JPS6221587A - Thermal transfer material and production thereof - Google Patents

Abstract

PURPOSE:To ensure that sharp printing with high density can be performed even on a recording medium having poor surface smoothness, by a method wherein one ink layer is constituted of fine particles of a heat-fusible resin and a non-particulate phase, and the other ink layer is constituted of different non-particulate phases of heat-fusible materials. CONSTITUTION:The first ink layer 3 and the second ink layer 4 comprising respective heat-fusible materials are provided on a sheet form base 2 to obtain the thermal transfer material 1. The first ink layer 3 is constituted of two kinds of non-particulate heat-fusible binder phases-kind A (indicated by solid circles) and kind B (indicated by hollow circles). The second ink layer 4 comprises one or more kinds each of domains constituted respectively of fine particles C of a heat-fusible resin and a non-particulate heat-soluble binder phase D. In the two or more kinds of domains, mutual fusing and homogenization proceed at a patternwise heated part, whereby a latent record image with high cohesive force is formed, and an adhesive force for adhesion of the image to a recording medium can be generated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a thermal transfer material that can provide a transferred recorded image with good print quality even on a recording medium with poor surface smoothness during thermal transfer recording. and its manufacturing method.

[Conventional technology]

In addition to the general features of thermal transfer recording methods, such as the equipment used is light, compact, noiseless, and has excellent operability and maintainability, the thermal transfer recording method does not require colored processed paper, and It has the feature of excellent durability of recorded images, and has been widely used recently.

This heat-sensitive transfer recording method uses a heat-sensitive transfer material in which a heat-transferable ink layer consisting of a colorant dispersed in a heat-melting binder is coated on a support, which is generally in the form of a sheet. is superimposed on the recording medium so that its thermally transferable ink layer is in contact with the recording medium, and heat is supplied from the support side by a thermal head to transfer the melted ink layer onto the recording medium, thereby supplying heat to the recording medium. shape (pattern)
It forms a transferred recorded image according to the

However, in conventional thermal transfer recording methods, the transfer recording performance, that is, the print quality, is greatly affected by the surface smoothness of the recording medium. In the case of media, there is a problem in that print quality is significantly degraded. For this reason, paper with high surface smoothness is generally used as a recording medium, but paper with high smoothness is rather special, and paper usually has various degrees of unevenness due to the entanglement of fibers. Therefore, in the case of paper with large surface irregularities, the hot melted ink cannot be transferred to the entire recording area of the paper during printing, but only penetrates and adheres to the convex parts of the surface or the vicinity thereof, resulting in sharp edges of the printed image. The image may be missing, or part of the image may be missing, resulting in a decrease in print quality.

Conventionally, in order to obtain a recorded image of good print quality on such a recording medium with poor surface smoothness, it has been necessary, for example, to use heat-melting binder with a low melt viscosity in at least the surface layer, or to use thermal transfer technology. This method was based on the idea that by increasing the thickness of the molten ink layer, the molten ink could faithfully adhere to or penetrate into the fine uneven structure of a recording medium such as paper.However, If a binder with a low melt viscosity is used, the ink layer becomes sticky even at relatively low temperatures, resulting in decreased storage stability, staining of non-printing areas of the recording medium, and smearing of transferred images. If the thickness of the transferable ink layer is increased, bleeding becomes larger and it is necessary to increase the amount of heat supplied from the thermal head, resulting in a decrease in printing speed.

[Problems to be solved by the invention]

The present invention solves the conventional problems, maintains various thermal transfer performances, and improves density not only for recording media with good surface smoothness, but also for recording media with poor surface smoothness. The present invention was made in order to provide a heat-sensitive transfer material that can provide high-quality and sharp prints.

The present invention has also been made to provide a novel method that can advantageously produce a thermal transfer material having the above-mentioned excellent characteristics.

[Means for solving problems]

That is, the thermal transfer material provided by the present invention is a thermal transfer material having a first ink layer and a second ink layer each containing a heat-melting material on a support -1- in order from the support side. In the first ink layer, two or more types of domains are formed by the heat-fusible material It, at least one of the domains is constituted by heat-fusible resin fine particles, and at least one of the other domains is formed of the heat-fusible material It. A layer A in which one type of domain is constituted by a non-particulate phase, and two or more types of domains are formed by the thermofusible material, and each domain is constituted by a different type of non-particulate phase. Which of the layers consists of the layer B and the layer Ii
The second ink layer is comprised of a layer different from the first ink layer among the layer A and the layer B.

In addition, the method for manufacturing the thermal transfer material of the present invention, which has been discovered as a novel method that can advantageously manufacture the thermal transfer material of the present invention having the above-mentioned structure, comprises forming the layer A with two or more different types of After applying a coating liquid containing a mixture of hot-melt resin fine particle dispersion as a main ingredient, the coating liquid is heated to a temperature between the lowest softening temperature and the highest softening temperature of the softening temperature of the hot-melt resin fine particle group. or/and after coating the layer B with a coating liquid containing a mixture of two or more different types of heat-melting resin fine particle dispersions as a main ingredient, the coating liquid is dried at the above-mentioned temperature. It is characterized in that it is provided by drying at a temperature higher than the highest softening temperature among the softening temperatures of the group of meltable resin fine particles.

[Detailed description and examples of the invention]

In the thermal transfer material of the present invention, since the heat-fusible material forms two or more types of domains in the first and second ink layers, the cohesive force within the ink layer is greater than that of a homogeneous system. It can be reduced to 1". These two or more types of domains proceed to fuse and become homogenized in the pattern heating section, forming a recorded latent image with high cohesive force, and the adhesive force that acts as the adhesive force of the recorded latent image to the recording medium. can occur. In addition, since it is composed of two or more types of domains, there are domains with different functions or physical properties, such as hot adhesion strength or cohesive force, so each function or physical property is expressed less than in the case of a homogeneous system. It can be made easy. In this way, in the first and second ink layers, there is a large difference in cohesive force between the heat application section (pattern heating section) and the non-heating section, which is a factor in obtaining a clear recorded image. Furthermore, when the first ink layer contains a heat-fusible material, it becomes possible to use a material with high cohesive force that cannot be used in a homogeneous system. Moreover, since it is a non-uniform system, the difference in cohesive force becomes clear when heat is applied, and a clear recorded image with good print quality can be obtained. The first ink layer further has a function of controlling the adhesion of the recorded image to the support when heat is applied. As a result, the thermal transfer material according to the present invention can form a recorded transfer image with good print quality even on a recording medium with poor surface smoothness.

The present invention will be explained in more detail below. In the following description, "%" and "part" expressing quantitative ratios are based on weight unless otherwise specified.

FIG. 1 and FIG. 2 respectively show one part of the thermal transfer material of the present invention.
FIG. 3 is a schematic cross-sectional view in the thickness direction showing an example.

In the present invention, a domain is a heterogeneous system with a composition,
An area that can be distinguished from others based on its physical properties.

The heat-sensitive transfer material 1 shown in FIGS. 1 to 5 has a first ink containing a heat-fusible material on a support 2-A, usually in the form of a sheet. It has a layer 3 and a second ink layer 4.

In the thermal transfer material 1 shown in FIG.
The two types of non-particulate phases (with hollow circles) are composed of, for example, a non-particulate heat-fusible binder phase.

In the second ink 4, domains of one type -1- are formed by heat-melting resin fine particles C and a non-particulate phase such as a non-particulate heat-melting binder phase. The thermofusible resin fine particles C may form domains by means of a structure, or may form domains by aggregation of higher order. Furthermore, two or more types of domains may be formed using different thermofusible resin fine particles C. Similarly, the non-particulate phase may form two types of domains in a phase-separated state, for example.

In the thermal transfer material 1 shown in FIG. 2, the first ink layer 3 is composed of a layer similar to the second ink layer 4 in the example shown in FIG. is composed of the same layer as the first ink layer 3 in the example shown in FIG.

Note that the term "thermofusibility" as used in the present invention means a property of melting and becoming liquid when heat is applied, or a property of softening by heat and exhibiting adhesive strength or adhesive strength.

At least one of the first ink layer 3 and the second ink layer 4
In addition to containing a coloring agent as necessary, each layer may also contain various additives such as a plasticizer and an oil agent.

As the support 2, conventionally known films and papers can be used as they are, such as films of relatively heat-resistant plastics such as polyester, polycarbonate, triacetylcellulose, polyphenylene sulfide, polyimide, cellophane, or parchment paper. , condenser paper, etc. can be suitably used. The thickness of the support should be 1 when considering a thermal head as a heat source during thermal transfer.
It is desirable that the thickness be about 15 microns. In addition, when using a thermal head, a heat-resistant protective layer made of silicone resin, fluororesin, polyimide resin, epoxy resin, phenol resin, melamine resin, acrylic resin, nitrocellulose, etc. is applied to the surface of the support that comes into contact with the thermal head. By providing this, the heat resistance of the support can be improved, or a support material that could not be used conventionally can be used.

The thermofusible resin constituting the thermofusible resin fine particles includes:
Wax, low molecular weight polyethylene, polyolefin resins such as ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, polyamide resin, polyester resin, epoxy resin, polyurethane resin, acrylic resin, polyvinyl chloride Fine particles of elastomers such as polyvinyl acetate resin, petroleum resin, phenol resin, polystyrene resin, styrene-butadiene rubber, and imprene rubber are used.

Examples of the heat-melting binder include waxes such as carnauba wax, paraffin wax, Sasol wax, microcrystalline wax, and castor wax, stearic acid, valmitic acid, lauric acid, aluminum stearate, lead stearate, barium stearate, Higher fatty acids such as zinc stearate, zinc palmitate, methyl hydroxystearate, glycerol monohydroxystearate, or their metal salts, derivatives such as esters, polyamide resins, polyester resins,
Extremely high molecular weight epoxy resins, polyurethane resins, acrylic resins (e.g. polymethyl methacrylate,
Polyacrylamide), vinyl acetate resins, vinyl resins including polyvinylpyrrolidone, polyvinyl chloride resins (e.g. vinyl chloride-vinylidene chloride copolymer, vinyl chloride-vinyl acetate copolymer, etc.), cellulose resins (e.g. methylcellulose, ethylcellulose, carboxycellulose, etc.), polyvinyl alcohol resins (e.g. polyvinyl alcohol, partially saponified polyvinyl alcohol, etc.), petroleum resins, rosin derivatives, coumaron-indene resins, terpene resins, novolak type phenols resins, polystyrene resins, polyolefin resins (e.g., polyethylene, polypropylene, polybutene, ethylene-vinyl acetate copolymers, etc.), polyvinyl ether resins, polyethylene glycol resins, and elastomers, natural rubber, styrene-butadiene rubber, Examples include inbrene rubber.

The softening temperature of the hot-melt binder is 40°C to 150°C,
Preferably it is in the range of 60°C to 140°C. Further, it is preferable that the melt viscosity is 20,000 to 200,000 centiboise (rotational viscometer) at 150°C.

These thermofusible resin particles and thermofusible binder are
Each of them can be used alone or in combination of two or more.

The thermofusible resin fine particles can be produced by polymerization processes such as emulsion polymerization and suspension polymerization, by mechanically dispersing the thermofusible resin using a dispersant, etc., by low-mechanical pulverization, by spray drying, by precipitation, etc. Among those obtained in
℃ is used. Note that the softening temperature here is
Load 1 using thermal flow tester CFT-500
This refers to the temperature at which the sample begins to flow out, measured under the conditions of 0 kg and a temperature increase rate of 2° C./min.

The average particle diameter of the heat-melting resin fine particles is 20 JLm or less (
~0.01gm), and even less than 10 (~0.1gm
degree) is preferable.

If it exceeds 20 gm, it is too large and the particle size may be the same as the ink layer thickness. In this case, voids are likely to occur in the recorded latent image when the particles are fused to adjacent particles by heat application, resulting in poor transferability, which is undesirable. Further, for this reason, it is not preferable that the particle diameter and the ink layer thickness are the same. The quantitative ratio of the domains in the second ink layer varies depending on the functions and physical properties expressed by each domain, and is not particularly determined.

The layer thickness of the first ink layer is 0.5 to 10 gm, the layer thickness of the second ink layer is 0.5 to 20 gm, and further 1 to 10 p.
The total thickness of the first and second ink layers is preferably 2 to 25 gm. If the thickness of the second ink layer is as thin as less than 0.5 pLm, the film properties of the latent image formed by heat application and the fusion of fine particles will become weak, and if it exceeds 20 JLm, the fine particles will become thin as a whole. This is not preferable because it is difficult to achieve uniform fusion.

The first ink layer in the example shown in FIG. 1 or the second ink layer in the example shown in FIG. By dispersing finely pulverized substances, coating them on the first ink layer, drying them by heating, and melting them, ethylene-vinyl acetate copolymer resins, vinyl acetate resins, cellulose resins, polyacrylic resins, etc. It is obtained by applying a combination of incompatible materials among hot-melt binders on the first ink layer in the form of a hot-melt mixture, solution, etc., and subjecting it to heat treatment to cause phase separation. .

In addition, as a method different from these methods, after suitably mixing and coating a dispersion of two or more types of thermofusible resin fine particles, such as a tree emulsion, a method higher than the highest softening temperature of the softening temperatures of the fine particles Particularly preferred is a method in which the layer is formed by drying at high temperature to remove the dispersion medium. In this case, colorants, additives, and the like, which are added as necessary, can be included in the dispersion or inside the fine particles.

The second ink layer in the example shown in FIG. 1 or the first ink layer in the example shown in FIG. It is provided by applying a coating liquid containing colorants, additives, etc. to be added by a conventional method, and subjecting it to heat treatment if necessary.

In order to cause the hot-melt resin fine particles to remain in the ink layer in particulate form, the coating liquid is usually heated at a temperature below the softening temperature of the hot-fusible resin fine particles when forming the ink layer.

Among these, in particular, two or more types of fine particles are selected from among the above-mentioned hot-melt resin fine particles, and a dispersion of these particles, for example, a resin emulsion, is appropriately mixed and coated. Particularly preferred is a method in which the layer is formed by drying at a temperature between the softening temperature and the maximum softening temperature to remove the dispersion medium. In this case as well, colorants, additives, etc., which are added as necessary, can be included in the dispersion or inside the fine particles. By this method, fine particles whose drying temperature is higher than the softening temperature form a non-particulate phase, and fine particles whose drying temperature is lower than the softening temperature exist in particulate form.

All of the various dyes and pigments used in the printing and recording fields can be used as colorants, and if the coating liquid is water-based, water-soluble dyes and water-dispersible dyes and pigments are used. Furthermore, in a system in which fine particles are dispersed in a solvent, an oil-soluble dye or a dye φ pigment that can be dispersed in a solvent can be used. 0 For example, carbon black, nigrosine dye, lamp black, Sudan black SM, first yellow G, benzidine yellow, picment yellow, India first orange, irgazine φ red, varanitroaniline red, toluidine red, carmine FB, Permanent Bordeaux FRR, Pigment Orange R, Resole Red 2
G, Rake Red C, Rhodamine FB, Rhodamine B
Lake, Methyl Violet B Lake, Phthalocyanine Blue, Pigment Blue, Brilliant Green B, Phthalocyanine Green, Oil Yellow GG, Zapon First 2RO10GG, Kayasera) Y963,
Kayaset YG, Sumiplast Orange GG, Savon First Orange RR, Oil Number Scarlet, Sumiplast Orange G, Orazole Brown G, Pomelo First Scarlet CG, Eisenspiron Red BEH, Oil Pink OF, Victoria Blue F4
R, First Gen Blue 5007, Sudan Blue,
One or more known dyes and pigments such as oil peacock blue can be used.

These colorants may be used in at least one of the first ink layer and the firj2 ink layer, but the second ink layer does not contain the colorant and the colorant is only used in the first ink layer. If the second ink layer in contact with the recording medium does not contain the coloring material, the recorded image after transfer can be easily corrected in case of erroneous printing.

The planar shape of the thermal transfer material of the present invention is not particularly limited, but it is generally used in the form of a typewriter ribbon or an 11-wide tape used for line printers. Further, for color recording, a heat-sensitive transfer material may be used in which heat-melting ink of several tones is applied separately in stripes or blocks.

A thermal transfer recording method using a thermal transfer material is not particularly different from a normal thermal transfer recording method, and a heat source such as a thermal head or a laser beam can be used as a heat source for thermal transfer recording.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 <Ink 1> - Sodium dodecylbenzenesulfonate as described above was dissolved in water, and while stirring with a propeller type stirrer, a crushed acrylic-styrene resin was added, and then other ingredients were added to form the ink. 1 was adjusted.

The heat resistance of a 3.5gm polyester film support was prepared by applying Ink 1 of the recipe No. 142 to the back side of 0.3g/m2 of a moldable silicone resin for release paper, and heating and drying at 70'C to form a heat-resistant protective layer. It was applied using an applicator on the side opposite to the protective layer and dried at 95°C to provide a first ink layer having a thickness of 3 gm.

It was confirmed from microscopic observation that this first ink layer consisted of two types of non-particulate phases.

<Ink 2> Ink 2 was prepared by mixing each component of the above formulation.

Apply ink 2 to the previously provided first ink layer 2 using an applicator and dry at 80°C to a thickness of 3 g.
A second ink layer consisting of fine heat-melting resin particles of m was formed to obtain a thermal transfer material CI) having the structure shown in FIG.

In this second ink layer, fine particles of low molecular weight polyethylene oxide 1/n were confirmed by microscopic observation.

Example 2 <Ink 3> Ink 3 was prepared by mixing each component of the above formulation.

Ink 3 was applied using an applicator on the previously provided first ink layer and dried at 70°C to form a first ink layer with a thickness of 3 pLm.
An ink layer was provided.

The presence of wax particles in this second ink layer was confirmed by microscopic observation.

<Ink 4> Ink 4 was prepared by dissolving sodium dodecylbenzenesulfonate according to the second prescription in water, adding crushed polyamide resin while stirring with a propeller stirrer, and further adding and mixing wax emulsion.

Ink 4 was applied onto the previously provided first ink layer using an applicator and dried at 90° C. to form a second ink layer with a layer thickness of 31 Lm to obtain a thermal transfer material (II).

Comparative Example On the first ink layer obtained in Example 1, <Ink 9
〉 Ink 9 with the following formulation was applied with an applicator and dried to form a second ink layer with a layer thickness of 3 pLm 17. A thermal transfer material (1* was obtained).

Thermal transfer materials (I), (II), obtained in this way,
Thermal transfer recording of (III) was carried out under the following conditions.

・Thermal head Thin film head 24 dots, dot configuration 1 dot size 0.14 x 0.1 bmm, distance between dots 1111E
0.015mm・Heating element resistance value 315Ω・Applied voltage 13.2V・Applied pulse Ill 1, 1 msec・
Applied energy: 29 mJ/mm 2 Recording paper: pound paper (Beck smoothness: 7 to 8 seconds) Printing and transfer properties were evaluated, and the results are shown in Table 1.

Table 1 However, 0 is practically excellent, △ is suitable for practical use,
× means unsuitable for practical use.

As shown in the table above, when the thermal transfer material of the present invention is used, high-quality prints with good sharpness, transferability, and high print density can be obtained even on paper with low smoothness.

〔Effect of the invention〕

The thermal transfer material of the present invention can provide high-density and sharp prints not only on recording media with good surface smoothness, but also on recording media with poor surface smoothness. . Furthermore, the method for producing a heat-sensitive transfer material of the present invention is a novel method, and it is possible to advantageously produce a heat-sensitive transfer material having such excellent characteristics.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 respectively show one part of the thermal transfer material of the present invention.
FIG. 3 is a schematic cross-sectional view in the thickness direction showing an example. l meeting...Thermal transfer material. 2...Support. 3...First ink layer. 4...Second ink layer. C---Thermofusible resin fine particles A, B, D... Non-particulate phase.

Claims (2)

[Claims] (1) A thermal transfer material having a first ink layer and a second ink layer each containing a heat-melting material on a support in order from the support side, wherein the first ink layer is A layer A in which two or more types of domains are formed of a meltable material, at least one type of domains is constituted by thermofusible resin fine particles, and at least one other type of domains is constituted by a non-particulate phase; a layer B in which two or more types of domains are formed from the heat-fusible material and each domain is composed of a different type of non-particulate phase, and the second ink layer is comprised of a layer different from the first ink layer among the layer A and the layer B. (2) A first ink layer and a second ink layer each containing a heat-fusible material are provided on the support in order from the support side, and the first ink layer contains the heat-fusible material. two or more types of domains are formed, at least one of which
A layer A in which one type of domain is composed of heat-fusible resin fine particles and at least one other type of domain is composed of a non-particulate phase, and two or more types of domains are formed by the heat-fusible material; and a layer B in which each domain is composed of a different type of non-particulate phase, and the second ink layer is the first ink layer of the layer A and the layer B. When producing a heat-sensitive transfer material consisting of a layer different from the above, after coating the layer A with a coating liquid whose main ingredient is a mixture of two or more different types of heat-melting resin fine particle dispersions, the coating liquid by drying at a temperature between the lowest softening temperature and the highest softening temperature of the softening temperatures of the group of thermofusible resin fine particles, or/and the layer B is formed of two or more different kinds of thermofusible resin particles. Providing by applying a coating liquid containing a mixture of resin fine particle dispersion as a main ingredient, and then drying the coating liquid at a temperature higher than the highest softening temperature among the softening temperatures of the group of heat-fusible resin fine particles. A method for producing a thermal transfer material characterized by: