JPS62101490A - Liquid composition for thermal recording sheet - Google Patents

Abstract

PURPOSE:To suppress development of ground color and ground contamination and enhance plasticizer resistance, by heating a specified color forming compound, a water-soluble high molecular weight compound and water in the presence of an alkaline compound in a specified temperature range. CONSTITUTION:An unground mixture of a colorless or light-colored color forming compound capable of forming a color by reacting with a phenolic compound, a water-soluble high molecular weight compound and water is prepared, and is ground to such an extent that the average particle diameter of the color forming compound becomes not larger than 2mum. An alkaline compound is added to the aqueous mixture thus pulverized to adjust the pH to 8-11, and a heating treatment is carried out at a temperature of 40-100 deg.C with agitation. The treatment is carried out for 10min-3hr, and it is ordinarily sufficient to carry out the treatment for 30-60min.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a heat-sensitive recording material.

More specifically, the present invention relates to a liquid composition containing a colorless to light-colored color-forming compound for preparing a heat-sensitive recording sheet that has little background coloration and has excellent preservability of colored images, especially resistance to abrasive agents.

Conventional technology Conventionally, thermal recording sheets, such as thermal recording paper, have been made by coating paper with an aqueous coating solution containing a colorless or light-colored color-forming compound, a phenolic compound, a binder, etc., and other additives in the form of fine particles. It is manufactured by coating on plastic sheets, etc.

The heat-sensitive recording sheet obtained in this way tends to have a phenomenon in which the coated surface becomes naturally colored during storage, and this phenomenon is known as "ground coloring" or "background staining." As a method to prevent such a phenomenon,
No. 164191 proposes a method in which a dispersion of a color-forming compound (leuco dye) is heat-treated at 50 to 100°C, and after cooling is mixed with a phenolic compound dispersion to obtain a coating liquid. Furthermore, Japanese Patent Laid-Open No. 57-195692 proposes a method using a coating liquid obtained by mixing a heat-treated liquid of a specific fluoran compound with a color developer liquid.

Problems to be Solved by the Invention The above-mentioned methods do not sufficiently improve background color development and background stains.In particular, in line with the recent demand for higher sensitivity of heat-sensitive recording materials, highly sensitive color-forming compounds have been developed. When used, the effect is not particularly sufficient.

On the other hand, thermosensitive recording sheets tend to cause a phenomenon in which the colored recorded images are erased by the dyes contained in the plastic sheets and the like.

Under the above circumstances, in order to obtain more stable thermally recorded images, it is desired to develop a thermal recording sheet that has improved background color development and background staining, and has high anti-soak properties.

Means for Solving the Problems The present inventors have completed the present invention as a result of various studies aimed at improving the above-mentioned drawbacks. That is, the present invention consists of a colorless to light-colored color-forming compound that develops color by reacting with a phenolic compound, water and a water-soluble polymer compound, and is heat-treated at a temperature of 40 to 100°C in the presence of an alkaline compound. A liquid composition for a heat-sensitive recording sheet is provided.

The present invention will be described in detail.

In the present invention, for example, an unpulverized mixture consisting of a color-forming compound, a water-soluble polymer, and water is prepared, and the particle size of the color-forming compound after being pulverized using a ball mill, sound grinder, attritor, paint conditioner, kneader, etc. Grind to an average particle size of 2μ or less. The above mixture contains 5 to 70 parts by weight of the color-forming compound, preferably 10 to 50 parts by weight, and 0.1 to 20 parts by weight of the water-soluble polymer compound.
The proportion is adjusted to be 0.5 to 10 parts by weight, preferably 0.5 to 10 parts by weight, and the remainder (100 parts by weight in total). To the aqueous mixture thus finely ground, an alkaline compound as described below is added until the pH of the treatment liquid becomes 8 to 11 (usually 0.01 to 10 parts by weight based on the above mixture).
The treatment is carried out at 0 to 100°C, preferably 50 to 80°C, with stirring. Processing time is 10 minutes to 3 hours, usually 30 to 6 hours.
0 minutes is enough.

As mentioned above, heat treatment in the presence of an alkaline compound is conveniently carried out after pulverizing a mixture consisting of a color-forming compound, a water-soluble polymer compound, and water. An alkaline compound may be added to a mixture consisting of a polymer and water to carry out hot pulverization treatment, or a method of pulverizing under heating and adding an alkaline compound during the pulverization may be adopted as necessary.

(A) Color-forming compound (B) Water-soluble polymer compound (C) that can be used in the present invention
Specific examples of alkaline compounds are given below.

(A) Rhodamine-β-anilinolactam, rhodamine (p-nitroanilino)lactam, 2-dibenzylamino-6-diethylaminofluorane, 2-anilino-6-methyl-6-dini as color-forming compound xanthine compound thylamino-fluorane, 2-anili-3-methyl-6-cyclohexylmethelaminofluorane, 2-anilino-6-methyl-6-itubentylethylaminofluorane, 2-
Anili-3-methyl-6-sibutylaminofluorane, 2-p-chloroanilino-3-methyl-6-diethylaminofluoran, 2-p-fluoroanilino-3-methyl-6-dinithylaminofluorane, 2- p-Fluoroanilino-3-methyl-6-diptylaminofluorane, 2-anilino-3-methyl-6-(p-)luidinoether)aminofluorane, 2-p-toluidino-5-
Methyl-6-diethylaminofluorane, 2-0-chloroanilino-6-diethylaminofluorane.

