JPH09150584A - Manufacture of thermosensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve recording sensitivity, developed-color density of a recorded image, storage characteristics and whiteness by applying and drying a coating liquid for a thermosensitive recording layer which contains a specific amide compound as a coloring agent and has pH in a specific range. SOLUTION: A thermosensitive recording layer is formed by applying and drying a coating liquid for the thermosensitive recording layer which contains an amide compound expressed by the formula (wherein R denotes an alkyl group of C1 -C6 , an alkoxy group of C1 -C6 , a halogen atom or a benzyl group) as a coloring agent and has pH of 4.5-7.0. As for this amide compound, two or more kinds of the compounds can be also be used jointly, and 2,4- dihydroxy-2'-methoxybenzanilide is preferable, since it is excellent particularly in recording sensitivity and storage characteristics. By forming an intermediate layer containing calcium carbonate or magnesium carbonate between a substrate and the thermosensitive recording layer, occurrence of ground blushing can be lessened very much.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thermosensitive recording material utilizing a color-forming reaction between a leuco dye and a color former.
In particular, the present invention relates to a method for producing a thermosensitive recording medium which is excellent in recording sensitivity, color density of a recorded image and storage characteristics and has high whiteness.

[0002]

2. Description of the Related Art A thermosensitive recording medium is known, which utilizes a color reaction between a colorless or light-colored leuco dye and an organic or inorganic coloring agent to bring both color-forming substances into contact with each other by heat to obtain a recorded image. ing. Since such a thermal recording medium is relatively inexpensive, the recording device is compact, and its maintenance is easy, it is used not only as a recording medium for facsimiles and various computers but also in a wide range of fields.

One of the fields of use thereof is, for example, POS.
(point of sales) A thermosensitive recording label or a thermosensitive recording tag for a system can be used. In conventional food label applications and clothing tag applications, labels with extremely high label issuance rates are not always required, and issued labels and tags are relatively rarely used in harsh environments. Met. However, recently, these thermosensitive recording labels have come to be used for industrial purposes, and as an example, 9
There is a demand for a heat-sensitive recording label that has little natural coloration on the background even after being exposed to a high temperature environment of 0 ° C. for a long time and whose recorded information can be clearly read. Moreover, such an industrial thermal recording label is required to have high-speed recording suitability as compared with conventional foods and clothing, and is required to have contradictory characteristics that there is little background fog in a high temperature environment and excellent recording sensitivity. There is.

Various leuco dyes and color formers have been proposed in order to improve recording sensitivity and storage characteristics of recorded images. Thermal recording using dyes and color formers having these characteristics improved. The body generally has a tendency to cause background fog to decrease in whiteness, and especially when exposed to a high temperature environment, there is little background fog, and thermal recording is excellent in recording sensitivity and storage stability of recorded images. The body has not been obtained. Further, various compounds have been proposed as sensitizers for the purpose of improving recording sensitivity, but the combined use of sensitizers also causes deterioration of background fog. Further, it has been proposed to add various preservative improving agents, but many of them also cause background fog, and the preservative improving effect is also insufficient, which makes them satisfactory as thermal recording media for industrial label applications. The current situation is that nothing has been obtained.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a thermosensitive recording medium which is excellent in recording sensitivity, color density of recorded images and storage characteristics and has high whiteness.

[0006]

The present invention is represented by the following general formula (1) as a color developing agent in a method for producing a heat sensitive recording material for forming a heat sensitive recording layer containing a leuco dye and a color developing agent. Contains an amide compound and has a pH of 4.5 to 7.0
By coating and drying the heat-sensitive recording layer coating liquid to form a heat-sensitive recording layer, the above-mentioned problems have been solved and completed.

