JPH05301461A - Thermal recording material and production thereof - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material good in chemical resistance, oil resistance or the like by successively laminating a thermal recording layer containing a leuco dye, a specific developer and aluminum hydroxide and a protective layer consisting an aqueous resin and a filler on a support. CONSTITUTION:A colorless or light-colored leuco dye and a diphenylsulfone compd. (developer) represented by formula I (wherein R is a 1-10C alkyl group or a benzyl group which may have a substituent) are respectively individually ground along with a dispersant and an aqueous resin being a binder by a media type wet dispersing machine. The respective dispersions are mixed to be compounded with an aluminum hydroxide dispersion to prepare a coating solution for a thermal recording layer. Separately, a filler such as inorg. pigment is dispersed in a aqueous solution of a water-soluble resin to prepare a coating solution. The coating solution for the thermal recording layer is applied to a support such as paper or a resin film and dried to form the thermal recording layer and the coating solution for the protective layer is applied to the thermal recording layer and dried to form the protective layer to obtain a thermal recording material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosensitive recording medium having a thermosensitive recording layer and a protective layer provided on a support.
It is a heat-sensitive recording material that has low background fog and high sensitivity, and has excellent recording stability such as chemical resistance and oil resistance as well as water resistance and water-resistant plasticizer, and is particularly suitable when used as heat-sensitive recording label paper. The present invention relates to a thermosensitive recording medium exhibiting characteristics and a method for producing the same.

[0002]

2. Description of the Related Art In general, a heat-sensitive recording material having a heat-sensitive recording layer mainly composed of a colorless or light-colored leuco dye and a color developer which reacts with the leuco dye to develop a color is disclosed in JP-B-45-1.
Published in No. 4035, etc., it has been widely put into practical use. A thermal printer or the like having a built-in thermal head is used to perform recording on this thermal recording medium, but such a thermal recording method has less noise during recording than other conventional recording methods that have been put to practical use. With the development of the information industry, various fields such as facsimile and computer have been developed due to the features such as no need for developing and fixing, maintenance-free, relatively inexpensive and compact equipment, and very clear color development. Widely used for measuring instruments and labels. However, the color development reaction between the leuco dye and the color developer in the thermal recording material of this kind is reversible, and the color image is easily formed by contact with a harsh environment or chemicals when used in the above various applications. It is also true that there is a problem with storage stability such as the reverse reaction and erasing.
For example, the image can be easily erased by contact with a plasticizer contained in packaging materials such as polyvinyl chloride film, adhesion of oils and fats such as cooking oil and industrial oil, and contact with adhesive such as cellophane tape and stick glue. It is the point that causes color. Therefore, as an attempt to improve the storage stability of an image with respect to these chemicals and to use this type of thermal recording material in a wider range of applications, for example, JP-A-57-188392 discloses that a thermosensitive coloring layer is formed on a thermosensitive coloring layer. Proposals have been made to provide a protective layer to prevent penetration of lipophilic chemicals such as plasticizers and oils.

However, although the above measures for providing a protective layer on the heat-sensitive recording layer contribute to the improvement of image storability due to the adhesion of lipophilic agents such as edible oil from the surface, they have been applied to food labels and the like. If the situation is assumed, such as when the label paper is soaked in water for a long time, the water resistance is insufficient, and the plasticizer contained in the food wrap film begins to dissolve in water and adhere to the label paper. However, the present situation is that it is not a means for sufficiently improving the storage characteristics due to lack of properties. This is because the support is paper and the material of the protective layer is an aqueous resin, that is, a water-soluble resin or a water-dispersible resin, and therefore has high water permeability, so the thermosensitive coloring part is water or a plasticizer dissolved in water. It is because it is easily affected by such as. On the other hand, attempts have been made to improve the water resistance with a color developer or the like.
For example, a specific 2,2'-bisphenol sulfone,
A 2,2'-bisphenol sulfide compound is used (JP-A-56-30896), and a specific 4,4'-bisphenol sulfide compound is used (JP-A-57-57).
41996), and bis (3-allyl-4-hydroxyphenyl) sulfone are used (JP-A-60-20828).
Many proposals such as No. 6) have been made. However,
Even if the effect of improving the water resistance is seen, it may lead to the phenomenon that fogging occurs on the background portion or the recording sensitivity and recording density are extremely lowered by providing a protective layer on the heat-sensitive recording layer. The current situation. As described above, in the conventional thermal recording material, despite various measures being taken, the recording sensitivity characteristic is still sufficient, good chemical resistance and oil resistance are provided, and at the same time the background fogging is small, Excellent water resistance,
At present, no one satisfying the water-resistant plasticizer resistance has been obtained.

[0004]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention is directed to a thermosensitive recording material, particularly a thermosensitive recording type label paper field, which is required to have chemical resistance, oil resistance, recording sensitivity, background whiteness and the like. The object of the present invention is to provide a heat-sensitive recording material having excellent water resistance and excellent water resistance, water resistance plasticizer resistance and the like, and a method for producing the same.

[0005]

The thermal recording material of the present invention comprises:
On at least one surface of the support, a colorless or light-colored leuco dye and a heat-sensitive recording layer containing a color developer as a main component that develops the color of the leuco dye under heat, and a protective layer containing an aqueous resin and a filler as main components are sequentially formed. In a laminated thermosensitive recording medium, at least one compound represented by the following general formula (1) is used as a developer in the thermosensitive recording layer, and the thermosensitive recording layer contains aluminum hydroxide. A thermal recording medium characterized by.

[Chemical 3] (In the formula, R represents an alkyl group having 1 to 10 carbon atoms or a benzyl group which may have a substituent.) In the method for producing a thermosensitive recording medium of the present invention, at least one surface of the support is colorless or Production of a heat-sensitive recording material comprising a light-color leuco dye, a heat-sensitive recording layer containing a color developer capable of coloring the leuco dye when heated, and a protective layer containing an aqueous resin and a filler as main components, which are sequentially laminated. At that time, as a coating liquid for the heat-sensitive recording layer, a developer containing at least one kind of the compound represented by the general formula (1), aluminum hydroxide and a dispersant were coexisted and pulverized with a media type wet disperser. A method for producing a heat-sensitive recording material, comprising forming a heat-sensitive recording layer using a coating liquid containing a dispersion liquid.

The diphenylsulfone compound represented by the general formula (1) used as a developer in the heat-sensitive recording layer in the present invention includes 4-hydroxy-4'-methoxydiphenylsulfone and 4-hydroxy-4'-ethoxy. Diphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-4'-n-propoxydiphenyl sulfone, 4-hydroxy-4'-
n-butoxydiphenyl sulfone, 4-hydroxy-
4'-n-pentyloxydiphenyl sulfone, 4-hydroxy-4'-n-hexyl diphenyl sulfone, 4
-Hydroxy-4'-n-heptyloxydiphenyl sulfone, 4-hydroxy-4'-n-octyloxydiphenyl sulfone, 4-hydroxy-4'-n-nonyloxydiphenyl sulfone, 4-hydroxy-4'-n
-Decyloxydiphenyl sulfone, 4-hydroxy-
4'-benzyloxydiphenyl sulfone, 4-hydroxy-4 '-(4-methylbenzyloxy) diphenyl sulfone, 4-hydroxy-4'-(4-methoxybenzyloxy) diphenyl sulfone, 4-hydroxy-
Examples thereof include, but are not limited to, 4 '-(4-chlorobenzyloxy) diphenyl sulfone and 4-hydroxy-4'-(2,6-dimethylbenzyloxy) diphenyl sulfone. Among them, 4-hydroxy-
4'-Isopropoxydiphenyl sulfone is particularly preferable because it shows a well-balanced property due to its storage property, recording sensitivity property and little background fog.

Aluminum hydroxide used in the heat-sensitive recording layer of the present invention is an inorganic pigment having a monoclinic crystal form represented by the chemical formula of Al (OH) ₃ , and is disclosed, for example, by "Hijilite" from Showa Denko KK The commercially available product under the name "." In the present invention, in the combination of the developer represented by the general formula (1) and aluminum hydroxide, there is little background fog and high sensitivity, excellent recording stability, and particularly improvement in water resistance and water resistant plasticizer is obtained. The proportion of aluminum hydroxide is preferably 10 to 300 parts by weight, and more preferably 20 to 150 parts by weight, based on 100 parts by weight of the color developer of the general formula (1). Here, if the amount of aluminum hydroxide is less than 10 parts by weight with respect to the color developer, the effect of improving water resistance and water resistant plasticizer and the effect of improving background whiteness are small, and conversely, if it is more than 300 parts by weight. There is a possibility that the amount of the filler in the heat-sensitive recording layer becomes excessive and the recording sensitivity is lowered.

