JPH05212970A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material having high sensitivity, reduced in background fog and excellent in image preservability by using a specific compd. such as a fluorane compound as a color forming compound and using a specific compd. such as alpha-naphthol as a developing compd. CONSTITUTION:In a thermal recording material wherein a thermal color forming layer based on a colorless or light-colored color forming compd. and a developing compd. capable of allowing the color forming compd. to form a color at the time of heating is provided on a support, a compd. represented by formula I is added as the color forming compd. and a compound represented by formula II (wherein R is a 1-4C alkyl group or a group represented by formula III) is added as the developing compd. As a result, the thermal recording material having high sensitivity, reduced in background fog and excellent in image preservability can be obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a heat-sensitive recording material.
More specifically, the present invention relates to a heat-sensitive recording material which is excellent in color development, has less background fog, and has high image storability.

[0002]

2. Description of the Related Art Generally, a heat-sensitive recording material is prepared by separately dispersing a leuco dye and a color developing agent such as a phenolic substance in the form of fine particles, and then mixing them together, and then adding a binder, a sensitizer,
A coating solution prepared by adding additives such as fillers and lubricants to a paper, film, synthetic paper, etc., and a chemical reaction that occurs when one or both of the leuco dye and developer melts and contacts when heated. Thus, color development recording is obtained. A thermal printer or the like having a built-in thermal head is used for coloring the thermal recording sheet. Compared with other recording methods, this heat-sensitive recording method has (1) no noise during recording,
Due to the features such as (2) no need for development and fixing, (3) maintenance-free, (4) relatively inexpensive machines, the field of facsimiles, computer output, printers such as calculators, medical It is widely used in the fields of measurement recorders, automatic ticket vending machines, and heat-sensitive recording labels.

Among these fields of use, the use of labels and station automation systems for passenger tickets is increasing with the expansion of POS systems in retail stores and supermarkets. In these applications, it is desired to further improve the storability of colored images.

Further, in recent years, the demand for high-speed recording has been further increased, and there has been a strong demand for the development of a heat-sensitive recording material capable of sufficiently responding to high-speed recording. The drawback of causing fog is likely to appear. Conventionally, various methods have been proposed to improve thermal responsiveness and further improve image storability, but a satisfactory method has not been established yet.

[0005]

The objects of the present invention are as follows.
It is to solve the drawbacks of the prior art. That is, it is to provide a heat-sensitive recording material having high sensitivity, less background fog, and good image storability.

[0006]

The inventors of the present invention have completed the present invention as a result of various studies to achieve the above object. That is, the present invention provides a thermosensitive recording material comprising a support and a thermosensitive coloring layer mainly composed of a colorless or light-colored coloring compound and a coloring compound capable of coloring the coloring compound when heated. And a compound represented by the following formula (1)
There is provided a heat-sensitive recording material containing a compound represented by

[0007]

[Chemical 4]

[0008]

[Chemical 5]

(In the formula (2), R is an alkyl group having 1 to 4 carbon atoms or

[0010]

[Chemical 6]

Represents The present invention will be described in detail. In the present invention, the above-mentioned color forming compound of formula (1) and formula (2)
The thermosensitive color-developing layer is prepared by using the color-developing compound as a main component and a binder as shown below and optionally a filler, a heat-fusible compound, a surfactant and the like. The proportion in the thermosensitive coloring layer is 1 to 10 parts by weight, preferably 1 to 5 parts by weight, of the color-developing compound of the formula (2) per 1 part by weight of the color-forming compound of the formula (1). Is. Further, other color-forming compounds and color-developing compounds can be used in combination in the thermosensitive color-forming layer.

The following are examples of color forming compounds that can be used in combination. Fluoran compounds, triarylmethane compounds, spiropyran compounds, diphenylmethane compounds, thiazine compounds, lactam compounds,
Examples thereof include fluorene compounds, and specific examples thereof include the following compounds. Fluoran compounds; 2-aniline-3-methyl-6-
Diethylaminofluorane, 2-anilino-3-methyl-6- (N-methyl-N-cyclohexylamino) fluorane, 2-anilino-3-methyl-6- (N-ethyl-N-isopentylamino) fluorane, 2 -(P-chloroanilino) -3-methyl-6-diethylaminofluorane, 2- (p-fluoroanilino) -3-methyl-
6-diethylaminofluorane, 2-anilino-3-methyl-6- (p-toluidinoethylamino) fluorane, 2- (p-toluidino) -3-methyl-6-diethylaminofluorane, 2- (o- Chloroanilino) -6
-Dibutylaminofluorane, 2- (o-fluoroanilino-6-diethylaminofluorane, 2- (o-fluoroanilino) -6-dibutylaminofluorane, 2-
Anilino-3-methyl-6-piperidinofluorane, 2
-Anilino-3-methyl-6-pyrrolidinofluorane,
2-Ethoxyethylamino-3-chloro-6-diethylaminofluorane, 2-anilino-3-chloro-6-diethylfluorane, 2-chloro-6-diethylaminofluorane, 2-methyl-6-diethylaminofluorane, etc. ,

Triarylmethane compounds; 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3-
(1,2-Dimethylaminoindole-3-) isophthalide and other spiropyran compounds; 3-methyl-3-spirodinaphthopyran, 1,3,3-trimethyl-6-
Nitro-8'-methoxyspiro (indoline-2,2 '
-Benzopyran), etc., diphenylmethane compounds; N
-Halophenyl-leuco auramine and other thiazine-based compounds; benzoyl leuco methylene blue and other lactam-based compounds; rhodamine-B-anilinolactam and other fluorene-based compounds; ) -6'-Dimethylaminophthalide, 3,6-bis (dimethylamino) fluorene spiro (9,3 ')-6'-pyrrolidinophthalide, 3-dimethylamino-6-diethylaminofluorenspiro (9,3) ') -6'-pyrrolidinophthalide and the like. These color forming compounds may be used alone or in combination.

Further, examples of the color-developing compound which can be used in combination are as follows. α-naphthol, β-naphthol, p-octylphenol, 4-t-octylphenol, p-t-butylphenol, p-phenylphenol, 1,1′-bis (p-hydroxyphenyl) propane, 2,2′-bis- (P-Hydroxyphenyl) propane, 2,2'-bis (p-hydroxyphenyl) butane, 1,1'-bis (p-hydroxyphenyl) cyclohexane, 4,4'-thiobisphenol, 4,4'-
Cyclo-hexylidene diphenol, 4,4'-sulfonyldiphenol, 4,4'-sulfonyl-bis (2-
Allylphenol), 2,2'-bis (2,5-dibromo-4-hydroxyphenyl) propane, 4,4'-isopropylidenebis (2-t-butylphenol),
Phenolic compounds such as 2,2′-methylenebis (4-chlorophenol), benzyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, dibenzyl 4-hydroxyphthalate, dimethyl 4-hydroxydiphthalate,
Ethyl 5-hydroxyisophthalate, 3,5-di-t-
Examples include aromatic carboxylic acid derivatives such as butylsalicylic acid and 3,5-di-α-methylbenzylsalicylic acid, aromatic carboxylic acids or polyvalent metal salts thereof.

In the present invention, a binder is used for providing the heat-sensitive recording layer, and the following binders can be used. Methylcellulose, methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, sodium carboxymethylcellulose, cellulose, polyvinyl alcohol (PVA), carboxyl group-modified polyvinyl alcohol, sulfonic acid group-modified polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, starch and derivatives thereof. , Casein, gelatin water-soluble isoprene rubber, alkali salt of styrene / maleic anhydride copolymer Iso (or diiso) butylene / alkali salt of maleic anhydride copolymer, water-soluble one or polyvinyl acetate / vinyl acetate copolymer Polymer, polystyrene, polyacrylic acid ester, polyurethane, styrene / butadiene (SB) copolymer, carboxylated styrene / butadiene ( B) copolymers,
Styrene / butadiene / acrylic acid type copolymers, water-soluble emulsions of colloidal silica and acrylic resin composite particles, and the like.

Examples of fillers that can be used are calcium carbonate, magnesium carbonate, magnesium oxide, silica,
There are white carbon, talc, clay, alumina, magnesium hydroxide, aluminum hydroxide, aluminum oxide, barium sulfate, polystyrene resin, urea-formalin resin and the like.

Examples of the heat-fusible compound that can be used include waxes such as animal and vegetable wax, polyethylene wax, and synthetic wax, and higher fatty acids, higher fatty acid amides, higher fatty acid metal salts, acetylated aromatic amines, and aromatic ethers. Examples thereof include compounds and biphenyl derivatives which are solid at room temperature and have a melting point of about 80 ° C. or higher. In addition, lubricants such as zinc stearate, calcium stearate and aluminum stearate, various surfactants, antifoaming agents and the like are added as necessary.

The heat-sensitive recording material of the present invention is prepared by using the above-mentioned material by the following method, for example. That is, according to a conventional method, first, a color-forming compound and a color-developing compound are separately pulverized and dispersed by a dispersing machine such as a ball mill, an attritor or a sand mill together with a binder or other additives as required. After mixing, a thermosensitive color developing layer coating solution is prepared and coated on a support such as paper, plastic sheet or synthetic paper by a bar coater or blade coater so that the dry weight is usually 1 to 20 g / m ^2. (The ratio of the color-forming compound to the color-developing compound is usually 1: 1 by dry weight ratio.
(1 to 10) and dried to obtain the heat-sensitive recording material of the present invention.

If necessary, an intermediate layer may be provided between the thermosensitive color developing layer and the support, or an overcoat layer may be provided on the thermosensitive color developing layer. The heat-sensitive recording material of the present invention containing the above-described color-forming compound of formula (1) and the color-developing compound of formula (2) has higher sensitivity and less background fog, and has better image storability than those conventionally known. Good.

[0020]

EXAMPLES The present invention will be described in more detail by way of examples, but the present invention is not limited thereto. In the examples, "part" indicates part by weight.

Example 1 A mixture having the following composition was pulverized for 30 minutes using a sand grinder to prepare a liquid [A] and a liquid [B], respectively. [A] liquid: 2-anilino-3-methyl-6-isobutylethyl aminofluorane 25 parts 25% PVA aqueous solution 20 parts water 55 parts [B] liquid: methyl bis (4-hydroxyphenyl) acetate 25 parts 25% PVA Aqueous solution 20 parts Water 55 parts

Next, the thermosensitive color developing layer coating liquid was prepared by mixing the following components. [A] Liquid 20 parts [B] Liquid 40 parts 48% Carboxylated styrene-butadiene copolymer latex 10 parts Water 30 parts

The thermosensitive color developing layer coating liquid was applied to a high-quality paper having a basis weight of 50 g / m ^{2 so} that the liquid amount was about 10 g / m ^2, and dried to obtain a thermosensitive recording material of the present invention.

Example 2 The heat-sensitive recording material of the present invention was prepared in the same manner as in Example 1 except that butyl bis- (4-hydroxyphenyl) acetate was used instead of methyl bis (4-hydroxyphenyl) acetate of Example 1. Got

Example 3 A thermosensitive recording material of the present invention was prepared in the same manner as in Example 1 except that benzyl bis- (4-hydroxyphenyl) acetate was used instead of methyl bis (4-hydroxyphenyl) acetate of Example 1. Got

Comparative Example 1 Example 1 except that bisphenol A was used in place of the methyl bis (4-hydroxyphenyl) acetate of Example 1.
A heat-sensitive recording material for comparison was obtained in the same manner as in.

Comparative Example 2 2-anilino-3-instead of 2-anilino-3-methyl-6-isobutylethylaminofluorane of Example 1
Methyl-6- (N-ethyl-N-isopentylamino)
A thermal recording material for comparison was obtained in the same manner as in Example 1 except that fluoran was used.

Comparative Example 3 Instead of 2-anilino-3-methyl-6-isobutylethylaminofluorane of Example 2, 2-anilino-3-
A thermosensitive recording material for comparison was obtained in the same manner as in Example 2 except that methyl-6-dibutylaminofluorane was used. The following quality performance tests were carried out using the heat-sensitive recording material of the present invention and the heat-sensitive recording material for comparison obtained as described above.

Table 1 Quality performance test Background color density Heat resistance Moisture heat resistance 23V 24V 25V Example 1 0.07 1.21 1.43 1.52 95% 90% Example 2 0.07 1.27 1.40 1.49 95% 90% Example 3 0.06 1.30 1.53 1.62 97% 95 % Comparative Example 1 0.09 0.81 0.98 1.25 79% 50% Comparative Example 2 0.07 0.88 1.07 1.26 78% 49% Comparative Example 3 0.07 1.11 1.26 1.37 70% 40%

1) Background: A value (reflection density) obtained by measuring the uncolored portion of the sample with a Macbeth reflection densitometer RD-914 type. 2) Color density: The reflection density of the sample printed with a thermal printer (D-805P) manufactured by Ishida Keiki Co., Ltd. at printing voltage = 23V, 24V, 25V. 3) Heat resistance: The residual rate (%) of the color image part of the sample after using the above-mentioned D-805P and leaving it in a thermostat at 55 ° C. for 100 hours for the sample colored at 25V. 4) Moisture and heat resistance: The residual rate (%) of the color image portion of the sample after being left for 24 hours in a thermo-hygrostat at 55 ° C. and a relative humidity of 90% for the sample colored at 25 V using D-805P.

As is apparent from the table, the heat-sensitive recording material of the present invention is excellent in color density, background, heat resistance and wet heat resistance.

[0032]

EFFECT OF THE INVENTION A heat-sensitive recording material having high sensitivity, little background fog and good image storability was obtained.

Claims (1)

[Claims] 1. A thermosensitive recording material comprising a support and a thermosensitive coloring layer containing a colorless or light-colored coloring compound and a color-developing compound capable of coloring the coloring substance under heat as a main component. A thermosensitive recording material comprising a compound of the following formula (1) as a compound and a compound of the following formula (2) as the color-developing compound. [Chemical 1] [Chemical 2] (In the formula (2), R is an alkyl group having 1 to 4 carbon atoms or Represents)