JPH01186373A - Multicolor thermal recording material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to a multicolor heat-sensitive recording material having a plurality of coloring layers each developing a different color tone. .

"Prior Art" Conventionally, heat-sensitive recording utilizes a coloring reaction between a coloring agent and a coloring agent that develops color when it comes into contact with the coloring agent, and brings a recoloring substance into contact with heat to obtain a colored image. The body is well known. Such heat-sensitive recording media are relatively inexpensive, and the recording equipment is compact and relatively easy to maintain.
It is used not only as a recording medium for facsimiles and various computers, but also in a wide range of fields.

However, with the expansion of applications, the performance and quality required has also diversified, such as higher sensitivity, image quality, and security.

Chemotaxis, polychromatic recording, etc. are mentioned. In particular, since multicolor recording has a wide range of applications, a large number of recording materials have been researched and proposed to date.

Conventional two-color recording materials can be broadly classified into the following two types. The first is to color the low-temperature thermosensitive coloring layer during low-temperature heating,
This is a method in which both the low-temperature heat-sensitive color forming layer and the high-temperature heat-sensitive color forming layer develop color during high-temperature heating to obtain a mixed color. Another method is to obtain the color tone of only the high-temperature thermosensitive coloring layer during high-temperature heating by using a decoloring agent that has a decolorizing effect on the low-temperature coloring system during high-temperature heating in the first method above. .

However, in the first method, the image becomes unclear due to color mixing and blurring occurs, so the second method is generally suitable as a method for obtaining a two-color image. In the second method, various color erasing agents have been proposed that have a color erasing effect on a color forming system consisting of a basic leuco dye and an organic acidic substance. However, if these decolorizing agents are simply used adjacent to the low-temperature coloring layer, the decoloring agent will affect the low-temperature coloring layer during the manufacturing process or storage, and sufficient color density will not be obtained when heated at low temperatures. It comes with a drawback. Increase the amount of coloring agent (
By doing so, it is possible to improve the color density when heated at a low temperature, but there is a risk that the decoloring effect will be insufficient when heated at a high temperature, making it impossible to prevent color mixing and bleeding. It is very difficult to strike a balance between color erasing and color development, and even if the balance is achieved, loss of color former and color erasing agent is unavoidable.
Satisfactory results have not always been obtained.

Therefore, methods have been proposed in which an intermediate layer is provided between the decoloring layer and the coloring layer, such as a method using a thermofusible substance [Japanese Patent Application Laid-open No. 116691/1983] and a method using a polymeric binder. JP-A-62-33671.

Japanese Unexamined Patent Publication No. 62-33672] and the like have been proposed.

However, during the manufacturing process, during storage, and during low-temperature heating, the intermediate layer requires a barrier effect between the decolorizing layer and the coloring layer, and the instantaneous mixing of the decolorizing component and the coloring component, which is required during high-temperature heating, Since this effect is contradictory to the effect of promoting the decoloring reaction, it is necessary to appropriately adjust the selection of materials, the method of forming the layer, etc. in order to achieve both of these effects.

"Problems to be Solved by the Invention" The present invention improves the above-mentioned problems associated with the use of color erasing agents, and provides a multilayer film that has good recording sensitivity and is capable of forming clear-toned images with less color mixture and bleeding. A color thermosensitive recording medium is provided.

"Means for Solving the Problems" The above-mentioned object of the present invention is to have two or more heat-sensitive coloring layers each producing a different color tone, and 3. At least one of the heat-sensitive coloring layers has leuco In a multicolor thermosensitive recording material that has a leuco coloring layer containing a dye and a coloring agent and a color erasing layer adjacent to the leuco coloring layer, the leuco coloring layer and the adjacent color erasing layer This is achieved by providing at least one intermediate layer containing a pigment as a main component.

