JPH06270541A - Reversible thermal recording material - Google Patents

Abstract

PURPOSE:To provide a reversible thermal recording material forming a recording image of which the hue is different from the hue due to the reaction of a basic dye with a developing/tone-reducing agent. CONSTITUTION:In a reversible thermal recording material wherein a thermal recording layer containing a colorless or light-colored basic dye, a developing/ tone-reducing agent thermally reacting with the basic dye to develop a color or to reduce a tone and a binder as main components is provided on a support, a layer containing pearl pigment is provided on at least a part of the thermal recording layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible thermosensitive recording medium capable of reversibly recording and erasing repeatedly by a thermal means, and particularly to a basic dye whose hue of recorded image is colorless or pale. It is a reversible thermosensitive recording medium having a hue different from that due to the reaction with the color-developing and reducing agent.

[0002]

2. Description of the Related Art Conventionally, a reversible thermosensitive recording medium having a thermosensitive layer whose transparency reversibly changes depending on temperature changes is used in balance display media such as cards and prepaid cards for which forgery prevention is required, in factories, etc. It is widely used such as production instructions written repeatedly. However, since it is difficult to obtain a recorded image with a high contrast by this method, a method of reversibly obtaining a recorded image by a reaction between a basic dye and a color-developing and reducing agent has been proposed. In this method, various hues can be obtained by changing the basic dye, but the kind is limited.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a reversible thermosensitive recording medium in which the hue of a recorded image is different from the hue due to the reaction between a colorless or light colored basic dye and a color-developing / reducing agent. .

[0004]

Means for Solving the Problems The present inventors have found that a colorless or light-colored basic dye is provided on a support, and a color-developing and reducing agent and a binder which are thermally reacted with the basic dye to develop or reduce color. In a reversible thermosensitive recording medium having a thermosensitive recording layer containing as a main component, it was found that the above object can be achieved by providing a layer containing a pearl pigment on at least a part of the thermosensitive recording layer, and the present invention has been completed. It was

[0005]

As described above, the present invention changes the hue of a recorded image by using a specific pigment. The specific pigment used in the present invention is a pearl pigment obtained by coating the surface of bismuth oxychloride, natural or synthetic mica with at least one metal oxide having a high refractive index such as titanium oxide, iron oxide or tin oxide. is there. Above all, the coating of titanium oxide or iron oxide is preferable because it is rich in hue change. Metal oxide coverage is 5
About 90%, preferably 10 to 70% is desirable. The particle size of the specific pigment is 1 to 500 μm, preferably 3
˜250 μm is desirable.

The layer having a specific pigment may be obtained by finishing the pearl pigment into an organic solvent-based paint or an aqueous paint, and applying it.
The printing ink such as a screen ink, a gravure ink, an offset ink or the like is finished and printed, or the like, to be provided over the entire area or a part of the thermal recording layer. In addition, a metallic hue can be obtained by using an appropriate amount of carbon black or the like when finishing the coating liquid or ink. The addition rate of the specific inorganic pearl pigment in the coating liquid or the ink is appropriately selected depending on the method of use, but is 0.01 to 9
It is desirable to adjust the amount in the range of 0% by weight, preferably 0.1 to 60% by weight.

As the colorless or light-colored basic dye used in the reversible thermosensitive recording layer of the present invention, various types are known, and the following are exemplified. 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide,
3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3- (1,
2-dimethylindol-3-yl) phthalide, 3-
(P-Dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3,3-bis (1,2)
-Dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3
-Bis (9-ethylcarbazol-3-yl) -6-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -6-dimethylaminophthalide,
Triarylmethane dyes such as 3-p-dimethylaminophenyl-3- (1-methylpyrrol-3-yl) -6-dimethylaminophthalide, 4,4'-bis-dimethylaminobenzhydrylbenzyl ether, Diphenylmethane dyes such as N-halophenyl-leuco auramine and N-2,4,5-trichlorophenyl leuco auramine, thiazine dyes such as benzoyl leuco methylene blue and p-nitrobenzoyl leuco methylene blue, 3-
Methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho- (6'-methoxybenzo) spiropyran, 3-propyl-spiro -Spiro dyes such as dibenzopyran, lactam dyes such as rhodamine-B anilinolactam, rhodamine (p-nitroanilino) lactam, rhodamine (o-chloroanilino) lactam, 3-dimethylamino-7-methoxyfluorane, 3- Diethylamino-6-methoxyfluorane, 3-diethylamino-
7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7
-Chlorofluorane, 3-diethylamino-6,7-dimethylfluorane, 3- (N-ethyl-p-toluidino) -7-methylfluorane, 3-diethylamino-7
-(N-acetyl-N-methylamino) fluorane, 3
-Diethylamino-7-N-methylaminofluorane,
3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7- (N-methyl-N-benzylamino) fluorane, 3-diethylamino-7-
(N-chloroethyl-N-methylamino) fluorane,
3-diethylamino-7-diethylaminofluorane,
3- (N-ethyl-p-toluidino) -6-methyl-7
-Phenylaminofluorane, 3- (N-cyclopentyl-N-ethylamino) -6-methyl-7-anilinofluorane, 3- (N-ethyl-p-toluidino) -6-
Methyl-7- (p-toluidino) fluorane, 3-diethylamino-6-methyl-7-phenylaminofluorane, 3-di (n-butyl) amino-6-methyl-7-phenylaminofluorane, 3-di (N-Pentyl) amino-6-methyl-7-phenylaminofluorane, 3-
Diethylamino-7- (2-carbomethoxy-phenylamino) fluorane, 3- (N-ethyl-N-isoamylamino) -6-methyl-7-phenylaminofluorane, 3- (N-cyclohexyl-N-methylamino) ) −
6-methyl-7-phenylaminofluorane, 3-pyrrolidino-6-methyl-7-phenylaminofluorane,
3-piperidino-6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, 3-diethylamino-7- (o-chlorophenylamino) fluorane, 3-dibutylamino-
7- (o-chlorophenylamino) fluorane, 3-pyrrolidino-6-methyl-7-p-butylphenylaminofluorane, 3- (N-methyl-N-tetrahydrofurfurylamino) -6-methyl-7-ani Fluoran dyes such as linofluorane and 3- (N-ethyl-N-tetrahydrofurfurylamino) -6-methyl-7-anilinofluorane.

Further, as a color-developing agent used in combination with a basic dye, a salt of bis (hydroxyphenyl) acetic acid and higher aliphatic amine, a salt of bis (hydroxyphenyl) propionic acid and higher aliphatic amine , A salt of gallic acid and a higher aliphatic amine, and the like. As the higher aliphatic amine, hexylamine, heptylamine,
Octylamine, nonylamine, decylamine, undecylamine, laurylamine, tridecylamine, tetradecylamine, pentadecylamine, cetylamine,
Examples thereof include heptadecylamine and stearylamine.

Further, in the present invention, as the binder, a polymer material which is soluble in water or an organic solvent which is usually used can be used. For example, polyvinyl alcohol, ethyl cellulose, cellulose acetate, polystyrene, polyvinyl chloride, linear saturated polyester, homopolymer or copolymer of methacrylic resin such as polymethylmethacrylate, polyethylmethacrylate, polyurethane, polybutyral, nitrocellulose, etc. A thermoplastic resin may be used, and is added in an amount of 10 to 40% by weight, preferably 15 to 35% by weight, based on the total solid content of the recording layer.

If necessary, various auxiliary agents can be added to the coating liquid, for example, disodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, fatty acid metal salt and the like, stearin. Waxes such as zincate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, defoaming agent,
Fluorescent dyes, coloring dyes, etc. are appropriately added.

Further, various pigments may be used in combination in the coating liquid as long as the characteristics of the present invention are not impaired. For example, the above-mentioned pearl pigment, kaolin, clay, calcium carbonate, calcined clay, calcined kaolin, Diatomaceous earth, finely particulate anhydrous silica, inorganic pigments such as activated clay, styrene microballs, nylon powder, polyethylene powder, urea
Examples include organic pigments such as formalin resin filler and raw starch particles.

In the present invention, the method for forming the heat-sensitive recording layer is not particularly limited, and examples thereof include air knife coating, varibar blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating, die coating and the like. The binder is dissolved in a coating solution which is uniformly dispersed or dissolved in water or an organic solvent by a suitable coating method of (1), and a thickener, a white pigment or the like is added as a liquidity improving agent to the recording layer if necessary. It is formed by a method of obtaining a coating liquid for application, coating and drying it on a support such as paper, plastic film and synthetic paper. Recording layer coating liquid 2~12g / m ² coating amount by dry weight of, it is regulated preferably in the range of about 3 to 10 g / m ^2.

The present invention provides a layer having the above-mentioned specific pigment on the heat-sensitive recording layer thus obtained, and the coating liquid for forming the layer having the specific pigment is, for example, an acrylic clear film containing the specific pigment. It is prepared as an ink or a coating liquid by being dispersed in a lacquer or the like, dispersed in an aqueous or solvent-based ink medium, or dispersed in water together with a water-soluble resin or the like.

Examples of the water-soluble resin used in the aqueous dispersion type coating liquid include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy modified polyvinyl alcohol and acetoacetyl group. Modified polyvinyl alcohol, silicon modified polyvinyl alcohol, sulfone modified polyvinyl alcohol, nitrile modified polyvinyl alcohol, amide modified polyvinyl alcohol, pyrrolidone modified polyvinyl alcohol, graft copolymer of polyvinyl alcohol and (acrylamide / acrylic acid derivative / acrylonitrile) copolymer Etc. can be illustrated.

Further, in the coating liquid, if necessary, a lubricant such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, etc., and a surfactant such as sodium dioctylsulfosuccinate (dispersant, wetting agent). Agents), defoaming agents, fluorescent dyes, coloring dyes, and various auxiliaries such as water-soluble polyvalent metal salts such as potassium alum and aluminum acetate may be appropriately added. Further, in order to further improve the water resistance, a curing agent such as glyoxal, boric acid, dialdehyde starch, and an epoxy compound can be used in combination.

The coating solution containing the specific pigment is sufficiently mixed and dispersed by a mixer / attritor, ball mill, roll mill or other mixing / stirring machine, if necessary, and then coated on the heat-sensitive recording layer by various known coating devices. To be dried. After application, it can be dried by irradiation with ultraviolet rays or electron beams. The coating amount of the coating liquid is not particularly limited,
If the coating amount after drying is less than 0.1 g / m ² , the desired effect of the present invention cannot be obtained, and if it exceeds 20 g / m ² , the recording sensitivity of the thermosensitive recording medium may be significantly reduced.
0.1 to 20 g / m ² , preferably 0.5 to 10 g / m
^It is desirable to prepare within a range of about ² .

The heat-sensitive recording material of the present invention has a protective layer on the heat-sensitive recording layer, on a layer containing a specific pigment, or on the back surface of the support for the purpose of improving the storability of recorded images against chemicals. It is also possible to provide. The protective layer is composed mainly of a binder made of a water-soluble or water-dispersible polymer compound. Specific examples of such a binder include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose,
Gelatin, casein, gum arabic, polyvinyl alcohol, carboxy modified polyvinyl alcohol, acetoacetyl group modified polyvinyl alcohol, silicon modified polyvinyl alcohol, diisobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride copolymer salt, ethylene. Acrylic acid copolymer salts, styrene / acrylic acid copolymer salts, styrene / butadiene copolymer emulsions, urea resins, melamine resins, amide resins, polyurethane resins, etc. can be exemplified, and among them, acetoacetyl group-modified polyvinyl alcohol and carboxy. Modified polyvinyl alcohol is particularly preferably used because it can form a strong film.

The pearl pigment may be added to the protective layer within a range that does not impair the effects of the present invention. Further, in order to further improve printability and sticking in the protective layer, a pigment can be added as necessary, and specific examples thereof include calcium carbonate, zinc oxide,
Inorganic pigments such as aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc, kaolin, clay, calcined kaolin, colloidal silica, styrene microballs, nylon powder,
Examples thereof include polyethylene powder, urea / formalin resin filler, and organic pigments such as raw starch particles. The amount used is generally 5 with respect to 100 parts by weight of the binder component.
It is desirable to adjust in the range of about 300 parts by weight.

Further, in the protective layer coating liquid, a lubricant such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, etc., and a surfactant (dispersion such as dioctyl sulfosuccinate) (dispersion), if necessary. Agent, wetting agent), defoaming agent,
Various auxiliaries such as water-soluble polyvalent metal salts such as potassium alum and aluminum acetate may be appropriately added. Further, in order to further improve the water resistance, a curing agent such as glyoxal, boric acid, dialdehyde starch, and an epoxy compound can be used in combination. The coating liquid for forming the protective layer is
Generally, water is used as the dispersion medium.

The protective layer coating solution thus prepared is coated on the heat-sensitive recording layer or the layer containing a specific pigment by a suitable coating device, but generally 0.3 to 10 g /
It is desirable that the amount is adjusted to m ² , preferably 0.5 to 7 g / m ² .

The heat-sensitive recording material of the present invention may be provided with two or more heat-sensitive recording layers which develop different color tones. Further, after applying each layer, smoothing treatment such as super calendering is applied, or the back surface of the recording material is subjected to adhesive treatment to be processed into an adhesive label, and a magnetic recording layer is provided on the back surface. The publicly known technology can be added as needed.

The method of forming an image or erasing an image according to the present invention is based on heat, and can be carried out by using an apparatus such as a thermal printer, a heat reflection copying apparatus, a hot stamper or a heat roll.

[0023]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" and "%" in the examples mean "parts by weight" and "% by weight", respectively.

Example 1 Liquid A Preparation 10 parts of 3-diethylamino-7- (o-chlorophenylamino) fluorane, 10% of polyvinyl alcohol
A composition comprising 20 parts of an aqueous solution and 22 parts of water was pulverized with a horizontal sand mill until the average particle size became 0.4 μm. Liquid B preparation 10 parts by weight of salt of 2,2-di- (p-hydroxyphenyl) propionic acid and stearylamine, calcium carbonate 10
Parts, 50 parts of 10% aqueous solution of polyvinyl alcohol, water 1
The average particle size of the composition consisting of 0 parts was 1.
The particles were pulverized to 0 μm. Formation of thermosensitive recording layer 104 parts of solution A and 400 parts of solution B were mixed and agitated to prepare a coating solution, and a coating amount after drying on 50 g / m ² of high quality paper was 7 g / m.
^A reversible thermosensitive recording layer was formed by coating and drying so as to be ² .

Formation of Pearl Pigment-Containing Layer Inorganic pearl pigment [trade name: Iriodin 205, titanium oxide coverage 43%, particle size 10 to 60 μm, manufactured by Merck Japan Ltd.] 80 parts, polyvinyl alcohol and (acrylamide / acrylic acid derivative / acrylonitrile) ) Graft copolymer with copolymer [trade name: Polymalon 2000, solid concentration 15%, manufactured by Arakawa Chemical Co., Ltd.] 130 parts, sodium di-2-ethylhexyl sulfosuccinate [trade name: Ravisol B-80] 0.1 Parts, antifoaming agent (solid concentration 15%)
A coating solution obtained by mixing and stirring 0.2 parts of water and 100 parts of water was applied and dried on the reversible thermosensitive recording layer so that the applied amount after drying was 3 g / m ² to form a pearl pigment-containing layer. .

Formation of protective layer Graft copolymer of polyvinyl alcohol and (acrylamide / acrylic acid derivative / acrylonitrile) copolymer [trade name: Polymalon 2000, solid concentration 15%,
Arakawa Chemical Co., Ltd.] 330 parts, aluminum hydroxide [trade name: Hydilite H-42, average particle size 1 μm, Showa Denko KK] 50 parts, zinc stearate 30% aqueous dispersion 3
0 parts, sodium di-2-ethylhexyl sulfosuccinate [trade name: Ravisol B-80, manufactured by NOF Corporation] 2
Parts, 1 part of antifoaming agent (solid concentration 15%), and 340 parts of water are mixed and stirred to apply the coating solution onto the pearl pigment-containing layer so that the coating amount after drying is 2 g / m ^2. After drying to form a protective layer, smoothing treatment was carried out with a super calender to obtain a reversible thermosensitive recording medium.

[0027]

Example 2 In the preparation of solution B, a salt of gallic acid and stearylamine was used in place of the salt of 2,2-di- (p-hydroxyphenyl) propionic acid and stearylamine, and a pearl pigment-containing layer was used. In the formation of, the same as Example 1 except that an inorganic pearl pigment [trade name: Iriodin 219, titanium oxide coverage 48%, particle size 10 to 60 μm, manufactured by Merck Japan Ltd.] was used in place of the inorganic pearl pigment Iriodin 205. A reversible thermosensitive recording medium was obtained.

[0028]

Comparative Examples 1 and 2 Reversible thermosensitive recording media were obtained in the same manner as in Examples 1 and 2 except that the pearl pigment-containing layer was not provided.

With respect to the four types of reversible thermosensitive recording media thus obtained, the hues recorded by NTTFAX-20R and the decolorized hues decolored by pressing the recording portion against a hot plate at 120 ° C. for 1 second were compared. , As shown in Table 1.

[0030]

[Table 1]

[0031]

EFFECTS OF THE INVENTION As is clear from the results of Table 1, the recording material of the present invention provides: a recorded image having a hue different from the hue due to the reaction between the leuco dye and the color former; It can be erased and re-recorded.-Because it can be partially changed to another hue, it is also useful as a forgery prevention and multi-color recording. Excellent reversible thermosensitive recording. It is the body.

Claims (1)

[Claims] 1. A thermosensitive recording layer comprising, as a main component, a colorless or light-colored basic dye and a color-developing / reducing agent which develops or reduces color by thermally reacting with the basic dye on a support. In the reversible thermosensitive recording medium, a layer containing a pearl pigment is provided on at least a part of the thermosensitive recording layer.