JPH06278364A - Thermal recording - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to provide a thermosensitive recording medium having high sensitivity and high gradation, excellent storage stability of printed images, and less fog in the blank area. . [Structure] In a heat-sensitive recording material comprising a support and an undercoat layer containing a pigment and a binder and a heat-sensitive recording layer containing a basic dye and a colorant, the heat-sensitive recording layer comprises a specific diphenyloxyalkane derivative and bis ( A thermosensitive recording medium containing p-methylbenzyl) oxalate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal recording material having high sensitivity, high gradation, excellent storage stability of printed images, and less fog on a blank portion.

[0002]

2. Description of the Related Art A thermosensitive recording medium is known in which a reaction between a colorless or light-colored basic dye and a coloring agent is utilized to bring both color-forming substances into contact with each other by heat to obtain a recorded image. Such a thermal recording medium is used in a wide range of fields as a recording medium because it is relatively inexpensive, the recording device is compact, and its maintenance is relatively easy.

As an example thereof, there is a video printer which records a video image of a camera as a still image. The video printer converts an image signal into intensity of applied energy for each dot and records it to obtain an image having image quality and gradation similar to a silver halide photograph. The quality required for thermal recording paper used in video printers is high smoothness that faithfully conveys the intensity of thermal energy controlled by the thermal head to the thermal recording layer, and the recording density that can respond to the intensity of thermal energy. Is important.

In order to obtain a high smoothness of the recording surface, the most effective means is to use a highly smooth film as the support, but the film is expensive, and it is difficult to handle because it does not have elasticity.
Alternatively, there is a drawback that the operability is poor. If used as a support for paper, this problem does not occur, but since the surface of paper is less smooth than film, it is necessary to provide an undercoat layer to create a highly smooth base to obtain high image quality. is there. Further, the provision of the undercoat layer has the advantages that a high-quality recorded image can be obtained and that the heat energy can be effectively used due to its heat insulating effect, and high sensitivity can be obtained.

However, when the undercoat layer is provided, as the applied energy becomes higher, the dye or color developing agent melted in the heat-sensitive recording layer penetrates into the undercoat layer, and as a result,
In recording in the high-energy portion, the reversal phenomenon that the recording density decreases as the energy increases, the upper limit of the recording density is suppressed, and the range of recording gradation is narrowed.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and does not have new drawbacks such as a decrease in whiteness even when stored under high temperature conditions, and it is possible to use high energy as described above. An object of the present invention is to provide a thermosensitive recording medium which is excellent in recording gradation and image quality, by eliminating the phenomenon of reduction in recording density that occurs when recording.

[0007]

The present invention provides a thermosensitive recording medium comprising a support and an undercoat layer containing a pigment and a binder, and a thermosensitive recording layer containing a basic dye and a colorant in that order.
A heat-sensitive recording material, wherein the heat-sensitive recording layer contains a compound represented by [Chemical Formula 1] and bis (p-methylbenzyl) oxalate.

[0008]

[Chemical 1]

[R _{1 and} R ₂ each represent a hydrogen atom, a methyl group or a methoxy group, and n represents 1 or 2. ]

[0010]

The compound represented by the above [Chemical formula 1] is 1,
2-di (phenoxy) ethane, 1,2-di (4-methylphenoxy) ethane, 1,2-di (3-methylphenoxy) ethane, 1- (2-methylphenoxy) -2- (4
-Methoxyphenoxy) ethane and the like can be exemplified.

The present invention is characterized in that at least one compound represented by the above [Chemical formula 1] and bis (p-methylbenzyl) oxalate are contained in the recording layer. Although the reason why the effect of the present invention is obtained is not necessarily clear, it is considered that the maximum recording density is increased and the range of gradation is widened by using a specific substance together. In addition, normally, when a heat-fusible substance is used in combination, fog coloration occurs, and the whiteness of the white paper portion tends to decrease, but it can be speculated that such an adverse effect does not occur specifically in the case of the present invention. . Even if dibenzyl oxalate is used instead of bis (p-methylbenzyl) oxalate, it is not possible to obtain a sufficient tone range.

The amounts of at least one of the compounds represented by the above [Chemical formula 1] and bis (p-methylbenzyl) oxalate are not particularly limited, but are based on 100 parts by weight of the basic dye. The compound represented by [Chemical Formula 1] is used in an amount of about 5 to 400 parts by weight, preferably about 30 to 200 parts by weight. Bis (p-methylbenzyl) oxalate is used in an amount of 10 to 50 with respect to 100 parts by weight of the basic dye.
It is preferable to adjust the amount in the range of about 0 parts by weight, preferably about 30 to 300 parts by weight.

The ratio between the amount of the compound represented by [Chemical formula 1] and the amount of bis (p-methylbenzyl) oxalate used is not particularly limited, but the compound represented by [Chemical formula 1] 100 Bis (p-methylbenzyl) oxalate is adjusted to about 5 to 2000 parts by weight, preferably 20 to 1000 parts by weight, based on parts by weight. In the present invention, various known dyes can be used as the colorless or light-colored basic dye that constitutes the recording layer,
Specific examples include the following.

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-methylindole -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 , 3-p-dimethylaminophenyl-3- (1-methylpyrrol-3-yl) -6-dimethylaminophthalide and other triarylmethane dyes, 4,4′-bis-dimethylaminobenzhydrylbenzyl ether , N-halophenyl-leuco auramine, N-2,4,5-trichlorophenyl leuco auramine and other diphenylmethane dyes, benzoyl leuco methylene blue, p-nitrobenzoyl leuco methylene blue and other thiazine dyes, 3-methyl-spiro-
Such as dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho (6'-methoxybenzo) spiropyran, 3-propyl-spiro-dibenzopyran. Spiro dyes, rhodamine-B-anilinolactam, rhodamine (p-nitroanilino) lactam, rhodamine (o-chloroanilino)
Lactam dyes such as 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-methylaminofluorane, 3-diethylamino-
7-N-methylaminofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-N-methyl-N-benzylaminofluorane,
3-diethylamino-7-N-chloroethyl-N-methylaminofluorane, 3-diethylamino-7-N-diethylaminofluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7-phenylaminofluor Oran, 3- (N-ethyl-p-toluidino) -6-methyl-7- (p-toluidino) fluorane, 3-dimethylamino-6-methyl-7-phenylaminofluorane, 3
-Diethylamino-6-methyl-7-phenylaminofluorane, 3-di-n-butylamino-6-methyl-7
-Phenylaminofluorane, 3-di-n-pentylamino-6-methyl-7-phenylaminofluorane, 3
-Diethylamino-7- (2-carbomethoxy-phenylamino) fluorane, 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
-Di-n-butylamino-7- (o-chlorophenylamino) fluorane, 3-pyrrolidino-6-methyl-7-
p-Butylphenylaminofluorane, 3- (N-methyl-Nn-amyl) amino-6-methyl-7-phenylaminofluorane, 3- (N-ethyl-Nn-amyl) amino-6 -Methyl-7-phenylaminofluorane, 3- (N-ethyl-N-isoamyl) amino-6-
Methyl-7-phenylaminofluorane, 3- (N-methyl-Nn-hexyl) amino-6-methyl-7-phenylaminofluorane, 3- (N-ethyl-Nn-)
Hexyl) amino-6-methyl-7-phenylaminofluorane, 3- (N-ethyl-N-β-ethylhexyl) amino-6-methyl-7-phenylaminofluorane, 3- (N-ethyl-N- Tetrahydrofurfuryl)
Amino-6-methyl-7-phenylaminofluorane,
3- (N-ethyl-N-cyclopentyl) amino-6-
Methyl-7-phenylaminofluorane, 2,2-bis {4- [6 '-(N-cyclohexyl-N-methylamino) -3'-methylspiro [phthalide-3,9'-xanthene] -2'- Fluoran dyes such as ilamino] phenyl} propane. Of course, the dyes are not limited to these dyes, and two or more dyes may be used in combination.

Among these dyes, 3-dibutylamino-7- (o-chlorophenylamino) fluorane,
3-diethylamino-7- (o-chlorophenylamino) fluorane, 3- (N-ethyl-p-toluidino)
-6-Methyl-7-phenylaminofluorane is more preferably used because a thermosensitive recording medium having a particularly high whiteness in the white paper portion can be obtained.

Various compounds are known as colorants used in combination with the above basic dyes, and the following are exemplified. 4-tert-butylphenol, α-
Naphthol, β-naphthol, 4-acetylphenol, 4-tert-octylphenol, 4,4'-sec-
Butylidene diphenol, 4-phenylphenol,
4,4'-dihydroxy-diphenylmethane, 4,4 '
-Isopropylidenediphenol, hydroquinone,
4,4'-cyclohexylidene diphenol, 4,4 '
-(1,3-dimethylbutylidene) bisphenol,
2,2-bis (4-hydroxyphenyl) -4-methylpentane, 4,4'-dihydroxydiphenyl sulfide, 4,4'-thiobis (6-tert-butyl-3-methylphenol), 4,4'- Dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 4-hydroxy-4'-methoxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy -3 ', 4'-trimethylene diphenyl sulfone, 4-hydroxy-3', 4'-tetramethylene diphenyl sulfone, 3,4-dihydroxy-4'-methyldiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) ) Sulfone, 1,3-di [2- (4-hydroxyphenyl) Phenyl) -2-propyl] benzene, hydroquinone monobenzyl ether, bis (4
-Hydroxyphenyl) acetic acid butyl ester, 4-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,4,4'-trihydroxybenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, 4-hydroxyphthalic acid Dimethyl, methyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate, 4
-Propyl hydroxybenzoate, sec-butyl 4-hydroxybenzoate, pentyl 4-hydroxybenzoate,
Phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, phenylpropyl 4-hydroxybenzoate, phenethyl 4-hydroxybenzoate, 4-hydroxybenzoic acid-p. -Chlorobenzyl,
4-hydroxybenzoic acid-p-methoxybenzyl, novolac type phenolic resin, phenolic compounds such as phenolic polymers, benzoic acid, p-tert-butylbenzoic acid,
Trichlorobenzoic acid, terephthalic acid, 3-sec-butyl-4-hydroxybenzoic acid, 3-cyclohexyl-4-
Hydroxybenzoic acid, 3,5-dimethyl-4-hydroxybenzoic acid, salicylic acid, 3-isopropylsalicylic acid, 3-tert-butylsalicylic acid, 3,5-di-tert-
Butyl salicylic acid, 3-benzyl salicylic acid, 3- (α
-Methylbenzyl) salicylic acid, 3-chloro-5- (α
-Methylbenzyl) salicylic acid, 3-phenyl-5-
Aromatic carboxylic acids such as (α, α-dimethylbenzyl) salicylic acid and 3,5-di-α-methylbenzylsalicylic acid, and these phenolic compounds, aromatic carboxylic acids and, for example, zinc, magnesium, aluminum, calcium, titanium, Examples thereof include organic acidic substances such as salts with polyvalent metals such as manganese, tin and nickel. As a matter of course, two or more kinds of the above-mentioned color developing agents can be used in combination.

The use ratio of the basic dye and the color developing agent should be appropriately selected according to the types of the basic dye and the color developing agent to be used and is not particularly limited, but in general, the basic dye 1 is used.
About 100 to 700 parts by weight, preferably about 150 to 400 parts by weight, of the coloring agent is used with respect to 00 parts by weight.

The preparation of a coating liquid containing these is generally represented by a basic dye, a coloring agent, and a general formula [Chemical formula 1] by using a stirring / grinding machine such as a ball mill, an attritor or a sand mill with water as a dispersion medium. It is prepared by dispersing the compound or the like together or separately. Further, if necessary, starches, hydroxyethyl cellulose, methyl cellulose,
Carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene / maleic anhydride copolymer salt, styrene / acrylic acid copolymer salt, styrene / butadiene copolymer emulsion, etc. should be used together as a binder or dispersion aid. You can also

In the above coating liquid, these binder components are usually contained in an amount of 2 to 40% by weight, preferably 5 to 40% by weight based on the total solids of the coating liquid.
It is blended so as to be in the range of 25% by weight.

Further, various auxiliary agents can be added to the coating liquid, for example, dioctylsulfosuccinic acid sodium salt, dodecylbenzenesulfonic acid sodium salt,
Examples thereof include dispersants such as lauryl alcohol sulfate / sodium salt and fatty acid metal salt, defoaming agents, fluorescent dyes, and coloring dyes.

In addition, kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, fine anhydrous silica, in order to improve the adhesion of dust to the recording head.
Inorganic pigments such as activated clay, styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and organic pigments such as raw starch particles can also be added. In addition, stearic acid, which prevents sticking due to contact with the recording equipment and recording head,
It is also possible to add a dispersion liquid or emulsion of polyethylene, carnauba wax, paraffin wax, zinc stearate, calcium stearate, ester wax or the like.

Further, in the heat-sensitive recording material of the present invention, fatty acid amides such as stearic acid amide, stearic acid methylene bisamide, oleic acid amide, palmitic acid amide, and coconut fatty acid amide are used as long as the desired effects of the present invention are not impaired. , 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 4,4'-butylidenebis (6-tert-butyl-3-methylphenol), 1,1,3-tris (2-methyl) -4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-
Hindered phenols such as tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, p
-Benzylbiphenyl, p- (4-tolyloxy) biphenyl, 1,5-bis (4-methoxyphenoxy) -3
-Ethers such as oxa-pentane and 2-naphthol benzyl ether, dibenzyl terephthalate, 1-hydroxy-2-naphthoic acid phenyl ester, oxalic acid dibenzyl ester, oxalic acid di (4-chlorobenzyl)
Esters such as esters, 2- (2'-hydroxy-
An ultraviolet absorber such as 5'-methylphenyl) benzotriazole and 2-hydroxy-4-benzyloxybenzophenone, and various known heat-fusible substances can be used together as a sensitizer. The amount of the heat-fusible substance used is not particularly limited, but the basic dye 1
It is desirable to use generally 50 to 1000 parts by weight, preferably 100 to 500 parts by weight, relative to 00 parts by weight.

As the support, paper, plastic film, synthetic paper and the like are used, but paper is preferred in terms of cost and coating suitability. Further, the present invention is characterized in that an undercoat layer is provided between the support and the heat-sensitive recording layer in order to obtain a recording material having high sensitivity and high image quality. The undercoat layer is mainly composed of a pigment and a binder, but the kind of the pigment is not particularly limited, and inorganic pigments such as calcined clay, amorphous silica, aluminum silicate, talc, light and heavy calcium carbonate and magnesium carbonate, amino It is possible to use various organic pigments such as resins, phenol resins, and styrene resins alone or in combination of two or more kinds.

The binder is used in an amount of about 1 to 50 parts by weight, preferably about 2 to 30 parts by weight, based on 100 parts by weight of the pigment. The type of binder is not particularly limited, and examples thereof include water-soluble polymers such as starch, casein, polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyacrylic acid, styrene / butadiene copolymer, and styrene / acrylic acid copolymer. Various synthetic resin emulsions such as polymers, acrylonitrile / butadiene copolymers, colloidal silica particle composite styrene / acrylic acid ester copolymers, acrylic acid copolymers and the like are used.

Further, various auxiliary agents can be added to the coating liquid, for example, dioctylsulfosuccinic acid sodium salt, dodecylbenzenesulfonic acid sodium salt,
Examples thereof include dispersants such as sodium lauryl alcohol sulfate / sodium salt and fatty acid metal salts, other defoaming agents, fluorescent dyes, and coloring dyes. In the present invention, the method for forming the undercoat layer and the heat-sensitive recording layer is not particularly limited, and it can be formed according to a conventionally well-known and common technique, such as an air knife coater, a blade coater, a bar coater, a gravure coater, and a curtain coater. Coating with a suitable coating device such as a short dwell coater
Examples of the method include drying. Further, the coating amount of the coating liquid is not particularly limited, and generally the undercoat layer has a dry weight of about 3 to 30 g / m ² , preferably 5 to 1
5 g / m ^2, about ² to 12 g / dry weight of the thermosensitive recording layer
m ² is adjusted, preferably in the range of ^{2 to} 8 g / m ² .

An overcoat layer may be provided on the thermosensitive recording layer for the purpose of protecting the thermosensitive recording layer, and a protective layer may of course be provided on the back surface of the support, and further, it is also possible. Various known techniques in the field of manufacturing thermosensitive recording media such as adhesion processing or magnetic recording layer on the back surface can be added.

[0027]

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, unless otherwise indicated, the part and% in an example show a weight part and weight%, respectively.

Example 1 Formation of Undercoat Layer Baked clay (trade name: Ansilex, manufactured by EMC)
100 parts, styrene / butadiene copolymer latex (solid content: 50%) 15 parts, 10% polyvinyl alcohol aqueous solution 30 parts, and water 20 parts were mixed and stirred to prepare a coating liquid for the undercoat layer. 50 g of the obtained coating liquid
/ M ² of high-quality paper was applied and dried so that the coating amount after drying was 10 g / m ² to form an undercoat layer. Solution A Preparation 3-di-n-butylamino-6-methyl-7-phenylaminofluorane 10 parts, 1,2-di (3-methylphenoxy) ethane 5 parts, 5% aqueous solution of methylcellulose 5 parts, and water 30 parts were pulverized with a sand mill until the average particle size became 0.7 μm. Preparation of Liquid B 20 parts of 4,4′-isopropylidenediphenol, 20 parts of di (p-methylbenzyl) oxalate, 10 parts of a 5% aqueous solution of methylcellulose, and 60 parts of water were added, and the average particle size was adjusted to 0. It was crushed to 7 μm.

Formation of Recording Layer 50 parts of solution A, 110 parts of solution B, light calcium carbonate 10
Parts, silicon oxide pigment 20 parts, 30% zinc stearate 10
Parts, and 100 parts of a 15% aqueous solution of polyvinyl alcohol (Kuraray Co., Ltd .; trade name, PVA210) and stirred, and then coated and dried on the undercoat layer so that the coating amount after drying is 4 g / m ^2. A thermosensitive recording material was obtained.

Example 2 Example 1 was repeated except that 1,2-di (3-methylphenoxy) ethane was used in place of 1,2-di (3-methylphenoxy) ethane in the preparation of the liquid A of Example 1. A thermosensitive recording medium was obtained in the same manner as described above.

Comparative Example 1 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 1,2-di (3-methylphenoxy) ethane was not used in the preparation of solution A in Example 1.

Comparative Example 2 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that bis (p-methylbenzyl) oxalate was not used in the preparation of solution B in Example 1.

Comparative Example 3 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that p-benzylbiphenyl was used in place of bis (p-methylbenzyl) oxalate in the preparation of solution B in Example 1.

Comparative Example 4 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that metaterphenyl was used in place of bis (p-methylbenzyl) oxalate in the preparation of solution B in Example 1.

Comparative Example 5 In the preparation of solution B of Example 1, 1,2-di (phenoxy) was used instead of bis (p-methylbenzyl) oxalate.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that ethane was used.

The various types of thermal recording materials thus obtained were evaluated by the following methods, and the results are shown in [Table 1]. [Recording Density] A thermal recording material was recorded with an applied energy of 0.3 mJ using a thermal paper color tester, and the recording density was measured with a Macbeth densitometer (RD-914 type, manufactured by Macbeth Co.), and the value was obtained. Was defined as D ₁ . Also, recording and measurement were carried out similarly with an applied energy of 0.45 mJ, and the value was designated as D ₂ .

[Temperature resistance of recorded image] Applied energy 0.3
After the thermal recording paper after printing with mJ was left in an atmosphere of 60 ° C. and 10% RH for 72 hours, the recording density (D ₃ ) was measured again using a Macbeth densitometer. In addition, the recording density residual rate (%) was determined by the following formula. Recording density residual rate (%) = D ₃ / D ₂ × 100

[Fog Color Development] Heat-sensitive recording paper was heated at 60 ° C. for 10 minutes.
After left in an atmosphere of% RH for 72 hours, the fog color density (F) of the white paper portion was measured using a Macbeth densitometer.

[Gradation of Image] A test pattern was recorded on a thermosensitive recording medium using a video printer Sony UP-702, and the gradation of the image was visually evaluated according to the following evaluation criteria. ⊚: The gradation of the recorded image is very excellent. X: The contrast of the recorded image is poor and difficult to see.

[0040]

[Table 1]

[0041]

As is clear from the results of Table 1, the thermosensitive recording medium of the present invention has high sensitivity and high gradation.
The heat-sensitive recording material was excellent in storability of printed images and had less fog in the blank area.

Front page continued (72) Inventor Ken Fukuda 4-3-1 Jōkoji, Amagasaki City, Hyogo Prefecture Kanzaki Paper Co., Ltd. Kanzaki Mill

Claims (1)

[Claims] 1. A thermosensitive recording medium comprising a support, an undercoat layer containing a pigment and a binder, and a thermosensitive recording layer containing a basic dye and a colorant, wherein the thermosensitive recording layer is represented by [Chemical Formula 1]. And a bis (p-methylbenzyl) oxalate. [Chemical 1] [R _{1 and} R ₂ each represent a hydrogen atom, a methyl group, or a methoxy group, and n represents 1 or 2. ]