JPS6034892A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enhance recording sensitivity of a thermal recording material without lowering brightness, by jointly using a heat-fusible substance having a specified melting point in a thermal recorind layer. CONSTITUTION:At least one compound of the formula having a melting point of not lower than 70 deg.C, preferably, 80-140 deg.C, is incorporated in the thermal recording layer. Examples of the heat-fusible substance include di-2,6-xylyl carbonate (m.p. 121.5 deg.C) and di-2,5-xylyl carbonate (m.p. 104 deg.C). The heat-fusible substance is desirably used in an amount of generally 10-1,000pts.wt., preferably, 50- 500pts.wt. per 100pts.wt. of a color reaction agent. The color forming agent is used in an amount of 100-700pts.wt., preferably, about 150-400pts.wt., per 100pts.wt. of a basic dye. In the quoted formula, each of R1 and R2 is an aryl group or an aralkyl group which may be substituted by an alkyl group, an aralkyl group, a halogen atom, a hydroxyl group, an alkoxyl group, an aryloxyl group, an alkycarbonyloxyl group, arylcarbonyloxyl group, an alkoxylcarbonyl group or an aryloxycarbonyl group.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording material, and particularly to a heat-sensitive recording material that has high whiteness and excellent high-speed recording performance.

2. Description of the Related Art Conventionally, heat-sensitive recording materials have been well known that utilize a color reaction between a colorless or light-colored basic dye and a coloring agent to bring the two coloring substances into contact with each other using heat to obtain a colored image. In recent years, with the improvement of thermal recording apparatuses such as thermal facsimile-1 thermal printers using such thermal recording bodies, the speed of thermal recording methods has been significantly increased. As the speed of such equipment and hardware increases, the heat-sensitive recording media used are naturally required to significantly improve the recording sensitivity, and many proposals have been made in this regard. However, as the recording sensitivity improves, new drawbacks such as a decrease in the whiteness of the recording layer are accompanied, so that satisfactory results are not necessarily obtained. In view of the current situation, the present inventors conducted various studies with the aim of improving the recording sensitivity of a heat-sensitive recording medium without reducing whiteness.

In particular, many proposals have been made to improve recording sensitivity by using a thermofusible substance in combination with a basic dye and a coloring agent, but the scope of investigation of this thermofusible substance has been greatly expanded. As a result of extensive research, we have found that when a compound represented by the following general formula (1) is used as a thermofusible substance, stearic acid amide, palmitic acid amide, etc., which have been proposed as a thermofusible substance, can be produced. The present inventors have discovered that an extremely good recording sensitivity improvement effect can be obtained without causing a decrease in whiteness compared to fatty acid amides, etc., and have achieved the present invention.

The present invention provides a heat-sensitive recording material that utilizes a color reaction between a colorless or light-colored basic dye and a coloring agent that can develop a color when it comes into contact with the dye. is 80°C to 140°C, and is a heat-sensitive recording material characterized by containing at least one compound represented by the following general formula (1).

1 R1-0-C-0-R2(1) (wherein Rz and R2 each represent an aryl group or an aralkyl group, and these further represent an alkyl group, an aralkyl group, a halogen atom, a hydroxyl group, an alkoxyl group, Aryloxy group, alkylcarbonyloxy group,
It may be substituted with a carbonyloxy group, an alkoxycarbonyl group or an aryloxycarbonyl group. ) It is not clear why certain thermofusible substances such as those mentioned above exhibit the effect of improving recording sensitivity without reducing whiteness, but the chemical structure is similar to that of basic dyes or organic coloring agents. One factor is considered to be that the compatibility of the entire mixed system is increased as a result.

Specific examples of such thermofusible substances include di-2,6-xylyl carbonate (+, p, 121.5°C) and di-2,5-xylyl carbonate-1 (m, p, 104°C). 3,5-xylyl carbonate (m, p, 117°C) 3,4-xylyl carbonate (m, p, 124°C) terbutylphenyl carbonate (+++
, p, 102.5°C) C21 a, 5-trimethylphenyl carbonate)
(m, p, 112°C) 2.5°-xylyl-phenyl carbonate (m, p,
71°C) p-terbutylphenyl-phenyl carbonate
(m, p, 73 °C) p-diphenyl-phenyl carbonate (m, p, 13
6°C) α-naphthyl-phenyl carbonate (m, p, 95°C) β-naphthyl-phenyl carbonate (m, p, 132°C) p-methoxycarbonylphenyl-phenyl carbonate
1-(m, p, 93°C) and the like.

Two or more of these thermofusible substances may be used in combination, and within a range that does not inhibit the desired effects of the present invention, for example, stearic acid amide, stearic acid methylene bisamide, oleic acid amide, palmitic acid amide, coconut fatty acid may be used. Fatty acid amides such as amides, and various known thermofusible substances can also be used in combination. The amount of the thermofusible substance having the above-mentioned specific structure used is not necessarily limited, but is generally 10 to 10 parts by weight per 100 parts by weight of the coloring agent.
It is desirable to adjust the amount to about 1000 parts by weight, preferably about 50 to 500 parts by weight.

In the heat-sensitive recording material of the present invention, examples of the colorless or light-colored basic dye constituting the recording layer include the following.

3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, a,-a-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl)-3-(1, 2-dimethylindole-3-
yl)phthalide, 3-(p-dimethylaminophenyl)
-,3-(2-methylindol-3-yl)phthalide, 3.3-)-7su(l,2-dimethylindole-3
-yl)-5-dimethylaminophthalide, 3.3-bis(1゜2-dimethylindol-3-yl)-6-dimethylaminophthalide, 3.3-bis(9-ethylcarbazol-3-yl) )-6-dimethylaminophthalide, 3
．． 3-bis(2-phenylindol-3-yl)-6
-dimethylaminophthalide, 3-p-dimethylaminophenyl-3-(1-methylpyrrol-3-yl)-6-
triallylmethane dyes such as dimethylaminophthalide,
4.4'-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leucoolamine, N
- diphenylmethane dyes such as 2,4,5-trichlorophenylleucoolamine, thiazine dyes such as benzoylleucomethylene blue and p-nitrobenzoylleucomethylene blue, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-
Spiro dyes such as dinaphthopyran, 3-methyl-naphtho(6'-methoxybenzo) spiropyran, 3-propyl-spiro-dibenzopyran, rhodamine-B-anilinolactam, rhodamine (p-nitroanilino)lactam, rhodamine (O- Lactam dyes such as chloroanilino)lactam, 3-dimethylamino-7-methoxyfluoran, 3-diethylamino-6-methoxyfluoran,
3-diethylamino-7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluoran, methylfluorane, 3-diethylamino-7-N-acetyl-N-methylaminofluorane, 3-diethylamino-7-N-methylaminofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-N
-Methyl-N-benzylaminofluorane, 3-diethylamino-7-N-chloroethyl-N-methylaminofluorane, 3-diethylamino-7-N-diethylaminofluorane, 3-(N-ethyl-p-)luidino )−
6-Methyl-7-phenylaminofluorane, 3-(N
-ethyl-p-)luidino)-6-methyl-7-(p-
) luidino) fluorane, l-(N-cyclohexyl-N
-Methylamino)-6-methyl-7-phenylaminofluorane, 3-pyrrolidino-6-methyl-7-phenylaminofluorane, 3-piperidino-6-methyl-7-
Phenylaminofluorane, 3-diethylamino-6-
Methyl-7-xylidinofluorane, 3-diethylamino-7-(0-chlorophenylamino)fluoran, 3
-dibutylamino-7-(O-chlorophenylamino)
Fluoran dyes such as fluoran, 3-pyrrolidino-6-methyl-7-p-butylphenylaminofluoran, etc.

Furthermore, fluoran dyes represented by the following general formula (n) are also effective, (wherein, Ra represents a methyl group or an ethyl group, and R4 represents
Indicates an alkyl group from t to C&. ) Specifically, for example, 3-(N-methyl-Nn-amyl)amino-6-methyl-7-anilite fluorane, 3-
(N-ethyl-Nn-amyl)amino-6-methyl-
7-anirithufluorane, 3-(N-ethyl-N-
1so-amyl)amino-6-methyl-7-anilite fluorane, 3-(N-methyl-Nn-hexyl)amino-6-methyl-7-anilite fluorane, 3-(N-
Ethyl-Nn-hexyl)amino-6-methyl-7-
Examples include anirite fluoran, 3-(N-ethyl-N-β-ethylhexyl)amino-6-methyl-7-anirite fluorane, and the like. Since these dyes have excellent compatibility with the specific thermofusible substance used in the present invention, they can be expected to have better effects in terms of suitability for high-speed recording.

Furthermore, as described in Japanese Patent Publication No. 56-52759, these dyes have excellent characteristics in terms of suitability for both whiteness and recording sensitivity. This dye is particularly preferably used in the present invention because of its enhanced properties.

