JPH044958B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to binders and recording paper. More specifically, the present invention relates to a binder for binding a heat-sensitive recording material to a support in a heat-sensitive recording paper, and a heat-sensitive recording paper. Thermosensitive recording paper is made by bonding to a support a recording material whose main components are a leuco dye and a color developer that melts upon heating and develops a color from the leuco dye.
The binder that binds the recording material to the support includes
Polyvinyl alcohol has traditionally been used. In addition, in order to improve water resistance, which is a drawback of polyvinyl alcohol, Japanese Patent Publication No. 57-46752 discloses a copolymer of diisobutylene and maleic anhydride; Copolymers with amino(meth)acrylate and the like have been proposed. However, these binders have little effect on increasing the sensitivity, which has become a strong demand for thermal recording paper in recent years. The present inventors have arrived at the present invention as a result of intensive studies on binders that enable high recording sensitivity. That is, the present invention provides a cationic group-containing monomer unit (A) selected from the group consisting of dialkylaminoalkyl (meth)acrylamide, dialkylaminoalkyl (meth)acrylate, and a monomer containing a quaternary ammonium group; An anionic group-containing monomer unit (B) selected from the group consisting of monomers containing a carboxyl group, a sulfone group, a sulfate ester group, and a phosphate ester group and, if necessary, other monomer units (C). a cation selected from the group consisting of dialkylaminoalkyl (meth)acrylamide, dialkylaminoalkyl (meth)acrylate, and a monomer having a quaternary ammonium group (first invention); anionic group-containing monomer unit (A) and an anionic group-containing monomer unit (B) selected from the group consisting of monomers containing a carboxyl group, a sulfone group, a sulfate ester group, and a phosphate ester group, and the necessary This is a heat-sensitive recording paper (second invention) having a coating layer comprising a binder for heat-sensitive recording materials made of a copolymer having another monomer unit (C), a leuco dye, and a color developer. In the copolymer of the present invention, examples of the monomer providing the cationic monomer unit (A) include the following monomers and mixtures of two or more thereof. a Alkylaminoalkyl (meth)acrylamide Dimethyl or diethylaminoethyl (meth)acrylamide, dimethyl or diethylaminopropyl (meth)acrylamide, etc. b Dialkylaminoalkyl (meth)acrylate Dimethyl or diethylaminoethyl (meth)acrylate, dimethyl or diethylaminopropyl (meth)acrylate, etc. The above amino group-containing monomer may be a salt. 2 Quaternary ammonium group-containing monomer a (meth)acryloyloxyalkyl trialkylammonium salt 2-(meth)acryloyloxyethyltrimethylammonium chloride, 3-(meth)
Acryloyloxy-2-hydroxypropyltrimethylammonium chloride and the like. b (meth)acrylamidoalkyltrialkylammonium salt 3-(meth)acrylamidopropyltrimethylammonium chloride, 3-(meth)
Acryloylamino-2-hydroxypropyltrimethylammonium chloride and the like. c Others Dimethyldiallylammonium chloride, β-vinyloxyethyltrialkylammonium salts (β-vinyloxytrimethylammonium chloride, etc.), vinylbenzylammonium salts (vinylbenzyltrimethylammonium chloride, etc.), etc. Preferred among these cationic monomers are dialkylaminoalkyl (meth)acrylate and dialkylaminoalkyl (meth)acrylamide, and particularly preferred is dimethylaminopropyl (meth)acrylamide. Examples of the monomer providing the anionic monomer unit (B) include the following monomers and mixtures of two or more thereof. 1 Carboxyl group-containing monomer a Unsaturated monocarboxylic acid Fatty acid unsaturated monocarboxylic acid such as (meth)acrylic acid, crotonic acid, etc.; Aromatic unsaturated monocarboxylic acid such as vinylbenzoic acid. b Unsaturated polycarboxylic acids Maleic acid, fumaric acid, itaconic acid, citraconic acid, aconitic acid, etc. 2 Sulfonic group-containing monomer a Fatty acid vinylsulfonic acid Vinylsulfonic acid, (meth)allylsulfonic acid, etc. b Aromatic vinylsulfonic acid Styrenesulfonic acid (O and P forms), styrene disulfonic acid, 3-vinyltoluene-
