JPH022079A - Thermal transfer recording sheet and preparation thereof - Google Patents

Abstract

PURPOSE:To make repeated use over many times possible and to reduce running cost by providing an intermediate color material layer containing a binder and a dye sublimed or gasified by heat between a substrate and a color material layer. CONSTITUTION:A thermal transfer recording sheet 6 consists of a substrate 2, an intermediate color material layer 3 containing a binder and a dye sublimed or gasified by heat and a color material layer 4, and the intermediate color material layer 3 may be provided as a multilayer structure. The thermal transfer recording sheet 6 is superposed on an image receiving material 5 to be heated by a thermal head 1 and the dye sublimed or gasified by the heat contained in the color material layer 4 is transferred to the image receiving material 5 to form an image. At this time, the dye contained in the color material layer 4 is reduced because of the transfer to the image receiving material 5 but, at the same time, the dye contained in the intermediate color material layer 3 is diffused and migrated to the color material layer 4 by the heat of the thermal head to perform replenishment and, therefore, repeated use over many times becomes possible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a heat-sensitive transfer recording sheet, and more particularly to a heat-sensitive transfer recording sheet that can be used repeatedly many times.

[Prior Art] In recent years, with the spread of personal computers, televisions, VTRs, video discs, etc. as information terminals and the use of color displays, the demand for color printers that output these still images as color images has increased year by year. are doing. Recording methods for this color printer include an electrophotographic method, an inkjet method, and a thermal transfer method, among which the thermal transfer method is often used because it is noiseless and easy to maintain.

This thermal transfer method consists of a thermal transfer recording sheet and an image receptor, which have a coloring material layer that is solid or semi-solid at room temperature, and uses thermal energy controlled by electrical signals from a laser or thermal head to transfer the coloring material layer. This is a recording method in which an image is formed by thermal melt transfer or sublimation transfer of the dye in the coloring material layer to a receiver, and is divided into thermal melt transfer type and sublimation transfer type depending on the transfer method of the coloring material layer. The heat-melt transfer type uses a heat-sensitive transfer recording sheet that has a color material layer in which pigments or dyes are bonded with heat-melt wax, and transfers the pigments or dyes to an image receptor together with the wax melted by the thermal energy of a thermal head. The drawbacks are that it is difficult to obtain the necessary halftones for image quality, and that clear colors cannot be obtained due to the transferred wax. In addition, the sublimation transfer printing method, which uses dyes that sublimate or vaporize by heat, is an application of conventional sublimation transfer printing technology, in which disperse dyes, which sublimate or vaporize by heat and are generally relatively easy to sublimate, are bound with a binder. Using a heat-sensitive transfer recording sheet having a colored coloring material layer, a color image can be obtained by sublimating and transferring only the dye to the image receptor using the thermal energy of the thermal head. At this time, the dye sublimates and transfers in response to the thermal energy of the thermal head, making it easy to obtain intermediate tones, and also having the advantage of being able to control the gradation at will, making it the most suitable method for full color printing. It is considered.

The heat-sensitive transfer recording sheet used in this sublimation transfer type heat-sensitive transfer recording method has a coloring material layer on a substrate in which a dye that sublimes or vaporizes by heat is bound with a binder resin such as polyester resin, epoxy resin, or polyvinyl butyral resin. It is known that
issue).

[Problems to be Solved by the Invention] However, in the above-mentioned conventional thermal transfer recording sheet,
No consideration was given to the fact that this process would be repeated many times, and the thermal energy of the thermal head would cause -
If a double print is made, most of the dye is used up, or if the same thing is printed a second time after a double print, the density of the first and second prints will be significantly different. For this reason, the current situation is that heat-sensitive transfer recording sheets are discarded after only one print, which poses a problem of high running costs.

An object of the present invention is to make it possible to use a conventionally disposable heat-sensitive transfer recording sheet many times, thereby significantly reducing running costs.

[Means to solve the problem]

The above problem is solved in a swear transfer recording sheet in which a coloring material layer containing a binder and a dye that sublimes or vaporizes by heat is provided on a substrate, and at least a binder and a dye that sublimes or vaporizes by heat are provided between the substrate and the coloring material layer. Alternatively, the problem can be solved by providing an intermediate coloring material layer containing a vaporizable dye or a plurality of intermediate coloring material layers.

[Function] As shown in FIG. 1, the thermal transfer recording sheet (6) of the present invention basically consists of a substrate (2), an intermediate coloring material layer (3), and a coloring material layer (4). , the intermediate coloring material N(3) may be provided in one or more layers. [(3a), (3b),...]
. However, in Figure 1, (1) is the thermal head, (5)
indicates an image receptor. In the present invention, the thermal transfer recording sheet (6) is superimposed on the image receptor (5), heated by the thermal head (1), and sublimated or vaporized by the heat contained in the coloring material layer (4). An image is formed by sublimating and transferring the dye to the image receptor (5). At this time, the dye contained in the color material layer (4) is transferred to the image receptor (5) and is reduced, but at the same time, the dye contained in the intermediate color material layer (3) is absorbed by the color material layer (4) due to the heat of the thermal head. ), it is replenished by diffusion and transfer, making it possible to use it repeatedly many times. In that case, it is necessary to transfer the dye contained in the intermediate color material layer (3) into the color material layer (4) sufficiently efficiently, and if the amount of migrated dye is small, the image color density will increase as the number of printings increases. As a result, it becomes difficult to obtain a proper image. It is also necessary to ensure stable transfer, and it is desirable that the dye be replenished in just the right amount even after repeated printings. Regarding these points, as a result of repeated research by the present inventors, the binder contained in the intermediate color material N (3) is compatible with the binder contained in the color material layer (4), particularly preferably. It has been found that if the same material is used, the diffusibility is improved and the dye contained in the intermediate coloring material layer (3) can be diffused and transferred into the coloring material layer (4) sufficiently efficiently and stably. In addition, by providing multiple layers of the intermediate coloring material N(3) [(3a), (3b),... It has also been found that 4) can be replenished and the number of printings possible can also be increased. This effect will be explained below with reference to FIG. 1 in the case where two layers (3a) and (3b) are provided as the intermediate coloring material layer (3), but the same effect can be obtained even with two or more layers. The effect becomes more pronounced as the number increases. That is, the thermal transfer recording sheet (6) is superimposed on the image receptor (5), and by heating the thermal head (1), the dye contained in the coloring material layer (4) is transferred to the image receptor (5).
), as mentioned above, the coloring material layer (4)
The decreased dye inside is replenished by the dye contained in the intermediate coloring material layer (3b) diffusing into the coloring material layer (4). In that case, at the same time, the dye contained in the intermediate coloring material layer (3a) diffuses and transfers into the intermediate coloring material layer (3b), and the dye concentration in the intermediate coloring material layer (3b) is stabilized, so that as a result, the intermediate coloring material layer ( The diffusion and transfer of the dye from 3b) into the coloring material layer (4) is also stabilized, and the number of printings possible can also be increased.

In order to effectively implement the present invention, an intermediate coloring material layer (3)
Alternatively, the content of dye contained in the color material layer (4) is important. According to the research of the present inventor, the dye content in the intermediate color material layer (3a) in contact with the substrate is preferably 2 to 20 times the dye content in the color material N (4); ), the dye content contained in the coloring material layer (4) is the same as that of each intermediate coloring material NiC3a), (3b),...
It is preferable that the content of dye is smaller than that contained in . In particular, each intermediate color material layer (3a), (3b),
It is preferable that the content of the dye contained in .

As described above, the thermal transfer recording sheet (6
) is one in which, due to the action of the intermediate coloring material layer (3), the necessary printed color density can be obtained very effectively without any decrease in printed color density when printing is repeated many times.

As the substrate (2) that can be used in the present invention, a wide variety of resin films can be used, such as capacitor paper, polycarbonate film, polyimide film,
Although polyester film etc. can be mentioned as an example, it is not limited to these. Further, a stake prevention layer may be provided on the surface of the base (2) that comes into contact with the thermal head (1), if necessary.

The intermediate coloring material N (3) and the coloring material layer (4) according to the present invention consist of at least a binder and a dye that sublimes or vaporizes when heated. As the dye, any dye that has sublimation property can be used, and various commercially available Examples include disperse dyes, oil-soluble dyes, etc., but are not limited to these. Furthermore, as a binder, any material can be used in a wide range as long as it can effectively dye the dye, such as saturated polyester resin, polyamide resin, epoxy resin, polycarbonate resin, polyvinyl butyral resin, acrylic resin, etc. However, it is not limited to these. Compatible resins may be used for each intermediate coloring material layer (3) and coloring material layer (4), but as already mentioned, it is particularly preferable to use the same resins. Among these resins, it is preferable to use saturated polyester for each of the intermediate color material layer (3) and the color material layer (4) since it can provide particularly good printing characteristics.