"Function" As described above, the heat-sensitive recording material of the present invention has an important feature in that an intermediate layer containing a pigment as a main component is provided between the leuco coloring layer and the decoloring layer. Examples of useful pigments include diatomaceous earth, calcined diatomaceous earth,
Inorganic pigments such as kaolin, calcined kaolin, white carbon, magnesium carbonate, calcium carbonate, zinc oxide, aluminum oxide, titanium oxide, silicon oxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc, clay, calcined clay, styrene micro Examples include organic pigments such as ball, nylon powder, polyethylene powder, urea/formalin resin filler, and raw starch granules. Of course, the substances are not limited to these exemplified substances, and two or more types can be used in combination if necessary.

Although it is not necessarily clear why the intermediate layer containing pigment as the main component exhibits the desired effect of the present invention, the moderate gaps in the intermediate layer obtained by using pigment as the main component are It does not have a negative effect on the barrier effect against leuco coloring components and color erasing components, and allows both components to easily pass through in a molten state when heated at high temperatures, and the pigment itself has a positive absorption and adsorption effect on both components. It is presumed that this is to promote the decoloring reaction of the leuco coloring component.

The above characteristics exhibited by pigments are influenced by the oil adsorption ability of the pigment itself, and in the present invention, in particular, the oil absorption amount measured based on the JIS-5101 method is 30 to 300 cc/100 g.
Pigments that are preferably used are as follows. Also, the average particle diameter is 1
The thickness is preferably 0 μm or less, and particularly preferably about 0.2 to 6 μm. Further, in consideration of hendomasotizing properties and image characteristics during recording, calcium carbonate, silicon oxide, and talc are particularly preferably used among various pigments.

The proportion of the pigment contained in the intermediate layer is desirably adjusted within a range of approximately 50 to 95% by weight of the total solid content of the intermediate layer, and particularly preferably within a range of 60 to 90% by weight. In addition, in order to achieve a good balance between the barrier effect and the effect of promoting the decoloring reaction, the coating amount of the intermediate layer should be 1 to 5 g on a dry weight basis.
It is desirable to adjust within a range of about / m.

In such an intermediate layer, there are usually binders such as starches, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, gum arahya, 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 emulsion, etc. are used in an amount of 5 to 35% by weight, preferably 8 to 20% by weight of the total solid content. Furthermore, various auxiliary agents can be added to the intermediate layer coating solution, such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, alginate, fatty acid metal salt, etc. Examples include dispersants, other antifoaming agents, and the like.

In addition, if necessary, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax, and fatty acids such as stearic acid amide, stearic acid methylene bisamide, oleic acid amide, palmitic acid amide, and coconut fatty acid amide are added. Amides, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 4,4'-
Hindered phenols such as butylidene bis(6-tert-butyl-3-methylphenol), 1.1.3-tris(2-methyl-4-hydroxy-5-tert-butylphenol)butane, dibenzyl terephthalate, 1, 2-di(3-methylphenoxy)ethane, 1,2
~diphenoxyethane, 4.4'=ethylenedioxy-
Bis-benzoic acid diphenylmethyl ester and various known thermofusible substances can also be used together.

By adding an appropriate amount of lubricants and thermofusible substances, it is possible to sharpen recorded images when heated at low temperatures and to adjust the decoloring sensitivity when heated at high temperatures; however, if too large amounts are added, intermediate Since the barrier effect of the layer may be impaired, it is desirable to limit the content to 30% by weight or less of the total solid content of the intermediate layer.

In the present invention, the color erasing agent contained in the color erasing layer is not particularly limited, and includes aliphatic amines, piperidines, piperazines, pyridines, imidazoles, imidacillines, morpholines, guanidines, and amidine. , polyethers, glycols, etc. are preferably used.

Specifically, for example, the following compounds are described in various known documents. Alkylene oxide adducts of bisphenols [JP-A-54-139741] Ethylene oxide adducts of acids [JP-A-55-25306] Long-chain 1,2-glycols [JP-A-55-1989] 2721
Publication No. 7] Glycerin fatty acid ester [JP-A-55-1
Publication No. 13593] Urea derivative [JP-A-55-1392
No. 90] Alkylene oxide adduct of linear glycol [
JP-A-55-152094] Morpholine derivative [
JP-A-56-40588] Solid alcohol [JP-A-50-17865] - Tel and polyethylene glycol derivatives [JP-A-50-17867, JP-A-50-17868] Nitrogen-containing crystalline organic Compounds [Japanese Patent Publication No. 51-19991], guanidine derivatives [Japanese Patent Publication No. 51-29024], amines or quaternary ammonium salts [Japanese Patent Publication No. 50-18048], and the like.

Further, specific examples of amidines include N.

N'-diphenylformamidine, N, N'-di0-
) Lylformamidine, N,N'-diphenylbenzamidine, N,N'-di-p-tolyl-N'-phenylbenzamidine, N,N,'NτN'''-tetraphenyl-hebutacyamidine, N.

N ; N ;'N"'-tetraphenyl-P-xylylenecyamidine, etc., and specific examples of piperidines include (2,2,6,6-tetramethyl-4-piperidyl/tridecyl)-L2 -ethanedicarboxylate, (1,2,2,6,6-bentamethyl-4-piperidyl)-L 2.3゜4-butanetetracarboxylate, (1-methyl-4-piperidyl)-1,2,
3,4-butanetetracarboxylate, (2,2,6
,6-tetramethyl-4-piperidyl/β,β,β;β
'-Tetramethyl-3.9- (2,4,8,10-tetraoxaspiro(5,5)undecanecdiethyl)-
1,2,3,4-butanetetracarboxylate, (
1,2,2,6,6-bentamethyl-4-piperidyl/
β, β, β: β'-tetramethyl-3,9-[2,4,
8,10-tetraoxaspiro(5,5)undecanecdiethyl)-1,2゜3.4-butanetetracarboxylate, to (1゜2.2.6.6-bentamethyl-4-piperidyl)-1- Butane carboxylate, (2,2
, 6°6-tetramethyl-4-piperidyl)-1,2°3,4-butanetetracarboxylate.

Among these various color erasing agents, piperidines have excellent permeability to the pigment intermediate layer and adsorption to pigments in the molten state by high-temperature heating, and exhibit a good color erasing reaction. It is particularly preferably used in the invention.

The above-mentioned various color erasing agents are generally used in a color erasing layer at a rate of 0.00% relative to the total weight of the heat-sensitive color forming basic dye and coloring agent to be erased in the color erasing layer.
It is contained in an amount of about 1 to 20 times by weight, more preferably in a range of about 0.5 to 6 times by weight. Note that it is of course possible to use two or more types of decolorizing agents in combination.

In the present invention, there are no particular limitations on the combination of the coloring agent and the coloring agent contained in the coloring layer, and any combination that causes a coloring reaction when the two come into contact with each other due to heat can be used. Examples include combinations of colorless or light-colored basic dyes and inorganic or organic acidic substances, and combinations of higher fatty acid metal salts such as ferric stearate and phenols such as gallic acid. Furthermore, various thermosensitive coloring layers capable of obtaining a colored image (recorded image) by heat, such as a thermosensitive coloring layer containing a combination of a diazonium compound, a coupler, and a basic substance, may be included as part of the structure.

However, since a decoloring agent exerts a decoloring effect on a coloring system consisting of a basic dye and an acidic substance, at least the coloring layer to be decolored must be composed of a coloring system consisting of a basic dye and an acidic substance. There is.

Various colorless to light-colored basic dyes are known, such as 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-dimethylaminophenyl, 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- Triallylmethane dyes such as dimethylaminophthalide, 3-p-dimethylaminophenyl-3-(1-methylpyrrol-3-yl)-6-dimethylaminophthalide, 4,4'-bis-dimethyl Diphenylmethane dyes such as aminobenzhydryl benzyl ether, N-halophenyl leuco auramine, N-2,4,5-1-rif' lorophenyl leuco auramine, hendiyl leucomethylene plu-, p-nitrobenzoyl leuco Thiazine dyes such as methylene blue, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-
Spiro dyes such as benzyl-spiro-dinaphthopyran, 3-methyl-naphtho-(6'-methoxybenzo)spiropyran, 3-propyl-spiro-dibenzopyran, rhodamine-B anilinolactam, rhodamine (p-nitroanilino)lactam, Lactam dyes such as rhodamine (0-chloroanilino)lactam, 3-dimethylamino-
7-methoxyfluoran, 3-diethylamino-6-methoxyfluoran, 3-diethylamino-7-methoxyfluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-diethylamino-7゜8-benzofluorane, 3-diethylamino-5-methyl-7-dibenzylaminofluorane, 3-diethylamino-6,7-dimethylfluorane, 3-(N-ethyl-p- Truigino)
-7-methylfluorane, 3-diethylamino-7-N
-acetyl-N-methylaminofluorane, 3-diethylamino-7-N-methylaminofluorane, 3-diethylamino-7-dihendylaminofluorane, 3-diethylamino-7-N-methyl-N-benzylamino Fluoran, 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-)luidino)-6-methyl~7-(p
-Toluidino)fluoran, 3-diethylamino-6-
Methyl-7-phenylaminofluorane, 3-diethylamino-7-(2-carbomethoxy-phenylamino)
Fluorane, 3. -(N-ethyl-N-isoamylamino)-6-methyl-7-phenylaminofluorane, 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-f-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-N
Examples include fluoran dyes such as -ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane.

Various types of inorganic or organic acidic substances that develop color upon contact with basic dyes are known, such as activated clay, acid clay, acpulgite, bentonite, colloidal silica, aluminum silicate, and other inorganic acidic substances; -tert
-butylphenol, 4-hydroxydiphenoxide,
α-naphthol, β-naphthol, 4-hydroxyacetophenol, 4 tert-octylcatechol,
2.2'-dihydroxydiphenol, 2.2'-methylenebis(4-methyl-5-ter't-isobutylphenol), 4.4'-isopropylidenebis(2-t
ert-butylphenol), 4.4'-5ec-butylidenediphenol, 4-phenylphenol, 4.4
'-isopropylidene diphenol (bisphenol A
), 2,2'-methylenebis(4-chlorophenol)
, hydroquinone, 4.4'-cyclohexylidene diphenol, benzyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, hydroquinone monobenzyl ether, 4-hydroxyphenyl-4'-isopropyloxyphenyl sulfone, novolac type phenol resin , phenolic compounds such as phenol polymers, benzoic acid, p-'tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, 3-sec-butyl-4-hydroxybenzoic acid, 3-cyclohexyl-4-hydroxy Benzoic 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-methylbenzyl)salicylic acid, 3,5-diter
t-Butylsalicylic acid, 3-phenyl-5-(α, α
Aromatic carboxylic acids such as -dimethylbenzyl)salicylic acid, 3,5-di-α-methylbenzylturicylic acid, and these phenolic compounds, aromatic carboxylic acids such as zinc, magnesium, aluminum, calcium, titanium, manganese, Examples include organic acidic substances such as salts with polyvalent metals such as tin and nickel.

In the heat-sensitive recording material of the present invention, the ratio of the color former and color former in the color forming layer is appropriately selected depending on the type of color former and color former used, and is not particularly limited. For example, when using a basic colorless dye and an acidic substance,
Generally, from 1 to 50 parts by weight, preferably from 1 to 10 parts by weight, of the acidic substance are used per part by weight of the basic colorless dye.

The coating amount of the coloring layer is not particularly limited, but is generally about 2 to 12 g/m in terms of dry weight, preferably 3 g/m.
It is adjusted in the range of ~8 g/m.

The coating liquid forming the decoloring layer and the coloring layer contains various binders, dispersants, lubricants, thermofusible substances, inorganic pigments, organic pigments, etc., as described in the explanation of the intermediate layer coating liquid. Other various auxiliary agents such as antifoaming agents, ultraviolet absorbers, fluorescent dyes, and coloring dyes can be appropriately blended. Coating liquids containing these substances generally use water as a dispersion medium and are appropriately processed by ball milling,
It is prepared using a stirring or grinding machine such as an attritor or sand mill.

In the thermosensitive recording material of the present invention, there are no particular limitations on the method of forming the coloring layer, color erasing layer, intermediate layer, etc.
It can be formed according to conventionally well-known and commonly used techniques,
For example, it is formed by applying a coating liquid onto a support by air knife coating, blade coating, etc. and drying it.

The support is not particularly limited, and may include wood-free paper, base paper made with a Yankee machine, single-sided glossy base paper, double-sided glossy base paper, cast coated paper, art paper, coated paper, medium-quality coated paper, etc. paper, synthetic fiber paper, synthetic resin film, etc. are used as appropriate.

In addition, after coating and drying the coloring layer, smoothing treatment such as super calendering can be performed as necessary. Furthermore, it is possible to provide an overcoat layer on the coloring layer for the purpose of protecting the coloring layer, etc., and various known techniques in the field of thermal recording materials can be added, such as providing an undercoat layer or a backing layer on the support. It's something you get.

Accordingly, in the heat-sensitive recording material of the present invention, among the two or more heat-sensitive color-forming layers each forming a different color tone formed as described above, a color-forming layer containing a color-forming system of a leuco dye and a coloring agent is particularly preferred. For example, in the case of a two-color thermosensitive recording material, a high-temperature coloring layer is first formed on the support. After applying an intermediate layer if necessary, a decoloring layer, an intermediate layer, and a leuco-based low-temperature coloring layer are formed by coating in this order.

Of course, it goes without saying that various variations are possible within the scope of the invention.

In addition, various variations are possible for the color-forming materials and color tones constituting each color-forming layer of the multicolor thermosensitive recording material, and can be appropriately selected depending on the intended multicolor thermosensitive recording material. It is something.

The heat-sensitive recording material of the present invention thus obtained is an extremely excellent multicolor heat-sensitive recording material that can obtain recorded images with clear color tones without color mixing or bleeding.

"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 "%" in the examples indicate "parts by weight" and "% by weight," respectively.

[Confirmation test of heat-sensitive coloring property and color erasing sensitivity] Monochrome coloring thermosensitive recording paper having a color erasing layer, an intermediate layer, and a low-temperature heat-sensitive coloring layer was prepared, and their thermosensitive coloring property and color erasing sensitivity were confirmed.

Example I Preparation of liquid A 3-(N-cyclohexyl-N-methylamino)-6-
Methyl-7-phenylaminofluorane 10 parts Dihenzyl terephthalate 20 parts Methylcellulose 5% aqueous solution 15 parts Water
80 parts of this composition was ground in a sand mill until the average particle size was 3 μm.

Preparation of Solution B 4. 30 parts of 4'-isopropylidenediphenol 5% aqueous solution of methylcellulose 30 parts of water
70 parts of this composition was ground in a sand mill until the average particle size was 3 μm.

C-wave preparation (2,2,6,6-tetramethyl-4-piperidyl)-
L 2.3.4-butanetetracarboxylate
50 parts methylcellulose 5% aqueous solution 25 parts water
110 parts of this composition was ground in a sand mill until the average particle size was 3 μm.

(Preparation of coating liquid for low temperature heat-sensitive recording layer) 125 parts of liquid A, 130 parts of liquid B, silicon oxide pigment (trade name:
Mizukashiru P~527. (manufactured by Mizusawa Chemical Co., Ltd.) 30 copies, 20%
150 parts of an oxidized starch aqueous solution and 55 parts of water were mixed and stirred to prepare a coating liquid.

