JPS58153693A - Heat-sensitive recording product - Google Patents

Abstract

PURPOSE:To provide a heat-sensitive recording product which is prevented from the occurrence of fog, and improves a continuous recording property and resistance to water, by manufacturing the recording product such that aqueous dispersion product of a vinyl copolymer containing nitrocellulose is contained in a coloring layer. CONSTITUTION:In a heat-sensitive recording product having a coloring layer containing a colorant and a developer conducting a colorantion as a result of contact with said colorant, an aqueous dispersion product of a vinyl copolymer (preferably that which consists of 40-70% methylmethacrylate and 30-60% 2-ethylhexylacrylate) containing preferably 3-55% nitrocellulose (having preferably 10.7-12.2wt% nitrogen content and degree of polymerization of 20-300) is contained in said coloring layer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording material containing an aqueous vinyl copolymer dispersion containing nitrified cotton in a coloring layer. In particular, it relates to a heat-sensitive recording material that has improved (1) unnecessary color development (hereinafter referred to as fog) in coating liquids or coatings over time (hereinafter referred to as fog), (2) continuous recording performance, and (3) water resistance.

Conventionally, water-soluble resins such as polyvinyl alcohol, gelatin, methyl cellulose, hydroxyethyl cellulose, starch, gum arabic, and water-soluble acrylic resins have been used as fixing agents in the coloring layer of thermosensitive recording materials. Therefore, when water comes into contact with the coated surface of the recording medium, the coated surface becomes contaminated. Furthermore, heat-sensitive recording bodies using these have the disadvantage that the surfaces of the thermal head and the heat-sensitive recording body become sticky or "sticky" (hereinafter referred to as "sticking") when heat is applied. Sticking makes it impossible to feed the recording medium smoothly, making continuous use impossible, and sometimes even causing damage to the thermal head. As a result of various studies to improve the above-mentioned drawbacks, the present invention provides a heat-sensitive recording material provided with a color-forming layer containing a color-forming agent and a color-developing agent capable of forming a color upon contact with the color-forming agent, which contains nitrified cotton. The vinyl copolymer aqueous dispersion is achieved by including the vinyl copolymer aqueous dispersion as a fixing agent in a color forming layer containing a color former and a color developer that develops a color when in contact with the color former.

The aqueous vinyl copolymer dispersion containing nitrified cotton of the present invention usually has a nitrogen content of 10.7 to 12.2% by weight and a degree of polymerization of 20 to 20.
300 nitrified cotton is used, and the content of nitrified cotton is 3 to 55% by weight in the nitrified cotton-containing vinyl copolymer.If the content in the northern latitude is less than 10% by weight, the sticking will be bad, and if it is more than 40% by weight, the film will not stick. becomes too hard and cracks occur.

The vinyl copolymer is a copolymer of a vinyl monomer mixture and is compatible with nitrified cotton, and the nitrified cotton is soluble in the vinyl monomer mixture. As a vinyl monomer (
meth)acrylic acid esters such as methyl acrylate,
Methyl methacrylate, ethyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, etc., aromatic compounds such as styrene, vinyltoluene, nitriles such as acronitrile, methacrylonitrile, others such as vinyl acetate, methyl vinyl ether, unsaturated carbon Acids such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid and the like can be mentioned. Among these, the preferable vinyl monomer in the vinyl copolymer is methyl methacrylate) 40
~7σ weightits, 2-ethylhexyl acrylate 30
If the amount of methyl methacrylate is less than 40% by weight, the film will be soft and stickiness will occur, and if it is more than 70% by weight, the flexibility of the film will be poor.

In order to prevent fogging, the nitrified cotton-containing vinyl copolymer to which carboxyl groups are bonded needs to be neutralized with an alkaline substance to form a nitrated cotton-containing vinyl copolymer to form a basic salt. When producing an aqueous vinyl copolymer dispersion containing nitrified cotton, the surfactant for emulsion polymerization must be one that does not participate in the coloring reaction of the coloring agent and does not develop color over time. Polyoxyethylene alkyl sulfate salt, polyoxyethylene alkyl allyl sulfate salt, alkylbenzene sulfonate, alkylnaphthalene sulfonate, dialkyl sulfosuccinic acid derivative, naphthalene sulfonic acid formalin condensate, polyoxyethylene alkyl ether, holoxy Ethylene allyl ether, polyoxyethylene polyoxybropyrene derivatives and composite phosphate esters alone or 11.

is used in combination. Preferably, sia)lekylsulposuccinic acid derivatives and polyoxyethylene alkylaryl sulfate salts are used.

To obtain a vinyl copolymer aqueous dispersion containing nitrified cotton, use the above-mentioned surfactant to form a bra emulsion consisting of nitrified cotton, a vinyl monomer mixture, and water, and then
Conventional emulsion polymerization means may be employed using a radical polymerization catalyst such as potassium persulfate or ammonium persulfate.

In the heat-sensitive recording material of the present invention, examples of coloring agents in the coloring layer include fluoran colorless dyes, triallylmethane dyes, and phenothiazine dyes, and examples of color developers include phenolic compounds and aromatic carboxylic acids.

In addition, the ratio of the color former and the color developer used in the color forming layer is appropriately selected depending on the type of color former and color developer used, and is not particularly limited, but generally the basic colorless dye is 1 part An acidic substance is used in an amount of 1 to 50 parts by weight based on the weight part, and a solid content of 40 to 50% by weight is further used as a color forming layer binder.
Vinyl copolymer aqueous dispersion containing nitrified cotton 10-2
00 parts by weight are used.

The method for forming the coloring layer of the heat-sensitive recording material of the present invention is generally to add an aqueous dispersion of a vinyl copolymer containing nitrified cotton to a coating solution prepared by stirring and pulverizing a coloring agent and a color developer using a ball mill or the like. It is obtained by applying a coating solution prepared by dispersion onto a support such as paper, plastic film, metal film, etc., usually in a dry weight range of 2 to 15 g/I using a coating machine.

Furthermore, in order to improve the smoothness of the recording medium, calendering may be applied.

In order to improve the adhesion of thermal head residue during coating,
Pigments with large oil absorption, benzophenone-based and triazole-based ultraviolet absorbers, fatty acid amides, and dispersants such as naphthalene sulfonic acid formalin condensates are used as sensitivity modifiers, as well as mold release agents of metal stearate and base plasticizers. Various auxiliary agents such as fluorescent dyes, colorants, and water-soluble resins can be added as necessary.

Examples of the present invention are shown below. Parts and parts in the examples are based on weight.

Example-1゜■ Production of an aqueous vinyl copolymer dispersion containing nitrified cotton Nitrified cotton/vinyl copolymer = 30 parts/7 in an ice-cooled container
0 parts, and the monomer composition ratio was 70 parts/30 parts (methyl methacrylate/2-ethylhexyl acrylate).

That is, nitrified cotton (88% moisture content 30%) 119. cg1
Anionic diadialkylsulfokono1 derivative 17.1
9.Pour distilled water 238.5.9 into a 1p flask,
Then methyl methacrylate (100,051,2-ethylhexyl acrylate) 100. ,! 9. Chain transfer agent 0
．． The monomer phase consisting of 29 was added and the mixture was mixed for 30 minutes in a homomixer type M. A condenser, a stirrer, and a nitrogen inlet tube were attached to this container, and after sufficient nitrogen substitution, the contents were heated to 65°C. Then distilled water 40
9. 254 g of a solution consisting of 0.49 potassium persulfate was initially added.

60 minutes from the time the reaction begins and the exotherm subsides.
After keeping the temperature at 5°C, add the remainder of the above potassium persulfate aqueous solution and distilled water 1. ．． 09. 0.1 g of sodium bisulfite was added and the temperature was raised to 80° C. and maintained at this temperature for 60 minutes. As a result, PH3.3, viscosity 14 ep18,
An aqueous vinyl copolymer dispersion containing nitrified cotton with a solid content of 49.5% was obtained.

(2) Preparation of Solution A Crystal violet lactone 1.0 parts Dispersant (naphthalene sulfonic acid formalin condensate) Ol 55 parts The above mixture was ground in a ball mill to an average particle size of 4 microns to obtain a coloring agent.

(2) Preparation of Bl 4.4' Isopropylidenediphenol 70 parts 50.0 parts The above mixture was ground in a ball mill to an average particle size of 4 microns to obtain a color developer.

■ Formation of coloring layer 100 parts of vinyl copolymer aqueous dispersion containing nitrified cotton, 55 parts of color former, and 50 parts of color developer were thoroughly mixed and stirred, and a dispersion obtained was used as a coating liquid. Apply it on the base paper,
Dry with hot air at 60°C for 1 minute, linear pressure 30kg/cIIL,
Glazed at a temperature of 60°C and a calendar speed of 30 frL/mm, and the coating amount after drying was 8.0 g/rr? A thermosensitive recording medium was obtained. The quality of this heat-sensitive recording material was checked using a heat-sensitive facsimile machine by recording all marks for 1 minute at a recording dot density of 5 dots/rhythm, a scanning line density of 443/mm, and an applied voltage of 19 V to check the occurrence of sticking. . Regarding water resistance, the recorded image surface is rubbed five times under the same conditions with a fingertip moistened with water, and the degree of contamination of the recorded image surface is determined.

Moreover, the fog 6 of the coating liquid determines whether or not coloring occurs due to changes over time from the time of forming the coloring layer. The heat-sensitive recording material obtained according to the present invention had a well-balanced property, excellent in water resistance and sticking, and free from the bulge phenomenon. The results are summarized in Table 1.

Example 2 In the production of the vinyl copolymer aqueous dispersion containing nitrified cotton used in Example 1, the same procedure as in Example 1 was carried out using an anionic polyoxyethylene alkylaryl sulfate salt as a surfactant. Emulsion polymerization is carried out by the method of
An aqueous vinyl copolymer dispersion containing nitrified cotton with a viscosity of 92%, a viscosity of 16 cps, and a pH of 29 was obtained. A heat-sensitive recording material obtained by mixing this with the same coloring agent and developer as in Example-1 to form a coloring layer similar to that in Example-1 was subjected to quality evaluation in the same manner as in Example-1, and the results were as follows. are shown in Table 1.

Comparative Example-1゜Instead of the vinyl copolymer aqueous dispersion containing nitrified cotton used in Example-1, latex commercially available from Company A (styrene-
The thermosensitive recording material in which a coloring layer was formed by mixing the butadiene copolymer (solid content 50%) with the same coloring agent and color developer as in Example-1 was evaluated in the same manner as in Example-1. The results are shown in Table 1.

Comparative Example-2 Instead of the vinyl copolymer aqueous dispersion containing nitrified cotton used in Example-1, polyvinyl alcohol (30% aqueous solution) was mixed with the same color forming agent and color developer as in Example-1. The heat-sensitive recording material on which a coloring layer could be formed was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Notes to Table 1: (1) Fogging property; Appearance evaluation after 48 hours at 30°C from the time of coloring layer formation (21 Sticking; Good with no sticking) , Sticking occurs (Poor) 1□ Patent applicant Daicel Chemical Industrial Co., Ltd.

Claims (1)

[Claims] In a thermosensitive recording material provided with a coloring layer containing a coloring agent and a coloring agent that develops a color when in contact with the coloring agent, an aqueous vinyl copolymer dispersion containing nitrified cotton is contained in the coloring layer. A heat-sensitive recording material characterized by: