JPH062430B2 - Thermal recording material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat-sensitive recording material. More specifically, it relates to a heat-sensitive recording material that can be fixed by irradiation with ultraviolet rays.

[Prior Art] In general, a heat-sensitive recording material is a recording material having a structure in which a so-called heat-sensitive color-developing layer that develops color by heating is formed on a support such as paper, synthetic paper, or resin film. A thermal printer having a built-in thermal head is used. Compared with other recording materials, such a recording material can obtain recording in a relatively short time without performing a complicated process such as development, generate no noise, and are relatively inexpensive. Due to certain advantages, it is widely used not only for copying books, documents, etc., but also for recording various information such as electronic calculators, facsimiles, telexes, medical measuring instruments, and measuring instruments. There are various types of heat-sensitive recording materials such as dye type, metal type, silver salt type, etc., but the dye type is often used because of the sharpness of the image, the whiteness of the background, the naturalness, and the relatively low cost. However, dye-type heat-sensitive recording materials have problems such that the color image disappears with an organic solvent and the non-image area is colored by heating, and it is used in fields where importance is placed on reliability, especially securities and receipts. Not adopted yet.

〔Purpose〕

The present invention is intended to solve the above-described problems. After heating and printing, by irradiating the entire surface of the recording paper with ultraviolet rays, no color is developed even when reheated or reprinted, that is, the background can be fixed. The purpose of the present invention is to provide a thermosensitive recording material.

〔Constitution〕

According to the present invention, on a support, in a thermosensitive recording material provided with a thermosensitive coloring layer containing a leuco dye and a developer as a main component, at least one of the leuco dye and the developer, If necessary, the leuco dye and the color developer are encapsulated in a microcapsule formed of a material containing a photocurable resin and a photopolymerization initiator as main components together with a heat-fusible substance. A thermal recording material is provided which is characterized by being isolated from each other.

In the heat-sensitive recording material of the present invention, since the leuco dye and the color developer are separated from each other by the microcapsule film, contact between the two cannot occur unless the film is broken, and thus the storage stability is improved, for example, The risk of background coloration due to contact with oils and fats and solvents is reduced. Further, since this microcapsule film is formed of a photo-curable (particularly UV-curable) resin, the photo-curable resin is cured by irradiating the surface of the recording material after heating and printing with ultraviolet rays, and as a result, The capsule film does not melt even when it is reheated, and the background part no longer exhibits thermochromic properties.
That is, the heat-sensitive recording material of the present invention can fix the background by irradiating with ultraviolet rays after heating and printing.
The color development sensitivity (thermoresponsiveness) will be lower due to the presence of the microcapsule coating, compared to the case without the coating, but by incorporating a heat-fusible substance inside and / or outside the microcapsule, the thermal response will be improved. You can improve your sex. In a normal heat-sensitive recording material, when a heat-fusible substance is used to enhance the thermal response, the problem of background fog is encountered, but in the case of the present invention, this problem is caused by the presence of the microcapsule film. It does not happen.

The leuco dyes used in the present invention may be used alone or as a mixture of two or more, and as such leuco dyes,
What is applied to this kind of heat-sensitive material is arbitrarily applied, and for example, leuco compounds of dyes such as triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based and spiropyran-based dyes are preferably used. Specific examples of such leuco dyes include those shown below.

