JP2009286060A - Thermal transfer sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal transfer sheet having improved preservation property. <P>SOLUTION: A dye layer comprising a thermally migrating dye and a binder resin is formed on one side surface 2a of a base 2, a heat-resistant smooth layer is formed on the other side surface, the thermally migrating dye includes an indoaniline type dye, the binder resin includes a polyvinyl acetal resin (A) and a polyvinyl acetal resin (B) both of which are represented by general formula (1), and a mass ratio of the polyvinyl acetal resin (A) to the polyvinyl acetal resin (B) is set as follow: polyvinyl acetal resin (A)/polyvinyl acetal resin (B)=9/1 to 5/5. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a thermal transfer sheet in which a dye layer is formed on one surface of a substrate, and a heat resistant slipping layer is formed on the other surface of the substrate. More specifically, the present invention can suppress the hue change of the printed material before and after the environmental preservation of the thermal transfer sheet (ink ribbon), can suppress the migration of the dye to the heat-resistant slipping layer facing the dye layer, and can also cause scumming. The present invention relates to a thermal transfer sheet that can be prevented and can form a print of excellent quality.

  Conventionally, various thermal transfer recording methods are known. Among them, as a thermal transfer recording method, a method using a thermal transfer sheet having a dye layer in which a dye for sublimation transfer is used as a recording material and this is supported on a base material such as a polyester film with a suitable binder resin has been proposed. .

  In this thermal transfer recording method, a sublimation dye is thermally transferred from a thermal transfer sheet onto a transfer material that can be dyed with a sublimation dye, for example, a paper or a plastic film, and a dye-receiving layer is formed. Form. In this method, as a heating means, a color dot in which a large number of heating colors of three colors or four colors are adjusted is transferred to a dye receiving layer of a thermal transfer image receiving sheet by heating with a thermal head of a printer, and the multicolored color dots are transferred. To reproduce the full color of the document. The image formed in this way is very clear and excellent in transparency since the color material used is a dye. For this reason, the obtained image is excellent in reproducibility and gradation of intermediate colors, is similar to an image obtained by conventional offset printing or gravure printing, and can form a high-quality image comparable to a full-color photographic image.

  In such a thermal transfer recording system by sublimation transfer, as the printing speed of the thermal transfer printer is increased, there has been a problem that a sufficient print density cannot be obtained with the conventional thermal transfer sheet. Further, in the thermal transfer recording system, a higher density and clearer image is required for a printed image by thermal transfer. In the thermal transfer recording system, many attempts have been made to improve a thermal transfer sheet and a thermal transfer image receiving sheet on which an image is formed by receiving a sublimation dye transferred from the thermal transfer sheet.

  For example, attempts have been made to improve transfer sensitivity in printing by thinning a thermal transfer sheet. However, when the thermal transfer sheet is thinned, there is a problem that wrinkles are generated due to heat, pressure, or the like during manufacture of the thermal transfer sheet or during thermal transfer recording, and in some cases, the thermal transfer sheet is cut.

  As a method for improving the transfer sensitivity, attempts have been made to increase the ratio of the dye / binder resin in the dye layer to achieve a higher concentration. According to this method, since the dye density per unit area is certainly high, the dye printing density is high. However, in this method, since an excessive amount of dye is contained with respect to the amount of the binder resin, when the product is stored in the form of an ink ribbon, the dye easily bleeds out from the dye layer depending on the temperature environment. Progresses. As a result, when the dye bleeds out, the hue change from the initial state increases, and the dye transfer to the back layer (heat resistant slipping layer) that faces the dye occurs. In addition, when the dye bleeds out, “ground fog” occurs in which the dye bleed from the dye layer is transferred to a white background area where no energy is applied.

  In order to solve these problems, the following Patent Document 1 proposes a method of mixing a polyvinyl acetoacetal resin having a polymerization degree of 1500 or more and a polyvinyl butyral resin in an ink layer. However, in the following Patent Document 1, the degree of acetalization is specified, but the amount of acetyl group is not specified.

  The thermal transfer sheet as described above cannot provide excellent storage stability and transferability. In particular, in the cyan dye layer, the cyan dye is likely to bleed and fogging is likely to occur.

Japanese Patent No. 31006166

  Therefore, the present invention has been proposed in view of such conventional circumstances, and it is possible to suppress the hue change of a printed matter before and after environmental preservation of a thermal transfer sheet, It is possible to suppress transfer of a dye, particularly an indoaniline-based dye, to the heat-resistant slip layer facing the layer. In addition, the present invention provides a thermal transfer sheet that can prevent background fogging and can form an excellent quality printed matter without abnormal transfer that causes the entire dye layer to be transferred when printing on a transfer object. For the purpose.

  In the thermal transfer sheet according to the present invention that achieves the above-mentioned object, a dye layer comprising a heat transferable dye and a binder resin is formed on one side of a substrate, and a heat resistant slipping layer is formed on the other side. The formed heat transfer dye contains an indoaniline dye, and the binder resin contains both the polyvinyl acetal resin A and the polyvinyl acetal resin B represented by the following general formula 1, and the polyvinyl acetal resin A And the polyvinyl acetal resin B have a mass ratio of polyvinyl acetal resin A: polyvinyl acetal resin B = 9: 1 to 5: 5.

(In the above general formula 1, X, Y, and Z represent mol% of each structural unit in each polyville acetal resin, and R represents a methyl group or an n-propyl group. Here, in the polyvinyl acetal resin A, Is 0.5 ≦ Y ≦ 5, and for the polyvinyl acetal resin B, 10 ≦ Y ≦ 20.)

  In the present invention, an indoaniline dye is contained in the dye layer, and the polyvinyl acetal resin A and the polyvinyl acetal resin B represented by the general formula 1 are used as the binder resin, and the mass ratio of the polyvinyl acetal resin A and the polyvinyl acetal resin B. Is contained so as to be polyvinyl acetal resin A: polyvinyl acetal resin B = 9: 1 to 5: 5, the retention of indoaniline dye in the dye layer is increased, and the hue of the printed matter before and after storage It is possible to suppress the occurrence of changes, and it is possible to prevent the transition to the heat-resistant slip layer during storage, the fogging of the ground during printing, and the occurrence of abnormal transfer.

  Hereinafter, a thermal transfer sheet to which the present invention is applied will be described in detail with reference to the drawings.

  As shown in FIG. 1, in the thermal transfer sheet 1, a dye layer 3 containing a sublimation dye and a binder resin is formed on one surface 2a of the substrate 2, and the other side opposite to this is formed. On the surface 2b, a heat-resistant slipping layer 4 that improves running performance is formed.

  The thermal transfer sheet 1 is in a state in which the form of the final product is wound in a roll shape, and the base materials 2 are overlapped. That is, in the thermal transfer sheet 1, when wound in a roll shape, the dye layer 3 formed on one surface 2a of the substrate 2 and the heat-resistant slip layer 4 formed on the other surface 2b overlap. . Thus, in the thermal transfer sheet 1, the dye layer 3 and the heat-resistant slip layer 4 are stored as a final product in a state where they overlap each other.

  The thermal transfer sheet 1 is attached to, for example, a thermal transfer printer apparatus including a thermal head as a heating unit, and the dye layer 3 is heated by the thermal head from the heat-resistant slipping layer 4 side, and is transferred into the thermal transfer printer apparatus. For example, the dye is thermally transferred to photographic paper to form an image.

  Specifically, any material can be used for the substrate 2 as long as it is used as a thermal transfer sheet (ink ribbon). Examples of the substrate 2 include polyester film, polystyrene film, polypropylene film, polysulfone film, polycarbonate film, polyimide film, and aramid film. In addition, as this base material 2, the thing whose thickness is 1-30 micrometers, Furthermore, 2-10 micrometers is preferable.

