JP2012101362A - Thermal transfer sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal transfer sheet which can suppress a change with time of a dye layer.SOLUTION: This thermal transfer sheet includes the dye layer which is provided on one surface of a base material and contains at least dye having a prescribed hue and binder resin. The binder resin contains a mixture of polyvinyl acetal resin having a prescribed glass transition temperature and amorphous saturated polyester resin, in which the mass ratio of the polyvinyl acetal resin to the amorphous saturated polyester resin is 95:5-70:30.

Description

  The present invention relates to a thermal transfer sheet.

  In recent years, due to the high degree of immediate printability in dye diffusion thermal transfer printers, photographs replaced with silver salt photographs have been selected by a computer, which is a terminal device, and selected by the above dye diffusion thermal transfer printers. Installation of photo kiosks that output images is expanding. At this time, in order to increase the number of output images per unit time, it is required to increase the printing speed, and in order to obtain the necessary dye dyeing concentration by heating in a short time, the sensitivity of the thermal transfer sheet and transferred sheet is increased. Is underway.

  When high-speed printing is performed using a conventional thermal transfer sheet, the print density is insufficient due to insufficient sensitivity, and the applied energy is increased to obtain a higher density. May cause a peeling failure, or may cause a running failure due to elongation or wrinkling of the thermal transfer sheet.

  In such a situation, in order to increase the sensitivity of the thermal transfer sheet, generally, the thermal conductivity is improved by reducing the thickness of the base film of the thermal transfer sheet, and the dye / resin ratio in the dye layer of the thermal transfer sheet is increased. Often measures are taken. However, in particular, when the dye / resin ratio is increased, a phenomenon called shelf life, in which the storage stability of the thermal transfer sheet (change in density characteristics or dye crystallization) is likely to occur.

  Thus, attempts have been made to improve the printing density and storage stability by improving the resin used in the dye layer of the thermal transfer sheet (see, for example, Patent Documents 1 to 7 below).

  Specifically, in Patent Documents 1 to 4 shown below, it is described that a polyvinyl acetal resin is used as the resin used for forming the dye layer. More specifically, Patent Document 1 discloses thermal transfer including 90% by mass or more of a polyvinyl acetal resin having a molecular weight of 60,000 to 200,000, a glass transition temperature of 60 to 110 ° C., and a mass% of a vinyl alcohol portion of 10% to 40%. It is described that a high-density and clear image (printed material) can be obtained by using a thermal transfer sheet having a layer.

  Patent Documents 2 and 3 describe the use of polyvinyl acetoacetal as the binder resin for the thermal transfer layer. A thermal transfer ink ribbon using such a resin is excellent in preservability because the dye does not leach out on the surface of the thermal transfer layer and does not crystallize during storage, and is further heated by heating means such as a thermal head. It is described that image recording with excellent recording density can be realized without hindering heat transfer of the dye.

  Patent Document 4 describes a technique for improving the dye releasability during thermal transfer by using a polyvinyl acetoacetal resin and a phenylaldehyde-modified polyacetal as a binder resin for the dye layer.

  Further, cited document 2 and cited documents 5 to 7 describe a method for improving performance by blending other resins with polyvinyl acetal resin.

  For example, Patent Document 2 describes that the drying property at the time of coating and forming a thermal transfer layer is improved by blending a cellulose resin in a range of up to 10% by mass in the binder resin with polyvinyl acetal resin. Has been.

  Patent Document 5 describes a method of blending a cellulose-based resin with a polyvinyl acetal resin in a range of less than 10% by mass in the binder resin of the thermal transfer layer. In Patent Document 5, by using such a method, agglomeration, crystal growth and precipitation of the dye in the thermal transfer layer with time are prevented, and a high density and clear image is obtained with relatively low energy without causing scumming. It is described that it is possible to form (printed material).

  Patent Document 6 describes that polyvinyl butyral and nitrocellulose are used for the ink layer of the thermal transfer recording sheet. In Patent Document 6, by using such a method, fusion with the image-receiving sheet for thermal transfer recording and occurrence of background contamination of the sheet are prevented, and a decrease in image density is suppressed, and storage stability is improved. Is stated.

  Patent Document 7 describes the use of an incompatible polymer blend as the binder resin for the dye-donating layer. By using such a method, even if a release agent is used for improving heat fusion, paper feedability, and transportability, no slip occurs between the dye-donating material and the dye-receiving material. It becomes possible to obtain a printed matter without “color shift transfer”. That is, by blending an incompatible polymer with a binder resin, phase separation occurs, static friction between the dye-donating material and the dye-receiving material increases, and slippage between the two is reduced. As a result, in Patent Document 7, it is possible to suppress printing deviation, contamination of the thermal head due to dye transfer to the back side of the ink ribbon, reduction in transfer density, and density unevenness.

