JPH09123597A - Thermal recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a highly sensitive thermal recording material provided with a thermal coloring layer, principally comprising a leuco dye, a developer and a sensitizer, on a support inexpensively while preventing generation of white powder by employing a thermally fusible substance having specified molecular weight and melting point as the sensitizer. SOLUTION: In a thermal recording material provided with a thermal coloring layer principally comprising a leuco dye, a developer and a sensitizer on a support, a thermally fusible substance having molecular weight of 250 or less and melting point of 110 deg.C or below is employed as the sensitizer and dispersed with mean grain size of 1.5μm or above. The thermally fusible substance employs at least one kind of compound selected from a group of m-terphenyl, p-toluen sulfolate phenyl ester, p-benzyl biphenyl, 1,2-bis(3,4-dimethylphenyl) ethane, and 4-chlorobenzoic amide-4'-methylphenyl ester. An undercoat layer may be provided between the support and thermal coloring layer as required.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material having a support and a heat-sensitive coloring layer containing a leuco dye, a developer and a sensitizer as main components.

[0002]

2. Description of the Related Art A heat-sensitive recording material is a recording material having a structure in which a heat-sensitive coloring 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 to other recording methods, this recording method has the advantages that it does not require processing such as development and fixing, can be recorded in a short time using a relatively simple device, and is inexpensive, etc. Copy, facsimile, ticket machine,
It is used in various fields such as labels and recorders.

However, for such a heat-sensitive recording material as well, it is general to use a sensitizer having a melting point lower than that of a dye or a developer in order to further increase the sensitivity. Therefore, there is a problem in that white powder is generated during storage after printing and the sensitizer is sublimated when exposed to high temperatures during raw storage, resulting in a decrease in sensitivity.

Therefore, if the molecular weight is increased to a level at which white powder or sublimation does not occur, the molecular structure becomes complicated, resulting in high manufacturing costs and insufficient sensitivity enhancement.

In order to improve this point, attempts have been made to increase the sensitivity by making the particles of the sensitizer finer (JP-A-59-85788 and JP-A-60-6349).
2, JP-A-2-137971). Further, a method of mixing and dispersing one of a dye and a color developer and a sensitizer to have an effect close to eutectic and to increase sensitivity (JP-A-61-280).
988, Japanese Patent Application Laid-Open No. 4-71889, Japanese Patent Application Laid-Open No. 4-7189.
3) Also, a method has been proposed in which the dispersibility of the sensitizer is increased by using a specific protective colloid agent to make the particles finer and the sensitivity is increased (JP-A-3-218888).

[0006]

However, there is still nothing sufficient to solve the problems of sensitivity, generation of white powder and cost at the same time.

It is an object of the present invention to provide a heat-sensitive recording material which overcomes the above-mentioned problems of the prior art, is highly sensitive, does not generate white powder, and is inexpensive to manufacture.

[0008]

According to the present invention, firstly, there is provided a thermosensitive recording material having a thermosensitive coloring layer containing a leuco dye, a developer and a sensitizer as main components on a support. A sensitizer with a molecular weight of 250 or less and a melting point of 1
Provided is a heat-sensitive recording material comprising a heat-fusible substance at 10 ° C. or lower and dispersing the heat-fusible substance in an average particle size of 1.5 μm or more.

Secondly, in the heat-sensitive recording material described in the above-mentioned first, there is provided a heat-sensitive recording material characterized in that the heat-fusible substance is at least one selected from the following compound group. m-terphenyl, p-toluenesulfonic acid phenyl ester, p-benzylbiphenyl, 1,
2-Bis (3,4-dimethylphenyl) ethane, 4-chlorobenzoic amide-4'-methylphenyl ester.

With the heat-sensitive recording material having the above structure, the above-mentioned problems of sensitivity, white powder and cost can be solved at the same time. That is, it has been known that a heat-fusible substance having a molecular weight of 250 or less and a melting point of 110 ° C. or less can be incorporated into the thermosensitive coloring layer to obtain a highly sensitive thermosensitive recording material at a low cost. However, it was not fully used due to the generation of white powder and the decrease in sensitivity due to sublimation in a high heat environment.

Then, as a result of diligent research on this problem, the following was found. 1) Dyes, developers and sensitizers have higher sensitivity when their particle sizes are made smaller, but among these, the contribution to sensitivity due to the sensitization of the sensitizers is smaller than that of the other two substances. 2) The sublimation sensitizer has a larger specific surface area when the particle size is made finer by dispersion, and sublimates in a much larger amount than the heating loss value measured by TGA or the like.

Then, the average particle size of the sensitizer was changed and the average particle size of the sensitizer was changed to 1.5 μm.
Above 100 μm, preferably above 3 μm and above 20 μm
It was found that when used in a dispersed state of not more than m, not only high sensitivity and low cost, but also a heat-sensitive recording material which does not generate white powder or sublimation during storage in a high temperature environment can be obtained. The present invention has been completed based on such knowledge.

[0013]

Embodiments of the present invention will be described below. First, the heat-fusible substance used as the sensitizer in the present invention is, for example, a substance shown in Table 1 (having a molecular weight of 170 or more and 250 or less, a melting point of 70 ° C. or more and 110 ° C. or more).
The following are listed), but the present invention is not limited thereto.

[0014]

[Table 1]

The leuco dyes used in the thermosensitive coloring layer of the present invention may be used alone or in admixture of two or more, and as such leuco dyes, those applied to this thermosensitive material may be arbitrarily applied. , For example, triphenylmethane type, fluorane type, phenothiazine type, auramine type,
Leuco compounds of dyes such as spiropyran type and indolinophtalide type 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-dimethyl) Aminophenyl) -6-diethylaminophthalide,
3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dibutylaminophenyl) phthalide, 3, cyclohexylamino-6-chlorofluorane 3, dimethylamino-5,7- Dimethyl fluorane,
3, N-methyl-N-isobutyl-6-methyl-7-anilinofluorane, 3-N-ethyl-N-isoamyl-
6-methyl-7-anilinofluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7
-Methylfluorane, 3-diethylamino-7,8-benzfluorane, 3-diethylamino-6-methyl-7
-Chlorfluorane, 3- (N-ethyl-N-p-tolyl) -6-methyl-7-anilinofluorane, 3- (N
-P-tolyl-N-ethylamino) -6-methyl-7-
Anilinofluorane, 3-pyrrolidino-6-methyl-7
-Anilinofluorane, 2- {N- (3'-trifluoromethylphenyl) amino) -6-diethylaminofluorane, 2- (3,6-bis (diethylamino) -9-
(O-Chloranilino) xanthylbenzoic acid lactam), 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluorane, 3-diethylamino-7- (o-chloroanilino) fluorane, 3-dibutylamino-7 -(O-Chloranilino) 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-diethylamino-6- Methyl-7-
(2 ', 4'-Dimethylanilino) fluorane, 3-
(N, N-diethylamino) -5-methyl-7- (N,
N-dibenzylamino) fluorane, benzoylleucomethylene blue, 6'-chloro-8'-methoxy-benzoindolino-pyrrilospirane, 6'-bromo-3'-
Methoxy-benzoindolino-pyrrilospirane, 3-
(2'-hydroxy-4'-dimethylhuminophenyl)
-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-piperidinofluorane, 2-chloro-3- (N-methyltoluidino) -7-
(Pn-Butylanilino) fluorane, 3- (N-methyl-N-isopropylamino) -6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-
7-anilinofluorane, 3,6-bis (dimethylamino) fluorenspiro (9,3 ')-6-dimethylaminophthalide, 3- (N-benzyl-N-cyclohexylamino) -5,6-benzo -7-α-naphthylamino-
4'-Bromofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-N-ethyl-N-
(2-Ethoxypropyl) amino-6-methyl-7-anilinofluorane, 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl -7-mesitidino-4 ', 5'-benzofluorane and the like.

As the color developer used in the thermosensitive coloring layer of the present invention, various electron-accepting compounds which cause the leuco dyestuff to develop color upon contact, for example, phenolic compounds, thiophenolic compounds, thiourea derivatives, Organic acids and metal salts thereof are preferably applied, and specific examples thereof include those shown below.