[0007]

Embedded image

[Wherein R is a C ₁ -C ₆ alkyl group, C
An alkoxyl group ₁ -C _6, a halogen atom or a benzyl group. ]

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to an amide compound represented by the above general formula (1) as a color developing agent in a method for producing a heat sensitive recording material for forming a heat sensitive recording layer containing a leuco dye and a color developing agent. And a coating solution for a heat-sensitive recording layer having a pH of 4.5 to 7.0 is applied and dried to form a heat-sensitive recording layer, wherein the coating solution for a heat-sensitive recording layer has a pH of 4.5. If it is less than the range, the fog on the heat-sensitive recording layer is generated, and the whiteness is lowered. On the other hand, if the pH exceeds 7.0, the coating solution for the heat-sensitive recording layer may thicken with time and gel, or the color density may decrease, so that the pH range of 5.0 to 6.5 is more preferable.

The above general formula (1) contained in the thermosensitive recording layer.
Specific examples of the amide compound represented by the following include, for example, the following, but are not limited thereto, and it is also possible to use two or more kinds in combination. 2,4
-Dihydroxy-2'-methoxybenzanilide, 2,
4-dihydroxy-3'-methoxybenzanilide,
2,4-dihydroxy-4'-methoxybenzanilide, 2,5-dihydroxy-2'-methoxybenzanilide, 2,5-dihydroxy-4'-methoxybenzanilide, 2,6-dihydroxy-2'-methoxybenz Anilide, 2,6-dihydroxy-4'-methoxybenzanilide, 3,4-dihydroxy-2'-methoxybenzanilide, 3,4-dihydroxy-4'-methoxybenzanilide, 3,5-dihydroxy-2'- Methoxybenzanilide, 2,4-dihydroxy-2'-ethoxybenzanilide, 2,4-dihydroxy-4'-ethoxybenzanilide, 3,5-dihydroxy-2'-
Ethoxybenzanilide, 2,4-dihydroxy-2 '
-Isopropoxybenzanilide, 2,4-dihydroxy-2'-isoamyloxybenzanilide, 2,4-
Dihydroxy-2'-methylbenzanilide, 2,4-
Dihydroxy-4'-methylbenzanilide, 3,5-
Dihydroxy-2'-methylbenzanilide, 2,4-
Dihydroxy-2'-ethylbenzanilide, 3,5-
Dihydroxy-4'-ethylbenzanilide, 2,4-
Dihydroxy-4'-isoamylbenzanilide, 2,
4-dihydroxy-2'-chlorobenzanilide, 2,
4-dihydroxy-2'-benzylbenzanilide and the like.
Among these amide compounds, 2,4-dihydroxy-2′-methoxybenzanilide is preferable because it is particularly excellent in recording sensitivity and storage characteristics.

In the present invention, by forming an intermediate layer containing calcium carbonate or magnesium carbonate between the support and the heat-sensitive recording layer, a heat-sensitive recording material with very little background fog can be obtained. The content of calcium carbonate or magnesium carbonate is preferably in the range of about 5 to 50% by weight based on the total solid amount of the intermediate layer.

Further, as an oil-absorbing pigment, JIS is used in the intermediate layer.
Oil absorption based on K 5101 method is 80-1000ml / 100g
20 to 80% by weight based on the total solid content of the intermediate layer is preferable, and examples of such pigments include calcined clay, calcined kaolin, aluminum oxide, magnesium carbonate, diatomaceous earth, amorphous silica, and aluminum silicate. Inorganic pigments such as magnesium silicate, calcium silicate, sodium aluminosilicate, and magnesium aluminosilicate that have the above oil absorption amount, and organic pigments such as urea resin particles and urea-formalin resin particles that have such oil absorption amount are exemplified. it can. Of course, in the present invention, when these pigment fine particles themselves have the above specific oil absorption amount, and when the pigment fine particles are physically or chemically treated to form secondary particles or agglomerates, a specific oil absorption amount range is obtained. Both cases shown are included.

Among these oil-absorbing pigments, calcined clay, calcined kaolin, amorphous silica urea resin particles and urea-formalin resin particles are particularly excellent in heat insulating property and whiteness, and dynamic recording sensitivity and initial whiteness are excellent. It is preferably used because it has a remarkable improving effect.

