JP2001246853A - Heat sensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a heat sensitive recording material, which is excellent in color forming property, in which a small ground fogging develops against heat and which is excellent in storage stability. SOLUTION: This heat sensitive recording material, which is produced by providing a heat sensitive coloring layer mainly made of a normally colorless or light-colored color forming compound, a color developing compound, which thermally develops the color of the color forming compound, and a sensitizer on a support, includes formula 1, in which X represents a halogen atom and Y represents a 4C or less alkyl group, as the color forming compound, a bis(3- aryl-4-hydrophenol)sulfon and formula 2, in which R1 represents a 4C or less group or a cyclohexyl group and R2 represents a 4C or less alkyl group, as the color developing compound and a 1,2-bis(3,4-dimethylphenyl)ethane as the sensitizer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material having excellent coloring properties, less fogging due to heat, and excellent storage properties such as water resistance, plasticizer resistance and oil resistance. Things.

[0002]

2. Description of the Related Art A heat-sensitive recording material using a colorless or light-colored color-forming substance and a color-developing substance capable of coloring the color-forming substance when heated is disclosed in JP-B-43-4160 and JP-B-45-14039.
And widely used. In general, a thermosensitive recording material is obtained by separately dispersing a developer such as a leuco dye and a phenolic substance into fine particles, and then mixing both.
Additives such as binders, sensitizers, fillers, lubricants, etc. are added to this to form a coating solution, which is applied to a support such as paper, film, synthetic paper, etc., and heated to produce a leuco dye and a developer. One or both of them is used to obtain a color recording by a chemical reaction caused by melting and contacting, and usually a sheet-like heat-sensitive recording material is prepared. A thermal printer with a built-in thermal head or the like is used for coloring the heat-sensitive recording sheet. Compared with other recording methods, this thermal recording method is (1) no noise is generated at the time of recording, (2) there is no need for development and fixing, and (3) maintenance-free. (4) Widely used in facsimile field, computer output, printers such as calculators, recorders for medical measurement, automatic ticket vending machines, thermosensitive labeling, etc. Have been.

[0003] Among these fields of use, the use of POS systems in retail stores and supermarkets has led to the widespread use of labels and price tags. Particularly, heat-sensitive labels affixed to fresh foods, lunch boxes, processed foods, and the like. The image area may be discolored by water or a wrapping film containing a plasticizer (wrap film), leaked edible oil or fat, etc., or background fog (coloring of unprinted areas) due to heat or humidity during heating or thawing )
There is a problem that is easily caused.

In recent years, the demand for high-speed recording has been further increased, and the development of a heat-sensitive recording material for responding to the demand has been strongly desired. However, in general, if the sensitivity of the heat-sensitive recording material is increased to improve the thermal responsiveness, background fogging will occur. The disadvantage that it occurs is likely to appear. Further, many of the above-mentioned preservability improvers, stabilizers, and the like used for improving the plasticizer resistance and oil resistance have a defect of causing a decrease in sensitivity and background fogging. Conventionally, various methods have been proposed for improving heat responsiveness, excellent storage stability, and improving heat resistance and wet heat resistance of an unprinted portion, but a satisfactory method has not yet been established.

[0005] For example, Japanese Patent Publication No. 52-20142 discloses that the thermal responsive layer is improved in thermal responsiveness by increasing the smoothness of the heat-sensitive coloring layer by a super calendering process. In contrast, when the value is improved, there is a problem that the matching with the thermal head becomes poor. Japanese Patent Application Laid-Open No. Sho 56-164890 discloses a method using a leuco dye having a lowered melting point. However, this method has a defect that heat fogging is increased, although thermal response is improved. . Another method is to provide a specific intermediate layer between the support and the heat-sensitive recording layer.
5093, JP-A-60-248390, JP-A-1-
No. 113282, JP-A-2-214688 and the like are not satisfactory in consideration of economic aspects such as material availability and processing costs.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to overcome the disadvantages of the prior art as described above. That is,
It is an object of the present invention to provide a heat-sensitive recording material having high sensitivity, excellent storage stability of an image portion, and less background fogging against heat and humidity.

[0007]

Means for Solving the Problems The present inventors have made intensive studies to improve the above-mentioned drawbacks of the thermosensitive recording material, 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 generating the color-forming compound upon heating, and a sensitizer on a support. Thermal recording material
The heat-sensitive coloring layer is represented by the following formula (1) as a coloring compound.

[0008]

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(In the formula (1), X represents a halogen atom, Y represents an alkyl group having 4 or less carbon atoms), and bis (3-allyl-4-hydroxyphenyl) sulfone is used as a color developing compound. And the following equation (2)

[0010]

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In the formula (2), R1 represents an alkyl group or cyclohexyl group having 4 or less carbon atoms, and R2 represents an alkyl group having 4 or less carbon atoms. Thermosensitive recording material comprising: 2,2-bis (3,4-dimethylphenyl) ethane; (2) a thermosensitive recording material according to (1), wherein an intermediate layer was provided between the thermosensitive coloring layer and the support. , Concerning.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the formula (1), X is
Examples thereof include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the alkyl group having 4 or less carbon atoms in Y include, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, Examples include a sec-butyl group and a t-butyl group. Preferred examples of X include a fluorine atom and a chlorine atom, and examples of Y include an ethyl group and an n-butyl group. Specific examples of the color-forming compound of the formula (1) include, for example, 3-diethylamino-7- (o-chloroanilino)
Fluoran, 3-di-n-butylamino-7- (o-chloroanilino) fluoran, 3-diethylamino-7-
(O-fluoroanilino) fluoran, 3-di-n-butylamino-7- (o-fluoroanilino) fluoran and the like.

The alkyl group having 4 or less carbon atoms in R1 and R2 of the formula (2) includes, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, t-butyl group. Butyl group and the like. Specific examples of the compound represented by the formula (1) include, for example, 1,
1,3-tris (2-methyl-4-hydroxy-5-t
-Butylphenyl) butane, 1,1,3-tris (2-
Ethyl-4-hydroxy-5-t-butylphenyl) butane and 1,1,3-tris (2-methyl-4-hydroxy-5-t-cyclohexylphenyl) butane.

In the heat-sensitive recording material of the present invention, the heat-sensitive coloring layer comprises a compound represented by the formula (1) as a coloring compound, bis (3-allyl-4-hydroxyphenyl) sulfone and a compound represented by the formula ( The compound represented by 2) is composed of 1,2-bis (3,4-dimethylphenyl) ethane as a main component as a sensitizer, a binder as shown below, and other fillers and heat It is prepared using a fusible compound, a lubricant, a surfactant and the like. The amount of each compound is usually 0.5 to 20 parts by weight of bis (3-allyl-4-hydroxyphenyl) sulfone and the compound represented by formula (2) with respect to 1 part by weight of the compound represented by formula (1). Parts, preferably 1 to 5 parts by weight of bis (3-allyl-4-hydroxyphenyl) sulfone, 0.5 to 2 parts by weight of the compound represented by the formula (1), 1,2-bis (3,4 (Dimethylphenyl) ethane is generally used in a proportion of 0.5 to 20 parts by weight, preferably 1 to 5 parts by weight.

In forming the thermosensitive coloring layer in the present invention, the compound represented by the formula (1) is usually 1 to 50% by weight, preferably 5 to 30% by weight, bis (3-allyl-4).
-Hydroxyphenyl) sulfone and the compound represented by the formula (2) are each usually 1 to 80% by weight, preferably 5 to 80% by weight, respectively.
-40% by weight, 1,2-bis (3,4-dimethylphenyl) ethane is usually 1-80% by weight, preferably 5-40% by weight.
% By weight, usually 1 to 90% by weight of a binder, 0 to 80% by weight of a filler and a heat-fusible compound each, and an arbitrary ratio of other lubricants, surfactants, defoamers, ultraviolet absorbers, etc. For example, each is usually used in an amount of 0 to 30% by weight (weight% is the weight ratio of each component in the thermosensitive coloring layer).

