JPS62132669A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enable thermally printed images to be fixed by irradiation with electron rays, by providing a layer comprising an electron ray curable resin between a layer comprising a color forming substance and a layer comprising a color developing substance. CONSTITUTION:A layer comprising an electron ray curable polyacrylate resin or polymethacrylate resin is provided between a layer comprising a light-colored or colorless color forming substance and a layer comprising a color developing substance capable of developing the color of the color forming substance when being heated. After thermal printing of images by a thermal head or the like, this thermal recording material is irradiated with electron rays, whereby the electron ray curable resin is cured to form a cured resin film, which isolates the layer comprising the color forming substance and the layer comprising the color developing substance from each other, so that the thermal recording material hardly undergoes color development even when being again heated. Accordingly, heating of the thermal recording material after thermal color forming is once affected won't cause any color development or will give only a developed color image which can be clearly distinguished from the developed color images previously recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to heat-sensitive recording materials. More specifically, the present invention relates to a heat-sensitive recording material with excellent tamper-proofing properties.

Conventional technology In general, heat-sensitive recording materials, such as heat-sensitive recording paper, are made by separately dispersing leuco dyes (color-forming substances) and color developers (color-developing substances) such as phenolic substances into fine particles. The mixture is mixed with auxiliary agents such as binders, fillers, and lubricants, and applied as a coating liquid to a support such as paper, film, or synthetic paper.By heating, one of the leuco dye and color developer is mixed. Alternatively, colored recording can be obtained by a chemical reaction that occurs when the two are melted and brought into contact.A thermal printer or the like having a built-in thermal helad is used to heat such a heat-sensitive recording sheet to develop color.

Compared to other recording methods, thermal recording has the following advantages: (1) it makes no noise during recording, (2) it does not require development, fixing, etc., (3) it is maintenance-free, and (4) it is easy to produce colored images. Due to its relatively low price, it is widely used in the facsimile field, computer output, printers such as calculators, medical measurement recorders, automatic ticket vending machines, thermal recording labels, etc. It is being

However, such heat-sensitive recording materials have the problem that even after the specified heat-sensitive recording by heating is completed, coloring occurs if heat is applied to the non-printed areas, and tampering with securities, receipts, etc. is not allowed. The disadvantage is that it is difficult to use in the field.

Problems to be Solved by the Invention Once the color is developed by heating, the color does not develop even after heating, or even if it does develop color, only a colored image that can be clearly distinguished from the already recorded colored image can be produced. The development of heat-sensitive recording materials is desirable.

Means for Solving the Problems The present inventors have conducted extensive research to develop the above-mentioned heat-sensitive recording material, and as a result they have arrived at the present invention. That is, the present invention provides a layer made of electron beam curable polyacrylate resin or polymethacrylate resin between a layer containing a light-colored or colorless color-forming substance and a layer containing a color-developing substance that can cause the color-forming substance to develop color when heated. To provide a heat-sensitive recording material characterized by being provided with.

In the heat-sensitive recording material of the present invention, when the electron beam is irradiated after heating printing with a thermal head or the like, the electron beam-curable resin is cured, and the layer containing the color-forming substance and the layer containing the color-developing substance are formed by the cured resin film. Since it is isolated, it is difficult to develop color even if it is reheated.That is, the heat-sensitive recording material of the present invention can fix the printed image by applying an electron beam after heating printing.

The electron beam curable resin used in the present invention includes acrylates such as liquid or solid polyol acrylate, polyester acrylate, epoxy acrylate, and urethane acrylate, polyol methacrylate, polyester methacrylate, epoxy methacrylate,
When methacrylates such as urethane methacrylate are used and are in liquid form, those with a viscosity of 10,000 CI)S or more are desirable. Specific examples of acrylates or methacrylates used in the present invention include a combination of pentaerythritol and acrylic acid or methacrylic acid, a condensate of spiroglycol and acrylic acid or methacrylic acid, adipic acid, etc. , a condensate of 6-hexanediol and acrylic acid or methacrylic acid, a condensate of phthalic anhydride, propylene oxide, and acrylic acid or methacrylic acid, a condensate of trimellitic acid, diethylene glycol, and acrylic acid or methacrylic acid, a condensate of phthalic anhydride, and acrylic acid or methacrylic acid. Condensate of neopentyl glycol and acrylic acid or methacrylic acid, condensate of bisphenol A, epichlorohydrin and acrylic acid or methacrylic acid, condensate of phenol novolac, epichlorohydrin and acrylic acid or methacrylic acid, tolylene diisocyanate and 1, 6-hexanediol and adipic acid and 2-hydroxyethyl acrylate or 2
Examples include a condensate of -hydroxyethyl methacrylate, a mixture of a condensate of toluylene diisocyanate, propylene glycol, and acrylic acid or methacrylic acid.