6-sulfonic acid, 3-vinylethylbenzene-6-sulfonic acid, etc. c Acrylic sulfonic acid (meth)acryloyloxyalkane (or hydroxyalkane) sulfonic acid, 3-
(meth)acryloyloxypropanesulfonic acid and 3-(meth)acryloyloxy-2-hydroxypropanesulfonic acid, and the like. d (meth)acrylamidoalkanesulfonic acid 2-(meth)acrylamido-2-methylpropanesulfonic acid, 3-(meth)acrylamido-2-hydroxypropanesulfonic acid, and the like. 3 Monomer containing sulfate ester group d Sulfate ester of unsaturated alcohol, (meth)allyl alcohol sulfate, etc. b Unsaturated esters of polyols or sulfuric acid esters of ethers Polyols include alkylene glycols, glycerin, and polyalkylene glycols. Examples of sulfuric esters include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, polyoxyethylene-oxypropylene glycol mono(meth)allyl ether, and the like. 4 Monomer containing phosphate ester group Unsaturated alcohol phosphoric acid (mono, di) ester, (meth)allylic alcohol phosphoric acid (mono, di)
such as ester. The anionic monomer may be a salt, and salts of water-soluble amines with low volatility are preferred, considering that the salts do not damage the heat-sensitive head and have little odor. Such water-soluble amines include (mono, di, tri) alkanolamines such as triethanolamine, 2-amino-2-methyl-
Examples include 1,3-propanediol. The anionic group may be completely neutralized or partially neutralized. In addition to the above-mentioned monomer units, the copolymer in the present invention may have other nonionic monomer units (C) if necessary, and provides a nonionic monomer unit (C). Examples of monomers include the following and mixtures of two or more thereof. 1 Hydrophilic nonionic monomer (C ₁ ) Amide group-containing monomer [(meth)acrylamide, N-methylol (meth)acrylamide, etc.], hydroxyl group-containing monomer [hydroxy lower (meth)acrylate (hydroxy ethyl (meth)acrylate, etc.), polyethylene glycol (meth)acrylate, etc.). 2 Lipophilic nonionic monomers (C ₂ ) Aromatic vinyl monomers (styrene, α-alkylstyrene, etc.), unsaturated carboxylic acid esters (methyl (meth)acrylate, ethyl (meth)
acrylates, etc.), vinyl esters (vinyl acetate, etc.), unsaturated nitriles ((meth)acrylonitrile, etc.), etc. Among the nonionic monomers (C), preferred are hydrophilic nonionic monomers (C ₁ ), and particularly preferred are (meth)acrylamide and hydroxyethyl (meth)acrylate. In the copolymer of the present invention, the content of (A), (B) and (C) is usually 5 to 90% for (A), preferably 7 to 50% for (B), based on the weight of all monomers. is usually 1-95%
Preferably it is 3 to 75%, and (C) is usually 0 to 94%, preferably 5 to 90%. The weight ratio of (C ₁ ) and (C ₂ ) in (C) is usually 40:60 to 100:0, preferably
It is 65:35 to 100:0. Within the above range, there is a particularly excellent effect on improving recording sensitivity. The copolymer in the present invention includes a monomer that provides a cationic monomer unit, a monomer that provides an anionic monomer unit (an anhydride may be used in the case of an unsaturated polycarboxylic acid), and, if necessary, other monomers. It can be easily obtained by copolymerizing monomers that provide nonionic monomer units. For example, a mixed solvent of water and a water-soluble solvent (water-soluble alcohols such as methyl alcohol, ethyl alcohol, n- or iso-propyl alcohol and cellosolve, such as methyl, ethyl, butyl cellosolve, preferably isopropyl alcohol) (compounding ratio is based on weight). Normal 1:
9 to 9:1 (preferably 2:8 to 8:2), monomers imparting cationicity, monomers imparting anionicity, and if necessary other monomers imparting nonionicity are combined with a radical initiator (azo It can be obtained by polymerization in the presence of azo compounds such as bisisobutyronitrile, peroxides, etc.). The polymerization temperature is, for example, from room temperature to the reflux temperature of the solvent. When neutralizing amino group-containing monomers and anionic monomers, the amount of neutralizing agent is usually 0 to 0.
