JPH02120080A - Production of thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a favorable thermal recording material remarkably superior in recording density and image quality and free from a scum adhesion to a thermal head by providing a coating composition mainly composed of a pigment having a specific oil absorption and an adhesive as an intermediate layer, and using near infrared rays for setting or drying the intermediate layer. CONSTITUTION:In the production of a thermal recording material formed by successively providing an intermediate layer and a recording layer on a substrate, the intermediate layer is made of a coating composition mainly composed of a pigment having an oil absorption of 80cc/100g or more according to a JIS K-500 method and an adhesive, and the intermediate layer is set or dried by using near infrared rays. As the pigment specified in oil absorption, particularly a calcined clay and an amorphous silica having superior heat insulating properties and a higher effect of improving a recording sensitivity are most preferably used among various pigments. If the oil absorption of the pigment is less than 80cc/100g, an effect of improving sensitivity, image quality, and others cannot be expected. The pigment of 80cc/100g oil absorption is incorporated in the amount of at least 60wt.% per total pigments. If the content of the pigment is less than 60wt.%, a required effect cannot be expected.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to a heat-sensitive recording medium, and particularly to a method for manufacturing a heat-sensitive recording medium that has high recording sensitivity, provides high image quality, and does not adhere to a thermal head.

"Prior Art" Conventionally, heat-sensitive recording utilizes a coloring reaction between a coloring agent and a coloring agent that develops color when it comes into contact with the coloring agent, and brings a recoloring substance into contact with heat to obtain a colored image. The body is well known. Such a thermal recording medium is relatively inexpensive, and the recording device is compact and its maintenance is relatively easy.
It is used not only as a recording medium for facsimiles and various computers, but also in a wide range of fields.

On the other hand, as recording equipment becomes faster, there is an increasing demand for heat-sensitive recording materials with excellent dynamic recording sensitivity.

In addition, with the diversification of uses, there is an increasing demand for thermosensitive recording materials that can provide high-quality recorded images in any range from low density to high density. Various measures have been proposed to meet the above demands. For example, various attempts have been made to provide high image quality and high density recording by providing an intermediate layer, but satisfactory results have not yet been achieved.

``Problems to be Solved by the Invention'' In view of the above-mentioned circumstances, the present inventors conducted intensive research on the composition and drying method of the intermediate layer provided on the support, and found that pigments with a specific oil absorption amount and When a coating composition containing an adhesive as a main component is provided as an intermediate layer and near infrared rays are used to solidify or dry the intermediate layer, a good thermal sensitivity with extremely excellent recording density and image quality and no residue adhering to the thermal head can be achieved. It was discovered that a recording medium could be obtained, and the present invention was finally completed.

"Means for Solving the Problems" The present invention provides a method for producing a heat-sensitive recording material in which an intermediate layer and a recording layer are sequentially provided on a support, in which the intermediate layer conforms to JIS K
- It is formed from a coating composition whose main components are a pigment and an adhesive with an oil absorption of 80 cc/10 h or more according to the 5101 method,
Further, the method for producing a heat-sensitive recording material is characterized in that near-infrared rays are used as means for solidifying or drying the intermediate layer.

"Function" As described above, the heat-sensitive recording material obtained by the method of the present invention uses near-infrared rays after providing a coating composition containing a pigment having a specific oil absorption amount and an adhesive as main components on a support. The feature is that the intermediate layer is obtained by drying.

Here, the pigment with a specific oil absorption amount is JIS K51.
Pigments with an oil absorption amount of 80cc/100g or more based on the 01 method, such as fired clay, aluminum oxide,
Titanium oxide, magnesium carbonate, diatomaceous earth, amorphous silica, aluminum silicate, magnesium silicate, calcium silicate, sodium aluminosilicate, magnesium aluminosilicate, etc. that have the above-mentioned specific oil absorption, or general pigments can be physically or chemically processed. Examples include inorganic and organic pigments that have been treated to have the above-mentioned specific oil absorption amount. Among these various pigments, calcined rays and amorphous silica are particularly excellent in heat insulating properties and are therefore more effective in improving recording sensitivity, and are therefore most preferably used.

