JPH0299385A - Thermal recording material - Google Patents

Abstract

PURPOSE:To improve a matching property with a thermal head by a method wherein a thermal recording layer is formed by applying a heat sensitive coating liquid containing a colorless or light-colored basic dye and a coloring agent onto a base material to be dried, and a protective layer containing a specific component is laminated thereon. CONSTITUTION:A thermal recording layer prepared by applying a heat sensitive coating liquid containing a colorless or light-colored basic dye of 0.8mum or under in average particle size and a coloring agent of 0.8mum or under in average particle size onto a transparent base material to be dried is formed. A protective layer containing polyvinyl alcohol or denatured polyvinyl alcohol and amorphous silica or kaolin is laminated on the thermal recording layer. By this structure, a thermal recording material which is efficient in transparency and efficient in a matching property with a thermal head can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording material, and particularly to a heat-sensitive recording material having excellent transparency and head matching properties.

``Prior art'' Conventionally, thermosensitive technology utilizes a color reaction between a color former and a color former that develops color when it comes into contact with the color former, and brings both photochromic substances into contact with each other using heat to obtain a colored image. Recording bodies are well known. Such heat-sensitive recording media are relatively inexpensive, and the recording equipment is compact and relatively easy to maintain.
Not only can it be used as a medium for facsimiles and various computers, but also
[1 Used in a wide range of fields.

With the diversification of applications, there is also an increasing demand for transparent heat-sensitive recording materials that can be directly recorded with a thermal head for use in overhead projectors (OHP). A heat-sensitive recording material has been proposed in which a heat-sensitive recording layer containing a light-colored basic dye and a coloring agent is formed.

``Problems to be Solved by the Invention'' However, sufficient transparency cannot be obtained only by using a transparent film as a support, and as a result, a clear projected image cannot be obtained even when used for OI-IP. In addition, since the support is a film, the smoothness of the recording medium inevitably increases, causing sticking (a phenomenon in which the heat-sensitive recording medium adheres to the surface of the thermal head), and the film used for the support has a higher oil absorption than paper. There were drawbacks such as the tendency for debris to adhere to the thermal head due to the poor quality. The purpose of the present invention is to solve the above problems, to provide excellent transparency and excellent matching with a thermal head (i.e., no problems of sticking or head debris).
An object of the present invention is to provide a thermosensitive recording medium.

"Means for Solving the Problems" The present invention provides colorless or light-colored basic dye with an average particle diameter of 0.8 μm or less and a colorless or light-colored basic dye with an average particle diameter of 0.8 μm or less on a transparent support.
A heat-sensitive recording layer is formed by coating and drying a heat-sensitive coating liquid containing a coloring agent of m or less, and a protective layer containing polyvinyl alcohol or modified polyvinyl alcohol and amorphous silica or kaolin is provided on the heat-sensitive recording layer. This is a heat-sensitive recording material formed by laminating layers.

"Function" As described above, the heat-sensitive recording material of the present invention consists of a colorless or light-colored basic dye having an average particle diameter of 0.8 μm or less and a coloring agent having an average particle diameter of 0.8 μm or less on a transparent support. A protective layer made of polyvinyl alcohol or modified polyvinyl alcohol and amorphous silica or kaolin is then provided.This structure provides excellent transparency and is easy to match with a thermal head. A thermosensitive recording material with excellent properties can be obtained.

Various types of colorless to light-colored basic dyes are known to be used in the present invention, and the following are exemplified.

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-methylindol-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-
Triallylmethane dyes such as (l-methylpyrrol-3-yl)-6-dimethylaminophthalide, 4,4'-bis-dimethylaminobenzhydryl benzyl ether,
N-herophenyl leukoolamine, N-2,4,5
-Diphenylmethane dyes such as trichlorophenyl leuco auramine, benzoyl leucomethylene blue, p-
Thiazine dyes such as nitrobenzoylleucomethylene blue, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-
Spiro dyes such as dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho-(6'-methoxybenzo)spiropyran, 3-propyl-spirodibenzopyran, rhodamine B anilinolactam, rhodamine (p-nitroanilino) Lactam, rhodamine (0
-lactam dyes such as chloroanilino)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
-Simethylfluorane, 3-(N-ethyl-p-toluidino)-7methylfluorane, 3-diethylamino-
7-N-acetyl-N-methylaminofluorane, 3-diethylamino-7-N-methylaminofluorane, 3-
diethylamino-7-dibenzylaminofluorane, 3
-diethylamino-? -N-Methyl-N-benzylaminofluorane, 3-diethylamino-7-N-chloroethyl-N-methylaminofluorane, 3-diethylamino-7-N-diethylaminofluorane, 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-)luidino)fluoran, 3-diethylamino-6
-Methyl-7-phenylaminofluorane, 3-diethylamine-7 (2-carbomethoxy-phenylamino)
Fluoran, 3-(N-ethyl-N-isoamylamino)-6-methyl-7-phenylaminofluoran, 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-dibutylamino-7-(0
-chlorophenylamino)fluorane, 3-pyrrolidino-6-methyl-7-p-butylphenylaminofluorane, 3-N-methyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane, 3- monoethyl-N-tetrahydrofurfurylamino-6-methyl-
Fluoran dyes such as 7-anilinofluorane, etc.

Various types of inorganic or organic coloring agents that develop color upon contact with basic dyes are also known, including the following.

Inorganic acidic substances such as activated clay, acid clay, attapulgite, bentonite, colloidal silica, and calculated aluminum, 4-tert-butylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol,
4-Hydroxyacetophenol, 4-tert-octylcatechol, 2゜2'-dihydroxydiphenol, 2,2'-methylenebis(4-methyl-5-tert)
-butylphenol), 4.4'-isopropylidene bis(2-tert-butylphenol), 4. 4'
-5ec -butylidenediphenol, 4-phenylphenol, 4.4'-isopropylidenediphenol (bisphenol A), 2.2'-methylenebis(4-chlorophenol), hydroquinone, 4゜4'-cyclohexyl Phenolic compounds such as dendiphenol, 2.2-bis(4-hydroxyphenyl)4-methylpentane, benzyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, hydroquinone monobenzyl ether, novolac type phenolic resin, and phenolic polymer Compound,
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 acid,
salicylic acid, 3-isoprobilisalicylic acid, 3-ter
t-butylsalicylic acid, 3-benzylsalicylic acid, 3-
(α-methylbenzyl)salicylic acid, 3-chloro-5-
(α-methylbenzyl)salicylic acid, 3,5-di-te
r t-butylsalicylic acid, 3-phenyl-5-(α,
Aromatic carboxylic acids such as α-dimethylbenzyl)salicylic acid, 3,5-di-α-methylbenzylsalicylic acid, and these phenolic compounds, aromatic carboxylic acids such as zinc, magnesium, alumina, calcium, titanium, manganese, tin, Examples include organic acidic substances such as salts with polyvalent metals such as nickel.

In the present invention, the usage ratio of the coloring agent and coloring agent in the recording layer is appropriately selected depending on the type of coloring agent and coloring agent used, and is not particularly limited, but generally basic colorless 1 to 50 parts by weight, preferably 1 to 10 parts by weight of color former are used per 1 part by weight of dye.

To prepare a heat-sensitive coating solution containing these substances, generally, water is used as a dispersion medium, and the dye and coloring agent are mixed together or separately in a pulverizer such as a sand mill or homogenizer until the average particle size is 0.
．． A coating liquid is prepared by dispersing the resin to a particle size of 8 μm or less and adding a binder and the like. Generally, the smaller the diameter of the grinding media used in the sand mill and the longer the processing time, the smaller the dispersed particles can be obtained. For example, if the glass beads have a diameter of about 2 cranes, only a basic dye or coloring agent of about 1 μm to 3 μm can be obtained;
By using glass beads having a diameter of about 0.6 μm, the average dispersed particle diameter can be reduced to about 0.6 μm. When the average particle size of the basic dye or coloring agent is set to 0.8 μm or less, the transparency of the resulting heat-sensitive recording layer is dramatically improved, but this is because the wavelength of light is approximately the same value. It can be assumed that they are related.