The amount is 2.0 times the molar amount, preferably 0 to 1.2 times the molar amount, and it may be carried out either before or after the polymerization. Copolymers can be obtained by copolymerizing monomers that provide cationic monomer units and anionic monomer units, or by modifying them after polymerization to obtain cationic groups,
Alternatively, it can also be obtained by methods of introducing anionic groups, such as Mannitz modification and hydrolysis methods. The apparent viscosity of the aqueous solution of this copolymer is usually 10 to 10,000 CPS at a concentration of 20% by weight and a temperature of 20°C, preferably 50
~5000CPS. If the viscosity is less than 10CPU,
Poor ability to bind recording material to support
If it is higher than 10,000 CPS, coating suitability will be inhibited.
The apparent viscosity of the copolymer aqueous solution is
It can be adjusted by appropriately selecting the type and amount of chain transfer agents such as mercaptans, radical initiators, polymerization temperature, etc. The binder of the present invention consists of the above copolymer.
The binder of the present invention is used for the purpose of binding a conventional heat-sensitive recording material to a support. As a heat-sensitive recording material, a leuco dye, a color developer, a color development accelerator and a white pigment are used depending on the purpose. Examples of leuco dyes include leucolactone compounds and spiropyran compounds. Examples of the color developer include organic acids that are solid at room temperature and melt by heating, such as phenolic acids such as bisphenol A and benzyl P-oxybenzoate, and other organic acids. Color accelerators include higher fatty acid amides,
Examples of the white pigment include calcium carbonate. The amount of the binder used in the present invention is usually 1 to 10 times the weight of the leuco dye. The binder of the present invention can be added at the time of mixing dispersions of a leuco dye and a color developer to prepare a coating solution, or it can be added at the time of preparing a dispersion of a leuco dye and a color developer. It may be used at the stage of The obtained coating liquid is applied to a support and dried. Examples of the support include conventionally commonly used paper made of cellulose fibers and synthetic paper made of plastic. The coating amount is usually 0.5 to 10 g/m ² in terms of dry weight. The binder of the present invention exhibits an excellent effect in improving recording sensitivity, which has been strongly desired in recent years for thermal recording paper, and this effect is something that cannot be achieved with conventional binders. Conventionally, low melting point color developers and color development accelerators have been used to increase sensitivity, but the binder of the present invention provides even better sensitivity than these. Furthermore, although the copolymer of the present invention has a high molecular weight, an aqueous solution exhibits a low apparent viscosity. Therefore, when used as a binder, excellent coating suitability can be obtained. The present invention will be further explained below with reference to Examples and Reference Examples, but the present invention is not limited thereto. Example 1 150 g of water and 150 g of isopropyl alcohol in a 10,000 c.c. colben equipped with an agitator, cooler, dropping funnel, nitrogen suction pipe and thermometer.
was charged, and the temperature was raised to reflux temperature under a nitrogen gas stream and stirring. A solution of 1 g of asobisisobutyronitrile in isopropyl alcohol was charged into a Kolben, followed by 60 g of dimethylaminopropyl methacrylamide and 180 g of methacrylic acid, which were charged into a dropping funnel.
The mixture of g was added dropwise to the Kolben over a period of 2 hours. After the dropwise addition, 200 g of triethanolamine was added to perform a neutralization reaction after aging for 3 hours. Thereafter, the isopropyl alcohol was azeotropically distilled off with water, and water was added so that the polymer concentration was 20% to obtain a binder sample (a) of the present invention. The apparent viscosity of sample (a) was 280 cps at 20°C. Example 2 Dimethylaminopropyl methacrylamide 50
A binder sample (b) of the present invention was obtained in the same manner as in Example 1, except for using 70 g of methacrylic acid, 240 g of 50% aqueous acrylamide solution, and 120 g of triethanolamine. The apparent viscosity of sample (b) is
It was 95 cps at 20℃. Example 3 Dimethylaminopropyl methacrylamide 30
g, 10 g of methacrylic acid, 330 g of 50% aqueous acrylamide solution, 10 g of butyl methacrylate and 2-
Amino-2-methyl-1,3-propanediol
A binder sample (C) of the present invention was obtained in the same manner as in Example 1 except that the amount was 15 g. The apparent viscosity of sample (C) was 95 cps at 20°C. Example 4 50 g of dimethylaminoethyl methacrylate, 50 g of maleic acid, 200 g of 50% aqueous acrylamide solution
After polymerization in the same manner as in Example 1 except that 20 g of vinyl acetate was used, isopropyl alcohol was distilled off to obtain a binder sample (d) of the present invention.
