JPH07172056A - Thermal recording material - Google Patents

Abstract

PURPOSE:To improve heat resistance, dynamic color developing sensitivity, light resistance, etc., by incorporating UV absorption substance having a melting point of a specific temperature. CONSTITUTION:A thermal recording material comprises an intermediate layer containing non-foamed plastic fine hollow particles having a mean particle size of 2-10mum and percentage of hollowness of 90% or greater as a main component and a thermal color developing layer containing leuco dye and developer for color developing the dye at the time of heating as main ingredients to be sequentially laminated on a support, having a static color development starting temperature of 100-150 deg., wherein the material contains UV absorber having a melting point of 135 deg.C or higher. In order to improve light resistance of a skin, the UV absorber is incorporated. Particularly, 2-2'-methylenebis{4-(1,1,3,3- tetramethylbutyl)-6-(2H-benzotriazole-2-il)phenol} and/or bis(2-methoxy-4- hydroxy-5-benzoylphenyl)methane having a melting point of 190 deg.C or higher are preferable.

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, and more particularly to a heat-sensitive recording material which is excellent in dynamic color development sensitivity and heat resistance of the background portion, and also excellent in light resistance of the background portion.

[0002]

2. Description of the Related Art A general heat-sensitive recording material is a colorless or light color developing agent such as a leuco dye as a coloring agent on a support such as paper or film, and a phenolic compound (especially as a color developing agent) for coloring the coloring when heated. Bisphenol A), a coloring system composed of an acidic substance such as an organic acid, and a thermosensitive coloring layer in which a binder, a filler, a sensitivity improver, a lubricant and other auxiliaries are dispersed in a coloring system. For example, JP-B-43- No. 4160, Japanese Examined Patent Publication No. 45-14039, and Japanese Unexamined Patent Publication No. 48-27736, and they are widely used. This type of heat-sensitive recording sheet obtains a colored image by an instantaneous chemical reaction between the color-developing agent and the color-developing agent during heating (a thermal printer facsimile machine having a thermal head is used for heating). Compared to other recording materials, recording can be obtained in a short time with a relatively simple device without complicated processing such as development and fixing, low noise and environmental pollution, low cost, etc. Is used not only as a recording material for various information and measuring instruments such as electronic calculators, facsimiles, telexes, medical measuring instruments, etc., but also for CAD paper, food POS, etc.
It is also useful as a label and industrial label, and is a useful recording material.

On the other hand, in addition to being used in such a wide range of fields, the quality required for the heat-sensitive recording material is also increasing. In particular, mainly for food labels used in hot storage and industrial labels attached to machine parts used in high temperature places such as engine rooms, etc., to improve the color development of the background in high temperature environments (hereinafter referred to as heat-resistant fog). ) Is strongly requested. The heat resistance desired in such application fields is 80 ° C., 2
Quality of more than 4 hours is often required. However, the recording conditions among those skilled in the art in the heat resistance test applied to the conventional heat-sensitive recording material are generally 60 ° C., 24 hours or 70 ° C., 1 to 2 hours, and satisfy the required quality. is not.

Further, conventionally, in order to improve such heat resistance, means for increasing the static color development start temperature by selecting a developer, a leuco dye and other heat fusible substances used in the thermosensitive color developing layer. However, in such a case, there is a drawback that the energy for printing with an actual printer, facsimile, etc. becomes high (that is, the dynamic color development sensitivity is low). Therefore, as a method for improving the heat resistance without lowering the dynamic color development sensitivity, a heat insulating layer having fine hollows is formed on a support, and the static color development start temperature is set to 90 ° C. or more (JP Japanese Patent Laid-Open No. 64-64887), but further improvement is desired in view of the recent high demand for heat resistance and sensitivity.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording material which has both heat resistance and sensitivity, which are contradictory properties, and which is excellent in light resistance.

[0006]

Means for Solving the Problems As a result of intensive investigations by the present inventors, an intermediate layer which has a very high heat insulating property and improves adhesion to a thermal head is provided on a support, and an appropriate melting point is provided thereon. In a heat-sensitive recording material provided with a heat-sensitive color forming layer using a color developer, a paint, etc., it was found that the above-mentioned object can be achieved by containing an ultraviolet absorber having an appropriate melting point, and the present invention has been completed. Came to do.

