JPH0410874B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a heat-sensitive recording material, and specifically relates to a heat-sensitive recording material with improved storage properties, particularly plasticizer resistance, oil resistance, light resistance, chemical resistance, etc. . <Prior art> Heat-sensitive recording materials, which record images by heating and developing colors using thermal heads, thermal pens, etc., are widely used as recording paper for computer output, facsimile machines, recorders, etc., and for tickets, cards, etc. is also used. However, when recording sheets using this heat-sensitive recording material come into contact with water, plasticizers, oils, etc. for a long time, the colored areas will fade, and furthermore, the uncolored areas will develop unnecessary color due to contact with organic solvents, making it difficult to improve the recording sheets. is necessary. As a method to overcome these drawbacks, it has been proposed to use a water-soluble polymer compound or an aqueous emulsion as a binder for the heat-sensitive layer, or to provide a protective layer on the heat-sensitive layer for the purpose of preventing penetration of water, oil, plasticizers, chemicals, etc. Although it has been
It is not always possible to obtain the effect of simultaneously preventing water, oil, plasticizers, chemicals, etc. from penetrating into the heat-sensitive layer. <Problems to be Solved by the Invention> In view of the above-mentioned problems, the present invention improves the storage stability, particularly the water resistance, oil resistance, plasticizer resistance, and chemical resistance of heat-sensitive recording materials that produce colored images by heating. The purpose is to <Means for Solving the Problems> The present invention provides a method in which a heat-sensitive coloring layer containing a leuco dye and an acidic substance as main components and a protective layer are sequentially laminated on one side of a support, or a protective layer is provided on one side of a support, or a protective layer is formed on the heat-sensitive coloring layer. In a heat-sensitive recording material provided with a protective layer via an intermediate layer, at least the binder of the heat-sensitive coloring layer and the main component resin of the intermediate layer have a sulfonic acid group content of 3 to 30 mol%.
It is a hot water-soluble sulfonic acid group-containing polyester resin, and by forming the protective layer with an ultraviolet curable resin, it has remarkable storage stability, especially water resistance, oil resistance, plasticizer resistance, chemical resistance, etc. They have discovered that they can be obtained at the same time and have completed the present invention. Furthermore, it has been found that by using urethane acrylate or polyester acrylate as the main component of the ultraviolet curable resin, the binding strength with the heat-sensitive layer or the intermediate layer can be improved and higher storage stability can be provided. The hot water-soluble sulfonic acid group-containing polyester resin of the present invention is an aqueous resin that hardly dissolves in water at room temperature, and exhibits extremely high water resistance and solvent resistance. The heat-sensitive layer using this polyester resin or the protective layer provided on the intermediate layer can be formed of water-soluble, water-based or solvent-based resin, but this heat-sensitive recording material, which cannot be cured by heat, has sufficient water resistance. However, there is a drawback that a protective layer having plasticizer resistance, oil resistance, and chemical resistance cannot be provided. In the present invention, by providing a protective layer of an ultraviolet curable resin on a hot water-soluble sulfonic acid group-containing polyester resin component, not only can a protective layer with extremely high binding strength be obtained, but also it is resistant to water, solvents, etc. A heat-sensitive recording material having a layer structure with high barrier properties and high storage stability can be obtained. The sulfonic acid group-containing polyester resin in the present invention can be prepared by any method. For example, the most common method is to condense dicarboxylic acid, alkylene glycol, and sulfonic acid group-containing dicarboxylic acid. Examples of dicarboxylic acids are oxalic malonic acid, dimethylmalonic acid, succinic acid, glutaric acid, adipic acid,
Trimethyladipic acid, pimelic acid, 2,2-dimethylglutaric acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, itaconic acid, 1,
3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, phthalic acid, terephthalic acid, isophthalic acid, 2,5-norporanedicarboxylic acid ,
Examples include 1,4-naphthalic acid, 4,4'-oxybenzoic acid, diglycolic acid, thiodipropion, and 2,5-naphthalene dicarboxylic acid. These may be acid anhydrides, esters, chlorides, etc. Examples of alkylene glycols include ethylene glycol, propylene glycol, 1,3-propanediol, 2,4-dimethyl-2-ethylhexane-1,3diol, 2,2-dimethyl-
1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-
2-isobutyl-1,3propanediol, 1-
3-butanediol, 1,4-butanediol,
1,5-pentanediol, 1,6-hexanediol, 2,2,4-trimethyl-1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol,
1,4-cyclohexanedimethanol, 2,2,
4,4-tetramethyl-1,3-cyclobutanediol, 4,4'-thiodiphenol, 4,4'-methylenediphenol, 4,4'-(2-norbornylidene)diphenol, 4,4'-dihydroxy phenol, m- and p-dihydroxybenzene,
4,4'-isopropylidenediphenol, 4,
4'-isopropylidene bis(2,6-dichlorophenol), 2,5-naphthalenediol and p
-xylene diol. Examples of the sulfonic acid group-containing dicarboxylic acids include sulfonium phthalate, sulfokalium phthalate, sulfonium terephthalate, sulfokalium terephthalate, sulfonium isophthalic acid, and sulfokalium isophthalic acid. These may be esters. The above polyester resin used in the present invention has a hydroxyl value of 2 to 20 KOH mg/g, preferably 4 to 10 KOH.
mg/g is desirable. If it exceeds 20 KOHmg/g, it is difficult to obtain sufficient adhesive strength, coating strength, etc. Also, the content of sulfonic acid groups is 3
~30 mol% is required. If the content is less than 3 mol %, it is insoluble in water and it is difficult to prepare an aqueous liquid, while if the content is 30 mol % or more, it becomes hygroscopic. The sulfonic acid group-containing polyester resin obtained in this way is soluble in hot water and not only exhibits remarkable water resistance to water at temperatures below 40°C, but also has a remarkable barrier to oils, plasticizers, chemicals, etc. It improves the storage stability of thermal paper. The basic composition of the ultraviolet curable resin for the protective layer of the present invention consists of an oligomer, a crosslinking agent, and a photoinitiator. As the oligomer, epoxy acrylic, urethane acrylic, polyester acrylic, alkyd acrylic, silicone acrylic, polyene/polythiol type spiran resin, epoxy type, amino alkyd resin, etc. can be used. In the present invention, polyester acrylate or urethane acrylate is preferred because it has good adhesion to the heat-sensitive layer or intermediate layer of the present invention. In addition, as a crosslinking agent, MTP-triacrylate, venter triacrylate, ethylene glycol diacrylate, tetraethylene glycol diacrylate,
These include 1,6 hexanediol diacrylate, neobentyl glycol diacrylate, vinylpyrrolidone, 2, hydroxylethyl (meth)acrylate, 2, hydroxylpropyl (meth)acrylate, and the like. Examples of the photoinitiator include benzoyl alkyl ether, benzophenone, benzoyl, w-promoacetophenone, chloroacetophenone, benzoquinone, anthraquinone, and the like. Silicone oil, silicone resin, waxes, pigments, etc. can be added to the ultraviolet curable protective layer prepared and formed using the above-mentioned oligomer as a main component to improve the matching property with the thermal head. The coloring component constituting the heat-sensitive coloring layer in the present invention is a combination of an organic acid metal salt and a reducing agent, commonly called NCR type, which is used in ordinary heat-sensitive recording paper;
A combination of a leuco dye called NCR and an acidic substance is used. Specific examples of leuco dyes as components of this NCR type material include crystal violet lactone, 3-indolino-3-p
-dimethylaminophenyl-6-dimethylaminophthalide, 3-diethylamino-7-chlorofluoran, 3-diethylamino-5-methyl-7-
t-Butylfluorane, 3-diethylamino-6
-Methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-p-butylanilinofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-cyclohexylamino-6-chlorofluorane , 3-diethylamino-
6-Methyl-7-xylidinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-pyrrolidino-7-cyclohexylaminofluorane, 3-piperidino-6-methyl-7-
Toluidinofluorane, 3-pyrrolidino-6-methyl-7-(p-toluidino)fluorane, 3-
Piperidino-6-methyl-7-anilinofluorane, 3-N-methylcyclohexylamino-6-
Methyl-7-anilinofluorane, 3-diethylamino-7-(m-trifluoromethylanilino)
Examples include, but are not limited to, fluoran. In addition, as a color developer that develops color by reacting with the above leuco dye under heat, for example, 4-phenylphenol, 4-t-butylphenol, 4-hydroxyacetonephenol, α-naphthol, β-naphthol, 2, 2'-hydroxydiphenyl, 2,2'-methylenebis(4-chlorophenol), 2,2'-methylenebis(4-methyl-6-t-butylphenol), methyl-4-
Hydroxybenzoate, benzyl-4-hydroxybenzoate, 4,4'-isopropylidene bis(2-methylphenol), 4,4'-ethylenebis(2-methylphenol), 1,1'-bis(4-hydroxybenzoate) enyl) cyclohexane. 4,
4'-isopropylidene diphenyl, 4,4'-cyclohexylidene bis(2-isopropylphenol), novolak type phenolic resin, 3,5-
Examples include, but are not limited to, di-α-methylbenzylsalicylic acid, 4-hydroxybenzoic acid ester, and bis(4-hydroxyphenyl)acetic acid ester. Furthermore, inorganic and organic pigments, such as aluminum hydroxide, heavy and light calcium carbonate, titanium oxide, barium sulfate, siligel, activated clay, talc, clay, and satin, may be used as components for forming the heat-sensitive layer of the present invention, if necessary. White kaolinite, calcined kaolinite, diatomaceous earth, synthetic kaolinite, polyolefin particles, polystyrene particles, urea-formalin resin particles, etc., and sensitizers such as stearamide, palmitamide, oleic acid amide, laurin acid amide,
Ethylene bis stearoid, methylene bis stearamide, methylol stearamide, paraffin wax, higher alcohol, higher resin acid, etc. may be added. The above-mentioned heat-sensitive components of the present invention can be used as a support, for example,
Water-soluble or non-water-soluble or non-sulfonic acid group-containing polyester resins other than the sulfonic acid group-containing polyester resin of the present invention may be used as a binder for forming a heat-sensitive layer on paper, synthetic paper, resin film, or a composite thereof, or as a film-forming agent for an intermediate layer. It can be used in combination with water-soluble resin binders. For example, casein, gelatin, styrene-maleic anhydride resin, polyvinyl alcohol, modified polyvinyl alcohol, polyvinylpyrrolidone, starch, modified starch, isobutylene-maleic anhydride resin,
Diisobutylene-maleic anhydride resin, polyacrylmide, modified polyacrylamide, methyl vinyl ether, maleic acid copolymer, carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and as a water-soluble emulsion, vinyl acetate, polystyrene, acrylic. Acid esters, vinyl chloride-vinyl acetate copolymers, etc. may be used alone or in combination. Further, if necessary, a curing agent may be added to harden these binders and the resin of the present invention to improve water resistance and chemical resistance. Furthermore, if necessary, for the purpose of improving the light resistance of the heat-sensitive recording material of the present invention, antioxidants, ultraviolet absorbers, and other light stabilizers may be added to the heat-sensitive layer or an intermediate layer on the heat-sensitive layer.
It may be included in the protective layer. <Examples> The present invention will be explained in detail below using Examples and Comparative Examples. Hereinafter, parts represent parts by weight. The sulfonic acid group-containing polyester resin used in the present invention was synthesized as follows. 500 with stirrer, thermometer, nitrogen blowing device, and packed tower
116.3g of terephthalic acid, adipic acid in cc flask
21.9g, 5-sodium sulfoisophthalic acid dimethyl ester 44.4g, ethylene glycol 55.5g
g, 75.0 g of neopentyl glycol, 27.0 g of triethylene glycol, 0.2 g of zinc acetate, and 0.4 g of antimony trioxide were charged and subjected to an esterification reaction at 190 to 220°C for 4 hours, followed by a condensation reaction at 230 to 250°C under 1 mmHg. I went there. Melt viscosity 2000 poise (190℃,
A sulfonic acid group-containing polyester resin having a sulfonic acid group content of 6 mol % (measured with a Koka type flow tester) was obtained. This resin was dissolved in hot water at 90°C to form a polyester resin containing sulfonic acid groups.
A 20% aqueous solution was prepared. Furthermore, each mixture consisting of the following formulations was ground and dispersed in a ball mill for one day to prepare solutions A to C. Part A 3-N-Methylcyclohexylamino-6-methyl-7-anilinofluorane 25 parts 5% hydroxyethyl cellulose aqueous solution 50 parts Water 25 parts Part B Bis(4-hydroxyphenyl)acetic acid methyl ester 15 parts 5% hydroxy Ethyl cellulose aqueous solution 60 parts Stearamide 15 parts Water 10 parts Light calcium carbonate 40 parts 10% polyvinyl alcohol aqueous solution 40 parts Water 20 parts Example 1 10 parts of the above Part A, 33.3 parts of Part B, 49 parts of Part C, the above A heat-sensitive recording paint was obtained by mixing 15 parts of a 20% aqueous solution of polyester resin and 46 parts of water. The paint is 188μ
The amount of coating after drying on the polyester resin sheet is 6
g/m ² and dried, then knead UV-curable ink with the composition shown in Liquid D below using three rolls, and then coat it to a film thickness of 2μ using the reverse roll coater method. After coating, ultraviolet rays were irradiated using an ultraviolet irradiation device (three 5.6Kw mercury lamps) at a distance of 100 mm from the lamp and at a conveyance speed of 15 m/min to obtain a heat-sensitive recording sheet with a coating amount of 1 g/m ² k ultraviolet curing protective layer. Ta. D-liquid polyester acrylate (Aronix
M8060, manufactured by Toagosei Kagaku Co., Ltd.) 100 parts Photoinitiator (Dalkyur 953, manufactured by MERCK)
5 parts polyethylene wax 5 parts silicone oil 1 part Example 2 A mixture of 30 parts of a 20% aqueous solution of the polyester resin and 3 parts of a 1% aqueous sodium alkylbenzenesulfonate solution was applied onto the heat-sensitive layer obtained in Example 1. - After drying, an intermediate layer with a coating amount of 3 g/m ² was provided.
A mixed solution of 50 parts of liquid D and 50 parts of toluene was applied onto this intermediate layer using a wire bar, and after drying, the mixture was exposed to the same ultraviolet rays as in Example 1 and passed through the curing device to coat an amount of 1
A heat-sensitive recording sheet of the present invention was obtained by providing an ultraviolet curing protective layer of g/m ² . Example 3 A heat-sensitive recording sheet of the present invention was obtained in exactly the same manner as in Example 1, except that the polyester/acrylate in the protective layer coating solution D was changed to urethane acrylate (Aronix, manufactured by Toagosei Chemical Industry Co., Ltd.). . Comparative Example 1 The sheet prepared in Example 2, coated up to the intermediate layer, was further coated with a protective layer paint of liquid E below and dried to provide a protective layer with a coating amount of 1 g/m ² , and a comparative heat-sensitive record was prepared. Got a sheet. E liquid 30% polyurethane resin (Hypren PS-623,
(manufactured by Mitsui Nisso Urethane) 10 parts Polymethyl methacrylate resin (Paraloid A-11, manufactured by Rohm and Haas) 2 parts 8% fluororesin liquid (MOLDWIZ F-57) 15 parts Toluene 30 parts Obtained in each example and comparative example The resulting heat-sensitive recording sheet was pressed with a hot plate at 130° C. for 5 seconds to develop color, and the following tests were conducted. The results are shown in the table. The water resistance, plasticizer resistance, and alcohol resistance were measured as follows. Water resistance: Soak the heat-sensitive recording sheet in aquarium water for 24 hours.
Changes in the colored area after a period of time were observed. In addition, the surface of the heat-sensitive sheet was strongly rubbed in a water tank to examine whether the film peeled off. Plasticizer resistance: A dioctyl phthalate solution was dropped onto the colored area, and changes in the surface of the dropped area 24 hours later were observed. Alcohol resistance: Methanol was dropped onto the scalp and changes in the drop area were observed 3 minutes later.

[Table] In the table: ◎: No change, ○: Slight change,
△: Significant change; ×: Film peeling occurs or color develops.
<Effects of the Invention> As is clear from the table, by providing a protective layer of an ultraviolet curable resin on the heat-sensitive layer or further provided intermediate layer using the sulfonic acid group-containing polyester resin of the present invention, remarkable water resistance, It can be seen that plasticizer resistance and alcohol resistance can be obtained.

Claims (1)

[Scope of Claims] 1. A heat-sensitive coloring layer containing a leuco dye and an acidic substance as main components and a protective layer are sequentially laminated on one side of a support, or a protective layer is provided on the heat-sensitive coloring layer via an intermediate layer. In the heat-sensitive recording material, at least the binder of the heat-sensitive coloring layer and the main component resin of the intermediate layer are hot water-soluble sulfonic acid group-containing polyesters having a sulfonic acid group content of 3 to 30 mol%. 1. A heat-sensitive recording material, wherein the protective layer is made of an ultraviolet curable resin. 2. The heat-sensitive recording material according to claim 1, wherein the ultraviolet curable resin is mainly composed of urethane acrylate or polyester acrylate. 3. The heat-sensitive recording material according to claim 1 or 2, wherein the support is a polyester resin or a matted polyester resin.