JPH06255243A - Heat sensitive recording material - Google Patents

Abstract

PURPOSE:To provide a heat sensitive recording material which is superior in heat matching properties such as adhesion or sticking of residues, and imparted with favorable color development sensitivity and writing properties with a pencil. CONSTITUTION:In heat sensitive recording material comprised by applying a heat sensitive recording layer containing a dye precursor, developer and a pigment, the pigment is silicon dioxide having a specific surface area of at least 180m<2>/g, and an oil absorbing quantity of at least 50ml/100g.

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 head matching properties such as sticking of dust to a thermal head and sticking, and good color development sensitivity and pencil writing property. It concerns recording materials.

[0002]

2. Description of the Related Art A heat-sensitive recording material forms a color image by simply heating it, and the recording apparatus can be made relatively simple and compact. Therefore, it is easy to handle and inexpensive to maintain. Although it is widely used as various information recording materials because it has certain advantages, it still leaves much room for improvement as a heat-sensitive recording material that requires high-speed printing such as a facsimile.

In order to enable high-speed recording using a heat-sensitive recording material, it is necessary to enhance the thermal response of the color forming reaction, that is, increase the color forming sensitivity. Increasing the content ratio of the coloring main component by decreasing the addition amount of the pigment or binder in the thermosensitive coloring layer or adding a heat-fusible component is also effective for improving the coloring sensitivity, but in this case, Is the
This causes a problem of sticking of mull head residue or sticking (hereinafter referred to as head matching property). In order to improve the head matching property, it is necessary to prevent the color-forming component from being separated from the thermosensitive color-forming layer during the color-forming reaction by adding a pigment or increasing the amount of the binder.
As described above, the increase in the amount of the pigment or the binder has an inhibitory effect on the color forming reaction, and thus the color forming sensitivity is lowered.

Therefore, in order to improve the head matching property without deteriorating the color developing sensitivity, a pigment or a binder which exerts a sufficient effect by adding a small amount thereof.
Must be selected and used. Heretofore, a method of improving head matching property by using a pigment has been reported. For example, as described in JP-A-61-118287, a specific surface area of 150 m ² / g or less and an oil absorption amount of 100 ml / 100 g. When the above-mentioned silicon dioxide is used, the color development sensitivity and the head matching property can be improved, but on the other hand, it is difficult to say that satisfactory characteristics can be obtained with respect to the writability with a pencil or the like.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat-sensitive recording material having improved head matching properties such as dust adhesion and sticking, high color development sensitivity, and good pencil writability.

[0006]

As a result of intensive studies, the inventors of the present invention have found that as a pigment in a thermosensitive coloring layer, 180 m ² / g
By using silicon dioxide having the above specific surface area and an oil absorption of 50 ml / 100 g or more, a heat-sensitive recording material having excellent head matching properties, good color-developing sensitivity, and pencil writability could be obtained.

As for the pigment, as a result of studying various compositions, it was found that good coloring sensitivity can be obtained by using silicon dioxide. This is believed to be due to the low refractive index of silicon dioxide. Pigment having a high refractive index such as calcium carbonate or magnesium carbonate deteriorates the color development sensitivity. Further, it has been found that silicon dioxide having a specific surface area and oil absorption in the above-mentioned specific region is effective for satisfying the head matching property and the pencil writing property. When the specific surface area is less than 180 m ² / g, the pencil writability deteriorates, but when it is 180 m ² / g or more, good pencil writability is obtained.

When the oil absorption is less than 50 ml / 100 g, the effect of improving the head matching property is small,
When the oil absorption amount is 50 ml / 100 g or more, it is very effective for improving the head matching property. The average particle size of the pigment is not particularly limited, but is 0.5 μm.
It is preferably m or more, and more preferably 1.0 μm or more. However, if the average particle size exceeds 10 μm, color development may be hindered, which is not preferable.

The specific surface area referred to here is based on the BET method, and the oil absorption amount is based on JIS-5101.

The silicon dioxide used in the present invention can be used in a mixture with a generally used pigment, if necessary. As the pigment in this case, conventionally known pigments,
For example, calcium carbonate, titanium oxide, aluminum hydroxide, clay, talc and the like can be mentioned.

The binder for the thermosensitive color developing layer used in the present invention may be any binder that has been conventionally used in general, and will be specifically mentioned below, but the binder is not limited thereto. For example, as the water-soluble polymer compound, alginate, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, carboxy modified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, sulfonated modified polyvinyl alcohol, gelatin, casein, sodium polyacrylate. , Polyacrylamide, acrylamide / acrylic acid ester copolymer, acrylamide / acrylic acid ester / methacrylic acid terpolymer, and the like, and these can be used alone or in combination of two or more kinds. In addition, film-forming polymers such as acrylic latex, vinyl acrylic resin, vinyl acetate / ethylene copolymer, silicon acrylate compound, styrene butadiene latex, casein, gum arabic, oxidized starch, etherified starch, cationized starch And so on.

The dye precursor used in the present invention includes:
There is no particular limitation as long as it is generally used for pressure-sensitive recording materials and heat-sensitive recording materials. Specifically, the following can be illustrated. These can be used alone or as a mixture of two or more. (1) Triarylmethane compound 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) phthalide, 3- ( p-dimethylaminophenyl) -3-
(1,2-dimethylindol-3-yl) phthalide,
3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-phenylindole-
3-yl) phthalide, 3,3-bis (1,2-dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindole-3-)
Yl) -6-Dimethylaminophthalide, 3,3-bis (9-ethylcarbazol-3-yl) -5-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -5 -Dimethylaminophthalide, 3-
p-dimethylaminophenyl-3- (1-methylpyrrol-2-yl) -6-dimethylaminophthalide and the like.

(2) Diphenylmethane compounds 4,4'-bis-dimethylaminophenylbenzhydrylbenzyl ether, N-halophenylleucoauramine, N-2,4,5-trichlorophenylleucoauramine and the like.

(3) Xanthene compound Rhodamine B anilinolactam, Rhodamine B p-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-octylaminofluorane, 3- Diethylamino-7-phenylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-7- (3,4-dichloroanilino) fluorane, 3 -Diethylamino-7
-(2-chloroanilino) fluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3- (N
-Ethyl-N-tolyl) amino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-tolyl) amino-6- Methyl-7-phenethylfluorane, 3-diethylamino-7- (4-nitro) anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3- (N-methyl-N-propyl) ) Amino-
6-Methyl-7-anilinofluorane, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane, 3- (N-methyl-N-cyclohexyl) amino-6- Methyl-7-anilinofluorane, 3
-(N-ethyl-N-tetrahydrofuryl) amino-6
-Methyl-7-anilinofluorane and the like.

(4) Thiazine-based compounds Benzoyl leuco methylene blue, p-nitrobenzoyl leuco methylene blue and the like.

(5) Spiro compound 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3'-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho- (3 -Methoxybenzo) spiropyran, 3-propylspirobenzopyran and the like.

As the color developer used in the present invention, an electron-accepting substance generally used in a heat-sensitive recording material is used, and particularly, a phenol derivative, an aromatic carboxylic acid derivative or a metal compound thereof, N, N. A'-diarylthiourea derivative or the like is used. Of these, particularly preferred are phenol derivatives, and specific examples include the following. 1,1-bis (p-hydroxyphenyl) propane, 2,2-bis (p-hydroxyphenyl) propane, 2,2-bis (p-hydroxyphenyl) butane,
2,2-bis (p-hydroxyphenyl) hexane, bisphenol sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4'-
Isopropyloxydiphenyl sulfone, 3,4-dihydroxy-4′-methyldiphenyl sulfone, diphenol ether, benzyl p-hydroxybenzoate,
Propyl p-hydroxybenzoate, butyl p-hydroxybenzoate and the like.

In order to further improve the sensitivity, as a sensitizer, waxes such as N-hydroxymethylstearic acid amide, stearic acid amide and palmitic acid amide, naphthol derivatives such as 2-benzyloxynaphthalene, p- Biphenyl derivatives such as benzylbiphenyl and 4-allyloxybiphenyl, 1,2-bis (3-methylphenoxy) ethane, 2,2′-bis (4-methoxyphenoxy) diethyl ether, bis (4-methoxyphenyl) ether, etc. The above-mentioned polyether compound, carbonic acid such as diphenyl carbonate, dibenzyl oxalate, di (p-chlorobenzyl) oxalate, or an oxalic acid diester derivative can be added.

Paper is mainly used as a support for the heat-sensitive recording material according to the present invention. In addition to paper, various non-woven fabrics, synthetic resin films, laminates, synthetic papers,
A metal foil or the like, or a composite sheet in which these are combined can be arbitrarily used according to the purpose.

In addition, for the purpose of preventing head wear and sticking, higher fatty acid metal salts such as zinc stearate and calcium stearate, waxes such as paraffin, oxidized paraffin, polyethylene, oxidized polyethylene, stearic acid amide and castor wax are used. In addition, a dispersant such as sodium dioctylsulfosuccinate, an ultraviolet absorber such as a benzophenone type or a benzotriazole type, and a surfactant or a fluorescent dye are added as necessary.

In order to obtain the heat-sensitive recording material of the present invention, a commonly known method can be used. That is, a leuco dye, a color developer, a binder, and other additives alone or in a mixture other than the leuco dye, a protective colloid substance such as polyvinyl alcohol, a surfactant, etc. are added, and a ball mill or a sand mill. A thermosensitive color developing layer coating solution is prepared according to the formulation after dispersion with a disperser such as a blender, coated on a support, dried and calendered to obtain the thermosensitive recording material of the present invention.

[0022]

The heat-sensitive recording material of the present invention uses silicon dioxide having a specific surface area of 180 m ² / g or more and an oil absorption of 50 ml / 100 g or more as a pigment in the heat-sensitive color forming layer, and has a head matching property. It is a heat-sensitive recording material having excellent color development sensitivity and pencil writability.

[0023]

EXAMPLES Next, the present invention will be described in more detail by way of examples. All parts shown below are based on weight.
Using pigments A to K shown in Table 1, a mixture of the components shown below was dispersed in a homomixer for 10 minutes to prepare dispersion A.
I got ~ K.

[0024]

[Table 1]

[Preparation of A to K Pigment Dispersions] Pigment 30 parts 10% polyvinyl alcohol aqueous solution 5 parts water 65 parts Further, a mixture of the components shown below was mixed with a paint conditioner (manufactured by Red Devil Co.). ) For 10 hours,
Dispersions L and M of the dye and developer were obtained.

[Preparation of Solution L] 3-Dibutylamino-6-methyl-7-anilinofluorane 30 parts 10% polyvinyl alcohol aqueous solution 5 parts water 65 parts

[Preparation of Solution M] Bisphenol A 40 parts 2-Benzyloxynaphthalene 50 parts 10% Polyvinyl alcohol aqueous solution 10 parts Water 135 parts

Using these dispersions, a heat-sensitive recording layer coating liquid shown in Table 2 was prepared, and smeared on a base paper having a basis weight of 50 g / m ² to a solid content of 3.0 g / m ² and dried. Then, calendering was performed so that the Beck's smoothness was 500 seconds, to prepare the heat-sensitive recording materials of Examples 1 to 3 and Comparative Examples 1 to 8 of the present invention.

The thermal recording materials were evaluated by the following methods. [Coloring sensitivity] Using a thermal printing tester (made by Matsushita Electronics Co., Ltd.) having a thin film head, head power 0.45 W / do
Printing was performed for 200 lines with a pulse width of 1.2 ms under the condition of t, 1 line recording time of 20 ms / line, and the color density at that time was measured by a Macbeth densitometer. [Printed residue] Panafax UF-22 (manufactured by Matsushita Electronic Parts Co., Ltd.) was used for continuous printing for 30 m, and then the amount of residue attached to the thermal head was visually ranked relatively. [Pencil Writing Property] The ease of writing with pencils of B and HB was ranked. In the ranking, ∘ was very excellent, Δ was a level with no practical problem, and x was a level with practical problem.

As can be seen from the results shown in Table 2, the heat-sensitive recording material of the present invention was excellent in head matching property, and had good color developing sensitivity and pencil writing property.

[0031]

[Table 2]

[0032]

INDUSTRIAL APPLICABILITY The heat-sensitive recording material of the present invention uses, as a pigment in the heat-sensitive recording layer, silicon dioxide having a specific specific surface area and an oil absorption amount, so that head matching such as sticking of dust to a thermal head or sticking can be achieved. It is possible to obtain excellent coloring properties, good color development sensitivity and good pencil writability.

Claims (1)

[Claims] 1. A heat-sensitive recording material comprising a heat-sensitive recording layer containing a color developer and a pigment which react with a normally colorless or light-colored dye precursor upon heating to develop the dye precursor. A heat-sensitive recording material, wherein the pigment in the recording layer is silicon dioxide having a specific surface area of 180 m ² / g or more and an oil absorption of 50 ml / 100 g or more.