That is, according to the present invention, an intermediate layer mainly composed of non-expandable plastic fine hollow particles having an average particle diameter of 2 to 10 μm and a hollowness of 90% or more on a support, a leuco dye and A heat-sensitive recording material having a static color-developing start temperature of 100 to 150 ° C., which is formed by sequentially laminating a thermosensitive color-developing layer containing a color developing agent as a main component that develops the leuco dye when heated.
Provided is a heat-sensitive recording material containing an ultraviolet absorbing substance having a melting point of 135 ° C. or higher.

In the present invention, the heat insulating property is very high,
Since the intermediate layer for improving the adhesion with the thermal head is composed mainly of non-expandable plastic fine hollow particles having an average particle diameter of 2 to 10 μm and a hollow ratio of 90% or more, the heat from the thermal head or the like is used. The efficient use of energy further improves the dynamic color development sensitivity by improving the adhesiveness with the thermal head due to the heat insulating property of the intermediate layer.

The non-expandable plastic fine hollow particles used in the intermediate layer of the present invention have a shell made of a thermoplastic resin and contain air and other gases inside, and are fine particles which are already in a foamed state. Yes, the average particle size is 2
Those having a thickness of 10 μm, preferably 3 to 5 μm are used. Those having an average particle size of less than 2 μm have production problems such as difficulty in achieving an arbitrary hollowness, and are difficult in terms of cost, and conversely, those having an average particle size of more than 10 μm have a surface roughness after coating and drying. Since the smoothness is lowered, the adhesion to the thermal head or the like is lowered, and the effect of improving the sensitivity is small. Further, the particle distribution is preferably such that the particle size is in the above range and the distribution peak is uniform.

Further, the plastic micro hollow particles used in the present invention have a hollowness of 90% or more, preferably 95% or more. When the hollowness is less than 90%, the heat insulating property is insufficient, so that the heat energy from the thermal head is released to the heat-sensitive recording material through the support, and the effect of improving the sensitivity is small. The hollowness referred to here is the ratio of the outer diameter to the inner diameter of the hollow particles, and is represented by the following formula.

The fine hollow particles used in the present invention have a shell made of a thermoplastic resin as described above. Examples of the resin include polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate and polyacrylic. Examples thereof include acid esters, polyacrylonitrile, polybutadiene, and copolymer resins thereof. Among these, a copolymer resin mainly containing vinylidene chloride and acrylonitrile is preferable.

To provide the intermediate layer on the support, the fine hollow particles described above are dispersed in water together with a binder such as a known water-soluble polymer or aqueous polymer emulsion, and this is coated on the surface of the support, Obtained by drying. In this case, the coating amount of the hollow microparticles is at least 0.5 g, preferably about 1 to 15 g per 1 m ² of the support,
The amount of the binder resin applied may be such that the intermediate layer is strongly bonded to the support, and is usually 10 to 75% by weight based on the total amount of the hollow microparticles and the binder resin.

In the present invention, the binder used when forming the intermediate layer is appropriately selected from conventionally known water-soluble polymers and / or aqueous polymer emulsions. Specific examples thereof include water-soluble polymers such as polyvinyl alcohol, starch and derivatives thereof, methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, cellulose derivatives such as ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide / acrylic acid. Examples thereof include ester copolymers, acrylamide / acrylic acid ester / methacrylic acid terpolymers, styrene / maleic anhydride copolymer alkali salts, polyacrylamide, sodium alginate, gelatin, and casein. Further, as the aqueous polymer emulsion, a latex such as styrene / butadiene / acrylic copolymer or vinyl acetate resin, vinyl acetate / acrylic acid copolymer, styrene / acrylic ester copolymer, acrylic ester resin,
Examples include emulsions of polyurethane resin and the like.

In the intermediate layer of the present invention, an auxiliary additive component such as a filler or a heat-fusible substance, which is commonly used in heat-sensitive recording materials of this type, may be added together with the fine hollow particles and the binder, if necessary. , A surfactant and the like can be used in combination. In this case, as specific examples of the filler and the heat-fusible substance, various ones described in connection with the components of the heat-sensitive recording layer will be mentioned.

Further, since the surface of the intermediate layer formed on the support as described above has considerable unevenness, the flat surface may be smoothed by calendering after the intermediate layer is formed. In order to prevent heat-resistant fogging even in a high temperature environment, the thermosensitive recording material has a static color development start temperature of 100 to 100.
When the temperature is 150 ° C., the heat-resistant fogging occurs when the temperature is less than 100 ° C., and the dynamic color development sensitivity is poor when the temperature exceeds 150 ° C. The term "color development start temperature" as used herein means a Macbeth densitometer R in which a heat block is brought into contact with the surface of a heat-sensitive recording material under the conditions of a heat gradient tester (manufactured by Toyo Seiki) for 1.0 sec and a pressure of 2 kg / cm ^2.
This is the temperature at which the image density was measured at D-914 to be 0.2.

To improve the light resistance of the background part,
The inclusion of an ultraviolet absorber has a great effect, but the melting point is 135 ° C in order to keep the color formation starting temperature at 100 to 150 ° C.
Must be more than that. In particular, 2,2'-methylenebis {4- (1,1,3,3-
Tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol} and / or bis (2-methoxy-4-hydroxy-5-benzoylphenyl) methane are preferred. Further, the melting point of the developer is preferably 180 to 240 ° C. in order to reduce heat-resistant fogging and to improve the sensitivity. Considering the strength of a light-resistant image,
2,4'-diphenol sulfone is preferred.

The leuco dyes used in the heat-sensitive recording layer of the present invention are applied singly or as a mixture of two or more kinds, and as such leuco dyes, those applied to this kind of heat-sensitive material are arbitrarily applied. For example, leuco compounds of dyes such as triphenylmethane type, fluorane type, phenothiazine type, auramine type, spiropyran type and indolinophtalide type dyes are preferably used. Specific examples of such leuco dyes include those shown below.

3,3-bis (p-dimethylaminophenyl) -phthalide, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis ( p-dimethylaminophenyl) -6-diethylaminophthalide,
3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dibutylaminophenyl) phthalide, 3-cyclohexylamino-6-chlorofluorane, 3-dimethylamino-5,7 -Dimethylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-
Diethylamino-7,8-benzfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-
(Np-tolyl-N-ethylamino) -6-methyl-
7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2- {N- (3'-trifluoromethylphenyl) amino} -6-diethylaminofluorane, 2- {3. 6-bis (diethylamino)-
9- (o-chloroanilino) xanthyl benzoate lactam}, 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluorane, 3-diethylamino-7- (o-chloroanilino) fluorane, 3-di- n-Butylamino-7- (o-chloroanilino) fluorane, 3-N-methyl-N, n-amylamino-6-
Methyl-7-anilinofluorane, 3-N-methyl-N
-Cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3- (N, N-diethylamino) -5
-Methyl-7- (N, N-dibenzylamino) fluorane, benzoyl leuco methylene blue, 6'-chloro-
8'-methoxy-benzoindolino-spiropyran, 6 '
-Bromo-3'-methoxy-benzoindolino-spiropyran, 3- (2'-hydroxy-4'-dimethylaminophenyl) -3- (2'-methoxy-5'-chlorophenyl) phthalide, 3- (2 '-Hydroxy-4'-dimethylaminophenyl) -3- (2'-methoxy-5'-nitrophenyl) phthalide, 3- (2'-hydroxy-4'-diethylaminophenyl) -3- (2'-methoxy -5'-
Methylphenyl) phthalide, 3- (2'-methoxy-4 '
-Dimethylaminophenyl) -3- (2'-hydroxy-4'-chloro-5'-methylphenyl) phthalide, 3-
(N-ethyl-N-tetrahydrofurfuryl) amino-
6-methyl-7-anilinofluorane, 3-N-ethyl-N- (2-ethoxypropyl) amino-6-methyl-
7-anilinofluorane, 3-N-methyl-N-isobutyl-6-methyl-7-anilinofluorane 3-morpholino-7- (N-propyl-trifluoromethylanilino) fluorane, 3-pyrrolidino- 7-m-
Trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7- (N-benzyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7-
(Di-p-chlorophenyl) methylaminofluorane, 3
-Diethylamino-5-chloro-7- (α-phenylethylamino) fluorane, 3- (N-ethyl-p-toluidino) -7- (α-phenylethylamino) fluorane, 3-diethylamino-7- (o- Methoxycarbonylphenylamino) fluorane, 3-diethylamino-
5-methyl-7- (α-phenylethylamino) fluorane, 3-diethylamino-7-piperidinofluorane, 2-chloro-3- (N-methyltoluidino) -7-
(Pn-Butylanilino) fluorane, 3- (N-methyl-N-isopropylamino) -6-methyl-7-anilinofluorane, 3-di-n-butylamino-6-methyl-7-anilino Fluoran, 3,6-bis (dimethylamino) fluorene spiro (9,3 ′)-6′-dimethylaminophthalide, 3- (N-benzyl-N-cyclohexylamino) -5,6-benzo-7- α-naphthylamino-4′-bromofluorane, 3-diethylamino-
6-chloro-7-anilinofluorane, 3-diethylamino-6-methyl-7-mesitidino-4 ', 5'-benzofluorane, 3-N-methyl-N-isopropyl-6-
Methyl-7-anilinofluorane, 3-N-ethyl-N
-Isoamyl-6-methyl-7-anilinofluorane,
3-diethylamino-6-methyl-7- (2 ', 4'-dimethylanilino) fluorane and the like.

As the color developer used in the heat-sensitive recording layer of the present invention, various electron-accepting compounds that cause the above leuco dye to develop color upon contact, or an oxidizing agent is used. Such a material is conventionally known, and specific examples thereof include the following.

4,4'-isopropylidenediphenol, 4,4'-isopropylidene bis (o-methylphenol), 4,4'-secondary butylidene bisphenol 4,4'-isopropylidene bis (2-tertiary) Butylphenol), zinc p-nitrobenzoate, 1,3
5-tris (4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid, 2,2
-(3,4'-dihydroxydiphenyl) propane, bis (4-hydroxy-3-methylphenyl) sulfide,
4- {β- (p-methoxyphenoxy) ethoxy} salicylic acid, 1,7-bis (4-hydroxyphenylthio)
-3,5-dioxaheptane, 1,5-bis (4-hydroxyphenylthio) -5-oxapentane, phthalic acid monobenzyl ester monocalcium salt, 4,4'-cyclohexylidene diphenol, 4,4 ' -Isopropylidenebis (2-chlorophenol), 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 4,4'-butylidenebis (6-tert-butyl-2-methyl) phenol, 1, 1,3-Tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-Tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 4,4 ′ -Thiobis (6-tert-butyl-2)
-Methyl) phenol, 4,4'-diphenol sulfone, 4-isopropoxy-4'-hydroxydiphenyl sulfone, 4-benzyloxy-4'-hydroxydiphenyl sulfone, 4,4'-diphenol sulfoxide,
Isopropyl P-hydroxybenzoate, benzyl P-hydroxybenzoate, benzyl protocatechuate, stearyl gallate, lauryl gallate, octyl gallate,
1,3-bis (4-hydroxyphenylthio) -propane, N, N'-diphenylthiourea, N, N'-di (m
-Chlorophenyl) thiourea, salicylanilide, methyl bis- (4-hydroxyphenyl) acetate, bis- (4
-Hydroxyphenyl) benzyl acetate, 1,3-bis (4-hydroxycumyl) benzene, 1,4-bis (4
-Hydroxycumyl) benzene, 2,4'-diphenol sulfone, 2,2'-diallyl-4,4'-diphenol sulfone, 3,4-dihydroxyphenyl-4'-methyldiphenyl sulfone, 1-acetyloxy Zinc-2-naphthoate, zinc 2-acetyloxy-1-naphthoate, zinc 2-acetyloxy-3-naphthoate, α, α
-Bis (4-hydroxyphenyl) -α-methyltoluene, antipyrine complex of zinc thiocyanate, tetrabromobisphenol A, tetrabromobisphenol S,
4,4'-thiobis (2-methylphenol), 4,4 '
-Thiobis (2-chlorophenol) and the like.

In the heat-sensitive recording layer of the present invention, various conventional binders can be appropriately used in order to coat the above-mentioned leuco dye and developer on the intermediate layer. The same examples as those exemplified in the coating of the intermediate layer can be mentioned.

Further, in the heat-sensitive recording layer of the present invention, together with the above-mentioned leuco dye and developer, if necessary, further auxiliary additives commonly used in heat-sensitive recording materials of this kind, such as fillers and heat-fusible components, are used. It is possible to use together a substance and a surfactant. In this case, as the filler, for example,
Calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay,
Inorganic fine powders such as talc and surface-treated calcium and silica, as well as organic fine powders such as urea-formalin resin, styrene / methacrylic acid copolymer, polystyrene resin, etc. Examples of the functional substance include higher fatty acids or esters, amides or metal salts thereof, various waxes, condensates of aromatic carboxylic acids and amines, benzoic acid phenyl esters, higher linear glycols, 3,4- Examples thereof include epoxy-dialkyl hexahydrophthalate, higher ketones, p-benzylbiphenyl, and other heat-fusible organic compounds having a melting point of about 50 to 200 ° C.

In the present invention, a layer containing a filler, a binder, a heat-fusible substance, etc. may be provided as another intermediate layer between the intermediate layer and the heat-sensitive recording layer, if necessary. In this case, specific examples of the filler, the binder and the heat-fusible substance include the same as those exemplified in connection with the heat-sensitive recording layer or the intermediate layer.

Further, in the heat-sensitive recording material of the present invention, a protective layer may be provided on the heat-sensitive recording layer for the purpose of improving matching property of a thermal head or the like and further improving storability of recorded image. Very preferred. In this case, as the resin constituting the protective layer, for example, polyvinyl alcohol, cellulose derivative, starch and its derivative, carboxyl group-modified polyvinyl alcohol, polyacrylic acid and its derivative, styrene / acrylic acid copolymer and its derivative, poly (Meth) acrylamide and derivatives thereof, styrene / acrylic acid / acrylamide copolymer, amino group modified polyvinyl alcohol, epoxy modified polyvinyl alcohol, polyethyleneimine, aqueous polyester, aqueous polyurethane, isobutylene / maleic anhydride copolymer and derivatives thereof Water-soluble resin such as polyester, polyurethane, acrylic ester (co)
Examples thereof include polymers, styrene / acrylic copolymers, epoxy resins, polyvinyl acetate, polyvinylidene chloride, polyvinyl chloride and derivatives thereof, among which water-soluble resins are preferable.

In addition to the above-mentioned resins, the protective layer further contains conventionally used auxiliary additives such as fillers, water-proofing agents, surfactants, heat-fusible substances (or lubricants), and pressure coloring prevention. Agents and the like can be used in combination. In this case, specific examples of the filler and the heat-fusible substance are the same as those exemplified in relation to the heat-sensitive recording layer.

The heat-sensitive recording material of the present invention is produced, for example, by applying the above-mentioned coating liquid for forming each layer on a suitable support such as paper or plastic film and drying. In particular, the heat-sensitive recording material of the present invention is remarkably improved in adhesion with the thermal head by the calendering treatment,
It is very preferable to subject the intermediate layer, heat-sensitive recording layer or protective layer to a calendering treatment. That is, by controlling the smoothness of the surface by controlling the calender pressure on the intermediate layer, the heat-sensitive recording layer or the protective layer, a heat-sensitive recording material having no background fog and higher definition than before can be obtained.

[0027]

EXAMPLES Next, the present invention will be described in more detail by way of examples. The parts and% shown below are based on weight.

Example 1 [Solution A] 3-di-n-butylamino-6-methyl-7-anilinofluorane 20 parts Polyvinyl alcohol 10% aqueous solution 20 parts Water 60 parts [Solution B] 2,4'- Diphenol sulfone 10 parts 2,2′-methylenebis {4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol} (melting point 195 ° C.) 1 part polyvinyl alcohol 10% aqueous solution 26 parts Calcium carbonate 15 parts Water 48 parts A mixture having the above composition was dispersed using a sand mill so that the average particle diameter was 2 μm or less to prepare [solution A] and [solution B]. [Liquid C] Non-expandable plastic fine hollow particles 40 parts (solid content 24%, average particle size 3 μm, hollowness 95%) Styrene / butadiene copolymer latex 10 parts (solid content 47%) water 50 parts From the above composition The resulting mixture is stirred and dispersed with a disper to prepare an intermediate layer forming liquid, which is then put on a commercially available high-quality paper (basis weight 60
(g / m ² ), and then dried to give a weight of 6 g / m ² after drying to obtain an intermediate layer coated paper. Next, the above [A
Liquid] and [B liquid] were mixed and stirred at a weight ratio of 1: 8, coated and dried to 7 g / m ^2, and a thermosensitive recording layer was provided. [Solution D] Polyvinyl alcohol 10% aqueous solution 63 parts Silica 3 parts Zinc stearate 1 part Water 33 parts Further, the above [Solution D] is dried on the thermosensitive coloring layer in a dry weight of 5 parts.
The coating was dried so as to obtain g / m ² to form a protective layer, and then calendered at a pressure of 35 kg / cm ² to obtain a heat-sensitive recording material of the present invention.

Example 2 In the same manner as in Example 1 except that bis (2-methoxy-4-hydroxy-5-benzoylphenyl) methane (melting point 225 ° C.) was used as the ultraviolet absorber in [B liquid]. A heat-sensitive recording material of the present invention was obtained.

Example 3 [Liquid C] In the non-foaming plastic fine hollow particles, solid content 24%, average particle size 8 μm, hollowness 90%
A thermosensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the above particles were used.

Example 4 In the [B liquid], as an ultraviolet absorber, 2- (2-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole (melting point 140
C.) was used to obtain a thermosensitive recording material of the present invention in the same manner as in Example 1.

Example 5 In [B liquid], 1,1-bis- (4
A thermosensitive recording material of the present invention was obtained in the same manner as in Example 1 except that -hydroxyphenyl) -1-phenylethane was used.

Comparative Example 1 A thermosensitive recording material for comparison was obtained in the same manner as in Example 1 except that the ultraviolet absorbent was not used in [B liquid].

Comparative Example 2 In the [B liquid], 2- (2'-
A thermosensitive recording material for comparison was obtained in the same manner except that hydroxy-5′-methylphenyl) benzotriazole (melting point 129 ° C.) was used.

Comparative Example 3 In the [C liquid], the non-foaming plastic fine hollow particles had a solid content of 24%, an average particle diameter of 12 μm, and a hollowness of 90%.
A heat-sensitive recording material for comparison was obtained in the same manner as in Example 1 except that the above particles were used.

Comparative Example 4 Comparative Example 4 was carried out in the same manner as in Example 1 except that as the non-foaming plastic micro hollow particles, particles having a solid content of 24%, an average particle diameter of 1 μm and a hollowness of 80% were used. A heat-sensitive recording material of was obtained.

Comparative Example 5 [Solution B] 4-isopropoxy-
4'-hydroxyphenyl sulfone (melting point 128 ° C)
A thermal recording material for comparison was obtained in the same manner except that was used.

Comparative Example 6 A thermosensitive recording material for comparison was obtained in the same manner as in [B liquid] except that tetrabromobisphenol S (melting point 290 ° C.) was used as a developer.

For each of the heat-sensitive recording materials obtained as described above, the static color development start temperature, heat resistance, dynamic color development sensitivity,
A test for light resistance and water resistance was conducted. The results are shown in Table 1. The test was conducted as follows.

(1) Static color development start temperature 1.0 sec with a thermal gradient tester (manufactured by Toyo Seiki), 2 kg /
Color was developed under the condition of cm ² , and Macbeth densitometer RD-91
The image density was measured at 4 and the temperature at 0.2 was used as the color development start temperature. (2) Heat resistance (background fog) The heat-sensitive recording material was left in an environment of 105 ° C. for 24 hours,
The density of the background portion was measured with a Macbeth densitometer RD-914. (3) Dynamic Color Sensitivity Using a thermal printing experiment device having a thin film head manufactured by Matsushita Electronic Components Co., Ltd., a head power of 0.68 W / dot, a line recording time of 20 msec / line, and a scanning linear density of 8 × 3.
Under the condition of 85 dots / mm ² , the pulse width is 0.2 to 1.
After printing for 2 msec, the printed image density was measured with a Macbeth densitometer RD-914. As the dynamic color development sensitivity value,
The image density is shown with a pulse width of 1.0 msec. (4) Light resistance Time was 1.0 sec and pressure was 2 kg / c in the thermal tilt tester.
Area where color was developed under conditions of m ² and temperature of 180 ° C (image area)
And the background part (background part) was irradiated with xenon light for 15 hours, and the density was measured with a Macbeth densitometer RD-914. A bull filter was used for the background part.

[0041]

[Table 1]

[0042]

From the results shown in Table 1, it can be seen that the heat-sensitive recording material of the present invention is superior in heat resistance, dynamic color development sensitivity, light resistance and the like to the heat-sensitive recording material of the comparative example.

Front Page Continuation (72) Inventor Yasutomo Mori 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd.

Claims (3)

[Claims] 1. An intermediate layer mainly composed of non-expandable plastic fine hollow particles having an average particle size of 2 to 10 μm and a hollowness of 90% or more on a support, a leuco dye and the leuco dye when heated. A static color development starting temperature is 100 to 1 formed by sequentially laminating thermosensitive color developing layers containing a color developing agent as a main component.
A heat-sensitive recording material having a melting point of 135 ° C. or higher, which is contained in a heat-sensitive recording material at 50 ° C. 2. The ultraviolet absorber is 2,2′-methylenebis {4- (1,1,3,3-tetramethylbutyl)-
6- (2H-benzotriazol-2-yl) phenol} and / or bis (2-methoxy-4-hydroxy-
The heat-sensitive recording material according to claim 1, which is 5-benzoylphenyl) methane. 3. The heat-sensitive recording material according to claim 1, wherein the developer is 2,4′-diphenol sulfone.