JPH01272487A - Multi-color thermal recording medium - Google Patents

Abstract

PURPOSE:To obtain recording paper enhanced in recording sensitivity and superior in shelf stability under high-temperature and high-humidity conditions, by providing an intermediate layer containing a pigment as a main ingredient and a specific compound between a leuco color-forming layer and a decoloring layer adjacent thereto. CONSTITUTION:An intermediate layer of recording paper contains 1,1-bis(4- hydroxyphenyl)-cyclohexane or a hindered phenol compound. As a pigment mainly composing the intermediate layer, an inorganic pigment, such as clay, an organic pigment, such as raw starch power, and the like are used. As a decoloring agent incorporated in a decoloring layer, piperidines etc. is used. As a basic dye, a triarylmethane dye, such as 3,3-bis(p-dimethylaminophenyl)-6- dimethylaminophthalide, is used. As an acid substance, an acid clay etc. is used. These color forming layers, decoloring layer, and intermediate layer are formed by firstly applying the high-temperature color forming layer on a substrate of wood free paper etc. and successively applying and drying the decoloring layer, the intermediate layer, and the leuco low-temperature color forming layer; in this manner, a high-quality recording medium is made available.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" 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, 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.
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 are also diversifying, such as higher sensitivity, image stabilization, and multicolor recording. 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 a method in which the low temperature range thermochromic layer develops color during low temperature heating, and both the low temperature thermosensitive coloring layer and the high temperature thermosensitive coloring layer develop color during high temperature heating to obtain a mixed color. The other method is to obtain the color tone of only the high-temperature range thermochromic layer during high-temperature heating by using a decoloring agent that has a decoloring effect on the low-temperature color-forming system during high-temperature heating in the first method above. be.

However, in the first method, the image becomes unclear and blurring occurs due to color mixture, 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. Although it is possible to improve the color density during low-temperature heating by increasing the amount of color former, there is a risk that the decoloring effect will be insufficient during high-temperature heating, making it impossible to prevent color mixing and bleeding. It is very difficult to strike a balance between color erasure and color development.
Even if the balance is achieved, loss of the coloring agent and color erasing agent is unavoidable, and satisfactory results are not always 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.

Therefore, as a result of intensive research into improving the above-mentioned problems associated with the use of color erasing agents, the present inventors have developed a method of providing an intermediate layer containing pigment as a main component between the color forming layer and the color erasing layer. The heading was previously proposed as Japanese Patent Application No. 11089/1989.

``Problems to be Solved by the Invention'' By providing a specific intermediate layer containing pigment as a main component as described above, the problems associated with the use of a decolorizing agent can be solved, and the recording sensitivity can be improved while preventing color mixing and blurring. A multicolor thermosensitive recording material was obtained that gave images with clear tones with little color.
According to the results of subsequent detailed studies, it became clear that there was still room for improvement.

In other words, it is clear that the barrier effect of the above-mentioned specific intermediate layer is gradually reduced especially under high-temperature conditions, and the decoloring agent affects the low-temperature color-forming layer, making it impossible to obtain sufficient color density. Therefore, the present invention provides a multicolor thermosensitive recording material that has improved storage stability especially under high temperature conditions.

"Means for Solving the Problems" The above-mentioned object of the present invention is to have two or more heat-sensitive coloring layers each developing a different color tone, and at least one of the heat-sensitive coloring layers is colored with a leuco dye. In a multicolor thermosensitive recording material having a leuco coloring layer containing a coloring agent and a color erasing layer adjacent to the leuco coloring layer, at least one layer between the leuco coloring layer and the adjacent color erasing layer is provided. This is achieved by providing an intermediate layer containing a pigment as a main component and at least one of 1,1-bis(4-hydroxyphenyl)-cyclohexane or a hindered phenol compound.

"Function" The intermediate layer in the heat-sensitive recording material of the present invention has 1.1-bis(
It contains 4-hydroxyphenyl)-cyclohexane or a hindered phenol compound, and among the hindered phenol compounds, phenol or a derivative thereof in which at least one of the 2 or 6 positions is substituted with an alkyl group is preferable. Particularly preferred are compounds substituted with a tert-butyl group. Further, compounds having a plurality of phenol groups in the molecule are preferred, and among them, compounds having 2 to 3 phenol groups are most preferred.

Specific examples of these compounds include, for example, 1°1.3-
Tris(2-methyl-4-hydroxy-5-tert-
butylphenyl)butane, 1.1; 3-tris(2
-Methyl-4-hydroxy-5-cyclohexylphenyl)butane, 4,4'-thiobis(3-methyl-5-t
ert-butylphenol), 4,4'-thiobis(2
-methyl-6-tert-butylphenol), 2.2
'-thiobis(4-methyl-5-tert-butylphenol), 2,2'-methylenebis(4-methyl-6-
tert-butylphenol), 2,2'-methylenebis(4-ethyl-5-tert-butylphenol),
4.4'-Butylidenebis(3-methyl-5-tert)
-butylphenol), 4,4'-methylenebis (2゜6-di-tert-butylphenol), among others, 1,1,3-1-lis (2-methyl-4-
Hydroxy-5-tert-butylphenyl)butane is the most preferred compound.

The proportion of 1,1-bis(4-hydroxyphenyl)-cyclohexane or hindered phenol compound contained in the intermediate layer is 1 to 20% by weight of the total solids of the intermediate layer.
It is desirable to adjust the weight percent box size, and a range of 3 to 10 weight percent is particularly preferable.

Specific examples of pigments that are the main components of the intermediate layer include:
For example, diatomaceous earth, calcined diatomaceous earth, kaolin, calcined kaolin,
Inorganic pigments such as white carbon, magnesium carbonate, calcium carbonate, zinc oxide, aluminum oxide, titanium oxide, silicon oxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc, clay, calcined resin, styrene microballs, nylon powder, polyethylene paratha,
Examples include organic pigments such as urea/formalin resin fillers 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.

1. The reason why the intermediate layer containing 1-bis(4-hydroxyphenyl)-cyclohexane or a hindered phenol compound exhibits the desired effect of the present invention is as follows.
Although it is not entirely clear, it is presumed that these compounds act like antioxidants and cause the intermediate layer to exhibit a stable barrier effect even under high temperature conditions.

The proportion of the pigment contained in the intermediate layer is desirably adjusted within a range of about 50 to 95% by weight of the total solid content of the intermediate layer, and particularly preferably adjusted to 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/dry weight.
It is desirable to adjust within a range of about rrf.

Such an intermediate layer usually contains binders such as starches, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, gum arabic, polyvinyl alcohol, diisobutylene/maleic anhydride copolymer salt, styrene/maleic anhydride copolymer. Coalescence 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 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, imidazo 4nones, morpholine necks, and guanidines. , amidines, polyethers, glycols, etc. are preferably used.

Specifically, for example, the following compounds are described in various known documents. Alkylene oxide adduct of bisphenols [JP-A-54-139741] Ethylene oxide adduct of terephthalic acid [JP-A-55-25306] Long-chain 1,2-glycol [JP-A-55-2721]
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] Polyether and polyethylene glycol Derivatives [Japanese Patent Publication No. 50-17867, Japanese Patent Publication No. 50-17868] Nitrogen-containing crystalline organic compounds (Japanese Patent Publication No. 51-19991) Guanidine derivatives [Japanese Patent Publication No. 51-29024] Amine or quaternary ammonium Salt [Unexamined Japanese Patent Publication No. 50-18048]
etc.

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'N'N''-tetraphenyl-hebutacyamidine, N.

Examples of piperidines include (2,2,6,6-tetramethyl-4-piperidyl/
tridecyl)-1,2-ethanedicarboxylate, (
1,2,2,6,6-pankumethyl-4-piperidyl)
-1,2,3゜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)undecane]diethyl)-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)undecane]diethyl)-1
, 2゜3.4-butanetetracarboxylate, (1゜2.2,6.6-bentamethyl-4-piperidyl)-1
-hebutanecarboxylate, (2,2,6°6-tetramethyl-4-piperidyl)-1,2°3,4-butanetetracarboxylate, and the like.

Among these various color erasing agents, piperidines exhibit good color erasing reactions, probably due to their excellent permeability through the pigment intermediate layer and adsorption to pigments in the molten state caused by high-temperature heating. It is particularly preferably used in the invention.

The various color erasing agents as mentioned above are used in -C in the color erasing layer at a rate of 0.00% to the total weight of the thermosensitive coloring basic dye and the coloring agent to be colored 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 coloring agent contained in the coloring layer (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. , a diazonium compound, a coupler, and a basic substance in combination, various heat-sensitive color-forming layers capable of obtaining a colored image (recorded image) by heat may be included as part of the structure.

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

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-methyl indol-3-yl)phthalide, 3,3-bis(1,2-dimethylindol-3-yl)-5-dimethylaminophthalide, 3,3
-bis(1,2-dimethylindol-3-yl)-6
-dimethylaminophthalide, 3゜3-bis(9-ethylcarbazol-3-yl)-6-dimethylaminophthalide, 3,3-bis(2-phenylindol-3-yl)-6-dimethylaminophthalide 3-p-dimethylaminophenyl-3-(1-methylpyrrol-3-yl)
-Triallylmethane dyes such as 6-dimethylaminophthalide, 4,4'-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leucoauramine, N-2,4,5-1-lichlorophenyl Diphenylmethane dyes such as leuco auramine, thiazine dyes such as benzoyl leucomethylene blue and p-nitrobenzoyl leucomethylene blue, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3
-phenyl-spiro-dinaphthopyran, 3-benzyl-
Spiro-dinaphthopyran, 3-methyl-naphtho-(6'
- Spiro dyes such as methoxybenzo) spiropyran, 3-propyl-spiro-dibenzopyran, Rhodamine-B
Anilinolactam, rhodamine (p-nitroanilino)
lactam, lactam dyes such as rhodamine (O-chloroanilino)lactam, 3-dimethylamino-7-methoxyfluoran, 3-diethylamino-6-methoxyfluoran, 3-diethylamino-7-methoxyfluoran, 3-diethylamino- 7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3
-diethylamino-7゜8-benzofluorane, 3-diethylamino-5-methyl-7-dibenzylaminofluorane, 3-diethylamino-6.7-dimethylfluorane, 3-(N-ethyl-p-) Luidino)-7-methylfluorane, 3-diethylamino-7-N-acetyl-N-methylaminofluorane, 3-diethylamino-
7-N-methylaminofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamine-7-N-methyl-N-benzylaminofluorane,
3-diethylamino-7-N-chloroethyl-N-methylaminofluorane, 3-diethylamino-7-N-diethylaminofluorane, 3-(N-ethyl-p-toluidino)-6-methyl-7-phenylaminofluoran Oran, 3-(N-cyclobenti-N-ethylamino)-6
-Methyl-7-anilinofluorane, 3-(N-ethyl-P-)luidino)-6-methyl-7-(p-toluidino)fluorane, 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
-) thyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, 3
-diethylamino-7-(o-chlorophenylamino)
Fluoran, 3-dibutylamino-7-(0-chlorophenylamino)fluoran, 3-pyrrolidino-6-methyl-7-p-butylphenylaminofluoran, 3-N
-Methyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane, 3-N-ethyl-N-
Examples include fluoran dyes such as tetrahydrofurfurylamino-6-methyl-7-anilinofluoran.

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-tert-isobutylphenol), 4,4'-isopropylidenebis(2-tert
t-butylphenol), 4.4'-5ec-butylidene diphenol, 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- Phenolic compounds such as 4'-isoprobyloxyphenylsulfone, novolac type phenolic resin, phenol polymer, benzoic acid, p
-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, 3-sec-butyl-4-hydroxybenzoic acid, 3-cyclohexyl-4-hydroxybenzoic acid,
3,5-dimethyl-4-hydroxybenzoic acid, salicylic acid, 3-isopropylsalicylic acid, 3-jert-butylsalicylic acid, 3-benzylsalicylic acid, 3-(α-methylbenzyl)salicylic acid, 3-chloro-5-(α- methylbenzyl) salicylic acid, 3,5-tert-
Aromatic carboxylic acids such as butylsalicylic acid, 3-phenyl-5-(α,α-dimethylbenzyl)salicylic acid, 3,5-di-α-methylbenzylsalicylic acid, and these phenolic compounds, aromatic carboxylic acids and zinc, for example. , organic acidic substances such as salts with polyvalent metals such as magnesium, aluminum, calcium, titanium, manganese, 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 adjusted in a dry weight range of about 2 to 12 g/rrf, preferably about 3 to 8 g/r4.

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. A coating solution containing these substances is prepared by using -S with water as a dispersion medium, and applying a ball mill or a ball mill as appropriate.
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.

In addition, there are no particular limitations on the support, and papers such as high-quality 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. etc., 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. However, in the case of a two-color thermosensitive recording material, a high-temperature coloring layer is first formed on the support. After coating and, if necessary, coating an intermediate layer, a decoloring layer, an intermediate layer, and a leuco-based low-temperature coloring layer are sequentially coated and formed.

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

In addition, various variations are possible in 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. .

The heat-sensitive recording material of the present invention thus obtained is a multicolor heat-sensitive recording material that can obtain a recorded image with clear color tone without color mixing or bleeding, and has excellent storage stability under high temperature conditions.

"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.

Example 1 Preparation of liquid A 3-(N-cyclohexyl-N-methylamino)-6-
Methyl-7-phenylaminofluorane 10 parts Dibenzyl terephthalate 20 parts Methyl cellulose 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.

cl preparation (2,2,6,6-tetramethyl-4-piperidyl)-
1,2,3,4-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.

