JP3397005B2 - Thermal recording medium - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material utilizing a color-forming reaction between a colorless or light-colored basic dye and a coloring agent, and more particularly to a heat-sensitive recording material excellent in running property during recording.

[0002]

2. Description of the Related Art A thermosensitive recording medium is well known, which utilizes a coloring reaction between a colorless or pale basic dye and a coloring agent to bring a coloring substance into contact with heat to obtain a recorded image. With the remarkable progress of thermal recording systems, their fields of application and forms are also diversifying, and not only as recording media for thermal facsimiles and thermal printers, but also magnetic thermal recording media or POS labels and ticket cards that require forgery prevention. There is a rapid increase in the use for new applications such as products, prepaid cards, and sealless fixed terms.

Above all, there is an increasing demand for thermal recording media for medical use, OHP use, or drafting, which are required to have excellent recording quality. In such a thermosensitive recording medium, a highly smooth paper or a film is used as a support in order to improve recording image quality. Therefore, there are drawbacks such as sticking and blocking between the thermal head and the recording surface during recording.

A heat-sensitive recording material containing an epoxy-modified silicone oil in the protective layer in order to improve such a defect is described in JP-A-3-67688, but for a protective layer containing the epoxy-modified silicone oil. There is a problem with the stability of the coating liquid and coatability. Further, if a large amount of epoxy-modified silicone oil is added to the coating liquid for protective layer, cissing may occur.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermosensitive recording medium having excellent sticking resistance during recording.

[0006]

DISCLOSURE OF THE INVENTION The present inventors have found that a support is provided with a recording layer containing a colorless or light-colored basic dye and a coloring agent, and a protective layer containing an aqueous resin. In the recording material, in the protective layer, by adding an epoxy-modified silicone oil and an alkyl phosphate ester salt, found that the above problems can be solved,
The present invention has been completed.

[0007]

The present invention provides a heat-sensitive recording material in which a recording layer containing a colorless or light-colored basic dye and a coloring agent, and a protective layer containing an aqueous resin as a main component are sequentially provided on a support. The content of the epoxy-modified silicone oil and the alkyl phosphate ester salt is not particularly limited, but the content of the epoxy-modified silicone oil and the alkyl phosphate ester salt is not particularly limited. The modified silicone oil content is preferably 2 to 20% by weight, and the alkyl phosphate ester salt content is preferably 1 to 10% by weight. If the epoxy-modified silicone oil is less than 3% by weight, sticking will occur strongly, and if it exceeds 20% by weight, cissing will occur and the coating surface will be deteriorated, and the epoxy-modified silicone oil in the protective layer will ooze out, resulting in a recorded image. New defects such as blurring occur. Further, if the amount of the alkyl phosphate ester salt is less than 1% by weight, the effect of improving the coatability is not provided, and if it exceeds 10% by weight, the amount of ions is too large, which causes damage to the thermal head.

The epoxy-modified silicone oil used in the present invention is a silicone compound having a lower alkylsilyl group such as a trimethylsilyl group, which is obtained by emulsifying a silicone oil having an epoxy group introduced at the terminal or side chain with an emulsifier or the like. It Epoxy-modified silicone oil emulsions have a bird's eye (coating liquid on the support surface) coating surface compared to, for example, silicone oil emulsions whose terminals or side chains are modified with carboxyl groups, amino groups, ester groups, ether groups, etc. (The state of being flipped by) is less likely to occur, and as a result, a uniform coating surface can be obtained.

Further, by using an epoxy-modified silicone oil emulsion and a specific amount of an alkyl phosphate ester salt in combination, the occurrence of bird's eyes and the repelling caused by the poor compatibility of the silicone oil emulsion and water are extremely caused. The effect is small and the running property during recording is excellent. It is desirable that the number of carbon atoms of the alkyl of such an alkyl phosphate ester salt be about 8 to 24.
If the carbon number is 7 or less or 25 or more, the effect of suppressing the generation of bird's eyes may be reduced. Further, examples of the salt include potassium, sodium, calcium, zinc, ammonium and the like. Of these, monovalent ones such as potassium, sodium, calcium and ammonium are preferable.

Specific examples of the aqueous resin used in the protective layer include starches such as oxidized starch, enzyme-modified starch, cation-modified starch, esterified starch and etherified starch, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, methoxy cellulose. Polyvinyl alcohol such as hydroxyethyl cellulose, completely (or incomplete) saponified polyvinyl alcohol, carboxy modified polyvinyl alcohol, acetoacetyl group modified polyvinyl alcohol, silicon modified polyvinyl alcohol, polyacrylamide, polyvinylpyrrolidone, acrylic acid amide / acrylic acid ester Polymer, acrylic acid amide / acrylic acid ester / methacrylic acid copolymer, styrene
Water-soluble resin such as alkali salt of maleic anhydride copolymer, alkali salt of isobutylene / maleic anhydride copolymer, casein; polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic acid ester, polybutyl methacrylate, styrene / butadiene copolymer Examples of the water dispersible resin include polymers, vinyl chloride / vinyl acetate copolymers, ethylene / vinyl acetate copolymers, styrene / butadiene / acrylic copolymers. Among these, completely (or incompletely) saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, and silicon-modified polyvinyl alcohol that exhibit excellent effects of sticking resistance and storage stability of recorded images are preferable. Particularly, acetoacetyl group-modified polyvinyl alcohol is preferable because it is excellent in heat resistance and running property during recording. The amount of the aqueous resin used in the protective layer is preferably adjusted in the range of 30 to 90% by weight based on the total solid amount of the protective layer.

Further, in the protective layer, calcium hydroxide, aluminum hydroxide, calcium carbonate, zinc oxide, aluminum oxide, as long as the desired effect is not impaired,
It is also possible to contain pigments such as silicon dioxide, talc, kaolin and colloidal silica.

The protective layer coating liquid is prepared by mixing and stirring an aqueous resin, an epoxy-modified silicone oil, an alkyl phosphate ester salt and the like with water as a dispersion medium. If necessary, a dispersant, a defoaming agent, a coloring dye, a fluorescent dye, a curing agent, an ultraviolet absorber, a lubricant and the like can be added to the coating liquid.

Specific examples of the lubricant include zinc stearate, calcium stearate, carnauba wax, paraffin wax, ester wax and the like.

As the colorless or light-colored basic dye, various known dyes can be used in the recording layer. Specific examples thereof include the following. 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, crystal violet lactone, 3- (N-
Ethyl-N-isopentyl) amino-6-methyl-7-
Anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-di (n-butyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7 -(O, p-dimethylanilino) fluorane, 3- (N-ethyl-N-p-toluidino) -6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluor Oran, 3-
(N-Cyclohexyl-N-methyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-7
-(O-chloroanilino) fluorane, 3-di (n-butyl) amino-7- (o-chloroanilino) fluorane, 3-diethylamino-7- (m-trifluoromethylanilino) fluorane, 3-diethylamino-6- Methyl-7-chlorofluorane, 3-diethylamino-6
-Methylfluorane, 3-cyclohexylamino-6-
Chlorofluorane, 3- (N-ethyl-N-hexyl)
Amino-6-methyl-7- (p-chloroanilino) fluorane and the like. Of course, two or more kinds of such basic dyes can be used in combination.

Various compounds are known as colorants used in combination with basic dyes, for example, 4-cumylphenol, hydroquinone monobenzyl ether, 4,
4'-isopropylidenediphenol, 1,1-bis (4-hydroxyphenyl) cyclohexane, 4,4 '
-Dihydroxydiphenyl-2,2-butane, 4,4 '
-Dihydroxydiphenyl sulfide, bis (4-hydroxy-3-methylphenyl) sulfide, 4,4'-
Dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 3,3'-allyl-4,
4'-hydroxydiphenyl sulfone , 4-hydroxyphenyl-4'-benzyloxyphenyl sulfone, 4
-Hydroxy-3 ', 4'-tetramethylene biphenyl sulfone, 3,4-dihydroxyphenyl-p-tolyl sulfone, 4-hydroxybenzoic acid benzyl ester,
N, N'-di-m-chlorophenylthiourea, 4,4 '
-Bis (p-tolylsulfonylaminocarbonylamino) diphenylmethane, 4- [2- (p-methoxyphenoxy) ethyloxy] salicylic acid, 4- [3- (p-
Tolylsulfonyl) propyloxy] zinc salicylate ,
Examples include 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid zinc. In addition, these coloring agents can be used in combination of two or more, if necessary.

In the present invention, the use ratio of the basic dye and the color developing agent in the recording layer is appropriately selected according to the types of the basic dye and the color developing agent used, and is not particularly limited. Generally, 1 to 10 parts by weight, preferably 1 to 5 parts by weight, of a coloring agent is used for 1 part by weight of a colorless or light-colored basic dye.

In the recording layer, as a binder, starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene / maleic anhydride copolymer alkali salt, ethylene / acrylic acid copolymer are usually used as binders. Alkali salt of polymer, alkali salt of styrene / acrylic acid copolymer, 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, etc. are added in an amount of about 5 to 35% by weight of the total solid content of the recording layer.

Further, if necessary, various additives are used in combination in the recording layer. For example, zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, and other lubricants, pigments, preservability improvers, An ultraviolet absorber, a sensitizer, etc. are mentioned.

Examples of the pigment include inorganic pigments such as calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, talc, kaolin, clay, calcined clay and colloidal silica; styrene microballs. Nylon powder,
Organic pigments such as polyethylene powder and urea / formalin resin filler can be used.

Examples of the storage stability improver added to improve the storage stability of the recorded image include 4,4'-butylidene bis (6-tert-butyl-3-methylphenol),
2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 2,4-di-tert-butyl-3-methylphenol, 1,1,3-tris (2-methyl-4-)
Hydroxy-5-tert-butylphenyl) butane, 1,
1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,3,5-tris (5
-Tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanur, 4- (2-methyl-1,2-epoxyethyl) diphenylsulfone, 4- (2-ethyl-1,2-epoxyethyl) diphenyl Sulfone,
4-benzyloxy-4 '-(2,3-glycidyloxy) diphenyl sulfone and the like can be mentioned.

Examples of the ultraviolet absorber added to improve the light resistance of the recorded image and the background part include 2-
(2'-hydroxy-5'-methylphenyl) benzotriazole, 2-hydroxy-4-benzyloxy benzophenone, etc. are mentioned.

Examples of sensitizers added to enhance recording sensitivity include stearic acid amide, N-methylstearic acid amide, benzalinide, stearic acid methylenebisamide, 1,2-di (3-methylphenoxy) ethane, 1,2-diphenoxyethane, parabenzyl biphenyl, naphthylbenzyl ether, benzyl-4-methylthiophenyl ether, 1-hydroxy-2-naphthoic acid phenyl ester, oxalic acid dibenzyl ester, oxalic acid-di-p-methylbenzyl Ester, oxalic acid-di-p-chlorobenzyl ester, terephthalic acid dibutyl ester, terephthalic acid dibenzyl ester,
Examples include isophthalic acid dibutyl ester.

To prepare a coating liquid containing these substances, water is generally used as a dispersion medium, and a basic dye, a color former, a preservative improver, and an ultraviolet ray are stirred by a ball mill, an attritor, a sand mill or the like and a pulverizer. The average particle size of the absorbent and the sensitizer, together or separately, is 2 μm or less, preferably 1
It is dispersed in a particle size of not more than μm to prepare a coating liquid for a recording layer.

The amount of the above additives to be contained in the recording layer is not particularly limited. For example, the amount of the sensitizer used is generally 4 parts by weight per 1 part by weight of the color developing agent. It is desirable to adjust within the following range.

The method for forming the recording layer and the protective layer is not particularly limited, and suitable examples include air knife coating, varibar blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating and die coating. The coating liquid for the recording layer and the coating liquid for the protective layer are sequentially applied and dried on the support by any of various coating methods. The coating amount of the coating liquid for the recording layer is 1 to 20 g / m ^{2 on} a dry weight basis, preferably 5 to 15 g.
It is adjusted in the range of / m ² . The coating amount of the coating liquid for the protective layer is adjusted in the range of 0.5 to 5 g / m ^{2 in} dry weight.

As the support, high quality paper (acidic paper, neutral paper), coated paper, synthetic paper, laminated paper, film and the like are used. Usually, even if a transparent film having a thickness of 20 to 150 μm, which easily causes sticking during recording, is used as the support, the thermosensitive recording medium of the present invention has an excellent running property during recording.