Japanese Patent Laid-Open No. 60-101087 JP 63-151484 A JP-A-4-236205 JP-A-6-048053 JP-A-6-24159 Japanese Patent Laid-Open No. 4-115991 JP-A-5-58055

  As described above, various methods as described in Patent Documents 1 to 7 have been studied with the aim of improving the print density and storage stability of the thermal transfer sheet. While studying the binder resin used in the dye layer, the inventors have found a problem that the printing characteristics before and after storage of the thermal transfer sheet change with time. In addition, as a result of further studies on such problems, the inventors have arrived at the idea that the techniques described in Patent Documents 1 to 7 cannot suppress changes in print characteristics over time before and after storage. did.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a new and improved thermal transfer sheet capable of suppressing a change with time of a dye layer. It is in.

  In order to solve the above-described problem, according to one aspect of the present invention, a dye layer including at least a dye having a predetermined hue and a binder resin provided on one surface of a base material, A mixture of a polyvinyl acetal resin having a predetermined glass transition temperature and an amorphous saturated polyester resin, wherein the mass ratio of the polyvinyl acetal resin and the amorphous saturated polyester resin is 95: 5 to 70:30. A thermal transfer sheet is provided.

  Here, the amorphous saturated polyester resin preferably has a glass transition temperature of 40 to 70 ° C. and a number average molecular weight of 8000 to 25000.

  Moreover, it is preferable that a dye layer contains the polyvinyl acetoacetal resin or polyvinyl acetoacetal / polyvinyl butyl acetal copolymer whose glass transition temperature is 90-110 degreeC as a polyvinyl acetal resin.

  As described above, according to the present invention, the binder resin of the dye layer is composed of a polyvinyl acetal resin having a specific glass transition temperature and an amorphous saturated polyester, and these mass ratios are in a specific range. The change with time of the dye layer can be suppressed.

It is sectional drawing which shows the thermal transfer sheet which concerns on embodiment of this invention.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  In the following description, the term “parts” means parts by mass.

The description will be made in the following order.
(1) Outline of Thermal Transfer Sheet According to Embodiment of the Present Invention (2) First Embodiment (2-1) Configuration of Thermal Transfer Sheet (3) Examples and Comparative Examples (3-1) Production Example of Thermal Transfer Sheet (3-2) Storage method (3-3) Printing method (3-4) Evaluation

(Outline of Thermal Transfer Sheet According to Embodiment of the Present Invention)
First, prior to detailed description of the thermal transfer sheet according to the embodiment of the present invention, an outline of the thermal transfer sheet according to the embodiment of the present invention will be briefly described.

  The present inventors have studied a binder resin used in a dye layer for the purpose of improving the print density and storage stability of a thermal transfer sheet in a thermal transfer printer. As a result of such studies, the present inventors have conceived that there is an unsolved problem that has not yet been known, in which the print characteristics before and after storage of the thermal transfer sheet change with time.

  As a result of intensive studies by the present inventors in order to solve such problems, as described in detail below, as a binder resin used in the dye layer, a polyvinyl acetal resin having a specific glass transition temperature, and an amorphous resin It was conceived that the change with time of the printing characteristics before and after storage can be suppressed by using a mixture with a water-soluble saturated polyester resin.

  The above-mentioned patent document, for example, Patent Document 7, describes a technique of blending a polyvinyl acetal resin and a polyester resin, a polystyrene resin, a polyvinyl chloride resin, or the like that is incompatible with the polyvinyl acetal resin. However, the above cited references including Patent Document 7 do not even recognize the change in the printing characteristics due to the storage of the thermal transfer sheet as found by the present inventors. In addition, by combining the binder resin as described in the above-mentioned patent document, it is impossible to suppress the temporal change of the printing characteristics before and after storage of the thermal transfer sheet, which is a problem found by the present inventors. It was.

  In addition, the compatibility referred to in the above-mentioned patent document varies depending on the molecular weight of the amorphous saturated polyester and the difference in glass transition temperature (in other words, the difference in constituent monomers and the like). However, even if it has poor compatibility and loses gloss due to fine irregularities on the surface, or even if it is compatible and maintains gloss, the effect found for the first time in the present invention will be affected. Note that there is no point.

  In the following description, the change in printing characteristics is shown as ΔE. For example, when yellow or cyan dyes are used, an increase in density is observed by storage, whereas when magenta dyes are used, there is a decrease in density. It has been observed and generally does not appear as a decrease in density due to dye transfer. In addition, in some compositions where crystallization is caused by addition, settling to the backcoat layer is confirmed, but in other compositions there is no difference in setback, and this effect depends on the settling amount. Not. Therefore, the present inventors presume that this effect is mainly caused by stabilization or homogenization of the dye in the binder resin in the paint drying process.

  Based on the outline as described above, the thermal transfer sheet according to the embodiment of the present invention will be described in detail below.

(First embodiment)
<Configuration of thermal transfer sheet>
First, the configuration of the thermal transfer sheet 10 according to the first embodiment of the present invention will be described with reference to FIG.

  The thermal transfer sheet 10 according to this embodiment includes a thermal transfer sheet substrate 101, a heat-resistant slip layer 103 formed on one surface of the thermal transfer sheet substrate 101, and a heat-resistant slip layer 103 formed on the thermal transfer sheet substrate 101. A dye layer 107, a laminate layer 109, and a sensor mark layer 111 are mainly provided on a surface opposite to the surface to be formed. As shown in FIG. 1, a primer layer 105 may be formed between the thermal transfer sheet substrate 101 and the dye layer 107, the laminate layer 109, and the sensor mark layer 111.

