JPH0648038A - Thermosensitive recording medium - Google Patents

Abstract

(57) [Summary] [Object] It is an object of the present invention to provide a thermosensitive recording medium which forms a recorded image readable by an optical reading device and is excellent in the appearance of a blank sheet and the storage stability of the recorded image. . A heat-sensitive recording material comprising a support, on which a thermosensitive recording layer containing a colorless or light-colored basic dye and a coloring agent capable of coloring when contacted with the dye and a protective layer are sequentially provided. And aromatic secondary amine anti-aging agent, 3,3-bis [1- (4-methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-2-yl] -4,5,
6,7-Tetrachlorophthalide or 3,3-bis [1
-(4-methoxyphenyl) -1- (4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, and an optical brightener in the protective layer. Thermal recording material contained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has excellent characteristics for an optical character (or mark) reading device having a reading wavelength range in the near infrared region, and moreover, has a blank appearance of a recording surface and preservation of a recorded image. The present invention relates to a thermosensitive recording material having excellent properties.

[0002]

2. Description of the Related Art A heat-sensitive recording material which utilizes a coloring reaction between a colorless or light-colored basic dye and an organic or inorganic coloring agent to bring both coloring substances into contact with each other by heat to obtain a recorded image is often used. Are known. Such a thermal recording material is relatively inexpensive,
Also, since the recording equipment 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.

On the other hand, in recent years, the number of cases in which a recorded image is read by an optical character reading device (including mark reading) has increased remarkably in combination with the rationalization of office processing, and in particular, optical having a reading wavelength in the near infrared region. In many cases, a character reading device is used. For example, in the distribution industry, in order to quickly respond to the needs of consumers, as the POS (point of sales) system is expanded, the case where it is used as a thermal recording label is increasing, and this reading device is A small and inexpensive device having a reading wavelength in the near infrared region is used.

However, the recorded image (black color image, blue color image, red color image, green color image, etc.) obtained by the above-mentioned recording body has an optical character reader having a reading wavelength range in the visible region (400 to 700 nm). In contrast, although it can be read as a lead color, it is in the near infrared region (700-1100).
It cannot be applied to an optical character reader having a reading wavelength range of (nm) because it functions as a dropout color regardless of the color tone.

Therefore, as a basic dye used for various recording materials, a dye suitable for an optical character reader utilizing light in the near infrared region is under development, and for example, a divinyl group-containing phthalide derivative ( Japanese Patent Publication 58-5940
No.) is proposed. However, when these compounds are used in a thermal recording material for POS labels,
There is a problem in storability, and in particular, the contrast between the recording portion and the background portion tends to decrease due to the influence of room light. Generally, thermal recording materials for labels have a protective layer provided on the recording layer to prevent deterioration of the recording layer due to water, plasticizer, oil, etc., and the water resistance and chemical resistance of the recording layer are improved. Has been done. However, as described above, in the case of a POS label using a dye suitable for an optical character reading device, since the stability of the dye with respect to room light is poor, the contrast between the recorded part and the background part of the label after the room light is irradiated is low. There is also a possibility that it will decrease and cause misreading by the reading device.

[0006]

The phthalide derivative having a divinyl group, which is a dye suitable for an optical character reading device, is itself colored in pale yellow, and therefore, of course,
The recording layer is colored light yellow. Therefore, although the coloring of the recording layer is improved by adding the fluorescent whitening agent to the recording layer colored light yellow, a new defect that the recorded image is easily discolored with time appears. Further, when a fluorescent whitening agent was added to the support, the whitening efficiency was poor because the fluorescent whitening agent functioned through the recording layer, and practically satisfactory results could not be obtained.

An object of the present invention is to solve the above problems and to provide a thermosensitive recording medium which can form a recorded image readable by an optical reader and is excellent in the appearance of a blank sheet and the storability of the recorded image. It is in.