If necessary, a resin layer may be provided on the protective layer and / or on the back surface of the heat-sensitive recording material to further improve the storability of the heat-sensitive recorded image and impart conductivity. Further, various known techniques in the field of producing a thermal recording medium can be applied by subjecting the back surface to an adhesive label processing to form an adhesive label or providing a magnetic layer. Of course, it is also possible to improve the image quality and the image density by performing a super calendar process after forming the recording layer and the protective layer.

[0028]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" and "%" in the examples mean "parts by weight" and "% by weight" respectively.

Example 1 Preparation of Solution A 3-di (n-butyl) amino-6-methyl-7-anilinofluorane 20 parts, 1,2-di (3-methylphenoxy) ethane 10 parts, methylcellulose 5% aqueous solution of 20
Parts and 60 parts of water were pulverized with a sand mill until the average particle size became 0.8 μm.

Preparation of solution B 3,3 ′ diallyl-4,4′-dihydroxydiphenyl sulfone 20 parts, 5% aqueous solution of methylcellulose 20
Parts and 40 parts of water were pulverized with a sand mill until the average particle size became 0.8 μm.

Preparation of coating liquid for recording layer Liquid A 120 parts, liquid B 80 parts, solid content 30% colloidal silica (average particle size 10 nm) 70 parts, solid concentration 50%
Of 58 parts of styrene / butadiene, 1 part of a 10% aqueous solution of sodium dioctylsulfosuccinate, and 75 parts of water were mixed and stirred to obtain a coating liquid for recording layer.

Preparation of coating liquid for protective layer 150 parts of 10% aqueous solution of polyvinyl alcohol modified with acetoacetyl group, 2 parts of aluminum hydroxide having an average particle size of 1.2 μm, 1 part of 10% aqueous solution of sodium dioctylsulfosuccinate, modified with epoxy group 8 parts of silicone emulsion (solid concentration 30%), 10 parts of potassium stearyl phosphate
% Aqueous solution (7 parts) was mixed and stirred to obtain a protective layer coating liquid.

Formation of Recording Layer and Protective Layer On the polyester film [trade name: A-1300, manufactured by Toyobo, thickness 100 μm], the coating amount after drying the above coating liquid for recording layer and coating liquid for protective layer is 7 g / m ² , respectively
After coating and drying to form a recording layer and a protective layer in order to obtain ² g / m ² , a super calendering treatment is performed,
A thermosensitive recording medium was obtained.

[Example 2] In the preparation of the protective layer coating liquid of Example 1, 8 parts of the epoxy group-modified silicone emulsion was replaced by 1.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 5 parts were used.

Example 3 In the preparation of the protective layer coating liquid of Example 1, 15 parts of epoxy group-modified silicone emulsion was used instead of 8 parts of epoxy group-modified silicone emulsion.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that parts were used.

Example 4 Example 1 was repeated except that 1 part of potassium stearyl phosphate was used in place of 7 parts of potassium stearyl phosphate in the preparation of the protective layer coating liquid of Example 1.
A thermosensitive recording medium was obtained in the same manner as described above.

[Example 5] Thermosensitive recording was carried out in the same manner as in Example 1 except that 30 parts of potassium stearyl phosphate was used in place of 7 parts of potassium stearyl phosphate in the preparation of the protective layer coating liquid of Example 1. Got the body

Example 6 In the preparation of the coating liquid for protective layer of Example 1, instead of 150 parts of a 10% aqueous solution of acetoacetyl group-modified polyvinyl alcohol, 75 parts of a 10% aqueous solution of acetoacetyl group-modified polyvinyl alcohol and polyester were used. -Based polyurethane emulsion (solid concentration 25
%) A thermal recording material was obtained in the same manner as in Example 1 except that 30 parts was used.

Example 7 In the preparation of the protective layer coating liquid of Example 1, 150 parts of a 10% aqueous solution of silicon-modified polyvinyl alcohol was used in place of 150 parts of a 10% aqueous solution of acetoacetyl group-modified polyvinyl alcohol. A thermal recording material was obtained in the same manner as in Example 1.

Example 8 In the same manner as in Example 1, except that kaolin having an average particle diameter of 0.8 μm was used in place of 2 parts of aluminum hydroxide in the preparation of the protective layer coating liquid of Example 1. A thermosensitive recording medium was obtained.

