesive properties with the binder resin that constitutes the base layer below. It is provided using a coating material for forming the top coat layer, which is prepared by adding a mold release agent or a lubricant to the resin, if necessary, and kneading it with a solvent or diluent. The purpose of providing such an overcoat layer is (a) to prevent stagnation during thermal printing, (b) to suppress the generation of bubbles caused by nitrogen gas generated by photofixing, and (c) to prevent environmental damage such as humidity. However, it is difficult to make the binder resin used in the paint for forming the top coat layer have all of the properties (a) to (c) above, and especially (a) and (b). It is difficult to satisfy them at the same time. As a result of research in view of the above-described shortcomings of the conventional art, the present inventors have discovered that the above-mentioned method can be achieved by interposing an undercoat layer having other functions between the topcoat layer having the function of preventing staining and the base layer. The present invention has been achieved by discovering that all of the conventional drawbacks can be overcome. That is, the present invention relates to each of the following layers (a) to (d), namely: (a) a sensitive layer in which a diazo compound and a coupling agent are dispersed in a binder resin; (b) A base layer in which a pyrolyzable alkali generator is dispersed in a binder resin. (c) An undercoat layer made of a synthetic resin selected from styrene/maleic acid copolymer resin, polyvinyl alcohol resin, polyacrylic acid ester resin, melamine resin, polyamide resin, or polyvinyl acetate resin. (d) An overcoat layer consisting of a synthetic resin in which a lubricant and a mold release agent are dispersed. The main idea is a heat-sensitive recording material characterized by sequentially laminating layers on a base material. The present invention will be explained in detail below. FIG. 1 is a sectional view of an embodiment of the heat-sensitive recording material A of the present invention, in which a sensitive layer 2, a base layer 3, an undercoat layer 4, and an overcoat layer 5 are sequentially laminated on a base material 1. be. The substrate 1 may be any material used as a substrate for ordinary heat-sensitive recording materials, such as wood-free paper, medium-quality paper, art paper, coated paper, Kent paper, polyester, polyethylene, etc.
Films of various synthetic resins such as polypropylene and triacetate can be used. The sensitive layer 2 is formed by dispersing a diazo compound and a coupling agent in a binder resin. In the above, the diazo compound includes, for example,
Those described in Japanese Patent Publication No. 55-49730 can be used. As a coupling agent, the general formula is I can give an example of what is expressed by . However, in the above, R ¹ , R ² , R ³ , R ⁵ are hydrogen, an alkyl group, an aryl group, an alkoxy group, a sulfonic acid or sodium sulfonate group, an alkylamino group, an arylamino group, an amino group, a carboxylic acid group, a carboxylic acid ester group or a halogen, R ⁴ is an alkyl group, an aryl group, or a heterocycle,
R ⁶ is a sulfonic acid or sodium sulfonate group or a carboxyl group, R ⁷ and R ⁸ are R ¹ ,
The same as R ² , R ³ or R ⁵ and a hydroxyl group, X is a halogen, m is an integer of 1 to 3, n
is 1 or 2. Among the above, coupling agents belonging to A and B give blue or red dyes, those belonging to C give brown or blue dyes, and coupling agents D and E
Those belonging to the following formula give red or yellow dyes. You can also use something like this. Specifically, resorcinol and its derivatives 4
- 1-phenyl-3 which is benzoylresorcinol, 2-methylresorcinol, 5-methylresorcinol, diresorcinol and diresorcinol sulfide, phloroglycin, pyrazolones;
-Methyl-5-pyrazolone, 4,4'-bis(1-
phenyl-3-methyl-5-pyrazolone), 1.
(4'-sulfophenyl)-3-methyl-5-pyrazolone, naphthols include 2-hydroxy-
3-naphthoic acid-2'-ethoxyanilide, 2-hydroxy-3-naphthoic acid-2',5'-dimethoxyanilide, 2-hydroxy-3-naphthoic acid-
2'-Methoxy-5-nitroanilide, 2-hydroxy-3-naphthoic acid-2-methyl-4-chloroanilide, 2-hydroxy-3-naphthoic acid-morpholinopropioamide, 2-hydroxy-3-
Naphthoic acid ethanolamide, dihydroxynaphthalene, 2-hydroxy-3-naphthoic acid naphthamide, 1,8-dihydroxynaphthalene-3
(or 4)-sodium sulfonate, sodium 1-hydroxy-8-benzoylaminonaphthalene-3-sulfonate, sodium 1-hydroxy-8-phenylaminonaphthalene-4-sulfonate, 1-hydroxy-9-methylamino Sodium naphthalene-5-sulfonate, sodium 1-hydroxynaphthalene-4-sulfonate, 2,8
- Sodium dihydroxynaphthalene-6-sulfonate. As acidic coupling agents, 2-hydroxy-3-naphthoic acid, 2-hydroxy-6-naphthoic acid, 2-hydroxy-1-naphthoic acid, 2,
6-dihydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 3,5-dihydroxybenzoic acid,
2,4,6-trihydroxybenzoic acid and cyanoacetic acid, as well as m-hydroxyphenylurea,
N,N-ethylenebisacetoacetamide, 2,
6-dihydroxyacetophenone, acetoacetanilide, 2,4,6-trihydroxyacetophenone, N-benzylacetoacetamide, catechol, acetoacetic benzamide, or alternatively 2,4-dihydroxybenzoic acid ethanolamide, 3,5 -Dihydroxybenzoic acid ethanolamide and the like can also be used. As coupling agents it is also possible to use compounds which have in their structure a group in the form of a metal carboxylate salt as well as a coupling position. To give a specific example,
2-hydroxy-1-naphthoic acid, 2-hydroxy-3-naphthoic acid, 2-hydroxy-4-naphthoic acid, 2-hydroxy-6-naphthoic acid, 2,
3- (or 2,4-, 2,5-, 2,6-, 3,
4-,3,5-)dihydroxybenzoic acid, 2,
3,4- (or 2,4,6-, 3,4,5-)
Trihydroxybenzoic acid, 2-hydroxyanthracene-3-carboxylic acid, 3-hydroxybenzofuran-2-carboxylic acid 2-hydroxycarbazole-3-carboxylic acid, 2-hydroxy-α-benzocarbazole-3-carboxylic acid, 1. (4'-sulfophenyl)-3-carboxy-5-pyrazolone, 4,4'-methylenebis-(3-hydroxy-
2-naphthoic acid)-2-(or 3-, 4-)acetoacetaminobenzoic acid, 3-(or 4-, 5-)
-, 6-) acetoacetaminosalicylic acid, 5,
Metal salts of aromatic compounds such as 5'-carboxyacetoacetobenzidide. Metals that form salts include monovalent or polyvalent metals such as lithium, sodium, potassium, calcium, magnesium, strontium, barium, aluminum, chromium, manganese, iron, cobalt, nickel, copper, zinc, or cadmium. You can choose whatever you like. Among the compounds listed as compounds having a coupling position and a group in the form of a metal carboxylic acid salt in the structure, particularly preferred are 2-hydroxy-1-naphthoic acid, 2-hydroxy-3-naphthoic acid, 2, 4-dihydroxybenzoic acid, 4-
acetoacetaminobenzoic acid or 4-acetoacetaminosalicylic acid, calcium, zinc,
Salts of strontium, manganese or cadmium. The conditions for the binder resin are: (1) It must be dissolved in water, methanol, or ethanol, which is a solvent for the diazo compound, and (B) It must be softened or melted to the extent that the coloring reaction of the diazo compound is easy during thermal printing. can be mentioned. Those that meet the above conditions include polyvinyl alcohol, polyvinyl butyral,
polyvinyl acetal, polyvinyl formal,
Epoxy, polyacrylic acid, polymethacrylic acid,
Polymethacrylic acid ester, polyacrylate,
polyamide, polyvinyl chloride, polyvinyl acetate,
Synthetic or natural resins such as vinyl chloride/vinyl acetate copolymer, cellulose acetate, cellulose acetate butyrate, melamine, polyvinylpyrrolidone, gelatin, and casein can be mentioned. It is more preferable to use a binder having an acidic residue in terms of stabilizing the diazo compound and accelerating the rate of photodecomposition during fixing. Examples of such binders include styrene/maleic acid copolymer, isobutylene/ It is preferable to use a maleic acid copolymer or a vinyl chloride-vinyl acetate-maleic acid ternary copolymer resin. The above-mentioned diazo compound, coupling agent, and binder resin are further kneaded with a solvent or a diluent to form a coating material for forming a sensitive layer. The mixing ratio of the diazo compound and coupling agent in the above is 1/0.5~
It is 1/5, more preferably 1/3 to 1/2. Further, the blending ratio of the diazo compound and the binder resin is 1/1 to 1/20, more preferably 1/3 to 1/10.
It is. It is desirable to add an acidic stabilizer to the sensitizer-forming paint in order to improve the storage stability of the diazo compound and the rate of photodecomposition during the fixing operation. Examples include citric acid, oxalic acid, malonic acid, malic acid, adipic acid, and maleic acid. The coating material for forming a sensitive layer prepared as described above can be coated on the surface of a base material using a known coating method such as gravure coating, roll coating, air knife coating, kiss coating, spray coating, continuous coating, dip coating, spinner coating, and wheel coating. Coating, brush coating, solid coating by silk screen, wire bar coating, flow coating, gravure printing, gravure offset printing, lithographic offset printing, die-line printing, letterpress printing, intaglio printing, jet printing, silk screen printing, electrostatic printing. A heat-sensitive recording layer is formed by coating the film to a thickness of about 2 to 5 μm. Next, the base agent layer 3 is formed by dispersing in the binder resin an organic or inorganic pyrolyzable alkali generator that becomes alkaline when heated or thermally decomposed to generate alkali. Examples of thermally decomposable or heat-soluble alkali generators include organic urea, thiourea, aminopyridine, imidazole, phenylimidazole, guanidine, diphenylguanidine, di-o-tolylguanidine and its derivatives, and inorganic ones. NH ₄ HCO ₃ , NH ₄ H ₂ PO ₄ ,
Examples include (NH ₄ ) ₂ HPO ₄ , (NH ₄ ) ₃ PO ₄ and NaHNH ₄ PO ₄ . The above-mentioned pyrolyzable alkali generator is dispersed in a binder resin, a solvent, or a diluent in the same manner as when forming a sensitive layer to form a coating material for forming a base layer, and can be prepared using a known coating method or printing method. A base agent layer 3 is formed on the heat-sensitive recording layer 2 by the following steps. In the above, the ratio of pyrolytic alkali generator/binder resin is 1/0.5
It is about 1/5 to 1/5, preferably 1/0.5 to 1/2. The thickness of the base agent layer is 1 to 2 μm. In addition, if the pyrolytic alkali generator is dissolved in the paint for forming the base layer, there is a strong possibility that it will penetrate into the underlying sensitive material layer 2 and develop color when the base layer 3 is formed.
Preferably decentralized. Next, explaining the undercoat layer 4, the purpose of providing the undercoat layer 4 is to combine the base agent layer 3 and the top coat layer 5 described below.