In the present invention, the coating liquid composed of the above-mentioned material is applied on the intermediate layer provided on the support in a dry weight of 1 to 5.
The composition is coated and dried at 40 g / m2, preferably 5 to 15 g / m2 to form a thermosensitive coloring layer. Further, a protective layer or the like can be provided on the thermosensitive coloring layer.

Examples of the sensitizer (thermofusible compound) usable 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 acetyls of aromatic amines. Compounds, 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. Those having a melting point can be used.

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

The amount of the sensitizer that can be used in combination is within a range that does not impair the effects of the present invention, for example, a range that does not exceed the amount of 1,2-bis (3,4-dimethylphenyl) ethane. Ratios are preferred.

In the present invention, specific examples of the binder which can be used for providing the intermediate layer, the thermosensitive coloring layer and the protective layer include 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, silyl group-modified polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid,
Water-soluble ones such as starch and derivatives thereof, casein, gelatin, water-soluble isoprene rubber, alkali salts of styrene / maleic anhydride copolymer, iso (or diiso) butylene / maleic anhydride copolymer salt, and styrene / Butadiene (SB) copolymer, carboxylated styrene / butadiene (SB) copolymer, styrene / butadiene / acrylic acid copolymer, polyvinyl acetate, polyvinyl chloride, vinyl chloride / vinyl acetate copolymer, polystyrene ,
Acrylic resin, acrylic / styrene resin, polyacrylate, polyester, polycarbonate, polyurethane, polybutyral, epoxy resin, furan resin,
Examples include hydrophobic polymer compounds such as vinyl toluene resin, rosin ester resin, composite particles of colloidal silica and acrylic copolymer, and emulsions thereof.

Examples of fillers that can be used include calcium carbonate, magnesium carbonate, magnesium oxide, silica,
Examples include white carbon, talc, clay, alumina, magnesium hydroxide, aluminum hydroxide, aluminum oxide, barium sulfate, polystyrene resin, acrylic resin, polyolefin resin, benzoguanamine resin, melamine resin, and urea-formalin resin.

Examples of other additives that can be used include higher fatty acid metal salts such as zinc stearate and calcium stearate for the purpose of preventing abrasion and sticking of a thermal head, and phenol derivatives imparting an antioxidant or antiaging effect. UV absorbers such as benzophenone-based and benzotriazole-based surfactants, various surfactants, antifoaming agents and the like are added as required.

When an intermediate layer is provided between the heat-sensitive color-forming layer and the support, the color-forming properties become better. The coating agent for this intermediate layer is
It is prepared by using the above-mentioned filler and binder as main components and using a crosslinking agent and various surfactants as necessary. Filler: binder 20: 1 to 1:10, preferably 10: 1
Used in a weight ratio of 1-1: 1. The filler is generally a fine particle made of a large heat-insulating organic polystyrene resin, acrylic resin, polyolefin resin, benzoguanamine resin, melamine resin, urea-formalin resin, and the like, and the average particle size is 0.4. ２2 μm is preferred.

In the present invention, it is preferable to use a crosslinking agent together in order to enhance the effect of the binder. Specific examples of the crosslinking agent that can be used include glyoxal, formalin,
Borax, aziridine, dialdehyde starch, melamine resin, polyethyleneimine resin, polyamide / epichlorohydrin resin, ketone / aldehyde resin, epoxy resin, glycine, glycidyl ester, glycidyl ether, ketene dimer, dimethylol urea, ammonium chloride, magnesium chloride, chloride Examples include calcium, aluminum sulfate, magnesium sulfate, calcium hydroxide, and zirconium ammonium carbonate.

The amount of the crosslinking agent to be used is usually 0.1 to the binder.
It is used in an amount of 1 to 50% by weight, preferably 1 to 20% by weight.