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-dimethylaminophenyl) phthalide, 3-cyclohexylamino-6-chlorofluorane, 3-dimethylamino-5,7-dimethylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino -7-Methylfluorane, 3-diethylamino-7,8-benzfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3- (Np-tolyl-N-ethylamino) -6- Methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluora , 2- {N- (3'-trifluoromethylphenyl) amino} -6-diethylaminofluorane, 2- {3,6-bis (diethylamino) -9- (o-chloroanilino) xanthyl benzoate lactam}, 3 -Diethylamino-6-methyl-7- (m-trichloromethylanilino) fluorane, 3-diethylamino-7- (o-chloroanilino) fluorane, 3-dibutylamino-7- (o-chloroanilino) fluorane, 3-N- Methyl-N-amylamino-6-methyl-7-
Anilinofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3- (N, N-diethylamino) ) -5-Methyl-7-
(N, N-dibenzylamino) fluorane, benzoyl leuco methylene blue, 6'-chloro-8'-methoxy-benzoindolino pyrirospirane, 6'-bromo-3'-methoxy-benzoindolino-pyrrillospirane, 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-5'-
Methylphenyl) phthalide, 3-morpholino-7- (N-propyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7- (N -Benzyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluorane, 3-diethylamino-5-chloro-7- (α-phenylethylamino) fluorane, 3 -(N-ethyl-p-toluidino) -7- (α-phenylethylamino) fluorane, 3-diethylamino-7- (o-methoxycarbonylphenylamino) fluorane, 3-diethylamino-5-methyl-7- (α -Phenylethylamino) fluorane, 3-diethylamino-7-piperidi Fluoran, 2-chloro-3-(N-Mechirutoruijino)-7-(p
-N-butylanilino) fluorane, 3- (N-benzyl-N-cyclohexylamino)-
5,6-benzo-7-α-naphthylamino-4′-bromofluorane, 3-diethylamino-6-methyl-7-mesitidino-
4 ', 5'-benzofluorane and the like.

Further, as the developer used in the present invention, various electron-accepting substances that react with the leuco dye when heated to develop a color thereof are applied, and specific examples thereof include phenols as shown below. Examples thereof include organic substances, organic or inorganic acidic substances, and salts thereof.

Gallic acid, salicylic acid, 3-isopropylsalicylic acid,
3-cyclohexylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4,4′-isopropylidenediphenol,
4,4'-isopropylidene bis (2-chlorophenol), 4,4'-isopropylidene bis (2,6-dibromophenol), 4,4'-isopropylidene bis (2,6-dichlorophenol), 4 , 4'-isopropylidene bis (2-methylphenol), 4,4'-isopropylidene bis (2,6-dimethylphenol),
4,4'-isopropylidene bis (2-tert-butylphenol), 4,4'-sec-butylidene diphenol, 4,4'-cyclohexylidene bisphenol,
4,4'-Cyclohexylidenebis (2-methylphenol), 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 3,5-xylenol, thymol, methyl -4-hydroxybenzoate, 4-hydroxyacetophenone, novolac type phenol resin,
2,2'-thiobis (4,6-dichlorophenol),
Catechol, resorcin, hydroquinone, pyrogallol, phloroglysin, phloroglysin carboxylic acid, 4-
tert-octylcatechol, 2,2'-methylenebis (4-chlorophenol), 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,
2'-dihydroxydiphenyl, ethyl p-hydroxybenzoate, propyl p-hydroxybenzoate, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, p-hydroxybenzyl benzyl p-hydroxybenzoate, p
-Hydroxybenzoic acid-o-chlorobenzyl, p-hydroxybenzoic acid-p-methylbenzyl, p-hydroxybenzoic acid-n-octyl, benzoic acid, zinc salicylate,
1-hydroxy-2-naphthoic acid, 2-hydroxy-6
-Naphthoic acid, zinc 2-hydroxy-6-naphthoate,
4-hydroxydiphenyl sulfone, 4-hydroxy-
4'-chlorodiphenyl sulfone, bis (4-hydroxyphenyl) sulfide, 2-hydroxy-p-toluic acid, zinc 3,5-di-tert-butylsalicylate, 3,
5-di-tert-butylsalicylate tin, tartaric acid, oxalic acid, maleic acid, citric acid, succinic acid, stearic acid,
4-hydroxyphthalic acid, boric acid and the like.

In the present invention, either one of the leuco dye and the developer is encapsulated in a microcapsule, or both of them are separately encapsulated in a microcapsule. The microcapsules are made of a material containing a photocurable resin and a photopolymerization initiator as main components. As the photocurable resin, various conventionally known ones may be adopted, but as a particularly important one, a cinnamic acid derivative such as polyvinyl cinnamate,
Ethylene-cinnamic acid ester of vinyl alcohol copolymer, cinnamic acid ester of glyptal resin, cinnamoyl type polymer having a styrene skeleton, cinnamic acid ester of styrene-maleic anhydride copolymer, polyvinyl cinnamylidene acetate, Examples thereof include polyvinyl benzal acetophenone, polyvinyl stil ketone, and epoxy-acrylate resin. Examples of the photopolymerization initiator include benzoin, benzoin methyl ether, benzophenone and its derivatives, 2-chloroanthraquinone, and benzoyl peroxide.