By the way, if the oil absorption amount is less than 80cc/100g,
This is undesirable, as improvements such as higher sensitivity and higher image quality cannot be expected.

Examples of adhesives include starch, casein, polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, water-soluble polymers such as polyacrylic acid, styrene-butadiene copolymers, styrene-acrylic acid copolymers, Examples include various synthetic resin emulsions such as acrylonitrile-butadiene copolymers, colloidal silica particle composite styrene-acrylic acid ester copolymers, and acrylic acid copolymers.

Next, the composition of the intermediate layer coating composition used in the present invention will be described.

As mentioned above, the intermediate layer of the present invention has an oil absorption of 80 cc.
It is important that the coating composition is composed of a coating composition whose main components are a pigment with an oil absorption of 80 cc/100 g or more and an adhesive, and a pigment with an oil absorption of 80 cc/100 g or more is contained in an amount of at least 60% by weight based on the total pigment. Incidentally, if the amount of the pigment is less than 60% by weight, the desired effect cannot be expected. Of course, ordinary pigments, various auxiliary agents, etc. can be appropriately incorporated into the coating liquid for forming the intermediate layer within a range that does not impede the desired effects of the present invention.

There are no particular limitations on the method of applying the coating composition for the intermediate layer, but according to the study results of the present inventors, forming the intermediate layer by the blade coating method is extremely effective in smoothing the surface of the intermediate layer. It was clear that it worked well. Therefore, if the intermediate layer is formed using the blade coating method, there is no need to apply excessive pressure to the intermediate layer surface using a super calender to smooth it, resulting in a uniform surface with many voids and excellent heat insulation properties. This makes it easier to obtain a clear intermediate layer, and a recorded image of high quality and high density can be obtained. The blade coating method is not limited to a coating method using a bevel type or bent type blade, but also includes a coating method using a rod blade or the like. In addition, coaters such as short dwell time coaters, which take a short time from supplying the coating liquid to the support to scraping off excess coating liquid with a blade, use intermediate layer coating liquids mainly composed of oil-absorbing pigments. It is preferably used because of its excellent coating suitability. The intermediate layer obtained by blade coating the specific coating liquid on the support has extremely excellent surface smoothness, unlike air knife coating, etc., and does not require excessive calendering. As a result, the porosity is high, and as a result, it greatly contributes to the formation of a heat-sensitive recording medium that provides high-sensitivity and high-quality recorded images. Moreover, in the case of blade coating, unlike the case of air knife coaters,
Because the coating is applied at a high concentration, the coating layer dries quickly.
This also has the effect of significantly reducing expenses such as equipment and energy required for drying. Note that blade coating is not limited to an off-machine coater, and may be applied using an on-machine coater integrated with a paper machine. In particular, when the support is high-quality paper, coating with an on-machine coater is one of the preferred embodiments because the amount of coating is easily deposited due to the influence of the temperature of the paper surface immediately before coating, and drying properties are also good.

Further, the coating amount of the intermediate layer is not particularly limited, and is preferably adjusted appropriately within a range of about 1 to 30 g/m depending on the characteristics of the intended heat-sensitive recording material. Furthermore, the intermediate layer can also have a multilayer structure of two or more layers.

Therefore, the present invention has a very important significance in that after coating the intermediate layer coating liquid on the support, it is dried or solidified using near infrared rays as a drying means.

Conventionally, methods for drying wet coating layers include steam heating,
Various heating methods are used, such as hot air heating, gas heater, electric heater, infrared heater, high frequency, laser light heating, and electron beam, and infrared drying is also well known.

In addition, infrared rays generally include near infrared rays with wavelengths of 0.75 to 2.5 μm, mid-infrared rays of 2.5 to 25 μm, and wavelengths of 25 to 200 μm.
It is roughly divided into far infrared rays with a wavelength of 0 μm (see Instrumental Analysis Guide Ichi Kagaku Dojin / 19' published on April 20, 2019), but in the conventional infrared dryer, the wavelength is 2.5 μm.
Infrared rays in the above-mentioned mid-infrared region and far-infrared region are exclusively used, and infrared drying in the near-infrared region as used in the present invention is a relatively new drying method.

