JPH06122274A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material having high sensitivity and a distinct image by containing calcium carbonate, oil absorption of which is specified, and polystyrene sulfonic acid salt as the dispersing agent of calcium carbonate in a thermal recording layer disposed onto a support. CONSTITUTION:A thermal color-developing layer is arranged onto the top face of a support in a thermal recording material. Calcium carbonate having oil absorption of 100ml/100g or more and polystyrene sulfonic acid salt as the dispersing agent of calcium carbonate are contained in the thermal color- developing layer at that time. Calcium carbonate is used jointly with either of kaolin, talc or silica. Polystyrene sulfonic acid salt is contained in 0.5-3wt.%, to dyestuffs. Accordingly, the dispersion properties and liquid stability of a dispersion employed as a heat-sensitive coating fluid are improved, thus acquiring the thermal recording material having high sensitivity and a distinct image.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a thermal recording material,
More specifically, the present invention relates to a heat-sensitive recording material having high sensitivity and excellent image clarity by improving dispersibility and liquid stability of a dispersion liquid used as a heat-sensitive coating liquid.

[0002]

2. Description of the Related Art Recording materials using an electron-donating dye precursor (hereinafter referred to as a color former) and an electron-accepting compound (hereinafter referred to as a developer) are pressure-sensitive recording paper, thermal recording paper, and light-sensitive pressure-sensitive recording paper. It is well known as a recording paper and a heat-sensitive recording paper. For example, British Patent No. 2140449, US Patent No. 4480052, and US Patent No. 4436920.
Japanese Patent Publication No. 60-23922, Japanese Patent Laid-Open No. 57-179836, 60-1235.
56, 60-123557, and the like. In recent years, there have been strong demands for high-sensitivity heat-sensitive recording materials, but various studies have been made, but they have not yet been sufficiently developed.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermosensitive recording material having high sensitivity and excellent image sharpness.

[0004]

The object of the present invention is to obtain an oil absorption of 10
It was achieved by a thermosensitive recording material containing 0 ml / 100 g or more of calcium carbonate and polystyrene sulfonate as a dispersion aid of the calcium carbonate in the thermosensitive color developing layer. The above calcium carbonate can be used not only by itself but also together with other inorganic oil absorbing substances (silica, kaolin, talc, etc.).

The oil absorption amount in the present invention is a value measured by the Kokura method. When using a highly oil-absorbing material as described above in the thermosensitive color developing layer, sodium hexametaphosphate, which has been widely used as a dispersion aid for conventional pigments, maleic acid copolymers, sodium salts, carboxylic acid copolymers, etc. It is difficult to provide sufficient dispersion stability with a dispersion aid.

The polystyrene sulfonate used as the dispersion aid in the present invention is used in an amount of 0.5 to 3% by weight, preferably 1 to 2% by weight, based on the pigment. The calcium carbonate dispersion thus dispersed has low viscosity and high dispersion stability, and thus has excellent production suitability.

In the present invention, the color former, the developer and the heat-fusible substance are dispersed in a water-soluble binder. The binder used in the present invention is 5% by weight with respect to water at 25 ° C. Compounds that dissolve above are preferred, and specifically,
Polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, starches (including modified starch), gelatin, gum arabic, casein, styrene-
Examples thereof include maleic anhydride copolymer hydrolyzate, carboxy-modified polyvinyl alcohol, polyacrylamide, and saponified vinyl acetate-polyacrylic acid copolymer.
These binders are used not only for dispersion but also for the purpose of improving the coating strength. For this purpose, styrene-butadiene copolymer, vinyl acetate copolymer, acrylonitrile-butadiene copolymer, poly A synthetic polymer latex binder such as vinylidene chloride may also be used in combination. Alternatively, the same binder can be used for the undercoat layer.

The color former (leuco dye) used in the present invention may be used alone or as a mixture of two or more kinds.
As such a leuco dye, those applied to this type of recording material are arbitrarily applied, for example, triphenylmethanephthalide type, triallylmethane type, fluorane type,
Phenothian, thioferorane, methine, rhodamine anilinolactam, rhodamine lactam,
Leuco compounds such as quinazoline type, diazaxanthene type and bislactone type are preferably used. Examples of such compounds include those shown below. 3,3-bis (p-dimethylaminophenyl) -phthalide, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6- Diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dibutylaminophenyl) phthalide, 3-cyclohexylamino-6-chlorofluorane, 3-dimethyl amino-
5,7-Dimethylfluorane, 3- (N-methyl-N-isoamylamino) -6-methyl-7-anilinofluorane, 3- (N-methyl-N-isobutylamino) -6-methyl-7 -Anilinofluorane, 3- (Np-tolyl-N-ethylamino) -6-methyl-7-
Anilinofluorane, 3- (N-methyl-N-amylamino)-
6-methyl-7-anilinofluorane, 3- (N-methyl-N-cyclohexylamino) -6-methyl-7-anilinofluorane,
3- (N-methyl-N-iso-propylamino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-N-tetrahydrofurfurylamino) -6-methyl-7-anilinoflu Olane, 3-diethylamino-7,8-benzfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3- Pyrrolidino-6-methyl-7-anilinofluorane,
3-diethylamino-6-methyl-7- (m-trichloroanilino) fluorane, 3-diethylamino-7- (o-chloroanilino) fluorane, 3-dibutylamino-7- (o-chloroanilino) fluorane, 3-diethylamino- 6-methyl-7-anilinofluorane, 3-diptylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (2 ',
4'-Dimethylanilino) fluorane, 3- (N, N-diethylamino) -5-methyl-7- (N, N-dibenzylamino) fluorane, benzoylleucomethylene blue, 6'-chloro-
8'-methoxybenzoindolinospiropyran, 6'-bromo
-8'-Methoxybenzoindolinospiropyran, 3- (2'-
Hydroxy-4'-dimethylaminophenyl) -3- (2'-methoxy-5'-chlorophenyl) phthalide, 3- (2'-hydroxy-4'-dimethylaminophenyl) -3- (2'-methoxy-5 '-
Nitrophenyl) phthalide, 3- (2'-hydroxy-4'-diethylaminophenyl) -3- (2'-methoxy-5'-methylphenyl) phthalide, 3- (2'-methoxy-4'-dimethylaminophenyl ) -3- (2'-Hydroxy-4'-chloro-5'-methylphenyl) phthalide, 3-morpholino-7- (N-propyltrifluoromethylanilino) fluorane, 3-pyrrolidino
-7-Trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7- (N-benzyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluor Olane, 3-diethylamino-5-chloro-7- (α-phenylethylamino) fluorane, 3- (N-ethyl-Np-toluidino) -7- (α-phenylethylamino) fluorane, 3-diethylamino-7-
(O-methoxycarbonylphenylethyl) fluorane,
3-diethylamino-5-methyl-7- (α-phenylethylamino) fluorane, 3-diethylamino-7-piperidinofluorane, 2-chloro-3- (N-methyltoluidino) -7- (p-
N-Butylanilino) fluorane, 3,6-bis (dimethylamino) fluorenspyro (9,3 ')-6'-dimethylaminophthalide, 3- (N-ethyl-N-cyclohexylamino) -5,6-
Benzo-7-α-naphthylamino-4′-bromofluorane, 3-
Diethylamino-6-chloro-7-anilinofluorane, 3-
(N-ethyl-N-2-ethoxypropylamino) -6-methyl-7
-Anilinofluorane, 3- (N-ethyl-N-tetrafurfurylamino) -6-methyl-7-anilinofluorane 3-diethylamino-6-methyl-7-mesitidino-4 ', 5'-benzo Fluoran, 3- (p-dimethylaminophenyl) -3- {1,1-bis (p
-Dimethylaminophenyl) ethylene-2-yl} phthalide, 3- (p-dimethylaminophenyl) -3- {1,1-bis (p
-Dimethylaminophenyl) ethylene-2-yl} -6-dimethylaminophthalide, 3- (p-dimethylaminophenyl)
-3- (1-p-dimethylaminophenyl-1-phenylethylene
-2-yl) phthalide, 3- (p-dimethylaminophenyl)-
3- (1-p-Dimethylaminophenyl-1-p-chlorophenylethylene-2-yl) -6-dimethylaminophthalide, 3- (4 '
-Dimethylamino-2'-methoxy) -3- (1 "-p-dimethylaminophenyl-1" -p-chlorophenyl-1 ", 3" -butadiene
-4 "-yl) benzophthalide, 3- (4'-dimethylamino-2 '
-Benzyloxy) -3- (1 "-p-dimethylaminophenyl-
1 "-phenyl-1", 3 "-butadiene-4" -yl) benzophthalide, 3-dimethylamino-6-dimethylamino-fluorene
-9-spiro-3 '(6'-dimethylamino) phthalide 3,3-bis {2- (p-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl} -4,5,6,7- Tetrachlorophthalide, 3-
Bis {1,1-bis (4-pyrrolidinophenyl) ethylene-2-
Ill} -5,6-dichloro 4,7-dibromophthalide, bis (p-
Dimethylaminostyryl) -1-naphthalenesulfonylmethane, bis (p-dimethylaminostyryl) -1-p-tolylsulfonylmethane and the like.

In the present invention, various electron-accepting compounds such as phenolic compounds are used as color developers.
A thiophenolic compound, a thiourea derivative, an organic acid and a metal salt thereof can be used, and specific examples thereof include, but are not limited to, those shown below. 4,4'-isopropylidenediphenol, 4,
4'-isopropylidene bis (o-methylphenol), 4,
4'-sec-butylidene bisphenol, 4,4 'isopropylidene bis (2-tert-butylphenol), zinc p-nitrobenzoate, 1,3,5-tris (4-tert-butyl-3-hydroxy)
-2,6-Dimethylbenzyl) isocyanuric acid, 2,2 (3,4'-
Dihydroxydiphenyl) propane, bis (4-hydroxy-3-methylphenyl) sulfide, 4 (β (p-methoxyphenoxy) ethoxy) salicylic acid, 1,7-bis (4-hydryloxyphenylthio) -3,5-dioxahebutane , 1,5-bis (4-hydroxyphenylthio) -5-oxapentane,
Phthalic acid monobenzyl ester monocalcium salt, 4,4 '
-Cyclohexylidene diphenol, 4,4'-isopropylidene bis (2-chlorophenol), 2,2'-methylene bis (4-methyl-6-tert-butylphenol), 4,4'-butylidene bis (6-tert- Butyl-2-methylphenol), 1,1,
3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-
5-cyclohexylphenyl) butane, 4,4'-thiobis (6
-tert-butyl-2-methylphenol), 4,4'-diphenol sulfone, 4-isopropoxy-4'-hydroxydiphenyl sulfone, 4-benzyloxy-4'-hydroxydiphenyl sulfone, 4,4-diphenol sulfoxide , Isopropyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, benzyl protocatechuate, stearyl gallate,
Lauryl gallate, octyl gallate, 1,3-bis (4-hydroxyphenylthio) propane, N, N'-diphenylthiourea, N, N'-di (m-chlorophenyl) thiourea, salicylanilide, bis ( 4-hydroxyphenyl) methyl acetate, bis (4-hydroxyphenyl) benzyl acetate, 1,3-
Bis (4-hydroxycumyl) benzene, 1,4-bis (4-hydroxycumyl) benzene, 2,4'-diphenolsulfone, 2,2'-diallyl-4,4'diphenolsulfone, 3, 4-dihydroxy-4'-methyldiphenyl sulfone, zinc 1-acetyloxy-2-naphthoate, zinc 2-acetyloxy-1-naphthoate, zinc 2-acetyloxy-3-naphthoate, α, α
-Bis (4-hydroxyphenyl) α-methyltoluene, antipyrine complex of zinc thiocyanate, tetrabromobisphenol A, tetrabromobisphenol S, 4,4'-thiobis (2-methylphenol), 4,4'-thiobis ( 2-chlorophenol) etc.

These color developers are 50 to 800% by weight of the color developer.
It is preferable to use, more preferably 100 to 500
% By weight. If it is less than 50% by weight, color development is not sufficient, and if more than 800% by weight is added, no further effect can be expected, which is not preferable.

In the present invention, various heat-fusible substances can be used as the sensitivity improver, and specific examples thereof include the followings, but the present invention is not limited thereto. Fatty acids such as stearic acid and behenic acid, fatty acid amides such as stearic acid amide and palmitic acid amide, fatty acid metal salts such as zinc stearate, aluminum stearate, calcium stearate, zinc palmitate and zinc behenate, p- Benzylbiphenyl, terphenyl, triphenylmethane, p-
Benzylic oxybenzoic acid benzil, β-benzyloxynaphthalene, β-naphthoic acid phenyl ester, 1-hydroxy-2-naphthoic acid phenyl, 1-hydroxy-
2-methyl naphthoate, diphenyl carbonate, guaiacol carbonate, dibenzyl terephthalate, dimethyl terephthalate, 1,4-dimethoxynaphthalene,
1,4-diethoxynaphthalene, 1,4-dibenzyloxynaphthalene, 1,2-diphenoxyethane, 1,2-
Bis (3-methylphenoxy) ethane, 1,2-bis (4-methylphenoxy) ethane, 1,4-diphenoxybutane, 1,4 diphenoxy-2-butene, 1,2-
Bis (4-methoxyphenylthio) ethane, dibenzoylmethane, 1,4 diphenylthiobutane, 1,4-diphenylthio-2-butene, 1,3-bis (2-vinyloxyethoxy) benzene, 1,4- Bis (2-vinyloxyethoxy) benzene, p (2-vinyloxyethoxy) biphenyl, p-aryloxybiphenyl, p-
Propagyloxybiphenyl, dibenzoyloxymethane, dibenzoyloxypropane, dibenzyl disulfide, 1,1-diphenylethanol, 1,1-diphenylpropanol, p-benzyloxybenzyl alcohol, 1,3-phenoxy-2-propanol, N-octadecylcarbamoyl-p-methoxycarbonylbenzene, N-octadecylcarbamoylbenzene, 1,2
-Bis (4-methoxyphenoxy) propane, 1,5-
Bis (4-methoxyphenoxy) -3-oxapentane, dibenzyl oxalate, bis (4-methylbenzyl) oxalate, bis (4-chlorobenzyl) oxalate and the like.

The above-mentioned heat-fusible substances may be used alone or as a mixture, and in order to obtain a sufficient heat response, it is preferably used in an amount of 10 to 200% by weight with respect to the developer, and more preferably 20 to 150% by weight.

The inorganic oil-absorbing substance used in the present invention must be calcium carbonate having an oil absorption of 100 ml / 100 g or more, and can be used in combination with other inorganic oil-absorbing substances (silica, kaolin, talc, etc.). However, the calcium carbonate
It is preferable that the amount is 0.2 g / m ² or more.

If necessary, metal soap, wax,
You may add surfactant, an antistatic agent, a ultraviolet absorber, a defoaming agent, a conductive agent, a fluorescent ray, etc. As a metal soap,
Higher fatty acid metal salts are used, such as zinc stearate, causium stearate, and aluminum stearate. Paraffin wax,
Microcrystalline wax, carnauba wax, methylol stearamide, polyethylene wax, polystyrene wax, fatty acid amide wax, etc. may be used alone or in combination. As a surfactant,
A sulfosuccinic acid-based alcar metal salt and a fluorine-containing surfactant are used.