Physically suppresses the generation of bubbles caused by nitrogen gas generated by thermal printing, blocks moisture, acid, alkaline components, etc. that enter from the air through the overcoat layer 5, which will be described later, and improves the adhesion of the base layer 4. It smoothes the surface and imparts elasticity to improve adhesion during thermal head compression. The undercoat layer 4 provided for the above purpose is, for example, a styrene/maleic acid copolymer resin, a polyvinyl alcohol resin, a polyacrylic acid resin, a polyacrylic ester resin, a melamine resin, a polyamide (nylon) resin, a polyvinyl acetal resin, or a polyvinyl acetal resin. Polyvinyl acetal resin such as resin is used as the binder resin, and polyvinyl alcohol resin, polyamide resin, polyvinyl acetate resin is preferably used as the binder resin, which has flexibility, low air permeability, and high film forming ability. It is desirable to use it as As a solvent for dissolving these binder resins,
After selecting and using a base agent that does not dissolve the base agent in the lower layer of the undercoat layer 4, appropriately blending and kneading the above binder resin, solvent, further diluent, etc. to obtain a paint for forming the undercoat layer. Film thickness 0.5~ by known coating/printing methods
Form to a thickness of 2 μm. The overcoat layer 5 is provided to protect the underlying photosensitive material layer 2 and base layer 3 and to prevent so-called staking, in which the coloring component and binder resin adhere to the thermal head during thermal printing. . The top coat layer 4 can be formed by a known coating method using a coating composition made of a thermoplastic resin or a thermosetting resin mixed with a lubricant and a mold release agent. Hydroxyethyl cellulose, cellulose acetate propionate,
Cellulose derivatives such as nitrocellulose and cellulose acetate, styrene resins and styrene copolymer resins such as polystyrene and polyα-methylstyrene, acrylic or methacrylic such as polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate, and polybutyl acrylate. Resin alone or copolymer resin, rosin, rosin-modified maleic acid resin, rosin-modified phenol resin, rosin ester resin such as polymerized rosin, polyvinyl acetate resin, coumarone resin, vinyltoluene resin, vinyl chloride resin, polyester resin, polyurethane resin , butyral resin, polyamide resin, vinyl chloride-vinyl acetate copolymer resin, cyclized rubber, chlorinated rubber, etc., and a lubricant and a mold release agent are further blended with a solvent and a diluent. It can be prepared by adding an agent and kneading. Dot line type thermal printers use pressure as a thermal head during thermal printing, causing strong friction between the thermal recording material and the thermal head, making it effective to use lubricants and release agents. The typical substances that serve as lubricants are metal soaps, that is, metal salts of fatty acids such as lauric acid and stearic acid, but there are also the following substances. Organic tin fatty acid salts such as dibutyl-tin dilaurate, dibutyl-tin dinonylate, fatty acid amides such as stearylamide, palmitylamide, oleylamide, bis fatty acid amides, higher ketones such as stearone, higher alcohols and their derivatives such as myristyl alcohol, cetyl alcohol. , stearyl alcohol, polyethylene glycol, polyglycerol, hydrocarbons such as liquid paraffin, paraffin wax, microwax, polyethylene with a low degree of polymerization, as well as natural waxes such as carnauba wax, candelilla wax, beeswax, spermaceti wax, ipotal wax, montan wax. Furthermore, the term "mold release agent" refers to an agent that is generally used for the purpose of improving mold release during processing of rubber or plastic. A wide variety of substances can serve as mold release agents, but the main ones include mineral oils, such as petroleum ethers, vegetable oils, such as olive oil or castor oil, petrolatum or lanolin, fatty acids, especially alkanoic or alkenoic acids having 11 to 24 carbon atoms, and The ester especially has 6 carbon atoms.
Esters with alkyls or alkenyls of ~24, esters of phosphites, especially phenyl or alkyl (8 to 13 carbon atoms), fatty acid esters of glycerin-sorbitan condensates, alkenoyl (7 to 21 carbon atoms) amino acid esters, fluorocarbons and These include Teflon and silicone. The thickness of the above-mentioned top coat layer 5 is 0.5 to 2 μm. The heat-sensitive recording material A of the present invention basically has the above structure, but a primer layer 6 may be further laminated between the base material 1 and the sensitive layer 2 for the purpose of improving adhesion. good. FIG. 2 shows a cross-sectional view of a heat-sensitive recording material B provided with a primer layer 6. The primer layer 6 can be formed using a solution-type or aqueous emulsion-type paint in which a synthetic resin selected in consideration of the materials of the base material 1 and the sensitive material layer 2 is dissolved in an appropriate solvent. Film thickness is 1~
It is 3μm. Examples of solution-type resins include those obtained by dissolving thermoplastic resins such as polyester, polyacrylic acid ester, vinyl chloride/vinyl acetate copolymer, polyvinyl butyral, and cellulose acetate butyrate using a solvent. The above thermoplastic resins can also be used as emulsions or aqueous solutions. Examples of aqueous solutions include those using synthetic resins such as polyvinyl alcohol, polyvinylpyrrolidone, and polyacrylic acid, and those using natural resins such as gelatin and casein. In order to record using the heat-sensitive recording material of the present invention, first thermal printing is performed using a thermal pen or a thermal head, and then the entire surface is irradiated with an ultraviolet light source such as an ultraviolet light of a diazo copier to fix the image. . The heat-sensitive recording material of the present invention has a protective layer consisting of two layers, an undercoat layer and a topcoat layer, compared to the conventional one having a single topcoat layer, so the adhesion of the protective layer is Since the undercoat layer is used to smooth out the irregularities of the lower layer and then the topcoat layer is formed, the surface has excellent smoothness, which is advantageous in preventing statesking. Furthermore, by selecting the resins for the undercoat layer and the topcoat layer, it is possible to physically suppress the generation of air bubbles during thermal printing. Furthermore, it is possible to eliminate the transfer of plasticizer even when it comes into contact with polyvinyl chloride resin sheets etc. containing plasticizer, and unlike the coloring system used, there is no discoloration once the color is developed, and the plasticizer does not permeate. It is also possible to prevent the dye from dissolving and moving. Example 1 A base material and a paint for forming each layer were prepared as described below. Base material Milky white polyester film (manufactured by Toray Industries, Ltd., Lumirror (manufactured by VAGH) Xylene diisocyanate 1 part by weight (Takenate D-110N, Takeda Pharmaceutical Co., Ltd.) Methyl ethyl ketone 20 parts by weight Toluene 30 parts by weight Paint for forming a sensitive layer p-(N,N-dimethylamino)benzenediazonium borate 1 Part by weight 2-hydroxy-3-naphthoic acid anilide
2 parts by weight PVC/vinyl acetate copolymer resin 7 parts by weight (manufactured by Union Carbide, VAGH) Methyl ethyl ketone 55 parts by weight Ethanol 15 parts by weight Base layer forming paint Diphenylguanidine 5 parts by weight Vinyltoluene/butadiene copolymer resin
5 parts by weight (Priolite VT manufactured by Gutdeyer) Ethylcyclohexane 55 parts by weight Paint for forming the undercoat layer Styrene/maleic acid copolymer resin 5 parts by weight (Sprapal AP manufactured by BASF) Ethanol 38 parts by weight Water 7 parts by weight For forming the top coat layer Paint Cellulose acetate propionate resin 5 parts by weight (manufactured by Eastman Kodak, CAP504-02) Polyethylene wax 0.5 parts by weight (manufactured by Gutdeyer, MF-8F) Soybean lecithin 1.5 parts by weight Isopropanol 36 parts by weight Water 9 parts by weight Above polyester First, a paint for forming a primer layer is used on the surface of the film, and a primer layer with a thickness of 1 μm after drying is formed using the gravure coating method.A paint for forming a sensitive layer is used on the primer layer.
A sensitive layer having a thickness of 3 μm after drying was formed by a roll coating method, and a base agent layer having a thickness of 1 μm after drying was formed by a rod coating method using a paint for forming a base layer on the sensitive layer. Furthermore, a paint for forming an undercoat layer is used on the surface of the base layer, and an undercoat layer is formed using the gravure coating method so that the film thickness after drying is 1 μm, and an overcoat layer is formed on the surface of the formed undercoat layer. An overcoat layer was formed using a commercial paint by gravure coating so that the film thickness after drying was 1 μm. Comparative Example 1 The same materials as in Example 1 were used, and the same procedure as in Example 1 was conducted except that the undercoat layer and topcoat layer were removed. Comparative Example 2 The same procedure as in Example 1 was carried out except that only the undercoat layer was removed. Example 2 A base material and a paint for forming each layer were prepared as described below. Base material Milky white polyester film (manufactured by Toray Industries, Ltd., Lumirror, X-24, thickness 188 μm) Paint for forming primer layer Polyester resin 10 parts by weight (manufactured by Dupont, #490000) Cyclohexanone 45 parts by weight Methyl ethyl ketone 45 parts by weight Paint for forming sensitive layer p -(N,N-diethylamino)-benzene Diazochloride 1/2ZnCl ₂ double salt 1 part by weight 2-hydroxy-3-naphthoic acid-(2'-ethoxyanilide) 1.5 parts by weight PVC/vinyl acetate/maleic acid copolymer resin 6 parts by weight Methyl ethyl ketone 50 parts by weight Ethanol 15 parts by weight Base agent layer forming paint Di-o-tolylguanidine 5 parts by weight Vinyltoluene/butadiene copolymer resin
5 parts by weight (Manufactured by Gutdeyer, Priorite VT) Ethylcyclohexane 55 weight Paint for forming the undercoat layer Polyvinyl alcohol resin 10 parts by weight (Nippon Gosei Kagaku Kogyo, L-7514, degree of saponification 50
%) Ethanol 80 parts by weight Water 10 parts by weight First, a primer layer with a dry film thickness of 1 μm was formed on the above base material using a paint for forming a primer layer using the rod coating method, and then a paint for forming a sensitive layer was sequentially applied. Gravure coating method using a roll coating method to form a sensitive layer and a base layer with a dry thickness of 2 μm, and a roll coating method to use a paint to form a base layer and an undercoat layer with a dry thickness of 1 μm. An undercoat layer with a dry thickness of 3 μm and a top coat layer with a dry thickness of 1 μm were formed by gravure coating using the same paint for forming the top coat layer as used in Example 1. . The evaluation results of the heat-sensitive recording sheets obtained in Example 1, Comparative Example 1, Comparative Example 2, and Example 2 are shown in the following table. In the table, temperature and humidity storage stability refers to the time when the fog density exceeds 0.5 when stored under conditions of 40°C and 90% RH. As shown in the following table, by providing an overcoat layer, staking and head residue adhesion can be improved, and by using the overcoat layer and undercoat together, adhesion, temperature/humidity storage stability, and smoothness can be improved. Recognize. 【table】

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the heat-sensitive recording material of the present invention, and FIG. 2 is a cross-sectional view showing another embodiment of the heat-sensitive recording material of the present invention. 1...Base material, 2...Sensitive layer, 3...Base layer,
4...undercoat layer, 5...top coat layer, 6...primer layer.

Claims (1)

[Scope of Claims] 1. A heat-sensitive recording material characterized in that the following layers (a) to (d) are laminated in sequence on a base material. (a) A sensitive layer in which a diazo compound and a coupling agent are dispersed in a binder resin. (b) A base layer in which a pyrolyzable alkali generator is dispersed in a binder resin. (c) A bottom made of a synthetic resin selected from styrene/maleic acid copolymer resin, polyvinyl alcohol resin, polyacrylic acid resin, polyacrylic ester resin, melamine resin, polyamide resin, polyvinyl acetal resin, or polyvinyl acetate resin. Paint layer. (d) An overcoat layer consisting of a synthetic resin in which a lubricant and a mold release agent are dispersed. 2. The heat-sensitive recording material according to claim 1, characterized in that a primer layer is laminated between the base material and the photosensitive material layer.