JP2000079762A - Thermal recording body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sufficient color-developing density, and at the same time, develop a color into dark blue or grayish blue by setting a color difference value L*, a color difference value a* and a color difference value b* of a color-developing image, which are specified in JIS-Z-8729, in specified ranges. SOLUTION: A color difference value L*, a color difference value a* and a color difference value b* of a color-developing image, which are specified in JIS-Z-8729, are set in either range of 30-50 for the value L*, $15-0 for the value a*, and also, -30-10 for the value b*, or 30-50 for the value L*, 0-10 for the value a*, and also, -30-0 for the value b*, or 30-50 for the value L*, 10-20 for the value a*, and also, -30--15 of the value b*. The thermal recording body becomes a required tone of dark blue or grayish blue by setting the color difference value L*, value a* and value b* of the color-developing image in these ranges. In addition, setting the color difference value L* at 30-45, and also, the value a* at -15-0, and the value b* at -25-10, or the value a* at 0-10, and the value b* at -25-0 is preferable to obtain a clearer tone.

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 which develops a dark blue or gray blue (grayish blue) color.

[0002]

2. Description of the Related Art In general, a heat-sensitive recording layer mainly comprising a colorless or light-colored electron-donating dye precursor (hereinafter referred to as a dye precursor) and a developer which reacts with the dye precursor when heated to form a color is provided. The heat-sensitive recording medium has
No. pp. 139, and widely used. In order to perform recording on this thermosensitive recording medium, a thermal printer or the like having a built-in thermal head is used.However, such a thermosensitive recording method has less noise at the time of recording as compared with other recording methods that have been practically used conventionally. With no development and fixing, maintenance-free, relatively inexpensive and compact equipment, and very clear color development, the facsimile and computer fields Widely used for various measuring instruments and labels. Most of the color-developed images of such a thermosensitive recording medium are black-colored images, but red-colored, blue-colored, green-colored, full-color-colored and two-color-colored images are also known.

[0003] Also, the color image of the heat-sensitive recording medium is relatively high-resolution and close to a photograph, and has recently been used for outputting an image taken by a camera attached to a game machine. There has been a growing demand for a thermosensitive recording medium that develops an intermediate color such as dark blue or gray blue (grayish blue). However, in the field of conventional thermal recording, a color image is changed to dark blue or gray blue (grayish blue) due to fading or discoloration due to environmental conditions such as sunlight and temperature, chemicals, and the like. However, this is a phenomenon that is recognized as an adverse effect such as poor image storability or poor appearance,
There has been no example of a heat-sensitive recording medium in which a color image itself exhibits a dark blue or gray blue (grayish blue) color.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a thermosensitive recording medium which has a sufficient color density and develops a dark blue or gray blue (grayish blue) color.

[0005]

In order to achieve the above object, according to the first aspect of the present invention, a thermosensitive coloring layer containing a colorless or pale color dye precursor and an organic developer as main components is provided. JIS-Z-8 of the color image in the thermosensitive recording medium
729, a color difference L * value, a color difference a * value, and a color difference b
* A thermosensitive recording material characterized in that the value is in any one of the following ranges A to C: A. L * value is 30 to 50, a * value is -15 to 0, and b
* Value is -30 to 10 B. C. L * value is 30 to 50, a * value is 0 to 10, and color difference b * value is -30 to 0. L * value is 30-50, a * value is 10-20, and b
* Value is -30 to -15

In the present invention, the color difference L * value is a parameter indicating the degree of brightness, and the larger the value, the brighter the color. The color difference a * value is a parameter representing greenishness. As the value increases, the greenishness increases as the value increases. The greenishness decreases as the value approaches zero, and the redness increases as the value increases. Also, the color difference b
* The value is a parameter representing the bluish color. It indicates that the bluish color becomes stronger as the value becomes larger in the negative direction, the bluish color becomes weaker as the value approaches zero, and the yellow color becomes stronger as the value becomes larger in the positive direction. The thermosensitive recording medium of the present invention has a color difference L * value of a color image,
When the a * value and the b * value are in the above ranges, the color tone to be obtained is a dark blue or gray blue (grayish blue) color. Further, when the color difference L * value is 30 to 45 and the a * value is -15 to 0 and the b * value is -25 to 10, or the a * value is 0 to 10 and the b * value is -25 to 25. If it is 0,
A more vivid color tone is obtained, which is preferable. On the other hand, if the ratio is out of the range specified in the present invention, a blue or black color image is formed, and a desired color tone cannot be obtained.

In the present invention, the color is referred to as dark blue or gray blue (grayish blue), which means a bluish, dark or grayish intermediate color, such as "color". One Point 10: Color Names and Their Episodes "(Japan Standards Association, issued November 19, 1993), pages 108-111," 46 SOFT & DULL "
BLUE "and" 47 GRYISH BLUE ". These are expressed as dull blue or dark grey-blue in the JIS general color name, and as indigo or navy blue in the customary color name. Further, the color is expressed differently depending on the subjectivity of the viewer, the lighting conditions, and the like. In the present invention, the color generally includes a range represented by dark blue, cyan, ultramarine, etc., and is dark blue or gray blue (greyish blue). ) The expression of color is typically used, but is not limited thereto.

According to a second aspect of the present invention, there is provided the thermosensitive recording medium according to the first aspect, wherein 3,3-bis (p
-Dimethylaminophenyl) -6-dimethylaminophthalide or 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindole-
3-yl) -4-azaphthalide and at least one of the maximum absorption wavelengths of 420 to 480 nm and 550 to 640 nm
And a thermosensitive recording medium containing at least one leuco dye which develops a black color. Where 3,
3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide and 3- (4-diethylamino-2)
-Ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide is a leuco that develops a blue color, and the maximum absorption wavelength is measured in a 99% acetic acid solution. It is. As described above, by mixing and using specific leuco dyes having different color developing tones, a thermosensitive recording medium that develops an intermediate color of navy blue or gray blue (grayish blue) while maintaining a sufficient color density. Can be easily obtained.

The invention according to claim 3 further comprises 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide or 3- (4-diethylamino-2-ethoxyphenyl) -3- (1- Ethyl-2-methylindol-3-yl) -4-azaphthalide has a maximum absorption wavelength of 420 to 480 nm and 550 to 640 n based on 1 part.
m is a thermosensitive recording medium containing 0.05 to 1 part of a leuco dye which develops a black color. When the content of the leuco dye that develops a black color is less than 0.05 part with respect to 1 part of the dye that develops a blue color, the desired color tone is obtained, but the bluish color is slightly increased. On the other hand, when the content is more than 1 part, the blackness is slightly increased. Therefore, in order to obtain a thermosensitive recording medium in which a color image looks vividly navy blue or gray blue (grayish blue), the ratio of the leuco dye that develops black to the leuco dye that develops blue is the above ratio. It is preferred to contain.

According to the fourth aspect of the present invention, there is provided a heat-sensitive recording material which develops a dark blue or gray blue color. As described above, the color tone intended in the present invention is limited to the expression of dark blue or gray blue. Not something.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The blue-based leuco dye used in the present invention is 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide or 3- (4-diethylamino-2). -Ethoxyphenyl) -3- (1-ethyl-2-methylindole-3-
Il) -4-azaphthalide is preferred, but any leuco dye that develops a blue color can be used without particular limitation. These leuco dyes may be used alone or as a mixture of two types.

As the leuco dye which develops a black color used in the present invention, those having a maximum absorption wavelength of 420 to 480 nm and 550 to 640 nm in a 99% acetic acid solution are used. A specific example is 3-diethylamino-
6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7- (o, p-dimethylanilino)
Fluoran, 3-diethylamino-6-methyl-7-
(P-chloroanilino) fluoran, 3-diethylamino-6-methyl-7-m-methylanilinofluoran,
3-diethylamino-6-methyl-7-n-octylaminofluoran, 3-diethylamino-6-chloro-7
-Anilinofluoran, 3-diethylamino-7- (m
-Trifluoromethylanilino) fluoran, 3-diethylamino-7- (o-chloroanilino) fluoran,
3-diethylamino-7- (o-fluoroanilino) fluoran, 3-diethylamino-6-methyl-7- (p
-N-butylanilino) -fluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3-dibutylamino-6-methyl-7- (o, p-dimethylanilino) fluoran, 3-dibutylamino -7- (o-chloroanilino) fluoran, 3-dibutylamino-7-
(O-fluoroanilino) fluoran, 3-di-n-pentylamino-6-methyl-7-anilinofluoran,
3-di-n-pentylamino-7- (m-trifluoromethylanilino) fluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-piperidino-6
Methyl-7-anilinofluoran, 3- (N-methyl-
N-propylamino) -6-methyl-7-anilinofluoran, 3- (N-methyl-N-cyclohexylamino) -6-methyl-7-anilinofluoran, 3- (N
-Ethyl-p-toluidino) -6-methyl-7-anilinofluoran, 3- (N-ethyl-N-isoamylamino) -6-methyl-7-anilinofluoran, 3-
(N-ethyl-N-tetrahydrofurfurylamino)-
6-methyl-7-anilinofluoran, 3- (N-ethyl-N-isobutylamino) -6-methyl-7-anilinofluoran, 3- (N-ethyl-N-ethoxypropylamino) -6 -Methyl-7-anilinofluoran,
Examples thereof include 2,4-dimethyl-6-[(4-dimethylamino) anilino] -fluoran and the like, but are not particularly limited thereto. These leuco dyes may be used alone or in combination of two or more.

The organic developer used in the heat-sensitive recording medium of the present invention includes, for example, bisphenol A described in JP-A-3-207688 and JP-A-5-24366.
4-hydroxybenzoic acid esters, 4-hydroxyphthalic acid diesters, phthalic acid monoesters, bis-
(Hydroxyphenyl) sulfides, 4-hydroxyphenyl aryl sulfones, 4-hydroxyphenyl aryl sulfonates, 1,3-di [2- (hydroxyphenyl) -2-propyl] -benzenes, 4-hydroxybenzoyloxy Benzoic acid esters and bisphenol sulfones are exemplified. Specific examples of typical known color developers are shown below, but the present invention is not particularly limited thereto. These developers may be used alone or in combination of two or more.

<Bisphenol A>4,4'-isopropylidenediphenol (also called bisphenol A) 4,4'-cyclohexylidenediphenol p, p '-(1-methyl-normalhexylidene) diphenol 1, 7-di (hydroxyphenylthio) -3,5-dioxaheptane <4-hydroxybenzoates> Benzyl 4-hydroxybenzoate Ethyl 4-hydroxybenzoate Propyl 4-hydroxybenzoate 4-Isopropyl benzoate 4 -Butyl hydroxybenzoate 4-Isobutyl 4-hydroxybenzoate Methylbenzyl 4-hydroxybenzoate <Diesters of 4-hydroxyphthalic acid> Dimethyl 4-hydroxyphthalate 4-Diisopropyl 4-hydroxyphthalate 4-Dibenzyl 4-hydroxyphthalate 4-hydro Dihexyl phthalate <Monoesters of phthalic acid> Monobenzyl phthalate Monocyclohexyl phthalate Monophenyl phthalate Monomethyl phthalate Monoethyl phthalate Monoethyl phenyl phthalate Monopropyl benzyl phthalate Monohalogen benzyl phthalate Phthalic acid Monoethoxybenzyl ester

<Bis- (hydroxyphenyl) sulfides> Bis- (4-hydroxy-3-tert-butyl-6-
Methylphenyl) sulfide bis- (4-hydroxy-2,5-dimethylphenyl)
Sulfide bis- (4-hydroxy-2-methyl-5-ethylphenyl) sulfide bis- (4-hydroxy-2-methyl-5-isopropylphenyl) sulfide bis- (4-hydroxy-2,3-dimethylphenyl)
Sulfide bis- (4-hydroxy-2,5-dimethylphenyl)
Sulfide bis- (4-hydroxy-2,5-diisopropylphenyl) sulfide bis- (4-hydroxy-2,3,6-trimethylphenyl) sulfide bis- (2,4,5-trihydroxyphenyl) sulfide bis- ( 4-hydroxy-2-cyclohexyl-5-methylphenyl) sulfide bis- (2,3,4-trihydroxyphenyl) sulfide bis- (4,5-dihydroxy-2-tert-butylphenyl) sulfide bis- (4- Hydroxy-2,5-diphenylphenyl) sulfide bis- (4-hydroxy-2-tert-octyl-5)
-Methylphenyl) sulfide <4-hydroxyphenylarylsulfones>4-hydroxy-4'-isopropoxydiphenylsulfone4-hydroxy-4'-propoxydiphenylsulfone4-hydroxy-4'-n-butyloxydiphenylsulfone 4- Hydroxy-4'-n-propoxydiphenyl sulfone

<4-hydroxyphenylarylsulfonates> 4-hydroxyphenylbenzenesulfonate 4-hydroxyphenyl-p-tolylsulfonate 4-hydroxyphenylmethylenesulfonate 4-hydroxyphenyl-p-chlorobenzenesulfonate 4- Hydroxyphenyl-p-tert-butylbenzenesulfonate 4-hydroxyphenyl-p-isopropoxybenzenesulfonate 4-hydroxyphenyl-1'-naphthalenesulfonate 4-hydroxyphenyl-2'-naphthalenesulfonate <1,3- Di [2- (hydroxyphenyl) -2-propyl] benzenes> 1,3-di [2- (4-hydroxyphenyl) -2-propyl] benzene 1,3-di [2- (4-hydroxy-3) -Alkylfe ) -2-propyl] benzene 1,3-di [2- (2,4-dihydroxyphenyl) -
2-propyl] benzene 1,3-di [2- (2-hydroxy-5-methylphenyl) -2-propyl] benzene <resorcinols> 1,3-dihydroxy-6 (α, α-dimethylbenzyl) -benzene <4-Hydroxybenzoyloxybenzoate> Benzyl 4-hydroxybenzoyloxybenzoate Methyl 4-hydroxybenzoyloxybenzoate Ethyl 4-hydroxybenzoyloxybenzoate Propyl 4-hydroxybenzoyloxybenzoate Butyl 4-hydroxybenzoyloxybenzoate Isopropyl 4-hydroxybenzoyloxybenzoate tert-butyl 4-hydroxybenzoyloxybenzoate hexyl 4-hydroxybenzoyloxybenzoate octyl 4-hydroxybenzoyloxybenzoate 4-h Roxybenzoyloxy nonyl 4-hydroxybenzoyloxybenzoate cyclohexyl 4-hydroxybenzoyloxybenzoate β-phenethyl 4-hydroxybenzoyloxybenzoate phenyl 4-hydroxybenzoyloxybenzoate α-naphthyl 4-hydroxybenzoyloxybenzoate β -Naphthyl sec-butyl 4-hydroxybenzoyloxybenzoate

<Bisphenolsulfones (I)> bis- (3-1-butyl-4-hydroxy-6-methylphenyl) sulfone bis- (3-ethyl-4-hydroxyphenyl) sulfone bis- (3-propyl-) 4-hydroxyphenyl) sulfone bis- (3-methyl-4-hydroxyphenyl) sulfone bis- (2-isopropyl-4-hydroxyphenyl)
Sulfone bis- (2-ethyl-4-hydroxyphenyl) sulfone bis- (3-chloro-4-hydroxyphenyl) sulfone bis- (2,3-dimethyl-4-hydroxyphenyl)
Sulfone bis- (2,5-dimethyl-4-hydroxyphenyl)
Sulfone bis- (3-methoxy-4-hydroxyphenyl) sulfone 4-hydroxyphenyl-2'-ethyl-4'-hydroxyphenylsulfone 4-hydroxyphenyl-2'-isopropyl-4'-
Hydroxyphenylsulfone 4-hydroxyphenyl-3'-isopropyl-4'-
Hydroxyphenylsulfone 4-hydroxyphenyl-3'-secbutyl-4'-
Hydroxyphenylsulfone 3-chloro-4-hydroxyphenyl-3'-isopropyl-4'-hydroxyphenylsulfone 2-hydroxy-5-t-butylphenyl-4'-hydroxyphenylsulfone 2-hydroxy-5-t-aminophenyl -4'-hydroxyphenylsulfone 2-hydroxy-5-t-isopropylphenyl-4 '
-Hydroxyphenylsulfone 2-hydroxy-5-t-octylphenyl-4'-hydroxyphenylsulfone 2-hydroxy-5-t-butylphenyl-3'-chloro-4'-hydroxyphenylsulfone 2-hydroxy-5-t -Butylphenyl-3'-methyl-4'-hydroxyphenylsulfone 2-hydroxy-5-tert-butylphenyl-3'-isopropyl-4'-hydroxyphenylsulfone 2-hydroxy-5-tert-butylphenyl-2 '-Methyl-4'-hydroxyphenylsulfone

<Bisphenolsulfones (II)>4,4'-sulfonyldiphenol2,4'-sulfonyldiphenol3,3'-dichloro-4,4'-sulfonyldiphenol3,3'-dibromo-4 , 4'-Sulfonyldiphenol 3,3 ', 5,5'-Tetrabromo-4,4'-sulfonyldiphenol 3,3'-Diamino-4,4'-sulfonyldiphenol <Others> p-tert-butylphenol 2,4-dihydroxybenzophenone novolak-type phenol resin 4-hydroxyacetophenone p-phenylphenol benzyl-4-hydroxyphenylacetate p-benzylphenol

In the present invention, a developer having a plurality of phenolic hydroxyl groups may have higher ground color stability because the ground color may be stained (ground color development) by aqueous coating or moisture in the air. When required, a monophenol-based developer is preferably used. In particular, the monophenol-based sulfone developer represented by the above-mentioned 4-hydroxyphenylaryl sulfones has a sulfonyl group in the structure, and a strong electron accepting portion is formed by the electron withdrawing action of the sulfonyl group. In addition, it is possible to obtain a heat-sensitive recording material which exhibits high reactivity with the dye precursor and high color-forming property and also has excellent ground color stability.

In the present invention, conventionally known sensitizers can be used as long as the desired effects on the above objects are not impaired. Such sensitizers include stearamide, palmitamide, methoxycarbonyl-N
-Stearic acid benzamide, N-benzoylstearic acid amide, N-eicosanoic acid amide, ethylenebisstearic acid amide, behenic acid amide, methylenebisstearic acid amide, methylolamide, N-methylolstearic acid amide, dibenzyl terephthalate, terephthalic acid Acid dimethyl, dioctyl terephthalate, benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, dibenzyl oxalate, di-oxalate
p-methylbenzyl, di-p-chlorobenzyl oxalate, 2-naphthylbenzyl ether, m-terphenyl, p-benzylbiphenyl, 4-biphenylparatolyl ether, di (p-methoxyphenoxyethyl) ether, 1,2-di (3-methylphenoxy) ethane,
1,2-di (4-methylphenoxy) ethane, 1,2-
Di (4-methoxyphenoxy) ethane, 1,2-di (4
-Chlorophenoxy) ethane, 1,2-diphenoxyethane, 1- (4-methoxyphenoxy) -2- (2-methylphenoxy) ethane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p
-Acetotoluidide, p-acetophenethidide, N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane, 1, 2-bis (phenoxymethyl) benzene, p-
Toluenesulfonamide, o-toluenesulfonamide, di-p-tolylcarbonate, phenyl-α-naphthylcarbonate and the like can be exemplified.
It is not limited to these. These sensitizers may be used alone or in combination of two or more.

The binder used in the present invention is a completely saponified polyvinyl alcohol having a degree of polymerization of 200 to 1900, a partially saponified polyvinyl alcohol, a carboxy-modified polyvinyl alcohol, an amide-modified polyvinyl alcohol, a sulfonic acid-modified polyvinyl alcohol, a butyral-modified polyvinyl alcohol. Modified polyvinyl alcohol such as alcohol, cellulose derivatives such as hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, acetyl cellulose, styrene-maleic anhydride copolymer, styrene-butadiene copolymer, polyvinyl chloride, polyvinyl acetate, polyacrylamide , Polyacrylate, polyvinyl butyral, polystyrene and copolymers thereof, polyamide resin, silicone Butter, petroleum resins, terpene resins, ketone resins, and coumarone resins. These polymeric substances include water, alcohol, ketones, esters,
In addition to being used by dissolving in a solvent such as a hydrocarbon, it can be used in a state of being emulsified or dispersed in water or another medium in the form of a paste, and used in combination depending on required quality.

The fillers that can be used in the present invention include silica, calcium carbonate, kaolin, calcined kaolin, diatomaceous earth, talc, titanium oxide, zinc oxide, aluminum hydroxide, polystyrene resin, urea-formalin resin, styrene- Examples thereof include methacrylic acid copolymers, styrene-butadiene copolymers, and inorganic or organic fillers such as hollow plastic pigments.

In addition, release agents such as fatty acid metal salts, lubricants such as waxes, benzophenone and triazole ultraviolet absorbers, water resistance agents such as glyoxal, dispersants, defoamers, antioxidants, fluorescent Dyes and the like can be used.

As the support, paper, recycled paper, synthetic paper, plastic film, foamed plastic film, non-woven fabric, metal foil and the like can be used, or a composite sheet combining these can be used.

Further, an overcoat layer of a polymer substance or the like can be provided on the thermosensitive coloring layer for the purpose of enhancing the abrasion resistance and image storability. Further, for the purpose of increasing the color-forming sensitivity, an undercoat layer containing an organic filler or an inorganic filler can be provided between the color-forming layer and the support.

