JPH04135786A - Composition for thermal recording paper - Google Patents

Abstract

PURPOSE:To prevent a texture from being covered and to obtain a composition for thermal recording paper which is excellent in both wettability resistance and coloring proprty by a method wherein a copolymer latex to be obtained by a emulsification polymerization of a monomer mixture under presence of a surface active agent as given by the formula to 100 pts.wt. of a monomer mixture consisting of a conjugate diene monomer and other monomer capable of being therewith, is contained as a binder. CONSTITUTION:1,3-Butadiene, 2-methyl-1, 3-butadiene, etc., are exemplified as a conjugate diene monomer constructing copolymer latex. Further, aromatic vinyl type monomer or the like of styrene, vinyltoluene, etc., are exemplified as other monomer capable of being copolymerized. Surface active agents to be used are compounds as given by the formula (a) or (b). A use amount of those surface active agent is 0.01-1 pts.wt. to 100 pts.wt. of a monomer mixture. Those surface active agents are used as an emulsifying agent. Thereby, thermal recording paper which prevents texture from being covered and which is excellent in both wettability resistance and coloring property can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a composition for thermal recording paper that prevents background fog and has excellent moisture resistance and color development.

<Prior art> Thermal recording paper, which utilizes a color-forming reaction between a color-forming agent and a color-developing agent that develops color when heated, has recently been used in a wide range of applications such as facsimiles and printer labels, and the demand for it is increasing. It is expanding.

Along with this, the quality required for these thermal recording papers has also become more stringent.

For example, as recording speeds increase, there is a strong demand for color development that produces color with high density even with small thermal energy. It is difficult to obtain sufficient color development in this high-speed recording, and the main reason for this is that heat conduction between the thermal head and the thermosensitive coloring layer is not sufficient, and therefore sufficient recording density cannot be obtained. In order to improve the recording density, it is necessary to bring the thermal head and the thermosensitive coloring layer into closer contact with each other, so that heat can be efficiently conducted from the thermal head to the thermosensitive coloring layer. In order to bring the thermal head into close contact with the thermosensitive coloring layer, the smoothness of the thermosensitive coloring layer is improved by calender treatment such as a super calender or a machine calender.

However, this calendering process for thermal recording paper is
It has the disadvantage that background fogging occurs due to the pressure during processing, which significantly reduces the commercial value.

Further, such heat-sensitive recording paper has the disadvantage that, depending on its usage conditions, if it is left in a wet state for a long time, the non-printed areas develop color and the whiteness decreases.

Therefore, there is a demand for heat-sensitive recording paper that also has excellent moisture resistance.

<Problems to be Solved by the Invention> The present inventors have obtained a composition for thermal recording paper that prevents background fogging due to pressure during calendering as described above and has excellent moisture resistance and color development. As a result of intensive research, the present invention was completed by discovering that the problem could be solved by using a copolymer latex obtained by emulsion polymerization in the presence of a specific surfactant as a binder.

<Means for Solving the Problems> That is, the present invention provides a composition for thermal recording paper comprising a color former, a color developer that develops color when heated with the color former, and a binder, wherein the binder is a conjugated A surfactant represented by the following general formula (a) and/or ('b) is added to 100 parts by weight of a monomer mixture consisting of a diene monomer and other monomers copolymerizable with the diene monomer. A heat-sensitive recording material that prevents background fog and has excellent moisture resistance and color development, characterized by containing a copolymer latex obtained by emulsion polymerization of the monomer mixture in the presence of 0.01 to 1 part by weight. A paper composition is provided.

General formula: Here, R is an alkyl group having 4 to 20 carbon atoms or a hydrocarbon group containing an aromatic ring, n is an integer of 2 to 70, and M is Na
, K or NH4.

(b) R'-0+CCH2CH20-)-7-3O
a' where R1 is an alkyl group having 4 to 20 carbon atoms, n'
is an integer from 2 to 70 and M' is Na, K or NH4.

