JPS61185492A - Thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To obtain highly concentrated image with high heat sensitivity and excellent shelf life and tone expression by providing a heat fusion type dye ink layer consisting of a special low melting substance and needle crystal pigment of mesh structure on a substrate. CONSTITUTION:A thermal transfer recording medium has a heat fusion type dye ink layer consisting of a low melting substance and needle crystal pigment which has a mesh structure constituted in the above substance. The low melting substance has a repeated structure of the general formula (I) and contains a thermoplastic polycaprolactan of number-average molecular weight of 1,000-100,000. The thermal transfer medium is contained in a transfer layer 2 with pigment 5 of needle crystal which is arranged in a mesh structure. a receptor sheet 3 is overlapped on a transfer sheet which has a transfer layer 2 on one side of a substrate 1, and pressed by a thermal head 4 to cause to melt a heat fusion type coloring ink in the transfer layer 2, and an image with tone is transferred onto the receptor sheet 3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal transfer medium, and particularly to a thermal transfer medium that melts and transfers ink by heating with a thermal head or the like to create a recorded image, and relates to a thermal transfer medium that has excellent gradation expression.

2. Description of the Related Art Conventionally, a method is known in which a transfer sheet having a layer of a heat-fusible substance and a pigment provided on a support is used as a heat-sensitive transfer medium, and an image is formed on a receiving sheet by thermal printing from the transfer sheet.

Most of the thermofusible materials used are natural and synthetic waxes.

However, a thermal transfer layer containing wax such as carnauba wax has the advantage of being highly sensitive to printing from a thermal head and being able to be melted and transferred quickly. It is unsuitable for expressing gradation by changing the amount of transfer, and the resulting printed image lacks sharpness, leading to distortion of characters during melt transfer.Furthermore, the adhesion strength to the copy sheet is weak, which makes the transfer difficult. causing unevenness,
Alternatively, if it is rubbed, it may stain the copy sheet.

Purpose This invention aims to provide a thermal transfer recording medium that has higher thermal sensitivity than conventional thermal transfer media, and is capable of producing high-a degree images with excellent storage stability and gradation expression. .

This invention relates to a heat-sensitive transfer recording medium having a heat-melting dye ink layer on a support, which is composed of a low-melting point substance and a pigment in the form of needle-like crystals forming a network structure therein. The low melting point substance has the following general formula (I) +CHz CH2CH2CH2CH2Co+n...(
I) A number-average molecule m i,oo having a repeating structure (in the formula, n indicates the number of repeating units).

The present invention is a thermal transfer recording medium characterized by containing thermoplastic polycaprolactone of ~100,000%.

In order to perform recording that can express gradation using the thermal transfer medium of the present invention, for example, as shown in FIG. 3 are overlapped and pressed by the thermal head 4 from above the support of the transfer sheet, the heat-melting colored ink of the transfer layer 2 melts and is simultaneously pressed against the receiving sheet 3, so the image in that area is transferred to the receiving sheet. be done.

In the heat-sensitive transfer medium of this invention, the needle-like crystal pigment 5 is transferred W4.
Since these crystals are arranged in a network structure as shown in FIG. 2, the binding force is strong and heat-fusible colored dyes and the like are held in the network portions. Therefore, the dye ink melted by the heat of the thermal head oozes out from between the network structures and gradually oozes onto the surface of the receiving sheet 3. The amount of this oozing varies depending on the thermal energy applied by the thermal head. Therefore, by controlling the applied thermal energy, the transferred color j can also be changed, and an image that faithfully represents the gradation can be obtained.

A feature of the present invention is that polybrocton having the repeating structure shown in the general formula (I) is used as the low melting point substance contained in the transfer layer 2.

The polycaprolactone used in the present invention forms a strong thin film and at the same time has a melting point of 40 to 70°C (determined by the number of repetitions of the unit.

) and has good properties in thermal transfer recording.

The polycaprolactone is a polyester resin, and ε
- prepared by ring-opening polymerization of caprolactone. Because it has a repeating structure of a single unit of a so-called methylene group and an ester group, it exhibits a melting point despite a high degree of polymerization compared to conventional polyethylene terephthalate-based polyesters, and reaches equilibrium at about 60 to 70°C. Table 1 shows the relationship between average molecular weight and melting point.

Table-1: Relationship between average molecular weight (mw> and melting point (mp) +1
1W mp(”C)10000
60-63.540000~60000
61-6470000~100.000
63-71 Furthermore, by repeating purification, it is possible to obtain a sharp melt; for example, by dissolving a substance with an average molecular fi of 10,000 in an appropriate organic solvent, such as tetrahydrofuran, and reprecipitating with ethanol. The melting point is 59.5-61°C.

Melt viscosity and elongation at break also increase with molecular weight, but in terms of clarity of transferred images, distortion of characters during melt transfer, and transferability, the molecular weight is about aooo-eoooo, preferably about 10,000 (90 in terms of repeating units). ) is optimal.

Furthermore, in order to strengthen the adhesion with the heat-resistant support, we added an average molecular weight of 70,000 to one with an average molecular weight of m 1oooo.
Good results can be obtained by adding 5 to 30% of ~ioo and ooo. Alternatively, styrene-butadiene rubber, ethylene-vinyl acetate copolymer with a softening point of about 80 to 110°C,
Vinyl chloride-vinyl acetate copolymer, ethyl cellulose,
Polyvinyl butyral and other backbone polyesters can also be used.

The thermal transfer layer in the present invention is made by blending the above-mentioned low melting point substance in a proportion of 99 to 60% and the coloring agent in a proportion of 1 to 40% of the total amount. It has improved strength, prevents deformation and scratches, has high melt transferability, and can prevent peeling from a heat-resistant support.

The thermal transfer layer in the present invention includes benzene, toluene, xylene, methyl ethyl ketone, carbon tetrachloride, methylene chloride, cyclohexanone, ethyl acetate, and tetrahydrofuran, respectively.

After being uniformly dissolved or dispersed in an organic solvent such as dioxane, dimethylformamide, or pyridine, it is applied onto a heat-resistant support and dried. The thermal transfer layer obtained in this way can contain multiple layers of colorants compared to a normal thermal transfer layer using wax, and therefore the thickness of the thermal transfer layer can be made thinner, and the resulting transferred image is also extremely clear. It will be excellent at the same time.

To further explain the pigment of the acicular crystals 5 used in this invention, the length of the acicular crystals is about 0.3 to 3 μm, and the width and thickness are 0.3 μm or less. Although this pigment essentially does not ooze out when heated like dye ink, it is safer to select and use a pigment that matches the color of the dye ink.

The appropriate thickness of the transfer layer is 2 to 8 .mu.m from the viewpoint of recording texture.

The amount of the needle-like crystal pigment added is 0 per part by weight of the dye.
．． The amount is 5 to 10 parts by weight, preferably 1 to 5 parts by weight.

Pigments that form such needle-like crystals are not limited to amorphous pigments, but also include organic pigments. Specific examples include: ocher, yellow lead G, phthalocyanine blue, lithore red, Bonmartone Rye 1~, white clay, acicular zinc oxide, 2.7-pis[2-hydroxy-3-( 2-chlorophenylcarbamoyl-9-fluorenone, 4",4"-bis[2-hydroxy-3-(2,4-dimethylphenyl)carbamoylnaphthalen-1-yl7zo)-1,4-distyrylbenzene, etc. However, any material can be used as long as the crystals are acicular and the crystals are arranged in a network structure in the transfer layer.

Pigments that form needle-like crystals form a network structure when an ink layer is applied to a support, but they do not require any special means for application; they can be formed by commonly used means. Just apply it.

Further, specific examples of the colored dyes used in this invention include the following. - It is suitable that the eutectic temperature of the hot-melt ink is 50 to 140° C., although it varies somewhat depending on the type of binder resin mixed together.

Examples of such dyes include the following direct dyes, acid dyes, basic dyes, mordant dyes, sulfur dyes, architectural dyes, azoic dyes, oil dyes, heat-sublimable disperse dyes, and the like.

1) Direct dyes: Direct Sky Blue, Direct Black W, etc.

2) Acid dye: tartrazine, acid violet 6
B, Acid Fast Red 3G, etc.

3) Basic dyes: safranin, auramine, crystal violet, methylene blue, rhodamine B1 Victoria blue B, etc.

4) Mordant dyes: Sunchromine Fast Alu MB1 Eriochrome Azurol B1 Alizarin Yellow B, etc.

5) Sulfur dye: Sulfur Brilliant Green 4G, etc.

6) Vat dye: Indanthrene blue, etc.

7) Azoic dye: Naphthol A8 etc.

8) Oil dye: Nigrosine, Spirit Black EB,
Varifast Orange 3206, Oil Black 215
, Butter Yellow, Sudan Blue ■, Oil Red 8
10-Damin B et al.

9) Heat-loving disperse dyes (9-1) Monoazo disperse dyes: Disbirds First Yellow G, Disbirds First Yellow 5G,
Disbirds First Yellow SR, Disbirds Red R, etc.

(9-2) Anthraquinone disperse dye: Disbird's First Violet OR, Disbird's First Violet B1 Disbird's Blue Extra, Disbird's First Brilliant Blue B, etc.

(9-3) Nitrodiphenylamine-based disperse dyes Disbird's Fast Yellow RR, Disbird's Fast Yellow GL, etc.

It is sufficient that the particle size of these dyes is smaller than that of the needle-like crystal pigment having a network structure, and it is preferable that the dye be in a dissolved state.

In the present invention, in addition to the thermal transfer composition, a plasticizer or wax, and even an extender pigment may be added if necessary. Examples of waxes include carnauba wax, montan wax, paraffin wax, and microcrystalline wax, and examples of plasticizers include dioctyl phthalate, tricresyl phosphate, dibutyl phthalate, etc. It is blended in a proportion of 10% or less.

Such plasticizers or waxes improve heat sensitivity. The extender pigments include, for example, silicic acid powder, calcium carbonate, magnesium carbonate, silicic acid, phosphorus, and white carbon, and these extender pigments are blended in a proportion of 30% or less of the total amount of the thermal transfer layer. be done. Such extender pigments improve melt transferability and improve the clarity of printing.

The support 1 in the present invention has a thickness of, for example, 3
Examples include polyester film, polypropylene film, polycarbonate film, cellulose triacetate film, polyimide film, glassine paper, condenser paper, etc. of about 20 μm.

Further, in order to firmly hold the molten ink layer (particularly the acicular crystal pigment) on the support, it is also possible to provide an intermediate adhesive layer using the following resin.

Examples of such resins include polyethylene, polypropylene, polystyrene, petroleum resin, acrylic resin,
Vinyl chloride resin, vinyl acetate resin, vinylidene chloride resin, polyvinyl alcohol, cellulose 3 resin, polyamide, polyacetal, polycarbonate, polyester,
Examples include fluororesin, silicone resin, natural rubber, chlorinated rubber, butadiene rubber, olefin rubber, phenolic resin, urea resin, melamine resin, epoxy resin, polyimide, etc.
Can be raised.

Example 1 (1) Preparation of transfer sheet (A-1) Sudan Blue II 10 parts 2.7-bis[2-hydroxy-3-(2-chlorophenylcarbamoyl) naphthalen-1-ylazo]-9-fluorenone ( Acicular crystal pigment) 10 parts Average molecular weight 2,000 Polycaprolactone 20 parts The above composition was sufficiently dispersed in a ball mill with 200 parts of dichloroethane, and then milled using a wire bar to a thickness of 6 μm.
Approximately 3.
A transfer layer having a thickness of 5 μm was formed.

By observing this surface with an electron microscope, it was confirmed that it had a network structure.

(2) Test of transfer sheet (A-1) The transfer layer of the transfer sheet (A-1) obtained in this way is stacked so that it faces the plain paper that is the receiving sheet, and heating energy is applied from the back side of the transfer sheet using a thermal head. When images were recorded with different values, a cyan image was recorded on the receiving sheet as shown in Table 1 below.

As shown in Table 1 above, it can be seen that the image density changes as the heating energy changes, making it possible to display different gradations.

Further, even after this recorded image was stored in a constant temperature bath at 60° C. for 5 oeR, the density of the recorded image hardly changed.

fruit/! IrA2 (1) Preparation of transfer sheet (A-2) Rhodamine B 10 parts 4=,4''-bis[2-hydroxy-3-(2,4-dimethylphenyl)carbamoylnaphthalen-1-ylazo]1,4- Distyrylbenzene 10 parts Average molecular weight 6,000 Polycaprolactone 10 parts The above composition was sufficiently dispersed in a ball mill with 200 parts dichloroethane, and then milled using a wire bar to a thickness of 6 μm.
The transfer layer was coated on a polyester film and dried to form a transfer layer with a thickness of about 4.5 μm.

Electron microscopic observation of this surface confirmed that it had a network structure.

(2) Test of transfer sheet (A-2) The transfer layer of the transfer sheet (A-2) thus obtained and the receiving sheet used in Example 1 were superimposed, and
When an image was recorded in the same manner as above, a magenta image was recorded on the receiving sheet. The results are shown in the table below.

It can be seen that gradation can be expressed in this case as well.

Example 3 (1) Preparation of transfer sheet (A-3) Butter yellow 10 parts Ocher (acicular crystal pigment) 10 parts Average molecular weight 110. O'00 20 parts of polycaprolactone The above composition was thoroughly dispersed with 200 parts of dichloroethane using a ball mill, and the thickness was 6 μm using a wire bar.
It is coated on the surface of a polyester film of about 4 m and dried.
A transfer layer having a thickness of μ was formed.

Electron microscopy of the surface of this transfer layer? Upon observation, it was observed that a network structure was formed.

(2) Test of transfer sheet <A-3) The transfer layer of the transfer sheet (A-3') thus obtained and the receiving sheet used in Example 1 were superimposed, and a thermal head was applied from the back side of the transfer sheet. When we recorded images by changing the heating energy, the results shown in Table 3 below were 1.
I was pissed.

As is clear from the table above, the image density changes in response to changes in heating energy, which indicates that gradation recording is possible.

Effects As is clear from the above explanation, in the thermal transfer medium of the present invention, ink oozes out from between the fillers (sword-shaped crystals) having a network structure, depending on the magnitude of heating energy.
Since the transfer is transferred to the first surface of the receiving sheet, by controlling the heating energy during transfer, it is possible to create a transferred image with excellent gradation expression. It is also possible to produce 1q color images by selecting dyes.

The thermoplastic polycaprolactone used in the present invention has a wax-like melting point and is a substance that forms a strong thin film, so it has excellent printing sensitivity and can form clear transferred images without background smudges. can.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is an explanatory diagram of transfer using the thermal transfer recording medium of the present invention, and FIG. 2 is a bottom view showing the structure of the heat-melting dye ink layer of FIG. 1. . DESCRIPTION OF SYMBOLS 1...Support, 2...Transfer layer, 3...Receiving sheet, 4...Thermal head, 5...Acicular crystal, 6...
・Coloring dye.

Claims (1)

[Scope of Claims] A heat-sensitive transfer recording medium having a heat-melting dye ink layer on a support comprising a low-melting point substance and a pigment in the form of acicular crystals forming a network structure therein; is the following general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. A thermal transfer recording medium characterized by containing thermoplastic polycaprolactone.