JPS58222882A - Heat-sensitive recording material - Google Patents

Abstract

PURPOSE:To improve resistance to chemicals and ground fogging during a long- period preservation, by shielding a leuco dye layer and a color developer layer therefor from each other by a thin layer of a thermoplastic resin, in a leuco base heat-sensitive recording material. CONSTITUTION:A leuco dye layer, the thin layer of a thermoplastic resin and the color developer layer for the leuco dye are sequentially laminated on a base. The thin layer of the thermoplastic resin used as an intermediate layer is preferably produced by a dry lamination method using a thin thermoplastic resin film. When laminating the leuco dye layer and the color developing agent layer on the base, it is preferable to provide the color developer layer as an upper layer and the leuco dye layer as a lower layer, from the viewpoints of chemical resistance and long-period preservability.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a leuco-based heat-sensitive recording material that improves chemical resistance and long-term storage by separating a leuco dye layer and a color developer layer therefrom by a thin layer of thermoplastic resin. The present invention relates to a heat-sensitive recording material with improved background fog.

A thermosensitive recording material is a recording material that has a so-called thermosensitive coloring layer formed on a support such as paper, synthetic paper, or resin film, which develops color when heated.Thermal head is heated by a laser equipped with a built-in thermal head. A multi-printer or the like is used. Compared to other recording materials, such recording materials can produce records in a relatively short time without complex processes such as development and fixing, do not generate noise, and are relatively inexpensive. Due to these advantages, it is widely used not only for copying books, documents, etc., but also as a recording material for various information and measuring instruments such as electronic computers, facsimiles, telex machines, and medical measuring instruments.

The thermosensitive coloring layer that develops color and records an image when heated contains both a leuco dye and a color developer that reacts with the leuco dye during heating to develop color. In this case, the leuco dye used is, for example, a colorless or light-colored leuco dye having lactone, lactam or spiropyra/ring, and various acidic substances are used as the color developer. Such a combination of a leuco dye and a color developer has been applied to many heat-sensitive recording materials since the color tone is clear and the amount of capri is small.

However, when a leuco dye and a color developer coexist in the heat-sensitive coloring layer as described above, problems such as chemical resistance, background fogging during long-term storage, and pressure coloring occur, and these problems can be fundamentally solved. It was extremely difficult to resolve.

As a result of intensive research aimed at fundamentally solving these problems, the present inventors supported the leuco dye and the color developer as separate layers on the support, and added a thin layer of thermoplastic resin between them. It was discovered that the object could be achieved by interposing a layer, and the present invention was completed.

In the present invention, a thin layer of thermoplastic resin is interposed between the leuco dye layer and the color developer layer, and the thermoplastic resin in this case may be various conventionally known ones, such as polyethylene, polypropylene, In addition to polyolefins such as polybutadiene, examples thereof include polyethylene, polyvinyl acetate, polyvinyl chloride, polyester, polyamide, styrene/acrylic copolymer, vinyl acetate/vinyl chloride copolymer, and the like. In the case of the present invention, the softening point or melting point is 5
A temperature of 0 to 150°C, preferably 60 to 120°C is preferred. In the present invention, the thin layer of thermoplastic resin used as the intermediate layer can be formed by coating with hot melt resin or solution resin, but preferably by dry lamination using a thin thermoplastic resin film. It is preferable to form it by However, emulsion type adhesives are unsuitable because they do not form a continuous resin film. The thickness of the thermoplastic resin layer is 1-10μ, preferably 2-5μ.

The stacking order of the leuco dye layer and developer layer on the support is as follows:
When considering chemical resistance and long-term storage stability, it is preferable to provide a color developer layer as an upper layer and a leuco dye layer as a lower layer.

As the leuco dye used in the present invention, triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, and spiropyran-based dyes are preferably applied. Specific examples of these leuco dyes are shown below.

