JPH0280287A - Dichromatic thermal recording medium - Google Patents

Abstract

PURPOSE:To form an image of sharp color tone with high recording sensitivity and almost free from color contamination or ink run by using at least one kind of specific phenol substance as a coloring agent. CONSTITUTION:A dichromatic thermal recording medium contains at least, one kind of compound shown in formula I (R1 to R4 are hydrogen atoms or alkyl groups with 1 to 4C) as a coloring agent in a leuco coloration layer. The typical example of the compound is 1.1-bis (4-hydroxyphenyl)-1-phenyl ethane which is preferably used. This coloring agent is less susceptible of the adverse effects of a discharging agent during the storage of a recording medium, and also characteristic of its density adequacy during recording. Therefore, a dichromatic recording medium with high preservability can be obtained. However, if the coloring agent is used as one for a low temperature coloration layer, it is subject to the instantaneous action of a discharging agent during heating at high temperature and also produces a uniform and sharp color image at high temperature as properties. Therefore, the coloring agent is best suited to a low-temperature coloration layer.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a two-color thermosensitive recording material having a plurality of color-forming layers each of which develops a distinct 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 required performance qualities have also diversified, including 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 heat-sensitive coloring layer develops color during low-temperature heating, and both the low-temperature heat-sensitive coloring layer and the high-temperature heat-sensitive coloring 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. .

In the first method, the image becomes unclear and blurring occurs due to color mixing, 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, when these decolorizing agents are simply used adjacent to a leuco coloring layer, conventional coloring agents are affected by the decolorizing agent during storage and may not produce sufficient color density during heating recording. , the disadvantage is that the original color tone of the dye changes.

``Problems to be Solved by the Invention'' The present invention improves the above-mentioned problems associated with the use of decolorizing agents, and provides two-color images that have good recording sensitivity and are capable of forming clear-toned images with less color mixture and bleeding. A thermosensitive recording medium is provided.

"Means for Solving the Problems" The above-mentioned object of the present invention is obtained by sequentially laminating at least a high-temperature coloring layer, an intermediate layer containing a decoloring agent, and a low-temperature coloring layer on a support, and the coloring layer is This is achieved by using at least one type of phenolic substance represented by the following general formula as the coloring agent in a two-color thermosensitive recording material that is a leuco coloring layer containing a leuco dye and a coloring agent.

[In the formula, Rl'' Ra is each a hydrogen atom or a carbon number of 1
~4 represents an alkyl group] "Function" The two-color thermosensitive recording material of the present invention has an important feature in that, as described above, at least one compound represented by the above general formula is used as a coloring agent in the leuco coloring layer. It has unique characteristics.

Specific examples of the compound represented by the above general formula include the following compounds, but are of course not limited to these.

1.1-bis(4-hydroxyphenyl)-1-phenylethane 1.1-bis(4-hydroxy-3-methylphenyl)
-1-phenylethane 1, t-bis(4-hydroxy-3,5-dimethylphenyl)-1-phenylethane 1,1-bis(4-hydroxy-3-ethylphenyl)
-1-phenylethane 1.1-bis(4-hydroxy-3,5-dimethylphenyl)-1-phenylethane 1.1-bis(4-hydroxy-3-propylphenyl)-1-phenylethane 1.1 -bis(4-hydroxy-3-isopropylphenyl)-1-phenylethane 1.1-bis(4-hydroxy-3-tert-butylphenyl)-1-phenylethane 1.1-bis(4-hydroxy-3 -methyl 5-te
rt-7'tylphenyl)-1-phenylethane, etc.

Among these, 1,1-bis(4-hydroxyphenyl)-1-phenylethane (melting point: 188°C) has a high melting point, so there is no background fog, and it can be used as a two-color thermal recording material with extremely high whiteness. It is particularly preferably used to provide

Of course, two or more of the above-mentioned compounds may be used in combination, and various known coloring agents may also be used in combination as appropriate within a range that does not impair the desired effects of the present invention.

The above-mentioned specific coloring agent used in the present invention has a characteristic that it is hardly affected by a decoloring agent during storage of the recording medium and that sufficient image density can be obtained during recording, so it has an extremely long shelf life. To provide a two-color thermosensitive recording medium with excellent properties. However, especially when used as a coloring agent in a low-temperature coloring layer, it also has the property of being instantly acted upon by a decoloring agent when heated to high temperatures, giving a uniform and clear high-temperature coloring image, so it cannot be used in a low-temperature coloring layer. This is one of the preferred embodiments of the present invention.

The coloring layer constituting the recording medium of the present invention is a leuco coloring layer containing a leuco dye and a coloring agent, and various useful colorless to light-colored basic dyes are known.
For example, 3.3-bis(pdimethylaminophenyl)-6
-dimethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl)-3-(1,2-dimethylindole-3
-yl)phthalide, 3-(p-dimethylaminophenyl)-3-(2-methylindol-3-yl)phthalide, 3,3-bis(1,2-dimethylindol-3-yl)-5-dimethyl Aminophthalide, 3,3-bis(1
, 2-dimethylindol-3-yl)-6-dimethylaminophthalide, 3,3-bis(9-ethylcarbazol-3yl)-6-dimethylaminophthalide, 3,3bis(2-phenylindole- 3-yl)6-dimethylaminophthalide, 3-p-dimethylaminophenyl-3
-(1-methylpyrrol-3-yl)-6-dimethylaminophthalide and other triallylmethane dyes, 4,4'-
Bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leucoolamine, N-2,4,
Diphenylmethane dyes such as 5-trichlorophenylleucoauramine, benzoylleucomethylene blue, p
-Nitrobenzoylleucomethylene blue, etc. (7)
f azine dye, 3-methyl-spirodinaphthopyran,
3-ethyl-spiro-dinaphthopyran, 3-phenyl-
Spiro dyes such as spiro-dinaphthopyran, 3-pendylose 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-cyclohexylamino-6-chlorofluoran, 3-dimethylamino-7-methoxyfluoran, 3-diethylamino-6-methoxyfluoran, 3-
Diethylamine-7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7,8-benzofluorane, 3-diethylamino-5- Methyl-7-dibenzylaminofluorane, 3-
Diethylamino-67-dimethylfluorane, 3-(N
-ethyl-1)-toluidino)-7-methylfluorane, 3-diethylamino-? -N-acetyl-N-methylaminofluorane, 3-diethylamino-? -N-methylaminofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-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-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-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-7-xylidinofluorane, 3-diethylamino-7-(o-chlorophenylamino)fluoran, 3-
Dibutylamino-7-(o-chlorophenylamino)fluoran, 3-pyrrolidino-6-methyl-7-p-butylphenylaminofluoran, 3-N-methyl-N-tetrahydrofurfurylamino-6-methyl-7- Examples include fluoran dyes such as anilinofluoran and 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluoran.

In the two-color thermosensitive recording material of the present invention, the color tone of the color-forming layer is appropriately adjusted by selecting various basic dyes as described above. It is desirable that the coloring system is a low-temperature coloring layer and the red coloring system is a high-temperature coloring layer.

The usage ratio of the basic dye and coloring agent is 1 to 30 parts by weight of the coloring agent per 1 part by weight of the basic dye in the low-temperature coloring layer.
It is preferable to use about 1 to 8 parts by weight, and in the high-temperature coloring layer, 1 part by weight of the coloring agent is used per 1 part by weight of the basic dye.
It is desirable to use up to 50 parts by weight, preferably 2 to 10 parts by weight.

The coating liquid that forms the coloring layer contains adhesive components such as starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, diisobutylene/maleic anhydride copolymer salt, and 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 added in a range of about 15 to 50% by weight of the total solid content. Pigment components include, for example, diatomaceous earth, calcined diatomaceous earth, kaolin, calcined kaolin, white carbon, magnesium carbonate, calcium carbonate, zinc oxide, aluminum oxide, titanium oxide, silicon oxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc, Inorganic pigments such as fired clay, styrene microballs, nylon powder, polyethylene powder urea/formalin resin fillers, organic pigments such as raw starch granules, etc. may be added.

Furthermore, various other auxiliary agents may be added to the coating liquid forming the coloring layer, such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, alginate, Dispersants such as fatty acid metal salts, ultraviolet absorbers such as benzophenone and triazole, and other antifoaming agents.
Examples include fluorescent dyes and colored dyes. In addition, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax, fatty acid amides such as stearic acid amide, stearic acid methylene bisamide, oleic acid amide, palmitic acid amide, and coconut fatty acid amide [, 2,2'-
Methylenebis(4-methyl-6-tert-butylphenol), 4゜4'-butylidenebis(6-tert-butylphenol),
butyl-3-methylphenol), hindered phenols such as 1.1.3-tris(2-methyl-4-hydroxy-5-tart-butylphenol)butane, dibenzyl terephthalate, 1.2-di(3- Methylphenol)ethane, 1,2-diphenoxyethane, 4.4'
-Naphthol derivatives such as ethylenedioxy-bisbenzoic acid diphenyl methyl ester, 1-naphthylbenzyl ether, 2-naphthylbenzyl ether, 1-hydroxy-2-naphthoic acid phenyl ester, benzyl 2-hydroxy-3-naphthoic acid Naphthoic acid derivatives such as esters, various known thermofusible substances, etc. can also be used in combination.

Incidentally, the coating amount of each coloring layer is not particularly limited, and is generally adjusted within a range of about 1.5 to 12 g/b on dry weight.

In the heat-sensitive recording material of the present invention, the intermediate layer contains a decoloring agent as a main component, and in addition, various adhesives, pigments, thermofusible substances, etc. as described above may be appropriately blended. Furthermore, the layer structure of the intermediate layer is not limited to a single layer, but may be a laminate of two or more layers, including a decoloring layer containing a decoloring agent as a main component and a layer containing other materials as a main component. An intermediate layer with a two-layer structure in which a layer containing a pigment and/or a thermofusible substance as a main component is laminated on a decoloring layer containing as a main component is the most preferred embodiment because it is excellent in achieving the desired effects of the present invention. It is a mode.

In the present invention, the decoloring agent contained in the decoloring layer is not particularly limited, and includes aliphatic amide 7M, piperidines, piperazines, pyridines, imidazoles, imidacillines, morpholines, guanidines, amidine. Polyesters, polyethers, glycols, aromatic amides, 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
) No. 3593] Urea derivatives [JP-A-55-1392
No. 90] Alkylene oxide adduct of linear glycol [
JP-A-55-152094] Morpholine derivative [
JP-A-56-40588] Coal for publication [JP-A-50-17865] Teru and polyethylene glycol derivatives [JP-A-5017867, JP-A-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 [JP 50-18048] Disubstituted amide compounds of aliphatic and aromatic carboxylic acids [JP-A-61-120792, JP-A-61-169277
No. Publication] etc.

Further, specific examples of amidines include N.

N''-diphenylformamidine, N, N'-G〇-
Tolylformamidine, N,N'-diphenylbenzamidine, N,N'-jp-tolylN'-phenylbenzamidine, N,N'N"N"-tetraphenyl-hebutacyamidine, N.

Examples of piperidines include (2,2,6,6-tetramethyl-4-piperidyl/
tridecyl)-1,2-ethanedicarboxylate, tetrakis(1,2,2゜6.6-bentamethyl-4-piperidyl)-1゜2.3.4-butanetetracarboxylate, tetrakis(1-methyl-4 -Piperidyl)-
1゜2.3.4-butanetetracarboxylate, (2
,2,6,6-tetramethyl-4-piperidyl/β,β
, β′β′-tetramethyl-3.9-(2,4,8,1
0-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, tetrakis(2,2,6,6-tetramethyl-4-piperidyl")-1,2,3,4-butanetetracarboxylate, and the like.

Among these various decolorizing agents, piperidines, amidines, and di-substituted amide compounds of aromatic carboxylic acids are particularly preferred, and among them, tetrakis(2゜2.6.6-tetramethyl-4-piperidyl)-1, 2,3,4-butanetetracarboxylate, tetrakis(1,2,2,6,
6-bentamethyl-4-piperidyl)-1,2,3,4
-butanetetracarboxylate, (1,2,2,6,
6-bentamethyl-4-piperidyl/β, β, βIβ・
Tetramethyl-3,9-(2,4,8,10-tetraoxaspiro(5,5)undecane]diethyl)-1,2
, 3,4-butanetetracarboxylate and other piperidines; Disubstituted amide compounds of aromatic dihydric carboxylic acids such as (ethylamide) have extremely low influence on the coloring layer using the above-mentioned specific coloring agent during storage, and are excellent for low-temperature coloring layers during recording. It is particularly preferably used because it exhibits a color erasing effect.

The various decoloring agents mentioned above are generally used in an amount of 0.1 to 20% relative to the total weight of the leuco dye and coloring agent in the low-temperature coloring layer in the decoloring layer.
The content is preferably about twice the weight, but more preferably 0.5
It is adjusted in the range of ~6 times the weight. In addition, use 2 decolorizers.
Of course, it is also possible to use more than one species in combination.

The coating liquid forming the intermediate layer contains various adhesives, dispersants, lubricants, thermofusible substances, inorganic pigments, organic pigments, etc., as described in the explanation of the coloring layer coating liquid, as well as other antifoaming agents. Various auxiliary agents such as dyes, ultraviolet absorbers, fluorescent dyes, and colored dyes can be appropriately blended. In addition, as mentioned above, the layer structure of the intermediate layer is not limited to a single layer, but may be a laminate of two or more layers, including a decoloring layer mainly composed of a decoloring agent and a layer mainly composed of other materials. Depending on the situation, adhesive may also be used between the high temperature coloring layer and the decoloring layer.
A layer containing a thermofusible substance, pigment, etc. may be formed as appropriate.

In the heat-sensitive recording material of the present invention, the coating liquid for each coloring layer and intermediate layer is generally prepared using water as a dispersion medium, using an appropriate stirring or grinding machine such as a ball mill, attritor, or sand mill. The method of forming each coloring layer and intermediate layer is not particularly limited, and may be formed by applying a coating liquid onto a support and drying it, for example, by air knife coating, blade coating, etc., according to conventionally well-known and commonly used techniques. .

The support is not particularly limited, and may include 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, and synthetic fibers. Paper, synthetic resin film, etc. are used as appropriate. Further, after coating and drying the coloring layer, smoothing treatment such as super calendering can be performed as necessary.

Furthermore, various variations are possible without exceeding the gist of the present invention; for example, an overcoat layer may be provided on the coloring layer for the purpose of protecting the coloring layer, or an undercoat layer or backing layer may be provided on the support. Various known techniques in the field of heat-sensitive recording materials can be added, such as providing a. Furthermore, the color-forming materials and color tones constituting each color-forming layer can be varied in various ways, and can be appropriately selected depending on the intended two-color thermosensitive recording material.

The heat-sensitive recording material of the present invention obtained in this way has excellent 2-color printing which can form images with clear color tones with less color mixture and bleeding.
It is a color thermosensitive recording medium.

"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 I A-wave preparation 3-diethylamino-7-chlorofluoran 10 parts methylcellulose 5% aqueous solution 5 parts water
25 parts of this composition was ground in a sand mill until the average particle size was 3 μm.

Preparation of Solution B 1. 1-bis(4-hydroxyphenyl)-1 phenylethane 30 parts Methyl cellulose 5
% aqueous solution 30 parts water
70 parts of this composition was ground in a sand mill until the average particle size was 3 μm.

C lacquer preparation Tetrakis (1,2,2,6,6-bentamethyl-4-
piperidyl) 1.2i, 3.4-butanetetracarboxylate 50 parts methylcellulose 5% aqueous solution 25 parts water
1) 0 parts This composition was ground in a sand mill until the average particle size was 3 μm.

Preparation of Solution D 3-(N-Ethyl-N-isoamylamino)=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 coating liquid for high temperature heat-sensitive recording layer]

20 parts of liquid A, 65 parts of liquid B, kaolin (product name: UW-9)
0, manufactured by EMC) 60 parts, 20% oxidized starch aqueous solution 100
155 parts of water were mixed and stirred to prepare a coating liquid.

[Preparation of coating liquid for decolorizing intermediate layer]

185 parts of liquid C, 50 parts of a 20% oxidized starch aqueous solution, and 65 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 D, 130 parts of liquid B, silicon oxide pigment (product name:
Mizukashiru P-527. (manufactured by Mizusawa Chemical Co., Ltd.) 20 copies, 20%
100 parts of oxidized starch aqueous solution and 125 parts of water were mixed and stirred to prepare a coating liquid.

[Formation of recording layer]

High-temperature heat-sensitive recording layer coating liquid was applied to high-quality paper with a basis weight of 50 g/m.
The coating amount of the decolorizing intermediate layer coating liquid and the low temperature range heat recording layer coating liquid after drying was 7 g/rri and 3 g/ld, respectively, in this order.
, 4 g/rd, dried, and subjected to super calendering to obtain a two-color thermosensitive recording material.

