JP2002079758A - Thermal recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a thermal recording material, reduced in skin blushing, high in sensitivity and excellent in the storage stability of the color-developed image of the same. SOLUTION: In the thermal recording material provided on a substrate with a heat sensitive color developing layer, containing the principal constituents of a color developing compound having no color or thin color ordinarily, a heat sensitive color developing layer containing the principal constituents of a developer compound, capable of developing color upon heating the color developing compound, and a sensitizer, bis(3-allyl-4-hydroxy phenyl)sulfone having an α-type crystal form is contained as the developer compound while p-toluenesulfonic acid-β-phenoxy ethyl ester is contained as the 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, 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. By 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.

[0003] In recent years, with the introduction of POS systems in retail stores and supermarkets, and automation systems in transportation, applications to labels, tickets, coupons, and the like have been increasing. In these applications, it is desired that the heat-sensitive recording material be further improved in storage stability. In addition, the demand for high-speed recording has further increased, and the development of a thermosensitive recording material that can sufficiently cope with high-speed recording has been strongly desired.
In general, when the sensitivity of the heat-sensitive recording material is increased to improve the thermal response, the disadvantage that background fogging occurs tends to appear. Conventionally,
Various methods have been proposed for improving the sensitivity and storage stability without impairing the whiteness of the heat-sensitive recording material, but no satisfactory method has yet been found.

[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, low background fog, and excellent image storability.

[0005]

Means for Solving the Problems The present inventors have made various studies to achieve the above object, and as a result, completed the present invention. That is, the present invention

(1) A heat-sensitive color-developing layer comprising, as main components, a colorless compound which is usually colorless or pale, a color-developing compound capable of developing the color-forming compound when heated, and a sensitizer as a main component. In the recording material, α is used as a color developing compound.
A heat-sensitive recording material comprising bis (3-allyl-4-hydroxyphenyl) sulfone having a crystalline form of p-toluenesulfonic acid-β-phenoxyethyl ester as a sensitizer.

[0007]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, a colorless or light-colored color-forming compound, bis (3-allyl-4-hydroxyphenyl) sulfone having an .alpha.-type crystal form as a color-developing compound, and a sensitizer are generally used. As a main component, p-toluenesulfonic acid-β-phenoxyethyl ester is used as a main component, and a thermosensitive coloring layer is prepared by using a binder and other fillers and other additives as necessary as shown below. Is done.

The bis (3-allyl-4-hydroxyphenyl) sulfone having an α-form crystal form used in the present invention is described in JP-A-11-29549, and its physical properties are Cu-Kα radiation. The diffraction angle (2θ) [°] 7.2 and 2
A crystalline form characterized by an X-ray diffractogram with a peak at 2.0 and a differential scanning calorimeter (Differenti)
It is a bis (3-allyl-4-hydroxyphenyl) sulfone having a melting point of 149 ° C. or higher at an extrapolation melting temperature (Te) in an al scanning calorimeter.

In forming the thermosensitive coloring layer in the present invention, the color-forming compound is usually 1 to 50% by weight, preferably 5 to 30% by weight, and bis (3-allyl-4-hydroxyphenyl) having an α-type crystal form. ) Sulfone is usually 1-60
%, Preferably 5 to 30% by weight, p-toluenesulfonic acid-β-phenoxyethyl ester is usually 1 to 80% by weight.
% By weight, preferably 5 to 60% by weight;
90% by weight, a filler is usually used in an amount of 0 to 80% by weight, and other lubricants, surfactants, defoaming agents, ultraviolet absorbers and the like are used in arbitrary ratios, for example, generally 0 to 30% by weight, respectively ( % By weight is the weight ratio of each component in the thermosensitive coloring layer). As a further preferred embodiment, among the above-described compositions,
The amount of bis (3-allyl-4-hydroxyphenyl) sulfone having an α-type crystal form is usually 0.5 to 20 times, preferably 1 to 1, of the coloring compound 1 in weight ratio.
The ratio of p-toluenesulfonic acid-β-phenoxyethyl ester is usually 0.5 to 20 times, preferably 1 to 8 times. In the heat-sensitive recording material of the present invention, a known or publicly-known color developing compound, a sensitizer or other additives other than the above-mentioned main components may be used 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 fluoran compounds that can be used 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)
Fluorane, 3-diethylamino-7- (o-fluoroanilino) fluoran, 3-dibutylamino-7- (o
-Fluoroanilino) 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-chlorofluoran, 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 are specific examples of diphenylmethane-based compounds such as N-halophenyl-leuco auramine, 4,4-bis-dimethyl. Aminophenylbenzhydryl benzyl ether, N-2,
Specific examples of thiazine compounds include 4,5-trichlorophenylleuco auramine and the like, for example, benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue and the like, specific examples of lactam compounds include
For example, rhodamine B anilinolactam, rhodamine B-
Specific examples of fluorene-based compounds such as p-chloroanilinolactam include, for example, 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.

The color-developing compound that can be used in combination 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. 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 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, 4-hydroxy-4'-isopropoxydiphenylsulfone, bis (4-hydroxyphenyl) methyl acetate, bis (4-hydroxyphenyl) butyl acetate,
Phenolic compounds such as benzyl bis (4-hydroxyphenyl) acetate; benzyl p-hydroxybenzoate;
-Ethyl hydroxybenzoate, dibenzyl 4-hydroxyphthalate, dimethyl 4-hydroxyphthalate, 3,5
Examples of color-developing compounds to which aromatic carboxylic acid derivatives such as -di-t-butylsalicylic acid, 3.5-di-α-methylbenzylsalicylic acid, aromatic carboxylic acids or polyvalent metal salts thereof can be used in combination. Can be

Specific examples of sensitizers (thermofusible compounds) that can be used in the present invention include waxes such as animal and vegetable waxes and synthetic waxes, higher fatty acids, higher fatty acid amides, higher fatty acid anilides, and naphthalene derivatives. , Aromatic ethers, aromatic carboxylic acid derivatives, aromatic sulfonic acid ester derivatives, carbonic acid or oxalic acid diester derivatives, biphenyl derivatives, terphenyl derivatives, sulfone derivatives, etc., which are solid at room temperature and have a melting point of about 70 ° C. or more Can be used.

Specific examples of waxes include, for example, wood wax, carnauba wax, shellac, paraffin, montan wax, oxidized paraffin, polyethylene wax, polyethylene oxide, and the like. Specific examples of higher fatty acids include, for example, stearic acid and behenic acid. Specific examples of higher fatty acid amides include, 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. Examples of the higher fatty acid anilide include anilide stearate and anilide linoleate, and specific examples of the naphthalene derivative include 1-benzyloxynaphthalene and
-Benzyloxynaphthalene, 1-hydroxynaphthoic acid phenyl ester and the like are specific examples of aromatic ethers such as 1,2-diphenoxyethane, 1,4-diphenoxybutane, 1,2-bis (3-methyl Phenoxy) ethane, 1,2-bis (4-methoxyphenoxy)
Ethane, 1,2-bis (3,4-dimethylphenyl) ethane, 1-phenoxy-2- (4-chlorophenoxy)
Specific examples of the aromatic carboxylic acid derivative include ethane, 1-phenoxy-2- (4-methoxyphenoxy) ethane and the like, for example, p-hydroxybenzoic acid benzyl ester, p-benzyloxybenzoic acid benzyl ester, terephthalic acid diester. Benzyl esters and the like are specific examples of aromatic sulfonic acid ester derivatives such as phenylmesitylenesulfonate and 4-methylphenylmesitylenesulfonate; specific examples of carbonic acid or oxalic acid diester derivatives include diphenyl carbonate and oxalic acid. Acid dibenzyl ester, oxalic acid di (4-chlorobenzyl) ester, oxalic acid di (4-methylbenzyl) ester and the like. Specific examples of biphenyl derivatives include, for example, p-benzylbiphenyl, p-allyloxybiphenyl and the like. ,
Specific examples of the terphenyl derivative include, for example, m-terphenyl, and specific examples of the sulfone derivative include, for example, diphenyl sulfone.

The amounts of the color developing compound and the sensitizer which can be used in combination as described above are within a range not to impair the effects of the present invention, for example, α
The ratio is preferably in a range that does not exceed the amount of bis (3-allyl-4-hydroxyphenyl) sulfone and p-toluenesulfonic acid-β-phenoxyethyl ester each having the same crystal type.

Specific examples of the binder that can be used include, for example, methylcellulose, methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, sodium carboxymethylcellulose, 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-based copolymer, and composite particles of colloidal silica and acrylic resin are used. 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. And urea-formalin resins.

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, benzotriazole compounds, various surfactants, defoamers And the like.

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 color-forming compound, bis (3-allyl-4-hydroxyphenyl) sulfone having an α-type crystal form, p
-Toluenesulfonic acid-β-phenoxyethyl ester is separately pulverized and dispersed in a dispersing machine such as a ball mill, an attritor, a sand mill or the like together with a binder or other additives as necessary (pulverization, dispersion). When using a wet method, water is usually used as a medium) to prepare a coating solution for the heat-sensitive coloring layer, which is usually dried on a support such as paper, plastic sheet, or synthetic paper so that the dry weight is 1 to 20 g / m ^2. Is coated with a bar coater or a blade coater and dried to obtain the heat-sensitive recording material of the present invention. 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 in the same manner as in the preparation of the thermosensitive coloring layer coating solution together with, for example, the above-mentioned binder or other additives as necessary, or the intermediate layer coating solution or After forming the overcoat layer (protective layer) coating solution, the dry weight is usually 0.1 to 10
It is provided by applying and drying to about g / m ² .

The heat-sensitive composition of the present invention usually contains a colorless or pale-colored color-forming compound, bis (3-allyl-4-hydroxyphenyl) sulfone having an α-type crystal form, and p-toluenesulfonic acid-β-phenoxyethyl ester. The recording material has higher sensitivity and less background fogging than the conventionally known materials, and is excellent in storability of a recorded image that has been colored.

[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 and "%" indicates% 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: α-type crystal bis (3-allyl-4-hydroxy) Phenyl) sulfone (powder X-ray diffraction angle (2θ) by Cu-Kα ray (°) [°] 7.2, 14.5, 16.3, 18.0, 20.0, 21.0, 22.0, 24. Relatively strong peaks at 7 and 29.0. DSC (Te) = 155.5 ° C) 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, the respective liquids obtained above and the following chemicals were mixed in the following proportions to prepare a coating solution for the thermosensitive coloring layer, which was dried on a high-quality paper having a basis weight of 50 g / m ² at a weight of 8 g / m ² when dried. ² so as applied to obtain a thermosensitive coloring layer was dried. [A] solution 8 parts [B] solution 16 parts [C] solution 24 parts 50% aqueous 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 was applied onto the above-mentioned thermosensitive coloring layer so that the dry weight was 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 aqueous dispersion 3 parts

Example 2 A 25% aqueous dispersion of 3-dibutylamino-7- (o-chloroanilino) fluoran obtained by pulverizing and dispersing in the same manner as in Example 1 instead of the solution [A] of Example 1 Using the liquid, a thermosensitive recording material of the present invention was obtained in the same manner as in Example 1.

Example 3 25% 3-dipentylamino-6-methyl-7-anilinofluoran obtained by pulverizing and dispersing in the same manner as in Example 1 in place of the solution [A] of Example 1 A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1 using an aqueous dispersion.

Example 4 A 25% α-form bis (3-allyl-4-hydroxyphenyl) obtained by pulverizing and dispersing in the same manner as in Example 1 in place of the solution [B] of Example 1 ) Sulfone (C
6. X-ray powder diffraction angle (2θ) by u-Kα ray [°]
2, 14.5, 16.3, 18.0, 20.0, 21.
It has relatively strong peaks at 0, 22.0, 24.7 and 29.0. A thermosensitive recording material of the present invention was obtained in the same manner as in Example 1 using an aqueous dispersion of DSC (Te) = 150.0 ° C.

Comparative Example 1 In place of the α-form bis (3-allyl-4-hydroxyphenyl) sulfone of Example 1, JP-A-61-890 was used.
Bis (3-allyl-4-hydroxyphenyl) sulfone having a crystal form different from the crystal form of α-form obtained according to Example 1 described in No. 90 (X-ray diffraction angle (2θ) by Cu-Kα ray (2θ) [°] 7.04, 10.85, 14.14, 1
It has relatively strong peaks at 5.78, 17.51, and 22.98. DSC (Te) = 145.8 ° C.)
A heat-sensitive recording material for comparison was obtained in the same manner as in Example 1, except that m-terphenyl was used instead of -toluenesulfonic acid-β-phenoxyethyl ester. The following quality performance tests were performed using the present invention and the comparative thermosensitive recording material obtained as described above.

Table 1 Quality Performance Test Ground 1) Color density 2) Color density 3) Color density 4) Moisture resistance 5) Oil resistance 6) Example 1 0.05 1.02 1.40 1.66 1.41 1 .42 Example 2 0.04 1.00 1.37 1.60 1.37 1.37 Example 3 0.04 1.02 1.40 1.64 1.41 1.41 Example 4 0.05 1.03 1.41 1.66 1.41 1.42 Comparative Example 1 0.08 0.83 1.22 1.49 1.23 1.22

1) Background: The uncolored portion of the sample is a value (Macbeth reflection density) measured by a Macbeth reflection densitometer (RD-914, manufactured by Macbeth). 2) Coloring density: Thermal printer (D-805P,
Macbeth reflection density value of the image portion printed under low energy conditions (Isida Co., Ltd.). 3) Color density: Thermal printer (D-805P,
The Macbeth reflection density value of the image portion printed under medium energy conditions (produced by Ishida Co., Ltd.). 4) Color density: Thermal printer (D-805P,
Macbeth reflection density value of the image portion printed under high energy conditions (Isida Co., Ltd.). 5) Moisture resistance: The Macbeth reflection density of the image portion after leaving the sample subjected to medium energy color development with the above printer in a humidity chamber at a relative humidity of 90% and a temperature of 40 ° C. for 24 hours. 6) Oil resistance: Cotton seed oil is applied to the surface of the sample that has been colored with medium energy by the above printer, and the relative humidity is 90%.
The Macbeth reflection density of the image portion after being left in a humidity chamber at a temperature of 40 ° C. for 24 hours.

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

[0033]

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

Claims (1)

[Claims] 1. A thermosensitive recording system comprising a support having thereon a heat-sensitive coloring layer containing, as main components, a colorless compound which is usually colorless or pale, a color-forming compound capable of forming a color when heated, and a sensitizer. The material is characterized by containing bis (3-allyl-4-hydroxyphenyl) sulfone having an α-type crystal form as a color developing compound and p-toluenesulfonic acid-β-phenoxyethyl ester as a sensitizer. Thermosensitive recording material.