JPH08230332A - Red and black two-color thermal recording material - Google Patents

Abstract

PURPOSE: To provide a red and black two-color thermal recording material reduced in the color mixture of a developed red color by a low temp. color forming layer at the time of the development of a black color at high temp. CONSTITUTION: In a red and black two-color thermal recording material wherein a high temp. color forming layer developing a black color and a low temp. color forming layer developing a red color are successively laminated on a support and both color forming layers contain electron donating color forming dyes and electron acceptive coupling compds., di-p-chlorobenzyl oxalate and di-p-methylbenzyl oxalate are added to the high temp. color forming layer and/or the low temp. color forming layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-color heat-sensitive recording material having color-developing layers which develop different color tones. More specifically, the present invention relates to a red-black two-color thermosensitive recording material characterized by reducing the color mixture of red color due to the low-temperature color-developing layer during black color development during heating at high temperature.

[0002]

2. Description of the Related Art Conventionally, a color developing reaction between a color developing agent and a color developing agent that develops color by contacting with the color developing agent is utilized, and both substances are melted by heat to bring them into contact with each other to obtain a color image. Thermal recording materials are widely known. Since such a heat-sensitive recording material is relatively inexpensive and the recording device is compact and its maintenance is relatively easy, it is used in a wide range of fields including recording media such as facsimiles and various computers. The quality required for such a heat-sensitive recording material has been diversified with the expansion of its application, and it has been desired to improve the sensitivity, stabilize the image, and record multiple colors. In particular, because of its wide range of application for multicolor recording, many recording materials have been researched and proposed so far.

For example, JP-A-48-86543,
Japanese Patent Application Laid-Open No. 51-146239 and the like describe a method of providing two distinguishable colors by providing two coloring layers capable of coloring different colors and applying different amounts of heat. Although such a method has an advantage that it can be produced at a relatively low cost, it causes a problem that the color tone of the low temperature color layer is mixed with the color tone of the high temperature color layer because the low temperature color layer is also colored at the same time when the high temperature color is developed. there were. For example, in a red-black two-color thermosensitive recording material in which red coloring is used as a low-temperature coloring layer and black coloring is used as a high-temperature coloring layer, red coloring due to low-temperature heating disappears on the black layer even if black is colored by high-temperature heating. Since it remains uncolored, it becomes black with a strong reddish color. In addition, there is also a problem in that when a black color is formed at a high temperature, a red border is generated around the black color, and a fine print portion such as characters and ruled lines looks dark brown, which is a problem in practical use.

As a solution to color mixing and edging,
For example, JP-A-55-81193 and JP-A-2-8
As disclosed in JP-A-0287, there is a method of obtaining a color tone of only the high temperature color developing layer at the time of high temperature heating by using a decoloring agent having a decoloring effect on the color forming system of the low temperature color developing layer at the time of high temperature heating. However, the use of the decolorizing agent has not always been satisfactory in that the storage stability after printing is deteriorated and the cost is increased. Further, an attempt to make multicolor by combining heat and light by utilizing the property that a diazo compound is decomposed by light is described in JP-A-60-242093 and JP-A-6140192. . Although such a method provides excellent storability, it has a drawback that the apparatus becomes large and the compactness which is an advantage of the thermal recording system is lost.

[0005]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a thermosensitive recording material in which a high-temperature coloring layer that develops black color and a low-temperature coloring layer that develops red color are laminated, and there is little color mixture of red color when high temperature black color is formed, and It is intended to produce a red-black two-color thermal recording material with little edging due to red coloring when fine characters and ruled lines are colored black.

[0006]

In order to solve the above-mentioned problems, the inventors of the present invention have conducted a wide range of material searches and studied the layer structure, and in the course of this, a high-temperature color-developing layer that develops black on a support. And a low-temperature color-developing layer that develops red color, and the color-developing layer contains an electron-donating color-developing dye and an electron-accepting color-developing compound, respectively. Sometimes red coloring dyes, color developing compounds, etc. in the red coloring layer melt and mix with the black coloring layer, and by balancing the coloring start temperature and coloring sensitivity of the red coloring layer, very little color mixing occurs. It was also found that black color without borders can be obtained.