Further, in order to prevent decolorization of the image printed part and to make the produced image fast, it is preferable to add an anticolor erasing agent to the thermosensitive color developing layer. Phenol compounds, particularly hindered phenol compounds, are effective as the decoloring inhibitor, and examples thereof include 1,1,3-tris (2-methyl-4-hydroxy-tert-butylphenyl) butane, 1,
1,3-tris (2-ethyl-4-hydroxy-5-t
ert-butylphenyl) butane, 1,1,3-tris (3,5di-tert-butyl-4-hydroxyphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert). -Butylphenyl) propane,
2,2'-methylene-bis (6-tert-butyl-4
-Methylphenol), 4,4'-butylidene-bis (6-tert-butyl-3-methylphenol),
4,4'-thio-bis- (3-methyl-6-tert-
Butylphenol), and the like.

The amount of such a phenolic compound used is preferably 1 to 200% by weight, more preferably 5 to 50% by weight, based on the color developer. Each of these materials is mixed and then applied to the support.

As the support, paper, synthetic paper, various bases and the like are used, but it is preferable to previously provide an undercoat layer on the support in order to obtain high smoothness. The applied heat-sensitive recording material is dried and treated with a calender or the like before use.

[0018]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples. Example-1 (Preparation of undercoat paper) 80 g of calcined kaolin (manufactured by Engelhardt: Ansilex 93) was dispersed with a homogenizer together with 160 g of a 0.5% aqueous solution of sodium hexametaphosphate to obtain a pigment dispersion. Styrene-butadiene latex (Sumitomo Nogatax: SN30) was added to the pigment dispersion.
7, solid content concentration of 48%) 16 g, and polyvinyl alcohol (Kuraray Co., Ltd .: PVA-117) 10% aqueous solution 24 g were added to obtain a coating liquid for undercoat layer. The undercoat layer coating solution was prepared undercoat paper was coated and dried so as to be 8 g / m ² on a high-quality paper 50 g / m ^2.

(Preparation and coating of coating solution for thermosensitive color developing layer) 20 g of 3-dibutylamino-6-methyl-7-anilinofluorane was added to polyvinyl alcohol (Kuraray Co .: P
VA-105) was dispersed in a ball mill for 24 to 48 hours together with 100 g of a 5% aqueous solution to obtain a dispersion having an average particle size of 1.0 μm. Furthermore, 40 g of bisphenol A and 40 g of naphthyl benzyl ether are added to polyvinyl alcohol (Kuraray Co., Ltd .: PVA-105) 10
% Aqueous solution 400 g to disperse in a ball mill for 24 to 48 hours to obtain a dispersion having an average particle size of 1.0 μm.

Further, 80 g of calcium carbonate having an oil absorption of 140 ml / 100 g (Callite KT manufactured by Shiraishi Central Research Institute) was used as a dispersion aid for calcium carbonate, sodium polystyrene sulfonate (Sanyo Kasei Co., Ltd .: Chemist SA-9). A pigment dispersion was obtained by dispersing with a homogenizer together with 160 g of a 1% aqueous solution.

The dispersions obtained as described above were mixed, and 50 g of 21% zinc stearate emulsion was further added to obtain a coating solution for thermal paper. Then, the undercoat paper was coated with a wire bar so that the dry coating amount was 7 g / m ² and dried in an oven at 50 ° C. to obtain a heat-sensitive recording material of the present invention.

Example-2 Example-2 except that the dispersion aid of calcium carbonate used in the thermosensitive coloring layer in Example-1 was changed to ammonium polystyrene sulfonate (Sanyo Kasei Co., Ltd .: Chemistat SA-101). A thermal recording material was obtained in the same manner as in 1.

Example 3 Example 1 was repeated except that the calcium carbonate used in the thermosensitive coloring layer in Example 1 was changed to calcium carbonate having an oil absorption of 100 ml / 100 g (manufactured by Shiraishi Central Research Institute: KK-12). A heat sensitive recording material was obtained in the same manner.

