JPS5968296A - Chemical-resistant heat-sensitive paper - Google Patents

Abstract

PURPOSE:To obtain a heat-sensitive paper having favorable chemical resistance, by a method wherein a water-insoluble polymer having a carboxylic group in its molecule is used as a color developer, and a zinc salt of a fatty acid is jointly used, in a heat-sensitive recording paper comprising a color forming dye precursor and a color developer. CONSTITUTION:A water-insoluble polymer having a carboxylic group in its molecule such as a styrene-butadiene resin modified with acrylic acid, methacrylic acid, methyl methacrylate or meleic acid, a similarly modified vinylidene chloride resin or a similarly modified styrene resin is used as a color developer for developing the color of a colorless or light-colored dye precursor such as crystal violet lactone when being heated. In addition, since the color- developing capability of the polymer is insufficient, a zinc salt of a fatty acid is added in a quantity of 80-20wt% to the polymer. The fatty acid may be either a straight-chain saturated fatty acid or a straight-chain unsaturated fatty acid. In addition to the dye precursor and the color developer, a binder, a surface active agent or the like is appropriately incorporated into the heat-sensitive paper.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal recording paper whose main components are a dye precursor and a color developer that develops color when the dye precursor is heated. The purpose of the present invention is to provide a thermal recording paper with less

Heat-sensitive recording paper is coated with (1) Substrate-H coated with carbon dye and pigment, and coated with an opaque thermoacidic substance. A method in which images are formed using colored layers. (2) A method that uses heat to form a complex between an electron donor and an electron acceptor. (3) Dispersing and coating a dye precursor such as crystal violet lactone and an acidic color developer such as a phenol compound [7]
There is a method in which one or both of them dissolve and develop color when heated. Among these, it is excellent overall in terms of image clarity, resolution, image color tone, problem of dust, etc. (3)
This method is used in general facsimiles, printers, etc.

The characteristics required for this heat-sensitive recording paper include, of course, nine sensitivity levels that can be used with various types of oil, a white background, long-term stable colored images that do not fade, and recording. Sometimes, there is no residue, and there is no sticking to the heat during recording. Excellent products that meet many of these requirements can be manufactured, but the image area has poor preservability (hereinafter referred to as chemical resistance) due to chemicals such as ffi agents, alcohol, acetone, benzene, and xylene, making it particularly difficult for practical use. From the perspective of 75 people, images can be erased if they come into contact with erasers or vinyl chloride bags that contain a large amount of plasticity, or if they come into contact with hands that are covered with hand cream, hair styling oil, etc. The disadvantage is that the characters are colored and difficult to read. In this development, the lactone ring of the color-forming lactone compound opened with an acidic color developer,
This is because the rings are opened in the presence of plasticizers such as digityl 7-thalerate and dioctyl phthalate (V-), and if a film is formed on the thermal recording paper to prevent penetration of the plasticizer, this phenomenon can be prevented. It has also been proposed that this should not occur. C) JP-A-54-128347, JP-A-54-3549) In addition, the present inventors have good chemical resistance, printability, and color development sensitivity, and
Developed an overcoat agent that does not cause scum or sticking, and published JP-A-57-105390 and JP-A-57-11.
It has been filed as No. 5391.

However, conventional thermal paper with chemical resistance is expensive because it requires an overcoat process, and it is difficult to record characters with water-based or oil-based ink stamps on the overcoat layer. , ink absorption is poor, and there are many drawbacks in practical use.

The present inventor has arrived at the present invention as a result of extensive studies aimed at improving the chemical resistance of conventional single-layer coating thermal paper.

That is, in thermal recording paper that mainly contains a colorless or light-colored color-forming dye precursor (hereinafter referred to as a dye precursor) and a color developer that develops color from the dye precursor when heated, the color developer By using a water-insoluble polymer having a carboxyl group in the molecule and a fatty acid zinc salt with a weight ratio of 20 to 200 percent relative to the color developer, a thermal paper with good chemical resistance was invented. It was.

Conventional color developers mainly use diphenols such as 4,4'-isoglopylidene diphenol (bisphenol A) and p-hydroxybenzoic acid benzyl ester, and monophenolic compounds. Monomers having carboxyl groups within them (eg salicylic acid) are also known. However, the water-insoluble polymer with a carboxyl group in the molecule of the present invention has a low color developing ability, so it is not used as a color developer, but it is used as an adhesive in the paper manufacturing industry, taking advantage of its adhesive ability. It is what is used. As a result of various studies in order to increase the color development sensitivity of the present invention, the present inventor has found that the color development sensitivity is synergistically improved by using organic metal salts, especially fatty acid zinc salts, in combination with the color developer of the present invention. It has become clear that thermal paper with excellent chemical resistance can be obtained.

Examples of the color developer of the present invention include the following.

Styrene-butadiene resins modified with acrylic acid or methacrylic acid or methyl methacrylic acid or maleic acid, similarly modified vinylidene chloride resins, similarly modified styrene resins.

Although these are generally known, newly polymerized carboxyl-modified resins are also expected to be effective in the present invention.

In carrying out the present invention, water-soluble resins with a low degree of polymerization are not preferred because they cause background fogging (coloring) of thermal paper.
Water-insoluble ones are best.

In addition, the degree of carboxyl modification is directly related to the coloring ability,
It is preferably at least 15% by weight or more, preferably 25% by weight or more.

Regarding the types of resins to be carboxyl-modified, vinylidene chloride resins with a low heat softening point have particularly good coloring ability, and
Vinylidene chloride resin has a high film-forming ability, so when it is finished as thermal paper, it prevents penetration of chemicals from the outside, so it has particularly good chemical resistance.

Next, the following fatty acid zinc salts are essential substances of the present invention.

Zinc salts of straight chain saturated fatty acids such as palmitic acid, stearic acid, myristic acid, diuriric acid, cabronic acid, arachidic acid, decanoic acid, and melisic acid.

Zinc salts of linear unsaturated fatty acids such as oleic acid, linoleic acid, arachidonic acid, and stearolic acid.

The amount added is 20 to 200 times the color developer of the present invention, preferably 50 to 100 times! j#,% was good. , below 20%, there is no sensitivity improvement effect;
If it is more than 0% by weight, it is not preferable because it increases the cost and causes the generation of waste when it is processed into thermal paper.

The present inventor has also conducted detailed studies on fatty acid metal salts other than zinc; for example, calcium salts, magnesium salts,
Barium salts, iron salts, etc. all had little or no effect on improving color development sensitivity.

Next, other materials used in the present invention will be explained.

As dye precursors, crystal violet lactone, 3-indolino-3-P-dimethylaminophenyl-
6-dimethylamino-7thalide, 3-diethylamino-7
-ri0 fluorofluorane, 3-diethylamino-7-cyclohexylaminofluorane, 3-jebruamino-5
-Methyl-7-t-butylfluorozine, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-P-butylanilinofluorane, 2-(N- phenyl-N-ethyl)aminofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-cyclohexylamino-6-chloronororane, 3-diethylamino-6-methyl-7-xylidinofluorane, 2- Anilino-3-methyl-6-(N
-ethyl-P-toluidino)fluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-pyrrolidino-7-cyclohexylaminofluorane, 3-piperisino-6-methyl-7-)lucinofluorane, 3-
Pyrrolidino-6-methyl-7-(p-toluidino)fluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-N methylcyclohexylamino-6-methyl-7-anilinofluorane, 3- diethylamino-
Examples include, but are not limited to, 7-(m-trifluoromethylanilino)fluorane.

In addition, when manufacturing thermal paper, in addition to dye precursors and color developers, inorganic and organic pigments and binders to prevent residue from adhering to facsimile heads, and other surfactants are used.
Additives such as waxes are used. Known and publicly available additives are used. For example, pigments include aluminum hydroxide, heavy and light calcium carbonate, zinc oxide, titanium oxide, and sulfuric acid. Barium, silica gel, activated clay, talc, clay, satin white, kaolinite, calcined kaolinite, diatomaceous earth, synthetic kaolinite, polyolefin particles, polystyrene particles, urea-formalin resin particles, etc. , styrene-maleic anhydride resin alkali salt, polyvinyl alcohol, modified polyvinyl alcohol, starch, modified starch, inbutylene-maleic anhydride resin alkali salt, diinoptylene-maleic anhydride resin alkali salt, polyacrylamide, modified polyacrylamide, carboquine methylcellulose,
Methyl vinyl ether/maleic acid co-X combination, hydroxyethyl cellulose, hydroquinglovir cellulose,
Alkaline salts of carboxy-modified polyethylene are used.

Nonionic and anionic surfactants are used, and amphoteric and cationic surfactants are generally not used because they cause aggregation of the coating liquid depending on the type of surfactant.

In addition, waxes include sudearic acid amide, palmitic acid amide, oleic acid amide, lauric acid amide, ethylene bis stearamide, methylene bis stearamide, methylol stearamide, paraffin wax, and higher alcohols and higher resins. Acids may also be used.

Further, a known heptadol color developer other than the one of the present invention can also be used in combination with the color developer of the present invention. However, although an improvement in color development sensitivity can be expected, an improvement in chemical resistance cannot be expected, and when used together, the sensitized color developed by a phenolic color developer and a dye precursor will be faded by chemicals (plasticizers). It was something. Therefore, a phenolic color developer may be used in combination within a range that does not significantly impair the effects of the present invention.

This will be explained in more detail in Examples below.

Example 1 Comparison using ■ acrylic acid 25% by weight modified vinyl chloride resin and ■ methyl methacrylic acid 25% by weight modified styrene butadiene resin as the color developer of the present invention, and the presence or absence of zinc stearate as a sensitizer. I was frugal.

Further, as a comparative example, a case is shown in which bisphenol A is used as a color developer and zinc stearate is used as a sensitizer.

Liquid A and B Liquid A and B were ground and dispersed in separate ball mills for 24 hours.
A coating liquid was prepared with the following formulation.

The finished coating liquid has a basis weight of 501/rr? The dye was coated on high-quality paper so that the total amount of dye was 0.5 r/rr/ and dried to obtain heat-sensitive recording paper. This thermal paper was heated to 150° C. and stamped to obtain a black colored paper, and the color density, chemical resistance, and background density were measured and compared.

The background density and color density were determined by measuring the optical density using a Macbeth densitometer using an amber filter.

Chemical resistance was determined by layering 10 sheets of commercially available soft vinyl chloride film (Shin-Etsu Wrap) on the colored surface, applying a load of 609/ct4, and leaving it at 40°C for 72 hours. In the invention, by adding a sensitizer (zinc stearate), a color density equivalent to that of conventionally used bisphenol A can be obtained, and the chemical resistance is overwhelmingly better than that of the comparative example. Met.

Claims (1)

[Claims] 1. A colorless to flame-colored color-forming dye precursor, and upon heating,
In the heat-sensitive recording paper mainly containing a color developer for coloring the dye precursor, the color developer is a water-insoluble polymer having a carboxyl group in the molecule, and the color developer has a ratio of 20 to 2
A chemical-resistant thermal paper made in combination with fatty acid zinc salt of 00-fold bar tips. 2. Chemical-resistant thermal paper according to claim 1, wherein the W4 colorant is an acrylic acid-modified vinylidene chloride resin;