JPH045558B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a heat-sensitive recording material having improved storage stability by providing a surface layer on a heat-sensitive coloring layer. Conventionally, heat-sensitive recording materials are known to have a structure in which a leuco dye such as crystal violet lactone and an organic acid such as a phenolic compound are coated on a support such as paper or plastic film together with a binder. . (U.S. Patent No.
No. 2712507, No. 2730457, Special Publication No. 14039, etc. ) When this type of heat-sensitive recording material comes into contact with polyvinyl chloride plastic, the heat-colored areas disappear or the uncolored areas stop developing color. For example, if a plastic eraser is placed on this type of heat-sensitive recording material, the colored areas will disappear within a few hours. Furthermore, if a heat-sensitive recording type ticket having this type of heat-sensitive recording layer is placed in a leather wallet, the colored portion will become faint. These phenomena occur because the plasticizers contained in plastics and the penetrants used when tanning leather products dissolve or react with the leuco dyes used as color formers or the phenolic compounds used as color developers. It is thought that the colored areas will disappear or the uncolored areas will stop developing color. In the case of plasticizers, phenolic compounds in particular are easily dissolved in the plasticizer, which causes the above-mentioned disadvantages. In the case of a penetrating agent, it is presumed that inconveniences occur particularly because the penetrating agent and the phenolic compound react with each other. The present invention improves these drawbacks, and as shown in the figure, a heat-sensitive coloring layer 2 provided on a support 1.
A heat-sensitive recording material, wherein a surface layer 3 containing a binder and a curing agent, a pigment and/or a lubricant is provided thereon, and the amount of the binder and curing agent in the surface layer is 40% by weight or more of the surface layer components. It is. By providing this surface layer, storage stability against plasticizers and penetrants was increased, and excellent staking resistance was obtained, and properties such as water resistance, oil resistance, and acid resistance were also significantly improved. For example, when a plastic eraser is placed on a heat-sensitive recording layer and left to stand, the colored area disappears in 1 to 2 hours in a conventional heat-sensitive recording material without a surface layer, but in the heat-sensitive recording material of the present invention, the colored area disappears within 1 to 2 hours. It hardly disappears even after hours. Note that in the case of a heat-sensitive recording material provided with a surface layer that does not contain a curing agent, it hardly disappears in 1 to 2 hours, but it disappears considerably in 24 hours. The thermal recording medium of the present invention can be expected to be applied to the field of recording that requires preservation. For example, when used in thermal recording tickets such as those currently used, the print will not fade even after storage. Due to its advantages, it can be used for coupon tickets, commuter passes, etc. Also, water resistance,
Since it also improves oil resistance, it can also be applied to labels for foods, bottles, etc. Furthermore, since the provision of the surface layer eliminates any residue during recording, it is also advantageous for use in general heat-sensitive recording type printers and facsimile machines. Next, materials used in the present invention will be explained. Supports include high quality paper, medium quality paper, art paper,
Papers such as coated paper, paperboard, and tissue paper, and sheets such as cellophane, plastic film, and metal foil can all be used. Materials used for the thermosensitive coloring layer include colorless or light-colored leuco dyes such as lactone dyes such as crystal violet tract, lactam dyes such as rhodamine B lactam, and 3-diethylamino-
6-methyl-7anilinofluorane, 3-diethylamino-7-0-chloroanilinofluorane, 3
- Fluoran dyes such as piperidino-6methyl-7-anilinofluorane, auramine dyes such as N-halophenylleucoauramine, N-2,4,5,-trichlorophenylleucoauramine,
Examples include spiropyran dyes such as benzo-β-naphthospiropyran. As the color developer that causes the leuco dye to develop color when heated, phenolic compounds such as bisphenol A and bisphenol C, other organic acids, or salts thereof can be used. Water-soluble polymers are mainly used as binders, such as polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, starch, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, and styrene-butadiene-rubber. etc. are also used. In addition, white pigments, waxes, dispersants, antifoaming agents, etc. may be used as necessary. Next, as the material used for the surface layer forming the surface layer on the heat-sensitive coloring layer, a binder and a curing agent are used as main components, and a pigment, a lubricant, etc. are used. As a binder, casein and polyvinyl acetate,
Polyurethane, hydroxyethyl cellulose, hydroxypropyl cellulose, polyvinyl alcohol, isobutylene-maleic anhydride copolymer,
At least one resin selected from vinyl acetate-acrylic copolymer and modified polyacrylamide is used. As the curing agent, a polyamine type curing agent such as polyethyleneimine, a dialdehyde type curing agent such as glyoxal and dialdehyde starch, and a diglycidyl type curing agent such as glycerin diglycidyl ether are used. As the pigment, clay talc, aluminum hydroxide, calcium carbonate, fine silica, etc. can be used. As the lubricant, fatty acids such as stearic acid and palmitic acid or metal salts thereof, fatty acid amides such as stearic acid amide, paraffin wax, microcrystalline wax, etc. can be used. The amount of the binder and curing agent must be at least 40% by weight of the total surface layer components, and if it is less than this, there will be little effect on storage stability. Preferably it is 50% or more. When a curing agent is used, the effect on storage stability is greater than when it is not used, and therefore the effect can be exerted from a smaller amount of binder than when no curing agent is used. The amount of the curing agent is required to be at least 5% by weight of the binder component, preferably at least 10% by weight. 5
If it is less than % by weight, there is little effect on improving storage stability. Pigments and lubricants improve recording characteristics by preventing sticking with the thermal recording head and generation of scum. Next, the present invention will be explained with reference to examples. Example 1 10 parts by weight of calcium carbonate and methylcellulose
After dispersing 20 parts by weight of a 0.1% aqueous solution in a paint conditioner for 90 minutes, add 200 parts by weight of casein ammonium solution (5% aqueous solution), 10 parts by weight of polyvinyl acetate emulsion (50%), and 2 parts by weight of glycerin diglycidyl ether. A mixture of 1 and 2 parts was applied onto general thermal paper using bisphenol A (for example, thermal recording paper LFB-04 manufactured by Tomoekawa Paper Mills) so that the coating amount after drying was 4 g/ ^m2 . A surface layer was formed. Example 2 Calcium carbonate dispersion 10 used in Example 1
Parts by weight, 10 parts by weight of a dispersion obtained by placing 5 parts by weight of zinc stearate and 20 parts by weight of sodium dodecylbenzenesulfonate (1% aqueous solution) in a ball mill and grinding them for 48 hours, 200 parts by weight of ammonium casein solution (5% aqueous solution) , polyurethane emulsion (50
%) and 3 parts by weight of glycerin diglycidyl ether was applied onto the same thermal paper as in Example 1 at 4 g/m ² . Comparative Example 1 General thermal recording paper (for example, LFB manufactured by Tomoekawa Paper Co., Ltd.)
-04, etc.) Comparative Example 2 A paint obtained by removing the curing agent and glycerin diglycidyl ether from the surface layer paint used in Example 1 was used.
4g/ ^m2 coated on LFB-04. The heat-sensitive recording materials of the above Examples and Comparative Examples were color-recorded using a heat-sensitive recording device (Panafuax 7000), a plastic eraser was placed on the colored part, and 500
A decolorization test was carried out by applying a pressure of 1.5 g and leaving it for 24 hours. The recorded color density at this time and the density after the color erasure test are shown in the table below. (Concentration measurement is Macbeth RO-
(Using 100R type)

[Table] As is clear from the comparison of the densities after the decolorization test in the table above, it was found that the densities after the test were significantly improved in Examples 1 and 2 of the present invention compared to Comparative Examples 1 and 2. It will be done.

[Brief explanation of drawings]

The figure is a cross-sectional view of the heat-sensitive recording material of the present invention. 1...Support, 2...Thermosensitive coloring layer, 3...Surface layer.

Claims (1)

[Claims] 1 On the thermosensitive coloring layer provided on the support, casein and polyvinyl acetate, polyurethane, hydroxyethyl cellulose, hydroxypropyl cellulose, polyvinyl alcohol, isobutylene-maleic anhydride copolymer, vinyl acetate-acrylic copolymer, modified A surface layer containing a binder made of at least one resin selected from the group consisting of polyacrylamides, at least one curing agent selected from the group consisting of polyamines, dialdehydes, and glycidyls, and a pigment and/or a lubricant. established,
A heat-sensitive recording material further characterized in that the amount of the binder and curing agent in the surface layer is 40% by weight or more of the surface layer components.