JP2771566B2 - Thermal transfer image receiving sheet - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a thermal transfer image-receiving sheet, and more particularly, to a recording image excellent in color density, sharpness, and various fastnesses, particularly, migration resistance and stain resistance. An object of the present invention is to provide a heat transfer image receiving sheet that can be formed.

(Prior Art) Conventionally, various thermal transfer methods are known. Among them, a sublimable dye is used as a recording agent, and this is carried on a base sheet such as paper to form a thermal transfer sheet, which is then dyed with a sublimable dye. A sublimation transfer method in which a sublimable dye is transferred to a transfer-receiving material by applying heat energy in a pattern form from the back side of a thermal transfer sheet to a transferable material, for example, a woven polyester fabric, is performed.

(Problems to be Solved by the Invention) In the above-described sublimation transfer method, in the sublimation printing method in which the material to be transferred is, for example, a woven fabric made of polyester or the like, the heat energy is applied for a relatively long time. As a result, relatively good dye transfer is achieved as a result of heating with the applied thermal energy.

However, due to the progress of recording methods, using a thermal head or the like at a high speed, for example, using a transfer material provided with a dye receiving layer on a polyester sheet or paper, and delicate characters, figures or photographs on these transfer materials. In the case of forming an image, the application of heat energy is required to be extremely short in seconds or less, and therefore, in such a short time, the sublimable dye and the material to be transferred are not sufficiently heated. , An image having a sufficient density cannot be formed.

Therefore, in order to cope with such high-speed recording, sublimable dyes having excellent sublimability have been developed.However, dyes having excellent sublimability generally have a small molecular weight, and therefore, dyes are not contained in a transferred material after transfer. However, there is a problem in that the image is shifted with time or bleeds on the surface, so that the formed image is disturbed, unclear, or contaminates surrounding articles.

In order to avoid such a problem, when a sublimable dye having a relatively large molecular weight is used, the sublimation speed is inferior in the high-speed recording method as described above, so that an image having a satisfactory density cannot be formed as described above. Met.

As a method for increasing the dye receptivity, it is considered to form a dye receiving layer from a resin having a relatively low softening point (glass transition point) on an image receiving sheet. In this case, the dye receptivity is improved. However, during thermal transfer, the thermal transfer sheet and the receptor layer adhere to each other, or the dye layer itself transfers, so that a satisfactory image cannot be formed, and after the transfer, the dye forming the image remains in the receptor layer. The problem is that the image is easily transferred, and the image bleeds or dyes other articles in contact with the image.

On the other hand, when the receiving layer is formed of a resin having a high softening point,
An image having a satisfactory density cannot be formed due to reduced acceptability of the dye.

Therefore, an object of the present invention is to provide a clear image having a sufficient density in a thermal transfer method using a sublimable dye,
Moreover, an object of the present invention is to provide a thermal transfer image-receiving sheet in which a formed image exhibits excellent various fastnesses, particularly, migration resistance and stain resistance.

(Main stage for solving the problem) The above object is achieved by the present invention described below.

That is, the present invention comprises a substrate sheet and a dye receiving layer formed on at least one surface of the substrate sheet,
The thermal transfer image-receiving sheet, wherein the dye receiving layer comprises a block or graft copolymer containing a hard segment and a soft segment.

(Function) By forming the receiving layer of the thermal transfer image-receiving sheet from a copolymer containing a hard segment having a relatively high softening point and crystallinity and a soft segment having a relatively low softening point and low crystallinity, the soft segment portion is formed. Demonstrates good dye receptivity, prevents hard segments from sticking to the thermal transfer sheet during thermal transfer and prevents the diffusion of the dye forming the image, and provides sharpness, density and various fastnesses, especially transfer resistance and resistance. An image excellent in contamination and the like can be formed.

Preferred Embodiment Next, the present invention will be described in more detail with reference to preferred embodiments.

The thermal transfer image receiving sheet of the present invention comprises a base sheet and a dye receiving layer provided on at least one surface thereof.

As the base sheet used in the present invention, synthetic paper (polyolefin, polystyrene, etc.), woodfree paper, art paper, coated paper, cast-coated paper, wallpaper, backing paper, synthetic resin or emulsion impregnated paper, synthetic rubber latex Various plastic films or sheets, such as impregnated paper, paper with synthetic resin, paperboard, cellulose fiber paper, polyolefin, polyvinyl chloride, polyethylene terephthalate, polystyrene, polymethacrylate, polycarbonate, etc., can be used. A white opaque film formed by adding a white pigment or a filler to a resin, a foamed foamed sheet, or the like can be used, and is not particularly limited.

Also, a laminate formed by any combination of the above base sheets can be used. Examples of typical laminates include synthetic paper of cellulose fiber paper and synthetic paper or cellulose fiber paper and plastic film or sheet.

When the base sheet as described above has a poor adhesion to the receiving layer formed on the surface, it is preferable to subject the surface to a primer treatment or a corona discharge treatment.

The receiving layer formed on the surface of the base sheet is for receiving the sublimable dye transferred from the thermal transfer sheet and maintaining the formed image.

The present invention is characterized in that the receiving layer is formed mainly of a copolymer having a soft segment and a hard segment.

The hard segment is a portion whose softening point is relatively high, or a portion having a relatively high glass transition temperature, which can be a resin, for example, a polyester containing a large number of bulky components such as an aromatic group such as a benzene ring or a naphthalene ring, polyethers, polyamides, a polymer segment of polyimide, polycarbonate, polysulfide, Poriutaren, polystyrene, and a functional group having an interaction such as hydrogen bonds or covalent bonds, for example, -OH, -COOH, -NH _2, - CO
It contains many polar groups such as NH ₂ , —F, and —Cl, and forms a highly crystalline portion.

On the other hand, the soft segment is a portion that can be a resin having a relatively low softening point or a relatively low glass transition temperature, for example, a polymer segment such as an aliphatic polyester, polyether, polyamide, or polyurethane; It has a branched structure and a large number of bonds such as -O- and -S-, which can freely rotate the molecule, and has relatively low crystallinity.

The copolymer comprising the hard segment and the soft segment as described above can be easily obtained by a conventionally known polymerization technique, and various copolymers can be easily obtained from a market. In the present invention, as long as it has a hard segment and a soft segment, it may be either a block copolymer or a graft copolymer.

When the receiving layer is formed mainly of the copolymer as described above, the receiving layer has a soft segment portion having good dye-dyeing properties and a hard segment having heat resistance and hindering dye transfer from a microscopic viewpoint. As a result, the object of the present invention is achieved.

Therefore, in the present invention, if there are too many hard segments, the dye receptivity will be insufficient, while if there are too many soft segments, the heat resistance of the receiving layer, the migration resistance of the dye in the receiving layer, the stain resistance, etc. Becomes insufficient. According to the study of the present inventor, it has been found that a copolymer composed of a hard segment and a soft segment has a particularly preferable ratio of hard segment / soft segment = 10 to 50:90 to 50 by weight. In the present invention, other synthetic resins can be used in combination as long as the above-mentioned copolymer is the main component.

The thermal transfer image-receiving sheet of the present invention is obtained by adding at least one surface of the above-mentioned base sheet to a copolymer as described above or a mixture of the above-mentioned resin and other resins or a necessary additive, into an appropriate organic solvent. A dispersion which is dissolved or dispersed in an organic solvent or water is applied and dried by a forming means such as a gravure printing method, a screen printing method, and a reverse roll coding method using a gravure plate to form a dye receiving layer. Alternatively, it can be obtained by heat melting and extruding from a nozzle or the like to form a thermal transfer image receiving sheet. When the copolymer and another resin are used as a mixture, it is preferable that the copolymer accounts for 50% by weight or more, preferably 70% by weight or more in the total of both.

In the formation of the receiving layer, a pigment or filler such as titanium oxide, zinc oxide, kaolin clay, sodium carbonate, fine powdered silica, etc. is used for the purpose of improving the whiteness of the receiving layer to further enhance the sharpness of the transferred image. Can be added.
Further, in order to further enhance the light fastness of the transferred image, an ultraviolet absorber and / or a light stabilizer can be added to the receiving layer.

Such a dye-receiving layer may be of any thickness, but generally has a thickness of 1 to 10 .mu.m. Further, such a dye receiving layer is preferably a continuous coating, but may be formed as a discontinuous coating using a resin emulsion or a resin dispersion.

Although the thermal transfer image-receiving sheet of the present invention can basically be used satisfactorily even with the above-described configuration, the receiving layer of the present invention contains a release agent in order to impart good releasability from the thermal transfer sheet. It is preferred to contain.

Preferred release agents include silicone oil, phosphate ester-based surfactants, fluorine-based surfactants, and the like, with silicone oil being preferred.

As the silicone oil, modified silicone oils such as epoxy-modified, alkyl-modified, amino-modified, carboxyl-modified, alcohol-modified, fluorine-modified, alkylaralkyl-polyether-modified, epoxy / polyether-modified, and polyether-modified are preferable.

One or more release agents are used.
The amount of the release agent is preferably 1 to 20 parts by weight based on 100 parts by weight of the resin for forming the receiving layer. If the addition amount is not satisfied, problems such as fusion of the thermal transfer sheet and the receiving layer or reduction in printing sensitivity may occur. Such a release agent preferably accounts for about 0.5 to 30% by weight of the weight of the dye receiving layer.

The image-receiving sheet of the present invention can be applied to various uses such as a heat-transferable recording sheet, cards, and a sheet for making a transmission type original by appropriately selecting a base sheet.

Further, the image receiving sheet of the present invention can have a cushion layer between the base sheet and the receiving layer if necessary, and by providing such a cushion layer, noise during printing is reduced and the image information is reduced. Images can be transferred and recorded with good reproducibility.

Examples of the material constituting the cushion layer include polyurethane resin, acrylic resin, polyethylene resin, butadiene rubber, and epoxy resin. The thickness of the cushion layer is preferably about 2 to 20 μm.

Further, a lubricating layer can be provided on the back surface of the base sheet. Examples of the material of the lubricating layer include a methacrylate resin such as methyl methacrylate or a corresponding acrylate resin, and a vinyl resin such as a vinyl chloride-vinyl acetate copolymer.

Furthermore, it is also possible to provide a detection mark on the image receiving sheet. The detection mark is extremely convenient when positioning the thermal transfer sheet and the image receiving sheet. For example, a detection mark that can be detected by a photoelectric tube detection device can be provided on the back surface of the base sheet by printing or the like.

The thermal transfer sheet used when performing thermal transfer using the thermal transfer image-receiving sheet of the present invention as described above is provided with a dye layer containing a sublimable dye on paper or polyester film. Any of them can be used as it is in the present invention.

As a means for applying thermal energy at the time of thermal transfer, any conventionally known applying means can be used. For example, a thermal printer (for example, a video printer VY-
The intended purpose can be sufficiently achieved by applying a thermal energy of about 5 to 100 mJ / mm ² by controlling the recording time with a recording device such as 100).

(Effects) According to the present invention as described above, the receptor layer of the thermal transfer image-receiving sheet is formed from a copolymer containing a hard segment having a relatively high softening point and crystallinity and a soft segment having a relatively low softening point and crystallinity. By doing so, the soft segment exhibits good dye receptivity, the hard segment prevents adhesion to the thermal transfer sheet during transfer and prevents the dye forming the image from bleeding, and provides sharpness, density and migration resistance. And an image having excellent durability such as stain resistance.

(Examples) Next, the present invention will be described more specifically with reference to examples and comparative examples. In the following description, parts and% are based on weight unless otherwise specified.

Examples 1 to 6 and Comparative Examples 1 to 7 Synthetic paper (manufactured by Oji Oil Chemical Co., Ltd.,
Using m), a coating solution having the following composition was applied to one surface of the coating with a wire bar at a rate of 5.0 g / m ² when dried, and the thermal transfer image-receiving sheets of the present invention and comparative examples were obtained.

Polymers shown in Tables 1 and 2 below 20.0 parts Amino-modified silicone (KF-393, manufactured by Shin-Etsu Chemical Co., Ltd.)
0.8 parts Methyl ethyl ketone / toluene (weight ratio 1/1) 80.0 parts On the other hand, an ink composition for forming a dye-carrying layer having the following composition was prepared, and applied to a 6 μm-thick polyethylene terephthalate film having a heat-treated rear surface by a wire bar so that the dry coating amount was 1.0 g / m ^2. After drying, a thermal transfer sheet was obtained.

CI Disperse Blue 24 1.0 part Polyvinyl butyral resin 10.0 parts Methyl ethyl ketone / toluene (weight ratio 1/1) 90.0 parts The above-mentioned thermal transfer sheet and the thermal transfer image-receiving sheet of the present invention and the comparative example were respectively dyed and dye-received. The recording was performed with a thermal head from the back of the thermal transfer sheet under the conditions of a head applied voltage of 12.0 V, a pulse width of 16 msec, and a dot density of 6 dots / line, and the results shown in Table 3 below were obtained. In addition, the evaluation method of each performance shown in Table 3 was performed as follows.

(1) Printing sensitivity The reflection density of the image on the thermal transfer image receiving sheet on which the image was formed under the above printing conditions was measured (Macbeth densitometer RD-914).
And the highest concentration was selected. In Table 3,
The maximum density of Comparative Example 1 was set to 1.0, and Examples 1 to 6 and Comparative Examples 2 to 7 were shown by converting the density difference from Comparative Example 1.

(2) Dot Diffusion The degree of dot diffusion when the thermal transfer image-receiving sheet on which an image was formed under the above printing conditions was left indoors (25 ° C., 50% RH) for 3 days was visually evaluated. The results are shown on a scale.

1; no dot diffusion; 2; small dot diffusion; 3; large dot diffusion. (3) Contamination of printed matter The image-formed surface of the thermal transfer image-receiving sheet on which images were formed under the above printing conditions and a synthetic paper having a thickness of 110 µm were used. Superposition, 2
After applying a load of 0 g / cm ² and leaving at 60 ° C. for 3 days, the reflection density of the dye transferred to the synthetic paper was measured (Macbeth densitometer RD-91
4) The results are shown in Table 3.

As described above, according to the present invention, by using a copolymer resin comprising a hard segment and a soft segment as a resin for forming a receiving layer in an image receiving sheet, the dye transferred from the thermal transfer sheet can be sufficiently converted into a soft segment. Since the hard segments are fixed and the diffusion of the dye is prevented, there is an effect that a color image having high migration resistance and stain resistance can be obtained at a high density.

Claims (3)

(57) [Claims] 1. A base sheet and a dye receiving layer formed on at least one surface of the base sheet, wherein the dye receiving layer is made of a block or graft copolymer containing a hard segment and a soft segment. A heat transfer image receiving sheet characterized by the above-mentioned. 2. The weight ratio of the hard segment to the soft segment of the block or graft copolymer is from 10 to 50:90 to 5
The thermal transfer image-receiving sheet according to claim 1, wherein the value is 0. 3. The thermal transfer image receiving sheet according to claim 1, wherein the dye receiving layer further contains a release agent.