The present invention will be explained in detail below.

Conjugated diene monomers constituting the copolymer latex of the present invention include 1,3-butadiene, 2-methyl-1,
Examples include 3-butadiene, 2,3-dimethyl-1,3-butadiene, and the like.

In addition, other copolymerizable monomers include styrene, α
- Aromatic vinyl monomers such as methylstyrene and vinyltoluene; ethylenically unsaturated carboxylic acid ester monomers such as methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate; cyanogens such as acrylonitrile and methacrylonitrile; vinyl monomers, unsaturated carboxylic acid monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, unsaturated carboxylic acid amide monomers such as acrylamide and methacrylamide, β Examples include hydroxyalkyl group-containing unsaturated monomers such as -hydroxyethyl acrylate, β-hydroxyethyl methacrylate, β-hydroxypropyl acrylate, and β-hydroxypropyl methacrylate, and one or two types of each can be used.

There is no particular restriction on the composition ratio of these monomer mixtures; however, 10 to 80% by weight of aliphatic conjugated diene monomers, 0 to 10% by weight of ethylenically unsaturated carboxylic acid monomers, and 0 to 10% by weight of aromatic vinyl monomers. The surfactant used in the present invention is represented by the following general formula (a).
and/or a compound represented by (b).

General formula: Here, R is an alkyl group having 4 to 20 carbon atoms or a hydrocarbon group containing an aromatic ring, n is an integer of 2 to 70, and M is Na
, K or NH4.

(b) R'-0+CCH2CH20-)7SOa'
Here, R' is an alkyl group having 4 to 20 carbon atoms, and n' is 2
an integer between 70 and M' is Na, K or NH4.

The amount of these surfactants used is 0.01 to 1 part by weight per 100 parts by weight of the monomer mixture.

If it is less than 0.001 part by weight, stability during polymerization will be poor, and if it exceeds 1 part by weight, the object of the present invention cannot be achieved.

In the present invention, the above-mentioned surfactant is used as an emulsifier, but other common emulsifiers such as sodium dodecylbenzenesulfonate and sodium lauryl sulfate are not preferred because of poor color fogging and wet resistance.

The method of adding various components in the emulsion polymerization of the present invention is not particularly limited, and may be any of a batch addition method, a divided addition method, and a continuous addition method. Alternatively, a so-called two-stage polymerization method or a power feed polymerization method may be used, in which the monomer composition is changed during the polymerization process. Furthermore, in emulsion polymerization,
Commonly used polymerization initiators, electrolytes, polymerization accelerators, chain transfer agents,
Chelating agents and the like can be used.

The color forming agent used in the present invention is not particularly limited as long as it is used in general pressure-sensitive recording paper, heat-sensitive recording paper, etc. Specific examples include: (1) As triarylmethane compounds, 3゜3-bis(p-dimethylaminophenyl)6-dimethylaminophthalide (crystal violet lactone), 3
．． 3-bis(pdimethylaminophenyl)phthalide, 3
-(p-dimethylaminophenyl)-3-(1゜2-dimethylindol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-3-(2-methylindol-3-yl)phthalide, 3 -(p-dimethylaminophenyl)3-(2-phenylindol-3-yl)phthalide, 3,3-bis-(1,2-dimethylindole-
3-yl)-5-dimethylaminophthalide, 3,3-bis-(1,2-dimethylindol-3-yl)-6-
Dimethylaminophthalide, 3,3-bis-(9-ethylcarbazol-3-yl)-5-dimethylaminophthalide, 3,3-bis-(2-phenylindol-3-yl)-5-dimethylamide Tutaride, 3-p-dimethylaminophenyl-3-(1-methylpyrrol-2-yl)
-6-dimethylaminophthalide, etc.: (2) Diphenylmethane compounds such as 4,4'bis-dimethylaminobenzhydrin benzyl ether, N-halophenylleukoolamine, N-2,4,5-) Chlorophenylleucoauramine, etc.: (3) As a xanthine compound, rhodamine B-
Anilinolactam, Rhodamine B-p-nitroanilinolactam, Rhodamine B-p-chloroanilinolactam, Rhodamine B-p-chloroanilinolactam, 3-diethylamino-7-sibenzylaminofluorane, 3-diethylamino-7 -octylaminofluorane, 3-diethylamino-7-phenylfluorane, 3-diethylamino-7-3゜4-dichloroanilinofluorane, 3
-diethylamine-7-(2-chloroanilino)fluorane, 3-diethylamine-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-ethyltrilamino-6 -Methyl-7anilinofluorane, 3-ethyl-tolylamino-
6-Methyl-7-phenylfluoran, 3-diethylamino-7-(4-nitroanilino)fluoran, etc.: (4) As a thiazine compound, benzoylleucomethylene blue, p-nitrobenzoylleucomethylene blue, etc.: (5) As a spiro compound , 3-methyl-spiro-dinaphthopyran, 3-ethyl-spirodinaphthopyran, 3,8'-dichloro-spirodinaphthopyran, 3-
Benzylspiro-dinaphthopyran, 3-methylnaphtho-
Examples include (3-methoxy-benzo)-spiropyran, 3-propyl-spiro-dibenzopyran, and mixtures thereof.

Examples of the color developer used in the present invention include phenols such as p-octylphenol, p-ter
t-butylphenol, p-phenylphenol, 1,
1-bis(p-hydroxyphenyl)propane, 2,2
-bis(1)-hydroxyphenyl)propane, 11-
Bis(11)-hydroxyphenyl)pentane, 11-bis(p-hydroxyphenyl)hexane, 2゜2-bis(p-hydroxyphenyl)hexane, 1.1-bis(
1)-Hydroxyphenyl)-2ethyl-hexane, 2
, 2-bis(4-hydroxy-3,5-dichlorophenyl)propane and other aromatic carboxylic acid derivatives include p-hydroxybenzoic acid, ethyl p-hydroxybenzoate, butyl p-hydroxybenzoate, 3.5-dichlorophenyl Examples of tert-butylsalicylic acid, 3,5-silomethylbenodylsalicylic acid, and carboxylic acid include polyvalent metal salts thereof.

The composition for thermal recording paper of the present invention contains the above-mentioned color forming agent, color developer, and the above-mentioned copolymer latex as a binder, and optionally contains polyhinyl alcohol, carboxymethyl cellulose, starch, and modified starch. , casein, etc. can also be used together with the copolymer latex.

In addition, inorganic pigments such as kaolin, calcinable orino, calcium carbonate, talc, aluminum hydroxide, magnesium hydroxide, titanium oxide, organic pigments such as polystyrene resin, urea-formalin resin, paraffin wax, carnauba wax, microcrystalline wax, Waxes such as polyethylene wax and aliphatic amide, higher fatty acid metal salts such as zinc stearate, calcium stearate, and aluminum stearate, benzyl p-benzyloxybenzoate, β-naphthylbenzyl ether, stearamide, stearyl urea, p -benzylbiphenyl, di(2-methylphenoquine)ethane, di(2-methoxyphenoxy)ethane, β-naphthol-(p-methylbenzyl)ether, α-naphthylbenzyl ether,
1,4-butanediol-p-methylphenyl ether, 1,4-butanediol-p-isopropylphenyl ether, 1,4-butanediol-p-tert-
Octyl phenyl ether, l-phenoxy-2-(4
-ethylphenoxy)ethane, ■-phenoxy2-(
4-chlorophenoxy)ethane, 1,4-butanediol phenyl ether, diethylene glycol-bis(4
It is also possible to use a thermofusible substance such as -methoxyphenyl) ether, a dispersant, an antifoaming agent, an ultraviolet absorber, and the like.

In the present invention, methods for applying the above composition onto a support include a blade coater, an air knife coater,
Coating can be performed using a known coating machine such as a roll coater, a rod coater, or a curtain coater.