In the present invention, a high temperature coloring layer which develops black color and a low temperature coloring layer which develops red color are sequentially laminated on a support, and the high temperature coloring layer and the low temperature coloring layer are electron donative coloring dyes. Red and black containing respectively and electron-accepting color developing compound 2
In a color heat-sensitive recording material, the high-temperature color-developing layer and / or the low-temperature color-developing layer contain oxalic acid di-p-chlorobenzyl ester and oxalic acid di-p-methylbenzyl ester. It exists in thermosensitive recording materials.
Furthermore, a high-temperature coloring layer that develops black color and a low-temperature coloring layer that develops red color are sequentially laminated on a support, and the high-temperature coloring layer and the low-temperature coloring layer are composed of an electron-donating color-forming dye and an electron-accepting dye. In a red-black two-color heat-sensitive recording material each containing a color compound, a weight mixing ratio of oxalic acid di-p-chlorobenzyl ester and oxalic acid di-p-methylbenzyl ester is 1: 9 to 9 in the low temperature color forming layer. Two colors of red and black, characterized in that it is contained in a ratio of 9 to 1, and 4,4′-isopropylidenediphenol is contained as an electron-accepting color-developing compound in the high-temperature color-developing layer and the low-temperature color-developing layer. It exists in thermosensitive recording materials.

In the conventional monochromatic heat-sensitive recording material,
Thermofusible substance with low melting point (sensitizer) for high sensitivity
There have been many proposals to add the. However, as a result of a detailed study by the present inventors, a sensitizer which is compatible with a color-forming dye or a color-developing compound, which has been conventionally used in a heat-sensitive recording material, was used in a red-black two-color heat-sensitive recording material. In some cases, it was found that when high-temperature black color is developed, the fringe that causes the periphery of the color-developed portion to be colored red is enlarged. It is considered that this is because the sensitizer in the same layer as the color-forming dye and the color-developing compound caused a melting point drop due to eutectic and drastically lowered the static color development start temperature.

The present inventors have previously mentioned that by containing oxalic acid di-p-chlorobenzyl ester and oxalic acid di-p-methylbenzyl ester in the heat sensitive layer, the heat sensitive material is excellent in heat resistance and does not develop color even when heated by a microwave oven. It has been proposed that a label can be manufactured (Japanese Patent Laid-Open No. 5-13903).
No. 1). However, an oxalic acid di-p-chlorobenzyl ester and an oxalic acid di-p-methylbenzyl ester are used as a red-black two-color thermosensitive recording material in which a high-temperature coloring layer that develops black color and a low-temperature coloring layer that develops red color are sequentially laminated. It has not been known at all that the inclusion of the compound makes it possible to reduce the color mixture due to the red color at the time of high temperature black color development and to reduce the edging due to the red color formation around the black color portion. This is because the heat-fusible substance alloy having a high melting point, which is produced by mixing oxalic acid di-p-chlorobenzyl ester and oxalic acid di-p-methylbenzyl ester, raises the static color initiation temperature. Is considered to be.

In the present invention, the mixing ratio of oxalic acid di-p-chlorobenzyl ester and oxalic acid di-p-methylbenzyl ester is preferably 1: 9 to 9: 1, respectively. More preferably, 2 to 3 and 3 to 2 are used. If it is out of this range, the effect of improving the edging due to the red color around the black color part is poor.

Examples of the electron-donating color-forming dye that develops a color by reacting with the electron-accepting color-developing compound in the present invention include triallyl dyes, diphenylmethane dyes, thiazine dyes, spiro dyes, lactam dyes, and fluoranes. System dyes are known. Examples of dyes that give a red color include, for example, 3,3'-bis (1-
Among n-butyl-2-methylindol-3-yl) phthalide, 3,3′-bis (1-ethyl-2-methylindol-3-yl) phthalide, and lactam dyes, rhodamine B-anilinolactam , Rhodamine B- (o-
Among chloroanilino) lactam, rhodamine B- (p-nitroanilino) lactam and fluorane dyes, 3
-Diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-di-n-butylamino-6-methyl-7-bromofluorane, 3-cyclohexylamino-6-chloro Fluorane, 3-diethylamino-6,8-dimethylfluorane, 3-diethylamino-benzo [a] -fluorane, and the like.

Among the above compounds, for example, 3,3'-bis (1-n-butyl-2-methylindol-3-yl)
Phthalide, 3,3′-bis (1-ethyl-2-methylindol-3-yl) phthalide, etc. give a deep purple color, and rhodamine B-anilinolactam, rhodamine B- (o-chloroanilino) lactam, Rhodamine B
-(P-Nitroanilino) lactam and the like have a light purple color tone. Among the fluorane dyes, 3-cyclohexylamino-6-chlorofluorane and 3-diethylamino-6,8-dimethylfluorane have a color tone close to orange, and 3-diethylamino-benzo [a] -fluorane is deep purple. It becomes the color of the system.

Among the red-coloring dyes, 3-diethylamino-7-chlorofluorane and 3-diethylamino-6
-Methyl-7-chlorofluorane and 3-di-n-butylamino-6-methyl-7-bromofluorane are suitable for the present invention as dyes capable of producing a clear red color. Di-n-butylamino-6-methyl-7-bromofluorane has difficulty in preserving the printed portion. Therefore,
3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane are the most suitable for the present invention.

Also for the black color forming layer, conventionally known electron donating color forming dyes can be used. A particularly preferred black color-forming dye is 3-dibutylamino-
6-methyl-7-anilinofluorane, 3- (N-isoamyl-N-ethylamino) -6-methyl-7-anilinofluorane, 3-dibutylamino-7- (2-chloroanilino) fluorane, 3 -Diethylamino-7- (2
-Chloroanilino) fluorane, 3-diethylamino-
6-methyl-7-anilinofluorane, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-anilinofluorane and the like can be mentioned. An electron-donating color-forming dye that has been conventionally known can be used in combination in both the red-coloring layer and the black-coloring layer.

The electron-accepting color-developing compound used in the present invention has the property of liquefying or dissolving when the temperature rises and having the property of developing color by contact with the above-mentioned electron-donating color-forming dye. If it is good. A specific example of a typical electron-accepting color developing compound is 4-tert-
Butylphenol, 4-acetylphenol, 4-te
rt-octylphenol, 4,4′-sec-butylidene diphenol, 4-phenylphenol, 4,4 ′
-Dihydroxydiphenylmethane, 4,4'-isopropylidene diphenol, 4,4'-cyclohexylidene diphenol, 4,4'-dihydroxydiphenyl sulfide, 4,4'-thiobis (6-tert-butyl-3-methylphenol) ), 4,4′-dihydroxydiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4′-isopropoxydiphenyl sulfone, 4-hydroxybenzophenone, dimethyl 4-hydroxyphthalate, 4- Methyl hydroxybenzoate, propyl 4-hydroxybenzoate, -sec-butyl 4-hydroxybenzoate, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, Four A phenolic compound such as 4'-dihydroxydiphenyl ether, or
Benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, salicylic acid, 3-tert-
Butyl salicylic acid, 3-isopropyl salicylic acid, 3-
Aromatic carboxylic acids such as benzylsalicylic acid, 3- (α-methylbenzyl) salicylic acid, 3,5-di-tert-butylsalicylic acid, and phenolic compounds thereof, aromatic carboxylic acids and, for example, zinc, magnesium, aluminum, calcium, etc. Examples thereof include organic acid substances such as salts with polyvalent metals.

Among these compounds, 4,4'-isopropylidene diphenol, 4,4'-cyclohexylidene diphenol, 4,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone is preferable from the viewpoint of sensitivity and whiteness. In particular, 4,4'-isopropylidene diphenol includes oxalic acid di-p-chlorobenzyl ester and oxalic acid di-p.
When used in combination with methylbenzyl ester, it is most suitable for the present invention because of less edging at high temperature black color development.
The color-developing compound is usually 0.7 with respect to 1 part by weight of the color-forming dye.
-5 parts by weight, preferably 1-3 parts by weight. In order to prevent background coloration and obtain a heat-sensitive recording material with high whiteness, it is desirable to use the same color developing compound for the high temperature black color developing layer and the low temperature red color developing layer.

In the present invention, the low temperature red coloring layer and the high temperature black coloring layer may contain a compound for improving the storage stability after printing, that is, a so-called storage stability improver. Examples of the storage stability improver include 1,1,3-tris (2-methyl-4-)
Hydroxy-5-cyclohexylphenyl) butane,
1,3,5-tris (4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid,
4-benzyloxyphenyl-4 '-(2-methyl-
2,3-epoxypropyloxy) phenyl sulfone,
1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,
1-bis (2-methyl-4-hydroxy-5-tert
-Butylphenyl) butane, 4,4 '-[1,4-phenylenebis (1-methylethylidene)] bisphenol, 4,4'-[1,3-phenylenebis (1-methylethylidene)] bisphenol, and other phenols Compounds and 4- (2-methyl-1,2-epoxyethyl) diphenyl sulfone, 4- (2-ethyl-1,2-
Examples thereof include epoxy compounds such as epoxyethyl) diphenyl sulfone, but the present invention is not limited thereto. Further, two or more kinds of these storability improvers may be contained.

These organic heat-fusible substances are prepared by using water as a dispersion medium and using various wet pulverizers such as a sand grinder, an attritor, a ball mill and a cobo mill, to obtain polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, methylcellulose, carboxymethylcellulose, A water-soluble polymer compound such as a styrene-maleic anhydride copolymer salt and derivatives thereof, and a surfactant and the like are dispersed to prepare a dispersion liquid, which is then used for preparing a thermosensitive color developing layer coating material.

In the present invention, other materials constituting the thermosensitive coloring layer include adhesives, waxes, metal soaps, and if necessary, ultraviolet absorbers and fluorescent dyes. Examples of the adhesive include polyvinyl alcohol and its derivatives, starch and its derivatives, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, ethyl cellulose and other cellulose derivatives, sodium polyacrylate,
Polyvinylpyrrolidone, acrylamide-acrylic acid ester copolymer, acrylamide-acrylic acid ester-methacrylic copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, casein, gelatin, etc. and their derivatives. In addition to water-soluble polymers such as polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic acid ester, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, ethylene-vinyl acetate copolymer and the like, and styrene- Examples thereof include a butadiene copolymer and a latex of a styrene-butadiene-acrylic copolymer.

As the wax, paraffin wax,
Carnauba wax, microcrystalline wax, polyethylene wax, stearamide,
Examples include higher fatty acid amides such as ethylenebisstearic acid amide, and higher fatty acid esters. 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 addition, an oil repellent, an antifoaming agent, a viscosity modifier, etc. within the range that does not impair the effects of the present invention
It is acceptable to add various additives such as fluorescent dyes.

The support material used in the present invention is not particularly limited and includes, for example, high quality paper (acidic paper, neutral paper), medium quality paper, coated paper, art paper, cast coated paper, resin laminated paper, Polyolefin-based synthetic paper, synthetic fiber paper, synthetic resin film and the like can be appropriately used. An undercoat layer may be provided for the thermosensitive coloring layer mainly for the purpose of improving sensitivity. As a method for forming the thermosensitive coloring layer, any known coating method such as air knife method, blade method, gravure method, roll coater method, spray method, dip method, bar method, and extrusion method may be used. . The heat-sensitive coloring layer coating material is applied to the surface of the support in an amount of 2 to 10
The thermal recording layer is formed by coating so as to have g / m ² (dry weight). In the present invention, the red coloring layer is formed on the black coloring layer, but an intermediate layer for improving color separation may be provided between the black and red layers. It is also possible to further develop the present invention and to provide, for example, three or more colors by providing a thermosensitive coloring layer that develops another color between the red coloring layer and the black coloring layer.

If necessary, a protective layer may be provided to prevent abrasion of the thermal head during printing, and to suppress color development due to scratches on the heat sensitive layer. The protective layer has a dry weight of 0.1 to 6 g / m ² , and more preferably 0.5 to.
4 g / m ^{2 is} applied. If it is less than 0.1 g / m ² , the effect as a protective layer is poor, and if it exceeds 6 g / m ² , the coloring sensitivity is lowered. Further, the protective layer may be a multilayer having two or more layers. Further, a back layer may be provided for suppressing the penetration of oil or plasticizer from the back surface and controlling curl.

[0023]

EXAMPLES The present invention will be described more specifically below with reference to examples. Unless stated otherwise, parts and% refer to parts by weight and% by weight, respectively. [Solution A] Preparation of oxalic acid di-p-chlorobenzyl ester dispersion liquid Component Amount (parts by weight) Oxalic acid di-p-chlorobenzyl ester 40 Polyvinyl alcohol 10% aqueous solution (polymerization degree 500, saponification degree 90%) 40 Water 20 [Solution B] Preparation of oxalic acid di-p-methylbenzyl ester dispersion liquid Component Amount (parts by weight) Oxalic acid di-p-methylbenzyl ester 40 Polyvinyl alcohol 10% aqueous solution (polymerization degree 500, saponification degree 90%) 40 Water 20 [Liquid C] Preparation of Black Coloring Dye Dispersion Component Amount (parts by weight) 3-dibutylamino-7- (o-chloroanilino) 40 Fluoran polyvinyl alcohol 10% aqueous solution (polymerization degree 500, saponification degree 90%) 40 Water 20

