JPH02164582A - Thermal recording material - Google Patents

Abstract

PURPOSE:To form a thermal recording material of high sensitivity by laminating a thermal color forming layer containing calcium carbonate having oil absorbency of 100ml/100g or more and a carboxylic acid copolymer having a mean MW of 2000-20000 to a support. CONSTITUTION:Calcium carbonate having oil absorbency of 100ml/100g or more, a carboxylic acid copolymer having a mean MW of 2000-20000 being a dispersion aid of said calcium carbonate are compounded with a binder such as a water-soluble polymer along with a color former, a coupler and a heat- meltable substance to be dispersed in water to prepare a coating solution for forming a thermal color forming layer. Subsequently, this coating solution is applied to a support such as paper, synthetic paper or a plastic film and dried to form a thermal color forming layer to prepare a thermal recording material. As the monomer unit constituting the aforementioned carboxylic acid copolymer, acrylic acid or maleic acid is suitable and the addition amount of the carboxylic acid copolymer is suitably 0.5-3% by wt. of pigment.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material having high sensitivity and excellent facsimile running properties.

(Prior art) Recording materials using electron-donating dye precursors (hereinafter referred to as color formers) and electron-accepting compounds (hereinafter referred to as color developers) are used in pressure-sensitive recording paper, heat-sensitive recording paper, photosensitive pressure-sensitive recording Paper, well known as electrically conductive thermal recording paper.

For example, British Patent No. 2140449, US Patent No. 4480
No. 052, No. 4436920, Special Publication No. 60-2392
No. 2, JP-A-57-179836, JP-A No. 60-1235
It is described in detail in No. 56 and No. 60-123557.

In recent years, there has been a strong demand for high-sensitivity heat-sensitive recording materials, and various studies have been carried out, but so far nothing that is considered to be sufficient has been developed. There is a growing demand for heat-sensitive recording materials with high sensitivity and excellent running properties.

(Object of the Invention) An object of the present invention is to provide a heat-sensitive recording material with high sensitivity and excellent running properties.

(Structure of the invention) The purpose of the present invention is an oil absorption of 100 mj! /1009 or more and a carboxylic acid copolymer having an average molecular weight of 2,000 or more and 20,000 or less as a dispersion aid for the calcium carbonate are simultaneously used in the heat-sensitive coloring layer. Ta. The carboxylic acid copolymer used as a dispersion aid must contain acrylic acid, maleic acid, and their alkali gold R salts and ammonium salts as constituent units.

The oil absorption amount in the present invention is a value measured by the Ogura method.

When using the birch oil-absorbing pigment described above in a heat-sensitive coloring layer, low-molecular dispersion aids such as sodium hexametaphosphate, which have been widely used as dispersion aids for pigments, cannot provide sufficient dispersion stability. It is difficult to do so. The dispersion aid used in the present invention has a molecular weight of 2000 or more and 200
00 or less, and is characterized in that the knitting units constituting the carboxylic acid copolymer contain acrylic acid, maleic acid, and their alkali metal salts and ammonium salts. If the molecular weight is less than 2,000, the stability of the dispersion is low, and if the molecular weight is more than 20,000, the sensitivity of the heat-sensitive recording material may decrease, which is not preferable.

The carboxylic acid copolymer is 0.5 to 3% by weight based on the pigment.
Preferably 2-3% by weight is used. The calcium carbonate dispersion liquid dispersed in this manner has a low viscosity and high dispersion stability, and therefore has excellent manufacturing suitability.

In the present invention, the dispersion of the color forming agent, developer, and thermofusible substance is carried out in a water-soluble binder. Preferred compounds include polyvinyl alcohol, methylcellulose, carboxymethylcellulose, starches (including modified starch), gelatin, gum arabic, casein, styrene-maleic anhydride copolymer hydrolyzate, carboxy-modified polyvinyl alcohol, Examples include saponified products of polyacrylamide and vinyl acetate-polyacrylic acid copolymers.

These binders are used not only for dispersion but also for the purpose of improving coating film strength. , methyl acrylate-butadiene copolymer, and synthetic polymer latex binder such as polyvinylidene chloride can also be used in combination. Alternatively, a similar binder can be used for the undercoat layer as well.

Examples of the coloring agent used in the present invention include triarylmethane compounds, diphenylmethane compounds, xanthine compounds, thiazine compounds, and spiropyran compounds. A specific example is JP-A-55-22725.
Examples include those described in No. 3. If some of these are disclosed, triarylmethane compounds include 3,3-bis(p-dimethyl7minophenyl)-6-
Dimethylaminophthalide, 3,3-bis(p-dimethyl7minophenyl) phthalide, 3-(p-dimethyl7
Minofue:L)-3-(L3dimethylindole-3-
yl) phthalide, 3-(p-dimethyl 7-minophenyl)
-3-(2-methylindol-3-yl) phthalide, etc., and diphenylmethane compounds include 4.
4”-bis-dimethylaminobenzhydrin benzyl ether, N-halophenyl-leucoolamine, N-
2,4,5-trichlorophenylleucoauramine, etc., and xanthine compounds include rhodamine-B-
7 Nilinolactam, rhodamine-(p-nitrino)lactam, 2-(dibenzyl 7mino)fluorane, 2-7 dilino 3-methyl-6-diethylaminofluorane, 2
-7 Nilino 3-methyl-6-dibutyl 7minofluorane, 2-7 Nilino 3-methyl-6-N-ethyl-N-
Iso-7-mylaminofluorane, 2-7-nylino-3-methyl-6-N-methyl-N-cyclohexylaminofluorane, 2-7-nylino-3-riO-6-diethylaminofluorane, 2-7-nylino-3-methyl -6-N-Ethyl-N-isobutylaminofluorane, 2-7 Nilino 6-dibutylaminofluorane, 2-7 Nilino 3-methyl-6-tomethyl-N-tetrahydrofurfurylaminofluorane, 2-7 Nilino 3 -Methyl-6-piperidinoaminofluorane, 2-(0-chloro7nylino)-
There are 6-diethylaminofluorane, 2-(3,4-dichloroanili/)-6-diethylaminofluorane, etc. Thiazine compounds include hendiylleucon methylene blue, p-nitrobenzylleucomethylene blue, etc. Examples of the system compounds include 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3,3''-cyclosbirow dinaphthopyran, 3-benzylspiro-dinaphthopyran, and 3-methyl-spiro-dinaphthopyran.
naphtho-(3-methoxy-benzo)-spiropyran, 3
-buOpyr-spiro-dibenzopyran and the like.

The color developer used in the present invention is preferably a phenolic compound, a salicylic acid derivative, or a polyvalent metal salt thereof.

To give some examples of these, phenolic compounds include 2,2'-bis(4-hydroxyphenyl)buOpan, 4-t-butylphenol, 4-phenylphenol, 4-humanOoxydiphenoxide, 1,1”-screw (
3-rioo-4-hydroxyphenyl)cyclohexane, 1.1'-bis(4-hydroxyphenyl)cyclohexane, 1.1'-bis(3-chloro-4-hydroxyphenyl)-2-ethylbutane, 4,4 ' -5ec-
Isooctylidene diphenol, 4,4'-5ec-butylidene diphenol, 4-tert-octylphenol, 4-p-methylphenylphenol, 4,4'-
Examples include methylcyclohexylidenephenol, 4°4'-isopentylidenephenol, and benzyl ρ-hydroxybenzoate. Salicylic acid derivatives include 4-pentadecylsalicylic acid, 3,5-di(α-methylbenzyl)
Salicylic acid, 3.5-di(ter-octyl)salicylic acid, 5-octadecylsalicylic acid, 5-α-(p~α-
Methylbenzylphenyl)ethylsalicylic acid, 3-α-
Methylbenzyl-5-ter-octylsalicylic acid, 5
-tetradecylsalicylic acid, 4-hexyloxysalicylic acid, 4-cyclohexyloxysalicylic acid, 4-decyloxysalicylic acid, 4-dodecyloxysalicylic acid,
Examples include 4-pentadecyloxysalicylic acid, 4-octadecyloxysalicylic acid, etc., and their zinc, aluminum, calcium, copper, and lead salts. These color developers are preferably used in an amount of 50 to 800% by weight, more preferably 100 to 500% by weight of the color former. If it is less than 50% by weight, the color development will not be sufficient, and if it is added more than 800% by weight, no further effect can be expected, which is not preferable.

In the heat-sensitive recording material of the present invention, a heat-fusible substance can be contained in the heat-sensitive coloring layer in order to improve its heat responsiveness. Examples of preferred thermofusible materials include benzyl p-benzyloxybenzoate, β-naphthyl-benzyl ether, stearamide, stearyl urea, p-hensylbiphenyl, di(2-methylphenoxy)ethane, di( 2-methoxyphenoxy)ethane, β-naphthol-
(p-methylbenzyl) ether, α-naphthylbenzyl-thyl, 1,4-butanediol-ρ-methylphenyl ether, 1,4-butanediol-p-isopropylphenyl ether, 1,4-butanediol-p-
tert-octylphenyl ether, 1-phenoxy-2-(4-ethylphenoxy) ethane, 1-phenoxy-2-(4-chlorophenoxy)ethane, 1.4-
Examples include butanediol phenyl ether, diethylene glycol-bis(4-methoxyphenyl) ether, and the like.

The thermofusible substances may be used alone or in combination,
In order to obtain sufficient thermal responsiveness, it is preferably used in an amount of 10 to 200% by weight, more preferably 20 to 150% by weight, based on the electron-accepting compound.

The pigment used in the present invention has an oil absorption of 100 m12/1009
It is necessary that the calcium carbonate is above 0.0%, and other pigments may be used in combination.
It is preferable to set it to 5q/rrf or more.

In addition, metal soap, wax, surfactant, etc., as necessary.
Antistatic agents, ultraviolet absorbers, antifoaming agents, conductive agents, fluorescent dyes, and the like may be added.

As the metal soap, higher fatty acid metal salts are used, such as zinc stearate, calcium stearate, aluminum stearate, and the like.

As the wax, paraffin wax, microcrystalline wax, carnauba wax, methylol stearamide, polyethylene wax, polystyrene wax, fatty acid amide wax, etc. are used alone or in combination.

As the surfactant, a sulfosuccinic acid-based fluorine metal salt and a fluorine-containing surfactant are used.

Further, it is preferable to add a decoloring inhibitor to the heat-sensitive color forming layer in order to prevent decoloring of the image-printed area and to make the generated image more robust. Phenol compounds, especially hindered phenol compounds, are effective as anti-fading agents, such as L
l,3-tris(2-methyl-4-hydroxy-ter
t-butylphenyl) butane, 1.1.3-tris(
2-Ethyl-4-hydroxy-5-tert-butylphenyl)butane, Ll, 3-1-lis(3,5-dit)
ert-butyl-4-hydroxyphenyl)butane, 1
．． 1.3-tris(2-methyl-4-hydroxy-5-
tert-butylphenyl] Propane, 2.2'-methylene-bis(5-tert-butyl-4-methylphenol), 2°2'-methylene-bis-(6-tert-butyl-4-methylphenol),
t-butyl-4-ethylphenol), 4.4-butylidene-bis(6-tert-butyl-3-methylphenol), 4.4″-thio-bis-(3-methyl-5-
tert-butylphenol), etc.

The amount of such a phenolic compound to be used is preferably 1 to 200% by weight, more preferably 5 to 50% by weight, based on the color developer.

After each of these materials is mixed, it is applied to a support.

Paper, synthetic paper, various bases, etc. are used as the support, but it is preferable to provide an undercoat layer on the support in advance in order to obtain high smoothness. The coated heat-sensitive recording material is dried and subjected to a process such as a calender before being used.

EXAMPLES The present invention will be specifically explained below with reference to Examples, but the present invention is not limited only to the Examples below.

(Example-1) (Preparation of undercoated paper) Calcined kaolin (manufactured by Engelhardt Co., Ltd.; 7Ncilex 9)
3) 809 was dispersed with a 0.5% sodium hexametaphosphate aqueous solution 1609 using a homogenizer to obtain a pigment dispersion. Styrene-butadiene latex (manufactured by Sumitomo Naugatax Co., Ltd. 1sN307, solid content concentration 48%) 169 and polyvinyl alcohol (manufactured by Kuraray Co., Ltd.; PVA-117) 10% aqueous solution 249 were added to the pigment dispersion to apply an undercoat as required. I got the liquid. The above coating liquid for undercoat was applied to 509/rrf high-quality paper to a thickness of 897d and dried to prepare undercoat paper.

(Preparation and coating of coating liquid for heat-sensitive coloring layer) 3-dibutylamino-6-methyl-7-7nilinofluorane 209
Polyvinyl alcohol (manufactured by Kuraray; PVA-105
) It was dispersed in a ball mill for 24 to 48 hours with a 5% aqueous solution 1009 to obtain a dispersion having an average particle size of 1.0 μm. Furthermore, bisphenol A409 and naphthylhensyl ether 409 were added to polyvinyl alcohol (Kuraray Co., Ltd. 1PVA-
105) Dispersion was performed with a 10% aqueous solution 4009 in a ball mill for 24 to 48 hours to obtain a dispersion having an average particle size of 1.0 μm. Also, calcium carbonate with oil absorption of 140 mfI/100' (9 Karrai 1-KT manufactured by Shiroishi Central Institute) 809
Acrylic acid/maleic acid copolymer sodium salt with a molecular weight of 5,000 to +oooo (Kao Soap; Boise 520) 1
% aqueous solution with a homogenizer to obtain a pigment dispersion.

The dispersion obtained in the above manner was mixed, and 21% zinc stearate emulsion 509 was further added to obtain a coating solution for thermal paper, and a dry coating amount of 7% was obtained on the undercoated paper.
It was coated with a wire bar to give a coating of 97° and dried in an oven at 50°C to obtain a heat-sensitive recording material of the present invention.

(Example-2) Example-1 except that the calcium carbonate dispersion aid used in the thermosensitive coloring layer in Example-1 was changed to a carboxylic acid copolymer with a molecular weight of 2000 to 3000 (Kao Soap; Demol EP) A heat-sensitive recording material was obtained in the same manner as above.

(Example-3) The same procedure as in Example-1 was carried out except that the calcium carbonate used in the thermosensitive coloring layer in Example-1 was changed to calcium carbonate (1KK-12 manufactured by Shiraishi Chuo Research Institute) with an oil absorption of 110 d/100 g. A heat-sensitive recording material was obtained.

(Comparative Example-1) Heat-sensitive recording was carried out in the same manner as in Example-1, except that the calcium carbonate used in the heat-sensitive coloring layer in Example-1 was changed to an oil absorption of 80 mjl/1009 (manufactured by Shiroishi Central Research Institute; Callite SA). I got the material.

(Comparative Example-2) A 0.5% aqueous solution of hexametaphosphoric acid 1609 was added to the calcium carbonate dispersion aid used in the heat-sensitive coloring layer in Example-1.
A heat-sensitive recording material was obtained in the same manner as in Example-1 except that .

The heat-sensitive recording paper obtained as described above was surface-treated with a low-pressure xarender, and the thermal head manufactured by Kyocera ■ (KLT) was
-216-8MPDI) and 100kg just before the head
In a thermal printing experimental device having a pressure roll of /cA, the pulse width was set to 0.8.1.0.
1.2, and the print density was measured using a Macbeth reflection densitometer RD-918.

The runnability was evaluated by copying the Institute of Image Electronics Engineers Test Chart No. 3 using Fujitsu's high-speed facsimile FF-2000, and evaluating the accumulation, sticking, and head staining of the print sample using the following criteria.

(accumulation) The stacking property was good in stacking 07100 sheets.

Of the 61,100 sheets that were stacked, less than 5 sheets were not stacked properly.

X: Out of 100 sheets stacked, 6 or fewer sheets were not stacked properly.

(sticking) O: No occurrence of sticking was observed.

Δ; 2 to 3 areas of overexposure (due to stick-slip,
Although there are some areas that are not printed, there is no shrinkage of the print.

×: There are many overexposed areas, and the printed characters are also shrunken.

(head dirty) No head stains are observed even after printing 100 Oi sheets.

Δ: Head stains are observed after printing 100 sheets, but do not affect the printed surface.

x: After printing too many sheets, the head is very dirty and scratches the printing surface, causing printing problems.

The evaluation results for the above evaluation items are shown in Table 1.

Furthermore, the stability of the pigment dispersion was evaluated by the under-breath method.

(2) The viscosity of the 40% by weight pigment dispersion was measured using a B-type viscometer.

The degree of sedimentation when the 0 dispersion was placed in a beaker and allowed to stand for 1 hour was visually observed.

O: Almost no sedimentation.

△: A small amount of pigment is precipitated.

X: A large amount of pigment settles.

The above evaluation results are shown in Table 2.

As shown in Table 1, Table 2, and Table 1, it can be seen that the present invention provides a heat-sensitive recording material having high sensitivity, excellent running properties, and good manufacturing suitability.

featured

Claims (2)

[Claims] (1) A thermosensitive coloring layer characterized in that calcium carbonate with an oil absorption of 100 ml/100 g or more and a carboxylic acid copolymer with an average molecular weight of 2,000 or more and 20,000 or less as a dispersion aid for the calcium carbonate are simultaneously used in the thermosensitive coloring layer. Recording materials. (2) Claims characterized in that the monomer units constituting the carboxylic acid copolymer according to Claim 1 include acrylic acid, maleic acid, and alkali metal salts and ammonium salts thereof. Thermal recording material according to item 1