JPH08192578A - Thermal recording - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a heat-sensitive recording material excellent in light resistance, which is extremely resistant to discoloration of the background portion and fading of a recorded image when exposed to a fluorescent lamp or sunlight for a long time. [Structure] A heat-sensitive recording material comprising a support and a heat-sensitive recording layer containing a colorless or light-colored basic dye and a coloring agent,
4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane as a colorant and 2-tert-butyl-6-as an antioxidant in the heat-sensitive recording layer.
A thermosensitive recording medium containing a compound represented by the following general formula (1) such as (3′-tert-butyl-5′-methyl-2′-hydroxybenzyl) -4-methylphenyl acrylate. Embedded image

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 the color-forming reaction between a colorless or light-colored basic dye and a coloring agent.
In particular, the present invention relates to a heat-sensitive recording material excellent in light stability of a recorded image and suppression of discoloration of a background portion.

[0002]

2. Description of the Related Art A heat-sensitive recording material which utilizes a color reaction between a colorless or light-colored basic 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 is well known. Are known. Such a thermal recording material is relatively inexpensive,
Since the recording device is compact and easy to maintain, 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 thermal recording paper for POS (point of sales) systems of retail stores and the like. Along with the expansion of the system, the uses attached to products are increasing. However, depending on the product, the attached heat-sensitive recording paper is often exposed to room light or sunlight, which has a drawback that the recorded image is easily discolored. Conventionally, in order to improve the light resistance of a recorded image,
A method of adding an antioxidant or an ultraviolet absorber to the heat-sensitive recording layer is disclosed in JP-A-49-54040 and JP-A-50-10.
Although it is described in Japanese Patent No. 4650 and Japanese Patent Laid-Open No. 60-48395, there are problems in background discoloration and stability of recorded images with time.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording material excellent in light resistance, in which discoloration of the background portion and fading of a recorded image upon exposure to a fluorescent lamp or sunlight for a long time is extremely small. To provide.

[0005]

Means for Solving the Problems The present inventors have
A heat-sensitive recording material comprising a support and a heat-sensitive recording layer containing a colorless or light-colored basic dye and a color-forming agent, wherein 4,4'-bis (p-toluene) is used as a color-forming agent in the heat-sensitive recording layer. Sulfonylaminocarbonylamino) diphenylmethane,
It has been found that, by containing a compound represented by the following general formula (1) as an antioxidant, it is possible to improve the light resistance of the printed part and suppress discoloration of the background part, and completed the present invention. .

[0006]

Embedded image

[Wherein R ₁ is a tert-butyl group, tert
Represents an amyl group or an isoamyl group, and R ₂ represents a methyl group, a tert-amyl group, or an isoamyl group. ]

[0008]

According to the present invention, a thermosensitive recording layer containing a colorless or monochromatic basic dye and 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane as a coloring agent is used as an antioxidant. tert-butyl-6-
(3'-tert-butyl-5'-methyl-2'-hydroxybenzyl) -4-methylphenylacrylate and other compounds represented by the above general formula (1) are added to discolor and record on the background. The lightfastness of the image was specifically improved.

The amount of the specific antioxidant and the coloring agent used is not particularly limited, but generally 1 to 200 parts by weight of the specific antioxidant per 100 parts by weight of the basic dye, It is desirable to use in the range of 1 to 100 parts by weight.

