JP2762860B2 - Manufacturing method of thermal recording material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a heat-sensitive recording material, and more particularly, to a method for producing a heat-sensitive recording material having high sensitivity and excellent storage stability of recorded images. .

[0002]

2. Description of the Related Art A thermosensitive recording system is highly evaluated for its advantages such as the ability to obtain a color image simply by heating and the fact that a recording apparatus can be relatively easily made compact.
It is widely used as various information recording systems such as facsimile, printer and word processor. In particular, in recent years, facsimile printers using such a thermal recording system have been improved, and high-speed recording, which has been conventionally difficult, has become possible. With the speeding up of such devices,
Further improvement in recording sensitivity is required for the heat-sensitive recording material used therein, and materials having excellent thermal responsiveness have been provided one after another by recent development of high sensitivity technology.

A heat-sensitive recording material used in such a heat-sensitive recording method is generally prepared by contacting a colorless or pale-colored basic dye with a basic dye on a sheet-like support such as paper, synthetic paper, or plastic film. A thermosensitive coloring layer containing a coloring material such as a phenolic compound and a bonding agent as main components. Images can be obtained.

However, conventionally, this type of heat-sensitive recording material has a drawback in storage stability in both a colored portion and a non-colored portion. That is, when an oil or a plasticizer comes into contact with the surface of the heat-sensitive coloring layer, the color-developed portion is discolored, or the uncolored portion is not colored.
For example, if a plastic eraser is left on the surface of the heat-sensitive coloring layer for a long time or is brought into contact with a PVC film for a long time, the plasticizer contained therein migrates and the color-developed image disappears. There are also disadvantages such as decoloring by fingerprints, coloring and decoloring by fluorescent pens. The uncolored portion develops color when an organic solvent such as alcohol, toluene, or ethyl acetate is dropped by mistake or is exposed to the vapor of the organic solvent, and cannot be distinguished from a recorded image. Further, there is also a disadvantage that when the surface is lightly scratched with a nail, dirt (scratch dirt) occurs.

As one of the means for solving such a problem of the conventional heat-sensitive recording material, there is a laser facsimile using a heat fixing method of toner using plain paper as a recording medium. However, they have the major drawbacks that they require a large, expensive, high-output power source, require maintenance and require regular maintenance.

In order to solve these problems while taking advantage of the heat-sensitive recording material, many proposals have been made to provide a protective layer on the surface of the heat-sensitive coloring layer. (JP-A-48-516
No. 44, JP-A-54-128347, JP-A-56-126193
JP, JP-A-58-058434, JP-A-59-232893, JP-A-60-99696, JP-A-60-31996,
JP-A 1-230681, etc.)

The purpose of providing such a protective layer is to prevent various chemical substances from penetrating into the thermosensitive coloring layer, that is, to provide a barrier property. It is effective and has a great effect on scratch dirt. However, when a protective layer is provided on the thermosensitive coloring layer, the transfer of heat from the thermal head during printing is hindered, and there is a disadvantage that the sensitivity is significantly reduced. In particular, in a heat-sensitive recording material requiring high sensitivity such as a facsimile machine, the decrease in sensitivity due to the protective layer has been a serious problem. In this case, if the amount of the protective layer applied is reduced, the reduction in sensitivity can be suppressed, but there is a limit in terms of barrier properties.

[0008]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems in the heat-sensitive recording material and to provide a method for producing a heat-sensitive recording material having high sensitivity and excellent storage stability of recorded images. Is what you do.

[0009]

Means for Solving the Problems The present inventors have repeatedly studied a method for forming a protective layer on a thermosensitive coloring layer.
It has been found that the barrier property of the formed layer is greatly affected by the solid content concentration of the protective layer coating solution when the protective layer is applied. That is, the higher the solid content concentration of the coating liquid for the protective layer at the time of coating, the higher the barrier property of the formed protective layer. The reason for this is that when the solid content concentration of the coating solution is high, the penetration and migration of the coating solution into the lower thermosensitive coloring layer during coating and drying are reduced as compared with the case where the solid content is low. It is considered that the generation of holes is suppressed and the coating film becomes denser. As described above, a protective layer having a high barrier property can be obtained by increasing the concentration of the protective layer coating solution, but conventional methods such as an air knife method, a gravure method, a roll coater method, a bar coater method, a spray method, a dip method, and an extrusion method are used. In the coating method used for coating the protective layer, there is a limit in increasing the concentration of the coating liquid.

[0010] On the other hand, there are a tip blade method and a rod blade method as coating methods capable of coating at a high concentration.
These methods have the advantage that a very uniform and highly smooth coated surface can be obtained, but at the same time, streaks and scratches are liable to occur due to foreign substances and dust mixed in the coating liquid. Therefore, these methods have not been conventionally used for coating the protective layer. As a solution to this problem, a method of removing foreign matter using a screen is also effective, but in addition, the present inventors have found that the rod blade method can improve very effectively by increasing the rotation speed of the rod. Was further found. That is, the rod is usually rotated in the reverse direction with respect to the coating direction, but its peripheral speed is 1/200 to the coating speed.
Streak frequently occurs at a low speed of 400, but the frequency of occurrence decreases as the rotation speed increases,
When the coating speed is 1/100 or more, no problem occurs. As a result, coating can be performed without generating streaks or scratches.

According to the present invention, a thermosensitive coloring layer containing at least one basic dye and a color developer capable of forming a color in contact with the basic dye is provided on a support, and a thermosensitive coloring layer is formed thereon by a coating method. In the method for producing a thermosensitive recording material provided with a protective layer, the method for coating the protective layer is such that a high-concentration protective layer coating solution is applied from a jet fountain onto the thermosensitive coloring layer, and then coated with a rod blade. A method in which the rotation speed is 1/100 or more of the coating speed in the direction opposite to the coating direction in the direction opposite to the coating direction.

In the present invention, the coating liquid used for coating the protective layer has a solid content of 10 to 25% by weight. If the solid content concentration is 10% by weight or less, the coating liquid is soaked or migrated into the heat-sensitive coloring layer before the coating film is dried, and if it is 25% by weight or more, the fluidity of the coating liquid is poor. In addition, it is not preferable because not only is it difficult to apply, but also the coating amount increases and the sensitivity decreases due to the protective layer.

In the rod blade method employed in the present invention, the rod is rotated in a direction reverse to the coating direction at a rotational peripheral speed of 1/100 or more with respect to the coating speed. It is important that the peripheral speed of the rod is 1/100 or more with respect to the coating speed. Usually, the rod speed is 1/100 to 1/10, but preferably 1/25 to 1/100. When the peripheral speed of the rod is 1/10 or more, not only is there no further improvement effect, but also the coated surface is undesirably roughened.

According to the coating method of the present invention, not only can a protective layer having excellent uniformity and high barrier properties be formed on the thermosensitive coloring layer, but also the coating amount of the protective layer can be greatly reduced. This makes it possible to suppress a decrease in sensitivity due to the protective layer. In addition, the adoption of the rod blade method enables high-speed coating as compared with other coating methods, and has the advantage of improving productivity. As described above, according to the method of the present invention,
While having excellent storage stability, it is possible to obtain a high sensitivity which cannot be obtained with a conventional thermosensitive recording material provided with a protective layer.

As the basic dye constituting the thermosensitive coloring layer of the present invention, known colorless or light-colored basic dyes can be used, and specific examples thereof are as follows. (1) As a triallylmethane compound, for example, 3,3
-Bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) phthalide, and the like. (2) As the diphenylmethane compound, for example,
4'-bis-dimethylaminobenzhydryl benzyl ether, N-2,4,5-trichlorophenyl leuco auramine, N-halophenyl-leuco auramine and the like.

(3) As xanthene compounds, for example, rhodamine B-anilinolactam, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino-7-butylaminofluoran, 3-diethylamino-7- (2 -Chloroanilino) fluoran, 3-piperidino-6-methyl-7-anilinofluoran, 3-ethyl-tolylamino-6-methyl-7-anilinofluoran, 3-cyclohexyl-methylamino-6-methyl-
7-anilinofluoran, 3-diethylamino-6-chloro-7- (β-ethoxyethyl) aminofluoran,
3-diethylamino-6-chloro-7- (γ-chloropropyl) aminofluoran, 3-dibutylamino-6
Methyl-7-anilinofluoran, 3- (N-isoamyl-N-ethylamino) -6-methyl-7-anilinofluoran, 3-ethyl-isoamylamino-6-methyl-7-anilinofluoran , 3-dibutylamino-7-
Chloroanilinofluoran and the like. These dye precursors can be used alone or in combination of two or more, and are appropriately selected and used depending on the use of the heat-sensitive recording material and desired properties.