4,4'-isopropylidene bisphenol, 4,4'-isopropylidene bis (o-methylphenol), 4,4'-secondary butylidene bisphenol, 4,4'-isopropylidene bis (2-tersia) Lithylphenol), 4,4'-cyclohexylidenediphenol, 4,4'-isopropylidenebis (2-chlorophenol), 2,2'-methylenebis (4-methyl-6-tertiarybutylphenol),
2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 4,4'-butylidenebis (6-tertiarybutyl-2-methylphenol),
1,1,3-tris (2-methyl-4-hydroxy-5
-Everyday butylphenyl) butane, 1,1,3-
Tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 4,4'-thiobis (6-tert-butyl-2-methylphenol), 4,4'-
Diphenol sulfone, 4-isopropoxy-4'-hydroxydiphenyl sulfone, 4-benzyloxy-4 '
-Hydroxydiphenyl sulfone, 4,4'-diphenol sulfoxide, isopropyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, benzyl p-protocatechuate, stearyl gallate, lauryl gallate, octyl gallate, 1,7- Bis (4-hydroxyphenylthio) -3,5-dioxaheptane, 1,5-
Bis (4-hydroxyphenylthio) -3-oxapentane, 1,3-bis (4-hydroxyphenylthio)-
Propane, l, 3-bis (4-hydroxyphenylthio) -2-hydroxypropane, N, N'-diphenylthiourea, N, N'-di (m-chlorophenyl) thiourea, salicylanilide, 5-chloro- Salicylanilide, 2-hydroxy-3-naphthoic acid, 2-hydroxy-1-naphthoic acid, 1-hydroxy-2-naphthoic acid,
Metal salts of hydroxynaphthoic acid such as zinc, aluminum and calcium, bis- (4-hydroxyphenyl) acetic acid methyl ester, bis- (4-hydroxyphenyl) acetic acid benzyl ester, 1,3-bis (4-hydroxycumyl) Benzene, 1,4-bis (4-hydroxycumyl) benzene, 2,4'-diphenol sulfone, 3,
3'-diallyl-4,4'-diphenol sulfone,
α, α-bis (4-hydroxyphenyl) -α′-methyltoluene, antipyrine complex of zinc thiocyanate, tetrabromobisphenol S and the like.

In order to produce the heat-sensitive recording material of the present invention,
When a leuco dye and a color developer are bound and supported on a support, various commonly used binders can be appropriately used, and specific examples thereof include the following.

Polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as hydroxymethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose and ethyl cellulose,
Sodium polyacrylate, polyvinylpyrrolidone, acrylamide / acrylic acid ester copolymer, acrylamide / acrylic acid ester / methacrylic acid terpolymer,
Styrene / maleic anhydride copolymer alkali salts, isobutylene / maleic anhydride copolymer alkali salts, polyacrylamide, sodium alginate, gelatin, water-soluble polymers such as casein, polyvinyl acetate, polyurethane,
Polyacrylic acid ester, polymethacrylic acid ester,
Emulsion of vinyl chloride / vinyl acetate copolymer, ethylene / vinyl acetate copolymer, etc., latex such as styrene / butadiene copolymer, styrene / butadiene / acrylic copolymer, etc.

In the thermosensitive color developing layer of the present invention, if necessary, together with the above-mentioned leuco dye and developer, auxiliary additive components such as fillers, surfactants, and thermal additives commonly used in thermosensitive recording materials of this type are used. A fusible substance (or 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,
Examples include inorganic fine powders of clay, talc, surface-treated calcium, silica and the like, and organic fine powders of urea-formalin resin, styrene / methacrylic acid copolymer, polystyrene resin and the like. Examples of heat-fusible substances include fatty acids such as stearic acid and behenic acid, fatty acid amides such as stearic acid amide and palmitic acid amide, zinc stearate, aluminum stearate, causium stearate and palmitin. Examples thereof include fatty acid metal salts such as zinc acid salt and zinc behenate.

In the present invention, if necessary, an undercoat layer may be provided between the support and the thermosensitive coloring layer, or another protective layer may be provided between the thermosensitive coloring layer and the protective layer. Further, a back coat layer may be provided on the back surface of the support.

[0022]

EXAMPLES The present invention will now be described in more detail by way of examples. The parts and% shown below are based on weight.