The basic dye used in the present invention includes:
Various known colorless or pale basic dyes may be mentioned, and specifically, for example, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3,3-bis (p-dimethylamino). Phenyl) phthalide, 3- (p-
Dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3,3-bis (2-phenylindol-3-yl) -6-dimethylaminophthalide, 3-p-dimethylaminophenyl- Triallylmethane dyes such as 3- (1-methylpyrrol-3-yl) -6-dimethylaminophthalide, N-halophenyl-leuco auramine, N-2,4,5-trichlorophenyl leuco auramine, etc. Diphenylmethane dyes, benzoyl leuco methylene blue, p-nitrobenzoyl leuco methylene blue and other thiazine dyes, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-propyl-spiro- Spiro dyes such as dibenzopyran, Rhodamine-B Anili Lactams, lactam dyes such as rhodamine (o-chloroanilino) lactam, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluorane , 3- (N-ethyl-p-toluidino) -7-methylfluorane, 3-diethylamino-7-N-chloroethyl-N-methylaminofluorane, 3-diethylamino-7-N-diethylaminofluorane, 3- (N-ethyl-p-toluidino)
-6-Methyl-7-phenylaminofluorane, 3-
(N-ethyl-p-toluidino) -6-methyl-7-
(P-Toluidino) fluorane, 3-dimethylamino-
6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-phenylaminofluorane, 3- (N-cyclohexyl-N-methylamino)-
6-methyl-7-phenylaminofluorane, 3-piperidino-6-methyl-7-phenylaminofluorane,
3-diethylamino-6-methyl-7-xylidinofluorane, 3-diethylamino-7- (o-chlorophenylamino) fluorane, 3-pyrrolidino-6-methyl-
7-p-Butylphenylaminofluorane, 3-diethylamino-7- (o-fluorophenylamino) fluorane, 3-dibutylamino-7- (o-fluorophenylamino) fluorane, 3-dibutylamino-6-methyl- 7-Phenylaminofluorane, 3- (N-methyl-Nn-amyl) amino-6-methyl-7-phenylaminofluorane, 3- (N-ethyl-Nn-amyl) amino-6- Fluoran dyes such as methyl-7-phenylaminofluorane and 3- [N- (3-ethoxypropyl) -N-ethyl] amino-6-methyl-7-anilinofluorane. Of course, two or more of these basic dyes can be used in combination.

The present invention uses 4,4'-bis (p
-Toluenesulfonylaminocarbonylamino) diphenylmethane is used, and its use amount is not particularly limited, but it is desirable to adjust it in the range of 50 to 500 parts by weight, preferably 100 to 300 parts by weight with respect to 100 parts by weight of the basic dye. Also, various known colorants may be used in combination within a range that does not impair the desired effects of the present invention.
Specific examples of such a coloring agent include p-octylphenol, p-tert-butylphenol, p-phenylphenol, 2,2-bis (p-hydroxyphenyl) propane, 1,1-bis (p-hydroxyphenyl). Propane, 2,2-bis (p-hydroxyphenyl) pentane, 1,1-bis (p-hydroxyphenyl) hexane, 2,2-bis (p-hydroxyphenyl) hexane, 1,1-bis (p-hydroxy) Phenyl) -2-ethylhexane, 2,2-bis (4-hydroxy-3,5
-Dichlorophenyl) propane, dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-isopropyloxydiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, p-hydroxybenzoic acid, p- Butyl hydroxybenzoate, zinc 3,5-di-tert-butylsalicylate, zinc 3,5-di-α-methylbenzylsalicylate, zinc 4- [3- (p-tolylsulfonyl) propyloxy] salicylate and the like can be mentioned. .

These heat-sensitive recording materials are generally used by using water as a dispersion medium and pulverizing them with an agitating / pulverizing machine such as a ball mill or a sand mill so that the average particle size becomes 2 μm or less.

The coating liquid for forming the heat-sensitive recording layer contains approximately 10 to 40% by weight of the total solid content, more preferably 15 to 40% by weight.
About 30% by weight of binders are mixed. Specific examples of the binders include, for example, methylcellulose, methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, sodium carboxymethylcellulose, polyvinyl alcohol (PVA), carboxy group-modified polyvinyl alcohol, sulfonic acid group-modified polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, and polyacrylamide. Acrylic acid, starch and its derivatives,
Casein, gelatin Water-soluble isoprene rubber, styrene /
Water-soluble substances such as alkali salts of maleic anhydride copolymers, alkali salts of iso (or diiso) butylene / maleic anhydride copolymers, or ethylene / vinyl acetate copolymers, polystyrenes, polyacrylic esters, polyurethanes , Styrene / butadiene copolymer, carboxylated styrene / butadiene copolymer, styrene / butadiene / acrylic acid copolymer, acrylonitrile / butadiene copolymer, ethylene / acrylic acid copolymer, colloidal silica / acrylic resin composite A water-soluble emulsion such as particles is used.

