JPH02141286A - Thermal transfer ink sheet - Google Patents

Abstract

PURPOSE:To improve the controllability of initial density and repeating characteristics by forming an ink layer by mixing a dye, a low m.p. material and a solid fine powder and coating or impregnating the solid fine powder with two or more kinds of the low m.p. material. CONSTITUTION:Paraffin wax is melted to be mixed with carbon black roughly and the resulting mixture is solidified under cooling. Next, this mixture is thrown in a kneader to be kneaded and dispersed at room temp. and taken out of the kneader to be cooled and subsequently ground by a grinder and classified to obtain a filler. Next, an intermediate adhesive layer 2 consisting of a polyester resin, a vinyl chloride/vinyl acetate copolymer resin and carbon black is formed on a polyester film 1 and, thereafter, an ink coating solution 3 prepared by mixing and dispersing urethane wax, ester wax, a dye and the filler in acetone is applied to the intermediate adhesive layer 2 and dried to obtain an ink layer. By this method, the compatibility of the ink layer with the low m.p. material is improved and both of initial density and repeating properties can be well controlled.

Description

[Detailed description of the invention] [Table of contents] Overview Industrial field of application Prior art (Figures 5 to 7) Means for solving the problem to be solved by the invention (Figure 1) Working examples (a) Description of one embodiment (Figures 2 to 4) (b)
Description of other embodiments Effects of the invention [Summary] Regarding a reusable thermal transfer ink sheet with improved solid fine powder in the ink layer, the initial density and repetition characteristics are well controllable, and appropriate initial density and repetition characteristics are achieved. A reusable thermal transfer ink sheet formed by sequentially laminating an intermediate adhesive layer and an ink layer on a substrate, the ink layer comprising a dye, a low melting point material, and a solid. The solid fine powder is coated with or impregnated with one or more kinds of low melting point materials.

[Industrial application field]

The present invention relates to a reusable thermal transfer ink sheet with improved solid fine powder in the ink layer.

A thermal transfer recording device is a device in which a thermal transfer ink sheet is provided between a thermal head and a sheet of paper, and the thermal transfer ink on the thermal transfer ink sheet is melted or quenched by heat applied by the thermal head and transferred onto the sheet of paper.

In recent years, as thermal transfer ink sheets, reusable thermal transfer ink sheets have been put on the market in place of one-time thermal transfer ink sheets that consume an ink layer in one use.

It is desired that such a thermal transfer ink sheet that can be used repeatedly be able to control initial density and repeatability characteristics well.

[Conventional technology] FIG. 5 is an explanatory diagram of a thermal transfer ink sheet.

As shown in FIG. 5, a reusable thermal transfer ink sheet is constructed by forming an intermediate adhesive layer 2 on a base material 1 made of polyester resin, and forming a thermal transfer ink layer 3 on this intermediate adhesive layer 2. be done.

On the base material I side of the thermal transfer ink sheet, there is a
d, paper PP is positioned on the thermal transfer ink layer 3 side,
The ink material of the thermal transfer ink layer 3 oozes out due to the heating of the thermal head hd, and transfer is performed.

As this reusable thermal transfer ink sheet,
The intermediate adhesive layer 2 contains a resin and solid fine powder for antistatic purposes (carbon black, etc.), and the ink layer 3 further includes:
It contains a dye (colorant), a low melting point material, and a solid fine powder.

As a low melting point material for this ink layer, patent application publication No. 62
-142690, etc. are known, and as a solid fine powder, patent application publication No. 60-2554
As disclosed in Japanese Patent Application No. 90, a material containing a surface liquid plus l of a material containing an adhesive resin in solid fine powder was used.

The purpose of adding solid fine powder to this ink layer is that due to the cohesiveness of the solid fine powder in the ink layer, the cohesive force of the solid fine powder forms a kind of stone wall, and the ink composition whose viscosity has decreased due to heat. , it oozes out from between the dispersed fine powders and can be used repeatedly.

In addition, solid fine powder such as carbon black itself has good oil absorption and poor dispersibility in organic solvents when preparing the ink layer coating liquid, but if the solid fine powder is coated with adhesive resin, it can be
The dispersibility in the solvent is improved, and an ink layer with a sponge structure in which solid fine powder is uniformly dispersed can be obtained.

Furthermore, the adhesive resin increases the mutual bonding strength of the solid fine powder, and even when the dye and low-melting point material melt during heat transfer, the solid fine powder does not fall off, resulting in good recording characteristics with no uneven transfer density. can get.

[Problem to be solved by the invention]

By the way, the filler made of solid fine powder whose surface is coated with a conventional adhesive resin-based material is a structure that forms a kind of stone wall or sponge in the ink layer 3. The first time by controlling the precision! IJ1 (1st time) Density and repeat performance can be controlled, and thermal transfer ink sheet with desired characteristics
You should be able to get

That is, by varying the amount of filler relative to dye and low melting point material, initial (first time) concentration and repeat performance can be controlled.

Based on the above considerations, the first! tJ] (first time) The concentration and repeat performance were investigated.

First, on a polyester film 1 having a thickness of 6 μm, an intermediate adhesive layer 2 made of a polyester resin, a vinyl chloride/vinyl acetate copolymer resin, and a carbon black for preventing static electricity was formed to a thickness of 1 μm.

Next, 10 parts by weight of urethane wax (manufactured by Nippon Oil & Fats), 1 part by weight of ester wax (manufactured by Mitsubishi Chemical Industries, Ltd.), 5 parts by weight of dye (Nippon Kayaku!!), and a filler made of adhesive resin coated with carbon black ( An ink coating liquid 3 prepared by mixing and dispersing Nippon Kaso) in acetone was applied onto the intermediate adhesive layer 2, and after drying, an ink layer of 7 μm was obtained.

Figure 6 shows the changes in the initial density when printing the obtained ink sheet with respect to the ratio of [filler]/[dye and low melting point material] in this ink layer material. 5th/1 showing the repeat performance for the ratio of low melting point material]
FIG. 7 shows the change in the rotational transfer density ratio.

When using a filler made of solid fine powder whose surface is coated with a conventional adhesive resin, the initial concentration decreases greatly in proportion to the increase in the mix ratio of the filler, as shown in Figure 6, and the initial concentration decreases significantly as the mix ratio increases. Great controllability.

However, as shown in FIG. 7, the rotation 4a ratio (that is, the repeatability characteristic) does not change much as the mixing ratio of the filler increases, and the controllability with respect to changes in the mixing ratio is poor.

Generally, it is preferable to monotonically decrease the initial concentration and monotonically increase the repeatability as the mixing ratio of the filler increases, in order to obtain a heat transfer ink sheet with desired properties that can be used repeatedly.

However, in the prior art, if a mixing ratio with good repeatability (for example, a transfer density ratio of about 0.30) is selected, the initial density will drop significantly, making it unsuitable for use.
If one with a high initial concentration is chosen, the repeatability will be too poor and this will also be inappropriate for use.

For example, the initial concentration is 1.0 to 161, and the repeatability is 30.
% or more, but according to FIGS. 6 and 7, the mixing ratio in the initial concentration range of 1.0 to 1.1 is 0.0.
15 to 0.20, but as shown in FIG. 7, with this mixing ratio, the repeatability can only be obtained in the range of 12 to 13%.

On the other hand, the mixing ratio with repeatability of 30% or more is 0.20
As described above, the initial concentration within this range is only O18 or less.

As described above, in the prior art, the characteristics do not change satisfactorily depending on the mixing ratio, so there is a problem that a thermal transfer ink sheet with satisfactory initial density and repeated characteristics cannot be changed.

Therefore, it is an object of the present invention to provide a thermal transfer ink sheet that has good controllability of initial density and repeatability and can realize appropriate initial density and repeatability.

[Means to solve the problem]

FIG. 1 is a diagram showing the principle of the present invention.

The present invention provides a reusable thermal transfer ink sheet formed by sequentially laminating an intermediate adhesive layer 2 and an ink layer 3 on a rigid material, in which the ink layer 3 is composed of a dye and a low melting point material. It is formed by mixing with solid fine powder, and the solid fine powder is coated or impregnated with one or more kinds of low melting point materials.

[Effect]

In the conventional technology, adhesive resin was used as the material to be coated, so it was possible to make the stone wall or sponge structure in the ink layer 3 uniform and strong, but adhesive resin and low melting point material (wax) were used. It has been found that when used in combination, it becomes like a hot melt adhesive, the viscosity of the ink layer increases, and the ink components ooze out when heated.

Therefore, in the present invention, by coating or impregnating a solid fine powder with a low melting point material having a lower adhesive property, the viscosity of the low melting point material in the ink layer is prevented from increasing and the viscosity is maintained.

Along with this, it has good compatibility with the low melting point material of the ink layer,
It has good dispersibility in organic solvents and forms a good sponge structure in the ink layer.

This improves the controllability of the initial density and repeatability, allowing thermal transfer ink sheets with appropriate initial density and repeatability.
can be obtained.

〔Example〕

(a) Explanation of one embodiment FIG. 2 is a concentration characteristic diagram of one embodiment of the present invention;
The figure is a concentration ratio characteristic diagram of one embodiment of the present invention, and FIG. 4 is a repetition characteristic diagram of one embodiment of the present invention.

To carry out the present invention, a filler was first formed as follows.

■ 5 parts by weight of carbon black (manufactured by Masu Carbon) as a solid fine powder and 2 parts by weight of paraffin wax (manufactured by Nippon Seihata), which is a type of low melting point material that can be used as an ink layer, were first mixed with wax. After roughly mixing in the molten state, the mixture is cooled and solidified.

(2) Next, the above mixture is put into a kneader such as a kneader, and kneaded and dispersed at room temperature. Inside the kneader, the mixture itself generates heat due to shear stress depending on the rotational speed of the kneader teeth, and kneading and dispersion proceed with the effect of the heat. At this time, in order to improve dispersion, a dispersion aid such as an interfacial lubricant may be added as necessary. The mixture that has been sufficiently kneaded and dispersed in this way was taken out of the kneader and cooled sufficiently. The filler was obtained by pulverizing it with a pulverizer or the like and classifying it.

Next, an ink sheet was formed using the filler obtained by the above method.

■ First, on a polyester film 1 with a thickness of 6 μm,
An intermediate adhesive layer 2 made of polyester resin, vinyl chloride/vinyl acetate copolymer resin, and carbon black for antistatic purposes was formed to have a thickness of 1 μm.

■ Next, urethane wax (Japan oil type) 10 weight:
Ink coating liquid 3 prepared by mixing and dispersing 1 part by weight of ester wax (manufactured by Mitsubishi Chemical Industries, Ltd.), 11 parts by weight of ester wax (manufactured by Mitsubishi Chemical Industries), 5 parts by weight of dye (Nippon Kaso) and the filler obtained by the above method in acetone was mixed and dispersed in acetone. After coating on intermediate adhesive layer 2 and drying, ink layer 7μ
I got m.

In this ink layer material, the change in initial jjJ] density when printing an ink sheet with j: ↓ in relation to the ratio of [filler]/[dyeshi low melting point material] is shown in Figure 2. FIG. 3 shows the change in the 5th/1st transfer centrality ratio, which indicates the repeatability with respect to the ratio of [filler]/[dye 1-low melting point material].

From Figure 2, the density shows a good monotonous decrease as the filler mixture ratio increases, and from Figure 3, the transfer density ratio shows a good monotonous decrease as the filler mixture ratio increases. It can be seen that it shows a monotonous increase.

This seems to be because the low melting point materials of urethane wax and ester wax in the ink layer bond well with the paraffin wax coated on carbon black, forming a sponge structure with less strong adhesive force. .

That is, by coating or impregnating it with paraffin wax, carbon black has good dispersibility in organic solvents, and a suitable sponge structure is formed by good bonding between the paraffin wax and the urethane wax and ester wax of the ink layer. be done.

For example, the range of the optimal initial concentration of 1.0 to 1.1 is the mixing ratio of 0.20 to 0.27 from FIG.
% or more is a mixing ratio of 0.20 to 0.27 from Figure 3.
An appropriate initial concentration and concentration ratio can be obtained within a mixing ratio of 0.20 to 0.27.

In this way, it has been found that when a filler consisting of a solid fine powder whose surface is coated with one type of low melting point material is used, the controllability of both the initial concentration and the repeat performance is good.

Next, the fall-off of the filler was evaluated.

First, as a sample, as described above, an intermediate adhesive layer 2 made of polyester resin, vinyl chloride/vinyl acetate copolymer resin, and carbon black for antistatic purpose was formed to a thickness of lum on a polyester film 1 having a thickness of 6 μm. Then, 10 parts by weight of urethane wax (Nippon Oil type),
Ester wax (Mitsubishi Chemical Industries “A) 1 Jusha Department,
5 parts by weight of dye (Nippon Kaso) and 1 filler obtained by the above method
Ink coating liquid 3 prepared by mixing and dispersing parts by weight in acetone,
After coating on intermediate adhesive layer 2 of L and drying, apply ink layer 7.
μm was obtained.

In addition, as a comparison sample, an ink sheet with an ink layer using only carbon black, which is a solid fine powder, as a filler was prepared and compared. Using the two types of ink sheets formed in this manner, printing was repeatedly performed using a thermal transfer printer.

The results are shown in FIG. 4, where △ is for the sample according to the present invention, and ◯ is for the comparative sample.

This evaluation is based on the Fujitsu word processor Oasis Lite FRO.
Using MIO, recording energy 35mJ/mmZ
This figure shows the change in recording density when a pattern with a coverage rate of 15% was repeatedly printed.

In FIG. 4, an ink ribbon prototyped using only a carbon blank as a filler, which is a comparison sample marked with a circle, shows a severe decrease in density due to repeated printing, and unstable changes in density.

However, the ink sheet using carbon black coated with paraffin wax as a filler, as shown by the symbol Δ,
It can be seen that the density decrease due to repeated printing is gradual and the density change is stable.

This experiment revealed that the ink using paraffin wax-coated capon plack as a filler does not cause the filler to fall off and is effective in providing stable repeatability.

This is thought to be because the paraffin wax forms a sponge structure with appropriate bonding strength, so it is less likely to fall off compared to carbon black alone.

(b) Description of other embodiments In the above embodiments, urethane wax and ester wax are used as low melting point materials in the ink layer, and are also used as low melting point materials for coating the solid fine powder. Although an example using paraffin wax, which can be used as an ink layer, has been described, the low melting point material actually used for the ink layer may also be used for coating the solid fine powder.

For example, as the low melting point material for the ink layer, 10 parts by weight of urethane wax, 1 part by weight of ester wax, and 2.5 parts by weight of paraffin wax are used. A thermal transfer ink sheet was prepared.

As a result, the same results as in FIGS. 2 to 4 were obtained.

Further, the low melting point material used for coating or impregnating the solid fine powder does not have to be one type, but may be a plurality of types. For example, if paraffin wax, which is difficult to dissolve in organic solvents, and urethane wax, which is easy to dissolve in organic solvents, are used as such low melting point materials, it is possible to obtain a product that has good dispersion in organic solvents and a short dispersion time.

Furthermore, the low melting point material for the ink layer and solid fine powder is not limited to urethane wax, ester wax, and paraffin wax, and various waxes with properties matching the properties required for the ink sheet can be used. .

Although the present invention has been described above using examples, the present invention can be modified in various ways according to the gist of the present invention, and these are not excluded from the present invention.

〔Effect of the invention〕

As explained above, according to the present invention, since the solid fine powder is coated or impregnated with the low melting point material, the ink layer has good compatibility with the low melting point material and the filling has good dispersibility in organic solvents. This has the effect of providing wood. Furthermore, since the above-mentioned low melting point material does not exhibit strong adhesive properties, it is possible to control both the initial (first time) c, degree and repeat performance well by adjusting the amount of filler added.

[Brief explanation of the drawing]

Fig. 1 is a principle diagram of the present invention, Fig. 2 is an initial concentration characteristic diagram of an embodiment of the present invention, Fig. 3 is a concentration ratio characteristic diagram of an embodiment of the present invention, and Fig. 4 is an embodiment of the present invention. 5 is an explanatory diagram of a thermal transfer ink sheet, FIG. 6 is an initial density characteristic diagram of the prior art, and FIG. 7 is a density ratio characteristic diagram of the prior art. In the figure, 1-base material, 2-intermediate adhesive layer, 3-thermal transfer ink layer.

Claims (2)

[Claims] (1) In a reusable thermal transfer ink sheet formed by sequentially laminating an intermediate adhesive layer (2) and an ink layer (3) on a base material (1), the ink layer (3) ,
1. A thermal transfer ink sheet formed by mixing a dye, a low melting point material, and a solid fine powder, wherein the solid fine powder is coated with or impregnated with one or more kinds of low melting point materials. (2) The low melting point material of the ink layer (3) is composed of a low melting point wax, and the low melting point material of the solid fine powder is composed of a low melting point wax. Heat transfer ink sheet.