JPH0720731B2 - Heat-sensitive recording sheet and manufacturing method thereof - Google Patents

Description

The present invention relates to a heat-sensitive recording sheet and a method for producing the same, more specifically, the color development sensitivity and the image quality are remarkably enhanced, and the storage stability and the surface of the image portion and the background portion are improved. The present invention relates to a heat-sensitive recording sheet having improved strength and a method for manufacturing the same.

(Prior Art) In general, a thermosensitive recording sheet is one in which a thermosensitive coloring layer containing a thermochromic composition as a main component is provided on a support such as paper, synthetic paper, film, and the like. A colored image can be obtained by heating with, for example. Compared to other recording methods, the thermal recording method has the advantages that recording can be obtained in a short time with a relatively simple device, that noise and environmental pollution are low, and that the cost is low. Widely used in many applications such as recorders, computer terminals, ticket vending machines, and labels. On the other hand, the thermal recording sheet also has an extremely high sensitivity due to higher speed and higher quality of equipment (for example, a G IV type facsimile is 3 seconds in A4 format /
Ultra high image quality (for example, a resolution of 16 / mm or more, and no unevenness in the density of the image area) is a necessary condition, and it is desirable that the appearance does not cause background coloration during storage or a decrease in the density of the image area. Has been done. Such a thermal recording sheet is conventionally
A thermosensitive coloring layer is formed on a support such as paper, synthetic paper or film by a conventional coating method, for example, reverse roll coater, transfer roll coater, blade coater, bar coater, air knife coater, spray coater, gravure coater, multi-layer coater, etc. It is manufactured by applying a smoothing treatment with a machine calender, a super calender or the like in order to improve the surface smoothness after coating and drying using the coating machine of No.

(Problems to be Solved by the Invention) In order to obtain a high-sensitivity and high-quality heat-sensitive recording sheet by such a manufacturing method, for example, a dye or a developer having excellent color development sensitivity is selected, Techniques such as making finer, improving surface smoothness, and increasing the ratio of components involved in color development are applied individually or in combination. However, even with such a method, a thermosensitive recording sheet having an ultrahigh sensitivity and an ultrahigh image quality cannot be obtained yet, and there is a problem that the background color is likely to be developed and the density of an image portion is lowered during storage. Therefore, various types of thermal recording sheets have been proposed, which are excellent in part or all of the required characteristics such as high sensitivity, high image quality, and storage stability. For example, an undercoat layer is provided (JP-A-59-171685,
JP-A-59-174390, JP-A-59-184693, JP-A-59-
196287, JP-A-59-204594) and a two-layer structure (JP-A-59-169886 and JP-A-59-214688) to prevent the heat-sensitive layer from penetrating the support. (JP-A-59-2028
No. 90) An overcoat layer is provided (JP-A-59-1743).
89).

However, even with the method described in such a publication, there is a problem in that a heat-sensitive recording sheet satisfying all of ultra-high sensitivity, ultra-high image quality and storage stability cannot be obtained.

(Means for Solving Problems) The inventors of the present invention have conducted diligent research to solve such problems, and as a result, as compared with the conventional thermal recording sheet, the coloring sensitivity and the image quality are remarkably excellent, and the background portion and The present invention has been completed by finding a thermal recording sheet having improved storage stability and surface strength in the image area and a method for producing the same.

That is, in order to solve the above problems, the present invention provides (1)
In a heat-sensitive recording sheet comprising a heat-sensitive layer that develops color by heating and a support (A) holding the heat-sensitive layer, the heat-sensitive layer is transferred from another support (B) to the support (A). And a heat-sensitive recording sheet comprising (2) a heat-sensitive layer that develops color by heating, and a support (A) that holds the heat-sensitive layer. The present invention provides a method for producing a heat-sensitive recording sheet, which comprises forming a layer on another support (B) in advance and then transferring the layer from the support (B) to the support (A). In the method for producing a heat-sensitive recording sheet of (2), the heat-sensitive layer coating liquid is applied onto another support (B), and the coating liquid is semi-dried to form a coating liquid layer surface and the support (A). After bonding to the surface and drying, only the support (B) is peeled off and removed, or the heat-sensitive layer coating liquid is applied onto another support (B) and dried,
Applying a substance having adhesiveness to the surface of the heat-sensitive layer and / or the surface of the support (A), joining the surface of the heat-sensitive layer and the surface of the support (A), and peeling and removing only the support (B) Is preferred.

As the support (A) used in the present invention, any flexible sheet such as paper, synthetic paper or plastic film can be used, but one having low thermal conductivity is preferable.

The support (B) used in the present invention is preferably a sheet-like, endless belt-like or roll-like one having a small dimensional change upon heating, good peelability from the heat-sensitive layer, and a smooth surface. However, a metal, a fluororesin, a silicone resin or a resin having a good releasability from the heat sensitive layer is preferably used.

Examples of the heat-sensitive layer component used in the present invention include the following combinations.

(1) A combination of a fluoran-based, triphenylmethane-based, spiropyran-based, auramine-based, phenothiazine-based leuco dye and a color developer which reacts with these to develop a color upon heating, (2) a combination of resorcin and a nitroso compound Forming an oxazine dye, or forming an azo dye, (3) forming an azo dye with a diazonium salt and a coupler, (4) a compound having a secondary alcoholic hydroxyl group and a metal inorganic salt or Containing a component in combination with metal acetates,
(5) Combination of carbohydrate and dehydrating agent, (6) Combination of long-chain fatty acid metal salt and phenolic substance, (7) Combination of organic acid heavy metal salt and alkaline earth metal sulfide, (8) Organic acid Combination of heavy metal salt and organic chelating agent, (9) Combination of heavy metal oxalate and sulfur compound, (10) Combination of fatty acid metal salt and aromatic polyhydroxy compound, (11) Organic acid noble metal salt and organic polyhydroxy compound Combination with compounds,
(12) A combination of an organic acid noble metal salt and an aromatic organic reducing agent,
(13) A combination of higher fatty acid heavy metal salt and zinc dialkyldithiocarbamate.

However, the heat-sensitive layer component used in the present invention is not limited to these combinations, and may be a texture that develops color upon heating. Hereinafter, the combination of the leuco dye and the color developer that is widely used at present will be illustrated in detail.

Specific examples of such leuco dyes include 3,3
-Bis (p-dimethylaminophenyl) phthalide, 3,3
-Bis (p-dimethylaminophenyl) -6 dimethylphthalide, 3,3-bis (p-dimethylaminophenyl)-
6-aminophthalide, 3,3-bis (p-dimethylaminophenyl) -6nitrophthalide, 3,3-bis (p-dimethylaminophenyl) -4,5,6,7-tetrachlorophthalide, 3-dimethylamino- 7-methylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-phenylaminofluorane, 3
-N-ethyl-N-pentylamino-6-methyl-7-
Phenylaminofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-phenylaminofluorane, 3-dibutylamino-7-o-chlorophenylaminofluorane, 3-diethylamino-7-o-chlorophenyl Aminofluorane, 3-N-ethyl-N-
p-tolyl-6-methyl-7-phenylaminofluorane, 3-pyrrolidino-6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-p
-N-butylphenylaminofluorane, 3-N-methyl-N-propylamino-6-methyl-7-phenylaminofluorane, 3-dibutylamino-7-o-fluorophenylaminofluorane, 3-diethylamino- 7
-Trifluoromethylphenylaminofluorane, 3-
N-ethyl-p-toluidino-7-methylphenylaminofluorane, rhodamine B lactam, 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran,
Examples thereof include 3-benzylspironaphthopyran.

Specific examples of the color developer include 4-phenylphenol, 4-hydroxyacetoquinone, 2,2'-dihydroxydiphenyl, n-butylbis (4-hydroxyphenyl) acetate, methylbis (4-hydroxyphenyl) acetate. , Iso-butylbis (4-hydroxyphenyl) acetate, 2,2'-methylenebis (4
-Chlorophenol), 2,2'-methylenebis (4-methyl-6-t-butylphenol), 4,4'-isopropylidene diphenol (also known as bisphenol A, hereinafter BP
Abbreviated as A), 4,4′-isopropylidene bis (2-chlorophenol), 4,4′-isopropylidene bis (2
-Methylphenol), 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,3-di [2- (4-
Hydroxyphenyl) -2-propyl] -benzene, 4,
4'-ethylenebis (2-methylphenol), 4,
4'-thiobis (6-t-butyl-3-methylphenol), resorcyl monobenzoate, 1,1-bis (4
-Hydroxyphenyl) -cyclohexane, 2,2'-bis (4-hydroxyphenyl) -n-heptane, 4,4 '
-Cyclohexylidenebis (2-isopropylphenol), 4,4'-dihydroxy-diphenyl sulfone, 4
-Hydroxy-4'-iso-propyloxy-diphenyl sulfone, 4,4'-dihydroxy-3,3'-diallyl diphenyl sulfone, salicylic acid anilide, novolac type phenol resin, benzoic acid, pt-butylbenzoic acid,
o-chlorobenzoic acid, p-chlorobenzoic acid, dichlorobenzoic acid, trichlorobenzoic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, p-hydroxybenzoic acid benzyl ester, o-toluic acid, m-toluic acid,
p-toluic acid, phthalic acid, isophthalic acid, terephthalic acid, gallic acid, trimellitic acid, salicylic acid, 3-ethylsalicylic acid, 4-ethylsalicylic acid, 3-phenylsalicylic acid, 5-phenylsalicylic acid, 3-hydroxysalicylic acid, 4- Examples thereof include hydroxysalicylic acid, 5-hydroxysalicylic acid, 6-hydroxysalicylic acid, dimethyl 4-hydroxyphthalate, α-naphthoic acid and β-naphthoic acid.

Examples of the binder include polyvinyl alcohol, starch, starch derivatives, cellulose derivatives such as methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, sodium polyacrylate, styrene-maleic acid copolymer, polyacrylamide, polyvinylpyrrolidone, and acrylic acid amide. / Acrylic acid ester copolymer, Acrylic acid / Acrylic acid ester / Methacrylic acid terpolymer, Isobutylene / Maleic anhydride copolymer Alkaline salt, Sodium alginate, Gelatin, Water-soluble polymer such as casein, Polyvinyl acetate , Polyurethane, styrene / butadiene copolymer, polyacrylic acid,
Examples thereof include polyacrylic acid ester, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene / vinyl acetate copolymer, and styrene / butadiene / acrylic copolymer.

Further, as the above-mentioned filler, calcium carbonate, talc,
Examples thereof include clay, kaolin, kaolinite, zinc oxide, titanium oxide, barium sulfate and the like.

Examples of the heat-fusible substance include higher fatty acids, higher fatty acid esters, higher fatty acid amides, higher fatty acid metal salts, various wax species, aromatic carboxylic acid / amine condensates, benzoic acid phenyl esters, and higher linear glycols. ,
Examples thereof include dialkyl 3,4 epoxy hexahydrophthalate and higher ketones, and among them, those having a melting point of about 50 to 200 ° C. are preferable.

In order to produce the heat-sensitive recording paper according to the present invention, first, the rocoy dye (color former), the developer, the binder and the filler, the heat-fusible substance, the surfactant and the like are dispersed in water and mixed, The heat-sensitive layer coating liquid thus obtained is applied onto the support (B) by the conventional coating method to form a heat-sensitive layer. At this time, two or more kinds of heat-sensitive layer coating liquids having different compositions, compounding ratios and the like may be laminated and coated as desired. Next, the support (A) is bonded to the surface of the heat-sensitive layer coating liquid by using a nip roll, air pressure, paper tension, etc. before the applied coating liquid becomes semi-dried and loses its fluidity. If the viscosity of the heat-sensitive layer coating liquid is too low during this bonding, the coating liquid layer will not be able to withstand the bonding pressure and will become a non-uniform layer, so the drying conditions should be adjusted so that the coating liquid viscosity or coating liquid concentration matches the bonding pressure. , It is necessary to control the coating speed. When the heat-sensitive layer is bonded to the support (A) in this way and then dried until the fluidity of the heat-sensitive layer coating liquid disappears, the adhesive force between the heat-sensitive layer and the support (A) is increased. The adhesive strength with (B) is exceeded. At this time, by peeling and removing only the support (B), a heat-sensitive recording sheet having the heat-sensitive layer transferred onto the support (A) can be obtained. In order to increase the adhesive force between the heat-sensitive layer and the support (A) in such a manufacturing method, a substance having adhesiveness to the surface of the heat-sensitive layer coating liquid and / or the surface of the support (A) is used prior to the joining. You may apply. In order to improve the releasability of the support (B) from the heat-sensitive layer, the surface of the support (B) may be previously treated with a surfactant, a silicone resin, a fluororesin or the like. In the above-mentioned manufacturing method, the case where the heat-sensitive layer coating liquid is applied on the support (B) and the heat-sensitive layer coating liquid is bonded to the support (A) when the heat-sensitive layer coating liquid is in a semi-dried state has been described. However, after drying the heat-sensitive layer coating liquid, a substance having adhesiveness is applied to the surface of the heat-sensitive layer and / or the surface of the support (A) to bond the surface of the heat-sensitive layer and the surface of the support (A). After drying, only the support (B) may be peeled off and removed. Examples of the substance having adhesiveness include a leuco dye, a color developer, a filler, and a thermosetting binder which are used in the heat-sensitive layer, alone or in a mixture with other substances, or in a range where the adhesiveness is maintained. It is used after adding a fusible substance and a surfactant. The heat-sensitive recording sheet obtained by the above production method does not require smoothing treatment with a machine calender, a super calender or the like because it has sufficiently high smoothness, but if desired, an overcoat layer and / or a backcoat layer may be further added. May be provided.

Further, the support (B) after peeling and removing can be repeatedly used.

(Action and Effect) The thermal recording sheet obtained by the present invention has excellent color development sensitivity and image quality, and the reason why the storage stability and the surface strength of the background portion and the image portion are improved is not clear.
The present inventors consider as follows. First, as a factor for improving the color development sensitivity and the image quality, the heat-sensitive layer is formed on the support (B) having high smoothness and then transferred from the support (B) to the support (A). , (1) a heat-sensitive layer having a high surface smoothness and a uniform film thickness can be obtained, and (2) the penetration of the heat-sensitive layer into the support (A) is so small that the components of the heat-sensitive layer are effectively layered. Since it is formed on the support (A), it is conceivable that a heating element such as a thermal head or a heating pen is always brought into close uniform contact with the heat-sensitive layer to improve thermal efficiency. In addition, as factors that improve the storage stability of the background portion and the image portion,
Since the surface of the heat-sensitive layer transferred onto the support (A) has a high level of smoothness and flatness, a smoothing treatment using a machine calendar such as a heat-sensitive recording sheet by a conventional manufacturing method or a super calendar is performed. There is no need to do it. That is, the problem of light and shade of an image due to background color development (so-called fog) and pressure unevenness that are secondarily generated as a result of such processing is solved. As a factor for improving the surface strength, in the vicinity of the surface of the heat-sensitive layer obtained by peeling and removing the support (B), as compared with the surface of the heat-sensitive layer produced by a conventional manufacturing method not using the transfer method, a binder, etc. It is presumed that the content of the resin component is high.
Further, it is considered that due to the same factor as in the case of the surface strength, it has become more resistant to external stimuli such as water, oils and fats, fingerprints and friction.

(Examples) Next, the present invention will be described more specifically by way of examples, but the present invention is not limited to the description of these examples.

The measuring method in the examples of the present invention is as follows.

1. Sensitivity Measure using a tester manufactured by Matsushita Electronic Components Co., Ltd.

2. Image quality Using the above tester, pulse width 1.0ms to 2.5ms
The image is changed by 0.3 ms each, and evaluated by visual inspection and enlarged photographs.

3. Storage stability Evaluate after processing the colored image area and background area under the following conditions.

(1) Water rub resistance test After immersion in water for 10 minutes, the surface is rubbed with absorbent cotton at a constant pressure and then evaluated.

(2) Oil resistance test Castor oil is thinly applied and left standing at 60 ° C for 24 hours, and then evaluated.

(3) Heat resistance test Evaluate after exposure to 60 ° C for 24 hours.

(4) Lightfastness test It is evaluated after being exposed to sunlight for substantially 20 days.

4. Surface Strength A commercially available cellophane adhesive tape is attached to the surface of the thermosensitive layer at a constant pressure, the cellophane adhesive tape is peeled off, and then the amount of fine powder adhering to the cellophane adhesive tape from the thermosensitive layer is evaluated.

5. Smoothness Measure according to JIS P-8119.

Example 1 parts by weight Solution A: 3-N-ethyl-N-pentylamino-6-methyl-7-phenylaminofluorane (Yamada Chemical Industry Co., Ltd. product S-205) 20 Hydroxyethylcellulose 10% aqueous solution 10 Water 30 Solution B: BPA (bisphenol A) 10 Hydroxyethyl cellulose 10% aqueous solution 15 Water 25 Solution C: Calcium carbonate 20 Hydroxyethyl cellulose 10% aqueous solution 10 Water 20 Solution D: Zinc stearate 10 Hydroxyethyl cellulose 10% aqueous solution 15 Water 25 Above A ~ Liquid D was pulverized with a sand grinder to an average particle size of 3 μm or less, and these liquids were blended as follows to prepare a heat-sensitive layer coating liquid.

Liquid A 10 parts by weight Liquid B 30 parts by weight Liquid C 20 〃 Liquid D 20 〃 Polyvinyl alcohol 10% aqueous solution 20 〃 Water 10 〃 This heat-sensitive layer coating liquid is a 75 μm thick polyester film (trade name, manufactured by Toray Industries, Inc., trade name: Lumirror) with a Mayer bar to a dry weight of 6 g / m ² , and then put it in a hot air dryer at 60 ° C to reduce the fluidity of the coating solution (60% by weight or less in the above coating solution). ) The surface of the coating liquid and the base paper (50 g / m ² ) are pressed together with a rubber roller to bond them together,
Further drying was continued. After drying, the polyester film could be easily peeled off and removed, and a heat-sensitive recording sheet in which the heat-sensitive layer was transferred to the base paper was obtained. The resulting sheet was measured for sensitivity as a thermal recording sheet, image quality, storage stability, and surface strength, and the results are shown in Table 1.

Example 2 A heat-sensitive layer coating solution having the same composition as in Example 1 was applied to the surface of a chrome-plated metal plate by a blade coater so that the dry weight was 6 g / m ² . After coating, this metal plate was heated in a hot air dryer at 60 ° C., and when the water content of the coating liquid reached 30% by weight, the surface of the heat-sensitive layer coating liquid and the surface of the base paper were joined. Next, the coating liquid was dried and peeled from the metal plate to obtain a heat-sensitive recording sheet in which the heat-sensitive layer was transferred to the base paper. The resulting sheet was measured for sensitivity, image quality, storage stability and surface strength as a thermal recording sheet, and the results are shown in Table 1.

Example 3 A heat-sensitive layer coating solution having the same composition as in Example 1 was coated on a 75 μm-thick polyester film with a Mayer bar so that the dry weight was 6 g / m ² . After the application, it was placed in a hot air dryer at 60 ° C. and dried. After drying, a polyacrylic acid latex as an adhesive was applied to the surface of the heat-sensitive layer with a Mayer bar so that the dry weight was 2 g / m ² , and the base paper (50 g / m ² ) and a nip roll were used for adhesion and drying. Next, the polyester film was peeled off to obtain a heat-sensitive recording sheet in which the heat-sensitive layer was transferred to the base paper. The sensitivity, image quality, storage stability and surface strength of this sheet as a thermal recording sheet were measured, and the results are shown in Table 1.

Comparative Example 1 The heat-sensitive layer coating solution used in Example 1 was directly applied to a base paper (50 g / m ² ) by a Mayer bar so that the dry weight was 6 g / m ² . After drying, since the smoothness was poor, it was treated with a super calender to improve the smoothness and obtain a thermosensitive recording sheet.
The sensitivity, image quality, storage stability and surface strength of this sheet as a thermal recording sheet were measured, and the results are shown in Table 1.

Example 4 10 parts of leuco dye (3-N-ethyl-N-pentylamino-6-methyl-7-phenylaminofluorane: 8 parts of S-205 manufactured by Yamada Chemical Co., Ltd., 3-N-methyl- N-
Cyclohexylamino-6-methyl-7-phenylaminofluorane: 2 parts PSD-150 manufactured by Shin Nisso Kako Co., Ltd.,
Parahydroxybenzoic acid benzyl ester 21 parts, dibenzyl terephthalic acid 6 parts, 1-hydroxy-2 naphthoic acid phenyl ester 4 parts, zinc stearate 10 parts, palmitic acid 4 parts, ethylenebisamide 5 parts, calcium carbonate
35 parts and 10 parts of kaolin were pulverized and dispersed so as to have an average particle diameter of 2 μm or less, and 20 parts of a binder (2 parts of hydroxyethyl cellulose, 10 parts of oxidized starch, 5 parts of acrylamide copolymer resin, 3 parts of carboxyl group-modified polyvinyl alcohol) Part) to prepare a heat-sensitive layer coating solution having a solid content concentration of 35%. This coating liquid was applied onto the induction heating roll 4 by the fountain type applicator 1 of the transfer coater having the structure shown in FIG. 1 so that the dry coating amount was 7 g / m ² . The heating roll 4 had a diameter of 4.2 m, and its surface was plated with chrome, and then treated with a fluororesin, and the temperature was controlled at 70 to 80 ° C. by an induction heating method.

The coating liquid is dried with an air dryer 3 to a moisture content of 25 to 45%, and then bonded with a base paper by a press roll 8.
Further, a moisture sensor 5 is installed immediately in front of the press roll 8 so that the drying conditions are adjusted so that an appropriate amount of moisture is obtained and the bonding process of the base paper and the heat sensitive layer is preferably performed. The processing conditions of the humidity adjusting (rewetting) applicator 6 installed immediately after that are automatically controlled. After the bonding, it is further dried by a high frequency dryer 9 to a moisture content of 20% or less, and peeled from a heating roll 4 by a peeling roll 10 to transfer a heat sensitive coating film 2 to a base paper 7.
11 was obtained. The thermal recording sheet 11 had a remarkably high surface smoothness of 5000 seconds or more, and the thickness uniformity of the coating film was also very good. Further, as in the case of Example 1, both the resolution and the gradation were very excellent, and the uniformity of the image particularly in the highlight portion was extremely good, and dot omission did not occur. The dynamic color density was 1.06 with a pulse width of 1.2 ms.

