JP2936349B2 - Composition for thermal recording paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a composition for heat-sensitive recording paper, which prevents background fog and has excellent wet resistance and color development.

<Related Art> In recent years, heat-sensitive recording paper utilizing a color-forming reaction between a color-forming agent and the color-forming agent and a color-developing agent that forms color when heated has been used in a wide range of applications such as facsimile machines, printers, and labels. Is expanding. Along with this, the quality is stricter than the quality required for these thermal recording papers.

For example, with the increase in recording speed, there is a strong demand for a color developing property in which even a small amount of heat energy is used to form a color at a high density.
In this high-speed recording, it is difficult to obtain a sufficient coloring property. This is largely because heat conduction between the thermal head and the heat-sensitive coloring layer is not sufficiently performed, so that a sufficient recording density cannot be obtained. In order to improve the recording density, it is necessary to make the thermal head and the heat-sensitive coloring layer more closely contact each other so that the heat transfer from the thermal head to the heat-sensitive coloring layer is performed efficiently. In order to make the thermal head and the heat-sensitive coloring layer adhere to each other, the smoothness of the heat-sensitive coloring layer is improved by calendering such as a super calender or a machine calendar.

However, such a calendering process on the heat-sensitive recording paper has a drawback that background fogging occurs due to the pressure at the time of the treatment and the quality value is remarkably reduced.

Further, such a thermosensitive recording paper has a drawback that the non-printed portion develops color and its whiteness is reduced when it is placed in a wet state for a long time due to its use conditions and the like.

Therefore, there is a demand for a heat-sensitive recording paper having excellent wet resistance.

<Problems to be Solved by the Invention> The present inventors have obtained a composition for heat-sensitive recording paper which prevents background fogging due to the pressure during calendering as described above, and is excellent in wet resistance and color development. As a result of intensive studies, the present inventors have found that the problem can be solved by using a copolymer latex obtained by emulsion polymerization in the presence of a specific surfactant as a binder, and have completed the present invention.

<Means for Solving the Problems> That is, the present invention relates to a thermosensitive recording paper composition comprising a color former, a color developer and a color developer which develops color when heated, and a binder. With respect to 100 parts by weight of a monomer mixture comprising a diene-based monomer and another monomer copolymerizable therewith, a surfactant represented by the following general formula (a) and / or (b):
A thermosensitive recording, which is characterized by containing a copolymer latex obtained by emulsion-polymerizing the monomer mixture in the presence of 01 to 1 part by weight, thereby preventing background fog, and having excellent wet resistance and color development. A composition for paper 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 NH ₄ .

Here, R 'is an alkyl group having 4 to 20 carbon atoms, and n' is 2
70 integers and M 'is Na, K or NH _4.

 Hereinafter, the present invention will be described in detail.

The conjugated diene-based monomers constituting the copolymer latex of the present invention include 1,3-butadiene and 2-methyl-1,3-
Butadiene, 2,3-dimethyl-1,3-butadiene and the like.

Other copolymerizable monomers include styrene,
α-methylstyrene, aromatic vinyl monomers such as vinyltoluene, methyl acrylate, ethyl acrylate,
Methyl methacrylate, ethylenically unsaturated carboxylic acid ester monomers such as ethyl methacrylate, acrylonitrile, vinyl cyanide monomers such as methacrylonitrile, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, Unsaturated carboxylic acid monomers such as maleic acid, unsaturated carboxylic acid amide monomers such as acrylamide and methacrylamide, β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, β-hydroxypropyl acrylate, β-hydroxypropyl methacrylate And the like, and one or two types can be used respectively.

Although the composition ratio of these monomer mixtures is not particularly limited,
10 to 80% by weight of an aliphatic conjugated diene monomer, 0 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer, and an aromatic vinyl monomer, an ethylenically unsaturated carboxylic acid ester monomer, and cyan. It is preferably 20 to 90% by weight of a monomer selected from a vinyl-based monomer, an unsaturated carboxylic acid amide monomer, and a hydroxyalkyl group-containing unsaturated monomer.

The surfactant used in the present invention is a compound represented by the following general formula (a) and / or (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 NH ₄ .

Here, R 'is an alkyl group having 4 to 20 carbon atoms, and n' is 2
70 integers and M 'is Na, K or NH _4.

These surfactants are used in an amount of 0.01 to 1 part by weight based on 100 parts by weight of the monomer mixture. If the amount is less than 0.01 part by weight, the stability at the time of polymerization is inferior. If the amount 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. However, other common emulsifiers such as sodium dodecylbenzenesulfonate and sodium lauryl sulfate are not preferred because of poor color fog and wet resistance.

The method of adding the various components in the emulsion polymerization of the present invention is not particularly limited, but may be any of a batch addition method, a division addition method, and a continuous addition method. Further, a so-called two-stage polymerization method or a power feed polymerization method in which the monomer composition is changed on the way may be used. Further, in the emulsion polymerization, conventional polymerization initiators, electrolytes, polymerization accelerators, chain transfer agents, chelating agents and the like can be used.

The color former used in the present invention is not particularly limited as long as it is used for general pressure-sensitive recording paper, heat-sensitive recording paper and the like. Specific examples are as follows: (1) As triarylmethane compounds, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone);
3,3-bis (p-dimethylaminophenyl) 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-
Dimethylaminothalide, 3-p-dimethylaminophenyl-3- (1-methylpyrrol-2-yl) -6-dimethyl-aminophthalide and the like: (2) 4,4'-bis-dimethylamino as a diphenylmethane compound Benzhydrin benzyl ether,
N-halophenyl leuco auramine, N-2,4,5-trichlorophenyl leuco auramine and the like: (3) As xanthene compounds, rhodamine B-anilinolactam, rhodamine Bp-nitroanilinolactam, rhodamine B -P-chloroanilinolactam,
Rhodamine B-p-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino-7-octylaminofluoran, 3-diethylamino-7-phenylfluoran, 3-diethylamino-7-3 , 4-Dichloroanilinofluoran, 3-
Diethylamino-7- (2-chloroanilino) fluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-piperidino-6-methyl-7-anilinofluoran, 3-ethyl-tolylamino-6-methyl −
7-anilinofluoran, 3-ethyl-tolylamino-
6-methyl-7-phenylfluoran, 3-diethylamino-7- (4-nitroanilino) fluoran, etc .: (4) As thiazine compounds, benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue, etc .: (5) Spiro compounds As 3-methyl-spiro-
Dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3,3'-dichloro-spiro-dinaphthopyran, 3-
Benzylspiro-dinaphthopyran, 3-methylnaphtho-
Examples thereof include (3-methoxy-benzo) -spiropyran, 3-propyl-spiro-dibenzopyran and the like, or a mixture thereof.

As the developer used in the present invention, for example, phenols such as p-octylphenol and p-tert-
Butylphenol, p-phenylphenol, 1,1-bis (p-hydroxyphenyl) propane, 2,2-bis (p-hydroxyphenyl) propane, 1,1-bis (p
-Hydroxyphenyl) pentane, 1,1-bis (p-hydroxyphenyl) hexane, 2,2-bis (p-hydroxyphenyl) hexane, 1,1-bis (p-hydroxyphenyl) -2-ethyl-hexane, 2,2-bis (4-
Hydroxy-3,5-dichlorophenyl) propane and the like: As aromatic carboxylic acid derivatives, p-hydroxybenzoic acid, ethyl p-hydroxybenzoate, butyl p-hydroxybenzoate, 3,5-di-tert-butylsalicylic acid, Examples of 3,5-di-α-methylbenzylsalicylic acid and carboxylic acid include polyvalent metal salts thereof.

The composition for heat-sensitive recording paper in the present invention, the color former,
It contains the above-mentioned copolymer latex as a developer and a binder, and it is also possible to use polyvinyl alcohol, alkoxymethylcellulose, starch, modified starch, casein, etc. together with the copolymer latex as necessary. .