3.3-bis(p-dimethylaminophenyl)-phthalide 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as Crystal i++, violet lactone) 3.3-bis(p- dimethylaminophenyl) = 6-diethylaminophenyl 3. 3-bis(p-dimethylaminophenyl) = 6-chlorophthalide 3. 3-bis(p-dibutylaminophenyl) phthalide 3-cyclohexylamino-6-chlorofluorane 3 -(N,N-diethylamino)-5-methyl-7-(
N,N-dibenzylamino)fluoran 3-dimethylamino-5,7-dimethyl? Luolan 3-diethylamino-7-methylfluoran/3-diethylamine-7,8-penzfluorano 3-diethylamine-6-methyl-7-chlorofluoran 3-pyrrolidino-6-methyl-7-anilinofluoran 2-IN-( 3'-)Lifluoromethylfumonyl)amine)-6-diethylaminophenyl/2-13.6-bis(diethylamino)-9-(o-chloroanilino)xanthyl)benzoic acid lactam) 3-diethylamino-'t-( o-10-(anilino)fluoran 3-dibutylamino-7-(o-chlorlev-21-)fluoran 3-N-methyl-N-amylamino-6-methyl-7-
Anilinofluoran 3-N-Mef-N-cyclohekynylamino-6-methyl-7-anilinofluoran a -(2'-hydroxy-47-dimethylaminophenyl)-3-(2'-methoxy- 5'-Chlorphenyl)phthalide 3-(2'-hydroxy-4'-dimethylaminophenyl)-3(2/-methoxy-5'-nitrophenyl)
Phthalide a (2/e droxy-4'-diethylaminophenyl) -, a- (2'-methoxy-5'-methylphenol I;) phthalide 3- (2'-methoxy-4'-dimethylaminophenyl) -3- (2'-Hydroquine-47-chloro-5'
-Methylphenyl)phthalide Furthermore, as the color developer used in the present invention, various electron-accepting substances that react with the leuco dye to develop color when heated are used, and specific examples thereof include the following: Examples include phenolic substances such as, inorganic acidic substances, organic acidic substances, and salts thereof.

Phenolic substances; 3.5-xylenol, thymol, p-terl-butylphenol, 4-hydroquinphenoxide, methyl-4-hydroxybenzoate, 4-hydroxyacetophenone, α-naphthol, β-naphthol, catechol, Resolun 7 ', hydroquinone, 4 Lerl-octylcatechol, 4+4 5ec-butyrizo/phenol, 2,2'-dihydroxydiphenyl, 2,2-methylenebis(4-methyl-6''-tert-butylphenol), 2,2-bis(4 -hydroxyphenyl)furopane, 4,4-impropylidene-bis(2-Ler
l-butylphenol), 4.4-5ee-butylidene diphenol, pyrogallol, phloroglucin, phloroglucin carboxylic acid, '! ”-tert-octylphenol, 4-phenylphenol, 2,2-bis(p
-hydroxyphenyl)butane, 4.4'-cyclohequinylidene diphenol, 2,2-bis(2,5-dibromo-4-hydroxyphenyl)furopane, 4.4'
-isopropylidene bis(2-1erl-butylphenol), 2,2'-methylenebis(4-chlorophenol), etc.

Acidic substances or their salts; benzoic acid, gallic acid, salicylic acid, zinc salicylate, ■
-Hydroxy-2-naphthoic acid, 0-hydroxybenzoic acid, m-hydroxybenzoic acid, benzyl p-hydroxybenzoate, 2-hydroxy-p-toluic acid, tartaric acid, oxalic acid, maleic acid, citric acid, succinic acid, stearic acid ,
4-oxynediphthalic acid, boric acid, etc.

In the present invention, fillers, thermofusible substances, etc. are added to the leuco dye layer and the color developer layer as necessary ("□'
Examples of fillers include calcium carbonate, magnesium carbonate, alumina, silica, Merck,
Examples include barium sulfate, magnesium hydroxide, aluminum hydroxide, styrene resin, fluororesin, urea-formalin resin, and the like.

Furthermore, examples of thermofusible substances include the following.

Animal waxes such as beeswax and shellac wax, vegetable waxes such as carnauba wax, mineral waxes such as montan wax, petroleum waxes such as paraffin wax and microcrystalline wax, polyhydric alcohol esters of higher fatty acids, and higher amides. , higher amine condensates of fatty acids and amines, condensates of aromatics and amines, synthetic paraffins, chlorinated paraffins, higher linear glycols, dialkyl 3,4-epoxy-hexahydrophthalates, metal salts of higher fatty acids, etc. Synthetic waxy substance.

゛In the heat-sensitive coloring layer, a binder is used as necessary in order to strongly bind additive components such as RO dye and color developer to the support. A water-soluble resin can be used.

In addition, a binder is usually applied to the leuco dye and color developer layer, such as methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, Starch and its derivatives, casein, gelatin, alkali salts of styrene-maleic anhydride copolymers,
Examples include alkali salts of yne (or diyne) butylene-maleic anhydride copolymers. If necessary, an aqueous dispersion type polymer resin can be used in combination with the water-soluble resin. Typical water-based dispersion polymer resins in this case include polyvinyl acetate, vinyl chloride/
Vinyl acetate copolymer, polyurethane, polyacrylic acid ester, styrene/butadiene/acrylic copolymer,
Polyvarnish/chill etc. can be mentioned.

Next, the present invention will be explained in more detail using examples.

Example A mixture consisting of the following formulation was pulverized and dispersed in a sulfuric ball mill for 24 hours to prepare Solution A.

Color former layer A liquid formulation 5% polyvinyl alcohol aqueous solution 150. Department water 20
0 parts 20 parts of 20% polyvinyl alcohol as a binder was mixed with 10 parts of this liquid A to prepare a coloring agent coating solution.

Next, a mixture consisting of the following formulation was pulverized and dispersed in a sulfuric ball mill for 24 hours to prepare Solution B.

Color developer layer B liquid formulation Bisphenol A 120 parts Stearamide 120 parts 5 tips Polyvinyl alcohol aqueous solution 120 parts Water
20 parts of this B solution was mixed with 20 parts of 20% polyvinyl alcohol as a binder to prepare a color developer coating solution.

Next, a coloring agent coating liquid was applied and dried on a high-quality paper with a basis weight of s 2 y-7 m'' so that the dry weight was 27%/m'', and then a thermoplastic resin film with a thickness of 4 μm was coated on top of this. Heat melt laminate the polyethylene sheet. Next, a color developer coating solution was applied onto the paper 9 and dried to a dry weight of 51 parts m''.The surface of this was treated using a super calender to obtain a heat-sensitive recording paper.

Comparative Examples 1 to 4 As Comparative Example 1, products were obtained in the same manner as in the example except that the intermediate layer of the hot-melt resin was not provided.

As Comparative Example 2, a product was obtained in the same manner as in Example except that a color developer layer was provided as a lower layer and a color former layer was provided as an upper layer.

As Comparative Example 3, 10 parts of liquid A, 20 parts of liquid B, and 20 parts of 20% polyvinyl alcohol as a binder were mixed,
A heat-sensitive coloring layer coating solution was prepared. .

This liquid was applied to high-quality paper with a basis weight of 52 f/m'' in the same manner as in the example.
It was coated on a 1"i" surface and dried to a dry weight of 7 f/1n", and then surface-treated with a super calender to obtain a product.

As Comparative Example 4, a product was obtained in the same manner as in the example except that a 4 μm thick layer of polyvinyl acetate emulsion adhesive was applied instead of the thin layer of hot-melt resin.

Next, the five types of thermal paper obtained as described above were subjected to a color development test using a thermal head, and the color density was measured.
% conditions for 40 hours, and the residual density and background density of the colored image were measured.
Furthermore, a weather resistance test was conducted by leaving the thermal paper on which color recording had been carried out for 100 hours under fluorescent lighting at 5000 lux, and the residual density and background density of the colored image were measured. The results are shown in Table-1. The color density was measured using a Macbeth densitometer.

Table 1 From the results shown in this table, it can be seen that the products of the present invention have less background discoloration (blurring) and less discoloration of images during storage, and have excellent color development.

Patent applicant: Ri, Co., Ltd. Agent Patent Attorney Toshiaki Ikeura

Claims (1)

[Claims] (1) A heat-sensitive recording material characterized in that a leuco dye layer, a thin layer of thermoplastic resin, and a color developer layer for the leuco dye are laminated in this order on a support.