JPH01178582A - Colorant for thermal transfer recording - Google Patents

Abstract

PURPOSE:To provide a vivid magenta colorant excellent in transferability, tinting power and fastness, by preparing a specific pyrazoloimidazole azomethine colorant. CONSTITUTION:This colorant for thermal transfer recording of formula I, wherein R1 is alkyl, alkoxy, alkoxycarbonyl, aryl, or substd. amino; R2 is H, a halogen atom, alkyl, or alkoxy; R3 and R4 are each substd. or unsubstd. alkyl, aralkyl, or aryl; and R5 and R6 are each H, alkyl, alkoxy, or a halogen atom, can be easily prepared by coupling a pyrazoloimidazole of formula II with an aniline of formula III through oxidation under alkaline conditions in the presence of an oxidizing agent such as silver chloride, ammonium persulfate or red prussiate.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magenta dye for thermal transfer recording, and more specifically, to a magenta dye for thermal transfer recording. The purpose is to provide a magenta color pigment.

(Prior Art) Currently, a sublimation type thermal transfer recording method has been proposed as a method for obtaining hard copies from ephemeral images of televisions, videos, styril video cameras, and the like.

In this method, a dye is sublimated by heat to form an image on a recording medium, and a heating element or a semiconductor laser is used as a heat source. Since the amount of dye sublimation transfer can be controlled by changing the energy applied to this heat source, this method is considered to be particularly advantageous for Victorian color recording with good gradation.

(Problems to be Solved by the Invention) When obtaining a full-color image by the subtractive color method, the three primary colors that are the basis of saturation expression are yellow, magenta, and cyan. Among these, magenta is a complementary color of green, and is a clear reddish-purple color with a maximum absorption wavelength of 520 to 580 nm.
m is required. Disperse dyes currently used for thermal transfer lack chroma, making it impossible to obtain color images with excellent color reproducibility.

In addition, with recent advances in recording methods, there is a need for materials that can support high-speed recording and that can provide clear images with sufficient density at low energy levels.In this respect, the currently used disperse dyes does not have satisfactory performance.

In view of this situation, in order to solve the problems of the conventional technology, the present inventor conducted intensive research and found that a pyrazoloimidazole-based azomethine dye has extremely excellent sublimation properties, exhibits a clear magenta color, yellow, They discovered that it exhibits excellent color reproducibility when mixed with cyan dye, leading to the completion of the invention.

(Means for Solving the Problems) That is, the gist of the present invention is a dye for angry heat transfer i-recording represented by the general formula N).

The dye represented by the -S formula (,1) can be prepared by a known method, for example, by combining the pyrazoloimidazole represented by the formula (II) and the aniline represented by the general formula (III) with silver chloride,
It can be easily produced by oxidative coupling in alkaline conditions in the presence of an oxidizing agent such as ammonium persulfate or red blood salt.

+ α The above-mentioned -ritual (R1 represented by Il is a methyl group,
Straight chain or branched alkyl groups such as ethyl group, propyl group, butyl group, alkoxy groups such as methoxy group, ethoxy group, propoxy group, butoxy group, alkoxycarbonyl groups such as methoxycarbonyl group, ethoxycarbonyl group, propoxycarbonyl group, Examples thereof include aryl groups such as phenyl group and tolyl group, substituted amide groups such as acetamido group, benzenecarbonamide group, methoxycarbonamide group, methanesulfonamide group, benzenesulfonamide group, and methylureido group.

Examples of R2 include hydrogen atoms, halogen atoms such as fluorine and chlorine, alkyl groups such as methyl and ethyl groups, and alkoxy groups such as methoxy and ethoxy groups.

R3 and R4 are alkyl groups such as methyl group, ethyl group, propyl group, butyl group, alkoxyalkyl groups such as methoxyethyl group and ethoxyethyl group, hydroxyalkyl groups such as hydroxyethyl group and β-hydroxypropyl group, Halogenoalkyl groups such as chloroethyl groups, cyanoalkyl groups such as cyanomethyl groups and cyanethyl groups, aralkyl groups such as benzyl groups and phenethyl groups, phenyl groups,
Examples include tolyl groups, halogenoalkyl groups, and tolyl groups such as alkoxyphenyl.

R2 and R6 are hydrogen atoms, alkyl groups such as methyl, ethyl, propyl, and butyl, alkoxy groups such as methoxy, ethoxy, propoxy, and butoxy, and halogen atoms such as fluorine and chlorine. Examples include.

A method for producing a thermal transfer recording ink using the dye of the present invention includes a method in which the dye is dissolved or atomized using a ball mill or the like in a solvent together with a suitable binder to form an ink. Examples of the binder include epoxy resin, phenol resin, urethane resin, acrylic resin, silicone resin, cellulose resin, polyvinyl chloride, polyethylene, polystyrene, polycarbonate, polyester, polyimide, polyvinyl butyral, gum arabic, and casein. Solvents include water, alcohols such as methanol, ethanol, propatool, and butanol, aromatic hydrocarbons such as toluene, xylene, and monochlorohenzene, ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, dichloroethane, and trichloroethylene. , hydrogen halides such as perchlorethylene,
Examples include esters such as ethyl acetate and butyl acetate, and cellosolves such as methyl cellosolve and ethyl cellosolve.

As for the transfer method, the ink obtained above is applied onto a suitable substrate using a bar coater to create a transfer sheet, the sheet is overlapped with the recording medium, and then a heating element etc. is applied from the back side of the sheet. There is a heating method, in which the dye on the sheet is transferred onto the recording medium. As a transfer substrate, -i is passed through a plus film having good heat resistance such as capacitor paper, cellophane, or polyimide resin or polyester resin. Plain paper can also be used as the recording medium, but to increase color sensitivity, paper coated with polyester resin or polyamide resin, or synthetic paper such as polypropylene, polyvinyl chloride, or polyester is used. be done.

Since the dye of the present invention has a vivid magenta color, it is suitable for obtaining a full color when combined with, for example, a yellow dye represented by the following structural formula and a cyan dye represented by the following structural formula.

(Effects of the Invention) According to the present invention, by using a pyrazoloimidazole-based azomethine dye that exhibits - ritual [■] and has good sublimation properties, a bright magenta-colored thermal transfer recording can be obtained.

EXAMPLES The present invention will be specifically explained below with reference to Examples, but these Examples do not limit the present invention.

Example 1 (a) Production of dye 14.5 g of silver nitrate is dissolved in 60 d of water, and 5.0 g of sodium chloride is added to the aqueous solution and stirred. Thereafter, 1.7 g of a compound represented by the following structural formula dissolved in ethyl chloride was added. Next, ammonia water9. 0II11 was added, and 2.7 g of a compound represented by the following structural formula was dissolved in 40 ml of water, and the solution was added dropwise. After completion of the dropwise addition, the reaction was allowed to proceed at room temperature for 1 hour, after which the inorganic matter was filtered off and the liquid was separated. After the solvent in the organic layer was distilled off, column purification was performed using chloroform to obtain a pyrazoloimidazole azomethine dye represented by the following structural formula 2.
5g was obtained. The maximum absorption wavelength (ethyl acetate) of the main island is 54
It was 4 nm.

(B) Preparation of ink and transfer sheet An ink composition containing 4 parts of the dye (pyrazoloimidazole azomethine dye obtained in (a) above), 8 parts of ethyl cellulose, 44 parts of methyl ethyl ketone, and 44 parts of toluene was thoroughly kneaded using a ball mill. Thereafter, it was coated on condenser paper using a bar coater and dried to obtain a transfer sheet.

(c) Transfer Recording Recording was performed by placing this transfer sheet opposite to high-quality paper coated with polyester resin and heating it using a thermal head, resulting in a clear magenta high color density recording.

Examples 2 to 15 The dyes shown in Table 1 were synthesized in the same manner as in Example 1, and thermal transfer was performed on each dye to obtain a clear magenta color record with high color density.

Two knee 1-1■

Claims (1)

[Claims] General formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [I] [In the formula, R_1 represents an alkyl group, an alkoxy group, an alkoxycarbonyl group, an aryl group, a substituted amino group,
R_2 represents a hydrogen atom, a halogen atom, an alkyl group, or an alkoxy group, and R_3 and R_4 each represent a substituted or unsubstituted alkyl group, an aralkyl group, or an aryl group,
R_5 and R_6 each represent a hydrogen atom, an alkyl group, an alkoxy group, or a halogen atom. ] A dye for thermal transfer recording represented by.