JPH06183146A - Thermal recording material - Google Patents

Abstract

PURPOSE:To prevent the lowering of recording density and color forming capacity at high temp., and to enhance recording sensitivity, in a thermal recording material for a facsimile using a thermal head, by adding bisphenol S diaryl ether and dibenzyloxalic acid to a recording layer. CONSTITUTION:Bisphenol S diaryl ether and dibenzyloxalic acid are added to the recording layer containing a colorless or light-colored basic dye, for example, 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide and a developer, for example, 4-cumylphenol formed on a support. In this case, bisphenol S diaryl ether and dibenzyloxalic acid are used in an amt. of 10-1000 pts.wt. per 100 pts.wt. of the basic. The amt. of bisphenol S diaryl ether is set to 5-1000 pts.wt. based on 100 pts.wt. of dibenzyloxalic acid.

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 high-sensitivity heat-sensitive recording material which is excellent in storage stability of recorded images with time and has little deterioration in color forming ability of a blank portion.

[0002]

2. Description of the Related Art Heretofore, a heat-sensitive recording material has been well known which uses a heat energy of a heat-sensitive head or the like to develop a colorless or light-colored basic dye and a color developer. Since such a thermal recording material is relatively inexpensive, the recording device is compact, and its maintenance is relatively easy, it is used not only as a recording medium for facsimiles and various computers but also in a wide range of fields such as thermal labels. There is.

However, the conventional leuco dye-based thermosensitive recording medium does not have sufficient storage stability of the recorded image with time, and the recorded image is discolored within a relatively short time especially under high temperature conditions. There are drawbacks. For the purpose of improving the storage stability of the recorded image, methods of using various storage stability improving agents have been proposed, but the previously proposed storage stability improving agents do not provide sufficient effects, Even if it is effective in improving the storability of the recorded image under the conditions, it may cause new defects such as sticking, and satisfactory results have not been obtained.

Further, the heat-sensitive recording material is a heat-fusible substance added to the heat-sensitive color-developing layer in order to enhance the recording sensitivity when the heat-sensitive recording material is left in an environment of about 50 ° C. for a long time during transportation or storage. However, there is also a drawback that the color development ability is deteriorated due to the loss of color. Then, there is a problem that this phenomenon is apt to be prominently manifested particularly in a high-sensitivity thermosensitive recording medium. For this reason, there is a strong demand for a thermosensitive recording medium that can stably maintain a recorded image even when exposed to high temperature conditions for a long time, and that has little deterioration in color forming ability.

[0005]

In view of the above situation, it is an object of the present invention to provide a thermosensitive recording medium which has little deterioration in recording density and color forming ability even when exposed to high temperature conditions and has excellent recording sensitivity. It is in.

[0006]

DISCLOSURE OF THE INVENTION The present inventors have found that in a heat-sensitive recording material having a recording layer containing a colorless or light-colored basic dye and a color developer on a support, bisphenol is contained in the recording layer. It was found that the above-mentioned object can be achieved by containing S diallyl ether and dibenzyl oxalate, and the present invention has been completed.

[0007]

As described above, the present invention has an important feature in using bisphenol S diallyl ether and dibenzyl oxalate in combination. Bisphenol S diallyl ether has an excellent effect of preventing a decrease in recording density when a recorded image is exposed to a high temperature condition, but has a low recording sensitivity. Therefore, as a result of attempting to use various sensitizers in combination with bisphenol S diallyl ether in order to enhance the recording sensitivity, dibenzyl oxalate as a sensitizer is particularly effective in preventing a decrease in recording density and color developing ability, and further, recording is performed. The effect was excellent in sensitivity.

In the present invention, the amounts of bisphenol S diallyl ether and dibenzyl oxalate used are not particularly limited, but in general, basic dye 10 is used.
Bisphenol S diallyl ether or dibenzyl oxalate is adjusted to 10 to 1000 parts by weight, preferably 50 to 500 parts by weight, relative to 0 parts by weight, and bisphenol S diallyl ether is added to 100 parts by weight of dibenzyl oxalate. On the other hand, it is desirable to adjust the amount in the range of 5 to 1000 parts by weight, preferably 10 to 300 parts by weight.

In the heat-sensitive recording material of the present invention, various known compounds can be used as the colorless or light-colored basic dye to be contained in the recording layer. 3,3
-Bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl)-
6-dimethylaminophthalide, 3-diethylamino-7
-Dibenzylamino-benzo [a] fluorane, 3-
(N-Ethyl-Np-tolyl) amino-7-N-methylanilinofluorane, 3-diethylamino-7-anilinofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3,6- Bis (diethylamino) fluorane-γ-anilinolactam, 3-cyclohexylamino-6-chlorofluorane, 3-diethylamino-
6-methyl-7-chlorofluorane, 3-diethylamino-7-chlorofluorane, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane, 3- (N-methyl) -N-cyclohexyl) amino-
6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-di (n-butyl) amino-6-methyl-7-anilinofluorane, 3-di (N-pentyl) amino-6-methyl-
7-anilinofluorane, 3-diethylamino-7-
(O-chlorophenylamino) fluorane, 3-di (n
-Butyl) amino-7- (o-chlorophenylamino)
Fluorane, 3-diethylamino-7- (o-fluorophenylamino) fluorane, 3-di (n-butyl) amino-7- (o-fluorophenylamino) fluorane, 3- (N-ethyl-p-toluidino)- 6-methyl-7-anilinofluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7- (p-toluidino) fluorane, 3- (N-ethyl-N-furfurylamino)-
6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3- (N
-Methyl-N-n-propylamino) -6-methyl-7
-Anilinofluorane, 3,3-bis [1- (4-methoxyphenyl) -1- (4-dimethylaminophenyl)
Ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,3-bis [1- (4-methoxyphenyl) -1- (4-pyrrolidinophenyl) ethylene-2-
Il] -4,5,6,7-tetrachlorophthalide, 3,
3-bis [1,1-bis (4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6,7-tetrabromophthalide, 3-p- (p-anilinoanilino) anilino-
6-methyl-7-chlorofluorane, 2,2-bis {4
-[6 '-(N-cyclohexyl-N-methylamino)
-3'-methylspiro [phthalide-3,9'-xanthen-2'-ylamino] phenyl} propane, 3,6
-Bis (dimethylamino) fluorene-9-spiro-
3 '-(6'-dimethylamino) phthalide and the like can be mentioned. Of course, it is not limited to these, and two or more kinds may be used in combination as required.

Among these dyes, 3-diethylamino-7- (o-chlorophenylamino) fluorane and 3-di (nbutylamino) -7- (o-chlorophenylamino) fluorane have the desired effects. It is one of the preferred embodiments because it provides a heat-sensitive recording material that is fully exhibited and has a high degree of whiteness in the white paper portion.

As the color former contained in the recording layer, which is combined with a colorless or light-colored basic dye to form a color-developing system, various known colorants can be used, and examples thereof include the following. 4-cumylphenol, hydroquinone monobenzyl ether, 4,4'-isopropylidenediphenol, 1,1-bis (4-hydroxyphenyl) cyclohexane, 4,4'-dihydroxydiphenyl-2,2
-Butane, 4,4'-dihydroxydiphenylmethane,
2,2-bis (4-hydroxyphenyl) -4-methylpentane, 2,2-bis (4-hydroxyphenyl) heptane, bis (4-hydroxyphenylthioethoxy)
Methane, 1,5-di (4-hydroxyphenylthio)-
3-oxapentane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,4-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 1,3-bis [Α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 4,4′-dihydroxydiphenyl sulfide, bis (4-hydroxy-3)
-Methylphenyl) sulfine, 2,4'-dihydroxydiphenylsulfone, 4,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxy Phenyl-4'-benzyloxyphenyl sulfone, 4-hydroxy-
3 ', 4'-tetramethylene biphenyl sulfone, 3,
4-dihydroxyphenyl-p-tolyl sulfone, 4-
Benzyl hydroxybenzoate, butyl bis (p-hydroxyphenyl) acetate, bis (p-hydroxyphenyl)
Methyl acetate, (4-hydroxyphenylthio) acetic acid-2
-(4-hydroxyphenylthio) ethyl ester, di (p-hydroxyphenylthioethyl) ether, N,
N'-di-m-chlorophenylthiourea, phenolic compounds such as N- (phenoxyethyl) -4-hydroxyphenylsulfonamide, 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid, 4- [2 -(P
-Methoxyphenoxy) ethyloxy] salicylic acid, 5
-[P- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid, aromatic carboxylic acids such as p-chlorobenzoic acid, and zinc, magnesium, aluminum, calcium, titanium, manganese of these aromatic carboxylic acids,
Salts of polyvalent metals such as tin and nickel, and organic acid substances such as antipyrine complexes of zinc thiocyanate.

In the present invention, dibenzyl oxalate is used as the heat-fusible substance, but it is also possible to use the following other compounds in combination as long as the desired effects of the present invention are not impaired. For example, stearic acid amide, methoxycarbonyl-N-stearic acid benzamide, N-benzoylstearic acid amide, N-eicosanoic acid amide,
Ethylenebistearic acid amide, behenic acid amide, methylenebisstearic acid amide, N-methylolstearic acid amide, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate, benzyl p-benzyloxybenzoate, 1-hydroxy-2-naphthoate. Acid phenyl, 2-naphthylbenzyl ether, m-terphenyl, p-benzylbiphenyl, tolylbiphenyl ether, di (p-methoxyphenoxyethyl) ether,
1,2-di (3-methylphenoxy) ethane, 1,2-
Di (4-methylphenoxy) ethane, 1,2-di (4-
Methoxyphenoxy) ethane, 1,2-di (4-chlorophenoxy) ethane, 1,2-diphenoxyethane, 1
-(4-Methoxyphenoxy) -2- (2-methylphenoxy) ethane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p-acetotoluidide, p-acetophenetizide, N-acetoacetyl -P-toluidine, di (β-biphenylethoxy)
Benzene, p-di (vinyloxyethoxy) benzene,
Examples include 1-isopropylphenyl-2-phenylethane and the like.

To prepare a coating liquid for a recording layer containing these substances, water is generally used as a dispersion medium, and a basic dye, a color developer, and further a basic dye, a color developer, and a necessary amount are required by a stirring and crushing machine such as a ball mill, an attritor or a sand mill. A sensitizer or the like added according to the above is dispersed together or separately to prepare a coating liquid.
In the coating liquid, starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, arabic gum as an adhesive,
Polyvinyl alcohol, diisobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride copolymer salt,
The ethylene / acrylic acid copolymer salt, the styrene / acrylic acid copolymer salt, the styrene / butadiene copolymer emulsion, etc. are 10 to 40% by weight of the total solid content, preferably 15
It is used in an amount of about 30% by weight.

It is also possible to use various pigments in combination in the coating liquid, for example, kaolin, clay, calcium carbonate, calcined clay, calcined kaolin, titanium oxide, diatomaceous earth,
Inorganic pigments such as fine particulate anhydrous silica and activated clay, styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and organic pigments such as raw starch particles can be used.

Furthermore, various auxiliaries can be added to the coating liquid, for example, sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate / sodium salt, alginate, fatty acid metal salt and the like. Dispersant, benzophenone type,
Examples thereof include UV absorbers such as triazole type, defoaming agents, fluorescent dyes, and coloring dyes.

In the present invention, the method for forming the recording layer and the like are not particularly limited, and the recording layer can be formed according to a conventionally known and commonly used technique, for example, air knife coating, varibar blade coating, pure blade coating, It can be formed by a method of coating and drying a coating liquid on a support by short dwell coating, curtain coating or the like. The coating amount of the coating liquid is also not particularly limited, and is usually ² to 12 g / m ² , preferably 3 to 10 g / m ² in dry weight.
It is in the range of m ² . As the support, paper, synthetic paper, plastic film or the like is appropriately selected and used.

In the present invention, it is possible to further improve the storability of a recorded image by providing a resin layer on the thermal recording material and / or on the back surface side thereof, if necessary.
Further, in the field of heat-sensitive recording material manufacturing, such as providing an undercoat layer on the support to improve image quality and sensitivity, processing the back surface of the recording material into an adhesive label by processing with an adhesive, and providing a magnetic layer on the back surface of the recording material. Various known techniques can be added. Further, the image quality and the image density can be improved by performing a super calendering process after forming the recording layer.

[0018]

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. In addition, "part" and "%" in an example show "weight part" and "weight%", respectively, unless there is particular notice.

Example 1 Preparation of solution A 3-di (n-butyl) amino-6-methyl-7-anilinofluorane 10 parts, dibenzyl oxalate (mp = 81)
C.) 25 parts, 5 parts of a 5% aqueous solution of methyl cellulose, and 35 parts of water were pulverized with a horizontal sand mill until the average particle size became 0.5 μm. Preparation of Solution B A composition consisting of 20 parts of 4,4′-isopropylidenediphenol, 5 parts of a 5% aqueous solution of methylcellulose, and 30 parts of water was pulverized with a horizontal sand mill until the average particle diameter became 0.8 μm. Preparation of liquid C Bisphenol S diallyl ether (mp = 141 ° C)
A composition consisting of 20 parts, 5 parts of a 5% aqueous solution of methyl cellulose, and 30 parts of water was pulverized with a horizontal sand mill until the average particle diameter became 0.8 μm. Formation of recording layer 75 parts of solution A, 55 parts of solution B, 55 parts of solution C, 7 parts of fine particle silicon oxide (oil absorption amount 180 ml / 100 g), 8 parts of light calcium carbonate (oil absorption amount 90 ml / 100 g), silicon modified polyvinyl alcohol A recording layer coating solution obtained by mixing 100 parts of a 10% aqueous solution, 15 parts of a 30% aqueous dispersion of zinc stearate, and 70 parts of water with stirring is applied to one surface of a high-quality paper of 50 g / m ² after drying. A recording layer was formed by coating and drying so that the amount was 4 g / m ² .

Example 2 In preparation of solution A, 3-di (n-butyl) amino-6-
Instead of 10 parts of methyl-7-anilinofluorane, 3
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 10 parts of -di (n-butyl) amino-7- (o-chlorophenylamino) fluorane was used.

Example 3 Preparation of liquid D A composition comprising 100 parts of calcined clay [trade name: Ansilex, manufactured by EMC, oil absorption: 110 ml / 100 g], 100 parts of a 10% aqueous solution of polyvinyl alcohol, and 200 parts of water was prepared. By mixing and stirring, a coating liquid for the undercoat layer was obtained. On one surface of woodfree paper of Preparation 45 g / m ² of the heat-sensitive recording material, after coating and drying the solution D so that the coating amount after drying of 8 g / m ^2, coating the recording layer was prepared as in Example 1 Coating amount after drying is 4 g /
After coating and drying so as to be m ² , super calender treatment was carried out to obtain a heat-sensitive recording material.

Comparative Example 1 In the preparation of solution A, instead of dibenzyl oxalate,
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 1,2-diphenoxyethane (mp = 97 ° C.) was used.

Comparative Example 2 In the preparation of solution A, di (β-biphenylethoxy) benzene (mp = 81 ° C.) was used instead of dibenzyl oxalate.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that was used.

Comparative Example 3 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the liquid C was not used.

The following six evaluation tests were carried out on the thus obtained six kinds of thermal recording materials, and the results are shown in [Table 1]. [Color density] Thermal recording material evaluation machine [Product name: TH-PM
D, manufactured by Okura Electric Co., Ltd., and recorded under the conditions of an applied voltage of 16 V, a pulse cycle of 0.51 ms and a pulse width of 0.30 ms, and the obtained recording density (D ₁ ) was measured by a Macbeth densitometer [RD
-914 type, manufactured by Macbeth Co., Ltd.] in visual mode. [Heat resistance of recorded image] Heat-sensitive recording paper after recording is at 50 ° C-10
After being left in an atmosphere of% RH for 48 hours, the density (D ₂ ) of the recording portion was measured using a Macbeth densitometer. Also,
The recording density residual rate (%) was determined by the following formula. Recording density residual rate = D ₂ / D ₁ × 100 [Coloring ability of blank area] Heat sensitive recording paper before recording at 50 ° C.-10
After being left in an atmosphere of% RH for 48 hours, recording was performed by the method of [Recording Density] described above, and the recording density (D ₃ ) was measured with a Macbeth densitometer. Further, the color forming ability (%) was determined by the following formula. Color development = D ₃ / D ₁ × 100

[0026]

[Table 1]

[0027]

As is clear from the results shown in Table 1, each of the thermosensitive recording materials of the present invention is excellent in storage stability and recording sensitivity of a recorded image and has less deterioration in coloring ability of a white paper portion. It was a record.

Claims (1)

[Claims] 1. A thermosensitive recording medium comprising a support and a recording layer containing a colorless or light-colored basic dye and a color developer, wherein the recording layer contains bisphenol S diallyl ether and dibenzyl oxalate. A heat-sensitive recording material characterized by the following.