In addition to these, the intermediate layer contains an adhesive in an amount of 5 to 25% by weight based on the total solid content of the intermediate layer. Examples of such an adhesive include casein, starch and its derivatives, methyl cellulose, ethyl cellulose, Hydroxyethyl cellulose, carboxymethyl cellulose, methoxy cellulose, fully (partially) saponified polyvinyl alcohol, various modified polyvinyl alcohols such as carboxyl group modified, acetoacetyl group modified, silicon modified, sodium polyacrylate, polyvinylpyrrolidone, polyacrylamide, acrylamide-acryl Acid ester copolymer,
Acrylamide-acrylic acid ester-methacrylic acid terpolymer, water-soluble polymer such as styrene-maleic anhydride copolymer salt, isobutylene-maleic anhydride copolymer salt, styrene-butadiene copolymer, styrene-butadiene -Acrylic copolymers, vinyl acetate resins, vinyl acetate-acrylic copolymers, styrene-acrylic ester copolymers, acrylic ester resins, aqueous emulsions of polyurethane resins and the like, but of course are not limited to these Not a thing.

Further, various auxiliary agents such as a dispersant and a defoaming agent are added, if necessary, to prepare a coating liquid for the intermediate layer.
The coating amount of the coating liquid is not particularly limited, and is generally adjusted in the range of about ² to ²⁰ g / m ² ,
If necessary, it can be formed in two or more layers. Further, it is desirable to carry out smoothing treatment such as super calendar treatment after the application of the intermediate layer.

In the heat-sensitive recording material of the present invention, the leuco dye used in the heat-sensitive recording layer is not particularly limited, and various known colorless or light-colored leuco dyes can be used. Specific examples of such leuco dyes include the following.

3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylamino Phthalide, 3-
Diethylamino-7-dibenzylamino-benzo [a]
Blue-coloring dye such as fluoran; 3- (N-ethyl-N-)
green-coloring dyes such as p-tolyl) amino-7-N-methylanilinofluorane and 3-diethylamino-7-anilinofluorane;

3,6-bis (diethylamino) fluorane-γ-anilinolactam, 3-diethylamino-7-
Methylfluorane, 3-diethylamino-6-methyl-
7-chlorofluorane, 3-diethylamino-7-chlorofluorane, rhodamine (p-chloroanilino) lactam, 3- (N-ethyl-p-toluidino) -7-methylfluorane, 3,3'-bis (1 -N-butyl-2-
Methylindol-3-yl) phthalide and other red-coloring dyes;

3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane, 3- (N-
Methyl-N-cyclohexyl) amino-6-methyl-7
-Anilinofluorane, 3-dimethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6
-Methyl-7-anilinofluorane, 3-di (n-butyl) amino-6-methyl-7-anilinofluorane, 3
-Di (n-amyl) amino-6-methyl-7-anilinofluoran, 3-diethylamino-7- (o-chloroanilino) fluoran, 3-di (n-butyl) amino-7
-(O-chloroanilino) fluoran, 3-diethylamino-7- (o-fluoroanilino) fluoran, 3-
Di (n-butyl) amino-7- (o-fluoroanilino) fluoran, 3-diethylamino-7- (m-trifluoromethylanilino) fluoran, 3- (N-ethyl-p-toluidino) -6 Methyl-7-anilinofluoran, 3- (N-ethyl-p-toluidino) -6-methyl-7- (p-toluidino) fluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3 −
Di (n-butyl) amino-6-methyl-7-m-toluidinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 2,2-bis {4- [6 '-( N-
A black color-developing dye such as cyclohexyl-N-methyl) amino-3′-methylspiro [phthalide-3,9′-xanthen-2′-ylamino] phenyl} propane;

3,3-bis [1- (4-methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-
2-yl] -4,5,6,7-tetrachlorophthalide,
3,3-bis [1- (4-methoxyphenyl) -1-
(4-pyrrolidinophenyl) ethylene-2-yl]-
4,5,6,7-tetrachlorophthalide, 3-p- (p
-Dimethylaminoanilino) anilino-6-methyl-7
-Chlorofluoran, 3-p- (p-chloroanilino)
Anilino-6-methyl-7-chlorofluoran, 3,6
-Bis (dimethylamino) fluorene-9-spiro-
Dyes and the like having an absorption wavelength in the near infrared region at the time of color development such as 3 '-(6'-dimethylamino) phthalide. Of course, it is not limited to these, and two or more kinds may be used in combination as required.

