JPH0334471B2 - - Google Patents

Description

[Detailed description of the invention]

In recent years, thermal recording methods that use heat have the great advantage of being able to easily obtain records without the need for processes such as development and fixing or replenishing materials, which are required in conventional print recording methods. As a result, its uses are expanding more and more. In particular, in this method, heating a color-forming substance such as crystal violet lactone and a color developer such as a phenol compound,
The method of reacting and developing color has been comprehensively evaluated in terms of print clarity and has been put into practical use. However, for example, cellulose, starch, polyvinyl alcohol, etc. are often used as binders for the color-forming substance and the color developer, but if the printed recording paper comes into contact with water or plasticizer, the printing may disappear or the recording paper may become damaged. There remains the problem of water resistance, which is stickiness. As a countermeasure against this problem, proposals have been made such as providing a protective layer of carboxylic acid-modified polyvinyl alcohol on the recording paper, but if heating and recording are continued for a long period of time using a recording paper with such a layer, the thermal head may There are disadvantages in that debris adheres to the thermal head due to friction, and the so-called staking problem occurs in which the thermal head itself and the thermal recording paper adhere to each other at high temperatures. The problem of statesking and scum appears to be related to complex factors such as the strength of the resin film used as the protective layer and the glass transition temperature, and no effective solution has yet been proposed. Also, regarding the problem of water resistance, methods have been proposed in which the protective layer is made using a crosslinking agent such as formalin or glyoxal as a water resistance agent, or a method using a metal chelate, but due to the nature of the coloring substance, drying treatment is Since the temperature or heat treatment temperature is limited to a relatively low temperature range, water resistance is still not necessarily sufficient. However, as a result of extensive research in order to solve these problems, the present inventors have developed a heat-sensitive recording material having a heat-sensitive color-forming layer consisting of a color-forming substance, a color developer that causes the color-forming substance to develop color when heated, and a binder. , on the heat-sensitive coloring layer, the general formula [