[Preparation of coating liquid for intermediate layer]

Silicon oxide pigment (trade name: Mizukasil P-527° oil absorption 170 cc/100g, manufactured by Suiko Kagaku Co., Ltd.) 35 parts, 30
% paraffin wax liquid (product name: Hydrin P-7.
(manufactured by Chukyo Yushi Co., Ltd.), 75 parts of a 10% polyvinyl alcohol aqueous solution, and 115 parts of water were mixed and stirred to prepare a coating liquid.

[Preparation of coating liquid for decolorizing layer]

100 parts of liquid C, 10% polyvinyl alcohol aqueous solution 12
5 parts were mixed and stirred to prepare a coating liquid.

[Formation of recording layer]

A coating liquid for decolorizing layer, a coating liquid for intermediate layer, and a coating liquid for low-temperature heat-sensitive recording layer were applied to a high-quality paper with a basis weight of 50 g/m in this order, and the coating amounts after drying were 5 g/mj and 3 g, respectively. /rd, 4 g Z
It was coated and dried so as to give r&, and subjected to a super calender to obtain a monochromatic thermosensitive recording paper.

23-Example 2 In the preparation of a coating liquid for an intermediate layer, 30 parts of silicon oxide pigment, 3
A monochromatic thermosensitive recording paper was obtained in the same manner as in Example 1, except that 33 parts of 0% paraffin wax liquid, 100 parts of 10% polyvinyl alcohol aqueous solution, and 87 parts of water were mixed and stirred to prepare a coating liquid.

Example 3 In preparing a coating solution for an intermediate layer, 25 parts of silicon oxide pigment, 3
A monochromatic thermosensitive recording paper was obtained in the same manner as in Example 1, except that 33 parts of 0% paraffin wax solution, 150 parts of 10% polyvinyl alcohol aqueous solution, and 42 parts of water were mixed and stirred to prepare a coating solution.

Example 4 In preparing a coating solution for an intermediate layer, 20 parts of silicon oxide pigment, 3
A monochromatic thermosensitive recording paper was obtained in the same manner as in Example 1 except that 50 parts of 0% paraffin wax solution, 150 parts of 10% polyvinyl alcohol aqueous solution, and 30 parts of heather were mixed and stirred to prepare a coating solution.

Example 5 In preparing a coating solution for an intermediate layer, a silicon oxide pigment was replaced with a calcium carbonate pigment (trade name: Softon 170).
A monochromatic thermosensitive recording paper was obtained in the same manner as in Example 1, except that a paper sheet with an oil absorption of 30 cc/100 g, manufactured by Bihoku Funka Co., Ltd.) was used.

Example 6 In preparing the coating liquid for the intermediate layer, Tarta pigment (trade name: 2NK Talc, oil absorption: 30cc/1) was used instead of the silicon oxide pigment.
00g, manufactured by Chuo Kaolin Co., Ltd.), and stearic acid amide (trade name: Hydrin Z-7, manufactured by Chukyo Yushi Co., Ltd.) was used instead of paraffin wax. Obtained.

Example 7 In preparing a coating solution for an intermediate layer, 45 parts of Tarta pigment and 30 parts of Tarta pigment were added.
A monochromatic thermosensitive recording paper was obtained in the same manner as in Example 5, except that 8 parts of % paraffin wax solution, 25 parts of 10% polyvinyl alcohol aqueous solution, and 172 parts of water were mixed and stirred to prepare a coating solution.

Example 8 In C-wave preparation, (2,2,6,6-tetramethyl-
4-Piperidyl)-L Instead of 2,3.4-butanetetracarboxylate, (1゜2.2.6.6-bentamethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate was used. In addition, in the preparation of the coating liquid for the intermediate layer, oil-absorbing calcium carbonate (trade name: Callite SA, oil absorption 100 cc) was used instead of the silicon oxide pigment.
A monochromatic thermosensitive recording paper was obtained in the same manner as in Example 1, except that 100 g of the material was used (manufactured by Shiroishi Calcium Co., Ltd.).

Comparative Example 1 A monochromatic color was produced in the same manner as in Example 1, except that no silicon oxide pigment was blended, and 135 parts of a 30% paraffin wax solution and 100 parts of a 10% polyvinyl alcohol aqueous solution were used to prepare a coating solution for the intermediate layer. A thermosensitive recording paper was obtained.

Comparative Example 2 A monochromatic thermosensitive recording paper was obtained in the same manner as in Example 1, except that in preparing the coating liquid for the intermediate layer, the silicon oxide pigment and the paraffin wax liquid were not mixed, and only a 15% aqueous polyvinyl alcohol solution was used. .

The dynamic coloring characteristics and decoloring sensitivity of the 10 types of single-color thermosensitive recording papers thus obtained were tested using the following method, and the results are listed in Table 1.

[Recording conditions]

6 Donoto/Tsuru's Thermal Nod (Made by Matsushita Electronic Components Co., Ltd. 2)
Using a heating element resistance of 300 ohms/dot, main scanning recording speed: 130 m5ec/1ine, sub-scanning near, 7 lines/*, head height 0.
90W/dot.

Coloring energy: 1.3mJ, color erasing energy: 3゜0
Recording was performed under the conditions of mJ, and the black density of the recorded portion was measured using a Macbeth densitometer (manufactured by Macbeth, Model RD-100R).

Table 1 [Manufacture of multicolor thermosensitive recording paper] DNti, preparation 3-diethylamino-75,8-benzofluorane

10 parts methylcellulose 5% aqueous solution
5 parts water
25 parts This composition was sand milled to an average particle size of 3.
It was ground to a size of μm.

[Preparation of coating liquid for high temperature heat-sensitive recording layer]

40 parts of liquid D, 130 parts of liquid B, 30 parts of silicon oxide pigment (trade name: Mizukasil P-527), 20% oxidized starch aqueous solution 7
5 parts and 70 parts were mixed and stirred to prepare a coating liquid.

[Preparation of coating liquid for barrier intermediate layer]

100 parts of 10% polyvinyl alcohol aqueous solution, 25 parts of kaolin, 5 parts of 1% geltaraldehyde aqueous solution, 50 parts of water
The two parts were mixed and stirred to prepare a coating liquid.

[Formation of high temperature thermosensitive recording layer] 'Basic weight 50
g/m high-quality paper, the coating liquid for the high-temperature heat-sensitive recording layer and the coating liquid for the barrier intermediate layer were applied in this order to a coating amount of 3 after drying.
g/cl, 4 g/rl and dried to obtain a recording paper (A) having a high temperature heat-sensitive recording layer.

[Preparation of multicolor thermosensitive recording paper]

130 - A decoloring layer, an intermediate layer, and a low temperature layer were placed on the recording paper (A) in the same manner as in Examples 1 to 4 and Comparative Examples 1 to 2, except that the above recording paper (A) was used instead of the high-quality paper. A two-color thermosensitive recording paper was obtained by sequentially forming a thermosensitive recording layer.

When the dynamic coloring characteristics of the six types of two-color thermosensitive recording paper thus obtained were investigated, black coloring was obtained at 1.3 mJ, and red coloring was obtained at 3.0 mJ. Ta.

The colored images of the thermal recording paper of each Example were extremely clear without any color mixture or bleeding, but in the recording paper of the Comparative Example, color mixture occurred and the image was significantly lacking in sharpness.

Patent applicant: Kanzaki Paper Co., Ltd.

Claims (2)

[Claims] (1) It has two or more thermosensitive coloring layers that each develop a different color tone, and at least one of the thermosensitive coloring layers is a leuco coloring layer containing a leuco dye and a coloring agent,
In the multicolor thermosensitive recording material having a decoloring layer adjacent to the leuco coloring layer, at least one intermediate layer containing a pigment as a main component is provided between the leuco coloring layer and the adjacent decoloring layer. A multicolor thermosensitive recording medium characterized by: (2) Claim (1), wherein the intermediate layer contains 50 to 95% by weight of the pigment component, and the coating amount is in the range of 1 to 5 g/m^2.
The multicolor thermosensitive recording material described above.