JPH0958135A - Thermal recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thermal recording material excellent in recording sensitivity and background fog by providing a thermal recording layer containing a leuco dye and coupler and, if necessary, a protective layer on a support and using hydroxyphenylethane with a specific average particle size as the coupler. SOLUTION: In a thermal recording material using a transparent film for OHP and plate making as a support and obtained by providing a thermal recording layer containing a leuco dye and coupler and, if necessary, a protective layer on the support, 1,1,1-tris-p-hydroxyphenylethane is used as the coupler. This coupler has an average particle size of 0.05-1.0μm and, as the support, a transparent film having an anchor coating layer on the surface thereof or subjected to corona discharge treatment composed of polypropylene, polystyrene, nylon or polyvinyl chloride is used.

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 utilizing a color-developing reaction between a leuco dye and a coloring agent, and more particularly to a heat-sensitive recording material having less background fog.

[0002]

2. Description of the Related Art A heat-sensitive recording material is known which utilizes a color-forming reaction between a leuco dye and a coloring agent to bring both substances into contact with each other by heat to obtain a color-developed image. Since such a thermosensitive recording medium 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. .

As one of the fields of application, one having excellent transparency using a transparent film as a support for, for example, X-ray film, OHP and plate making, or a difference in transmission density between a printed portion and an unprinted portion Very large ones are receiving attention. As one of the methods for increasing the recording sensitivity or obtaining a heat-sensitive recording material having excellent transparency, there is a case where a leuco dye or a color former finely pulverized to 1 μm or less is used. However, the finer the leuco dye or color developing agent, the more improved the recording sensitivity and transparency, but there is a problem that the color is developed at the same time when the dye and the color developing agent are mixed, and the background fog easily occurs during drying.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording material having excellent recording sensitivity and less background fog.

[0005]

DISCLOSURE OF THE INVENTION The present inventors have found that a thermosensitive recording layer containing a leuco dye and a color-developing agent on a support and a protective layer, if necessary, as a color-developing agent. By using 1,1,1-tris-p-hydroxyphenylethane, it has been found that the above problems can be solved, and the present invention has been completed.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention provides a heat-sensitive recording layer comprising a support, a heat-sensitive recording layer containing a leuco dye and a color former, and a protective layer if necessary.
A specific coloring agent of tris-p-hydroxyphenylethane is used, and the specific coloring agent is preferably used in the range of 20 to 60% by weight based on the total solid amount of the heat-sensitive recording layer. .

The average particle size of such a specific color developing agent is 0.0
By using a transparent film such as polypropylene, polyethylene terephthalate, polystyrene, nylon, or vinyl chloride having a surface of anchor coat or corona discharge treatment as a support,
In particular, it is possible to obtain a heat-sensitive recording material having a large difference in transmission density between a recorded portion and an unrecorded portion, which is suitable for an original drawing of a printing plate. If the average particle size of the specific color-developing agent is less than 0.05 μm, background fog may occur, and if it exceeds 1.0 μm, the transparency of the thermosensitive recording material decreases and the difference in transmission density between the recorded and unrecorded areas. There is a risk that a large thermal recording material may not be obtained. The haze value of the heat-sensitive recording material is 85% or less, preferably 70% or less. If the haze value exceeds 85%, it becomes impossible to measure the transmission density, or the transmission density value of the unrecorded area increases, so that the contrast with the recorded area decreases.

Various known leuco dyes can be used as the leuco dye used in combination with the specific color-forming agent, and examples thereof include the following. 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindole-3
-Yl) -4-azaphthalide, crystal violet lactone, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane , 3-diethylamino-6-methyl-7- (o, p-dimethylanilino) fluorane, 3- (N-ethyl-N-p-toluidino) -6-methyl-7-anilinofluorane, 3-
Pyrrolidino-6-methyl-7-anilinofluorane, 3
-Di (n-butyl) amino-6-methyl-7-anilinofluorane, 3- (N-cyclohexyl-N-methyl)
Amino-6-methyl-7-anilinofluoran, 3-
(N-ethyl-Nn-hexylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-7-
(O-chloroanilino) fluorane, 3-di (n-butyl) amino-7- (o-chloroanilino) fluorane,
3-diethylamino-7- (m-trifluoromethylanilino) fluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6-methylfluorane, 3-cyclohexylamino-6-chlorofluor Oran, 3- (N-ethyl-N-hexyl) amino-6-methyl-7- (p-chloroanilino) fluorane and the like. Of course, it is also possible to use two or more of these leuco dyes in combination.

As the coloring agent, 1,1,1-tris-p-
Although hydroxyphenylethane is used, various other known color formers can be used in combination as long as the desired effects of the present invention are not impaired. Specific examples of such a coloring agent include 4-cumylphenol, hydroquinone monobenzyl ether, 4,4′-isopropylidenediphenol, 1,1-bis (4-hydroxyphenyl) cyclohexane, 4,4′- Dihydroxydiphenyl-2,2-butane, 4,4′-dihydroxydiphenyl sulfide, bis (4-hydroxy-3-methylphenyl) sulfide, 4,4′-dihydroxydiphenyl sulfone, 2,4′-dihydroxydiphenyl sulfone, 4 -Hydroxy-4'-methyldiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxyphenyl-4'-benzyloxyphenyl sulfone, 4- Hydroxy-3 ',
4'-tetramethylene biphenyl sulfone, 3,4-dihydroxyphenyl-p-tolyl sulfone, 4-hydroxybenzoic acid benzyl ester, N, N'-di-m-chlorophenylthiourea, 4,4'-bis (p- Tolylsulfonylaminocarbonylamino) diphenylmethane,
4- [2- (p-methoxyphenoxy) ethyloxy]
Zinc salicylate, 4- [3- (p-tolylsulfonyl)
Zinc propyloxy] salicylate, 5- [p- (2-p
-Methoxyphenoxyethoxy) cumyl] zinc salicylate and the like. In addition, if necessary, two or more kinds of these color-developing agents can be used in combination.

The ratio of the leuco dye to the specific coloring agent used in the heat-sensitive recording layer should be appropriately selected according to the type of the leuco dye to be used and is not particularly limited. For example, 1 part by weight of the leuco dye is used. On the other hand, about 1 to 7 parts by weight, preferably about 1 to 4 parts by weight of a coloring agent is used.

Preparation of a coating liquid for a heat-sensitive recording layer containing a leuco dye and a specific color developing agent is generally carried out by using water as a dispersion medium and stirring the mixture with a ball mill, an attritor, a sand mill or the like to obtain the leuco dye and the color developing agent. Are dispersed together or separately.

In such a coating liquid, starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, diisobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride are usually used as binders. Copolymer salt, ethylene / acrylic acid copolymer salt,
Styrene / acrylic acid copolymer salt, natural rubber emulsion, styrene / butadiene copolymer emulsion, acrylonitrile / butadiene copolymer emulsion, methyl methacrylate / butadiene copolymer emulsion, polychloroprene emulsion, vinyl acetate emulsion, ethylene -At least one of vinyl acetate emulsion and the like is 10 to 40 based on the total solid content of the thermosensitive recording layer.
%, Preferably 20 to 35% by weight.

If desired, various auxiliary agents can be added to the coating liquid. For example, dispersants such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, and fatty acid metal salts. , Zinc stearate, calcium stearate, polyethylene wax, carnauba wax,
Waxes such as paraffin wax and ester wax, antifoaming agents, fluorescent dyes, coloring dyes, pigments and the like are appropriately added.

Examples of pigments include kaolin, clay,
Calcium carbonate, calcined clay, calcined kaolin, diatomaceous earth,
Inorganic pigments such as fine particulate anhydrous silica and activated clay, and organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and raw starch particles can be mentioned.

Further, a sensitizer may be used in combination for increasing the recording sensitivity. Specific examples of the sensitizer include stearic acid amide, ethylenebistearic acid amide,
Methylenebisstearic acid amide, N-methylolstearic acid amide, dibenzyl terephthalate, benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, 2-naphthylbenzyl ether, m-
Terphenyl, dibenzyl oxalate, oxalic acid-di-p
-Methylbenzyl, oxalic acid-di-p-chlorobenzyl, 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 Examples include -p-toluidine, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane and the like. The amount of these sensitizers used is not particularly limited, but is generally 4 per 1 part by weight of the color developing agent.
It is desirable to adjust the content within the range of parts by weight or less.

In order to further improve the storage stability of the recorded image, a storage stability improving agent may be used in combination. Specific examples of such a storage stability improver include, for example, 2,2′-methylenebis (4
-Methyl-6-tert-butylphenol), 2,2'-
Methylenebis (4,6-di-tert-butylphenol), 2,2'-ethylidenebis (4,6-di-tert-
Butylphenol), 2,2'-ethylidenebis (4-
Ethyl-6-tert-butylphenol), 2,2'-
(2,2-Propylidene) bis (4,6-di-tert-butylphenol), 2,2′-methylenebis (6-tert
-Butylphenol), 4,4'-thiobis (3-methyl-6-tert-butylphenol), 4,4'-butylidenebis (6-tert-butyl-m-cresol), 1-
[Α-Methyl-α- (p-hydroxyphenyl) ethyl] -4- [α ′, α′-bis (p-hydroxyphenyl) ethyl] benzene, 1,1,3-tris (2-methyl-4-) Hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl) ) Hindered phenol compounds such as propane, N, N'-di-
2-naphthyl-p-phenylenediamine, 2,2'-methylenebis (4,6-di-tert-butylphenyl) sodium phosphate and the like can be mentioned.

