JP2013180521A - Thermal transfer sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal transfer sheet which exhibits good print density and preserving property even when an amount of thermal transferable dye contained in the thermal transfer sheet is reduced.SOLUTION: A thermal transfer sheet 11 includes a base material 2, and a dye layer 3 containing binder resin and thermal transferable dye of which a weight is in a range of 2.5-3.5 to the binder resin in an amount of 1 by weight. The binder resin is made by modifying polyvinyl butyral resin with both or either acid of maleic anhydride and/or succinic anhydride.

Description

  The present invention relates to a thermal transfer sheet.

  A technique for forming a color image on a dedicated image receiving paper by heating a thermal transfer sheet coated with a thermal transfer dye on the basis of a data signal of an electronic image with a thermal head is known as a so-called sublimation transfer recording technique. Patent Document 1 describes a thermal transfer sheet in which a dye layer is provided on a film, and the dye layer holds a thermal transferable dye in a dissolved state in a polyvinyl butyral resin.

  Patent Document 2 describes a thermal transfer sheet using a carboxylic acid-modified polyvinyl acetal resin obtained by reacting a polyvinyl acetal resin with succinic anhydride or phthalic anhydride as a binder resin.

  At the time of filing of the original patents in Patent Documents 1 and 2, the thermal head is only used for thermal recording paper and melt transfer recording, and there is concern about the durability of the head when the amount of heat necessary for sublimation transfer recording is applied There was only. Currently, there is a thermal head dedicated to sublimation transfer recording that can record at high speed. Furthermore, a dedicated thermal transfer dye has been developed, and a heat-sensitive sublimation image-receiving sheet that efficiently uses heat has also been developed. The related art has been remarkably advanced since the filing of the original patents in Patent Documents 1 and 2.

  As for the usage environment, it was originally assumed that the printer was for home use, and the specifications were adopted so that the performance of the thermal transfer sheet did not change even if it was placed in a harsh environment, but now it is used for commercial printers Is in a situation where the usage environment can be controlled to some extent, and the specifications of the thermal transfer sheet that does not assume storage stability under severe conditions may be reviewed again.

Furthermore, there is a high demand for cost reduction for commercial use, and from the viewpoint of efficient use of thermal transfer dyes, a thermal transfer sheet that uses less thermal transfer dye than conventional thermal transfer sheets is desired.

Japanese Patent Publication No. 7-29504 Japanese Patent No. 4216833

  It is an object to obtain a thermal transfer sheet having a good print density even if the transfer efficiency of the thermal transfer dye is increased and the amount of the thermal transfer dye contained in the thermal transfer sheet is reduced.

  1st invention is equipped with the base | substrate and the dye layer containing the thermal transferable dye whose weight is the range of 2.5-3.5 with respect to the weight 1 of binder resin and binder resin on a base | substrate. The binder resin is a thermal transfer sheet obtained by modifying a polyvinyl butyral resin with either or both of maleic anhydride and succinic anhydride.

  A second invention is the thermal transfer sheet according to the first invention, wherein the coating amount of the dye layer is 0.25 g / square meter to 0.35 g / square meter.

  A thermal transfer sheet having a necessary printing density and good storage stability and a small amount of thermal transferable dye can be obtained.

Schematic diagram of sublimation transfer recording method

  FIG. 1 is a schematic diagram of a sublimation transfer recording method. The dye layer 3 of the thermal transfer sheet 11 and the receiving layer 4 of the sublimation transfer image receiving sheet 12 are overlapped and sandwiched between the thermal head 21 and the platen roll 22, and the thermal transfer sheet and the sublimation are heated and printed by the thermal head based on the image signal. This is a method for recording an image by transferring a thermal transfer dye into a receiving layer by conveying a transfer image receiving sheet.

  In the schematic diagram of FIG. 1, as the sublimation transfer image receiving sheet, the heat insulating layer 6 and the cushion layer 5 are provided in addition to the receiving layer, but the present invention is not necessarily limited to the use of the sublimation transfer image receiving sheet having this structure. Absent. In order to print using the thermal transfer sheet of the present invention, a substrate and a receiving layer 4 applied thereon may be provided as a sublimation transfer image receiving sheet.

