JP2001328355A - Thermal recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a thermal recording material having small skin fog and excellent color developability and storage stability. SOLUTION: In the thermal recording material comprising a heat sensitive color developing layer containing a normally colorless or pale color developable compound and a developable compound capable of color developing the color developable compound at a heat time on a support, the developing layer contains a compound represented by formula (1) as the color developable compound and an N-acetylxylidine as a sensitizer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a heat-sensitive recording material. More specifically, it has high sensitivity and low background fog,
The present invention relates to a heat-sensitive recording material having excellent image storability.

[0002]

2. Description of the Related Art Generally, a thermosensitive recording material is prepared by separately dispersing a developer such as a leuco dye and a phenolic substance into fine particles, and then mixing the two with a binder, a sensitizer, a filler and a lubricant. A coating liquid is prepared by adding additives such as, etc., and applied to paper, film, synthetic paper, etc., and the color record is formed by the chemical reaction that occurs when one or both of the leuco dye and the developer melts and contacts by heating. What you get. For color development of the heat-sensitive recording sheet, a thermal printer or the like having a built-in thermal head is used. Compared with other recording methods, this thermal recording method is (1) no noise during recording, (2) there is no need for development and fixing, (3) maintenance-free, (4) machine is relatively inexpensive. With features such as
Facsimile field, computer output, printer field such as calculator, medical measurement recorder field,
It is widely used in the field of automatic ticket vending machines, the field of heat-sensitive recording labels, and the like.

[0003] In recent years, the use of POS systems in retail stores and supermarkets and automated systems in transportation have increased the use of labels, tickets, coupons, and the like. In these applications, it is desired that the heat-sensitive recording material is further improved in storage stability. The demand for high-speed recording has further increased, and there has been a strong demand for the development of heat-sensitive recording materials that can sufficiently cope with high-speed recording. However, the drawback that background fogging generally occurs when the sensitivity of heat-sensitive recording materials is increased to improve thermal response. Is easy to appear. Conventionally, various methods have been proposed for improving thermal responsiveness and further improving storage stability, but none of them have been satisfactory.

[0004]

The object of the present invention is as described above.
It is to solve the disadvantages of the prior art. That is, it is an object of the present invention to provide a heat-sensitive recording material having high sensitivity, less background fogging, and excellent image storage stability.

[0005]

The present inventor has made various studies to achieve the above object, and as a result, completed the present invention. That is, the present invention provides (1) a heat-sensitive color-forming layer comprising, as main components, a colorless or light-colored color-forming compound, a color-developing compound capable of coloring the color-forming compound when heated, and a sensitizer on a support. In the heat-sensitive recording material, the heat-sensitive coloring layer is represented by the following formula (1) as a color-developing compound.

[0006]

Embedded image

The present invention also relates to a heat-sensitive recording material characterized in that the compound contains N-acetylxylidine as a sensitizer.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a colorless or pale-colored color-forming compound, a compound represented by the formula (1) as a color developing compound, and N-acetylxylidine as a sensitizer are mainly used. A thermosensitive coloring layer is prepared by using the following binders and other fillers and other additives as necessary. The amounts of the compound represented by the formula (1) and N-acetylxylidine are usually 0.5 to 20 parts by weight, preferably 1 to 5 parts by weight, based on 1 part by weight of the chromogenic compound.
Parts by weight are appropriate. Further, in the heat-sensitive recording material of the present invention, a color-developing compound or a sensitizer (a heat-fusible compound) other than the main component of the present invention may be used in combination.

The N-acetylxylysine used in the present invention is preferably an isomer having a melting point of 80 ° C. or higher or a mixture thereof. Specific examples of isomers include, for example, N-
Acetyl-2,3-xylysine, N-acetyl-2,4
-Xylidine, N-acetyl-2,5-xylidine, N
-Acetyl-2,6-xylysine, N-acetyl-3,
4-xylidine, N-acetyl-3,5-xylidine and the like. In forming the thermosensitive coloring layer in the present invention, the coloring compound is usually 1 to 50% by weight, preferably 5 to 30% by weight, and the compound represented by the formula (1) is usually 1%.
To 80% by weight, preferably 5 to 40% by weight, and N-acetylxylysine is usually 0.5 to 80% by weight, preferably 5 to 80% by weight.
~ 40% by weight, binder 1 ~ 90% by weight, filler 0 ~ 0
80% by weight, other lubricants, surfactants, defoamers, ultraviolet absorbers, etc. are used in arbitrary proportions, for example, each in an amount of 0 to 30% by weight. Weight ratio).

The color-forming compound is not particularly limited as long as it is generally used for pressure-sensitive recording paper or heat-sensitive recording paper. Examples of the coloring compounds that can be used include, for example, fluoran compounds, triarylmethane compounds, spiro compounds, diphenylmethane compounds, thiazine compounds, lactam compounds, fluorene compounds, and the like.

Of these, specific examples of fluoran compounds include, for example, 3-diethylamino-6-methyl-
7-anilinofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3- (N-methyl-N
-Cyclohexylamino) -6-methyl-7-anilinofluoran, 3- (N-ethyl-N-isopentylamino) -6-methyl-7-anilinofluoran, 3- (N
-Ethyl-N-isobutylamino) -6-methyl-7-
Anilinofluoran, 3- [N-ethyl-N- (3-ethoxypropyl) amino] -6-methyl-7-anilinofluoran, 3- (N-ethyl-N-hexylamino)
-6-methyl-7-anilinofluoran, 3-dipentylamino-6-methyl-7-anilinofluoran, 3-
(N-methyl-N-propylamino) -6-methyl-7
-Anilinofluoran, 3- (N-ethyl-N-tetrahydrofurylamino) -6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7- (p-
Chloroanilino) fluoran, 3-diethylamino-6
-Methyl-7- (p-fluoroanilino) fluoran,
3- [N-ethyl-N- (p-tolyl) amino] -6
Methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7- (p-toluidino) fluoran, 3
-Diethylamino-7- (o-chloroanilino) fluoran, 3-dibutylamino-7- (o-chloroanilino) fluoran, 3-diethylamino-7- (o-fluoroanilino) fluoran, 3-dibutylamino-7-
(O-fluoroanilino) fluoran, 3-diethylamino-7- (m-trifluoromethylanilino) fluoran, 3-diethylamino-7- (3,4-dichloroanilino) fluoran, 3-pyrrolidino-6-methyl -7
-Anilinofluoran, 3-diethylamino-6-chloro-7-ethoxyethylaminofluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-
Diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluoran, 3-diethylamino-
7-octylfluoran, 3- [N-ethyl-N- (p
-Tolyl) amino] -6-methyl-7-phenethylfluoran and the like.

Next, specific examples of triarylmethane compounds include, for example, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone or CVL), 3,3 -Bis (p-dimethylaminophenyl) phthalide, 3- (p
-Dimethylaminophenyl) -3- (1,2-dimethylaminoindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3- ( p-dimethylaminophenyl) -3- (2-phenylindol-3-yl) phthalide, 3,3-bis (1,2-dimethylindole-
3-yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3-bis (9-ethylcarbazole-3- Yl) -5-dimethylaminophthalide,
3,3- (2-phenylindol-3-yl) -5
Dimethylaminophthalide, 3-p-dimethylaminophenyl-3- (1-methylpyrrol-2-yl) -6-dimethylaminophthalide and the like.

Further, specific examples of spiro compounds include:
For example, 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3′-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-propylspirobenzopyran, 3-methylnaphtho- (3-
Methoxybenzo) spiropyran, 1,3,3-trimethyl-6-nitro-8'-methoxyspiro (indoline-
2,2′-benzopyran) and diphenylmethane compounds, for example, N-halophenyl-leuco auramine, 4,4-bis-dimethylaminophenylbenzhydryl benzyl ether, N-2,4,5-trichlorophenyl Leuco auramine and the like, thiazine compounds such as benzoyl leucomethylene blue and p-nitrobenzoyl leucomethylene blue, and lactam compounds such as rhodamine B anilinolactam and rhodamine B-p-chloroanilinolactam. ,
Examples of the fluorene-based compound include 3,6-bis (dimethylamino) fluorenespiro (9,3 ′)-6′-
Dimethylaminophthalide, 3,6-bis (dimethylamino) fluorenespiro (9,3 ′)-6′-pyrrolidinophthalide, 3-dimethylamino-6-diethylaminofluorenespiro (9,3 ′)-6 ′ -Pyrrolidinophthalide and the like. These coloring compounds are used alone or in combination.

Examples of the color-developing compound that can be used in combination in the present invention are not particularly limited, as long as they are those generally used for pressure-sensitive recording paper or heat-sensitive recording paper. Specific examples thereof include, for example, α-naphthol, β-naphthol, p-octylphenol, 4-t
-Octylphenol, pt-butylphenol, p
-Phenylphenol, 1,1-bis (p-hydroxyphenyl) propane, 2,2-bis- (p-hydroxyphenyl) propane (alias: bisphenol A or BP
A), 2,2-bis- (p-hydroxyphenyl) butane, 1,1-bis- (p-hydroxyphenyl) cyclohexane, 4,4′-thiobisphenol, 4,4′-
Cyclo-hexylidenediphenol, 2,2'-bis-
(2,5-dibromo-4-hydroxyphenyl) propane, 4,4′-isopropylidenebis (2-t-butylphenol), 2,2′-methylenebis (4-chlorophenol), 4,4′-dihydroxydiphenyl Hong,
2,4'-dihydroxydiphenyl sulfone, bis (3
-Allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone,
4-hydroxy-4′-benzyloxydiphenyl sulfone, methyl bis (4-hydroxyphenyl) acetate, butyl bis (4-hydroxyphenyl) acetate, bis (4-hydroxyphenyl) acetate
Phenolic compounds such as hydroxyphenyl) benzyl acetate, benzyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, dibenzyl 4-hydroxyphthalate, dimethyl 4-hydroxyphthalate, ethyl 5-hydroxyisophthalate, 3,5- Examples include, but are not limited to, aromatic carboxylic acid derivatives such as di-t-butylsalicylic acid, 3.5-di-α-methylbenzylsalicylic acid, and aromatic carboxylic acids or polyvalent metal salts thereof.

The sensitizers (thermofusible compounds) which can be used in combination in the present invention include, for example, waxes such as animal and vegetable waxes and synthetic waxes, higher fatty acids, higher fatty acid amides, higher fatty acid anilides, naphthalene derivatives, and aromatics. Ether, aromatic carboxylic acid derivative, aromatic sulfonic acid ester derivative, carbonic acid or oxalic acid diester derivative, biphenyl derivative, terphenyl derivative, sulfone derivative, etc., which are solid at room temperature but melt at about 70 ° C or higher Can be used.

As waxes that can be used in combination, for example, wood wax, carnauba wax, shellac, paraffin, montan wax, paraffin oxide, polyethylene wax, polyethylene oxide, etc., and as higher fatty acids, for example, stearic acid, behenic acid, etc. As higher fatty acid amides,
For example, stearic acid amide, oleic acid amide, N-methylstearic acid amide, erucic acid amide, methylolbehenic acid amide, methylenebisstearic acid amide, ethylenebisstearic acid amide and the like, as higher fatty acid anilide, for example, stearic acid anilide, Linoleic acid anilide and the like, as naphthalene derivatives, for example, 1-
Benzyloxynaphthalene, 2-benzyloxynaphthalene, 1-hydroxynaphthoic acid phenyl ester and the like, and aromatic ethers such as 1,2-diphenoxyethane, 1,4-diphenoxybutane, 1,2-bis (3 -Methylphenoxy) ethane, 1,2-bis (4
-Methoxyphenoxy) ethane, 1,2-bis (3,4
-Dimethylphenyl) ethane, 1-phenoxy-2-
(4-chlorophenoxy) ethane, 1-phenoxy-2
Examples of aromatic carboxylic acid derivatives include-(4-methoxyphenoxy) ethane and the like. Examples of aromatic carboxylic acid derivatives include p-hydroxybenzoic acid benzyl ester, p-benzyloxybenzoic acid benzyl ester, terephthalic acid dibenzyl ester and the like. Derivatives include, for example, p-toluenesulfonic acid phenyl ester, phenylmesitylenesulfonate, 4-methylphenylmesitylenesulfonate, and the like. Carbonic acid or oxalic acid diester derivatives include, for example, diphenyl carbonate, dibenzyl oxalate, dioxalate. (4-chlorobenzyl) ester, oxalic acid di (4-methylbenzyl) ester and the like include biphenyl derivatives such as p-benzylbiphenyl and p-benzylbiphenyl.
Examples of allyloxybiphenyl and the like are terphenyl derivatives such as m-terphenyl, and examples of the sulfone derivative are diphenyl sulfone and the like.

The amounts of the color-developing compound and the sensitizer which can be used in combination are within the ranges not impairing the effects of the present invention, for example, the amounts of the compound represented by the formula (1) and N-acetylxylidine. A ratio not exceeding this range is preferred.

In the present invention, examples of the binder that can be used include, for example, methyl cellulose, methoxy cellulose,
Hydroxyethyl cellulose, carboxymethyl cellulose, sodium carboxymethyl cellulose, 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, styrene /
Water-soluble products such as alkali salts of maleic anhydride copolymer, alkali salts of iso (or diiso) butylene / maleic anhydride copolymer, and polyvinyl acetate, vinyl chloride / vinyl acetate copolymer, polystyrene, polyacryl Acid ester, polyurethane, styrene / butadiene (SB) copolymer, carboxylated styrene / butadiene (SB)
Examples thereof include copolymers, styrene / butadiene / acrylic acid copolymers, and hydrophobic polymer emulsions such as composite particles of colloidal silica and an acrylic resin.

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

Other additives include higher fatty acid metal salts such as zinc stearate and calcium stearate for the purpose of preventing thermal head wear and sticking, phenol derivatives having an antioxidant or antiaging effect, and benzophenone. UV absorbers of various types, such as benzotriazole type, various surfactants, antifoaming agents and the like are added as required.

Using the above materials, the heat-sensitive recording material of the present invention is prepared, for example, by the following method. That is, first, a coloring compound, a compound represented by the formula (1),
After N-acetylxylidine is separately pulverized and dispersed in a dispersing machine such as a ball mill, an attritor, or a sand mill together with a binder or other additives as necessary (when the pulverization and dispersion are performed by a wet method, (Usually using water as a medium) to prepare a coating solution for the thermosensitive coloring layer.
The heat-sensitive recording material of the present invention is obtained by coating on a support such as a plastic sheet or synthetic paper so as to have a dry weight of usually 1 to 20 g / m ² using a bar coater, a blade coater, or the like. If necessary, an intermediate layer may be provided between the thermosensitive coloring layer and the support, or an overcoat layer may be provided on the thermosensitive coloring layer.

The heat-sensitive recording material of the present invention, which is usually contained in a colorless or pale-colored color-forming compound, the compound represented by the formula (1), or N-acetylxylidine, in the heat-sensitive color-forming layer, has high sensitivity and low background fog. There is a feature that the image storability is excellent.

[0023]

EXAMPLES The present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In the examples, "parts" indicates parts by weight.

Example 1 A mixture having the following composition was pulverized and dispersed using a sand grinder so that the average particle size became 1 μm or less, to obtain a liquid [A], a liquid [B] and a liquid [C]. [A] solution: 3-dibutylamino-6-methyl-7-anilinofluoran 25 parts 25% PVA aqueous solution 20 parts water 55 parts [B] solution: compound of formula (1) 25 parts 25% PVA aqueous solution 20 parts 55 parts of water [C] liquid: N-acetyl-2,4-xylidine (melting point: 129 to 130 ° C) 25 parts 25% PVA aqueous solution 20 parts Water 55 parts

Next, a thermosensitive coloring layer coating solution was prepared by mixing at the following ratios, coated on a high-quality paper having a basis weight of 50 g / m ² so that the weight when dried was 8 g / m ^2, and dried to obtain a thermosensitive coloring layer. A coloring layer is obtained. [A] solution 8 parts [B] solution 16 parts [C] solution 24 parts 50% calcium carbonate dispersion 12 parts 50% carboxylated styrene / butadiene copolymer latex 7 parts (formation of protective layer) The protective layer coating solution having the above ratio is applied onto the above-mentioned thermosensitive coloring layer so that the dry weight becomes 2 g / m ² and dried to obtain the thermosensitive recording material of the present invention having a protective layer. 40% styrene / acrylate copolymer emulsion 20 parts 5% bentonite aqueous dispersion 40 parts 30% zinc stearate dispersion 3 parts

Example 2 Instead of N-acetyl-2,4-xylidine in Example 1, N-acetyl-2,5-xylidine (melting point 142 ° C.)
To obtain a heat-sensitive recording material of the present invention having a protective layer in the same manner as in Example 1.

Example 3 A protective layer was prepared in the same manner as in Example 1 except that N-acetyl-3,4-xylidine (melting point: 99 ° C.) was used instead of N-acetyl-2,4-xylidine. With the heat-sensitive recording material of the present invention. Table 1 shows the quality performance table of the heat-sensitive recording material of the present invention obtained as described above.

Table 1 Quality performance test Ground 1) Color density 2) Moisture resistance 3) Water resistance 4) Plasticizer resistance 5) Example 1 0.04 1.62 1.54 1.59 1.54 Example 2 0.04 1.63 1.56 1.60 1.55 Example 3 0.04 1.62 1.54 1.58 1.53 1.53

1) Background: The value of the uncolored portion of the sample measured with a Macbeth reflection densitometer RD-914 (Macbeth reflection density). 2) Color density: Macbeth reflection density value of an image portion printed by a thermal printer (D-805P) manufactured by Ishida Koki Co., Ltd. 3) Moisture resistance: 4 samples of color developed by the above printer
The Macbeth reflection density of the image portion after being left in a humidity chamber at 0 ° C. and 90% relative humidity for 24 hours. 4) Water resistance: Macbeth reflection density of an image portion after immersing a sample colored with the above printer in tap water at room temperature for 24 hours. 5) Plasticizer resistance: P is applied to the sample colored with the printer.
0.3kg / cm for both sides of VC wrap film
The Macbeth reflection density of the image portion after 15 hours of standing at room temperature under a load of ² .

As is clear from the table, the heat-sensitive recording material of the present invention is excellent in whiteness and color density of the background, and in the color image, excellent in moisture resistance, water resistance and plasticizer resistance.

[0031]

As described above, a heat-sensitive recording material having high sensitivity, little background fog, and excellent image storability was obtained.

Claims (1)

[Claims] 1. A heat-sensitive recording material comprising a support and a heat-sensitive color-forming layer mainly comprising a colorless or light-colored color-forming compound, a color-developing compound capable of forming the color-forming compound when heated, and a sensitizer as main components. Wherein the heat-sensitive color-forming layer is a color-developing compound represented by the following formula (1): A heat-sensitive recording material comprising the compound of formula (I) as N-acetylxylidine as a sensitizer.