JPH03218894A - Thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To improve the sharpness of a character of the reproducibility of a dot even with respect to paper to be transferred low in surface smoothness by providing the first heat-meltable ink layer and the second ink layer having a porous discontinuous structure based on a thermoplastic resin on a base material. CONSTITUTION:The first heat-meltable ink layer is provided on a base material and the second ink layer having a porous discontinuous structure based on a thermoplastic resin is provided on the surface of the first ink layer. The first ink layer provided on the base material using a resin film such as a polyester film or paper such as condenser paper is constituted of a colorant and a heat-metable binder. As the thermoplastic resin of the second ink layer, an acrylic resin, a ketone resin, a petroleum resin, polyvinyl butyral or a vinyl chloride/vinyl acetate copolymer can be used and the porous discontinuous structure is formed by coating the first ink layer with a resin solution prepared by a thermoplastic resin in a solvent mixture consisting of a main solvent having high solubility to the thermoplatic resin and a separate solvent having low solubility to said resin and slower than the main solvent in evaporation speed and evaporating the solvents to precipitate the resin.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a thermal transfer recording medium such as a thermal ink ribbon, and more specifically, it relates to a thermal transfer recording medium such as a thermal ink ribbon. The present invention relates to a thermal transfer recording medium that enables transfer recording.

[Conventional technology]

In thermal transfer printers, thermal transfer recording media are conventionally known in which two or more ink layers are formed on a base material in order to enable transfer even to paper with low surface smoothness. This is because the cohesive force of the ink on the surface layer is increased, and the ink layer on the surface layer, which has been softened by the heat of the thermal head, adheres to the convex portions of the surface of the transfer paper, which is less smooth, and the cohesive force of the ink on the softened portions is increased. By covering the recesses on the paper surface and simultaneously transferring the lower ink layer thereon, even transfer paper with large recesses and low surface smoothness that cannot come into contact with the ink layer of the thermal recording medium can be uniformly transferred. It is possible to transfer ink to The surface ink layer of this conventional thermosensitive recording medium is mainly composed of thermoplastic resin, and this surface ink layer has a structure in which molecules of the thermoplastic resin, which is the main component, are densely continuous on the lower ink layer. It is coated. Therefore, when transferring to paper, the heat from the thermal head is conducted to the area around the heated area and the ink is softened, so the cohesive force between the resin molecules causes not only the area heated by the thermal head but also the area around it. There is a tendency to be pulled and transferred easily, and the surface ink layer at the boundary between the heated area by the thermal head and other areas has poor ink sharpness, resulting in areas where the ink is thread-like or flat and stands on the paper surface. As a result, the clarity of characters and the reproducibility of dots are poor, and the ink standing on the paper surface breaks off and scatters due to rubbing, etc., resulting in problems such as staining of the paper surface.

[Problem to be solved by the invention]

An object of the present invention is to solve the above-mentioned problems, and to obtain high-quality transfer recording with good character clarity, dot reproducibility, and sharp ink even on transfer paper with low surface smoothness. It is an object of the present invention to provide a thermal transfer recording medium that can be used as a heat-sensitive transfer recording medium.

[Means to solve the problem]

The present invention provides a thermal transfer recording medium comprising a first heat-melting ink layer on a base material, and a second ink layer having a porous discontinuous structure mainly composed of a thermoplastic resin on the surface layer. It is.

In order to make this outermost second ink layer have a porous and discontinuous structure, for example, the thermoplastic resin for the second ink layer is
A resin solution that is dissolved in a mixture of a main solvent that has high solubility for the resin and another solvent that is compatible with the main solvent, has low solubility for the resin, and has a slower evaporation rate than the main solvent,
coating on the first ink layer and evaporating the solvent;
This is achieved by precipitating the resin. In other words, the main solvent of the applied resin solution evaporates quickly, the proportion of the solvent with low resin solubility increases, the resin dissolving power of the solution decreases, and the resin molecules aggregate in the solution in the form of fluff and precipitate. However, as the solvent evaporates, a porous and discontinuous structure is formed.

As another method for forming the second ink layer into a porous and discontinuous structure, a similar result can be obtained by mixing a foaming agent into the coating ink and coating it.

As the thermoplastic resin of the second ink layer, acrylic resin,
Ketone resin, petroleum resin, polyvinyl butyral, vinyl chloride vinyl acetate copolymer resin, etc. can be used.

Further, colorants, softeners, dispersants, etc. can be added to these as necessary. The thickness of the second ink layer is 0.1-10
μm is appropriate.

As the base material, a resin film such as polyester or paper such as capacitor paper can be used, and the thickness thereof is 1 to 2.
Approximately 0 μm is appropriate. In order to improve heat resistance and slipperiness, a back surface treatment layer of silicone resin or the like may be provided on the surface opposite to the ink layer.

The first ink layer provided on the base material is composed of a colorant and a heat-melting binder that have been conventionally used in thermal transfer recording media.

Various dyes and pigments can be used as colorants.

As the heat-melting binder, various waxes such as paraffin wax, polyethylene wax, and carnauba wax, and easily heat-melting thermoplastic resins such as ethylene-vinyl acetate copolymer and ethylene-ethyl acrylate copolymer may be used alone or in combination. A mixture of the above is used.

Additives such as softeners and dispersants may be added as necessary.

The thickness of the first ink layer is suitably 1 to 10 microns.

Further, a release layer can be provided between the base material and the first ink layer.

[Effect]

In the thermosensitive recording medium of the present invention, since the second ink layer in the surface layer has a porous discontinuous structure, the thermal conductivity in the ink layer in the surface layer decreases, and the bonding force in the ink layer in the surface layer weakens.

When the image is transferred to paper having a low surface smoothness, the following operation occurs. First, the heated part of the second ink layer on the surface layer by the thermal head softens and becomes a continuous structure with adhesive strength, and when the softened part faces the convex part on the surface of the transfer paper and adheres, The part facing the four parts of the surface of the transfer paper in the softened part is pulled by the cohesive force between the resin molecules of the softened ink, and the ink is transferred to the four parts, covering the uneven part, and then it is heated by the thermal head. At the same time, the melted lower ink layer is transferred, and the heated portion is uniformly transferred onto the uneven portions of the transfer paper.

As mentioned above, the surface second ink layer has low thermal conductivity within the ink layer and the bonding force within the surface ink is weak, so the area around the heated part by the thermal head is difficult to soften and maintains a discontinuous structure. Therefore, the so-called sharpness of the ink becomes better at the boundary between the heated part and other parts, and therefore the clarity of characters and the reproducibility of dots are improved.

〔Example〕

The present invention will be specifically explained below with reference to Examples.
The present invention is not limited in any way by this example.

(Example 1) FIG. 1 shows an enlarged cross-sectional elevational view of a thermal transfer recording medium of Example 1. 1 is a polyester resin film as a base material;
The thickness is 6 μm. On top of that is a heat-melting ink layer (first
Ink layer) 2 was provided.

It is made by adding pigments, softeners, and dispersants to paraffin wax. The thickness is 3μ.

In the present invention, a second ink layer 4 is provided on this heat-melting ink layer. For this second ink layer, a resin solution consisting of 20 parts by weight of styrene-acrylate copolymer, 40 parts by weight of methyl ethyl ketone (MEK), and 40 parts by weight of isopropyl alcohol (IPA) was prepared, and this was applied on the first ink layer. It was coated to a thickness of 1μ and dried.

When this thermal ink ribbon was applied to transfer paper with low surface smoothness, the ink was sharp, the characters were clear, and the reproducibility of dots was also good.

(Example 2) FIG. 2 shows an enlarged cross-sectional elevational view of a thermal transfer recording medium of Example 2. 1 is the base material capacitor paper, and the thickness is 10
μ.

On top of that, a release layer 3 of silicone resin is provided, the thickness is 1 μm.
It is.

On top of that, pigment, softener, ethylene vinyl acetate copolymer,
Hot-melt ink layer containing a dispersant (first ink layer)
2 was established. The thickness is 5μ.

In the present invention, a second ink layer 4 is provided on this heat-melting ink layer. The thickness is 2μ. This second ink layer is obtained by coating and foaming a vinyl chloride-vinyl acetate copolymer resin to which a foaming agent is added, and further a colorant, a softener, and a dispersant are added.

When this thermal ink ribbon was applied to transfer paper with low surface smoothness, the ink was clean and the characters were clear, and the paper surface did not become stained even if the surface was rubbed after transfer.

〔Effect of the invention〕

In the thermal transfer recording medium of the present invention, the second ink layer as the outermost layer has a discontinuous structure, has low thermal conductivity, and has weak bonding force within the ink. The so-called sharpness of the ink is extremely good at the boundary with other parts, so even on transfer paper with a low surface smoothness with a Bekk smoothness of 30 seconds or less, it is a high-quality product with excellent character clarity and dot reproducibility. Transcript records are now available.

[Brief explanation of drawings]

FIG. 1 is an enlarged cross-sectional elevational view of a thermal transfer recording medium of the present invention corresponding to Example 1 and FIG. 2 corresponding to Example 2. DESCRIPTION OF SYMBOLS 1...Base material, 2...Thermofusible ink layer (first ink layer), 3...
・Release layer, 4... second ink layer

Claims (1)

[Claims] A thermal transfer recording medium comprising a first heat-melting ink layer on a base material, and a second ink layer having a porous discontinuous structure mainly composed of a thermoplastic resin on the surface layer.