JPH0834162A - Thermal recording - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a thermosensitive recording medium from which a clear projected image can be obtained. [Structure] A thermosensitive recording medium comprising a support and a thermosensitive recording layer containing a leuco dye and a colorant, wherein the support is 40
A thermal recording material having a maximum absorption peak at a light wavelength of 0 to 500 nm, a haze value (based on JIS K 7105) of 5 or less, and a recording material having a haze value of 20 or less.

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 for OHP, and more particularly to a thermal recording material capable of obtaining a clear projected image.

[0002]

2. Description of the Related Art A thermosensitive recording medium in which a colored image is obtained by contacting a coloring substance with heat by utilizing a coloring reaction between a colorless or light-colored leuco dye and a coloring agent is well known and supported. A thermal recording material using a film or synthetic paper as a body has also been proposed. Since such a thermosensitive recording medium is inexpensive and has a simple apparatus, it is used not only as a recording medium for facsimiles and various computers but also in a wide range of fields.

With the recent diversification of needs, for OHP,
There is an increasing demand for a heat-sensitive recording material having excellent transparency in an unrecorded area that can be used for X-ray and plate making. Especially OHP
The sheet for use needs high transparency. For that purpose, not only a highly transparent support is used, but also high transparency is required in the heat-sensitive recording layer. In order to increase the transparency of the heat-sensitive recording layer, a method of making the particle diameter of the material used for the heat-sensitive recording layer 1 μm or less is adopted, but a clear projected image is not obtained at present. .

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermosensitive recording medium which can obtain a clear projected image.

[0005]

DISCLOSURE OF THE INVENTION The present inventors have found that in a thermosensitive recording medium having a thermosensitive recording layer containing a leuco dye and a color former, the substrate has a light wavelength of 400 to 500 nm. Has a maximum absorption peak in the haze value (JIS K
It was found that the above problems can be solved by setting the haze value of the thermosensitive recording medium to be 20 or less and the present invention has been completed.

[0006]

According to the present invention, a leuco dye and a coloring agent are provided on a transparent film having a yellow or red haze value (based on JIS K 7105) of 5 or less, which has a maximum absorption peak at a light wavelength of 400 to 500 nm. The heat-sensitive recording material provided with the heat-sensitive recording layer contains a haze value of 20 or less, and when the maximum absorption peak wavelength exceeds 500 nm, the brightness of the unrecorded projection portion is remarkably reduced and a clear projected image is obtained. I can't get it. Further, when the maximum absorption peak wavelength is less than 400 nm, the projected portion of the unrecorded portion becomes gray, and a clear projected image cannot be obtained. Further, when the haze value of the film is 5 or the haze value of the thermosensitive recording material exceeds 20, diffuse reflection becomes strong and a clear projected image cannot be obtained for OHP.

As the support, a colored transparent film having a maximum absorption peak at 400 to 500 nm and a haze value of 5 or less is used. For example, propylene resin, styrene resin, vinyl chloride resin, ester resin, polyamide resin,
Acrylic resin, nitrile resin, urethane resin, cellulose resin, etc. are appropriately selected and used. It is also possible to provide an antistatic layer and an anchor coat layer on the front and back surfaces of the support.

As the colorless or light-colored leuco dye used in the recording layer, various known ones can be used.
Of these, the black-colored leuco dyes listed below are preferable because a clear projected image can be obtained. 3- (N-ethyl-p
-Toluidino) -6-methyl-7-phenylaminofluorane, 3- (N-cyclopentyl-N-ethylamino) -6-methyl-7-anilinofluorane, 3- (N
-Ethyl-p-toluidino) -6-methyl-7- (p-
Toluidino) fluorane, 3-diethylamino-6-methyl-7-phenylaminofluorane, 3-di (n-butyl) amino-6-methyl-7-phenylaminofluorane, 3- (N-ethyl-N-isoamyl Amino) -6
-Methyl-7-phenylaminofluorane, 3- (N-
Cyclohexyl-N-methylamino) -6-methyl-7
-Phenylaminofluorane, 3-piperidino-6-methyl-7-phenylaminofluorane, 3-dibutylamino-7- (o-chlorophenylamino) fluorane,
3-pyrrolidino-6-methyl-7-p-butylphenylaminofluorane, 3- (N-methyl-N-tetrahydrofurfurylamino) -6-methyl-7-anilinofluorane, 3- (N-ethyl Fluorane dyes such as -N-tetrahydrofurfurylamino) -6-methyl-7-anilinofluorane. Such dyes may be used alone or in combination of two or more.

Various compounds are known as the acidic substance used in combination with the leuco dye, and the following are exemplified. 4-hydroxydiphenoxide, α-naphthol,
β-naphthol, 4-hydroxyacetophenone, 4-
tert-butylphenol, hydroquinone, 4-tert-
Octylcatechol, 4,4'-isopropylidene diphenol (bisphenol A), 4,4'-cyclohexylidene diphenol, 2,2'-dihydroxydiphenol, 2,2'-methylenebis (4-methyl-6-te)
rt-butylphenol), 4,4'-isopropylidenebis (2-tert-butylphenol), 4,4'-sec
-Butylidene diphenol, 4-phenylphenol,
2,2'-methylenebis (4-chlorophenol),
4,4'-dihydroxydiphenyl sulfone, 2,4 '
-Dihydroxydiphenylsulfone, 4-hydroxy-
4'-methyldiphenylsulfone, 4-hydroxy-
4'-chlorodiphenyl sulfone, 4-hydroxy-
4'-methoxydiphenylsulfone, 4-hydroxy-
4'-isopropoxydiphenyl sulfone, benzyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, hydroquinone monobenzyl ether, novolac type phenolic resin, phenolic compounds such as phenolic polymers, benzoic acid, p-tert-butylbenzoic acid Acid, trichlorobenzoic 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-benzylsalicylic acid, 3- (α-methylbenzyl) salicylic acid, 3-chloro-5- (α- Aromatic carboxylic acids such as methylbenzyl) salicylic acid, 3,5-di-tert-butylsalicylic acid, 3-phenyl-5- (α, α-dimethylbenzyl) salicylic acid, 3,5-di-α-methylbenzylsalicylic acid, And these phenolic compounds, aromatic carboxylic acids and for example zinc, magnesium, aluminum, calcium, titanium, manganese,
Organic acid substances such as polyvalent metal salts such as tin and nickel.

In the present invention, the use ratio of the leuco dye and the color-developing agent in the recording layer should be appropriately selected depending on the types of the leuco dye and the color-developing agent to be used, and it is not particularly limited. When a leuco dye and an acidic substance are used, it is generally 1 for 1 part by weight of the black color leuco dye.
~ 7 parts by weight, preferably about 1 to 4 parts by weight of acidic substance is used. The coating liquid containing these substances is generally prepared by using water as a dispersion medium and stirring the mixture with a ball mill, an attritor, a sand mill or the like, and a leuco dye and a color former together or separately with an average particle diameter of 0. It is pulverized to a size of 8 μm or less and prepared as a coating liquid.

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 kind such as vinyl acetate emulsion is added in an amount of 10 to 40% by weight, preferably 15 to 35% by weight, based on the total solid content of the recording layer.

If desired, various auxiliaries 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, paraffin wax, ester wax, and other waxes,
An antifoaming agent, a fluorescent dye, etc. are appropriately added.

Further, a sensitizer may be used in combination depending on the purpose. Specific examples of the sensitizer include dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate, benzyl p-benzyloxybenzoate, 1-
Phenyl hydroxy-2-naphthoate, 2-naphthylbenzyl ether, m-terphenyl, dibenzyl oxalate, oxalate-di-p-methylbenzyl, oxalate-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-p-toluidine, di (β-biphenyl) Examples include ethoxy) benzene, p-di (vinyloxyethoxy) benzene and 1-isopropylphenyl-2-phenylethane. The amount of these sensitizers used is not particularly limited, but it is generally desirable to adjust the amount within the range of 4 parts by weight or less relative to 1 part by weight of the color developing agent.

Further, a preservative improving agent may be used in combination so as to further enhance the preservability of the recorded image depending on the purpose as long as the effect is not impaired. Specific examples of such a storage stability improver include, for example, 2,2'-methylenebis (4-methyl-6).
-Tert-butylphenol), 2,2'-ethylenebis (4-methyl-6-tert-butylphenol) 2,2 '
-Methylenebis (4-ethyl-6-tert-butylphenol), 2,2'-methylenebis (6-tert-butylphenol), 4,4'-thiobis (3-methyl-6-te)
rt-butylphenol), 4,4'-thiobis (2-methyl-6-tert-butylphenol), 4,4'-thiobis (5-methyl-6-tert-butylphenol),
4,4′-butylidene bis (6-tert-butyl-m-cresol), 1- [α-methyl-α- (4′-hydroxyphenyl) ethyl] -4- [α ′, α′-bis (4 ″)
-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, 4,4'-thiobis ( 3-methylphenol),
4,4'-dihydroxy-3,3 ', 5,5'-tetrabromodiphenyl sulfone, 4,4'-dihydroxy-
3,3 ′, 5,5′-tetramethyldiphenyl sulfone, 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, 2,2-bis (4-hydroxy-)
Hindered phenol compounds such as 3,5-dichlorophenyl) propane and 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, N, N'-di-2.
-Naphthyl-p-phenylenediamine, 2,2'-methylenebis (4,6-di-tert-butylphenyl) sodium phosphate, etc. may be mentioned.

In the present invention, a protective layer containing an aqueous resin as a main component may be provided on the heat-sensitive recording layer in order to improve recording suitability and storability. Specific examples of the aqueous resin include, for example, oxidation. Starch, enzyme-modified starch, cation-modified starch, esterified starch, etherified starch and other starches, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, methoxy cellulose, hydroxyethyl cellulose and other cellulose derivatives, completely (or incompletely) saponified polyvinyl alcohol, carboxy Polyvinyl alcohol such as modified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, and silicon-modified polyvinyl alcohol, polyacrylamide, polyvinylpyrrolidone, acrylic acid amide / acrylic acid ester copolymer, acrylic acid amide / acrylic Ester-methacrylic acid copolymer, styrene-maleic anhydride copolymer alkali salts, isobutylene-maleic anhydride copolymer alkali salts, sodium alginate, gelatin, water-soluble polymer such as casein,
Polyvinyl acetate, polyurethane, polyacrylic acid ester, polybutyl methacrylate, styrene / butadiene copolymer, vinyl chloride / vinyl acetate copolymer, ethylene / vinyl acetate copolymer, styrene / butadiene / acrylic copolymer, etc. Examples include latex. Among these, polyvinyl alcohols such as completely (or incompletely) 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. .

Further, in the protective layer, silicone oil modified with an epoxy group, a carboxyl group, an amino group, a methacryl group, a polyether group or the like is used in the form of an emulsion in an amount of 5 to 30% by weight based on the solid amount of the protective layer. Preferably 10-20
Addition by weight% improves transparency and running property during recording. If it exceeds 30% by weight, the surface strength of the protective layer is lowered and the lees adhere to the thermal head during recording to cause recording failure.

The coating liquid for the protective layer is prepared by using water as a dispersion medium and mixing and stirring a water-soluble resin. In the coating liquid, if necessary, a dispersant, a defoaming agent, a fluorescent dye, a curing agent,
It is also possible to use together auxiliary agents such as ultraviolet absorbers, lubricants such as zinc stearate, calcium stearate, carnauba wax, paraffin wax and ester wax, and inorganic pigments such as kaolin, fine particle silica and colloidal silica. In particular, when colloidal silica and silicone oil are used together in the protective layer, the running property during recording is significantly improved without lowering the transparency.

The method for forming the recording layer and the protective layer is not particularly limited, and suitable examples include air knife coating, varibar blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating and die coating. It is formed by a method such as coating and drying the coating liquid for the recording layer on the support by various coating methods. A transparent plastic film is appropriately selected and used as the support. The coating amount of the coating liquid for the heat-sensitive recording layer is 1 to 10 g / m ^{2 on} a dry weight basis, preferably 2 to 6 g.
It is adjusted in the range of / m ² . The coating amount of the protective layer coating liquid is 0.5 to 7 g / m ^{2 on} a dry weight basis, preferably 1 to 3 g.
It is adjusted in the range of g / m ² .

[0019]

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 10 parts of 3-di (n-butyl) amino-6-methyl-7-phenylaminofluorane, 20 parts of 1,2-di (3-methylphenoxy) ethane, methylcellulose A composition consisting of 30 parts of a 5% aqueous solution of 60 parts of water and 60 parts of water was pulverized with a sand mill until the average particle size became 0.3 μm.

Liquid B Preparation 20 parts of 4-hydroxy-4′-isopropoxydiphenyl sulfone, 20 parts of 5% aqueous solution of methylcellulose,
A composition comprising 40 parts of water and water was pulverized with a sand mill until the average particle size became 0.3 μm.

Preparation of coating liquid for recording layer: 120 parts of solution A, 80 parts of solution B, 70 parts of colloidal silica having a solid concentration of 30% (average particle diameter 20 nm), solid concentration of 50
% Styrene-butadiene latex, 1 part of a 10% aqueous solution of sodium dioctylsulfosuccinate, and 71 parts of water were mixed and stirred to obtain a coating liquid for recording layer.

Preparation of Coating Liquid for Protective Layer 100 parts of 10% aqueous solution of polyvinyl alcohol modified with acetoacetyl group, 10 parts of sodium dioctylsulfosuccinate
% Aqueous solution and 40 parts of colloidal silica having a solid concentration of 30% (average particle diameter 10 nm) were mixed and stirred to obtain a coating liquid for protective layer.

Formation of Recording Layer and Protective Layer The above recording layer coating solution and protective layer coating solution were dried on a yellow PET film [thickness 100 μm] having a maximum absorption peak at 420 nm and a haze value of 1.7. coating amount after successively coating and drying so that each becomes ^{3g / m 2, 2g / m} 2, subjected to a super calender treatment to obtain a heat-sensitive recording material.

[Example 2] Thermosensitive recording was carried out in the same manner as in Example 1 except that the liquid A and the liquid B of Example 1 were prepared until the average particle size of the dispersion liquid was 0.5 μm. Got the body

Example 3 In the formation of the recording layer and protective layer of Example 1, a yellow PET film having a maximum absorption peak at 420 nm and a haze value of 1.7 [thickness 10
0 μm], a yellow PET film having a maximum absorption peak at 460 nm and a haze value of 1.0 [thickness 18
8 μm] was used, and a thermosensitive recording medium was obtained in the same manner as in Example 1.

Example 4 In the preparation of the coating liquid for the recording layer, 20 parts of 3-di (n-butyl) amino-6-methyl-7-phenylaminofluorane and 4-hydroxy-4 'were used.
-A coating solution obtained by mixing and stirring a composition consisting of 30 parts of isopropoxydiphenyl sulfone, 50 parts of a methyl methacrylate resin having a solid concentration of 40%, and 50 parts of a tetrahydrofuran / toluene = 5/5 solution has a maximum absorption at 420 nm. A PET film having a haze value of 1.7 [thickness 100 μm] was coated and dried so that the coating amount after drying was 3 g / m ² to obtain a thermosensitive recording medium.

Comparative Example 1 In the formation of the recording layer and protective layer of Example 1, a yellow PET film having a maximum absorption peak at 420 nm and a haze value of 1.7 [thickness 10
0 μm], a red PET film having a maximum absorption peak at 550 nm and a haze value of 1.5 [thickness 10
0 μm] was used to obtain a thermosensitive recording medium in the same manner as in Example 1.

Comparative Example 2 In the formation of the recording layer and protective layer of Example 2, a yellow PET film having a maximum absorption peak at 420 nm and a haze value of 1.7 [thickness 10
0 μm] instead of PET with uncolored haze value of 1.5
Example 2 except that a film [thickness 100 μm] was used
A thermosensitive recording medium was obtained in the same manner as described above.

Comparative Example 3 In the preparation of the recording layer and protective layer of Example 1, a yellow PET film having a maximum absorption peak at 420 nm and a haze value of 1.7 [thickness 10
0 μm], an orange PET film having a maximum absorption peak at 480 nm and a haze value of 12 [thickness 100
[μm] was used to obtain a thermosensitive recording medium in the same manner as in Example 1.

The heat-sensitive recording material thus obtained was subjected to the following evaluation tests, and the results are shown in Table 1. (1). OHP suitability A thermal printer [trade name: Mitsubishi SCTP-65, manufactured by Mitsubishi Electric Corporation] was used for recording, and the obtained recorded image was projected on an OHP projector to visually judge the sharpness of the recorded image. ◯: The print is clearly readable and the contrast with the unprinted part is clear. Δ: The print can be read, but the contrast with the unprinted part is slightly unclear. × The print is difficult to read and the contrast with the unprinted part is not clear.

(2). Transparency of thermosensitive recording medium Transparency of unrecorded area is measured by a haze meter [trade name: TC-H
IV, manufactured by Tokyo Denshoku Co., Ltd.).

[0033]

[Table 1]

[0034]

As is clear from the results of [Table 1], according to the present invention, an OHP sheet having a clearly visible printed portion was obtained.

Claims (2)

[Claims] 1. A heat-sensitive recording material comprising a support and a heat-sensitive recording layer containing a leuco dye and a colorant, the support comprising:
Has a maximum absorption peak at a light wavelength of 400 to 500 nm,
A heat-sensitive recording material having a haze value (based on JIS K 7105) of 5 or less, and a haze value of 20 or less. 2. The heat-sensitive recording material according to claim 1, wherein the leuco dye is a black-colored leuco dye.