The amounts of the developer and the dye precursor and the types and amounts of other various components used in the heat-sensitive recording medium of the present invention are determined according to the required performance and recording suitability, and are not particularly limited. Usually, 0.5 to 4 parts of a filler and 1 to 25% of a total solid content of a filler are suitable for 1 part of an organic developer. 3,3-bis (p-dimethylaminophenyl) -6 which develops a blue color used as a dye precursor
-Dimethylaminophthalide or 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2
-Methylindol-3-yl) -4-azaphthalide with a maximum absorption wavelength of 420 to 480 nm and 550 to 640
In the case of using a leuco dye that develops a black color having a wavelength of nm, the mixing ratio is determined by the required color tone. 0.05 to 1 part, and the total number of both is preferably 0.1 to 2 parts per 1 part of the organic developer. The color tone of the color image is slightly changed depending on the stabilizers, sensitizers and other additives to be added, but does not have a decisive effect.

These developers, dyes and optional materials are pulverized by a pulverizer such as a ball mill, an attritor, a sand grinder or an appropriate emulsifying device to a particle size of several microns or less, and a binder and Various coating materials are added according to the purpose to form a coating liquid. Examples of the coating method include hand coating, size press coater method, roll coater method, air knife coater method, blend coater method, flow coater method, comma direct method, gravure direct method, gravure reverse method, reverse roll coater method and the like. . After spraying, spraying or dipping, drying may be performed.

[0028]

EXAMPLES <Manufacture of thermosensitive recording medium> The thermosensitive recording medium of the present invention will be described below by way of examples. In addition, parts and% in the description
Represents parts by weight and% by weight, respectively, unless otherwise specified.

[Example 1] In Example 1, the thermosensitive recording medium of the present invention developed 4,4'-isopropylidene diphenol (bisphenol A, abbreviated as a in the table) as a color developer and developed a blue color. 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (abbreviated as C-1 in the table) having a maximum absorption wavelength of 420 to 4
3-Dibutylamino-6-methyl-7 as a leuco dye which develops a black color having a wavelength of 80 nm or 550 to 640 nm.
-An example using anilinofluoran (abbreviated as B-1 in the table). A developer dispersion liquid (liquid) having the following composition, a leuco dye dispersion liquid (liquid) that develops a blue color, and a leuco dye (liquid) that develops a black color are separately obtained with a sand grinder to an average particle diameter of 1 micron. Wet grinding was carried out until. Liquid (developing agent dispersion) 4,4'-isopropylidene diphenol (a) 6.0 parts 10% polyvinyl alcohol 18.8 parts Water 11.2 parts Liquid (blue leuco dye dispersion) 3,3- Bis (p-dimethylaminophenyl) -6-dimethylamino phthalide (C-1) 1.0 part 10% polyvinyl alcohol 2.3 parts Water 1.3 parts Liquid (black leuco dye dispersion) 3-dibutylamino- 6-methyl-7-anilinofluoran (B-1) 1.0 part 10% polyvinyl alcohol 2.3 parts Water 1.3 parts Next, the dispersion was mixed and stirred at the following ratio to prepare a dispersion. . Liquid (Developer [a] dispersion) 36.0 parts Liquid (blue leuco dye [C-1] dispersion) 10.58 parts Liquid (black leuco dye [B-1] dispersion) 3.22 Part Kaolin clay (50% dispersion) 12.0 parts After applying the prepared coating liquid to one side of a base paper of 50 g / m ² , drying is performed, and the sheet is super-calendered to a smoothness of 500 to 600 seconds. To obtain a thermosensitive recording medium having a coating amount of 6.0 g / m ² .

Examples 2 to 5 A thermosensitive recording medium was produced in the same manner as in Example 1. However, when preparing the solution,
4-hydroxy-4'-isopropoxydiphenylsulfone (abbreviated as b in the table; Example 2), 4-hydroxy-4'-propoxydiphenylsulfone (instead of 4'-isopropylidenediphenol (a)) Example 3), benzyl 4-hydroxybenzoate (abbreviated as d in the table; Example 4), 4,4'-sulfonyldiphenol (abbreviated as e in the table; Example 5) ) Was used.