  As shown in FIG. 1, the primer layer 105 may be provided on the entire surface of the thermal transfer sheet substrate 101 opposite to the surface on which the heat-resistant slip layer 103 is provided. It may be provided only between 101 and a specific layer. For example, the primer layer 105 is provided only between the thermal transfer sheet substrate 101, the dye layer 107, and the sensor mark layer 111, and may not be provided between the thermal transfer sheet substrate 101 and the laminate layer 109. .

[Thermal transfer sheet substrate]
The thermal transfer sheet substrate 101 has a flat plate shape with a thickness of 0.5 to 50 μm, preferably 1 to 10 μm. The resin constituting the thermal transfer sheet substrate 101 may be any resin as long as it is a resin constituting a known thermal transfer sheet substrate and has a certain degree of heat resistance and strength.

  Examples of such resins include polyethylene terephthalate film, 1,4-polycyclohexylenedimethylene terephthalate film, polyethylene naphthalate film, polyphenylene sulfide film, polystyrene film, polypropylene film, polysulfone film, aramid film, polycarbonate film, Examples thereof include polyvinyl alcohol films, cellophane, cellulose derivatives such as cellulose acetate, polyethylene films, polyvinyl chloride films, nylon films, polyimide films, ionomer films, and the like.

[Heat resistant slipping layer]
The heat-resistant slip layer 103 is provided on one surface of the thermal transfer sheet substrate 101 in order to prevent adverse effects such as sticking or printing wrinkles due to heat of the thermal head. It consists of a filler to be added.

  The resin constituting the heat resistant slip layer 103 may be any resin as long as it is a resin that constitutes a known heat resistant slip layer. Examples of such resins include polyvinyl butyl acetal 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, polycarbonate resin, chlorinated polyolefin Butter, and the like can be mentioned.

  The slipperiness imparting agent is added to or coated on the heat resistant slipping layer 103. Examples of the slipperiness-imparting agent include higher fatty acids and salts thereof, higher fatty acid graft polymers, organic fine particles such as nylon fillers, inorganic fine particles such as graphite powder, phosphate esters, silicone oils, silicone-based graft polymers, and fluorine-based grafts. Examples thereof include silicone polymers such as polymers, acrylic silicone graft polymers, acrylic siloxanes, and aryl siloxanes.

  The heat-resistant slip layer 103 may be a layer made of a polyol, for example, a polyalcohol polymer compound, a polyisocyanate compound, and a phosphate ester compound.

The heat resistant slip layer 103 is formed by the following method. That is, first, a heat-resistant slipping layer composition (composition liquid) is prepared by dissolving or dispersing a resin, a slipperiness imparting agent, and a filler that is optionally added in a predetermined solvent. Next, this composition is applied to the back surface of the thermal transfer sheet substrate 101 by a forming means such as a gravure printing method, a screen printing method, a reverse roll coating method using a gravure plate, and dried. Thereby, the heat-resistant slip layer 103 is formed. Heat-resistant lubricating layer 103 is preferably a film thickness when dry becomes ^{0.1g / m 2 ~3.0g / m 2} .

[Primer layer]
The primer layer 105 is formed on the surface of the thermal transfer sheet substrate 101 (the surface opposite to the heat-resistant slip layer 103), and the thermal transfer sheet substrate 101, a dye layer 107, a laminate layer 109, and a sensor mark layer 111, which will be described later, It is intended to strengthen the adhesive strength. The resin constituting the primer layer 105 may be any resin as long as it is a resin that constitutes a known primer layer. As such a resin, in particular, the adhesive force between the thermal transfer sheet substrate 101 and the dye layer 107 is strong in order to suppress abnormal transfer, and the dye is dyed to the primer layer 105 in order to suppress a decrease in printing density. Difficult ones are preferred.

  Examples of such preferable resins include polyester resins, polyacrylate resins, polyvinyl acetate resins, polyurethane resins, styrene acrylate resins, polyacrylamide resins, polyamide resins, polyether resins, Examples thereof include polystyrene resins, polyethylene resins, polypropylene resins, vinyl resins such as polyvinyl chloride resins, polyvinyl alcohol resins and polyvinyl pyrrolidone resins, and polyvinyl acetal resins such as polyvinyl acetoacetal and polyvinyl butyl acetal.

The primer layer 105 is formed as follows, for example. That is, the primer layer composition (composition solution) is prepared by dissolving or dispersing the resin in a predetermined solvent. Next, this composition is applied to the thermal transfer sheet substrate 101 by a forming means such as a gravure printing method, a screen printing method, a reverse roll coating method using a gravure plate, and dried. Thereby, the primer layer 105 is formed. Moreover, you may add suitably additives, such as a fluorescent whitening agent, a filler, etc. to the composition for primer layers (composition liquid). The primer layer 105 is applied so that the film thickness when dried is 0.01 to 2.0 g / m ² . The primer layer 105 is formed by applying the primer layer 105 on the thermal transfer sheet substrate 101 before the thermal transfer sheet substrate 101 is stretched and then stretching the thermal transfer sheet substrate 101 together with the thermal transfer sheet substrate 101. You may make it.

  In the case where the primer layer 105 is formed on the surface of the thermal transfer sheet substrate 101 as a layer for strengthening the adhesive force between the thermal transfer sheet substrate 101 and a dye layer 107, a laminate layer 109, and a sensor mark layer 111 described later. However, it is also possible to carry out various types of adhesion treatment instead of the primer layer formation treatment. As such adhesion treatment, known resin surface modification techniques such as corona discharge treatment, flame treatment, ozone treatment, ultraviolet treatment, radiation treatment, surface roughening treatment, chemical treatment, plasma treatment, low temperature plasma treatment, grafting treatment, etc. It can be applied as it is. The bonding treatment may be a combination of two or more of the above treatments.

[Dye layer]
In the present embodiment, the case where the dye layer 107 includes dye layers 107Y, 107M, and 107C having different colors from each other will be described. However, a dye layer having a single hue may be used.

O Dye The dye layer 107 has dye layers 107Y, 107M, and 107C that are sequentially formed on the primer layer 105. The dye layers 107Y, 107M, and 107C include a dye and a binder resin that carries the dye. Here, the dye layer 107Y is a dye layer containing a dye having a yellow hue, the dye layer 107M is a dye layer containing a dye having a magenta hue, and the dye layer 5C has a cyan hue. It is a dye layer containing the dye having. As the dye added to the dye layer 107, a known dye can be used as long as it is a dye that melts, diffuses, or sublimates by heat.

  Examples of such known dyes include methine series such as diarylmethane series, triarylmethane series, thiazole series, merocyanine, pyrazolone methine, indoaniline, acetophenone azomethine, pyrazoloazomethine, imidazolazomethine, imidazoazomethine, pyridone. Azomethine typified by azomethine, xanthene, oxazine, dicyanostyrene, cyanomethylene typified by tricyanostyrene, thiazine, azine, acridine, benzeneazo, pyridoneazo, thiophenazo, isothiazole azo, pyrrole azo , Azo series such as pyrazole azo, imidazole azo, thiadiazole azo, triazole azo, dizazo, spiropyran series, indolino spiropyran series, fluorane series, rhodamine lactam series, Futokinon, anthraquinone, and a quinophthalone-based dye. The dye layers 107Y, 107M, and 107C may further include other known dyes used in the thermal transfer method in addition to the above-described dyes.

  The dye added to the dye layers 107Y, 107M, and 107C is determined in consideration of characteristics such as hue, print density, light resistance, storage stability, and solubility in a binder.

  The mass ratio between the binder resin and the entire dye in each of the dye layers 107Y, 107M, and 107C can be a value normally applied as a dye layer of the thermal transfer sheet. What is necessary is just to make it the whole dye be 30-300 mass parts with respect to 100 mass parts of resin.

Binder resin The binder resin constituting the dye layer 107 is composed of a polyvinyl acetal resin and an amorphous saturated polyester resin, and the mass ratio thereof is 95: 5 to 70:30 (the mass of the polyvinyl acetal resin: amorphous). The value is within the range of (mass of the reactive saturated polyester resin) (when dried).

  A polyvinyl acetal resin is a resin obtained by reacting a polyvinyl alcohol resin with an aldehyde to form an acetal. There is no restriction | limiting in particular as an aldehyde component, For example, acetaldehyde, butyraldehyde, etc. can be selected. Moreover, this polyvinyl acetal resin may consist of what made two or more types of aldehyde components simultaneously acetalize, and what consists of a mixture of two or more types of polyvinyl acetal resin.

  Examples of the polyvinyl acetal resin include, for example, ESREC BL-S, ESREC BX-1, ESREC BX-5, ESREC KS-1, ESREC KS-3, ESREC KS-5, ESREC KS-10 (all trade names, Sekisui Chemical Industry Co., Ltd.), Denkabutyral # 5000-A, Denkabutyral # 5000-D, Denkabutyral # 6000-C, Denkabutyral # 6000-EP, Denkabutyral # 6000-CS, Denkabutyral # 6000-AS Also, a trade name, manufactured by Denki Kagaku Kogyo Co., Ltd.) is used.

  Here, it is preferable that the glass transition temperature (Tg) of the polyvinyl acetal resin used for the binder resin of the dye layer which concerns on this embodiment is 90 to 110 degreeC. A glass transition temperature of less than 90 ° C. is not preferable because blocking during storage and dye recrystallization in the dye layer are promoted and storage stability is lowered. On the other hand, when the glass transition temperature exceeds 110 ° C., it is not preferable because the dye releasing property at the time of printing is lowered.

  The polyester resin is obtained by polycondensation of dicarboxylic acid (including derivatives thereof) and diol (including derivatives thereof).

  Examples of the dicarboxylic acid include adipic acid, azelaic acid, isophthalic acid, trimellitic acid, terephthalic acid, 1,4-cyclohexanedicarboxylic acid, and the like, or a mixture of two or more thereof.

  Examples of the diol include ethylene glycol, polyethylene glycol, tricyclodecane dimethanol, 1,4-butanediol, bisphenol, and the like, or a mixture of two or more thereof.

