JP4216833B2 - Thermal transfer sheet - Google Patents

Description

  The present invention relates to a thermal transfer sheet in which a heat-resistant slipping layer is provided on one side of a base material and a dye layer is formed on the other side of the base material. More specifically, the highest transfer density in printing is high, and the winding state It is possible to suppress the transfer of dye to the back layer facing the dye layer in the wound state without causing blocking even during storage in the medium, and transfer the entire dye layer when printing on the transfer object. Thermal transfer with excellent gradation reproducibility from highlight (low density) to shadow (high density). It relates to the sheet.

  Conventionally, various thermal transfer recording methods are known. Among them, 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. From the above, there are proposed methods for forming various full-color images by thermally transferring a sublimation dye onto a transfer material that can be dyed with a sublimation dye, for example, a thermal transfer image-receiving sheet having a dye-receiving layer formed on paper or a plastic film. Yes. In this case, as the heating means, the color dots having a large number of three or four colors adjusted by heating with the thermal head of the printer are transferred to the receiving layer of the thermal transfer image receiving sheet, 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 because the coloring material used is a dye, so the resulting image is excellent in the reproducibility and gradation of intermediate colors, It is possible to form a high-quality image similar to an image obtained by offset printing or gravure printing and comparable to a full-color photographic image.

  In such a thermal transfer recording method using sublimation transfer, as the printing speed of the thermal transfer printer is increased, there is a problem that a sufficiently satisfactory print density cannot be obtained with a conventional thermal transfer sheet. In addition, there has been a demand for higher density and clearer prints of images by thermal transfer. From this viewpoint, an image is formed by receiving a thermal transfer sheet and a sublimation dye transferred from the thermal transfer sheet. Many attempts have been made to improve thermal transfer image receiving sheets. For example, attempts have been made to improve transfer sensitivity in printing by thinning a thermal transfer sheet. However, the reduction in the thickness of the thermal transfer sheet causes a new problem that wrinkles are generated due to heat, pressure, or the like when the thermal transfer sheet is manufactured or during thermal transfer recording.

  In addition, as shown in Patent Document 1, an attempt was made to increase the dye density / resin binder (Dye / Binder) ratio in the dye layer of the thermal transfer sheet to improve the printing density and the transfer sensitivity in the printing. During take-up storage, the dye transferred to the heat-resistant slipping layer on the back side of the thermal transfer sheet, and when the transferred dye was rolled back, it was re-transferred (kickback) to another dye layer, etc. When the layer is thermally transferred to the image receiving sheet, there has been a problem that a hue different from a designated color or a so-called background stain occurs. In the thermal transfer printer, not on the thermal transfer sheet side, high energy was applied during thermal transfer during image formation. However, the dye layer and the receiving layer are fused, and so-called abnormal transfer is likely to occur. When a large amount of a release agent is added to the receiving layer to prevent the abnormal transfer, blurring of the image, background smearing, etc. occur.

It has also been proposed to increase the maximum transfer density by selecting a resin binder with a relatively low glass transition temperature in the dye layer of the thermal transfer sheet, but in this case, the binder is applied at a relatively low level. Dye release occurs even with energy, and the transfer density becomes higher than the setting even in the highlight portion of the print, which causes a problem that the reproducibility of the thermal transfer image is conversely lowered. Furthermore, as shown in Patent Document 2, a binder resin containing 90% by weight or more of a polyvinyl butyral resin that defines the range of molecular weight and glass transition temperature and defines the content of the vinyl alcohol portion is used as a component of the dye layer. However, even if this thermal transfer sheet is used, the maximum transfer density has not yet reached a satisfactory level.
JP-A-8-295083 Japanese Patent Publication No. 7-29504

  Accordingly, the present invention has been made in view of the above-described problems of the prior art, and has a high maximum transfer density in printing, and does not cause blocking during storage in the winding state, and the dye in the winding state. Transfer of the dye to the back layer facing the layer can be suppressed, there is no abnormal transfer that causes the entire dye layer to be transferred when printing on the transfer object, and the density of the highlight part in the print can be suppressed, It is an object of the present invention to provide a thermal transfer sheet capable of forming a printed matter excellent in gradation reproducibility from highlight to shadow without trouble.

In order to achieve the above object, a thermal transfer sheet according to the present invention is a thermal transfer sheet in which a heat-resistant slipping layer is provided on one surface of a substrate and a dye layer is formed on the other surface of the substrate. The loss elastic modulus at 60 ° C. of the binder resin constituting the layer is 10 ⁷ Pa or more, the loss elastic modulus at 100 ° C. is 10 ⁶ Pa or more, and the loss elastic modulus at 150 ° C. is 10 ⁴ Pa to 10 ^5. It is the range of Pa.
In a preferred embodiment of the present invention, the glass transition temperature of the binder resin is 60 ° C. or higher.

The present invention provides a loss elastic modulus at 60 ° C. of a binder resin constituting the dye layer in a thermal transfer sheet in which a heat-resistant slipping layer is provided on one side of the base and a dye layer is formed on the other side of the base. Is 10 ⁷ Pa or higher, the loss elastic modulus at 100 ° C. is 10 ⁶ Pa or higher, and the loss elastic modulus at 150 ° C. is 10 ⁴ Pa or higher and 10 ⁵ Pa or lower. Satisfying the regulation of loss elastic modulus improves the transfer sensitivity during thermal transfer, and even when high energy is not applied, the maximum transfer density in printing is high, and blocking or winding during storage in the winding state is possible. Dye transfer to the back layer facing the dye layer in the removed state, abnormal transfer that causes the entire dye layer to be transferred when printing on the transfer target, and further increasing the density of highlights in printing It is possible to prevent each of the printing product excellent in tone reproduction throughout the highlight shadow could without any trouble formation.