The microcapsule used in the present invention can be manufactured by a conventionally known method. For example, U.S. Pat.
No. 2730456, No. 2730457, No. 3418250, or the method described in the publication "Microcapsule" Sankyo Publishing Co., Ltd.

In the present invention, various conventional binders can be appropriately used in order to bind and support the leuco dye and the developer (at least one of which is microencapsulated) on a support. , For example, polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylic acid amide / acrylic acid ester copolymer, acrylic acid amide / Acrylic ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, case In addition to water-soluble polymers such as vinyl acetate, polyvinyl acetate, polyurethane, styrene / butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene / vinyl acetate copolymer A latex such as a polymer or a styrene / butadiene / acrylic copolymer can be used.

Further, in the present invention, together with the leuco dye and the color developer, if necessary, further auxiliary additives commonly used in this type of heat-sensitive recording material, for example, a filler, a surfactant, a heat-fusible substance ( Alternatively, a lubricant) or the like can be used in combination. In this case, as the filler, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, inorganic fine powder such as surface-treated calcium or silica, etc. , Urea-formalin resin, styrene / methacrylic acid copolymer, polystyrene resin, and other organic fine powders,
Examples of heat-fusible substances include higher fatty acids or their esters, amides or metal salts, as well as various waxes,
Condensation product of aromatic carboxylic acid and amine, benzoic acid phenyl ester, higher linear glycol, 3,4-epoxy-
Examples thereof include dialkyl hexahydrophthalate, higher ketones, and other heat-fusible organic compounds having a melting point of about 50 to 200 ° C. In the present invention, when a heat-fusible substance is used, it may be mixed with a leuco dye and / or a color developing agent so as to coexist in a microcapsule, if necessary. The action can be effectively made.

〔effect〕

By coating the leuco dye and / or the color developer with a photo-curable resin to form microcapsules, the recording material after thermal printing is fixed by irradiation with light and does not develop color even when reheated.

〔Example〕

 Next, the present invention will be described in more detail with reference to Examples.

Example 1 Preparation of photocurable microcapsules containing leuco dye: 20 parts by weight of 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, photocurable resin 78
10 parts by weight of the dispersion [trade name: Aronix 8030 manufactured by Toagosei Kagaku Kogyo Co., Ltd.] and 2 parts by weight of benzophenone as a photopolymerization initiator are dispersed in an attritor for 5 hours in the dark. Is added to 50 parts by weight of a 10% gelatin aqueous solution, and the mixture is uniformly stirred at a liquid temperature of 60 ° C for about 30 minutes. Then 10
Quench to 0 ° C. and add 50 parts by weight of 10% aqueous gum arabic solution. After the addition is complete, raise the liquid temperature to 40 ° C and add water at 40 ° C to 15 ° C.
Add 0 parts by weight, then add 10% acetic acid dropwise to bring the pH to 4.
Then, cool to 5 ° C., add 20 parts by weight of 3% formalin, add 10% NaOH aqueous solution dropwise to adjust the pH to 9, gradually raise the temperature, raise the liquid temperature to 50 ° C. and continue stirring for 10 minutes, then It was filtered and air-dried to prepare a photocurable capsule containing a leuco dye. Then, a liquid having the following composition was prepared.

[Dispersion A]

Bisphenol A 8 parts by weight N-octadecylcarbamoyl 3 〃 benzene Calcium carbonate 2 parts by weight Polyvinyl alcohol 40 parts by weight (10% aqueous solution) water 47 parts by weight The above composition was dispersed for 24 hours using a ball mill to prepare a dispersion liquid A. Prepared. The photocurable microcapsules prepared above and the dispersion liquid A were mixed at 1:10 (parts by weight) to obtain a thermosensitive coloring layer forming liquid liquid B. The solution B is a high-quality paper (about 50 g /
It was coated on m ² ) so as to have a dry adhesion amount of 7 g / m ² and dried to obtain a heat-sensitive recording material of the present invention.

