JPH0839930A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material excellent in recording sensitivity and recording image quality and reducing head refuse. CONSTITUTION:In a thermal recording material wherein a thermal recording material wherein a thermal recording layer containing a leuco dye and a coupler is provided on a support, an intermediate layer based on pigment with oil absorption (JIS K5101) of 100ml/100g or more and an ammonium salt of a styrene/ acrylic acid copolymer or an ammonium salt of a styrene/maleic anhydride copolymer being a water-soluble adhesive is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material utilizing a color-forming reaction between a leuco dye and a color-developing agent, and more particularly to a heat-sensitive recording material having excellent recording sensitivity and recording image quality and less head residue.

[0002]

2. Description of the Related Art A thermosensitive recording medium is generally provided on a sheet-shaped support such as paper, synthetic paper, or plastic film, by presenting a colorless or light-colored electron-donating leuco dye and an electron-accepting phenolic compound. A heat-sensitive recording layer containing a colorant and an adhesive as main components is provided, and a color-recorded image can be obtained by reacting the leuco dye and the color former with heat energy.

On the other hand, the thermosensitive recording system has been evaluated for its advantages such that a color image can be obtained by simply heating it and that the recording apparatus can be made relatively compact. Bowl, ATM, POS
It is widely used as various information recording methods. However, in the heat-sensitive recording method, the coloring component melts during printing, so if no measures are taken to treat the heat-melting component, part of the melted component cools and solidifies on the thermal head, causing head scum, and Defects such as tailing occur in which the non-printed portion that follows is contaminated by the melted component.

As one of the most effective means for improving the above-mentioned drawbacks, a method is provided in which an intermediate layer containing a highly oil-absorbing pigment is provided, and the generated melt is absorbed by the intermediate layer (JP-A-54-235).
45, JP 56-86792, JP 6
1-56118, JP-A-61-139485, JP-A-3-21490), the use of a highly oil-absorptive pigment in the intermediate layer simultaneously increases the water absorption of the intermediate layer surface. When a heat-sensitive recording layer is applied, a so-called migration phenomenon occurs in which the water-soluble component of the heat-sensitive recording layer paint sinks into the intermediate layer, making it impossible to form a uniform heat-sensitive recording layer. As a result, new problems occur such that the color density is lower than the design value and the image quality is deteriorated, and the effect of the intermediate layer is not obtained as expected.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a thermal recording medium which is excellent in recording sensitivity and image quality and has less head residue.

[0006]

DISCLOSURE OF THE INVENTION The present inventors have found that in a heat-sensitive recording material having a support and a heat-sensitive recording layer containing a leuco dye and a color developing agent, between the heat-sensitive recording layer and the support, Oil absorption (based on JIS K 5101) is 100 ml / 1
The above problems are solved by providing an intermediate layer containing 00 g or more of a pigment and an ammonium salt of a styrene-acrylic acid copolymer or an ammonium salt of a styrene-maleic anhydride copolymer as a main component as a water-soluble adhesive. It was found that the present invention has been completed.

[0007]

In the present invention, the oil absorption (J
100 ml / 100 g) (based on IS K 5101)
Ammonium salt of styrene- (meth) acryl acid copolymer or styrene-as the above-mentioned pigment and water-soluble adhesive
It is characterized by using an ammonium salt of a maleic anhydride copolymer. When a heat-sensitive recording layer is coated with this constitution, even if a porous pigment having an oil absorption of 100 ml / 100 g or more is used in the intermediate layer, it is heat-sensitive. A uniform heat-sensitive recording layer can be formed without the components of the recording layer-forming coating liquid sinking into the intermediate layer. As a result, it is possible to obtain a heat-sensitive recording material in which the color density and the recording image quality are improved and the head residue is small. In particular,
This effect is enhanced by coating the heat-sensitive recording layer with a blade coater at high density and at high speed.

[0008] The above-mentioned specific water-soluble adhesive film itself has strong water resistance, and since ammonia is scattered during the drying process, it does not form salt again to dissolve even when it comes into contact with water, It is considered that the penetration of the coating liquid for forming the thermal recording layer into the intermediate layer can be suppressed.