Example 5 20 parts by weight of gallic acid lauryl ester, stearic acid, 100 parts by weight of ferric acid, and 40 parts by weight of titanium oxide were used in a mixed solvent having a ratio of toluene / isopropanol = 5/1 to obtain an average particle size of 2 μm or less. As a result, a dispersion prepared by using an attritor was mixed with 85 parts by weight of a binder (Mitsubishi Rayon Co., Ltd., trade name: DIANAL LR-188) to prepare a heat-sensitive layer coating liquid having a solid content of 25%. Prepared. This heat-sensitive layer coating solution was applied onto the same polyester film as in Example 1 using a Mayer bar so that the dry weight was 5 g / m ² , and dried in a hot air dryer at 60 ° C. The same coating liquid was applied on the above so that the dry weight was 3 g / m ² . Next, the surface coating layer and the base paper were pressed together by using a rubber roller to be bonded and dried in a hot air dryer at 60 ° C. As a base paper, an undercoat having a composition of 10 parts by weight of polyvinyl alcohol and 40 parts by weight of a hollow pigment (Dainippon Ink and Co., Ltd., trade name: Boncoat PP-1000) on a light-weight coated paper of 53 g / m ² The layer was applied so as to have a dry weight of 5 g / m ² to improve heat insulation. After drying, the polyester film was peeled off to obtain a heat-sensitive recording sheet in which the heat-sensitive layer was transferred to the base paper. The sensitivity, image quality, storage stability and surface strength of this heat-sensitive recording sheet were measured, and the results are shown in Table 1.

Comparative Example 2 The same base paper and heat-sensitive layer coating solution as in Example 5 were used, and the heat-sensitive layer coating solution was applied onto the base paper using a Mayer bar so that the dry weight was 8 g / m ² and the coating was carried out at 60 ° C. In a hot air drier. Since the smoothness was poor after drying, a thermal recording sheet was obtained by treating with a super calendar to improve the smoothness. The sensitivity, image quality, storage stability and surface strength of this heat-sensitive recording sheet were measured, and the results are shown in Table 1.

(Effect of the Invention) As described above, according to the present invention, after the heat-sensitive layer is formed on the other support (B) in advance, the support (B) is then formed.
Since the thermal recording sheet is manufactured by transferring it from above onto the support (A), the surface of the obtained thermal recording sheet is smooth, and the color development sensitivity and the image quality are remarkably excellent and the storage stability of the background portion and the image portion is stable. It is possible to obtain a thermosensitive recording sheet having improved properties and surface strength.

[Brief description of drawings]

FIG. 1 is a side view showing the outline of the transfer coater used in Example 4. 1 ... Applicator, 2 ... Heat-sensitive agent coating film, 3 ... Air dryer, 4 ... Induction heating roll, 5 ... Moisture sensor, 6 ... Humidity control (rewetting) applicator, 7 ... Base paper, 8 ...... Press roll, 9 …… High frequency dryer, 10 …… Peeling roll, 11 …… Thermal recording paper.

Claims (4)

[Claims] 1. A heat-sensitive recording sheet comprising a heat-sensitive layer which develops a color when heated and a support (A) which holds the heat-sensitive layer, wherein the heat-sensitive layer is from the other support (B) to the support (A). A heat-sensitive recording sheet, which is obtained by being transferred onto the heat-sensitive recording sheet. 2. A method for producing a heat-sensitive recording sheet comprising a heat-sensitive layer which develops color when heated and a support (A) which holds the heat-sensitive layer, wherein the heat-sensitive layer is previously formed on another support (B). And then transferring from the support (B) onto the support (A). 3. The heat-sensitive layer coating liquid is applied onto another support (B), and the coating liquid is brought into a semi-dried state so that the surface of the coating liquid layer and the surface of the support (A) are bonded and dried. After that, the support (B)
The method for producing a heat-sensitive recording sheet according to claim 2, characterized in that only the heat-sensitive recording sheet is peeled off and removed. 4. The heat-sensitive layer coating liquid is applied onto another support (B) and dried, and then a substance having adhesiveness is applied to the heat-sensitive layer surface and / or the support (A) surface. The method for producing a heat-sensitive recording sheet according to claim 2, wherein the surface of the heat-sensitive layer and the surface of the support (A) are bonded together, and only the support (B) is peeled off and removed.