Further, a preservative improving agent may be used in combination for the purpose of further preserving the preservability of the recorded image, as long as the effects of the present invention are not impaired. Specific examples of such storage improvers include 1,4-diglycidyloxybenzene, 4,4′-diglycidyloxydiphenyl sulfone, diglycidyl terephthalate, 4-benzyloxy-
4 '-(2-methyl-2,3-epoxypropyloxy) diphenyl sulfone, 2,2'-dithiodibenzoic acid, 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 (3-methyl-6-tert-butylphenol), 4,4'-thiobis (2-methyl-6-te
rt-butylphenol), 4,4′-butylidenebis (6-tert-butyl-m-cresol), 2,5-di (tert-butyl) hydroquinone, 2,5-di (tert-
Amyl) hydroquinone, 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-dibromophenyl) propane,
2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2,2-bis (4-hydroxy3.5
-Hindered phenol compounds such as dimethylphenyl) propane, 1- [α-methyl-α- (4'-hydroxyphenyl) ethyl] -4- [α ', α'-bis (4 "-
Hydroxyphenyl) ethyl] benzene, N, N'-di-2-naphthyl-p-phenylenediamine, 2,2-
Examples thereof include methylenebis (4,6-di-tert-butylphenyl) phosphoric acid sodium, a copolymer of glycidyl methacrylate and styrene, and tris (2,3-epoxypropyl) isocyanurate.

If desired, various auxiliary agents can be added to the coating solution. For example, dispersant such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate / sodium salt, and fatty acid metal salt. , UV absorbers, other defoaming agents, fluorescent dyes, coloring dyes, etc. are appropriately added.

Specific examples of the ultraviolet absorber include, for example, phenyl salicylate, p-tert-butylphenyl salicylate, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxynzophenone, 2-hydroxy-4-octylbenzophenone. , 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2-
(2'-Hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2-
(2'-hydroxy-5'-tert-octylphenyl)
Benzotriazole, 2- (2'-hydroxy-3 ',
5'-di-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-
Amylphenyl) benzotriazole, 2,4-di-te
rt-Butylphenyl-3,5-di-tert-butyl-4-
Hydroxybenzoate, 2- (2'-hydroxy-
5'-tert-butylphenyl) benzotriazole, 2
-(2'-hydroxy-3 ', 5'-tert-butylphenyl) -5-chlorobenzotriazole, 2- (2H-
Benzotriazol-2-yl) -4-methyl-6-dodecylphenol, bis [2-hydroxy-3- (2 '
H-yl-benzotriazol-2′-yl) -5-octylphenyl] methane.

Further, if necessary, zinc stearate,
Add waxes such as calcium stearate, polyethylene wax, carnauba wax, paraffin wax and ester wax, inorganic pigments such as kaolin, clay, talc, calcium carbonate, calcined kaolin, titanium oxide, diatomaceous earth, fine anhydrous silica and activated clay. It is also possible to use a sensitizer together depending on the purpose.

Specific examples of the sensitizer include stearic acid amide, stearic acid methylenebisamide, oleic acid amide, palmitic acid amide, coconut fatty acid amide and other fatty acid amides, and 2,2'-methylenebis (4-methyl-). 6-tert-butylphenol), 4,4'-butylidenebis (6-tert-butyl-3-methylphenol), 2,2'-methylenebis (4-ethyl-6-tert)
-Butylphenol), 2,4-di-tert-butyl-3
-Hindered phenols such as methylphenol, 2-
Ultraviolet absorbers such as (2'-hydroxy-5'-methylphenyl) benzotriazole and 2-hydroxy-4-benzyloxybenzophenone, p-benzylbiphenyl, 1,2-di (3-methylphenoxy) ethane, 1,
2-diphenoxyethane, 1- (2-methylphenoxy) -2- (4-methoxyphenoxy) ethane, naphthylbenzyl ether, benzyl-4-methylthiophenyl ether, oxalic acid dibenzyl ester, oxalic acid-
Di-p-methyl-benzyl ester, oxalic acid-di-p
-Chloro-benzyl ester, terephthalic acid dimethyl ester, terephthalic acid dibutyl ester, terephthalic acid dibenzyl ester, isophthalic acid dibutyl ester,
Examples thereof include 1-hydroxynaphthoic acid phenyl ester, benzyl-4-methylthiophenyl ether, and various known heat-fusible substances.

