JP2003112480A - Heat sensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a heat sensitive recording material, which has a few ground fogging and a high sensitivity and is excellent in preservability. SOLUTION: In a heat sensitive recording material formed by providing a heat sensitive color forming layer mainly made of a normally colorless or light-colored color forming compound, a color developing compound allowing to develop color in the color forming compound under heat and a sensitizer on a support, a bis(3-allyl-4-hydroxyphenyl)sulfone having an α-type crystal form is included as the color developing compound and a benzyloxynaphthalene is included as the sensitizer.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a thermal recording material. More specifically, it has high sensitivity and less fog,
The present invention relates to a heat-sensitive recording material having excellent storage stability.

[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 mixing them together, and then adding a binder, a sensitizer, a filler and a lubricant. It is applied as a coating liquid by adding additives such as etc. to paper, film, synthetic paper, etc., and color recording is made by a chemical reaction that occurs when one or both of the leuco dye and the developer melts and is heated by heating. I will get it. A thermal printer or the like having a built-in thermal head is used for coloring the heat-sensitive recording sheet. Compared with other recording methods, this thermal recording method has (1) no noise during recording, (2) no need for development and fixing, (3) maintenance-free, (4) relatively inexpensive machine By the characteristics such as
Facsimile field, computer output, calculator field printer field, medical measurement recorder field,
It is widely used in the fields of automatic ticket vending machines and heat-sensitive recording labels.

In recent years, with the introduction of POS systems in retail stores and supermarkets, and automation systems in transportation facilities, the use of labels, tickets, coupons, etc. has increased. In these applications, heat-sensitive recording materials are required to have further improved storage stability such as heat resistance, water resistance and plasticizer resistance. Further, the demand for high-speed recording is further increased, and development of a thermal recording material capable of sufficiently supporting high-speed recording is strongly desired, but in general, when the sensitivity of the thermal recording material is improved and the thermal response is improved, background fogging occurs. Is more likely to appear. Conventionally, various methods have been proposed in order to improve thermal responsiveness and further improve storability, but none is still satisfactory.

[0004]

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 excellent storage stability.

[0005]

The present inventors have completed the present invention as a result of various studies to achieve the above object. That is, the present invention provides (1) a thermosensitive recording material comprising a support, which is usually provided with a colorless or light-colored color-forming compound, and a thermosensitive color-developing layer containing a color-developing compound capable of coloring the color-forming compound under heat as a main component. 2. A heat-sensitive recording material containing bis (3-allyl-4-hydroxyphenyl) sulfone having an α-type crystal form as a color-developing compound and benzyloxynaphthalene as a sensitizer.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The thermosensitive color developing layer in the present invention is usually composed of a colorless to light color developing compound, bis (3-allyl-4-hydroxyphenyl) sulfone having an α-type crystal form, and benzyloxynaphthalene as main components. It is what In the present invention, the bis (3
-Allyl-4-hydroxyphenyl) sulfone functions as a color-developing compound and benzyloxynaphthalene functions as a sensitizer, but other color-developing compounds and sensitizers (heat-fusible) are used as necessary. Compound) may be used in combination, and if desired, a thermosensitive color developing layer is prepared by adding a binder, a filler, other additives and the like.

The bis (3-allyl-4-hydroxyphenyl) sulfone having an α-type crystal form used in the present invention is described in JP-A No. 11-29549, and its physical properties are Cu-Kα rays. In the powder X-ray diffraction method according to US Pat.
A crystalline form characterized by an X-ray diffractogram with a peak at 2.0 and a differential scanning calorimeter (Differentii).
It is a bis (3-allyl-4-hydroxyphenyl) sulfone having an extrapolation melting onset temperature (Te) in al Scanning Calorimeter) of 149 ° C. or higher.

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 and benzyloxynaphthalene are each usually 1 to 80% by weight, preferably 5
-40% by weight, and the sensitizer, binder and filler are usually 0-
80% by weight, other lubricants, surfactants, defoaming agents, ultraviolet absorbers, etc. in arbitrary proportions, for example, usually 0 to 3 respectively.
0 wt% is used (wt% is the weight ratio of each component in the thermosensitive color developing layer). In a further preferred embodiment, among the above-mentioned compositions, each of the used amounts of bis (3-allyl-) has a crystal form of α type with respect to the color forming compound.
4-hydroxyphenyl) sulfone is usually 0.5 to 20
Double, preferably 1 to 5 times, and benzyloxynaphthalene is usually used in a weight ratio range of 0.5 to 20 times, preferably 1 to 8 times.

Specific examples of benzyloxynaphthalene used in the present invention include 1-benzyloxynaphthalene and 2-benzyloxynaphthalene.

Specific examples of the color forming compound that can be used include:
There is no particular limitation as long as it is one generally used for pressure-sensitive recording paper and heat-sensitive recording paper. Specific examples include, for example, fluoran compounds, triarylmethane compounds,
Examples thereof include spiro compounds, diphenylmethane compounds, thiazine compounds, lactam compounds, fluorene compounds, and the like.

Specific examples of the fluorane compound include 3-diethylamino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane and 3- (N-methyl). -N-cyclohexylamino) -6-methyl-7-anilinofluorane, 3
-(N-ethyl-N-isopentylamino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-N-
Isobutylamino) -6-methyl-7-anilinofluorane, 3- [N-ethyl-N- (3-ethoxypropyl) amino] -6-methyl-7-anilinofluorane,
3- (N-ethyl-N-hexylamino) -6-methyl-7-anilinofluorane, 3-dipentylamino-6
-Methyl-7-anilinofluorane, 3- (N-methyl-N-propylamino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-N-tetrahydrofurylamino) -6- Methyl-7-anilinofluorane, 3-
Diethylamino-6-methyl-7- (p-chloroanilino) fluorane, 3-diethylamino-6-methyl-7
-(P-Fluoroanilino) fluorane, 3- [N-ethyl-N- (p-tolyl) amino] -6-methyl-7-
Anilinofluorane, 3-diethylamino-6-methyl-7- (p-toluidino) fluorane, 3-diethylamino-7- (o-chloroanilino) fluorane, 3-dibutylamino-7- (o-chloroanilino) fluorane, 3 -Diethylamino-7- (o-fluoroanilino) fluorane, 3-dibutylamino-7- (o-fluoroanilino) fluorane, 3-diethylamino-7-
(3,4-Dichloroanilino) fluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-ethoxyethylaminofluorane, 3-diethylamino-6-chloro- 7-anilinofluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane,
3-diethylamino-7-octylfluorane, 3-
[N-ethyl-N- (p-tolyl) amino] -6-methyl-7-phenethylfluorane and the like can be mentioned.

Specific examples of triarylmethane compounds include, for example, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone or CVL) and 3,3-bis ( p
-Dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3- (1,2-dimethylaminoindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methyl Indole-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-ethylcarbazol-3-yl) -5-dimethylaminophthalide,
3,3- (2-phenylindol-3-yl) -5-
Examples thereof include dimethylaminophthalide and 3-p-dimethylaminophenyl-3- (1-methylpyrrol-2-yl) -6-dimethylaminophthalide.

Specific examples of the spiro compounds include, for example, 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3'-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3- Propyl spirobenzopyran, 3-methylnaphtho- (3-methoxybenzo) spiropyran, 1,3,3-trimethyl-6
-Nitro-8'-methoxyspiro (indoline-2,
2'-benzopyran) and the like are specific examples of the diphenylmethane compound, for example, N-halophenyl-leuco auramine, 4,4-bis-dimethylaminophenylbenzhydrylbenzyl ether, N-2,4,5-triene. Chlorophenyl leuco auramine and the like are specific examples of thiazine compounds such as benzoyl leuco methylene blue and p-nitrobenzoyl leuco methylene blue, and specific examples of lactam compounds are, for example, rhodamine B anilinolactam and rhodamine B-p. -Chloroanilinolactam and the like are specific examples of the fluorene-based compound, for example, 3,6-bis (dimethylamino) fluorene spiro (9,3 ')-6'-dimethylaminophthalide, 3,6-bis ( Dimethylamino) fluorenspyrro (9,3 ′)-6′-pyrroli Nofutarido, 3-dimethylamino-6-diethylamino fluorene spiro (9,
3 ')-6'-pyrrolidinophthalide and the like, respectively. These color forming compounds may be used alone or as a mixture.

The color-developing compound usable in the present invention is not particularly limited as long as it is a compound 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 (also known as bisphenol A or BPA) ), 2,2-bis- (p-hydroxyphenyl) butane, 1,1-bis- (p-hydroxyphenyl) cyclohexane, 4,4′-thiobisphenol,
4,4'-cyclo-hexylidene diphenol, 2,
2'-bis- (2,5-dibromo-4-hydroxyphenyl) propane, 4,4'-isopropylidene bis (2
-T-butylphenol), 2,2'-methylenebis (4-chlorophenol), 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, bis Methyl (4-hydroxyphenyl) acetate, butyl bis (4-hydroxyphenyl) acetate,
Phenolic compounds such as benzyl bis (4-hydroxyphenyl) acetate, benzyl p-hydroxybenzoate, p
-Ethyl hydroxybenzoate, dibenzyl 4-hydroxyphthalate, dimethyl 4-hydroxyphthalate, ethyl 5-hydroxyisophthalate, 3,5-di-t-butylsalicylic acid, 3.5-di-α-methylbenzylsalicylic acid, etc. Examples of the color-developing compound that can be used in combination with those generally used for pressure-sensitive recording paper and heat-sensitive recording paper, such as aromatic carboxylic acid derivatives, aromatic carboxylic acids or polyvalent metal salts thereof. Not limited to.

Specific examples of the sensitizer (heat-fusible compound) 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. , An aromatic ether, an aromatic carboxylic acid derivative, an aromatic sulfonic acid ester derivative, a carbonic acid diester derivative, a biphenyl derivative, a terphenyl derivative, a sulfone derivative, etc., which are solid at room temperature and have a melting point of about 70 ° C. or higher are used. be able to.

Specific examples of waxes that can be used in combination 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 stearic acid and behenic acid, and specific examples of higher fatty acid amides. , For example stearic acid amide,
Examples of the higher fatty acid anilide include oleic acid amide, N-methylstearic acid amide, erucic acid amide, methylolbehenic acid amide, methylenebisstearic acid amide, and ethylenebisstearic acid amide. Anilides and the like are specific examples of the naphthalene derivative, for example, 1-hydroxynaphthoic acid phenyl ester and the like, and specific examples of the aromatic ether are, for example, 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- (4-methoxyphenoxy) ethane and the like are specific examples of the aromatic carboxylic acid derivative, for example, p-hydroxybenzoic acid benzyl ester, p -Benzyloxybenzoic acid benzyl ester, terephthalic acid dibenzyl ester and the like are specific examples of the aromatic sulfonic acid ester derivative, for example, p-
Toluenesulfonic acid phenyl ester, phenyl mesitylene sulfonate, 4-methylphenyl mesitylene sulfonate, etc. are specific examples of carbonic acid or oxalic acid diester derivatives, for example, carbonic acid diphenyl, oxalic acid dibenzyl ester, oxalic acid di (4-methyl). Benzyl) ester, oxalic acid di (4-chlorobenzyl) ester and the like, and specific examples of the biphenyl derivative include p-benzylbiphenyl, p-allyloxybiphenyl and the like.
Specific examples of the terphenyl derivative include m-terphenyl and the like, and specific examples of the sulfone derivative include diphenyl sulfone and the like.

The amounts of the color-developing compound and sensitizer which can be used in combination are within the range which does not impair the effects of the present invention, for example, α
The ratio of the bis (3-allyl-4-hydroxyphenyl) sulfone having a crystal type of γ-type and the amount of benzyloxynaphthalene each within the ranges not exceeding the amounts used is preferable.

The binder which can be used in the present invention includes
There is no particular limitation as long as it can be used for a heat-sensitive recording material, but the point of combination with bis (3-allyl-4-hydroxyphenyl) sulfone having an α-type crystal form and benzyloxynaphthalene used in the present invention. Therefore, it is preferable to use an ethylene / acrylic acid copolymer. This ethylene / acrylic acid copolymer has an ethylene mole number of 6
It is a compound having a molecular weight of usually 100,000 or less and an acid value of about 150, and is commercially available. For example, trade name: Saixen-AC (NH ₄ Salt), Saixen-N
(Na salt), Saixen-L (alkanolamine salt)
Etc. Particularly preferable ethylene / acrylic acid copolymers in the present invention include ethylene / acrylic acid ammonium salt and ethylene / acrylic acid sodium salt. The ethylene / acrylic acid copolymer is usually used in the heat-sensitive color forming layer in an amount of 0.5 to 50% by weight, preferably 2 to 20% by weight, and the weight ratio to the color forming compound is preferably 0.5. -30 times, more preferably 1-10 times.

Even when an ethylene / acrylic acid copolymer is used as the binder, other binders can be used in combination. Specific examples of such a binder that can be used are, for example, 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,
Water-soluble substances such as alkali salt of styrene / maleic anhydride copolymer, alkali salt of iso (or diiso) butylene / maleic anhydride copolymer, polyvinyl acetate, vinyl chloride / vinyl acetate copolymer, polystyrene , Polyacrylic acid ester, polyurethane, styrene / butadiene (SB) copolymer, carboxylated styrene / butadiene (SB) copolymer, styrene / butadiene / acrylic acid copolymer, colloidal silica and acrylic resin composite particles And the like, such as hydrophobic polymer emulsions.
The amount of the binder that can be used in combination with the ethylene / acrylic acid copolymer is preferably within the range that does not impair the effects of the present invention, for example, within the range that does not exceed the amount of the ethylene / acrylic acid copolymer used.

Specific examples of usable fillers include 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.

In addition, as additives, for example, higher fatty acid metal salts such as zinc stearate and calcium stearate for the purpose of preventing thermal head wear and sticking, and phenol derivatives for imparting antioxidative or antiaging effects. UV absorbers such as benzophenone compounds and benzotriazole compounds, various surfactants, antifoaming agents and the like are added as necessary.

The heat-sensitive recording material of the present invention is prepared by the following method using the above materials. That is, according to a conventional method, first, a chromophoric compound, bis (3-allyl-4-hydroxyphenyl) sulfone having an α-type crystal form, and benzyloxynaphthalene are separately added together with a binder or, if necessary, other additives. After pulverizing and dispersing with a disperser such as a ball mill, attritor, or sandmill (usually water is used as a medium when pulverizing and dispersing is performed in a wet state), and further mixed with ethylene / acrylic acid / copolymer. A thermosensitive color developing layer coating solution is prepared, and usually 1-by dry weight on a support such as paper, plastic sheet and synthetic paper.
Coating with a bar coater, blade coater, or the like so that the amount is 20 g / m ² (the ratio of the color-developing compound to the color-developing compound is usually 1: 1 to 1:10 by dry weight ratio) and dried to obtain the heat-sensitive material of the present invention. Obtain recording material. 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 together with a binder and, if necessary, other additives in the same manner as in the preparation of the coating solution for the thermosensitive color developing layer. Layer) After being made into a coating solution, it is applied so that the dry weight thereof is usually about 0.1 to 10 g / m ² .

The heat-sensitive recording material of the present invention, which usually contains a colorless to light-coloring compound, bis (3-allyl-4-hydroxyphenyl) sulfone having an α-type crystal form, and benzyloxynaphthalene, particularly a binder And a heat-sensitive recording material of the present invention containing an ethylene / acrylic acid copolymer have high sensitivity, less background fog, and excellent storage stability as compared with conventionally known materials.

[0024]

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" means part by weight and "%" means% by weight.

Example 1 (Formation of thermosensitive coloring layer) A mixture having the following composition was pulverized and dispersed by a sand grinder so as to have an average particle diameter of 1 μm or less, and each of the liquids [A], [B] and [B]. C] liquid was prepared. [A] liquid: 3-dibutylamino-6-methyl-7-anilinofluorane 25 parts 25% PVA aqueous solution 20 parts water 55 parts [B] liquid: α-type crystalline bis (3-allyl-4-hydroxy) Phenyl) sulfone (powder X-ray diffraction angle by Cu-Kα ray (2θ) [°] 7.2, 14.5, 16.3, 18.0, 20.0, 21.0, 22.0, 24. It has 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] solution: 2-benzyloxynaphthalene 25 parts 25% PVA Aqueous solution 20 parts Water 55 parts

Next, a thermosensitive color developing layer coating solution was prepared by mixing in the following proportions, coated on a wood free paper having a basis weight of 50 g / m ^{2 so} that the dry weight was 8 g / m ² , dried and heat-sensitive. A colored layer was obtained. [A] liquid 16 parts [B] liquid 32 parts [C] liquid 40 parts 50% calcium carbonate aqueous dispersion 16 parts 30% ethylene / ammonium acrylate emulsion (trade name: Saixen-AC, Sumitomo Seika Chemicals Ltd.) 13 parts (formation of protective layer) Further, a protective layer coating liquid having the following composition ratio is applied onto the thermosensitive color developing layer to give a dry weight of 3 g / m.
^It was coated so as to be ² and dried to obtain a heat-sensitive recording material of the present invention with a protective layer. 40% styrene / acrylic acid ester copolymer emulsion 20 parts 5% bentonite aqueous dispersion 40 parts 30% zinc stearate aqueous dispersion 3 parts

Example 2 Instead of the 30% ethylene / acrylic acid ammonium salt emulsion of Example 1, a 30% ethylene / acrylic acid sodium salt emulsion (trade name: Saixen-NC,
Using Sumitomo Seika Co., Ltd., a thermal recording material of the present invention with a protective layer was obtained in the same manner as in Example 1.

Example 3 A 25% 1-benzyloxynaphthalene aqueous dispersion obtained by pulverizing and dispersing in the same manner as in Example 1 was used in place of the liquid [C] of Example 1 to obtain Example 1. Similarly, a thermal recording material of the present invention having a protective layer was obtained.

Example 4 Instead of the liquid [A] of Example 1, 25% 3-dipentylamino-6- was obtained by pulverizing and dispersing in the same manner as in Example 1.
Using a methyl-7-anilinofluorane aqueous dispersion,
A thermal recording material of the present invention with a protective layer was obtained in the same manner as in Example 1.

Table 1 shows the quality performance of the thermal recording material of the present invention obtained as described above.

Table 1 Quality performance test Background ¹⁾ Color density ²⁾ Heat resistance ³⁾ Water resistance ⁴⁾ Plasticizer resistance ⁵⁾ Example 1 0.04 1.66 1.65 1.38 1.58 Example 2 0.04 1.65 1.65 1.37 1.59 Example 3 0.04 1.62 1.62 1.37 1.57 Example 4 0.04 1.65 1.64 1.38 1. 58

1) Background: A value (Macbeth reflection density) of the uncolored portion of the sample measured by Macbeth reflection densitometer RD-914 type. 2) Color density: Macbeth reflection density value of the image portion printed by a thermal printer (D-805P) manufactured by Ishida Co., Ltd. 3) Heat resistance: 6 samples of color developed by the above printer
Macbeth reflection density of the image portion after standing in a 0 ° C incubator for 24 hours. 4) Water resistance: Macbeth reflection density of the image portion after the sample developed by the printer was immersed in tap water at room temperature for 24 hours. 5) Plasticizer resistance: P was added to the sample colored by the above printer.
0.0294MP with VC wrap film on both sides
Macbeth reflection density of the image portion after standing at room temperature for 24 hours under a load of a (300 g / cm ² ).

As is apparent from the table, the heat-sensitive recording material of the present invention is excellent in the whiteness of the background and the coloring density, and is excellent in the storage stability such as heat resistance, water resistance and plasticizer resistance.

[0034]

EFFECT OF THE INVENTION A heat-sensitive recording material having high sensitivity, little background fog and excellent storage stability was obtained.

Claims (3)

[Claims] 1. A heat-sensitive recording material comprising a support, which is usually provided with a colorless or light-colored color-forming compound, and a heat-sensitive color-developing layer containing a color-developing compound capable of coloring the color-forming compound under heat as a main component. A heat-sensitive recording material comprising bis (3-allyl-4-hydroxyphenyl) sulfone having an α-type crystal form as a color compound and benzyloxynaphthalene as a sensitizer. 2. The heat-sensitive recording material according to claim 1, further comprising an ethylene / acrylic acid copolymer as a binder. 3. The heat-sensitive recording material according to claim 2, wherein the ethylene / acrylic acid copolymer is ethylene / acrylic acid ammonium salt or ethylene / acrylic acid sodium salt.