  In the base material 2, an adhesion treatment is often performed on the surface 2 a on which the dye layer 3 is formed. When the dye layer 3 is applied and formed on the surface 2a of the substrate 2, since the wettability, adhesiveness, and the like of the coating solution are likely to be insufficient, an adhesion treatment is performed. As the adhesion treatment, known resin surfaces such as corona discharge treatment, flame treatment, ozone treatment, ultraviolet treatment, radiation treatment, surface roughening treatment, chemical treatment, plasma treatment, low temperature plasma treatment, primer treatment, grafting treatment, etc. The reforming technique can be applied as it is. Two or more of these treatments can be used in combination. The primer treatment can be performed, for example, by applying a primer solution to an unstretched film at the time of film formation by melt extrusion of a plastic film and then stretching the film.

  Furthermore, as the above-described adhesion treatment of the substrate 2, a primer layer (not shown) may be applied between the substrate 2 and the dye layer 3. The primer layer preferably has a high adhesive force between the substrate 2 and the dye layer 3 in order to suppress abnormal transfer, and is difficult to be dyed with a dye in order to suppress a decrease in print density. The primer layer can be formed from a resin as shown below. Examples of the resin that forms the primer layer include polyester resins, polyacrylate resins, polyvinyl acetate resins, polyurethane resins, styrene acrylate resins, polyacrylamide resins, polyamide resins, and polyether resins. And polystyrene resins, polyethylene resins, polypropylene resins, vinyl resins such as polyvinyl chloride resins and polyvinyl alcohol resins, and polyvinyl acetal resins such as polyvinyl acetoacetal and polyvinyl butyral.

Primer layer is a gravure printing method or screen printing method prepared by dissolving or dispersing the above resin with additives as necessary dissolved in water or an aqueous solvent or organic solvent of alcohols. It can be formed using a known coating means such as a reverse roll coating method using a gravure plate. The primer layer thus formed is about 0.01 to 2.0 g / m ^{2 in} terms of the coating amount when dried.

  A single type of dye layer 3 having a single hue is formed on one surface 2a of the substrate 2, or a plurality of types of dye layers 3 containing dyes having different hues are arranged on the same surface in a surface sequential manner. Can be formed repeatedly. The dye layer 3 is a layer formed by supporting a heat transfer dye with a binder resin. In the thermal transfer sheet 1, at least one kind of dye layer 3 contains an indoaniline dye as a heat transfer dye and a binder resin that carries this dye.

  In the thermal transfer sheet 1, a heat transfer dye other than the indoaniline dye may be used in combination with the indoaniline dye. Conventionally, any of the dyes used in known sublimation transfer type thermal transfer sheets can be used, but is selected in consideration of hue, printing sensitivity, light resistance, storage stability, solubility in binder resin, and the like.

  Examples of dyes other than indoaniline dyes include methine series such as diarylmethane series, triarylmethane series, thiazole series, merocyanine, pyrazolone methine, acetophenone azomethine, pyrazoloazomethine, imidazolazomethine, imidazoazomethine, and pyridone azomethine. Azomethine, xanthene, oxazine, dicyanostyrene, cyanomethylene represented by tricyanostyrene, thiazine, azine, acridine, benzeneazo, pyridoneazo, thiophenazo, isothiazoleazo, pyrroleazo, pyralazo, Azos such as imidazole azo, thiadiazole azo, triazole azo, and dizazo, spiropyran, indolinospiropyran, fluoran, rhodamine lactam, naphthoquino System, anthraquinone, include the quinophthalone like.

  In addition, the preferable sublimation dye which can be used in this invention is not specifically limited, The dye conventionally used as a sublimation dye for thermal transfer sheets can be used suitably.

  The binder resin carrying the dye is mainly composed of a polyvinyl acetal resin obtained by acetalizing polyvinyl alcohol. The binder resin contains two types of polyvinyl acetal resins A and B having a vinyl alcohol unit, a vinyl acetate unit, and a vinyl acetal unit represented by the following general formula 1 and different amounts of vinyl acetate units.

(In the above general formula 1, X, Y, and Z represent mol% of each structural unit in each polyville acetal resin, and R represents a methyl group or an n-propyl group. Here, in the polyvinyl acetal resin A, Is 0.5 ≦ Y ≦ 5, and for the polyvinyl acetal resin B, 10 ≦ Y ≦ 20.)
In the polyvinyl acetoacetal resins A and B, the content of vinyl alcohol units obtained by saponifying vinyl acetate is (X) mol%, the content of vinyl acetal units obtained by acetalizing vinyl acetate with butyraldehyde or acetaldehyde is (Y ) Is mol%, and the content (residual amount) of vinyl acetate is (Y) mol%.

The polyvinyl acetal resin A has a vinyl acetate unit (Y) of 0.5 to 5 mol%, and in general formula 1, R is a polyvinyl acetoacetal having an n-propyl group (C ₃ H ₇ ), or R is a methyl group ( CH ₃ ) polyvinyl butyral. The polyvinyl acetal resin A improves the film formability when the dye layer 3 is formed.

The polyvinyl acetal resin B has a vinyl acetate unit (Y) of 10 to 20 mol%, and in general formula 1, R is a polyvinyl acetoacetal having an n-propyl group (C ₃ H ₇ ), or R is a methyl group (CH ₃ ) Polyvinyl butyral. The polyvinyl acetal resin B improves the dye holding power of the dye layer 3.

  The content of the polyvinyl alcohol unit represented by X in the polyvinyl acetal resins A and B is preferably 10 to 35 mol%. By making it within this range, the effect of holding power or the like for retaining a dye such as indoaniline dye, which is the object of the present invention, can be obtained without impairing the original characteristics of the acetal resin.

  The vinyl acetal unit represented by Z in the polyvinyl acetal resins A and B is preferably 50 to 90 mol%. By setting the amount within this range, the binder resin holding power and transfer sensitivity with respect to the dye are ensured. Moreover, when the polyvinyl alcohol unit is contained, the compatibility between the solvent used when forming the dye layer 3 and the binder resin is improved, and the coating properties are improved.

  The vinyl acetate units in the polyvinyl acetal resin A and the polyvinyl acetal resin B are attributed to vinyl acetate as a starting material at the time of synthesis. The polyvinyl acetal resins A and B have a certain amount of vinyl acetate units remaining, so that they act on amine groups in the dye structure and improve the dye retention of the dye layer 3. This effect is particularly great when an indoaniline dye is used as the dye.

  Polyvinyl acetal resin B composed of polyvinyl acetoacetal or polyvinyl butyral in which 10 to 20 mol% of vinyl acetate units (Y) remain has a high content of vinyl acetate, and thus has a high dye retention, but when used alone Since film formability is poor, it is difficult to use alone. From polyvinyl acetoacetal or polyvinyl butyral in which 0.5 to 5 mol% of vinyl acetate units (Y) remain, the polyvinyl acetal resin A has good film formability.

  Such a polyvinyl acetal resin A and a polyvinyl acetal resin B are contained in the dye layer 3 so that the mass ratio is polyvinyl acetal resin A: polyvinyl acetal resin B = 9: 1 to 5: 5. By setting the mass ratio of the polyvinyl acetal resin A and the polyvinyl acetal resin B within this range, the film formability when forming the dye layer 3 is good, and the retention of the dye can be improved. Moreover, when the ratio of the polyvinyl acetal resin A in which 0.5 to 5 mol% of vinyl acetate units (Y) remain is 5 or less, the concentration change after storage cannot be suppressed, and the effect cannot be obtained.

  In addition to the polyvinyl acetal resins A and B, other resins can be mixed and used for the dye layer 3 within a range not impairing the effects of the present invention. Other resins include cellulose resins such as ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate, and acetic acid / butyric acid cellulose; vinyl resins such as polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl acetoacetal, and polyvinyl pyrrolidone Examples thereof include acrylic resins such as poly (meth) acrylate and poly (meth) acrylamide; polyurethane resins, polyamide resins, polyester resins and the like. Of these, cellulose-based, polyvinyl butyral, polyvinyl alcohol, and polyester-based resins that are favorable in terms of heat resistance, storage stability (dye transferability and background stains), and the like are preferably used.

  The dye layer 3 is generally indicated by a D / B ratio (where D represents the weight of the dye and B represents the weight of the binder resin). The D / B ratio is preferably in the range of 0.3 to 3.0, more preferably in the range of 0.5 to 2.5, and is determined according to the purpose such as the quality of the printed matter.

Moreover, you may add various well-known additives to the dye layer 3 as needed. Examples of the additive include organic fine particles such as polyethylene wax, inorganic fine particles, silicone oil, and phosphate esters in order to improve releasability from an image receiving sheet such as photographic paper and suitability for ink coating. It is done. The dye layer 3 is usually prepared by adding the above-described dye, binder resin, and, if necessary, a desired additive in an appropriate solvent to dissolve or disperse each component to prepare a coating solution. It can be formed by applying and drying the working liquid on the substrate 2. As this coating method, known means such as a gravure printing method, a screen printing method, a reverse roll coating method using a gravure plate, or the like can be used. The dye layer thus formed has a coating amount at the time of drying of 0.1 to 6.0 g / m ² , preferably 0.2 to 3.0 g / m ² .

  The heat-resistant slip layer 4 formed on the other surface 2b of the substrate 2 is provided with a heat-resistant slip layer (back layer) 4 in order to prevent adverse effects such as sticking and print wrinkles due to the heat of the thermal head. The resin for forming the heat-resistant slip layer 4 may be any conventionally known resin, such as polyvinyl butyral resin, polyvinyl acetoacetal resin, polyester resin, vinyl chloride-vinyl acetate copolymer, polyether resin, polybutadiene resin. , Styrene-butadiene copolymer, acrylic polyol, polyurethane acrylate, polyester acrylate, polyether acrylate, epoxy acrylate, urethane or epoxy prepolymer, nitrocellulose resin, cellulose nitrate resin, cellulose acetate propionate resin, cellulose acetate butyrate Rate resin, cellulose acetate hydrodiene phthalate resin, cellulose acetate resin, aromatic polyamide resin, polyimide resin, polyamideimide resin, polycarbonate Sulphonate resins, and chlorinated polyolefin resins.

  In the heat resistant slipping layer 4 made of these resins, as a slipperiness imparting agent to be added or overcoated, phosphate ester, silicone oil, graphite powder, silicone graft polymer, fluorine graft polymer, acrylic silicone graft polymer, acrylic siloxane And silicone polymers such as arylsiloxanes. Among these, a polyol is preferable, for example, a layer composed of a polyalcohol polymer compound, a polyisocyanate compound, and a phosphate ester compound, and it is more preferable to add a filler.

The heat-resistant slip layer 4 is prepared by dissolving or dispersing the resin, slipperiness-imparting agent, and filler in a suitable solvent on the base material 2 to prepare a heat-resistant slip layer coating solution. Can be formed by, for example, coating by a gravure printing method, a screen printing method, a reverse roll coating method using a gravure plate, and the like, followed by drying. The coating amount of the heat-resistant lubricating layer 4 is a ^{solid, 0.1g / m 2 ~3.0g / m} 2 is preferred.

  In the thermal transfer sheet 1 having the above-described configuration, the dye layer 3 on one surface 2a of the substrate 2 contains an indoaniline dye and polyvinyl acetal resins A and B represented by the general formula 1 as binder resins. Thus, the indoaniline dye is held in the dye layer 3 by the polyvinyl acetal resins A and B. Thereby, in this thermal transfer sheet 1, it is possible to suppress the hue change of the printed matter before and after environmental preservation, and to suppress the transfer of the dye to the heat-resistant slipping layer facing the dye layer even when wound and stored. . In addition, this thermal transfer sheet can prevent background fogging, and can produce an excellent quality printed matter without an abnormal transfer in which the entire dye layer is transferred during printing on the transfer target.

  Hereinafter, specific examples to which the present invention is applied will be described in detail based on experimental results. In the text, “part” or “%” is based on mass unless otherwise specified.

  In Example 1, first, as a substrate, a polyethylene terephthalate film having a thickness of 6 μm (Toray Co., Ltd., Lumirror) was subjected to corona irradiation treatment (production of an ink ribbon) on one side of a polyester film substrate having a thickness of 6 μm. The composition for forming a heat-resistant slipping layer having the composition shown in Table 1 below was applied with a wire bar so as to have a dry thickness of 1 μm, and dried to form a heat-resistant slipping layer.

  Next, in Example 1, a composition for forming a dye layer was prepared with the composition shown in Table 2 below. The prepared dye layer forming composition was applied to the other surface of the polyester film substrate with a wire bar so as to have a dry thickness of 0.8 μm, and dried to form an ink layer. As the dye, an indoaniline dye was used.

  Table 3 shows the mol% ratio of each structural unit in the polyvinyl acetal resin used for the binder resins 1 to 4 in Table 2 and the functional group R used in the vinyl acetal unit.

  In Examples 2 to 6 and Comparative Examples 1 to 7, dyes, binder resins and solvents were blended as shown in Table 2 in the same manner as in Example 1 to prepare thermal transfer sheets.

  Using the thermal transfer sheets of Examples and Comparative Examples prepared as described above, evaluations of hue change, dye transfer to a heat-resistant slip layer, and ground fog were performed by the following methods.

<Hue change>
Evaluation of the hue change is carried out by firstly facing the dye layer of the thermal transfer sheet prepared in each example and comparative example and the heat-resistant slipping layer, applying a load of 10 kgf / cm ² , a temperature of 55 ° C., and a humidity of 60% RH. For 48 hours. And the heat-resistant slipping layer used what applied and dried the heat-resistant slipping layer coating liquid of Example 1 on the PET base material used in Example 1 on the conditions of Example 1. FIG. The primer layer and the dye layer were not formed. The dye layer after the test was cut and pasted on the cyan portion of the ribbon included in the UPC2010 color print pack (Sony Corporation), and 12 gradations were printed on the bundled photographic paper using a sublimation video printer UP-2100 (Sony Corporation). Stair step printing (gradation gradation printing) was performed. An untested sample applied together with this was cut and pasted in the same manner and printed. The hues of the two samples were measured with CM-2600d (color difference meter, manufactured by Konica Minolta), and the color difference (ΔEa * b *) between the two levels was obtained. Judged.

<Dye transfer to heat resistant slipping layer>
The dye transfer to the heat resistant slipping layer was evaluated by measuring the transfer density of the dye to the heat resistant slipping layer stored opposite to the dye layer, and Δ before and after storage using a Macbeth reflection densitometer (TR-924). Was measured and calculated. If it was 0.02 or less, a pass / fail judgment was made with ○ and 0.03 or more as x.

<Ground cover>
With the above combination, the printing pattern was solid white (tone value 0/255; no applied heat), and printing was performed in an environment of a temperature of 30 ° C. and a humidity of 50% RH. However, the thermal transfer sheets prepared in each of the examples and comparative examples were stored in advance in an environment of a temperature of 55 ° C. and a humidity of 60% RH for 2 weeks. The evaluation of the ground cover here is not a transfer of the dye from the dye layer to the heat-resistant slip layer, and the dye adhering to the heat-resistant slip layer being re-transferred (kickback) to the dye layer. It was stored in an environment of a temperature of 55 ° C. and a humidity of 60% RH, and it was examined whether or not the dye in the dye layer formed on the base material was recrystallized and precipitated to contaminate the dye layer. The reflection density was measured with a Macbeth reflection densitometer (TR-924), and the O.D. The difference in D (print density) was evaluated. O. A pass / fail judgment was made with D being 0.01 or less and x being 0.02 or more.

<Membrane state>
The uniformity of the coating state of the coated and dried hand-coated sheet was visually determined.

  Table 4 below shows all the evaluation results.

  From the results shown in Table 4, in Examples 1 to 6 in which the polyvinyl acetal resin A and the polyvinyl acetal resin B were mixed at a predetermined ratio as compared with the comparative examples 1 to 7, the hue change and the dye transferability were obtained. It was good in all evaluations of ground cover and film condition.

  Since Comparative Example 1 to Comparative Example 3 in which the binder resin is composed only of the polyvinyl acetal resin A is composed only of the polyvinyl acetal resin A having a small number of vinyl acetate units, the retention of the dye is weak, and when stored in a high temperature and high humidity environment, The dye migrated to the heat resistant slipping layer, the hue change and the dye migration were increased, and the ground fog was generated by the dye bleed out on the surface of the dye layer.

  In Comparative Example 4 consisting only of the polyvinyl acetal resin B, since it consists only of the polyvinyl acetal resin B having a large amount of vinyl acetate units, the retention of the dye is increased, and the hue change and dye transferability can be suppressed. During the formation, the coating state was not uniform.

  In Comparative Examples 5 to 7 containing more polyvinyl acetal resin B than polyvinyl acetal resin A, good results could not be obtained in all evaluations.

  In contrast to these comparative examples, in Examples 1 to 6, the polyvinyl acetal resin A and the polyvinyl acetal resin B are mixed in a range of 90%: 10% to 5%: 5%, thereby allowing dyes Even if it is stored under high temperature and high humidity environment, the dye does not bleed out on the surface of the dye layer, and even if the heat resistant slipping layer is overlaid and stored, the dye becomes a heat resistant slipping layer. It does not shift, hue change and dye transferability are suppressed, ground fogging can be prevented, and a uniform dye layer can be formed.

  As described above, in the thermal transfer sheet, the polyvinyl acetal resin A having a small amount of vinyl acetate units and the polyvinyl acetal resin B having a large amount of vinyl acetate units represented by the general formula 1 in the range of 90%: 10% to 5%: 5% By containing it as a binder resin, the dye layer has high dye holding power without impairing film formability, suppresses hue change and dye transfer, prevents the occurrence of ground fog, and forms high-quality images. be able to.

It is sectional drawing of the thermal transfer sheet to which this invention is applied.

Explanation of symbols

  1 thermal transfer sheet, 2 substrate sheet, 3 dye layer, 4 heat-resistant slipping layer

Claims (1)

A dye layer comprising a heat transferable dye and a binder resin is formed on one surface of the substrate, and a heat resistant slipping layer is formed on the other surface,
The heat transfer dye contains an indoaniline dye, and the binder resin contains a polyvinyl acetal resin A and a polyvinyl acetal resin B both represented by the following general formula 1, and the polyvinyl acetal resin A and A thermal transfer sheet in which the mass ratio of the polyvinyl acetal resin B is polyvinyl acetal resin A: polyvinyl acetal resin B = 9: 1 to 5: 5.

(In the above general formula 1, X, Y, and Z represent mol% of each structural unit in each polyville acetal resin, and R represents a methyl group or an n-propyl group. Here, in the polyvinyl acetal resin A, Is 0.5 ≦ Y ≦ 5, and for the polyvinyl acetal resin B, 10 ≦ Y ≦ 20.)

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