JP3314287B2 - Thermal recording material - Google Patents

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 having excellent picking resistance and water resistance, which are excellent in dynamic coloring sensitivity and heat resistance of a background portion.

[0002]

2. Description of the Related Art A general heat-sensitive recording material is a colorless or light-colored color former such as leuco dye as a color former on a support such as paper or film, and a phenolic compound (particularly a phenolic compound as a color developer when heated). A thermosensitive coloring layer in which a binder, a filler, a sensitivity enhancer, a lubricant, and other auxiliaries are further provided in a coloring system composed of an acidic substance such as bisphenol A) and an organic acid. No. 4160, JP-B-45-14039, and JP-A-48-27736, and are widely used. This type of heat-sensitive recording sheet obtains a color-formed image by an instantaneous chemical reaction between a color-developing agent and a developer during heating (a thermal printer facsimile with a built-in thermal head is used for heating). Compared to other recording materials, recording can be obtained in a short time with relatively simple equipment without complicated processing such as development and fixing, less noise and environmental pollution, lower cost, etc. Due to its advantages, it is used not only for copying of books and documents, but also for various information such as electronic calculators, facsimile machines, telex, medical measuring machines, etc. and as a recording material for measuring instruments, as well as CAD paper, food POS.
It is also used as a label and industrial label, and is a useful recording material.

On the other hand, the quality required for a heat-sensitive recording material is increasing as well as being used in such a wide field. In particular, the improvement of the color development of the background under high-temperature environments (hereinafter referred to as heat-resistant fog) is focused on industrial labels and the like that are affixed to food labels used for warm storage and the like and mechanical parts used for high-temperature places such as engine rooms. ) Is strongly desired. The heat resistance desired in such an application field is 80 ° C., 2
In many cases, a quality of 4 hours or more is 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.

[0004] Conventionally, in order to improve such heat resistance, means for increasing the static color-forming onset temperature by selecting a developer, a leuco dye and other heat-fusible substances to be used in the thermosensitive coloring layer. However, in such a case, there is a disadvantage that the energy when printing with an actual printer, facsimile or the like becomes high (that is, the dynamic color sensitivity is low). Therefore, as a method for improving heat resistance without lowering dynamic color sensitivity, a heat insulating layer having minute hollows is formed on a support, and a static color development start temperature is set to 90 ° C. or higher (Japanese Patent Application Laid-Open However, there is a demand for further improvement in recent years with respect to high demands on heat resistance and sensitivity.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to balance the opposite properties of heat resistance and sensitivity, water resistance (the layer does not peel off when immersed in water), and picking resistance (adhesive tape or printing. (A layer is not peeled off).

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventors have provided an intermediate layer on a support which has a very high heat insulating property and improves adhesion to a thermal head, and has an appropriate melting point on the intermediate layer. In a heat-sensitive recording material comprising a heat-sensitive coloring layer using a developer, a paint, or the like having the above, the intermediate layer contains a binder having good water resistance and a binder having good heat resistance (background portion) to achieve the above object. And found that the present invention was completed.

That is, according to the present invention, an intermediate layer mainly composed of non-foamable plastic fine hollow particles having an average particle size of 2 to 10 μm and a hollowness of 90% or more, a leuco dye, In a thermosensitive recording material having a static coloring start temperature of 100 to 150 ° C., which is formed by sequentially laminating a thermosensitive coloring layer containing a developer as a main component that causes a leuco dye to develop a color when heated, a styrene / butadiene copolymer is used as an intermediate layer. Isobutylene /
A heat-sensitive recording material containing a maleic anhydride copolymer salt is provided.

The styrene / butadiene copolymer used in the present invention has good heat resistance and picking resistance, and the isobutylene / maleic anhydride copolymer salt has an effect on heat fog. The use ratio of the styrene / butadiene copolymer and the isobutylene / maleic anhydride copolymer salt is 30: 1 to 3: 1.
When the styrene / butadiene copolymer content is high, the heat resistance of the buoy increases, and when the isobutylene / maleic anhydride copolymer salt content is high, the water resistance and picking resistance deteriorate.

[0009] In the present invention, very high heat insulation,
Since the non-foamable plastic micro hollow particles having an average particle size of 2 to 10 μm and a hollow ratio of 90% or more are mainly used as the intermediate layer for improving the adhesion to the thermal head, the heat from the thermal head or the like can be improved. Due to the efficient use of energy, and also from the heat insulating properties of the intermediate layer, the adhesion to the thermal head is improved, thereby improving the dynamic color sensitivity.

The non-expandable plastic hollow microparticles used in the intermediate layer of the present invention are made of a thermoplastic resin as a shell and contain air and other gases inside, and are already in the foamed state. Yes, average particle size is 2
10 μm, preferably 3 to 5 μm is used. If the average particle size is less than 2 μm, there is a problem in production such as difficulty in obtaining an arbitrary degree of hollowness, and it is difficult in terms of cost. Conversely, if the average particle size is larger than 10 μm, Since the smoothness is reduced, the adhesion to a thermal head or the like is reduced, and the effect of improving the sensitivity is small. Further, it is desirable that the particle distribution is such that the particle diameter is within the above range and the distribution peak is uniform.

Further, the microscopic hollow hollow particles used in the present invention have a hollowness of 90% or more, preferably 95% or more. If the degree of hollowness is less than 90%, the heat insulating property is insufficient, so that the thermal 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. Here, the hollowness is a ratio of the outer diameter to the inner diameter of the hollow particles, and is represented by the following equation.

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 polyacryl. Examples include acid esters, polyacrylonitrile, polybutadiene, and copolymer resins thereof. Among these, a copolymer resin mainly containing vinylidene chloride and acrylonitrile is particularly preferable.

In order to provide the intermediate layer on a support, the fine hollow particles are dispersed in water together with a known binder such as a water-soluble polymer or an aqueous polymer emulsion, and the dispersion is applied to the surface of the support. Obtained by drying. In this case, the coating amount of the fine hollow particles 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 fine hollow particles and the binder resin.

In the present invention, as described above, the binder used for forming the intermediate layer is styrene /
The butadiene copolymer and the isobutylene / maleic anhydride copolymer salt are mixed and, if necessary, are appropriately selected from conventionally known water-soluble polymers and / or aqueous polymer emulsions. Specific examples thereof include, as water-soluble polymers, for example, polyvinyl alcohol, starch and derivatives thereof, methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose,
Cellulose derivatives such as ethyl cellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide / acrylate copolymer, acrylamide / acrylate / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, polyacrylamide ,
Examples include sodium alginate, gelatin, casein and the like. As the aqueous polymer emulsion, styrene
Latexes such as / butadiene / acrylic copolymers, and emulsions of vinyl acetate resins, vinyl acetate / acrylic acid copolymers, styrene / acrylate ester copolymers, acrylate ester resins, polyurethane resins, and the like.

In the intermediate layer of the present invention, together with the fine hollow particles and the binder, if necessary, auxiliary additives commonly used in this type of heat-sensitive recording material, for example, fillers, heat-fusible materials , A surfactant and the like can be used in combination. In this case, specific examples of the filler and the heat-fusible substance include various substances described below in relation to the heat-sensitive recording layer component.

Since the surface of the intermediate layer formed on the support as described above has considerable irregularities, the surface may be smoothed by calendering after the formation of the intermediate layer. In order to prevent heat fogging even in a high temperature environment, the thermal recording material should have a static color development onset temperature of 100 to
When the temperature is higher than 150 ° C., heat fogging occurs. When the temperature exceeds 150 ° C., the dynamic color development sensitivity is poor. The term "coloring start temperature" used herein means a heat gradient tester (manufactured by Toyo Seiki Co., Ltd.) for a time of 1.0 sec, a pressure of 2 kg / cm ² , and a heat block brought into contact with the surface of the heat-sensitive recording material.
The temperature at which the image density is measured at D-914 to be 0.2. In order to obtain a heat-sensitive recording material having a static color-forming start temperature of 100 to 150 ° C, those having an appropriate melting point for a developer and a leuco dye contained in the heat-sensitive coloring layer are used.
Those having a temperature of 180 to 240 ° C are preferred. In addition, it is more preferable that an isobutylene / maleic anhydride copolymer is contained in the color-forming layer, because heat fogging is reduced. This is a dye,
It is considered that there is an effect of suppressing the reaction of the color developer at a low temperature.

The leuco dye used in the heat-sensitive recording layer of the present invention is used alone or as a mixture of two or more kinds. As such a leuco dye, those applied to this kind of heat-sensitive material can be arbitrarily applied. For example, leuco compounds of dyes such as triphenylmethane type, fluoran type, phenothiazine type, auramine type, spiropyran type and indolinophthalide type are preferably used. Specific examples of such leuco dyes include, for example, 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-chlorofluoran, 3-dimethylamino-5,7 -Dimethylfluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-7-methylfluoran, 3-
Diethylamino-7,8-benzfluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-
(Np-tolyl-N-ethylamino) -6-methyl-
7-anilinofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 2- {N- (3'-trifluoromethylphenyl) amino} -6-diethylaminofluoran, 2- {3 6-bis (diethylamino)-
Lactam 9- (o-chloroanilino) xanthylbenzoate, 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluoran, 3-diethylamino-7- (o-chloroanilino) fluoran, 3-di- n-butylamino-7- (o-chloroanilino) fluoran, 3-N-methyl-N, n-amylamino-6-
Methyl-7-anilinofluoran, 3-N-methyl-N
-Cyclohexylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3- (N, N-diethylamino) -5
-Methyl-7- (N, N-dibenzylamino) fluoran, benzoylleucomethylene 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-anilinofluoran, 3-N-ethyl-N- (2-ethoxypropyl) amino-6-methyl-
7-anilinofluoran, 3-N-methyl-N-isobutyl-6-methyl-7-anilinofluoran 3-morpholino-7- (N-propyl-trifluoromethylanilino) fluoran, 3-pyrrolidino- 7-m-
Trifluoromethylanilinofluoran, 3-diethylamino-5-chloro-7- (N-benzyl-trifluoromethylanilino) fluoran, 3-pyrrolidino-7-
(Di-p-chlorophenyl) methylaminofluoran, 3
-Diethylamino-5-chloro-7- (α-phenylethylamino) fluoran, 3- (N-ethyl-p-toluidino) -7- (α-phenylethylamino) fluoran, 3-diethylamino-7- (o- Methoxycarbonylphenylamino) fluoran, 3-diethylamino-
5-methyl-7- (α-phenylethylamino) fluoran, 3-diethylamino-7-piperidinofluoran, 2-chloro-3- (N-methyltoluidino) -7-
(Pn-butylanilino) fluoran, 3- (N-methyl-N-isopropylamino) -6-methyl-7-anilinofluoran, 3-di-n-butylamino-6-methyl-7-anilino Fluorane, 3,6-bis (dimethylamino) fluorenespiro (9,3 ')-6'-dimethylaminophthalide, 3- (N-benzyl-N-cyclohexylamino) -5,6-benzo-7- α-naphthylamino-4′-bromofluoran, 3-diethylamino-
6-chloro-7-anilinofluoran, 3-diethylamino-6-methyl-7-mesitidino-4 ′, 5′-benzofluoran, 3-N-methyl-N-isopropyl-6
Methyl-7-anilinofluoran, 3-N-ethyl-N
-Isoamyl-6-methyl-7-anilinofluoran,
3-diethylamino-6-methyl-7- (2 ', 4'-dimethylanilino) fluoran and the like.

As the color developer used in the heat-sensitive recording layer of the present invention, various compounds having an electron-accepting property or a oxidizing agent which develop the color of the leuco dye upon contact are applied. Such materials are conventionally known, and specific examples thereof include the following.

4,4'-isopropylidenediphenol, 4,4'-isopropylidenebis (o-methylphenol), 4,4'-secondarybutylidenebisphenol 4,4'-isopropylidenebis (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, monobenzyl phthalate 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'-diphenolsulfone, 4-isopropoxy-4'-hydroxydiphenylsulfone, 4-benzyloxy-4'-hydroxydiphenylsulfone, 4,4'-diphenolsulfoxide,
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'-diphenolsulfone, 2,2'-diallyl-4,4'-diphenolsulfone, 3,4-dihydroxyphenyl-4'-methyldiphenylsulfone, 1-acetyloxy Zinc-2-naphthoate, zinc 2-acetyloxy-1-naphthoate, zinc 2-acetyloxy-3-naphthoate, α, α
-Bis (4-hydroxyphenyl) -α-methyltoluene, an 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, in order to apply the leuco dye and the developer on the intermediate layer, various conventional binders can be appropriately used. And the same as those exemplified in the application of the intermediate layer.

