JPH064795B2 - Thermosensitive color ink composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a phenolic compound constituting a thermosensitive color developing agent in a vehicle prepared by dissolving a specific resin in a specific solvent. Enables gravure printing with dispersed leuco dye,
The present invention relates to a thermosensitive color-forming ink composition that adheres well to not only paper but also synthetic paper, plastic film, etc. without an anchor coat and has good ink stability.

(Prior art) Leuco dye such as crystal violet lactone,
Since a thermal recording material in which a phenolic compound such as bisphenol A is coated on a support together with a vehicle has the characteristic that noise, offensive odor, smoke, etc. do not occur at the time of recording, a thermal printer used as a terminal of a computer is used. It has been widely applied to the field of information equipment such as thermal pen recorders for various medical equipment such as printing and electrocardiography, recording by printers of industrial measuring equipment, or recording for heat-sensitive facsimile.

In addition, recently, by taking advantage of its features, its applications are expanding, such as the use for ticket papers such as commuter passes, coupons, cards, labels, etc. The demand for thermal recording materials has also changed from one-time use to one that can withstand multiple uses, and the support for the heat-sensitive recording material is made from paper to mechanical strength,
It is desired to convert it to a plastic film or synthetic paper having good water resistance.

On the other hand, as a thermosensitive color ink composition capable of pattern printing by gravure printing, a naphthene having a boiling point of 50 to 150 ° C., which is inert to phenolic compounds and leuco dyes as disclosed in JP-A-56-32563. Some vehicles use a vehicle obtained by dissolving a vinyltoluene copolymer resin or a rosin ester resin in a hydrocarbon solvent. However, although this thermosensitive color-forming ink composition has a good adhesiveness to paper, it has a drawback that it has a low adhesiveness to a plastic film or synthetic paper and has poor ink stability.

(Problems to be Solved by the Invention) The present invention improves the above-mentioned various drawbacks and enables gravure printing, and can adhere not only to paper but also to synthetic paper or plastic film without an anchor coat, and It is intended to provide a thermosensitive color-forming ink composition having good stability.

[Structure of Invention]

(Means for Solving Problems) The present invention provides a thermosensitive color-forming ink composition comprising a vehicle and a phenolic compound and a leuco dye that reacts with the phenolic compound under heating to form a color. The vehicle is a mixed solvent of an aromatic hydrocarbon solvent, a naphthene hydrocarbon solvent and (or) paraffin hydrocarbon solvent, styrene as a main component,
A thermosensitive color-forming ink composition characterized by dissolving this and an acrylic resin obtained by copolymerizing one or more monomers of acrylic acid alkyl ester, methacrylic acid alkyl ester, vinyl acetate and the like.

In the present invention, as the phenolic compound, known compounds are used. Examples of such a phenolic compound include phenol, o-cresol, p-cresol and p.
-Ethylphenol, tert-butylphenol, 2,6
-Di-tert-butyl-4-methylphenol, nonylphenol, dodecylphenol, styrenated phenol, 2,2'-methylene-bis- (4-methyl-6-te
rt-butylphenol), α-naphthol, β-naphthol, hydroquinone monomethyl ether, guaiacol, eugenol, p-chlorophenol, p-bromophenol, o-bromophenol, o-chlorophenol, 2,4,6-trichlorophenol, o-phenylphenol, p-phenylphenol, p- (p-chlorophenyl) phenol, o- (o-chlorophenyl) phenol, salicylic acid, methyl p-oxybenzoate, butyl p-oxybenzoate, octyl p-oxybenzoate , Dodecyl p-oxybenzoate, catechol, hydroquinone, resorcin, 3-methylcatechol, 3-
Isopropylcatechol, p-tert-butylcatechol, 2,5-di-tert-butylhydroquinone, 4,4 ′
-Methylenediphenol, Bisphenol A, 1,2-
Dioxynaphthalene, chlorcatechol, bromocatechol, 2,4-dihydroxybenzophenone, phenolic phthalein, o-cresolphthalein, methyl protocatechuate, ethyl protocatechuate, propyl protocatechuate, octyl protocatechuate ，
Dodecyl protocatechuate, pyrogallol, oxyhydroquinone, phloroglucin, 2,4,6-trioxymethylbenzene, 2,3,4-trioxyethylbenzene, gallic acid, methyl gallate, ethyl gallate, propyl gallate, gallic Butyl acid, hexyl gallate, octyl gallate, dodecyl gallate, cetyl gallate,
It is a compound having a phenolic hydroxyl group such as stearyl gallate, 2,3,5-trioxynaphthalene, tannic acid, and phenol resin.

Known leuco dyes can be used in the present invention. Examples of such leuco dyes include triphenylmethane compounds such as crystal violet lactone and malachite green lactone, 1,2-benz-6-diethylaminofluorane, and the like. The fluoran dyes, auramine dyes such as N-benzoyl auramine, phenothiazine dyes, and spiropyran dyes such as leuco dyes can be used.

