JPH07125456A - Thermal transfer sheet - Google Patents

Abstract

PURPOSE:To make the long-term preservability of a dye layer excellent and to form an image of high quality generating no background staining, in a thermal transfer sheet wherein the dye layer consisting of a dye and a binder resin is provided on a base material film, by using an acrylic resin modified cellulosic resin as the binder resin. CONSTITUTION:In a thermal transfer sheet wherein a dye layer consisting of a dye and a binder resin is provided on a base material film useful for a thermal transfer system using a sublimable dye, as the binder resin, an acrylic resin modified cellulosic resin is used. The acrylic resin modified cellulosic resin is obtained by polymerizing an acrylic monomer in a cellulosic resin soln. and, for example, ethyl cellulose, hydroxyethyl cellulose, ethylhydroxy cellulose and the like are designated. As the acrylic monomer used at the time of the modification of a cellulosic resin, one having a hydrophilic group in its molecule is pref. used. The acrylic monomer is used in a ratio of 5-25 pts.wt. per 100 pts.wt. of the cellulosic resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer sheet, and more particularly, it is useful for a thermal transfer system using a sublimable dye (heat transfer dye), has excellent long-term storage stability of a dye layer, and causes scumming. An object of the present invention is to provide a thermal transfer sheet capable of forming a high-quality image that does not.

[0002]

2. Description of the Related Art Inkjet systems, thermal transfer systems, etc. have been developed as a method for simply and rapidly providing an excellent monocolor or full-color image in place of conventional general printing methods and printing methods. , The so-called sublimation heat transfer method, which uses a sublimable dye, has the best continuous gradation and gives a full-color image comparable to a color photograph. The thermal transfer sheet used in the sublimation type thermal transfer system described above forms a dye layer composed of a sublimable dye and a binder resin on one surface of a substrate film such as a polyester film, and on the other hand, in order to prevent the thermal head from sticking. In general, a substrate film provided with a heat-resistant layer on the other side is used. The dye layer surface of such a thermal transfer sheet is superposed on an image receiving sheet having a dye receiving layer made of polyester resin or the like, and the dye in the dye layer is transferred to the image receiving sheet by heating imagewise from the back surface of the thermal transfer sheet with a thermal head. Then, a desired image is formed.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the above-mentioned thermal transfer sheet, it is preferable that the dye in the dye layer is easily sublimated and transferred by heating, and therefore, a cellulose resin having a relatively low affinity for the dye is a binder resin. Often used as. However, since the cellulosic resin has a low affinity with the dye, the compatibility between the binder resin and the dye is not sufficient when the coating liquid used for forming the dye layer is prepared. Further, the thermal transfer sheet obtained by forming a dye layer with the coating solution has a high-concentration image because the dye is agglomerated, precipitated or crystallized in the dye layer during the long-term storage to reduce the heat transfer property of the dye. Is not formed. Further, there is a problem that the dye bleeds out onto the surface of the dye layer, and during thermal transfer, the surface of the image receiving sheet which is the material to be transferred is stained.
Therefore, an object of the present invention is to solve the above problems, to provide a thermal transfer sheet which is excellent in long-term storage stability of a dye layer and which can form a high-quality image in which background stain does not occur.

[0004]

The above object can be achieved by the present invention described below. That is, the present invention is a thermal transfer sheet in which a dye layer comprising a dye and a binder resin is provided on a base film, wherein the binder resin comprises an acrylic modified cellulose resin.

[0005]

[Function] By using an acrylic modified cellulose-based resin as a binder resin for forming the dye layer of the thermal transfer sheet, the thermal transfer capable of forming a high-quality image having excellent long-term storage stability of the dye layer and causing no background stain. Seats can be provided.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to the preferred embodiments. The thermal transfer sheet of the present invention,
Basically, as in the prior art, a dye layer is formed on a substrate film via an intermediate layer, if necessary. The substrate film of the thermal transfer sheet of the present invention as described above may be any one as long as it has a conventionally known degree of heat resistance and strength, for example, 0.5 to 50 μm, preferably 3 to 10 μm. Paper having a certain thickness, various processed papers, polyester film, polystyrene film, polypropylene film, polysulfone film, aramid film, polycarbonate film, polyvinyl alcohol film, cellophane, etc. are particularly preferable. These substrate films may be of single-wafer type or continuous film, and are not particularly limited. The dye layer formed on the surface of the base film is a layer in which the dye is carried by an arbitrary binder resin.

The dyes used in the present invention are not particularly limited, and any of the dyes used in conventionally known thermal transfer sheets can be effectively used in the present invention. For example, some preferred dyes include MS Red as a red dye.
G, Macrolex Red Violet R, C
eresRed7B, Samaron Red HBS
L, Resolin Red F3BS and the like,
In addition, examples of yellow dyes include Holon Brilliant Yellow 6GL, PTY-52, and Macrolex Yellow 6G, and examples of blue dyes include Kayaset Blue 714, Waxolin Blue AP-FW, and Holon Brilliant Blue S-. R, MS blue 100 and the like.

In the present invention, an acrylic modified cellulosic resin is used as a binder resin for carrying the above dye. The acrylic modified cellulosic resin is obtained by polymerizing an acrylic monomer in a cellulosic resin solution. As the cellulosic resin to be used, any conventionally known one can be used, and if preferable examples are shown, ethyl cellulose, hydroxyethyl cellulose,
Examples thereof include cellulosic resins such as ethylhydroxycellulose, hydroxypropylcellulose, methylcellulose, cellulose acetate, and cellulose butyrate acetate, and among these, ethylcellulose is most preferable. Examples of the organic solvent used when the cellulose resin is modified with an acrylic resin include ester solvents such as methyl formate, ethyl formate, ethyl acetate and butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone and the like. Ketone solvent, hydrocarbon solvent such as toluene, benzene, and xylene, alcohol solvent such as n-butanol and isopropanol, ether solvent such as n-butyl ether, and the like, and the cellulose resin is about 5 to 50 weight. It is preferably used at a concentration of%.

Acrylic monomers used when modifying the above cellulose-based resin include acrylic acid or methacrylic acid, their ester and amide derivatives, and the like.
Any acrylic monomer can be used,
Preferred acrylic monomers are those having a hydrophilic group in the molecule, such as (meth) acrylamide, N-
It is a hydrophilic acrylic monomer such as an alkyl derivative, mono- or dialkylaminoalkyl (meth) acrylate, and hydroxyalkyl (meth) acrylate. Specifically, for example, (meth) acrylamide, N-mono or dimethyl (meth) acrylamide, N-mono or diethyl (meth) acrylamide, N-mono or dipropyl (meth) acrylamide, mono or dimethylaminoethyl (meth) Acrylate, mono or diethylaminoethyl (meth) acrylate, mono or dipropylethyl (meth) acrylate, mono or dimethylaminopropyl (meth) acrylate, mono or diethylaminopropyl (meth) acrylate, mono or dipropylaminopropyl (meth) acrylate , Hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxyhexyl (meth) acrylate, 3
-Chloro-2-hydroxypropyl (meth) acrylate and the like can be mentioned.

Of course, the acrylic monomers used in the present invention are not limited to the above examples, and other acrylic monomers, mixtures of the above exemplified monomers, mixtures of the above exemplified monomers with other acrylic monomers or monomers other than acrylic. Can also be used. The amount of the acrylic monomer used is preferably 5 to 25 parts by weight per 100 parts by weight of the cellulosic resin. If the amount of the acrylic monomer is too small, the object of the present invention is insufficiently achieved. On the other hand, when the amount of the acrylic monomer is too large, the sublimation transferability of the dye from the formed dye layer becomes insufficient.

The modification of the cellulosic resin is carried out by adding the above-mentioned acrylic monomer and a proper amount of a polymerization initiator such as a peroxide or an azo compound to an organic solvent of the cellulosic resin, and heating the mixture at a temperature of about 65 to 100 ° C. And polymerize for about 8-12 hours. The solution of the acrylic modified cellulosic resin thus obtained can be used as it is as a raw material of the coating liquid for forming the dye layer depending on the type of the solvent used. The modified cellulosic resin can be taken out as a solid and used as a binder resin for the dye layer. The acrylic-modified cellulosic resin used in the present invention cannot be completely separated into a cellulosic resin as a raw material and an acrylic polymer by a usual method, and an acrylic component is actually chemically bonded to the cellulosic resin. Although it is unknown whether or not there is a clear difference in the characteristics from a simple mixture of the same raw materials.

In the present invention, it is essential to use the above-mentioned acrylic modified cellulosic resin as the binder resin for the dye layer, but it is not limited to the use of the acrylic modified cellulosic resin alone, and other binders may be used. Resins such as ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxy cellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate,
You may use together with cellulose resin, such as a cellulose acetate butyrate, polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, polyvinylpyrrolidone, polyacrylamide, etc. vinyl resin, polyester resin, etc. When used in combination, the amount of the acrylic modified cellulosic resin preferably accounts for 25% by weight or more in the entire binder resin.

The dye layer is preferably prepared by adding the sublimable dye, the binder resin, the release agent and other optional components in a suitable solvent to dissolve or disperse each component, or a coating for dye layer formation or An ink is prepared, which is applied and dried on the above-mentioned substrate film to form. The dye layer thus formed has a thickness of 0.2 to 5.0 μm, preferably 0.1.
It is preferable that the sublimable dye has a thickness of about 4 to 2.0 μm, and the sublimable dye in the dye layer is present in an amount of 5 to 90% by weight, preferably 10 to 70% by weight based on the weight of the dye layer. is there. The dye layer to be formed is formed by selecting one color from the above dyes when the desired image is a mono color image, and when the desired image is a full color image, for example, a suitable cyan, magenta and Yellow (and optionally black) is selected to form yellow, magenta and cyan (and optionally black) dye layers.

Further, in the present invention, an intermediate layer can be provided between the base film and the dye layer for the purpose of improving adhesiveness, cushioning property and the like. Examples of the material forming the intermediate layer include polyurethane resin, acrylic resin, polyethylene resin, butadiene rubber, and epoxy resin. The thickness of the intermediate layer is preferably about 0.1 to 5 μm. The method for forming the intermediate layer may be the same as that for the dye. The image-receiving sheet used for forming an image using the thermal transfer sheet as described above may be any one as long as its recording surface has a dye-accepting property for the dye, and a dye-accepting property. Without paper, metal, glass,
In the case of synthetic resin or the like, the dye receiving layer may be formed on at least one surface thereof. In particular, when the thermal transfer sheet of the present invention is used, even if the image receiving sheet has a smooth dye receiving layer, the slip property and the peeling property are good.

As the means for applying thermal energy used when performing thermal transfer using the above-mentioned thermal transfer sheet and the above thermal transfer image-receiving sheet, any conventionally known applying means can be used. For example, a thermal printer (for example, By controlling the recording time with a recording device such as a video printer VY-100 manufactured by Hitachi, Ltd., 5
A desired image is formed by applying thermal energy of about 100 mJ / mm ² .

[0016]

EXAMPLES Next, the present invention will be described more specifically with reference to Reference Examples, Examples and Comparative Examples. In the text, parts and% are based on weight unless otherwise specified. Reference Example 1 (Synthesis of acrylic modified cellulose resin) Ethyl cellulose (N-20 manufactured by Hercules Co., Ltd.) was added to 95 parts of a 1: 1 mixed solvent of toluene / methyl ethyl ketone.
0, degree of substitution of ethoxy group of anhydrous glycol unit 2.41-
2.5) 5 parts were added and completely dissolved by stirring at 50 ° C. for 4 hours. The solution viscosity was 550 cps. A mixture of the acrylic monomer shown in Table 1 below and a polymerization initiator (t-butyloxy-2-ethylhexanoate) corresponding to 1% of the monomer (toluene / methyl ethyl ketone 1: 1 mixed solvent) was added to the ethyl cellulose solution. 10
% Solution) was added dropwise over 2 hours, a predetermined amount of a solution of a polymerization initiator of toluene / methyl ethyl ketone 1: 1 mixed solvent was added, and the polymerization reaction was further performed at 80 ° C. for 4 hours. Then, the solution was cooled to 40 ° C. to obtain a solution of acrylic modified cellulose resin. For reference, a homopolymer was prepared from each acrylic monomer under the same conditions (see Table 2).

[0017]

[Table 1] (The molecular weight of the obtained acrylic modified cellulosic resin could not be measured.)

[0018]

[Table 2]

Examples 1 to 19 A 6 μm thick polyethylene terephthalate film having a heat-resistant back surface on which a dye layer is formed as a base film is coated with the following ink composition for forming a dye layer so as to have a dry thickness. A thermal transfer sheet of the present invention was prepared by applying and drying by gravure printing so as to obtain 1.0 g / m ² . Ink for dye layer : Sublimation dye (Nippon Kayaku, CI Solvent Blue 63) 4.0 parts Binder resin shown in Table 1 3.0 parts Methyl ethyl ketone / toluene (1/1) 93.0 parts Comparison Examples 1 to 15 Thermal transfer sheets were obtained in the same manner as in Examples except that the binder resin in Table 3 below was used instead of the binder resin in Example 1.

[0020]

[Table 3]

Reference Example 2 Next, synthetic paper YUPO (thickness 150 μm) was used as a substrate,
An image-receiving sheet used in the present invention and comparative examples was coated on one surface with a coating solution for receiving layer having the following composition at a rate of 4.5 g / m ² when dried and dried at 100 ° C. for 30 minutes. Obtained. Receptor layer coating liquid composition : Polyester resin (Toyobo, Vylon 103) 100 parts Amino-modified silicone oil (Shin-Etsu Chemical Co., X-22-343) 0.5 part Epoxy-modified silicone oil (Shin-Etsu Chemical Co., KF- 393) 0.5 part Toluene / methyl ethyl ketone (weight ratio 1/1) 500 parts

Thermal transfer test : The thermal transfer sheets of the above-mentioned Examples and Comparative Examples were sandwiched between synthetic papers (Yupo), a force of 25 g / cm ² was applied, the mixture was allowed to stand at 60 ° C. for 100 hours, and then the coloring amount on the synthetic paper was measured. (Reflection density) is measured by an optical densitometer RD-918.
(Manufactured by Macbeth Co.) to examine the bleed-out property from the dye layer to the surface. The aggregation, precipitation or crystallization of the dye in the dye layer was observed by an optical microscope at a magnification of 10 and the storability was judged according to the following criteria. ◯: Dye deposition was not observed. Δ: Some deposition of dye was observed. X: A large amount of dye was observed to be deposited. Further, by using these thermal transfer sheets, the dye layer of the thermal transfer sheet and the receiving layer of the image receiving sheet are superposed so as to face each other in a printer, and a thermal head (KMT-85-6, MPD2) is placed from the back surface of the thermal transfer sheet. Thermal head recording was performed under the conditions of a head applied voltage of 12.0 V and a printing time of 8 msec, and the obtained image densities were compared with each other to obtain the results shown in Tables 5 and 6 below.

[0023]

[Table 5]

[0024]

[Table 6]

Example 16 The same results as in Examples 1 to 19 were obtained by using hydroxyethyl cellulose, ethyl hydroxycellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate or cellulose butyrate acetate instead of ethyl cellulose in Example 1, respectively. was gotten.

[0026]

[Effects] According to the present invention as described above, by using an acrylic modified cellulosic resin as a binder resin for forming a dye layer of a thermal transfer sheet, the dye layer has excellent long-term storage stability and does not cause scumming. A thermal transfer sheet capable of forming a high quality image can be provided.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuubu Urabe 380-128 Shimoootsuka Shimo-Otsuka, Kashiwa-shi, Chiba Special Colors Industry Co., Ltd.

Claims (4)

[Claims] 1. A thermal transfer sheet comprising a substrate film and a dye layer comprising a dye and a binder resin provided on the substrate film,
A thermal transfer sheet, wherein the binder resin comprises an acrylic modified cellulose resin. 2. The thermal transfer sheet according to claim 1, wherein the acrylic modified cellulosic resin is obtained by polymerizing an acrylic monomer in a cellulosic resin solution. 3. The thermal transfer sheet according to claim 1, wherein the acrylic component comprises a hydrophilic acrylic monomer. 4. A cellulose resin and an acrylic component,
The thermal transfer sheet according to claim 1, wherein the former is in the range of 5 to 25 parts by weight per 100 parts by weight of the former.