[0008]

DISCLOSURE OF THE INVENTION The inventors of the present invention have found that a heat-sensitive recording layer and a protective layer containing, on a support, a colorless or light-colored basic dye and a coloring agent capable of coloring when contacted with the dye. In the heat-sensitive recording material in which the aromatic secondary amine-based antioxidant and 3,3-bis [1- (4-methoxyphenyl) -1- (4-dimethylaminophenyl) are added in the heat-sensitive recording layer, Ethylene-2-yl] -4,5,6,7-tetrachlorophthalide or 3,3-bis [1- (4-methoxyphenyl) -1- (4-pyrrolidinophenyl) ethylene-2-yl] By providing a thermal recording material containing -4,5,6,7-tetrachlorophthalide and a fluorescent whitening agent in the protective layer, the appearance of blank paper and the storage stability of recorded images are improved. The present invention has been completed and the present invention has been completed.

[0009]

The following are specific examples of the aromatic secondary amine anti-aging agent used in the present invention. Phenyl-1-naphthylamine, 4,4'-dioctyldiphenylamine, 4,4'-bis (α, α-
Dimethylbenzyl) diphenylamine, p- (p-toluenesulfonylamido) diphenylamine, N, N'-
Di-2-naphthyl-p-phenylenediamine, N, N '
-Diphenyl-p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, N-
Phenyl-N '-(1,3-dimethylbutyl) -p-phenylenediamine, N-phenyl-N'-(3-methacryloyloxy-2-hydroxypropyl) -p-phenylenediamine and the like. Of course, it is not limited to these, and two or more kinds can be used in combination. Above all, N,
N'-di-2-naphthyl-p-phenylenediamine is preferably used because the background part has less stain after light resistance and has an appropriate melting point.

Further, in the present invention, 3,3-bis [1- (4-methoxyphenyl) -1- (4-dimethyl) is used as a specific basic dye whose recorded image after coloring has an absorption wavelength in the near infrared region. Aminophenyl) 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 can be used alone or as a mixture, but 0.01 to 2.0 g / m ² , more preferably 0.05 to 2.0 g / m ² in the recording layer.
It is desirable to contain 1.0 g / m ² .

In the present invention, it is preferable to use a basic dye having an absorption wavelength in the visible region in addition to the near-infrared dye for the recorded image. Specific examples thereof include various known basic dyes. Specific examples of such basic dyes include the following. 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p
-Dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindole-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
-Ethylcarbazol-3-yl) -6-dimethylaminophthalide, 3,3-bis (2-phenylindole-
3-yl) -6-dimethylaminophthalide, 3-p-dimethylaminophenyl-3- (1-methylpyrrole-3
-Yl) -6-dimethylaminophthalide and other triallylmethane dyes, 4,4'-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leucoauramine, N-2,4,5-tri Diphenylmethane dyes such as chlorophenyl leuco auramine, benzoyl leuco methylene blue, thiazine dyes such as p-nitrobenzoyl leuco methylene blue, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, Spiro dyes such as 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho (6'-methoxybenzo) spiropyran, 3-propyl-spiro-dibenzopyran, rhodamine-B-anilinolactam, rhodamine (p-nitroanilino) Lactam, Damin (o- chloroanilino)
Lactam dyes such as lactam, 3-dimethylamino-7
-Methoxyfluorane, 3-diethylamino-6-methoxyfluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3 -Diethylamino-6,7-dimethylfluorane, 3- (N-ethyl-p-toluidino) -7-methylfluorane, 3-diethylamino-7-N-acetyl-N-methylaminofluorane, 3-diethylamino-
7-N-methylaminofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-N-methyl-N-benzylaminofluorane,
3-diethylamino-7-N-chloroethyl-N-methylaminofluorane, 3-diethylamino-7-diethylaminofluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7-phenylaminofluorane, Three
-(N-ethyl-p-toluidino) -6-methyl-7-
(P-Toluidino) fluorane, 3-dimethylamino-
6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-phenylaminofluorane, 3-di-n-butylamino-6-methyl-7-phenylaminofluorane, 3-di- n-pentylamino-
6-Methyl-7-phenylaminofluorane, 3-diethylamino-7- (2-carbomethoxy-phenylamino) fluorane, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-phenylaminofluor Oran, 3- (N-cyclopentyl-N-ethylamino)-
6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-phenylaminofluorane, 3-piperidino-6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7. -Xylidinofluorane, 3-diethylamino-7- (o-chlorophenylamino) fluorane, 3-di-n-butylamino-7- (o-chlorophenylamino) fluorane, 3-
Pyrrolidino-6-methyl-7-p-butylphenylaminofluorane, 3-diethylamino-7- (o-fluorophenylamino) fluorane, 3-dibutylamino-
7- (o-fluorophenylamino) fluorane, 3-
(N-methyl-Nn-amyl) amino-6-methyl-
7-phenylaminofluorane, 3- (N-ethyl-N
-N-amyl) amino-6-methyl-7-phenylaminofluorane, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-phenylaminofluorane, 3
-(N-Methyl-Nn-hexyl) amino-6-methyl-7-phenylaminofluorane, 3- (N-ethyl-Nn-hexyl) amino-6-methyl-7-phenylaminofluorane , 3- (N-ethyl-N-β-ethylhexyl) amino-6-methyl-7-phenylaminofluorane, 3- (N-ethyl-N-tetrahydrofurfuryl) amino-6-methyl-7-anilino Fluoran, 2,2-bis {4- [6 '-(N-cyclohexyl-N-methylamino) -3'-methylspiro [phthalide-3,9'-xanthene] -2'-ylamino] phenyl} propane, etc. Fluoran dyes. Two or more of these basic dyes can be used in combination, if desired.