The method of the present invention utilizes infrared rays in the near-infrared region, and uses near-infrared rays having a wavelength of 0.75 to 265 μm, more preferably 1.0 to 2.0 μm.

Incidentally, if the wavelength is less than 0.75 μm, the effect on water evaporation for drying and solidifying the coating layer will be extremely small, and the purpose cannot be achieved.
．． If it exceeds 5 μm, it is effective for mere evaporation of water and drying, but the desired effect of the present invention cannot be obtained.

As mentioned above, a heat-sensitive recording material obtained by applying near-infrared rays to dry and solidify the intermediate layer coating liquid containing a pigment having a specific oil absorption amount after coating the support is extremely recordable. It was discovered that the recording medium has high sensitivity, high image quality can be obtained, and there is no residue attached to the thermal head, and the present invention has finally been completed.

The reason why such excellent effects can be obtained is surmised as follows.

In other words, near-infrared rays have stronger penetrating power and higher energy density for coating layers than infrared rays in the mid-infrared region and far-infrared region, which have been conventionally used as heating sources. ) is dried instantaneously and uniformly, resulting in the formation of a bulky intermediate layer. Since the intermediate layer formed in this way is porous, it has an extremely high heat insulating effect (and has excellent coverage of the support (e.g., paper). The thermosensitive recording material obtained by forming a thermosensitive recording layer on an intermediate layer that is rich in heat insulation properties and coverage of the support has a highly smooth surface, excellent adhesion to the thermal head, and has excellent heat insulation properties. It is thought that the density of the recorded image increases and a recorded image of extremely high quality is realized due to the excellent thermal recording properties.Furthermore, the thermal recording material obtained by the method of the present invention is free from debris that adheres to the thermal head during thermal recording. This is because the intermediate layer obtained by the method of the present invention is porous, that is, it is composed of a layer with many voids and a highly oil-absorbing pigment. Because of this, when the thermal head is used to perform thermal recording, dyes, color developers, etc. in the recording layer that are melted by the heat are quickly absorbed by the intermediate layer, and the molten material adheres to the thermal head. This is thought to be because it prevents

A heat-sensitive recording layer is coated on the intermediate layer thus formed and dried to produce the heat-sensitive recording material of the present invention.

There are no particular limitations on the combination of the coloring agent and the coloring agent contained in the recording layer, and any combination that causes a coloring reaction when the two come into contact with each other due to heat can be used. For example, colorless or Examples include a combination of a pale basic dye and an inorganic or organic acidic substance, and a combination of a higher fatty acid metal salt such as ferric stearate and a phenol 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 combinations of basic dyes and acidic substances, and is therefore particularly preferably applied to such combinations.

Various types of colorless to light-colored basic dyes are known, and examples include the following.

