JP2912626B2 - Thermal recording medium - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a thermosensitive recording medium, and more particularly to a thermosensitive recording medium in which the whiteness and the recording density are extremely small even when stored under high-temperature conditions.

"Prior art" A heat-sensitive recording material using a colorless or pale-colored basic dye and a colorant to form a recorded image by contacting both color-forming substances by heat is well known. .

Such a thermosensitive recording medium is relatively inexpensive, and is used in a wide range of fields because the recording apparatus is compact and maintenance-free. May be used in an environment.

However, thermosensitive recording media, especially high-sensitivity thermosensitive recording media,
When stored in a high-temperature environment, a partial color-forming reaction occurs, and the whiteness of the recording layer is remarkably reduced so that the recording layer cannot be used.

Further, the thermosensitive recording medium generally has a disadvantage that the storage stability of the recorded image is not sufficient, and the recorded image disappears in a relatively short time especially under a high temperature condition.

For the purpose of improving the storage stability of a recorded image, methods using various storage stability improvers have been proposed. Even if effective, new results, such as a decrease in whiteness, accompany, and thus satisfactory results have not always been obtained.

For this reason, there is a strong demand for a thermosensitive recording medium that does not reduce the whiteness of the recording layer even when stored under high-temperature conditions and that can stably maintain a recorded image even under high-temperature conditions.

"Problems to be Solved by the Invention" In view of such a current situation, the present inventors have found that the content of the recording layer in the recording layer in order to obtain a thermosensitive recording material that does not cause a decrease in whiteness or recording density even when exposed to high temperature conditions Extensive studies were conducted on combinations of basic dyes and color formers. as a result,
By using a specific basic dye and a coloring agent, it has been found that the preservability of a recorded image can be remarkably improved without a new disadvantage such as easy occurrence of color fogging even at a high temperature, and the present invention has been completed. Reached.

"Means for Solving the Problems" The present invention provides a colorless or light-colored basic dye and a heat-sensitive recording material utilizing a color reaction of a colorant capable of forming a color upon contact with the dye. Using 3-di (n-butyl) amino-6-methyl-7-phenylaminofluoran as a colorant, 4,4'-dihydroxydiphenylsulfone as a colorant, and 1,2- Bis (phenoxy) ethane, 1,2-bis (4-methylphenoxy) ethane or 1,2-bis (3-methylphenoxy)
A heat-sensitive recording material characterized by using ethane.

As described above, the present invention is characterized in that a specific basic dye and a specific colorant are used in combination, but the ratio of both is generally 100 parts by weight of the basic dye. It is desirable to use 100 to 500 parts by weight, preferably 150 to 300 parts by weight, of the coloring agent.

Since the heat-sensitive recording material of the present invention uses a specific basic dye and a color former, even if a heat-fusible substance is used as a sensitizer, the decrease in whiteness due to color fog at high temperatures is extremely low. It has an excellent feature of less. For this reason, it is preferable that the present invention be applied to a high-sensitivity thermosensitive recording medium using a heat-fusible substance, since its effects are fully exhibited.

As such a heat-fusible substance, various known compounds can be used. For example, stearic acid amide, stearic acid methylbisamide, oleic acid amide, palmitic acid amide,
Fatty acid amides such as coconut fatty acid amide, 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 4,
4'-butylidenebis (6-tert-butyl-3-methylphenol), 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-
Hindered phenols such as tris (5-cyclohexyl-4-hydroxy-o-tolyl) butane, 1,2-bis (phenoxy) ethane, 1,2-bis (4-methylphenoxy) ethane, 1,2-bis Ethers such as (3-methylphenoxy) ethane and 2-naphthol benzyl ether, dibenzyl terephthalate, 1-hydroxy-2-
Esters such as phenyl naphthoate, 2-
(2'-hydroxy-5'-methylphenyl) benzotriazole, 2-hydroxy-4-benzyloxybenzophenone, p-benzylbiphenyl and the like.

Among these heat-fusible substances, in particular, 1,2-bis (phenoxy) ethane, 1,2-bis (4-methylphenoxy) ethane and 1,2-bis (3-methylphenoxy) ethane are described in the present invention. It is particularly preferably used because it has high compatibility with the specific colorant of the present invention and low melt viscosity, so that it exhibits excellent device characteristics and a high-quality, high-sensitivity thermosensitive recording material can be obtained.