In the present invention, the coloring agent used in combination with the above-mentioned basic dye is not particularly limited.
Various coloring agents are used that have the property of dissolving C1, which liquefies or vaporizes when the temperature rises, and also have the property of causing coloration when brought into contact with the above-mentioned basic dye. Typical specific examples include 4-tert-butylphenol, α-naphthol, β-naphthol, 4-acetylphenol, and 4-tert-butylphenol.
ert-octylphenol, L4'-5ec-butylidene diphenol, 4-phenylphenol, 4.
4'-dihydroxydiphenylmethane, 4.4'-isopropylidenediphenol, hydroquinone, 4.4
'-Cyclohexylidene diphenol, 4°4'-dihydroxydiphenyl sulfide, 4°4'-thiobis(6-tert-butyl-3-methylphenol), 4
．． 4'-dihydroxydiphenyl sulfone, hydroquinone monobenzyl ether, 4-hydroxybenzophenone, 2. , 4-dihydroxybenzophenone, 2.
4.4'-trihydroxybenzophenone, 2.2',
4.4'-tetrahydroxybenzophenone, dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, 5ec-butyl 4-hydroxybenzoate, 4 -pentyl hydroxybenzoate, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, phenylpropyl 4-hydroxybenzoate, phenethyl 4-hydroxybenzoate, 4 - Phenolic compounds such as Ftl-1-cybenzoate- p-chlorobenzyl, p-methoxybenzyl 4-hydroxybenzoate, novolac type phenolic resin, phenol polymer, benzoic acid, p-tert-butylbenzoic acid , trichlorobenzoic acid, terephthalic acid, 3-sec-butyl-4-hydroxybenzoic acid, 3-cyclohexyl-
4-Hydroxybenzoic acid, 3.5-dimethyl-4-hydroxybenzoic acid, salicylic acid, 3-isopropylsalicylic acid, 3-tert-butylsalicylic acid, 3-benzylsalicylic acid, 3-(α-methylbenzyl)salicylic acid, 3-chlor -5-(α-methylbenzyl)salicylic acid, 3,5-di-tert-butylsalicylic acid, 3-phenyl-5-(α,α-dimethylbenzyl)salicylic acid JL4
．． 3. Aromatic carboxylic acids such as 5-di-α-methylbenzylsalicylic acid, and their phenolic compounds, aromatic carboxylic acids and polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel, etc. Examples include organic acidic substances such as salts of

The ratio of the basic dye to the coloring agent is generally 100 to 700 parts by weight, preferably 150 to 400 parts by weight, per 100 parts by weight of the dye. Incidentally, it is of course possible to use two or more kinds of the basic dye and the coloring agent in combination as necessary.

Coating liquids containing these materials are generally prepared by using water as a dispersion medium and dispersing dyes and coloring agents together or separately using a ball mill, attritor, sand grinder, or other stirring or pulverizing machine. Ru.

Such coating liquids usually contain denzins and other binders as binders.
Hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene/maleic anhydride copolymer salt, styrene/butadiene copolymer emulsion, etc. account for 2 to 40% by weight of the total solids, preferably 5%. ~25% by weight is used. Furthermore, various auxiliary agents can be added to the coating liquid as necessary. Examples include dispersants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, and fatty acid metal salts, other antifoaming agents, fluorescent dyes, and coloring dyes.

In addition, in order to improve the adhesion of residue to the recording head and further whiten the heat-sensitive recording layer, kaolin, clay, talc, etc.
Inorganic pigments such as calcium carbonate, calcined resin, titanium oxide, diatomaceous earth, fine particulate anhydrous silica, and activated clay may also be added. Further, a dispersion of stearic acid, polyethylene, carnauba wax, paraffin wax, calcium stearate, ester wax, etc., or a wax such as Elsion may be added as appropriate to prevent the recording layer from sticking when it comes into contact with the recording head.

In the heat-sensitive recording material of the present invention, the method for forming the recording layer is not particularly limited, and can be formed according to conventionally well-known and commonly used techniques. For example, in a method of applying a heat-sensitive coating liquid to a support, an appropriate coating device such as an air knife coater or a blade coater is used.

Furthermore, the amount of coating liquid to be applied is not particularly limited, and is generally 2 to 12 g/rt in terms of dry weight. , preferably made of steel in the range of 3 to 10 g/rrr.

Note that the support is not particularly limited, and paper, synthetic fiber paper, synthetic resin film, etc. may be used as appropriate, but paper is generally preferably used.

Furthermore, it is possible to provide an overcoat layer on the recording layer for the purpose of protecting the recording layer, etc. On the other hand, it is of course possible to provide an undercoat layer on the support. This can be added using known techniques.

Thus, the heat-sensitive recording material obtained according to the present invention has excellent suitability for high-speed recording, high whiteness, and extremely well-balanced properties in terms of quality.

Examples are shown below to explain the present invention more specifically, but the present invention is of course not limited to these. Unless otherwise specified, parts and % in the examples are parts by weight and % by weight, respectively.
shows.

Example 1 ■ Preparation of liquid A 3-(N-cyclohexyl-N-methylamino)-6-
Methyl-7-anirithufluorane 10 parts Di-2,5-xylyl carbonate (+s, p, 104°C) 20 parts Methyl cellulose 5% aqueous solution 15 parts Water 120 parts The composition was ground with a sand grinder to an average particle size of 3 μm. did.