As the leuco dye used in the heat-sensitive recording layer in the present invention, any leuco dye applicable to this kind of heat-sensitive recording material can be used, for example, fluorane type, triarylmethanephthalide type, fluorenephthalide type. , Divinylphthalide-based, phenothiazine-based, auramine-based, spiropyran-based, rhodamine-lactam-based compounds and the like are used. Specifically, 3-diethylamino-6-methyl-7-anilinofluorane, 3-di-n-butylamino-6-methyl-7-anilinofluorane, 3-di-n-
Pentyl-6-methyl-7-anilinofluorane, 3-
N-ethyl-N-isopropylamino-6-methyl-7
-Anilinofluorane, 3-N-ethyl-N-isoamylamino-6-methyl-7-anilinofluorane, 3-
N-methyl-N-cyclohexylamino-6-methyl-
7-anilinofluorane, 3-N-methyl-N-isobutylamino-6-methyl-7-anilinofluorane, 3
-N-ethyl-N-p-tolylamino-6-methyl-7
-Anilinofluorane, 3-N-pyrrolidino-N-methylamino-6-methyl-7-anilinofluorane, 3-
N-piperidino-N-methylamino-6-methyl-7-
Anilinofluorane, 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-N-ethyl- N- (2-ethoxypropyl) amino-6-methyl-7-anilinofluorane,
3-Diethylamino-6-methyl-7- (o-chloroanilino) fluorane, 3-di-n-butylamino-6-
Methyl-7- (o-chloroanilino) fluorane, 3-
Diethylamino-6-methyl-7- (o-trifluoromethylanilino) fluorane, 3-diethylamino-7
-Chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-cyclohexylamino-
6-chlorofluorane, 3-N-ethyl-N-p-tolylamino-7-methylfluorane, 3-diethylamino-7,8-benzofluorane, 3-diethylamino-7
-T-butylfluorane, 3-N-ethyl-N-p-tolylamino-7-N-methyl-N-phenylaminofluorane, 3-diethylamino-7-dibenzylaminofluorane, 2-methyl-6- p- (p-dimethylaminophenyl) aminoanilinofluorane, 2-chloro-3
Fluorane compounds such as -methyl-6-p- (p-dimethylaminophenyl) aminoanilinofluorane, 3,3
-Bis (p-dimethylaminophenyl) phthalide, 3,
3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (p-dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl)
Phthalide, 3- (p-dimethylaminophenyl) -3-
(2-Methylindol-3-yl) phthalide, 3,3
-Bis (1,2-dimethylindol-3-yl) -5
-Dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3-bis (9-ethylcarbazole-3-
Yl) -6-Dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -6-dimethylaminophthalide, 3-p-dimethylaminophenyl-3
Triarylmethanephthalide compounds such as-(1-methylpyrrol-3-yl) -6-dimethylaminophthalide, 3,6-bis (dimethylamino) fluorene-9-
Spiro-3 '-(6'-dimethylamino) phthalide,
Fluorene phthalide compounds such as 3,6-bis (diethylamino) fluorene-9-spiro-3 '-(6'-diethylamino) phthalide, 3,3-bis [2- (p-dimethylaminophenyl) -2- ( p-methoxyphenyl)
Ethenyl] -4,5,6,7-tetrachlorophthalide,
3,3-bis [2- (p-dimethylaminophenyl)-
2- (p-methoxyphenyl) ethenyl] -4,5,
6,7-Tetrabromophthalide, 3,3-bis [2-
(P-Pyrrolidinophenyl) -2- (p-methoxyphenyl) ethenyl] -4,5,6,7-tetrachlorophthalide and other divinylphthalide compounds, benzoyl eucomethylene blue and other phenothiazine compounds, 4,4 ′ -Bisdimethylaminobenzohydrylbenzyl ether, N
-Aroamine compounds such as halophenyl-leukoauramine, spiropyran compounds such as 3-methyl-spiro-dinaphthopyran, 3-ethyl-spirodinaphthopyran, lactam compounds such as rhodamine B-anilinolactam, rhodamine (p-nitroanilino) lactam Etc. In particular, a fluoran-based leuco dye is a compound capable of producing a black color with a single dye, and is excellent in image stability as compared with other compounds, and is therefore preferable.

In the heat-sensitive recording layer of the present invention, an aqueous resin is used as a binder, that is, a water-soluble resin or a water-dispersible resin, and examples thereof include polyvinyl alcohol, modified polyvinyl alcohol, bidroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, Starch and its derivatives, casein, gelatin, sodium alginate, polyvinylpyrrolidone, polyacrylamide, modified polyacrylamide, isobutylene-maleic anhydride resin alkali aqueous solution, diisobutylene-maleic anhydride resin alkaline aqueous solution, styrene-maleic anhydride resin alkaline aqueous solution, etc. Water-soluble resin, aqueous polyester, aqueous polyurethane, (meth) acrylic acid ester-based copolymer, styrene- (meth) acrylic acid ester copolymer,
Water-dispersible resins such as polyvinyl acetate, polyvinylidene chloride and their derivatives can be used alone or in combination.

In the present invention, various heat-fusible substances can be added to the heat-sensitive recording layer in order to improve the recording sensitivity, if necessary. Examples of the heat-fusible substance include organic compounds having an appropriate melting point. Examples thereof include higher fatty acid amides such as stearic acid amide and N-methylol stearic acid amide, higher fatty acids, higher fatty acid esters, dimethyl terephthalate, and diphenyl phthalate. Such as aromatic carboxylic acid esters, oxalic acid dibenzyl ester, oxalic acid di (p-methylbenzyl) ester and other diarylalkyl esters of dibasic acid, β-naphthoic acid phenyl ether, β-naphthoic acid phenyl ester, A naphthalene derivative such as 1-hydroxy-2-naphthoic acid phenyl ester, a biphenyl derivative such as p-benzylbiphenyl, a terphenyl derivative or the like is used. In addition to the aluminum hydroxide, for example, heavy and light calcium carbonate, titanium oxide, zinc oxide, barium sulfate, talc, clay, satin white, kaolinite, polyolefin particles, urea-formalin resin particles and the like inorganic and Organic pigments can also be added as fillers. Furthermore,
If necessary, additives such as dispersants, surfactants, antioxidants, and ultraviolet absorbers can be used.

The protective layer in the present invention comprises a resin and a filler, which are excellent in chemical resistance and have good film-forming properties, as main components, and a water-proofing agent is also necessary in order to obtain more excellent water resistance. Is added according to. The resin used in the protective layer of the present invention is an aqueous resin, that is, at least one selected from water-soluble resins and water-dispersible resins. Specifically, the binder used in the heat-sensitive recording layer is used. The same resin can be used. Examples of the filler include inorganic and organic pigments such as heavy and light calcium carbonate, titanium oxide, zinc oxide, barium sulfate, talc, clay, satin white, kaolinite, polyolefin particles, and urea-formalin resin particles. Can be applied. Furthermore, as the water-proofing agent, glyoxal, chrome alum, melamine resin, melamine formaldehyde resin, polyamide resin, polyamide-epichlorohydrin resin, zirconium compound and the like can be added. Further, if necessary, metal soap, wax, etc. may be added to improve the matching property with the thermal recording head.

Next, the method for producing the thermosensitive recording medium of the present invention will be described in detail. The thermosensitive recording medium of the present invention is prepared by sequentially laminating the thermosensitive coloring layer and the protective layer as described above on a support made of, for example, paper, synthetic paper, resin film, and a composite of these. It In order to form the heat-sensitive recording layer and the protective layer, the dispersion liquid having the composition as described above is applied by a known coating method such as air knife coating, roll coating, bar coating or blade coating, and dried. Good. Here, the coating liquid for the heat-sensitive recording layer, the leuco dye and the developer of the general formula (1) are separately pulverized by a media type wet disperser together with an aqueous resin which functions as a dispersant and a binder, The particle size of the substance to be dispersed is 5 μm or less, preferably 2
It can be prepared by dispersing the aluminum hydroxide so as to have a particle size of not more than μm, and then mixing and adding the aluminum hydroxide dispersion prepared as a dispersion.

When the thermal recording material of the present invention is manufactured,
It is particularly preferable that the developer of the general formula (1), aluminum hydroxide, and a dispersion liquid are allowed to coexist to be pulverized by a media type wet disperser, because more excellent recording sensitivity and water plasticizer resistance can be obtained. That is, when preparing a leuco dye dispersion, a developer dispersion, a binder dispersion, and a dispersion of other additives in advance in preparing the coating liquid for the thermal recording layer, the general formula (1 ), A color developer, aluminum hydroxide and a dispersant are coexistent and pulverized by a media type wet disperser. Such a dispersion is mixed with a leuco dye dispersion and other dispersions at a desired mixing ratio. Thus, the coating liquid for the heat-sensitive recording layer is prepared. The media type wet disperser may be, for example, a ball mill, an attritor, a sand grinder, or the like, and is not particularly limited.

As described above, when the developer of the general formula (1) and the aluminum hydroxide are subjected to the dispersion treatment, the dispersant used in combination is a water-soluble resin such as polyvinyl alcohol or cellulose, and (di) isobutylene- A maleic anhydride copolymer system, a styrene copolymer system, an acrylic copolymer system, etc. are used. Among these, (di) isobutylene-maleic anhydride copolymer system and styrene copolymer system shown below as specific examples, that is, diisobutylene-
Maleic anhydride copolymer ammonium salt, isobutylene-maleic anhydride copolymer ammonium salt, styrene-
Ammonia-soluble type dispersants such as maleic acid monoester copolymer ammonium salt, styrene- (meth) acrylic acid copolymer ammonium salt, and styrene- (meth) acrylic acid- (meth) acrylamide copolymer ammonium salt aqueous solution can be used. preferable. Among them, particularly, the aqueous solution of styrene- (meth) acrylic acid- (meth) acrylamide copolymer ammonium salt is ionically stabilized with styrene as a hydrophobic component and a hydrophilic component with (meth) acrylic acid and a hydrophilic component. Since (meth) acrylamide having a protective colloid action is appropriately copolymerized, it is preferable in terms of making the dispersion liquid fine particles and improving the stability.

The coating amount of the heat-sensitive recording layer in the present invention is 2
-10 g / m ² , preferably 4-8 g / m ² . The coating amount of the protective layer is preferably from 1 to 10 g / m ^2, functions as a barrier to improve the low and chemical resistance than 1 g / m ² is impaired, and more than 10 g / m ² to the heat-sensitive recording layer Since heat transfer is hindered, recording sensitivity is lowered, which is not preferable. Particularly preferable coating amount of the protective layer is 2 to 8
g / m ² . Further, after forming the thermosensitive recording layer and the protective layer, in order to improve the adhesiveness with the thermosensitive head and improve the recording sensitivity, a calender device composed of a metal roll and an elastic roll is used, and the Beck smoothness is used as the surface smoothness. 700 degrees
It is desirable that the surface of the protective layer be smoothed so as to be not less than 2 seconds, preferably not less than 1000 seconds. Further, in the heat-sensitive recording material of the present invention, an under layer containing a filler and a binder as main components is provided between the support and the heat-sensitive recording layer, if necessary, to enhance the smoothness of the surface of the support, The sharpness of the image quality can be improved. Further, by providing a back layer containing a film-forming polymer as a main component on the surface of the support opposite to the surface on which the heat-sensitive recording layer is provided, various chemicals from the back surface of the heat-sensitive recording material can be removed. It is also possible to prevent permeation and prevent unnecessary color development of the heat-sensitive recording layer and decolorization of the recorded image.

[0016]

In the heat-sensitive recording material of the present invention, when the compound of the general formula (1) is used as the developer of the heat-sensitive recording layer and aluminum hydroxide is used in the heat-sensitive recording layer, the background whiteness is increased. It is presumed that the pH buffering action of aluminum hydroxide prevents fogging due to the hypersensitive reaction between the leuco dye and the color developing agent of the general formula (1) in the heat-sensitive recording layer coating material and in the heat-sensitive recording layer. Further, the reason why the water resistance or the water resistance plasticizer resistance of the color development part is improved is that the acid-base color development reaction between the leuco dye heated to a mixed state and the color developing agent of the general formula (1) is stabilized. It is considered that aluminum hydroxide contributes, and it is speculated that specific image stability was obtained.