Such heat-sensitive coating liquids usually contain starches, hydroxyethyl cellulose, methyl cellulose,
Carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, diisobutylene
Maleic anhydride copolymer salt, styrene/maleic anhydride 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, vinyl acetate emulbutane, etc. account for 1% of total solids.
It is added in an amount of 0 to 70% by weight, preferably 15 to 50% by weight.

Furthermore, various auxiliary agents can be added to the heat-sensitive coating liquid, such as sodium dioctyl sulfosuccinate, sodium dodecylbenzene sulfonate, sodium lauryl alcohol sulfate, alginate, fatty acid metal, and the like. dispersants, ultraviolet absorbers such as benzophenone type and triazole type, other antifoaming agents, fluorescent dyes, and colored dyes.

In addition, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax, calcium carbonate, zinc oxide, aluminum oxide, silicon dioxide,
Inorganic pigments such as aluminum hydroxide, talc, kaolin, clay, calcined clay, colloidal silica, organic pigments such as styrene microballs, nylon powder, polyethylene powder urea/formalin resin filler, raw starch,
Fatty acid amides such as stearic acid amide, stearic acid methylene bisamide, oleic acid amide, palmitic acid amide, coconut fatty acid amide, dibenzyl terephthalate, 1,2-di(3-methylphenoxy)ethane, 1,2
-diphenoxyethane, 4,4'-ethylenedioxy-
Bis-benzoic acid diphenylmethyl ester, 1,1.3
Tris(2-methyl-4-hydroxy-5-tert-
Butyl-phenyl)butane, 2,2'-methylenebis(
4-methyl-6-tert-butylphenol), 4.
Various known thermofusible substances such as hindered phenols such as 4'-butylidenebis (6-tert-butyl-3-methylphenol) can also be added.

When a thermofusible substance is used, a recording medium with excellent transparency can be obtained by reducing the average particle size to 0.8 μm or less using a sand mill, homogenizer, etc., as with basic dyes and coloring agents.

When an inorganic or organic pigment is contained in the recording layer, it is preferable to use a pigment with a particle size as small as possible, and it is particularly desirable to use a pigment with an average particle size of 0.8 μm or less.

In the present invention, the method of forming the heat-sensitive recording layer is not particularly limited; for example, a heat-sensitive coating liquid is applied onto the support using a coating device equipped with a suitable coater head such as an air knife coater or a blade coater, and then dried. Formed in a way. Further, the amount of coating liquid to be applied is not particularly limited, but is usually 2 to 12 g/I, preferably 3 to 10 g/I in terms of dry weight.
It is in the range of about g/po.

The transparent support used in the present invention has a light wavelength of 500 nm.
A film having a transmittance of 80% or more is preferable, such as a polypropylene film or a polyethylene terephthalate film having a thickness of about 20 μm to 100 μm.

Preferably, the film is subjected to corona discharge treatment to improve coating suitability.

In addition, the resin component used for the protective layer laminated on the heat-sensitive recording layer is polyvinyl alcohol or modified polyvinyl alcohol (
(hereinafter simply referred to as polyvinyl alcohol) is used. Examples of such resins include polyvinyl alcohol, esterification-modified polyvinyl alcohol, etherification-modified polyvinyl alcohol, butyralization-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, acetoacetylation-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, etc. From the viewpoint of stinking, amide-modified polyvinyl alcohol, acetoacetylated-modified polyvinyl alcohol, and silicon-modified polyvinyl alcohol are particularly preferred.

Two or more of these can also be used in combination.

As the pigment used for retaining atN, amorphous silica or kaolin is used in terms of transparency and head matching properties. Amorphous silica having a particle size of 5 to loomμ and a density of about 2.1 to 2.2 g/cO13 is preferably used. Kaolin preferably has a particle size of 50 to 800 mμ.

The blending ratio of polyvinyl alcohol and amorphous silica or kaolin in the protective layer is preferably 0.5 to 4 parts by weight, more preferably 1 to 2 parts by weight, per 1 part by weight of polyvinyl alcohol. The method of forming the protective layer is not particularly limited either, and for example, an air knife coater,
It is formed by applying a coating liquid onto the heat-sensitive recording layer using a coating device equipped with a suitable coater head such as a blade coater and drying it. There are no particular limitations on the amount of application, but it is usually 1 to Log/rd, preferably 2 to Log/rd in terms of dry weight.
It is in the range of about 6g1rd.

The protective layer coating solution may further contain one or more binders. Specific examples of binders that can be used in combination include starches, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, gum arabic, diisobutylene/maleic anhydride copolymer salt, styrene/maleic anhydride copolymer salt, and 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/vinyl acetate emulsion, and the like. The amount used in combination is preferably 0.5 parts by weight or less per 1 part by weight of polyvinyl alcohol.

The protective layer contains the thermal head and gWN during recording.
For the purpose of improving the mating properties of stearic acid, higher fatty acid metal salts such as zinc salts, calcium salts, and aluminum salts of stearic acid, polyethylene wax, carnauba wax, paraffin wax, stearic acid amide, stearic acid methylene bisamide, etc. were added to 1 weight of polyvinyl alcohol. It can be added in an amount of 0.1 to 0.5 parts by weight.

Furthermore, various auxiliary agents can be added to the protective layer coating solution if necessary, such as surfactants such as dioctylsulfone sodium succinate and ammonium dodecylbenzenesulfonate, antifoaming agents, fluorescent dyes, and waterproofing agents. Examples include a curing agent and the like.

"Example" The present invention will be described in more detail with reference to Examples below, but the present invention is of course not limited to these.

Further, unless otherwise specified, parts and percentages in the examples indicate parts by weight and percentages by weight, respectively.

"Examples" Example I [Formation of heat-sensitive layer] ■ Lacquer preparation A 3-(N-cyclohexyl-methylamino)-6-methyl-7-phenylaminofluorane 10 parts Dibenzyl terephthalate 20 parts 10% To polyvinyl alcohol 17) Aqueous solution 5 parts 5% sodium dioctyl sulfosuccinate aqueous solution
5 parts water
60 parts of this composition was milled in a sand mill (manufactured by Igarashi Kikai Co., Ltd.) until the average particle diameter was 0. 6
It was ground to a size of μm. Diameter of glass beads 0. 5
s■, amount of beads 250 g, processing time 3 hours. The dispersed particle size has a normal distribution, and both the dye and the thermofusible substance dibenzyl terephthalate have an average particle size of 0.
It can be estimated that the thickness is 6 μm.

■ Preparation of B solution 4. 30 parts of 4'-cyclohexylidene diphenol 10% polyvinyl alcohol (manufactured by Kuraray ■, PVA2
17) Aqueous solution 5 parts 5% sodium dioctyl sulfosuccinate aqueous solution
5 parts water
60 parts of this composition was ground with a sand mill (manufactured by Igarashi Kikai Co., Ltd.) until the average particle size was 0.6 μm. Glass beads diameter 0.5 mm, beads fl 1250 g, processing time 3 hours.

A heat-sensitive coating liquid was obtained by stirring and mixing 50 parts of liquid A, 50 parts of liquid B, and 10 parts of a 50% styrene-butadiene copolymer emulsion.

The resulting coating liquid was applied onto a transparent polyethylene terephthalate film (transmittance of 92% at a light wavelength of 500 nm) having a thickness of 50 μm so that the coating amount after drying was 5 g/1rd, and dried to form a heat-sensitive recording layer.

[Formation of protective layer]

10% acetoacetylated modified polyvinyl alcohol (manufactured by Nippon Gosei Kagaku Ill, Gosenal Z-200) aqueous solution 100 parts amorphous silica (
Manufactured by Asahi Denka Kogyo ■, Applied AT-30, average particle size 15
m, +7. Density 2.1) 50 parts Zinc stearate (Middle East Oil ■, Hydrin Z-7) 1
The obtained coating liquid was applied onto the heat-sensitive recording layer so that the coating amount after drying was 3 g/rd, and dried to obtain a heat-sensitive recording material.

Example 2 In the formation of the protective layer in Example 1, a solid content of 6 was used instead of amorphous silica (Asahi Denka Kogyo ■, Applied AT-30).
Example 1 except that 25 parts of 0% kaolin (manufactured by EMC, UW-90, average particle size 0.6 μm) aqueous dispersion was used.
A thermosensitive recording material was obtained in the same manner as above.

Example 3 Except for using 2,2-bis(4hydroxyphenyl)4-methylpentane (average particle size 0.6 μm) instead of 4.4'-cyclohexylidene diphenol in the preparation of Solution B in Example 1. A thermosensitive recording material was obtained in the same manner as in Example 1.

Comparative Example 1 Except for using oxidized starch (manufactured by Tamago Cornstarch Co., Ltd., Ace A) instead of acel-acetylated modified polyvinyl alcohol (manufactured by Nippon Gosei Kagaku ■, Gosenal Z-200) in forming the protective layer of Example 1. A thermosensitive recording material was obtained in the same manner as in Example 1.

Comparative example 2 The diameter of the glass beads was 1.5 mm in the preparation of Solution A in Example 1.

By setting the processing time to 30 minutes, the average particle size was reduced to 0.6
Example 1 except that it was ground to 2 μm instead of μm
A thermosensitive recording material was obtained in the same manner as above.

Comparative Example 3 The diameter of the glass beads was 1.5 mm in the B i & preparation of Example 1.
.

By setting the processing time to 30 minutes, the average particle size was reduced to 0.6
A thermosensitive recording material was obtained in the same manner as in Example 1 except that the thickness was 2 μm instead of μm.

Comparative Example 4 A thermosensitive recording material was obtained in the same manner as in Example 2 except that kaolin was not used in the formation of the protective layer in Example 2.

The transparency of the seven types of heat-sensitive recording materials thus obtained was measured using a visible and ultraviolet spectrophotometer (manufactured by JASCO Corporation, UVIDEC-505).
) and measured the transmittance of light at a measurement wavelength of 500 nm. In addition, regarding the matching property between the thermal head and the thermal recording medium, a thermal printer (manufactured by SONY ■, UP-7
The presence or absence of sticking was examined using a TV printer (Model 01). The recorded density was also measured using a Macbeth densitometer. The results of each evaluation are shown in Table 1.

Table 1: "Effects" As is clear from the results in Table 1, the heat-sensitive recording material of the present invention was a heat-sensitive recording material that had excellent transparency and excellent matching properties with the thermal head.

Claims (2)

[Claims] (1) A heat-sensitive coating solution containing a colorless or light-colored basic dye with an average particle size of 0.8 μm or less and a coloring agent with an average particle size of 0.8 μm or less is coated on a transparent support and dried. A heat-sensitive recording material comprising a heat-sensitive recording layer formed thereon, and a protective layer containing polyvinyl alcohol or modified polyvinyl alcohol and amorphous silica or kaolin laminated on the heat-sensitive recording layer. (2) The heat-sensitive recording material according to claim (1), wherein the heat-sensitive coating liquid further contains a heat-fusible substance having an average particle diameter of 0.8 μm or less.