JP2672150B2 - Thermal recording material - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a heat-sensitive recording material, and more specifically, a color-forming layer containing an electron-donating dye precursor and an electron-accepting compound is provided on a support. Thermal recording material.

(Prior Art) Many methods of thermal recording have been known for a long time. For example, recording materials using an electron-donating dye precursor and an electron-accepting compound are disclosed in JP-B-45-14039 and JP-B-4.
No. 3-4160 and the like. In recent years, much research has been conducted on increasing the sensitivity of heat-sensitive recording materials in increasing the speed and energy consumption of heat-sensitive recording systems. As a method for further improving the recording sensitivity, as disclosed in JP-A-53-48751, at least one of an electron-donating dye precursor and an electron-accepting compound is mixed with a low-melting heat-fusible substance. A method of fusion integration has been proposed. However, by mixing and fusing an electron-donating dye precursor and a low-melting heat-fusible substance, the recording sensitivity is increased, but the whiteness of the recording material is significantly reduced, and fog occurs depending on the storage condition. There is a problem.

(Object of the Invention) An object of the present invention is to provide a heat-sensitive recording material having high sensitivity, high whiteness, and less fog.

(Structure of the Invention) An object of the present invention is to provide an electron-donating dye precursor (hereinafter, referred to as a color former) and an electron-accepting compound (hereinafter, referred to as a color developer) that is contacted with the electron-donating dye precursor to develop a color. In the color-forming layer, containing 2-anilino-3-methyl-6-dibutylaminofluorane as an electron-donating dye precursor, and
It was achieved by a heat-sensitive recording material characterized by containing anilino-3-methyl-6-dibutylaminofluorane heat-melted with β-naphthylbenzyl ether as a sensitizer.

The recording sensitivity is increased by mixing and fusing the color former and the sensitizer, but there is a problem in that the whiteness of the recording material is remarkably reduced and fog is generated depending on the storage state. As a result of diligent study on this problem, it was found that the whiteness of the recording material is remarkably lowered by mixing and fusing the colorant with the sensitizer, because the colorant tends to be in an amorphous state. However, it has been discovered that the 2-anilino-3-methyl-6-dibutylaminofluorane used in the present invention is easily crystallized even if it is fused and integrated with β-naphthylbenzyl ether as a sensitizer. Therefore, a heat-sensitive recording material containing 2-anilino-3-methyl-6-dibutylaminofluorane heat-melted with β-naphthylbenzyl ether as a sensitizer has high sensitivity and is white. It was possible to achieve this object by finding that the degree of occurrence is high and no fog occurs, and the present invention has been accomplished.

The method of heat-melting 2-anilino-3-methyl-6-dibutylaminofluorane with β-naphthylbenzyl ether as a sensitizer is not particularly limited, but is disclosed, for example, in JP-A-53-48751. There is a method.

In order to obtain the effects of the present invention, 2-anilino-3-methyl-6-dibutylaminofluorane must account for 50% by weight or more of the total amount of the color former used. Under the conditions described above, other color formers can be used in combination.

Examples of color formers include triarylmethane compounds, diphenylmethane compounds, xanthene compounds, thiazine compounds, spiropyran compounds, and the like. Specific examples include those described in JP-A-55-227253. If a part of these is shown, as a triarylmethane compound, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide,
3,3-bis- (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3- (1,3
-Dimethylindol-3-yl) phthalide, 3- (p
-Dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, and the like, and examples of diphenylmethane compounds include 4,4'-bis-dimethylaminobenzhydrin benzyl ether and N-halophenyl-leuco. There are auramine, N-2,4,5-trichlorophenyl leuco auramine, and the like, and as the xanthene-based compound,
Rhodamine-B-anilinolactam, Rhodamine- (p
-Nitrino) lactam, 2- (dibenzylamino) fluorane, 2-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6-N-ethyl-N-isoamylaminofluorane, 2 -Anilino-3-methyl-6-N-methyl-N-cyclohexylaminofluorane, 2-anilino-3-chloro-6-diethylaminofluorane, 2-anilino-3-methyl-6
-N-ethyl-N-isobutylaminofluorane, 2-
Anilino-6-dibutylaminofluorane, 2-anilino-3-methyl-6-N-methyl-N-tetrahydrofurfurylmethylaminofluorane, 2-anilino-3-
Methyl-6-piperidinoaminofluorane, 2- (o-
Chloroanilino) -6-diethylaminofluorane, 2
-(3,4-Dichloroanilino) -6-diethylaminofluorane, 2-anilino-3-methyl-6-N-ethyl-Nn-hexylaminofluorane, 2-anilino-
3-Methyl-6-N-ethyl-N-γ-ethoxypropylaminofluorane, 2-anilino-3-methyl-6-
N-methyl-N-γ-ethoxypropylaminofluorane, 2-anilino-3-methyl-6-N-ethyl-N-
γ-methoxypropylaminofluorane, 2-anilino-3-methyl-6-dipentylaminofluorane, etc., and thiazine-based compounds include benzoylleucone methylene blue, p-nitrobenzyl leucomethylene blue, etc. The compounds include 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran 3,3'-dichloro-spiro-dinaphthopyran, 3
-Benzylspiro-dinaphthopyran, 3-methyl-naphtho- (3-methoxy-benzo) -spiropyran, 3-pyropyr-spiro-dibenzopyran and the like.

