JPH0361598B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a heat-sensitive recording material, and more particularly, the present invention relates to a heat-sensitive recording material containing as main components a color-forming substance that is normally colorless or light-colored at room temperature, and a color-developing substance that reacts with the color-forming substance to form a color when heated. Concerning recording materials. A thermosensitive recording material is usually a material in which a thermosensitive coloring layer that can record a colored image by heating is provided on a support such as paper, synthetic paper, plastic film, or metallized paper; Because records can be obtained, it is widely used not only for copying books and documents, but also for recording the output of computers, facsimiles, and various measuring instruments, and for writing on identification cards, commuter passes, train tickets, etc. . Many of these heat-sensitive recording materials have been put to practical use, and among them, heat-sensitive recording materials that use a colorless or light-colored leuco dye having a lactone, lactam, or spiropyran ring and an acidic substance as coloring components. The materials are particularly useful because of the sharpness of the tone in the resulting images. Generally, heat-sensitive recording materials after recording are used or stored by being covered with a transparent resin film or plate covering sheet, but at this time, the effects of components contained in these covering sheets, such as plasticizers, etc., and during handling. Due to the sebum in fingerprints, the density and sharpness of recorded images decrease over time, and eventually disappear.
This greatly impairs the preservation of the image. Therefore, an object of the present invention is to solve the above-mentioned conventional drawbacks, and more specifically, to provide a heat-sensitive recording material that can withstand long-term storage by preventing deterioration of recorded images due to the coating sheet components and sebum. There is a particular thing. In view of the above objective, as a result of various studies, we have found that a heat-sensitive color forming layer containing as main components a normally colorless or light-colored color forming substance and a color developing substance that reacts with the color forming substance and develops color upon heating is used as a support. In the heat-sensitive recording material formed above, carboxyl group-modified polyvinyl alcohol is present at one or more locations on the back of the support, between the support and the heat-sensitive coloring layer, and in the heat-sensitive coloring layer, and the heat-sensitive coloring layer It has been found that by providing a protective layer made of a mixed resin layer of carboxyl group-modified polyvinyl alcohol and polyester resin or polyurethane resin on top, deterioration of the recorded image can be prevented and the clarity of the recorded image can be maintained over a long period of time. did. Furthermore, by adding polyamide resin, melamine resin, glyoxal, and, if necessary, a catalyst such as ammonium chloride together with the resin of the protective layer, durability can be further improved and an even more excellent heat-sensitive recording material can be obtained. To further explain the heat-sensitive recording material of the present invention, the ratio of the carboxyl group-modified polyvinyl alcohol and polyester resin or polyurethane resin used in the protective layer is 0.1 to 1 part by weight of the polyester resin or polyurethane resin to 1 part by weight of the carboxyl group-modified polyvinyl alcohol. parts by weight,
Preferably, the range is 0.3 to 0.7 parts by weight. If the amount of polyester resin or polyurethane resin is less than 0.1 part by weight, oil resistance will deteriorate;
If it exceeds parts by weight, plasticizer resistance will deteriorate. Polyester resins or polyurethane resins are usually of the aqueous emulsion type. Carboxyl group-modified polyvinyl alcohol is a reaction product of polyvinyl alcohol and a carboxylic acid such as fumaric acid, maleic acid, itaconic acid, maleic anhydride, phthalic anhydride, trimellitic anhydride, itaconic anhydride, or an ester of these reaction products. or a saponified polymer of vinyl acetate and a small amount of ethylenically unsaturated carboxylic acid such as maleic acid, fumaric acid, and itaconic acid. Regarding the production method of such carboxyl group-modified polyvinyl alcohol,
-21312, JP-A No. 53-91995, JP-A No. 54-28389, and JP-A No. 54-28390. In order to form the heat-sensitive coloring layer of the present invention, it is sufficient to use a leuco dye and a color-developing substance therefor, which are normally used in this type of field, by a normal means. That's right. 1 Leuco dye 3,3-bis(p-dimethylaminophenyl)-phthalide 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone), 3,3- Bis(p-dimethylaminophenyl)-6-diethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)-6-chlorophthalide, 3,3-bis(p-dibutylaminophenyl) phthalide, etc. Triphenylmethane, 3-dichlorohexylamino-6-chlorofluorane, 3-(N,N-diethylamino)-5-methyl-7-(N,N-dibenzylamino)fluorane, 3-dimethylamino-5 , 7-dimethylfluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-pyrrolidino-6-methyl -7-anilinofluorane, 2-{N-(3'-trifluoromethylphenyl)amino}-6-diethylaminofluorane, 3-diethylamino-7-(0-chloroanilino)fluorane, 3-dibutylamino- 7-(0-chloroanilino)fluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, 3-N-methyl-N-amylamino-6-methyl-7-anilinofluoran Oran, 2-{3,6-bis(diethylamino)-9-
Fluoran dyes such as (0-chloroanilino)xantylbenzoic acid lactam}, 3-(2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-chlorophenyl) phthalide, 3- (2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-nitrophenyl)phthalide, 3-(2'-hydroxy-4'-diethylaminophenyl)-3-(2 '-methoxy-5'-methylphenyl)phthalide, 3-(2'-methoxy-4'-dimethylaminophenyl)-3-(2'-hydroxy-4'-chloro-
Phthalide dyes such as 5'-methylphenyl) phthalide. 2 Color developer Boric acid, oxalic acid, maleic acid, tartaric acid, citric acid, succinic acid, benzoic acid, stearic acid,
Gallic acid, salicylic acid, 1-hydroxy-2-
naphthoic acid, 0-hydroxybenzoic acid, m-hydroxybenzoic acid, 2-hydroxy-p-toluic acid, 3,5-xyresol, thymol, p
-tert-butylphenol, 4-hydroxyphenoxide, methyl-4-hydroxybenzoate, 4-hydroxyacetophenone, α-naphthol, β-naphthol, catechol, resorcinol, hydroquinone, 4-tert-octylcatechol, 4, 4'-sec-butylidenephenol, 2,2-dihydroxydiphenyl, 2,2
-methylenebis(4-methyl-6-tert-butylphenol), 2,2-bis(4-hydroxyphenyl)propane, 4,4'-isopropylidene-bis(2-tert-butylphenol),
Para-hydroxybenzoic acid esters such as 4,4'-sec-butylidene diphenol, pyrogallol, phloroglucin, phloroglucin carboxylic acid, ethyl para-hydroxybenzoate, and benzyl para-hydroxybenzoate. Furthermore, in the present invention, in addition to the above-mentioned resins, other resins may be used in combination with each coating layer within a range that does not impair the present invention. Examples of such resins include methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, starch and its derivatives, sodium alginate, casein, gelatin, and alkali salts of styrene-maleic anhydride copolymers. , water-soluble ones such as alkali salts of iso(or diiso)butylene-maleic anhydride copolymers, or polystyrene, polyvinyl acetate, vinyl chloride-vinyl acetate copolymers, polybutyl methacrylate, polyacrylic esters,
Examples include aqueous emulsions such as styrene-butadiene-acrylic copolymers. In addition, the present invention includes a filler, if necessary, in each coating layer.
Thermofusible substances can be added, and examples of fillers include calcium carbonate, magnesium carbonate, alumina, silica, talc, barium sulfate,
Magnesium hydroxide, aluminum hydroxide, styrene resin, fluororesin, urea-formalin resin, etc. can be mentioned, and examples of the thermofusible substance include the following. Animal waxes such as beeswax and ceramic wax, vegetable waxes such as carnauba wax, mineral waxes such as Montano wax, petroleum waxes such as paraffin wax and microcrystalline wax, polyhydric alcohol esters of higher fatty acids, and high-grade waxes. Amides, higher amines, 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 wax-like substances, etc. The present invention will be explained in more detail below using examples. Example 1 Mixtures having the following compositions were each ground and dispersed in a ball mill for 24 hours to prepare liquids A and B, and the obtained liquids A and B were further mixed at a ratio of 1:1 (parts by weight) to heat-sensitive. A coloring layer forming liquid was prepared. [Liquid A] 3-N-methyl-N-cyclohexylamino-6
