JPH02134291A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a recording material excellent in the whiteness retaining characteristic of a white paper part under high temp. environment and having high speed recording characteristics by using 2,2-bis(4-hydroxyphenyl)-4- methylpentane as a coupler and a specific compound as a heat-meltable substance. CONSTITUTION:In a thermal recording material provided with a recording layer containing a colorless - light colored basic dye and a coupler capable of forming color upon the contact with said dye, 2,2-bis(4-hydroxyphenyl)-4- methylpentane is used as the coupler and, as a heat-meltable substance, at least one kind of a compound represented by formula [I] (wherein R1 and R2 are respectively a halogen atom, a cyano group, a nitro group, a 1-4C alkyl group, a 1-4C alkoxy group, a 1-4C alkylthio group, and acetyl group, a propionyl group, a methoxycarbonyl group, an aryl group or a cyclohexenyl group, a and b are respectively 1 or 2 and c is 2 or 4) is used. In general, the coupler is used in an amount of about 1-7pts.wt. per 1pts.wt. of the basic dye.

Description

Detailed Description of the Invention "Industrial Application Field" The present invention relates to a heat-sensitive recording medium, and in particular, even if it is left in a high-temperature environment for a long time, the whiteness of the white paper area does not decrease and the recorded image is stable. The present invention relates to a heat-sensitive recording medium that can maintain the following properties.

``Prior art'' Heat-sensitive recording materials that utilize a color reaction between a colorless or light-colored basic dye and an organic or inorganic coloring agent to obtain a recorded image by bringing a recoloring substance into contact with heat are often used. Are known.

Recently, with the remarkable progress in thermal recording methods, thermal facsimiles and thermal printers have all become faster.
The heat-sensitive recording medium used is also required to have excellent high-speed recording suitability.

In addition, with the rapid spread of thermal facsimiles and thermal printers, their usage has become more widespread, and cases have arisen in which thermal facsimiles are installed and used inside automobiles. In this case, the temperature inside the vehicle during the day may rise to around 70° C., and naturally the heat-sensitive recording medium will also be placed in such an environment.

``Problem to be Solved by the Invention'' However, when a general heat-sensitive recording medium is placed in a high-temperature environment such as the one described above, the whiteness of the white paper portion decreases significantly, so there is a strong demand for improvement. .

In view of the current situation, the inventors of the present invention have conducted extensive research into improving the above-mentioned defects observed in heat-sensitive recording media, and have found that fading of recorded images and reduction in whiteness of blank areas (fogging phenomenon) are
It was determined that this phenomenon was caused by the interaction at the interface between the coloring agent and the dye.

As a result of extensive research into substances with low interaction at the dye interface, we decided to use 2,2-bis(4-hydroxyphenyl)-4-methylpentane as the coloring agent and add a specific thermoplastic to it. When used together with fusible substances,
The present inventors have discovered that it is possible to obtain a heat-sensitive recording material that not only exhibits excellent high-temperature stability but also is suitable for high-speed recording, leading to the completion of the present invention.

"Means for Solving the Problems" The present invention provides a heat-sensitive recording material provided with a recording layer containing a colorless or light-colored basic dye and a coloring agent capable of coloring when in contact with the dye. 2.2-bis(4-hydroxyphenyl)-4-methylpentane is used as a coloring agent, and at least one compound represented by the following general formula [I] is used as a thermofusible substance. This is a characteristic heat-sensitive recording material.

1.1. indicates l or 2, respectively; 1. indicates 2 or 4. [Function] In the present invention, various types of colorless or light-colored basic dyes constituting the recording layer are known, and the following are exemplified.

