JPH09142019A - Thermosensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermosensitive recording material excellent in the ligtht fastness and chemical resistance of its recording part and non-recording part and also excellent in recording running properties. SOLUTION: In a thermosensitive recording material wherein a thermosensitive recording layer containing an electron donating compd. and an electron acceptive compd. and a protective layer containing an ultraviolet absorber are successively provided, at least one kind of a bisbenzotriazole compd. represented by general formula (wherein R1 is a 1-4C, alkyl group and R2 and R3 are a hydrogen atom, a 1-4C alkyl group or a phenyl group and may be bonded to form cyclobenzylidene or cyclohexylidene) with an average particle size of 2μm or less such as 2,2'-methylenebis[4-tert-butyl-6-(2H- benzotriazol-2-yl)phenol] is added to the protective layer as the ultraviolet absorber.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a heat-sensitive recording material utilizing a color reaction between an electron-donating compound and an electron-accepting compound, which has excellent light resistance in recorded areas and unrecorded areas, and has excellent storage characteristics and recording running properties. The present invention relates to a thermosensitive recording material having excellent properties.

[0002]

2. Description of the Related Art A heat-sensitive recording material in which a plurality of color-forming substances are brought into contact with each other by heat to obtain a recorded image is well known.
Since such a thermal 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 facsimiles and various computers but also in a wide range of fields.

One of the fields of use thereof is, for example, POS.
(Point of sales) Thermal recording labels for systems can be mentioned. With the expansion of the system, labels attached to products for a long period of time are different from the conventional food labels whose mission is completed in a short period of time. The usage as tag paper used or handy terminal paper for collection and delivery that is often handled outdoors is increasing. However, in such applications, it is often exposed to indoor light or sunlight for a long period of time, and the effect of this is that the recorded image on the thermosensitive recording material may fade or the background part may turn yellow, resulting in a product image. Will be significantly damaged. For this reason, there is a strong demand for a heat-sensitive recording material having excellent light resistance, which does not cause fading of a recorded image or yellowing of a background portion even when exposed to room light or sunlight for a long time.

Then, for the purpose of improving the light resistance, a method of adding an ultraviolet absorber into the protective layer is disclosed in JP-A-60-8493.
No. 8, JP-A-60-107388, JP-A-60-
No. 112487, 61-193883, etc. However, since the ultraviolet absorber used in such a protective layer generally has a low melting point (200 ° C. or less), it is melted during recording to cause sticking and head residue between the thermal head and the protective layer, resulting in a uniform recorded image. Is not obtained, and because of its high solubility in organic solvents, contact with chemicals such as plasticizers and oils causes problems such as background fog and fading of recorded images.

Further, JP-A-7-47764 describes a heat-sensitive recording material containing a bistriazole compound in the heat-sensitive recording layer, but it is not possible to obtain a sufficient light resistance effect.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermosensitive recording medium which is excellent in light resistance and chemical resistance of a recorded portion and an unrecorded portion and is excellent in recording running property.

[0007]

DISCLOSURE OF THE INVENTION The present inventors have found that a heat-sensitive recording layer containing an electron-donating compound and an electron-accepting compound and a protective layer containing an ultraviolet absorber are sequentially provided on a support. In the recording material, the protective layer contains at least one bisbenzotriazole compound represented by the following general formula (1) having an average particle size of 2 μm or less as an ultraviolet absorber, which is excellent in solving the above problems. It was found that a thermosensitive recording medium was obtained, and the present invention was completed.

