JPH0966672A - Heat-sensitive recording body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the long-term preservation properties and recording sensitivity of a color image like resistance to oils, resistance to a plasticizer and others by laminating heat-sensitive coloring layers containing a leuco dye represented by the formula as a dye precursor, a developer compound and hindered phenol compound represented by the formula on a sheet-shaped base. SOLUTION: This heat-sensitive recording body is formed by laminating heat sensitive layers containing one member selected from among leuco dyes as a dye precursor represented by formula I (R represents ethyl or isopentyl.), one member selected from between 1, 3 bis (P-toluenesulfonyl aminocarbonyl hydrazinocarbonyl)benzene and its hydrate represented by formula II and used as a developer and at least one kind of hindered phenol compounds at least on one surface of a sheet-shaped base. As an actual example of the sheet-shaped base, an acidic paper, a neutral paper, a plastic film or the like is used. Also a coated layer such as a protective layer or a printed layer can be formed on a heat-sensitive coloring layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material which forms a color image by heating, and more particularly to a heat-sensitive recording material which is free from loss of a once-colored image and is excellent in storage stability of recording. More specifically, the long-term storability of the record is good, and at the same time the oil resistance and plasticizer resistance of the recorded image are excellent, and even if the unprinted part (commonly called the blank part) is exposed to light for a long time. It is a thermosensitive recording material with high recording sensitivity with little discoloration of the blank part, useful for image recording paper, cash dispenser paper, ticket, commuter pass, labels such as POS labels, cards such as prepaid cards and pass tickets. It concerns a recording body.

[0002]

2. Description of the Related Art A thermal recording material is generally composed of a support such as paper, synthetic paper or plastic film, a color-forming substance such as an electron-donating leuco dye and an electron-accepting phenolic compound provided on the support. It is composed of a thermosensitive coloring layer whose main component is a color-developing substance such as the organic acid substance. Thermal energy can be applied to the thermosensitive color developing layer to react the color forming substance with the color developing substance to form a color image for recording. Such a thermosensitive recording medium is disclosed in Japanese Patent Publication No. 4
It is disclosed in JP-A-3-4160, JP-B-45-14039, JP-A-48-27736 and the like and is widely put into practical use. Since the recording device is compact, inexpensive, and easy to maintain, thermal recording media are widely used in the output of electronic calculators, facsimiles, vending machines, printers of scientific measuring instruments, or printers for CRT medical measurement. in use. However, in a conventional so-called dye-type thermosensitive recording medium in which a thermosensitive coloring layer containing a color-developing dye substance, a color-developing substance and a binder as an active ingredient is coated on a support, the coloring reaction is reversible. For this reason, it is known that a colored image disappears over time. This decolorization is light exposure,
Accelerated in a high humidity and high temperature atmosphere, and when it is left in water for a long time, contact with oil such as salad oil and a plasticizer, it progresses remarkably and the image is erased to an unreadable level. It has been known.

Usually, a coloring system using a dye mainly composed of a colorless or light-colored lactone ring compound is used and a phenol type or carboxyl type compound is used as a developer.
Many techniques have been disclosed to suppress this decoloring phenomenon. For example, JP-A-60-78782 and JP-A-59
No. 167292, JP-A-59-114096, JP-A-59-93387, and a blend of phenolic antioxidants in the thermosensitive color-developing layer, and JP-A-56-146796. Using a hydrophobic polymer compound emulsion or the like as a protective layer, or a water-soluble polymer compound or a hydrophobic polymer compound emulsion on the thermosensitive coloring layer as seen in JP-A-58-199189. As an intermediate layer, on which a surface layer of an oil-based paint containing a hydrophobic polymer compound as a resin component is provided, and an epoxy compound for a phenol-based developer as disclosed in JP-A-62-164579. And those using a metal salt of a specific salicylic acid derivative, which is found in JP-A-62-169681, as a developer. There.