It is also possible to use other aqueous adhesives in combination in the intermediate layer to the extent that the effects of the present invention are not impaired. For example, polyvinyl alcohol, modified polyvinyl alcohol, starch, modified starch, casein, gelatin, Polyacrylamide, polyamide, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, sodium salt of styrene-maleic anhydride copolymer, sodium salt of styrene-acrylic acid copolymer, styrene-butadiene latex, polyurethane latex, acrylic latex, etc. Is mentioned.

The oil absorption of the pigment used in the intermediate layer is 100 m.
If it is less than 1/100 g, the heat insulating property of the intermediate layer decreases,
It becomes difficult to absorb the heat-melted component of the heat-sensitive recording layer. Oil absorption 1
Examples of the pigment of 00 ml or more include calcined clay, silicic acid, porous calcium carbonate, and urea-formalin resin pigment. Oil absorption used in the middle layer is 100
The proportion of the oil-absorbing pigment of ml / 100 g or more and the specific water-soluble adhesive is 5 to 50% by weight, preferably 7 to 30% by weight of the specific water-soluble adhesive with respect to the total solid amount of the oil-absorbing pigment. It is desirable to adjust within the range.

In the intermediate layer, pigments having an oil absorption of 100 ml / 100 g or less, such as talc, clay, calcium carbonate, magnesium carbonate, zinc oxide, titanium oxide, aluminum silicate, can be used as long as the effect of the present invention is not impaired. It is also possible to add calcium silicate, aluminum hydroxide and the like. The coating amount of the intermediate layer is not particularly limited, but is 3 to 30 g / m ² in dry weight, preferably 5
It is adjusted in the range of ˜15 g / m ² .

The leuco dye used in the heat-sensitive recording layer provided on the intermediate layer thus formed is not particularly limited as long as it is used in general pressure-sensitive recording paper, heat-sensitive recording paper and the like. Absent. Specific examples thereof include (1) triarylmethane compounds such as 3,
3-bis (P-dimethylaminophenyl) -6-dimethylaminophthalide and the like. (2) Examples of diphenylmethane compounds include 4,
4'-bis-dimethylaminobenzhydrin benzyl ether, N-2,4,5-trichlorophenyl leuco auramine and the like. (3) As the xanthene compound, for example, rhodamine B
-Anilinolactam, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-butylaminofluorane, 3-diethylamino-7- (2-
Chloroanilino) fluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-ethyl-tolylamino-6-methyl-7-anilinofluorane, 3-cyclohexyl-methylamino-6-methyl-7-ani Rinofluorane, 3-diethylamino-6-chloro-7-
(Β-Ethoxyethyl) aminofluorane, 3-diethylamino-6-chloro-7- (γ-chloropropyl) aminofluorane, 3-di (n-butyl) amino-6-methyl-7-anilinofluorane , 3-diethylamino-
6-methyl-7-anilinofluorane, 3- (N-isoamyl-N-ethylamino) -6-methyl-7-anilinofluorane, 3-ethyl-isoamylamino-6-methyl-7-anilino Fluoran, 3-dibutylamino-
7-chloroanilinofluorane and the like. These leuco dyes can be used alone or in combination of two or more, and are appropriately selected and used depending on the use of the heat-sensitive recording material and desired properties.

As the coloring agent used together with the leuco dye, phenol derivatives and aromatic carboxylic acid derivatives are preferable, and bisphenols are particularly preferable. Specific examples of the phenol derivative of the color developing agent include p-octylphenol, p-tert-butylphenol, p
-Phenylphenol, 2,2-bis (p-hydroxyphenyl) propane, 1,1-bis (p-hydroxyphenyl) propane, 2,2-bis (p-hydroxyphenyl) pentane, 1,1-bis (p -Hydroxyphenyl) hexane, 2,2-bis (p-hydroxyphenyl) hexane, 1,1-bis (p-hydroxyphenyl) -2-ethylhexane, 2,2-bis (4-hydroxy-3,5-) Dichlorophenyl) propane, dihydroxydiphenyl ether, 4,4′-dihydroxydiphenylsulfone, 4-hydroxy-4′-isopropyloxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone and the like can be mentioned.

Specific examples of the aromatic carboxylic acid derivative include p-hydroxybenzoic acid, butyl p-hydroxybenzoate, 3,5-di-tert-butylsalicylic acid,
3,5-di-α-methylbenzyl salicylic acid, 4- [3
Examples thereof include zinc- (p-tolylsulfonyl) propyloxy] salicylate and polyvalent metal salts of the above carboxylic acids. The mixing ratio of the leuco dye and the color-developing agent is not necessarily limited and may be adjusted depending on the materials used, but generally 1 to 10 parts by weight, preferably 1 part by weight to 1 part by weight of the leuco dye. 0.5 to 5 parts by weight of coloring agent are used.

These leuco dyes and color formers generally use water as a dispersion medium, and are subjected to polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol by a wet mill such as a ball mill, a coball mill, an attritor, or a vertical or horizontal sand mill. , Water-soluble synthetic polymer compounds such as methyl cellulose, styrene-maleic anhydride copolymer salt, etc. and a surfactant to form a dispersion liquid, which is then used for preparing a heat-sensitive color-developing paint.

Other materials constituting the heat-sensitive recording layer include binders, sensitizers, inorganic or organic pigments, waxes, metal soaps, and if necessary UV absorbers, storage stabilizers,
A fluorescent dye, a coloring dye, etc. can be mentioned. Water-soluble binders are generally used, such as polyvinyl alcohol, polyamide, styrene-acrylic acid copolymer salts,
Styrene-maleic anhydride copolymer salt, ethylene-maleic anhydride copolymer salt, water-soluble synthetic polymer compounds such as diisobutylene-maleic anhydride copolymer salt, and methyl cellulose, other cellulose derivatives, starch, Examples include water-soluble natural polymer compounds such as starch derivatives, gelatin, and casein, or derivatives thereof. Further, a water resistance imparting agent may be added to these binders for the purpose of imparting water resistance, or a synthetic polymer emulsion, specifically, SBR latex, acrylic resin emulsion, or the like may be added.

Examples of the sensitizer include fatty acid amides such as stearic acid amide, ethylenebisstearic acid amide, methylol behenic acid amide and palmitic acid amide, p-benzyl biphenyl, dibenzyl terephthalate, 1-hydroxy-2-naphthoic acid. Phenyl, dibenzyl oxalate, di-p-chlorobenzyl oxalate, di-p oxalate
-Methylbenzyl, di-o-chlorobenzyl adipate, 1,2-di (3-methylphenoxy) ethane, 1,
In addition to 2-bis (3,4-dimethylphenyl) ethane and the like, various known heat-fusible substances can be added.

The inorganic pigments include calcium carbonate, kaolin, calcined kaolin, talc, agatestone, diatomaceous earth, aluminum oxide, aluminum hydroxide, magnesium hydroxide, magnesia, titanium dioxide, barium carbonate, barium sulfate, finely divided silicic acid, calcium silicate. , Aluminum silicate, etc., organic pigments such as urea, phenol, epoxy,
Examples thereof include styrene, nylon, polyethylene, melamine and benzoguanamine resins.

Paraffin wax,
Examples thereof include carnauba wax, microcrystalline wax, polyethylene wax and higher fatty acid ester wax. Examples of the metal soap include higher fatty acid polyvalent metal salts, that is, zinc stearate, aluminum stearate, calcium stearate, zinc oleate and the like.

In the present invention, the intermediate layer and the thermosensitive recording layer
Air knife method, blade method,
Gravure method, roll coater method, spray method, dip
Known methods, such as method, bar method, and extrusion method
Depending on the application method, high-quality paper, medium-quality paper, glossy paper, coated paper,
Paper such as art paper, cast coated paper, synthetic paper, synthetic fiber
Apply it on a support such as fiber paper or synthetic resin film and dry it.
Is formed. About the coating amount of the coating liquid for the thermosensitive recording layer
Is 2 to 10 g / m², Preferably 3-8 g / m ²Range of
Adjusted in the fencing.

Various additives such as a cross-linking agent, an oil repellent, an antifoaming agent, a surfactant, a viscosity modifier, a fluorescent dye and a colorant may be added to the heat-sensitive recording layer and the intermediate layer. After forming the intermediate layer and the thermosensitive recording layer, it is possible to apply surface smoothing treatment such as supercalendering if necessary, and it is also possible to provide a coating layer on the back surface of the support for the purpose of curl control etc. Is.

[0022]

EXAMPLES The present invention will be specifically described below with reference to examples.
The present invention is not limited to these. In addition, "parts" and "%" in the examples are "parts by weight" unless otherwise specified.
And "% by weight" are shown.

Preparation of Solution A 40 parts of 10% aqueous solution of 40 parts of 3- (N-ethyl-N-isoamylamino) -6-methyl-7-anilinofluorane and polyvinyl alcohol (trade name: PVA205, manufactured by Kuraray Co., Ltd.) , A defoaming agent [trade name: San Nopco SN Defomer 250, manufactured by San Nopco Ltd.], and 18 parts of water were treated with a sand mill until the average particle diameter became 0.8 μm to obtain solution A. .

Preparation of solution B 40 parts of 4-hydroxy-4'-isopropoxydiphenyl sulfone, polyvinyl alcohol [trade name: PVA2
05, manufactured by Kuraray Co., Ltd.], 40 parts of a 10% aqueous solution, 2 parts of a defoaming agent [trade name: San Nopco SN Defomer 250, manufactured by San Nopco], and 18 parts of water were used to prepare a composition having an average particle size of 1. The solution was treated until it became 2 μm to obtain a solution B.

Preparation of liquid C 40 parts of 1,2-di (m-tolyloxy) ethane, polyvinyl alcohol [trade name: PVA205, manufactured by Kuraray Co., Ltd.]
40% of 10% aqueous solution of defoamer [Product name: San Nopco S
N Deformer 250, manufactured by San Nopco Ltd.] 2 parts, an anionic surfactant [trade name: Kao Perex TR], and 16 parts of water are treated with a sand mill until the average particle diameter becomes 0.8 μm, Liquid C was obtained.

Example 1 Formation of Intermediate Layer 85 parts of calcined kaolin having an oil absorption of 110 ml / 100 g [trade name: Anclix 93, manufactured by EMW], 2 parts of 40% aqueous solution of sodium polyacrylate, water-soluble adhesive A composition comprising 100 parts of a 20% aqueous solution of an ammonium salt of a styrene-maleic anhydride copolymer [trade name: WR300D, manufactured by Arakawa Chemical Co., Ltd.] and 100 parts of water as an agent,
The coating solution prepared by stirring is applied on a high-quality paper having a basis weight of 60 g / m ^{2 by} a rod blade method so that the coating amount after drying becomes 8 g / m ^2, and the coating speed is 800 m / min. It dried and formed the intermediate | middle layer.

Preparation of coating liquid for thermosensitive recording layer 25 parts of solution A, 75 parts of solution B, 50 parts of solution C, fine particle silicic acid pigment [trade name: Mizuka Seal P-603, manufactured by Mizusawa Chemical Co., Ltd.] 1
5 parts, 1 of acetoacetyl group-modified polyvinyl alcohol
80 parts of 0% aqueous solution, paraffin wax having a solid concentration of 30% [trade name: Hydrin P-7, manufactured by Chukyo Yushi Co., Ltd.] 20
Parts and 40 parts of water were mixed and stirred to obtain a coating liquid for a thermosensitive recording layer having a solid concentration of 33%.

Formation of Thermosensitive Recording Layer The above-mentioned coating material for thermal recording layer was applied onto the above-mentioned intermediate layer at a coating speed of 900 m / min using a pure blade so that the coating amount after drying was 4 g / m ^2. The heat sensitive recording layer was formed by coating and drying. After coating the heat-sensitive recording layer, smoothing treatment was performed with a super calendar to obtain a heat-sensitive recording material.

Example 2 In the formation of the intermediate layer of Example 1, a 20% aqueous solution of an ammonium salt of a styrene-maleic anhydride copolymer [trade name: WR300D, manufactured by Arakawa Chemical Co., Ltd.] as a water-soluble adhesive was used. Instead of parts, ammonium salt of styrene-acrylic acid copolymer [trade name: W
R800D, manufactured by Arakawa Chemical Co., Ltd.] A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 130 parts of a 15% aqueous solution was used.

[Example 3] In the formation of the intermediate layer of Example 1, instead of 85 parts of calcined kaolin having an oil absorption of 110 ml / 100 g [trade name: Anclix 93, manufactured by EMW], an oil absorption of 160 ml / 100 g of fine particle silica [trade name: Mizuka Seal P603, manufactured by Mizusawa Chemical Co., Ltd.] 8
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 5 parts were used.

[Example 4] In the formation of the intermediate layer of Example 1, instead of 85 parts of calcined kaolin having an oil absorption of 110 ml / 100 g (trade name: Anclix 93, manufactured by EMW), an oil absorption of 140 ml / 100g of coagulated calcium carbonate [Product name: Callite KT, manufactured by Shiraishi Industry Co., Ltd.]
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 85 parts were used.

Example 5 In the preparation of the coating liquid for the thermosensitive recording layer of Example 1, the coating liquid was diluted with water so that the solid concentration of the coating liquid was 20%, and in the formation of the thermosensitive recording layer, a pure blade was used instead. A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the coating was carried out at a coating speed of 300 m / min and the coating was dried to form a thermosensitive recording layer.

Comparative Example 1 In the formation of the intermediate layer of Example 1, instead of 85 parts of calcined kaolin (trade name: Anclix 93, manufactured by EMW) having an oil absorption of 110 ml / 100 g, an oil absorption of 50 ml / Other than using 100 g of kaolin [trade name: UW90, manufactured by EMC] 85 parts,
A thermal recording material was obtained in the same manner as in Example 1.

Comparative Example 2 In the formation of the intermediate layer of Example 1, a 20% aqueous solution of an ammonium salt of styrene-maleic anhydride copolymer [trade name: WR300D, manufactured by Arakawa Chemical Co., Ltd.] as a water-soluble adhesive 100. A thermosensitive recording medium was prepared in the same manner as in Example 1 except that 80 parts of a 25% aqueous solution of a styrene-maleic anhydride copolymer sodium salt [trade name: Polymalon 482, manufactured by Arakawa Chemical Co., Ltd.] was used in place of the parts. Got

Comparative Example 3 In the formation of the intermediate layer of Example 1, a 20% aqueous solution of an ammonium salt of styrene-maleic anhydride copolymer [trade name: WR300D, manufactured by Arakawa Chemical Co., Ltd.] as a water-soluble adhesive was used. Instead of parts, polyvinyl alcohol [trade name: PVA110, manufactured by Kuraray Co., Ltd.]
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 130 parts of a 15% aqueous solution was used.

Comparative Example 5 In the formation of the intermediate layer of Example 1, a 20% aqueous solution of an ammonium salt of a styrene-maleic anhydride copolymer [trade name: WR300D, manufactured by Arakawa Chemical Co., Ltd.] as a water-soluble adhesive was used. Instead of parts, SBR latex having a solid concentration of 45% [trade name: L-1571,
A thermal recording material was obtained in the same manner as in Example 1 except that 44 parts of Asahi Kasei Corporation was used.

The thermal recording material thus obtained was evaluated as follows, and the results are shown in Table 1. Recording Sensitivity Using a thermal recording medium evaluation machine (TH-PMD, Okura Electric Co., Ltd.), a recorded image is colored on the thermal recording medium at an applied energy of 0.4 mJ / dot, and the color density is measured by a Macbeth densitometer (Macbeth Co.). , RD-914) in visual mode.

The image quality of the recorded image obtained by the recorded image quality was visually determined. Evaluation Criteria ⊚ · There is almost no white spot in the image quality. ○ ・ ・ ・ ・ The image quality has some white spots. × ・ ・ ・ ・ There are many white spots in the image.

Head residue After the thermal recording material was developed for 30 m at an applied energy of 0.4 mJ / dot using a thermal recording material evaluation device (TH-PMD, Okura Electric Co., Ltd.), the amount of the head residue attached on the thermal head was measured. I checked the quantity. Evaluation criteria ○ ・ ・ ・ ・ Head residue is hardly seen × ・ ・ ・ ・ Head residue adhered

[0040]

[Table 1]

[0041]

As is clear from the results shown in Table 1, the thermal recording materials of the present invention are excellent in recording sensitivity and recording image quality,
Moreover, it was a heat-sensitive recording material with less head residue.

Continuation of the front page (72) Inventor Nakanao Obama 4-3-1, Jokoji, Amagasaki City, Hyogo Prefecture Shin-Oji Paper Co., Ltd. Kanzaki Mill

Claims (2)

[Claims] 1. A thermosensitive recording medium comprising a support and a thermosensitive recording layer containing a leuco dye and a colorant, wherein the oil absorption (based on JIS K 5101) is between the thermosensitive recording layer and the support. 100 ml / 100 g or more of pigment and a water-soluble adhesive provided with an intermediate layer containing a styrene-acrylic acid copolymer ammonium salt or a styrene-maleic anhydride copolymer ammonium salt as a main component Record body. 2. The heat-sensitive recording material according to claim 1, wherein the heat-sensitive recording layer is provided by blade coating.