JP2613770B2 - Thermal recording material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heat-sensitive recording material, and more particularly, to a colorless or slightly light-colored leuco dye at room temperature, and a developer which reacts with the leuco dye to form a color when heated. The present invention relates to an improvement of a heat-sensitive recording material in which a heat-sensitive coloring bath containing a coloring component is provided on a support.

(Prior art)

The thermosensitive recording material generally has a thermosensitive coloring layer mainly composed of a thermochromic composition provided on a support such as paper, synthetic paper, plastic film, etc., and is provided with a thermal head, a hot pen, a laser beam, a strobe lamp, or the like. By heating, a colored image is obtained. Compared to other recording materials, this type of recording material can be recorded in a short time with relatively simple equipment without performing complicated processing such as development and fixing, and it generates less noise and less environmental pollution. Due to its advantages such as low cost, it is widely used as a recording material in various fields such as electronic calculators, facsimile machines, ticket vending machines, labels, recorders, etc., in addition to being used for copying books and documents. The thermochromic composition used in such a thermosensitive recording material comprises a general color former and a developer which causes the color former to develop color when heated.Examples of the color former include lactone, lactam or colorless having a spiropyran ring. Alternatively, a light-colored leuco dye has been used, and as a developer, an organic acid or a phenolic substance has been conventionally used. The recording material in which the color former and the developer are combined has the advantages that the obtained image has a particularly clear color tone, a high whiteness of the background, and excellent weather resistance of the image. , Widely used.

Conventionally, bisphenol A, P-hydroxybenzoic acid esters and the like have been used as a developer for leuco dyes, but these phenols have a high coloring density, but lack the stability of a color image, so that they can be left naturally. It has the drawback that the concentration decreases and the concentration decreases at high temperature and high humidity.

On the other hand, as described in JP-A-59-145189 and JP-A-59-145190, it has been proposed to use a metal salt of an organic acid as a color developer. , The sensitivity is inferior.

〔Purpose〕

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording material which has overcome the problems of the prior art, that is, has high sensitivity, little deterioration over time and improved reliability.

〔Constitution〕

According to the present invention, there is provided a thermosensitive recording material utilizing a color development reaction between a leuco dye and a developer, wherein the developer is at least one compound represented by the following general formula. Materials are provided.

(In the formula, R ₁ represents a hydrogen atom or a methyl group, R ₂ represents a lower alkylene group, and n represents an integer of 1 to _3. ) That is, the heat-sensitive recording material of the present invention has the general formula Since at least one kind of the compound represented by the formula is used, the sensitivity is high and the deterioration of the recorded image with time is extremely small.

Examples of the developer represented by the general formula used in the present invention include the following compounds.

p-hydroxybenzoic acid (2-acryloyloxy)
Ethyl ester, p-hydroxybenzoic acid (2-methacryloyloxy) ethyl ester, p-hydroxybenzoic acid (3-acryloyloxy)
Propyl ester, p-hydroxybenzoic acid (3-methacryloyloxy) propyl ester, 3,4-dihydroxybenzoic acid (2-acryloyloxy) ethyl ester, 3,4-dihydroxybenzoic acid (2-methacryloyloxy) ethyl ester, 3 2,4-dihydroxybenzoic acid (3-acryloyloxy) propyl ester, 3,4-dihydroxybenzoic acid (3-methacryloyloxy) propyl ester, 2,4-dihydroxybenzoic acid (2-acryloyloxy) ethyl ester, 2,4 -Dihydroxybenzoic acid (2-methacryloyloxy) ethyl ester, 2,4-dihydroxybenzoic acid (3-acryloyloxy) propyl ester, 2,4-dihydroxybenzoic acid (3-methacryloyloxy) propyl ester, gallic acid (2- Acryloyl oki B) Ethyl ester, gallic acid (2-methacryloyloxy) ethyl ester, gallic acid (3-acryloyloxy) propyl ester, gallic acid (3-methacryloyloxy) propyl ester and the like.

These compounds are used in an amount of 0.5 parts by weight per 1 part by weight of the leuco dye.
It is preferable to use in a range of from 10 to 10 parts by weight.

The leuco dye used in the present invention is applied alone or as a mixture of two or more kinds. As such a leuco dye, those applied to this kind of heat-sensitive material are arbitrarily applied, for example, triphenyl dye. Leuco compounds of dyes such as methane, fluoran, phenothiazine, auramine, spiropyran and indolinophthalide are preferably used. Specific examples of such leuco dyes include, for example, 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-dimethyl Aminophenyl) -6-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dibutylaminophenyl) phthalide, 3-cyclohexylamino-6-chlorofurf Oran, 3-dimethylamino-5,7-dimethylfluoran, 3-N-methyl-N-isobutyl-6-methyl-7-
Anilinofluoran, 3-N-ethyl-N-isoamyl-6-methyl-7-
Anilinofluoran, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluoran, 3-diethylamino-7,8-benzfluoran, 3-diethylamino-6-methyl-7-chlorofluoran 3- (Np-tolyl-N-ethylamino) -6-methyl-7-anilinofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 2 @ N- (3'- Trifluoromethylphenyl) amino} -6-diethylaminofluoran, 2- {3,6-bis (diethylamino) -9- (o-chloroanilino) xanthyl} lactam benzoate, 3-diethylamino-6-methyl-7- ( m-trichloromethylanilino) fluoran, 3-diethylamino-7- (o-chloroanilino) fluoran, 3-dibutylamido -7-(o-Kuroruanirino) fluoran, 3-N-methyl--N- Amiruamino 6-methyl -7
-Anilinofluoran, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl -7- (2 ', 4'-
Dimethylanilino) fluoran, 3- (N, N-diethylamino) -5-methyl-7-
(N, N-dibenzylamino) fluoran, benzoylleucomethylene blue, 6'-chloro-8'-methoxy-benzoindolino-
Pyrirospiran, 6'-bromo-3'-methoxy-benzoindolino-
Pyrirospiran, 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) fluoran, 3-pyrrolidino-7-trifluoromethylanilinofluoran, 3-diethylamino-5-chloro-7- (N -Benzyl-trifluoromethylanilino) fluoran, 3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluoran, 3-diethylamino-5-chloro-7- (α-phenylethylamino) fluoran, 3 -(N-ethyl-p-toluidino) -7- (α-phenylethylamino) fluoran, 3-diethylamino-7- (o-methoxycarbonylphenylamino) fluoran, 3-diethylamino-5-methyl-7- (α -Phenylethylamino) fluoran, 3-diethylamino-7-piperidi Fluoran, 2-chloro-3-(N-Mechirutoruijino) -7-
(Pn-butylanilino) fluoran, 3- (N-methyl-N-isopropylamino) -6
Methyl-7-anilinofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3,6-bis (dimethylamino) fluorenesulpyro (9,3 ')-6'-dimethylaminophthalate , 3- (N-benzyl-N-cyclohexylamino)-
5,6-benzo-7-α-naphthylamino-4′-bromofluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-N-ethyl-N- (2-ethoxypropyl) amino -6-methyl-7-anilinofluoran, 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-mesitidino-
4 ', 5'-benzofluoran and the like.

In order to produce the heat-sensitive recording material of the present invention, when the leuco dye and the developer are bonded and supported on a support, various conventional binders can be appropriately used, and specific examples thereof include, for example, The following are mentioned.

Polyvinyl alcohol, starch and derivatives thereof, hydroxymethyl cellulose, hydroxyethyl cellulose,
Cellulose derivatives such as carboxymethylcellulose, methylcellulose and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide / acrylate copolymer, acrylamide / acrylate / methacrylic acid terpolymer, styrene / maleic anhydride copolymer Alkali salts, isobutylene / maleic anhydride copolymer alkali salts, water-soluble polymers such as polyacrylamide, sodium alginate, gelatin, casein, polyvinyl acetate, polyurethane, polyacrylic acid,
Polyacrylate, polymethacrylate,
Emulsions such as vinyl chloride / vinyl acetate copolymers and ethylene / vinyl acetate copolymers, and latexes such as styrene / butadiene copolymers and styrene / butadiene / acrylic copolymers.

Further, in the present invention, together with the leuco dye and the developer, if necessary, auxiliary additives commonly used in this type of heat-sensitive recording material, for example, fillers, surfactants, heat-fusible substances (or lubricants) ), A pressure coloring inhibitor and the like can be used in combination. In this case, examples of the filler include calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, surface-treated inorganic fine powder such as calcium and silica, and the like. Organic fine powder such as urea-formalin resin, styrene / methacrylic acid copolymer, and polystyrene resin. Examples of the heat-fusible substance include, in addition to higher fatty acids or their esters, amides or metal salts, various waxes, condensates of aromatic carboxylic acids and amines, benzoic acid phenyl esters, higher linear glycols, 3 Those having a melting point of about 50 to 200 ° C, such as dialkyl 1,4-epoxy-hexahydrophthalate, higher ketone, p-benzylbiphenyl, benzyl p-benzyloxybenzoate, and other heat-fusible organic compounds. .

Furthermore, in the present invention, it is possible to use a conventionally known developer if necessary, and such specific examples include:
For example, bis (4-hydroxyphenyl) sulfone, p
-Benzyl benzoate, tetrabromobisphenol S, tetrabromobisphenol A, 1,1,3-tris (4-hydroxy-2-methyl-5-tert-
Butylphenyl) butane, bis (2-methyl-4-hydroxy-5-tert-butylphenyl) sulfide, 1,1-bis (4-hydroxyphenyl) cyclohexane, and the like.

