JPH0323986A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enhance light fastness by incorporating a specific compound in a thermal recording material wherein a thermal color forming layer based on a leuco dye and a coupler is provided on a support. CONSTITUTION:A color forming compound, a coupling compound and compounds represented by formulae (I), (II) are separately ground and dispersed along with a binder and, if necessary, other additives by a dispersing machine such as a ball mill attritor or a sand mill and the resulting dispersions are mixed to prepare a coating solution for a thermal color forming layer and this coating solution is applied to a support such as paper, a plastic sheet or synthetic paper in an amount of 5 - 40g/m<2> by a bar coater or a blade coater and dried. This thermal recording material containing the compounds represented by the formulae (I), (II) becomes markedly excellent in the light fastness of its background and that of a developed color image by the synergistic action of the oxidation inhibiting action of the compound represented by the formula (I) and the ultraviolet absorbing action of the compound represented by the formula (II).

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material with excellent opacifying properties.

Prior 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 Japanese Patent Publication No. 43.
It was published in Japanese Patent Publication No. 4514039 and has been widely put into practical use.

Generally, heat-sensitive recording materials are produced by separately dispersing a leuco dye and a color developer such as a phenolic substance into fine particles.
Mix the two and add a binder and, if necessary, additives such as sensitizers, fillers, and lubricants to make a coating liquid, which is applied to a support such as paper, film, or synthetic paper and heated. A color record is obtained by a chemical reaction that occurs when one or both of a leuco dye and a color developer melt and come into contact with each other.
A heat-sensitive recording material is prepared.

A thermal printer or the like equipped with a built-in printer is used to color the heat-sensitive recording sheet.

Compared to other recording methods, this thermal recording method (1) produces less noise during recording; (2) There is no need for development and fixing. (3
) Maintenance free. (4) Due to the relatively low cost of the machine, it is widely used in the field of facsimiles, computer output printers, printers such as calculators, recorders for medical measurement, automatic ticket vending machines, thermal recording labels, etc. It is used.

In recent years, with the introduction of POS systems in retail stores and supermarkets, the use of heat-sensitive sheets for labels and price tags has increased, and the targets range from items with a short shelf life, such as fresh foods and daily items, to everyday items. It has begun to be used for everyday necessities and luxury goods as well as shelf goods.

However, although the heat-sensitive labels found on conventional fresh foods and daily items have sufficient storage properties such as water resistance, solubilizing agent resistance, and oil resistance, their light resistance is insufficient, and they cannot be exposed to sunlight or for long periods of time. There is a drawback that the printing on the label becomes blurred or disappears under lighting. This phenomenon is also seen when colored thermosensitive sheets 1, facsimile receiving paper, etc. are left on a desk or the like, and is considered to be a problem in terms of document preservation.

Solving this problem is a major technical challenge in heat-sensitive labels and price tags for products that are displayed over long periods of time in thermal recording sheets 1, η, and 7.

Problems to be Solved by the Invention In a heat-sensitive recording material comprising a support provided with a heat-sensitive recording color-forming layer containing a color-forming compound and a color-developing compound as main components, improved light resistance is desired.

Means for Solving the Problems As a result of intensive research to improve the above-mentioned drawbacks of heat-sensitive recording materials, the present inventors have developed a heat-sensitive recording material containing a leuco dye and a color developer as main components on a support. The following formula (I
) and (I]) The present invention provides a heat-sensitive recording material characterized by containing the compounds represented by (1) and (I).

In addition, R2 represents a methyl group or an ethyl group) (in the formula (sha),
R3 represents hydrogen or halogen; R4. R5 each independently represents hydrogen, methyl group, t-butyl group, t-octyl group,
t-amyl group or octoxy group) The heat-sensitive recording material of the present invention combines the compounds represented by the formulas (I) and (I) with (4) a color-forming compound as shown below, (
B) A color developing compound (obtained by incorporating it into a thermosensitive coloring layer together with a Q binder and other optional fillers, thermofusible compounds, other additives, etc.) The total amount of compounds in the heat-sensitive coloring layer is 1 to 50% by weight,
Preferably 5 to 20%, the usage ratio of the compound is (
It is used in a weight ratio of I):(rl)-10:1 to 1:10, preferably CI):01)-5-5 =1 to 1:5.

Specific examples of the compound represented by the formula (I) include 2,2'-methylenebis(4-methyl6-t-butylphenol), 2,2-methylenebis(4-ethyl-
6-t-butylphenol), 2,2-methylenebis(4-methyl-6methylcyclohexylphenol), and the like.

Further, specific examples of the compound represented by the formula (2) include 2-(2'-hydroxy-5'-methylphenyl)-hensotriazole, 2-(2'-hydroxy-
315'-t-butylphenyl)5-chlorobenzotriazole, 2-(2hydroxy-3-t-butyl-5-methylphenyl)-5-chlorobenzotriazole, 2(2'-hydroxy-5-1-octylphenyl) enil)
Pensotriazole, 2-(2'-hydroxy 4-octoxyphenyl)-benzotriazole, 2-( 2'
-Hydroxy-315'-di-t-butylphenyl)-benzo-1-lyazole, 26 (2-hydroxy-315'-di-t-amylphenyl) and other additives include the following.

(4) Rhodamine β-anilinolactam, rhodamine (p-nitroanilino)lactam as a color-forming compound xanthene compound,
2-dibenzylamino-6-diethylaminofluorane, 2-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6-cyclohexylmethylaminofluorane, 2-anilino-3-methyl-6
-isopentylethylaminofluorane, 2-anilino3-methyl-6-dibutylaminofluorane, 2-. −
p-chloroanilino-3-methyl-6 diethylaminofluorane, 2-p-fluoroanilino-3-methyl-6
-diethylaminofluorane, 2-p-fluoroanilino3-methyl-6-dibutylaminofluorane, 2-anilino-3-methyl-6-(p-1.luidinoethyl)
Aminonluorane, 2-1) 1-luidino 3-methyl-6-diethylaminofluorane, 2-0-chloroanilino-6-diethylaminofluorane, 2-0-chloroanilino-6-dibutylaminofluorane, 2-O-fluoro Anilino-6-dietheraminofluorane, 2-0
-Fluoroanilinite-dibutylaminofluorane, 2
-mchloroanilino-6-diethylaminofluorane,
2-anilino-3-methyl-6-piperidinofluorane, 2-anilino-3-methyl-6-pyrrolidinofluorane, 2-m-trifluoromethylanilino-6-diethylaminofluorane, 2-dihexylamino- 6-aminofluorane, 2-butylamino-3chloro-6-diethylaminofluorane, 2-ethoxyethylamino-3-
Chloro-6-diethylaminofluorane, 2-anilino-
3-chloro-6-diethylaminofluorane, 2-diphenylamino-6-diethylaminofluorane, 2-anilino-3-methyl 6-diphenylaminofluorane,
2-phenyl-6-diethylaminofluorane, 2-chloro-3-methyl-6-diethylaminofluorane, 2
3,3-bis(p-dimethyl Aminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone), 3.3-bis(p-dimethylaminophel)phthalide, 3-(p-dimethylaminoneenyl)-3-(1.2- Dimethylaminoindol-3-yl)phthalide, 3-(pdimethylaminophenyl) -. -3-(2-methylindole-3-
39 as spiropyran compounds such as il) phthalides, chromenes, etc. Chil-3-svirodinaphthopyran, 3-benzylspiro-dinaphthopyran, 3-methylnafur l- - (
3-Me1-xy-benzo)spirobilane, 3-globy-spirodibenzopyran, 1, 3. 3-}limethyl-6-nitro8-me1-xisbilo (indoline-22-penzopyran), ]. , 3. 3-1-limethyl-6'121-rosviro (indoline-2,2-
penzopyran), 4,4-bis-dimethylaminopenzhydrin benzyl ether as a diphenylmethane compound, ■-halophenylleucoauramine, N
-2. 4. Bis-3. 3-C bis-1,
1-(p-dimethylaminophenyl)ethyleno-2]fuclide, bis-3. 3-[bis-11-(p-dimethylaminophenyl)ethyleno-21-4.5,6.
7-te1 laclorofuclide, 10 bis-33-[bis-1. 1-(p-diethylaminophenyl)ethyleno-21-4.5,6.7 tetrachlorophthalide, bis-3. 3- [Bis-11-
(p-dimethylaminophenyl)ethyleno-2)-4(
or 7) Dipinyl group-containing phthalide derivatives such as mononitrophthalide, 3,6-bis(dimethylamino)fluorene spiro(9.3')-6'-dimethylaminophthalide, 36-bis(diethylamino)fluorene spiro
(9.3') Fluorene compounds such as -6-diethylaminophthalide may also be used.

These color-forming compounds may be used alone or in combination.

(B) Color-developing compound α-naph-1·-l, β-naph-1·-l, p-octylphenol, 4-t-octylphenol, p f-butylphenol, p-phenylphenol, l. ,1'
-bis(p-hydroxyphenyl)propane, 2.2'
-bis(p-hydroxyphenyl)propane, 2.2-
Bis(p-hydroxyphenyl)butane, 1.1bis(
p-hydroxyphenyl)cyclohexane, 4.4-thiobisphenol, 4.4-cyclohexylidene diphenol, d,4-sulfonyldiphenol, 44-sulfonylbis(2-allylphenol), 2.2'- Phenolic compounds such as bis(2,5-cyfurome-4-hydroxyphenyl)propane, 4,4-impropylidenebis(2t-butylphenol), 2,2'-methylenebis(4-chlorophenol), p -Benzyl hydroxybenzoate, ethyl p-hydroxybenzoate, dibenzyl 4-hydroxyphthalate, dimethyl 4-hydroxyphthalate, ethyl 5-hydroxyisophthalate, 3,5
Examples include aromatic carboxylic acid derivatives such as -di-t-butylsalicylic acid and 3,5-di-α-methylbenzylsalicylic acid, aromatic carboxylic acids or polyvalent metal salts thereof.

(Q Binder Methylcellulose, Methoxycellulose, Hydroxyethylcellulose, Carboxymethyl, Sodium carboxymethylcellulose, Cellulose, Polyvinyl alcohol (PVA), Carboxy group-modified polyvinyl alcohol, Sulfonic acid group-modified polyvinyl alcohol, Polyvinylpyrrolidone, Polyacrylamide , polyacrylic acid, starch and its derivatives, casein, gelatin, water-soluble isobrene rubber, alkali salts of styrene/maleic anhydride copolymers, and water-soluble ones such as alkali salts of iso(or diiso)butylene/maleic anhydride copolymers. Or polyvinyl acetate, vinyl chloride/vinyl acetate copolymer, polystyrene, polyacrylic ester, polyurethane, styrene/butadiene copolymer, carboxylated styrene/phtadiene copolymer, styrene/butadiene/acrylic acid copolymer, A water-soluble emulsion such as composite particles of colloidal silicon and acrylic resin is used.

13- Examples of other additives Examples of fillers include calcium carbonate, magnesium carbonate, magnesium oxide, silica, white carbon, talc, clay alumina, magnesium hydroxide, aluminum hydroxide, aluminum oxide, barium sulfate, polystyrene resin, Examples include urea and formalin resin.

Examples of the thermofusible compound include waxes such as animal and vegetable waxes, polyethylene waxes, and Gakkai waxes, higher fatty acids, higher fatty acid amides, and compounds that are solid at high temperatures and have a melting point of about 80° C. or higher.

Other lubricants such as zinc stearate, calcium stearate, aluminum stearate, various surfactants,
Antifoaming agents and the like are added as necessary.

The heat-sensitive recording material of the present invention is prepared using the above material, for example, by the following method.

14 That is, first, the color-forming compound, the color-developing compound, and the compounds of the formulas (I) and (self) are separately treated in a ball mill, sand mill, etc. with a VC binder or other additives as necessary. Grind with a disperser,
After being dispersed (the compounds of the above formulas (D) and (I) may be mixed in advance with a color-forming compound or a color-developing compound for dispersion), a heat-sensitive color-forming layer coating solution is prepared. Usually 5-4. 0 g/m2 using a bar coater blade coater or the like (the ratio of the color-forming compound to the color-developing compound is usually 1:1 to 1:10 in terms of dry weight), and dried to form the heat-sensitive recording material of the present invention. Get the materials.

The heat-sensitive recording material of the present invention containing the compounds of the formulas (I) and (I) has the synergistic effect of the antioxidant action of the compound of the formula (I) and the ultraviolet absorbing action of the compound of the formula (I). The light resistance of the background and colored images is much better than that of the original.

EXAMPLES The present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples.

In the examples, "parts" indicate parts by weight.

Example 1 A mixture having the following composition was ground and dispersed using a sand grinder so that the average particle size was 2 μm or less [A]
, [B), C (J and CD) solutions were prepared.

Next, a heat-sensitive coloring layer coating solution was prepared with the following mixing ratio,
A liquid volume of 30 g/m on high-quality paper with a basis weight of 50 g/m
The heat-sensitive recording material of the present invention was obtained by coating and drying to give a coating thickness of m2.

Thermosensitive coloring layer coating liquid: [A] liquid 10 parts [B] 2
0〃 [C]〃 10〃 [D]〃5〃 20% methylol stearamide dispersion 2 Q
rt50% calcium carbonate dispersion 1 0 tt40%
Acrylic resin emulsion 5 water
20 Example 2. 2-(2-hydroxy-
A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1, except that a liquid obtained by pulverizing and dispersing 3(5-di-t-phthylphenyl)-benzotriazole was used.

Example 3 2-(2-hydroxy-
A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1, except that a liquid obtained by pulverizing and dispersing 3'-t-phthyl-5'-methylphenyl)5-chlorobenzotriazole was used.

Example 4. Grind and disperse a mixture with the following composition using a sand grinder so that the average particle size is 2 μm or less [E],
[F] and [G] solutions were prepared.

18 Next, prepare a heat-sensitive coloring layer coating solution obtained with the following mixing ratio,
The liquid was applied to a high-quality paper with a basis weight of 50 g/m2 at a liquid amount of 30 g/m2, and dried to obtain a heat-sensitive recording material of the present invention.

Thermosensitive coloring layer coating liquid: [A] liquid 10 parts [:E:]”
20p [F]〃 20〃 [C]〃 10〃 [G''] rt 5A 48% boristyrene dispersion 10〃40% acrylic resin emulsion 5〃Water
20 Example 5. 2,2-methylenepis (
A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 4, except that a liquid obtained by pulverizing and dispersing 4-ethyl-6-t-butylphenol was used.

Example 6. 22-methylenebis(4
A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 4, except that a liquid obtained by pulverizing and dispersing methyl-6-methylcyclohexylphenol was used.

Example 7 A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 4, except that 5 parts of liquid [C] and 10 parts of liquid [G] of Example 4 were used.

Comparative example 1. Comparative heat-sensitive recording material strips were obtained in the same manner as in Example 4, except that liquids [C] and [D] of Example 1 were not used.

Comparative example 2. A comparative heat-sensitive recording material was obtained in the same manner as in Example 4, except that liquid [C] was not used in Example 1.

Comparative example 3. In Example 1, a comparative heat-sensitive recording material was obtained in the same manner as in Example 4 except that the DE liquid was not used.

Quality tests were conducted using these heat-sensitive recording materials of the present invention and comparative heat-sensitive recording materials, and the results shown in Table 1 were obtained.

Table 1 Quality test results 21 l) Background Unprinted sample with Macbeth reflection densitometer R
The value determined by the D-914 model.

2) Color Density The density of a sample printed with a commercially available thermal printer (D-805P, manufactured by Ishida Kouki) was measured using a Macbeth reflection densitometer RD-914.

3) Light resistance test When the unprinted and printed samples were left under a fluorescent light with an illuminance of ■10,000 lux for one month, the density before and after being left was measured using a Macbeth reflection densitometer.

As is clear from the above quality tests, the light resistance of the background and colored images of the heat-sensitive recording material of the present invention is significantly improved by containing the compounds of the formulas (■) and (ID).

Effects of the Invention A heat-sensitive recording material containing a color-forming compound and a color-developing compound as main components has improved light resistance of the background and color-forming image.

22

Claims (1)

[Scope of Claims] 1. Compounds represented by the following formulas (I) and (II) in a heat-sensitive recording material in which a heat-sensitive recording color-forming layer containing a color-forming compound and a color-developing compound as main components is provided on a support. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (In formula (I), R_1 is a t-butyl group or ▲There are mathematical formulas, chemical formulas, tables, etc.▼ groups. , and R_2 represents a methyl group or an ethyl group) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (
II) (In formula (II), R_3 is hydrogen or halogen, and R_4
, R_5 each independently represents hydrogen, methyl group, t-butyl group, t-octyl group, t-amyl group or octoxy group)