Furthermore, in order to improve the surface smoothness of the coated product, we use machine calender, super calender, gloss calender, etc.
You can also use devices such as brushing.

<Example> The present invention will be explained in more detail with reference to Examples below.
Of course, it is not limited to these.

Further, unless otherwise specified, parts and percentages in the examples indicate parts by weight and percentages by weight, respectively.

(Preparation of copolymer latex) In a 10N pressure container, the parts of the monomer and surfactant shown in Table 1, 0.5 parts of t-dodecyl mercaptan, 08 parts of potassium persulfate, and 0.4 parts of sodium hydrogen carbonate are added. and 100 parts of pure water were charged, and emulsion polymerization was carried out at 65°C without stirring. The polymerization conversion rates of the obtained copolymer latexes were all 97% or more. Next, after adjusting the pH of the copolymer latex to 7 with an aqueous sodium hydroxide solution, unreacted monomers were removed by steam distillation to obtain copolymer latexes A-E and a-C.

Lower margin (preparation and coating of composition for thermal recording paper) Crystal violet lactone as color former, 2.2- as color developer
Take 20 parts each of bis(p-hydroxyphenyl)propane and β-naphthylbenozyl ether as a thermofusible substance and separately add 5% polyvinyl alcohol water f8M100
The mixture was dispersed in a ball mill throughout the day and night.

Further, 100 parts of calcium carbonate was dispersed with 200 parts of hexametaphosphate sorter 05% solution using a homogenizer to obtain a pigment dispersant.

10 parts of the above color former dispersion, 20 parts of color developer dispersion, 10 parts of β-naphthylbenzyl ether dispersion, 20 parts of pigment dispersion
5 parts of a 20% zinc stearate dispersion and 15 parts of copolymer latex (solid content 48%) were added to obtain a composition for thermal recording paper.

This thermal recording paper composition has a basis weight of 489/rr? The coated paper was coated with a wire parser to a dry weight of 5 f/yP1' and dried, and then passed twice through a super calender with a linear pressure of 150 kQ/cm to obtain a thermal recording paper for evaluation.

(Evaluation) Recording was performed using a zero-color thermal printer with a printing pulse time of 8 ms, and the color density at that time was measured using a Macbeth densitometer.

The color density of the non-printed area of the 0 background fog thermosensitive recording paper was measured using a Macbeth densitometer.

The thermosensitive recording paper having a moisture resistance of 0.0 was left for 24 hours at 40° C. and 190 RH to undergo a wet treatment. The whiteness before and after the treatment was measured using a Hunter whiteness meter, and the difference was rated ◯ if the difference was within 50%, △ if it was 51% to 100%, and × if it was 101% or more.

The evaluation results are shown in Table-2.

Margins below <Effects of the Invention> As described above, the composition for thermal recording paper containing the copolymer latex of the present invention as a binder is a thermal recording paper composition that prevents background fogging and has excellent moisture resistance and color development. It provides paper and is very useful.

Claims (1)

[Scope of Claims] A composition for thermal recording paper comprising a color former, a color developer that develops color when heated with the color former, and a binder, wherein the binder comprises a conjugated diene monomer and a copolymer thereof. 0 of the surfactant represented by the following general formula (a) and/or (b) per 100 parts by weight of a monomer mixture consisting of other possible monomers.
．． 1. A composition for thermal recording paper, comprising a copolymer latex obtained by emulsion polymerization of the monomer mixture in the presence of 0.01 to 1 part by weight. General formula: (a) ▲ Numerical formula, chemical formula, table, etc. ▼ Here, R is an alkyl group having 4 to 20 carbon atoms or a hydrocarbon group containing an aromatic ring, n is an integer of 2 to 70, and M is Na
, K or NH_4. (b) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ Here, R' is an alkyl group having 4 to 20 carbon atoms, and n' is 2
an integer of ~70 and M' is Na, or NH_4.