JPH01215578A - Thermal recording sheet - Google Patents

Abstract

PURPOSE:To enhance resistance to solvent, resistance to water, and the like, by laminating a protective layer made of alpha-olefin, maleic anhydride, and imide maleate or a copolymer of an N-substituted derivative thereof on a color forming layer disposed on a substrate. CONSTITUTION:A thermal color forming layer is formed by a method in which ; a color forming substance and a color developer which reacts with the aforesaid substance under heat to produce a color are dispersed in a binder such as a polyvinyl alcohol, and this dispersion is applied and bound on a substrate, such as synthetic papers, films, and woven textile sheets. On the other hand, a coating liquid is prepared by heating alpha-olefin, maleic anhydride, and imide maleate or a copolymer of an N-substituted derivative thereof in water to make it soluble. This coating liquid is applied on the aforesaid thermal color forming layer and dried to laminate a protective layer, and a thermal recording sheet is formed. The obtained sheet is enhanced in resistance to solvent, resistance to plasticizer, and resistance to oil.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a heat-sensitive recording sheet comprising a heat-sensitive color forming layer provided on a support and a protective layer made of a specific resin component provided on top of the heat-sensitive coloring layer.

(Prior Art) Conventionally, sheet metal for heat-sensitive recording has not been manufactured by coating a colorless chromogenic lactone compound such as crystal violet lactone and an acidic compound such as a phenol compound together with a water-soluble binder onto a supporting substrate. It is publicly known. The heat-sensitive recording sheets thus obtained are widely used for recording in facsimiles, automatic ticket vending machines, calculators, medical measuring instruments, and the like. However, with heat-sensitive recording sheets manufactured using water-soluble binders, the coloring lines obtained are unstable against moisture or organic solvents, and when they come into contact with water, they tend to soften due to the plasticity in the PVC sheets. Please note that it has the disadvantage that the coloring part tends to fade or fade when it comes into contact with agents, etc. In addition, the accumulation of residue of the heat-sensitive layer on the thermal head due to sticking is attracting attention as a factor inhibiting the speeding up of thermal printers that require higher applied energy. Various methods have been proposed to overcome these drawbacks, including a method of using a water-resistant agent in combination with a water-soluble binder, a method of improving the binder resin, and a method of improving the protective layer.

(Problems to be Solved by the Invention) Properties required of the protective layer include the following.

1. Completely protect the coloring layer on the heat-sensitive recording sheet from moisture with a protective layer (water resistance).

2. Staticing does not occur during thermal printing, stuttering residue does not adhere to the thermal head, and the thermal head does not wear out (stating resistance).

3. There is little decrease in print density due to the effect of the protective layer.

and no reduction in whitening as a heat-sensitive recording sheet (
chromogenic).

4. Ability to prevent decolorizing and fading substances such as organic solvents, oils, and plasticizers from penetrating into the coloring layer (solvent resistance, oil resistance, plasticizer resistance).

Although many resin compositions have been proposed in the past with the aim of satisfying the above-mentioned required properties, at present no thermosensitive recording sheet that is practically satisfactory has been obtained.

By improving the protective layer provided on the heat-sensitive coloring layer on the support, the present invention improves solvent resistance, plasticizer resistance, and oil resistance, as well as significantly improves water resistance. It is an object of the present invention to provide a next heat-sensitive recording sheet with improved running properties of the head.

(Means for Solving the Problems) According to the present invention, the above object is achieved by providing a heat-sensitive recording sheet in which a heat-sensitive coloring layer is provided on a support.
b) α-olefin, (b) maleic anhydride and (/
The present invention has been found to be achieved by a heat-sensitive recording sheet having a protective layer comprising a copolymer of maleic acid imide or its N-substituted derivative.

The α-olefin used in the present invention refers to all linear or branched olefins having a carbon-carbon unsaturated double bond in the α position, especially olefins having 2 to 12 carbon atoms, especially 2 to 8 carbon atoms. . Typical examples include ethylene, propylene, n-butylene, imbutylene, n-pentene, isogrene, 2-methyl-1-butene, n-hexene, 2-
Methyl-1-,11-tene, 3-methyl-1-/l! l
Thene, 4-methyl-1-,4-thene, 2-ethyl-1-
Butene, 1,3-e entadiene, 1,3-hexadiene.

2.3-dimethylbutadiene, 2. s-e entadiene,
1.4-hethadiene, 2,4.4-)dimethyl-1
-4-tintene, etc. Among these, inbutylene is particularly preferred. Here, isobutylene also means return B-Bi containing isobutylene. These olefins may be used alone or in combination of two or more.

Maleic acid imides used in the present invention include maleic acid imide, N-methylmaleimide, N-ethylmaleimide, and N-globilmaleimide.

