JP2777144B2 - Thermal recording medium - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a thermosensitive recording medium, and more particularly to a thermosensitive recording medium having excellent print pixel reproducibility and high recording density.

"Prior art" Conventionally, a thermosensitive recording in which a color-forming image is obtained by contacting both color-forming substances by heat using a color-forming reaction between a color-forming agent and a color-forming agent that forms a color in contact with the color-forming agent. The body is well known. Such a thermosensitive recording medium is relatively inexpensive, and its recording equipment is compact and its maintenance is relatively easy. Therefore, it is used not only as a recording medium for facsimile machines and various computers but also in a wide range of fields.

With the versatility of applications, thermal recording media with excellent print pixel reproducibility in any region from low density to high density and capable of obtaining high-quality recorded images comparable to silver halide photographs Are increasing. Further, with the increase in the speed of the recording apparatus, there is an increasing demand for a thermosensitive recording medium having excellent dynamic recording sensitivity.

Since the surface of the base paper used for the support of the thermal recording medium has irregularities due to fibers, the surface of the thermal recording layer formed thereon also has minute irregularities. Therefore, the surface of the recording layer
It is not always in close contact with the thermal head of the recording device, and as a result, it is difficult to obtain excellent print pixel reproducibility. The base paper has irregularities of 10 to 15 μm.In the past, an improvement was attempted by providing an intermediate layer to eliminate the irregularities, performing a super calender treatment after forming the intermediate layer, and providing an intermediate layer having a multilayer structure, It was insufficient to completely eliminate irregularities on the base paper.

For example, to obtain a high-quality, high-sensitivity thermosensitive recording medium,
An intermediate layer composed of a film-forming polymer substance having a glass transition temperature of 60 ° C. or lower is provided between the support and the recording layer (Japanese Patent Laid-Open No. 54-92263), or an intermediate layer composed of an oil-absorbing pigment is provided. (Japanese Unexamined Patent Publications Nos. 59-155097 and 61-44683) and a method of improving smoothness and heat insulation by combining these layers in multiple layers (Japanese Patent Laid-Open Nos. 61-11286 and 61-193880). ) Etc. have been proposed.

However, none of them has sufficient print pixel reproducibility and sensitivity. In addition, the present inventors have set the layer thickness of the heat-sensitive recording layer itself.
An attempt was made to increase the thickness to 20 to 40 μm, but sufficient print pixel reproducibility could not be obtained.

"Problems to be Solved by the Invention" The present invention solves the above-mentioned problems, and has excellent print pixel reproducibility in any region from low density to high density,
It is an object of the present invention to provide a thermosensitive recording medium from which a high-quality recorded image can be obtained.

"Means for Solving the Problems" On a support, a pigment having an apparent specific gravity of 0.3 g / cm ³ or less, a colorless or light-colored basic dye, and a colorant capable of forming a color upon contact with the dye are contained. An intermediate layer is provided, a heat-sensitive recording layer is further provided on the intermediate layer, and the intermediate layer contains a pigment having an apparent specific gravity of 0.3 g / cm ³ or less based on the total solid content of the intermediate layer. It is a thermosensitive recording medium.

`` Function '' Since the intermediate layer contains a coloring material in the thermal recording medium of the present invention, the coloring of the intermediate layer complements the coloring of the thermal recording layer during recording to enable excellent print pixel reproducibility and recording density. is there.

By the way, if the amount of the heat-sensitive recording layer provided on the support is simply increased, the unevenness existing on the support cannot be completely eliminated, and sufficient print pixel reproducibility cannot be obtained. In addition, there is a new disadvantage such as easy accumulation of the residue on the thermal head. In the case where only two heat-sensitive recording layers are provided, the first heat-sensitive recording layer provided on the support has insufficient oil absorbency, so that waxes and the like which have been melted by heat become residue on the thermal head of the recording device. There are drawbacks.

In the present invention, a pigment having an apparent specific gravity of 0.3 g / cm ³ or less is contained in the intermediate layer in an amount of 50 to 90% by weight based on the total solid content of the intermediate layer. If a pigment having a large apparent specific gravity is used, or if the content of the pigment is small, the thermal head tends to accumulate, and if the content of the pigment is large, sufficient print pixel reproducibility is difficult to obtain.

As the pigment having an apparent specific gravity of 0.3 g / cm ³ or less used for the intermediate layer, various inorganic pigments and organic pigments are known, such as calcined kaolin, talc, light calcium carbonate, amorphous silica, and polystyrene fine particles. And urea-formalin resin fine powder.