Examples of the sensitizer used in the present invention include benzyl p-benzyloxybenzoate, β-naphthylbenzyl ether, stearamide, stearyl urea, p-benzylbiphenyl, di (2-methylphenoxy) ethane, di ( 2-methoxyphenoxy) ethane, β-naphthol-
(P-Methylbenzyl) ether, α-naphthylbenzyl ether, 1,4-butanediol-p-methylphenyl ether, 1,4-butanediol-p-isopropylphenyl ether, 1,4-butanediol-p-tert -Octyl phenyl ether, 1-phenoxy-2- (4-
Ethylphenoxy) ethane, 1-phenoxy-2- (4
-Chlorophenoxy) ethane, 1,4-butanediol phenyl ether, diethylene glycol-bis (4-methoxyphenyl) ether, 4'-methoxyphenyl-
4-methylbenzyl ether, 4'-methylphenyl-
4-methoxybenzyl ether, 4'-methoxyphenyl-4-chlorobenzyl ether, 4'-ethoxyphenyl-4-chlorobenzyl ether, 4'-chlorophenyl-4-methoxybenzyl ether, di (4-methoxyphenoxy) ethane, 1,3-di (4-methoxyphenoxy) propane, 1,2-bis- (4-methoxyphenoxy) propane, 1,2-bis- (4-ethoxyphenoxy)
Propane, 1- (4-methoxyphenoxy) -2- (4-
Ethoxyphenoxy) propane, 1- (4-ethoxyphenoxy) -2- (4-methoxyphenoxy) propane,
1,2-bis- (2-methoxyphenoxy) propane, 1-
(4-Methoxyphenoxy) -2- (2-methoxyphenoxy) propane, 1- (4-methoxyphenoxy) -2
-Phenoxypropane, etc. The sensitizers may be used alone or as a mixture, and in order to obtain sufficient thermal response, it is preferable to use 10 to 200% by weight, more preferably 20 to 150% by weight, based on the color developer. %. Further, it may be added in addition to the sensitizer to be mixed with the color former.

Next, a method for producing a typical thermosensitive coloring layer of the present invention will be described.

a color former mixed with β-naphthylbenzyl ether,
The developer and the sensitizer are generally dispersed together with a water-soluble polymer aqueous solution such as polyvinyl alcohol in a ball mill, a sand mill or the like to a size of several microns or less.

These dispersions are mixed after dispersion and, if necessary, a pigment,
Surfactant, binder, metal soap, wax, antioxidant, ultraviolet absorber, etc. are added to form a heat-sensitive coating liquid.

The resulting heat-sensitive coating liquid is applied to high-quality paper, high-quality paper having an undercoat layer, synthetic paper, plastics film, etc. and dried, and then imparted with smoothness by a calendering process to obtain a desired heat-sensitive recording material. . Further, a protective layer as described in JP-A-60-255478 may be provided.

Further, if necessary, a back coat layer may be provided on the surface of the support of the thermosensitive recording material opposite to the thermosensitive recording layer. As the back coat layer, any of those known as a back coat layer of a thermosensitive recording material can be used.

