JPH0390384A - Preparation of thermal recording material - Google Patents

Abstract

PURPOSE:To enhance smoothness while keeping the gap properties of an intermediate layer by forming the intermediate layer by applying a coating solution containing predetermined pigment and passing the same through a pressure nip so as to set the positive reflection smoothness of the surface of the intermediate layer to a predetermined value or more to apply calendar processing thereto. CONSTITUTION:An intermediate layer is formed by applying a coating solution containing pigment whose oil absorbancy according to JIS K-5101 is 100cc/100g or more and passed through the pressure nip constituted of an elastic roll and a metal roll heated to 80 deg.C or higher so as to set the positive reflection smoothness of the surface of the intermediate layer to 40% or more to be subjected to calender treatment. As the pigment, for example, one having specific oil absorbancy such as baked clay, aluminum oxide or titanium oxide and inorg. or org. pigment prepared by physically or chemically treating general pigment so as to provide the above mentioned specific oil absorbancy thereto are used. When the temp. of the metal roll is 80 deg.C or high, the surface of the intermediate layer is plasticized to a degree easily receiving smoothing action even under relatively low linear pressure and, therefore, the reduction of the void ratio in the intermediate layer is suppressed and a thermal recording material having high sensitivity and imparting high image quality is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to a method for manufacturing a heat-sensitive recording medium, and particularly to a method for manufacturing a heat-sensitive recording medium with high recording sensitivity and good image quality.

"Prior Art" Conventionally, a color former and a color former that develops color when in contact with the color former are
Thermosensitive recording materials that produce colored images by contacting with heat are well known. Such heat-sensitive recording media are relatively inexpensive, the recording equipment is compact, and maintenance is relatively easy, so they are used not only as recording media for facsimile machines and various computers, but also in a wide range of fields. As recording equipment speeds up, there is an increasing demand for heat-sensitive recording materials with excellent dynamic recording sensitivity. In addition, with the increasing variety of uses, there is an increasing demand for heat-sensitive recording materials that can provide high-quality recorded images in any range from low density to high density.

For this reason, a method for increasing the smoothness of base paper (Japanese Unexamined Patent Publication No. 56-16
5264, JP-A-57-142113), a method of providing an intermediate layer between the base paper and the recording layer, and a method of increasing the smoothness of the intermediate layer (JP-A-61-237,683). However, there are still issues to be solved in order to obtain a thermal recording medium of even higher quality.

For example, in order to improve the sensitivity and image quality of a heat-sensitive recording medium, the smoothness of the heat-sensitive recording layer and the support is important, and when an intermediate layer having a heat insulating effect is provided between the support and the heat-sensitive recording layer, the intermediate layer It is known that the smoothness of the surface has a large influence. Methods such as soft calendering, gloss calendering, and super calendering have been used to improve smoothness, but sufficient research has not been conducted on the calendering conditions. The present situation is that the pores of the pigment are reduced and the heat insulating effect becomes insufficient, resulting in a decrease in the sensitivity improvement effect, and as a result, the effect of the intermediate layer is not fully expressed.

"Problems to be Solved by the Invention" In view of the current situation, the present inventors have aimed to improve the smoothness of the intermediate layer while maintaining its porosity, thereby providing a heat-sensitive recording medium with high sensitivity and high image quality. With the aim of They discovered that a recording medium could be obtained and completed the present invention.

"Means for Solving the Problems" The present invention provides a method for manufacturing a heat-sensitive recording material in which an intermediate layer is provided between a support and a heat-sensitive recording layer, in which the intermediate layer is formed according to JIS K-
It is formed by applying a coating liquid containing a pigment with an oil absorption of 100 cc/100 g or more according to the 5101 method, and heated to 80°C or more with an elastic roll so that the specular reflection smoothness of the surface of the intermediate layer is 40% or more. This is a method for producing a heat-sensitive recording material, which is characterized in that the material is passed through a pressure nip composed of heated metal rolls and subjected to calendar treatment.

"Function" Pigments with an oil absorption of 100 cc/100 g or more based on the JIS K-5101 method that constitute the intermediate layer of the present invention include, for example, calcined clay, aluminum oxide, titanium oxide, magnesium carbonate, diatomaceous earth, and amorphous silica. , aluminum silicate, magnesium silicate, calcium silicate, sodium aluminosilicate, aluminum silicate, magnesium silicate, etc., which have the above-mentioned specific oil absorption amount, general pigments can be physically or chemically treated to achieve the above-mentioned specific oil absorption amount. Inorganic or organic pigments containing such pigments are used. Among these pigments, calcined clay and amorphous silica are preferably used because they have good porosity and are excellent in improving recording sensitivity.

Examples of binders include starch, casein, polyvinyl alcohol, methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, water-soluble polymers such as polyacrylic acid, styrene-butadiene copolymers, styrene-acrylic acid copolymers, acrylonitrile-butadiene. Various synthetic resin emulsions such as copolymers, copolymers of colloidal silica particles, styrene/acrylic acid ester copolymers, and acrylic acid copolymers are exemplified.

The blending ratio of the pigment and the binder is not particularly limited, but generally 5 to 50 parts by weight of the binder is used per 100 parts by weight of the pigment.

The coating solution for the intermediate layer is prepared by dispersing the above pigment and binder in water, and various auxiliary agents can be added to the coating solution, such as sodium dioctyl sulfosuccinate, dodecylbenzene, etc. Sodium sulfonate, lauryl alcohol sulfate ester sodium salt,
Examples include dispersants such as alginates and fatty acid metal salts, ultraviolet absorbers such as benzophenone and triazole, antifoaming agents, fluorescent dyes, and colored dyes.

Such a coating liquid can be applied to a coating device commonly used for manufacturing coating objects, such as a blade coater, an air knife coater,
The coating is applied onto the support using an on-machine or off-machine coater equipped with a roll coater, reverse roll coater, bar coater, curtain coater, die slot coater, gravure coater, chamberx coater, size press, or the like.

The support is not particularly limited either, and papers such as wood-free paper, medium-quality paper, cast-coated paper, art paper, coated paper, medium-quality coated paper, synthetic fiber paper, synthetic resin film, and the like can be used as appropriate.

The amount of application is also not particularly limited, but it is 5 to 20 g/
It is desirable to adjust within the range of ``+++''.

In addition, methods for drying the wet coating layer include steam heating, hot air heating, gas heater heating, electric heater heating, and (near)
Various methods such as infrared heater heating, high frequency heating, laser heating, and electron beam heating can be used.

In the present invention, the support on which the intermediate layer as described above is formed has a specular reflection smoothness (measured pressure: 20 kg/cm") of 40%.
The coating surface is passed between a pressure nip consisting of an elastic roll and a metal roll with a roll temperature of 80°C or higher so that the coating surface is in contact with the metal roll, and heat calendering is carried out so that the ratio is more preferably 50% or more. However, it has an important feature.

In other words, if the temperature of the metal roll is 80°C or higher, the surface of the intermediate layer is plasticized to such an extent that it is easily smoothed even with a relatively low linear pressure, so the decrease in the porosity inside the intermediate layer is suppressed. Furthermore, since the intermediate layer is processed to have a specular reflection smoothness of 40% or more, a heat-sensitive recording medium with high sensitivity and high image quality can be obtained as a result.

In addition, if the temperature of the metal roll is set to 100°C or higher, plasticization of the surface of the intermediate layer is further promoted, the applied linear pressure can be further reduced, and the decrease in porosity inside the intermediate layer can be significantly suppressed. preferable.

In addition, in order to obtain the desired smoothness, the pressure conditions are as follows:
should be selected appropriately depending on various processing conditions such as the type of recording medium, the hardness of the elastic roll used, the temperature conditions of the metal roll, the number of knobs, and the speed, but it is usually 20 to 1.
It is desirable to adjust within a range of about 50 kg/am.

The smoothness defined in the present invention is measured with a specular reflection type smoothness meter, but since such a smoothness meter measures the optical smoothness by pressing a sample against the prism surface under constant pressure conditions, - It is not affected by the air permeability of the sample like the Beck smoothness meter and Parker Print Surf, which are air leakage type smoothness measuring instruments used on boats, and according to the detailed study results of the present inventors. It has become clear that the degree of smoothing treatment desired by the present invention can be determined very appropriately from the measured value with this specular reflection type smoothness meter (measurement pressure: 20 kg/cm'').

