JP2002200850A - Thermal recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal recording medium which is almost free from a texture fog and shows outstanding coloring and image conservation properties. SOLUTION: This thermal recording medium comprises a thermal coloring layer composed mainly of a normally colorless or pale-colored coloring compound, a color developing compound which thermally develops a color in the coloring compound and a sensitizer. In addition, the medium is characterized in that it contains a chemical compound represented by the formula (1) (wherein, R is an alkyl group or a benzyl group with the number of carbon atoms of 4 or less) and a p-toluenesulfonic acid-β-phenyxyethyl ester.

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, Additives such as lubricants to make a coating liquid, applied to paper, film, synthetic paper, etc., and record the color by the chemical reaction that occurs when one or both of the leuco dye and the developer are melted and contacted by heating Is 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 thermal recording labels, and the like.

In recent years, retailers and supermarkets
With the introduction of OS systems and automated transportation systems, applications to labels, tickets, coupons, and the like are increasing. 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, in general, if the sensitivity of heat-sensitive recording materials is increased to improve thermal responsiveness, background fogging will occur. Is easy to appear. Conventionally, various methods have been proposed to improve the heat responsiveness and further improve the storage stability, but none of them are 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 fog, and excellent image storability.

[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 relates to a heat-sensitive recording material comprising (1) a heat-sensitive color-forming layer comprising, as main components, a colorless compound which is usually colorless or light-colored and a color-developing compound capable of developing the color-forming compound when heated. And a compound having the following formula (1)

[0006]

Embedded image

(Wherein, in the formula (1), R represents an alkyl group or a benzyl group having 4 or less carbon atoms) containing p-toluenesulfonic acid-β-phenoxyethyl ester as a sensitizer. And a heat-sensitive recording material.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a colorless or light-colored color-forming compound, a compound represented by the formula (1) as a color-developing compound, and p-toluenesulfonic acid-β-phenoxy as a sensitizer are usually used. Ethyl esters are used as main components, respectively, and a thermosensitive coloring layer is prepared by the following binders and other fillers and other additives as necessary.

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 1 to 5% by weight.
60% by weight, preferably 5 to 30% by weight, p-toluenesulfonic acid-β-phenoxyethyl ester is usually 1 to
80% by weight, preferably 5 to 60% by weight, the binder is 1 to
90% by weight, filler is 0-80% by weight, other lubricants,
Surfactants, defoamers, ultraviolet absorbers and the like are used in arbitrary proportions, for example, each usually in an amount of 0 to 30% by weight (weight% is the weight ratio of each component in the thermosensitive coloring layer). In a more preferred embodiment, among the above-mentioned compositions, the amount of each of them is the above formula (1) based on the color forming compound 1 in a weight ratio.
Is usually 0.5 to 20 times, preferably 1 to 20 times.
The weight ratio of p-toluenesulfonic acid-β-phenoxyethyl ester is usually 0.5 to 20 times, preferably 1 to 8 times. Further, in the heat-sensitive recording material of the present invention, a known color-developing compound and a sensitizer other than the main components of the present invention may be used in combination.

Specific examples of the alkyl group having 1 to 4 carbon atoms in the above formula (1) include, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl,
Examples include a sec-butyl group and a t-butyl group. Examples of the color-developing compound represented by the formula (1) include methyl bis (4-hydroxyphenyl) acetate, ethyl bis (4-hydroxyphenyl) acetate, propyl bis (4-hydroxyphenyl) acetate, and bis (4-hydroxyphenyl) acetate. 4-hydroxyphenyl) n-butyl acetate, bis (4-hydroxyphenyl)
Benzyl acetate and the like can be mentioned, and these are used alone or in combination.

The color-forming compound used in the present invention is not particularly limited as long as it is generally used for pressure-sensitive recording paper or heat-sensitive recording paper. Examples of color-forming 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.

Specific examples of the 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.

