JPS62278086A - Thermal recording sheet - Google Patents

Abstract

PURPOSE:To obtain a thermal recording sheet free of hindrance to color development or lowering in sensitivity on a thermal color forming layer, having favorable printing quality and highly resistant to chemicals, by incorporating a compound having one glycidyl group in its molecule and being solid at normal temperature into an overcoat layer. CONSTITUTION:At least one compound having one glycidyl group in its molecule and being solid at normal temperature is incorporated into an overcoat layer, in a thermal recording sheet in which a thermal color forming layer comprising a colorless or light-colored dye precursor and a color developer for developing the color of the dye precursor by reacting therewith when being heated as main constituents is provided on a base, and the overcoat layer comprising a water-soluble high molecular weight substance as a main body is provided on the color fomring layer. The compound is preferably a difficultly water-soluble one, and an aromatic compound or a sulfur- containing compound is useful as the compount. A base material for forming the overcoat alyer is preferably a graft compolymer of an acrylic monomer, at least one such copolymer being used either singly or in combination. The amount of the compound added to the overcoat layer is suitably at least 0.5 wt.%, preferably, 1-60 wt.%, from the viewpoints of chemical resistance, color forming sensitivity and printability.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (A) Industrial Field of Application The present invention relates to a heat-sensitive recording material whose main components are a dye precursor and a color developer that develops color when the dye precursor is heated. The present invention relates to heat-sensitive recording sheets used in facsimile machines, various printers, labels, tickets, etc., which prevent deterioration due to chemicals in the blank areas and colored areas.

(B) Prior art and its problems Heat-sensitive recording paper consists of (1) a substrate coated with carbon or colored dyes and pigments, and an opaque thermofusible substance coated on top of that; υ A method in which the opaque layer becomes transparent and an image is formed by the colored layer underneath. (2) Method of forming a complex compound between a stain donor and an electron acceptor by heat. (3) There is a method in which a dye precursor such as crystal violet lactone and an acidic color developer such as a phenol compound are dispersed and applied discontinuously, and one or both are dissolved by heating to develop color.

Of these, method (3) is used in general facsimile machines, printers, etc. because it is superior overall in terms of image clarity, resolution, image color tone, and problem with dust.

The characteristics required for this type of thermal recording paper include, of course, sensitivity suitable for various uses, a white background, long-term stable colored images that do not fade, and There is no generation of residue, no adhesion (sticking) to the thermal head during recording, etc. Excellent products that meet many of these requirements can be manufactured, but in terms of practical handling after recording, if they come into contact with erasers or vinyl chloride bags containing large amounts of plasticizers, hand creams or hair styling products may be difficult to handle. If you touch it with a hand that has paint oil on it, if you overlap it with diazo photosensitive paper that has just been developed, or if you write underlines etc. with a highlighter, the image will disappear (1) and the background will become colored and fogged. , there is a drawback that it becomes difficult to read the recorded image. This color-fading phenomenon is caused by the lactone ring of the color-forming lactone compound ring-opened with an acidic color developer, and the lactone ring of the color-forming lactone compound that is ring-opened with an acidic color developer. This is thought to be due to ring closure in the presence of . It is also believed that the Capri phenomenon is caused by the developer of the diazo photosensitive paper and the solvent contained in the highlighter pen dissolving the color developer and bringing it into contact with the dye precursor to cause a color reaction.

Therefore, it has been proposed that this phenomenon can be prevented by forming a film on the thermosensitive recording paper to prevent the penetration of plasticizers and the like. (Japanese Patent Application Laid-open Nos. 54-128347, 1982-3549) The present inventors also developed an oat glue coating agent with chemical resistance and filed a patent application in 1982-182.
No. 557 and Japanese Patent Application No. 56-981.

However, in the past, satisfactory chemical resistance could not be obtained unless the coating film of the overcoat layer was applied with a slightly thick coating. Therefore, it is not only undesirable that it requires a long drying time and that the speed of smearing cannot be increased, which causes production problems, but also causes a decrease in sensitivity. especially,
Recently, as there has been a trend towards high-speed printing, it has become necessary to reduce the thickness of the coating, which is the biggest factor in heat loss, as much as possible, and various methods have been proposed to improve the coating properties. ing. (Japanese Patent Application Laid-open No. 58-188689, JP-A No. 60-154095) However, under extremely harsh conditions such as contact with various chemicals such as extremely high temperature and high humidity9, and for a long period of time, Penetration and diffusion into the film cannot be completely prevented, and the image may partially fade, or the image may not fade, but
The blank area becomes colored. There is also a method of adding an oil repellent or the like, but in many cases this greatly deteriorates print quality due to inhibition of color development and reduction in sensitivity, and so far no satisfactory results have been obtained.

(C) Object of the Invention The object of the present invention is to provide a heat-sensitive recording sheet with good print quality and strong chemical resistance, which has an overcoat layer on the heat-sensitive coloring layer that does not inhibit color development or reduce sensitivity. There is a particular thing.

(D) Structure of the Invention The present invention provides a heat-sensitive coloring layer on a support, the main components of which are a colorless to light-colored dye precursor and a color developer that reacts with the dye precursor when heated to develop a color. In a heat-sensitive recording sheet further provided with an overcoat layer mainly composed of a water-soluble polymer, in the overcoat layer,
The present invention relates to a heat-sensitive recording sheet characterized by containing at least one compound having one glycidyl group in the molecule and being solid at room temperature.

Examples of the compounds according to the present invention include the following.

Compound (1) Compound (3) m, p, = 45-48°C Compound (4) Compound (5) m, p, = 34-35°C Compound (6) m, p, = 47-48°C Compound (7 ) m, p, = 58-60°C Compound (8) m, I), = 98-99°C Compound (10) Compound (11) Compound (14) Compound (15) Compound (16) Compound (17) Compound ( 18) Compound (19) Compound (20) Compound (21) Compound (24) Compound (27) Compound (28) Compound (29) Compound (30) Compound (32) Compound (33) Compound (34) Compound (35) Compound (36) Compound (37) Compound (38) ITl, p, = 152-153°C Compound (39) O2 Compound (40)! 1 Compound (41) Compound (42) Compound (43) Compound (44) The compound according to the present invention is preferably one that is dissolvable in water, and aromatic compounds or sulfur-containing compounds are useful.

The main components used in the present invention will be explained in detail below, but this is not intended to limit the present invention unless it goes beyond the gist of the present invention.

Typical examples of dye precursors that develop color with phenolic substances or organic acids are shown in Table 1.

Table 1 (1) Crystal violet lactone) 3-indolino-3-p-dimethylaminophenyl-6-dimethylaminophthalide (333-diethylamino-7-chlorofluorane (4)
) 3-diethylamino-7-cyclohexylaminofluorane (5) 3-diethylamino-5-methyl-7-1-
Butylamino-12=Luorane (6) 3-Diethylamino-6-methyl-7-anilinofluorane (7) 3-Diethylamino-6-methyl-7-p-butylanilinofluorane (832-(N-phenyl- N-ethyl)aminofluorane (933-diethylamino-7-dibenzylaminofluorane (1o) a-cyclohexylamino-6-chlorofluorane (11) 3-diethylamino-6-methyl-7
-Xylidinofluorane (12) 2-anilino-3-methyl-6-(N-ethyl-p-toluidino)fluorane (13) 3-pyrrolidino-6-methyl-7-anilinofluorane (14) 3- Pyrrolidino-7-cyclohexylaminofluorane (15) 3-piperidino-6-methyl-7-toluidinonefluorane (16) 3-biveridino-6-methyl-7-anilinofluorane (17) 3-(N -Methylcyclohexylamino)-6-methyl-7-anilite fluorane (18) 3-diethylamino-7-(m-trifluoromethylanilino)fluorane (19) 3-diethylamino-6-methyl-7-chlorofluorane Next, Table 2 shows typical examples of the phenolic substance or organic acid (color developer) used in the FJFJK of the present invention.