[0017]

EXAMPLES The present invention will be described in detail below with reference to examples. All parts in the examples represent parts by weight. Example 1 In order to produce a coating material for a heat-sensitive recording layer, the following composition [A] solution and [B] solution were dispersed using a sand grinder, and [C-1] solution was dispersed using a homogenizer. A liquid was prepared. [A] liquid-30 parts of 4-hydroxy-4'-isopropoxydiphenyl sulfone-30% aqueous solution of styrene-maleic acid monoester copolymer ammonium salt (manufactured by Dai-ichi Kogyo Seiyaku Co., DISCOAT N-14) 10 parts- Water 60 parts [B] liquid-3-N-ethyl-N-isoamylamino-6-methyl-7-anilinofluorane 30 parts-Polyvinyl alcohol 10% aqueous solution (Kuraray PVA203) 45 parts-Water 25 parts [C-1] liquid-Aluminum hydroxide (Showa Denko KK, Hydilite H-42) 30 parts-Styrene-maleic acid monoester copolymer ammonium salt 30% aqueous solution (Daiichi Kogyo Seiyaku Co., DISCOAT N -14) 5 parts Water 65 parts A thermosensitive recording layer having the following composition using the dispersion liquids of the liquids [A] to [C-1] obtained as described above. Paint was prepared, was applied to a dry weight of 6 g / m ² on a high-quality paper weighing 56 g / m ^2, provided with a heat-sensitive recording layer. -[A] solution 100 parts- [B] solution 30 parts- [C-1] solution 100 parts-Styrene-acrylic acid-acrylamide copolymer ammonium salt 25% aqueous solution (manufactured by Modern Chemical Industry Co., SA-6N-604 ) 60 parts Next, a coating material having the following composition was prepared as a coating material for the protective layer, and the coating material was applied onto the thermosensitive recording layer so as to have a dry weight of 4 g / m ² , to prepare a thermosensitive recording material of the present invention. -Carboxyl-modified polyvinyl alcohol 10% aqueous solution (Nippon Gosei Kagaku Co., Gosenol T-330) 100 parts-40% kaolin clay aqueous dispersion 20 parts-Zinc stearate 30% aqueous dispersion 5 parts-Polyamide epichlorohydrin resin 20% Aqueous solution (Showa High Polymer Co., Ltd., Polyfix 203) 20 parts Water 15 parts

Comparative Examples 1 to 4 Examples except that the dispersion liquid of the thermosensitive recording layer was replaced with the liquid [C-2] to the liquid [C-5] having the following composition instead of the liquid [C-1]. A thermal recording medium for comparison was prepared in exactly the same manner as in 1. [C-2] Liquid (Comparative Example 1) 30 parts of light calcium carbonate (manufactured by Shiraishi Industry Co., Ltd., Brilliant 15) 30% aqueous solution of styrene-maleic acid monoester copolymer ammonium salt (Daiichi Kogyo Seiyaku Co., Ltd. Coat N-14) 5 parts Water 65 parts [C-3] liquid (Comparative Example 2) Magnesium carbonate (Kanjima Chemical Industry Co., Ltd., Venus) 30 parts Styrene-maleic acid monoester copolymer ammonium salt 30% Aqueous solution (Daiichi Kogyo Seiyaku Co., Ltd., DISCOTE N-14) 5 parts Water 65 parts [C-4] liquid (Comparative Example 3) Clay (Anglo American Clay Co., Alpha Coat) 30 parts Styrene-malein Acid monoester copolymer ammonium salt 30% aqueous solution (manufactured by Dai-ichi Kogyo Seiyaku Co., DISCOTE N-14) 5 parts Water 65 parts [C-5] solution (Comparative Example 4) Mosquito (P-527D, manufactured by Mizusawa Kogyo Co., Ltd.) 30 parts ・ Styrene-maleic acid monoester copolymer ammonium salt 30% aqueous solution (manufactured by Dai-ichi Kogyo Seiyaku Co., DISCOTE N-14) 5 parts ・ Water 65 parts

Example 2 Filler dispersion liquid [C-1] used in Example 1 and Comparative Example 1
Solution and [C-2] solution were used, and a thermosensitive recording medium of the present invention was obtained in exactly the same manner as in Example 1 except that the coating composition for the thermosensitive recording layer was as follows. -[A] liquid 100 parts- [B] liquid 30 parts- [C-1] liquid 30 parts- [C-2] liquid 70 parts-Styrene-acrylic acid-acrylamide copolymer ammonium salt 25% aqueous solution (modern chemistry SA-6N-604, manufactured by Kogyo Co., Ltd. 60 parts Example 3 The following liquid [A-1] was used in place of the liquid [A] of Example 1 as the developer dispersion in the thermosensitive recording layer. A thermosensitive recording medium of the present invention was prepared in the same manner as in Example 1 except for the above. [A-1] liquid-30 parts of 4-hydroxy-4'-benzyloxydiphenyl sulfone-30% aqueous solution of styrene-maleic acid monoester copolymer ammonium salt (Daiichi Kogyo Seiyaku Co., DISCOAT N-14) 10 Parts / water 60 parts Comparative Examples 5 to 7 2,2-bis (instead of 4-hydroxy-4′-isopropoxydiphenyl sulfone in the liquid [A] of Example 1 as a developer dispersion for the heat-sensitive recording layer) Examples except that 4-hydroxyphenyl) propane (Comparative Example 5), 4-hydroxybenzoic acid benzyl ester (Comparative Example 6) and bis (3-allyl-4-hydroxyphenyl) sulfone (Comparative Example 7) were used respectively. A thermal recording medium for comparison was prepared in exactly the same manner as in 1.

Example 4 In order to produce a coating material for a heat-sensitive recording layer, a dispersion liquid was prepared by using a liquid [A] and a liquid [B] having the following compositions with a sand grinder. [D] liquid-30 parts 4-hydroxy-4'-isopropoxydiphenyl sulfone-20% styrene-acrylic acid-acrylamide copolymer ammonium salt aqueous solution (Modern Chemical Industry Co., SA-6N-604) 20 parts-water Aluminum oxide (Showa Denko KK, Hydilite H-42) 30 parts Water 120 parts [E] liquid 3-N-ethyl-N-isoamylamino-6-methyl-7-anilinofluorane 30 parts Polyvinyl Alcohol 10% aqueous solution (Kuraray Co., PVA203) 45 parts Water 25 parts Using the dispersion liquid of the [D] liquid and the [E] liquid obtained as described above, a coating material for a heat-sensitive recording layer having the following composition is prepared. The heat-sensitive recording layer was prepared by coating a fine paper having a basis weight of 56 g / m ^{2 so} that the dry weight was 6 g / m ² . -[D] liquid 200 parts- [E] liquid 30 parts-Styrene-acrylic acid-acrylamide copolymer ammonium salt 25% aqueous solution (manufactured by Modern Chemical Industry Co., SA-6N-604) 60 parts Next, for protective layer A coating material having the following composition was prepared as a coating material, and was coated on the thermal recording layer so as to have a dry weight of 4 g / m ² , to prepare a thermal recording material by the method for producing a thermal recording material of the present invention. -Carboxyl-modified polyvinyl alcohol 10% aqueous solution (Nippon Gosei Kagaku Co., Gosenol T-330) 100 parts-40% kaolin clay aqueous dispersion 20 parts-Zinc stearate 30% aqueous dispersion 5 parts-Polyamide epichlorohydrin resin 20% Aqueous solution (Showa High Polymer Co., Ltd., Polyfix 203) 20 parts Water 15 parts

Example 5 4-Hydroxy-, which is the developer of the liquid [D] of Example 4
A thermal recording material was prepared by the method for producing a thermal recording material of the present invention in the same manner as in Example 4 except that 4'-isopropoxydiphenyl sulfone was replaced with 4-hydroxyphenyl-4'-benzyloxydiphenyl sulfone. Comparative Example 8 A thermosensitive recording medium for comparison was prepared in the same manner as in Example 4 except that the aluminum hydroxide in the liquid [D] of Example 4 was replaced with light calcium carbonate (Brilliant 15 manufactured by Shiraishi Industry Co., Ltd.). Comparative Examples 9 to 10 4-hydroxy-4'-isopropoxydiphenyl sulfone of the liquid [D] of Example 4 was converted into 2,2-bis (4-hydroxyphenyl) propane (Comparative Example 9) and benzyl 4-hydroxybenzoate. A thermal recording medium for comparison was prepared in exactly the same manner as in Example 4 except that the ester (Comparative Example 10) was used.

Examples 1 to 5 and Comparative Example 1 obtained above
Table 1 shows the results of evaluation of each item of the thermosensitive recording media of Nos. 10 to 10 by the following methods. 1. Recording density Recording was performed with a thermal printing device manufactured by Matsushita Electronic Components Co., Ltd. at an applied power of 0.5 W / dot and a pulse width of 1.0 msec, and the solid density was measured with a Macbeth reflection densitometer RD-914.
The recording density was evaluated. 2. Background density The background density was measured with a Macbeth reflection densitometer RD-914 to evaluate the background fog. 3. Water resistance A printing sample was prepared with a label printer printing device manufactured by Teraoka Co., Ltd., and the printing sample was submerged in water having a water temperature of 25 ° C. for 24 hours, and the density of the printing portion was measured with a Macbeth reflection densitometer. The water resistance was evaluated by obtaining the residual rate from the following formula. Water resistance (residual rate,%) = (concentration of printed area after submersion / concentration of printed area before submersion) × 100 4. Water-resistant plasticizer resistance A printing sample was prepared using a label printer printer manufactured by Teraoka Co., Ltd., and added to 1 g of food wrap (Dialap G manufactured by Mitsubishi Plastics Co., Ltd.) per 1 liter of water in water at a temperature of 25 ° C. The density of the printed part after the printed sample was submerged in water for 24 hours was measured with a Macbeth reflection densitometer RD-914, and the residual rate was calculated from the following formula to evaluate the water plasticizer resistance. 4. Water resistant plasticizer resistance (residual rate,%) = (printed area density after submersion / printed area density before submersion) × 100 Oil resistance A label sample printer manufactured by Teraoka Co., Ltd. was used to prepare a printed sample, castor oil was applied to the sample surface in an environment of 40 ° C., and the sample was allowed to stand for 24 hours. The oil resistance was evaluated by measuring with RD-914 and obtaining the residual rate from the following formula. Oil resistance (residual rate,%) = (printed part density after leaving / printed part density before leaving) x 100

[0023]

[Table 1] As is clear from the results of Table 1, the thermosensitive recording medium of the present invention is confirmed to have good recording sensitivity from the recording density, has high background whiteness, and has excellent chemical resistance. It was found that the water resistance and the water resistance of the plasticizer were very excellent. Further, the thermal recording materials of Examples 4 and 5 produced by the method for producing a thermal recording material of the present invention have recording sensitivity (recording density) and recording stability (water resistance, water plasticizer resistance, oil resistance, etc.).
It has been found that it has more excellent properties.

[0024]

The heat-sensitive recording material of the present invention is a heat-sensitive recording material having less background fog and high sensitivity, and excellent recording stability such as chemical resistance and oil resistance as well as water resistance and water resistant plasticizer resistance. Therefore, it is possible to exhibit excellent characteristics as a heat-sensitive recording type label paper used for packaging of fresh foods, etc., which require particularly severe storage stability of recorded images.

Claims (4)

[Claims] 1. A heat-sensitive recording layer containing a colorless or light-colored leuco dye and a color developer that develops the color of the leuco dye when heated, on at least one side of a support, and an aqueous resin and a filler as main components. In the heat-sensitive recording material in which the protective layers are sequentially laminated, at least one compound represented by the following general formula (1) is used as a developer in the heat-sensitive recording layer, and hydroxylation is performed in the heat-sensitive recording layer. A thermosensitive recording medium comprising aluminum. [Chemical 1] (In the formula, R represents an alkyl group having 1 to 10 carbon atoms or a benzyl group which may have a substituent.) 2. The heat-sensitive recording material according to claim 1, wherein the developer is 4-hydroxy-4′-isopropoxydiphenyl sulfone. 3. A heat-sensitive recording layer containing a colorless or light-colored leuco dye and a color developer capable of coloring the leuco dye under heat on at least one side of the support, and an aqueous resin and a filler as main components. When a heat-sensitive recording material is formed by sequentially laminating the protective layers described above, as a coating liquid for the heat-sensitive recording layer, a developer containing at least one compound represented by the following general formula (1), aluminum hydroxide and a dispersion are used. A method for producing a heat-sensitive recording material, which comprises forming a heat-sensitive recording layer by using a coating liquid containing a dispersion liquid co-existing an agent and pulverized by a media type wet disperser. [Chemical 2] (In the formula, R represents an alkyl group having 1 to 10 carbon atoms or a benzyl group which may have a substituent.) 4. The dispersant is a diisobutylene-maleic anhydride copolymer, an isobutylene-maleic anhydride copolymer, a styrene-maleic acid monoester copolymer, a styrene- (meth) acrylic acid copolymer, The method for producing a thermosensitive recording medium according to claim 3, which is at least one ammonium salt selected from a styrene- (meth) acrylic acid- (meth) acrylamide copolymer.