JPH06227143A - Thermal recording body - Google Patents

Abstract

PURPOSE:To decrease yellowing of a texture part by using the specified material for basic dye of a thermal recording layer, incorporating the specified hindered phenol compound into the thermal recording layer and also incorporating an ultraviolet absorber into the thermal recording layer or a protective layer. CONSTITUTION:A thermal recording body is constituted by successively providing a thermal recording layer and a protective layer on a supporting body. Colorless or light-colored basic dye and a colorant are incorporated into the thermal recording layer. In the case, 3-dimethylamino-7-(3-trifluoromethylphenyl) aminofluoran is used as basic dye. Further at least one kind of hindered phenol compound selected from the respective general formulas mentioned elsewhere is incorporated into the thermal recording layer. Furthermore an ultraviolet absorber is incorporated into at least one layer selected from the thermal recording layer and the protective layer. Thereby, when a recording image in particular is irradiated with light, stability is enhanced and also yellowing of a texture part is controlled.

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 which is excellent in storage stability, particularly light resistance.

[0002]

2. Description of the Related Art A thermosensitive recording medium 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. Since such a thermosensitive recording medium is relatively inexpensive, the recording device is compact, and its maintenance is easy, it is used not only as a recording medium for a facsimile machine or various computers but also in a wide range of fields. One of the fields of use is, for example, POS (point
There is a thermal recording label for the system, but with the expansion of the system, it will be attached to products for a long period of time, apart from the label for food, which has completed its mission in a short period as before. The use as tag paper or handy terminal paper for collection and delivery, which is often handled outdoors, is increasing. However, in such applications, the thermal recording medium is often exposed to room light or sunlight for a long period of time, which causes the background of the thermal recording medium to turn yellow, impairing the product image, and further reducing the recorded image. Even the color fades, and the POS label does not function. Therefore, there is a strong demand for the development of a thermal recording medium that does not cause yellowing of the background portion even when exposed to room light or sunlight for a long time, and does not cause fading of a recorded image.

Conventionally, there has been proposed a method in which a finely pulverized ultraviolet absorber is added to the heat-sensitive recording layer or the protective layer in order to prevent the background portion of the heat-sensitive recording material from yellowing by light. . However, the finely pulverized ultraviolet absorber has some effect on the yellowing of the background, but not so much on the fading of the recorded image.
Further, a method for suppressing yellowing of the background part by light irradiation by using a fluorane compound having an anilino group in which a benzene ring is substituted with an electron-withdrawing group is proposed in JP-A-4-189180. Stability of the recorded image due to light irradiation is poor with the functional dye, and it easily fades,
The current situation is that satisfactory light resistance has not yet been obtained.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording material having a protective layer on the heat-sensitive recording layer, in which the yellowing of the background portion and the fading of the recorded image are small with long-term exposure to light. Another object is to provide an excellent thermal recording material.

[0005]

In a thermal recording medium in which a thermosensitive recording layer containing a colorless or light-colored basic dye and a coloring agent and a protective layer are sequentially provided on a support, the basic dye is 3 -Diethylamino-7- (3'-trifluoromethylphenyl) aminofluorane is used, and the heat-sensitive recording layer contains at least one hindered phenol compound selected from the following general formulas [Chemical Formula 1] and [Chemical Formula 2]. By incorporating an ultraviolet absorber into at least one of the heat-sensitive recording layer and the protective layer, the above object was achieved.

[0006]

[Chemical 1]

[In the formula, R ₁ represents an optionally substituted saturated or unsaturated alkylene group; an optionally substituted saturated or unsaturated alkylidene group; an optionally substituted cycloalkylene group, R ₂ and R ₃ are hydrogen atoms;
A halogen atom; an optionally substituted saturated or unsaturated alkyl group; and an optionally substituted saturated or unsaturated alkoxyl group. ]

[0008]

[Chemical 2] [In the formula, R ₄ , R ₅ , and R ₆ are hydrogen atoms; halogen atoms;
An optionally substituted saturated or unsaturated alkyl group;
The saturated or unsaturated alkoxyl group which may be substituted is shown. ]

Conventionally, it has been proposed to incorporate a hindered phenol compound in the heat-sensitive recording layer to improve the storability of a recorded image. However, the above general formulas [Chemical Formula 1] and [Chemical Formula 2] are mentioned.
In the case where 3-diethylamino-7- (3'-trifluoromethylphenyl) aminofluorane is used as the basic dye, the effect of improving the stability of the recorded image upon light irradiation is good. However, they have found that the effect is remarkable, and that yellowing of the background is less likely to occur, and have completed the present invention.

[0010]

The following are specific examples of the hindered phenol compound represented by the general formula [Chemical Formula 1] used in the present invention. 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,
2'-ethylenebis (4-methyl-6-tert-butylphenol), 2,2'-methylenebis (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-te)
rt-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) and the like.

Specific examples of the hindered phenol compound represented by the general formula [Chemical Formula 2] include the following. 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. Among the compounds represented by [Chemical Formula 1] and [Chemical Formula 2], 2,2′-methylenebis (4-methyl-6)
-Tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 2,
2'-ethylidene bis (4,6-di-tert-butylphenol), 4,4'-thiobis (2-methyl-6-tert)
-Butylphenol) is particularly preferably used. The amount of the hindered phenol compound represented by [Chemical Formula 1] or [Chemical Formula 2] is not particularly limited, but generally 1 to 100% by weight of the basic dye.
It is used in an amount of 500% by weight, preferably about 10 to 200% by weight.

In the present invention, the above general formulas [Chemical formula 1] and [Chemical formula 2]
It is also possible to use a hindered phenol compound other than the above and other preservative improving agents together. Examples of such storability improvers include the following. 4,4'-
Butylidene bis (6-tert-butyl-m-cresol), 1- [α-methyl-α- (4'-hydroxyphenyl) ethyl] -4- [α ', α'-bis (4 "-hydroxyphenyl) ethyl ] Benzene, 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), 4,
4'-dihydroxy-3,3 ', 5,5'-tetrabromodiphenyl sulfone, 4,4'-dihydroxy-3,
3 ', 5,5'-tetramethyldiphenyl sulfone,
2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, 2,2-bis (4-hydroxy-3,
5-dichlorophenyl) propane, 2,2-bis (4-
Hindered phenol compounds such as hydroxy-3,5-dimethylphenyl) propane, 1,4-diglycidyloxybenzene, 4,4′-diglycidyloxydiphenyl sulfone, 4-benzyloxy-4 ′-(2-methylglycidyl) (Oxy) diphenyl sulfone, diglycidyl terephthalate, cresol novolac type epoxy resin,
Epoxy compounds such as phenol novolac type epoxy resin and bisphenol A type epoxy resin, N, N'-di-
2-naphthyl-p-phenylenediamine, sodium or polyvalent metal salt of 2,2′-methylenebis (4,6-di-tert-butylphenyl) phosphate, bis (4-ethyleneiminocarbonylaminophenyl) methane and the like can be mentioned. To be Among them, 1,1,3-tris (2-methyl-
4-Hydroxy-5-cyclohexylphenyl) butane does not have a remarkable effect on light resistance, but it has an excellent effect on water resistance and is less likely to cause background fog, and is therefore preferably used.