3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3.3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl)-3-(1, 2-dimethylindole-3
-yl)phthalide, 3-(p-dimethylaminophenyl)-3-(2-methylindol-3-yl)phthalide, 3゜3-bis(l,2-dimethylindol-3-yl)-5dimethylamino Phthalide, 3,3-bis(1,
2-dimethylindol-3-yl)-6-dimethylaminophthalide, 313-bis(9-ethylcarbazol-3-yl)=6-dimethylaminophthalide, 3.3-
Bis(2-phenylindol-3-yl)-6-dimethylaminophthalide, 3-p-dimethylaminophenyl-3-(1methylpyrrol-3-yl)-6-dimethylaminophthalide, etc. Allylmethane dye, 4,4'-bis-dimethylaminobenzhydrylbenzyl ether/L/, N-herophenyl leuco t-lami 7, N-2
, diphenylmethane dyes such as 4,5-trichlorophenylleucoolamine, thiazine dyes such as benzoylleucomethylene blue and p-nitrobenzoylleucomethylene blue, 3-methyl-spiro-dinaphthopyran,
3-ethyl-spiro-dinaphthopyran, 3-phenyl-
Spiro-dinaphthopyran, 3-benzylphenyl-spiro-dinaphthopyran, 3-benzylspiro-dinaphthopyran, 3-methyl-naphtho-(6゛-methoxybenzo)
spiro dyes such as spiropyran, 3-propyl-spiro-dibenzopyran, rhodamine-B anilinolactam,
Lactam dyes such as rhodamine (p-nitroanilino)lactam and rhodamine (0-chloroanilino)lactam, 3-dimethylamino-7-methoxyfluorane, 3-
Diethylamine-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
-diethylaminol-N-methylaminofluorane,
3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-N-methyl-N-benzylaminofluorane, 3-diethylamino-7-N-chloroethyl-N-methylaminofluorane, 3-diethylamino- 7-N-diethylaminofluorane, 3-(N
Ethyl-p-toluidino)-6-methyl-7-phenylaminofluorane, 3-(N-cyclopentyl-N-ethylamino)-6-methyl-7-anilinofluorane,
3-(N-ethyl-p-toluidino)-6-methyl-7
-(p-)luidino)fluoran, 3-diethylamino-6-methyl-7-phenylaminofluoran, 3-diethylamino-7-(2-carbomethoxy-phenylamino)fluoran, 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-chlorophenylamino)fluorane, 3-dibutylamino-7-(o
-chlorophenylamino)fluorane, 3-pyrrolidino-6-methyl 7-p-butylphenylaminofluorane, 3-N-methyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane, 3-N -ethyl-N-tetrahydrofurfurylamino-6-methyl-
Fluoran dyes such as 7-anilite fluorane, etc.

Furthermore, various types of inorganic or organic acidic substances that develop color upon contact with basic dyes are known, for example, the following are exemplified.

Inorganic acidic substances such as activated clay, acid clay, acpulgite, bentonite, colloidal silica, aluminum silicate, 4-tert-butylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 4
-Hydroxyacetophenol, 4-tert-octylcatechol, 2,2'-dihydroxydiphenol,
2.2'-methylenebis(4-methyl5-tert-butylphenol, 4,4'-isopropylidenebis(2
-ter t-butylphenol), 4.4'-5e
c-butylidenediphenol, 4-phenylphenol, 4.4'-isopropylidenediphenol (bisphenol A), 2.2'-methylenebis(4-chlorophenol), hydroquinone, 4.4'-cyclohexylidenediphenol, Phenolic compounds such as benzyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, hydroquinone monobenzyl ether, novolac type phenolic resin, phenol polymer, 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-pendylsalicylic acid, 3-(α-methylbenzyl)salicylic acid, 3-chloro-5-(α- methylbenzyl) salicylic M, 3,5-di-Ler t-butylsalicylic acid, 3-phenyl-5-(α.

Aromatic carboxylic acids such as α-dimethylbenzyl)salicylic acid, 3,5-di-αmethylbenzylsalicylic acid, and their phenolic compounds, aromatic carboxylic acids such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, Examples include organic acidic substances such as salts with polyvalent metals such as 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, more 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, generally, water is used as a dispersion medium, and the coloring agent and the coloring agent are dispersed together or separately using a ball mill, an attritor sand mill, etc., stirring and grinding, and then the coating solution is prepared. prepared.

Such coating liquids usually contain starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, diisobutylene-maleic anhydride copolymer salt, styrene-maleic anhydride copolymer salt as binders. Coalescence 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 or the like is added in an amount of about 10 to 70% by weight, more preferably about 15 to 50% by weight of the total solid content.

Furthermore, various auxiliary agents can be added to the coating liquid.
For example, dispersants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, alginates, fatty acid metal salts, ultraviolet absorbers such as benzophenone and triazole, and other antifoaming agents, Examples include fluorescent dyes and colored dyes.