  The thermal transfer sheet is provided with a dye layer 3 containing a binder resin and a thermal transferable dye on one surface of a thin film substrate 2 such as a polyester film, and a heat resistant slipping layer that prevents fusion with a thermal head on the other surface of the substrate. 1 is often provided.

  A first embodiment of the present invention is a substrate and a dye layer comprising a binder resin and a thermal transfer dye having a weight in the range of 2.5 to 3.5 with respect to the weight 1 of the binder resin on the substrate. And the binder resin is a thermal transfer sheet obtained by modifying a polyvinyl butyral resin with either or both of maleic anhydride and succinic anhydride.

  A second embodiment of the present invention is the thermal transfer sheet according to the first embodiment, wherein the coating amount of the dye layer is from 0.25 g / square meter to 0.35 g / square meter.

  Below, each structure of the thermal transfer sheet which concerns on this invention is demonstrated in detail.

<Substrate>
The substrate is selected to be thin, uniform and high in heat resistance. For example, as the polymer compound used for the substrate, polyesters such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate; polymethylpentene; polysulfone; polyether such as polyether ether ketone, polyether sulfone and polyether imide; polyimide, Etc. Among these, polyethylene terephthalate is preferable from the viewpoint of strength, heat resistance, thin film uniformity, and production.
The thickness of the substrate is appropriately selected according to specifications or applications, and is usually 3 μm to 12 μm, preferably 3.5 μm to 9 μm. More preferably, it is 3.5 μm to 4.5 μm.

For the purpose of improving the adhesion with the layer provided on the surface of the substrate, one or both surfaces can be subjected to surface treatment by a surface oxidation method, a surface unevenness method, or the like, if necessary. Examples of the surface oxidation method include corona discharge treatment, flame treatment, hot air treatment, ozone treatment, ultraviolet irradiation treatment, plasma irradiation treatment, chromic acid treatment, etc., and surface concavo-convex methods include sandblasting, solvent treatment, etc. Is mentioned. These surface treatment methods are appropriately selected according to the type of the substrate, but in general, a corona discharge treatment method is preferably used.
You may apply | coat the primer for improving adhesiveness further as needed.

<Dye layer>
The dye layer includes a polyvinyl butyral resin modified with maleic anhydride and / or succinic anhydride, and / or a thermal transfer dye. In the dye layer, it is preferable that the thermal transfer dye is dissolved in the polyvinyl butyral resin. When the thermal transfer dye is present in a dissolved state, recording can be performed with less energy than when the thermal transfer dye is dispersed in the binder resin in a crystalline state.

  An ink obtained by dissolving the binder resin and the heat transferable dye in a solvent can be applied onto a substrate and dried to form a dye layer. At this time, a certain degree of affinity is required between the binder resin and the thermal transferable dye. If the affinity is insufficient, the thermal transferable dye is deposited and crystallized when the ink is dried. Moreover, even if there is too much heat transferable dye with respect to binder resin amount, heat transferable dye precipitates.

  The dye layer includes cyan, magenta, and yellow dye layers. If necessary, a black dye layer is also used. The cyan, magenta, yellow, and black dye layers are used by being applied to separate substrates, or may be used by being applied in a repeated pattern of each color on the same substrate.

(Polyvinyl butyral resin)
The polyvinyl butyral resin used in the present invention modified by reacting with either or both of maleic anhydride and succinic anhydride is a polyvinyl butyral resin acetalized by reacting polyvinyl alcohol resin with butyraldehyde.
As the polyvinyl butyral resin used for modification, a polyvinyl butyral resin having a butyralization degree in the range of 63 mol% to 77 mol% is preferable. A more preferred range is a polyvinyl butyral resin having a butyralization degree in the range of 65 mol% to 69 mol%.
The acetyl group residue is preferably 3 mol% or less.

  The mol% of the degree of butyralization indicates how many alcohol residues are butyralized in units of the number of moles of vinyl alcohol residues in the starting material. If the degree of butyralization of the polyvinyl butyral resin is low, the solubility in organic solvents is poor and modification is difficult. If the degree of butyralization is 63 mol% or more, the solubility in organic solvents is good.

The molecular weight of the starting polyvinyl butyral resin was determined by measuring the viscosity of a 10% polyvinyl butyral component in a 1: 1 ethanol / toluene mixed solution using a rotational viscometer (BM type) at a measurement temperature of 20 ° C. Calculated. The viscosity of a high molecular weight polyvinyl butyral resin having a molecular weight of about 100,000 was calculated by measuring the viscosity of a 5% solution with a measurement temperature of 20 ° C. using a rotational viscometer (BM type), and using the corresponding other viscosity equations.
A polyvinyl butyral resin having a molecular weight calculated from the viscosity formula in the range of 30,000 to 110,000 is preferred as a starting material to be modified in the present invention. More preferred is a polyvinyl butyral resin having a molecular weight in the range of 40,000 to 11,000,000.
The glass transition temperature of the polyvinyl butyral resin as a starting material is preferably 60 ° C. or higher. Furthermore, a polyvinyl butyral resin having a glass transition temperature of 67 ° C. or higher is more preferable, and a polyvinyl butyral resin having a high glass transition temperature has better storage stability.

(Reaction between polyvinyl butyral resin and acid anhydride)
The reaction for modifying the polyvinyl butyral resin with an acid anhydride is carried out in a solvent. Examples of the solvent used for this include various solvents such as hydrocarbon, ketone, ester, ether, and amide. Specific examples include N, N-dimethylformamide, methyl ethyl ketone, methyl isobutyl ketone, and toluene.

  Acid anhydrides that can be used in the reaction include divalent or higher carboxylic acid anhydrides such as phthalic anhydride, naphthalene-1,2-dicarboxylic anhydride, succinic anhydride, maleic anhydride, itaconic anhydride, glutaric anhydride. , Trimellitic anhydride, cyclohexane-1,2-dicarboxylic anhydride, norbornane-2,3-dicarboxylic anhydride, etc. Among 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.

  The reaction between the polyvinyl butyral resin and the acid anhydride 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.

In the reaction, it is preferable to add the acid anhydride alone or the acid anhydride mixture in a mole number of 20 mol% to 50 mol% of the hydroxyl number of the polyvinyl butyral resin with respect to 100 parts by weight of the raw material polyvinyl butyral resin. . The amount of the solvent used is 100 parts by weight or more and 2000 parts by weight or less, preferably 200 parts by weight or more and 1000 parts by weight or less. 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 in the range of 1 to 15 hours.
After the reaction is completed, the temperature is lowered, and the reprecipitation method is repeatedly dried to obtain the polyvinyl butyral resin modified with both maleic anhydride and succinic anhydride acids or one acid of the present invention. .

The introduction ratio of maleic acid and / or succinic acid, which is introduced into the polyvinyl butyral resin by ester bond by reaction with a hydroxyl group, is preferably 5 mol% to 20 mol% in terms of vinyl alcohol units. 8 mol%-12 mol% are more preferable.
When the introduction rate is 5 mol% or less, the effect of improving the printing density and the transfer efficiency of the heat transferable dye brought to the dye layer of the polyvinyl butyral resin is small, and when 20 mol% or more is introduced, the storage stability of the dye layer is deteriorated.
The introduction rate of maleic acid and / or succinic acid indicates how many mole% of alcohol residues are esterified based on the number of moles of vinyl alcohol residues in the starting material.

  In the present invention, the total weight of the thermal transfer dye is in the range of 2.5 to 3.5 with respect to the total weight 1 of the polyvinyl butyral resin modified with both maleic anhydride and / or succinic anhydride. The present inventors have found that the thermal transfer sheet has good storage stability, the transfer efficiency of the thermal transfer dye to the sublimation transfer image-receiving sheet, and the printing density is good.

  In addition, a dye layer in which the total weight of the thermal transfer dye is in the range of 2.5 to 3.5 with respect to the total weight 1 of the polyvinyl butyral resin modified with both maleic anhydride and / or succinic anhydride. When used, it has been found that when the coating amount of the dye layer is in the range of 0.25 g / square meter to 0.35 g / square meter, the required image density can be obtained using the dye layer. Moreover, the usage-amount of the thermal transferable dye in the dye layer in the said application quantity is less than the quantity of the thermal-transferable dye currently used with the thermal transfer sheet of patent document 2. FIG.

  That is. A preferable coating amount of the dye layer in the present invention is 0.25 g / square meter to 0.35 g / square meter. The maximum coating amount is 0.35 g / square meter, and since the ratio of binder resin to thermal transfer dye is a maximum of 1: 3.5, the maximum amount of thermal transfer dye applied is 0.27 g / square meter in calculation. It is. The minimum coating amount is 0.25 g / square meter, and the ratio of the binder resin to the heat transferable dye is a minimum of 1: 2.5. Therefore, the amount of the heat transferable dye applied at this time is calculated to be about 0.18 g. / Square meter. That is, the amount of the heat transferable dye used in the present invention is 0.18 g / square meter to 0.27 g / square meter.

  Patent Document 2 describes a thermal transfer sheet provided with a dye layer having a carboxylic acid-modified polyvinyl butyral resin as a binder. The total weight of oil-soluble dye and disperse dye is 1 with respect to 1 by weight of the carboxylic acid-modified polyvinyl butyral resin. .25 dye layers are described. Compared to the present invention, the ratio of the heat transferable dye to the binder resin is remarkably small. Moreover, the Example has described the example which apply | coats a dye layer 0.8g / square meter. The amount of the thermal transferable dye applied in Patent Document 1 is calculated to be 0.44 g / square meter, which shows that the amount of the thermal transferable dye used in the present invention is remarkably small.

(Thermal transfer dye)
As the thermal transfer dye, in addition to a dye selected from among disperse dyes, a thermal transfer dye developed for sublimation transfer recording is used.
As a thermal transfer dye developed, a cyan dye includes, for example, a dye having a skeleton structure of Compound 1. Examples of the magenta dye include a dye having a skeleton structure of Compound 2. Examples of the yellow dye include a dye having a skeleton structure of Compound 3.

  The heat transferable dye contained in each color dye layer may be one kind of heat transferable dye or a mixture of a plurality of heat transferable dyes. It is appropriately selected according to the required color tone.

(Additive)
In addition to the thermal transfer dye, an additive may be added to the dye layer. For example, there are a mold release agent, an antioxidant, a curing agent, a thermal transfer dye dissolving agent and the like.

<Other layers>
There may be other layers on the thermal transfer sheet. For example, a heat resistant slipping layer may be provided on the substrate opposite to the dye layer. Since the heat-resistant slipping layer is in contact with the thermal head and becomes hot during printing, the heat-resistant slipping layer needs to have both heat resistance and slipperiness. Various heat-resistant slip layers using a curable resin and a surfactant have been developed. The preferred thickness of the heat resistant slipping layer is 0.1 g / square meter to 2.0 g / square meter. A more preferable thickness is 0.2 g / square meter to 1.0 g / square meter.

  In order to improve the adhesion between the dye layer and the substrate, a primer layer may be provided between the substrate and the dye layer.

<Manufacturing method>
In order to manufacture the thermal transfer sheet of the present invention, first, a substrate is prepared by preparing a thin polyester film having a heat resistant slipping layer, and if necessary, corona treatment is performed on the film surface opposite to the surface having the heat resistant slipping layer. Or apply a primer layer.

  As the primer, for example, an ink of a dilute solution of a polymer compound having a polyvalent isocyanate and a hydroxyl group may be applied by gravure printing. Or you may apply | coat polyester resin, vinyl chloride-vinyl acetate copolymer resin, urethane resin etc. which have affinity with a base | substrate.

  The dye ink can be produced by adding a solvent to the binder resin and a predetermined heat transferable dye, and using an ordinary ink production method such as a ball mill method or a sand mill method.

  The dye ink can be applied to the substrate by ordinary gravure printing or single-color solid printing or multicolor pattern printing. After drying, if necessary, the film can be slit to a predetermined width, and the film can be wound around a bobbin for use.

<Preparation of sublimation transfer image receiving sheet>
A method for producing a sublimation transfer image receiving sheet used in combination with the thermal transfer sheet of the present invention will be described below.

An adhesive layer forming ink having the following composition was applied to one surface of a 39 μm-thick microvoided film provided with a fine void layer, and dried to form an adhesive layer. Next, the coated paper (186 g / square meter) was bonded so that the adhesive layer overlapped on one side.

Adhesive layer forming ink:
Polyfunctional polyol “Takelac (registered trademark) A-969V” 30.0 parts by weight
(Mitsui Chemicals)
Isocyanate “Takenate (registered trademark) A-5” 10.0 parts by weight
(Mitsui Chemicals)
60.0 parts by weight of ethyl acetate

Subsequently, a primer layer forming ink having the following composition was applied to the surface opposite to the surface provided with the adhesive layer of the microvoid film by wire bar coating so that the dry coating amount was 2.0 g / square meter. The primer layer was formed by drying.

Ink for primer layer formation:
Polyester polyol "Adcoat (registered trademark)" 15.0 parts by weight
(Toyo Morton Co., Ltd.)
Methyl ethyl ketone / toluene (weight ratio 2: 1) 85.0 parts by weight

On the formed primer layer, a receiving layer forming ink having the following composition is applied by wire bar coating so that the dry coating amount is 4.0 g / square meter, and dried to form a receiving layer. A transfer image-receiving sheet S was obtained.

Receptor layer forming ink:
20.0 parts by weight of vinyl chloride-vinyl acetate copolymer resin (vinyl chloride / vinyl acetate = 87/13, number average molecular weight 31,000,
Glass transition temperature 70 ° C.) “Solvine C (registered trademark) manufactured by Nissin Chemical Industry Co., Ltd.”
Carboxyl-modified silicone 1.0 part by weight (X-22-3701E, manufactured by Shin-Etsu Chemical Co., Ltd.)
Methyl ethyl ketone / toluene (weight ratio 1: 1) 79.0 parts by weight

<Creation of modified polyvinyl butyral resin>
The modified polyvinyl butyral resin used in the present invention was prepared by the following method.

(Synthesis Example 1: Synthesis of polyvinyl butyral resin A1)
In a 1-liter glass flask, 50 g of polyvinyl butyral resin having a molecular weight of 40,000, hydroxyl group of 34 mol%, butyralization degree of 65 mol%, glass transition temperature of 67 ° C., and acetyl group of 3 mol% or less, and succinic anhydride of 4.4 g After weighing 500 g of N, N-dimethylformamide, the contents were slowly stirred.
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 g of water.
The produced granular precipitate was separated by filtration, washed with 160 g of water, transferred to a 3 liter 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 g 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 120 hours for modification. 49 g of polyvinyl butyral resin A1 was obtained.

(Synthesis Example 2: Synthesis of modified polyvinyl butyral resin A2)
Instead of adding 4.4 g of succinic anhydride,
50 g of modified polyvinyl butyral resin A2 was obtained in the same manner as in Synthesis Example 1 except that 2.2 g of succinic anhydride and 2.2 g of maleic anhydride were added.

(Synthesis Example 3: Synthesis of Modified Polyvinyl Butyral Resin A3)
Instead of adding 4.4 g of succinic anhydride,
50 g of modified polyvinyl butyral resin A3 was obtained in the same manner as in Synthesis Example 1 except that 4.4 g of maleic anhydride was added.

(Synthesis Example 4: Synthesis of Modified Polyvinyl Butyral Resin B)
Modified polyvinyl butyral in the same manner as in Synthesis Example 1, except that the molecular weight was 110,000, the hydroxyl group was 34 mol%, the butyralization degree was 65 mol%, the glass transition temperature was 71 ° C, and the polyvinyl butyral resin was changed to 50 g of an acetyl group of 3 mol% or less. 51 g of Resin B was obtained.

(Synthesis Example 5: Synthesis of modified polyvinyl butyral resin C)
Modified in the same manner as in Synthesis Example 1 except that the molecular weight was 92,000, the hydroxyl group was 30 mol%, the butyralization degree was 69 mol%, the glass transition temperature was 67 degrees, and the polyvinyl butyral resin was 50 g having an acetyl group of 3 mol% or less. 50 g of polyvinyl butyral resin C was obtained.

(Synthesis Example 6: Synthesis of modified polyvinyl butyral resin D)
Modified in the same manner as in Synthesis Example 1, except that the molecular weight was 52,000, the hydroxyl group was 31 mol%, the butyralization degree was 68 mol%, the glass transition temperature was 67 ° C., and the polyvinyl butyral resin was 50 g having an acetyl group of 3 mol% or less. 49 g of polyvinyl butyral resin D was obtained.

  The introduction rate of maleic anhydride and / or succinic anhydride introduced into the modified polyvinyl butyral resins of Synthesis Examples 1 to 6 was in the range of about 8 mol% to 12 mol%.

(Synthesis Example 7: Synthesis of modified polyvinyl butyral resin L)
Modified polyvinyl acetate in the same manner as in Synthesis Example 1, except that the molecular weight was 53,000, the hydroxyl group was 22 mol%, the butyralization degree was 73 mol%, the glass transition temperature was 60 ° C., and the polyvinyl butyral resin was changed to 50 g of acetyl group. 50 g of butyral resin L was obtained.

(Synthesis Example 8: Synthesis of Modified Polyvinyl Butyral Resin M)
Modified polyvinyl acetate in the same manner as in Synthesis Example 1, except that the molecular weight was 32,000, the hydroxyl group was 21 mol%, the butyralization degree was 77 mol%, the glass transition temperature was 62 ° C., and the polyvinyl butyral resin was 4 g mol%. 49 g of butyral resin M was obtained.
The introduction rate of succinic anhydride introduced into the modified polyvinyl butyral resins of Synthesis Examples 7 to 8 was in the range of about 5 mol% to 8 mol%.

<Preparation of thermal transfer sheet>
(Heat resistant slipping layer)
A 4.5 μm thick polyester film was corona-treated, and a heat-resistant slip layer forming ink having the following composition was gravure-printed on the corona-treated surface, dried, and applied to a dry weight of 0.3 g / square meter. The sheet was aged in a wound state at a temperature of 60 ° C. for 4 days to obtain a sheet H with a heat resistant slipping layer provided with the heat resistant slipping layer 1.
Ink for forming heat resistant slipping layer:
4.55 parts by weight of polyvinyl butyral resin “ESREC (registered trademark) BX-1, manufactured by Sekisui Chemical Co., Ltd.”
21 parts by weight of polyisocyanate “Bernock (registered trademark) D750-45, solid content 45%, manufactured by DIC Corporation”
Phosphate ester surfactant 3 parts by weight “Plysurf (registered trademark) A208N, manufactured by Daiichi Pharmaceutical Co., Ltd.”
0.7 parts by weight of talc “Microace (registered trademark) P-3, manufactured by Nippon Talc Industrial Co., Ltd.”
Methyl ethyl ketone 100 parts by weight Toluene 100 parts by weight

(Dye layer)
A primer layer was provided on the surface opposite to the heat-resistant slip layer of the 4.5 μm thick polyester film provided with the heat-resistant slip layer, and a dye layer having the following composition was further applied thereon and dried. Each transfer film was evaluated by the following thermal transfer sheet evaluation method.
A magenta dye having the following composition was used in all Examples 1 to 12 and Comparative Examples 1 to 4. Compound 4 is a dye developed for sublimation transfer recording, and Compound 5 and Compound 6 are conventionally used disperse dyes.
Dye layer forming ink:
Compound 4 Dye 2.0 parts by weight Compound 5 (Disperse Red 60) 2.0 parts by weight Compound 6 (Disperse Violet 26) 3.0 parts by weight Binder resin 2.8 parts by weight Toluene / methyl ethyl ketone (one-to-one mixed solvent) 100 parts by weight

As the binder resin, the resins of Synthesis Examples 1 to 8 were used. Further, in Comparative Examples 3 to 4, a polyvinyl acetoacetal resin Z having a molecular weight of 130,000, a hydroxyl group of 25 mol%, an acetaldehyde degree of acetalization of 74 mol%, a glass transition temperature of 110 ° C., and an acetyl group of 3 mol% or less was used.

The composition of the dye layer forming ink is the composition when the weight ratio of the heat transferable dye and the binder is 2.5 to 1. When inks having different weight ratios of the thermal transfer dye and the binder were prepared, the ink was prepared and used at a predetermined weight ratio by appropriately increasing and decreasing the amount of the binder resin and the amount of the mixed solvent.