Example 2 Preparation of photocurable microcapsules containing a color developer: Bisphenol A 40 parts by weight, photocurable resin 58 parts by weight [trade name: Lipoxy L.400 Showa Highpolymer Co., Ltd.], and photopolymerization start 2 parts by weight of benzoin ethyl ether as an agent was dispersed in an attritor for 5 hours in the dark, 10 parts by weight of the dispersion was added to 10 parts by weight of melamine, 30 parts by weight of 30% formalin, and 50 parts by weight of water. Add, pH 9 with sodium hydroxide
Then, the temperature is gradually raised, the liquid temperature is raised to 60 ° C., the mixture is stirred for 2 hours, and then cooled to room temperature. Then, it was filtered and air-dried to prepare a photocurable capsule containing bisphenol A. Then, a liquid having the following composition was prepared.

[Dispersion C]

3-N-di-n-butylamino-7 2 parts by weight-(0-chloroanilino) fluorane stearic acid amide 1 〃 kaolin 1 〃 polyvinyl alcohol 30 〃 (10% aqueous solution) water 66 〃 using the above composition in a ball mill Dispersion liquid C was prepared by dispersing for 24 hours. The photocurable microcapsules thus prepared and the dispersion liquid C were mixed at a ratio of 1: 3 (parts by weight) to obtain a thermosensitive coloring layer forming liquid D liquid. The liquid D is a high-quality paper (about 50 g /
It was coated on m ² ) so as to have a dry adhesion amount of 7 g / m ² and dried to obtain a heat-sensitive recording material of the present invention.

Example 3 Dispersion E 10 parts by weight of leuco dye-encapsulated photocurable microcapsules of Example 1 Bisphenol A encapsulation of Example 2 40 〃 photocurable microcapsules Calcium carbonate (20% aqueous dispersion) 10 〃 stearic acid Amide 10 〃 (20% aqueous dispersion) Polyvinyl alcohol 20 〃 (20% aqueous solution) Water 10 〃 The above composition is uniformly mixed and stirred to obtain dispersion E liquid, which is fine paper (about 50 g / m ² ). The heat-sensitive recording material of the present invention was obtained by coating on the above so that the amount of adhesion when dried was 6 g / m ^2, and drying.

Comparative Example 1 Dispersion F Dispersion A 1 part by weight Dispersion C 1 〃 The above composition was uniformly mixed and stirred to obtain Dispersion F liquid, which was adhered to a fine paper (about 50 g / m ² ) when dried. The heat-sensitive recording material for comparison was obtained by coating so that the amount was 7 g / m ² and drying.

Example 4 Preparation of Photocurable Microcapsules Encapsulating Leuco Dye and Thermofusible Substance: 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane as leuco dye and heat-soluble Stearic acid amide as a melting substance was mixed at a ratio of 1: 1 (parts by weight), heated and melted, cooled to room temperature, and coarsely pulverized.
20 parts by weight of the coarsely crushed product, 78 parts by weight of a photocurable resin [trade name: Aronix 5700 manufactured by Toagosei Chemical Industry Co., Ltd.],
And 2 parts by weight of benzophenone as a photopolymerization initiator were dispersed in an attritor for 5 hours in the dark, and 10 parts by weight of the dispersion was added to 50 parts by weight of a 10% gelatin aqueous solution to obtain a liquid temperature of 60.
Stir for about 30 minutes at ℃ until uniform. Then, it is rapidly cooled to 10 ° C. and 50 parts by weight of a 10% aqueous solution of gum arabic is added. After completion of the addition, the liquid temperature is raised to 40 ° C., 150 parts by weight of water at 40 ° C. is added, and then 10% acetic acid is added dropwise to adjust the pH to 4. Then 5 ° C
Cool to 30% formalin, add 20 parts by weight, and 10
% Sodium hydroxide was added dropwise to adjust the pH to 9, the temperature was gradually raised, the liquid temperature was raised to 50 ° C., and stirring was continued for 10 minutes.
Air-dried to prepare a photocurable capsule containing a leuco dye and a heat-fusible substance. Then, a liquid having the following composition was prepared.

[Dispersion G]

Bisphenol A 8 parts by weight N-octadecylcarbamoyl 2 〃 benzene calcium carbonate 3 〃 polyvinyl alcohol 40 〃 (10% aqueous solution) water 47 〃 Disperse the above composition using a ball mill for 24 hours,
Dispersion G liquid was prepared. The prepared photocurable microcapsules and the dispersion liquid G were mixed at a ratio of 1: 5 (parts by weight) to obtain a thermosensitive coloring layer forming liquid liquid H. The H liquid is treated with high-quality paper (about
A heat-sensitive recording material of the present invention was obtained by coating on 50 g / m ² ) so as to have a dry adhesion amount of 7 g / m ² and drying.

Example 5 Preparation of photo-curable microcapsules containing a color developer and a heat-fusible substance: Parahydroxybenzoic acid benzyl ester as a color developer
20 parts by weight, 20 parts by weight of N-octadecylcarbamoylbenzene and 58 parts by weight of a photocurable resin [trade name: Lipoxy L-40
0 Showa High Polymer Co., Ltd.] and 2 parts by weight of benzoin ethyl ether as a photopolymerization initiator using an attritor.
Disperse in a dark place for 5 hours, add 10 parts by weight of the dispersion to 10 parts by weight of melamine, 30 parts by weight of 30% formalin, and 50 parts by weight of water, adjust the pH to 9 with sodium hydroxide, and gradually raise the temperature to 60 ℃
The liquid temperature is raised to 2, and the mixture is stirred for 2 hours and then cooled to room temperature. Then, the mixture was filtered and air-dried to prepare a photocurable capsule containing a color developer and a heat-fusible substance. Then, a liquid having the following composition was prepared.

[Dispersion liquid I]

3-N-di-n-butylamino-7 2 parts by weight-(0-chloroanilino) fluorane stearic acid amide 1 〃 kaolin 2 〃 polyvinyl alcohol 30 〃 (10% aqueous solution) water 65 〃 Using the above composition in a ball mill For 24 hours to prepare dispersion liquid I. The photocurable microcapsules thus prepared and the dispersion liquid I were mixed at a ratio of 1: 2 (parts by weight) to obtain a thermosensitive coloring layer forming liquid J liquid. Liquid J is a high-quality paper (about 50 g /
It was coated on m ² ) so as to have a dry adhesion amount of 7 g / m ² and dried to obtain a heat-sensitive recording material of the present invention.

Example 6 10 parts by weight of photocurable microcapsule of Dispersion Example 4 Capsule of photocurable micro of Example 5 40 〃 Capsule Calcium carbonate (20% aqueous dispersion) 10 parts by weight Stearamide 10 〃 (20% aqueous dispersion) Isobutylene maleic anhydride 20 〃 Copolymer ammonium salt (20 aqueous solution) Water 10 〃 The above composition was uniformly mixed and stirred, and the dispersion K liquid was dried on a fine paper (about 50 g / m ² ) to give a dry coating amount. The heat-sensitive recording material of the present invention was obtained by coating and drying so that the coating amount was 6 g / m ² . The thermal recording material of the present invention and the comparative thermal recording material obtained as described above are printed by a facsimile machine RIFAX-3300 [manufactured by Ricoh Co., Ltd.] to obtain a color image, and then Ricopy SM-1500 [manufactured by Ricoh Co., Ltd. ] The exposed portion was passed (100 m / H) to expose the entire surface. When this was reprinted again with the facsimile machine,
The thermal recording materials of Examples 1 to 6 were not reprinted. However, the thermal recording material of Comparative Example 1 can be reprinted,
The image is dub. Table 1 shows the results of measuring the image density and background density before and after exposure using a Macbeth densitometer RD-514.

Claims (1)

[Claims] 1. A thermosensitive recording material comprising a support and a thermosensitive coloring layer containing a leuco dye and a color developer as main components, wherein at least one of the leuco dye and the color developer is required. According to the heat fusible substance together with a microcapsule formed of a material mainly composed of a photocurable resin and a photopolymerization initiator, the leuco dye and the developer are mutually separated by a microcapsule wall. A heat-sensitive recording material characterized by being isolated.