2-0-chloroanilino-6-sibutylaminofluorane, 2-lofluoroanilino-6-diethylaminofluorane, 2-lofluoroanilino-6-sibutylaminofluorane, 2-m-chloroanilino-6- Diethylaminofluorane, 2-anilino-3-methyl-6-
Piperidinofluorane, 2-anilino-5-methyl-6
-pyrrolidinofluorane, 2-m-trifluoromethylanilino-6-diethylaminofluorane, 2-dihexylamino-6-diethylaminofluorane.

2-Butylamino-3-chloro-6-diethylaminofluorane, 2-ethoxyethylamino-3-chloro6
-Dietheraminofluorane-2-anilino-3-chloro-6-diethylaminofluorane, 2-diphenylamino-6-diethylaminofluorane, 2-anilino-
6-Methyl-6-siphenylaminofluorane, 2-phenyl-6-diethylaminofluorane, 2-chloro-
3-Methyl-6-diethylaminofluorane, 2-chloro-6-diethylaminofluorane, 2-methyl-6-
Diethylaminofluorane, 6-diethylamino-1,
5,5-bis(p-dimethylaminophenyl) as a triarylmethane compound such as 2-benzfluorane
-6-dimethylaminophthalide (also known as crystal violets) lactone)S3,3-bis(p-dimethylaminophenyl)phthalide, 3-(1)-dimethylaminophenyl)-5-(1,2- 3 as spiropyran compounds such as dimethylaminoindol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-3-(2-methylindol-5-yl)phthalide, chromenes, etc.
-Methyl-3-spiro-dinaphthopyran, 6-benzylspiro-dinaphthopyran, '5-methernaphtho (3
-methoxy-benzo)spiropyran, 6-propyl-spiro-dibenzobilane, 1,5,5-trimethyl-
6'-nitro 8'-methoxyspiro (indoline-2
, 2'-benzobilane).

1,3,3-trimethyl-6'-nitrospiro (indoline-2,2'-benzobilane), 4,4'-bis-dimethylaminobenzhydrin benzyl ether as a diphenylmethane compound, N-halophenyl-leucoola Examples include benzoyl leucomethylene blue and p-nitrobenzyl leucomethylene blue as thiazine compounds, N-2,4,5-trichlorophenyl leuco auramine, and the like. These leuco dyes may be used alone or in combination.

carboxymethyl, sodium carboxymethyl cellulose, cellulose, polyvinyl alcohol.

Carboxy group-modified polyvinyl alcohol, sulfonic acid group-modified polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid.

Starch and its derivatives, casein, gelatin.

Alkaline salt of styrene-maleic anhydride copolymer (in
or water-soluble ones such as alkali salts of diiso)butylene-maleic anhydride copolymers, polyvinyl acetate, vinyl chloride/vinyl acetate copolymers, polystyrene, polyacrylic esters, polyurethanes, styrene/butadiene/
A water-soluble emulsion such as an acrylic acid copolymer is used.

(C) Alkaline compounds Sodium carbonate, potassium carbonate, ammonium carbonate, sodium hydrogen carbonate, ammonium hydrogen carbonate, aqueous ammonia, sodium hydroxide, potassium hydroxide, calcium hydroxide, etc. are used.

The liquid composition of the present invention obtained as described above is mixed with a finely divided phenolic compound as a color developer and a binder according to a conventional method to form a coating solution, which is then coated with paper.
A thermosensitive recording sheet is prepared by coating a plastic sheet, synthetic paper, etc., and the usual method for preparing a coating liquid is as follows.

First, the color developer is crushed together with a water-soluble polymer, and then the ratio of the color-forming compound to the color developer is 1:1 to 1:10 (by weight).
A coating solution is prepared by mixing a color forming compound (color developer) as in step 7 and adding a binder. The coating solution may also contain sensitizers such as waxes (e.g. paraffin wax, polyethylene wax), biphenyls (e.g. parabenzylbiphenyl), fatty acid amides (e.g. stearic acid amide), and fillers (e.g. clay, talc, Calcium carbonate, kaolin), antifoaming agents, etc. can also be added.

Apply the coating solution obtained in this way on a sheet of paper, Plastic Snote 1 synthetic paper, etc. for 5 to 40 fflrr. Apply with a bar coater etc. so that

Dry to obtain a heat-sensitive recording sheet.

EXAMPLES The present invention will be explained in more detail by way of examples. In the example “
"Parts" indicates parts by weight.

Example 1 Using a sound grinder, use the following composition.

= 10- The color-forming compound was ground until the average particle size was 0.4 μm (liquid [A]).

To 100 parts of the above-mentioned pulverizing liquid, 0.1% aqueous sodium carbonate solution.
After stirring at SO~85°C for 30 minutes, the composition of the present invention was obtained (
(A-1) liquid).