-Methyl-7-anilinofluorane 1.5 parts by weight Itaconic acid modified polyvinyl alcohol (10% aqueous solution) 10.0 〃 Water 38.5 〃 [Liquid B] Bisphenol A 6.0 parts by weight Calcium carbonate 2.0 〃 Stearic acid amide 2.0 〃 Hydroxyethyl cellulose (10 % aqueous solution)
20.0 〃 Water 20.0 〃 Spread the above heat-sensitive coloring layer forming liquid on high-quality paper (approx. 50g/
m ² ) and dried to form a heat-sensitive coloring layer with a coating weight of 5 g/m ² .Furthermore, the following [liquid C] was coated on the heat-sensitive coloring layer and dried to form a heat-sensitive coloring layer with a coating weight of 2 g/m ^{2 .} A protective layer was provided to obtain a heat-sensitive recording material of the present invention. [Liquid C] Itaconic acid modified polyvinyl alcohol 4.0 parts by weight Polyurethane aqueous emulsion (solid content 50%)
(Product name: Izerax S-4040) [Manufactured by Hokoya Chemical Industry Co., Ltd.] 4.0 Fine silica powder 2.0 Water 90.0 Of the above ingredients, itaconic acid-modified polyvinyl alcohol is completely dissolved, and then fine silica powder is added. was added and dispersed for 30 minutes using a homomixer, and then an aqueous polyurethane emulsion was added and stirred until it was gently and uniformly dispersed to prepare liquid [C]. Example 2 Mixtures having the following compositions were pulverized and dispersed in a ball mill for 24 hours to prepare liquid D and liquid E,
The obtained liquid D and liquid E were further mixed at 1:1 (parts by weight).
and mixed to prepare a thermosensitive coloring layer forming liquid. [Liquid D] 3-di-n-butylamino-7-(0-chloroanilino)fluoran 1.5 parts by weight Hydroxyethyl cellulose (10% aqueous solution)
10.0 〃 Water 38.5 〃 [Liquid E] Bisphenol A 6.0 parts by weight Dimethyl terephthalate 1.0 〃 Kaolin 2.0 〃 Itaconic acid modified polyvinyl alcohol (10% aqueous solution) 20.0 〃 Water 21.0 〃 Spread the above heat-sensitive coloring layer forming liquid on high-quality paper (approx. 50 g) /
m ² ) and dried to form a heat-sensitive coloring layer with a coating weight of 6 g/m ² .Furthermore, the following [liquid F] was coated on the heat-sensitive coloring layer and dried to obtain a coating weight of 2 g/m ² . A protective layer was provided, and a 5% aqueous solution of itaconic acid-modified polyvinyl alcohol was applied to the back surface and dried to form a back coat layer with a coating weight of 1 g/m ² to obtain a heat-sensitive recording material of the present invention. [Liquid F] Maleic acid modified polyvinyl alcohol 4.0 parts by weight Polyester aqueous emulsion (solid content 20%)
(Product name: Vylonal ME-1900) [Toyobo Co., Ltd.
[Product] 5.0 [Urea formalin resin fine powder 1.0] Water 40.0 [Liquid F] was prepared by adjusting the above composition in the same manner as [Liquid C]. Example 3 Mixtures having the following compositions were each ground and dispersed in a ball mill for 24 hours to prepare liquid G and liquid H, and the obtained liquid G and liquid H were further mixed at a ratio of 1:1 (parts by weight). A thermosensitive color forming layer forming solution was prepared. [Liquid G] 3-N-methyl-N-cyclohexylamino-6
-Methyl-7-anilinofluorane 1.0 parts by weight 3-di-n-butylamino-7-(0-chloroanilino)fluoran 0.5 parts by weight Hydroxyethyl cellulose (10% aqueous solution)
10.0 Water 38.5 [H solution] Bisphenol A 2.0 parts by weight Benzyl p-hydroxybenzoate 3.0 Calcium carbonate 2.0 Polyvinyl alcohol (10% aqueous solution) 20.0 Water 23.0 One side of high-quality paper (approximately 50 g/m ² ) The following liquid I was applied and dried to form an undercoat layer with an adhesion amount of 2 g/m ² , and the heat-sensitive color forming layer forming liquid was applied on the undercoat layer and dried to form a heat-sensitive layer with an adhesion amount of 6 g/m ² A coloring layer is provided, and the following liquid J is applied on the heat-sensitive coloring layer and dried to form a protective layer with an adhesion amount of 2 g/m ² ,
