JP2731399B2 - Thermal transfer recording medium - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer recording medium provided with a thermal transfer layer on a heat-resistant substrate, and more particularly to a thermal transfer recording medium capable of transferring a plurality of times.

[Prior Art] A thermal transfer recording medium that can be transferred a plurality of times is already known. For example, a non-transferable resin layer having a microporous network structure made of a heat-resistant resin is formed on a substrate, and the resin layer is impregnated with a hot-melt ink composed of a vehicle and a dye incompatible with the resin. (Japanese Patent Publication No. 60-20198),
A porous resin containing an oil and a wax having an incompatibility with an oil having a good compatibility with a lanolin fatty acid metal salt or ester (Japanese Patent Application Laid-open No. Sho 62-160284). (Japanese Patent Application Laid-Open No. 61-47296) using an immiscible ink.

[Problems to be Solved by the Invention] However, even though these conventional microporous resin type thermal transfer recording media can be printed a plurality of times, when the number of times of printing overlaps, the density drops remarkably, In the case of printing, there is a disadvantage that so-called total transfer occurs in which the entire resin layer is transferred.

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermal transfer recording medium capable of performing a plurality of transfers without such a defect.

[Means for Solving the Problems] The thermal transfer recording medium of the present invention is provided with a microporous layer of a polymer substance on a heat-resistant base material, a wax component, a coloring component, and a compound represented by the following general formula: It is characterized by containing the compound represented by (I).

(In the formula, R ₁ and R ₂ each independently represent an alkyl group having 1 to 20 carbon atoms.) In the present invention, although the action mechanism of the above compound is not clear, it is printed several times that the compound has an appropriate supercooling property. It is thought to have contributed to the function of. That is, the surrounding ink replenishes the portion where the ink has been lost in the first printing. At this time, if there is no supercooling property, the ink fluidity is lost and the replenishment is not performed smoothly. Also,
It has been proposed to add oils in order to express such supercooling properties of the ink. However, adding oil which is liquid at normal temperature causes soiling.

Specific examples of the compound (I) include the following. The melting point is preferably 60 to 120 ° C.

Examples of the wax component used in the present invention include natural waxes such as paraffin wax, polyethylene wax, candelilla wax and carnauba wax, and synthetic waxes.

As the colorant used in the present invention, among organic or inorganic dyes or pigments, those having suitable properties as a recording material are preferable. For example, having a sufficient coloring density,
Those which do not change due to light, heat, temperature and the like are preferable.
In addition, a substance which is colorless when not heated but develops a color when heated, or a substance which develops a color when it comes into contact with a substance applied to a transfer receiving body may be used.

As the support of the thermal transfer recording medium of the present invention, for example, polyester, polycarbonate, triacetyl cellulose, nylon, other than a relatively heat-resistant plastic film such as polyimide, glassine paper, capacitor paper, metal foil and the like and A composite of materials can be exemplified.

Examples of the composite include an aluminum / paper composite,
Metal-deposited paper or metal-deposited plastic film can be used. When considering the head as a heat source at the time of thermal transfer, the thickness of the support is desirably about 2 to 15 microns.For example, when using a heat source that can selectively heat the heat transferable ink layer such as laser light Is not particularly limited. When using a thermal head, provide a heat-resistant protective layer made of silicone resin, fluorine resin, polyimide resin, epoxy resin, phenol resin, melamine resin, nitrocellulose, etc. on the surface of the support that comes into contact with the thermal head. Thereby, the heat resistance of the support can be improved, or a support material that could not be used conventionally can be used.

The weight ratio of the compound of the formula (I) to the wax component is preferably from 1: 9 to 9: 1, and more preferably from 3: 7 to 7: 3. The weight ratio of the colorant to the total of the compound of the formula (I) and the wax component is preferably 8: 1 to 3: 1, more preferably 6: 1 to 4: 1.