[0012] The amount of the dyes having the visible region of the absorption wavelength recording layer 0.01 to 2 g / m ^2, and more preferably is used in an amount of about 0.05 to 1 g / m ^2.

Various known compounds are used as the color developing agent which develops a color by reacting with a basic dye, and specific examples thereof include the following. 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 1,3-bis [1- (4-hydroxyphenyl) -1-methylethyl] benzene, 1,4-bis [1- (4- Hydroxyphenyl) -1-methylethyl] benzene, 4-tert-butylphenol, 4-hydroxydiphenoxide, α
-Naphthol, β-naphthol, 4-hydroxyacetophenone, 4-tert-octylcatechol, 2,2'-
Dihydroxydiphenyl, 4,4'-isopropylidene bis (2-tert-butylphenol), 4,4'-sec
-Butylidene diphenol, 4-phenylphenol,
4,4'-isopropylidenediphenol, 4,4'-
Cyclohexylidene diphenol, 2,2'-methylenebis (4-chlorophenol), hydroquinone, hydroquinone monobenzyl ether, 4-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,
4,4'-trihydroxybenzophenone, 2,2 ',
4,4'-tetrahydroxybenzophenone, bis (3
-Tert-butyl-4-hydroxy-6-methylphenyl) sulfide, bis (2-methyl-4-hydroxy-
6-tert-butylphenyl) sulfide, 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 4-hydroxy -4'-methoxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-3 ', 4'-
Tetramethyldiphenyl sulfone, bis (3-allyl-
4-hydroxyphenyl) sulfone, 4-hydroxy-
4'-methyldiphenyl sulfone, 3,4-dihydroxydiphenyl sulfone, 3,4-dihydroxy-4'-
Methyldiphenylsulfone, 4,4'-methylenebis (oxyethylenethio) diphenol, 1,5-di (4
-Hydroxyphenylthio) -3-oxapentane, bis (4-hydroxyphenylthioethoxy) methane, 4
-Dimethyl hydroxyphthalate, methyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, sec-butyl 4-hydroxybenzoate, pentyl 4-hydroxybenzoate, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate. Tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, phenylpropyl 4-hydroxybenzoate, phenethyl 4-hydroxybenzoate, p-chlorobenzyl 4-hydroxybenzoate, p-methoxy 4-hydroxybenzoate. Phenolic compounds such as benzyl, novolac type phenolic resin, phenolic polymer, benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, 3-
sec-Butyl-4-hydroxybenzoic acid, 3-cyclohexyl-4-hydroxybenzoic acid, 3,5-dimethyl-
4-hydroxybenzoic acid, 3-tert-butylsalicylic acid, 3-benzylsalicylic acid, 3- (α-methylbenzyl) salicylic acid, 3-chloro-5- (α-methylbenzyl) salicylic acid, 3,5-di-tert- Butyl salicylic acid, 3-phenyl-5- (α, α-dimethylbenzyl)
Aromatic carboxylic acids such as salicylic acid and 3,5-di-α-methylbenzyl salicylic acid, and these phenolic compounds, aromatic carboxylic acids and, for example, zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel and the like. Salts with polyvalent metals, as well as organic acidic substances such as antipyrine complexes of zinc thiocyanate. still,
The amount of the developer used is not particularly limited,
It is desirable that the basic dye is contained in an amount of about 50 to 1000 parts per 100 parts.