Specific examples of triarylmethane compounds that can be used 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-phenylindole-
3-yl) phthalide, 3,3-bis (1,2-dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindole-3-
Yl) -6-dimethylaminophthalide, 3,3-bis (9-ethylcarbazol-3-yl) -5-dimethylaminophthalide, 3,3- (2-phenylindole-
3-yl) -5-dimethylaminophthalide, 3-p-dimethylaminophenyl-3- (1-methylpyrrole-2
-Yl) -6-dimethylaminophthalide and the like.

Further, specific examples of spiro compounds that can be used include, for example, 3-methylspirodinaphthopyran,
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 the like, as diphenylmethane compounds, for example, N-halophenyl-leucouramine, 4,4-bis-dimethylaminophenylbenz Hydryl benzyl ether, N-2,4,5-
Trichlorophenyl leuco auramine and the like; thiazine compounds such as benzoyl leucomethylene blue and p-nitrobenzoyl leucomethylene blue;
Examples of lactam compounds include rhodamine B anilinolactam and rhodamine B-p-chloroanilinolactam, and examples of fluorene compounds 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.

In the present invention, as the color-developing compound which can be used in combination with the compound represented by the above formula (1), any compounds which are generally used in pressure-sensitive recording paper or heat-sensitive recording paper may be used. And there is no particular limitation. Specific examples include 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 (alias: bisphenol A or BPA), 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'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 3,4-dihydrokidiphenyl-p
-Tolylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, benzyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, dibenzyl 4-hydroxyphthalate, dimethyl 4-hydroxyphthalate,
Ethyl 5-hydroxyisophthalate, 3,5-di-t-
Examples include aromatic carboxylic acid derivatives such as butylsalicylic acid, 3.5-di-α-methylbenzylsalicylic acid, aromatic carboxylic acids and polyvalent metal salts thereof, but are not limited thereto.

In the present invention, p-toluenesulfonic acid-
Examples of sensitizers (thermofusible compounds) that can be used in combination with β-phenoxyethyl ester include 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. Use 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 and have a melting point of about 70 ° C. or more. be able to.

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 anilides, 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 that can be used in combination can be in a range that does not impair the effects of the present invention, for example, the compound of the formula (1) and p-toluenesulfonic acid-β-
A ratio within a range not exceeding the amount of phenoxyethyl ester used is preferred.

Specific 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, Polyvinyl pyrrolidone, polyacrylamide, polyacrylic acid, starch and derivatives thereof, casein, gelatin, water-soluble isoprene rubber, alkali salt of styrene / maleic anhydride copolymer, iso (or diiso) butylene / maleic anhydride copolymer Water-soluble ones such as alkali salts or polyvinyl acetate, vinyl chloride / vinyl acetate copolymer, polystyrene, polyacrylate, polyurethane, styrene / Hydrophobic polymer emulsions such as tadiene (SB) copolymer, carboxylated styrene / butadiene (SB) copolymer, styrene / butadiene / acrylic acid copolymer, and composite particles of colloidal silica and acrylic resin. Can be

Specific examples of the filler 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.

Further, in the present invention, various additives other than those described above can be used. Examples of other additives that can be used include, for example, stearin for the purpose of preventing thermal head abrasion and sticking. Higher fatty acid metal salts such as zinc acid and calcium stearate, phenol derivatives for imparting antioxidant or antiaging effects, ultraviolet absorbers such as benzophenone compounds and benzotriazole compounds, various surfactants, defoamers And the like.

The heat-sensitive recording material of the present invention is prepared using the above-mentioned materials by, for example, the following method. That is, first, a color-forming compound, a compound represented by the above formula (1), and p-toluenesulfonic acid-β-phenoxyethyl ester are separately separated by a ball mill, an atomizer and a binder, if necessary, together with other additives. After pulverizing and dispersing with a disperser such as a lighter or a sand mill (usually using water as a medium when pulverizing and dispersing are performed by a wet method), they are mixed to prepare a coating solution for the thermosensitive coloring layer. 1-20 g / dry weight on a support such as paper
bar coater so that m ^2, coating by a blade coater (the ratio of the color forming compound and color-developing compound is usually a dry weight ratio 1: 1及至1:10) dried heat-sensitive recording material of the present invention Get. If necessary, an intermediate layer may be provided between the thermosensitive coloring layer and the support, or an overcoat layer (protective layer) may be provided on the thermosensitive coloring layer. The intermediate layer and the overcoat layer (protective layer) are pulverized and dispersed, for example, in the same manner as in the preparation of the thermosensitive coloring layer coating solution together with the above-mentioned binder or other additives as necessary. After the overcoat layer (protective layer) coating solution is formed, it is applied by drying so as to have a weight of usually about 0.1 to 10 g / m ² and dried.

Usually, a colorless or light-colored color-forming compound, a compound represented by the above formula (1), p-toluenesulfonic acid
The heat-sensitive recording material of the present invention containing β-phenoxyethyl ester has higher sensitivity, less background fog, and excellent image storability as compared with conventionally known materials.

[0024]

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 diameter became 1 μm or less, to prepare a solution [A], a solution [B] and a solution [C], respectively. [A] solution: 3-dibutylamino-6-methyl-7-anilinofluoran 25 parts 25% PVA aqueous solution 20 parts water 55 parts [B] solution: n-butyl bis (4-hydroxyphenyl) acetate 25 parts 25 % PVA aqueous solution 20 parts Water 55 parts [C] liquid: p-toluenesulfonic acid-β-phenoxyethyl ester 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 was 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) Was applied onto the above-mentioned thermosensitive coloring layer so that the weight when dried was 2 g / m ^2, and dried to obtain a 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 The procedure of Example 1 was repeated, except that the liquid [A] of Example 1 was replaced with a 25% 3-dibutylamino-7- (o-chloroanilino) fluoran dispersion obtained by pulverization and dispersion. In the same manner as in Example 1, a heat-sensitive recording material of the present invention having a protective layer was obtained.

Example 3 25% 3- (N-ethyl-N-isopentylamino) -6-methyl-7-anilino obtained by pulverizing and dispersing in the same manner as in Example 1 except that the solution [A] was used. Using a fluoran dispersion, a heat-sensitive recording material of the present invention having a protective layer was obtained in the same manner as in Example 1.

Example 4 A book having a protective layer was prepared in the same manner as in Example 1 except that benzyl bis (4-hydroxyphenyl) acetate was used instead of n-butyl bis (4-hydroxyphenyl) acetate of Example 1. The heat-sensitive recording material of the invention was obtained.

Comparative Example 1 A comparative thermosensitive recording material having a protective layer was obtained in the same manner as in Example 1 except that bisphenol A was used instead of n-butyl bis (4-hydroxyphenyl) acetate of Example 1.

Comparative Example 2 A comparative thermosensitive recording material having a protective layer was obtained in the same manner as in Example 1 except that stearic acid amide was used in place of p-toluenesulfonic acid-β-phenoxyethyl ester of Example 1. Was. Table 1 shows a quality performance table of the present invention and the comparative thermosensitive recording material obtained as described above.

(Table 1) Table 1 Quality performance test Background 1) Color density 2) Heat resistance 3) Water resistance 4) Plasticizer resistance 5) Example 1 0.04 1.55 1.55 1.46 1.46 53 Example 2 0.04 1.52 1.53 1.42 1.50 Example 3 0.04 1.59 1.59 1.52 1.57 Example 4 0.04 1.57 1.58 1 .50 1.55 Comparative Example 1 0.05 1.41 0.28 1.09 0.94 Comparative Example 2 0.06 1.39 1.35 1.30 0.54

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) Heat resistance: 1 color of the sample developed by the printer
The Macbeth reflection density of the image portion after left in a thermostat at 00 ° C. 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.
0.0294MP combined with VC wrap film on both sides
a) Macbeth reflection density of the image portion after being left at 40 ° C. for 15 hours under a load of 0.3 kg / cm ² .

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

[0035]

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, as a color developing compound, the following formula (1): (In the formula (1), R represents an alkyl group having 4 or less carbon atoms or a benzyl group.) A compound represented by the formula: p-toluenesulfonic acid-β-phenoxyethyl ester as a sensitizer. Characteristic thermal recording material.