In addition, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax, calcium carbonate, zinc oxide 1, 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-formalin resin filler, organic pigments such as raw starch, stearamide, methylene stearate Fatty acid amides such as bisamide, oleic acid amide, palmitic acid amide, coconut fatty acid amide, dibenzyl terephthalate, 1.2
-di(3-methylphenoxy)ethane, 1,2-diphenoxyethane, 4141-ethylenedioxy-bis-benzoic acid diphenylmethyl ester, 1.1.3-)lis(2-methyl, 4-hydroxy 5-tert) Hindered phenols such as -butylphenyl)butane, 2.2"-methylenebis(4-methyl-5-tert-butylphenol), 44"-butylidenebis(6-tert-butyl-3-methylphenol), and various known It is also possible to add thermosoluble substances.

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 for example, a coating device equipped with a suitable coater head such as an air knife coater or blade coater may be used.
It is formed by applying a coating liquid onto the intermediate layer and drying it.

Furthermore, the amount of coating liquid to be applied is not particularly limited, and is usually 2 to 12 g/I, more preferably 3 to 10 g/I in terms of dry weight.
It is in the range of g/a.

Further, the support is not particularly limited, and papers such as high-quality paper, base paper made with a Yankee machine, single-sided glossy base paper, double-sided glossy base paper, cast coated paper, art paper, coated paper, medium-quality coated paper, Synthetic fiber paper, synthetic resin film, etc. are used as appropriate.

Incidentally, after coating and drying the intermediate layer and the recording layer, smoothing treatment such as super calendering can be performed as necessary. Furthermore, it is 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 heat-sensitive recording materials can be added, such as providing a backing layer on the support. .

Thus, the heat-sensitive recording material obtained by the method of the present invention is
As described above, since an intermediate layer having a specific composition is provided between the support and the heat-sensitive recording layer, the recording sensitivity is high and the recording image quality is extremely high.

"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.

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

Example 1 [Preparation of coating composition for intermediate layer] Baked Ray (trade name: Ansilex, oil absorption 110c)
c/ 100g; manufactured by Engelhard) 90 parts Aluminum hydroxide 10 parts Styrene-butadiene copolymer latex (Product name: DOW-15)
71, solid content/48%; manufactured by Asahi Kasei Industries)
17 parts carboxymethylcellulose 2
% aqueous solution 50 parts water
A coating composition for an intermediate layer was prepared by mixing and stirring 150 parts of the above composition.

[Formation of intermediate layer]

The coating liquid for the intermediate layer obtained as above was coated on a paper machine equipped with an on-machine coater to a weight of 50 g/rd.
Blade coating was applied to high-quality base paper to a dry weight of 78 partsm, and a near-infrared irradiation device (infrared wavelength;
An intermediate layer was formed by initial drying (1.2 μm), followed by auxiliary drying using an air floating dryer so that the paper moisture content was 6%.

[Preparation of coating liquid for recording layer]

■Preparation of solution A 3-(N-cyclohexyl-N-methylamine)6-methyl-7-phenylaminofluorane 10 parts 1.2-bis-(3-methylphenoxy)-ethane 1
5 parts 5% methylcellulose aqueous solution 15 parts water 8 parts This composition was ground in a sand mill until the average particle size was 3 μm.

■Preparation of B solution 4,4"-isopropylidene diphenol 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 3 μm.

120 parts of solution A and 130 parts of solution B obtained in this way,
30 parts of amorphous silica, 150 parts of 20% oxidized starch aqueous solution,
A recording layer coating liquid was prepared by mixing and stirring 55 parts of water.

[Formation of recording layer]

The recording layer coating liquid obtained as described above was coated onto the intermediate layer using an air knife coater to give a dry weight of 4 g/rrr, dried, and then treated with a super calender to form a thermosensitive recording material. I got a body.

Example 2 A thermosensitive recording material was obtained in the same manner as in Example 1, except that the wavelength of the infrared ray was 1.8 μm in the infrared irradiation during the intermediate layer forming process.

Example 3 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the formulation of the intermediate layer coating composition was changed as follows.

[Formulation of coating composition for intermediate layer]

Amorphous silica (oil absorption: 200cc/100g)
80 parts calcium carbonate (product name: Tamavar TP~1
21, Okutama Kogyo ■) 20 parts styrene-butadiene copolymer latex (product name:
DOW-1571) 17 parts carboxymethyl cellulose 2% aqueous solution 50 parts water
150 parts Comparative Example 1 A thermosensitive recording material was obtained in the same manner as in Example 1 except that infrared irradiation was omitted during the process of forming the intermediate layer.

Comparative Example 2 A thermosensitive recording material was obtained in the same manner as in Example 1, except that the wavelength of the infrared rays was set to 0.7 μm in the infrared ray irradiation during the intermediate layer forming process.

Comparative Example 3 A thermosensitive recording material was obtained in the same manner as in Example 1 except that the wavelength of the infrared ray was 5.7 μm in the infrared irradiation during the intermediate layer forming process.

Comparative Example 4 A heat-sensitive recording material was obtained in the same manner as in Example 1, except that the formulation of the intermediate layer coating composition was changed as follows.

[Formulation of coating composition for intermediate layer] Kaolin (product name: UW-90, oil absorption 45cc/1
00g; manufactured by Engelhard) 100 parts styrene-butadiene copolymer latex (product name: D
O-1571) 17 parts carboxymethyl cellulose 2% aqueous solution 50 parts water
150 parts Comparative Example 5 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the formulation of the intermediate layer coating composition was changed as follows.

[Formulation of coating composition for intermediate layer]

Firing Ray (Product name: Ansilex, oil absorption 110c)
c/100g) 50 parts aluminum hydroxide 50 parts styrene-butadiene copolymer latex (trade name = DOXI-157
1> 17 parts carboxymethylcellulose 2% aqueous solution 50 parts water
150 parts The light source of the infrared irradiation device used in Examples 1 to 3 and Comparative Examples 2 to 5 is composed of a filament, a light condensing plate, and an opposing reflector. 3
(Near) infrared radiation was obtained by electrical heating to 800@K.

Then, the obtained near-infrared rays were collected by a gold-coated light collecting plate (placed above the filament) and radiated onto the paper. In addition, the near-infrared rays that have passed through the paper are reflected by an aluminum plate placed on the back side of the paper and re-radiated onto the paper, which is designed to dry the coated layer more evenly. There is.

Further, the infrared rays of the infrared irradiation device of Comparative Example 3 were obtained by heating the radiator with city gas. That is, a zirconium oxide compound was coated on the surface of a special glass tube as a radiator, and this tube was heated from the inside with a city gas burner to generate far-infrared rays, which were radiated onto the paper. In addition, in Comparative Example 1, only an air floating dryer with a temperature of 170°C was used. That's how I got it
Print various types of thermal recording materials using a thermal printer,
The color density was measured using a Macbeth densitometer (model RD-100R, manufactured by Macbeth). At the same time, the recorded image quality was visually evaluated. In addition, after loading these thermal recording media into a thermal facsimile (Hitachi DIFAX-400) and copying the Electronic Imaging Society No. 2 test chart 400 times in a row, the state of adhesion of debris to the thermal head was visually evaluated. did. Furthermore, the presence or absence of printing defects was also observed for the copied images.

The evaluation criteria for recorded image quality and thermal head residue are as follows.

[Evaluation criteria for recording image quality]

◎: Extremely excellent.

O: Excellent.

△: Inferior.

×: Extremely poor.

[Evaluation criteria for thermal head residue]

○: No debris was observed at all, and the image quality was good.

Δ: Slight adhesion of debris is observed, but there is almost no effect on image quality.

×: A lot of debris is observed, and the image is blurred.

"Effects" As is clear from the results in Table 1, the heat-sensitive recording material obtained in the examples of the present invention has a high recording density, excellent recording image quality,
Moreover, it was an extremely excellent thermal recording material with almost no residue adhering to the thermal head.

Claims (1)

[Claims] A method for producing a heat-sensitive recording material comprising sequentially providing an intermediate layer and a recording layer on a support, wherein the intermediate layer is coated with a pigment whose main components have an oil absorption of 80 cc/100 g or more according to JISK-5101 method and an adhesive. 1. A method for producing a heat-sensitive recording material formed from a composition, characterized in that near-infrared rays are used as means for solidifying or drying the intermediate layer.