JPH06316881A - Sheet for heat-sensitive transfer - Google Patents

Abstract

PURPOSE:To provide a sheet giving an image having distinct gradation and high color density by making a substrate support an ink layer containing a specific benzopyran compound. CONSTITUTION:An ink layer containing a benzopyran compound of formula (R1 and R2 are respectively H, a 1-4C alkyl or allyl; X is an imino or O; Y1 and Y2 are respectinely CH3, OCH3 or a halogen), especially an ink layer containing a clear red pigment and a cellulosic resin, acrylic resin, starch resin, etc., as a binder is applied to a substrate sheet such as plastic sheet or paper to obtain a heat-sensitive transfer sheet exhibiting excellent light-resistance, weather resitance and durability. The pigment used in the transfer is easily sublimated by the heat of a heat-sensitive recording head without causing thermal decomposition and forms an image having excellent light-resistance, weather resistance, etc., on a receiving sheet in excellent color reproducibility. A recorded image having high storability can be developed by this process.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a heat-sensitive transfer sheet. More specifically, it relates to a heat-sensitive transfer sheet in which an ink layer containing a red dye having excellent sharpness is carried on a support.

[0002]

2. Description of the Related Art As a color recording technique, electrophotography, ink jet, thermal transfer and the like have been proposed. The thermal transfer recording method is considered to be advantageous because the maintenance and operability of the apparatus are easy. Conventionally, a red to magenta dye applied to thermal transfer recording has been selected and used from disperse dyes, oil-soluble dyes and the like. Specifically, JP-A-59-78
896, JP-A-60-30392, JP-A-60-303
94, JP-A-60-131293, JP-A-60-159.
091, JP-A-61-227092, and JP-A-61-222.
7093, JP-A-1-174490, JP-A-1-183
584, JP-A-1-263082, JP-A-4-8026
5 and many others have been proposed. The dye used in the transfer sheet easily sublimes due to the heat of the thermal recording head and does not cause thermal decomposition, has a large molecular extinction coefficient, has good color reproducibility, and has excellent light resistance, weather resistance, and heat resistance. ,
Various quality characteristics are required, such as safety and health issues. From the above viewpoint, almost satisfactory red to magenta dyes are found. However, with the development of color recording technology, high-definition image quality close to that of silver halide photography has been demanded. In order to meet this requirement, the conventional one was not satisfactory in sharpness.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat-sensitive transfer sheet satisfying the above quality characteristics.

[0004]

The inventor of the present invention has reached the present invention as a result of earnest research to find an extremely clear red dye. That is, the present invention provides the following general formula (1)

[Chemical 2]

(In the formula, R ₁ and R ₂ each independently represent a hydrogen atom, a linear or branched alkyl group (C ₁ -C ₄ ) or an allyl group, and X represents an imino group or an oxygen atom. And Y ₁ and Y ₂ each independently represent a hydrogen atom, a methyl group, a methoxy group or a halogen atom), and an ink layer containing a benzopyran compound represented by the formula) is carried on a support. The present invention relates to a heat-sensitive transfer sheet.

The compound represented by the general formula (1) is represented by the general formula (2)

[Chemical 3]

(Wherein R ₁ , R ₂ , Y ₁ and Y ₂ have the same meanings as described above) and an iminocoumarin represented by the formula (3)

[0008]

[Chemical 4]

It can be produced by reacting malondinitrile represented by: in an organic solvent, usually at a temperature of 50 to 200 ° C., and optionally hydrolyzing it in water or an organic solvent in the presence of an acid. .

For the heat-sensitive transfer sheet of the present invention, an ink is prepared in advance by dissolving the dye of the general formula (1) together with a binder in a medium or dispersing it in the form of fine particles, and the ink is prepared from a plastic film or paper. It is manufactured by coating on a sheet-shaped support and drying. As the binder for ink preparation, for example, cellulose-based, acrylic acid-based,
Water-soluble resin such as starch-based resin, acrylic resin, methacrylic resin, polystyrene resin, polycarbonate resin, polysulfone resin, polyester resin, polyethersulfone resin, ethyl cellulose and other organic solvent or water-soluble resin may be used alone or in combination. Used above.

Water as a medium for preparing the ink; alcohols such as methanol, ethanol, butanol;
Cellosolves such as methyl cellosolve and ethyl cellosolve; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; toluene,
Aromatic hydrocarbons such as xylene and chlorobenzene; Chlorine solvents such as methylene chloride, chloroform, dichloroethane and trichloroethane; Acetic acid esters such as ethyl acetate and butyl acetate; Ethers such as tetrahydrofuran and dioxane; N, N -Dimethylformamide,
Organic solvents such as N-methylpyrrolidone and dimethylimidazolidinone are used alone or as a mixture of two or more.

As the support to which the ink is applied for preparing the heat-sensitive transfer sheet, condenser paper, cellophane, or a plastic film having good heat resistance such as polyester, polyamide, polyimide or polyether sulfone is used.

The ink can be applied onto the support by using a bar coater, a roll coater, a knife coater, a gravure printing machine or the like. The thickness of the ink coating layer is 0.1 to 10 μm after drying, preferably 0.4.
It is applied so that the thickness becomes ˜5.0 μm. Next, the ratio of the dye to the binder and the medium is usually 0.5 to 15% by weight of the dye, 3 to 15% by weight of the binder, 70 to 96.5% of the medium, preferably 1 to 10% by weight of the dye. , 4 to 12% by weight of binder,
The medium is 78 to 95% by weight. However, this ratio does not restrict the present invention.