The ultraviolet absorber used in the present invention is not particularly limited, but examples thereof include the following. Salicylic acid-based UV absorbers such as phenyl salicylate, p-tert-butylphenyl salicylate, p-octylphenyl salicylate, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, etc. Benzophenone UV Absorber, 2-Ethylhexyl-2-cyano-3,3 '
-Diphenyl acrylate, ethyl-2-cyano-3,
Cyanoacrylate UV absorbers such as 3'-diphenyl acrylate, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, succinic acid-bis (2,2
2,6,6-tetramethyl-4-piperidyl) ester, 2- (3,5-di-tert-butyl-4-hydroxybenzyl) -2-n-butylmalonic acid bis (1,2,2,2
Hindered amine UV absorbers such as 2,6,6-pentamethyl-4-piperidyl) ester, 2- (2'-hydroxyphenyl) benzotriazole, 2- (2'-
Hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-5'-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-
3 ', 5'-di-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'- Hydroxy-3 ', 5'-di-tert
-Butylphenyl) -5-chlorobenzotriazole,
2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5-tert-butylbenzotriazole,
2- (2'-hydroxy-3 ', 5'-di-tert-amylphenyl) benzotriazole, 2- [2'-hydroxy-3'-(3 ", 4", 5 ", 6" -tetrahydrophthalimide -Methyl) -5'-methylphenyl] benzotriazole, 2- (2'-hydroxy-5'-tert
-Octylphenyl) benzotriazole, 2- (2 '
-Hydroxy-3'-dodecyl-5'-methylphenyl) benzotriazole, 2- [2'-hydroxy-
4 '-(2 "-ethylhexyl) oxyphenyl] benzotriazole, 5-tert-butyl-3- (5-chloro-2H-benzotriazol-2-yl) -4-hydroxybenzene-octyl propionate, 3- [ 3-tert
-Butyl-5- (2H-benzotriazol-2-yl) -4-hydroxyphenyl] propionate methyl and polyethylene glycol (molecular weight about 300), benzotriazole-based UV absorbers such as condensates. Among them, benzotriazole-based UV absorbers are preferably used because of their high UV-absorbing ability.

These UV absorbers are generally used by finely pulverizing them together with a dispersion medium such as water, or they are contained in microcapsules and contained in the heat-sensitive recording layer or the protective layer. , But not particularly limited, generally 10 to 5 relative to 100 parts by weight of the basic dye.
It is used in an amount of 00 parts by weight, preferably 20 to 250 parts by weight.

In the present invention, it is possible to add a fluorescent dye or fluorescent pigment having an absorption in the ultraviolet region to the heat-sensitive recording layer or the protective layer as an ultraviolet absorber.
For example: Examples of fluorescent dyes include diaminostilbene disulfonic acid derivatives, imidazole derivatives, coumarin derivatives, triazole derivatives, carbazole derivatives, pyridine derivatives, naphthalic acid derivatives, and imidazolone derivatives. Examples of fluorescent pigments include diaminostilbene dyes, water-soluble fluorescent dyes such as fluorescein, thioflavin, eosin, and rhodamine B fixed with a resin such as urea resin, and water-insoluble fluorescent dyes such as Lumogen L yellow. To be Among these, a diaminostilbene disulfonic acid derivative is preferably used. The amount of the fluorescent dye or fluorescent pigment used is not particularly limited because the fluorescence intensity varies depending on the type and the system used, but it is generally 0.001 to 0.3 g / m ² , and more preferably 0. 0
It is adjusted in the range of about 05 to 0.1 g / m ² .

In the present invention, 3-diethylamino-7- (3'-trifluoromethylphenyl) aminofluorane is used as the basic dye, but other known basic dyes can be used as long as the effects of the present invention are not impaired. A dye can also be used in combination.

Examples of the color former used in the present invention in combination with the basic dye include the following. Inorganic acidic substances such as activated clay, attapulgite, colloidal silica, aluminum silicate, 4,4'-
Isopropylidene diphenol, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis (4
-Hydroxyphenyl) -4-methylpentane, 4,
4'-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, benzyl 4-hydroxybenzoate, 4,4'-dihydroxydiphenyl sulfone,
2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone,
4-hydroxy-4'-methyldiphenyl sulfone, 4
-Hydroxyphenyl-4'-benzyloxyphenyl sulfone, 3,4-dihydroxyphenyl-4'-methylphenyl sulfone, bis (4-hydroxyphenylthioethoxy) methane, 1,5-di (4-hydroxyphenylthio)- 3-oxapentane, bis (p-hydroxyphenyl) butyl acetate, methyl bis (p-hydroxyphenyl) acetate, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,4-bis [α- Methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 1,3-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, di (4-hydroxy-)
Phenolic compounds such as 3-methylphenyl) sulfide, 2,2′-thiobis (3-tert-octylphenol), 2,2′-thiobis (4-tert-octylphenol), N, N′-di-m-chlorophenyl Thiourea compounds such as thiourea, p-chlorobenzoic acid, 4- [2-
Aromatic carboxylic acids such as (p-methoxyphenoxy) ethyloxy] salicylic acid, 4- [3- (p-tolylsulfonyl) propyloxy] salicylic acid, 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid, And salts of these aromatic carboxylic acids with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin and nickel, and further, antipyrine complexes of zinc thiocyanate, terephthalaldehyde acids and other aromatic carboxylic acids. Examples thereof include organic acidic substances such as complex zinc salts with. Among them, when 1,1-bis (4-hydroxyphenyl) cyclohexane is used, the light fastness of the recorded image is excellent, and 4-hydroxy-4′-isopropoxydiphenyl sulfone and bis (3-allyl- Four
When -hydroxyphenyl) sulfone is used, it is preferably used because the general storability of the recorded image is excellent.

The use ratio of the basic dye and the color developing agent is appropriately selected according to the type of the basic dye or the color developing agent to be used and is not particularly limited, but in general, the basic dye 1 is used. 1 to 50 parts by weight, preferably 2 to parts by weight
About 10 parts by weight of coloring agent is used. A coating material for a heat-sensitive recording layer containing these substances is generally prepared by dispersing water and a dye and a coloring agent together or separately by a stirring / grinding machine such as a ball mill, attritor or sand mill. It

In the coating liquid, as binders, starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy modified polyvinyl alcohol, acetoacetyl group modified polyvinyl alcohol, silicon modified polyvinyl alcohol, etc. Diisobutylene / maleic anhydride copolymer salt, styrene /
Maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, styrene /
At least one of butadiene copolymer emulsion, urea resin, melamine resin, amide resin, polyurethane resin and the like is blended in the range of about 5 to 30% by weight based on the total solid content of the heat-sensitive recording layer.

Further, various auxiliary agents and pigments can be appropriately added to the coating liquid, if necessary.
For example, sodium dioctyl sulfosuccinate, sodium dodecylbenzene sulfonate, sodium lauryl alcohol sulfate, dispersant such as fatty acid metal salt, zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, and other defoaming agents. Examples of agents, coloring dyes, and pigments include kaolin, clay, calcium carbonate, calcined clay, calcined kaolin, titanium oxide, diatomaceous earth,
Inorganic pigments such as fine particulate anhydrous silica and activated clay, styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and organic pigments such as raw starch particles can be used.

Further, a sensitizer may be used in combination depending on the purpose. Specific examples of the sensitizer include stearic acid amide, methoxycarbonyl-N-stearic acid benzamide, N-benzoylstearic acid amide, N-eicosanoic acid amide, ethylenebisstearic acid amide, behenic acid amide, and methylenebisstearic acid amide. , N-
Methylol stearamide, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate,
Benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, 2-naphthylbenzyl ether, m-terphenyl, dibenzyl oxalate, oxalate-di-p-methylbenzyl, oxalate-di-p- Chlorobenzyl, p-benzylbiphenyl, p-tolylbiphenyl 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- (3
-Methylphenoxy) ethane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p-acetotoluidide, p-acetophenetizide,
Examples include N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane and the like. The amount of these sensitizers used is not particularly limited, but it is generally desirable to adjust the amount within the range of about 4 parts by weight or less relative to 1 part by weight of the color developing agent.