Example 2 In the preparation of C lacquer, tetrakis (1,2,2°6.6-
Instead of (bentamethyl-4-piperidyl)-1゜2.3.4-butanetetracarboxylate,
,6,6-pentamethyl4-piperidyl/β,β,β'
β'-tetramethyl-3,9-(2,4,8,10-tetraoxaspiro(5,5)undecanefudiethyl)-
A two-color thermosensitive recording paper was obtained in the same manner as in Example 1, except that 1,2°3,4-butanetetracarboxylate (trade name: DN-56, manufactured by Adeka Argus Chemical Co., Ltd.) was used.

Example 3 In preparing Solution B, 1.1-bis(4-hydroxy-3-isopropylphenyl)-1- was substituted for 1.1-bis(4-hydroxyphenyl)-1-phenylethane.
2 in the same manner as in Example 1 except that phenylethane was used.
A colored thermosensitive recording paper was obtained.

Example 4 B? & In the preparation of 1.1-bis(4-hydroxyphenyl)-1-phenylethane t)liny, 1)-
Tetrakis(1,2,2,6,6-bentamethyl-4-piperidyl)-1,2,3,4- N instead of butane tetracarboxylate.

A two-color thermosensitive recording paper was obtained in the same manner as in Example 1 except that N'-isopropyl di(N-cyclohexyl-N-methylamide) was used.

Example 5 In preparing Solution B, 1.1-bis(4-hydroxy-3,5-diethylphenyl)-1- was substituted for 1.1-bis(4-hydroxyphenyl)-1-phenylethane.
Using phenylethane, N,N'- instead of tetrakis(1,2,2,6,6=pentamethyl-4-piperidyl)-1,2,3°4-butanetetracarboxylate in C lacquer preparation. A two-color thermosensitive recording paper was obtained in the same manner as in Example 1 except that terephthaloyluge (N-phenyl-N-ethylamide) was used.

Comparative Example I Two colors were prepared in the same manner as in Example 1 except that 4,4'-isopropylidenediphenol was used instead of 1,1-bis(4-hydroxyphenyl)-1-phenylethane in the preparation of B1. A colored thermosensitive recording paper was obtained.

The dynamic coloring properties of the six types of two-color thermosensitive recording papers thus obtained were tested in the following manner.

[Recording conditions]

Using a thermal printer (PS-8600, manufactured by ROHM Co., Ltd.), thermal head: 8 dots / 9 dots heating resistor: approx. 1
300 ohms/dot, main scanning recording speed: 20 m5
ec/1ine, sub-scan: 321ine/m.

Recording was carried out under the following conditions: 0.44 W/dot, low-temperature coloring energy: 0.26 mJ, and high-temperature coloring energy: t, o6 mJ.

The density of the recorded area was measured using a Macbeth densitometer (manufactured by Macbeth, Model RD914) using a visual filter for low-temperature colored images (black) and a green filter for high-temperature colored images (red). The results are listed in the table.

[Storability of unrecorded areas]

Unrecorded thermal recording paper was heated at 40°C and 90%RH for 2 hours.
After being left for 4 hours, recording was performed under the same conditions as above, and the recording density of the colored image was measured in the same manner, and the results are also listed in the table.

The one-color image on each table was clear for both the low-temperature color image and the high-temperature color image, and the storage stability of the unrecorded portion was also good.

Claims (3)

[Claims] (1) At least a high temperature coloring layer, an intermediate layer containing a decoloring agent, and a low temperature coloring layer are sequentially laminated on a support, and the coloring layer is a leuco coloring layer containing a leuco dye and a coloring agent. A certain two-color thermosensitive recording material, characterized in that at least one type of phenolic substance represented by the following general formula is used as the coloring agent. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [In the formula, R_1 to R_4 each represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms] (2) The two-color thermosensitive recording material according to claim 1, wherein the coloring agent in the low-temperature coloring layer is at least one type of phenolic substance represented by the general formula. (3) The two-color thermosensitive recording material according to claim (1) or (2), wherein the decoloring agent is a piperidine or a di-substituted amide of an aromatic carboxylic acid.