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 filler and a binder and, if necessary, a crosslinking agent, a wetting agent, an antifoaming agent, and the like are mixed and dispersed via water or an organic solvent such as toluene or IPA to prepare an intermediate layer coating solution. And 1 to 40 g / m 2, preferably 5 to 20 g / m 2 in dry weight on a support such as paper, plastic sheet or synthetic paper.
Is applied by a bar coater, a blade coater or the like, and dried to form an intermediate layer. Next, a compound represented by the formula (1), bis (3-allyl-4-hydroxyphenyl) sulfone, a compound represented by the formula (2) and 1,2-
Bis (3,4-dimethylphenyl) ethane is separately pulverized with a binder or other additives as necessary using a dispersing machine such as a ball mill, an attritor, or a sand mill.
After the dispersion (when pulverization and dispersion are performed by a wet method, water is usually used as a medium), they are mixed to prepare a coating solution for the heat-sensitive coloring layer, and 1 to 40 g / m 2 on the intermediate layer in a dry weight.
(The ratio of the color-forming compound to the color-developing compound is usually from 2: 1 to 1:10 by dry weight ratio), and then dried to form a thermosensitive color. A layer is provided to obtain the heat-sensitive recording material of the present invention. Further, if necessary, an overcoat layer may be provided on the thermosensitive coloring layer. Further, a thermosensitive coloring layer may be provided directly on the support without providing the intermediate layer.

Contains a compound represented by the formula (1), bis (3-allyl-4-hydroxyphenyl) sulfone, a compound represented by the formula (2) and 1,2-bis (3,4-dimethylphenyl) ethane The heat-sensitive recording material of the present invention is excellent in color developability, has little background fogging against heat, and is excellent in storability such as water resistance, plasticizer resistance and oil resistance.

[0028]

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

Example 1 (Formation of Intermediate Layer) A coating liquid for an intermediate layer having the following ratio was prepared, applied on a high-quality paper having a basis weight of 50 g / m 2 so that the weight when dried was 5 g / m 2, and dried. To form an intermediate layer. 48% polystyrene fine particle dispersion (average particle size: 0.5 μm) 166 parts 40% styrene / acrylate copolymer emulsion 50 parts Water 34 parts

(Formation of Thermosensitive Coloring Layer) A mixture having the following composition was pulverized and dispersed using a sand grinder so that the average particle size became 2 μm or less, and the solution [A] and the solution [B] were respectively obtained.
A solution, a solution [C] and a solution [D] are prepared. [A] solution: 3-dibutylamino-7- (o-chloroanilino) fluoran (compound represented by the formula (1)) 25 parts 25% PVA aqueous solution 20 parts water 55 parts [B] solution: bis (3-allyl- 4-hydroxyphenyl) sulfone 25 parts 25% PVA aqueous solution 20 parts Water 55 parts [C] liquid: 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane (Formula (2) Compound shown) 25 parts 25% PVA aqueous solution 20 parts Water 55 parts [D] liquid 1,2-bis (3,4-dimethylphenyl) ethane 25 parts 25% PVA aqueous solution 20 parts Water 55 parts

Next, the respective preparations are mixed in the following proportions to prepare a coating solution for the heat-sensitive coloring layer. The solution is coated on the above-mentioned intermediate layer so as to have a weight of 6 g / m2 when dried, and dried to form a coating solution for the heat-sensitive coloring layer. Get. [A] liquid 12 parts [B] liquid 24 parts [C] liquid 6 parts [D] liquid 30 parts 50% calcium carbonate aqueous dispersion 48 parts 50% carboxylated styrene / butadiene copolymer latex 18 parts water 42 parts ( Formation of Protective Layer) Further, a protective layer coating solution having the following ratio was applied onto the thermosensitive coloring layer in a dry weight of 3 g / m 2.
Is applied and dried to obtain the heat-sensitive recording material of the present invention. 40% styrene / acrylate copolymer emulsion 20 parts 5% bentonite aqueous solution 40 parts 30% zinc stearate dispersion 3 parts

Example 2 Instead of 3-dibutylamino-7- (o-chloroanilino) fluoran of Example 1, 3-dibutylamino-7-
Using (o-fluoroanilino) fluorane, a heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1.

Example 3 In place of 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane of Example 1, 1,1,3-tris (2-methyl-4-hydroxy −
Example 1 using 5-t-butylphenyl) butane
In the same manner as in the above, a heat-sensitive recording material of the present invention was obtained.

Example 4 In place of 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane of Example 1, 1,1,3-tris (2-ethyl-4-hydroxy −
Example 1 using 5-t-butylphenyl) butane
In the same manner as in the above, a heat-sensitive recording material of the present invention was obtained.

Example 5 An intermediate layer coating solution having the following ratio was prepared in place of the intermediate layer coating solution of Example 1, and the weight when dried on a high-quality paper having a basis weight of 50 g / m2 was 10 g / m2. The intermediate layer was formed by coating and drying as described above, and then the heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1. 30% polymethyl methacrylate fine particle dispersion liquid (average particle diameter 1 μm) 133 parts 40% styrene / acrylate copolymer emulsion 100 parts Water 17 parts

Tables 1 and 2 show the quality performance of the heat-sensitive recording material of the present invention obtained as described above.

Table 1 Quality Performance Test Ground 1) Color density 2) Color density 3) Heat resistance 4) Water resistance 5) Example 1 0.04 1.66 1.40 0.25 1.45 Example 20 0.04 1.67 1.40 0.24 1.47 Example 3 0.04 1.68 1.41 0.26 1.47 Example 4 0.04 1.68 1.41 0.25 1.47 Example 5 0.04 1.66 1.47 0.26 1.45

[0038]

The methods of the quality performance tests listed in Tables 1 and 2 above are as follows. 1) Background: The uncolored sample was measured using a Macbeth reflection densitometer R
A value measured with a D-914 model (Macbeth reflection density). 2) Coloring density: The printing density (Macbeth reflection density) of a sample printed using a commercially available POS label printer with the printing energy of normal use. 3) Coloring density: The printing density of a sample printed with the printing energy for high-speed use of the above printer. 4) Heat resistance: 0.098MPa hot plate at 100 ° C
(1 kg / cm2) under a printing pressure of 1 sec.
Every time). 5) Water resistance: Residual rate (%) of print density after immersing a sample printed by the above printer in tap water at room temperature for 15 hours. 6) Plasticizer resistance: The sample printed by the above printer was converted to PV
0.0294MPa for C wrap film on both sides
Percentage of print density remaining (%) after standing at room temperature for 24 hours under a load of (300 g / cm2). 7) Oil resistance: Residual rate (%) of print density after applying salad oil on a sample printed by the above printer and leaving it at room temperature for 24 hours.

As is clear from the table, the heat-sensitive recording material of the present invention is excellent in color developability, and excellent in heat resistance of the background portion against heat, water resistance of the color developed portion, plasticizer resistance, oil resistance, etc. I have.

[0041]

According to the present invention, there is obtained a heat-sensitive recording material which is excellent in coloring properties, has little background fogging against heat, and has excellent storage stability such as water resistance, plasticizer resistance and oil resistance.

Claims (2)

[Claims] 1. A heat-sensitive recording material comprising a support and a heat-sensitive color-forming 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. Wherein the thermosensitive coloring layer is represented by the following formula (1) as a coloring compound: (In the formula (1), X represents a halogen atom, and Y represents 4 carbon atoms.
The following alkyl groups are represented. ) Is represented by bis (3-allyl-4-hydroxyphenyl) sulfone as a color-developing compound and the following formula (2): (In the formula (2), R1 represents an alkyl group or cyclohexyl group having 4 or less carbon atoms, and R2 represents an alkyl group having 4 or less carbon atoms). A heat-sensitive recording material comprising bis (3,4-dimethylphenyl) ethane. 2. The heat-sensitive recording material according to claim 1, wherein an intermediate layer is provided between the heat-sensitive coloring layer and the support.