Each intermediate coloring material layer (3) and coloring material layer (4) are prepared by dissolving or dispersing the dye and binder in any suitable solvent, or by thermally melting the dye and binder, and applying the dye and binder to a fountain coater, multi-slide hopper coater, accumulator, etc. Multilayer coating may be performed using appropriate equipment, but the contacting 2N
It is preferable to prevent mixing of the components between them as much as possible, so that the effects of the present invention will be more pronounced. This point will be explained below. That is, the dye and the binder are melted or dispersed in any suitable solvent or melted by heat, and then coated with an intermediate color material layer in contact with the substrate (2) using a suitable coating machine such as a roll coater, gravure coater, or bar coater. (3a) is coated on the substrate (2), and the other intermediate coloring material layer (3b) and coloring material M (4) are coated on the release surface of a release substrate that is separate from the substrate (2) and has release properties. By overlapping the layer formed on the substrate (2) and the next layer, pressurizing and crimping, peeling off only the above-mentioned peeling substrate, and repeating this operation for other layers in sequence, Each intermediate coloring material layer (3) and coloring material layer (4) are formed on the substrate (2). When performing the above-mentioned pressurization and crimping, the crimping can be effectively performed by heating if necessary. The heating temperature in this case depends on the softening point of the binder used, but is from 60°C to
140°C, preferably 80°C to 120°C, and 60″
If the temperature does not reach C, proper adhesion is difficult to occur, and 140
When the temperature is higher than .degree. C., the components tend to mix between the two contacting layers due to softening or melting.

The above-mentioned release substrate includes at least an intermediate coloring material layer (3).
Alternatively, any material can be used as long as the surface forming the coloring material layer (4) has releasability, and in particular, at least the intermediate coloring material layer (3) or the coloring material layer (4) such as film or paper can be used.
Those with a release layer on the surface forming the surface are common and easy to use. Various types of release layer can be used in this case, but one containing a silicone compound is preferred from the viewpoint of handling.

In the present invention, the dye concentration of the color material layer (4) itself may be a conventional concentration, and is usually about 10 wt% to 80 wt%, preferably about 20 wt% to 50 wt%, and the thickness of the core layer can be the same as conventional ones. Usually 0.5 μm to 5 μm preferably 0
．． It is about 5 μm to 2 μm.

The overall thickness of the intermediate color material layer (3) may be appropriately determined depending on the dye concentration in the layer, but is usually preferably 0.8
It is about μm to 3 μm. When forming multilayers (3a), (3b), etc. as the intermediate coloring material layer (3), the thickness of each layer is usually 0.3 μm to 1 μm, preferably 0.5 μm.
μm, and the number of layers in this multilayer formation is usually 2.
The number of layers is about 6 to 6, preferably 3 to 5. The same type of dye may be used in the intermediate coloring material layer (3) and the coloring material layer (4), or different types of dyes may be used.

〔Example〕

The present invention will be described in detail below, but the present invention is not limited to this example.

In addition, parts in the examples indicate parts by weight.

Example 1 Ink a was prepared by dispersing the following liquid mixture in a ball mill for 24 hours.

Disperse dye r'Lurafix Blue 660J (BAS
(Manufactured by Company F) 15 parts Epoxy resin [Epicoat 1004J (Shell Company!) 5 parts Toluene 40 parts Methyl ethyl ketone 40 parts The dry coating amount of Bar Coke on the 6 μm polyester film used as the substrate (hereinafter referred to as substrate A) was Ig/ rr
Ink a was applied so as to be r, and air-dried to form an intermediate coloring material layer. Next, silicone resin rKS-774J (manufactured by Shin-Etsu Chemical) was coated on the 25 μm polyester film using a bar coater so that the dry coating amount was 0.1 g/rrr, and the film was heat-cured at 140"C for 3 minutes for release. A substrate (hereinafter referred to as substrate B) was formed. Subsequently, ink b was prepared by dispersing the following liquid mixture in a ball mill for 24 hours.

Polyvinyl butyral resin "S-LEC BM-IJ (Made by Block Chemical) 15 parts Toluene 40 parts Methyl ethyl ketone 40 parts The dry coating amount is Ig/rtf on the silicone layer of base B using a bar coater.
Ink B was applied so that the coloring material layer was formed by air drying. Subsequently, the intermediate coloring material layer formed on the substrate A and the substrate B
A heat-sensitive transfer in which an intermediate coloring material layer is formed on substrate A and a coloring material layer is formed thereon by pasting the coloring material layers formed on each other facing each other using a thermal laminator at approximately 90'C and peeling off substrate B. I got a record sheet.

On the other hand, the following dyed layer formulation solution was prepared.

Saturated polyester resin “Vylon 200J (manufactured by Toyobo) 20 parts toluene
The dyed layer mixture was applied onto a 77-part polypropylene synthetic paper (thickness: 70 μm) using a bar coater so that the dry coating amount was 10 g/rlf, and air-dried to form a dyed layer. Next, apply ultraviolet curable silicone resin rX-62-7223J (
Shin-Etsu Chemical) was coated with a bar coater to a dry coating amount of 0.1 g/nf, and then coated with a high-pressure mercury lamp (800 g/nf).
W) was irradiated with ultraviolet rays for 30 seconds to produce an image receptor.

Using the thus obtained thermal transfer recording sheet and image receptor, monochrome images were repeatedly printed five times at a recording energy of 6 mJ/dot using a thermal printer with an image density of 6 dots/ml11. Next, the printed color density of this image receptor was measured using a reflection densitometer DM-400 (manufactured by Dainippon Screen). The results are shown in Table 1.

In repeated printing up to 3 to 4 times, there was no decrease in print color density, and the necessary print color density was obtained.

Example 2 Ink C was prepared by dispersing the following liquid mixture in a ball mill for 24 hours.

Toluene 40 parts Methyl ethyl ketone 40 parts Example 1
Ink C was applied onto the substrate A used in Example 1 using a bar coater in the same manner as in Example 1, and the dry coating amount was 0.5 g.
A first intermediate coloring material layer of /rrr was formed. Next, ink d was prepared by dispersing the following liquid mixture in a ball mill for 24 hours.

Saturated polyester resin "Vylon 200 J" 7 parts Toluene 40 parts Methyl ethyl ketone 40 parts Example 1
Ink d was applied using a bar coater onto the silicone resin layer of the substrate B on which the silicone resin layer was formed in the same manner as described above to form a second intermediate coloring material layer with a dry coating amount of 0.5 g/po. Next, the first intermediate coloring material layer formed on the substrate A and the second intermediate coloring material layer formed on the substrate B are made to face each other,
The second intermediate coloring material layer was formed on the first intermediate coloring material layer provided on the substrate by bonding them together using a thermal laminator in the same manner as in Example 1 and peeling off the 7-substrate B.

Next, ink e was prepared by dispersing the following liquid mixture in a ball mill for 24 hours.

Saturated polyester resin "Vylon 200" 15 parts toluene 40 parts Methyl ethyl ketone 40 parts Substrate B on which a silicone resin layer was formed in the same manner as in Example 1
Ink e was applied onto the silicone resin layer using a bar coater to form a color material layer having a dry coating amount of Ig/rrfO. Subsequently, the second intermediate coloring material layer on the substrate A and the coloring material layer on the substrate B are made to face each other and bonded together using a thermal laminator in the same manner as in Example 1, and by peeling off the substrate B,
A heat-sensitive transfer recording sheet was obtained in which two intermediate coloring material layers were formed on substrate A, and a coloring material layer was formed thereon.

Thermal transfer recording sheet thus obtained and Example 1
Using the image receptor, images were printed using a thermal printer in the same manner as in Example 1, and the color density of the images was measured. The results are shown in Table 1.

In repeated printing up to 5 times, the required print color density was stably obtained without any decrease in print color density.

Example 3 On the substrate A used in Example 1, ink a used in Example 1 was applied using a bar coater in the same manner as in Example 1 to form an intermediate coloring material layer with a dry coating amount of Ig/nf. did. Next, ink B used in Example 1 was applied onto the intermediate coloring material layer on the substrate A using a bar coater in the same manner as in Example 1 to form a coloring material layer with a dry coating amount of Ig/rrf. Thus, a heat-sensitive transfer recording sheet was obtained in which an intermediate coloring material layer was formed on the substrate A, and a coloring material layer was formed thereon.

Thermal transfer recording sheet thus obtained and Example 1
Using the image receptor, images were printed using a thermal printer in the same manner as in Example 1, and the color density of the images was measured. The results are shown in Table 1.

In repeated printing up to 2 to 3 times, the necessary print color density is obtained without any decrease in print color density, and printing can be repeated many times, but the mixing of components between the intermediate color material layer and the color material layer is Because of this, the number of repetitions was slightly lower than in Examples 1 and 2.

Comparative Example Ink f was prepared by dispersing the following liquid mixture in a ball mill for 24 hours.

Disperse dye rLurafix Blue 660J
5 parts Saturated polyester resin "Vylon 200 J" 15 parts Toluene 40 parts Methyl ethyl ketone 40 parts Example 1
Ink f was coated on the substrate A used in Example 1 using a bar coater in the same manner as in Example 1, and the dry coating amount was 2 g/rr.
By forming the rO coloring material layer, a heat-sensitive transfer recording sheet provided with only the coloring material layer was obtained.

Thermal transfer recording sheet thus obtained and Example 1
Using the image receptor, images were printed using a thermal printer in the same manner as in Example 1, and the color density of the images was measured. The results are shown in Table 1.

A lot of dye migrated in the first print, and the print color density decreased significantly in the second print.

Table 1 [Effects of the Invention] As described above in detail, according to the present invention, the effect of the intermediate coloring material layer allows the required color density to be achieved extremely efficiently during repeated printing many times without reducing the printed color density. As a result, heat-sensitive transfer recording sheets, which were conventionally discarded after only one printing, can now be used many times, resulting in a significant reduction in running costs.

[Brief explanation of the drawing]

FIG. 1 shows a sectional view of the swearing transfer recording sheet of the present invention. (1)...Thermal head (2)...Base (3)...Intermediate coloring material layer (4)...Coloring material layer (5)... ... Image receptor (6) ... Thermal transfer recording sheet Figure (above)

Claims (8)

[Claims] (1) In a thermal transfer recording sheet comprising a coloring layer containing at least a binder and a dye that sublimes or vaporizes when heated on a substrate, at least the binder and a dye that sublimes or vaporizes when heated are disposed between the substrate and the coloring layer. A thermal transfer recording sheet characterized by having one or more intermediate coloring material layers containing a dye that sublimes or vaporizes. (2) The thermal transfer recording sheet according to claim 1, wherein the binder contained in the coloring material layer and the binder contained in the intermediate coloring material layer are compatible. (3) The thermal transfer recording sheet according to claim 1 or 2, wherein the content of dye contained in the coloring material layer is smaller than the content of dye contained in each intermediate coloring material layer. (4) The thermal transfer recording sheet according to claim 3, wherein the content of the dye contained in each intermediate coloring material layer decreases from the substrate side to the coloring material layer side. (5) One or more intermediate coloring material layers containing at least a binder and a dye that sublimes or vaporizes when heated is provided on the substrate, and then on the intermediate coloring material layer at least a binder and a dye that sublimes or vaporizes when heated. A method for producing a heat-sensitive transfer recording sheet comprising a coloring material layer containing: a method for producing a heat-sensitive transfer recording sheet comprising a coloring material layer formed on a substrate; 1. A method for producing a heat-sensitive transfer recording sheet, the method comprising: forming a heat-sensitive transfer recording sheet. (6) The method for producing a heat-sensitive transfer recording sheet according to claim 5, characterized in that the next intermediate coloring material layer is formed on the intermediate coloring material layer formed on the substrate by pressing/pressing and heating at the same time. (7) The method for producing a thermal transfer recording sheet according to claim 6, wherein the heating temperature is 60°C or more and 140°C or less. (8) One or more intermediate coloring material layers containing at least a binder and a dye that sublimes or vaporizes when heated is provided on the substrate, and further, on the intermediate coloring material layer, at least a binder and a dye that sublimes or vaporizes when heated. A method for producing a heat-sensitive transfer recording sheet comprising a coloring material layer containing: An intermediate coloring material layer or a coloring material layer is formed in advance on a release substrate having releasability, and then an intermediate coloring material layer or coloring material layer on the above-mentioned separation substrate is formed on the intermediate coloring material layer formed on the substrate. 8. The method for producing a heat-sensitive transfer recording sheet according to claim 5, wherein after pressurizing and crimping, only the peeling substrate is peeled off to form an intermediate coloring material layer or a coloring material layer.