<Evaluation method of thermal transfer sheet>
(1) Evaluation method of thermal transfer dye transfer efficiency Using the above thermal transfer sheet and sublimation transfer image receiving sheet S,
With a test printer (resolution 300 dpi, head resistance 5300Ω, applied voltage: 25.5 V, print line speed: 2.0 ms / Line, pulse duty 85%),
A magenta solid print was created. The gradation value at the time of printing was 255/255 (0 to 255 variable, 255 being the maximum energy).
The thermal transfer sheet used at the time of printing and the unused thermal transfer sheet were cut into 5 cm x 5 cm, and the thermal transfer dye was extracted with a one-to-one solvent of toluene / methyl ethyl ketone, and high performance liquid chromatography (LC-2010HТ, manufactured by Shimadzu Corporation) Was used to measure the thermal transferable dye content.
From the obtained results, the transfer efficiency was calculated by Equation 1.
The obtained values were evaluated according to the following criteria.
Good: The transfer efficiency was 75% or more. Bad: The transfer efficiency was less than 75%.

(2) Thermal transfer sheet storage stability evaluation method For the thermal transfer sheets of the above-described Examples and Comparative Examples, the dye layer surface of each thermal transfer sheet and the heat-resistant slip layer surface of the sheet H with the heat-resistant slip layer are superimposed, A load of 20 g / square centimeter was applied, left at 60 ° C. for 24 hours, then returned to room temperature, and the space between the dye layer and the heat-resistant slipping layer was peeled off. The heat transferable dye migrates from the dye layer to the surface of the heat resistant slipping layer, and the heat resistant slipping layer surface is colored.

A sample of the sheet H with a heat-resistant slipping layer before the storage test and a sample having the heat transferable dye transferred to the sheet H with the heat-resistant slipping layer after the storage test were obtained by a Spectrolino (registered trademark) spectrophotometer (manufactured by Gretag Macbeth, The L *, a *, and b * values of each sample were measured with a D65 light source, AnSi-A). The color difference (ΔE value) of the sample before and after the storage test was calculated using Equation 2.
Based on the obtained results, evaluation was made according to the following criteria.
Good: ΔE value was less than 7.0 Fair: ΔE value was 7.0 or more and less than 10.0 Bad: ΔE value was 10.0 or more

保存試験前の耐熱滑性層の各測定値をＬ＊未保存、ａ＊未保存、ｂ＊未保存とする。
保存試験後の耐熱滑性層の各測定値をＬ＊保存、ａ＊保存、ｂ＊保存とする。

Each measured value of the heat-resistant slip layer before the storage test is L * unstored, a * unstored, b * unstored.
Each measured value of the heat resistant slipping layer after the storage test is L * storage, a * storage, and b * storage.

(3) Print Density Evaluation Method The reflection density of a sample obtained by printing each thermal transfer sheet on the sublimation transfer image receiving sheet S with the highest gradation was measured with a Spectrolino (registered trademark) spectrophotometer.
Based on the obtained results, evaluation was made according to the following criteria.
Good: Necessary print density is obtained.
Fair: The print density is slightly low, but is practically usable.
Bad: Print density is low.

Examples 1 to 3 in Table 1 are polyvinyl butyral resin A-1 in which a butyral resin having a butyralization degree of 65 mol%, a glass transition temperature of 67 ° C., and an acetyl group of 3 mol% or less is modified with succinic anhydride, and anhydrous Using a polyvinyl butyral resin A-2 modified with succinic acid / maleic anhydride (one to one) and a polyvinyl butyral resin A-3 modified with maleic anhydride as a binder resin, the weight ratio of the heat transferable dye to the binder resin is 2 The coating amount of the dye layer was 0.35 g / square meter, and the influence of the type of dicarboxylic anhydride that modifies the polyvinyl butyral resin and the change in the mixing ratio was examined. All the resins showed good characteristics.
The D / B ratio in the table is the weight ratio of the heat transferable dye to the binder resin 1 in the dye layer. The acetyl group is one that remains without being hydrolyzed when vinyl acetate is hydrolyzed to polyvinyl alcohol.

  Example 1, Example 4, Example 5, and Example 6 in Table 2 show the effects of differences in polyvinyl butyral resin. The polyvinyl butyral resin before modification with carboxylic anhydride modification is a resin having a molecular weight of 40,000 to 110,000, a butyralization degree of 65% to 69%, and a glass transition temperature of 67 ° C to 71 ° C. is there. All acetyl groups are 3 mol% or less. All resins showed good results.

  Table 3 shows the composition of the dye layer with polyvinyl butyral resin A-1 having a molecular weight of 40,000, a butyralization degree of 65 mol%, a glass transition temperature of 67 ° C., and a butyral resin having an acetyl group of 3 mol% or less modified with succinic anhydride. The coating amount is constant at 0.35 g / square meter, and the ratio of the heat transferable dye and the binder resin is changed from 2.0 to 4.0. In Comparative Example 1, the transfer efficiency was low and the print density was low. In Comparative Example 2, the heat transferable dye was deposited and could not be used. Examples 1 and 7 were good.

Table 4 shows thermal transferable dyes and binders using polyvinyl butyral resin B having a molecular weight of 110,000, a butyralization degree of 65 mol%, a glass transition temperature of 71 ° C. and a acetyl group of 3 mol% or less modified with succinic anhydride as a binder. The ratio and the coating amount of the dye layer are changed. In Example 8 in which the D / B ratio was 2.5 and the coating amount of the dye layer was 0.25 g / square meter, the printing density was slightly low, but was practically usable.
Examples 9 and 10 were good.

Table 5 shows Examples 11 to 12 using a resin obtained by modifying a butyral resin having a high degree of butyral conversion with succinic anhydride, and Comparative Examples 3 to 4 using a polyvinyl acetoacetal resin.
A polyvinyl butyral resin L obtained by modifying a butyral resin having a molecular weight of 53,000, a butyralization degree of 73 mol%, a glass transition temperature of 60 ° C., and an acetyl group of 5 mol% with succinic anhydride as a binder, a D / B ratio of 2.5, In Example 11 in which the coating amount of the dye layer was 0.35 / square meter, the storage stability was worse than that in Examples 1 to 10, but it was at a level having no practical problem.

  A polyvinyl butyral resin M obtained by modifying a butyral resin having a molecular weight of 32,000, a butyralization degree of 77 mol%, a glass transition temperature of 62 ° C., and an acetyl group of 4 mol% with succinic anhydride as a binder, a D / B ratio of 2.5, In Example 12, in which the coating amount of the dye layer was 0.35 / square meter, the storage stability was worse than that in Examples 1 to 10, but it was at a level with no practical problem.

  Using a polyvinyl acetoacetal resin Z having a molecular weight of 130,000, a degree of acetoacetalization of 74 mol%, a glass transition temperature of 110 ° C., and an acetyl group of 3 mol% or less as a binder, a D / B ratio of 2.5 and a coating amount of the dye layer of 0. In Comparative Example 3 with 35 / square meter, the transfer efficiency was poor and the printing density was low.

  Comparative Example 4 using polyvinyl acetoacetal resin Z as a binder with a D / B ratio of 1.25 and a dye layer coating amount of 0.80 / square meter has good storage stability and print density but poor transfer efficiency and thermal transfer. There is a lot of waste due to the large amount of sex dyes used.

1: Heat-resistant slip layer 2: Substrate (film)
3: Dye layer 4: Receptive layer 5: Cushion layer 6: Heat insulation layer 7: Substrate 11: Thermal transfer sheet 12: Sublimation transfer image receiving sheet 21: Thermal head 22: Platen roll

Claims (2)

A substrate;
On the substrate, a dye layer containing a binder resin and a heat transferable dye having a weight in the range of 2.5 to 3.5 with respect to the weight 1 of the binder resin;
With
A thermal transfer sheet, wherein the binder resin is a modified polyvinyl butyral resin modified with maleic anhydride and / or succinic anhydride.   2. The thermal transfer sheet according to claim 1, wherein the coating amount of the dye layer is 0.25 g / square meter to 0.35 g / square meter.

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