The amount of the heat-fusible substance is not necessarily limited, but is preferably 50 to 500 parts by weight based on 100 parts by weight of the basic dye.
It is desirable to adjust the amount by weight, preferably in the range of 100 to 300 parts by weight.

As described above, in the present invention, a specific basic dye and a color former are used, but other basic dyes and color formers can be used in combination within a range that does not inhibit the desired effect of the present invention. It is.

Such basic dyes include, for example, 3- (N-ethyl-p-toluidino) -6-methyl-7-phenylaminofluoran, 3- (N-ethyl-N-cyclopentyl)
Amino-6-methyl-7-phenylaminofluoran,
3- (N-methyl-N-cyclohexyl) amino-6
Methyl-7-phenylaminofluoran, 3-diethylamino-6-methyl-7-phenylaminofluoran,
3-di (n-butyl) amino-7- (o-chlorophenyl) aminofluoran, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-phenylaminofluoran, 3- (N- Fluorane dyes such as ethyl-N-tetrahydrofurfuryl) amino-6-methyl-7-phenylaminofluoran.

Examples of the coloring agent include, for example, 4,4'-isopropylidenediphenol, 4,4'-cyclohexylidenediphenol, bis (3-allyl-4-hydroxyphenyl)
Sulfone, 2,2-bis (4-hydroxyphenyl)-
4-methylpentane, bis (2-methyl-5-tert-butyl-4-hydroxyphenyl) sulfide, 1,1-bis (4-hydroxyphenyl) -1-phenylethane,
Examples thereof include 1,3-di [2- (4-hydroxyphenyl) -2-propyl] benzene, 4-hydroxybenzoic acid benzyl ester, and 4-hydroxyphthalic acid dimethyl ester.

In the case where other basic dyes or colorants are used in combination as described above, the proportion of other dyes or colorants in the total basic dyes or colorants is 20% by weight or less. It is desirable to adjust.

Preparation of a coating liquid containing these is generally performed by using water as a dispersion medium and stirring with a ball mill, attritor, sand mill, or the like.
It is prepared by, for example, dispersing a dye, a coloring agent, and a heat-fusible substance to be added as needed together or separately by a pulverizer.

In such a coating solution, usually as a binder starches, hydroxyethylcellulose, methylcellulose,
Carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, various modified polyvinyl alcohols such as carboxyl group-modified / sulfone group-modified, acetoacetyl group-modified / silicon-modified, styrene /
A maleic anhydride copolymer salt, a styrene / acrylic acid copolymer salt, a styrene / butadiene copolymer emulsion and the like are blended in an amount of 2 to 40% by weight, preferably about 5 to 25% by weight of the total solid. Of course, two or more of these binders can be used in combination.

Further, various auxiliaries can be added to the coating liquid, for example, dioctyl sulfosuccinate sodium salt,
Dispersing agents such as sodium salt of dodecylbenzenesulfonic acid, sodium salt of lauryl alcohol sulfate and fatty acid metal salt, and other defoaming agents, fluorescent dyes, coloring dyes and the like.

In addition, to improve the adhesion of scum to the recording head, kaolin, clay, talc, calcium carbonate, calcined clay,
Inorganic pigments such as titanium oxide, diatomaceous earth, finely divided anhydrous silica and activated clay can also be added. In addition, stearic acid, polyethylene, carnauba wax,
Dispersions and emulsions of paraffin wax, zinc stearate, calcium stearate, ester wax and the like can also be added.

In the heat-sensitive recording medium of the present invention, the method of forming the recording layer is not particularly limited, and the recording layer can be formed according to a conventionally known technique. For example, a coating solution for a heat-sensitive recording layer is applied on a support by a suitable coating device such as an air knife coater, a blade coater, a bar coater, a gravure coater, a curtain coater or the like, and dried to form a recording layer.

The amount of the coating solution is not particularly limited, and is generally 1.5 to 12 g / m ² by dry weight, preferably 2.5 to 12 g / m ² .
It is adjusted in the range of 10 g / m ^2.

As the support, paper, plastic film, synthetic paper and the like are used, but paper is most preferably used in view of cost and applicability.

The heat-sensitive recording material of the present invention thus obtained has a recording layer composed of a specific basic dye and a coloring agent. It can exhibit excellent effects as a high-sensitivity thermosensitive recording medium.

If necessary, a protective layer may be provided on the front and / or back surface of the heat-sensitive recording medium, or an undercoat layer may be provided between the support and the heat-sensitive recording layer. Various known techniques in the heat-sensitive recording material manufacturing field can be added.

"Examples" Hereinafter, the present invention will be described more specifically with reference to examples, but is not limited thereto. In the examples, parts and% indicate parts by weight and% by weight, respectively, unless otherwise specified.

Example 1 Formation of undercoat layer Calcined clay (trade name: Ansilex, manufactured by EMC) 100 parts Styrene-butadiene copolymer latex (solid content: 5
0%) 15 parts 10% aqueous polyvinyl alcohol solution 30 parts Water 200 parts The above composition was mixed and stirred to prepare a coating liquid for an undercoat layer. Coating amount after drying the resulting coating solution on high quality paper of 50 g / m ² was formed an undercoat layer was coated and dried so that 10 g / m ^2.

Solution A preparation 3-di (n-butyl) amino-6-methyl-7-phenylaminofluoran 10 parts 1,2-bis (3-methylphenoxy) ethane 25 parts 5% methylcellulose aqueous solution 30 parts water 20 parts This composition The product was pulverized with a sand mill until the average particle size became 2.0 μm.

Solution B preparation 4,4'-dihydroxydiphenyl sulfone 30 parts 5% methylcellulose aqueous solution 30 parts Water 70 parts This composition was pulverized by a sand mill until the average particle diameter became 2.0 μm.

Formation of heat-sensitive recording layer 85 parts of solution A, 130 parts of solution B, 30 parts of silicon oxide pigment, 150 parts of a 20% aqueous solution of oxidized starch and 55 parts of water were mixed and stirred to obtain a coating solution for a heat-sensitive recording layer. The obtained coating liquid was applied on the undercoat layer so that the coated amount after drying was 4.5 g / m ^2, and dried to obtain a thermosensitive recording paper.

Comparative Example 1 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that 4,4'-dihydroxydiphenylsulfone was used in place of 4,4'-dihydroxydiphenylsulfone.

Comparative Example 2 In preparing solution A, 3-di (n-butyl) amino-6
Instead of -methyl-7-phenylaminofluoran,
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-phenylaminofluoran was used.

Comparative Example 3 In preparing solution A, 3-di (n-butyl) amino-6
3 instead of -methyl-7-phenylaminofluoran
-(N-ethyl-N-isoamyl) amino-6-methyl-7-phenylaminofluoran and, in the preparation of solution B, 4,4'-isopropylidenephenol instead of 4,4'-dihydroxydiphenylsulfone A thermosensitive recording paper was obtained in the same manner as in Example 1 except for using.

The seven types of heat-sensitive recording papers thus obtained were recorded with a high-speed heat-sensitive facsimile (Panafax UF-60, manufactured by Matsushita Electric Co., Ltd.). The color density and the density of the blank portion (non-print portion) of the obtained recorded image were measured using a Macbeth reflection densitometer (RD-914).
(Manufactured by Macbeth Co., Ltd.) and the results are shown in Table 1.

Also, after leaving the thermal recording paper after recording for 24 hours under the drying condition of 70 ° C, the densities of the recording part and the white paper part were measured again with a Macbeth reflection densitometer, and the storage stability at high temperatures was evaluated. The results are shown in Table 1.

"Effects" As is clear from the results in Table 1, the heat-sensitive recording materials obtained in each of the examples of the present invention are excellent in that the whiteness and the recording density are extremely small even when stored under high-temperature conditions. Was a heat-sensitive recording medium.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-2-239978 (JP, A) JP-A-59-190891 (JP, A) JP-A-60-13852 (JP, A) JP-A-63-1988 256482 (JP, A) JP-A-62-225391 (JP, A) JP-A-60-228188 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41M 5/28-5 / 34

Claims (1)

(57) [Claims] 1. A recording material utilizing a color reaction between a colorless or light-colored basic dye and a colorant capable of forming a color upon contact with said dye, wherein 3-di (n- Butyl) amino-6-methyl-7-phenylaminofluorane, 4,4'-dihydroxydiphenylsulfone as a color former, and 1,2-bis (phenoxy) ethane as a sensitizer. , 2-bis (4-methylphenoxy) ethane or 1,2-bis (3-methylphenoxy)
A heat-sensitive recording material using ethane.