N-substituted alkylmaleimides such as N-n-butylmaleimide, N-t-butylmaleimide, and N-cyclohexylmaleimide; Alkylphenylmaleimide, or N-
N-substituted alkoxyphenylmaleimide such as methoxyphenylmaleimide, N-ethoxyphenylmaleimide,
Preferred examples include these halides (eg, N-chlorophenylmaleimide). Among these, maleimides having a phenyl group at the N-position, particularly N-phenylmaleimide, are preferred.

(a) α-olefin, (b) maleic anhydride, and (c) maleic acid imide or its N, which constitute the copolymer.
-The composition ratio ((a)/(b)+(/)) with the substituted derivative is preferably within the range of 1/1 to 3/1 in terms of molar ratio, and (1) maleic anhydride and e→ The composition ratio ((b)/(=→) with maleic acid imide or N-substituted derivative is preferably within the range of 9515 to 30/70 in terms of molar ratio).

The copolymer contains an alkali, i.e., ammonia, NaOH, KOH, in an amount of 0.2 to 1.0 times equivalent to maleic anhydride.
.

It is used after being made water-soluble by heating it with Mg(OH)2 etc. in water.

There is no problem in using polyvinyl alcohol, starch, hydroxyethyl cellulose, methyl cellulose, styrene-maleic anhydride copolymer, etc., which have been conventionally used as national fat components for forming the protective layer, in combination with the above copolymer. In particular, the use of / ribinyl alcohol in combination with the copolymer.

It is effective in improving the physical properties of the protective layer.

In this case, polyvinyl alcohol and copolymer are 95:
It is preferable to use a weight ratio of 5 to 20:80, preferably 95:5 to 50:50. Polyvinyl alcohol can be crosslinked with a polyhydric aldehyde such as gluoxal, while the above copolymer can be crosslinked with a polyfunctional epoxy compound such as glycerin diglycidyl ether to form a protective layer. Water resistance can be made more complete.

In the present invention, the heat-sensitive color-forming components constituting the heat-sensitive color-forming layer are typically two components: a color-forming substance and a color-developing substance that reacts with the color-forming substance when heated to form a color. A typical example of the color-forming substance is a color-forming lactone compound. The color-forming lactone compound may be one that develops color by reacting with an acidic compound when heated, such as various leuco lactone compounds such as triphenylmethane type, triphenylmethane phthalide type, fluoran type, leuco auramine type, spiropyran type, etc. Examples include compounds.

Examples of color developing substances include 4-phenylphenol, 4-hydroxyacetophenone, 2.2'-diacetoxyphenyl, 2.2'-methylenebis(4-chlorophenol), and 2.2'-methylenebis(4- Methyl-
6-t-butylphenol), 4,4'-isoglopylidenediphenol, 4,4'-isoglopyridene bis(
2-10ruphenol), 4.4'-isoglogylidenebis(2-methylphenol), 4.4'-roC-butylidenephenol, 4.4'-ethylenediphenol,
4. A phenolic compound such as 4'-ethylenebis(2-methylphenol) is used.

Examples of the supporting substrate used in the heat-sensitive recording sheet of the present invention include paper, synthetic paper, film, and woven fabric sheet.

In the present invention, in order to bond and support the heat-sensitive coloring layer on the support, various conventional binders can be used as appropriate, such as polyvinyl alcohol, starch, methoxycellulose, hydroxyethylcellulose, cardoxymethylcellulose, methylcellulose. , cellulose derivatives such as ethylcellulose; I-sodium lyacrylate, polyvinylpyrrolidone, acrylic acid abado acrylic ester copolymer, acrylic amide-acrylic ester-methacrylic acid ternary copolymer, styrene-maleic anhydride copolymer Combined alkali salts, imbutylene-maleic anhydride copolymer alkali salts, water-soluble polymers such as polyacrylamide, sodium alginate, gelatin, casein; polyvinyl acetate, polyurethane, styrene-tutadiene copolymer, polyacrylic acid, ? Reacrylic acid ester, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, ethylene-vinyl acetate copolymer, styrene! Latexes such as tadiene-acrylic copolymers can be mentioned.

In the present invention, if necessary, auxiliary additive components commonly used in this type of heat-sensitive recording material, such as fillers, are added.

A surfactant, a thermofusible substance, etc. can be used in combination.

In this case, fillers include, for example, inorganic fine powders such as calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, Merck, surface-treated calcium and silica, etc. Examples include organic fine powders such as urea-formalin resin, styrene-methacrylic acid copolymer, and polystyrene resin.
Thermofusible substances include, for example, higher fatty acids or their esters, amides, or metal salts, as well as various waxes, condensates of aromatic cargenic acids and amines, benzoic acid phenyl esters, higher linear glycols, etc. - Engineering I xyhexahydrophthal dispersion sialic flat k, high R'lton, shihenzyl terephthalate, hydroxynaphthoic acid ester,
Examples include α-naphthohydroquinone diether.

The present invention will be explained in more detail below with reference to Examples.

(1) Formation of coloring layer Preparation of heat-sensitive layer composition The following composition solution was prepared.

Each solution was dispersed in fNN Silur for 24 hours and mixed well to obtain a thermosensitive coloring layer forming solution. This was coated on one side of a 6,517 ft high-quality paper using a percoater so that the coating amount was 717 m 2 , and dried to obtain a heat-sensitive recording sheet.

(2) Formation of protective layer 10% of a copolymer of inbutylene, maleic anhydride, and N-phenylmaleimide with a molar composition ratio of 50:27:23
Aqueous solution (degree of ammonia neutralization of maleic anhydride 60%)
-1 liquid and a 10% polyvinyl alcohol (Kuraray Bhopal PVA-105) aqueous solution were used as n liquid, and all of these were mixed in the following formulation to form a protective layer forming liquid.

The coating amount was 497 m on the heat-sensitive layer-formed sheet of t-(1).
2 to obtain a desired heat-sensitive sheet.

Comparative Example 1 The coating amount of the coating liquid consisting of the heat-sensitive recording sheet used in Example 1 before coating the protective layer was 4.9/? R2 was applied to obtain a heat-sensitive recording sheet. Example 2 Copolymer 104 of inbutylene, maleic anhydride, and N-phenylmaleimide in a molar ratio of 50:35:15
Aqueous solution (degree of ammonia neutralization of maleic anhydride 5(1)t
-1 liquid, 10%-rivinyl alcohol (Curaray Pearl PVA-105) aqueous solution 1N liquid. A coating amount of 4 on the heat-sensitive sheet in all of Example 1 of the coating liquid consisting of the following formulation.
A heat-sensitive recording sheet was obtained by coating to a thickness of 17 m.

Each heat-sensitive sheet thus obtained was dried in a hot air dryer at 50°C.
After drying for minutes, roll temperature 45℃, Niraguru pressure 75yu/c
T! The coated surface was made smooth by passing it through a calender three times at L2 and a roll speed of 10 m 7 min. Thereafter, the heat-sensitive sheet was cured for 6 days at a temperature of 20° C. and a humidity of 601 RH.

The physical properties of the heat-sensitive recording sheet and the pot life of the coating solution for forming the protective layer were investigated. The results are shown in the table.

(1) Water resistance: After immersing the test piece in water at 20'C and 40C for 24 hours, rub the coated surface strongly to prevent separation of the compounded silica.
Judgment was made visually.

(2) Water resistance fading: Color is developed at 110°C and 100°C for 5 seconds using a heat gradient printer, and a test piece is printed at 20°C.
The samples were immersed in water at 40[deg.] C. and 40[deg.] C. for 24 hours, and the color density before and after immersion was measured using a reflective color densitometer Macbeth RD-514 to compare the degree of discoloration.

(3) Sticking: Circular Printer MTP-2
After printing with 01 (manufactured by Seiko Electronics), the surface of the print was observed and judged using a scanning electron microscope.

(4) Print density: Measured using a sample color densitometer that developed color at 110° C. for 5 seconds using a heat gradient glitter.

(5) Solvent resistance: Methyl ethyl ketone and ethyl alcohol were dripped onto a sample piece that had been colored at 110° C. for 5 seconds using a heat gradient glitter, and all discoloration at the dripped portion was visually judged.

(6) Plasticizer: A sample piece colored at 110°C for 5 seconds using a heat gradient printer was sandwiched with a thickening vinyl chloride sheet, and 300g/cI! The sample was left at room temperature under a load of L2, and the degree of discoloration was visually determined.

(7) White discoloration: Murakami type GLO8S METERGM-3M
Please make sure to measure accordingly.

(8) Protective layer coating liquid 4-t life: Determined by the change in viscosity of the coating liquid left at room temperature. The one with the least increase in viscosity is better.

(Effects of the Invention) The present invention provides a thermosensitive recording sheet that has improved solvent resistance, plasticizer resistance, and oil resistance, as well as markedly improved water resistance and further improved stacking resistance.

Patent applicant: RiRashi Co., Ltd. Agent Patent Attorney Ken Motoda

Claims (1)

[Claims] In a heat-sensitive recording sheet in which a heat-sensitive coloring layer is provided on a support, (a) an α-olefin, (b)
1. A heat-sensitive recording sheet comprising a protective layer comprising a copolymer of maleic anhydride and (c) maleic imide or an N-substituted derivative thereof.