  In the present embodiment, among the polyester resins obtained by polycondensation of the dicarboxylic acid and the diol, an amorphous saturated polyester resin is used. The method for synthesizing the amorphous saturated polyester resin may be any known method.

  Examples of the amorphous saturated polyester include Byron 103, Byron 200, Byron 280, etc. (all trade names, manufactured by Toyobo Co., Ltd.), KA-1038C (trade names, manufactured by Arakawa Chemical Industries, Ltd.), TP220, TP235 (all And Elitel UE-3210, Elitel UE-3600, UE-3690, etc. (all are trade names, manufactured by Unitika Ltd.) and the like.

  The glass transition temperature (Tg) of the polyester resin is preferably 40 ° C. or higher and 70 ° C. or lower. A glass transition temperature of less than 40 ° C. is not preferable because storage stability is lowered, such as blocking or recrystallization of the dye in the dye layer. Further, when the glass transition temperature is less than 40 ° C., a phenomenon called “fogging” occurs in which the color is developed even at an unheated portion or with very low energy. On the other hand, when the glass transition temperature exceeds 70 ° C., the effect of storage stability is low, the compatibility is also lowered, and the strength and surface properties of the ink coating film are likely to be lowered.

  The number average molecular weight (Mn) of the polyester resin is preferably 8000 or more and 25000 or less. When the number average molecular weight (Mn) of the polyester resin is less than 8000 or more than 25,000, the effect of the storage stability is also inferior, and the strength and the surface property tend not to be preferable.

  In addition, the glass transition temperature of a polyvinyl acetal resin or a polyester resin can be measured, for example using the differential scanning calorimetry (Differential Scanning Calorimetry: DSC). The number average molecular weight of the polyester resin can be measured using, for example, gel permeation chromatography (GPC).

  In this embodiment, the mass ratio of the polyvinyl acetal resin and the amorphous saturated polyester resin is a value within the range of 95: 5 to 70:30 (the mass of the polyvinyl acetal resin: the mass of the amorphous saturated polyester resin). Yes. If the ratio of the polyvinyl acetal resin exceeds 95, the effect of the present embodiment (stability with time-dependent change in printing characteristics) is impaired. Even if the ratio of the polyvinyl acetal resin is less than 70, the thermal stability of the original polyvinyl acetal is impaired. Therefore, the effect of this embodiment is impaired. On the other hand, if the mass ratio of the amorphous saturated polyester exceeds 30, the dye is likely to crystallize, the roughness of the low-density printed part due to a decrease in compatibility, the surface deformation due to blocking or adhesion with the backcoat layer. It is easy to wake up.

  One of the reasons why the effect of this embodiment can be obtained is that the amorphous saturated polyester resin coexists in the dye layer 107, so that the dye is evenly distributed in the coating and drying process of the dye layer 107 (that is, the distribution is stable). Can be considered). As described above, it is considered that the dye is uniformly distributed, so that the change due to the heat history at the time of storage and storage after the dye layer 107 is formed is reduced, and the change in the printing characteristics is suppressed.

  Examples of other resin components that can be added to the dye layer 107 include cellulose resins such as ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate, and acetic acid / butyric acid cellulose; polyvinyl acetate, vinyl chloride vinyl acetate copolymer resin (vinyl chloride acetate) Vinyl copolymer resins), styrene resins, polyvinyl pyrrolidone and other vinyl resins; poly (meth) acrylate, poly (meth) acrylamide and other acrylic resins; polyurethane resins, polyamide resins, epoxy resins, phenoxy resins, etc. it can. In addition to the above components, other resin components can be appropriately added within the range not impairing the effects of the present invention.

  Moreover, you may add various well-known additives to the dye layer 107 as needed. Examples of the additive include organic fine particles such as polyethylene wax, acrylic, silicone, and benzoguanamine resin, inorganic particles such as calcium carbonate, silica, and mica, silicone resin, silicone oil, and phosphate ester. Such an additive is added to the dye layer 107 in order to improve releasability from the transfer sheet and application suitability of the dye.

The dye layer 107 as described above is formed as follows. That is, first, a dye layer composition (composition liquid) is prepared by adding a dye, a binder resin, and if necessary, a desired additive to a predetermined solvent and dissolving or dispersing each component. Next, this composition (composition liquid) is applied on the thermal transfer sheet substrate 101 and dried. Thereby, the dye layer 107 is formed. Examples of the coating method include known means such as a gravure printing method and a screen printing method. Various coating methods other than these can also be applied. The dye layer 107Y, 107M, thickness of 107C is, 0.1~6.0g / ^{m 2} when dry, preferably it is preferred to be 0.2 to 3.0 g / ^{m 2.}

[Laminate layer]
The laminate layer 109 is for protecting an image thermally transferred to a transfer sheet described later. That is, if the image containing the dye is only thermally transferred to the transfer sheet, the dye is exposed on the surface of the transfer sheet, and the printed matter (the dye is thermally transferred to the receiving layer of the transfer sheet) Light resistance, scratch resistance, chemical resistance, etc. may be insufficient. Therefore, after the image containing the dye is thermally transferred to the receiving layer of the transfer sheet, at least a part of the laminate layer 109 is thermally transferred to the receiving layer of the transfer sheet to cover the print, so that the print is transparent. A printed matter protective layer made of resin is formed to protect the transfer sheet.