[D Liquid] Preparation of Red Coloring Dye Dispersion Component Amount (parts by weight) 3-Diethylamino-7-chlorofluorane 40 Polyvinyl alcohol 10% aqueous solution (polymerization degree 500, saponification degree 90%) 40 Water 20 [ Solution E] Preparation of developer 4,4′-isopropylidenediphenol dispersion liquid Component amount (parts by weight) 4,4′-isopropylidenediphenol 40 Polyvinyl alcohol 10% aqueous solution (polymerization degree 500, saponification degree 90%) 40 Water 20 [F Liquid] Developer 4-Hydroxy-4′-isopropoxydiphenylsulfone Dispersion Liquid Preparation Component Amount (parts by weight) 4-Hydroxy-4′-isopropoxydiphenylsulfone 40 Polyvinyl alcohol 10% aqueous solution (polymerization Degree 500, saponification degree 90%) 40 water 20

These compositions were subjected to a vertical sand mill (made by AIMEX Co., Ltd., sand grinder) to obtain a particle size of 1.
Separately dispersed to 0 μm. Further, as an adhesive liquid, a 10% aqueous solution of polyvinyl alcohol (polymerization degree: 110
0, saponification degree 98%), calcium carbonate 50% as pigment
A 20% zinc stearate dispersion was prepared as a dispersion and a lubricant.

The above dispersion, adhesive, lubricant, and pigment are blended so that the weight ratio after drying is as shown in Table 1, Table 2 and Table 3, and a coating solution for black coloring layer and coating for red coloring layer are prepared. It was a liquid. Basis weight 60
g / m black coloring layer on a high-quality paper of ² coating solution 6 g / m ² (dry) was coated, after forming the black coloring thermosensitive layer, a red-color-forming layer coating solution thereon 5 g / m ² ( Dried) applied. After that, using a super calendar, the Beck smoothness (J
IS-P8119) was subjected to smoothing treatment so as to be 150 seconds to 200 seconds to obtain a red-black two-color heat-sensitive recording material.

A printing test was carried out on the red-black two-color heat-sensitive recording material obtained by the above operation. The test was carried out by using a commercially available heat-sensitive facsimile HIFAX-45 modified for the test.
Line recording time 5 msec, sub-scanning line density 8 lines / m
m, 1 when the applied energy per dot is 0.8 mJ
28 lines of solid printing and character printing were performed, and red color development was obtained at low temperature heating. For black color development at high temperature, the applied energy per dot was set to 2.2 mJ.

The red and black solid color products thus obtained were measured for density by using a Macbeth densitometer RD914 with a magenta filter and a cyan filter. The results are shown in Tables 1, 2 and 3.
If the red density is 0.5 or more as a magenta filter measurement value (indicated by M in the table), there is no problem in practical use. If the black density is a cyan value (indicated by C in the table) of 1.0 or more, there is no practical problem. Further, in order to express the redness in the black color development, a value obtained by subtracting the cyan filter measurement value from the magenta filter measurement value (indicated by MC in the table) was used. When M-C is 0.35 or less, there is little redness and good black color development is achieved. Further, the border of red color around the black color character was visually evaluated. ○ means that there is no problem in black letters, △
Slightly red edging is at a level of concern, and x represents a level at which the red edging is clearly visible in black letters, which is a practical problem.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

As is apparent from Table 1, Table 2 and Table 3,
According to the present invention, a red-black two-color heat-sensitive recording material is produced without using a decoloring agent, which has a color tone of black color due to high temperature heating, a small amount of red color mixture, and a small amount of red color in the periphery during high temperature black color development. Became possible.

Claims (2)

[Claims] 1. A high-temperature coloring layer that develops black color and a low-temperature coloring layer that develops red color are sequentially laminated on a support, and the high-temperature coloring layer and the low-temperature coloring layer are composed of an electron-donating coloring dye and an electron. In a red-black two-color thermosensitive recording material each containing a receptive color-developing compound, oxalic acid di-p-chlorobenzyl ester and oxalic acid di-p-methylbenzyl are contained in the high-temperature coloring layer and / or the low-temperature coloring layer. A red-black two-color heat-sensitive recording material containing an ester. 2. A high-temperature coloring layer that develops black and a low-temperature coloring layer that develops red are sequentially laminated on a support, and the high-temperature coloring layer and the low-temperature coloring layer are composed of an electron-donating coloring dye and an electron. A red-black two-color heat-sensitive recording material each containing a receptive color-developing compound, wherein di-p-oxalic acid is contained in the low-temperature color-developing layer.
-Chlorobenzyl ester and oxalic acid di-p-methylbenzyl ester in a weight mixing ratio of 1: 9 to 9: 1, and an electron-accepting color development in the high-temperature color-developing layer and the low-temperature color-developing layer. A red-black two-color heat-sensitive recording material containing 4,4'-isopropylidenediphenol as a polar compound.