JPH10203012A - Preparation method of thermosensitive recording liquid and thermosensitive recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance preservation stability and recording sensitivity by preparing heat sensitive recording coating liquid by the use of dispersion liquid made by grinding through water as a dispersion medium a coloring agent and two or more sensitizers selected from oxalic acid dibenzyl ester, oxalic acid di-p- methylbenzyl ester and the like. SOLUTION: Upon preparing heat sensitive recording coating liquid containing ground leuco dye, a coloring agent, and sensitizers, the sensitizers are two or more kinds selected from oxalic acid dibenzyl ester, oxalic acid di-p- methylbenzyl ester, and oxalic acid dibenzyl di-p-chlorobenzyl ester and, besides, the coloring agent and sensitizer are ground through water as a dispersion medium, thereby preparing heat sensitive recording coating liquid. In this case, a using ratio of the phenol compound and sensitizers is 0.2-5 pts.wt. with respect to the 1 pts.wt. coloring agent, preferably, it is used of the order of 0.5-2 pts.wt. Although a variety of known coloring agent are employed, a phenol compound is preferable because of superior recording sensitivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preparing a coating solution for a heat-sensitive recording material using a leuco dye, a color former and a color-forming reaction, and more particularly to a coating solution for heat-sensitive recording excellent in storage stability and recording sensitivity. And a thermosensitive recording medium.

[0002]

2. Description of the Related Art Generally, a heat-sensitive recording medium has a heat-sensitive recording layer which develops color by applying heat energy to a support such as paper, synthetic paper, plastic film or the like. For example, in a heat-sensitive recording medium containing a leuco dye and a colorant as color-forming components in the heat-sensitive recording layer, the leuco dye and the colorant react by heat energy to form a recorded image. Such a thermosensitive recording medium is relatively inexpensive, and because the recording equipment is compact and easy to maintain, the output of a facsimile or various computers, an automatic ticket vending machine, a printer for scientific measurement equipment, or a printer for CRT medical measurement. Widely used for etc. In particular, in recent years, facsimile printers using such a thermal recording system have been improved, and high-speed recording, which has been conventionally difficult, has become possible. As the speed of such devices has been increased, the thermal recording materials used therein have been required to have further improved recording sensitivity, and many proposals have been made regarding this.

Japanese Patent Application Laid-Open No. 57-476983 discloses that as a means for improving recording sensitivity, the size of dispersed particles is reduced, for example, by setting the average particle size of color forming component particles to 2.0 μm or less. However, when the particle diameter is reduced, there is a disadvantage that the stability of the dispersion liquid deteriorates and the particle diameter increases with time. Also, Japanese Patent Application Laid-Open No. 8-5824
No. 0 describes a heat-sensitive recording coating solution obtained by pulverizing both di-p-methylbenzyl oxalate and di-p-chlorobenzyl oxalate as sensitizers. A dispersion obtained by pulverizing both -p-methylbenzyl ester and oxalic acid di-p-chlorobenzyl ester has a problem that the particle size increases with time and the recording sensitivity decreases.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for preparing a thermosensitive recording liquid having excellent storage stability and recording sensitivity.
And a heat-sensitive recording medium.

[0005]

A ground leuco dye,
In a method for preparing a heat-sensitive recording coating solution containing a colorant and a sensitizer, as one means for solving the above problems, the present invention provides a sensitizer comprising dibenzyl oxalate and di-oxalate. Two or more selected from p-methylbenzyl ester and di-p-chlorobenzyl oxalate are used, and both a color former and a sensitizer are pulverized using water as a dispersion medium.

[0006]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color former and two sensitizers selected from dibenzyl oxalate, di-p-methylbenzyl oxalate, and di-p-chlorobenzyl oxalate. A phenolic compound and a specific sensitizer are prepared by using a dispersion obtained by pulverizing both of the above (hereinafter referred to as a specific sensitizer) with water as a dispersion medium, and using a phenolic compound and a specific sensitizer. The use ratio of the specific sensitizer is not particularly limited, but is about 0.2 to 5 parts by weight, preferably about 0.5 to 2 parts by weight, based on 1 part by weight of the coloring agent.

The ratio of each of the specific sensitizers used in the dibenzyl oxalate-based compounds such as dibenzyl oxalate, di-p-methylbenzyl oxalate and di-p-chlorobenzyl oxalate is not particularly limited. However, the amount of at least one other dibenzyl oxalate compound is about 0.2 to 5 parts by weight, preferably about 0.5 to 2 parts by weight, based on 1 part by weight of one dibenzyl oxalate compound.