(These are "Introduction to UV curing technology" (published by Kobunshi Kankai)
It is described in ) Conventionally known color-forming substances are used as color-forming substances, and specific examples include xanthine compounds, 2-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6- (Methylcyclohexylamino)-fluorane, 2-anilino-3-methyl-6=(ethylisopentylamino)fluorane, 2-anili2-3-methyl-6-sibutylaminofluorane, 2-(p-chloroanilino)-3 -Methyl-6-diethylaminofluorane, 2-(p-fluoroanilino)-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6-(p-1-luidinoethylamino)fluorane , 2-(p-toluidino)-3-methyl-6-diethylaminofluorane, 2
- (0-chloroanilino)-6-sibutylaminofluorane, 2-(o-fluoroanilino)-6-diethylaminofluorane, 2-(o-fluoroanilino)-6
-sibutylaminofluorane, 2-anilino-3-methyl-6-piperidinofluorane, 2-anilino-3-methyl-6-pyrrolidinofluorane, 2-ethoxyethylamino-3-chloro-6- diethylaminofluorane,
2-anilino-3-chloro-6-diethylaminofluorane, 2-chloro-6-diethylaminofluorane, 2
-Methyl-6-diethylaminofluorane, 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone) as a triarylmethane compound, 3,3--
His-(p-dimethylaminophenyl)phthalide, 3-
(3-methyl-3-spiro-dinaphthopyran as a spiropyran compound, such as p-dimethylaminophenyl 9-3-(1,2-dimethylaminoindol-3-yl)phthalide, 3.3- ) dimethyl- Examples include 6-nitro-8-methoxyspiro (indoline-2,2'-benzopyran), N-halophenyl-leukoolamine as a diphenylmethane compound, and benzoylleucomethylene blue as a thiazine compound, and their coloring properties The substances may be used alone or in combination.

In addition, conventionally known color developing substances are used as color developing substances, and specific examples thereof include p-octylphenol, p-octylphenol, p-octylphenol, p-octylphenol,
-tert-butylphenol, p-phenylphenol, 1. ,]-bis(p-hydroxyphenyl)furopane, 2.2-bis-(p-hydroxyphenyl)-propane, 1.1-his(p-hydroxyphenyl)-cyclohexane, 4.4-thiobisphenol, 4. 4-sulfonyldiphenol, bis-(3-71fluor-4-hydroxyphenyl)-sulfone, novolac type phenol resin, benzyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, dimethyl 4-hydroxyphthalate, 5-hydroxy Ethyl isophthalate, 3,5-di-t
For ert-fur salicylic acid, 3,5-di-α-methylbenzylsalicylic acid, etc. and aromatic carboxylic acids,
Examples include polyvalent metal salts thereof.

It is desirable to use a binder when providing the layer containing the color-forming substance and the layer containing the color developer. In addition, sensitizers, fillers, lubricants, various surfactants, etc. are also used as necessary. Binders used in preparing the layer containing the color-forming substance and the layer containing the color-developing substance include methylcellulose, methoxycellulose, hydroxyethylcellulose, carboxydimethylcellulose, polyvinyl alcohol, and carboxyl group-modified polyvinyl. Alcohol, polyvinylpyrrolidone, polyacrylamide,
polyacrylic acid, starch and its derivatives, casein,
Water-soluble ones such as gelatin, alkali salts of styrene-maleic anhydride copolymers, alkali salts of iso(or diiso)butylene-maleic anhydride copolymers, or polyvinyl acetate, vinyl chloride/vinyl acetate copolymers, polystyrene,
Polyacrylic acid ester, polyurethane, styrene/
Water-insoluble emulsions such as butadiene/acrylic acid copolymers and self-crosslinking acrylic polymers are used.