Solution D preparation 3-diethylamino-7,8-benzofluorane

10 parts methylcellulose 5% aqueous solution
5 parts water
25 parts This composition was milled with a sand mill until the average particle size was 3 μm.
It was crushed until it was.

Preparation of liquid E 1.1.3-tris(2-methyl-4-hydroxy-5
-tert-butylphenyl)butane 50 parts Methyl cellulose 5% aqueous solution 25 parts water
50 parts of this composition was ground in a sand mill until the average particle size was 3 μm.

[Preparation of coating liquid for high temperature heat-sensitive recording layer] 40 parts of liquid D, 130 parts of liquid B, kaolin (trade name 20W-
90) 45 parts of 20% oxidized starch aqueous solution, 75 parts of water, and 70 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.

[Preparation of coating liquid for intermediate layer] 12.5 parts of liquid E, silicon oxide pigment (product name: Mizukasil P
-527, oil absorption 170 cc/100g, manufactured by Mizusawa Chemical Co., Ltd.) 85 parts, 10% polyvinyl alcohol aqueous solution 100
1 part and 300 parts of water were mixed and stirred to prepare a coating liquid.

(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 parts, 20%
150 parts of oxidized starch aqueous solution and 55 parts of water were mixed and stirred to prepare a coating liquid.

[Manufacture of multicolor thermosensitive recording paper]

High-temperature heat-sensitive recording layer coating liquid on high-quality paper with a basis weight of 50 g/rd.
The coating amount of the decoloring layer coating liquid, the intermediate layer coating liquid, and the low-temperature heat-sensitive recording layer coating liquid after drying was 6 g/n'f and 3 g/n'f, respectively, in this order.
g/rtf, 2.5 g/r4.2 g/%, dried, and supercalendered to obtain a multicolor thermosensitive recording paper.

Example 2 1.1.3-tris(2-methyl-4
Example 1 was repeated except that 1.1.3-)lis(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane was used instead of -hydroxy-5-tert-butylphenyl)butane. A colored thermosensitive recording paper was obtained.

Example 3 In the preparation of Ei, 1.1.3-)lis(2-methyl-
1,1-bis(4-hydroxyphenyl) instead of 4-hydroxy-5-tert-butylphenyl)butane
- A multicolor thermosensitive recording paper was obtained in the same manner as in Example 1 except that cyclohexane was used.

Comparative Example 1 In preparing a coating liquid for an intermediate layer, a silicon oxide pigment (trade name: Mizukasil P-527° oil absorption 170
cc/100g, Suikagaku Kagaku Co., Ltd.) 90 copies, 10%
A multicolor thermosensitive recording paper was obtained in the same manner as in Example 1, except that 100 parts of an aqueous polyvinyl alcohol solution and 300 parts of water were mixed and stirred to prepare a coating liquid.

The dynamic color development characteristics, decolorization sensitivity, and storage stability of the four types of multicolor thermosensitive recording papers thus obtained were tested using the following methods, and the results are listed in Table 1.

[Recording conditions]

Using a 6-dot/Peng thermal head (manufactured by Matsushita Electronic Components Co., Ltd., 9 heating element resistance 300 ohms/dot), main scanning recording speed: 130 m5ec/1ine, sub-scanning near,
71ine/mm, head 0.90W/dot.

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

[Storage stability■]

After the recording paper was left in an atmosphere of 50° C. and 290% RH for 3 hours, recording was performed under the above recording conditions, and the black density and red density of the recorded portion were measured using a Macbeth densitometer.

[Storage Stability (■)] After the recording paper was left in an atmosphere of 40° C. and 290% RH for 24 hours, it was recorded under the above recording conditions, and the black density and red density of the recorded portion were measured using a Macbeth densitometer.

Table 1 "Effects" As is clear from the results in Table 1, all of the swear recording papers of the present invention have good recording sensitivity and are excellent in storage stability under high temperature conditions. Ta.

Patent applicant: Kanzaki Paper Co., Ltd.

Claims (1)

[Claims] It has two or more heat-sensitive color-forming layers each producing a different color tone, and at least one of the heat-sensitive color-forming layers is a leuco-based color-forming layer containing a leuco dye and a coloring agent, and the leuco-based color-forming layer contains In a multicolor thermosensitive recording material having a color erasing layer in an adjacent position, at least one between the leuco coloring layer and the adjacent color erasing layer contains a pigment as a main component and a 1,1-
1. A multicolor thermosensitive recording material comprising an intermediate layer containing at least one of bis(4-hydroxyphenyl)-cyclohexane or a hindered phenol compound.