The heat-sensitive recording material of the present invention is produced, for example, by applying a coating liquid for forming a heat-sensitive layer containing the above-mentioned components on a suitable support such as paper, synthetic paper, or plastic film, and then drying it. It is used as a heat-sensitive recording material for various recording fields, especially for high-speed recording requiring high image stability.

The heat-sensitive recording material of the present invention is used in various fields. In particular, it utilizes the above-described excellent color-developed image stability, and is advantageously used as a heat-sensitive recording label sheet or a heat-sensitive recording magnetic ticket paper. be able to. In the case of a heat-sensitive recording type label sheet, a heat-sensitive coloring layer containing a leuco dye and the developer is provided on one surface of the support, and a release sheet is provided on the other surface of the support via an adhesive layer. In the case of a magnetic paper, a magnetic recording layer mainly composed of a ferromagnetic material and a binder may be provided instead of the release backing paper.

Further, the leuco dye and the color developer can be used as thermal transfer materials provided on separate supports, respectively.

〔effect〕

The heat-sensitive recording material of the present invention, by using at least one of the compounds represented by the general formula as a color developer,
Compared to the conventional heat-sensitive recording material, it has higher sensitivity and less discoloration of the recorded image with time, and has improved reliability.

〔Example〕

The invention will now be described in more detail by way of examples. The following parts and percentages are all based on weight.

Example 1 [Solution A] 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluoran 10 parts 10% aqueous solution of polyvinyl alcohol 10 parts Water 80 parts [Solution B] p-hydroxybenzoic acid ( 2-acryloyloxy) ethyl ester 10 parts Calcium carbonate 15 parts Zinc stearate 5 parts 10% aqueous solution of polyvinyl alcohol 30 parts Water 40 parts Each mixture having the above composition is ground and dispersed by a sand glider for 2 to 4 hours [Solution A]. And [Solution B] were prepared.

Then, [Liquid A], the weight ratio of [B solution] 1: 3 and so as mixed and stirred to prepare a thermal color-forming layer coating solution, to a dry coating amount of 5 g / m ² on a commercial fine paper It was applied and dried with a Labo coating rod. The smoothness of this coated paper is 700-1200
The heat-sensitive recording material of the present invention was prepared by calendering in seconds.

Example 2 In Example 1, p-hydroxybenzoic acid (2-acryloyloxy) ethyl ester in [Solution B] was added to 3,4
-Dihydroxybenzoic acid (2-methacryloyloxy)
A heat-sensitive recording material of the present invention was prepared in the same manner as in Example 1 except that ethyl ester was used.

Example 3 In Example 1, 3-N-methyl-N in [solution A] was used.
-Cyclohexylamino-6-methyl-7-anilinofluoran with 3-N-ethyl-N-isoamylamino-6
P-Hydroxybenzoic acid (2-acryloyloxy) in [Solution B] in place of -methyl-7-anilinofluoran
A heat-sensitive recording material of the present invention was prepared in the same manner as in Example 1, except that the ethyl ester was changed to 2,4-dihydroxybenzoic acid (2-acryloyloxy) ethyl ester.

Comparative Example 1 In Example 1, p-hydroxybenzoic acid (2-acryloyloxy) ethyl ester in [Solution B] was replaced with p-hydroxybenzoic acid (2-acryloyloxy) ethyl ester.
Example 1 except that benzyl hydroxybenzoate was replaced.
A thermosensitive recording material for comparison was prepared in the same manner as described above.

Comparative Example 2 A heat-sensitive recording material for comparison was prepared in the same manner as in Example 1, except that bisphenol A was used in place of p-hydroxybenzoic acid (2-acryloyloxy) ethyl ester in [Liquid B]. Created.

The above heat-sensitive recording materials were tested for color development and wet heat storage resistance. Table 1 shows the results. The test method was as follows.

(1) Color development head power 0.60 W / dot, 1 line recording time 10 ms using a print tester with a thin film head manufactured by Matsushita Electronic Components, Ltd.
/ l, scanning line density 8 × 7.7 dots / mm, pulse width 1.0m
s, and the print density was measured with a Macbeth densitometer RD-514 (filter wratten-106).

(2) Moisture / heat storage stability The sample printed in the test of (1) was allowed to stand at 40 ° C. and 90% RH for 24 hours, and the image density was measured and evaluated.

As is clear from Table 1, the heat-sensitive recording material of the present invention has high sensitivity, excellent heat and humidity storage stability, and improved reliability as compared with the comparative example.

Claims (1)

(57) [Claims] 1. A thermosensitive recording material utilizing a color development reaction between a leuco dye and a color developer, wherein the color developer is at least one compound represented by the following general formula. . (Wherein, R ₁ represents a hydrogen atom or a methyl group, R ₂ represents a lower alkylene group, and n represents an integer of 1 to 3, respectively)