Among the above leuco dyes, 3-
(N-ethyl-N-isoamyl) amino-6-methyl-
7-anilinofluorane, 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluorane, 3-di (n-butyl) amino-6-methyl-7-
Anilinofluorane and 3-di (n-amyl) amino-6-methyl-7-anilinofluorane are preferably used because good recording sensitivity and storage characteristics can be obtained by combining with the specific color former. To be

Furthermore, 3-di (n-butyl) amino-7
When-(o-chloroanilino) fluorane is combined with the colorant of the present invention, a thermosensitive recording material having particularly excellent light resistance of the recorded image and the background portion can be obtained as compared with the combination with other leuco dyes and colorants. It is preferable because it can be obtained.

As described above, the heat-sensitive recording material of the present invention uses a specific amide compound as a coloring agent.
It is also possible to use other known color formers in combination within a range that does not impair the desired effects of the present invention.

Specific examples of such a coloring agent include 4,4'-isopropylidenediphenol, 1,1-bis (4-hydroxyphenyl) cyclohexane and 2,2.
-Bis (4-hydroxyphenyl) -4-methylpentane, benzyl 4-hydroxybenzoate, 4,4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone , Bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4'-
Methyldiphenylsulfone, 4-hydroxyphenyl-
4'-benzyloxyphenyl sulfone, 1,1-bis (4-hydroxyphenyl) -1-phenylethane,
1,4-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 1,3-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, di (4- Phenolic compounds such as hydroxy-3-methylphenyl) sulfide and 2,2′-thiobis (3-tert-octylphenol); Thiourea compounds such as N, N′-di-m-chlorophenylthiourea; N- (p
-Toluenesulfonyl) carbamoyl acid p-cumylphenyl ester, N- (p-toluenesulfonyl) carbamoyl acid p-benzyloxyphenyl ester, N-
(O-toluoyl) -p-toluenesulfoamide, N-
(P- toluenesulfonyl) -N '- (p- tolyl) compound having a -SO ₂ NH- bond in the molecule, such as urea; p
-Zinc chlorobenzoate, zinc 4- [2- (p-methoxyphenoxy) ethyloxy] salicylate, 4- [3-
Examples thereof include zinc salts of aromatic carboxylic acids such as (p-tolylsulfonyl) propyloxy] zinc salicylate and zinc 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylate.

The use ratio of the leuco dye and the color developing agent is appropriately selected depending on the presence or absence of the combination of the leuco dye to be used and other color developing agent, and is not particularly limited, but is generally leuco. About 1 to 50 parts by weight, preferably about 2 to 10 parts by weight, of the coloring agent is used with respect to 1 part by weight of the dye. When another colorant is used in combination, it is desirable to use at least 60% by weight of the total amount of the colorant as the specific amide compound.

The coating liquid for heat-sensitive recording layer containing these substances is
Generally, water is used as a dispersion medium, and a ball mill, attritor,
After the leuco dye and the coloring agent are dispersed together or separately by a stirrer / pulverizer such as a sand mill, and then an adhesive is added to the mixture, if necessary, the pH of the coating liquid is adjusted to 4.5 to 7.0. Adjusted with acid or alkali.

Specific examples of the acid and alkali used for adjusting the pH of the coating liquid for the heat-sensitive recording layer include inorganic acids such as boric acid, hydrochloric acid, sulfuric acid and phosphoric acid, acetic acid, lactic acid,
Examples thereof include organic acids such as acrylic acid and polyacrylic acid, acidic salts such as potassium alum, and basic salts such as sodium carbonate. Of these, organic acids such as acetic acid, lactic acid, acrylic acid and polyacrylic acid are preferable.

Examples of the adhesive include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, and diisobutylene.・ Maleic anhydride copolymer salt, styrene / maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, styrene / butadiene copolymer emulsion, urea resin, melamine resin At least one of amide resin, polyurethane resin and the like is added in an amount of about 5 to 30% by weight based on the total solid content of the recording layer.