Further, as the polymer substance used in the present invention, polyvinyl chloride, polyvinyl acetate, polyvinyl butyral, polyvinylidene chloride, vinyl chloride / vinyl acetate copolymer, vinyl chloride / vinylidene chloride copolymer, polyacrylic acid ester, In addition to various vinyl polymers or copolymers such as polymethacrylic acid ester, polystyrene, styrene / methacrylic acid copolymer, ethylene / vinyl acetate copolymer, polyolefins such as polyethylene and polypropylene, further, polyester, polyamide, gelatin, Gum arabic and fibrous resins such as ethylcellulose are exemplified. These polymer substances are used alone or in the form of a mixture.

In the present invention, the weight ratio of the polymer substance to the total of the compound of the formula (I), the wax component and the colorant is preferably from 4: 1 to 1: 4, more preferably from 3: 2 to 2: 3. is there.

The compound of the general formula (I) described above, a wax component,
Next, a method for producing a thermal transfer recording medium using a colorant, a polymer substance, and a support will be described.

An ink dispersion is prepared by dispersing the compound of the formula (I), the wax component, and the colorant in a predetermined ratio in an appropriate solvent.

Next, the polymer substance is dissolved in an appropriate solvent to prepare a polymer solution.

The ink dispersion and the polymer solution may be mixed at a predetermined ratio, applied to one surface of the support by an appropriate coating method, and dried.

[Example] Hereinafter, the present invention will be described in detail with reference to examples.

Example 1 An ink dispersion having the following formulation was prepared.

(Ink dispersion liquid) Carbon black 1.02 g Candelilla wax 2.55 g Bis (N-stearyl, N-cyclohexyl) phthalic acid amide (Compound of specific example No. 4 mp: 71-73 ° C.) 1.53 g Methyl ethyl ketone 16.6 g Toluene 8.3 g Next, a polymer solution having the following formulation was prepared.

(Polymer solution) 10 g of vinyl chloride / vinyl acetate copolymer [molar ratio 88:12] 40 g of methyl ethyl ketone 7.02 g of the above ink dispersion and 2.98 g of the polymer solution were mixed.
A heat-transfer recording medium (A) was prepared by coating a 3.5 μm thick polyester film having a heat-resistant layer on the back surface with a wire bar so as to have a coating thickness of 10 μm and drying.

Example 2 A thermal transfer recording medium (B) was prepared in the same manner as in Example 1 except that the formulation of the ink layer dispersion liquid was changed as follows.

(Ink dispersion liquid) Carbon black 1.02 g Candelilla wax 2.55 g Bis (N-octyl, N-cyclohexyl) phthalamide (Compound of specific example No. 3 mp: 80-81 ° C.) 1.53 g Methyl ethyl ketone 16.6 g Toluene 8.3 g Comparative Example 1 A thermal transfer recording medium (C) was prepared in the same manner as in Example 1 except that the formulation of the ink dispersion liquid was changed as follows.

(Ink dispersion liquid) Carbon black 1.02 g Candelilla wax 4.08 g Methyl ethyl ketone 16.6 g Toluene 8.3 g Using the thermal transfer recording materials (A) to (C) obtained as described above, a bar code printer manufactured by Autonics Co., Ltd. BC−
8, solid black printing was performed at a head energy of 7.6 mJ / mm ² . This solid black printing was repeatedly performed at the same place using the same thermal transfer recording medium. NA-55 manufactured by Kanzaki Paper was used as the receiving paper. Table 1 shows the results. The transfer image density was measured with a Macbeth densitometer.

Comparative Example 2 A thermal transfer recording medium (D) was prepared in the same manner as in Example 1 except that the formulation of the ink dispersion liquid was changed as follows.

(Ink dispersion liquid) Carbon black 1.02 g Candelilla wax 2.55 g Silicone oil 1.53 g Methyl ethyl ketone 16.6 g Toluene 8.3 g [Effects of the Invention] As described above, the thermal transfer recording medium according to the configuration of the present invention can print a plurality of times with a small decrease in density.

Claims (1)

(57) [Claims] 1. A microporous layer of a polymer substance is provided on a heat-resistant substrate, and the porous layer contains a wax component, a coloring component and a compound represented by the following general formula (I). A thermal transfer recording medium characterized by the above-mentioned. (Wherein, R ₁ and R ₂ each independently represent an alkyl group having 1 to 20 carbon atoms)