3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3.3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl)-3-(1,2 -dimethylindol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-
3-(2-methylindol-3-yl)phthalide, 3
,3-bis(l,2-dimethylindol-3-yl)
-5-dimethylaminophthalide, 3,3-bis(1°2
-dimethylindol-3-yl)-6-dimethylaminophthalide, 3,3-bis(9-ethylcarbazole-
3-yl)-6-dimethylaminophthalide, 3,3-bis(2-phenylindol-3-yl)-6-dimethylaminophthalide, 3-p-dimethylaminophenyl-
Triallylmethane dyes such as 3-(1-methylpyrrol-3-yl)-6-dimethylaminophthalide, 4,4'
-bis-dimethylaminobenzhydrylbenzyl ether, N-herophenyl leukoolamine, N-2,4
, 5-) diphenylmethane dyes such as dichlorophenyl leuco auramine, benzoyl leucomethylene blue,
Thiazine dyes such as p-nitrobenzoylleucomethylene blue, 3-methyl-spiro-dinaphthopyran, 3-
Spiro dyes such as ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho-(6'-methoxybenzo)spiropyran, and 3-propyl-spiro-dibenzobilane , lactam dyes such as rhodamine-B-anilinolactam, rhodamine (P-nitroanilino)lactam, rhodamine (0-chloroanilino)lactam, 3-dimethylamino-7-medoxyfluoran,
3-diethylamino-6-methoxyfluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-
6-Methyl-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluorane, 3-(N-ethyl-
p-Toluidino)-7-methylfluorane, 3-diethylamino-7-N-acetyl-N-methylaminofluorane, 3-diethylamino-7-N-methylaminofluorane, 3-diethylamino-7-dibenzylaminofluoran Oran, 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-
Toluidino)-6-methyl-7-(p-)luidino)fluoran, 3-diethylamino-6-methyl-7-phenylaminofluoran, 3-dibutylamino-6-methyl-7-phenylaminofluoran, 3- (N-ethyl-N-cyclopentyl)amino-6-methyl-7-phenylaminofluorane, 3-(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-(N-ethyl-N-isobutyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-N-isoamylamino)-6-methyl- 7-phenylaminofluorane, 3-(N-methyl-N-n-hexyl)amino-6-
Methyl-7-phenylaminofluorane, 3-(N-ethyl-Nn-hexyl)amino-6-methyl-7-phenylaminofluorane, 3-N,N-n-dibutylamino-6-methyl- 7-phenylaminofluorane, 3
-(N-ethyl-N-tetrahydrofurfuryl)amino-6-methyl-7-phenylaminofluorane, 3-diethylamino-7-(2-carbomethoxy-phenylamino)fluoran, 3-diethylamino-7-(o -chlorophenylamino)fluoran, 3-dibutylamino-7-(o-chlorophenylamino)fluoran, 3-
Dibutylamino-7-(o-fluorophenylamino)
Fluoran dyes such as fluoran.

In addition, two or more types of these basic dyes can be used in combination as necessary.

In the heat-sensitive recording material of the present invention, 2,2-bis(4-hydroxyphenyl)-4-methylpentane is used as a coloring agent that develops color when it comes into contact with such a basic dye. The ratio of the dye and coloring agent to be used is appropriately selected depending on the type of basic dye used, and is not particularly limited, but is generally 1 to 7 parts by weight per 1 part by weight of the basic dye. , preferably about 1.5 to 4 parts by weight of the coloring agent.

In addition to the above-mentioned specific coloring agents, for example, 4,4'-isopropylidene diphenol, 4,4'-cyclohexylidene diphenol, 4-hydroxybenzoic acid, within a range that does not impede the effects of the present invention. It is also possible to use common coloring agents such as benzyl ester and 4-hydroxyphthalic acid dimethyl ester.

The heat-sensitive recording material of the present invention selectively uses a specific coloring agent, so it is extremely suitable for high-temperature storage. A specific thermofusible substance represented by the general formula (11) is added.

Specific examples of the specific thermofusible substance represented by the general formula [1] include 1 (4-tert-butylphenoxy)-2-(2-methylphenoxy)ethane (■,
p, 96°C), 1,2-di(3-methylphenoxy)
Ethane (+w, p, 98°C), 1-(4-ethylphenoxy)-2-(3-methylphenoxy)ethane (m,
p, 106°C), 1,2-di(4-methylphenoxy)ethane (p, 135°C), 1-(3,4-dimethylphenoxy)-2-(4-methylphenoxy)ethane (m, p, 110°C), 1-(4-methylphenoxy)-2-(4-isopropylphenoxy)ethane (m
, p, 116°C), 1-(4-methylphenoxy)
-2-(4-tert-butylphenoxy)ethane (
a+, p, 118℃), 1゜2-di(2,3-dimethylphenoxy)ethane (p, 120℃), 1.2
-di(2,4-dimethylphenoxy)ethane (m, p,
111.5°C), 1-(4-ethylphenoxy)-2
-(2,5-dimethylphenoxy)ethane (a+, p,
99.5°C), 1,2 di(3,4-dimethylphenoxy)ethane (m.

p, 105°C), 1,2-di(3,5-dimethylphenoxy)ethane (m, p, 97.5°C), 1-(4-
phenylphenoxy)-2-(2-methylphenoxy)
Ethane (m, p, 110"C), 1,2-di(4methoxyphenoxy)ethane (m,p, 128 °C), 1
-(4-methoxyphenoxy)-2-(3-methylphenoxy)ethane (m, p, 112°C), 1(4-methoxyphenoxy)-2-(4-methylphenoxy)ethane (m, p, 129°C) ), 1,2-di(3,4-dimethylphenoxy)ethane (m, p.

105°C), 1,4-di(4-methylphenoxy)butane (m, p, 104°C), 1-(4-chlorophenoxy)-2-(4-methylphenoxy)ethane (m, p,
130°C), 1-(4-cyanophenoxy)-2-(
2-methylphenoxy)ethane (m, p, 98°C),
1-(4-cyanophenoxy)-2-(4-methylphenoxy)ethane (a+, p, 111.5°C), 1-(
4-chlorophenoxy) -2-(4-tertbutylphenoxy)ethane (a+, p, 111°C), 1-(
4-methoxyphenoxy)-2-(4-tert-butylphenoxy)ethane (m, p, 109.5°C),
1-(4-acetylphenoxy)-2-(2-methylphenoxy)ethane (m, p, 119.5°C), 1-(
Examples include 4-acetylphenoxy) 2 (4-tertbutylphenoxy)ethane (m, p, 98°C).

Among the above compounds, especially those having a melting point of 90 to 120
Compounds having a temperature of 90 to 110° C., which is more preferably 90 to 110° C., are more preferably used because a particularly sensitive recording medium can be obtained.

The amount of the thermofusible substance added is not particularly limited, but it is desirable to adjust the amount -m to 5 parts by weight or less per 1 part by weight of the specific coloring agent.

Coating solutions containing these substances are generally prepared by using water as a dispersion medium and dispersing the dye and coloring agent together or separately using a stirring/pulverizing machine such as a ball mill, attritor, or sand mill. Ru.

Such coating liquids usually contain starches and binders as binders.
Hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, gum arabic, polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, diisobutylene/maleic anhydride copolymer salt, styrene/maleic anhydride copolymer salt,
Ethylene/acrylic acid copolymer salt, styrene/acrylic acid copolymer salt, styrene/butadiene copolymer emulsion, urea resin, melamine resin, amide resin, etc. account for 10 to 40% by weight of the total solid content, preferably 15 to 40% by weight. 30% by weight
Used to some extent.

Furthermore, various auxiliary agents can be added to the coating liquid.
For example, dispersants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, fatty acid metal salts, ultraviolet absorbers such as triazoles, other antifoaming agents, fluorescent dyes, coloring dyes, etc. can be mentioned.

In order to prevent the thermal recording medium from causing sticking due to contact with recording equipment or recording heads, and to prevent scum from adhering to the recording heads, for example, zinc stearate, calcium stearate, polyethylene wax, carnauba wax, etc.
It is also possible to add waxes such as paraffin wax and ester wax, and inorganic pigments such as kaolin, clay, talc, calcium carbonate, calcined resin, titanium oxide, diatomaceous earth, fine particulate anhydrous silica, and activated clay.

In the heat-sensitive recording material of the present invention, there are no particular limitations on the method of forming the recording layer, and the recording layer can be formed according to conventionally well-known and commonly used techniques, such as applying a coating liquid by air knife coating, blade coating, etc.・It is formed by a method such as drying. Further, the amount of the coating liquid to be applied is not particularly limited, and is usually adjusted in a dry weight range of 2 to 12 g/I, preferably 3 to Log/I. Although paper is generally used as a support for forming such a recording layer, synthetic resin films, laminated papers, synthetic fiber sheets, nonwoven fabric sheets, etc. can also be used.

As mentioned above, the heat-sensitive recording medium of the present invention exhibits excellent print storage stability because it combines a specific coloring agent and a thermofusible substance. A resin layer containing a water-soluble polymer compound as a main component can also be provided on the heat-sensitive recording layer. In addition, various known techniques in the field of heat-sensitive recording material production may be added as necessary, such as providing an undercoat layer on the support, applying an adhesive treatment to the back surface of the recording material, and processing it into an adhesive label.

The heat-sensitive recording material of the present invention obtained in this manner has less tendency to fog in blank areas even when placed under high-temperature conditions of around 70°C, is suitable for high-speed recording, and is free from dust adhesion to the recording head. However, it exhibits excellent characteristics.