The metal rolls used in the present invention are not particularly limited, and may include chilled rolls, alloy chilled rolls, steel rolls used in normal smoothing processing equipment such as super calenders, gloss calenders, and soft calenders, as well as roll surfaces. A hard chrome-plated metal roll or the like is appropriately selected and used. Further, for heating the metal roll, a method using a medium such as electricity, steam, water, oil, etc. is appropriately selected and used.

The metal roll and the elastic roll constituting the pressure nip are not particularly limited, and examples include natural rubber, styrene rubber, nitrile rubber, chloroprene rubber, chlorosulfonated rubber, butyl rubber, polysulfide rubber, silicone rubber, and fluorine rubber. Rubber, urethane rubber, aromatic boria resin, boria resin, polyether resin, polyester resin,
Examples include various plastic resins such as polycarbonate resin, cotton, paper, wool, Tetoron, nylon, and mixtures thereof.

As the pressurizing device, various types of calenders such as super calenders, gloss calenders, and soft calenders are used as appropriate on-machine or off-machine, and the form of the pressurizing device, the number of pressurizing nips, etc. are similar to those of ordinary smoothing processing devices. Adjustments will be made accordingly.

Note that when base paper is used as a support, as a step before applying the intermediate layer, the base paper is passed between a pressure nip consisting of an elastic roll and a metal roll heated to 80°C or higher, preferably IOOO°C or higher. Then, heat calender treatment is performed so that the specular reflection smoothness (measured pressure 20 kg/cm") of the surface in contact with the metal roll is 15% or more, and then the surface of the base paper that has been subjected to such smoothing treatment is When the intermediate layer is applied, the intermediate layer obtained by the method of the present invention is extremely smooth, or the desired smoothness can be achieved with a lower nifve pressure, which is a more preferred method.

In addition, the pressure conditions when heating and calendering the base paper are as follows:
If the nip linear pressure is lower than 20 +r/cn, it is difficult to obtain the desired effect, and if it exceeds 400 kg/el, the heat generation phenomenon of the elastic roll itself increases, making stable operation difficult. It is desirable to adjust the linear pressure to about am.

In the present invention, a heat-sensitive recording layer is coated and dried on the thus-treated intermediate layer to produce a heat-sensitive recording material, but there are no particular limitations on the combination of the coloring agent and the coloring agent contained in the recording layer. Any combination that causes a coloring reaction when the two come into contact with each other due to heat can be used. For example, a combination of a colorless or light-colored basic dye and an inorganic or organic acidic substance can be used. Examples include combinations of higher fatty acid metal salts such as ferric stearate and phenols such as gallic acid. Furthermore, it is also possible to apply the present invention to various heat-sensitive recording bodies in which a recorded image is obtained by heat, such as a heat-sensitive recording body in which a diazonium compound, a coupler, and a basic substance are combined.

However, the specific intermediate layer of the present invention provided on the support exhibits an excellent effect particularly in combination of a basic dye and an acidic substance, and is therefore preferably applied. Various kinds of colorless to light-colored basic dyes are known, and the following are exemplified.

3.3-bis(p-dimethylaminophenyl)6-dimethylagonophthalide, 3,3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl)-3-(1,2-dimethyl Indol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-3
-(2-methylindol-3-yl)phthalide, 3.
3-1: "S(1,2-dimethylindol-3-yl)-5-dimethylaminophthalide, 3,3-bis(1°2-dimethylindol-3-yl)-6-dimethylaquinophthalide, 3.3-bis(9-ethylcarbazol-3-yl)-6-dimethylaminophthalide, 3,3-
Triallyl such as bis(2-phenylindol-3-yl)-6-dimethylaminophthalide, 3-P-dimethylaminophenyl-3-(1-methylpyrrol-3-yl)-6-dimethylaminophthalide, etc. Methane dye, 4.4
'-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leucoolamine, N-2,
Schiffenylmethane dyes such as 4,5-trichlorophenylleucoolamine, thiazine dyes such as benzoylleucomethylene blue and p-nitrobenzoylleucomethylene blue, 3-methyl-spiro-dinaphthopyran, 3
- Spiro series such as -ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho-(6'-methoxybenzo)spiropyran, 3-propyl-spiro-dibenzopyran dyes, lactam dyes such as rhodamine-B anilinolactam, rhodamine (p-nitroanilino) lactam, rhodamine (0-chloroanilino) lactam, 3-dimethylamino-7-methoxyfluoran,
3-diethylamino-6-methoxyfluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-
6-Methyl-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluorane, 3-(N-ethyl-
p-Toluidino)-7-methylfluorane, 3-diethylamino-7-N-acetyl-N-methylaminofluorane, 3-diethylamino-7-N-methylaminofluorane, 3-diethylamino-7-dipendylamino Fluoran, 3-diethylaminofluorane, 7-N-methyl-N-benzylaminofluorane, 3-diethylaminofluorane, 3-diethylaminofluorane, 7-N
-chloroethyl-N-methylaminofluorane, 3-diethylamino-7-N-diethylaminofluorane, 3
-(N-ethyl-p-1luidino)-6-methyl-7-
Phenylaminofluorane, 3-(N-cycloben-N-ethylamino)-6-methyl-7-anilinofluorane, 3-(N-ethyl-p-)luidino)-6-methyl-7-( p-Toluidino) fluorane, 3-diethylamino-6-methyl-merphenylaminofluorane, 3-dibutylamino-6-methyl-7-phenylaminofluorane, 3-dibentylamino-6-methyl-7
-phenylaminofluorane, 3-diethylamino-7
-(2-carbomethoxy-tunilylamino)fluorane, 3-(N-ethyl-N-isoamylamino))-6-methyl-7-phenylaminofluorane, 3-(N-cyclohexyl-N-methylamino))- 6-Methyl-7-phenylaminofluorane, 3-pyrrolidino-6-methyl-7-phenylaminofluorane, 3-piperidino-6
-Methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, 3
-diethylamino-7- (o-chlorophenolua also))
Fluoran, 3-dibutylamino-7-(o-chlorophenylamino)fluoran, 3-pyrrolidino-6-methyl-7-P-butylphenylaminofluorane, 3-N
-Methyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane, 3-N-ethyl-N-
Fluoran dyes such as tetrahydrofurfurylamino-6-methyl-7-anilinofluorane, etc.

Various types of inorganic or organic acidic substances that develop color upon contact with basic dyes are also known, and examples thereof include the following.

Activated clay, acid clay, acupurgite, bentonite, colloidal silica, inorganic acidic substances such as aluminum silicate, 4-tert-butylphenol, 4-hydroxyschiftoxito, α-naphthol, β-naphthol,
4-Hydroxyacetophenol, 4-tert-octylcatechol, 2゜2'-dihydroxydiphenol, 2.2'-methylenebis(4-methyl-5-tert)
t-butylphenol), 4,4'-isopropylidene bis(2-tart-butylphenol), 41 4'
-5ec-butylidenediphenol, 4-phenylphenol, 4.4'-isopropylidenediphenol (bisphenol A), 2.2'-methylenebis(4-
chlorophenol), hydroquinone, 4゜4'-cyclohexylidene diphenol, benzyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, hydroquinone monobenzyl ether, novolak type phenolic resin, phenolic polymers, and other phenolic compounds, benzoin 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-te
rt-butylsalicylic acid, 3-benzylsalicylic acid, 3
-(α-methylbenzyl)salicylic acid, 3-chloro-5
-(α-methylbenzyl)salicylic acid, 3,5-di-t
er t-butylsalicylic acid, 3-phenyl-5-(α
, α-dimethylbenzyl)salicylic acid, 3,5-di-α
- aromatic carboxylic acids such as methylbenzylsalicylic acid,
Examples include organic acidic substances such as these phenolic compounds, salts of aromatic carboxylic acids and polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, and nickel.

In the present invention, the usage ratio of the coloring agent and coloring agent in the recording layer is appropriately selected depending on the type of coloring agent and coloring agent used, and is not particularly limited. For example, basic colorless When using a dye and an acidic substance, generally 1 to 50 parts by weight, preferably 1 to 10 parts by weight of the acidic substance are used per 1 part by weight of the basic colorless dye.

To prepare a coating solution containing these substances, the coloring agent and the coloring agent are generally dispersed together or separately using water as a dispersion medium, stirring with a ball mill, attritor, sand mill, etc., or pulverizing the coating solution. It is prepared as

Such coating liquids usually contain starches and binders as binders.
Hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, 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/acetic acid Vinyl emulsions etc. have a total solid content of 10~
It is added in an amount of about 70% by weight, preferably 15 to 50% by weight.

Furthermore, it is of course possible to add various auxiliary agents that can be used in the intermediate layer to the coating liquid.

In addition, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax, calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, and sulfuric acid may also be used as necessary. Inorganic pigments such as zinc, talc, kaolin, clay, calcined clay, colloidal silica, styrene microballs,
Nylon powder, polyethylene powder, urea/formalin resin filler, organic pigments such as raw starch, fatty acids such as stearate, methylene bisamide stearate, oleic acid amide, palmitic acid amide, coconut fatty acid amide, etc. , dibenzyl terephthalate, 1,2-
Di(3-methylphenol)ethane, 1,2-diphenoxyethane, 4,4'-ethylenedioxy-bis-benzoic acid diphenylmethyl ester, 1,1,3-)lis(
2-Methyl-4-hydroxy-5-tert-butylphenyl)butane, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 4°4'-butylindenbis(6tert,-butyl-3 -Methylphenol) and the like can also be added.

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

In the present invention, the method of forming the recording layer is not particularly limited, and may be formed by applying and drying a coating liquid onto the intermediate layer using a coating device equipped with a suitable coater head such as an air knife coater or a blade coater. Ru. Further, the amount of coating liquid applied is not particularly limited, and is usually 2 to 12 g/nf in terms of dry weight, preferably 3 to 10 g/r.
The range is about RF.

Incidentally, after coating and drying the recording layer, smoothing treatment such as super calendering can be performed as necessary. It is also possible to provide an overcoat layer on the recording layer for the purpose of protecting the recording layer, etc., and various known techniques in the field of thermal recording materials such as providing a backing layer on the support or applying adhesive processing can be used. can be added.

"Example" The present invention will be described in more detail with reference to Examples below, but the present invention is of course not limited to these.

Further, unless otherwise specified, parts and % in the examples indicate parts by weight and % by weight, respectively.

Example 1 [Preparation of intermediate layer coating liquid - ■] Calcined clay (trade name: Ankle 7x, oil absorption:
110cc/100g, manufactured by EMC)
100 parts Styrene-butadiene copolymer latex (trade name: Don-1571, solid content: 48%, manufactured by Asahi Dow Co., Ltd.) 20 parts oxidized starch 25% aqueous solution 15 parts water
148 parts The above composition was mixed to prepare an intermediate layer coating liquid-I with a solid content of 40%.
Prepared.

[Formation of intermediate layer]

The obtained intermediate layer coating liquid-I was coated and dried on a base paper having a basis weight of 50 g/rd using a rod blade coater so that the coated amount after drying was 9 g/rd.

The obtained coated paper was heated at 90°C, 2 nips, and a linear pressure of 8°kg/
Pressure treatment was carried out using a soft calender under CI conditions so that the coated surface was in contact with a metal roll to obtain an intermediate layer with a specular reflection smoothness of the coated surface of 45%.

[Preparation of recording layer coating liquid]

■ Preparation of liquid A 3-(N-cyclohexyl-N-methylaξ))-6-
Methyl-7-phenylaminofluorane
10 parts 1.2-bis-(3-methylphenoxy)-ethane 15 parts 5% methylcellulose aqueous solution 15 parts water
80 parts of this composition was ground in a sand mill until the average particle size was 2 μm.

■ Preparation of B solution 4.41-Isopropylidenediphenol 30 parts Methyl cellulose 5% aqueous solution 30 parts water
70 parts of this composition was ground in a sand mill until the average particle size was 2 μm.

120 parts of liquid A, 130 parts of liquid B, 30 parts of amorphous silica, 2
0% oxidation: A recording layer coating liquid was prepared by mixing and stirring 150 parts of lithium powder ice aqueous solution and 55 parts of water.

[Formation of recording layer]

The obtained recording layer coating liquid was applied onto the intermediate layer using an air knife coater and dried so that the coating amount after drying was 5 g/rrr, and the surface was treated using a super calender to obtain a heat-sensitive recording material.

Example 2 A thermosensitive recording material was obtained in the same manner as in Example 1 except that the temperature of the metal roll was 120''C.The specular reflection smoothness of the intermediate layer was 53%.

Example 3 In Example 1, the base paper was heated at 90°C, 12 nips, and a linear pressure of 150
A heat-sensitive recording material was obtained in the same manner as in Example 1, except that the base paper was subjected to pressure treatment with a soft calender under the conditions of kg/cm to give a specular reflection smoothness of 20%, and then an intermediate layer was applied. . The specular reflection smoothness of the intermediate layer was 58%.

Example 4 In Example 3, the base paper was heated at 110°C, 2 nips, and a linear pressure of 15
Pressure treatment was performed using a soft calender under the conditions of 0 kg/CI to make the specular reflection smoothness of the base paper 25%, and then an intermediate layer was applied at 120'C, 2 nips, and a linear pressure of 60 kg/cm.
A thermosensitive recording material was obtained in the same manner as in Example 3 except that the pressure treatment was performed using a soft calender under the following conditions. Note that the specular reflection smoothness of the intermediate layer was 62%.

Example 5 Except that 100 parts of calcined clay in the intermediate layer coating solution in Example 1 was replaced with 100 parts of amorphous silica (trade name: Mizuka Seal P-527. Oil absorption: 180 cc/1.OOg, manufactured by Mizusawa Chemical Co., Ltd.) A thermosensitive recording material was obtained in the same manner as in Example 1. Note that the specular reflection smoothness of the intermediate layer was 50%.

Comparative Example 1 A thermosensitive recording material was obtained in the same manner as in Example 1 except that the pressure treatment conditions for the intermediate layer were 60° C., 2 nips, and a linear pressure of 80 kg/cm. Note that the specular reflection smoothness of the intermediate layer was 35%.

Comparative Example 2 In Example 1, a super calender was used as the pressure device for the intermediate layer, and the processing conditions were 60"C, 9 nips, and a linear pressure of 35
A thermosensitive recording material was obtained in the same manner as in Example 1 except that the weight was 0 kg/cm. Note that the specular reflection smoothness of the intermediate layer was 43%.

Comparative Example 3 A thermosensitive recording material was obtained in the same manner as in Example 1, except that the pressure treatment conditions for the intermediate layer were 90° C., 12 nips, and a linear pressure of 15 kg/c+a. Note that the specular reflection smoothness of the intermediate layer was 37%.

Comparative Example 4 In Example 2, 100 parts of calcined clay in the intermediate layer coating liquid was replaced with kaolin (trade name, tJW-90, oil absorption: 35 cc/
A thermosensitive recording material was obtained in the same manner as in Example 2 except that 100 parts of LOOg (manufactured by EMC) were used. Note that the specular reflection smoothness of the intermediate layer was 45%.

Comparative Example 5 In Example 1, 100 parts of the calcined clay in the intermediate layer coating liquid was replaced with calcium carbonate (trade name: Callite SA, oil absorption: 8
A thermosensitive recording material was obtained in the same manner as in Example 1, except that 100 parts of 0Cc/lQQg (manufactured by Shiraishi Calcium Co., Ltd.) were used. Note that the specular reflection smoothness of the intermediate layer was 40%.

The 1011 class heat-sensitive recording medium thus obtained was printed using a thermal printer, and the color density was measured using a Macbeth densitometer (
The measurement was carried out using a model RD-100R (manufactured by Macbeth). Furthermore, the recorded image quality was also evaluated, and the results are listed in the table.

The recorded image quality was evaluated visually, and the evaluation criteria were as follows.

"Evaluation criteria" ◎: Extremely excellent.

○: Excellent.

Δ: Slightly inferior.

Table 1: "Effects" The thermosensitive recording material obtained by the method of the present invention had high recording density and excellent recorded image quality.

Claims (3)

[Claims] (1) In a method for manufacturing a heat-sensitive recording material in which an intermediate layer is provided between a support and a heat-sensitive recording layer, the intermediate layer is
It is formed by applying a coating liquid containing a pigment with an oil absorption of 100 cc/100 g or more by method 1, and heated to 80°C or more with an elastic roll so that the specular reflection smoothness of the surface of the intermediate layer is 40% or more. 1. A method for producing a heat-sensitive recording material, which comprises passing the heat-sensitive recording material through a pressure nip composed of a heated metal roll and calendering the material. (2) The support was calendered by being passed through a pressure nip composed of an elastic roll and a metal roll heated to 80°C or higher so that the specular reflection smoothness of the surface was 15% or higher. The method for producing a heat-sensitive recording material according to claim (1), which is a base paper. (3) The method for producing a heat-sensitive recording material according to any one of (1) to (2), wherein the heat-sensitive recording material is calendared by being passed through a pressure nip composed of an elastic roll and a metal roll heated to 100° C. or higher.