Among them, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 1,5-di (4-hydroxyphenylthio) -3-oxapentane and bis (4-
Hydroxyphenylthioethoxy) methane is preferable because it has excellent storage stability.

Further, the following hindered phenolic antioxidants can be used in the recording layer, if necessary.
2,2'-Thimelen bis (4-methyl-6-tert-butylphenol), 2,2'-Thimeren bis (4-Ethyl-6-tert-butylphenol), 2,2'-Methylenebis (4,6-di-tert) -Butylphenol), 2,
2'-ethylidene bis (4,6-di-tert-butylphenol), 2,2'-ethylidene bis (4-methyl-6)
-Tert-butylphenol), 2,2'-ethylidenebis (4-ethyl-6-tert-butylphenol), 2,
2 '-(2,2-propylidene) bis (4,6-di-te
rt-butylphenol), 2,2'-methylenebis (4
-Methoxy-6-tert-butylphenol), 2,2 '
-Methylenebis (6-tert-butylphenol), 4,
4'-thiobis (3-methyl-6-tert-butylphenol), 4,4'-thiobis (2-methyl-6-tert-
Butylphenol), 4,4'-thiobis (5-methyl-6-tert-butylphenol), 4,4'-thiobis (2-chloro-6-tert-butylphenol), 4,
4'-thiobis (2-methoxy-6-tert-butylphenol), 4,4'-thiobis (2-ethyl-6-tert)
-Butylphenol) and the like. Of course, it is not limited to these, and two or more kinds can be used in combination.

In the present invention, the coating liquid for the heat-sensitive recording layer containing the basic dye, the color developer and the aromatic secondary amine anti-aging agent is generally prepared by using water as a dispersion medium and using a ball mill, attritor, sand mill or the like. It is prepared by dispersing with a stirrer / crusher. In such coating liquid, starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, etc. are usually used as a binder.
Carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, diisobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer A salt, a styrene / butadiene copolymer emulsion, a urea resin, a melamine resin, an amide resin and the like are added in an amount of 10 to 40% by weight, preferably 15 to 30% by weight, based on the total solid content of the coating liquid.

Further, various auxiliary agents can be added to the coating liquid as needed, and examples thereof include dioctylsulfosuccinic acid sodium salt, dodecylbenzenesulfonic acid sodium salt, lauryl alcohol sulfate / sodium salt, and fatty acid. A dispersant such as a metal salt, an ultraviolet absorber such as a benzophenone type, an antifoaming agent, a fluorescent dye, a coloring dye and the like are appropriately added.

If necessary, waxes such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax and ester wax, kaolin, clay, talc, calcium carbonate,
It is also possible to add an inorganic pigment such as calcined kaolin, titanium oxide, diatomaceous earth, fine particulate anhydrous silica, activated clay and the like, and a sensitizer may be used in combination 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'-hydroxy-5'- Methylphenyl) benzotriazole, 2-hydroxy-
4-benzyloxybenzophenone, 1,2-di (3-
Methylphenoxy) ethane, 1,2-diphenoxyethane, 1-phenoxy-2- (4-methylphenoxy) ethane, 1-phenoxy-2- (4-methoxyphenoxy) ethane, 1-phenoxy-2- (4- Chlorophenoxy) ethane, 1- (2-methylphenoxy) -2-
(4-Methoxyphenoxy) ethane, naphthylbenzyl ether, benzyl-4-methylthiophenyl ether, 4-methylthiophenyl-4'-chlorobenzyl ether, 4-methylthiophenyl-4'-bromobenzyl ether, 4-methylthiophenyl-4 ′ -Methylbenzyl ether, 4-methylthiophenyl-2′-methylbenzyl ether, 4-methylthiophenyl-4′-
Butyl benzyl ether, 4-methylthiophenyl-
4'-methoxybenzyl ether, oxalic acid dibenzyl ester, oxalic acid-di-p-methyl-benzyl ester, oxalic acid-di-p-chlorobenzyl ester, terephthalic acid dimethyl ester, terephthalic acid dibutyl ester, terephthalic acid dibenzyl Examples thereof include esters, dibutyl isophthalate, phenyl 1-hydroxynaphthoate and various known heat-fusible substances.