The following composition was ground for 50 minutes using a sound grinder (solution [B]).

Next, 8 parts of liquid (A-1), 70 parts of liquid [B], 5 parts of carphokyfur modified sB latex emulsion (solid content 48%)
Prepare a coating solution by mixing 17 parts of water and 17 parts of water, weighing 5 parts.
Liquid volume 301/rr on 01/- high quality paper? A heat-sensitive recording sheet using the composition of the present invention was obtained by coating and drying so as to give the following composition.

Example 2 The following composition was ground using a sound grinder until the average particle size of the color-forming compound was 0.7P (liquid [C]).

10% potassium carbonate aqueous solution 0.5 to 100 parts of the above pulverized liquid
After stirring for 30 minutes at 70-75°C (pHq),
The composition of the present invention was obtained by cooling to room temperature ((C-1)
liquid).

The following composition was ground using a sound grinder.

Next, (8 parts of C-1E liquid, 72 parts of [D] liquid, 5 parts of carboxyl-modified SB latex emulsion (solid content 48%)
Prepare a coating solution by mixing 15 parts of water and 15 parts of water, weighing 5 parts.
Is the liquid volume 30t/rr on 0f/- high quality paper? A heat-sensitive recording sheet using the composition of the present invention was obtained by coating and drying so as to give the following composition.

Example 3 2 parts of 28% ammonia water was added to 100 parts of the pulverized liquid of Example 2 (pH 1o to 11), stirred at 60 to 65C for 1 hour, and then allowed to cool to room temperature to obtain a composition of the present invention. ( (
C-2) Liquid).

In place of the (C-1) solution in Example 2, this [:C-2)
A heat-sensitive recording sheet using the composition of the present invention was obtained in the same manner as in Example 2 except that the liquid was used.

13 Example 4 A mixture of the following compositions was prepared using a sound grinder.
The composition of the present invention was obtained by grinding at a temperature of 50° C. for 30 minutes (liquid [E]).

Next, 8 parts of CF') solution and 70 parts of [B] solution of Example 1.

A coating solution was prepared by mixing 5 parts of carboxyl-modified EIB latex emulsion (solid content 48%) and 17 parts of water, and the weight was 50 f/yt? The amount of liquid on the surface of the high-quality paper is 30
A heat-sensitive recording sheet using the composition of the present invention was obtained by coating and drying so as to give a ratio of 1/-.

Example 5 A mixture consisting of the following composition was ground using a sound grinder at a temperature of 60 to 70°C for 4 hours to obtain a composition of the present invention (liquid [F]).

A heat-sensitive recording sheet using the composition of the present invention was obtained in the same manner as in Example 4 except that liquid CF) was used instead of liquid (F') in Example 4.

Comparative Example 1 A comparative heat-sensitive recording sheet was obtained in the same manner as in Example 1 except that liquid [A] was used instead of liquid (A-1) in Example 1.

Comparative Example 2 Liquid [A] was used instead of liquid (A-1) in Example 1 at 80 to 8
A comparative heat-sensitive recording sheet was obtained in the same manner as in Example 1, except that a liquid obtained by stirring at 5° C. for 30 minutes and cooling was used.

Comparative Example 6 A comparative heat-sensitive recording sheet was obtained in the same manner as in Example except that liquid [C] was used instead of liquid (C-4) in Example 2.

Comparative Example 4 A comparative heat-sensitive recording sheet was obtained in the same manner as in Example 4, except that the mixture in which 10% sodium carbonate was not added to the composition of Example 4 [E] was heat-treated.

Comparative Example 5 A comparative heat-sensitive recording sheet was obtained in the same manner as in Example 5, except that the mixture in which 10% sodium carbonate was not added to the composition of Example 5 [F] was heat-treated.

The quality performance test described below was carried out using a thermal recording sort using the composition of the present invention obtained as described above and a thermal recording sheet for comparison.

Table/Quality performance test results 1) Background color development The background of the uncolored thermal record 7-t was measured using a Macbeth reflection densitometer RD-914.

2) Color Density The density of the color developed using a commercially available thermal printer was measured with a Macbeth reflection densitometer RD-914.

5) Agent resistance: P on both sides of the colored heat-sensitive recording sheet.
Layer VC wrap film.

As is clear from the table, the thermal recording sheet prepared using the composition of the present invention has a higher level of retention than the comparative thermal recording sheet. Excellent background color development and dye resistance of colored images.

Effects of the Invention A liquid composition containing a color-forming compound for preparing a heat-sensitive recording sheet with low background color development, low background smearing, and excellent anti-soaking agent resistance of the colored image was obtained.

Patent applicant: Nippon Kayaku Co., Ltd. 118 completed-

Claims (1)

[Claims] 1. It consists of a colorless to light-colored color-forming compound that develops color by reacting with a phenolic compound, a water-soluble polymer compound, and water, and is heat-treated at a temperature of 40°C to 100°C in the presence of an alkaline compound. Characteristic liquid composition for heat-sensitive recording sheets