"Example" The present invention will be described in more detail with reference to Examples below, but it is of course not limited to these.

Note that "parts" and "%" in the examples indicate "parts by weight" and "% by weight", respectively, unless otherwise specified.

Example 1 ■ Preparation of Solution A 3-(N-ethyl-N-isoamylamino)6-methyl-7-phenylaminofluorane 10 parts 1.2-di(3-methylphenoxy)ethane 20 parts Methylcellulose 5% aqueous solution 15 parts water
120 parts of this composition was ground in a sand mill until the average particle size was 3 μm.

■ Preparation of B solution 2.2-bis(4-hydroxyphenyl)-4methylpentane 30 parts Methylcellulose 5% aqueous solution 30 parts water
70 parts of this composition was ground in a sand mill until the average particle size was 3 μm.

(2) Formation of Recording Layer 165 parts of liquid A, 130 parts of liquid B, 30 parts of fine particulate anhydrous silica (oil absorption ff 1180 cc/100 g), 150 parts of a 20% 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/bore so that the coated amount after drying was 7.5 g/bore to obtain a heat-sensitive recording material.

Examples 2 to 4 In preparing liquid A, 1-(4-methoxyphenoxy) was used instead of 1,2-di(3-methylphenoxy)ethane.
-2-(4-tert-butylphenoxy)ethane (Example 2), 1-(4-phenylphenoxy)-2
-(2-methylphenoxy)ethane [Example 3] and 1
Three types of heat-sensitive recording bodies were obtained in the same manner as in Example 1 except that (4-tert-butylphenoxy)-2-(2-methylphenoxy)ethane [Example 4] was used in each case.

Examples 5 to 6 In preparing liquid A, 3-(N-cyclohexyl-N-methylamino) was used instead of 3-(N-ethyl-N-isoamylamino)-6-methyl-7-phenylaminofluorane. )-6-methyl-7-phenylaminofluorane (Example 5) and 3-N.

Two types of heat-sensitive recording bodies were obtained in the same manner as in Example 4, except that Nn-dibutylamino-6-methyl-7-phenylaminofluorane [Example 6] was used in each case.

Comparative Examples 1 to 2 In Bfil formation, 4.4'-instead of 2.2-bis(4-hydroxydiphenyl)-4-methylpentane
Two types of heat-sensitive recording materials were obtained in the same manner as in Example 1, except that isopropylidene diphenol [Comparative Example 1] and benzyl 4-hydroxybenzoic acid ester [Comparative Example 2] were used, respectively.

The whiteness of the surface of the recording layer (initial whiteness) of the 8 types of heat-sensitive recording materials obtained in this manner and the whiteness after being left in a constant temperature bath at 70°C for 24 hours (storage whiteness) are respectively expressed as Hunter white. The measurements were taken with a temperature meter and the results are listed in the table.In addition, each heat-sensitive recording material was recorded with a heat-sensitive facsimile (Matsushita UF60 model), and the color density was measured with a Macbeth?aR meter (RD914 model) and the results are listed in the table. did.

Table ``Effects'' As is clear from the results in the table, all of the heat-sensitive recording materials of the present invention have excellent whiteness maintenance properties in blank areas even when placed in high-temperature environments, and have excellent high-speed recording properties. It was a record.

Patent applicant: Kanzaki Paper Co., Ltd.

Claims (3)

[Claims] (1) In a heat-sensitive recording material provided with a recording layer containing a colorless or light-colored basic dye and a coloring agent capable of coloring upon contact with the dye, the coloring agent is 2,2-bis(4 -Hydroxyphenyl)-4-methylpentane and at least one compound represented by the following general formula [I] as a thermofusible substance. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [I] [In the formula, R_1 and R_2 are each a halogen atom, a cyano group, a nitro group, an alkyl group of C_1_-_4, and C_1
_ to _4 alkoxyl group, C_1_ to _4 alkylthio group, acetyl group, propionyl group, methoxycarbonyl group, aryl group or cyclohexenyl group, a and b each represent 1 or 2, and c represents 2 or 4. show. ] (2) The heat-sensitive recording material according to claim 1, wherein the thermofusible substance has a melting point of 90 to 110°C. (3) The heat-sensitive recording material according to claim (1), wherein the thermofusible substance is 1,2-di(3-methylphenoxy)ethane.