In the heat-sensitive recording layer of the present invention, the leuco dye and the developer may be used, if necessary, in addition to auxiliary additives commonly used in this type of heat-sensitive recording material, for example, fillers, heat-fusible materials. Substances, surfactants and the like can be used in combination. In this case, as the filler, for example,
Calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay,
In addition to inorganic fine powders such as talc and surface-treated calcium and silica, organic fine powders such as urea-formalin resin, styrene / methacrylic acid copolymer, and polystyrene resin can be used. Examples of the active substance include higher fatty acids or esters, amides or metal salts thereof, various waxes, condensates of aromatic carboxylic acids and amines, phenyl benzoate, higher linear glycols, 3,4- Dialkyl epoxy-hexahydrophthalate, higher ketones, p-benzylbiphenyl, other heat-fusible organic compounds, and the like having a melting point of about 50 to 200 ° C can be mentioned.

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

Further, in the heat-sensitive recording material of the present invention, it is possible to provide a protective layer on the heat-sensitive recording layer for the purpose of improving the matching property of a thermal head or the like and further improving the storage stability of a 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, acrylate (co)
Examples thereof include a polymer, a styrene / acrylic copolymer, an epoxy resin, polyvinyl acetate, polyvinylidene chloride, polyvinyl chloride, and derivatives thereof. Among them, a water-soluble resin is preferable.

In the protective layer, in addition to the above-mentioned resins, 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 include those similar to those exemplified in relation to the thermosensitive 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 a plastic film and drying. In particular, the thermosensitive recording material of the present invention has a remarkable improvement in adhesion with a thermal head by calendering treatment.
It is very preferable to apply a calender treatment to the intermediate layer, the thermosensitive recording layer or the protective layer. That is, by controlling the smoothness of the surface by the magnitude of 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]

Next, the present invention will be described in more detail with reference to examples. The parts and percentages shown below are based on weight.

Example 1 [Solution A] 3-Di-n-butylamino-6-methyl-7-anilinofluoran 20 parts Polyvinyl alcohol 10% aqueous solution 20 parts Water 60 parts [Solution B] 2,4'- Diphenol sulfone 10 parts Polyvinyl alcohol 10% aqueous solution 25 parts Calcium carbonate 15 parts Water 50 parts Mixtures having the above composition were dispersed using a sand mill so that the average particle diameter was 2 μm or less, respectively, and [Solution A] and [B Liquid] was prepared. [Liquid C] Non-foamable plastic fine hollow particles 40 parts (solid content 24%, average particle size 3 μm, hollowness 95%) Styrene / butadiene copolymer latex 20 parts (solid content 47%) isobutylene / maleic anhydride 2.5 parts of ammonium salt of a polymer 37.5 parts of water A mixture having the above composition was stirred and dispersed by a disper to prepare an intermediate layer forming liquid.
g / m ² ), and then dried and applied so as to have a weight of 6 g / m ² to obtain an intermediate layer coated paper. Next, the [A
Liquid] and [Liquid B] were mixed and stirred at a weight ratio of 1: 8, and applied and dried at 7 g / m ² to form a heat-sensitive recording layer. [Solution D] Polyvinyl alcohol 10% aqueous solution 63 parts Polyamide epichlorohydrin (solid content 25%) 10 parts Silica 3 parts Zinc stearate 1 part Water 23 parts Further, the above [Solution D] was dried on the thermosensitive coloring layer with a dry weight of 5 parts.
g / m ² was applied and dried to provide 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 The intermediate layer coated paper obtained in Example 1 was prepared. Furthermore, [B
Solution B], 4 parts of an isobutylene / maleic anhydride copolymer (solid content: 20%) was added to obtain [B 'solution]. Next, the [A
Solution] and [Liquid B '] were mixed and stirred at a weight ratio of 1: 8, and applied and dried at 7 g / m ² to form a thermosensitive coloring layer. Further, [D solution] was provided on the thermosensitive coloring layer in the same manner as in Example 1.

Example 3 In the [liquid C], as non-foamable plastic micro hollow particles, the solid content was 24%, the average particle size was 8 μm, and the hollowness was 90%.
The heat-sensitive recording material of the present invention was obtained in the same manner as in Example 1 except that the particles of the above were used.

Comparative Example 1 [E liquid] 40 parts of non-foamable plastic fine hollow particles (solid content: 24%, average particle size: 3 μm, hollowness: 95%) Styrene / butadiene copolymer latex: 20 parts (solid content: 47%) A thermosensitive recording material for comparison was obtained in the same manner as in Example 1 except that 40 parts of water was replaced with [E solution].

Comparative Example 2 [F liquid] 40 parts of non-foamable plastic fine hollow particles (solid content: 24%, average particle size: 3 μm, hollowness: 95%) Acrylic ester copolymer emulsion: 20 parts (solid content: 47%) A thermosensitive recording material for comparison was obtained in the same manner as in Example 1 except that 2.5 parts of ammonium salt of an isobutylene / maleic anhydride copolymer was used, and 37.5 parts of water was used instead of [Solution C]. .

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

Comparative Example 4 A comparative sample was prepared in the same manner as in Example 1 except that particles having a solid content of 24%, an average particle size of 1 μm, and a hollowness of 80% were used as the non-expandable plastic micro hollow particles in [C solution]. Was obtained.

Comparative Example 5 In [solution B], 4-isopropoxy-
A comparative thermosensitive recording material was obtained in the same manner except that 4'-hydroxyphenylsulfone was used.

Comparative Example 6 A heat-sensitive recording material for comparison was obtained in the same manner as in [Liquid B] except that tetrabromobisphenol S was used as a color developer.

With respect to each of the heat-sensitive recording materials obtained as described above, the static color-forming start temperature, heat resistance, dynamic color-forming sensitivity,
A test for picking resistance and water resistance was performed. Table 1 shows the results. The test was performed as follows.

(1) Static color development start temperature: 1.0 sec, 2 kg / sec. With a thermal gradient tester (manufactured by Toyo Seiki)
The color was developed under the condition of cm ² , and Macbeth densitometer RD-91 was used.
The image density was measured at 4, and the temperature at 0.2 was taken 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 was measured with a Macbeth densitometer RD-914. (3) Dynamic Color Sensitivity A thermal printing test apparatus 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 line density of 8 × 3.
Under the condition of 85 dots / mm ² , the pulse width is 0.2 to 1.
Printing was performed at 2 msec, and the print image density was measured with a Macbeth densitometer RD-914. As the dynamic color sensitivity value,
The image density is shown at a pulse width of 1.0 msec. (4) Picking resistance IGI picking test Using an IGI printing machine, a standard ink (standard tack ink 1) was used.
0, 15, 20) (made by Toyo Ink Co., Ltd.). ○: No peeling at all △: Partial peeling ×: Full peeling (5) Water resistance Immerse in water for 15 hours, take out, rub strongly with fingers 5 times,
Observe the peeling condition.

[0039]

[Table 1]

[0040]

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

Continuation of front page (72) Inventor Yasutoshi Mori 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP-A-5-270132 (JP, A) JP-A-5-270 169818 (JP, A) JP-A-5-139035 (JP, A) JP-A-3-173680 (JP, A) JP-A-6-305256 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/28-5/34

Claims (3)

(57) [Claims] 1. An intermediate layer mainly composed of non-foamable 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 method of heating the leuco dye. A static coloring start temperature of 100 to 1 which is obtained by sequentially laminating thermosensitive coloring layers mainly containing a color developing agent.
In a thermosensitive recording material at 50 ° C., styrene /
A heat-sensitive recording material comprising a butadiene copolymer and an isobutylene / maleic anhydride copolymer salt. 2. The heat-sensitive recording material according to claim 1, wherein the color-forming layer contains an isobutylene / maleic anhydride copolymer . 3. The heat-sensitive material according to claim 1, wherein the ratio of the styrene / butadiene copolymer and the isobutylene / maleic anhydride copolymer salt contained in the intermediate layer is 30: 1 to 3: 1. Recording material.