Among these sensitizers, 1,2-di (3-methylphenoxy) ethane, 1,2-diphenoxyethane, 1-phenoxy-2- (4-methylphenoxy) ethane, 1- ( 2-methylphenoxy) -2- (4
-Methoxyphenoxy) ethane, oxalic acid dibenzyl ester, oxalic acid-di-p-methyl-benzyl ester, and oxalic acid-di-p-chlorobenzyl ester are particularly preferable because of their excellent sensitizing effect.

The amount of the sensitizer used is not particularly limited, but it is generally desirable to adjust the amount within a range of about 4 parts by weight or less relative to 1 part by weight of the color developing agent.

The method for forming the recording layer is not particularly limited, and examples thereof include air knife coating, varibar blade coating, pure blade coating, short dwell coating, curtain coating,
It is formed by a method such as coating the recording layer coating liquid on a support such as paper, plastic film or synthetic paper by an appropriate coating method such as die coating and drying. The coating amount of the coating liquid is not particularly limited, usually dry weight 2~12g / m ^2, is preferably adjusted in the range of about 3 to 10 g / m ^2.

In the heat-sensitive recording material of the present invention, a protective layer containing a fluorescent whitening agent is provided on the recording layer thus formed. The protective layer is mainly a water-soluble polymer such as polyvinyl alcohol. , Carboxyl group modified polyvinyl alcohol, acetoacetyl group modified polyvinyl alcohol, silicon modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, starch and its derivatives, casein, sodium alginate, polyvinyl pyrrolidone, polyacrylamide, styrene-maleic acid copolymer It is formed by applying a coating liquid in which a fluorescent whitening agent is added to salt or the like and drying. Among them, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, and silicon-modified polyvinyl alcohol are particularly preferably used for forming a strong film.

The fluorescent whitening agent contained in the protective layer is
For example, pyrene, coumarin, oxazole, thiazole,
Various fluorescent brightening dyes and pigments composed of derivatives such as imidazole, imidazolone, pyrozole, benzidine, diaminocarbazole, naphthalic acid and diaminostilbenedisulfonic acid are used. The addition amount is appropriately adjusted according to the amount of the phthalide derivative having the specific divinyl group, but if the addition amount is too small, a sufficient improvement effect cannot be obtained, and conversely if it is too large, the storability of a recorded image is increased. In order to exert a bad influence on
It is desirable to contain about 0% by weight, preferably about 0.5 to 10% by weight.

A pigment may be added to the protective layer, if necessary, in order to further improve printability and sticking. Specific examples thereof include 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 Examples include formalin resin fillers and organic pigments such as raw starch particles.
The amount used is generally 5 to 100 parts by weight of the resin component.
It is desirable to adjust within the range of about 500 parts by weight.

In the coating liquid for forming the protective layer, if necessary, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax and ester wax, and surfactants such as sodium dioctylsulfosuccinate (dispersing agent). , Wetting agent), defoaming agent,
Various auxiliaries such as water-soluble polyvalent salts such as potassium alum and calcium acetate may be appropriately added. Further, a curing agent such as glyoxal, boric acid, dialdehyde starch, or an epoxy compound may be added to further improve water resistance.

The coating liquid for forming the protective layer is generally prepared by using water as a dispersion medium. The coating solution for protective layer thus prepared is coated on the thermosensitive recording layer by a suitable coating device, but if the coating amount exceeds 20 g / m ² in dry weight, the recording sensitivity of the thermosensitive recording medium may be significantly lowered. Therefore, it is generally 0.1 to 20 g / m ² , preferably 0.5 to 10 g / m ² .
It is desirable to adjust in the range of g / m ² .

In the heat-sensitive recording material of the present invention, a surface layer containing no fluorescent whitening agent may be provided on the protective layer, or a protective layer may be provided on the back surface side of the heat-sensitive recording material to further improve the storage stability. is there. Further, it is possible to provide an undercoat layer on the support or to apply a super calender after coating each layer, and to apply a pressure-sensitive adhesive to the back surface of the recording material to process it into an adhesive label. The publicly known technology can be added as needed.