Example 6 A thermosensitive recording paper was prepared in the same manner as in Example 1. However, 4,4'-isopropylidene diphenol (a) and 4-hydroxy-
Two kinds of 4'-isopropoxydiphenyl sulfone (b) were used. In addition, each dispersion liquid is mixed as follows,
The mixture was stirred to prepare a coating solution. Liquid (developer [a] dispersion) 18.0 parts Liquid (developer [b] dispersion) 18.0 parts Liquid (blue leuco dye [C-1] dispersion) 10.58 parts liquid ( Black type leuco dye [B-1] dispersion) 3.22 parts Kaolin clay (50% dispersion) 12.0 parts

Example 7 A thermosensitive recording medium was produced in the same manner as in Example 2. However, when preparing the solution,
Instead of bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (C-1), 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-
2-Methylindol-3-yl) -4-azaphthalide (C-2) was used.

Example 8 A thermosensitive recording medium was produced in the same manner as in Example 2. However, as a blue leuco dye,
3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (C-1) and 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindole- Two types, 3-yl) -4-azaphthalide (C-2), were used. In addition, each dispersion liquid was mixed and stirred as described below to prepare a coating liquid. Liquid (Developer [a] dispersion) 36.0 parts Liquid (blue leuco dye [C-1] dispersion) 5.29 parts Liquid (blue leuco dye [C-2] dispersion) 5.29 Part liquid (black leuco dye [B-1] dispersion) 3.22 parts kaolin clay (50% dispersion) 12.0 parts

Examples 9 to 14 In the same manner as in Example 2, thermosensitive recording media were produced. However, when preparing the solution,
Instead of -dibutylamino-6-methyl-7-anilinofluoran (B-1), 3- (N-ethyl-N-isoamylamino) -6-methyl-7-anilinofluoran (B- in the table) Example 9) 3-Diethylamino-6-methyl-7-anilinofluoran (B-3 in the table)
Example 10), 3-Diethylamino-7-
(M-trifluoromethylanilino) fluoran (abbreviated as B-4 in the table; Example 11), 3-diethylamino-6-methyl-7-m-methylanilinofluoran (abbreviated as B-5 in the table) Example 12), 3- (N-methyl-N-propylamino) -6-methyl-7-anilinofluoran (abbreviated as B-6 in the table; Example 13), 3-
Di-n-pentylamino-6-methyl-7-anilinofluoran (abbreviated as B-7 in the table; Example 14) was used.

Example 15 A thermosensitive recording medium was produced in the same manner as in Example 2. However, as a black leuco dye,
3-dibutylamino-6-methyl-7-anilinofluoran (B-1) and 3- (N-ethyl-N-isoamylamino) -6-methyl-7-anilinofluoran (B-
Two types of 2) were used. In addition, each dispersion liquid was mixed and stirred as described below to prepare a coating liquid. Liquid (Developer [a] dispersion) 36.0 parts Liquid (blue leuco dye [C-1] dispersion) 10.58 parts Liquid (black leuco dye [B-1] dispersion) 1.61 Part liquid (black leuco dye [B-2] dispersion) 1.61 parts Kaolin clay (50% dispersion) 12.0 parts

Example 16 A thermosensitive recording medium was produced in the same manner as in Example 9. In addition, each dispersion liquid was mixed and stirred as described below to prepare a coating liquid. Liquid (Developer [a] dispersion) 36.0 parts Liquid (blue leuco dye [C-1] dispersion) 12.88 parts Liquid (black leuco dye [B-2] dispersion) 0.92 Part Kaolin clay (50% dispersion) 12.0 parts

Example 17 A thermosensitive recording medium was produced in the same manner as in Example 9. In addition, each dispersion liquid was mixed and stirred as described below to prepare a coating liquid. Liquid (Developer [a] dispersion) 36.0 parts Liquid (blue leuco dye [C-1] dispersion) 9.2 parts Liquid (black leuco dye [B-2] dispersion) 4.6 Part Kaolin clay (50% dispersion) 12.0 parts

Example 18 A thermosensitive recording medium was produced in the same manner as in Example 9. In addition, each dispersion liquid was mixed and stirred as described below to prepare a coating liquid. Liquid (developer [a] dispersion) 36.0 parts Liquid (blue leuco dye [C-1] dispersion) 13.34 parts Liquid (black leuco dye [B-2] dispersion) 0.46 Part Kaolin clay (50% dispersion) 12.0 parts

Example 19 A thermosensitive recording medium was produced in the same manner as in Example 9. In addition, each dispersion liquid was mixed and stirred as described below to prepare a coating liquid. Liquid (Developer [a] dispersion) 36.0 parts Liquid (blue leuco dye [C-1] dispersion) 5.06 parts Liquid (black leuco dye [B-2] dispersion) 8.74 Part Kaolin clay (50% dispersion) 12.0 parts

Comparative Example 1 A thermosensitive recording medium was produced in the same manner as in Example 9. However, the liquid was not mixed in the formation of the coloring layer. In addition, each dispersion liquid was mixed and stirred as described below to prepare a coating liquid. Liquid (developer [b] dispersion) 36.0 parts Liquid (blue leuco dye [C-1] dispersion) 13.8 parts Kaolin clay (50% dispersion) 12.0 parts

Comparative Example 2 A thermosensitive recording medium was produced in the same manner as in Example 9. However, the liquid was not mixed in the formation of the coloring layer. In addition, each dispersion liquid was mixed and stirred as described below to prepare a coating liquid. Liquid (developer [b] dispersion) 36.0 parts Liquid (black leuco dye [B-2] dispersion) 13.8 parts Kaolin clay (50% dispersion) 12.0 parts

<Evaluation Method> The thermal recording medium thus prepared was subjected to an applied energy of 0.41 mj / using a TH-PMD (a thermal recording paper printing tester manufactured by Okura Electric Co., Ltd., equipped with a thermal head manufactured by Kyocera Corporation). Dot printing. The color difference of the recorded sample specified by JIS-Z-8729 is measured by a spectral colorimeter (NF999; manufactured by Nippon Denshoku Industries Co., Ltd.).
And the color difference L * value, a * value, and b * value were determined. Further, the color tone of the color image was visually evaluated. Also,
The color density (OD in the table) of the color image was measured using a Macbeth densitometer (RD-914, using a red filter). The results are shown in Tables 1 and 2.

[0043]

[Table 1] (Note) Figures in parentheses are the ratio of black dye to blue dye

[0044]

[Table 2]

<Evaluation Results> In Examples 1 to 19 of the present invention,
3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide or 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl)- 4-Azaphthalide and maximum absorption wavelengths of 420 to 480 nm and 550 to 640 nm
And a leuco dye which develops a black color. These heat-sensitive recording materials have a color difference L * value of 30
５０50, the color difference a * value is −15 to 0 and the color difference b *
The value is -30 to 10, the color difference a * is 0 to 10 and the color difference b *
The value is -30 to 0, or the color difference a * value is in the range of 10 to 20 and the color difference b * value is in the range of -30 to -15, and the color tone is dark blue or gray blue (greyish blue). On the other hand, in Comparative Example 1, the color difference a * value and b * value of the color-developed image did not fall within the range specified in the present invention, and Comparative Example 2
In Comparative Example 1, the color difference L * value did not fall within the range specified in the present invention, and the desired color tone was not obtained in any case.

[0046]

The thermal recording medium of the present invention has a sufficient color density and develops a dark blue or gray blue color.
Suitable for applications where these colors are preferred.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshihide Kimura 1-30-6 Kamiochiai, Shinjuku-ku, Tokyo Japan Paper Manufacturing Co., Ltd. No. 1 Nippon Paper Industries Co., Ltd.

Claims (4)

[Claims] 1. A thermosensitive recording medium having a thermosensitive coloring layer containing a colorless or pale-colored dye precursor and an organic developer as main components on a support, the JIS-Z-8 of a color-developed image.
729, a color difference L * value, a color difference a * value, and a color difference b
* A thermosensitive recording material having a value in any one of the following ranges A to C: A. L * value is 30 to 50, a * value is -15 to 0, and b
* Value is -30 to 10 B. C. L * value is 30 to 50, a * value is 0 to 10, and color difference b * value is -30 to 0. L * value is 30-50, a * value is 10-20, and b
* Value is -30 to -15 2. A dye precursor comprising 3,3-bis (p-
Dimethylaminophenyl) -6-dimethylaminophthalide or 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindole-3
2. The composition according to claim 1, comprising at least one type of -yl) -4-azaphthalide and at least one type of leuco dye that emits a black color having a maximum absorption wavelength of 420 to 480 nm and 550 to 640 nm. Thermal recording medium. 3. A dye precursor comprising 3,3-bis (p-
Dimethylaminophenyl) -6-dimethylaminophthalide or 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindole-3
-Yl) -4-azaphthalide contains 0.05 to 1 part of a black leuco dye having a maximum absorption wavelength of 420 to 480 nm and 550 to 640 nm with respect to 1 part of 4-azaphthalide. The thermosensitive recording medium as described. 4. A thermosensitive recording medium which develops a dark blue or gray blue color.