Example-4 The calcium carbonate used in the thermosensitive coloring layer in Example-1 was changed to a mixture of this and silica (Mizusawa Chemical Co., Ltd .: FSP-101) so that the ratio was 1: 1. A thermosensitive recording material was obtained in the same manner as in Example 1 except for the above.

Example-5 Instead of the silica of Example-4, kaolin (Asia clay:
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the material was changed to Asia Coat HG).

Example-6 A thermosensitive recording material was obtained in the same manner as in Example-1, except that talc (Fuji Talc Industry Co., Ltd .: LMS200) was used instead of the silica of Example 4.

Comparative Example-1 The same as Example-1 except that the calcium carbonate used in the thermosensitive coloring layer in Example-1 was changed to calcium carbonate having an oil absorption of 80 ml / 100 g (Callite SA manufactured by Shiraishi Central Research Institute). A thermosensitive recording material was obtained.

Comparative Example-2 A thermosensitive recording material was obtained in the same manner as in Example-1, except that the calcium carbonate dispersion aid used in the thermosensitive coloring layer in Example-1 was changed to 160 g of 0.5% hexametaphosphoric acid aqueous solution. .

Comparative Example-3 The dispersion aid of calcium carbonate used in the thermosensitive coloring layer in Example-1 was replaced with a carboxylic acid copolymer (Kao Soap: Poise 52).
A thermosensitive recording material was obtained in the same manner as in Example 1 except that the temperature was changed to 0).

The heat-sensitive recording material obtained as described above was surface-treated with a calender, and evaluation tests of the following items were conducted. The results are shown in Tables 1 and 2. First, with a thermal head (KLT-216-8MPDI) manufactured by Kyocera Corp. and a thermal printing experimental device, head voltage 24 V, pulse cycle 10
While using the pressure roll in ms condition, pulse width 0.8,
Printing was performed with 1.0 and 1.2, and the printing density was measured with a Macbeth reflection densitometer RD-914.

The sharpness of the image is based on Fu of Xerox Co., Ltd.
ji XEROX 7005 Telecopier was used to copy Test Chart No. 3 of the Institute of Image Electronics Engineers of Japan, and evaluation was performed by sticking the printed sample and averaging the black rate per dot unit in the halftone portion. The formula for obtaining the black ratio per dot unit is as follows.

[0032]

[Equation 1]

The sticking evaluation results are displayed as follows. ○: No sticking was observed. △: 2 to 3 white spots (by stick-slip,
There is a part that is not printed) but no print shrinkage has occurred. X: There are many overexposed areas and the print is shrunk.

The stability of the pigment dispersion was evaluated by the following method. Using a 200 mesh filter, 50 l of 40% by weight pigment dispersion was filtered under pressure at a pressure of 100 kg / m ² , and the clogging of the filter was visually observed. ◯: Good, no clogging. Δ: A small amount is clogged but flows. X: Clogging is remarkable and almost no flow occurs. The degree of sedimentation of the pigment when the dispersion was placed in a beaker and allowed to stand for 24 hours was visually observed. ◯: Almost no sedimentation. Δ: A small amount of pigment settles. X: A large amount of pigment settles.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

As is apparent from Tables 1 and 2, according to the present invention, high sensitivity, excellent image clarity, and good production suitability such as dispersion stability of the heat-sensitive layer coating liquid are obtained. The thermosensitive recording material provided can be obtained.

Claims (3)

[Claims] 1. A thermosensitive recording material having a thermosensitive coloring layer provided on a support, wherein calcium carbonate having an oil absorption of 100 ml / 100 g or more is contained in the thermosensitive coloring layer, and polystyrene sulfonate is used as a dispersing aid of the calcium carbonate. A heat-sensitive recording material characterized by being contained. 2. The heat-sensitive recording material according to claim 1, wherein the calcium carbonate is used in combination with any of kaolin, talc and silica. 3. A polystyrene sulfonate is added to the pigment.
The heat-sensitive recording material according to claim 1 or 2, wherein the content is 0.5 to 3% by weight.