Various known colorants can be used. Specific examples of such coloring agents include, for example, 4-cumiphenol, hydroquinone monobenzyl ether,
1,1-bis (4-hydroxyphenyl) -1-phenylethane, 2,2′-bis (4-hydroxyphenyl)
Propane, 4,4'cyclohexylidenediphenol,
4,4′-dihydroxydiphenyl-2,2-butane,
Dihydroxydiphenylmethane, 4,4'-dihydroxydiphenylmethane, 4,4 '-(1,3-dimethylbutylidene) diphenol, 2,2-bis (4-hydroxyphenyl) heptane, bis (4-hydroxyphenylthioethoxy) Methane, 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxyphenyl- Phenolic compounds such as 4'-benzyloxyphenyl sulfone, 3,4-dihydroxyphenyl-p-tolylsulfone, and p-methoxyphenyl 2,4-dihydroxybenzoate; p-phenyl N- (p-toluenesulfonyl) carbamoylate; Millphenyl S , N- (p-toluenesulfonyl) carbamoyl acid p-benzyloxyphenyl ester, N- (o-toluoyl) -p-toluenesulfonamide, 4,4′-bis (Np-toluenesulfonylaminocarbonylamino ) having an -SO ₂ NH- bond in the molecule of diphenylmethane, p- chlorobenzoic acid zinc, 4- [2-(p-methoxyphenoxy) ethyloxy] zinc salicylate, 4- [3- (p-tolyl sulfonyl ) Propyloxy] zinc salicylate, 5-
[P- (2-p-methoxyphenoxyethoxy) cumyl] Zinc salts of aromatic carboxylic acids such as salicylic acid. Among them, phenolic compounds are preferred because of their excellent recording sensitivity.

Other sensitizers and colorants can be added as long as the desired effects of the present invention are not impaired.

The dispersion of the color former and the sensitizer has a total amount of about 10 to 100 parts by weight of the phenolic compound and the specific sensitizer per 100 parts by weight of water as a dispersion medium. The following surfactant (dispersant) may be used in an amount of 0.01 to 1
The undispersed liquid containing about 0 parts by weight is adjusted to have an average particle diameter of about 0.5 to 2.5 μm, preferably about 0.5 to 2.0 μm by a wet mill such as a sand mill, an aerator, a ball mill, or a cobol mill. To be obtained by grinding. If the average particle diameter is less than 0.5 μm, background fog may occur, and if it exceeds 2.5 μm, the recording sensitivity may decrease.

Specific examples of the surfactant (dispersant) include:
Examples include sodium di-2-ethylhexylsulfosuccinate, sodium dodecylbenzenesulfonate, ammonium salts of styrene-maleic acid copolymer, polyvinyl alcohol, sulfone-modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, and the like.

The heat-sensitive recording layer coating liquid is a leuco dye dispersion pulverized by a wet pulverizer to an average particle diameter of 3 μm or less,
It is obtained by mixing and stirring a dispersion of the above color former and sensitizer and an adhesive. Further, if necessary, a preservability improver, a water resistance agent, a pigment, a lubricant and the like can be added.

As the leuco dye and the adhesive contained in the coating solution for the heat-sensitive recording layer, various known ones can be used.
Examples of the leuco dye include the following.
3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2)
-Methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3-diethylamino-7-anilinofluoran, 3-diethylamino-7
-Dibenzylaminofluoran, 3-cyclohexylamino-6-chlorofluoran, 3-diethylamino-6
-Methyl-7-chlorofluoran, 3- (N-ethyl-
N-isoamyl) amino-6-methyl-7-anilinofluoran, 3-diethylamino-7- (m-trifluoromethylanilino) fluoran, 3- (N-methyl-N
-Cyclohexyl) amino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-di (n-butyl) amino-6-
Methyl-7-anilinofluoran, 3-di (n-pentyl) amino-6-methyl-7-anilinofluoran, 3
-Di (n-butyl) amino-7- (o-chloroanilino) fluoran, 3-diethylamino-7- (o-fluoroanilino) fluoran, 3- (N-ethyl-p-toluidino) -6-methyl-7 -Anilinofluoran, 3
-(N-ethyl-N-furfurylamino) -6-methyl-7-anilinofluoran, 3,3-bis [1- (4-
Methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,6, -bis (dimethylamino) fluorene-9-spiro-3 '-(6'-dimethylamino)
Phthalide, 3- (N-ethyl-N-2-tetrahydrofurfurylamino) -6-methyl-7-anilinofluoran, 3- (4-dimethylamino) anilino-5,7-dimethylfluoran and the like. Of course, the present invention is not limited to these, and two or more of them can be used as needed. The amount of the leuco dye used is not particularly limited, but may be 5 to 4% based on the total solids of the heat-sensitive recording layer coating solution.
About 0 parts by weight is preferable.

As the adhesive, for example, completely (partially) saponified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, starch, oxidized starch,
Gum arabic, gelatin, casein, chitosan, methylcellulose, hydroxyethylcellulose, hydroxymethylcellulose, styrene-acrylic acid copolymer salt, styrene-maleic anhydride copolymer salt, methylvinyl ether-maleic anhydride copolymer salt, iso Propylene-maleic anhydride copolymer, vinyl acetate latex, acrylate copolymer latex, methacrylate copolymer latex, vinyl acetate- (meth) acrylate copolymer latex, polyurethane latex, polychlorinated Water-dispersible resins such as vinyl latex, polyvinylidene chloride latex, and styrene-butadiene latex are exemplified. The amount of the adhesive used is preferably about 5 to 30% by weight based on the total solids of the coating solution for the heat-sensitive recording layer.

As the sensitizer, two or more selected from dibenzyl oxalate, di-p-methylbenzyl oxalate, and di-p-chlorobenzyl oxalate are used. As long as the effect is not impaired, various known sensitizers can be used in combination. Such sensitizers include, for example, stearic acid amide, methylolamide stearate, ethylenebisstearic acid amide, dimethyl terephthalate, dibenzyl terephthalate, 2-naphthylbenzyl ether,
2-di (3-methylphenoxy) ethane, 1,2-diphenoxyethane, 1-phenoxy-2-naphthoxyethane, 1-phenoxy-2- (4-methylphenoxy) ethane, 1- (4-methylphenoxy)- 2-naphthoxyethane, 1,3-naphthoxypropane, 1,4-naphthoxybutane, p-benzylbiphenyl, m-terphenyl, benzyl-2-naphthyl ether, 1,2-bis (3,4-dimethylphenyl) ethane, 1,4-bis (p-tolyloxy) benzene, diphenylsulfone,
Diphenyl carbonate, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, and the like.

As the preservability improver, for example, 2,2'-
Methylene bis (4-methyl-6-tert-butylphenol), 2,2′-ethylenebis (4-methyl-6-tert
-Butylphenol), 2,2′-ethylidenebis (4,6-di-tert-butylphenol), 1,1,3
-Tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, N, N'-di- 2-naphthyl-p-phenylenediamine, 2,2'-methylenebis (4,6-di-tert-
Butylphenyl) sodium phosphate, 4,4′-bis (ethyleneiminecarbonylamino) diphenylmethane,
Benzyloxy-4 '-(2-methyl-2,3-epoxypropyloxy) diphenylsulfone, novolak-type resins, and the like. These preservative improvers are usually used in an amount of about 0.05 to 4 parts by weight based on 1 part by weight of the leuco dye.

Examples of the water-proofing agent include dialdehyde compounds such as glyoxal and dialdehyde starch, polyamine compounds such as polyethyleneimine, epoxy compounds, polyamide resins, melamine resins, and diglycidyl compounds such as glycerin diglycidyl ether. Examples include a dimethylol urea compound, an aziridine compound, a blocked isocyanate compound, ammonium persulfate, boric acid, borax, ferric chloride, and magnesium chloride.

Examples of the pigment include calcium carbonate, magnesium carbonate, magnesium oxide, kaolin, clay, talc, calcined clay, amorphous silica, zinc oxide, titanium oxide, aluminum hydroxide, barium sulfate, and urea.
Formalin resin filler and the like can be mentioned.

Examples of the lubricant include zinc stearate,
Examples include calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax and the like.

The coating solution for the heat-sensitive recording layer thus prepared is
In order to form a heat-sensitive recording layer on a support such as high-quality paper (acid paper, neutral paper), film, synthetic paper, or coated paper, the coating amount after drying should be about ² to 8 g / m ^2. Coated and dried.

The coating method for applying the coating solution for the heat-sensitive recording layer includes an air knife method, a Meyer bar method, a pure blade method, which has been conventionally used by those skilled in the art.
A rod blade method, a reverse roll method, a slit die method and the like can be mentioned.

[0022]

The present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to these examples. In each example, "parts" and "%" indicate "parts by weight" and "% by weight", respectively.

Example 1 Preparation of Leuco Dye Dispersion 10 parts of 3-di (n-butyl) amino-7- (o-chloroanilino) fluoran, 10 parts of a 10% aqueous solution of sulfone-modified polyvinyl alcohol, and 10 parts of water Was pulverized using a sand mill until the average particle size became 0.7 μm to obtain a leuco dye dispersion.