In the above-described thermosensitive color developing layer containing a phenolic or carboxyl type color developer and a phenolic antioxidant, the time-decolored portion of the printed portion is slightly decolorized as compared with the image without it. Although it is improved, the oil resistance of printing (for example, the preservation ratio of the image density after a certain time when salad oil is brought into contact with the color developing surface) and the plasticizer resistance (such as a wrap film containing a plasticizer on the color developing surface) No improvement is observed in the storage ratio of the image density after a certain period of time when contacted. On the other hand, the thermosensitive recording medium provided with the protective layer and the surface layer suppresses the color fading of the image when contacted with water, oil or a plasticizer for a short time, but does not erase the color when contacted for a long time. It is unavoidable and cannot be said to be an essential solution to the above problems.
Further, in the case of using a phenol-based color developer and an epoxy compound in combination, a relatively long time is required from the heating color development operation until the color development image is stabilized. When applied or contacted with a plasticizer, a large part of the color image is erased. Furthermore, those using a specific salicylic acid metal salt,
Although the image storability is improved, it has the drawbacks that the white paper part is colored under the environment of 50 ° C to 60 ° C, and the effective specific chemical structure of salicylic acid is complicated and expensive.

[0005]

The present invention solves these problems and is excellent in long-term storability of color images such as oil resistance and plasticizer resistance, and the white paper can be exposed to white paper for a long time. An object of the present invention is to provide a thermosensitive recording medium having a high recording sensitivity with less discoloration of the part. One of the objects of the present invention is to
For example, a polyvinyl chloride film that can be used not only as a thermal recording type ticket for an automatic ticket vending machine, but also for use on multiple tickets and commuter tickets that require preservability, as well as avoiding contact with plasticizers and fats and oils. Attached to the packaging surface of the packaged food P
(EN) A thermal recording material that can be used as a label for an OS barcode system, facsimile paper or word processing paper for long-term storage, and also as an image printer paper for CRT.

[0006]

Means for Solving the Problems The present inventors have made the following chemical structural formula (II):

Embedded image By using at least one member selected from 1,3-bis (P-toluenesulfonylaminocarbonylhydrazinocarbonyl) benzene and its hydrate represented by A heat-sensitive recording material having good storage stability and excellent oil resistance and plasticizer resistance of a recorded image can be obtained. Further, as a color-forming substance of the heat-sensitive recording material, the following general formula (I) is used.

Embedded image (However, R in the formula (I) represents an ethyl group or an isopentyl group), by using a member selected from leuco dyes, a thermosensitive recording medium having high recording sensitivity can be obtained, and By adding at least one hindered phenol compound to the heat-sensitive recording layer containing a color substance and a color-forming substance, the white paper portion of the obtained heat-sensitive recording body is not discolored even if exposed to light for a long time. It was discovered that a small amount of thermosensitive recording material could be obtained, and the present invention was completed.

The thermal recording material of the present invention comprises a sheet-like substrate,
Formed on at least one surface of the sheet-like substrate, and
The dye has a thermosensitive coloring layer containing a colorless or light-colored dye precursor and a developer that reacts under heating to develop a color, and the dye has the following general formula (I):

Embedded image (Wherein, R in the formula (I) represents an ethyl group or an isopentyl group), which is a member selected from leuco dyes, and the developer has the following chemical structural formula (II):

[Chemical 6] Which is at least one member selected from the compound represented by and a hydrate thereof, and wherein the thermosensitive coloring layer further contains at least one hindered phenol compound.

[0008]

The compound of formula (II) and its hydrate used in the present invention act as a developer.
That is, the compound of the formula (II) and its hydrate do not have an acidic functional group such as a phenolic hydroxyl group or a carboxyl group, but have a strong color developing ability for a basic leuco dye. It is understood that this is because the sulfonylsemicarbazide group in the compound of formula (I) acts as a color-developing functional group. The clear reason for showing good recording sensitivity in combination with a specific dye is currently unknown, and the reason why the light resistance of the white paper part is improved by the addition of hindered phenols is that the specific dye is exposed to light. It is considered that this is because it undergoes a dehydrogenation reaction and inhibits decomposition.

BEST MODE FOR CARRYING OUT THE INVENTION The hindered phenol compound which can be used in the present invention has at least one phenol structure in the molecule, and at least one position of the ortho position of the hydroxyl group of the phenol structure site is C
4 or more alkyl groups, cycloalkyl groups, phenyl groups,
A compound substituted by a bulky substituent such as a substituted phenyl group is disclosed in, for example, JP-A-57-151394.
JP-A-58-160191, JP-A-58-69096
JP-A-59-2884, JP-A-59-95190
JP-A-60-22288 and JP-A-60-2554.
85, JP-A-61-44686, JP-A-62-16
9683, JP-A-63-17081, JP-A 1-2
And the compounds listed in No. 49385 and the like. Specific compounds include, for example, 2,2′-methylenebis (4-methyl-6-tert-butylphenol),
2,2'-methylenebis (4-ethyl-6-tert-
Butylphenol), 2,2'-ethylidene bis (4,
6-di-tert-butylphenol), 4,4′-thiobis (6-tert-butyl-o-cresol), 2
-Tert-butyl-6- (3-tert-butyl-2
-Hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2- [1- (2-hydroxy-3,
5-di-tert-pentylphenyl) ethyl] -4,
6-di-tert-pentylphenyl acrylate,
1,3,5-trimethyl-2,4,6-tris (3,5
-Di-tert-butyl-4-hydroxybenzyl) benzene, 4-methyl-2,6-di-tert-butylphenol, 1,1-bis (2-hydroxy-3,5-dimethylphenyl) -6,6-dimethylheptane , 4,
4'-butylidene bis (6-tert-butyl-m-cresol), 2,5-di-tert-butylhydroquinone, 2,5-di-tert-amylhydroquinone, 4,
4'-thiobis (m-cresol), 1,1,3-tris (2'-methyl-5'-cyclohexyl-4'-hydroxyphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy) -5-tert-butylphenyl) butane, 4,4'-thiobis (3-methyl-6-t
ert-butylphenol) and the like. In addition, tetrakis (1,2,2,6,6-pentamethyl-4-piperidinyl) -1,2,3,4-butanetetracarboxylate is used in order to suppress discoloration of the white paper portion within a range that does not impair the effects of the present invention. It is also possible to use a hindered amine compound such as

The leuco dye used as the dye precursor in the present invention is specifically 3-diethylamino-6-methyl-7-anilinofluorane and 3- (N-ethyl-N).
-Isopentylamino) -6-methyl-7-anilinofluorane, but other triphenylmethane-based compounds for the purpose of changing the color tone or adjusting the recording sensitivity,
It is safe to use fluorane-based and diphenylmethane-based basic dyes together. The leuco dye used in combination can be selected from conventionally known ones, for example, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-. Azaphthalide, crystal violet lactone, 3-diethylamino-6-methyl-7- (o, p-dimethylanilino) fluorane, 3- (N-ethyl-N-p-toluidino) -6-methyl-7-anilinoflu Oran, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane,
3- (N-cyclohexyl-N-methylamino) -6-
Methyl-7-anilinofluorane, 3-diethylamino-7- (o-chloroanilino) fluorane, 3-diethylamino-7- (m-trifluoromethylanilino) fluorane, 3-diethylamino-6-methyl-7-chloro Fluorane, 3-diethylamino-6-methylfluorane, and 3-cyclohexylamino-6-chlorofluorane, 3- (N-ethyl-N-hexylamino)-
One or more selected from 6-methyl-7- (p-chloroanilino) fluorane and the like can be used.

Further, in the present invention, N-arylsulfonylurea derivatives represented by the following structures (Japanese Patent Laid-Open Nos. 5-116459 and 5) are used within a range that does not impair the desired effect.
No. 147357) or phenols, or a conventionally known developer composed of an organic acid can be used in combination with the compound of the formula (II) of the present invention and its hydrate. These developers are, for example, N- (p-toluenesulfonyl)
-N'-phenylurea, N- (p-toluenesulfonyl) -N '-(p-methoxyphenyl) urea, N- (p
-Toluenesulfonyl) -N '-(o-tolyl) urea,
N- (p-toluenesulfonyl) -N '-(m-tolyl) urea, N- (p-toluenesulfonyl) -N'-
(P-tolyl) urea, 4,4′-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane,
4,4'-bis (o-toluenesulfonylaminocarbonylamino) diphenylmethane, 4,4'-bis (p-
Toluenesulfonylaminocarbonylamino) diphenyl ether, 2,2-bis (4-hydroxyphenyl)
Propane (bisphenol A), 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,4-bis (1-methyl-1- (4′-hydroxyphenyl) ethyl) benzene, 1,3-bis ( 1-methyl-1-
(4'-hydroxyphenyl) ethyl) benzene, p-
Benzyl hydroxybenzoate (JP-A-52-14048)
3), bisphenol S, 4-hydroxy-4'-isopropyloxydiphenyl sulfone (JP-A-60-1)
No. 3852), 1,1-di (4-hydroxyphenyl)
Cyclohexane, 1,7-di (4-hydroxyphenylthio) -3,5-dioxaheptane (JP-A-59-5)
2694), 3,3'-diallyl-4,4'-dihydroxydiphenyl sulfone (JP-A-60-208286).
No.) etc.

Further, in the present invention, it is preferable to use a heat-fusible substance (so-called sensitizer) in combination. As the sensitizer, a heat-fusible organic compound having a melting point of 50 to 150 ° C is used,
Examples thereof include 1-hydroxy-2-naphthoic acid phenyl ester (JP-A-57-191089), benzylnaphthyl ether (JP-A-58-87094), and dibenzyl terephthalate (JP-A-58-98285).
No.), benzyl p-benzyloxybenzoate (Japanese Patent Application Laid-Open No. 5 (1999) -58242)
7-201691), diphenyl carbonate, ditolyl carbonate (JP-A-58-136489), 1,2-bis (m).
-Tolyloxy) ethane (JP-A-60-56588)
No.), 1,5-bis (p-methoxyphenoxy) -3-
Oxapentane (JP-A-62-181183), oxalic acid diesters (JP-A-64-1583, JP-B-5)
-62597), 1,4-bis (p-tolyloxy)
Benzene (JP-A-2-153787), diphenyl sulfone (melting point: 124 ° C), p-toluenesulfonic acid phenyl ester (melting point: 96 ° C), mesitylenesulfonic acid p
-Tolyl ester (melting point 100-102 ° C), 4,4 '
-Diallyloxydiphenyl sulfone (melting point 145)
° C), 4,4'-diisopentyloxydiphenyl sulfone (melting point 100 ° C), 4,4'-dimethoxydiphenyl sulfone (melting point 130 ° C), 2,2-bis (4-benzenesulfonyloxyphenyl) propane (melting point 114
C.), 2,2-bis (4-methanesulfonyloxyphenyl) propane (melting point 101.degree. C.), p-toluenesulfonanilide (melting point 102.degree. C.), o-chloroacetoacetanilide (melting point 103.degree. C.), acetoacet p-anisidide ( Melting point 113 ° C.) and the like.

The heat-sensitive color forming layer of the heat-sensitive recording material of the present invention comprises at least one member selected from the leuco dye represented by the formula (I), the color-developing compound represented by the formula (II) and a hydrate thereof.
It contains a hindered phenol compound. The heat-sensitive color developing layer preferably further contains a sensitizer and organic or inorganic pigments, and may further contain a conventionally known phenol-based or organic acid-based developer, ultraviolet absorber, or wax, if necessary. it can. Further, it contains a binder for fixing these components to the support.

The content of the above-mentioned leuco dye in the thermosensitive coloring layer is generally 5% by dry weight of the thermosensitive coloring layer.
The content of the color-developing compound of the formula (II) and its hydrate is generally preferably from 5 to 50% by weight. If the content is less than 5% by weight, the color developing ability will be insufficient, and even if it exceeds 50% by weight, the color developing ability will be saturated and no particular improvement will be seen, which may be economically disadvantageous. The content of the hindered phenol compound is preferably 0.1 to 20% by weight based on the weight of the thermosensitive color developing layer. If the content is less than 0.1%, the light resistance stabilizing effect of the white paper portion due to the addition of these compounds is small, and even if a large amount exceeding 20% by weight is used, the light resistance stabilizing effect is saturated and further improvement is obtained. I can't see it.

When a conventionally known phenol type or organic acid type developer is used in the thermosensitive color developing layer, its content is
It is preferably 5 to 40% by weight, and the content of the sensitizer is preferably 10 to 40% by weight. When waxes and white pigments are contained in the thermosensitive coloring layer, their content is preferably 2 to 20% by weight and 2 to 50% by weight, respectively, and the content of the binder is generally 5 to 20% by weight. .

Examples of the above-mentioned organic or inorganic pigments include calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, calcined clay, talc, and surface-treated calcium carbonate. Inorganic fine powder such as silica and silica, urea-formalin resin, styrene / methacrylic acid copolymer,
Examples thereof include organic fine powders such as polystyrene resin, etc., but if an alkaline earth metal salt such as calcium carbonate is used in a large amount, it may cause a decrease in recording sensitivity of the obtained thermosensitive recording medium. Therefore, the amount used is preferably 20% by weight or less based on the dry weight of the thermosensitive coloring layer. .

As the waxes, known waxes such as paraffin, amide wax, bisimide wax, and metal salt of higher fatty acid can be used.
For the binder, polyvinyl alcohol of various molecular weights, starch and its derivatives, methoxycellulose, carboxymethylcellulose, methylcellulose,
Cellulose derivatives such as ethyl cellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylic acid amide /
Acrylic ester copolymer, acrylic acid amide / acrylic acid ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, and water-soluble polymer such as casein Materials, as well as polyvinyl acetate, polyurethane, styrene / butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene / vinyl acetate copolymer, and styrene / Each latex such as butadiene / acrylic copolymer can be used.

The sheet-like substrate used in the thermosensitive recording medium of the present invention is made of paper (acidic paper or neutral paper), coated paper having a surface coated with a pigment, latex, etc., laminated paper, or polyolefin resin. You can choose from synthetic paper, plastic film, etc. On at least one surface of such a sheet-like substrate, a coating solution containing a mixture of the above-mentioned required components is applied and dried to produce a thermosensitive recording medium. The coating amount is preferably 1 to 15 g / m ² in the dried state of the coating liquid layer, and particularly preferably ² to 10 g / m ² .

In the heat-sensitive recording material of the present invention, a coating layer such as a protective layer or a printing layer can be further formed on the heat-sensitive color developing layer. Further, an undercoat layer can be provided below the thermosensitive coloring layer. In addition, a back layer may be provided on the back surface of the thermosensitive recording medium for preventing blocking at the time of contact between the front and back surfaces, suppressing permeation of water or oil from the back surface, and curling control.

In the present invention, the heat-sensitive recording material can be further processed to enhance the added value of the heat-sensitive recording material to give a higher function. For example, heat-sensitive recording that can be magnetically recorded on the back side by applying pressure sensitive adhesive, rewetting adhesive, delayed tack type adhesive to make adhesive paper, rewetting adhesive, delayed tack paper, or magnetic processing It can be a material. Also, using the back side, thermal transfer paper, inkjet paper, carbonless paper,
The recording paper can be made to have a function as an electrostatic recording paper or a xerographic paper, and can be recorded on both sides.
Of course, a double-sided thermosensitive recording medium can also be used.

[0020]

The present invention will be specifically described below with reference to examples. Unless otherwise specified, "part" and "%" represent "part by weight" and "% by weight", respectively. Example 1 A thermosensitive recording paper was prepared by the following operation. (1) Preparation of pigment-coated base paper 85 parts of calcined clay (trade name Ansilex) in 320 parts of water
40 parts by weight of styrene-butadiene copolymer emulsion (solid content 50%) in the resulting dispersion.
48 g of coating liquid obtained by mixing 50 parts of oxidized starch aqueous solution
m ² high-quality paper coating amount after drying over (acid paper) is 7.0g
Coating was carried out so that it would be / m ² to obtain a pigment-undercoated paper. (2) Preparation of Dispersion A Component amount (parts) 3- (N-ethyl-N-isopentylamino) -6-methyl-7-anilinofluorane 20 Polyvinyl alcohol 10% liquid 10 Water 70 Above The composition was pulverized using a paint conditioner until the average particle size became 1 μm or less. (3) Preparation of Dispersion B Component Amount (parts) Compound of formula (II) 10 Acetoacet p-anisidide 10 Polyvinyl alcohol 10% liquid 10 Water 70 The above composition was used with a paint conditioner and the average particle size was 1 μm. Grind until the following:

(4) Preparation of Dispersion C Component quantity (part) 2,2′-methylenebis (4-methyl-6-tert-butylphenol) 20 Polyvinyl alcohol 10% liquid 10 Water 70 Paint the above composition Using a conditioner, it was pulverized until the average particle size became 1 μm or less. (5) Formation of Coloring Layer 50 parts of the above liquid A, 200 parts of liquid B, 25 parts of liquid C, 34 parts of clay pigment (HG clay: manufactured by Huber), 12 parts of 25% zinc stearate dispersion, and 10% polyvinyl. 80 parts of an alcohol aqueous solution was mixed and stirred to obtain a coating liquid.
This coating liquid was applied and dried on the pigment-coated surface of the pigment-undercoated paper prepared in (1) so that the coating amount after drying was 7.5 g / m ² to form a thermosensitive coloring layer.