Table-2 (1) 4,4'-isopropylidenediphenol (2)
4.4'-4sopropylidene bis(2-chlorophenol) (3) 4.4'-(sopropylidene bis(2-tert-butylphenol)) (4) 4.4'-Secondary-butylidene diphenol (5) 4.4'-(1-methyl-n-hexylidene)diphenol (6) 4-phenylphenol (7) 4-hydroxydiphenoxide (8) Methyl-4-hydroxybenzoate (9) Phenyl-4- Hydroxybenzoate (10) 4-Hydroxyacetophenone (11) Salicylic acid anilide (12) 4.4'-Cyclohexylidene diphenol (13) 4.4'-Cyclohexylidene bis(2-methylphenol) (14) 4. 4'-Hensilitenediphenol (15
) 4.4'-thiobis(6-tert-butyl-3
-Methylphenol) (16) 4.4'-isopropylidene bis(2-methylphenol) (17) 4.4'-ethylenebis(2-methylphenol) (18) 4.4'-cyclohexylidenebis(
2-Inglovirphenol (19) 2,2'-dihydroxydiphenyl (20)
2.2'-methylenebis(4-chlorophenol) (
21) 2.2'-methylenebis(4-methyl-6-t
-Butylphenol (22) 1,1'-bis(4-hydroxyphenol)-cyclohexane (23) 2,2-bis(4'-hydroxyphenyl)propane (24) Novolak-type phenolic resin (25) Halogenated novolak-forming phenol Resin (26
) α-naphthol (27) β-naphthol (28) 3.5-di-t-butylsalicylic acid (29
) 3.5-di-memethylbenzylsalicylic acid (3
0) 3-methyl-5-1-butylsalicylic acid (31
) Phthalic acid monoanilide barethoxybenzoic acid (32)
Bis(4-hydroxyphenyl)sulfone (33)
4-Hydroxy-4'-isopropyloxydiphenyl sulfone (34) Di(3-allyl-4-hydroxyphenyl) sulfone (35) Rose benzyloxybenzoic acid (36) Rose hydroxybenzoic acid benzyl ester (3
7) 1.7-bis(4-hydroxyphenyl)thio-3°5-dioxahebutane The thermal recording paper of the present invention can be obtained by the following method. That is, a phenolic substance or an organic acid, and a dye precursor that develops color with the phenolic substance or organic acid are pulverized and dispersed separately or simultaneously in a pulverizer into fine particles, and a binder,
A coating liquid is prepared by mixing with pigments, etc., and adding various additives as necessary.

Examples of binders include starches, hydroxyethyl cellulose, methyl cellulose, polyvinyl alcohol,
Water-soluble binders such as styrene-maleic anhydride copolymer, styrene-butadiene copolymer, polyacrylamide, carboxymethyl cellulose, gum arabic, casein, etc. Latexes such as styrene-butadiene latex can be used.

Examples of pigments include diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, urea-formalin resin, and the like.

In addition, higher fatty acid metal salts such as zinc stearate and calcium stearate, paraffin, oxidized paraffin,
Waxes such as polyethylene, polyethylene oxide, stearamide, castor wax, etc., wetting agents such as dioctyl sulfosuccinate, ultraviolet absorbers such as benzophenone type and benzotriazole type, surfactants, fluorescent dyes, etc. are used. It can be done.

Paper is mainly used as the support for the heat-sensitive recording material according to the present invention, but various nonwoven fabrics, plastic films, synthetic papers, metal foils, etc., or composite sheets of combinations of these can also be used as desired.

Next, regarding the materials forming the overcoat layer in the present invention, in general, alginic acid, salts, grafts with acrylic monomers such as hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, polyvinyl alcohol-acrylamide, etc. Copolymers may be used alone or in combination of two or more.

In addition, film-forming polymer emulsions such as acrylic latex, vinyl acrylic resin, vinyl acetate/ethylene copolymer, silicone/acrylate resin, and styrene/butadiene latex are also being introduced.
Although it has been effective, currently it is necessary that water-soluble polymer compounds be the main ingredient.

The compound according to the present invention is almost insoluble in water, colorless or white, and has the effect of improving chemical resistance even when contained in a heat-sensitive layer. However, it is difficult to use because it causes capri in the blank area and is noticeable in a high temperature and humid atmosphere. However, if it is present in the overcoat layer as described in the present invention, the above-mentioned drawbacks will not be a problem at all, and since it can be made to exist densely on the coloring layer, it will be possible to more effectively develop the full chemical resistance. It can be done.

The amount of the compound according to the present invention added to the overcoat layer (in the case of two or more, the total amount) is 0.5% by weight or more, preferably 1 to 60% by weight, to improve chemical resistance and color development sensitivity. , which is good in terms of printability.

This is because, if the amount added is a little less than 0.5% by weight, sufficient chemical resistance tends to not be obtained. If it exceeds 60% by weight, chemical resistance is sufficient, but since heat conduction to the coloring layer is inhibited, coloring sensitivity and printability tend not to be adversely affected.

The dry thickness of the overcoat layer is 0.2 μm to 15 μm1
Desirably, the thickness is from 0.5 to 5 μm, which is good in terms of chemical resistance, color development sensitivity, and printability.

(E) Examples The present invention will be explained in more detail by way of examples.

Example I Liquid B Liquids A and B were ground and dispersed in separate ball mills for 48 hours, and a coating liquid was prepared using the following formulation.

The amount of coating after drying of the prepared coating liquid on base paper with a basis weight of 49v~ is 5 f/n? After coating and drying, use a calendar to achieve a Beck smoothness of 100 seconds or more.
A thermosensitive recording paper was produced.

C liquid liquid Solution D was ground and dispersed in a ball mill for 48 hours.

An overcoat coating solution prepared by adding 5 parts of Solution D to 100 parts of Solution C was applied to the above thermal paper so that the dry film thickness was about 4 μm, and then using a super calendar.
An overcoated thermal recording paper was prepared so that the Bekk smoothness was approximately 700 seconds.

Example 2 An overcoated thermosensitive recording paper was produced in the same manner as in Example 1 except that Compound (2) was used as a substitute for Compound (1) in Example 1.

Example 3 An overcoated thermosensitive recording paper was produced in the same manner as in Example 1 except that the compound (1) of Example 1, Glue JK compound (3) was used.

Comparative Example An overcoated thermal recording paper was prepared in the same manner as in Example 1 except that Liquid D was not added to the overcoat coating liquid of Example 1.

Evaluation (Chemical Resistance Test) After coloring the overcoated thermal recording paper obtained in Example 1.2.3 and Comparative Example using Panafax UP-920 manufactured by Matsushita Densen, the blank paper area and the coloring area were Ethylene glycol and diazo developer (trade name Niactivator PD, manufactured by Bunshodo) were applied with 0.05 to 1.0-β, respectively, and Table 3
Under the conditions shown in Table 4, light-year density changes in the blank area and colored area were investigated.

Table-3 Change over time (room temperature) ○...Good, Δ...Slightly bad, ×...Poor.

Table-4 Environmental changes (24 hours) ] O...Good, Δ...Slightly bad, ×...Poor.

In the comparative example, as shown in Table 3, the coloring area due to ethylene glycol deteriorated over time and became unreadable. In addition, a phenomenon in which white paper areas were partially colored by the diazo developer was also observed. Furthermore, as shown in Table 4, when the storage conditions were set to high temperatures or high temperatures and high humidity, deterioration of the colored areas and coloring of the blank areas became more noticeable.

In Examples 1.2 and 3, no rapid deterioration occurred over time,
Furthermore, there was no deterioration due to storage conditions, and the results were satisfactory.

(F) Effects of the Invention As a result, a highly reliable thermosensitive recording sheet using a dye precursor was obtained, with no deterioration in colored areas or color development in blank areas. It has been recognized to have extremely high utility value in facsimile paper, POS labels, tickets, measurement record charts, etc., and we believe that it will be used in even more fields in the future.

Claims (1)

[Claims] A heat-sensitive color-forming layer is provided on the support, the main components of which are a colorless or light-colored dye precursor and a color developer that reacts with the dye precursor when heated to develop a color. A thermosensitive recording sheet provided with an overcoat layer mainly composed of , wherein the overcoat layer contains at least one compound that is solid at room temperature and has one glycidyl group in the molecule. sheet.