[0008]

Embedded image [In the formula, R ₁ represents a C _{1 to} C ₄ alkyl group, R ₂ and R ₃ each represent a hydrogen atom, a C _{1 to} C ₄ alkyl group, or a phenyl group. R ₂ and R ₃ may combine to form cyclopentylidene or cyclohexylidene. ]

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a heat-sensitive recording material in which a heat-sensitive recording layer containing an electron-donating compound and an electron-accepting compound and a protective layer containing an ultraviolet absorber are sequentially provided on a support. The protective layer contains at least one bisbenzotriazole compound represented by the general formula (1) having an average particle diameter of 2 μm or less (hereinafter referred to as a specific ultraviolet absorber) as an ultraviolet absorber. To do.
Here, if the average particle size of the specific ultraviolet absorber exceeds 2 μm, the ultraviolet absorption efficiency is remarkably reduced, and the desired effect cannot be obtained. Therefore, it is an essential condition that the average particle size is 2 μm or less. In particular, when the thickness is 0.5 μm or less, not only the ultraviolet absorption efficiency is remarkably improved, but also the protective layer hardly hides the recorded image, so that a clear recorded image is formed. Further, since the specific ultraviolet absorber is hardly dissolved in a solvent such as a plasticizer, an edible oil and an organic solvent, background fog may occur even if the surface of the protective layer is immersed in the solvent, or the recorded image may be discolored. It also has an excellent effect on chemical resistance.

Specific examples of the bisbenzotriazole compound represented by the general formula (1) include, for example, 2,2'-methylenebis [4-methyl-6- (2H-benzotriazol-2-yl) phenol], 2 , 2'-Methylenebis [4-ethyl-6- (2H-benzotriazole-2-
Yl) phenol], 2,2'-methylenebis [4-isopropyl-6- (2H-benzotriazol-2-yl) phenol], 2,2'-methylenebis [4-tert]
-Butyl-6- (2H-benzotriazol-2-yl) phenol], 2,2'-ethylidene bis [4-methyl-6- (2H-benzotriazol-2-yl) phenol], 2,2'- Ethylidene bis [4-tert-butyl-6- (2H-benzotriazol-2-yl) phenol], 2,2'-isopropylidenebis [4-methyl-6- (2H-benzotriazol-2-yl) phenol ], 2,2'-isopropylidene bis [4-ethyl-6- (2H-benzotriazol-2-yl) phenol], 2,2'-isopropylidene bis [4-te
rt-Butyl-6- (2H-benzotriazol-2-yl) phenol], 2,2′-isobutylidene bis [4
-Methyl-6- (2H-benzotriazol-2-yl) phenol], 2,2 '-(1,3-dimethylbutylidene) bis [4-methyl-6- (2H-benzotriazol-2-yl) Phenol], 2,2'-benzylidenebis [4-methyl-6- (2H-benzotriazol-2-yl) phenol], 2,2'-cyclopentylidenebisbis [4-methyl-6- (2H- Benzotriazol-2-yl) phenol], 2,2′-cyclohexylidenebis [4-methyl-6- (2H-benzotriazol-2-yl) phenol] and the like.

The content of the specific ultraviolet absorber is 1 to 50% by weight, especially 10 to 40% by weight based on the total solid content of the protective layer.
A range of weight% is preferred. When the content of such a specific ultraviolet absorber is less than 1% by weight based on the total solid content of the protective layer, the light resistance of the recorded image is remarkably lowered, and when it exceeds 50% by weight, the film forming property of the protective layer is lowered and the recorded image is lowered. The chemical resistance of is significantly reduced. Further, other known ultraviolet absorbers may be used in combination as long as the desired effects of the present invention are not impaired.

The amount of the above-mentioned specific ultraviolet absorber to be used cannot be decided unconditionally because it depends on the coating amount of the protective layer, but it is generally 0.05 to 2.0 g / m ² , preferably 0 in the protective layer. The range of 0.2 to 1.0 g / m ² is desirable. When the amount of the ultraviolet absorber in the protective layer is less than 0.05 g / m ² , the effect of preventing yellowing of the unrecorded portion of the thermosensitive recording medium is significantly reduced. Further, if it exceeds 2.0 g / m ² , the protective layer inevitably becomes thick, and the recording sensitivity is lowered.

The average particle diameter of the specific ultraviolet absorber is 2 μm
As a method of refining below, water is generally used as a dispersion medium, and additives such as a dispersant and an antifoaming agent are added as necessary, and the mixture is stirred by a ball mill, attritor, sand mill, or the like.
There are a method using a pulverizer, a method in which an ultraviolet absorber is dissolved in a low boiling point solvent, then emulsified, and the low boiling point solvent is evaporated and removed.
Above all, a sand mill type crusher is desirable, and the average particle diameter of the dispersion medium is preferably 1 mm or less, more preferably 0.5 mm or less.

In addition to a specific UV absorber, the protective layer may also be used as an adhesive such as starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy modified polyvinyl alcohol, aceto. Acetyl 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, At least one of urea resin, melamine resin, amide resin, polyester urethane resin and the like is used in the range of 15 to 80% by weight based on the total solid amount of the protective layer.

Of these, acetoacetyl group-modified polyvinyl alcohol is preferable because it can easily enhance the chemical resistance and the water resistance of the protective layer. The acetoacetyl group-modified polyvinyl alcohol is mainly composed of polyvinyl alcohol which is converted to acetoacetic acid. Acetoacetic esterification of polyvinyl alcohol is produced by adding diketene to a polyvinyl alcohol resin or transesterifying acetoacetic ester. The polymerization degree of this polymer is 200 to 200
A range of 0 is desirable.

If desired, a pigment may be added to the protective layer in order to improve printability and sticking. Specific examples of the pigment include calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, talc, kaolin,
Examples thereof include inorganic pigments such as clay, calcined kaolin and colloidal silica, organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and raw starch particles.

Further, in the protective layer, if necessary, a lubricant such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax and ester wax, and a surfactant such as sodium dioctylsulfosuccinate (dispersant, wetting agent). Agents), antifoaming agents, and various auxiliaries such as water-soluble polyvalent metal salts such as potassium alum and aluminum acetate may be appropriately added. Also,
In order to further improve the water resistance, a curing agent such as glyoxal, boric acid, dialdehyde starch, and an epoxy compound can be used, and a microencapsulated ultraviolet absorber or the like can be used in combination as necessary.

The method for preparing the coating liquid for the protective layer is not particularly limited, and generally, water is used as the dispersion medium, and in addition to the specific ultraviolet absorber and the adhesive, pigments, lubricants, etc., which are added as necessary. Is prepared by mixing and stirring.

The thermosensitive recording system utilizing the color reaction between the electron-donating compound and the electron-accepting compound to which the present invention is applied includes, for example, a combination of a leuco dye and a color former, a combination of a diazonium salt and a coupler, A combination of a transition element such as iron and a chelate compound, a combination of an aromatic isocyanate compound and an imino compound, and the like are included, but a combination of a leuco dye and a color former is also excellent in color density and recording sensitivity. The heat-sensitive recording material utilizing the color reaction between the leuco dye and the color-developing agent will be described in detail below.

As the leuco dye, various known leuco dyes can be used, and specifically, for example, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide and 3-cyclohexylamino-6. -Chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, rhodamine (o-chloroanilino) lactam, 3- (N-ethyl-p-toluidino) -7-methylfluorane, 3-diethylamino-6. , 8-Dimethylfluorane, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane, 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-
Anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-di-n-butylamino-6-methyl-7-anilinofluorane, 3-di-n-
Pentylamino-6-methyl-7-anilinofluorane, 3-di-n-butylamino-7- (o-chlorophenylamino) fluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7. -Anilino Fluoran, 3-
Diethylamino-7- (m-trifluoromethylanilino) fluorane, 3- (N-ethyl-N-tetrahydrofurfurylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7 -Anilinofluorane, 3-dimethylamino-6-methyl-7-anilinofluorane, 3-di-n-butylamino-6-methyl-7-m-toluidinofluorane, 3- (N- Ethyl-N-ethoxypropyl) amino-6-methyl-7-
Anilinofluoran, 3- (N-methyl-NNn-propyl) amino-6-methyl-7-anilinofluoran,
3,3-bis [1- (4-methoxyphenyl) -1-
(4-Dimethylaminophenyl) ethylene-2-yl]
-4,5,6,7-tetrachlorophthalide, 3- (4-
Dimethylaminophenyl) amino-5,7-dimethylfluorane, 3- (4-dibutylaminophenyl) amino-6-methyl-7-chlorofluorane, 3,3-bis (4-diethylamino-2-ethoxyphenyl) -4-
Azaphthalide and the like. Of course, it is not limited to these, and two or more kinds may be used in combination as required.

Various known coloring agents can be used in combination with the above leuco dye, for example, 4,4'-isopropylidenediphenol, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2, 2-bis (4-
Hydroxyphenyl) -4-methylpentane, 4,4 '
-Dihydroxydiphenyl sulfide, 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'-methyldiphenylsulfone, 4-hydroxyphenyl-4'-benzyloxyphenylsulfone, 3,4-dihydroxyphenyl-4'-methylphenylsulfone, bis (4-hydroxyphenylthio) Ethoxy) methane, 1,4-bis [α
-Methyl-α- (4'-hydroxyphenyl) ethyl]
Phenolic compounds such as benzene, 1,3-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, di (4-hydroxy-3-methylphenyl) sulfide, N, N′-di- Thiourea compounds such as m-chlorophenylthiourea, zinc p-chlorobenzoate,
Zinc 4- [2-p-methoxyphenoxyethoxy] salicylate, zinc 4- [3- (p-tolylsulfonyl) propyloxy] salicylate, zinc 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylate, etc. Examples thereof include zinc salts of aromatic carboxylic acids. Among them, 4-hydroxy-4′-isopropoxydiphenyl sulfone and bis (3-allyl-4-hydroxyphenyl) sulfone are preferably used because they are particularly excellent in storage stability of recorded images.

The ratio of the leuco dye to the coloring agent used is appropriately selected according to the type of leuco dye or coloring agent used and is not particularly limited, but generally 1 part by weight of the leuco dye is used. 1 to 10 parts by weight, preferably 2 to
About 5 parts by weight of the coloring agent is used.

Further, in the heat-sensitive recording layer, a sensitizer for increasing the recording sensitivity and a storability improving agent for increasing the storability of a recorded image with time can be used in combination. Specific examples of the sensitizer include, for example, stearic acid amide, methoxycarbonyl-N-stearic acid benzamide, ethylenebisstearic acid, methylenebisstearic acid amide, N-
Methylol stearate amide, dibenzyl terephthalate, p-benzyloxybenzoate benzyl, 2-naphthylbenzyl ether, m-terphenyl, dibenzyl oxalate, oxalate-di-p-methylbenzyl, oxalate-di-p-chloro. Benzyl, p-benzylbiphenyl,
Di (p-methoxyphenoxyethyl) ether, 1,2
-Di (3-methylphenoxy) ethane, 1,2-di (4
-Methylphenoxy) ethane, 1,2-di (4-methoxyphenoxy) ethane, 1,2-diphenoxyethane,
1- (4-methoxyphenoxy) -2- (3-methoxyphenoxy) ethane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p-biphenyl-p-tolyl ether, 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,
Generally, it is desirable to adjust the amount of the coloring agent in the range of about 4 parts by weight or less relative to 1 part by weight.

Specific examples of the storability improving agent include the following. 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 4,4'-thiobis (2-methyl-6-tert) -Butylphenol), 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-methyl-6-tert) -Butylphenol),
4,4'-dihydroxy-3,3 ', 5,5'-tetramethyldiphenyl sulfone, 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2,2-
Hindered phenol compounds such as bis (4-hydroxy-3,5-dimethylphenyl) propane, 1,4-diglycidyloxybenzene, 4,4′-diglycidyloxydiphenyl sulfone, 4-benzyloxy-4′-
(2-methylglycidyloxy) diphenyl sulfone,
Epoxy compounds such as diglycidyl terephthalate, cresol novolac type epoxy resin, phenol novolac type epoxy resin, and bisphenol A type epoxy resin,
N, N'-di-2-naphthyl-p-phenyldiamine,
Sodium or polyvalent metal salt of 2,2′-methylenebis (4,6-di-tert-butylphenyl) phosphate,
Bis (4-ethyleneiminocarbonylaminophenyl)
Such as methane. Among them, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane is preferably used because it has an excellent water resistance effect and does not easily cause background fog.

The coating liquid for the heat-sensitive recording layer, which contains a leuco dye, a color former, a sensitizer, a preservability improver and the like, generally uses water as a dispersion medium and is leuco-treated by a stirring / pulverizing machine such as a ball mill, attritor or sand mill. Dyes, colorants, sensitizers and storability improvers are finely dispersed together or separately, and an adhesive and, if necessary, a pigment, a lubricant, a surfactant, an antifoaming agent, a colored dye, etc. are added. And then prepared.

Specific examples of the adhesive include 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, styrene / butadiene copolymer emulsion, urea resin, melamine resin, amide resin, polyurethane resin and the like.
Such an adhesive is used in an amount of 5 to 30 relative to the total solid amount of the heat sensitive recording layer.
It is blended in the range of about wt%.

Specific examples of pigments, lubricants and surfactants include inorganic pigments such as kaolin, clay, calcium carbonate, calcined clay, calcined kaolin, titanium dioxide, diatomaceous earth, fine anhydrous silica and activated clay, and styrene microballs. Nylon powder, polyethylene powder,
Urea / formalin resin filler, organic pigments such as raw starch particles, zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax and other lubricants, sodium dioctyl sulfosuccinate, sodium dodecylbenzene sulfonate, sodium lauryl alcohol sulfate And surfactants such as fatty acid metal salts.

The method for forming the heat-sensitive recording layer and the protective layer is not particularly limited, and suitable coating such as air knife coating, varibar coating, pure blade coating, rod blade coating, short dwell coating, curtain coating, die coating, etc. Depending on the method, the coating liquid for the thermal recording layer is applied and dried on a support such as paper, plastic film, synthetic paper, and non-woven fabric, and then the coating liquid for the protective layer is applied and dried on the thermal recording layer. It is formed. 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 for a dry weight 0.5 to 15 g / m ² , preferably 1-7
It is prepared in the range of about g / m ² .

If desired, a protective layer may be provided on the back surface side of the support to further improve the storability. Furthermore, an undercoat layer is provided between the support and the heat-sensitive recording layer,
After coating each layer, smoothing treatment such as super calendering is applied, or the back surface of the thermosensitive recording material is treated with an adhesive to form an adhesive label, magnetic recording layer, coating layer for printing, and thermal transfer recording layer. Various well-known techniques in the field of manufacturing a thermal recording medium, such as the provision of a.

[0030]

The present invention will be described in more detail with reference to the following Examples, but it should be understood that the present invention is by no means restricted to such specific Examples. In the examples, "parts" and "%" indicate "parts by weight" and "% by weight", respectively, unless otherwise specified.

Preparation of solution A A composition consisting of 10 parts of 3-diethylamino-7- (m-trifluoromethylanilino) fluorane, 5 parts of a 5% aqueous solution of methylcellulose and 40 parts of water and having an average particle size of 1.5 μm was sand milled. Crushed until.

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 80 parts of water was ground by a sand mill until the average particle size became 1.5 μm. did.

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 ground by a sand mill until the average particle size became 1.5 μm. did.

Preparation of solution D 2,2'-methylenebis [4-tert-butyl-6- (2
H-benzotriazol-2-yl) phenol] 10
Parts, 5 parts of a 5% aqueous solution of methyl cellulose, and 40 parts of water were pulverized with a sand mill until the average particle size became 0.4 μm.

Example 1 Formation of Thermosensitive Recording Layer 55 parts of solution A, 115 parts of solution B, 80 parts of solution C, 80 parts of 10% aqueous solution of polyvinyl alcohol and calcium carbonate 3
The coating solution obtained by mixing and stirring 5 parts was applied and dried on one surface of a high-quality paper of 60 g / m ² so that the coating amount after drying was 5 g / m ² to form a heat-sensitive recording layer.

Formation of protective layer 55 parts of D liquid, 150 parts of 10% aqueous solution of polyvinyl alcohol modified with acetoacetyl group, kaolin [trade name: UW-
90, manufactured by EMC] 30 parts, 3 parts of a 10% aqueous solution of glyoxal, 6 parts of a 30% dispersion of zinc stearate and 30 parts of a composition, which is obtained by mixing and stirring a composition for a protective layer, The coating amount after drying on the thermosensitive recording layer is 4 g / m ^2.
After coating and drying so as to obtain a super calendering treatment, a thermosensitive recording medium was obtained.

Example 2 In the preparation of solution D, 2,2'-methylenebis [4-tert] was used.
-Butyl-6- (2H-benzotriazol-2-yl) phenol] instead of 2,2'-methylenebis [4-methyl-6- (2H-benzotriazol-2-
[Il) Phenol] was used to obtain a thermosensitive recording medium in the same manner as in Example 1.

Example 3 In the preparation of solution D, 2,2'-methylenebis [4-tert] was used.
-Butyl-6- (2H-benzotriazol-2-yl) phenol] is used in place of 2,2'-ethylidene bis [4-tert-butyl-6- (2H-benzotriazol-2-yl) phenol] A thermosensitive recording medium was obtained in the same manner as in Example 1 except that it was not used.

Example 4 In the preparation of solution D, 2,2'-methylenebis [4-tert]
-Butyl-6- (2H-benzotriazol-2-yl) phenol] instead of 2,2 '-(1,3-dimethylbutylidene) bis [4-tert-butyl-6- (2H
-Benzotriazol-2-yl) phenol] was used to obtain a thermosensitive recording medium in the same manner as in Example 1.

Example 5 In the preparation of solution D, 2,2'-methylenebis [4-tert]
-Butyl-6- (2H-benzotriazol-2-yl) phenol] is used in place of 2,2'-cyclohexylidenebis [4-methyl-6- (2H-benzotriazol-2-yl) phenol] A thermosensitive recording medium was obtained in the same manner as in Example 1 except that it was not used.

Example 6 In the preparation of solution D, 2,2'-methylenebis [4-tert]
-Butyl-6- (2H-benzotriazol-2-yl) phenol] instead of 2,2'-benzylidene bis [4-methyl-6- (2H-benzotriazole-2
-Yl) phenol] was used to obtain a thermosensitive recording medium in the same manner as in Example 1.

Example 7 In the preparation of solution A, 3-diethylamino-7- (m-trifluoromethylanilino) fluorane was replaced with 3-
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that di-n-butylamino-6-methyl-7-anilinofluorane was used.

Example 8 In the preparation of solution B, bis (3-allyl-) was used instead of 4-hydroxy-4'-isopropoxydiphenyl sulfone.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 4-hydroxyphenyl) sulfone was used.

Example 9 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the liquid D was prepared until the average particle size was 1.5 μm.

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

Comparative Example 2 In the preparation of solution D, 2,2'-methylenebis [4-tert]
-Butyl-6- (2H-benzotriazol-2-yl) phenol] in the same manner as in Example 1 except that 2- (2H-benzotriazol-2-yl) -4-methyl-phenol was used. A thermosensitive recording medium was obtained.

Comparative Example 3 In the preparation of solution D, 2,2'-methylenebis [4-tert]
-Butyl-6- (2H-benzotriazol-2-yl) phenol] was used in place of 2,2'-methylenebis [4-tert-octyl-6- (2H-benzotriazol-2-yl) phenol]. A thermal recording material was obtained in the same manner as in Example 1 except for the above.

Comparative Example 4 Formation of Thermosensitive Recording Layer 55 parts of solution A, 115 parts of solution B, 80 parts of solution C, 55 parts of solution D,
A coating solution obtained by mixing and stirring 80 parts of a 10% aqueous solution of polyvinyl alcohol and 25 parts of calcium carbonate was used.
coating amount after drying on one surface of woodfree paper g / m ² is 5 g / m ²
Was coated and dried to form a thermosensitive recording layer.

Formation of protective layer 10% water of polyvinyl alcohol modified with acetoacetyl group
Solution 150 parts, kaolin [trade name: UW-90, EMC
40 parts, 3 parts of 10% aqueous solution of glyoxal, su
From 6 parts of 30% zinc thearate dispersion and 30 parts of water
The coating solution for the protective layer obtained by mixing and stirring the composition
Coating amount after drying on the thermal recording layer is 4g / m ^TwoSo that
After coating and drying, heat-sensitive recording is performed by super calendar processing.
I got a copy.

Comparative Example 5 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the liquid D was prepared until the average particle size was 3.2 μm.

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

[Coloring property] Heat sensitive evaluation machine [Product name: TH-P
MD, manufactured by Okura Electric Co., Ltd., and applied energy 0.45
Each thermosensitive recording medium was color-developed at mJ / dot, and the color density of the obtained recorded image was measured by a Macbeth densitometer [RD-914 type, manufactured by Macbeth Co.] in a visual mode.

[Light resistance] The thermosensitive recording material recorded in the above evaluation of color development was exposed to direct sunlight for 10 days, and the unrecorded area and the recorded area were measured by a Macbeth densitometer (using a blue filter).

[Plasticizer resistance] Wrap film [Product name: KMA] on polycarbonate pulp (40 mmφ pipe)
-W, manufactured by Mitsui Toatsu Kagaku Co., Ltd.) is wound in three layers, the thermal recording material recorded in the above evaluation of the color developability is placed thereon, and a wrap film is further wound in three layers on the thermal recording material, and the film is wrapped at 24 ° C. at The color density after standing for a period of time was measured with a Macbeth densitometer (visual mode) to evaluate the plasticizer resistance.

[Oil resistance] Edible oil was applied onto the thermosensitive recording medium recorded in the above evaluation of color developability, and the color develop density after standing at room temperature for 8 hours was measured by a Macbeth densitometer (visual mode), The oil resistance was evaluated.

[Head Matching Property] The stain condition (head residue) of the thermal head after continuous recording of 200 mm in the evaluation of the color developing property was visually evaluated as follows. Evaluation criteria ⊚: No head shavings at all. ◯: There is some head shavings, but there is no practical problem. X: There are many head debris.

[Sharpness of Recorded Image] The sharpness of the recorded image obtained by the evaluation of the color developability was visually determined. Evaluation Criteria A: The recorded image is very clear. ◯: The recorded image is clear. X: The recorded image is slightly unclear.

[0058]

[Table 1]

[0059]

As is apparent from the results of [Table 1], the thermosensitive recording medium of the present invention is excellent in light resistance and chemical resistance of the recorded portion and the unrecorded portion, and is also excellent in head matching. It was something that had.

Claims (1)

[Claims] 1. A heat-sensitive recording material comprising a support, on which a heat-sensitive recording layer containing an electron-donating compound and an electron-accepting compound and a protective layer containing a UV-absorbing agent are sequentially provided. A heat-sensitive recording material, which is a bisbenzotriazole compound represented by the formula (1) and has an average particle diameter of 2 μm or less. Embedded image [In the formula, R ₁ represents a C _{1 to} C ₄ alkyl group, R ₂ and R ₃ each represent a hydrogen atom, a C _{1 to} C ₄ alkyl group, or a phenyl group. R ₂ and R ₃ may combine to form cyclopentylidene or cyclohexylidene. ]