On the heat-sensitive recording layer, a protective layer, which is provided if necessary for the purpose of enhancing the storability of a recorded image with respect to a chemical such as a plasticizer or an edible oil, or the recording running property, is composed mainly of an aqueous resin. However, specific examples of such an aqueous resin include starches such as oxidized starch, enzyme-modified starch, cation-modified starch, esterified starch and etherified starch, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, methoxy cellulose, hydroxyethyl cellulose and the like. Cellulose derivatives, completely (or partially) saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, polyvinyl alcohol such as silicon-modified polyvinyl alcohol, polyacrylamide, polyvinylpyrrolidone, acrylic Amide / acrylic acid ester copolymer, acrylic acid amide / acrylic acid ester / methacrylic acid copolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, sodium alginate, gelatin, Water-soluble polymers such as casein, polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic acid ester, polybutyl methacrylate, styrene-butadiene copolymer, vinyl chloride
Vinyl acetate copolymer, ethylene / vinyl acetate copolymer,
Examples of the latex include styrene / butadiene / acrylic copolymers. Among these, polyvinyl alcohols such as completely (or partially) saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, and silicon-modified polyvinyl alcohol, which exhibit an excellent effect of preserving recorded images, are particularly preferable. .

The protective layer coating liquid containing the aqueous adhesive is prepared by mixing water with a water-soluble resin and stirring the mixture. In the coating liquid, if necessary, a dispersant, a defoaming agent,
Coloring dyes, fluorescent dyes, hardeners, auxiliary agents such as UV absorbers, various modified silicone oil emulsions, lubricants such as zinc stearate, calcium stearate, carnauba wax, paraffin wax, ester wax, calcium carbonate, zinc oxide, aluminum oxide , Titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate,
Inorganic pigments such as talc, kaolin, clay, calcined clay and colloidal silica can also be used in combination.

The method for forming the heat-sensitive recording layer and the protective layer is not particularly limited, and examples thereof include air knife coating, varibar blade coating, pure blade coating, rod blade coating,
Apply the coating liquid for the heat-sensitive recording layer on the support by an appropriate coating method such as short dwell coating, curtain coating, die coating, bar coating, etc. to form a heat-sensitive recording layer, and then coat it for the protective layer. The protective layer is formed by applying and drying the liquid. As the support, high-quality paper, coated paper, synthetic paper, transparent film or the like is appropriately selected and used. The coating amount of the thermal recording layer coating liquid is 1 to 20 g / m ² in terms of dry weight, preferably 5 to
It is adjusted in the range of 15 g / m ² . The coating amount of the protective layer coating liquid is adjusted within the range of 0.5 to 5 g / m ² .

Further, a heat-sensitive material such as a glossy layer containing a resin which is hardened by electron beam or ultraviolet irradiation, a super calender treatment, an antistatic layer on the back surface, an adhesive treatment, etc. are formed on the protective layer. Various known techniques in the field of recording material production can be added as appropriate.

[0021]

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. Unless otherwise specified, "parts" and "%" in the examples mean "parts by weight" and "% by weight", respectively.

Example 1 Preparation of Liquid A 20 parts of 3-di (n-butyl) amino-6-methyl-7-anilinofluorane, 10 parts of 1,2-di (3-methylphenoxy) ethane, methylcellulose 5% aqueous solution of 30
Parts and 60 parts of water were pulverized with a sand mill until the average particle size became 0.4 μm.

Preparation of Solution B 1,1,1-tris-p-hydroxyphenylethane 2
0 part, 20 parts of a 5% aqueous solution of methylcellulose and 4 parts of water
A composition consisting of 0 parts was sand-milled to have an average particle size of 0.4.
It was pulverized to a size of μm.

Preparation of Coating Solution for Thermal Recording Layer Liquid A 100 parts, liquid B 120 parts, solid content 30% colloidal silica (average particle size 10 nm) 70 parts, solid concentration 50
% Styrene-butadiene (58 parts), a dioctyl sodium sulfosuccinate solution (1 part) and water (75 parts) were mixed and stirred to obtain a recording layer coating liquid.

Preparation of Coating Liquid for Protective Layer 150 parts of 10% aqueous solution of polyvinyl alcohol modified with acetoacetyl group, 50% aqueous dispersion of aluminum hydroxide 2
Parts, 10% aqueous solution of sodium dioctyl sulfosuccinate 1
Parts and 4 parts of an epoxy-modified silicone emulsion having a solid concentration of 30% were mixed and stirred to obtain a protective layer coating liquid.

Formation of Thermosensitive Recording Layer and Protective Layer On the transparent polyethylene terephthalate film (PET) [trade name: A-1300, manufactured by Toyobo, 100 μm] that has been subjected to corona discharge treatment, the above-mentioned coating liquid for thermal recording layer and protection. The coating amount after drying the layer coating liquid is 7 g / m ² , respectively.
A thermal recording layer and a protective layer were formed by sequentially coating and drying so as to have a coating weight of ² g / m ^2, and then subjected to a super calender treatment to obtain a thermal recording material. The transparency of the unrecorded area of the thermosensitive recording medium was measured using a haze meter [trade name: TC-HIV, manufactured by Tokyo Denshoku Co., Ltd.]. Haze value of thermal recording material is 50%
Met.

Example 2 In the preparation of solution A of Example 1, 3- (N-ethyl-N-isoamyl was used instead of 3-di (n-butyl) amino-6-methyl-7-anilinofluorane. A thermosensitive recording medium was obtained in the same manner as in Example 1 except that amino) -6-methyl-7-anilinofluorane was used. The haze value of the heat-sensitive recording material was 52%.

[Example 3] In the preparation of solution A of Example 1, 3- (N-ethyl-) was used instead of 3-di (n-butyl) amino-6-methyl-7-phenylaminofluorane.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that Nn-hexylamino) -6-methyl-7-anilinofluorane was used. The haze value of the heat-sensitive recording material was 54%.

Example 4 Preparation of Solution A and B of Example 1
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the average particle size was 0.8 μm in the liquid preparation. The haze value of the heat-sensitive recording material was 70%.

[Example 5] Thermal recording in the same manner as in Example 1 except that synthetic paper (trade name: YUPO FPG-80, manufactured by Oji Yuka Synthetic Paper Co., Ltd.) was used in place of PET. Got the body The haze value of the thermosensitive recording material could not be measured.

Example 6 Preparation of solution A and B of Example 1
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the average particle diameter was changed to 1.8 μm in place of 0.4 μm in the liquid preparation. The haze value of the heat-sensitive recording material was 90%.

Comparative Example 1 In the preparation of solution B of Example 1, 3,3 ′ diallyl-4,4′-dihydroxydiphenyl sulfone was used in place of 1,1,1-tris-p-hydroxyphenylethane. A thermal recording material was obtained in the same manner as in Example 1 except for the above. Haze value of thermal recording material is 48%
Met.

[Comparative Example 2] The procedure of Example 1 was repeated except that 4-hydroxy-4'-isopropoxydiphenylsulfone was used in place of 1,1,1-tris-p-hydroxyphenylethane. A thermal recording material was obtained in the same manner as in Example 1. The haze value of the thermosensitive recording material is 55%.
Met.

The heat-sensitive recording material thus obtained was subjected to the following evaluation tests, and the results are shown in Table 1. (1). Recording Transmission Density A thermal printer [trade name: Mitsubishi SCTP-65, recording energy 0.4 mJ / dot, manufactured by Mitsubishi Electric Corporation] was used for recording, and the transmission density of the obtained recorded image was measured by a Macbeth densitometer [ Product name: TD904 type, manufactured by Macbeth]. However, for the thermosensitive recording medium of Example 5, the reflection density of the recorded image was measured with a Macbeth densitometer [trade name: RD914 type, manufactured by Macbeth Co.].

(2). White paper fog A high quality paper of 80% whiteness is placed under the thermosensitive recording medium, and the reflection density of the unrecorded area is measured by a Macbeth densitometer [trade name: RD914.
Type, manufactured by Macbeth].

[0036]

[Table 1]

[0037]

As is clear from the results of [Table 1], the thermosensitive recording medium of the present invention has little background fog, and when a transparent film is used as the support, the difference in transmission density between the recorded portion and the unrecorded portion. It was a large thermosensitive recording medium.

Claims (2)

[Claims] 1. A thermosensitive recording medium comprising a support, a thermosensitive recording layer containing a leuco dye and a color former, and a protective layer if necessary, wherein the color former is 1,1,1-tris-. p
-Hydroxyphenylethane, a heat-sensitive recording material. 2. The support is a transparent film, and
The thermal recording medium according to claim 1, wherein the average particle size of 1,1-tris-p-hydroxyphenylethane is 0.05 to 1.0 µm.