Example 9 In the same manner as in Example 1, except that sodium palmityl phosphate was used in place of 7 parts of a 10% aqueous solution of potassium stearyl phosphate in the preparation of the coating liquid for protective layer of Example 1, A thermosensitive recording medium was obtained.

[Example 10] Thermal recording was carried out in the same manner as in Example 1 except that in the formation of the recording layer and the protective layer of Example 1, a high-quality paper having a basis weight of 60 g / m ² was used instead of the polyester film. Got the body

Comparative Example 1 In the preparation of the protective layer coating liquid of Example 1, 8 parts of amino group-modified silicone emulsion (solid concentration 30%) was used instead of 8 parts of epoxy group-modified silicone emulsion (solid concentration 30%). A thermosensitive recording medium was obtained in the same manner as in Example 1 except that was used.

Comparative Example 2 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the epoxy group-modified silicone emulsion was not used in the preparation of the protective layer coating liquid of Example 1.

Comparative Example 3 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that potassium stearyl phosphate was not used in the preparation of the protective layer coating liquid of Example 1.

Comparative Example 4 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that potassium stearate was used instead of potassium stearyl phosphate in the preparation of the protective layer coating liquid of Example 1. .

Comparative Example 5 In the preparation of the coating solution for protective layer of Example 1, 8 parts of epoxy group-modified silicone emulsion (solid concentration 30%) and 7 parts of 10% potassium stearyl phosphate aqueous solution were replaced by stearic acid. 3 of zinc
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 10.3 parts of 0% dispersion liquid was used.

The thermal recording material thus obtained was subjected to the following evaluation tests, and the results are shown in [Table 1]. (1). Recording density Recording was performed with a thermal printer [trade name: Mitsubishi SCTP-65, manufactured by Mitsubishi Electric Corporation], and the density of the recorded image obtained was measured with a Macbeth densitometer [trade name: RD914 Macbeth company]. did.

(2). Transparency of thermosensitive recording material (haze value) The haze value of the thermosensitive recording material is measured by a haze meter [trade name: TC
-HIV, manufactured by Tokyo Denshoku Co., Ltd.].

(3). Anti-sticking property (running property during recording) Hearing the strength of the sticking sound produced when recording with a thermal printer [trade name: Mitsubishi SCTP-65, manufactured by Mitsubishi Electric Corporation] It was judged. ⊚: Sticking sound is soft and slidability is good. ◯: Sticking sound is very soft and slipperiness is also good. Δ: Sticking sound is a little noisy and slipping is a little bad. ×: Sticking sound is noisy and slipperiness is poor.

(4). Coatability The coated surface of the thermosensitive recording medium was visually judged. ⊚: The coated surface is uniform without unevenness or cissing. ◯: Almost no unevenness or cissing. Δ: There is some unevenness and cissing. X: The coating surface is uneven and has unevenness and cissing.

[0052]

[Table 1]

[0053]

As is clear from the results shown in Table 1, the thermosensitive recording medium of the present invention has good sticking resistance and a uniform coated surface.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-345475 (JP, A) JP-A-3-67688 (JP, A) JP-A-3-61077 (JP, A) JP-A-3- 57693 (JP, A) JP 2-178084 (JP, A) JP 5-177940 (JP, A) JP 6-64326 (JP, A) JP 5-246140 (JP, A) JP-A-5-177939 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5 / 28-5 / 34

Claims (4)

(57) [Claims] 1. A thermosensitive recording medium in which a recording layer containing a colorless or light-colored basic dye and a coloring agent and a protective layer containing an aqueous resin are sequentially provided on a support, and an epoxy resin is contained in the protective layer. A heat-sensitive recording material comprising a modified silicone oil and an alkyl phosphate ester salt. Wherein in the protective layer, epoxy-modified silicone oil 3 to 20% by weight based on the total solids content of the protective layer and A
The heat-sensitive recording material according to claim 1, containing 1 to 10% by weight of a ruquil phosphate ester salt . 3. The heat-sensitive recording material according to claim 1, wherein the aqueous resin in the protective layer is acetoacetyl group-modified polyvinyl alcohol. 4. The heat-sensitive recording material according to claim 1, wherein the alkyl phosphoric acid ester salt has 8 to 24 carbon atoms in the alkyl group.