Preparation of Dispersion (Solution A) of Coloring Agent and Sensitizer 15 parts of 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 10 parts of di-p-methylbenzyl oxalate A composition comprising 10 parts of oxalic acid di-p-chlorobenzyl ester, 35 parts of a 10% aqueous solution of sulfone-modified polyvinyl alcohol, and 35 parts of water was pulverized using a sand mill until the average particle diameter became 1.3 μm,
Solution A was obtained. Measurement of particle size distribution is made by Shimadzu SALD
Performed using -2000.

Preparation of Coating Solution for Undercoat Layer 100 parts of calcined kaolin having an oil absorption of 110 ml, 2 parts of a 40% aqueous solution of sodium polyacrylate, 100 parts of water, and a 10% aqueous solution of polyvinyl alcohol (trade name: PVA110, manufactured by Kuraray Co., Ltd.) 100 parts and a styrene-butadiene latex (trade name: L-1537, solid concentration 4
A composition consisting of 10 parts (8%, manufactured by Asahi Kasei Corporation) was mixed and stirred to obtain a coating liquid for an undercoat layer.

Preparation of Coating Solution for Thermosensitive Recording Layer 30 parts of Leuco Dye Dispersion, Solution A 105 immediately after dispersion treatment
Parts, 60 parts of an aqueous dispersion of 60% calcium carbonate, polyvinyl alcohol (trade name: PVA117, manufactured by Kuraray Co., Ltd.)
Of a 10% aqueous solution, 20 parts of a 30% dispersion of zinc stearate, and 50 parts of water were mixed and stirred to obtain a coating solution for a heat-sensitive recording layer.

Preparation of Thermosensitive Recording Material 1 On one side of acidic paper having a basis weight of 53 g / m ² , the coating amounts of the above-mentioned undercoat layer coating solution and thermosensitive recording layer coating solution after drying were 8 g / m ² and 8 g / m ² , respectively. The coating was sequentially applied and dried with a rod blade coater to a concentration of 5 g / m ^2, and then subjected to a super calender treatment to obtain a thermosensitive recording medium 1. Preparation of heat-sensitive recording medium 2 Preparation of heat-sensitive recording medium was performed in the same manner as in preparation 1 of the heat-sensitive recording layer except that the liquid A immediately after the dispersion treatment was used instead of the liquid A immediately after the dispersion treatment. In the same manner, a thermosensitive recording medium 2 was obtained.

Example 2 Thermal recording was carried out in the same manner as in Example 1 except that dibenzyl oxalate was used instead of di-p-chlorobenzyl oxalate in the preparation of solution A in Example 1. A coating liquid for a layer and a thermosensitive recording medium were obtained.

Example 3 In the preparation of the solution A in Example 1, 2,2-bis (4-hydroxyphenyl) propane was used instead of 1,1-bis (4-hydroxyphenyl) -1-phenylethane. Except for using, a coating solution for a heat-sensitive recording layer and a heat-sensitive recording material were obtained in the same manner as in Example 1.

Example 4 In the preparation of solution A of Example 1, 4- [3- (p-tolylsulfonyl) propyloxy was used instead of 1,1-bis (4-hydroxyphenyl) -1-phenylethane. A coating solution for a heat-sensitive recording layer and a heat-sensitive recording material were obtained in the same manner as in Example 1 except that zinc salicylate was used.

Example 5 In the preparation of solution A of Example 1, 4,4'-bis (Np-toluenesulfonyl) was used instead of 1,1-bis (4-hydroxyphenyl) -1-phenylethane. A coating solution for a heat-sensitive recording layer and a heat-sensitive recording material were obtained in the same manner as in Example 1 except that (aminocarbonylamino) diphenylmethane was used.

Example 6 In the preparation of the solution A in Example 1, di-p-methylbenzyl oxalate 10 parts and di-p-chlorobenzyl oxalate 10 parts were replaced with di-p-oxalate. -Methylbenzyl ester 1
A coating solution for a heat-sensitive recording layer and a heat-sensitive recording material were obtained in the same manner as in Example 1, except that 6 parts and 4 parts of di-p-chlorobenzyl oxalate were used.

Example 7 A coating solution for a heat-sensitive recording layer and a heat-sensitive recording material were prepared in the same manner as in Example 1, except that the preparation of the solution A in Example 1 was pulverized until the average particle diameter became 2.6 μm. I got

Example 8 In the preparation of the solution A of Example 1, the coating liquid for the heat-sensitive recording layer and the heat-sensitive recording material were prepared in the same manner as in Example 1 except that pulverization was performed until the average particle diameter became 0.4 μm. I got

Comparative Example 1 The procedure of Example 1 was repeated except that, in the preparation of the coating solution for the heat-sensitive recording layer of Example 1, 75 parts of the following liquid B and 30 parts of the liquid C were used instead of 105 parts of the liquid A. In the same manner as in the above, a coating solution for a heat-sensitive recording layer and a heat-sensitive recording material were obtained.

Preparation of Dispersion (Solution B) of Coloring Agent and Sensitizer 15 parts of 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 10 parts of di-p-methylbenzyl oxalate , 10 of sulfone-modified polyvinyl alcohol
% Of an aqueous solution and 25 parts of water was pulverized using an Ultraviscomiler until the average particle diameter became 1.3 μm, to obtain a liquid B.

Preparation of Dispersion (Solution C) of Sensitizer 10 parts of di-p-chlorobenzyl oxalate, 10 parts of a 10% aqueous solution of sulfone-modified polyvinyl alcohol,
And 10 parts of water were pulverized using an Ultra Viscomill until the average particle diameter became 1.3 μm to obtain a liquid C.

Comparative Example 2 In the preparation of the coating solution for the heat-sensitive recording layer of Comparative Example 1, the following D solution 4 was used instead of 75 parts of the B solution.
A coating solution for a heat-sensitive recording layer and a heat-sensitive recording material were obtained in the same manner as in Comparative Example 1 except that 5 parts and 30 parts of Solution E were used.

Preparation of Coloring Agent Dispersion Solution (Solution D) Consisting of 15 parts of 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 15 parts of a 10% aqueous solution of sulfone-modified polyvinyl alcohol, and 15 parts of water. The composition was pulverized using an Ultra Viscomill until the average particle diameter became 1.3 μm, to obtain a liquid D.

Preparation of Sensitizer Dispersion (Solution E) 10 parts of di-p-methylbenzyl oxalate, 10 parts of a 10% aqueous solution of sulfone-modified polyvinyl alcohol,
And a composition consisting of 10 parts of water and 10 parts of water were pulverized using an Ultra Viscomill until the average particle diameter became 1.3 μm, to obtain a solution E.

Comparative Example 3 In the preparation of the colorant dispersion B of Comparative Example 1, 2,2-bis (4) was used instead of 1,1-bis (4-hydroxyphenyl) -1-phenylethane.
A coating solution for a heat-sensitive recording layer and a heat-sensitive recording material were obtained in the same manner as in Comparative Example 1 except that -hydroxyphenyl) propane was used.

Each of the thus obtained heat-sensitive recording media was recorded by using a heat-sensitive recording evaluation device (trade name: TH-PMD, manufactured by Okura Electric Co., Ltd.) at an applied energy of 0.3 mJ / dot. The recorded density and the unrecorded portion of the recorded image were measured in a visual mode using a Macbeth densitometer (trade name: RD-914, manufactured by Macbeth), and the obtained results are shown in Table 1.

Further, in Examples 1 to 7, a dispersion of a colorant and a sensitizer (solution A), and in Comparative Examples 1 and 3, 75 parts of a dispersion of a colorant (solution B) And a mixed solution comprising 30 parts of a sensitizer dispersion liquid (liquid C), and 45 parts of a colorant dispersion liquid (liquid D) and sensitizer dispersion liquid (liquid E) 3 for Comparative Example 2.
The volume particle size distribution was measured immediately after the preparation of a mixture consisting of 0 parts and 30 parts of the sensitizer dispersion (solution C) and after standing at room temperature for 15 days. Measurement of particle size distribution is made by Shimadzu S
This was performed using ALD-2000. Table 1 shows the results. However, solution B, solution C, solution D and solution E were prepared almost simultaneously.

[0044]

[Table 1]

[0045]

As shown in Table 1, the method for preparing a coating solution for a heat-sensitive recording layer of the present invention is excellent in storage stability and recording sensitivity.

Claims (4)

[Claims] 1. A method for preparing a thermal recording coating solution containing a pulverized leuco dye, a color former and a sensitizer, wherein the sensitizer is dibenzyl oxalate or di-p-methylbenzyl oxalate. A method for preparing a heat-sensitive recording coating liquid, comprising two or more selected from oxalic acid di-p-chlorobenzyl ester, and pulverizing both a color former and a sensitizer with water as a dispersion medium. . 2. The method according to claim 1, wherein the colorant is a phenolic compound. 3. The method for preparing a thermosensitive recording coating liquid according to claim 1, wherein the average particle diameter of the colorant and the sensitizer both pulverized is 0.5 to 2.0 μm. 4. A heat-sensitive recording material having a heat-sensitive recording layer formed by applying and drying the heat-sensitive recording coating liquid according to claim 1 on a support.