A heat-sensitive recording material of the present invention was obtained. [Liquid I] Urea/formalin resin fine powder 2.0 parts by weight Itaconic acid modified polyvinyl alcohol (10% aqueous solution) 50.0 parts by weight Glyoxal (20% aqueous solution) 5.0 Water 43.0 The above composition was uniformly mixed using a homomixer. The mixture was stirred until the mixture was mixed, and then glyoxal was added to prepare [Liquid I] as an undercoat layer forming solution. [Liquid J] Maleic acid-modified polyvinyl alcohol 4.0 parts by weight Polyamide resin (10% aqueous solution) 8.0 〃 Polyurethane aqueous emulsion (solid content 53%)
4.0 (Product name: Izerax S-2020) Calcium carbonate 2.0 Water 92.0 The above composition was adjusted in the same manner as the above [Liquid C] to prepare [Liquid J]. Note that the polyamide resin was added last. Comparative Example 1 A heat-sensitive recording material of Comparative Example 1 was obtained in the same manner as in Example 1 except that the following [Liquid K] was used instead of [Liquid C] in Example 1. [K liquid] Polyurethane aqueous emulsion (solid content 50%)
(Product name: Izerax S-4040) 12.0 parts by weight Silica fine powder 2.0 Water 96.0 Disperse the silica fine powder of the above composition in water using a homomixer, then add polyurethane aqueous emulsion and gently stir. [Liquid K] was prepared by stirring to make it homogeneous. Comparative Example 2 A heat-sensitive recording material of Comparative Example 2 was obtained in the same manner as in Example 1 except that the following [Liquid L] was used instead of [Liquid C] in Example 1. [Liquid L] Itaconic acid-modified polyvinyl alcohol 6.0 parts by weight Fine silica powder 2.0 Water 92.0 Of the above compositions, an aqueous solution of itaconic acid-modified polyvinyl alcohol was made, and fine silica powder was added to the aqueous solution and dispersed with a homomixer. , after dispersion [L
liquid] was prepared. Comparative Example 3 [Liquid M] was prepared in the same manner as in Example 3, except that the itaconic acid-modified polyvinyl alcohol in [Liquid I] was replaced with ammonium salt of styrene/maleic anhydride copolymer, and glyoxal was removed. In addition, [liquid J] maleic acid modified polyvinyl alcohol,
[Liquid N] was prepared in the same manner as Solution J except that 6.92 parts by weight of ammonium salt of styrene/maleic anhydride copolymer was used in place of the polyamide resin and aqueous polyurethane emulsion. Thermal recording of Comparative Example 3 was made in the same manner as in Example 3, except that the thermosensitive layer forming liquid of Example 3 was used, [Liquid M] was used as the undercoat layer forming liquid, and [Liquid N] was used as the protective layer forming liquid. I got the material. The quality evaluation results of the heat-sensitive recording materials obtained as described above are shown below.
1. It can be clearly seen from the evaluation results that the product of the present invention is superior.

[Table] In Table 1, RIFAX-3300 (manufactured by Ricoh Co., Ltd.) was used as a testing device to obtain the color density, and a Macbeth densitometer RD-514 was used to measure the density. Plasticizer resistance: Drop 0.05ml of dioctyl adipate and measure the concentration after 24 hours (Front: Dropped on the heat-sensitive coloring layer side (Back: Dropped on the opposite side (back side) of the heat-sensitive coloring layer) Fingerprint resistance: Heat-sensitive Place a fingerprint on the colored part and apply 40
Density measurement head stains after 24 hours at ℃, DRY: Visually observed stains on the thermal head after passing one sheet of A-4 with solid color ○: No stains △: Some stains.

Claims (1)

[Claims] 1. A heat-sensitive recording in which a heat-sensitive color-forming layer is formed on a support, the main components of which are a normally colorless or light-colored color-forming substance and a color-developing substance that develops color by reacting with the color-forming substance when heated. In the material, carboxyl group-modified polyvinyl alcohol is present on the back of the support, between the support and the heat-sensitive coloring layer, and at one or more locations in the heat-sensitive coloring layer, and carboxyl group-modified polyvinyl alcohol is present on the heat-sensitive coloring layer. 1. A heat-sensitive recording material comprising a protective layer made of a mixed resin layer of and a polyester resin or a polyurethane resin.