JPH0422158B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a thermal transfer material that can provide a transferred recorded image of good print quality even to a recording medium with poor surface smoothness during thermal transfer recording, and a method for producing the same. [Conventional technology] In addition to the general features of thermal transfer recording methods, such as the equipment used is lightweight, compact, noiseless, and easy to operate and maintain, the thermal transfer recording method does not require colored processed paper. It also 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. The heat-transferable ink layer is superimposed on the recording medium so that it 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 creating a heat-supplied shape on the recording medium. (pattern) to form a transferred recorded image according to the pattern. However, in the conventional thermal transfer recording method, the transfer recording performance, that is, the print quality, is greatly affected by the surface smoothness of the recording medium. Good printing is performed on recording media with high smoothness, but on recording media with low smoothness, In this case, there is a problem in that the 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 during printing cannot be transferred to the entire recording area of the paper, but penetrates and adheres only to the convex parts of the surface or the vicinity thereof, so that the edges of the printed image are The print quality may deteriorate due to lack of sharpness or part of the image being missing. Conventionally, in order to obtain recorded images with good print quality on such recording media with poor surface smoothness,
For example, by using a hot-melt binder with a low melt viscosity for at least the surface layer, or by increasing the thickness of the thermal transfer ink layer, the molten ink can adhere faithfully to the fine uneven structure of recording media such as paper. Or, a method based on the idea of permeation was adopted. However, when a binder with a low melt viscosity is used, the ink layer becomes sticky even at a relatively low temperature, resulting in problems such as decreased storage stability and staining of non-printed areas of the recording medium, and also causes bleeding of transferred images. Furthermore, when the thickness of the transferable ink layer is increased, bleeding increases and the amount of heat supplied from the thermal head also needs to be increased, resulting in a decrease in printing speed. [Problems to be Solved by the Invention] The present invention solves the conventional problems and is applicable not only to recording media with good surface smoothness while maintaining various thermal transfer performances, but also to recording media with good surface smoothness. The purpose of this invention is to provide a thermal transfer material that can provide high-density and sharp prints even on recording media that do not have a high density. 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 the Problems] That is, the heat-sensitive transfer material provided by the present invention has a heat-transferable ink layer containing a heat-meltable material on a support. The ink layer is characterized in that the heat-fusible material of the ink layer forms two or more types of domains, and each domain is composed of different types of heat-fusible resin particles. In addition, the method for producing the thermal transfer material of the present invention, which has been discovered as a novel method that can advantageously produce the thermal transfer material of the present invention having the above structure, includes the method of manufacturing the thermal transfer ink layer of two or more types. After applying a coating liquid containing a mixture of dispersions of different types of heat-melting resin fine particles as a main ingredient, the coating liquid is heated at a temperature lower than the lowest softening temperature among the softening temperatures of the group of hot-melting resin fine particles. It is characterized in that it is provided by drying. [Specific Description and Examples of the Invention] In the heat-sensitive transfer material of the present invention, the heat-fusible material forms two or more types of domains in the heat-transferable ink layer, and each domain is formed by different types of heat-fusible resin fine particles. Because of this structure, the cohesive force within the ink layer can be greatly reduced compared to a homogeneous system. 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, and there are domains with different functions or physical properties such as hot adhesive strength or cohesive strength, each function or physical property is more easily expressed than in a homogeneous system. It can be done. In this way, in the thermal transferable ink layer, there is a large difference in cohesive force between the heat applied part (pattern heating part) and the non-heated part, so a clear recorded image can be obtained, and
Since the recorded latent image generates adhesive force to the recording medium in a patterned manner, it is possible to form a transferred recorded 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. FIGS. 1 and 2 are schematic cross-sectional views in the thickness direction showing one example of the heat-sensitive transfer material of the present invention, respectively. In the present invention, a domain refers to a region in a heterogeneous system that can be distinguished from others by composition, physical properties, etc.
Each domain is composed of a single or a plurality of heat-melting resin fine particles. The thermal transfer material 1 shown in FIG. 1 and FIG. have. The thermal transferable ink layer 3 is composed of two types of heat-melting resin fine particles, for example, type A (hollow circle in the figure) and type B (solid black circle in the figure). A domain is formed by single heat-melting resin particles of type A and type B. Also,
In the example shown in FIG. 2, domains are formed by aggregates in which a plurality of A-type and B-type thermofusible resin fine particles are aggregated in a higher order. Alternatively, the state may be such that a domain made up of these single particles and a domain made up of an aggregate are mixed together. Note that the term "thermal meltability" 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. The thermal transferable ink layer 3 may contain a coloring material as necessary, and 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 relatively heat-resistant plastic films such as polyester, polycarbonate, triacetylcellulose, polyphenylene sulfide, polyimide, and cellophane. Alternatively, parchment paper, condenser paper, etc. can be suitably used. The thickness of the support is preferably about 1 to 15 microns when a thermal head is used as a heat source during thermal transfer. In addition, when using a thermal head, silicone resin, fluorine resin,
By providing a heat-resistant protective layer made of polyimide resin, epoxy resin, phenolic resin, melamine resin, acrylic resin, nitrocellulose, etc., the heat resistance of the support can be improved, or supports that could not be used conventionally. Materials can also be used. The thermofusible resins that make up the thermofusible resin particles include wax, polyolefin resins such as low-molecular polyethylene, polyamide resins, polyester resins, epoxy resins, polyurethane resins, acrylic resins, and polyvinyl chloride resins. Examples include elastomers such as resin, polyvinyl acetate resin, petroleum resin, phenol resin, polystyrene resin, styrene-butadiene rubber, and isoprene rubber. The thermofusible resin particles can be produced by polymerization processes such as emulsion polymerization and suspension polymerization, by mechanically dispersing the thermofusible resin using a dispersant, and by other methods such as mechanical crushing, spray drying, precipitation, etc. Among those obtained, the softening temperature of fine particles is between 50℃ and 160℃.
℃, preferably 60°C to 150°C.
The softening temperature mentioned here was measured using a Shimadzu flow tester CFT-500 with a load of 10 kg and a heating rate of 2.
This refers to the temperature at which the sample begins to flow out, measured at °C/min. The average particle diameter of the heat-melting resin fine particles is preferably 20 μm or less (about 0.01 μm), more preferably 10 or less (about 0.1 μm). If it exceeds 20 μm, 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 ratio of the different types of heat-melting resin fine particles constituting the heat-transferable ink layer can be arbitrarily selected depending on the functions or physical properties exhibited by each particle, and is not particularly limited. The thickness of the thermally transferable ink layer is preferably 1 to 20 μm, more preferably 2 to 10 μm. If the layer thickness of the thermal transfer ink layer is thin, less than 1 μm, the film properties of the latent image formed by heat application and fine particles fusing together will be weak, and if it exceeds 20 μm, the fine particles will not fuse together as a whole. It is difficult to make it uniform, which is not preferable. The thermal transferable ink layer is prepared by appropriately selecting two or more types of fine particles from among the above-mentioned examples of heat-melting resin fine particles, mixing the fine particles with each other as appropriate, and uniformly distributing the fine particles on the support, and then adjusting the softening temperature of the fine particles. The layer can be formed by heating to the following temperature conditions and fixing it on the support, but after appropriately mixing and coating a fine particle dispersion, for example, a resin emulsion, it is necessary to Particularly preferred is a method in which the layer is formed by drying at a temperature lower than the lowest softening temperature to remove the dispersion medium. In this case, coloring materials, additives, etc. added as necessary can be included in the dispersion or inside the fine particles. Colorants include carbon black, nigrosine dye, lamp black, Sudan Black SM, First Yellow G, benzidine yellow, pigment yellow, India first orange, irgazine red, paranitroaniline red, toluidine red. , Carmine FB, Permanent Bordeaux FRR, Pigment Orange R, Resole Red 2G, Lake 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 Yellow CGG, Kayasetsu
Y963, Kayaset YG, Sumiplast Yellow
GG, Zapon First Orange RR, Oil・
Scarlet, Sumiplast Orange G, Orazole Brown G, Zapon Fast Scarlet CG, Eisenspiron Red BEH, Oil Pink OP, Victoria Blue F4R, Fast Gen Blue 5007, Sudan Blue, Oil Peak Stock Blue, etc. One or two known dyes/pigments
More than one species can be used. 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 a wide tape used in line printers. Further, for color recording, a heat-sensitive transfer material may be used in which heat-melting ink of several different tones is applied in stripes or blocks. The thermal transfer recording method using the above thermal transfer material is as follows:
This method is not particularly different from ordinary thermal transfer recording methods, and a heat source such as a thermal head or laser light 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. Examples <Ink 1> Wax emulsion (softening temperature 80°C, average particle size 1 μm) 70 parts (solid content) Acrylic-styrene 30 parts (solid content) Copolymer emulsion (softening temperature 95°C, average particle size approx. 0.2μm) Fluorine surfactant 1 part Carbon black aqueous dispersion 18 parts Stir and mix each component of the above formulation thoroughly to achieve solid content concentration.
A 25% Ink 1 was prepared. Using an applicator, apply Ink 1 on the side opposite to the heat-resistant protective layer of a 3.5 μm polyester support coated with 0.3 g/m ² of additive-type silicone resin for release paper, dried, and provided with a heat-resistant protective layer. Water was evaporated at ℃ to form an ink layer with a thickness of 3 μm to obtain a thermal transfer material (). Comparative Example <Ink 2> Polyamide resin (softening temperature 90°C) 100 parts Isopropyl alcohol 400 parts Carbon black aqueous dispersion 18 parts Ink 2 with the above formulation was applied onto the same support surface as in Example 1 with an applicator and dried. Layer thickness 3μ
A heat-sensitive transfer material () was obtained by forming an ink layer of m. Thermal transfer materials obtained in this way (), ()
Thermal transfer recording was performed under the following conditions. ●Thermal head Thin film head 24 dots configuration 1 dot size 0.14×0.15mm Distance between dots 0.015mm ●Heating element resistance 315Ω ●Applied voltage 13.2V ●Applied pulse width 1.1msec ●Recording paper Bond paper (Beck smoothness 7-8 seconds) The printing and transfer properties were evaluated and the results are shown in Table 1.

〔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]

1 and 2 are schematic cross-sectional views in the thickness direction showing one example of the heat-sensitive transfer material of the present invention, respectively. 1... Thermal transfer material, 2... Support, 3... Thermal transferable ink layer, A, B... Different types of heat-melting resin fine particles.

Claims (1)

[Scope of Claims] 1. A heat-sensitive transfer material having a heat-transferable ink layer containing a heat-fusible material on a support, wherein the heat-fusible material of the heat-fusible ink layer forms two or more types of domains, and each A heat-sensitive transfer material characterized in that each domain is composed of different types of heat-melting resin fine particles. 2. A heat-transferable ink layer containing a heat-fusible material is provided on a support, and the heat-fusible material of the heat-fusible ink layer forms two or more types of domains, and each domain is made of a different kind of heat-fusible resin. When producing a heat-sensitive transfer material composed of fine particles, the heat-transferable ink layer is coated with a coating liquid containing a mixture of two or more types of dispersions of heat-melting resin fine particles as a main ingredient, and then the coating liquid is applied. 1. A method for producing a heat-sensitive transfer material, which is provided by drying a working solution at a temperature lower than the lowest softening temperature among the softening temperatures of the group of fine heat-melting resin particles.