The apparent viscosity of sample (d) was 120 cps at 20°C. Reference Example 1 Using the binder samples of Examples 1 to 4 of the present invention, the following first and second liquids were separately dispersed in a ball mill for one day and then mixed to prepare a coating liquid for each binder. Each coating liquid had low viscosity and good fluidity. Further, a coating liquid was similarly obtained using completely saponified polyvinyl alcohol (average degree of polymerization 1000) as a comparative binder. The viscosity of the coating liquid was high, and the fluidity was significantly inferior to that of the coating liquids made of the binder of the present invention. 1st liquid {crystal violet lactone 2 parts binder (20%) 20 parts water 8 parts 2nd liquid {P-oxybenzoic acid benzyl ester 8 parts binder (20%) 10 parts water 7 parts Example 5 2-methacrylate 40g of loyloxymethyltrimethylammonium chloride, 50g of methacrylic acid,
After polymerization was carried out in the same manner as in Example 1 except that 220 g of a 50% aqueous acrylamide solution and 85 g of triethanolamine were used as raw materials, the isopropyl alcohol was distilled off to obtain a binder sample (e) of the present invention. The apparent viscosity of sample (e) was 350 cps at 20°C. Example 6 50 g of 3-methacrylamidopropyltrimethylammonium chloride, 30 g of methacrylic acid,
After polymerization was carried out in the same manner as in Example 1 except that 240 g of a 50% aqueous acrylamide solution and 50 g of triethanolamine were used as raw materials, the isopropyl alcohol was distilled off to obtain a binder sample (f) of the present invention. The apparent viscosity of sample (f) was 320 cps at 20°C. Example 7 Dimethylacrylammonium chloride 10
After polymerization in the same manner as in Example 1 except that the raw materials were 80 g of methacrylic acid, 220 g of 50% aqueous acrylamide solution, and 140 g of triethanolamine, the isopropyl alcohol was distilled off to obtain the binder sample (g) of the present invention. Ta. The apparent viscosity of sample (g) is
It was 210 cps at 20℃. Example 8 Each of the coating solutions obtained in Reference Example 1 was applied onto 52 g/m ² of commercially available high-quality paper using a wire bar to obtain thermal paper with a dry coating weight of 3 g. Each thermal paper was subjected to a high-speed facsimile machine (manufactured by Ricoh Co., Ltd.) and the image density was measured using a Macbeth densitometer. The results are shown in Table 1. From Table 1, the thermal paper using the binder of the present invention showed higher sensitivity than the conventional paper. 【table】

Claims (1)

[Scope of Claims] 1. A cationic group-containing monomer unit (A ) and an anionic group-containing monomer unit (B) selected from the group consisting of monomers containing a carboxyl group, a sulfone group, a sulfate group, and a phosphate group, and if necessary other monomer units (C ) A binder for heat-sensitive recording materials comprising a copolymer having 2 The content of (A) is 5 to 90 based on the weight of total monomers.
%, the content of (B) is 1-95% and the content of (C) is 0-94
% of the binder according to claim 1. 3. The binder according to claim 1 or 2, wherein the aqueous solution of the copolymer has an apparent viscosity of 10 to 10,000 cps at a concentration of 20% by weight and a temperature of 20°C. 4 A cationic group-containing monomer unit (A) selected from the group consisting of dialkylaminoalkyl (meth)acrylamide, dialkylaminoalkyl (meth)acrylate, and a monomer containing a quaternary ammonium group, and a carboxyl group, a sulfone A copolymer having an anionic group-containing monomer unit (B) selected from the group consisting of monomers containing a group, a sulfate ester group, and a phosphate ester group, and optionally other monomer units (C). A heat-sensitive recording paper having a coating layer containing a binder for heat-sensitive recording materials, a leuco dye, and a color developer. 5. The recording paper according to claim 4, wherein the coating amount is 0.5 to 10 g/cm ³ in terms of dry weight.