[Formula] (R ₁ ; hydrogen or methyl group, R ₂ ; hydrogen or alkyl group,
R ₃ ; alkyl group, A; oxygen or amide nitrogen,
A layer of an epihalohydrin reaction product of a copolymer of an aminoalkyl group-containing (meth)acrylic acid derivative represented by B; represents an alkylene group and an alkyl group-containing ethylenically unsaturated monomer having 8 or more carbon atoms is provided. The present invention was completed by discovering that the heat-sensitive recording material can achieve the objective. By using the above-mentioned resin as the protective layer in the present invention, it not only exhibits an excellent effect in preventing staking and adhesion of residue, but also does not require any treatment with a crosslinking agent or waterproofing agent, and can be simply dried. Since a sufficient crosslinking reaction occurs with the low-temperature treatment, a recording paper with good water resistance and plasticizer resistance can be obtained. The protective layer used in the present invention is an epihalohydrin reaction product of a copolymer of an aminoalkyl group-containing (meth)acrylic acid derivative represented by the above general formula and an alkyl group-containing ethylenically unsaturated monomer having 8 or more carbon atoms. be. As aminoalkyl group-containing (meth)acrylic acid derivatives, dimethylaminomethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, diethylaminoethyl (meth)acrylate, diethylaminopropyl (meth)acrylate, Dipropylaminoethyl (meth)acrylate, dipropylaminopropyl (meth)acrylate, monomethylaminomethyl (meth)acrylate, monomethylaminoethyl (meth)acrylate, monomethylaminopropyl (meth)acrylate, monoethylaminoethyl (meth)acrylate , monoethylaminopropyl (meth)acrylate, monopropylaminoethyl (meth)acrylate, monopropylaminopropyl (meth)acrylate, dimethylaminomethyl (meth)acrylamide, dimethylaminoethyl (meth)acrylamide, dimethylaminopropyl (meth) Examples include acrylamide, diethylaminoethyl (meth)acrylamide, diethylaminopropyl (meth)acrylamide, dipropylaminoethyl (meth)acrylamide, dipropylaminopropyl (meth)acrylamide, etc., but the present invention is not necessarily limited to these. Dimethylaminoethyl methacrylate is preferably used. The component to be copolymerized with this must be an ethylenically unsaturated monomer having an alkyl group having 8 or more carbon atoms. Even with monomers that do not contain an alkyl group such as styrene or monomers that contain an alkyl group such as methyl acrylate, it is difficult to obtain the effects of the present invention if the alkyl group has 8 or fewer carbon atoms. drug properties,
Only recording paper with low water resistance etc. can be obtained. Copolymerization can be carried out by any method such as solution polymerization, emulsion polymerization, suspension polymerization, etc. The copolymerization ratio of the above two components varies somewhat depending on their type or the performance of the intended recording paper, but usually (meth)acrylic acid derivative: ethylenically unsaturated monomer = 60-15:40-
85 (molar ratio) is appropriate. Those used as the alkyl group-containing ethylenically unsaturated monomer having 8 or more carbon atoms are listed below. Ethylenically unsaturated carboxylic acid long chain alkyl ester octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, (meth)acrylate hexadecyl acrylate,
(meth)octadecyl acrylate, (meth)stearyl acrylate, octyl crotonate, decyl crotonate, octyl itaconate, decyl itaconate, octyl sorbate, decyl sorbate, dodecyl sorbate, dioctyl maleate, monooctyl maleate , didecyl maleate, didodecyl maleate, monodecyl maleate, monododecyl maleate, etc. Long-chain carboxylic acid vinyl esters Vinyl caprate, vinyl caprylate, vinyl laurate, vinyl versatate, vinyl valmitate, vinyl stearate, etc. Long-chain α-olefin α-octene, α-decene, α-dodecene, α
-Hexadecene, α-octadecene, etc. Long chain alkyl vinyl ether octyl vinyl ether, decyl vinyl ether, dodecyl vinyl ether, tetradecyl vinyl ether, hexadecyl vinyl ether, octadecyl vinyl ether, etc. Long chain alkyl allyl ether octyl allyl ether, decyl allyl ether, dodecyl allyl ether, tetradecyl allyl ether, hexadecyl allyl ether, octadecyl allyl ether, etc. Allyl ester of saturated carboxylic acid Allyl stearate, Allyl laurate, Allyl coconut oil fatty acid, Allyl octylate In the present invention, during copolymerization of these two components, other monomers that can be copolymerized with these are further copolymerized. Polymerization is also possible. Examples of these monomers are shown below. Ethylenically unsaturated carboxylic acid alkyl esters Methyl crotonate, ethyl crotonate, methyl itaconate, ethyl itaconate, methyl sorbate, ethyl sorbate, monoalkyl maleate, dialkyl maleate, alkyl oleate, (meth) ) Methyl acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, heptyl (meth)acrylate, and the like. α-olefin ethylene, propylene, α-hexene, etc. Ethylenically unsaturated carboxylic acids (meth)acrylic acid, crotonic acid, (anhydrous) maleic acid, fumaric acid, itaconic acid, and their alkali metal salts, ammonium salts, etc. Alkyl vinyl ether propyl vinyl ether, butyl vinyl ether, hexyl vinyl ether, etc. Alkyl allyl ether Propyl allyl ether, butyl allyl ether, hexyl allyl ether, etc. Other substances such as vinyl acetate, vinyl propionate, vinyl butyrate, (meth)acrylamide, (meth)acrylonitrile, (meth)allylsulfonate, ethylenically unsaturated sulfonate, styrene, vinyl chloride, allyl butyrate, etc. can also be used. be. The copolymer of the present invention needs to be further reacted with epihalohydrin, particularly epichlorohydrin, to quaternize the aminoalkyl group moiety. The reaction is optionally carried out according to known methods. Epihalohydrin is used in a proportion of 70 to 200 mol% based on the aminoalkyl groups in the copolymer. Of course, this method is not limited to this method, and aminoalkyl group-containing (meth)
It is also possible to produce it by copolymerizing a quaternized monomer obtained by reacting an acrylic acid derivative with epihalohydrin and an ethylenically unsaturated monomer containing an alkyl group having 8 or more carbon atoms. The resin thus obtained is coated with a thermosensitive coloring layer composed of a coloring substance, a color developer, and a binder. Coating can be done by any means. The appropriate concentration of the coating liquid is 1 to 10% by weight, taking into account coating properties and the like. The coating amount is preferably about 0.5 to 5 g/m ² . After coating, the desired coating layer is formed by air drying or mild heat treatment. Examples of color-forming substances in the present invention include 3,