In addition, inorganic pigments such as kaolin, calcined kaolin, calcium carbonate, talc, aluminum hydroxide, magnesium hydroxide, and titanium oxide; organic pigments such as polystyrene resin and urea-formalin resin; paraffin wax, carnauba wax, microcrystalline wax, and polyethylene Waxes, waxes such as aliphatic amides, metal salts of higher fatty acids such as zinc stearate, calcium stearate, aluminum stearate, benzyl p-benzyloxybenzoate, β-naphthylbenzyl ether, stearamide, stearyl urea, p- Benzylbiphenyl, di (2-methylphenoxy) ethane, di (2-methoxyphenoxy) ethane, β-naphthol- (p-methylbenzyl) ether, α-naphthylbenzylether, 1,4-butanediol p-methylphenyl ether, 1,4-butanediol-p-isopropylphenyl ether, 1,4-butanediol-p-tert-octylphenyl ether, 1-phenoxy-2- (4-ethylphenoxy) ethane, 1- Thermoplastic substances such as phenoxy-2- (4-chlorophenoxy) ethane, 1,4-butanediol phenyl ether, diethylene glycol-bis (4-ethoxyphenyl) ether, other dispersants, defoamers, ultraviolet absorbers, etc. It is also possible to use

In the present invention, as a method of applying the above composition on a support, a known coating machine such as a blade coater, an air knife coater, a roll coater, a rod coater, and a curtain coater can be used.

Further, in order to improve the surface smoothness of the coated product, a device such as a machine calender, a super calender, a gloss calender, and a brushing can be used.

<Examples> Hereinafter, the present invention will be described in more detail with reference to Examples, but it is needless to say that the present invention is not limited thereto.

Parts and% in Examples are parts by weight and% by weight, respectively, unless otherwise specified.

(Preparation of Copolymer Latex) In 10 pressure-resistant containers, 0.5 parts of t-dodecylmercaptan, 0.5 part of t-dodecylmercaptan, 0.8 part of potassium persulfate, 0.4 part of sodium hydrogen carbonate and pure water were added in 10 pressure-resistant containers. Ten
0 parts were charged and emulsion polymerization was carried out at 65 ° C. while stirring.
The polymerization conversion of the obtained copolymer latex was 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 to E and a to c.

(Preparation and Coating of Thermal Recording Paper Composition) Crystal violet lactone as a color former, 2,2-bis (p-hydroxyphenyl) propane as a color developer, and β-naphthyl benzyl ether as a heat-fusible substance were each 20. Parts were separately dispersed together with 100 parts of a 5% aqueous solution of polyvinyl alcohol in a ball mill for 24 hours.

In addition, 100 parts of calcium carbonate is sodium hexametaphosphate
The pigment was dispersed with a homogenizer together with 200 parts of a 0.5% solution to obtain a pigment dispersant.

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

After the dry weight of this heat-sensitive recording paper a composition for fine paper having a basis weight of 48 g / m ² was coated and dried with a wire bar so as to 5g / m ^{2, 2} times with the super calender linear pressure 150 kg / cm Paper was obtained to obtain a thermosensitive recording paper for evaluation.

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

Background fog The coloring density of the non-printed portion of the thermal recording paper was measured with a Macbeth densitometer.

Moisture resistance Leave the thermosensitive recording paper under the conditions of 40 ° C and 90% RH for 24 hours.
A wet treatment was applied. The whiteness before and after the treatment was measured using a Hunter whiteness meter.
△ 10.0% is indicated by Δ, and 10.1% or more is indicated by ×. Table-Evaluation results
It is shown in FIG.

<Effects of the Invention> As described above, the composition for heat-sensitive recording paper containing the copolymer latex of the present invention as a binder provides a heat-sensitive recording paper that prevents background fog and is excellent in wet resistance and color development. Is very useful.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B41M 5/28-5/34

Claims (1)

(57) [Claims] 1. A thermosensitive recording paper composition comprising a color former, a color developer, a color developer which develops color when heated, and a binder, wherein the binder is a conjugated diene monomer and copolymerizable therewith. A surfactant represented by the following general formula (a) and / or (b) is added to 100 parts by weight of a monomer mixture comprising
A composition for heat-sensitive recording paper, comprising a copolymer latex obtained by emulsion-polymerizing the monomer mixture in the presence of from 1 to 1 part by weight. General formula: Here, R represents a hydrocarbon group containing an alkyl group or an aromatic ring having 4 to 20 carbon atoms, n represents an integer and M 2 to 70 which is Na, K or NH _4. Here, R 'is an alkyl group having 4 to 20 carbon atoms, and n' is 2 to 2.
70 integers and M 'is Na, K or NH _4.