Further, phenol derivatives, aromatic carboxylic acid derivatives, acid clay, novolak resins, metal complexes and the like are used as a color developer as a component of the thermosensitive coloring layer. Specific examples of some of these include p-octylphenol and p-tert as phenol derivatives.
-Butylphenol, p-phenylphenol, 2,2
-Bis (p-hydroxyphenyl) propane, 1,1-
Bis (p-hydroxyphenyl) propane, 2,2-bis (p-hydroxyphenyl) pentane, 1,1-bis (p-hydroxyphenyl) hexane, 2,2-bis (p-hydroxyphenyl) hexane, 1-bis (p-hydroxyphenyl) -2-ethylhexane,
2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, dihydroxydiphenyl ether,
4,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-isopropyloxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, and the like.

The aromatic carboxylic acid derivatives include p
-Hydroxybenzoic acid, butyl p-hydroxybenzoate, 3,5-di-tert-butylsalicylic acid, 3,5
-Di-α-methylbenzylsalicylic acid, and polyvalent metal salts of the above carboxylic acids. Of these, bisphenols are particularly preferred.

The mixing ratio of the basic dye and the developer is not necessarily limited, and is adjusted according to the material used. In general, 1 to 1 part by weight of the basic dye is used.
0 parts by weight, preferably 1.5 to 5 parts by weight of developer are used.

In the present invention, a sensitizer can be used to improve the sensitivity of the heat-sensitive recording material. Examples of the sensitizer include thermally fusible substances such as aromatic ethers, esters and / or fatty acid amides, and specifically, stearic acid amide, ethylenebisstearic acid amide, methylolbehenic acid amide, oleic acid amide, Fatty acid amides such as palmitic acid amide, p-benzylbiphenyl, dibenzyl terephthalate, phenyl 1-hydroxy-2-naphthoate, dibenzyl oxalate, di-p-chlorobenzyl oxalate, di-p-methylbenzyl oxalate, adipine Examples thereof include di-o-chlorobenzyl acid, 1,2-di (3-methylphenoxy) ethane, and 1,2-bis (3,4-dimethylphenyl) ethane.

These basic dyes, developers and sensitizers are generally prepared by using water as a dispersing medium, and using various wet pulverizers such as a ball mill, a co-ball mill, an attritor, a vertical or horizontal sand mill, and the like. After being dispersed together with a water-soluble synthetic polymer compound such as polyvinylpyrrolidone, polyvinyl alcohol, methylcellulose, and a styrene-maleic anhydride copolymer salt, and other surfactants, the dispersion is used to prepare a thermosensitive coloring coating.
The sensitizer may be dispersed together with one or both of the basic dye and the developer, or may be dispersed after preparing a eutectic in some cases.

In the present invention, various known coloring layer forming materials are used in the thermosensitive coloring layer. As the binder, water-soluble binders are generally used, and polyvinyl alcohol, polyamide, styrene-acrylic acid copolymer salt, styrene-maleic anhydride copolymer salt, ethylene-maleic anhydride copolymer salt, diisobutylene- Water-soluble synthetic high-molecular compounds such as maleic anhydride copolymer salts, and water-soluble natural high-molecular compounds or derivatives thereof such as methylcellulose, other cellulose derivatives, starch, starch derivatives, gelatin, and casein. . Also, to add a water resistance imparting agent for the purpose of imparting water resistance to these binders,
A synthetic polymer emulsion, specifically, an SBR latex, an acrylic resin emulsion, or the like can be added.

Other materials constituting the heat-sensitive coloring layer include inorganic or organic pigments, waxes, metal soaps and the like. Inorganic pigments include calcium carbonate, kaolin, calcined kaolin, talc, fluorite, diatomaceous earth, aluminum oxide, aluminum hydroxide, magnesium hydroxide, magnesia, titanium dioxide, barium carbonate, barium sulfate, finely divided silicate, calcium silicate, and aluminum silicate And organic pigments such as urea, phenol, epoxy, styrene, nylon, polyethylene, melamine, and benzoguanamine resin. Examples of the wax include paraffin wax, carnauba wax, microcrystalline wax, polyethylene wax, higher fatty acid ester wax and the like. Examples of the metal soap include higher fatty acid polyvalent metal salts, such as zinc stearate, aluminum stearate, calcium stearate, and zinc oleate.

Further, if necessary, a surfactant, an antistatic agent, an ultraviolet absorber, a preservability improver, a fluorescent dye, a coloring dye, and the like may be added. In particular, it is desirable to add a storability improver in order to prevent decoloration of a recorded image. Examples of the preservability improver include 1,3,5-tris (4-tert
-Butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-tris ( 2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1-bis (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 4,4 ′-(1-phenylethylidene)
Bisphenol, 4,4 ′-[1,4-phenylenebis (1-methylethylidene)] bisphenol, 4,4 ′
Phenolic compounds such as-[1,3-phenylenebis (1-methylethylidene)] bisphenol and 4- (2-methyl-1,2-epoxyethyl) diphenylsulfone; -Epoxyethyl) diphenylsulfone, 4- (2-methyl-glycidyl) diphenylsulfone, 4- (2-ethyl-glycidyl) diphenylsulfone, 4- (2-butyl-glycidyl) diphenylsulfone, 4- (3-methyl- 3,4
-Epoxybutyl) diphenylsulfone, 4- (2-methyl-3,4-epoxybutyl) diphenylsulfone,
4- (2-methyl-2,3-epoxybutyl) diphenylsulfone, 4- (2-methyl-1,2-epoxyethyloxy) diphenylsulfone, 4- (2-methyl-
2,3-epoxybutyloxy) diphenyl sulfone,
4- (2-methyl-1,2-glycidyloxy) diphenyl sulfone, 4- (2-methyl-glycidyloxy)
-4'-chlorodiphenylsulfone, 4- (2-methyl-glycidyloxy) -4'-bromodiphenylsulfone, 4- (2-methyl-glycidyloxy) -4'-methyldiphenylsulfone, 4- (2-methyl -Glycidyloxy) -2 ', 4'-dimethyldiphenylsulfone, 4- (2-methyl-glycidyloxy) -2',
4'-dichlorodiphenylsulfone, 4- (2-methyl-glycidyloxymethoxy) diphenylsulfone,
And diphenylsulfone derivatives such as-(2-methyl-glycidyloxy) -4 '-(p-methoxybenzyloxy) diphenylsulfone.

After each of these materials is mixed, it is applied to a support. The support is not particularly limited, and papers such as high quality paper, medium quality paper, matte paper, coated paper, art paper, cast coated paper, synthetic paper, synthetic fiber paper,
A synthetic resin film and a laminate thereof are appropriately selected and used.

The thermosensitive coloring layer is formed on the undercoat layer by a known coating method such as an air knife method, a blade method, a gravure method, a roll coater method, a spray method, a dipping method, a bar method, and an extrusion method. It is formed by coating and drying, but it is preferable to adopt a coating method capable of forming a coating layer having good surface properties such as a blade. Even if the simultaneous multi-layer coating with the protective layer described later,
You may apply | coat sequentially. After the formation of the heat-sensitive coloring layer, if necessary, a surface smoothing treatment such as super calendaring can be performed. Further, the amount of the thermosensitive coloring layer to be applied is not particularly limited, and is usually 1 to 1 in terms of dry weight.
It is adjusted in the range of 12 g / m ² , preferably in the range of ^{3 to} 8 g / m ² .

In the present invention, the protective layer provided on the heat-sensitive color-forming layer contains a water-soluble polymer and a pigment as main components, and may use a crosslinking agent, wax, metal soap and the like as needed. As the water-soluble polymer, those having high resistance to oil and plasticizer, good film-forming properties, and strong coating film strength are desirable. Specific examples of such a water-soluble polymer include polyvinyl alcohol, carboxy-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, alkyl-modified polyvinyl alcohol, styrene-maleic anhydride copolymer salt, isobutylene-maleic anhydride copolymer salt. Styrene-acrylic acid copolymer salt, polyacrylamide, starch, chitosan, casein, gelatin, methylcellulose, carboxymethylcellulose, hydroxyethylcellulose and the like. In order to impart water resistance to these water-soluble polymers, a crosslinking agent such as melamine, epoxy, aziridine, glyoxal, dimethylol urea, polyaldehyde, and zirconium salt can be used in combination.

Examples of pigments include calcium carbonate, aluminum hydroxide, clay, talc, fluorite, diatomaceous earth, aluminum silicate, calcium silicate, finely divided silica, magnesium carbonate, magnesium hydroxide, magnesium oxide, barium carbonate, Examples include inorganic pigments such as barium sulfate, zinc oxide, titanium dioxide, aluminum oxide, and calcined clay, and organic pigments such as starch particles, urea, melamine, phenol, benzoguanamine, epoxy, polystyrene, polyethylene, nylon, and silicone resin.

Examples of waxes and metal soaps include paraffin wax, polyethylene wax, carnauba wax, microcrystalline wax, fatty acid amides such as stearic acid amide, oleic acid amide, erucic acid amide, behenic acid amide, and stearic acid. And higher fatty acid metal salts such as zinc, calcium stearate, aluminum stearate, and zinc behenate. In addition, various additives such as an oil repellent, an antifoaming agent, a viscosity modifier, a surfactant, and a fluorescent dye may be added as long as the effects of the present invention are not impaired.

After forming the protective layer on the thermosensitive coloring layer, it can be post-processed by a known technique, and can be subjected to a calendering treatment for improving sensitivity and image quality, and can prevent penetration of oil and plasticizer from the back surface. A back layer may be provided on the surface opposite to the surface on which the recording layer is formed for suppressing or curling. Also,
Various modifications, such as providing an undercoat layer below the thermosensitive coloring layer as needed, can be used at all.

[0031]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto. Parts and% in Examples are parts by weight and% by weight, respectively.

Example 1 Formation of thermosensitive coloring layer (1) Preparation of basic dye dispersion 20 parts of 3- (n-ethyl-n-isoamylamino) -6-methyl-7-anilinofluoran polyvinyl alcohol 10% solution 10 parts water 40 parts This composition was mixed with a vertical sand mill (manufactured by Imex Co., Ltd.)
(Sand grinder) until the average particle diameter became 0.5 μm. (2) Preparation of developer dispersion 4-hydroxy-4-isopropoxydiphenylsulfone 10 parts p-benzylbiphenyl 10 parts Polyvinyl alcohol 10% solution 10 parts water 40 parts This composition was prepared as the dye precursor dispersion. It grind | pulverized by the same method as the method until the average particle diameter became 1.5 micrometers. (3) Preparation of thermosensitive coloring layer coating solution 40 parts of the above-mentioned dye precursor dispersion and developer 16
0 parts, 60 parts of calcium carbonate, 60 parts of 10% aqueous solution of polyvinyl alcohol, 50% of SBR latex 25
, 10 parts of a 30% zinc stearate dispersion and 50 parts of water were mixed and stirred to prepare a thermosensitive coloring layer coating solution. The coating amount after drying of this coating solution on the felt side of the paper support was 5.0 g /
It was coated and dried with a blade coater so as to obtain m ² to form a thermosensitive coloring layer.

Formation of protective layer 50 parts of polyvinyl alcohol (PVA117, manufactured by Kuraray Co., Ltd.) 35 parts of kaolinite clay (UW-90, manufactured by EMC) 5 parts of glyoxal 10 parts of zinc stearate emulsion 10 parts (manufactured by Chukyo Yushi Co., Ltd.) , Hydrin Z-7) The above composition was blended at the above solid content ratio, and the solid content concentration was 20.
% Of a protective layer coating solution was prepared. This coating solution was applied onto the previously formed thermosensitive coloring layer by a rod blade method to a rod diameter of 10 m.
mφ, rod rotation speed 210 rpm (reverse rotation), coating speed 600 m / min (rod peripheral speed / coating speed = 1 /
In 91), application and drying were performed so that the application amount after drying was 1.0 g / m ² . Thereafter, a smoothing treatment was performed using a super calender to obtain a heat-sensitive recording material.

[0033]

Example 2 Thermal recording was performed in the same manner as in Example 1 except that the rotation speed of the rod was changed to 700 rpm (rod peripheral speed / coating speed = 1/27) in the method of coating the protective layer of Example 1. The material was obtained.

[0034]

Example 3 A heat-sensitive recording material was obtained in the same manner as in Example 1, except that water was added to the coating liquid for the protective layer prepared in the same manner as in Example 1 to dilute the solid content to 12%, and then applied. .

[0035]

Comparative Example 1 Thermal recording was performed in the same manner as in Example 1 except that the rotation speed of the rod was changed to 160 rpm (rod peripheral speed / coating speed = 1/119) in the coating method of the protective layer of Example 1. The material was obtained.

[0036]

Comparative Example 2 In the method for coating a protective layer in Example 1, the rotation speed of the rod was 1200 rpm, and the coating speed was 300 m.
/ Min (rod peripheral speed / coating speed = 1/8)
A heat-sensitive recording material was obtained in the same manner as in Example 1 except for the above.

[0037]

Comparative Example 3 A heat-sensitive recording material was obtained in the same manner as in Example 1, except that water was added to the protective layer coating solution prepared in the same manner as in Example 1 to dilute the solid content to 8%, and then applied. .

[0038]

Comparative Example 4 In the method for coating a protective layer in Example 1, the rotational speed of the rod was changed to 70 rpm (rod peripheral speed /
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the coating speed was 1/273).

[0039]

Comparative Example 5 A heat-sensitive recording material was obtained in the same manner as in Example 1, except that the coating was performed by the tip blade method instead of the rod blade method.

[0040]

Comparative Example 6 Water was added to a protective layer coating solution prepared in the same manner as in Example 1 to obtain a protective layer coating solution having a solid content of 8%.
This coating liquid is applied at a coating speed of 200 m / m by an air knife method.
The coating was dried on the same thermosensitive coloring layer as in Example 1 so that the coating amount after drying was 1.0 g / m ^{2 under the} conditions of “in”. Thereafter, the same smoothing treatment as in Example 1 was performed to obtain a thermosensitive recording material.

[0041]

Comparative Example 7 A thermosensitive recording material was prepared in the same manner as in Comparative Example 3, except that the amount of the protective layer after drying was changed to 3.0 g / m ² in the coating of the protective layer in Comparative Example 5. Obtained.

[0042]

Comparative Example 8 A heat-sensitive recording material was obtained in the same manner as in Comparative Example 3 except that the coating of the protective layer in Comparative Example 3 was performed by a bar coater method at a coating speed of 150 m / min.

The heat-sensitive recording material thus obtained was evaluated for recording sensitivity and PVC film resistance. The measurement of the recording sensitivity was performed by Matsushita Electric Transmission Co., Ltd. high-speed facsimile: UF-
Printing and recording were performed using a standard chart No. 2 of the Institute of Image Electronics Engineers of Japan using a 60 machine, and the color density at that time was measured using a Macbeth densitometer RD-9.
The measurement was performed at 14 to obtain a value representative of the recording sensitivity of the recording material. The PVC film resistance was measured by applying a PVC film (Hywrap K, manufactured by Mitsui Toatsu Co., Ltd.) on the surface of the recorded material obtained by measuring the recording sensitivity.
MA) was adhered and allowed to stand at 25 ° C. for one week, and then expressed by the residual ratio of the post-treatment concentration that withstands the original concentration. Table 1 shows the results.

[0044]

【table】

[0045]

According to the method of the present invention, the recording sensitivity is high,
It has become possible to produce a high-quality heat-sensitive recording material which is excellent in storage stability of a recorded image and free from scratch stains.

Claims (1)

(57) [Claims] 1. A heat-sensitive coloring layer containing at least one basic dye and a color developer which can be brought into contact with the basic dye is provided on a support, and a protective layer is formed thereon by a coating method. Wherein the coating method of the protective layer is such that the solid content concentration is 10% by weight or more and less than 25% by weight.
After applying the high concentration protective layer coating solution from the jet fountain onto the thermosensitive coloring layer and then metering with a rod blade, rotate the rod in the reverse direction to the coating direction and set the peripheral speed to the coating speed. A method for producing a heat-sensitive recording material, wherein the method is 1/100 or more and less than 1/10 .