3-bis(P-dimethylaminophenyl)-phthalide, 3,3-bis(P-dimethylaminophenyl)-6-dimethylaminophthalide [crystal violet lactone], 3,3-bis(P-dimethyl aminophenyl)-6-diethylaminophthalide, 3,3-bis(P-dimethylaminophenyl)-6-chlorophthalide, 3-dimethylamino-6-methoxyfluoran, 7-acetamino-3-diethylaminofluoran, 3-diethylamino-5,7-dimethylfluorane, 3-diethylamino-5,7-dimethylfluorane, 3,
6-bis-β-methoxyethoxyfluorane,
Examples include leuco derivatives of triphenylmethane dyes such as 3,6-bis-β-cyanoethoxyfluoran. The color developer is one that reacts with the color-forming substance when heated and liquefies or vaporizes at room temperature or higher, preferably 70°C or higher, such as phenol, P-methylphenol, P-tert-butylphenol, P- Phenylphenol, α-
Naphthol, β-naphthol, 4,4'-isopropylidene diphenol [bisphenol A], 4,
4'-Secondary butylidene diphenol, 4,
4'-cyclohexylidene diphenol, 4,4'-
Isopropylidene bis(2-tertiarybutylphenol), 4,4'-(1-methyl-n-hexylidene)diphenol, 4,4'-isopropylidene dicatechol, 4,4'-penzylidene diphenol, 4, 4-isopropylidene bis(2-chlorophenol), phenyl-4-hydroxybenzoate, salicylic acid, 3-phenylsalicylic acid, 5-methylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 1-oxy-2-naphthoate Examples include acid, m-oxybenzoic acid, 4-oxyphthalic acid, gallic acid, etc., but color-forming substances,
The color developer is not limited to these. In preparing the coating liquid for forming the heat-sensitive color forming layer of the present invention, an aqueous dispersion of a color forming substance and an aqueous dispersion of a color developer were prepared separately, and they were thoroughly stirred and pulverized. After that, a uniformly dispersed coating liquid can be obtained by simply mixing and stirring both liquids. The binder component is added to at least one of the aqueous dispersion of the color-forming substance and the aqueous dispersion of the color developer. The binder component is suitably used in an amount of 10 to 200% by weight based on the total amount of the color forming substance and color developer. The solid content concentration of the coating liquid is 10 to 10, considering workability etc.
Selected from a range of 40% by weight. As a binder, for example, modified PVA, carboxyl group-containing PVA, etc.
PVA, methylcellulose, carboxymethylcellulose, starches, latexes, or the same resin as the protective layer of the present invention can be used. Furthermore, known additives such as thermoplastic substances such as higher fatty acid amides, fillers such as calcium carbonate, clay, and titanium dioxide, dispersants, waterproofing agents, and crosslinking agents may also be added. There is no particular restriction on the paper on which the coating liquid is applied, and any paper can be used. For coating, any known method such as a roll coater method, an air doctor method, a blade coater method, etc. can be employed. However, the coating amount of the coating liquid is 1 to 20 g/m2, especially 3 to 10 g/ ^m2 .
It is appropriate to set it to about g/m ² . The present invention will be explained in more detail below with reference to examples. In the following, "parts" or "%" are based on weight unless otherwise specified. Example 1 Solution A Crystal violet lactone 10 parts Polyvinyl alcohol 5% aqueous solution (saponification degree 98
Mol%, degree of polymerization 1100) 10 parts Water 15 parts Solution B Bisphenol A 50 parts 5% aqueous solution of polyvinyl alcohol same as Solution A
50 parts Water 75 parts Part A and part B are ground separately with a sand grinder until the average particle size is about 3μ, then part A,
A coating solution was obtained by mixing Solution B, 50 parts of CaCO ₃ , and 270 parts of the same 15% aqueous solution of polyvinyl alcohol used in each solution. The coating liquid was applied to a base paper with a basis weight of 50 g/m ² so that the coating amount after drying was 5.0
It was applied at a concentration of g/m ² and dried. Furthermore, dimethylaminoethyl methacrylate/2
-Ethylhexyl methacrylate copolymer epichlorohydrin reactant (copolymerization molar ratio 35/65, epichlorohydrin reacts equimolarly with aminoethyl group)
1.06 using a Dickson coater with a 6% aqueous solution of
It was bar coated at a ratio of g/m ² (net) and air-dried to obtain thermal recording paper. The recording paper was evaluated for statesking, dross adhesion, water resistance, and plasticizer resistance using the following methods. Regarding States King and dross adhesion, a commercially available facsimile machine (Mitsubishi MELFAS-550) was used for 20 consecutive tests.
A checkered pattern was printed and the occurrence of staking and the degree of adhesion of dust to the thermal head were observed. Regarding water resistance, the printed recording paper was measured using a taper abrasion tester. In addition, plasticizer resistance can be determined by sandwiching the printed recording paper between soft PVC sheets.
A weight of 20 g/m ² was applied and the mixture was allowed to stand for 72 hours, and the color density relative to the original reaction concentration was calculated as a residual color rate in %. The results are shown in the table. Control Example 1 Instead of the protective layer used in Example 1, itaconic acid-modified polyvinyl alcohol (denaturation amount: 5 mol%,
The experiment was conducted in the same manner as in the same example except that a saponification degree of 88 mol% and a polymerization degree of 1500 were used. The results are also shown in Table 1. Examples 2 to 4 Experiments were conducted according to Example 1 using protective layers as shown in Table 1. The results are shown in the table.

【table】

[Table] Concomitant use with methylol urea

Claims (1)

[Scope of Claims] 1. In a heat-sensitive recording material having a heat-sensitive color-forming layer comprising a color-forming substance, a color developer that causes the color-forming substance to develop color when heated, and a binder, a compound having the general formula [[Formula] (R ₁ ; hydrogen or methyl group; R ₂ ; hydrogen or alkyl group; R ₃ ; alkyl group; A; oxygen or amide nitrogen; B; alkylene group)]. A heat-sensitive recording material comprising a layer of an epihalohydrin reaction product of a copolymer with an ethylenically unsaturated monomer containing an alkyl group having 8 or more carbon atoms.