(2) Solution B Opening 4.4'-Isopropylidene diphenol 30 parts 5% methylcellulose aqueous solution 30 parts Water 70 parts This composition was ground with a sand grinder to an average particle size of 3 μm.

■ Formation of recording layer 165 parts of liquid A, 130 parts of liquid B, 30 parts of silicon oxide pigment, 2
150 parts of 0% oxidized starch aqueous solution and 55 parts of water were mixed and stirred to prepare a coating liquid. The obtained coating liquid was applied to a base paper of 50 g/rrl so that the coating amount after drying was 7.5 g/n (drying) to obtain a heat-sensitive recording paper.

Example 2 α-naphthyl-phenyl carbonate (m, p,
1. except that 95°C) was used. A thermosensitive recording paper was obtained in the same manner as in Example 1.

Example 3 Thermal recording was carried out in the same manner as in Example 1, except that p-methoxycarbonylphenyl-phenyl carbonate (Il, p, 93°C) was used instead of di-2,5-xylyl carbonate in preparing liquid A. Got paper.

Example 4 Thermal recording was carried out in the same manner as in Example 1, except that di-p-ter-butylphenyl carbonate (m, p, 102°C) was used instead of di-2,5-xylyl carbonate in preparing liquid A. Got paper.

Example 5 ■ Preparation of liquid A 3-(N-ethyl-N-1so-amylamino)-6
-Methyl-7-Ayurifuru 19210 parts Di-2.5-xylyl carbonate 20 parts Methyl cellulose 5% aqueous solution 15 parts Water 120 parts The composition was ground with a sand grinder to an average particle size of 3 μm.

(2) Preparation of Solution B 4. 30 parts of 4'-isopropylidene diphenol 30 parts of 5% aqueous methylcellulose solution 70 parts of water This composition was ground with a sand grinder to an average particle size of 3 μm.

■ Formation of recording layer 165 parts of liquid A, 130 parts of liquid B, 30 parts of silicon oxide pigment, 2
150 parts of 0% oxidized starch aqueous solution and 55 parts of water were mixed and stirred to prepare a coating liquid. The obtained coating liquid was coated and dried on a base paper of 50 g/rd so that the coated amount after drying was 7.5 g/rrl to obtain a heat-sensitive recording paper.

Example 6 α-naphthyl-phenyl carbonate (m, p,
A thermosensitive recording paper was obtained in the same manner as in Example 5, except that a temperature of 95° C.) was used.

Example 7 Thermal recording was carried out in the same manner as in Example 5, except that p-methoxycarbonylphenyl-phenyl carbonate (m, p, 93°C) was used instead of di-2,5-xylyl carbonate in preparing liquid A. Got paper.

Example 8 A! p-ter-butylphenyl carbonate instead of di-2,5-xylyl carbonate)
A thermosensitive recording paper was obtained in the same manner as in Example 5 except that (m, p, 102° C.) was used.

Comparative Example I Example 1 except that stearamide was used in place of di-2,5-xylyl carbonate in the preparation of Part A.
A thermosensitive recording paper was obtained in the same manner as above.

Comparative Example 2 Example 5 except that stearic acid amide was used instead of di-2,5-xylyl carbonate in the preparation of Solution A.
A thermosensitive recording paper was obtained in the same manner as above.

A comparative test of recording sensitivity and whiteness of the recording layer was performed on the 10 types of thermal recording paper thus obtained, and the results are shown in the table. The recording sensitivity was determined by measuring the color density of a recorded image recorded using a Gull-type practical high-speed thermal facsimile (HI FAX-700 model, manufactured by Hitachi) using a Macbeth density needle (model RD-100R, manufactured by Macbeth). The brightness was measured using a Hunter whiteness needle.

Claims (1)

[Claims] +1) In a thermosensitive recording material that utilizes a color reaction between a colorless or light-colored basic dye and a coloring agent that can develop a color when it comes into contact with the dye, the thermosensitive recording layer has a melting point. 70℃～140℃
A heat-sensitive recording material characterized in that it contains at least one kind of compound represented by the following general formula [1]. 1 Rz -0-C-0-Rz (1) (In the formula, R) and R2 each represent an aryl group or an aralkyl group, and these further represent an alkyl group, an aralkyl group, a halogen atom, a hydroxyl group, an alkoxyl group (2) A basic dye represented by the following general formula (U) may be substituted with an aryloxy group, an alkylcarbonyloxy group, an arylcarbonyloxy group, an alkoxycarbonyl group or an aryloxycarbonyl group. The heat-sensitive recording material according to claim 11, using a dye of
, (indicates the alkyl group of -c8)