A pigment may be added to the heat-sensitive recording layer coating liquid in an amount of 40% by weight or less based on the total solid amount of the heat-sensitive recording layer. Specific examples of such pigments include kaolin, clay, talc, aluminum hydroxide, calcium carbonate, magnesium carbonate, calcined clay, calcined kaolin,
Examples thereof include inorganic pigments such as titanium oxide, diatomaceous earth, particulate anhydrous silica, activated clay and the like, and organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and raw starch particles. Among them, aluminum hydroxide is more preferable because it has little influence on pH and the coating solution is stable over time. Talc, calcium carbonate, and magnesium carbonate raise the pH of the coating liquid, and there is a risk that it will be difficult to adjust the pH due to its buffering action.

If desired, various auxiliary agents may be added to the heat-sensitive recording layer coating liquid. For example, sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, and fatty acid metal salt. And the like, waxes such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax and ester wax, defoaming agents, coloring dyes and the like are appropriately added.

Further, in the heat-sensitive recording layer coating liquid, a sensitizer for increasing the recording sensitivity and a storability improving material for increasing the storability of a recorded image may be used in combination. Specific examples of the sensitizer include stearic acid amide, ethylenebisstearic acid amide, behenic acid amide, methylenebisstearic acid amide, N-methylolstearic acid amide, m-terphenyl, 4-benzylbiphenyl, 1- Isopropylphenyl-2-phenylethane,
2-benzyloxynaphthalene, 4- (p-tolyl) oxybiphenyl, di (4-methoxyphenoxyethyl)
Ether, 1,2-diphenoxyethane, 1,2-di (3-methylphenoxy) ethane, 1,2-di (4-methylphenoxy) ethane, 1,2-di (4-methoxyphenoxy) ethane, 1 , 2-di (4-chlorophenoxy) ethane, 1- (4-methoxyphenoxy) -2-
(2-Methylphenoxy) ethane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, dibenzyl terephthalate, p- Benzyl benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, dibenzyl oxalate, di (p-methylbenzyl) oxalate, di (p-chlorobenzyl oxalate), p-acetotoluidide, p-
Acetophenetidide, N-acetoacetyl-p-toluidine and the like are exemplified. Of course, these compounds may be used in combination of two or more, if necessary.

The amount of the sensitizer used is appropriately selected depending on the desired sensitivity and the type of the sensitizer used, and is not particularly limited, but generally 0 per 1 part by weight of the color developing agent. It is desirable to adjust in the range of about 0.5 to 4 parts by weight.

Examples of the storability improver include the following. 2,2'-methylenebis (4-methyl-6-tert
-Butylphenol), 2,2'-methylenebis (4-
Ethyl-6-tert-butylphenol), 2,2'-ethylidenebis (4,6-di-tert-butylphenol), 4,4'-thiobis (2-methyl-6-tert-butylphenol), 4,4 ' -Butylidene bis (6-te
rt-butyl-m-cresol), 1- [α-methyl-α
-(4'-hydroxyphenyl) ethyl] -4-
[Α ', α'-bis (4 "-hydroxyphenyl) ethyl] benzene, 1,1,3-tris (2-methyl-4-)
(Hydroxy-5-cyclohexylphenyl) butane,
1,1,3-tris (2-methyl-4-hydroxy-5
-Tert-butylphenyl) butane, 4,4'-thiobis (3-methylphenol), 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2,2-
Hindered phenol compounds such as bis (4-hydroxy-3,5-dimethylphenyl) propane, 1,4-diglycidyloxybenzene, 4,4′-diglycidyloxydiphenyl sulfone, 4-benzyloxy-4′-
(2-methylglycidyloxy) diphenyl sulfone,
Epoxy compounds such as cresol novolak type epoxy resin, phenol novolak type epoxy resin, bisphenol A type epoxy resin, N, N'-di-2-naphthyl-
p-Phenylenediamine, sodium or polyvalent metal salt of 2,2′-methylenebis (4,6-di-tert-butylphenyl) phosphate, bis (4-ethyleneiminocarbonylaminophenyl) methane, 2- (2′- Hydroxyphenyl) benzotriazole, 2- (2'-
Hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-5′-tert-butylphenyl) benzotriazole and the like. Of course, it is not limited to these, and two or more kinds may be used in combination as required.

The amount of the storability improver used is not particularly limited, but it is generally desirable to adjust the amount in the range of about 10 to 100 parts by weight with respect to 100 parts by weight of the color developing agent.

In the present invention, a protective layer may be formed on the heat-sensitive recording layer, and examples of the adhesive used in such a protective layer include casein, starch and its derivatives, hydroxyethyl cellulose, methyl cellulose, carboxy. Methyl cellulose, completely (partially) saponified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, diisobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride copolymer salt, Ethylene / acrylic acid copolymer salt, silicone / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, styrene / butadiene copolymer emulsion, polyurethane / silicone copolymer emulsion, urea resin, melamine Down resin, amide resin, polyurethane ionomer, and the like. Among them, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol and silicon-modified polyvinyl alcohol are preferable as adhesives for the protective layer because they can form a strong coating, and particularly acetoacetyl group-modified polyvinyl alcohol is easily water resistant. Therefore, it is particularly preferably used.

Various kinds of pigments can be mixed in the protective layer. For example, calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, talc, kaolin, clay, and calcination. Examples thereof include inorganic pigments such as kaolin, calcined clay and colloidal silica, and organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea-formalin resin filler, and raw starch particles. The amount of such a pigment used is generally 5 per 100 parts by weight of the adhesive component.
It is desirable to adjust in the range of about 500 parts by weight.

Further, in the protective layer, if necessary, a lubricant such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, etc., a surfactant such as dioctyl sulfosuccinate (dispersant, wetting agent). ), Antifoaming agents, various aids such as water-soluble polyvalent metal salts such as potassium alum, aluminum acetate and the like can be appropriately added. Further, a curing agent such as glyoxal, boric acid, dialdehyde starch, or an epoxy compound can be added to further improve the water resistance.

The method for forming the heat-sensitive recording layer and the protective layer is not particularly limited, and examples thereof include air knife coating, varibar blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating, die coating and gravure coating. The coating liquid for heat-sensitive recording layer is applied and dried on the support by a suitable coating method, and then the coating liquid for protective layer is applied and dried on the recording layer.

As the support, paper (acidic paper, neutral paper),
It is used by appropriately selecting from plastic film, synthetic paper, non-woven fabric, metal vapor deposition sheet and the like. Further, 2~12g / m ² coating amount by dry weight of the heat-sensitive recording layer coating solution is preferably from 3 to 10 g / m ² approximately, the coating amount of the protective layer coating composition is 0.1 dry weight 20 g / m ^2, is preferably adjusted in the range of about 0.5 to 10 g / m ^2.

In the heat-sensitive recording material of the present invention, a protective layer (barrier) may be provided on the back surface side as necessary to further enhance the storability, or smoothing treatment such as super calendering may be performed after coating each layer. You can also In addition, various known techniques in the field of manufacturing a thermosensitive recording medium, such as providing a magnetic recording layer on the back surface or performing label processing, can be added.
For the label processing, a pressure-sensitive adhesive layer and a release paper may be laminated on the back surface, or a so-called delayed tack sheet using a heat-sensitive adhesive may be used, and a release layer may be provided on the recording medium. It is also possible to use a so-called linerless stack sheet that does not require release paper, and it is also possible to use a rewetting adhesive.

[0041]

The present invention will be described in more detail with reference to the following Examples, but it should be understood that the present invention is by no means restricted to such specific Examples. Parts and% in Examples are parts by weight and% by weight, respectively, unless otherwise specified.

Example 1 Preparation of coating liquid for intermediate layer 85 parts of calcined clay [trade name: Ansilex, manufactured by EMC, oil absorption 110 ml / 100 g] 85 parts, calcium carbonate [trade name: PZ, manufactured by Shiraishi calcium company] 15 parts , 100 parts of a 10% aqueous solution of polyvinyl alcohol and 200 water
The composition of 1 part was mixed and stirred to obtain a coating liquid for the intermediate layer.

Preparation of Solution A 10 parts of 3-di (n-butyl) amino-6-methyl-7-anilinofluorane, 5% aqueous solution of methylcellulose 5
And 40 parts of water were pulverized with a sand mill until the average particle size became 1.5 μm.

Preparation of Solution B 30 parts of 2,4-dihydroxy-2′-methoxybenzanilide, 5 parts of a 5% aqueous solution of methylcellulose and 8 parts of water
0 parts of the composition was sand milled to give an average particle size of 1.5
It was pulverized to a size of μm.

Preparation of Liquid C A composition consisting of 20 parts of 1,2-di (3-methylphenoxy) ethane, 5 parts of a 5% aqueous solution of methylcellulose and 55 parts of water was pulverized with a sand mill until the average particle diameter became 2 μm.

Preparation of coating liquid for heat-sensitive recording layer 55 parts of solution A, 115 parts of solution B, 80 parts of solution C, 80 parts of 10% aqueous solution of polyvinyl alcohol and aluminum hydroxide [trade name: Hydilite H-42, Showa Denko Company] 3
A 10% aqueous solution of acetic acid was added so that the pH of the coating liquid having a pH of 6.7 obtained by mixing and stirring 5 parts was 5.5 to obtain a coating liquid for a thermosensitive recording layer.

Preparation of coating liquid for protective layer Kaolin [trade name: UW-90, manufactured by EMC] 65 parts,
Acetoacetyl group-modified polyvinyl alcohol [Product name:
Gocefimer Z-200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.]
300 parts of 0% aqueous solution, 10% aqueous solution of glyoxal 3
Parts, 6 parts of a 30% dispersion of zinc stearate and 14 parts of water
The composition of 0 part was mixed and stirred to obtain a coating liquid for protective layer. Manufacture of thermal recording material 60 g / m ² of high-quality paper was coated and dried with a coating solution for intermediate layer so that the coating amount after drying was 10 g / m ^2, and then surface smoothing was performed with a super calender. to form an intermediate layer, the heat-sensitive recording layer and on the heat-sensitive recording layer coating composition and protective layer coating liquid application amount after drying sequentially applied and dried so as to ^{5g / m 2, 3g / m} 2 that After forming the protective layer, a super calender treatment was carried out to produce a thermosensitive recording medium.

Example 2 A thermosensitive recording medium was produced in the same manner as in Example 1 except that 15 parts of magnesium carbonate was used instead of 15 parts of calcium carbonate in the preparation of the coating liquid for the intermediate layer of Example 1.

Example 3 In the preparation of the coating liquid for the intermediate layer of Example 1, kaolin, trade name: UW-90, EM, was used instead of 15 parts of calcium carbonate.
A thermal recording material was manufactured in the same manner as in Example 1 except that 15 parts by C company was used.

Example 4 In the preparation of the coating solution for the intermediate layer of Example 1, instead of 85 parts of the baked clay, secondary particles of urea-formalin resin (oil absorption: 750 ml / 10) were used.
A thermosensitive recording medium was manufactured in the same manner as in Example 1 except that 85 parts of 0 g) was used.

Example 5 In the preparation of the coating liquid for the thermosensitive recording layer of Example 1, 1 part of acetic acid was used.
A thermosensitive recording medium was produced in the same manner as in Example 1 except that a coating solution for a thermosensitive recording layer having a pH of 6.7 was obtained without adding a 0% aqueous solution.

Example 6 In the preparation of the coating liquid for the heat-sensitive recording layer of Example 1, kaolin [trade name: UW- was used instead of 35 parts of aluminum hydroxide].
90, manufactured by EMC Co., Ltd.] and a 10% aqueous solution of acetic acid was added to obtain a thermosensitive recording layer coating solution having a pH of 6.2 to produce a thermosensitive recording medium in the same manner as in Example 1. did.

Example 7 In the preparation of the coating liquid for the thermosensitive recording layer of Example 1, 10 parts of amorphous silica [Mizukasil P-603, manufactured by Mizusawa Chemical Co.] and aluminum hydroxide [commercial product] were used instead of 35 parts of aluminum hydroxide. Name: Heidilite H-42, Showa Denko KK] 2
With 5 parts and without the addition of a 10% aqueous solution of acetic acid,
Example 1 except that a thermosensitive recording layer coating liquid having a pH of 6.8 was obtained.
A thermosensitive recording medium was manufactured in the same manner as in.

Example 8 In the preparation of the thermal recording layer coating solution of Example 1, 1 part of acetic acid was used.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that a 10% aqueous solution of lactic acid was used instead of the 0% aqueous solution.

Comparative Example 1 In the preparation of the thermal recording layer coating solution of Example 1, 1 part of acetic acid was used.
A thermosensitive recording medium was produced in the same manner as in Example 1 except that a 10% aqueous solution of sodium hydroxide was used in place of the 0% aqueous solution to obtain a coating solution for a thermal recording layer having a pH of 8.5.

Comparative Example 2 In the preparation of the coating liquid for the thermosensitive recording layer of Example 1, calcium carbonate [trade name:
Softon # 1500, manufactured by Bihoku Kogaku Kogyo Co., Ltd.] was used in the same manner as in Example 1 except that a thermosensitive recording layer coating solution having a pH of 8.0 was obtained without using a 10% aqueous solution of acetic acid. To produce a thermosensitive recording medium.

Comparative Example 3 In the preparation of the coating liquid for the thermosensitive recording layer of Example 1, 35 parts of magnesium carbonate was used in place of 35 parts of aluminum hydroxide, and a 10% aqueous solution of acetic acid was not added, and the pH was adjusted to 9. A thermosensitive recording medium was produced in the same manner as in Example 1 except that the thermosensitive recording layer coating liquid of 0 was obtained.

Comparative Example 4 In the preparation of the coating liquid for the thermosensitive recording layer of Example 1, 1 part of acetic acid was used.
A thermosensitive recording medium was prepared in the same manner as in Example 1 except that a 0% aqueous solution was used to obtain a thermosensitive recording layer coating liquid having a pH of 4.1.

[Evaluation] The thermal recording material thus obtained was evaluated as follows, and the results are shown in [Table 1].

[Viscosity Stability of Thermosensitive Recording Layer Coating Liquid] Regarding the 9 types of the obtained thermal recording layer coating liquids (common to Examples 1 to 4), the viscosities measured by a B-type viscometer at 20 ° C. Two
The viscosity was measured after standing at 0 ° C. for 3 days to evaluate the viscosity stability.

[Coloring property] Thermosensitive evaluation machine [Product name: TH-PMD, manufactured by Okura Electric Co., Ltd.]
The color density of the recorded image obtained by color development at 4 (mj / dot) was measured by a Macbeth densitometer [Macbeth RD-914 model] (visual mode).

[Whiteness] The whiteness of each of the obtained thermal recording media is measured according to JIS P-8123.
It measured based on.

[0063]

[Table 1]

[0064]

As is apparent from Table 1, the thermosensitive recording medium of the present invention has a stable viscosity of the coating liquid over time, is less likely to cause operational problems, and has good colorability and whiteness. It was also an excellent method for producing a thermosensitive recording medium.

Claims (3)

[Claims] 1. A method for producing a heat-sensitive recording material comprising a support and a heat-sensitive recording layer containing a leuco dye and a color-forming agent, wherein an amide compound represented by the following general formula (1) is used as the color-forming agent. A method for producing a heat-sensitive recording material, which comprises forming and forming a heat-sensitive recording layer by coating and drying a heat-sensitive recording layer coating liquid which contains and has a pH of 4.5 to 7.0. Embedded image [In the formula, R represents a C ₁ -C ₆ alkyl group, a C ₁ -C ₆ alkoxyl group, a halogen atom or a benzyl group. ] 2. The amide compound is 2,4-dihydroxy-
The method for producing a thermosensitive recording medium according to claim 1, which is 2'-methoxybenzanilide. 3. The method for producing a thermosensitive recording medium according to claim 1, wherein an intermediate layer containing calcium carbonate or magnesium carbonate is formed between the support and the thermosensitive recording layer.