[0029]

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 Preparation of Solution A 3,3-bis [1- (4-methoxyphenyl) -1-
(4-Dimethylaminophenyl) ethylene-2-yl]
-9 parts of 4,5,6,7-tetrachlorophthalide, N,
N'-di-2-naphthyl-p-phenylenediamine 9
Parts, 5 parts of a 5% aqueous solution of methyl cellulose, and water 27
Part of the composition is sand-milled to an average particle size of 1.5μ
The solution was pulverized to m.

Preparation of Solution B A composition consisting of 30 parts of 4-hydroxy-4′-isopropoxydiphenyl sulfone, 5 parts of a 5% aqueous solution of methylcellulose, and 55 parts of water was pulverized by a sand mill until the average particle size became 1.5 μm. Then, B liquid was obtained.

Preparation of Solution C 10 parts of 3-di-n-butylamino-6-methyl-7-phenylaminofluorane, 25 parts of 1,2-di (3-methylphenoxy) ethane, 5 parts of a 5% aqueous solution of methylcellulose , And 55 parts of water were pulverized by a sand mill until the average particle size became 1.5 μm to obtain C liquid.

Preparation of Liquid D: Acetoacetyl group-modified polyvinyl alcohol [trade name:
Gocefimer Z200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.]
% Aqueous solution 200 parts, kaolin [trade name: UW-90, E
Made by MC] 60 parts, fluorescent dye [Product name: WHITEX
BB, manufactured by Sumitomo Chemical Co., Ltd.] 4 parts, and 140 parts of water were mixed and stirred to obtain a liquid D as a coating liquid for the protective layer.

Preparation of Liquid E 100 parts of calcined clay (trade name: Ansilex, manufactured by EMC, oil absorption 110 cc / 100 g), 100 parts of a 10% aqueous solution of polyvinyl alcohol, and 200 parts of water were mixed and stirred. Liquid E was obtained as a coating liquid for the undercoat layer.

Formation of Recording Layer 50 parts of A solution, 90 parts of B solution, 60 parts of C solution, 15 parts of calcium carbonate, 160 parts of 10% polyvinyl alcohol aqueous solution were mixed and stirred to obtain a coating solution of 60 g / m ² . The base paper was coated and dried so that the coating amount after drying was 6 g / m ² to obtain a heat-sensitive layer.

Formation of Protective Layer Liquid D was applied on the heat-sensitive layer so that the coating amount after drying was 6 g / m ² and dried, and then supercalendering was performed to obtain a heat-sensitive recording material.

Example 2 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 8 parts of the fluorescent dye was used in place of 4 parts of the fluorescent dye in the preparation of the D liquid.

Example 3 In the preparation of solution D, a fluorescent dye [trade name: WHITEX
A thermal recording material was obtained in the same manner as in Example 1 except that 4 parts of a fluorescent dye [trade name: WHITEX ERN manufactured by Sumitomo Chemical Co., Ltd.] was used instead of 4 parts of BB, manufactured by Sumitomo Chemical Co., Ltd.

Example 4 In the preparation of liquid D, a fluorescent dye [trade name: WHITEX
A thermal recording material was obtained in the same manner as in Example 1 except that 2 parts of fluorescent dye [trade name: WHITEX ERN manufactured by Sumitomo Chemical Co., Ltd.] was used instead of 4 parts of BB, manufactured by Sumitomo Chemical Co., Ltd.

Example 5 In the preparation of solution A, 3,3-bis [1- (4-methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-2-yl] -4,5,6,7- Instead of 9 parts of tetrachlorophthalide, 3,3-bis [1- (4-methoxyphenyl) -1- (4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6,7-tetra A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 9 parts of chlorophthalide was used.

Example 6 Instead of 30 parts of 4-hydroxy-4'-isopropoxydiphenyl sulfone in the preparation of solution B, bis (4-
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 60 parts of hydroxyphenylthioethoxy) methane was used and 1,2-di (3-methylphenoxy) ethane was not used in the preparation of the liquid C. .

Example 7 In the preparation of solution B, 4,4'- was used instead of 30 parts of 4-hydroxy-4'-isopropoxydiphenyl sulfone.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 30 parts of isopropylidenediphenol was used.

Example 8 Instead of 10 parts of 3-di-n-butylamino-6-methyl-7-phenylaminofluorane in the preparation of solution C,
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 10 parts of 3-N-ethyl-N-iso-pentylamino-6-methyl-7-phenylaminofluorane was used.

Example 9 In the preparation of solution A, N, N'-di-2-naphthyl-p-
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 9 parts of 4,4′-bis (α, α-dimethylbenzyl) diphenylamine was used instead of 9 parts of phenylenediamine.

Example 10 Liquid E was applied onto a base paper of 60 g / m ² and the coating amount after drying was 7 g / m ^2.
An intermediate layer was formed by coating and drying so as to have a m ² thickness, and the heat-sensitive layer and the protective layer used in Example 1 were used thereon to obtain a heat-sensitive recording material.

Example 11 In the preparation of solution D, instead of 200 parts of a 10% aqueous acetoacetyl group-modified polyvinyl alcohol solution, a carboxyl group-modified polyvinyl alcohol [trade name: KL-3 was used.
No. 18, manufactured by Kuraray Co., Ltd.] was used, and a thermosensitive recording medium was obtained in the same manner as in Example 1 except that 60 parts of calcium carbonate was used instead of 60 parts of kaolin.

Comparative Example 1 In the preparation of liquid D, except that no fluorescent dye was used,
A thermal recording material was obtained in the same manner as in Example 1.

Comparative Example 2 Except that no fluorescent dye was used in the preparation of the D liquid,
A thermal recording material was obtained in the same manner as in Example 3.

Comparative Example 3 In the preparation of the D liquid, except that the fluorescent dye was not used,
A thermal recording material was obtained in the same manner as in Example 5.

Comparative Example 4 Liquid D was prepared except that no fluorescent dye was used.
A thermal recording material was obtained in the same manner as in Example 6.

Comparative Example 5 In the preparation of the D liquid, except that the fluorescent dye was not used,
A thermal recording material was obtained in the same manner as in Example 7.

Comparative Example 6 Except that no fluorescent dye was used in the preparation of solution D,
A thermosensitive recording medium was obtained in the same manner as in Example 8.

Comparative Example 7 In preparation of the D liquid, except that no fluorescent dye was used,
A thermosensitive recording medium was obtained in the same manner as in Example 9.

Comparative Example 8 Except that no fluorescent dye was used in the preparation of solution D,
A thermal recording material was obtained in the same manner as in Example 10.

Comparative Example 9 In the preparation of the D liquid, except that the fluorescent dye was not used,
A thermosensitive recording medium was obtained in the same manner as in Example 11.

The 20 types of heat-sensitive recording materials thus obtained were subjected to the following evaluation tests, and the results are shown in [Table 1]. [Blank Paper Appearance and Whiteness] The blank paper appearance is indicated by the color tone when the thermal recording paper is visually observed. The whiteness measurement conditions are as follows.

Measuring apparatus Erlejo 2000 [manufactured by Swiss Data Color Co.] Measuring conditions Light source D ₆₅ Main measurement wavelength 475 nm Measurement including UV light. [Coloring property in the near-infrared region] The coloring property in the near-infrared region is obtained by pressing the thermosensitive recording paper on a hot plate at 120 ° C for 5 seconds (4 kg /
cm ² ), and the recorded image obtained is measured with a spectrophotometer at a wavelength of 830n.
The reflectance (%) at m was displayed.

[0058]

[Table 1]

[0059]

As is clear from the results shown in Table 1, all of the thermal recording materials of the present invention have high whiteness and excellent appearance on white paper, and an optical reader having a reading wavelength range in the near infrared region. Was a readable thermal recording medium.

Claims (2)

[Claims] 1. A heat-sensitive recording medium comprising a support and a heat-sensitive recording layer containing a colorless or light-colored basic dye and a color-forming agent capable of exhibiting a color when contacted with the dye and a protective layer, which are successively provided. In the recording layer, an aromatic secondary amine anti-aging agent, 3,3
-Bis [1- (4-methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-2-yl] -4,
5,6,7-Tetrachlorophthalide or 3,3-bis [1- (4-methoxyphenyl) -1- (4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6,7-
A thermosensitive recording medium containing tetrachlorophthalide and a fluorescent whitening agent contained in a protective layer. 2. An aromatic secondary amine anti-aging agent is N,
The heat-sensitive recording material according to claim 1, which is N'-di-2-naphthyl-p-phenylenediamine.