The heat-sensitive recording material of the present invention has a protective layer on the heat-sensitive recording layer. The protective layer comprises a binder composed of a water-soluble or water-dispersible polymer compound and ultraviolet rays used as necessary. It is composed mainly of an absorbent. When the ultraviolet absorber is contained in the protective layer, it is used in microencapsulated form to improve the ultraviolet absorption efficiency,
It is desirable from the viewpoint of the barrier property of the protective layer and the recording sensitivity of the thermosensitive recording medium. In addition, as specific examples of such a binder,
For example, starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol,
Carboxy-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, diisobutylene / maleic anhydride copolymer salt,
Styrene / maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt,
Examples thereof include styrene / butadiene copolymer emulsion, urea resin, melamine resin, amide resin, polyurethane resin, and the like. Among them, acetoacetyl group-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol,
Silicon-modified polyvinyl alcohol is particularly preferably used because it can form a strong film.

In order to improve printability and sticking, a pigment may be added to the protective layer if necessary. Specific examples thereof include calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, and Silicon dioxide,
Inorganic pigments such as aluminum hydroxide, barium sulfate, zinc sulfate, talc, kaolin, clay, calcined kaolin, colloidal silica, styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, raw starch particles, etc. Is mentioned. It is generally desirable to adjust the amount used in the range of about 5 to 300 parts by weight with respect to 100 parts by weight of the binder component.

The method for preparing the coating liquid for forming the protective layer is not particularly limited, and is generally prepared by using water as a dispersion medium and mixing a binder, an ultraviolet absorber optionally added, a pigment and the like. . Furthermore, in the coating liquid for the protective layer,
If necessary, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, etc., surfactants (dispersing agents, wetting agents) such as sodium dioctyl sulfosuccinate, defoaming agents, potassium alum and acetic acid. Various auxiliaries such as water-soluble polyvalent metal salts such as aluminum can also be appropriately added. Further, a curing agent such as glyoxal, boric acid, dialdehyde starch, or an epoxy compound may be used in combination for further improving the water resistance.

The method for forming the heat-sensitive 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 heat-sensitive recording layer is applied and dried on the support by the coating method, and then the coating liquid for protective layer is further applied and dried on the heat-sensitive recording layer. The support may be appropriately selected from paper, plastic film, synthetic paper, non-woven fabric, metal deposit, etc., and used. The coating amount of the heat-sensitive recording layer coating composition is 2~12g / m ² in dry weight, preferably 3 to 10 g / m ² approximately,
The coating amount of the protective layer coating liquid is 0.1 to 20 g / m on a dry basis
² , preferably in the range of about 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, an undercoat layer may be provided on the support, smoothing treatment such as super calendering may be applied after coating each layer, or an adhesive label may be applied to the back surface of the recording material to form an adhesive label, or a magnetic thermosensitive recording layer or If necessary, various known techniques in the field of producing a thermosensitive recording medium can be added, such as providing a coating layer for printing and a thermal transfer thermosensitive recording layer.

In the heat-sensitive recording material of the present invention, it is preferable to perform a smoothing treatment after forming the protective layer in order to enhance the color development sensitivity and image quality of the recorded image, and the Bekk smoothness (JIS P) after the smoothing treatment. (According to 8119) is preferably 300 seconds or longer, more preferably 500 seconds or longer. As the smoothing device used at that time, a super calender or a gloss calender in which an elastic roll and a metal roll are combined is used, and the elastic roll is ASTM D-224.
It is preferable to use an elastic roll having a Shore D hardness defined by 0 of 60 to 90 °, preferably 70 to 90 °. Further, the nip linear pressure during the treatment should be appropriately selected according to the hardness of the elastic roll to be used and the desired smoothness, but it is preferably adjusted in the range of 30 to 300 Kg / cm. The material of the elastic layer of the elastic roll is, for example, rubber such as natural rubber, styrene rubber, nitrile rubber, chloroprene rubber, chlorosulfonated ethylene rubber, butyl rubber, polysulfide rubber, silicone rubber, fluororubber, urethane rubber and the like. , Various plastic resins,
Examples include cotton, paper, wool, tetron, nylon, or a mixture thereof. On the other hand, as the metal roll, a chilled roll, an alloy chilled roll, a steel roll, or a metal roll having a hard chrome plated surface is used. .

[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. In the examples, “parts” and “%” represent “parts by weight” and “% by weight”, respectively, unless otherwise specified.

[Example 1] Preparation of solution A A composition comprising 10 parts of 3-diethylamino-7- (3'-trifluoromethylphenyl) aminofluorane, 5 parts of a 5% aqueous solution of methylcellulose and 40 parts of water was sand-milled. It was pulverized until the average particle size became 1.5 μm.

Preparation of Solution B A composition consisting of 30 parts of 1,1-bis (4-hydroxyphenyl) cyclohexane, 5 parts of a 5% aqueous solution of methylcellulose, and 80 parts of water was sand milled to give an average particle size of 1.
It was pulverized to 5 μm.

Preparation of Solution C A composition consisting of 20 parts of 1,2-di (3-methylphenoxy) ethane, 5 parts of a 5% aqueous solution of methylcellulose and 55 parts of water was pulverized with a sand mill until the average particle size became 1.5 μm. did.

Preparation of Solution D A composition comprising 10 parts of 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 5 parts of a 5% aqueous solution of methylcellulose, and 40 parts of water was sand milled to an average particle diameter of 2 μm. Crushed until

Formation of Thermosensitive Recording Layer 55 parts of solution A, 115 parts of solution B, 80 parts of solution C, 30 parts of solution D,
A coating solution obtained by mixing and stirring 80 parts of a 10% aqueous solution of polyvinyl alcohol and 30 parts of calcium carbonate was used.
coating amount after drying on one surface of woodfree paper g / m ² is 6 g / m ²
Was coated and dried to form a thermosensitive recording layer.

Preparation of Solution E A composition consisting of 10 parts of 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 5 parts of a 5% aqueous solution of methylcellulose and 40 parts of water was used in a sand mill to have an average particle diameter of 1.5 μm. Crushed until.

Formation of Protective Layer 265 parts of a 10% aqueous solution of polyvinyl alcohol modified with acetoacetyl group, kaolin [trade name: UW-90, EMC
54 parts, E solution 50 parts and zinc stearate 3
A coating solution for a protective layer obtained by mixing and stirring a composition consisting of 6 parts of 0% dispersion liquid has a coating amount of 6 g on a thermosensitive recording layer after drying.
After coating and drying so as to be / m ² , a super calendering process was performed to obtain a thermosensitive recording medium.

[Example 2] In the preparation of solution D of Example 1, 2,2'-methylenebis (4-methyl-6-tert-
2,2'-methylenebis (4-ethyl-6-tert-butylphenol) 1 instead of 10 parts of butylphenol)
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 0 part was used.

Example 3 In the preparation of solution D of Example 1, 2,2'-methylenebis (4-methyl-6-tert-
Butylphenol) 10 parts instead of 2,2'-ethylidene bis (4,6-di-tert-butylphenol) 10
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that parts were used.

Example 4 In the preparation of solution D of Example 1, 2,2'-methylenebis (4-methyl-6-tert-
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 10 parts of 4,4′-thiobis (2-methyl-6-tert-butylphenol) was used instead of 10 parts of butylphenol).

Example 5 In the preparation of the liquid B of Example 1, 30 parts of 4-hydroxy-4′-isopropoxydiphenyl sulfone was used instead of 30 parts of 1,1-bis (4-hydroxyphenyl) cyclohexane. A thermal recording material was obtained in the same manner as in Example 1 except for the above.

Example 6 In the preparation of solution B of Example 1, 30 parts of bis (3-allyl-4-hydroxyphenyl) sulfone was used instead of 30 parts of 1,1-bis (4-hydroxyphenyl) cyclohexane. Example 1 except that
A thermosensitive recording medium was obtained in the same manner as described above.

Example 7 Preparation of Liquid F A composition consisting of 100 parts of calcined clay [trade name: Ansilex, manufactured by EMC, oil absorption 110 ml / 100 g], 100 parts of a 10% aqueous solution of polyvinyl alcohol and 200 parts of water was prepared. By mixing and stirring, a coating liquid for the undercoat layer was obtained.

Formation of Thermosensitive Recording Medium 60 ° C./m ² of fine paper was coated with the F liquid so that the coating amount after drying was 7 g / m ² and dried, and then the thermal recording layer used in Example 1 was used. The coating composition for the protective layer and the coating composition for the protective layer were coated and dried so that the coating amounts after drying were each 6 g / m ^2, and supercalendering was performed to obtain a heat-sensitive recording material.

Example 8 Preparation of Liquid G 12% of acetoacetyl group-modified partially saponified polyvinyl alcohol [trade name: Gocefimer Z-210, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.] was placed in a stirring and mixing container equipped with a heating device. 220 parts of an aqueous solution was added to obtain an aqueous medium for capsule production. Separately, 2- (2'-hydroxy-3'-dodecyl-5'-
20 parts of methylphenyl) benzotriazole, 57 parts of diisopropylnaphthalene, and a main component of isocyanurate type hexamethylene diisocyanate derivative [trade name: Takenate D-170HN, Takeda Pharmaceutical Co., Ltd.] 33 parts 4 parts
The solution obtained by heating, mixing, and stirring to 0 ° C. was added to the above-mentioned aqueous medium for capsule production using a TK homomixer [Model HV-
M, manufactured by Tokushu Kika Kogyo Co., Ltd., and the average particle size is 2 μm.
It was emulsified and dispersed while cooling so that Next, 175 parts of water was added to this emulsified dispersion and reacted at 90 ° C. for 5 hours with stirring to prepare a microcapsule dispersion having a wall film made of a polyurethane / polyurea resin containing an ultraviolet absorber.

Formation of protective layer 220 parts of G liquid, 150 parts of 10% aqueous solution of polyvinyl alcohol modified with acetoacetyl group, kaolin [trade name: UW
-90, manufactured by EMC] 15 parts, zinc stearate 30
% Of the dispersion liquid and 30 parts of water were mixed and stirred to obtain a coating solution for a protective layer, and a coating for a heat-sensitive layer previously used in Example 1 was applied to one surface of a high-quality paper of 60 g / m ^2. coating amount after drying over those that had been applied and dried such that the 6 g / m ² of the coating amount after drying was supercalendered after coating and drying so that 6 g / m ² heat-sensitive recording material Got

Example 9 A thermosensitive recording medium was prepared in the same manner as in Example 1 except that 10 parts of 10% diaminostilbenedisulfonic acid type fluorescent dye (maximum absorption wavelength 350 nm) was added in the formation of the thermosensitive layer of Example 1. Got

Comparative Example 1 In the preparation of solution A of Example 1, 3- (N) was used instead of 10 parts of 3-diethylamino-7- (3′-trifluoromethylphenyl) aminofluorane.
-Methyl-N-cyclohexylamino) -6-methyl-
Example 1 except that 10 parts of 7-anilinofluorane was used.
A thermosensitive recording medium was obtained in the same manner as described above.

Comparative Example 2 In the preparation of solution A of Example 1, 3- (N) was used instead of 10 parts of 3-diethylamino-7- (3′-trifluoromethylphenyl) aminofluorane.
-Ethyl-N-iso pentylamino) -6-methyl-7
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 10 parts of anilinofluoran was used.

Comparative Example 3 In the preparation of solution A of Example 1, 3-di-amino was used instead of 10 parts of 3-diethylamino-7- (3'-trifluoromethylphenyl) aminofluorane.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 10 parts of n-butylamino-6-methyl-7-anilinofluorane was used.

[Comparative Example 4] In the preparation of solution A of Example 1, 3-di-amino was used in place of 10 parts of 3-diethylamino-7- (3'-trifluoromethylphenyl) aminofluorane.
Ethylamino-6-methyl-7-anilinofluorane 1
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 0 part was used.

Comparative Example 5 In the preparation of solution D of Example 1, 4,4'-butylidene bis (6-tert-butyl) was used instead of 10 parts of 2,2'-methylenebis (4-methyl-6-tert-butylphenol). A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 10 parts of -m-cresol) was used.

Comparative Example 6 1- [α-methyl-α was used in place of 10 parts of 2,2′-methylenebis (4-methyl-6-tert-butylphenol) in the preparation of the liquid D of Example 1.
-(4'-hydroxyphenyl) ethyl] -4-
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 10 parts of [α ', α'-bis (4 "-hydroxyphenyl) ethyl] benzene was used.

[Comparative Example 7] In the preparation of solution D of Example 1, 1,1,3-tris (2-methyl-) was used instead of 10 parts of 2,2'-methylenebis (4-methyl-6-tert-butylphenol). A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 10 parts of 4-hydroxy-5-cyclohexylphenyl) butane was used.

[Comparative Example 8] In the preparation of the liquid D of Example 1, 4,4'-dihydroxy-3,3 ', instead of 10 parts of 2,2'-methylenebis (4-methyl-6-tert-butylphenol), was prepared. A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 10 parts of 5,5'-tetramethyldiphenyl sulfone was used.

[Comparative Example 9] In the preparation of the liquid D of Example 1, 2,2-bis (4-hydroxy-3,2,2'-methylenebis (4-methyl-6-tert-butylphenol) was used instead of 10 parts. A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 10 parts of 5-dimethylphenyl) propane was used.

The 18 types of thermal recording materials thus obtained were subjected to the following evaluation tests, and the results are shown in Table 1. [Evaluation] [Coloring property] Each thermosensitive recording medium was colored with an applied energy of 0.4 mJ / dot using a thermosensitive evaluation machine [trade name: TH-PMD, manufactured by Okura Electric Co., Ltd.], and a coloring density of a recorded image obtained. Was measured in a visual mode with a Macbeth densitometer [RD-914 type, manufactured by Macbeth Co.], and the background density was measured with a Macbeth densitometer (blue filter). [Light resistance] The initial density of the background part of the thermal recording material after recording as described above and the density of the recorded image after being exposed to direct sunlight for 15 days were measured with a Macbeth densitometer (visual mode), and the density of the background part was also measured. It was measured with a Macbeth densitometer (using a blue filter).

[0056]

[Table 1]

[0057]

As is clear from the results of [Table 1], the heat-sensitive recording material of the present invention has very little discoloration of the background portion even when exposed to sunlight, and the light resistance which does not cause a decrease in the density of the recorded image. It was a heat-sensitive recording material having excellent properties.

Claims (3)

[Claims] 1. A thermosensitive recording medium in which a thermosensitive recording layer containing a colorless or pale basic dye and a coloring agent and a protective layer are sequentially provided on a support, and 3-diethylamino-7- is used as the basic dye. (3'-trifluoromethylphenyl) aminofluorane is used, and at least one hindered phenol compound selected from the following general formulas [Chemical Formula 1] and [Chemical Formula 2] is contained in the thermosensitive recording layer, and the thermosensitive recording is performed. A heat-sensitive recording material comprising an ultraviolet absorber contained in at least one of the layer and the protective layer. [Chemical 1] [In the formula, R ₁ represents an optionally substituted saturated or unsaturated alkylene group; an optionally substituted saturated or unsaturated alkylidene group; an optionally substituted cycloalkylene group, R ₂ , R ₃ represents a hydrogen atom; a halogen atom; an optionally substituted saturated or unsaturated alkyl group; an optionally substituted saturated or unsaturated alkoxyl group. ] [Chemical 2] [In the formula, R ₄ , R ₅ , and R ₆ are hydrogen atoms; halogen atoms;
An optionally substituted saturated or unsaturated alkyl group;
The saturated or unsaturated alkoxyl group which may be substituted is shown. ] 2. A compound selected from [Chemical formula 1] and [Chemical formula 2] is 2,2'-methylenebis (4-methyl-6-tert-
Butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 2,2'-ethylidenebis (4,6-di-tert-butylphenol),
The thermal recording material according to claim 1, which is 4,4'-thiobis (2-methyl-6-tert-butylphenol). 3. The heat-sensitive recording material according to claim 2, wherein the ultraviolet absorber is a benzotriazole derivative.