As the vehicle-forming solvent used in the present invention, a mixed solvent comprising an aromatic hydrocarbon solvent and a naphthene-based hydrocarbon solvent and / or a paraffin-based hydrocarbon solvent is used. Representative examples of the aromatic hydrocarbon solvent include benzene, toluene, xylene, ethylbenzene and the like, or a mixture thereof, and among them, it is preferable to use toluene and / or xylene. Further, as typical examples of the naphthene-based hydrocarbon solvent, cyclopentane, methylcyclopentane, 1,1-dimethylcyclopentane, 1,3-dimethylcyclopentane, cyclohexane, methylcyclohexane, ethylcyclohexane,
Examples include 1,2,4-trimethylcyclohexane and the like, or a mixture thereof, and among them, cyclohexane and / or ethylcyclohexane are preferably used. Typical examples of paraffinic hydrocarbon solvents include:
Examples thereof include n-hexane, n-heptane, n-octane, n-nonane, isomers thereof, or a mixture thereof. The aromatic hydrocarbon solvent and the naphthenic hydrocarbon solvent and / or the paraffinic hydrocarbon solvent are different depending on their types.
It is preferable to use the naphthene hydrocarbon solvent and / or the paraffin hydrocarbon solvent in a ratio of 5/5 to 8/2 (weight ratio). Further, 5 wt% or less of a chlorine-based hydrocarbon, such as trichloroethylene, perchlorethylene, or diethylene chloride, can be added to these mixed solvents based on the total amount. In addition, alcohol system,
Mixing of ketone, ester or ether solvents should be strictly avoided as it will cause the leuco dye to dissolve and develop color.

In addition, the boiling point that is the main component of the mixed solvent is 50 to 150 ° C.
Is preferably in the range of 80 to 140 ° C.
It is preferably in the range of. If the boiling point of the solvent that is the main component of the mixed solvent is less than 50 ° C, drying tends to occur quickly and the viscosity of the solvent may increase due to evaporation of the solvent, which may easily cause plate jams. There is a tendency for unevenness to occur and the printing speed to slow down.

In the present invention, an acrylic resin is used as the vehicle resin. As such an acrylic resin, styrene is the main component, and acrylic acid alkyl ester,
One obtained by copolymerizing one kind or two or more kinds of other monomers such as other alkyl methacrylate, vinyl acetate and the like is preferably used.

In the present invention, as the vehicle, a vehicle prepared by dissolving the acrylic resin in the mixed solvent at room temperature or by heating is used.

The thermosensitive color-forming ink composition of the present invention comprises the above-mentioned phenolic compound and the above-mentioned leuco dye dispersed in the above-mentioned vehicle. However, in such a form, there is a risk of color development when stored for a long period of time. Prepare a solution A in which the phenolic compound is dispersed and a solution B in which the leuco dye is dispersed in the vehicle, and store these separately,
It is preferable to mix and use the solutions A and B immediately before use. Dispersion can be carried out by kneading with a dispersing machine such as a ball mill or paint conditioner.

In addition to the above-mentioned vehicle, phenolic compound and leuco dye, the thermosensitive color-forming ink composition of the present invention may further contain inorganic substances such as calcium carbonate, acid clay, silica gel, clay, magnesium carbonate and silicon oxide, if necessary. Fillers, solid paraffin wax at normal temperature, polyethylene wax, carnauba wax, microcrystalline wax, waxes such as amide wax, plasticizers such as ethyl phthalate, citrate ester, adipate ester, anion, nonion or cationic type A surfactant or the like can be added.

The thermosensitive color-forming ink composition of the present invention is printed or applied on paper, plastic film, synthetic paper or the like to prepare a thermosensitive recording material. As a coating or printing method, a method using a coating machine such as a roll coater, a reverse coater, or a doctor coater as in the past, or a method using gravure printing is also possible. Therefore, in addition to solid printing using a conventional coating machine, pattern printing by gravure printing is also possible.

(Examples) Hereinafter, the present invention will be described with reference to Examples. In the examples, “part” means “part by weight” and “%” means “% by weight”.

Example 1 Ink A Bisphenol A 30 parts Styrene-butyl methacrylate copolymer (molecular weight about 70,000, Tg 103 ° C) 13.5 parts Toluene 31.5 parts Methylcyclohexane 25 parts Ink B Fluoran leuco dye "TH107" (preserved) Tsuchiya Chemical Industry Co., Ltd., trade name 10 parts Styrene-butyl methacrylate copolymer (molecular weight about 7,000, Tg 103 ° C) 18 parts Toluene 52 parts Methylcyclohexane 20 parts Obtained by kneading with a porcelain ball mill for 24 hours. Ink A and Ink B having the above composition were mixed at a ratio of Ink A / Ink B = 3/2 (weight ratio), and a mixed solvent of toluene / methylcyclohexane = 1/1 (weight ratio) was mixed. It was used as a diluent and the viscosity was adjusted to 23 seconds by Zahn cup # 3 to obtain a thermosensitive color-forming ink composition. Approximately 3 g of the obtained thermosensitive color-forming ink composition was dried and coated on a milky white polyester film by a gravure printing method.
It was printed in a pattern so that the film had a color of / m ³ to obtain a thermosensitive coloring film. When the obtained thermosensitive coloring film was heated, a clear black pattern was exhibited. At this time, Table 1 shows the results of evaluation of the presence or absence of color development in Ink B, the storage stability of Inks A and B, the adhesiveness of the thermosensitive color forming ink composition to the film, the thermosensitive color forming property, and the presence or absence of background stain. .

Example 2 Table 1 shows the results of evaluation performed in the same manner as in Example 1 except that benzyl p-oxybenzoate was used in place of bisphenol A and n-heptane was used in place of methylcyclohexane. The coloration at this time was clear black.

Example 3 Ink A Bisphenol A 20 parts Styrene-ethyl acrylate copolymer (molecular weight about 60,000, Tg 97 ° C.) 20 parts Toluene 30 parts Ethylcyclohexane 30 parts Ink B Fluoran-based leuco dye “PSD-170” (Nippon Soda Chemical Co., Ltd. Product name: Sakae Co., Ltd. 20 parts Synthetic ethylene-ethyl acrylate copolymer (Molecular weight about 60,000, Tg 97 ° C) 20 parts Toluene 30 parts Ethylcyclohexane 30 parts Ink A and ink B having the above composition are used. ，
Toluene / ethylcyclohexane = 1/1 as diluent
A thermosensitive color developing film was obtained in the same manner as in Example 1 except that the mixed solvent (weight ratio) was used, and the same evaluation as in Example 1 was performed. The coloration by heating was clear black.

Comparative Example 1 Table 1 shows the results of evaluation performed in the same manner as in Example 3 except that toluene was used instead of ethylcyclohexane.

Comparative Example 2 Table 1 shows the results of evaluation performed in the same manner as in Example 3 except that 2-butanone was used instead of ethylcyclohexane.

Comparative Example 3 The evaluation was performed in the same manner as in Example 3 except that ethylcyclohexane was used instead of toluene, but the acrylic resin did not dissolve in ethylcyclohexane.

Comparative Example 4 Same as Example 3 except that polymerized rosin pentaerythritol ester “Pentaline C” (Hercules, trade name) was used in place of the styrene-ethyl acrylate copolymer, and ethylcyclohexane was used in place of toluene. Table 1 shows the results of the evaluation.

Comparative Example 5 Same as Example 3 except that a vinyltoluene butadiene resin “Pryolite VT” (manufactured by Goodyear Co., Ltd.) was used in place of the styrene-ethyl acrylate copolymer, and ethylcyclohexane was used in place of toluene. Table 1 shows the results of the evaluation.

Comparative Example 6 Evaluation was performed in the same manner as in Example 3 except that a chlorinated polyolefin resin “Super Clone 602” (Sanyo Kokusaku Pulp Co., Ltd., Sakae, trade name) was used in place of the styrene-ethyl acrylate copolymer. The results are shown in Table 1.

Comparative Example 7 The same as Example 3 except that ethylene-vinyl acetate copolymer “Evaflex 250” (trade name, manufactured by Mitsui DuPont Polychemical Co., Ltd.) was used in place of the styrene-ethyl acrylate copolymer. Table 1 shows the evaluation results.

Ink B with or without color development: ◯: No color development △: Slight color development ×: Significant color development −: Not tested Storage stability of inks A and B: ○: No change for 1 week or more at 25 ° C ×: 1 at 25 ° C Separation of solvent and resin within a day −: Not tested Adhesion to film: ○: Good ×: Poor Thermosensitive color development ^* : ○: Good −: Not tested Ground stain ^* : ○: None −: Tested No * By optical density measurement using a Macbeth reflection densitometer.

Examples 4 and 5 Instead of "TH107", "Red DCF" (Hodogaya Chemical Co., Ltd., trade name, Example 4) and "CVL"
When a heating test was performed in the same manner as in Example 1 except that (Hodogaya Chemical Co., Ltd., trade name, Example 5) was used, a bright red color and a vivid blue color were respectively formed in a pattern. .

〔The invention's effect〕

According to the present invention, it is possible to obtain a thermosensitive color-forming ink composition which can be gravure-printed and can be sufficiently adhered not only to paper but also to a plastic film or synthetic paper without an anchor coat and has good storage stability.

Claims (1)

[Claims] 1. A thermosensitive color-forming ink composition comprising a vehicle, and a phenolic compound and a leuco dye that reacts with the phenolic compound under heating to develop a color, wherein the vehicle is an aromatic hydrocarbon solvent. , And naphthene-based hydrocarbon solvent and / or paraffin-based hydrocarbon solvent in a mixed solvent containing styrene as a main component,
A thermosensitive color-forming ink composition, which is obtained by dissolving an acrylic resin obtained by copolymerizing this with one or more monomers such as acrylic acid alkyl ester, methacrylic acid alkyl ester, and vinyl acetate.