JPH0675996B2 - Thermal transfer material - Google Patents

Description

The present invention relates to a heat-sensitive transfer material that gives a transfer-recorded image with good print quality even on a recording medium having poor surface smoothness.

In recent years, along with the rapid development of the information industry, various information processing systems have been developed, and recording methods and apparatuses suitable for the respective information processing systems have also been developed and adopted. As one of such recording methods, the heat-sensitive recording method uses a device that is lightweight and compact and has no noise,
It has excellent operability and maintainability, and has been widely used recently.

However, among the recording papers used in the thermal recording method, the normal thermal recording paper is expensive because it is a color-forming processed paper containing a color former and a developer, and the recording can be falsified. There are drawbacks in that the preservability of the recording is poor, such that the paper easily develops color due to heat or an organic solvent, and the recorded image fades in a relatively short time.

Recently, the thermal transfer recording method has attracted particular attention as a method for maintaining the advantages of the thermal recording method described above and compensating for the drawbacks associated with the use of the thermal recording paper.

This heat-sensitive transfer recording method generally uses a heat-sensitive transfer material obtained by melt-coating a heat-transferable ink obtained by dispersing a colorant in a heat-meltable binder on a sheet-shaped support. The thermal transferable ink layer is superposed on the recording medium so as to be in contact with the recording medium, and heat is supplied from the support side of the thermal transfer material by a thermal head to transfer the melted ink layer to the recording medium, thereby forming the thermal transferable ink layer on the recording medium. The transfer ink image is formed according to the shape of heat supply. According to this method, the above-mentioned advantages of the heat-sensitive recording method can be maintained, plain paper can be used as a recording medium, and the above-mentioned drawbacks associated with the use of heat-sensitive recording paper can be eliminated.

However, the conventional thermal transfer recording method is not without its drawbacks. This is because the conventional thermal transfer recording method has a transfer recording performance, that is, the print quality is greatly affected by the surface smoothness, and good printing is performed on a recording medium with high smoothness, but in the case of a recording medium with low smoothness. Means that the print quality is significantly deteriorated. However, even when using paper, which is the most typical recording medium, highly smooth paper is rather special, and ordinary paper has various degrees of unevenness due to the entanglement of fibers. Therefore, in the case of paper with large surface irregularities, the heat-melted ink at the time of printing cannot penetrate into the fibers of the paper and sticks only to the convex parts of the surface or in the vicinity thereof, resulting in a sharp edge part of the printed image. If there is no image or a part of the image is missing, the print quality is degraded. Further, in order to improve the printing quality, it is possible to use a heat-meltable binder having a low melting point,
In this case, the heat transferable ink layer exhibits adhesiveness even at a relatively low temperature, resulting in inconveniences such as deterioration of storability and stains on the non-printed portion of the recording medium.

The main object of the present invention is not only for a recording medium having a good surface smoothness but also for a recording medium having a poor surface smoothness, except for the above-mentioned drawbacks of the conventional thermal transfer recording method. Another object of the present invention is to provide a heat-sensitive transfer material capable of giving excellent printing.

According to the research by the present inventor, in order to achieve the above object,
It has been found that it is extremely effective to disperse a fine particulate filler containing an easily volatile organic liquid in the heat transferable ink layer. That is, when the thermal transferable ink layer thus formed is heated in contact with the recording medium, the heat-fusible binder in the thermal transferable ink layer is melted or softened, and the thermal transferable ink layer is transferred to the recording medium. The volatile organic liquid contained in the fine particulate filler is vaporized and the pressing force allows the ink to adhere to the surface recess of the recording medium or penetrate into the fiber structure. For this reason, it is possible to prevent the print image from being chipped even on a recording medium having a poor surface smoothness, and to improve the print quality. Further, since the easily volatile organic liquid is contained in the fine particulate filler, it does not lower the melting point of the thermal transferable ink layer as a whole or the preservability before use.

The heat-sensitive transfer material of the present invention is based on the above findings, and more specifically, it is formed by forming a heat-transferable ink layer on a support, and the heat-transferable ink layer is colored in a heat-meltable binder. It is characterized in that an agent and a fine particulate filler containing a volatile organic liquid are dispersed.

Hereinafter, the present invention will be described in more detail with reference to the drawings as necessary. In the following description, "%" represents the quantitative ratio
Unless otherwise specified, "parts" and "parts" are based on weight.

FIG. 1 is a schematic sectional view in the thickness direction of a heat-sensitive transfer material according to the most basic aspect of the present invention. That is, the thermal transfer material 1
Is usually a sheet (used to include films)
The heat transferable ink layer 3 is formed on the support 2 having a sheet shape.

As the support 2, a conventionally known film or paper can be used as it is, for example, a film of a relatively heat-resistant plastic such as polyester, polycarbonate, triacetyl cellulose, nylon or polyimide, cellophane or sulfuric acid paper. Can be preferably used.
The thickness of the support is preferably about 2 to 15 μm when considering a thermal head as a heat source for heat transfer, but a heat source capable of selectively heating the heat transferable ink layer such as laser light is used. When doing, there is no particular limitation. When using a thermal head, provide a heat-resistant protective layer made of silicone resin, fluororesin, polyimide resin, epoxy resin, phenol resin, melamine resin, nitrocellulose, etc. on the surface of the support that contacts the thermal head. By this, the heat resistance of the support can be improved,
Alternatively, it is also possible to use a support material which cannot be used conventionally.

The heat transferable ink layer 3 is formed by dispersing or compatibilizing a colorant (not shown) in a heat-meltable binder 4 and further dispersing a fine particulate filler 5 containing an easily volatile organic liquid therein. It is composed of a coating layer of a functional ink.

As the heat-meltable ink composed of the coloring material and the heat-meltable binder, the one conventionally used for the heat-sensitive transfer material can be used as it is. That is, as the colorant, various dyes, pigments or carbon black widely used in the fields of printing and recording can be used. As the heat-meltable binder, waxes such as carnauba wax, paraffin wax, sazol wax, microcrystalline wax and castor wax; stearic acid,
Derivatives of higher fatty acids such as palmitic acid, lauric acid, aluminum stearate, lead stearate, barium stearate, zinc stearate, zinc palmitate, methyl hydroxystearate and glycerol monohydroxystearate, or metal salts and esters thereof;
Polyethylene, polypropylene, polyisobutylene, polyethylene wax, polyethylene oxide, polytetrafluoroethylene, ethylene-acrylic acid copolymer, ethylene-
Thermoplastic resins made of olefin homopolymers or copolymers such as ethyl acrylate copolymers and ethylene-vinyl acetate copolymers or derivatives thereof, and the like are used. These hot-melt binders may be used alone or in admixture of two or more.

The heat-meltable ink constituting the heat-transferable ink layer 3 is made by dispersing the fine particulate filler 5 containing the easily volatile organic liquid in the above-mentioned ordinary heat-meltable ink. The easily volatile organic liquid is generally impregnated in a fine particle made of a resin or encapsulated in the form of a microcapsule. As the volatile organic liquid, a compound generally used as an evaporative foaming agent or a volatile foaming agent in the field of resin processing and the like can be used as it is in the present invention. The easily volatile organic liquid is selected according to the form encapsulated in the finely divided filler, but is generally liquid at room temperature and around normal pressure, and is 130 ° C or less, particularly 100 ° C.
Compounds having the following boiling points are preferably used. Examples of typical easily volatile organic liquids are shown below.

(A) Aliphatic hydrocarbon type For example, n-propane, n-pentane, n-hexane,
Hydrocarbons having 4 to 7 carbon atoms such as neopentane, isohexane, n-heptane and isoheptane. These are low in toxicity and inexpensive.

(B) Chlorinated aliphatic hydrocarbons For example, methyl chloride, methylene dichloride, trichlorethylene, dichloroethane (sym), etc.

(C) Fluorinated aliphatic hydrocarbons such as Freon 11 (CCl ₃ F), Freon-12 (CCl
₂ F ₂ ), Freon-21 (CHCl ₂ F), Freon-22 (CHClF
_2), Freon _{-113 (CCl 2 F-CClF 2} ), freon -114
Chlorine of methane or ethane such as (CClF ₂ −CClF ₂ ) −
Fluorine derivatives are often used.

(D) Aromatic hydrocarbons Benzene, toluene, etc.

The fine particulate filler containing these easily volatile organic liquids,
It can be obtained by a known resin impregnation method or microencapsulation method. In the case of the resin impregnation method, for example, a method of adding an easily volatile organic liquid in the process of suspension polymerization of an appropriate monomer (Japanese Patent Publication No. 33190/1988) or swelling beads obtained by suspension polymerization with a solvent or the like. A method of adding a readily volatile organic liquid (Japanese Patent Publication No. 36-10628) is adopted. If necessary, a method is used in which the resin is miniaturized and then the easily volatile organic liquid is impregnated.

Also in the case of the microencapsulation method, a known method such as a complex coacervation method, an interfacial polymerization method, or a phase separation method can be adopted. Microcapsules containing easily volatile organic liquids are commercially available, for example, Matsumoto Yushi-Seiyaku Co., Ltd. Matsumoto Microspheres F30, F50,
F60 or EXPANCEL manufactured by Nippon Philite Co., Ltd. (vinylidene chloride / acrylonitrile copolymer as a wall material and encapsulating isobutane as a foaming agent) can be used.

The fine particulate filler containing easily volatile organic liquids including those mentioned above has a particle size of 0.1 to 30 μm, especially 0.1 to 30 μm.
Those having a size of 10 microns are used, and those having a small particle size are preferably used.

In the heat transferable ink layer 3, it is generally preferable to disperse 50 parts or less of fine particulate filler in 100 parts of the above-mentioned heat-meltable binder.

The heat-sensitive transfer material 1 according to the present invention comprises, on the support 2, a coating liquid containing, as a main component, a heat-meltable ink composed of a fine particulate filler containing the above-mentioned heat-meltable binder, colorant and easily volatile organic liquid. It is obtained by forming a thermal transferable ink layer 3 by applying the composition onto a substrate and drying it. The thickness of the heat transferable ink layer 3 is generally 1 to 30 μm, preferably 2 to 20 μm.

The planar shape of the heat-sensitive 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 for line printers and the like. Further, for color recording, a heat-sensitive transfer material in which heat-melting inks of several kinds of colors are separately applied in stripes or blocks can be used.

Next, the thermal transfer recording method using the above thermal transfer material will be described for the case where the most typical thermal head is used as the heat source. FIG. 2 is a schematic cross-sectional view in the thickness direction of the heat-sensitive transfer material showing its outline. That is, the recording medium 6 is brought into close contact with the heat-meltable ink 3 of the heat-sensitive transfer material 1, and if necessary, the heat pulse is applied by the thermal head 8 from the back surface of the recording medium while applying the heat pulse by the platen 7.
Is locally heated according to the desired printing or transfer pattern. The heated portion of the ink layer 3 rises in temperature and softens or melts when reaching a certain temperature, and the fine particulate filler containing the easily volatile organic liquid dispersed in the ink layer 3 is also heated. As a result, the easily volatile organic liquid is vaporized to generate gas. Due to the volume expansion of the ink layer and the gas pressure caused by the generated gas, it becomes possible to sufficiently permeate and fill the recesses on the surface of the recording medium that could not be permeated with conventional thermal transfer inks, and recording media with poor surface smoothness. It is possible to obtain a recorded image 3a with good print quality.

In the above description, an example in which a thermal head is used as a heat source for thermal transfer recording has been described, but it can be easily understood that the same can be done when another heat source such as a laser beam is used.

As described above in detail, the heat-sensitive transfer material of the present invention contains a readily volatile organic liquid in the heat-transferable ink layer, so that recording with good print quality can be performed even on a recording medium having poor surface smoothness. It is also possible to prevent the deterioration of the storability of the thermal transfer material. Therefore,
It is considered to be widely applicable to information recording systems that will be diversified in the future.

Hereinafter, the present invention will be described in more detail with reference to Examples. Example 1 1 part of carbon black, polyethylene wax (softening point
1 part of paraffin wax (softening point 70) and 1 part of carnauba wax were dispersed and mixed by using an attritor while heating to about 100 ° C. Then add 30 parts of petroleum solvent (trade name: Isopar H, made by Esso),
The solution was heated to about 100 ° C. and cooled to room temperature with vigorous stirring to obtain Isopar H liquid in which carbon black / wax was finely dispersed. Further, 1 part of a fine particulate filler (trade name: Microsphere F, manufactured by Matsumoto Yushi-Seiyaku Co., Ltd.) containing an easily volatile organic liquid was added to the above dispersion liquid, and mixed by stirring to obtain a coating liquid. This coating liquid was applied onto a polyester film having a thickness of 6 μm and dried to obtain a thermal transfer material having a transfer ink layer thickness of 10 μm. Using the above-mentioned heat-sensitive transfer material, an electrophotographic chart was used as an original and a heat-sensitive transfer type facsimile was used to perform recording on paper of different smoothness to evaluate the resolution. As a result, 6.
A record with a resolution of 3 lines / mm and a resolution of 5.6 lines / mm was obtained on paper of 15 sec. Further, the sharpness of the recorded image was good for all the papers.

Comparative Example Only the isoper liquid in which carbon black / wax of Example 1 was finely dispersed was coated on a 6-micron polyester film and dried to obtain a thermal transfer material having a transfer ink layer thickness of 10 micron.

Using this thermal transfer material, thermal transfer recording and evaluation of the resolution of the recorded image were performed in the same manner as in Example 1. As a result, a resolution of 6.3 lines / mm was obtained for paper with Beck smoothness of 100 sec, but a resolution of 3.6 lines / mm for paper of 15 sec.
And the sharpness of the recorded image was also poor.

Example 2 A thermal transfer material was obtained in the same manner as in Example 1 except that fine particles obtained by crushing styrene beads containing butane were used instead of the microspheres of Example 1. By using this heat-sensitive transfer material, high resolution recording similar to that in Example 1 was possible.

[Brief description of drawings]

FIG. 1 is a schematic sectional view in the thickness direction of an embodiment of the heat-sensitive transfer material of the present invention, and FIG. 2 is a heat-sensitive transfer material for explaining an embodiment of a heat-sensitive transfer recording method using the heat-sensitive transfer material of FIG. It is a schematic cross-sectional view seen in the thickness direction. 1 ... Thermal transfer material 2 ... Support 3 ... Thermal transfer ink layer 4 ... Hot melt ink 5 ... Fine particulate filler 6 ... Recording medium 7 ... Platen 8 ... Thermal head

Claims (1)

[Claims] 1. A heat transferable ink layer is formed on a support, and the heat transferable ink layer is contained in a heat fusible binder.
A heat-sensitive transfer material comprising a colorant and a fine particulate filler containing an easily volatile organic liquid dispersed therein.