Among these various pigments, calcined kaolin and amorphous silica are particularly preferably used because they have excellent heat insulating properties and have the effect of further improving the recording sensitivity.

As the colorless or light-colored basic dye contained in the intermediate layer, the same dye as that contained in the recording layer or a different dye may be used, or both may be used in combination.

 Examples of the basic dye include the following.

3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3- (1,2 -Dimethylindol-3-yl)
Phthalide, 3- (p-dimethylaminophenyl) -3-
(2-methylindol-3-yl) phthalide, 3,3-
Bis (1,2-dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide,
3-bis (9-ethylcarbazol-3-yl) -6
Dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -6-dimethylaminophthalide,
Triallylmethane dyes such as 3-p-dimethylaminophenyl-3- (1-methylpyrrol-3-yl) -6-dimethylaminophthalide, 4,4'-bis-dimethylaminobenzhydryl benzyl ether, Diphenylmethane dyes such as N-halophenyl-leuco auramine and N-2,4,5-trichlorophenyl 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-
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 (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-6,7-dimethylfluoran, 3- (N-ethyl-p-toluidino) -7-methylfluoran, 3-diethylamino-7-N-acetyl-N-methylaminofluoran, 3-diethylamino-
7-N-methylaminofluoran, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino-7-N-methyl-N-benzylaminofluoran,
3-diethylamino-7-N-chloroethyl-N-methylaminofluoran, 3-diethylamino-7-N-diethylaminofluoran, 3- (N-ethyl-p-toluidino) -6-methyl-7-phenylaminofluor Oran, 3- (N-cyclopentyl-N-ethylamino)-
6-methyl-7-anilinofluoran, 3- (N-ethyl-p-toluidino) -6-methyl-7- (p-toluidino) fluoran, 3-diethylamino-6-methyl-
7-phenylaminofluoran, 3-diethylamino-
7- (2-carbomethoxy-phenylamino) fluoran, 3- (N-ethyl-N-isoamylamino) -6
Methyl-7-phenylaminofluoran, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-
Phenylaminofluoran, 3-pyrrolidino-6-methyl-7-phenylaminofluoran, 3-piperidino-
6-methyl-7-phenylaminofluoran, 3-diethylamino-6-methyl-7-xylidinofluoran,
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-anilinofluoran, 3-N-ethyl-
N-tetrahydrofurfurylamino-6-methyl-7-
Fluoran dyes such as anilinofluoran;

As the colorant contained in the intermediate layer, the same colorant or a different colorant as that contained in the recording layer may be used, or both may be used in combination.

 The following are examples of the coloring agent.

4-tert-butylphenol, α-naphthol, β-
Naphthol, 4-acetylphenol, 4-tert-octylphenol, 4,4'-sec-butylidenediphenol, 4-phenylphenol, 4,4'-dihydroxy-
Diphenylmethane, 4,4'-isopropylidene diphenol, hydroquinone, 4,4'-cyclohexylidene diphenol, 4,4 '-(1,3-dimethylbutylidene) bisphenol, 4,4'-dihydroxydiphenyl sulfide, 4 4,4'-thiobis (6-tert-butyl-3-methylphenol), 4,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxy-4'-methoxydiphenylsulfone, -Hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxy-3 ', 4'-trimethylenediphenylsulfone, 4-hydroxy-3', 4'-tetramethylenediphenylsulfone, 3,4-dihydroxy-
4'-methyldiphenyl sulfone, bis (3-allyl-
4-hydroxyphenyl) sulfone, 1,3-di [2-
(4-hydroxyphenyl) -2-propyl] benzene, 1- [α-methyl-α- (4′-hydroxyphenyl) ethyl] -4- [α ′, α′-bis (4′-hydroxyphenyl) ethyl Benzene, hydroquinone monobenzyl ether, bis (4-hydroxyphenyl) acetic acid butyl ester, 4-hydroxybenzophenone, 2,4
-Dihydroxybenzophenone, 2,4,4'-trihydroxybenzophenone, 2,2'-4,4'-tetrahydroxybenzophenone, dimethyl 4-hydroxyphthalate,
-Methyl hydroxybenzoate, ethyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, sec-butyl 4-hydroxybenzoate, pentyl 4-hydroxybenzoate, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate , 4-Hydroxybenzoic acid tolyl, 4-hydroxybenzoic acid chlorophenyl, 4-hydroxybenzoic acid phenylpropyl, 4-hydroxybenzoic acid phenethyl, 4-hydroxybenzoic acid-p-chlorobenzyl, 4-hydroxybenzoic acid-p-methoxy Benzylic compounds, phenolic compounds such as novolak type phenolic resins and phenolic polymers, 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-tert-butylsalicylic acid, 3,5-di-t
ert-butylsalicylic acid, 3-benzylsalicylic acid, 3
-(Α-methylbenzyl) salicylic acid, 3-chloro-5
-(Α-methylbenzyl) salicylic acid, 3-phenyl-
5- (α, α-dimethylbenzyl) salicylic acid, 3,5-
Aromatic carboxylic acids such as di-α-methylbenzylsalicylic acid, and phenolic compounds, salts of aromatic carboxylic acids with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel and the like. Organic acidic substances and the like. Of course, two or more of these colorants can be used as needed.

Among them, 4.4'-isopropylidene diphenol, 4,
4 '-(1,3-dimethylbutylidene) bisphenol, 4
-Hydroxy-4'-isopropoxydiphenylsulfone and the like are preferably used because they do not cause background fog on the obtained recording medium.

In the present invention, the total weight of the basic dye and the colorant (that is, the color-forming material) contained in the intermediate layer is 1% of the total solid content of the intermediate layer.
~ 40% by weight, and the weight ratio of the dye to the color former is 1:
1-1 to 1:50 is preferred. If the amount of the coloring material is small, it is difficult to obtain sufficient print pixel reproducibility, and if the amount is large, the thermal head tends to accumulate.

In general, a binder described below in relation to the heat-sensitive recording layer is added to the coating liquid for the intermediate layer in an amount of about 1 to 30% by weight based on the total solids of the intermediate layer.

Preparation of the coating liquid for the intermediate layer is generally performed using water as a dispersion medium,
The stirring is performed by a ball mill, an outwriter, a sand mill, or the like, and a pigment, a basic dye, a color former, and the like are dispersed together or separately by a pulverizer.

The dry coating amount of the intermediate layer is usually 5 to 40 g / m ² .

It is also possible to provide a multi-layered intermediate layer in order to further increase the oil absorption of the intermediate layer and reduce the residue of the thermal head, or to further improve the recording density by increasing the heat insulating effect. When the intermediate layer has a multilayer structure, a first intermediate layer having no color-forming material may be provided on the support, and then a second intermediate layer having the color-forming material described above may be provided.

The heat-sensitive recording layer of the present invention is manufactured by coating and drying the heat-sensitive recording layer on the intermediate layer thus formed. The combination of the color former and the color former to be contained in the heat-sensitive recording layer is not particularly limited, and any combination may be used as long as the two are brought into contact by heat to cause a color reaction. Examples thereof include a combination of a colorless or light-colored basic dye and an inorganic or organic acidic substance, and a combination of a metal salt of a higher fatty acid such as ferric stearate and a phenol such as gallic acid. Further, a diazonium compound,
The present invention can be applied to various kinds of heat-sensitive recording media in which a recorded image is obtained by heat, such as a heat-sensitive recording layer in which a coupler and a basic substance are combined.

However, the recording medium of the present invention exerts an excellent effect particularly in the combination of a colorless or light-colored basic dye and an acidic substance as a color former, and is therefore preferably applied particularly to such a combination.

Various types of colorless to light-colored basic dyes are known and can be selected from those described above in the description of the intermediate layer.

Various inorganic or organic colorants which are colored upon contact with a colorless or light-colored basic dye are known, and can be selected from the above-described colorants as components of the intermediate layer.

In the present invention, the use ratio of the color former and the color former in the recording layer is appropriately selected depending on the type of the color former and the color former to be used, and is not particularly limited. And when using an acidic substance as a colorant, generally 1 to 50 parts by weight per 1 part by weight of the basic dye,
Preferably 1 to 10 parts by weight of acidic substance is used.

The preparation of a coating solution for a heat-sensitive recording layer containing these substances is generally performed by dispersing a color former and a color former together or separately with a stirring device such as a ball mill, an attritor, and a sand mill, and a pulverizer using water as a dispersion medium. This is done by:

In such a coating solution, usually as a binder starches, hydroxyethylcellulose, methylcellulose,
Carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, diisobutylene
Maleic anhydride copolymer salt, styrene / maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, natural rubber emulsion, styrene / butadiene copolymer emulsion, acrylonitrile Butadiene copolymer emulsion, methyl methacrylate butadiene copolymer emulsion, polychloroprene emulsion, vinyl acetate emulsion,
Ethylene vinyl acetate emulsion etc.
To 70% by weight, preferably about 15 to 50% by weight.

Further, various auxiliaries can be added to the coating solution for the heat-sensitive recording layer, for example, sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcoholate, sodium alginate, metal salt of fatty acid, and the like. Dispersants such as benzophenone,
Examples thereof include a triazole-based ultraviolet absorber, an antifoaming agent thereof, a fluorescent dye, and a coloring dye.

Also, if necessary, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate,
Inorganic pigments such as zinc sulfate, talc, kaolin, clay, calcined clay, colloidal silica, styrene microballs, nylon powder, polyethylene powder, urea
Organic pigments such as formalin resin filler, raw starch, fatty acid amides such as stearic acid amide, methylene bisamide stearate, oleic acid amide, palmitic acid amide, coconut fatty acid amide, dibenzyl terephthalate, 1,2
-Di (3-methylphenoxy) ethane, 1,2-diphenoxyethane, 4,4'-ethylenedioxy-bis-benzoic acid diphenylmethyl ester, 1,1,3-tris (2-methyl-4-hydroxy -5-tert-butylphenyl) butane, 2,2'-methylenebis (4-methyl-6-tert-
Butylphenol), 4,4'-butylidenebis (6-
Hindered phenols such as tert-butyl-3-methylphenol) and various known heat-fusible substances can also be added.

When an inorganic or organic pigment is contained in the heat-sensitive recording layer, it is preferable to use a pigment having as small a particle size as possible, and particularly to use a pigment having an average particle size of 2 μm or less.

The coating amount of the heat-sensitive recording coating liquid is not particularly limited, either.
Usually dry weight 2~12g / m ^2, preferably in the range of about 3 to 10 g / m ^2.

The method for forming the intermediate layer and the heat-sensitive recording layer is not particularly limited. For example, each coating liquid is coated on the support or the intermediate layer by a coating apparatus having an appropriate coater head such as an air knife coater or a blade coater. ,
It is formed by a method of drying.

Support materials include high-quality paper, base paper made with a Yankee machine, single-side glossy base paper, double-sided glossy base paper, cast-coated paper, art paper, coated paper, medium-coated paper, etc., synthetic fiber paper, synthetic resin film Etc. are used as appropriate.

After the application and drying of the intermediate layer and the recording layer, a smoothing treatment such as super calendering can be performed as necessary. Further, it is possible to provide an overcoat layer on the recording layer for the purpose of protecting the recording layer and the like, and various known techniques in the heat-sensitive recording material field such as providing a backing layer on the support can be added. .

The thus obtained thermosensitive recording medium of the present invention has an intermediate layer having a specific composition provided between the support and the thermosensitive recording layer, so that the pixel reproducibility can be improved in any region from low density to high density. Excellent thermal recording medium with high recording density.

"Examples" Examples are shown below to explain the present invention more specifically, but of course the present invention is not limited thereto. Unless otherwise specified, parts and% in the examples are parts by weight and% by weight, respectively.

Example 1 Preparation of Intermediate Layer Coating Solution Preparation of Solution A 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-phenylaminofluoran 10 parts Methylcellulose 5% aqueous solution 15 parts Water 50 parts The composition was pulverized with a sand mill until the average particle size became 2 μm.

Preparation of Solution B 4,4'-isopropylidene diphenol 30 parts Methyl cellulose 5% aqueous solution 30 parts Water 80 parts This composition was pulverized with a sand mill until the average particle diameter became 2 μm.

[Intermediate layer coating liquid-1] Calcined clay (apparent specific gravity 0.22 g / cm ³ ) 100 parts SBR (glass transition point -20 ° C, solid content: 50%) 20 parts 10% aqueous solution of polyvinyl alcohol 20 parts A liquid 60 parts Solution B 100 parts Water 50 parts The above composition was mixed to prepare Intermediate Layer Coating Solution-1.

(Formation of intermediate layer)

The coating amount after drying fine paper obtained weighed intermediate layer coating liquid -1 50 g / m ² to form an intermediate layer by coating and drying so that 10 g / m ^2.

(Preparation of recording layer coating liquid)

125 parts of liquid A, 130 parts of liquid B, 30 parts of silicon oxide, 150 parts of a 20% starch oxide aqueous solution and 55 parts of water were stirred and mixed to prepare a coating liquid for a recording layer.

(Formation of recording layer)

The obtained coating liquid for a recording layer was applied and dried on the intermediate layer so that the coating amount after drying was 5 g / m ^2, and a super calender treatment was performed to obtain a thermosensitive recording medium.

Example 2 [Intermediate layer coating liquid-2] Amorphous silica (apparent specific gravity 0.18 g / cm ² ) 100 parts SBR (glass transition point -20 ° C, solid content: 50%) 20 parts 10% aqueous solution of polyvinyl alcohol 20 parts Solution A 10 parts Solution B 10 parts Water 50 parts The above composition was mixed to prepare an intermediate layer coating liquid-2.

A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the intermediate layer coating liquid-2 was used instead of the intermediate layer coating liquid-1.

Example 3 Preparation of Solution C 3-Dibutylamino-6-methyl-7-phenylaminofluoran 10 parts Methylcellulose 5% aqueous solution 15 parts Water 50 parts The above composition was pulverized with a sand mill until the average particle size became 2 μm.

Preparation of Liquid D 4-hydroxy-4'-isopropoxydiphenylsulfone 30 parts Methylcellulose 5% aqueous solution 30 parts Water 80 parts This composition was pulverized with a sand mill until the average particle size became 2 μm.

[Intermediate layer coating liquid-3] Calcined clay (apparent specific gravity 0.22 g / cm ³ ) 100 parts SBR (glass transition point -20 ° C, solid content: 50%) 20 parts 10% aqueous solution of polyvinyl alcohol 20 parts C liquid 60 parts Solution D 100 parts Water 50 parts The above composition was mixed to prepare Intermediate Layer Coating Solution-3.

A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the intermediate layer coating liquid-3 was used instead of the intermediate layer coating liquid-1.

Example 4 [Preparation of Intermediate Layer Coating Solution-4] Calcined clay (apparent specific gravity 0.22 g / cm ³ ) 100 parts SBR (glass transition point −20 ° C., solid content: 50%) 20 parts 10% aqueous solution of polyvinyl alcohol 20 Part 50 parts of water The above composition was mixed to prepare Intermediate Layer Coating Liquid-4.

(Formation of intermediate layer)

The resulting coating weight after drying of the intermediate layer coating liquid -4 fine paper weighing 50 g / m ² was formed first intermediate layer was applied and dried so that 10 g / m ^2. On the first intermediate layer, an intermediate layer coating solution-1
Coating and drying were performed so that the amount of the dried coating layer was 5 g / m ² to obtain a multilayer intermediate layer.

A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the above-mentioned intermediate layer was used.

Comparative Example 1 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the intermediate layer coating liquid-4 was used instead of the intermediate layer coating liquid-1.

Comparative Example 2 A thermosensitive recording medium was obtained in the same manner as in Example 4, except that the intermediate layer coating liquid-4 was used instead of the intermediate layer coating liquid-1.

Comparative Example 3 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 60 parts of the liquid A was not added to the coating liquid for intermediate layer 1 of Example 1.

Each thermal recording medium obtained in this way is transferred to a thermal printer (SONY
Using a UP-701 type video printer, recording was performed with a print pulse time of 3 ms and 8 ms, and the color density was measured with a Macbeth densitometer (RD-100R, using an amber filter). It is shown in the table. In addition, the reproducibility of the printing pixels was evaluated, and the results are shown in Table 1.

The reproducibility of the print pixels was evaluated by the ratio of the area of the print dots to the area of one dot of the thermal head (dot reproducibility), and the evaluation criteria were as follows.

◎: 86% or more ○: 76 to 85% △: 70 to 75% ×: 74% or less A4 size recording chart (printing ratio) using a facsimile (NEFAX-27, NEC) (50%) was recorded, and the state of the lees adhering to the thermal head was observed by visual observation.

Head residue evaluation…: No head residue is observed.

…: Head residue can be slightly confirmed.

Δ: Head meal can be confirmed.

"Effects" As is clear from the results in Table 1, the thermosensitive recording medium of the present invention has excellent print pixel reproducibility and high recording density in any region from low density to high density. It was a record.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-98582 (JP, A) JP-A-57-189879 (JP, A) JP-A-60-234881 (JP, A) JP-A 61-9881 182983 (JP, A) JP-A-61-11286 (JP, A) JP-A-59-57786 (JP, A) JP-B-49-27708 (JP, B1) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41M 5/28-5/34

Claims (1)

(57) [Claims] An intermediate layer containing a pigment having an apparent specific gravity of 0.3 g / cm ³ or less, a colorless or light-colored basic dye and a colorant capable of forming a color upon contact with the dye is provided on a support. Further, a heat-sensitive recording layer is provided on the intermediate layer, and the apparent specific gravity of the intermediate layer is 0.
A heat-sensitive recording material containing a pigment of ³ g / cm ³ or less based on the total solid content of the intermediate layer in an amount of 50 to 90% by weight.