Sensitizers include higher fatty acid amides such as stearic acid amide, waxes such as beeswax and carnauba wax, fatty acid anilides, carboxylic acid esters such as dimethyl terephthalate and diphenyl phthalate, p-toluenesulfonic acid phenoxyethyl ester, and benzene. Sulfonic acid esters such as sulfonic acid phenyl ester, naphthol derivatives such as 1-benzyloxynaphthalene, 2-pentyloxynaphthalene, etc. may be used. Further, as fillers, calcium carbonate, magnesium carbonate, magnesium oxide, silica, white carbon, talc, clay, alumina, magnesium hydroxide, aluminum hydroxide, barium sulfate, polystyrene resin, urea-formalin resin, etc. are used.

As the lubricant, zinc stearate, calcium stearate, aluminum stearate, etc. are used.

Paper, synthetic paper, film, etc. are used as the support on which the thermosensitive coloring layer is provided.

In preparing the heat-sensitive recording material of the present invention, first, a mixture of the above-described color-forming substance and a binder and a mixture of a color-developing substance and a binder are prepared by a conventional method. A coating liquid is prepared by adding a lubricant and various surfactants and performing a separate microparticulation treatment.

On the other hand, a binder used when preparing the above-mentioned heat-sensitive coloring layer to the above-mentioned electron beam curable acrylate or methacrylate]: 0.05 to 1, preferably l: o, 1
~0.5 (acrylate or methacrylate: binder,
A coating liquid containing electron beam curable acrylate or methacrylate is prepared by mixing them in a dry weight ratio (dry weight ratio) and, if necessary, micronizing them to a particle size of 1 to 5 μm.

Next, the coating liquid containing the color-forming substance obtained as described above is first applied at a rate of 0.1 to 5 g/m2, usually 0.3 to 2.0 g/m2.
m2 (W dry weight) and dry, then apply the coating liquid containing the acrylate or methacrylate to O, 1 to 20 g/m", preferably 05 to 0.0 g/m".
m2 (dry weight).
．． The heat-sensitive recording material of the present invention can be changed by coating and drying to a weight of 5 to 10 g/m<2> (dry weight). In addition, in the above, it is preferable to carry out drying in the range of 30 to 70°C. Furthermore, it is also possible to change the order of application in the order of the coating liquid containing the color-developing substance, the coating liquid containing acrylate or methacrylate, and the coating liquid containing the color-developing substance.

Further, if necessary, a protective layer made of, for example, a hydrophilic or hydrophobic polymer may be provided on the thermosensitive coloring layer prepared as described above.

In the heat-sensitive recording material of the present invention, in order to cure the layer containing electrocurable acrylate or methacrylate after heat-sensitive coloring by a normal method, the amount of 0.1 to I
The electron beam is irradiated with an electron beam of 5 Mrad, more preferably 0.5 to 10 Mrad.

In the heat-sensitive recording material of the present invention, after being thermally colored (initially colored) and irradiated with electron beams, the coloring caused by heating is kept to an extremely low level, so the resulting image can be clearly distinguished from the initially colored image, making falsification extremely difficult. In this respect, it has an extremely large advantage in the field of securities, receipts, etc. In the heat-sensitive recording material of the present invention, the layer containing the color-forming substance and the layer containing the color-developing substance are separated by the layer containing electron beam-curable acrylate or methacrylate, so that the background color is not developed before heat-sensitive coloring. It has excellent storage stability such as gender.

EXAMPLES Next, the present invention will be specifically explained by examples, but the present invention is not limited to these examples. In the example,
Parts indicate parts by weight.

Example 1 Solutions [A] to [D] were prepared by separately grinding and dispersing mixtures having the following compositions using a sand grinder so that the average particle size was 1 to 3 μm.