  FIG. 1 shows one embodiment of a thermal transfer sheet according to the present invention. A heat-resistant slipping layer (back layer) that improves the slipperiness of the thermal head and prevents sticking on one surface of a substrate 1. 3, and the dye layer 2 is formed on the other surface of the substrate 1. FIG. 2 shows another embodiment of the thermal transfer sheet according to the present invention. A heat-resistant slipping layer 3 is provided on one surface of the substrate 1, and a primer layer 4 is provided on the other surface of the substrate 1. The dye layer 2 is sequentially provided.

Hereinafter, each layer constituting the thermal transfer sheet of the present invention will be described in detail.
(Base material)
The base material 1 of the thermal transfer sheet used in the present invention may be any material as long as it has a conventionally known degree of heat resistance and strength. For example, it has a thickness of about 0.5 to 50 μm, preferably about 1 to 10 μm. Polyethylene terephthalate film, 1,4-polycyclohexylenedimethylene terephthalate film, polyethylene naphthalate film, polyphenylene sulfide film, polystyrene film, polypropylene film, polysulfone film, aramid film, polycarbonate film, polyvinyl alcohol film, cellophane, acetic acid Examples thereof include cellulose derivatives such as cellulose, polyethylene film, polyvinyl chloride film, nylon film, polyimide film, ionomer film, and the like.

  In the above-mentioned base material, an adhesion treatment is often performed on the surface on which the dye layer is formed. When the plastic film of the base material is formed by applying a dye layer on the surface, the wettability of the coating solution, the adhesiveness, etc. are likely to be insufficient, and therefore, the plastic film is subjected to an adhesion treatment. As the adhesion treatment, known resin surface modification 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. Quality technology 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, it is also possible to apply and form the primer layer 4 between the base material and the dye layer as an adhesive treatment of the base material. The primer layer can be formed from a resin as shown below. Polyester resin, Polyacrylate resin, Polyvinyl acetate resin, Polyurethane resin, Styrene acrylate resin, Polyacrylamide resin, Polyamide resin, Polyether resin, Polystyrene resin, Polyethylene resin, Polypropylene Examples thereof include vinyl resins such as resin, polyvinyl chloride resin, polyvinyl alcohol resin and polyvinyl pyrrolidone, and polyvinyl acetal resins such as polyvinyl acetoacetal and polyvinyl butyral.

The primer layer is a gravure printing method in which a resin obtained by adding or adding additives to the resins listed above is dissolved or dispersed in water, an aqueous solvent of an alcohol or an organic solvent, It can be formed using a known coating means such as a screen printing method or a reverse roll coating method using a gravure plate. The primer layer thus formed is about 0.01 to 0.3 g / m ^{2 in} terms of the coating amount when dried.

(Dye layer)
In the thermal transfer sheet of the present invention, the dye layer 2 is provided on the other surface of the base material provided with the heat resistant slipping layer on one surface. The dye layer may be composed of a single layer of one color, or a plurality of dye layers containing dyes having different hues may be repeatedly formed on the same surface of the same substrate in the surface order. The dye layer is a layer formed by supporting a heat transfer dye with a binder resin. As the dye to be used, a dye that melts, diffuses or sublimates by heat, and is used in a conventionally known sublimation transfer type thermal transfer sheet can be used in the present invention. The selection is made in consideration of printing sensitivity, light resistance, storage stability, solubility in a binder resin, and the like.

  Examples of the dye include azomethines such as diarylmethane, triarylmethane, thiazole, merocyanine, pyrazolone methine and the like, indoaniline, acetophenone azomethine, pyrazoloazomethine, imidazolazomethine, imidazoazomethine, and pyridone azomethine. , Xanthene, oxazine, dicyanostyrene, cyanomethylene represented by tricyanostyrene, thiazine, azine, acridine, benzeneazo, pyridoneazo, thiophenazo, isothiazoleazo, pyrroleazo, pyralazo, imidazoleazo, Azos such as thiadiazole azo, triazole azo, dizazo, spiropyran, indolinospiropyran, fluoran, rhodamine lactam, naphthoquinone, anne Rakinon system include the quinophthalone like.

The binder resin of the dye layer is characterized in that the loss elastic modulus at 60 ° C., 100 ° C. and 150 ° C. of the binder resin is defined in the present invention. That is, the loss elastic modulus at 60 ° C. of the binder resin of the dye layer is 10 ⁷ Pa or more, the loss elastic modulus at 100 ° C. is 10 ⁶ Pa or more, and the loss elastic modulus at 150 ° C. is 10 ⁴ Pa or more. ⁵ Pa or less. In the measurement method of the loss modulus in the present invention, ARES manufactured by Rheometrics was used as a measuring instrument, and the measurement conditions were parallel plate 25 mmΦ, strain 0.1%, amplitude 1 Hz, heating rate 2 ° C./min. The temperature of the binder resin is raised from 30 ° C. to 200 ° C., and the values of the loss elastic modulus at 60 ° C., 100 ° C., and 150 ° C. are read.

The loss elastic modulus is a viscosity factor of the measured substance, that is, represents the strength of the film in the film by the binder resin, and is considered to be equivalent to a static shear stress. In the present invention, the binder resin in the dye layer has a loss elastic modulus at 60 ° C. of 10 ⁷ Pa or more, preferably the lower limit of the loss elastic modulus at 60 ° C. is 1 × 10 ⁷ Pa, and the loss elastic modulus at 60 ° C. The upper limit is about 10 ⁸ Pa, preferably about 1 × 10 ⁸ Pa. The lower limit value of the loss elastic modulus at 100 ° C. of the binder resin in the dye layer is 1 × 10 ⁶ Pa, and the loss elastic modulus at the upper limit value of 100 ° C. is about 10 ⁸ Pa, preferably about 1 × 10 ⁸ Pa. It is desirable to be. Similarly, the lower limit value of the loss elastic modulus at 150 ° C. of the binder resin in the dye layer is 10 ⁴ Pa, preferably 1 × 10 ⁴ Pa. The loss elastic modulus at the upper limit value of 150 ° C. is 10 ⁵ Pa, preferably 1 × 10 ⁵ Pa.

When the binder resin in the dye layer has a loss elastic modulus at 60 ° C. lower than 10 ⁷ Pa, blocking may occur during storage in a wound state, or during high-temperature storage such as summertime, and winding may occur. In this state, the dye transfer to the back layer facing the dye layer occurs, and when the transferred dye rolls back, it is re-transferred (kickback) to another color dye layer or the like, and the thermal transfer image is likely to be stained. If the loss elastic modulus at 60 ° C. is too high, the maximum transfer density in printing tends to decrease.

The binder resin in the dye layer has a loss elastic modulus at 100 ° C. lower than 10 ⁶ Pa. Dye release occurs even at a relatively low applied energy, and the transfer density is set in the highlight portion of the print. And the reproducibility of the thermal transfer image is lowered. On the other hand, if the loss elastic modulus at 100 ° C. is too high, the sensitivity in thermal transfer is lowered. Further, when the binder resin in the dye layer has a loss elastic modulus at 150 ° C. lower than 10 ⁴ Pa, abnormal transfer tends to occur during thermal transfer. If the loss elastic modulus at 150 ° C. is too high, the maximum transfer density in printing will decrease. The dye layer binder resin preferably has a glass transition temperature of 60 ° C. or higher, and the upper limit is preferably about 100 ° C.

  As the dye layer binder resin, any resin can be used as long as it satisfies the above-mentioned loss elastic modulus, but preferable examples are ethyl cellulose resin, hydroxyethyl cellulose resin, ethyl hydroxy cellulose resin, hydroxypropyl. Cellulose resins such as cellulose resin, methyl cellulose resin, cellulose acetate resin, cellulose butyrate resin, polyvinyl alcohol resin, polyvinyl acetate resin, polyvinyl acetal resin such as polyvinyl acetoacetal resin and polyvinyl butyral resin, polyvinyl pyrrolidone resin, polyacrylamide resin, etc. Vinyl resin, polyester resin, phenoxy resin, and the like. Among them, a grade (molecular weight, structure, etc.) satisfying the above numerical definition of the loss elastic modulus is selected. Among these, cellulose resins, acetal resins, polyester resins, phenoxy resins, and the like are particularly preferable from the viewpoints of heat resistance, dye transferability, and the like.

  More preferable as the dye layer binder resin is a carboxylic acid-modified polyvinyl acetal resin. In this case, the carboxylic acid-modified polyvinyl acetal resin means a resin in which at least a part of the polyvinyl acetal is modified with carboxylic acid. The proportion of modification by carboxylic acid in such a carboxylic acid-modified polyvinyl acetal resin can be appropriately selected depending on the color material used, etc., but is usually 1 mol in terms of vinyl alcohol unit in the carboxylic acid-modified polyvinyl acetal resin. It is desirable to be in the range of% to 20 mol%. If the ratio of carboxylic acid modification is too small, the effect of modification is poor, while if the modification ratio is too large, the water absorption of the carboxylic acid modified polyvinyl acetal resin increases, and conversely, the film performance of the dye layer tends to decrease. Is seen.

  Moreover, the residual hydroxyl group amount in the carboxylic acid-modified polyvinyl acetal resin is preferably 40 mol% or less in terms of vinyl alcohol units in the carboxylic acid-modified polyvinyl acetal resin. If there are too many remaining hydroxyl groups, the solvent solubility will decrease, and the water absorption will increase too much, which may reduce the film performance of the dye layer. The molecular weight of the carboxylic acid-modified polyvinyl acetal resin can be appropriately selected depending on the color material to be used, and is preferably in the range of 60000 to 120,000, for example.

The carboxylic acid-modified polyvinyl acetal resin as described above can be produced by the following known method.
(1) A method of acetalizing carboxylic acid-modified polyvinyl alcohol.
(2) A method of acetalizing polyvinyl alcohol together with an aldehyde usually used for acetalization and an aldehyde having a carboxyl group.
(3) A method of preparing a carboxylic acid-modified polyvinyl acetal by reacting a polyvinyl acetal resin with a carboxylic anhydride such as phthalic anhydride.
Among these, the method (3) is particularly preferable. This is because a variety of carboxylic acid-modified polyvinyl acetal resins that are easy to react and have higher purity can be obtained. In the above methods (1) and (2), since a base is used for neutralizing the catalyst in the acetalization reaction after carboxylic acid modification, this and the carboxylic acid in the carboxylic acid modified polyvinyl acetal resin are used. The acid part becomes a salt, and an additional step of converting the carboxylate into a carboxylic acid is required. Considering such points, the method (3) is the most reasonable and preferable. Hereinafter, a method for producing a carboxylic acid-modified polyvinyl acetal resin by this preferred method will be described.

  The acetalization reaction of polyvinyl alcohol is performed by reacting polyvinyl alcohol and an aldehyde in water or an organic solvent using an acid catalyst. Specific examples of aldehydes include formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, capronaldehyde, caprylaldehyde, caprinaldehyde, benzaldehyde, 1-naphthaldehyde, phenylacetaldehyde, o-tolualdehyde, p-tolualdehyde, o- Anthaldehyde, m-anthaldehyde, p-anthaldehyde, p-ethylbenzaldehyde, o-chlorobenzaldehyde, p-chlorobenzaldehyde, cinnamic aldehyde and the like can be mentioned. These aldehydes may be used in combination of any two or more as required. Of these, butyraldehyde, acetaldehyde, and phenylacetaldehyde can achieve better effects by using a resin obtained by modifying a polyvinyl acetal resin obtained by acetalization with these aldehydes with a carboxylic acid. Examples of the acid catalyst used in the acetalization reaction include inorganic acids such as hydrochloric acid, sulfuric acid, and phosphoric acid, acetic acid, p-toluenesulfonic acid, and the like. Of these, hydrochloric acid, sulfuric acid, and p-toluenesulfonic acid are preferable. The amount of the catalyst is preferably 0.005 to 0.2 mol with respect to 1 mol of aldehyde used in the reaction. The acetalization reaction temperature is usually 20 ° C. or higher, preferably 40 ° C. or higher and 100 ° C. or lower, preferably 90 ° C. or lower. The reaction time is usually 2 to 10 hours.

  Next, the resulting polyvinyl acetal is reacted with a carboxylic acid, preferably a divalent or higher carboxylic acid anhydride. Divalent or higher carboxylic acid anhydrides include phthalic anhydride, naphthalene-1,2-dicarboxylic anhydride, succinic anhydride, maleic anhydride, itaconic anhydride, glutaric anhydride, trimellitic anhydride, cyclohexane-1, Examples include 2-dicarboxylic acid anhydride and norbornane-2,3-dicarboxylic acid anhydride. Of these, succinic anhydride and phthalic anhydride are particularly preferable. Moreover, you may use it in combination of 2 or more types of these acid anhydrides as needed.

  This reaction may be performed without using a catalyst, but the reaction can be performed under milder conditions by using a catalyst. Examples of the catalyst include pyridine, lutidine, 4-dimethylaminopyridine, triethylamine, diisopropylethylamine, N-ethylpiperidine, diazobicycloundecene and other tertiary amines, sodium acetate and other bases, sulfuric acid, hydrochloric acid, zinc chloride, Examples include acids such as perchloric acid. Of these, tertiary amines are preferred. In addition, the usage-amount of a catalyst is 0.001-1 mol normally with respect to 1 mol of acid anhydrides. This reaction is usually carried out in a solvent, and examples of the solvent used for the reaction include hydrocarbon solvents, ketone solvents, ester solvents, ether solvents, amide solvents and the like. Specific examples include N, N-dimethylformamide, methyl ethyl ketone, methyl isobutyl ketone, and toluene. The amount of the solvent used is 100 parts by weight or more, preferably 200 parts by weight or more and 2000 parts by weight or less, preferably 1000 parts by weight or less with respect to 100 parts by weight of the raw material polyvinyl acetal resin. The reaction temperature is usually 30 ° C. or higher, preferably 50 ° C. or higher and 200 ° C. or lower, preferably 150 ° C. or lower. The reaction time is usually about 1 to 15 hours.

  In a preferred embodiment of the present invention, the above-described carboxylic acid-modified polyvinyl acetal resin can be used. In that case, any carboxylic acid-modified polyvinyl acetal resin can be used alone or in any combination of a plurality of types. Specifically, carboxylic acid-modified polyvinyl acetal resin obtained by arbitrarily combining raw materials such as the above-mentioned polyvinyl acetal resin and carboxylic acid can also be dispersed, and in particular, it has been modified with a divalent or higher carboxylic acid anhydride. A polyvinyl acetal resin is preferred. Specifically, a succinic anhydride modified product of polyvinyl formal, polyvinyl acetoacetal, polyvinyl butyral or polyvinylphenylacetoacetal is preferably used.

The dye layer may contain the above-described dye, binder resin, and other various additives that are conventionally known as necessary. As the binder resin, a mixture of the carboxylic acid-modified polyvinyl acetal resin and the resin listed in paragraph (0022) may be used. Examples of the additive include organic fine particles such as polyethylene wax and inorganic fine particles in order to improve the releasability from the image receiving sheet and the ink coating suitability. Such a dye layer is usually prepared by adding the above-mentioned dye, binder, and additives as necessary in an appropriate solvent, and dissolving or dispersing each component to prepare a coating solution. It can be formed by applying and drying the liquid on a substrate. 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 is formed with a coating amount during drying of about 0.2 to 6.0 g / m ² , preferably about 0.3 to 3.0 g / m ² .

(Heat resistant slipping layer)
In the thermal transfer sheet of the present invention, a heat-resistant slipping layer (also referred to as a back layer) 3 is provided on one surface of the substrate in order to prevent adverse effects such as sticking and printing wrinkles due to the heat of the thermal head. The resin for forming the heat-resistant slipping layer 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 resin, cellulose acetate hydrodiene phthalate resin, cellulose acetate resin, aromatic polyamide resin, polyimide resin, polyamideimide resin, poly Boneto resins, and chlorinated polyolefin resins.

  The slipperiness imparting agent added to or overcoating the heat resistant slipping layer made of these resins includes phosphate ester, silicone oil, graphite powder, silicone graft polymer, fluorine graft polymer, acrylic silicone graft polymer, acrylic siloxane, aryl Examples thereof include silicone polymers such as siloxane, but a layer made of a polyol, for example, 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 is prepared by dissolving or dispersing the above-described resin, slipperiness-imparting agent, and filler in an appropriate solvent on the base sheet to prepare a heat-resistant slip layer coating solution. This can be formed by applying and drying by a forming means such as a gravure printing method, a screen printing method, or a reverse roll coating method using a gravure plate. The coating amount of the heat-resistant slip layer is a ^{solid, 0.1g / m 2 ~3.0g / m} 2 is preferred.
Example 1

Next, an Example and a comparative example are given and this invention is further explained in full detail. In the text, “part” or “%” is based on mass unless otherwise specified. On the surface of the easy adhesion treatment of a biaxially stretched polyethylene terephthalate film (PET) having a thickness of 3.5 μm as a base material, a dye layer coating liquid 1 having the following composition is applied by gravure coating, so that the dry coating amount is The dye layer was formed by coating and drying so as to be 0.8 g / m ^2, and the thermal transfer sheet of Example 1 was produced. On the other side of the substrate, a heat resistant slipping layer coating solution having the following composition was applied in advance by gravure coating and dried so that the dry coating amount was 1.0 g / m ^2. A sex layer was formed.

Production method of polyvinyl butyral resin A. In a 1000 ml glass flask, weigh 80 grams of polyvinyl butyral resin (trade name ESREC B BL-S, manufactured by Sekisui Chemical Co., Ltd.), 7.1 grams of succinic anhydride, and 200 grams of N, N-dimethylformamide. Stir slowly. The flask was attached to an oil bath and heated to 60 ° C. over 30 minutes to completely dissolve the contents, and then heated to 100 ° C. over 30 minutes. After holding at 100 ° C. for 6 hours, this was allowed to cool, and the entire content was slowly added dropwise to a beaker containing 1600 grams of water. The produced granular precipitate was filtered off, washed with 160 g of water, transferred to a 3 L flask, charged with 1600 g of water and 160 g of methanol, and stirred at 45 ° C. for 1 hour. The precipitate was filtered off, washed with 160 grams of water, transferred to a stainless steel vat, dried in a hot air dryer at 60 ° C. for 42 hours, transferred to a vacuum dryer and dried at a vacuum degree of 5 Torr and a temperature of 70 ° C. for 119 hours. 83 grams of modified polyvinyl acetal resin was obtained. The acid value of this resin was 40 mgKOH / g, and the molecular weight was about 120,000. As a result, in the following formula, a polymer having R ′ = C ₃ H ₇ , R ″ = — CH ₂ CH ₂ —, a = 0, b = 60, c = 29, d = 3, and e = 8 was obtained. .

<Dye layer composition liquid 1>
Solvent Blue 63 3.0 parts Disperse Blue 354 2.0 parts Polyvinyl butyral resin A 4.0 parts (loss elastic modulus at 60 ° C. is 1.7 × 10 ⁷ Pa, loss elastic modulus at 100 ° C. is 1.5 × 10 ⁷ Pa, loss elastic modulus at 150 ° C. is 3.9 × 10 ⁴ Pa)
Methyl ethyl ketone 45.5 parts Toluene 45.5 parts

<Heat resistant slipping layer composition>
13.6 parts of polyvinyl butyral resin (manufactured by SREC BX-1 by Sekisui Chemical Co., Ltd.)
0.6 parts of polyisocyanate curing agent (Takenate D218, Takeda Pharmaceutical Company Limited)
Phosphate 0.8 parts (Plysurf A208S, Daiichi Kogyo Seiyaku Co., Ltd.)
Methyl ethyl ketone 42.5 parts Toluene 42.5 parts
Example 2

A PET film substrate having the same conditions as in Example 1 was used, and a heat-resistant slipping layer similar to that in Example 1 was previously formed on the other surface of the substrate. On the surface opposite to the surface on which the heat resistant slipping layer of the base material is provided, the dye layer coating solution 2 having the following composition is applied by gravure coating so that the dry coating amount is 0.8 g / m ² and dried. Then, a dye layer was formed, and a thermal transfer sheet of Example 2 was produced. Further, polyvinyl butyral resin B was synthesized by according a similar manner as in paragraph (00 33). (Reaction time: 5 hours, molecular weight: about 100,000)

<Dye layer composition liquid 2>
Solvent Blue 63 3.0 parts Disperse Blue 354 2.0 parts Polyvinyl butyral resin B 4.0 parts (loss elastic modulus at 60 ° C. is 3.3 × 10 ⁷ Pa, loss elastic modulus at 100 ° C. is 3.1 × 10 ⁷ Pa, loss elastic modulus at 150 ° C. is 8.4 × 10 ⁴ Pa)
Methyl ethyl ketone 45.5 parts Toluene 45.5 parts
Example 3

A PET film substrate having the same conditions as in Example 1 was used, and a heat-resistant slipping layer similar to that in Example 1 was previously formed on the other surface of the substrate. On the surface opposite to the surface on which the heat-resistant slip layer of the base material is provided, the dye layer coating solution 3 having the following composition is applied by gravure coating so that the dry coating amount is 0.8 g / m ² and dried. Thus, a dye layer was formed, and a thermal transfer sheet of Example 3 was produced.

<Dye layer composition 3>
Solvent Blue 63 3.0 parts Disperse Blue 354 2.0 parts Polyvinyl butyral resin B 2.0 parts Polyvinyl acetal resin 2.0 parts (manufactured by ESREC KS-5 Sekisui Chemical Co., Ltd.)
(The loss elastic modulus at 60 ° C. of the mixed resin is 3.6 × 10 ⁷ Pa, the loss elastic modulus at 100 ° C. is 1.5 × 10 ⁷ Pa, and the loss elastic modulus at 150 ° C. is 3.2 × 10 ⁴ Pa)
Methyl ethyl ketone 45.5 parts Toluene 45.5 parts
Example 4

A PET film substrate having the same conditions as in Example 1 was used, and a heat-resistant slipping layer similar to that in Example 1 was previously formed on the other surface of the substrate. On the surface opposite to the surface on which the heat resistant slipping layer of the base material is provided, the dye layer coating solution 4 having the following composition is applied by gravure coating so that the dry coating amount is 0.8 g / m ² and dried. Then, a dye layer was formed, and a thermal transfer sheet of Example 4 was produced.

<Dye layer composition liquid 4>
Disperse Yellow 201 2.0 parts Disperse Yellow 231 2.0 parts Polyvinyl butyral resin B 4.0 parts (loss elastic modulus at 60 ° C. is 3.3 × 10 ⁷ Pa, loss elastic modulus at 100 ° C. is 3.1 × 10 ⁷ Pa, loss elastic modulus at 150 ° C. is 8.4 × 10 ⁴ Pa)
Methyl ethyl ketone 45.5 parts Toluene 45.5 parts

Comparative Example 1
A PET film substrate having the same conditions as in Example 1 was used, and a heat-resistant slipping layer similar to that in Example 1 was previously formed on the other surface of the substrate. On the surface opposite to the surface on which the heat-resistant slipping layer of the substrate is provided, the dye layer coating solution 5 having the following composition is applied by gravure coating so that the dry coating amount is 0.8 g / m ² and dried. Then, a dye layer was formed, and a thermal transfer sheet of Comparative Example 1 was produced. Polyvinyl butyral resin C was synthesized by the same method as in paragraph number (00 33 ). (Reaction time: 4 hours, molecular weight: about 80,000)

<Dye layer composition liquid 5>
Solvent Blue 63 3.0 parts Disperse Blue 354 2.0 parts Polyvinyl butyral resin C 4.0 parts (loss elastic modulus at 60 ° C. is 3.5 × 10 ⁶ Pa, loss elastic modulus at 100 ° C. is 1.6 × 10 ⁶ Pa, loss elastic modulus at 150 ° C. is 3.0 × 10 ⁴ Pa)
Methyl ethyl ketone 45.5 parts Toluene 45.5 parts

Comparative Example 2
A PET film substrate having the same conditions as in Example 1 was used, and a heat-resistant slipping layer similar to that in Example 1 was previously formed on the other surface of the substrate. On the surface opposite to the surface on which the heat resistant slipping layer of the substrate is provided, the dye layer coating liquid 6 having the following composition is applied by gravure coating so that the dry coating amount is 0.8 g / m ² and dried. Then, a dye layer was formed, and a thermal transfer sheet of Comparative Example 2 was produced.

<Dye layer composition liquid 6>
Solvent Blue 63 3.0 parts Disperse Blue 354 2.0 parts Acrylic polyol resin 2.0 parts (Acryt 6AN-213 (50 wt% solution) manufactured by Taisei Kako Co., Ltd.)
Polyvinyl acetal resin 2.0 parts (SREC KS-5, manufactured by Sekisui Chemical Co., Ltd.)
(The loss elastic modulus at 60 ° C. of the mixed resin is 2.4 × 10 ⁶ Pa, the loss elastic modulus at 100 ° C. is 2.0 × 10 ⁶ Pa, and the loss elastic modulus at 150 ° C. is 4.5 × 10 ⁴ Pa).
Methyl ethyl ketone 45.5 parts Toluene 45.5 parts

Comparative Example 3
A PET film substrate having the same conditions as in Example 1 was used, and a heat-resistant slipping layer similar to that in Example 1 was previously formed on the other surface of the substrate. On the surface opposite to the surface on which the heat resistant slipping layer of the substrate is provided, the dye layer coating solution 7 having the following composition is applied by gravure coating so that the dry coating amount is 0.8 g / m ² and dried. Then, a dye layer was formed, and a thermal transfer sheet of Comparative Example 3 was produced.

<Dye layer composition liquid 7>
Solvent Blue 63 3.0 parts Disperse Blue 354 2.0 parts Polyvinyl butyral resin 4.0 parts (ESREC BL-2 by Sekisui Chemical Co., Ltd.)
(Loss elastic modulus at 60 ° C. 6.6 × 10 ⁶ Pa, loss elastic modulus at 100 ° C. is 1.5 × 10 ⁵ Pa, loss elastic modulus at 150 ° C. is 2.2 × 10 ⁴ Pa)
Methyl ethyl ketone 45.5 parts Toluene 45.5 parts

Comparative Example 4
A PET film substrate having the same conditions as in Example 1 was used, and a heat-resistant slipping layer similar to that in Example 1 was previously formed on the other surface of the substrate. On the surface opposite to the surface on which the heat resistant slipping layer of the base material is provided, a dye layer coating solution 8 having the following composition is applied by gravure coating so that the dry coating amount is 0.8 g / m ² and dried. Then, a dye layer was formed, and a thermal transfer sheet of Comparative Example 4 was produced.

<Dye layer composition liquid 8>
Solvent Blue 63 3.0 parts Disperse Blue 354 2.0 parts Acrylic polyol resin 4.0 parts
(ACRYT 6AN-213 (50wt% solution) Taisei Kako Co., Ltd.)
(Loss elastic modulus at 60 ° C. is 1.0 × 10 ⁶ Pa, loss elastic modulus at 100 ° C. is 3.2 × 10 ⁴ Pa, loss elastic modulus at 150 ° C. is 3.1 × 10 ² Pa)
Methyl ethyl ketone 45.5 parts Toluene 45.5 parts

Comparative Example 5
A PET film substrate having the same conditions as in Example 1 was used, and a heat-resistant slipping layer similar to that in Example 1 was previously formed on the other surface of the substrate. On the surface opposite to the surface on which the heat resistant slipping layer of the base material is provided, a dye layer coating solution 9 having the following composition is applied by gravure coating so that the dry coating amount is 0.8 g / m ² and dried. Thus, a dye layer was formed, and a thermal transfer sheet of Comparative Example 5 was produced.

<Dye layer composition liquid 9>
Solvent Blue 63 3.0 parts Disperse Blue 354 2.0 parts Polyvinyl acetal resin 4.0 parts (ESREC KS-5 Sekisui Chemical Co., Ltd.)
(Loss elastic modulus at 60 ° C. is 3.3 × 10 ⁷ Pa, loss elastic modulus at 100 ° C. is 3.1 × 10 ⁷ Pa, loss elastic modulus at 150 ° C. is 1.2 × 10 ⁵ Pa)
Methyl ethyl ketone 45.5 parts Toluene 45.5 parts

Comparative Example 6
A PET film substrate having the same conditions as in Example 1 was used, and a heat-resistant slipping layer similar to that in Example 1 was previously formed on the other surface of the substrate. On the surface opposite to the surface on which the heat-resistant slipping layer of the substrate is provided, a dye layer coating solution 10 having the following composition is applied by gravure coating so that the dry coating amount is 0.8 g / m ² and dried. Thus, a dye layer was formed, and a thermal transfer sheet of Comparative Example 6 was produced.

<Dye layer composition liquid 10>
Disperse Yellow 201 2.0 parts Disperse Yellow 231 2.0 parts Polyvinyl acetal resin 4.0 parts (ESREC KS-5 Sekisui Chemical Co., Ltd.)
(Loss elastic modulus at 60 ° C. is 3.3 × 10 ⁷ Pa, loss elastic modulus at 100 ° C. is 3.1 × 10 ⁷ Pa, loss elastic modulus at 150 ° C. is 1.2 × 10 ⁵ Pa)
Methyl ethyl ketone 46.0 parts Toluene 46.0 parts

Comparative Example 7
A PET film substrate having the same conditions as in Example 1 was used, and a heat-resistant slipping layer similar to that in Example 1 was previously formed on the other surface of the substrate. On the surface opposite to the surface on which the heat resistant slipping layer of the substrate is provided, the dye layer coating solution 11 having the following composition is applied by gravure coating so that the dry coating amount is 0.8 g / m ² and dried. Then, a dye layer was formed, and a thermal transfer sheet of Comparative Example 7 was produced.

<Dye layer composition liquid 11>
Solvent Blue 63 3.0 parts Disperse Blue 354 2.0 parts Acrylic resin 4.0 parts (Diananal BR-85 manufactured by Mitsubishi Rayon Co., Ltd.)
(Loss elastic modulus at 60 ° C. is 2.8 × 10 ⁷ Pa, loss elastic modulus at 100 ° C. is 1.5 × 10 ⁷ Pa, loss elastic modulus at 150 ° C. is 1.9 × 10 ⁵ Pa)
Methyl ethyl ketone 45.5 parts Toluene 45.5 parts

Comparative Example 8
A PET film substrate having the same conditions as in Example 1 was used, and a heat-resistant slipping layer similar to that in Example 1 was previously formed on the other surface of the substrate. On the surface opposite to the surface on which the heat-resistant slipping layer of the base material is provided, a dye layer coating solution 12 having the following composition is applied by gravure coating so that the dry coating amount is 0.8 g / m ² and dried. Then, a dye layer was formed, and a thermal transfer sheet of Comparative Example 8 was produced.

<Dye layer composition liquid 12>
Solvent Blue 63 3.0 parts Disperse Blue 354 2.0 parts Acrylic resin 4.0 parts (Dianar BR-80 manufactured by Mitsubishi Rayon Co., Ltd.)
(Loss elastic modulus at 60 ° C. is 9.4 × 10 ⁷ Pa, loss elastic modulus at 100 ° C. is 7.8 × 10 ⁷ Pa, loss elastic modulus at 150 ° C. is 4.1 × 10 ⁵ Pa)
Methyl ethyl ketone 45.5 parts Toluene 45.5 parts

  Using the thermal transfer sheets of Examples and Comparative Examples prepared above, each evaluation of heat-resistant adhesion at room temperature and high temperature and high humidity and adhesion to an image receiving sheet was performed by the following methods.

  Using the thermal transfer sheets of each Example and Comparative Example prepared above, evaluation of maximum printing density, reproducibility of highlight part, presence / absence of abnormal transfer, blocking resistance, dye transfer to heat-resistant slipping layer Each evaluation of was performed by the method shown below.

(Maximum print density)
Printing was performed under the following conditions, and the maximum density of the obtained print was measured. A combination of the thermal transfer sheets prepared in Examples 1 to 4 and Comparative Examples 1 to 8, Canon Inc., and Standard Photo Paper for Compact Photo Printer CP-200, Canon Inc. and Compact Photo Printer CP-200 were used. The maximum density (yellow or cyan) of the printed part was measured with a Macbeth densitometer RD-918 (manufactured by Sakata Inx Corporation). The thermal transfer sheet was cut and pasted on a yellow or cyan panel portion of genuine media and printed with a yellow or cyan solid (tone value 255/255: density max) print pattern. Printing was performed in an environment of a temperature of 30 ° C. and a humidity of 50% RH.

The maximum print density was evaluated according to the following criteria. The cyan ribbon has a maximum print density compared to Comparative Example 5 and the yellow ribbon has a maximum print density compared to Comparative Example 6.
A: 105% or more, which is a satisfactory high concentration.
X: Less than 100%, which is not satisfactory as a high concentration.

(Reproducibility of highlight part)
Printing was performed under the following conditions, and the gradation reproducibility of the highlight portion of the obtained printed matter was examined. A combination of the thermal transfer sheets prepared in Examples 1 to 4 and Comparative Examples 1 to 8, Canon Inc., and Standard Photo Paper for Compact Photo Printer CP-200, Canon Inc. and Compact Photo Printer CP-200 were used. The density (yellow or cyan) of the printed part was measured with a Macbeth densitometer RD-918 (manufactured by Sakata Inx Corporation). The thermal transfer sheet is cut and pasted on the yellow or cyan panel of genuine media.
Printing was performed with a gradation printing pattern that is a highlight portion of yellow or cyan (gradation value 1/255 to 50/255). Printing was performed in an environment of a temperature of 30 ° C. and a humidity of 50% RH.

The evaluation of the reproducibility of the highlight portion was performed according to the following criteria.
The cyan ribbon is compared with Comparative Example 5 and the yellow ribbon is compared with Comparative Example 6. Good: Good gradation reproducibility at the same level.
X: The tone reproducibility is not satisfactory. (The print density is higher than the standard.)

(Absence of abnormal transcription)
Similar to the above printing conditions for the evaluation of the maximum printing density, when the entire surface of the printed material is printed with a solid printing pattern (gradation value 255/255; density max), and the printing is performed, the thermal transfer sheet It was visually examined whether the dye layer and the material to be transferred were thermally fused, or whether so-called abnormal transfer occurred in which the dye layer was transferred to the material to be transferred.

Evaluation was performed according to the following criteria.
○: The dye layer and the material to be transferred are not thermally fused and abnormal transfer does not occur.
X: The dye layer and the transfer material are thermally fused or abnormal transfer occurs.

(Blocking resistance)
The dye layers and heat-resistant slip layers of each thermal transfer sheet were overlapped with each other on the thermal transfer sheets of Examples and Comparative Examples prepared above, and a load of 20 g / cm ² was applied and stored at 60 ° C. for 100 hours. The blocking between the dye layer and the heat-resistant slip layer of the thermal transfer sheet after storage was visually evaluated according to the following criteria.
○: No blocking between the dye layer and the heat-resistant slip layer. It is good.
X: There is blocking between the dye layer and the heat-resistant slipping layer. It is bad.

(Dye transfer to heat resistant slipping layer)
For the thermal transfer sheets of the above-mentioned Examples and Comparative Examples, the dye layer and the heat-resistant slip layer of each thermal transfer sheet were overlapped with each other, applied with a load of 20 g / cm ² , and allowed to stand at 60 ° C. for 24 hours. The temperature was returned to room temperature, the space between the dye layer and the heat-resistant slipping layer was peeled off, and the degree of migration of the dye to the heat-resistant slipping layer side was visually confirmed and evaluated as follows.
○: Dye transfer is not good.
X: Dye transfer is recognized and is poor.

The evaluation results of the above examples and comparative examples are shown in Table 1 below.

From the above results, in all of the thermal transfer sheets of Examples 1 to 4, the loss elastic modulus at 60 ° C. is 10 ⁷ Pa or more, the loss elastic modulus at 100 ° C. is 10 ⁶ Pa or more, and at 150 ° C. Loss elastic modulus is 10 ⁴ Pa or more and 10 ⁵ Pa or less, the maximum print density is satisfactory, the reproducibility of the highlight part is good, there is no abnormal transfer, no blocking, and heat-resistant lubricity There was no dye transfer to the layer.

On the other hand, the thermal transfer sheets of Comparative Examples 1 and 2 have a loss elastic modulus at 60 ° C. lower than 10 ⁷ Pa. Blocking occurs under high temperature conditions such as summertime, and heat-resistant lubricity facing the dye layer Dye transfer to the layer occurred.

The thermal transfer sheet of Comparative Example 3 has a loss elastic modulus at 60 ° C. lower than 10 ⁷ Pa and a loss elastic modulus at 100 ° C. lower than 10 ⁶ Pa, causing blocking or heat resistant slipping facing the dye layer. The transfer of the dye to the layer occurred, and the transfer density was higher than the setting at the highlight portion, resulting in poor reproducibility of the thermal transfer image. In the thermal transfer sheet of Comparative Example 4, the loss elastic modulus at 60 ° C. is lower than 10 ⁷ Pa, the loss elastic modulus at 100 ° C. is lower than 10 ⁶ Pa, and the loss elastic modulus at 150 ° C. is lower than 10 ⁴ Pa. Low, blocking occurs, dye transfer to the heat-resistant slip layer opposite to the dye layer occurs, and the transfer density is higher than the setting in the highlight area, resulting in poor reproducibility of the thermal transfer image, Abnormal transfer occurred during thermal transfer. The thermal transfer sheets of Comparative Examples 5 to 8 are not satisfactory because the loss elastic modulus at 150 ° C. is higher than 1 × 10 ⁵ Pa and the maximum transfer density in printing is low.

  Regarding the binder resin contained in the dye layer composition liquid used in the thermal transfer sheet prepared in Example 1 above, the temperature and loss elastic modulus when the temperature of the binder resin was raised from 30 ° C. to 200 ° C. A graph showing the change is shown in FIG.

It is a schematic sectional drawing which shows one best form of embodiment which is the thermal transfer sheet of this invention. It is a schematic sectional drawing which shows the other best form of implementation which is the thermal transfer sheet of this invention. It is a graph which shows the change of the temperature and loss elastic modulus of binder resin used with the dye layer of the thermal transfer sheet of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base material 2 Dye layer 3 Heat resistant slipping layer 4 Primer layer

Claims (5)

A heat transfer sheet provided with a heat-resistant slipping layer on one side of a substrate and a dye layer formed on the other side of the substrate,
The loss elastic modulus at 60 ° C. of the binder resin constituting the dye layer is 10 ⁷ Pa or more, the loss elastic modulus at 100 ° C. is 10 ⁶ Pa or more, and the loss elastic modulus at 150 ° C. is from 10 ⁴ Pa to 10 ⁴ Pa. 10 ⁵ Pa,
The binder resin is obtained by reacting polyvinyl acetal resin with succinic anhydride or phthalic anhydride, has an acid value of 40 mg KOH / g, a molecular weight of 120,000, and has the following formula:

Where R ′ is C ₃ H ₇ , R ″ is —CH ₂ CH ₂ —, b is 60, c is 29, d is 3, and e is 8. A thermal transfer sheet made of a modified polyvinyl acetal resin.   The thermal transfer sheet according to claim 1, wherein the binder resin has a glass transition temperature of 60 ° C. or higher. 2. The thermal transfer sheet according to claim 1, wherein the loss elastic modulus at 60 ° C. of the binder resin constituting the dye layer is in the range of 10 ⁷ Pa to 10 ⁸ Pa. 3. The thermal transfer sheet according to claim 1, wherein the loss elastic modulus at 100 ° C of the binder resin constituting the dye layer is in the range of 10 ⁶ Pa to 10 ⁸ Pa.   The thermal transfer sheet according to claim 1, wherein a primer layer is formed between the substrate and the dye layer.

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