As the receiving sheet, paper coated with polyester resin or polyamide resin, synthetic paper such as polypropylene, polyvinyl chloride or polyester, and transparent sheets of synthetic resin such as polyester are usually used as the receiving sheet. You can use what you have.

[0015]

The present invention will be described in more detail by way of examples. In the examples, "parts" and "%" are parts by weight and% by weight, respectively.

Production Example 1 Formula (4)

[0017]

[Chemical 5]

33.2 parts of the compound (3) and 7.3 parts of malondinitrile are suspended in 500 parts of ethanol and reacted under reflux for 10 hours. After confirming the completion of the reaction, the mixture is cooled to room temperature and the crystals are separated by filtration. The obtained crystals are washed with ethanol, then with water and dried to obtain the following formula (5).

[0019]

[Chemical 6] 32.4 parts of the compound (mp. 275 ° C.) were obtained.

Production Example 2 16.2 parts of the compound of the formula (5) obtained in Production Example 1 was added to 30%.
Dissolve in 72 parts of sulfuric acid. Then, the reaction is performed at 100 to 105 ° C. for 10 hours. After confirming the completion of the reaction, the mixture is cooled to room temperature and neutralized with a 35% aqueous sodium hydroxide solution, and the crystals are filtered off. The obtained crystals are washed with water and dried to obtain the following formula (6).

[0021]

[Chemical 7] 15.4 parts of the compound (mp 273 to 275 ° C.) were obtained.

Example 1 1) Method of preparing ink An ink composition was prepared by treating a mixture of 2 parts of the dyestuff of Preparation Example 2, 6 parts of ethyl cellulose, 46 parts of toluene and 46 parts of methyl ethyl ketone for 3 hours using a ball mill. did. 2) Method for producing transfer sheet Using a bar coater, the above ink composition was applied to a polyethylene terephthalate (PET) film to give a dry film thickness of 1 μm.
To obtain a transfer sheet. The transfer sheet of this product was good with no crystal precipitation. 3) Method for producing receiving sheet The receiving sheet is 15 parts of polyester resin (Nippon Gosei Co., Ltd., product name: TP-220), amino-modified silicone (Shin-Etsu Chemical Co., Ltd., product name: KF393) 0.5.
Part, methyl ethyl ketone 20 parts, and xylene 10 parts were applied to a 150 μm synthetic paper (manufactured by Oji Yuka Co., Ltd., product name: FPG-150) to a dry film thickness of about 5 μm, and 100 ° C. for 30 minutes. Curing was performed to prepare a receiving sheet. 4) Transfer recording An ink applied surface of the transfer sheet is applied to the receiving sheet and a thermal head having a heating resistor of 250Ω at a density of 4 dots / mm from the back surface of the superposed transfer sheet.
When heating recording is performed under the condition that the printing time is 6 milliseconds, λmax =
Uniform recording was obtained with an extremely clear red color of 555 μm. As a result of measuring the color density with a densitometer RD-914 (manufactured by Macbeth, USA), the result was 1.28, which was excellent.

Examples 2 to 5 Inks were prepared in the same manner as in Example 1 using 2.0 parts of the dyes shown in Table 1, and then transfer sheets were prepared. Transfer recording was performed in the same manner as in Example 1 using these transfer sheets. The recordings with high color density shown in Table 1 were obtained.

[0024]

[Chemical 7]

[0025]

[Table 1] Table 1 Examples R ₁ R ₂ X Y ₁ Y ₂ λmax Color density 2 C ₂ H ₅ C ₂ H ₅ NH HH 552 1.26 3 C ₂ H ₅ C ₂ H ₅ NH H Cl 548 1. 25 4 C ₂ H ₅ C ₂ H ₅ NH Cl Cl 547 1.23 5 C ₂ H ₅ C ₂ H ₅ OH Cl 551 1.27 6 C ₂ H ₅ C ₂ H ₅ O Cl Cl 550 1.25 7 C ₄ H ₉ C ₄ H ₉ NH HH 552 1.30 8 C ₄ H ₉ C ₄ H ₉ OHH 556 1.32 9 C ₄ H ₉ C ₄ H ₉ NH H Cl 548 1.28 10 C ₄ H ₉ C ₄ H ₉ OH Cl 552 1.29 11 CH ₂ CHCH ₂ CH ₂ CHCH ₂ NH HH 545 1.31 12 CH ₂ CHCH ₂ CH ₂ CHCH ₂ OHH 548 1.33 13 CH ₂ CHCH ₂ CH ₂ CHCH ₂ NH H CH ₃ 546 1.30 14 CH ₂ CHCH ₂ CH ₂ CHCH ₂ OH CH ₃ 551 1.31 15 CH ₂ CHCH ₂ CH ₂ CHCH ₂ NH H OCH ₃ 547 1.30 16 CH ₂ CHCH ₂ CH ₂ CHCH ₂ OH OCH ₃ 550 1.30

[0026]

EFFECTS OF THE INVENTION By performing thermal transfer recording with a heat-sensitive transfer sheet containing a specific red dye according to the present invention, it is possible to obtain a red image having an extremely sharp color tone and excellent gradation and a high color density. Furthermore, since the color reproducibility is good and the light resistance, weather resistance and heat resistance are excellent, it is possible to record images with high storage stability.

Claims (1)

[Claims] 1. A general formula (1): (In the formula, R ₁ and R ₂ each independently represent a hydrogen atom, a linear or branched alkyl group (C _{1 to} C ₄ ), or an allyl group; X represents an imino group or an oxygen atom; ₁ , Y
_{And 2} each independently represent a hydrogen atom, a methyl group, a methoxy group or a halogen atom), and a thermal transfer sheet comprising an ink layer containing a benzopyran-based compound represented by the formula: