JPH02188295A - Image receiving medium for thermal transfer and its manufacture - Google Patents

Abstract

PURPOSE:To obtain an image receiving medium for thermal transfer free from thermal deformation such as curl by providing paired base sheets of the same layer structure of layers arranged symmetrically, located at symmetrical positions with the center surface of a base, and setting the physical property of the layer and the central base sheet at a specific value. CONSTITUTION:An image receiving medium 1 is basically made of a dyeing layer 2 and a base 3, and the base 3 consists of a base sheet 3b adjoining the dyeing layer 2 centering around a central base sheet 3b and a base sheet c which is positioned symmetrically with the base sheet 3a and located below the base sheet 3b in the center. The modulus of surface compression elasticity of the surface of the base sheet 3a adjoining the dyeing layer 2 is 14kg/cm<2> or more, and the heat conductivity is 3.5X10<-4>cal/cmXsec.. deg.C or less. In addition, the coefficient of heat contraction of the central base sheet 3b is 0.3% or less. Furthermore, the base sheet itself has a symmetrical layer structure with its central surface.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermal transfer image receptor and a method for manufacturing the same. It is an object of the present invention to provide a thermal transfer image receptor and a method for manufacturing the same.

[Conventional technology]

In recent years, personal computers, televisions, VTRs
, video discs, etc. have become widespread, and the demand for color printers that can easily print these color images is increasing year by year. The recording methods of this color printer include electrophotographic, inkjet, and thermal transfer methods, but among these, features include no noise, easy maintenance, and low cost equipment. Since then, thermal transfer methods have been widely used.

This thermal transfer method uses a thermal transfer sheet having a color material layer that is solid or semi-solid at room temperature and a thermal transfer image receptor, and is divided into melting type and sublimation type depending on the transfer method. The melt-type thermal transfer method uses a thermal transfer sheet with a coloring material layer in which pigments or dyes are bonded with heat-melting wax, and the pigments or dyes are transferred to a thermal transfer image receptor along with the wax melted by thermal energy from a thermal head, etc. This method basically allows only binary recording, making it difficult to obtain halftones, and furthermore, it has the disadvantage that it is difficult to obtain clear tones due to the transferred wax.

On the other hand, the sublimation thermal transfer method is an application of the conventional sublimation transfer printing technology, and uses a thermal transfer sheet with a coloring material layer made of a dye that sublimes relatively easily (hereinafter referred to as sublimable dye) bound with a binder. Using heat energy from etc., only the sublimable dye is sublimated, evaporated, and transferred onto the thermal transfer image receptor.
A color print can be obtained by thermal transfer (hereinafter referred to as sublimation transfer) by diffusion or the like. At this time, since the amount of sublimation transfer of the sublimable dye changes in response to the amount of heat energy from the thermal head etc., it has the advantage that intermediate tones can be easily obtained and the gradation can be controlled at will. , is considered the most suitable method for full-color recording.

As described in JP-A-59-14994, the thermal transfer sheet used in this sublimation type thermal transfer method is made by binding a sublimable dye with a thermoplastic resin such as polyester resin, epoxy resin, or polyvinyl butyral resin. It is known that a color material layer is provided on a base film.

On the other hand, as described in JP-A No. 57-107885, the thermal transfer image receptor used in this recording method is made of thermally saturated polyester resin, etc., which is easily dyed with sublimable dyes and has good fixing properties. 2. Description of the Related Art A thermal transfer image receptor comprising a dye layer containing a plastic resin provided on a substrate is generally known. Furthermore, as a substrate, polypropylene synthetic paper with a porous layer on the surface is generally used, and thermal transfer image receptors using this paper have high image quality with no white spots on the transferred image. It is characterized by the ability to obtain images with higher density than those using paper or natural paper.

[Problem to be solved by the invention]

However, during image formation, heat is applied only from the printing surface side of the substrate due to compression heating by a thermal head, etc., and the surface temperature of the thermal head reaches 250°C or higher, so polypropylene with a porous layer on the surface Thermal transfer image receptors using synthetic paper as a substrate have the disadvantage that the printing surface undergoes significant heat shrinkage and deformation such as curling occurs.

In response to this, attempts have been made to use films with high heat resistance and large rigidity, such as polyester films, as the substrate, and it has been shown that there is almost no deformation due to printing.
In terms of density and image quality, it was not as good as the one using the above-mentioned polypropylene synthetic paper as a substrate.

An object of the present invention is to solve the above problems, and to combine the advantages of polypropylene-based synthetic paper and the advantages of substrates such as polyester film, to create an image receptor that does not have the disadvantages of each, in other words, a high-density image receptor. An object of the present invention is to provide a thermal transfer image receptor capable of forming high-quality images and free from deformation due to heat such as curling.

[Means to solve the problem]

The above problem uses a stack of three base sheets as a base, each base sheet is composed of layers of IN or more, and a pair of base sheets located symmetrically with respect to the center plane of the base are identical. The layer structure is such that the layer structure is symmetrical with respect to the center plane, and the center base sheet has a layer structure symmetric with respect to the center plane of its own base sheet, and the base sheet in contact with the dyeing layer is arranged in a layer structure symmetrical with respect to the center plane. The surface compressive elastic modulus of the surface of the sheet in contact with the dyeing layer is 14 kgf/cff1 or more and the thermal conductivity is 3.5.
This problem can be solved by adjusting the heat shrinkage rate of the central base sheet to 0.3% or less.

[For production]

The image receptor (1) of the present invention basically has the following as shown in FIG.
It consists of a dyeing layer (2) and a substrate (3), and this substrate (3) is composed of a substrate sheet (3a) which is in contact with the dyeing layer (2) around a central substrate sheet (3b), and a substrate sheet (3a) in contact with the dyeing layer (2). The base sheet (3a) is located symmetrically with the base sheet (3a) and is located in the center.
It consists of a base sheet (3C) on the underside of 3b). Then, a coloring material layer containing a sublimable dye (a thermal transfer sheet (5) is placed on the base film (6) and the thermal transfer image receptor (1) is heated with a thermal head (4). By doing so, the sublimable dye contained in the color material layer (7) is sublimated and transferred to the dyeing layer (2) to form an image.

Here, physical property values defined in the present invention will be explained. Surface compressive elastic modulus refers to the compressive elastic modulus at room temperature, but unlike conventional compressive elastic modulus, the surface area of the compressed part is as small as 1 mm, and furthermore, the pressure is equivalent to the head pressure of a thermal transfer printer used on a boat. 5 kg f/
It is calculated from the amount of deformation when it is set to c+11. This reflects the fact that when forming an image using a thermal head, the contact area of one pixel is quite small, and it also evaluates the compressive elastic modulus of only a very small surface area. It is closer to the system. Note that this physical property can be obtained by TMA (thermomechanical analysis). Next, the thermal conductivity is measured at room temperature and is obtained by a commonly used laser flash method. The thermal shrinkage rate refers to the shrinkage rate when a sample is heated at a temperature of 100''C for 3 minutes and then left at room temperature for 5 minutes.

As mentioned above, the base of the image receptor of the present invention is composed of three layers of base sheets, and each of these three base sheets has the following configuration. That is, (a) the surface compressive elastic modulus of the surface of the base sheet (3a) in contact with the dyeing N(2) is 14 kgf.
/cd or more and thermal conductivity is 3.5X 10-'cal
7 cm-sec-'C or less; (b) The heat shrinkage rate of the central base sheet (3b) is 0.3%.
(c) The base sheet (3
a) and (3c) have mutually symmetrical layer configurations and the same layer configuration; (d) Base sheet) (3b) With respect to the center plane of itself, It has a symmetrical layer structure.

In the present invention, by setting the surface compressive elastic modulus of the surface of the dyeing layer (2) side of the upper substrate sheet (3a) in contact with the dyeing layer (2) to the above-mentioned specific value, that is, the Since the elastic modulus is increased to provide cushioning properties, the adhesion with the thermal head is good, and the thermal conductivity is decreased as described above, so the heat retention effect is large, and when forming an image, the dyeing layer (2 ) is sufficiently heated, a high-quality, high-density image without white spots on the transferred image can be obtained. However, on the other hand, it tends to shrink easily due to heat. Therefore, the heat shrinkage rate of the central base sheet (3b) located in the center is reduced as described above (
However, deformation due to heat shrinkage of the base sheet (3a) is absorbed and effectively prevented.

Due to this effect, the thermal transfer image receptor (1) does not curl during image formation.

In addition, the upper base sheet (3a) and the lower base sheet)
(3c) have the same layer structure and are arranged so that the layer structure is symmetrical with respect to the center plane of the base (3);
The central base sheet 1- (3b) has a symmetrical layer structure with respect to the center plane of its own base sheet, so the base (3) as a whole is balanced and there is no difference between the top and bottom, so it is resistant to high temperatures and / Or deformation such as curling does not occur even if stored under high humidity.

In the present invention, a base sheet (3a) and a base sheet (
3c) needs to have the same layer structure.

Here, having the same layer structure means that the base sheet (3a) and (3
This means that the layers constituting C) have the same structure and the number of layers is the same, and in FIG. 1, layers (3a) and (3c) with the same structure are respectively - Consists of layers. The base sheets (3a) and (3c) may have a -layer structure or may have a layer structure of two or more layers.

Furthermore, when arranging these two base sheets, it is necessary to arrange and stack them symmetrically with respect to the center plane of the base.

As a result, the substrate as a whole has a well-balanced and symmetrical structure with respect to the central plane, and deformation such as curling does not occur even when stored at high temperatures and/or at high temperatures.

These substrate sheets) (3a) have a surface compressive elastic modulus of 14 kgf/CTII or more on the surface in contact with the dyeing layer and a thermal conductivity of 3.5 x 10-'cal/cm-sec-'C.
It is necessary that the surface compressive elastic modulus is 14k or less.
If gf/ctl is less than 1, sufficient cushioning properties will not be obtained, the adhesion of the thermal head will be insufficient, and not only will a satisfactory print density not be obtained, but white spots will occur in the transferred image. Image quality cannot be obtained. Further, if the thermal conductivity is higher than 3.5X I O"'cal 7cm-sec'C, sufficient heat retention effect cannot be obtained and satisfactory print density cannot be obtained. In the present invention, the base sheet ( 3a
) and (3c) have the same structure, it follows that the base sheet (3c) must also satisfy the above-mentioned physical properties. In addition, when the base sheet (3a) and the base sheet (3C) have different layer configurations,
Storage at high temperatures and/or high humidity tends to cause deformations such as curling. These sheets include, for example, polyethylene, polypropylene, polyvinylidene chloride, polyamide, polybutadiene, polyisoprene, polyisobutene,
A film such as polychloroprene, a foam or porous sheet selected from polyethylene, polypropylene, polyurethane, polyvinyl chloride, polyacrylate, polymethacrylate, etc., or a laminate of two or more selected from the above. body etc. can be used, but are not limited to these.

As mentioned above, the central base sheet (3b) of the present invention has a layer structure that is symmetrical with respect to the center plane of the base sheet, and can be used in a wide range as long as the sheet has a heat shrinkage rate of 0.3% or less. Can be used. Since the layer structure is symmetrical with respect to the central plane, the overall balance of the substrate is achieved in combination with the substrate sheets (3a) and (3C), and curling can be effectively prevented during storage. . In addition, since the heat shrinkage rate is 0.3% or less, stable printing is possible with less heat shrinkage.For example, plastic films include polyester, polycarbonate, polyimide, etc. films, and cellulose fiber paper , high quality paper, art paper, coated paper, imitation paper, impregnated paper, etc. Furthermore, although these may be used alone, they may also be used as a laminate film or laminate fiber paper in which polyethylene, polypropylene, polyester, etc. are laminated on both sides. Also, when significant heating is performed to form a high-density image, the substrate sheet (3)
Large heat shrinkage occurs in a), and the central base sheet (3b
) The substrate sheet (3a) may become wavy along the surface irregularities of (3a), and as a result, the surface smoothness of the printed surface may be impaired. This is because the heat shrinkage rate of the base sheet (3a) is large;
This tends to occur when the thickness is small. In such a case,
It is preferable that the Bekk smoothness of the surface of the central substrate sheet (3b) on the side receiving the dye transfer is 3000 seconds or more.

It is preferable that the base sheet (3a) and the base sheet (3c) of the present invention have approximately the same thickness because of the need for balance in order to reduce curling under high temperature and/or high humidity. The thickness of the central base sheet (3b) is preferably greater than or equal to the thickness of the base sheet (3a) or (3c); if it is smaller than that, the thickness of the central base sheet (3b)
(3b) is the base sheet) The effect of absorbing heat shrinkage in (3a) is small.Furthermore, the overall thickness of the base body (3) is preferably 100μm to 250μm, and if it is smaller than this, the rigidity is low. If it is too large, the effect of the present invention cannot be obtained sufficiently with respect to curling, and if it is larger than 250 μm, although it does not impede the effect of the present invention, it is disadvantageous in terms of cost.

It is not possible to prevent the white pigment from being kneaded into any base sheet in the base (3) of the present invention within a range that satisfies each of the above requirements.

A wide variety of white pigments can be used as long as they improve whiteness and provide hiding properties, such as titanium white, zinc white, alumina white, silica white, calcium carbonate, and the like.

Further, the substrate (3) of the present invention may be transparent,
It is suitable for use in overhead projects (OHP).

As the dyeing layer (2) of the present invention, a wide variety of materials can be used as long as they are easily dyed with sublimable dyes (and have good fixing properties; for example, saturated polyester resin, polyvinyl butyral resin, epoxy resin, polycarbonate resin) , acrylic resin, cellulose resin, etc., and they can be used alone or in a mixture in any ratio, but are not limited to these.The dyeing layer (2) is made by dyeing the above resins in a suitable solvent. or emulsion, and coated on the upper base sheet (3a) with a roll coater.
Reverse coater, fountain coater, gravure coater,
It is coated with a suitable coating machine such as a bar coater and dried. Alternatively, if it is thermoplastic, it may be heat-fused and provided by extrusion coating using an accumator or the like. The thickness of the dyeing layer (2) is 0.3 g/rrf to 1.5 g/rrf in terms of dry coating amount.
rr (is preferable; if it is less than this, effective dyeing property cannot be obtained, and if it is more than this, it is difficult to obtain sufficient adhesion to the substrate (3). In addition, the dyeing layer (2) is suitable for image formation. In some cases, the dyeing layer (2) may be thermally fused with the coloring material layer (7), but to prevent this, the dyeing layer (2) may be partially cross-linked or a release material such as silicone may be applied to the dyeing layer (2). A release layer containing a molding agent or a lubricant may be provided.

The base body (3) of the present invention can be simply manufactured by providing an adhesive N (8) made of adhesive between a plurality of base sheets and bonding them together, as shown in an example in FIG. Moreover, the thermal transfer image receptor (1) of the present invention can be provided at low cost. The adhesive used for the adhesive layer (8) may be arbitrarily selected from solvent type, emulsion type, hot melt type, etc., and may also be used as a pressure sensitive adhesive. Examples include, but are not limited to, vinyl acetate adhesives, acrylic adhesives, meccrylic adhesives, and ethylene-vinyl acetate copolymer adhesives.

Furthermore, an optional adhesive layer (8) as shown in FIG.
and dyeing layer (2) of the base sheet adjacent to the adhesive layer.
) may be provided with a release layer (9) between the base sheet and the base sheet further away from the thermal transfer image receptor (1) obtained by this method.
) can be used as a seal that is peeled off between the release layer and the adhesive layer in contact with it after image formation and is pasted on any desired location.

[Example] The present invention will be described in detail below, but the present invention is not limited to this example. Note that parts in the examples indicate parts by weight.

Example 1 Transparent polypropylene film (thickness 80 μm 1 surface compressive elastic modulus (13.1 kgf/afl, thermal conductivity 3
．． Apply acrylic adhesive to one side of 2X 10-'cal/cu+-5ec/'C with an applicator so that the dry coating amount is 10g/n (dry), then apply a transparent polyethylene terephthalate film ( Thickness 25μm
1 (heat shrinkage rate: 0.2%)), and the rolls were laminated together using a laminator heated to 100°C. Furthermore, the above adhesive is applied and dried in the same manner as above on the side of the above polyethylene terephthalate film on which the polypropylene film is not attached, and another same polypropylene film as above is attached on that side in the same manner as above to form a substrate. Obtained. Next, a dyed layer composition liquid having the following composition was applied onto the above substrate using an applicator so that the dry coating amount was Log/%, and dried to form a dyed layer.

Tolylene diisocyanate, 3 parts Toluene 77 parts Next, a 1% hexane solution of ultraviolet curable silicone resin was coated on top of this using a bar coater so that the dry coating amount was 0.1 g/I, and after drying, a high pressure mercury lamp was used. (800 W) for 30 seconds to form a release layer to obtain a thermal transfer image receptor (for OHP).

Example 2 132 parts of a pressure-sensitive adhesive formulation having the composition shown below was added with 0.1 part of benzoyl peroxide while stirring under a nitrogen atmosphere, and heated to 60°C to 70°C to give 4. The reaction mixture was allowed to react for an hour, and then aged at 70 to 80°C for 2 hours to obtain a copolymer solution having a weight average molecular weight of 400,000.

(N-butyl acrylate 50 parts 2-ethylhexyl acrylate 50 parts acrylic acid
2 parts toluene
30 parts Next, to 100 parts of the solid content of this solution, 2 parts of butoxymethylmelamine resin, 1 part of tolylene diisocyanate, and 200 parts of toluene were added and thoroughly mixed to obtain a pressure-sensitive adhesive formulation. Ta.

Next, on one side of a polypropylene film (thickness 60 μm, surface compressive modulus 13, 1 kg f/Cl11, thermal conductivity 3.2 × 10-' cat 7 cm, 5 ec-°C), the above pressure-sensitive adhesive was applied. The dry coating amount of the formulation is 10
It was applied with an applicator and dried to give a ratio of g/rrf. On the other hand, a 1% hexane solution of thermosetting silicone resin was applied to one side of a white polyethylene terephthalate film (thickness 75 μm, heat shrinkage rate 0.2%), dried,
After heat treatment at .degree. C. for 3 minutes, this surface and the pressure-sensitive adhesive-coated surface of the polypropylene film were made to face each other and laminated together at room temperature using a laminator.

Furthermore, the above pressure-sensitive adhesive formulation was applied in the same manner as above to the side of the white polyethylene terephthalate film to which the polypropylene film was not bonded, and dried.
The same polypropylene film as above was attached to the surface in the same manner as above to obtain a substrate. Next, a dyeing layer is applied to the non-adhesive side of the polypropylene film bonded to the silicone-treated side of the white polyethylene terephthalate film of this base, and a release layer is applied on top of that. A thermal transfer image receptor (for seals) was obtained in the same manner as in Example 1.

Example 3 Polypropylene synthetic paper (thickness 60 μm, surface compression modulus 11.8 kgf/ctM, thermal conductivity 2.9×10
The adhesive used in Example 1 was applied to one side of a sheet of paper (60 μm thick, heat shrinkage rate 0.1%) and dried in the same manner as in Example 1. , Beck smoothness of 800 seconds on both sides) and bonded together in the same manner as in Example 1,
Furthermore, the adhesive used in Example 1 was applied to the surface of the above imitation paper on which the polypropylene synthetic paper was not bonded, in the same manner as in Example I, dried, and the same polypropylene synthetic paper as described above was applied to that surface as in Example 1. A substrate was obtained by bonding in the same manner. Next, a dyeing layer was provided on the above substrate, and a release layer was further provided thereon in the same manner as in Example 1 to obtain a thermal transfer image receptor.

Example 4 A porous material composition having the composition shown below was sufficiently stirred and mixed,
This mixture was thoroughly kneaded using a twin-shaft H machine, and the resulting composition was granulated by a conventional method.

Ethylene-propylene terpolymer 20 (1 stearin M 1.6 parts) This composition was melted and formed into a film using a 65φ inflation extruder.The film thus obtained was biaxially stretched ( A polyethylene porous film (thickness 60 μm
1 Surface compressive elastic modulus 12.3 kgf/ci, thermal conductivity 3
．． 3X 10-'cat/cm-sec-°C) was obtained.

The adhesive used in Example 1 was applied to one side of the polyethylene porous film thus obtained in the same manner as in Example 1, dried, and coated paper (thickness 70 μm, heat shrinkage rate 0.2 %, Bekk smoothness (4000 seconds on both sides) in Example 1
The adhesive used in Example 1 was applied and dried in the same manner as in Example 1 to the surface of the above coated paper on which the polyethylene porous film was not bonded, and the same polyethylene porous film as above was applied to that surface. The quality films were bonded together in the same manner as in Example 1 to obtain a substrate. Next, a dyeing layer was provided on the above substrate, and a release layer was further provided thereon in the same manner as in Example 1 to obtain a thermal transfer image receptor.

Example 5 Example 1 was applied to one side of the same polypropylene synthetic paper as Example 3.
The adhesive used in Example 1 was applied and dried in the same manner as in Example 1, and then laminated paper (40 μm thick coated paper laminated with 20 μm thick low density polyethylene on both sides) was applied to the surface.Thermal shrinkage rate was 0. 2%, Beck smoothness is 1200 on both sides
0 seconds) in the same manner as in Example 1, and then apply the adhesive used in Example 1 on the side of the laminated paper that is not bonded with the polypropylene synthetic paper in the same manner as in Example 1.
After drying, the same polypropylene synthetic paper as above was attached to the surface in the same manner as in Example 1 to obtain a substrate. Next, a dyeing layer was provided on the above substrate, and a release layer was further provided thereon in the same manner as in Example 1 to obtain a thermal transfer image receptor.

Comparative Example 1 Polypropylene synthetic paper (thickness 200 μm, surface compression modulus 13.1 kgf/C11l, thermal conductivity 3.2×1
0-'cal/c to sec: Cz heat shrinkage rate is 1.5%
) was provided with a dyeing layer on one side and a release layer thereon in the same manner as in Example 1 to obtain a thermal transfer image receptor.

Comparative Example 2 White polyethylene terephthalate film (thickness 150
μm, surface compressive elastic modulus 21.7 kgf/c++t, thermal conductivity 5.8X IO-'cal/■-5ec-℃
) was provided with a dyeing layer on one side and a release layer thereon in the same manner as in Example 1 to obtain a thermal transfer image receptor.

Comparative Example 3 White polyethylene terephthalate film (thickness 120
The adhesive used in Example 1 was applied to one side of the paper (heat shrinkage rate: 0.2%) in the same manner as in Example 1, dried, and polypropylene synthetic paper (thickness: 60 μm) was applied in the same manner as in Example 1. A substrate was obtained by bonding the substrate to the substrate.

Subsequently, a dyeing layer was provided on the polypropylene synthetic paper side of the substrate, and a release layer was further provided thereon in the same manner as in Example 1 to obtain a thermal transfer image receptor.

Experimental example The ink liquid with the following composition was dispersed in a ball mill for 24 hours.
The mixture was applied onto a polyethylene terephthalate film (thickness: 6 μm) using a bar coater at a dry coating amount of 3 g/rd, and dried to obtain a thermal transfer sheet.

-Eji 2υGood- Disperse dye Kayaset Blue 136 15 parts Toluene 40 parts Methyl ethyl ketone 40 parts Thus obtained,
Using each of the thermal transfer image receptors and thermal transfer sheets of Examples 1 to 5 and Comparative Examples 1 to 3, a resolution of 6.
Images were formed on each thermal transfer image receptor with a recording energy of 6 mJ/dot using a dot/mm thermal printer. Next, this thermal transfer image receptor is placed on a flat surface (reference surface) as shown in FIG. The height (h) was measured and determined as the curl (torso) after printing. Further, the optical density (print density) of the printed surface was measured using a reflection densitometer DM-4000 (Dainippon Screen Manufacturing ■). Furthermore, the print surface was visually observed to evaluate the presence or absence of roughness on the print surface. On the other hand, each thermal transfer image receptor without image formation was heated to a temperature of 60°C.
Placed in a constant temperature chamber at a humidity of 90% RH for 24 hours.
After being left at room temperature for 1 hour, the curl height was measured in the same manner as above to determine the curl (ceramic) after storage.

The above results are shown in Table 1. Comparative Example 1, which is a conventional thermal transfer image receptor, had a large curl after printing, and Comparative Example 2 had a low printing density and white spots were observed in the transferred image, but Examples 1 to 5 of the present invention In all cases, there was almost no curl after printing, and appropriate print density was obtained. However, the first
The curl after printing of Example 1 in which the thickness of the central substrate sheet 1- (3b) shown in the figure is smaller than the thickness of the substrate sheet (3a) or the substrate sheet (3C) is different from that of the other examples. It was slightly larger. Also, the central base sea)
In Example 3 (3b) in which the Bekk smoothness was 800 seconds, some roughness was observed on the printed surface. In addition, in Comparative Example 3, which has a substrate configuration that is not symmetrical with respect to the center plane of the substrate, the curl after storage became large, but in the example of the present invention, the
It was mm. It was confirmed that the thermal transfer image receptors of Examples 1 and 2 could be used for OHP and seals, respectively.

Table 1 [Effects of the Invention] As explained above in detail, according to the present invention, the substrate used is a laminate of three substrate sheets, and at least the surface in contact with the dyeing layer has cushioning properties. Since it is large and has low thermal conductivity, and the thermal shrinkage rate of the central base sheet is low, it is possible to form a high-density, high-quality image and to obtain a thermal transfer image receptor that is free from deformation due to heat such as curling. Further, since a manufacturing method is used in which arbitrary base sheets are bonded together with an adhesive, the image receptor of the present invention can be manufactured simply, easily, and at low cost.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the thermal transfer image receptor of the present invention. FIG. 2 is a sectional view showing an embodiment of the thermal transfer image receptor of the present invention provided with an adhesive layer. FIG. 3 is a sectional view showing an embodiment of the thermal transfer image receptor of the present invention applied to a seal. FIG. 4 is a diagram illustrating a method for measuring the curl height of a thermal transfer image receptor according to the present invention. (1)...Image receptor for thermal transfer (2)...Dyeing layer (3)...Base (3a)...Upper base sheet (3b )...
...Central base sheet (3c) ...Lower base sheet (4) ...Thermal head (5) ...Thermal transfer sheet (6) ...・Base film (7)...Coloring layer (8)...Adhesive layer (9)...Peeling layer (and above)

Claims (10)

[Claims] (1) In a thermal transfer image receptor consisting of a base and a dyed layer, the base is composed of three base sheets, and each of these three base sheets has: (a) an upper part in contact with the dyed layer; The surface compressive elastic modulus of the surface of the base sheet is 14 kgf/cm^2 or more, and the thermal conductivity is 3
．． 5×10^-^4 cal/cm・sec・℃ or less, (b) the heat shrinkage rate of the central base sheet is 0.3% or less, (c) with respect to the horizontal center plane of the base, The upper and lower base sheets have symmetrical layer configurations and the same layer configuration, and (d) the base sheet itself is a symmetrical layer with respect to the center plane of the central base sheet itself. An image receptor for thermal transfer, characterized in that it has the following structure. (2) In the thermal transfer image receptor, the upper and lower base sheets located symmetrically with respect to the center plane of the base have approximately the same thickness and are greater than or equal to the thickness of the center base sheet. The thermal transfer image receptor according to claim 1, characterized in that: (3) The thermal transfer image receptor according to claim 1 or 2, wherein the entire base has a thickness of 100 μm to 250 μm. (4) In the thermal transfer image receptor, the Bekk smoothness of the surface of the central base sheet on the side receiving the dye transfer is 300.
The image receptor for thermal transfer according to any one of claims 1 to 3, characterized in that the time is 0 seconds or more. (5) The thermal transfer image receptor according to any one of claims 1 to 4, wherein the central base sheet includes cellulose fiber paper. (6) The thermal transfer image receptor according to any one of claims 1 to 4, wherein the central base sheet includes a plastic film selected from polyester, polycarbonate, and polyimide. body. (7) In the thermal transfer image receptor, the central base sheet is formed by laminating plastic films selected from polyethylene, polypropylene, and polyester on both sides of cellulose fiber paper. image receptor for thermal transfer. (8) In the thermal transfer image receptor, the base sheet in contact with the dyeing layer is at least one of polyethylene, polypropylene, polyvinylidene chloride, polyamide, polybutadiene, polyisoprene, polyisobutene, and polychloroprene, or polyethylene, polypropylene, polyurethane, Any one of claims 1 to 7, characterized in that it is a foam or porous body selected from polyvinyl chloride, polyacrylate, and polymethacrylate, or a laminate of two or more selected from the above. An image receptor for thermal transfer according to the invention. (9) In the thermal transfer image receptor, an optional adhesive layer;
The thermal transfer image receptor according to any one of claims 1 to 8, characterized in that a release layer is provided between the base sheet adjacent to the adhesive layer and further from the dyeing layer. body. (10) A method for manufacturing a thermal transfer image receptor, characterized in that when manufacturing the thermal transfer image receptor, the base sheet is bonded together via an adhesive layer to form a base.