  As shown in FIG. 1, the laminate layer 109 according to this embodiment includes a releasable layer 151 and a transfer material coating layer 153. When heated by a heating means such as a thermal head, the transfer material coating layer 153 of the laminate layer 109 is peeled off to cover the transferred image on the transfer sheet and to protect the transferred image. It becomes a resin layer (printed material protective layer).

  Here, the transfer material coating layer 153 according to the present embodiment includes a protective layer 155 and an adhesive layer 157 as shown in FIG.

  The releasable layer 151 remains on the primer layer 105 when heated by a heating means such as a thermal head, and peels off a transfer material coating layer 153 (a protective layer 155 and an adhesive layer 157) described later from the thermal transfer sheet 10. Is a layer. The releasable layer 151 includes, for example, various waxes such as silicone wax, silicone resin, fluororesin, acrylic resin, water-soluble resin, cellulose derivative resin, urethane resin, acetic acid vinyl resin, polyvinyl acetal resin, acrylic vinyl ether. Resin, various resins such as maleic anhydride resin, and mixtures thereof. As the resin constituting the releasable layer 151, it is preferable to use a polyvinyl acetal resin or a cellulose derivative resin in order to obtain good recording characteristics.

  The protective layer 155 constituting the transfer material coating layer 153 has thermal transfer properties, and is thermally transferred onto an image containing a dye transferred to the transfer sheet when heated by a heating means such as a thermal head. It is a transparent resin layer that protects the transfer sheet as a printed product protective layer. In FIG. 1, the protective layer 155 according to this embodiment is illustrated as a single layer, but the protective layer 155 may be composed of a plurality of layers.

  Examples of the resin constituting the protective layer 155 include polyester resins, polystyrene resins, acrylic resins, polyurethane resins, acrylic urethane resins, polycarbonate resins, epoxy-modified resins of these resins, and resins obtained by modifying these resins with silicone. And mixtures of these resins, ionizing radiation curable resins, ultraviolet blocking resins and the like. Preferred resins include polyester resin, polystyrene, acrylic resin, polycarbonate resin, and epoxy-modified resin. Among them, at least one copolymer selected from styrene, methyl methacrylate, ethyl methacrylate, vinyl chloride-vinyl acetate (a copolymer of vinyl chloride and vinyl acetate), vinyl chloride, and cellulose ester derivatives has a close contact property during non-transfer. It is preferable because it has releasability during heat transfer and good gloss, and is most preferably a polystyrene resin and a modified product or copolymer thereof, or an acrylic resin and a modified product or copolymer thereof.

  The adhesive layer 157 constituting the transfer material coating layer 153 is thermally transferred together with the protective layer 155 onto the image containing the dye transferred to the transfer sheet when heated by a heating means such as a thermal head. Is a transparent resin layer that adheres to the transfer sheet. As the resin constituting the adhesive layer 157, any resin containing a known pressure-sensitive adhesive, heat-sensitive adhesive, or the like can be used, but the glass transition temperature (Tg) is 30 to 80 ° C. It is preferable to use a thermoplastic resin. Specific examples of such thermoplastic resins include polyester resins, vinyl chloride-vinyl acetate copolymer resins, acrylic resins, butyral resins, epoxy resins, polyamide resins, and vinyl chloride resins.

The laminate layer 109 according to this embodiment has been described above.
In the present embodiment, the case where the laminate layer 109 has a three-layer structure of the releasable layer 151, the protective layer 155, and the adhesive layer 157 has been described. However, the structure of the laminate layer 109 is limited to the above example. Do not mean. That is, if the transfer material covering layer 153 composed of the protective layer 155 and the adhesive layer 157 can be easily peeled off from the thermal transfer sheet 10 by heating by a heating means such as a thermal head, the release layer 151 may not be formed. . In addition, as long as it can be easily peeled off from the thermal transfer sheet 10 by heating with a heating means such as a thermal head, only the protective layer 155 that also functions as the adhesive layer 157 may be formed as the laminate layer 109.

[Sensor mark layer]
The sensor mark layer 111 is provided for the printer that performs thermal transfer to recognize the positions of the dye layer 107 and the laminate layer 109.

  The configuration of the thermal transfer sheet 10 according to the present embodiment has been described in detail above with reference to FIG.

  Thus, the thermal transfer sheet according to the embodiment of the present invention uses a mixture of a polyvinyl acetal resin having a specific glass transition temperature and an amorphous saturated polyester resin as the binder resin of the dye layer. As a result, the thermal transfer sheet according to the embodiment of the present invention has a high transfer density (print density), can suppress the temporal change in print characteristics before and after storage, and has excellent print suitability. As a result, the thermal transfer sheet according to the embodiment of the present invention can realize an increase in the thermal transfer printing speed, an increase in the density and quality of the thermal transfer image.

(Examples and Comparative Examples)
Next, the present invention will be described more specifically with reference to examples and comparative examples. In the examples and comparative examples shown below, “part” or “%” is based on mass unless otherwise specified.

<Manufacture of thermal transfer sheet>
In this example and comparative example, the thermal transfer sheet 10 was manufactured by the following method.

First, as the thermal transfer sheet base material 101, a polyethylene terephthalate film (PET) (Mitsubishi Resin Co., Ltd., K604E 4.5W) having a thickness of 4.5 μm having a primer layer 105 formed by bonding the surface was prepared. Next, the heat-resistant slip layer composition having the following composition is applied to the back surface of the thermal transfer sheet substrate 101 by gravure coating so that the coating amount after drying is 1.0 g / m ² and dried. The conductive layer 103 was formed. The drying conditions were a coating speed of 100 m / min and a maximum drying temperature of 110 ° C. Thereafter, curing was performed at 50 ° C. for 5 days.

  Next, a dye layer composition having the following composition was applied to the surface of the thermal transfer sheet substrate 101 by gravure coating so as to have a dry thickness of 0.5 μm, and dried to form a dye layer 107. Here, the drying conditions were a coating speed of 100 m / min and a maximum drying temperature of 110 ° C. Thereafter, curing was performed at 50 ° C. for 5 days. Thereby, the thermal transfer sheet 10 is formed.

○ Heat-resistant slip layer composition Polyvinyl acetal resin 3.0 parts (Sekisui Chemical Co., Ltd. S-REC BX-1)
Polyisocyanate 2.0 parts (Japan Polyurethane Coronate L)
Phosphate ester 1.0 part (Plysurf A208S, manufactured by Daiichi Kogyo Seiyaku)
Methyl ethyl ketone 47.0 parts Toluene 47.0 parts

○ Dye layer composition Dye (mass ratio a: b = 2: 1) 5 parts Polyvinyl acetal resin 5-x part Amorphous saturated polyester resin x part Toluene 45 parts Methyl ethyl ketone 45 parts

  In this Example and Comparative Example, a plurality of thermal transfer sheets were formed by changing the dye, the polyvinyl acetal resin, the amorphous saturated polyester resin, and the value of x (value of parts by mass of the amorphous saturated polyester resin) ( Examples 1 to 15 and Comparative Examples 1 to 16). The relationship between each Example and Comparative Example and dyes is shown in Table 1 below.

  As shown in Table 1, dyes 51 to 55 are used in each example and comparative example. The dye layer of each manufactured thermal transfer sheet 10 is formed using two kinds of dyes, dye a and dye b, and the mass ratio a: b of these two kinds of dyes is 2: 1. Dye a and dye b used in this example are compounds represented by the following structural formulas (51a) to (55b). For example, the dye a contained in the dye 51 is represented by the structural formula (51a), and the dye b contained in the dye 51 is represented by the structural formula (51b).

  Here, a dye layer formed using two types of dyes of structural formula (51a) and structural formula (51b), and formed using two types of dyes of structural formula (52a) and structural formula (52b) The dye layer and the dye layer formed using the two types of dyes of structural formula (53a) and structural formula (53b) are each a dye layer having a cyan hue. The dye layer formed using the two types of dyes of the structural formula (54a) and the structural formula (54b) is a dye layer having a magenta hue. Further, the dye layer formed using the two types of dyes of the structural formula (55a) and the structural formula (55b) is a dye layer having a yellow hue.

  In each example and comparative example, polyvinyl acetal resins A to C are used. The polyvinyl acetal resin A is Denka Butyral # 6000-AS, the polyvinyl acetal resin B is Denka Butyral # 6000-CS, and the polyvinyl acetal resin C is Eslek KS-1.

  Here, Denkabutyral # 6000-AS is a resin made of polyvinyl acetoacetal, Denkabutyral # 6000-CS is a resin made of polyvinyl butyl acetal resin and polyvinyl acetoacetal resin, and ESREC KS-1 is made of polyvinyl. It is a resin made of acetoacetal resin.

  Denkabutyral # 6000-AS has a glass transition temperature of 110 ° C., Denkabutyral # 6000-CS has a glass transition temperature of 95 ° C., and Eslek KS-1 has a glass transition temperature of 107 ° C.

<About the storage method>
The thermal transfer sheets 10 produced in Examples 1 to 15 and Comparative Examples 1 to 16 were crumpled in the same manner as known products and stored in an environment of a temperature of 45 ° C. and a humidity of 50% for 336 hours (ie, 2 weeks). did.

<About the printing method>
Each of the thermal transfer sheets 10 before storage and after storage was printed by the following method. Specifically, the transfer sheet of the thermal transfer sheet 10 and genuine media (UPC-R204 manufactured by Sony Corporation) was set on a printer (UP-DR200 manufactured by Sony Corporation), and printing was performed with a 16 gradation printing pattern. Printing was performed in an environment of a temperature of 23 ° C. and a humidity of 50%.

<Evaluation>
For each of the thermal transfer sheets 10 produced in Examples 1 to 15 and Comparative Examples 1 to 16, the color difference ΔE, the degree of fogging, the degree of crystallization of the dye layer 107 and the degree of surface roughness of the dye layer 107 were evaluated. .

[Color difference ΔE]
First, a colorimetric color difference meter (SPM100-II manufactured by Macbeth Gretag Co., Ltd.) is used to measure L ^* a ^* b ^* colorimetric values in the same print portion of the printed matter obtained by the above printing before and after storage in the above environment. It measured using. Furthermore, the color difference ΔE was calculated based on the obtained colorimetric value and the following formula (1). It is evaluated that the change with time of the thermal transfer sheet 10 progresses as the color difference ΔE increases.

Here, in the formula (1), the number “0” added next to the L ^* a ^* b ^* value indicates the L ^* a ^* b ^* colorimetric value before storage, and the number “ “1” indicates an L ^* a ^* b ^* colorimetric value after storage.

[Degree of fog]
“Fog” means that color develops in a portion that is not originally colored (white portion). Therefore, it was evaluated that “fogging” occurred when the color had developed from the first stage of 16 gradations. As is apparent from the above, the smaller the degree of fog, the higher the quality of the printed matter. Therefore, in this example, the degree of fogging was evaluated as follows.

  That is, for the printed matter using the thermal transfer sheet 10 before storage, the reflection density of the printed portion (white background portion) of the first stage of 16 gradations is measured using the above colorimetric colorimeter, and the polyvinyl acetal resin alone is measured. The degree of fogging was evaluated as follows in comparison with the reflection density of the thermal transfer sheet formed by use.

◯: The value of the reflection density to be evaluated before storage is increased by less than 0.02 compared to the case of the polyvinyl acetal resin alone.
Δ: The value of the reflection density to be evaluated before storage is increased by 0.02 or more and less than 0.04 compared to the case of the polyvinyl acetal resin alone.
X: The value of the reflection density to be evaluated before storage is increased by 0.04 or more compared to the case of the polyvinyl acetal resin alone.

[Degree of crystallization of dye layer]
As the crystallization of the dye layer 107 progresses, the quality of the printed matter decreases, and it can be determined that the thermal transfer sheet 10 has changed over time. In this example, the dye layer 107 of the thermal transfer sheet 10 after storage was observed with a microscope, and the degree of crystallization was evaluated as follows.

○: Dye has not crystallized △: Dye has started to crystallize ×: Crystal has expanded

[Degree of surface roughness of the dye layer]
It can be determined that as the surface roughness of the dye layer 107 increases, the quality of the printed material decreases and the thermal transfer sheet 10 changes with time. In this example, the surface state of the dye layer was visually observed for the thermal transfer sheet 10 before storage, and it was judged how the gloss was changed as compared with the thermal transfer sheet formed using the polyvinyl acetal resin alone. At this time, the degree of surface roughness of the dye layer was evaluated according to the following criteria.

○: No change in gloss of the dye layer △: Gloss is clearly lowered ×: Gloss is lost (completely matte)

  The results of the evaluation performed as described above are shown in Table 2 below.

  Since the effect of suppressing changes in printing hue due to storage varies depending on the hue of the dye used, comparison was made for each dye used. That is, for the results shown in Table 2, Examples and Comparative Examples having the same combination of dye and polyvinyl acetal resin were compared with each other. As shown in Table 2, the mass ratio of the polyvinyl acetal resin having a specific glass transition temperature and the amorphous saturated polyester is 95: 5 to 70 as compared with the comparative example in which the dye layer is formed with the polyvinyl acetal resin alone. : It can be seen that the color difference ΔE is low when the value is within the range of 30. Furthermore, when the glass transition temperature and the number average molecular weight of the amorphous saturated polyester are within the above-described ranges, it can be seen that the degree of crystallization, the degree of fogging, and the degree of surface roughness are all low.

  As described above, according to the embodiment of the present invention, by setting the mass ratio of the polyvinyl acetal resin and the amorphous saturated polyester resin to a value in the range of 95: 5 to 70:30, the value of the color difference ΔE is set. It can be kept low. That is, according to the embodiment of the present invention, the change with time of the dye layer 107 can be suppressed.

  Furthermore, by setting the glass transition temperature of the amorphous saturated polyester to a value within the range of 40 to 70 ° C. and the number average molecular weight within the range of 8000 to 25000, the degree of crystallization, the degree of fogging, and the surface The degree of roughness is a preferred value.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Thermal transfer sheet 101 Thermal transfer sheet base material 103 Heat resistant slipping layer 105 Primer layer 107 Dye layer 109 Laminating layer 151 Release layer 153 Transfer material coating layer 155 Protective layer 157 Adhesive layer

Claims (3)

Provided with a dye layer provided on one surface of the base material and containing at least a dye having a predetermined hue and a binder resin;
The binder resin includes a mixture of a polyvinyl acetal resin having a predetermined glass transition temperature and an amorphous saturated polyester resin,
The thermal transfer sheet whose mass ratio of the said polyvinyl acetal resin and the said amorphous saturated polyester resin is 95: 5-70: 30.   The thermal transfer sheet according to claim 1, wherein the amorphous saturated polyester resin has a glass transition temperature of 40C to 70C and a number average molecular weight of 8000 to 25000. The thermal transfer sheet according to claim 1, wherein the dye layer contains a polyvinyl acetoacetal resin or a polyvinyl acetoacetal / polyvinyl butyl acetal copolymer having a glass transition temperature of 90 to 110 ° C. as the polyvinyl acetal resin. .

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