JPH0323992A - Thermal transfer recording material and preparation thereof - Google Patents

Abstract

PURPOSE:To achieve smooth gradation expression and certain medium contrast reproduction by forming the first ink layer on a support from an uniform film composed of a colorant-containing thermoplastic and/or heat-meltable resin and forming the second ink layer from an aggregate composed of colorant containing thermoplastic and/or heat-meltable resin fine particles. CONSTITUTION:The first ink layer 1 is formed to a support 2 using paint prepared by adding a colorant to a thermoplastic or heat-meltable resin (binder) using a solvent capable of dissolving said binder and the solvent is volatilized to form a uniform film. Next, the second ink layer 4 is applied and laminated to said film using ink paint composed of a dispersion prepared by dispersing the binder in a solvent not dissolving the binder. Therefore, the binder remains in a particulate state as it is after the dispersing solvent is volatilized and, as a result, film strength lowers. That is, there is difference between the cohesive forces of the first and second ink layers and the second ink layer separated from the support may result in cohesive failure more easily as compared with the first ink layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermal transfer recording material capable of reproducing good halftones depending on the printing energy level, and a method for manufacturing the same.

[Conventional technology]

In recent years, it has become possible to obtain Victorian color hard copies by thermally transferring sublimable dyes to special paper in response to a desired image signal. However, sublimable dyes and special paper are expensive, and furthermore, a considerable amount of thermal energy is required to thermally transfer the dye, which increases the size of the power supply, which in turn increases the size and cost of the device.

Furthermore, a color image can be obtained using a thermal transfer agent in which an ink layer containing a heat-melting binder and a coloring agent is provided on the base layer. In this case, there is an advantage that printing can be performed with lower energy than sublimation dye, and the recording material is not limited. However, when heating an ink layer, if the heating level is low to a certain extent, there will be almost no transfer, but if the temperature exceeds a certain level and exceeds the melting point or softening point of the ink layer,
All of the ink layer is suddenly transferred to the recording material, and the color density of the printed matter suddenly increases. Therefore, achieving gradation is limited to digital methods such as pseudo-area gradation.

With this method, even though the gradation is improved, the image appears grainy and the image quality is not sufficient for a Victorian hard copy.

Therefore, there is a need for gradation expression that can produce shading in each pixel.

[Problem that the invention is trying to solve]

The purpose of the present invention is to provide a heat-melting transfer recording material that takes advantage of the advantages of low-energy printing and low-cost recording materials, and a method for manufacturing the same. The objective is to achieve high image quality close to that of a silver halide hard copy by enabling smoother gradation expression and reliable halftone reproduction.

[Means to solve the problem]

The present invention provides a thermal transfer recording material having a first ink layer and a second ink layer in this order on a support, wherein the first ink layer is a thermoplastic and/or thermal ink layer containing a colorant. This is a thermal transfer recording material characterized in that it is a uniform film of meltable resin, and the second ink layer is an aggregate of thermoplastic and/or heat-meltable resin fine particles containing a colorant.

In particular, it is preferable to use a thermal transfer recording material in which the melting point of the resin forming the first ink layer is not lower than the melting point of the resin forming the second ink layer; The thermal transfer recording material is such that the resin forming the second ink layer is compatible with the resin forming the first ink layer at the interface between the two layers, and the resin forming the first ink layer has sufficient adhesion to the support. preferable.

Furthermore, the thermal transfer recording material described in item 2 is preferable, which is characterized in that it has an adhesive subbing layer between the first ink layer and the support for adhering both with sufficient adhesive force.

The present invention provides a method for manufacturing the above-mentioned thermal transfer recording material, that is,
A solution containing a colorant and a thermoplastic resin and/or a thermofusible resin dissolved therein is coated on a support and dried to form a first ink layer, and a colorant-containing thermoplastic resin fine particle and /or A thermal transfer recording material comprising applying a dispersion in which heat-melting resin fine particles are dispersed onto a first ink layer and then drying the fine particles under conditions that do not melt them to form a second ink layer. The first ink layer is formed on the support using an ink paint made by adding a coloring agent to a thermoplastic or heat-melting resin (hereinafter referred to as Hinter) using a solvent in which this binder is dissolved. When formed, the binder is uniformly dissolved, so that a uniform film is formed after the solvent evaporates.

Next, a second ink layer is coated and laminated on this first ink layer. The ink paint for the second ink layer uses a dispersion liquid in which painter is dispersed in a solvent that cannot dissolve ink paintr. The binder in the dispersion is in the form of particles, and after the dispersion solvent has volatilized, the binder remains in the form of particles unless it is melted under pressure or heat. Therefore, since the second ink layer formed from the dispersion coating has a non-uniform binder, the film strength is lower than that of the first ink layer which is a uniform film. That is, there is a difference in cohesive force between the first and second ink layers, and the second ink layer farther from the support is more likely to undergo cohesive failure than the first ink layer.

When the applied energy level is low, the second ink layer is exclusively transferred to the recording material, and as the impression level becomes higher, cohesive failure progresses toward the first ink layer, so that transfer recording is performed. do. As a result, cohesive failure, peeling, and transfer are performed in the thickness direction of the ink layer depending on the energy level of the printing process, and by changing the thickness of the transfer material for each pixel, it is possible to create shading in an analog manner. Tonal expression becomes possible.

The present invention will be specifically explained using figures. FIG. 1 is a conceptual cross-sectional view of a thermal transfer recording material 1 of the Wood invention, in which a first ink layer 3 and a second ink layer 4 are laminated on one side of a support 2. As shown in FIG.

As the support 2, conventionally known films and papers can be used as they are, such as polyester, polycarbonate, triacetylcellulose, polyamide, polyimide, plastic films with relatively good heat resistance, cellophane, etc. Alternatively, parchment paper, condenser paper, etc. can be suitably used. The thickness of the support is preferably about 2 to 15 microns when considering a thermal head as a heat source during thermal transfer, but for example, a heat source such as a laser beam that can selectively heat the thermal transferable ink layer is used. There are no particular restrictions when doing so. In addition, when using a thermal head, the surface of the support that comes into contact with the thermal head is coated with a heat-resistant material such as silicone resin, fluororesin, polyimide resin, epoxy resin, phenol resin, melamine jugeji, 21-cellulose, etc. By providing a protective layer, the heat resistance of the support can be improved, or it is also possible to use a support material that could not be used conventionally.

The binder of the first ink layer 3 includes natural waxes such as spermaceti wax, beeswax, lanolin, Carnaha wax, candelilla wax, montan wax, and ceresin wax, petroleum waxes such as paraffin wax and microcrystalline wax, oxidized waxes, etc. Ester wax, low molecular weight polyethylene, synthetic wax such as Fischer-Tropsch wax, higher fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid, higher alcohols such as stearyl alcohol and behenyl alcohol, and sucrose. Fatty acid esters, esters such as fatty acid esters of sorbitan, amides such as oleyl amide, polyamide resins, polyester resins, epoxy resins, polyurethane resins, polyurethane resins, polyolefin resins, polyacrylic resins, polyethylene resins Vinyl resin, cellulose resin,
Mix appropriate elastomers such as polyvinyl alcohol resin, petroleum resin, phenol resin, polystyrene resin, natural rubber, styrene-butadiene rubber, imprene rubber, chloroprene rubber, or extracting agent such as plasticizer, mineral extraction, or vegetable oil. The degree of melting, the melting viscosity, the adhesion to the support during heating recording, and the cohesive force as an ink layer can be adjusted to suit the head characteristics or drive system.

Furthermore, after coating the first ink layer 3 on the support, the film strength may be intentionally increased by heating to a temperature higher than the melting temperature of the binder to completely melt the entire ink layer.

If the thickness of the ink layer 3 is too thin, the density at high gradation levels will be insufficient. On the other hand, if it is too thick, the film strength will become higher than necessary in the future, and when a certain amount of high energy is applied, interfacial separation between the support and the ink layer will occur before cohesive failure occurs, and the ink layer will peel off before cohesive failure occurs. All the layers are transferred, and the print density suddenly increases from a certain level, making it impossible to produce halftones.

In view of the above, the thickness of the first ink layer 3 needs to be determined appropriately taking cohesive force, contact force, dissolution of the second ink layer 4 into the paint solvent, etc. Range is preferred.

It is desirable that the second ink layer 4 has some degree of compatibility with the first ink layer 3. The binder constituting the second ink layer 4 is made of the same thermoplastic or heat-melting material as the first ink layer 3, and its softening point or melting point is not higher than that of the binder of the first ink layer. preferable. After the paint of the second ink layer 4 is applied on top of 3,
Heat to a temperature sufficient to destroy the solvent alone, but not melt the binder resin particles.

1 0 If the Jf of the second ink layer is too thin, the gradation of the highlight 1 section will be insufficient, and if it is too thick, the total thickness of the ink layer will become thicker, and the heat conduction efficiency from the head will deteriorate, resulting in poor transfer. Efficiency decreases. In view of the above-12, the thickness of the ink layer 4 of the printer 52 is preferably in the range of 0.1 to 20 μm.

For producing the paint for the ink layer 4, the above-mentioned thermoplastic or heat-melting substances used for the paint of the ink layer 3 can be used. To prepare a dispersion of an ink hider resin, for example, in the case of a water-depleted liquid, an emulsifier may be added and the dispersion may be emulsified in water using an existing method such as a transfer method, a high-temperature emulsification method, or an ultrasonic dispersion method. The emulsifier can be selected from nonionic, anionic, cationic, etc. emulsifiers suitable for the system.

As the coloring agent, various dyes and pigments widely used in the field of printing and recording are used.

Specifically, for example, carbon black, nicrosine dye,
Lamp black, Sutan black SM, Fast yellow 0
1 Benzine Yellow, Pigmen 1...Erow, Indofirth 1...Orange, Dolphin 11 Gin Red, Paranitroaniline Rhett, Toluidine Rhett, Carmine Fli, Permanent Bordeaux Ii II R, Bigmen L...Orange R , Linur Red 2G, Rake Red O, Rhodamine Fl
1. Rhodamine B Lake, Methyl Violet B Lake, Phthalocyanine Blue, Pigment Blue, Prilliant Clean B, Phthalocyanine Clean, Oil Yellow GG, Pomelo Fast Yellow OGG, Kayaset Y9fi'3, Kayaset YG, Sumiplus 1
・・Ero GG, Pomelo First Orange RR, Oil Scarlet, Sumiblast Orange G, Orazole Brown B, Pomelo First Scarlet OG
All known dyes and pigments can be used, such as , Eisensbiron Red Blil+, Oil Bink OI), Victoria Blue F4R, First Gen Blue 5007, Sudan Flu, and Oil Beacock Blue.

Inclusion of colorants. lii° is 80% or less for each of ink layers 3 and 4, and 1 for the entire thermal transferable ink layer.
A range of ~80% is suitable. Further, each of the ink layers 1 2 1.2 may further contain a dispersant, a fine metal powder, a fine inorganic powder, a metal oxide, etc., if necessary. (Additives such as a filler consisting of () may be added as appropriate.

In order to obtain the thermal transfer recording material of the present invention, for the first component, the above-mentioned thermoplastic material and optionally a colorant and additives are melt-kneaded by passing through a dispersion device such as an attritor, or
Alternatively, it can be obtained by kneading with a suitable solvent to obtain a hot-melt ink or a solution or dispersion ink, which is coated on a support and dried if necessary.

How the thermal transfer material 1 reproduces halftones will be explained using diagrams. In FIG. 3, when the printing energy by the head is at a low gradation level, only the ink layer 4 is broken in the direction of the ink. As the printing energy level increases, the depth of this denting fracture position increases, and only the thickness of the imprinted ink becomes thicker, leading to an increase in the transfer density.

Next, when the stamping energy reaches a certain level or higher, the fourth
As shown in the figure, cohesive failure occurs in the ink layer 3. At this time, if the ink layers 3 and 4 are not compatible to some extent, delamination may occur between the ink layers 3 and 4 as shown in FIG. 5, and only the ink layer 4 may be transferred. In this case, when a higher gradation level printing density is required, it is necessary to turn the printing press 1'' until the ink layer 3 is completely transferred as shown in FIG.
, Then, as shown in FIG. 7, the print density increases rapidly, making it impossible to record halftones at high gradation levels.

That is, cohesive failure occurs in the ink layer 3 as shown in FIG. 4 because the ink layer 3 adheres to the ink layer 4 and is pulled by the ink layer 4 during one transfer and one recording, and at the same time, the ink layer 3 is not supported. This is because separation occurs within the ink layer 3 without being completely transferred because it is adhered to the body. In order for the ink layer 3 and the supporting layer 2 to have sufficient adhesive strength, an adhesive subbing layer 5 may be interposed between the ink layer 3 and the supporting layer 2 (FIG. 2).

As explained above, the present invention provides a thermal transfer recording material having two ink layers, one of which uses a solution paint to form the ink layer IA I++, and the other uses a liquid paint to form the ink layer. By layering the coating to maintain the strength of the film, the strength of the ink cohesive force has a gradient in the depth direction of the film, which improves the halftone reproducibility of the melt-type thermal transfer material. It is encouraging.

(Example) Length Example 1 Ink for the first ink layer Carbon black 30 parts Lanolin wax 15 parts Ethylene-vinyl acetate copolymer 5 parts Toluene
100 parts Ink for the second ink layer Carbon black 15 parts Ethylene wax emulsion 75 parts (solid content 20%
) Emulsion (solid content 20%, wax content 30%) pure water
20 parts The ink for the first ink layer was heated to 40°C and stirred for about 1 hour to dissolve the solid content, and then mixed in 15 ml of Santomil for 30 minutes to disperse carbon black. did. The second ink layer was similarly prepared by dispersing carbon black using a sand mill. The ink for the first ink layer is coated on a 6 μm thick PET film using a bar coater so that the dry film thickness is 3 μm! After 5 hours, it was heated in an oven at 45° C. for 1 hour. Thereafter, the ink for the second ink layer was applied onto the first ink layer using a bar coater to a dry film thickness of 6 μm, and heated in an oven at a temperature of 50°C for 1.5 hours to evaporate water. Ta.

Example 2 Ink for the first ink layer Carbon black 30 parts Lanolin wax 15 parts Ethylene-vinyl acetate copolymer 5 parts Toluene
100 parts Ink for second ink layer Carphone black 30 parts Ethylene wax emulsion 75 parts 1 6 (Solid content 20%) Emulsion Element (solid content 20%, wax content 30%) Pure water
23 parts Paint for adhesive Togawa layer Ethylene-vinyl acetate polymer 10 parts Toluene 100 parts Inks for the first and second ink layers were prepared in the same manner as in Example 1. In addition, the adhesive subbing layer paint was heated to 40°C for approximately 10 minutes.
Some are stirred for hours to dissolve. First, the adhesive undercoat layer coating material was applied to PUT film 7 in the same manner as in Example 1 so that the dry film J9 was 0.5 μm.
Heated for 1 minute at a temperature of 0°C. Next, the first ink layer, the second ink layer
The ink layers were applied and laminated in the same order as in Example 1.

Comparative Example Ink for the second ink layer used in Example 2 Ink for the second ink layer used in Example 2 Ink for the second ink layer used in Example 1 + 1VXT film! Second, coating, lamination, and drying were performed in the same manner as for the second ink layer of the example.

Using the ink sheets prepared in Examples 1, 2 and Comparative Example, the heating time (applied pulse width) for n gradation level was t = 2300 + 28 On [μs].
ec], written M L, written 'Jt A=A is Braco 1
- When using the set (Epson 8 IOO), 11 gradation characteristic +1゛ curves as shown in Figs. 8 to 10 were obtained.

Comparing Figures 8 to 10, in Figures 8 and 9 a smooth increase in density can be seen as the gradation level increases, but in Figures
In Figure 0, the gradation level rises rapidly at a lower gradation level, and the gradation range becomes narrower. In particular, Figure 8 and I
Regarding S I OIKJ, although the ink layer structure and the composition ratio of ethylene-vinyl acetate copolymer and waxes are almost the same, and the thermal properties such as melting point are almost the same, the first ink Non-uniform layer ink compared to solution paint
There was a difference in halftone reproducibility depending on whether the dispersion liquid 1 7 1 8 was used or not.

〔Effect of the invention〕

As described above, the thermal transfer recording material of the present invention can be used in Te11. Compared to flower-type thermal transfer materials, it is not only cheaper and more sensitive, but also allows for the expression of density gradations on a pixel-by-pixel basis, with good halftone reproducibility, which allows for the production of high-quality Victorian full-color images. You can get

[Brief explanation of the drawing]

Figure 1 and Figure S2 are cross-sectional views of the thermal transfer recording of the present invention, Figures 3 to 6 are schematic cross-sectional views showing how ink is transferred, and Figures 7 to 10 are schematic cross-sectional views showing the applied pulse width. FIG. 3 is a gradation characteristic west line diagram showing the relationship between print density. 1... Thermal transfer recording material 2... Support 3... First ink layer 4... Second ink layer 5... Adhesive subbing layer 1 9 ’7nD no vt1 or rM (psec) Fig. 8 Fig. 9 (V Toguchi J”X Lus vS (JJsec) Fig. 10

Claims (5)

[Claims] (1) A thermal transfer recording material having a first ink layer and a second ink layer in this order on a support, wherein the first ink layer is a thermoplastic and/or thermofusible ink layer containing a colorant. A thermal transfer recording material characterized in that it is a uniform film of resin, and the second ink layer is an aggregate of fine thermoplastic and/or heat-melting resin particles containing a colorant. (2) The thermal transfer recording material according to claim 1, wherein the melting point of the resin forming the first ink layer is not lower than the melting point of the resin forming the second ink layer. (3) The resin forming the first ink layer and the resin forming the second ink layer are compatible at the interface between the two layers, and the resin forming the first ink layer is supported. Claim 1 characterized in that it has sufficient adhesion to the body.
The thermal transfer recording material described in . (4) The thermal transfer recording material according to claim 3, further comprising an adhesive subbing layer between the first ink layer and the support for adhering both with sufficient adhesive force. (5) A solution containing a colorant and a thermoplastic resin and/or a thermofusible resin dissolved therein is coated on a support and then dried to form a first ink layer, and a solution containing a colorant and a thermoplastic resin is applied and dried. Thermal transfer, which involves coating a first ink layer with a dispersion in which fine particles and/or heat-melting resin fine particles are dispersed, and then drying the fine particles under conditions that do not melt them to form a second ink layer. Method of manufacturing recording material.