Among these sensitizers, 1,2-di (3-methylphenoxy) ethane and oxalic acid-di-p-methylbenzyl ester are preferably used in the heat-sensitive recording material of the present invention. Further, it is generally desirable to adjust the amount of the sensitizer to be used in the range of about 400 parts by weight or less with respect to 100 parts by weight of the color developing agent.

The method for forming the recording layer is not particularly limited, and the heat-sensitive recording layer forming coating liquid is applied to the support by a suitable application method such as air knife coating, varibar blade coating, pure blade coating, short dwell coating. It is formed by a method such as drying. The coating amount of the coating liquid is not particularly limited, 2~12g / m ² is usually dry weight, preferably 3 to 10 g / m ²
It is adjusted within a range.

In the thermosensitive recording medium of the present invention, by providing a protective layer on the thermosensitive recording layer, it is possible to further improve the storability of recording and printing. The protective layer is generally formed by using a water-soluble or water-dispersible polymer as a main component, and specific examples of such a polymer include various binders as described above. Among these, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, and silicon-modified polyvinyl alcohol are particularly preferably used because they have excellent effects as a protective layer.

In order to further improve the water resistance of the protective layer, glyoxal, formalin, glycine, glycidyl ester, glycidyl ether, dimethylol urea, ketene dimer, dialdehyde starch, melamine resin, polyamide resin, polyamide-epichlorohydrin resin, ketone-aldehyde. A curing agent such as resin, borax, boric acid, ammonium zirconium carbonate, or an epoxy compound may be used in combination.

Further, in order to further improve printability and sticking, the protective layer may contain, for example, calcium carbonate,
Inorganic pigments such as zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc, kaolin, clay, calcined kaolin, colloidal silica, styrene microballs, nylon powder, polyethylene powder, urea Formalin resin filler, organic pigments such as raw starch particles, and the like can be blended as necessary. In addition, it is desirable that the amount of such a pigment is adjusted within a range of about 5 to 500 parts by weight with respect to 100 parts by weight of the binders.

In the coating liquid for forming the protective layer, if necessary, a lubricant such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, and a surfactant such as sodium dioctylsulfosuccinate ( Various auxiliaries such as a dispersant, a lubricant) and an antifoaming agent can be added as appropriate.

The coating solution for protective layer thus prepared is applied onto the thermosensitive recording layer by a suitable coating device. When the coating amount is 20 g / m ² in dry weight, the recording sensitivity of the thermosensitive recording material is lowered. Generally, 0.1-20 g /
It is desirable to adjust in the range of about m ² , preferably 0.5 to 10 g / m ² .

If necessary, a protective layer may be provided on the back side of the thermosensitive recording medium to further improve the storage stability. Furthermore, providing an undercoat layer on the support,
If necessary, various publicly known techniques in the field of heat-sensitive recording material production can be added, such as processing the back surface of the recording material with an adhesive to process it into an adhesive label. As a support,
Paper, plastic film, synthetic paper, etc. are used,
Paper is most preferably used in terms of price, coating suitability and the like.

[0027]

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. In addition, "part" and "%" in an example show "weight part" and "weight%", respectively, unless there is particular notice.

Example 1 Formation of Undercoat Layer Calcined clay [trade name: Ansilex, manufactured by EMC] 1
00 parts, styrene-butadiene copolymer latex (solid content: 50%) 15 parts, polyvinyl alcohol 10%
A composition comprising 30 parts of an aqueous solution and 200 parts of water was mixed and stirred to prepare a coating liquid for undercoat layer. The obtained coating liquid was applied to 70 g / m ² of high-quality paper so that the coating amount after drying was 7 g / m ^2, and dried to form an undercoat layer.

Preparation of solution A 3-dibutylamino-6-methyl-7-phenylaminofluorane 20 parts, 1,2-bis (3-methylphenoxy) ethane 40 parts, 5% aqueous solution of methylcellulose 2
A composition consisting of 0 part and 50 parts of water was pulverized with a sand mill until the average particle size became 0.8 μm.

Preparation of Solution B A composition consisting of 40 parts of 4,4′-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane, 20 parts of a 5% aqueous solution of methylcellulose, and 10 parts of water having an average particle size of 1. It was crushed to 2 μm.

Preparation of Solution C 2-tert-butyl-6- (3′-tert-butyl-5′-
A composition consisting of 10 parts of methyl-2′-hydroxybenzyl) -4-methylphenyl acrylate, 5 parts of a 5% aqueous solution of methylcellulose, and 15 parts of water was pulverized with a sand mill until the average particle size became 1.5 μm.

Formation of Recording Layer Liquid A 130 parts, liquid B 70 parts, liquid C 30 parts, polyvinyl alcohol 10% aqueous solution 160 parts, fine particle silicon oxide 20
Parts, 10 parts of a 30% zinc stearate dispersion, and 100 parts of water were mixed and stirred to obtain a coating liquid for the heat-sensitive recording layer. The obtained coating liquid was applied to the above undercoat layer so that the dry weight was 3 g / m.
After coating and drying so as to be ² , a super calender treatment was performed to obtain a heat-sensitive recording material.

Example 2 In the preparation of solution C, 2-tert-butyl-6- (3'-te was used.
rt-Butyl-5′-methyl-2′-hydroxybenzyl) -4-methylphenylacrylate instead of 2-
tert-amyl-6- (3'-tert-amyl-5'-tert
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that -amyl-2'-hydroxybenzyl) -4-tert-amylphenyl acrylate was used.

Example 3 In the preparation of solution B, 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane 40 was used.
20 parts of 4,4′-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane instead of 4 parts
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 20 parts of -hydroxy-4'-isopropoxydiphenyl sulfone was used.

Example 4 On the thermosensitive recording layer obtained in Example 1, 80 parts of a 10% aqueous solution of acetoacetylated polyvinyl alcohol, partially saponified polyvinyl alcohol (trade name; PVA-21) were used.
20% 10% aqueous solution of Kuraray, 20 kaolin
Parts, 2 parts of a 10% aqueous solution of glyoxal, and 50 parts of water
The coating amount obtained by mixing and stirring the parts is 1 g / m 2 after drying.
^It was coated and dried so as to be ² , to obtain a thermosensitive recording medium having a protective layer.

Comparative Example 1 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the liquid C was not used in forming the recording layer of Example 1.

Comparative Example 2 A thermosensitive recording medium was obtained in the same manner as in Example 4 except that the liquid C was not used in the formation of the recording layer of Example 4.

The heat-sensitive recording material thus obtained was subjected to the following evaluation tests and the results are shown in Table 1.

[Coloring Density] Thermal recording material evaluation machine (trade name:
THP-MD, manufactured by Okura Electric Co., Ltd., and applied energy
The color density of the recorded image obtained by recording at 0.2 mJ / dot was measured by a Macbeth densitometer (RD-914 type, manufactured by Macbeth).
Measured in visual mode. [Whiteness] Spectral reflectance meter (Product name: ELREPHO20
00) Measured with _R457 . [Environmental test] A weather meter (trade name: SUNSH) in which the thermal recording material is set to light source xenon, 63 ° C., 50% RH.
INE XENON LONG LIFE WEATH
After leaving it in ER METER, manufactured by Suga Test Instruments Co., Ltd. for 8 hours, the background part is subjected to a spectral reflectometer (ELREPHO200).
0), the whiteness was measured with R _457, the recording unit by measuring at Macbeth reflection densitometer to measure the photostability. After leaving the thermosensitive recording medium at 50 ° C. in the air for 7 days,
The whiteness of the background portion and the storage stability of the recording portion were measured under the conditions as described above.

[0040]

[Table 1]

[0041]

As is clear from the results shown in Table 1, the thermosensitive recording materials obtained in the respective examples of the present invention are heat-sensitive recording materials having excellent light resistance, that is, the background discoloration due to oxidation is small and the recording is low. The heat-sensitive recording material was excellent in light stability of the image.

Claims (1)

[Claims] 1. A thermosensitive recording medium comprising a support and a thermosensitive recording layer containing a colorless or light-colored basic dye and a color former, wherein 4,4′-as a color former is contained in the thermosensitive recording layer. Screw (p
-Toluenesulfonylaminocarbonylamino) diphenylmethane, a thermosensitive recording medium comprising a compound represented by the following general formula (1) as an antioxidant. Embedded image [Wherein R ₁ is a tert-butyl group, a tert-amyl group,
Alternatively, it represents an isoamyl group, and R ₂ represents a methyl group, a tert-amyl group, or an isoamyl group. ]