JPH02165994A - Thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To enable recording at high speed by forming an ink layer composed of sublimating transferring dyes, a thermal non-transferring binder and heat- fusing particulates onto a supporter. CONSTITUTION:An ink layer 25 consisting of sublimating transferring dyes 22, a thermal non-transferring binder 23 and heat-fusing particulates 24 is shaped onto the surface of a supporter 21. The heat-fusing particulates are particulates, surfaces and insides of which are impregnated with the sublimating transferring dyes contained in the thermal non-transferring binder on heat-fusion, and the dyes are impregnated in response to the quantity of heating through heating at the time of transfer and the particulates are transferred to a medium to be transferred, the particulates having the low melting point of 50-150 deg.C and mainly comprising a colorless transparent group compound are favorable, and ester wax, oxide wax, low molecular polyethylene wax, acid wax, etc. and polyvinyl alcohol, polystyrene, polyvinyl chloride, etc. are cited. It is preferable that the particulates are employed at the rate of approximately 100-2,000pts. per 100pts. dyes as usage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a recording medium for thermal transfer recording, and particularly to a thermal transfer material that is capable of expressing gradation, can print on plain paper, and has a high recording speed.

[Prior Art and Problems to be Solved by the Invention 1] There have conventionally been recording apparatuses using many recording methods such as an inkjet method, an electrophotographic method, and a thermal transfer method.

The types of objects required to be recorded by these recording devices are becoming more advanced, from characters to images, and from monochrome to color. In order to realize a high-quality full-color printer, which is the final form of this requirement, it is necessary to achieve not only high resolution but also faithful halftone expression.

Regarding this point, in the conventional method described above, binary recording is common in principle, so to express gradation, multiple dots are treated as one unit, and halftones are determined by the on/off ratio of the dots in that unit. A method is used to reproduce halftones in a pseudo manner using an area gradation method such as a dither method.

On the other hand, in the thermal melt transfer method, which is one of the thermal transfer methods, the amount of energy applied to the head is changed to change the amount of ink transferred within one dot in order to obtain halftones. Unable to print density. In other words, conventional thermal melt transfer methods including the above melt transfer method can only perform binary recording at present.

On the other hand, a thermal sublimation transfer method is known apart from the above-mentioned thermal melt transfer method. In this sublimation transfer method, the amount of dye transferred changes depending on the amount of thermal energy, so it is a desirable method for obtaining gradation. However, since this method performs recording by sublimating sublimation dye from the recording medium, the required thermal energy is large, making it difficult to increase the speed, and there are problems with the durability, fixability, and other storage properties of recorded images. In addition to being virtually impossible to print on plain paper, it also has drawbacks such as limited sublimation dyes and high costs for consumables.

In addition, in order to overcome the above-mentioned drawbacks peculiar to this thermal sublimation transfer method, as shown in FIG.
It is known to have a configuration in which 3 are provided. With this configuration, the sublimation dye corresponding to the heating charge melts into the heat-fusible layer, and the heat-fusible layer containing the sublimation dye is transferred to the paper, making it possible to print on plain paper. . However, such a configuration has several drawbacks.

One of the reasons is that the cost of the ink sheet increases due to the multilayer structure. Since the cost of the ink sheet is largely due to the cost of coating the ink layer, it is necessary to reduce the number of layers as much as possible to reduce the cost.

Another problem is that although it is possible to print on plain paper, the fixability to recording paper for thermal sublimation transfer becomes poor.

Recording paper for thermal sublimation transfer generally has a material on its surface that is difficult to transfer the binder so that only the sublimation dye is transferred and the dye binder is not transferred. Therefore, this recording paper for thermal sublimation transfer has a peeling effect even with heat-fusible compounds, and stable thermal transfer cannot be performed.

Furthermore, in order to change the amount of sublimation dye transferred, the amount of heating energy must be changed, so in areas where heating energy is low, such as the highlighted areas of a recorded image, the thermofusible compound will only melt near the melting temperature. As a result, especially when performing thermal transfer recording at high resolution, the melt viscosity is high at the edges of the transfer area, making it difficult to clean the ink, making it unclear whether or not to transfer. . Therefore, sometimes adjacent dots that should not be transferred are also transferred, or conversely, dots that should be transferred are not transferred, and as a result, the resolution is not good.

In other words, the thermal sublimation transfer method is a relatively effective method for obtaining halftones, but conventional thermal transfer methods including this method have problems with at least one of the following: gradation, plain paper recording performance, recording speed, running cost, etc. There was a problem, and there was no method that satisfied all of these problems.

The purpose of the present invention is to improve the conventional heat sublimation transfer method in order to solve the above-mentioned problems, and to achieve excellent gradation, resolution, high-speed recording, storage stability of recorded images, low running cost, and plain paper recording. The purpose of the present invention is to provide a thermal transfer recording medium capable of

[Means for Solving the Problems] According to the present invention, an ink comprising heat-melting fine particles capable of impregnating a support with at least a sublimation transferable dye, a heat non-transferable binder, and the sublimation transferable dye during heat melting. By providing a thermal transfer recording medium with layers, the above object can be achieved.

The present invention will be described below with reference to the drawings.

FIG. 1 shows one embodiment of the thermal transfer recording medium of the present invention. That is, an ink layer 25 consisting of a sublimation transferable dye 22, a heat non-transferable binder 23, and heat-fusible fine particles 24 is provided on the surface of a support 21.

In FIG. 1, the heat-melting fine particles 24 have a structure that protrudes from the surface of the heat-non-transferable binder 23 containing the sublimation transferable dye 22, but the thermal transfer recording medium of the present invention is not limited to the above structure. As shown in FIG. 3, the binder 23 may be placed on the upper surface of the binder 23, or as shown in FIG.
4 may not protrude from the binder 23 and the fine particles 24 may be provided directly on the support 21 via the binder 26, and as shown in FIG. 27 may be provided, and the fine particles 24 may be arranged on the upper surface thereof. That is, the structure may be such that at least a heat non-transferable binder containing a sublimation transferable dye and heat-melting fine particles are provided on a support.

Heat-melting fine particles are fine particles that can impregnate the sublimation transferable dye contained in the heat-non-transferable binder into the surface and inside of the fine particles when they are thermally melted, and the dye is heated by being heated during transfer. It is impregnated according to the amount and transferred to the transfer medium.

The dye is impregnated into the fine particles by sublimation of the dye, and
This occurs with phenomena such as melting and diffusion, but usually occurs simultaneously with the transfer of the fine particles to the transfer medium. However, the timing varies depending on the positional relationship between the fine particles and the dye, that is, the structure of the thermal transfer recording medium, the heating method, etc. For example, when the fine particles protrude considerably from the surface of the ink layer, transfer occurs first, and impregnation of the dye occurs. The timing of dye impregnation and transfer to the transfer medium may be around the time of transfer, such as continuing to some extent even after transfer.

When the thermal transfer recording medium has the above-described structure, the transfer characteristics can be significantly improved. That is, since the sublimation transfer dye is not transferred to the transfer medium with an air layer in between, it can be performed with relatively low energy. Furthermore, since the transfer is performed by the fine particles, and the dye is not directly transferred to the surface of the recording medium, the storage stability of the recorded image is excellent.Furthermore, since each transfer is made up of independent fine particles, the resolution of the transferred image, The gradation becomes very good.

The heat-melting fine particles are preferably those whose main component is a colorless and transparent compound that has a low melting point of 50 to 150° C. and can be impregnated with a dye when hot-melted.

The amount used is preferably about 100 to 2000 parts per 100 parts of dye.

These are waxes and resins that are solid at room temperature, and specifically, ester waxes (carnauba wax, montan wax, synthetic ester waxes), oxidized waxes (paraffin wax 5 microcrystalline wax, etc.) ), low-molecular polyethylene wax, acid wax, etc. In addition to wax, suitable materials include polyvinyl alcohol, polystyrene, polyvinyl chloride, polyester, polycarbonate, polyethylene, polyamide, polyvinylidene chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, etc. It is.

Using one or more of these compounds, the diameter is 0.1 to 10.
Heat-fusible fine particles are produced by forming fine particles with a size of about 0 μm. The heat-melting fine particles are heat-melted and transferred to the overlapping recording paper during transfer by heating, but the sublimation transfer dye in the fine particles transferred at the same time (or immediately before or after transfer) is transferred in proportion to the amount of heating. Since recording is performed by impregnating the dye with only a small amount of the dye, it is preferable that the fine particles have excellent retention of the sublimation transferable dye. For example, those containing polyester and polyvinyl butyral are preferred.

Since the fine particles are used as a transfer medium, the particles can be clearly separated from adjacent particles, and transfer with higher resolution than a general molten ink layer is possible.

The fine particles mainly contain a heat-fusible compound, and as shown in FIG.
This heat-meltable material may be a collection of several ultrafine particles (A) or a non-porous one.
It may be single particles (B) or porous (C). The thermally non-fusible substance is, for example, polystyrene for resin;
Among polyvinyl chloride, polycarbonate, polyvinyl butyral, etc., those that do not melt when heated are preferred;
Inorganic substances include metals such as aluminum, silicon, and iron, metal oxides such as alumina, silicon oxide, zinc oxide, titanium oxide, and molybdenum oxide, and minerals, metal sulfides, and magnesium carbonate, calcium carbonate, barium carbonate, and magnesium sulfate. , calcium sulfate, barium sulfate, and other inorganic salts are used. Mixing such a substance has the effect of improving the transferability of the heat-fusible fine particles.

Further, the heat-fusible fine particles may have a multilayer structure, for example, a heat-fusible compound having a low melting point and difficult to be impregnated with dye is formed around a compound that has excellent retention of sublimation transferable dyes. Possible examples include thermofusible fine particles.

By using fine particles with such a structure, the fine particles before heating will not be gradually impregnated with dye, and after heat transfer, the sublimation transferable dye will be absorbed into the compound with excellent dye retention inside the fine particles. Since the ink sheet is impregnated with the ink, the ink sheet before recording and the recorded matter after recording can have excellent storage stability.

Next, as the sublimation transferable dye that can be used in the present invention, any sublimation transferable dye conventionally used in thermal sublimation transfer media can be used, but particularly preferred dyes in the present invention have a molecular weight of about 150 to 500. about 10
It is a dye that sublimes at 0 to 400°C, more preferably a dye that sublimes at about 120 to 250°C. Specifically, disperse dyes, basic dyes, etc. are preferred.

The non-thermal transferable binder may be any material as long as it does not melt when heated by recording energy from a thermal head or the like and will not be thermally transferred to the overlapping recording element side. Preferably, a material is selected that has high heat resistance and does not prevent dye transfer during heating; for example, vinyl resins (polyvinyl butyral, polyvinyl alcohol, polyvinyl acetate, polyacrylamide, etc.) and cellulose resins such as cellulose acetate are preferred. Regarding the amount used, it is preferable to use it at a ratio of about 50 to 2000 parts per 100 parts of dye, but it is preferable to mix both a sublimation transferable dye and a heat non-transferable binder in the ink solvent used when coating on the support. The type and amount of the binder must be selected so that the heat non-transferable binder does not impair the solubility of the sublimation transferable dye in the ink solvent.

The ink solvent is used to dissolve the dye and binder resin and disperse the heat-meltable particles. Specifically, alcohols (methanol, ethanol, isopropyl alcohol, butanol, etc.), aromatics (toluene, xylene, etc.), and ketones (methyl ethyl ketone, etc.)
and mixtures thereof. The amount used is preferably about 5 to 100 times the total amount of dye and binder.

Apply the ink consisting of the above components onto the support using a bar coater.
The thermal transfer recording medium of the present invention can be obtained by coating with a coating tool such as an applicator and drying. or,
Of the ink of the above-mentioned components, which is a coating liquid, only the heat-melting fine particles may be formed separately. In other words, a sublimation transfer ink consisting of a sublimation transferable dye, a heat non-transferable binder, and a solvent is coated on a support in advance, and then a coating liquid containing heat-melting fine particles is applied so that the fine particles are transferred to the upper side of the ink layer. (Fig. 3), or conversely, a coating liquid containing thermofusible fine particles and an adhesive resin 26 as the main components is applied onto the support, the fine particles are formed on the support, and then sublimated. A configuration as shown in FIG. 4 may be created by applying transfer ink.

Furthermore, in order to prevent the heat-fusible fine particles from peeling off from the support before heating, an adhesive layer 27 is provided between the support and the hot-fusible fine particles, as shown in FIG. 5, and then the fine particles are formed thereon. However, a structure may be adopted in which sublimation transfer ink is further applied thereon. However, in this case, if the adhesive layer becomes too thick, heat conduction will deteriorate, so it is desirable that it be as thin as possible, preferably about 0.01 to 20 parts per 100 parts of the fine particles. Polyamide resin, polyester resin, etc. are suitable for the adhesive layer.

Next, other components according to the present invention will be explained.

Approximately 2 of paper, plastic, metal, etc. can be used as a support.
Suitable materials are those that do not soften or change in quality when heated to about 00° C. for a short period of time, and among these, polyethylene terephthalate, aromatic polyamide film, etc. are particularly preferred. The thickness is desirably about 2 to 20 x tm, but more preferably about 3 to 10 m in view of ease of application and thermal conductivity during coating of the colorant layer. If sticking or the like is likely to occur due to the heat of the thermal head, a heat-resistant protective layer may be provided on the back surface of the support as a backside treatment.

As the heat-resistant protective layer, silicone resins, epoxy resins, polyimide resins, unsaturated aldehyde resins, acrylate resins, etc. are preferable.
13359. The thickness of these films is not particularly limited, but is generally 0.1+! It is preferable that the protective layer be coated uniformly with a thickness of 3 μm or more and 3 μm or less, and by incorporating a metal or inorganic filler into this protective layer, effects of heat resistance and slipperiness can be expected. As the fine particles, amorphous silica, carbon black, alumina, titanium oxide, etc. are useful. Furthermore, it is also useful to apply a liquid lubricant to the back surface of the support to prevent stenting. Examples include fluorine silicone oil, dimethyl silicone oil, various modified silicone oils (epoxy modified, alkyl modified, etc.), phosphoric acid esters, synthetic oils such as polyalkylene gelcol oil, and the like.

【Example〕

The present invention will be explained below with reference to Examples. Note that parts are parts by weight.

Example 1 Paraffin wax 50 parts surfactant
1 part water
49 parts total 10
0 parts A mixed solution of the above formulation was stirred and mixed in a homomixer while being heated to 90° C. to obtain a mixed solution A. In this mixed liquid A, wax particles having a particle size of 5 μm were dispersed. Mixed liquid A
The fine particles obtained by drying were designated as heat-fusible fine particles B.

To create an ink sheet, a polyethylene terephthalate film with a thickness of 6 μm is used as a support, and the following mixed dispersion is applied onto this film using an applicator so that the thin film when dried is 3 μm thick, and dried to form a thermal transfer recording medium. I got it.

This device has a configuration as shown in FIG.

Sumiplast Blue S (Sumitomo Chemical)
1 part polyvinyl butyral 5 parts thermofusible fine particles 8 5 parts surfactant
1 part ethanol/toluene 1 part
00 parts (1:1 mixed solvent) When this thermal transfer recording medium was subjected to a printing test on plain paper using a 6 dot/mm thermal head, a clear transferred image was obtained. Also, the pulse width is 1ms, I. 5ms, 2ms
, 2.5ms, 3ms, 3.5ms, 4ms
(Applied voltage: 12V) When recording is performed, the recording density is 0.10°0, 30.0.52.0.73.0.
The result was 90.1.05.1.19, and halftones could be recorded with good reproducibility.

Example 2 Carnauba wax 40 parts Silica fine powder (particle size 2 μm) 20 parts Surfactant
1 part water
39 parts total: 100 parts A mixed solution of the above formulation was heated to 90° C. and stirred and mixed in a wet homomixer to obtain a mixed solution C. Fine particles containing fine silica powder and having a particle size of 5 μm were dispersed in this liquid mixture. The fine particles obtained by drying the mixed liquid C were used as heat-melting fine particles.

A thermal transfer recording medium was obtained in the same manner as in Example 1 except that heat-fusible fine particles B were changed to heat-fusible fine particles.

When the same evaluation as in Example 1 was carried out using this thermal transfer recording medium, it was possible to record halftones with good reproducibility at recording densities of 0.1 to 1.20.

Example 3 The thermal transfer recording medium obtained in Example 1 was evaluated in the same manner as in Example 1 except that sublimation transfer recording paper was used instead of plain paper, and the recording density was 0.05 to 1. .30
I was able to record halftones with good reproducibility.

Example 4 In order to create an ink sheet, a polyethylene terephthalate film with a thickness of 6 μm was used as a support, and a polyester resin was applied on the support by a ball mill using toluene as a solvent.
Approximately one coat of the mixed solution was applied using a bar coater to form an adhesive layer. Before the adhesive layer was dry, heat-fusible fine particles B prepared in Example 1 were sprinkled on the adhesive layer, excess ink particles not adhered to the adhesive layer were wiped off, and the adhesive layer was sufficiently dried.

The following composition was applied onto this using an applicator so that the dry film thickness was 3 μm and dried to obtain a thermal transfer recording medium. This device has a configuration as shown in FIG.

Sumiplast Yellow GC (Sumitomo Chemical)
1 part polyvinyl butyral 5 parts ethanol/toluene 100 parts (1:1 mixed solvent) Using this thermal transfer recording medium, the same evaluation as in Example 1 was carried out, and halftones with good reproduction were obtained from recording density of 0.1 to 1.17. I was able to record.

Comparative Examples Thermal transferable recording media prepared by removing the heat-melting fine particles from Examples 1 and 2.4 were used as recording media of Comparative Examples 1 and 2.3, respectively.

When the recording media of Comparative Examples 1, 2, and 3 were evaluated in the same manner as in Example 1, almost no recording was performed on the recording paper in either case.

〔Effect of the invention〕

As explained above, by forming an ink layer consisting of at least a sublimation transferable dye, a heat non-transferable binder, and heat-melting fine particles on a support to form a thermal transfer recording medium, the thermal transfer recording medium can contain a sublimation transferable dye. The heat-fusible fine particles that are used have the property of easily retaining dye, and unlike sublimation transfer to paper, the distance to the heat-fusible fine particles, which is the transfer medium, is very small, so it is necessary for thermal transfer. The amount of energy required is small, and as a result, high-speed recording is possible. In addition, the sublimation transferable dye does not have to be transferred only by sublimation, but by using a dye with a high sublimation temperature, the dye may be transferred not only by sublimation but also by phenomena such as melting and diffusion.
Therefore, the amount of energy is still small, and there are effects such as excellent storage stability of recorded images.

Further, in this recording medium, since the thermofusible fine particles are melted and transferred to a recording medium such as plain paper, recording on plain paper is possible.

On the other hand, when a sublimation transfer type recording paper is used, it is possible to transfer only the dye from the sublimation ink layer to the recording paper even if the heat-melting fine particles are not transferred.

Furthermore, since the sublimation transferable ink consisting of a sublimation transferable dye, a binder, and heat-melting fine particles can be applied in one application, an inexpensive ink sheet can be produced.

That is, according to the thermal transfer recording medium of the present invention, transferred images with excellent gradation and resolution can be recorded at high speed at low running costs, and furthermore, transfer is possible even on plain paper, and the storage stability of the recorded images is extremely high. Becomes good.

Among the above-mentioned effects, when the heat-fusible fine particles are made of a heat-fusible compound and a heat-meltable substance, the transferability is particularly good.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing the structure of one embodiment of the thermal transfer recording medium of the present invention, FIG. 2 is a schematic cross-sectional view showing an example of the structure of heat-fusible fine particles, and FIGS. 3 to 5 are the thermal transfer recording medium of the present invention. FIG. 6 is a schematic cross-sectional view showing the structure of a conventional thermal sublimation transfer medium. 21... Support, 22... Sublimation transferable dye 23... Heat non-transferable binder 24
...Thermofusible fine particles, 25 ... Ink layer, 26 ... Adhesive resin, 27 ... Adhesive layer, 31 ...・Thermofusible fine particles, 32...Thermonon-fusible substance,

Claims (2)

[Claims] (1) A thermal transfer recording medium characterized in that an ink layer comprising at least a sublimation transferable dye, a heat non-transferable binder, and heat-fusible fine particles that can be impregnated with the sublimation-transferable dye during thermal melting is provided on a support. . (2) The thermal transfer recording medium according to claim 1, wherein the heat-fusible fine particles are composed of a heat-fusible compound and a heat-non-fusible substance.