(6) Calender treatment The thermal recording material obtained as described above was treated with a super calender and the surface smoothness was 900 to 120.
It was set to 0 seconds. (7) Color test, color print storage stability test, and blank paper light resistance test The samples thus obtained were printed using a color tester THPMD manufactured by Okura Electric Co., Ltd. under the conditions of a print voltage of 21.7 V and a print pulse of 1.0 ms. did. The density of this printed color portion was measured with a Macbeth reflection densitometer RD-914 (this is called the original density). Also, prepare a predetermined test piece from the color-developed sample, apply the salad oil to the test piece within 30 minutes after color development, leave it at room temperature for 1 hour, wipe off excess oil, and determine the residual image density by Macbeth reflection density. The image retention rate was calculated according to the following formula. Image preservation rate (%) = (density after oil resistance test) / (original density) × 100 Further, the whiteness of the uncolored portion (white paper portion) was measured by a Hunter whiteness meter using a blue filter (this). Is called the original whiteness), and then the white paper part is separated by 15 cm under a fluorescent lamp of 15w.
(0 lux) was irradiated with light for 100 hours. After completion of the light irradiation, the whiteness was measured again by the above method (this is called whiteness after light resistance test). Table 1 shows the measured original density value, image storage ratio (%), original whiteness and whiteness after the light resistance test.

Example 2 The same operation as in Example 1 was performed. However, in the preparation of Dispersion A, 3-diethylamino-6-methyl-7-anilino was used instead of 10 parts of 3- (N-ethyl-N-isopentylamino) -6-methyl-7-anilinofluorane. 10 parts of fluoran was used. Table 1 shows the test results. Example 3 The same operation as in Example 1 was performed. However, in the preparation of Dispersion C, 2,2′-methylenebis (4-methyl-6)
-Tert-butylphenol) instead of 2,2 '
-Methylenebis (4-ethyl-6-tert-butylphenol) was used. Table 1 shows the test results.

Example 4 The same operation as in Example 1 was performed. However, in the preparation of Dispersion C, 2,2′-methylenebis (4-methyl-6)
-Tert-butylphenol) instead of 1,1,
3-tris (2'-methyl-5'-cyclohexyl-
4'-hydroxyphenyl) butane was used. Table 1 shows the test results.

Example 5 The same operation as in Example 1 was performed. However, in the preparation of Dispersion B, oxalic acid di (p-methylbenzyl) ester was used instead of acetoacetate p-anisidide. Table 1 shows the test results. Comparative Example 1 The same operation as in Example 1 was performed. However, in the preparation of the dispersion liquid B, 2,2-bis (4-hydroxyphenyl) propane (bisphenol A) was used in place of the compound of the formula (II), and oxalic acid di (p- Methylbenzyl) ester was used.
Table 1 shows the test results. Comparative Example 2 The same operation as in Example 1 was performed. However, in the preparation of Dispersion A, 3-diethylamino-7- (o-chloroanilino) fluorane was used instead of 3- (N-ethyl-N-isopentylamino) -6-methyl-7-anilinofluorane. I was there. Table 1 shows the test results.

Comparative Example 3 The same operation as in Example 1 was performed. However, in the preparation of Dispersion C, 2,2′-methylenebis (4-methyl-
6-tert-butylphenol) was not used. Table 1 shows the test results.

[Table 1] As is clear from Table 1, the thermal recording paper of the present invention is
High recording sensitivity, high storability in the printed area, and little white paper coloring when exposed to light for a long time.

INDUSTRIAL APPLICABILITY The thermosensitive recording material of the present invention uses a leuco dye represented by the formula (I) as a coloring dye in the thermosensitive coloring layer and a compound represented by the formula (II) as a developer. And at least one member selected from hydrates thereof and containing a hindered phenol compound, the color image obtained has good recording sensitivity, storability in the printed area and light resistance in the blank area.

Claims (1)

[Claims] 1. A thermosensitive coloring layer comprising a sheet-shaped substrate, a colorless or light-colored dye precursor which is formed on at least one surface of the sheet-shaped substrate, and a color developer which reacts under heating to develop a color thereof. And the dye precursor has the following general formula (I): (Wherein R in the formula (I) represents an ethyl group or an isopentyl group), and the developer is a member represented by the following chemical structural formula (II): ] A heat-sensitive recording material which is at least one member selected from the compounds represented by and the heat-sensitive color forming layer further contains at least one hindered phenol compound.