As the color developer used in the present invention, a phenolic compound or a salicylic acid derivative and a polyvalent metal salt thereof are preferable. Some examples of these are 2.2'-bis (4-hydroxyphenyl) propane, 4-t-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, 1,1'-bisphenol as the phenolic compound. (3-chloro-4-hydroxyphenyl) cyclohexane, 1,1'-bis (4-hydroxyphenyl) cyclohexane, 1.1'-bis (3-chloro-4-hydroxyphenyl) -2-ethylbutane, 4,4'- sec-isooctylidene diphenol, 4, -sec-butylidene diphenol, 4-tert-octylphenol, 4-p-methylphenylphenol 4,4'-methylcyclohexylidenephenol, 4,4'-isopentylidenephenol , P-
Benzyl hydroxybenzoate and the like. As the salicylic acid derivative, 4-pentadecyl salicylic acid, 3,5-di (α
-Methylbenzyl) salicylic acid, 3,5-di (ter-octyl) salicylic acid, 5-octadecylsalicylic acid, 5-α
-(P-α-methylbenzylphenyl) ethylsalicylic acid, 3-α-methylbenzyl-5-ter-octylsalicylic acid, 5-tetradecylsalicylic acid, 4-hexyloxysalicylic acid, 4-cyclohexyloxysalicylic acid, 4-decyloxysalicylic acid , 4-dodecyloxysalicylic acid, 4-pentadecyloxysalicylic acid, 4-
Octadecyloxysalicylic acid, etc., and zinc thereof,
There are aluminum, calcium, copper and lead salts. These developers are preferably used in an amount of 50 to 800% by weight of the color former, more preferably 100 to 500% by weight. If the content is less than 50% by weight, the coloring is not sufficient, and if it is added more than 800% by weight, no further effect can be expected, which is not preferable.

As the binder used in the present invention, polyvinyl alcohol (including modified polyvinyl alcohol such as carboxy-modified, itaconic acid-modified, maleic acid-modified, and silica-modified), methyl cellulose, carboxymethyl cellulose, starches (including modified starch), gelatin, Examples thereof include gum arabic, casein, hydrolyzate of styrene-maleic anhydride copolymer, polyacrylamide, and saponified product of vinyl acetate-polyacrylic acid copolymer. These binders are used not only at the time of dispersion but also for the purpose of improving the coating film strength. For this purpose, a styrene-butadiene copolymer, a vinyl acetate copolymer, an acrylonitrile, a butadiene copolymer are used. , Methyl acrylate
A latex binder of a synthetic polymer such as a butadiene copolymer or polyvinylidene chloride can also be used together. If necessary, a crosslinking agent for an appropriate binder may be added according to the type of the binder.

As the pigment, calcium carbonate, barium sulfate, lithopone, wax, kaolin, silica, amorphous silica and the like are used.

As the metal soap, higher fatty acid metal salts are used, such as zinc stearate, calcium stearate, and aluminum stearate. As wax,
Paraffin wax, microcrystalline wax,
Carnauba wax, methylol stearoamide, polyethylene wax, polystyrene wax, fatty acid amide wax and the like are used alone or in combination.

Further, a surfactant, an antistatic agent, an ultraviolet absorber, an antioxidant, an antifoaming agent, a conductive agent, a fluorescent dye, a coloring dye, and the like may be added as necessary.

Further, an anti-decoloring agent may be added to the heat-sensitive color developing layer in order to prevent decoloration of the image-printed portion and to solidify the generated image. Phenol compounds, particularly hindered phenol compounds, are effective as decoloring inhibitors. The amount of phenolic compound used is 1 to 20 relative to the electron-accepting compound.
It is preferable to use 0% by weight, more preferably 5%.
~ 50% by weight.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples.

(Example-1) 20 g of 2-anilino-3-methyl-6-dibutylaminofluorane and 40 g of β-naphthylbenzyl ether were added to 20 g.
Heat to 0 ° C to mix. After cooling and solidifying this mixed melt, polyvinyl alcohol (Kuraray Co .; PVA-105) 5
% Aqueous solution (300 g) for 24 hours to disperse in a ball mill to obtain a dispersion having an average particle size of 1.0 μm. Bisphenol A 40g
Polyvinyl alcohol (Kuraray; PVA-105) 5%
It was dispersed in a ball mill together with 200 g of the aqueous solution for 24 hours to obtain a dispersion having an average particle size of 1.0 μm. 80 g of calcium carbonate (manufactured by Shiraishi Kogyo; Univer 70) 0.5 g of sodium hexametaphosphate
% Aqueous solution (160 g) to obtain a pigment dispersion.

The dispersion obtained as described above was mixed, and further, 50 g of 21% zinc stearate emulsion was added to obtain a coating solution for thermal paper, and a dry coating amount of 5 g / m ^{2 on} a high-quality paper of basis weight 50 g / m ^2. It was coated with a wire bar so as to have m ² and dried in an oven at 50 ° C. to obtain a heat-sensitive recording material of the present invention.

Comparative Example-1 In Example-1, 2-anilino-3-methyl-6-
A thermosensitive recording material was obtained in the same manner as in Example 1 except that 20 g of 2-anilino-3-methyl-6-diethylaminofluorane was used in place of 20 g of dibutylaminofluorane.

(Comparative Example-2) In Example-1, 2-anilino-3-methyl-6-
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 20 g of 2-anilino-3-methyl-6-N-ethyl-N-isoamylaminofluorane was used instead of 20 g of dibutylaminofluorane.

(Comparative Example-3) In Example-1, 2-anilino-3-methyl-6-
A thermosensitive recording material was obtained in the same manner as in Example 1 except that 20 g of 2-anilino-3-methyl-6-N-methyl-N-cyclohexylaminofluorane was used instead of 20 g of dibutylaminofluorane.

(Comparative Example-4) 20 g of 2-anilino-3-methyl-6-dibutylaminofluorane was mixed with polyvinyl alcohol (Kuraray; PVA-1).
05) Dispersed with 100 g of 5% aqueous solution for 24 hours in a ball mill to obtain a dispersion having an average particle size of 1.0 μm. Further, 40 g of bisphenol A and 40 g of β-naphthylbenzyl ether were dispersed in a ball mill for 24 hours together with 400 g of a 5% aqueous solution of polyvinyl alcohol (Kuraray Co .; PVA-105) to obtain an average particle size of 1.
A 0 μm dispersion was obtained. Calcium carbonate (manufactured by Shiraishi Kogyo;
80 g of Univer 70) was dispersed with 160 g of a 0.5% aqueous solution of sodium hexametaphosphate in a homogenizer to obtain a pigment dispersion.

The dispersion obtained as described above was mixed, and further, 50 g of 21% zinc stearate emulsion was added to obtain a coating solution for thermal paper, and a dry coating amount of 5 g / m ^{2 on} a high-quality paper of basis weight 50 g / m ^2. It was coated with a wire bar so as to be m ² and dried in an oven at 50 ° C. to obtain a heat-sensitive recording material.

The heat-sensitive recording paper obtained as described above is surface-treated with a low-pressure calender, and a thermal head (KLT-216-8MPD1) manufactured by Kyocera Corporation and a heat-sensitive paper having a pressure roll of 100 kg / cm ² immediately before the head. Head voltage 24
While using a pressure roll under the conditions of V and pulse cycle of 10 ms, printing was performed with a pulse width of 0.6 ms, and the print density and the density of the white background were measured with a Macbeth reflection densitometer RD-918.

The heat resistance was measured by using a Macbeth reflection densitometer RD-918 to measure the density of a white background portion when stored in an environment of 60 ° C. and 30 RH for 24 hours.

 The results are shown in Table 1.

As shown in Table-1, the thermal recording material according to the present invention is
It can be seen that the heat-sensitive recording material exhibits good print density even at low energy, has little fog, and has good heat resistance.

Claims (1)

(57) [Claims] 1. A heat-sensitive recording material containing, as a main component, an electron-donating dye precursor and an electron-accepting compound that is brought into contact with the electron-donating dye precursor to develop a color. 2-anilino-3-methyl-6 as
-Dibutylaminofluorane and 2-anilino-3-methyl-6-dibutylaminofluorane
A heat-sensitive recording material containing a material which is heat-melted with naphthylbenzyl ether.