[Liquid A] 3-dibutylamino-6-methyl-7-anilinofluorane 10 parts Polyvinyl alcohol (saponification degree 99%, polymerization degree 1000) 10% aqueous solution 10 parts water 20 parts

[Liquid B] 2,2'-bis (4-hydroxyphenyl) propane 10 parts Polyvinyl alcohol (saponification degree 99%, polymerization degree 1000) 10% aqueous solution 10 parts water 20 parts

The above [solution A] and [solution B] are dispersed in a sand mill (manufactured by Igarashi Co., Ltd.) until an average particle diameter of 1 μm (median diameter by Horiba laser particle size distribution analyzer LA700) is used.

[C liquid] m-terphenyl 10 parts Polyvinyl alcohol (saponification degree 99%, polymerization degree 1000) 10% aqueous solution 10 parts water 20 parts The above [C liquid] is a sand mill (made by Igarashi Co., Ltd.) and has an average particle size. Three
Disperse until μm (using LA700 above).

[Liquid D] The same as [Liquid C] except that 4-chlorobenzoic amide-4′-methylphenyl ester was used in place of m-terphenyl in [Liquid C].

[Liquid E] The same as [Liquid C] except that the average particle diameter in [Liquid C] was dispersed to 1 μm (using the above LA700).

[Liquid F] The same operation as in [Liquid D] was conducted except that the average particle diameter in [Liquid D] was dispersed to 1 μm (using the above LA700).

[Liquid G] The same operation as in [Liquid C] was carried out except that m-terphenyl in [Liquid C] was replaced by di-p-methylbenzyl oxalate (molecular weight 298, melting point 102 ° C.).

[Example 1] 10 parts of [A liquid], [B]
Solution] 20 parts, [C solution] 30 parts, and calcium carbonate 5 parts were used to prepare a heat-sensitive solution [H solution]. Next, basis weight 40g / m
[H-solution] was coated on a high-quality paper of No. 2 at 14 g / m 2 (wet) to prepare a thermosensitive recording paper.

[Example 2] A thermosensitive recording paper was prepared in the same manner as in Example 1 except that [D liquid] was used instead of [C liquid].

[Comparative Example 1] A thermosensitive recording paper was prepared in the same manner as in Example 1 except that [solution E] was used instead of [solution C].

Comparative Example 2 A thermosensitive recording paper was prepared in the same manner as in Example 1 except that [F liquid] was used instead of [C liquid].

[Comparative Example 3] A thermosensitive recording paper was prepared in the same manner as in Example 1 except that [G liquid] was used instead of [C liquid].

[Evaluation] The thermal recording paper obtained as described above was printed with a printing device manufactured by Matsushita Electronic Parts Co., Ltd. at a printing power of 0.68 w.
/ Dot, line cycle was 10 ms / line, and the color density was measured by Macbeth densitometer RD-914. Further, the obtained image was put in a transparent pocket made by King Jim Co., Ltd. for one week, and white powder was compared and ranked (1: high to 5: none). On the other hand, the cost of the thermal recording paper by changing the sensitizer was compared, and this was also ranked (5: low cost to 1: expensive). The above results are shown in Table 2.

[0037]

[Table 2]

It can be seen from Table 2 that the heat-sensitive recording materials of the examples have high sensitivity, little white powder is generated, and the cost is low.

[0039]

As described above, according to the present invention, the thermosensitive coloring layer has a molecular weight of 250 or less as a sensitizer and a melting point of 11
By dispersing a heat-fusible substance at 0 ° C. or less in an average particle size of 1.5 μm or more, a heat-sensitive recording material having high sensitivity, less white powder generation, and low manufacturing cost can be obtained.

[Table 1]

[Table 2]

Claims (2)

[Claims] 1. A thermosensitive recording material comprising a support and a thermosensitive coloring layer containing a leuco dye, a color developer and a sensitizer as main components, wherein the sensitizer has a molecular weight of 250 or less and a melting point. Is a heat-fusible substance having a temperature of 110 ° C. or less, and the heat-fusible substance is dispersed to have an average particle size of 1.5 μm or more. 2. The heat-fusible substance is at least one selected from the following compound group.
The heat-sensitive recording material as described. m-terphenyl, p-toluenesulfonic acid phenyl ester, p-benzylbiphenyl, 1,2-bis (3,4-dimethylphenyl) ethane, 4-chlorobenzoicamide-4'-methylphenyl ester.