[A]Liquid CB]Liquid [C]Liquid [DlLiquid The above liquid was applied to the surface of paper with a basis weight of about 50 g/m2 to obtain a heat-sensitive recording material (paper) of the present invention.

■ Liquid [A]: Liquid [C] mixed at a weight ratio of 1 and 4 was applied to a solid content of 5 g/m2, and dried at 60°C ■ [D] Liquid was mixed with a solid content of 1. [13] Coating and drying the liquid to a solid content of 4.5 g/m2.Example 2゜In Example 1, [A] 2-(0- 2-anilino-3-methyl-6-(methylcyclohexylaminofluoran) was used instead of fluoroanilino)-6-sibutylaminofluorane, and [D] xylylene diacrylate was used instead of spiroglycol diacrylate in the liquid. A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1 except that isocyanate-2-hydroxyethyl acrylate (solid) was used.

Example 3 In Example 1, [B] bis-(3-allyl-4
-Using p-hydroxybenzoic acid benzyl ester instead of hydroxyphenylnosulfone, and [C] using stearamide instead of p-acetotoluide in the liquid, A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1, except that polyester methacrylate (average molecular weight 3,200) consisting of phthalic anhydride and neopentyl glycol was used instead.

Example 4 In Example 1, urethane acrylate (average molecular weight 15,000) consisting of toluylene diisocyanate and propylene glycol was used in place of [D] spiroglycol diacrylate in the liquid, and the order of application was changed to develop color. The coating liquid containing the substance, the coating liquid containing the urethane acrylate, the coating liquid containing the color-forming substance, and then the PV
The protective layer of A has a solid content of 1. The heat-sensitive recording material of the present invention was prepared in the same manner as in Example 1, except that it was coated and dried to give a coating weight of 5 g/m2.

Example 5 In Example 1, [A] 2-anilino-3-methyl-6-dinithylaminofluorane was used instead of 2-(o-fluoroanilino)-6-sibutylaminofluorane in the liquid. [B] bis(3-allyl-4-hydroxyphenylnosulfone is used instead of bisphenol A) in the liquid; and [D] the liquid consists of bisphenol A and epichlorohydrin instead of spiroglycol diacrylate. Epoxy compound methacrylate (average molecular weight 5,
A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1 except that 000) was used.

Example 6 A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the mixing ratio (liquid [A] and liquid [C]) and coating amount were changed as follows.

■ A mixture of liquid [A] and liquid [C] in a weight ratio of 1:3 was applied and dried so that the solid content was 8 g/m2.■ Liquid CD] was mixed with a solid content of 3 g/m2. ■ Apply and dry liquid [B] so that the solid content is 7.5 g/m2 Example 7゜ In Example 1, apply the amount of liquid [D] to 1.5 g/m2
A heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the concentration was changed from 1 to 7 g/m2.

Image densities of the heat-sensitive recording materials obtained in the above examples were measured during heating color development and reheating color development after electron beam irradiation. The results are shown in the table below.

(1) The color density is determined by pressing the heat-sensitive recording material at 1.40°C for 5 seconds using a hot plate, using a Macbeth reflection densitometer RD-914 to determine the color density at 6111 (2) above (
After heating and coloring in the same manner as in 1), an electrocurtain type electron beam irradiation device (CB- manufactured by Energy Science Co., Ltd.) was used.
150) at an irradiation dose of 3 Mrad to develop color again in the same manner as in (1) above, and the color density was measured. (The background density was measured using the above-mentioned RD-914.) As is clear from the table, the heat-sensitive recording material of the present invention has a much higher color than the initial color even after being heated and heated (initial color) and heated again by electron beam irradiation. The originally colored image and the new colored image could be clearly distinguished, giving only inferior color density.

Effects of the Invention A heat-sensitive recording material has been developed which, after being heated to form a colored image (originally colored image) and irradiated with electrons, produces only a colored image that can be clearly distinguished from the originally colored image.

Claims (1)

[Claims] (1) A layer made of electron beam curable polyacrylate resin or polymethacrylate resin is provided between a layer containing a light-colored or colorless color-forming substance and a layer containing a color-developing substance that can cause the color-forming substance to develop color when heated. A heat-sensitive recording material characterized by: