JP2740269B2 - Thermal transfer image receiving sheet - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a thermal transfer image-receiving sheet useful in a thermal transfer method using a sublimable dye (heat-migrating dye), and more specifically to dye dyeing properties and image light fastness. It is another object of the present invention to provide a thermal transfer image receiving sheet which is excellent in image quality, can perform high-speed recording without using a usual release agent, and can form a high-density and high-resolution transfer image.

(Conventional Technology and Problems Thereof) As a method for easily and quickly providing an excellent mono-color or full-color image instead of the conventional general printing method or printing method, an ink-jet method and a thermal transfer method have been developed. Among these, the so-called sublimation thermal transfer method using a sublimable dye is the most excellent, as it has excellent continuous gradation and gives a full-color image comparable to a color photograph.

The thermal transfer sheet used in the above sublimation type thermal transfer method is
In general, a dye sheet containing a sublimable dye is formed on one surface of a base material sheet such as a polyester film, and a heat-resistant layer is provided on the other surface of the base material sheet to prevent adhesion of a thermal head. Used.

The dye layer surface of such a thermal transfer sheet is superimposed on an image receiving sheet having an image receiving layer made of a polyester resin or the like, and the image is heated by a thermal head from the back of the thermal transfer sheet so that the dye in the dye layer is transferred to the image receiving sheet. Thus, a desired image is formed.

The image formed as described above is very clear and beautiful because the coloring material used is a dye, but there is a problem that the image has insufficient light resistance based on the dye. As a method for improving the light resistance of an image, there are a method of adding a light-resistant agent such as an ultraviolet absorber to a dye-receiving layer of an image-receiving sheet, and a method of selecting an appropriate resin as a material for forming the dye-receiving layer.

The present inventors have previously proposed a specific resin, that is, a copolymer of vinyl chloride, a (meth) acrylic acid-based monomer, and a polymer having a vinyl group, as the latter method for improving image light fastness.

However, in the case of a thermal transfer image receiving sheet using the above resin, an image having excellent light fastness is given, but if the temperature of the thermal head is increased in order to further increase the image density, the dye layer adheres to the image receiving sheet and the thermal transfer image receiving sheet is thermally transferred. Inconvenience occurs in that the sheet and the image receiving sheet adhere to each other. In an extreme case, a problem occurs in that the dye layer is peeled off at the time of peeling and transferred to the surface of the image receiving sheet as it is.

As a method for solving such a problem, a release agent such as silicone oil is contained in the dye receiving layer of the image receiving sheet. However, since the silicone oil is liquid at normal temperature, it is stored during storage. However, there is a drawback in that it is raised on the surface of the receptor layer and causes problems of blocking and contamination. On the other hand, there is a method using a thermosetting silicone oil. However, these methods require a heat treatment after the formation of the receptor layer, and have a problem that the production process is very complicated.

Furthermore, if a relatively large amount of silicone is added to give sufficient releasability to the receiving layer, the receptivity of the dye is reduced,
This causes a problem that the image receiving sheet is discolored and storage stability is deteriorated.

Accordingly, an object of the present invention is to provide a thermal transfer image-receiving sheet capable of forming a high-density and high-resolution transfer image excellent in light resistance and capable of high-speed recording without using a release agent when forming a receptor layer. It is.

(Means for Solving the Problems) The above object is achieved by the present invention described below.

That is, the present invention provides a thermal transfer image-receiving sheet having a dye-receiving layer provided on the surface of a base sheet, wherein the dye-receiving layer comprises a copolymer of vinyl chloride, a (meth) acrylic acid-based monomer and a polymer having a vinyl group. A thermal transfer sheet comprising a graft copolymer having at least one releasable segment selected from a polysiloxane segment, a fluorocarbon segment, and a long-chain alkyl segment grafted to the main chain.

(Function) By forming the dye receiving layer from a main chain having good light fastness and dye dyeing ability with grafted releasable segments, an image excellent in light fastness is provided, and a release agent is used. Thus, an image receiving sheet having excellent releasability, dye-dyeing property, adhesiveness to a substrate, and the like can be obtained.

That is, in the present invention, the polymer for forming the dye receiving layer is a main chain having at least one type of releasable segment, and if this is schematically represented, as shown in FIG. Thus, the releasable segment is graft-bonded as a side chain.

Such a grafted releasable segment itself,
Generally, it has low compatibility with the main chain. Thus, when a dye receiving layer is formed from such a graft copolymer, the releasable segments tend to microphase separate from the dye receiving layer and bleed to the surface of the dye receiving layer. On the other hand, the main chain is integrally bonded to the base sheet. When these effects are achieved, the releasable segment becomes rich on the surface of the dye receiving layer as shown in FIG. However, the releasable segment is not separated from the dye receiving layer by the main chain, and thus the releasable segment does not migrate to the surface of another article. Further, by selecting a main chain having a good dye-dyeing property and light resistance, excellent dye-dyeing property and light resistance can be provided.

(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 substrate sheet and a dye-receiving layer provided on at least one surface thereof with a releasable graft copolymer.

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. The thickness of these base sheets may be arbitrary, and for example, a thickness of about 10 to 300 μm is generally used.

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 dye receiving layer formed on the surface of the base sheet receives the sublimable dye transferred from the thermal transfer sheet and maintains the formed image.

In the present invention, the polymer forming the dye receiving layer is
A graft copolymer having at least one releasable segment selected from a polysiloxane segment, a fluorocarbon segment, and a long-chain alkyl segment grafted to a specific main chain.

The polymer as the main chain is a copolymer of vinyl chloride, a (meth) acrylic acid-based monomer and a polymer having a vinyl group, and (meth) acrylic acid (this term includes both acrylic acid and methacrylic acid. Examples of the monomer include (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and 2-ethoxy. Ethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, n-stearyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, glycidyl (meth) acrylate and the like can be mentioned. In the case of grafting with a releasing compound after the formation of the main chain as described later, a monomer having a functional group such as a hydroxyl group, a glycidyl group, and a carboxyl group can be used as a part of the above-mentioned monomer.

Examples of the polymer having a vinyl group include terminals of polymers such as polystyrene, styrene / acrylonitrile copolymer, polyester, polyvinyl chloride, polyvinyl acetate, vinyl chloride / vinyl acetate copolymer, polyamide, and poly (meth) acrylate. And a vinyl ester group or a (meth) acrylate group introduced therein. Various types of macromers are available from the market under the general name of macromer, and any of them can be used in the present invention. The molecular weight of these polymers is preferably about 1,000 to 15,000.

Although the copolymerization ratio of these main-chain copolymers is arbitrary,
A preferred range is that the weight ratio of vinyl chloride, the (meth) acrylic acid-based monomer and the polymer having a vinyl group is from 30 to
It is in the range of 90/5 to 60/3 to 20. When the ratio is outside the above range, favorable properties such as dye-dyeing property and light fastness are hardly compatible. Of course, other monomer units may be included as long as they are in a small amount other than the above monomers.

The production of these copolymers can be easily carried out by known emulsion polymerization, suspension polymerization, bulk polymerization, solution polymerization, and the like. Can be used. The molecular weight is 5,000 to 4
A preferred range is about 0,000.

The releasable graft copolymer used in the present invention is obtained by grafting a releasable compound to the above main chain copolymer, and can be synthesized by various methods. One preferred method is a method in which, after formation of the main chain, a functional compound present in the main chain is reacted with a release compound having a functional group that reacts with the functional group.

As an example of the release compound having the above functional group, the following compounds may be mentioned.

(A) Polysiloxane compound In the above formula, a part of the methyl group may be substituted with another alkyl group or an aromatic group such as a phenyl group.

(B) Fluorocarbon compounds (8) C ₈ F ₁₇ C ₂ H ₄ OH (9) C ₆ F ₁₃ C ₂ H ₄ OH _{(11) G 8 F 17 C} 2 H 4 OH (12) C 10 F 21 C 2 H 4 OH (13) C 8 F 17 SO 2 N (C 2 H 5) C 2 H 4 OH (14) C 8 _{F 17 SO 2 N (C 2} H 5) C 2 H 4 OH (15) C 6 F 13 COOH (16) C 6 F 13 COO1 (17) C 8 F 17 C 2 H 4 SH (C) Long-chain alkyl compounds Higher fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid and their acid halides, nonyl alcohol, caprylic alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol And higher alcohols such as stearyl alcohol, oleyl alcohol, linoleyl alcohol, and ricinoleyl alcohol; higher aldehydes such as caprinaldehyde, lauryl aldehyde, myristic aldehyde and stearin aldehyde; and higher amines such as decylamine, laurylamine and cetylamine.

The above examples are merely examples, and various other reactive release compounds can be obtained from, for example, Shin-Etsu Chemical Co., Ltd., and any of them can be used in the present invention. Particularly preferred is a monofunctional release compound having one functional group in one molecule, and when a polyfunctional compound having two or more functionalities is used, the obtained graft copolymer is used. Are not preferred because they tend to gel.

The relationship between the functional release compound and the resin as exemplified above is as shown in Table 1 below, where the functional group of the release compound is represented by X and the functional group of the main chain is represented by Y. Of course, the relationship between X and Y may be reversed, and each may be used in combination, and the present invention is not limited to these examples as long as both react.

Further, as another preferred production method, the functional release compound is reacted with a vinyl compound having a functional group that reacts with the functional group, and a monomer having a release segment is formed. The desired graft copolymer can be similarly obtained by copolymerizing with the monomer to be formed.

The above is an example of a preferable production method, and the present invention can naturally use a graft copolymer produced by other methods.

The content of the releasable segment in the above block copolymer is preferably in a range where the amount of the releasable segment is 3 to 60% by weight in the polymer. If the amount of the releasable segment is too small, the releasability is reduced. On the other hand, if it is too much, on the other hand, the transferability of the dye and the film strength are lowered, and the discoloration of the dye and the problem of storage stability occur, which is not preferable.

The thermal transfer image-receiving sheet of the present invention is obtained by dissolving a resin obtained by adding the necessary additives to the resin as described above on at least one surface of the base sheet in a suitable organic solvent or dispersing in an organic solvent or water. The dispersion thus obtained can be obtained by applying and drying a gravure printing method, a screen printing method, a gravure plate, or by a forming means such as a reverse roll coating method to form a dye receiving layer.

In forming the receiving layer, a pigment or filler such as titanium oxide, zinc oxide, kaolin clay, calcium carbonate, and finely powdered silica is used for the purpose of improving the whiteness of the receiving layer to further enhance the sharpness of a transferred image. Can be added.
Further, in order to further improve the discoloration resistance of the transferred image formed on the receiving layer, particularly the discoloration resistance in a room and the discoloration resistance in a dark place, an ultraviolet absorber or an antioxidant may be added to the receiving layer. I can do it.

In forming the dye receiving layer, a conventionally known resin for forming a receiving layer can be used in combination. When these known resins are used in combination, it is preferable that the graft copolymer accounts for 30% by weight or more of the entire resin.

The dye-receiving layer formed as described above may have any thickness, but generally has a thickness of 1 to 50 μm. 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.

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.

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 useful when positioning the thermal transfer sheet with the image receiving sheet. For example, a detection mark that can be detected by the 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 using the image receiving sheet of the present invention, any conventionally known applying means can be used, for example, a thermal printer (for example, Video Printer VY-100, manufactured by Hitachi, Ltd.) or the like. By controlling the recording time by using the recording apparatus described above, the intended purpose can be sufficiently achieved by applying an energy of about 5 to 100 mJ / mm ² .

(Effects) According to the present invention as described above, by forming a dye receiving amount from a specific resin, a releasing property, a dye dyeing property, an adhesive property to a substrate and a cushion can be achieved without using a releasing agent. An image receiving sheet having excellent properties can be obtained.

Therefore, a thermal transfer image receiving sheet capable of forming a high-density and high-resolution image with high speed and excellent light resistance can be prevented without using a release agent that causes various problems, thereby preventing fusion with the thermal transfer sheet at the time of transfer. Provided.

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

Reference Example 1 40 parts of vinyl chloride / n-butyl acrylate / hydroxyethyl methacrylate / vinyl-modified polystyrene copolymer (copolymerization weight ratio = 75/10/5/10) (molecular weight 120,000) was mixed in an equal amount of methyl ethyl ketone and toluene. Solvent 400
10 parts of the polysiloxane compound (5) (molecular weight 3,000) described above was gradually added dropwise at 60 ° C.
Allowed to react for hours. The product was a homogeneous product, and the polysiloxane compound could not be separated by the fractional precipitation method, and the polysiloxane compound reacted with the main chain polymer. Analysis showed that the amount of polysiloxane segment was about 7.4%.

REFERENCE EXAMPLE 2 A releasable graft copolymer was obtained in the same manner as in Reference Example 1, except that the above-mentioned Exemplary Compound (4) was used instead of the polysiloxane compound in Reference Example 1.

Reference Example 3 In place of the polysiloxane compound in Reference Example 1, a mixture of the above exemplified compounds (4) and (18) was used in an equal amount, and the same procedure was followed as in Reference Example 1 to obtain a releasable graft copolymer. Obtained.

Reference Example 4 100 parts of a monomer mixture of vinyl chloride / methyl methacrylate / vinyl-modified acrylonitrile-styrene copolymer / methacrylate of the polysiloxane compound (3) (molecular weight 1,000) (weight mixing ratio = 75/10/10/5) And 3 parts of azobisisobutyronitrile were dissolved in 1,000 parts of a mixed solvent of the same amount of methyl ethyl ketone and toluene, and polymerized at 70 ° C. for 6 hours to obtain a viscous polymerization solution. The product was a homogeneous product, and the polysiloxane compound could not be separated by the fractional precipitation method. Analysis showed that the amount of polysiloxane segments was about 4.9%.

Reference Example 5 A releasable graft copolymer was obtained in the same manner as in Reference Example 4, except that the acrylate of the above-mentioned exemplary compound (8) was used instead of the polysiloxane compound in Reference Example 4.

REFERENCE EXAMPLE 6 A releasable graft copolymer was obtained in the same manner as in Reference Example 4, except that the acrylate of Exemplified Compound (10) was used instead of the polysiloxane compound in Reference Example 4.

Reference Example 7 Instead of the polysiloxane compound in Reference Example 4, an equivalent mixture of the methacrylate of Exemplified Compound (1) and the methacrylate of Compound (14) was used.
In the same manner as in the above, a releasable graft copolymer was obtained.

Reference Example 8 A releasable graft copolymer was obtained in the same manner as in Reference Example 4, except that laurylaminoacrylate was used instead of the polysiloxane compound in Reference Example 4.

Reference Example 9 Instead of the main chain polymer in Reference Example 1, vinyl chloride was used.
/ n-butyl acrylate / glycidyl methacrylate /
Using a vinyl-modified polymethyl methacrylate copolymer (copolymerization weight ratio = 77/10/5/8) (molecular weight 100,000) and an equivalent mixture of the exemplified compound (10) and stearyl alcohol as a releasing compound The rest was the same as in Reference Example 1 to obtain a releasable graft copolymer.

Reference Example 10 Instead of the main chain polymer in Reference Example 1, vinyl chloride was used.
/ n-butyl acrylate / p-aminostyrene / vinyl-modified polymethyl methacrylate copolymer (copolymerization weight ratio =
70/10/10/10) (molecular weight: 150,000) and an equimolar mixture of Exemplified Compound (6) and stearyl acid chloride as a releasing compound. A graft copolymer was obtained.

Examples 1 to 10 Synthetic paper (Yupo FRG-150, thickness 150) was used as a base sheet.
μm, manufactured by Oji Yuka Co., Ltd.), and applying and drying a coating solution having the following composition at a ratio of 5.0 g / m ² when dried with a bar coater on one surface to obtain a thermal transfer image-receiving sheet of the present invention. Was.

Composition for receptor layer: 15.0 parts of graft copolymer of reference example Solvent (butyl acetate / toluene / xylene (2/1/2) 85.0 parts Comparative Example 1 95 mol% of methyl methacrylate and hydroxyethyl were used in place of the graft copolymer of the example. Methacrylate 5
A thermal transfer image-receiving sheet of a comparative example was obtained in the same manner as in Example except that 4.0 parts by mol of a copolymer and 0.3 part of silicone oil (trade name: KF-96, manufactured by Shin-Etsu Chemical Co., Ltd.) were used.

Comparative Example 2 A thermal transfer image-receiving sheet of a comparative example was obtained in the same manner as in the example except that 4.0 parts of polyvinyl butyral (polymerization degree: 1,700, hydroxyl group content: 33 mol%) was used instead of the graft copolymer of the example.

Comparative Example 3 A thermal transfer image-receiving sheet of Comparative Example was obtained in the same manner as in Example except that the copolymer used as a raw material in Reference Example 1 was used instead of the graft copolymer of Example.

Prepare an ink composition for forming a dye layer having the following composition, apply it to a 6 μm-thick polyethylene terephthalate film having a heat-resistant rear surface, and apply and dry it with a wire bar so that the dry application amount becomes 1.0 g / m ^2. A thermal transfer sheet was obtained.

Disperse dye (Kayaset Blue 714, manufactured by Nippon Kayaku) 4.0 parts Polyvinyl butyral resin (ESREC BX-1, manufactured by Sekisui Chemical) 4.3 parts Fluorinated fatty acid-modified silicone wax (X-24-3525,
0.4 parts Methyl ethyl ketone / toluene (weight ratio 1/1) 80.0 parts Isobutanol 10.0 parts The above-mentioned thermal transfer image-receiving sheet and the above-mentioned thermal transfer sheet were
Thermal dye sublimation transfer printer (VY-50, manufactured by Hitachi, Ltd.)
The recording was performed with a thermal head from the back surface of the thermal transfer sheet at a printing energy of 90 mJ / mm ² using the above method, and the results shown in Table 2 below were obtained.

Evaluation criteria; Adhesion to substrate: Cellotape peel test ○: No peeling ×: 50% or more peeling Release property: Peeling by hand after printing ○: Easy peeling and no problem ×: Difficult to peel and one of dye layer The part was transferred as it was.

White spots on printed matter: Inspection of solid printed area with a microscope ○: No omission Δ: Partial white spots ×: 10% or more white spots Print density: Relative optical density when Comparative Example 1 is set to 1.00 Discoloration of base material: Visual observation of non-printed area after leaving at 80 ° C and 90% RH for 2 hours ○: No change △: Slightly yellow discoloration Preservability of printed matter: Visual observation of printed area after standing at 40 ° C and 90% RH for 48 hours ○: No change Δ: Slightly dull discoloration Light fastness: According to JIS L 0842, those with an initial fastness exceeding 3 grade in the second exposure method of JIS L 0841 were rated as ○, and those with less than that were rated as Δ.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a graft copolymer used in the present invention, and FIG. 2 is a schematic diagram of a dye receiving layer.

Claims (3)

(57) [Claims] 1. A thermal transfer image-receiving sheet having a dye-receiving layer provided on the surface of a substrate sheet, wherein the dye-receiving layer is made of a copolymer of vinyl chloride, a (meth) acrylic acid-based monomer and a polymer having a vinyl group. A thermal transfer image-receiving sheet comprising a graft copolymer having at least one releasable segment selected from a polysiloxane segment, a fluorocarbon segment and a long-chain alkyl segment grafted to the main chain. 2. The copolymerization ratio (weight) of the main chain is vinyl chloride /
2. The thermal transfer image-receiving sheet according to claim 1, wherein (meth) acrylic acid monomer / polymer having a vinyl group = 30 to 90/5 to 60/3 to 20. 3. The thermal transfer image-receiving sheet according to claim 1, wherein the content of the releasable segment is 3 to 60% by weight.