JP5655350B2 - Thermal transfer sheet - Google Patents

Description

The present invention relates to a thermal transfer sheet.

Conventionally, various thermal transfer recording methods have been used as simple printing methods. In such a variety of thermal transfer recording methods, when obtaining a color image, for example, yellow, magenta and cyan, and if necessary, a black color material layer is provided on one side of a continuous base sheet. A thermal transfer sheet is used in which a large number are repeatedly provided in sequence, and a heat-resistant slipping layer is provided on the opposite surface of the base sheet.
In such a thermal transfer recording method using a thermal transfer sheet, (1) a heat melting type in which a color material layer is melted and softened by heating and transferred to a transfer target to form an image; and (2) in the color material layer by heating. The dye is sublimated and is roughly classified into a sublimation type in which an image is formed by moving onto a transfer target.

A sublimation type thermal transfer sheet transfers a color dot in which a large number of heating colors of three or four colors are adjusted to the receiving layer of the thermal transfer image receiving sheet by heating with a thermal head of a printer. It reproduces the full color.
An image formed using a sublimation thermal transfer sheet is very clear and excellent in transparency because the color material used is a dye. For this reason, the reproducibility and gradation of intermediate colors are excellent, and it is possible to form a high quality image that is similar to an image by conventional offset printing or gravure printing and comparable to a full color photographic image.

In recent years, the printing speed of a thermal transfer printer using a sublimation type thermal transfer sheet has been steadily increased, and it has become difficult to obtain a sufficient print density with a conventional thermal transfer sheet. In addition, a higher density and clearer image has been required for a printed image by thermal transfer.

In order to improve printing density and transfer sensitivity in printing, attempts have been made to increase the dye / resin (Dye / Binder) ratio in the dye layer of the thermal transfer sheet, for example.
However, when such a thermal transfer sheet is stored in a wound state after production, the dye layer and the heat resistant slipping layer provided on the opposite side of the substrate come into contact with each other, whereby the dye is transferred from the dye layer to the heat resistant slipping layer. Had the problem of migrating. The dye transferred to the heat-resistant slipping layer is re-transferred to a dye layer of another color, a protective layer, etc. when the sheet is rewound, and further, the contaminated layer is thermally transferred to the thermal transfer image receiving sheet. Is done. In this case, the obtained printed matter has a hue different from the designated color, and there is a problem that the printing accuracy is significantly impaired.

In addition, as a method for improving the printing density and the transfer sensitivity in printing, high energy is also applied to a thermal transfer printer during thermal transfer during image formation.
However, in this case, so-called abnormal transfer, in which the dye layer of the thermal transfer sheet is transferred to the thermal transfer image-receiving sheet, and kogation (black solids) in the high density portion of black in which yellow, magenta, and cyan are sequentially stacked. It tends to occur. In order to prevent abnormal transfer, a method of adding a large amount of a release agent to the receiving layer of the thermal transfer image-receiving sheet is also conceivable. However, in this case, there is a problem that blurring or background smearing occurs in the obtained image.

For the purpose of improving transfer sensitivity in printing, for example, Patent Document 1 discloses a thermal transfer sheet having an adhesive layer containing a polyvinylpyrrolidone resin and a modified polyvinylpyrrolidone resin.
However, although such a thermal transfer sheet can prevent abnormal transfer, it has been difficult to prevent kogation and has not reached a sufficient level.

For example, Patent Document 2 discloses a thermal transfer sheet including an undercoat layer containing a thermoplastic resin and colloidal inorganic pigment ultrafine particles between a base material and a dye layer. According to the thermal transfer sheet disclosed in Patent Document 2, it is possible to improve transfer sensitivity and obtain a high-density print.
However, the thermal transfer sheet disclosed in Patent Document 2 cannot sufficiently prevent kogation and abnormal transfer after storage under high temperature and high humidity.

In addition, for example, in Patent Document 3, an undercoat layer formed mainly of a copolymer resin of vinyl pyrrolidone and vinyl acetate and colloidal inorganic pigment ultrafine particles is provided between a base material and a dye layer. A thermal transfer sheet is disclosed.
However, in recent years, the level of kogation required for thermal transfer sheets has become extremely high, and even the thermal transfer sheet disclosed in Patent Document 3 cannot sufficiently respond to kogation at such high levels. It was becoming.

JP-A-2005-231354 JP 2006-150956 A JP 2008-155612 A

In view of the above situation, the present invention has a high thermal transfer image sharpness and a high density of black in which three color dyes of yellow, magenta, and cyan are sequentially stacked even after being stored at high temperature and high humidity. It is an object of the present invention to provide a thermal transfer sheet that can suitably prevent the occurrence of kogation (black solid blur), has high transfer sensitivity in thermal transfer printing, and can obtain high-density printing in high-speed printing. To do.

The present invention is a thermal transfer sheet in which a primer layer and a dye layer are sequentially formed on one surface of a substrate, and the primer layer is formed from a composition containing a cationic aqueous dispersion or a cationic aqueous emulsion resin. becomes, solids content from the cationic aqueous dispersion or cationic aqueous emulsion resin, the total solids in the 65 to 100% by mass of the composition is, the cationic aqueous dispersion or cationic aqueous emulsion The resin is a thermal transfer sheet characterized in that it is a dispersion or emulsion made of a cationic acrylic resin or a cationic urethane resin .
The primer layer preferably contains 50% by mass or less of colloidal inorganic pigment ultrafine particles.
The colloidal inorganic pigment ultrafine particles are preferably alumina sol.
The substrate is preferably subjected to an adhesion treatment.
The present invention is described in detail below.

As a result of intensive studies on a thermal transfer sheet in which a primer layer and a dye layer are sequentially laminated on one surface of a base material, the present inventors have found that a conventional thermal transfer sheet becomes a primer layer when stored at high temperature and high humidity. It was found that moisture absorption occurred, and moisture absorption of the primer layer was a cause of burns in printing.
Therefore, as a result of further intensive studies, the composition for forming the primer layer has a specific composition, specifically, a composition containing a specific amount of cationic aqueous dispersion or cationic aqueous emulsion resin. It was found that the moisture absorption of the primer layer can be effectively suppressed, and even after the thermal transfer sheet having the primer layer is stored under high temperature and high humidity, kogation in the print can be sufficiently suppressed, and the present invention has been completed. . Furthermore, an increase in printing density can be expected from a thermal transfer sheet having a primer layer having such a composition.

(Base material)
The thermal transfer sheet of the present invention has a structure in which a primer layer and a dye layer are sequentially formed on one surface of a substrate.
The substrate is not particularly limited as long as it is made of a conventionally known resin having a certain degree of heat resistance and strength. For example, a plastic film having a thickness of about 0.5 to 50 μm, preferably about 1 to 10 μm. Are preferably used.
Examples of the resin constituting the plastic film include polyethylene terephthalate, 1,4-polycyclohexylenedimethylene terephthalate, polyethylene naphthalate, polyphenylene sulfide, polystyrene, polypropylene, polysulfone, aramid, polycarbonate, polyvinyl alcohol, cellophane, and acetic acid. Examples thereof include cellulose derivatives such as cellulose, polyethylene, polyvinyl chloride, nylon, polyimide, and ionomer. Of these, polyethylene terephthalate is preferably used.
In addition, the said base material may consist only of 1 type of the above-mentioned resin, and may consist of 2 or more types of resin.

Moreover, it is preferable that the said base material has the adhesion process performed on the surface which forms the primer layer mentioned later. That is, when the base material is the above-described plastic film, it is preferable to perform an adhesion treatment because the adhesion between the base material and the primer layer tends to be insufficient when the primer layer is formed thereon.

Examples of the adhesion treatment include known 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, and the like. A resin surface modification technique can be mentioned.
Two or more of these treatments can be used in combination. Moreover, the said adhesion process can apply | coat a primer liquid to an unstretched film at the time of film-forming of the melt extrusion of a plastic film, and can perform it by extending | stretching after that.
Among the above-mentioned adhesion treatments, a corona discharge treatment or a plasma treatment is preferable in that a general-purpose treatment method can be used without increasing the cost and the adhesion between the substrate and the primer layer can be further improved.

(Primer layer)
The primer layer is formed on one surface of the base material and plays a role of suitably bonding the base material and a dye layer to be described later, and even after being stored under high temperature and high humidity. It is a layer that plays a role in preventing kogation in printing. Furthermore, an increase in print density can be expected.
In the thermal transfer sheet of the present invention, the primer layer is made of a composition containing a cationic aqueous dispersion or a cationic aqueous emulsion resin.
Here, even after a thermal transfer sheet having a primer layer made of a composition containing a cationic aqueous dispersion or a cationic aqueous emulsion resin is stored under high temperature and high humidity, so-called kogation phenomenon occurs in printing. It is the fact that the present inventors have found for the first time that the transfer sensitivity is high in thermal transfer printing, and high-density printing can be obtained in high-speed printing.

The cationic aqueous dispersion or the cationic aqueous emulsion resin is a dispersion or emulsion made of a resin having a cationic group in the molecule or a resin having a group easily cationized in the molecule.
Examples of the cationic group or easily cationized group include a quaternary ammonium salt structure, a substituted or unsubstituted amino group, a substituted or unsubstituted pyridyl group, and the like.
These resins may have a substituent such as an alkyl group, and may be chain-like or cyclic.

In the thermal transfer sheet of the present invention, the cationic aqueous dispersion or the cationic aqueous emulsion resin is preferably an acrylic resin, a urethane resin, or a polyester resin having a cationic group or an easily cationizable group in the molecule. Can be used. These resins may be used alone or in combination of two or more (for example, as a mixture of two or more).

The solid content derived from the cationic aqueous dispersion or the cationic aqueous emulsion resin is 50 to 100% by mass in the total solid content of the composition. If it is less than 50% by mass, a problem of kogation occurs in the thermal transfer sheet of the present invention. The lower limit of the content is preferably 65% by mass from the viewpoint of suppressing burnt problems, and the upper limit is preferably 97% by mass from the viewpoint of suppressing abnormal transfer and improving the concentration.

The primer layer preferably contains colloidal inorganic pigment ultrafine particles.
The primer layer contains the above-described cationic aqueous dispersion or cationic aqueous emulsion resin in combination with colloidal inorganic pigment ultrafine particles, so that the thermal transfer image is highly clear and stored at high temperature and high humidity. Even after this, it is possible to suppress the phenomenon of koge (black solid blurring), to achieve a thermal transfer sheet that has high transfer sensitivity in thermal transfer printing and can obtain high-density printing in high-speed printing.
In addition, when the composition for forming the primer layer is prepared, if the colloidal inorganic pigment ultrafine particle solution is mixed, the dispersion stability of the colloidal inorganic pigment ultrafine particle solution may not be maintained. This is a problem that easily occurs when the chemical properties of the colloidal inorganic pigment ultrafine particles and other components are greatly different. However, the colloidal inorganic pigment ultrafine particles can be mixed without inhibiting the dispersion stability of the composition because the chemical properties are similar to those of the cationic aqueous dispersion or the cationic aqueous emulsion resin.

The colloidal inorganic pigment ultrafine particles are not particularly limited and include conventionally known compounds. Specifically, for example, silica (colloidal silica), alumina or alumina hydrate (alumina sol, colloidal alumina, cationic aluminum oxide or hydrate, pseudoboehmite, etc.), aluminum silicate, magnesium silicate, magnesium carbonate, Examples thereof include magnesium oxide and titanium oxide.
In the primer layer, these colloidal inorganic pigment ultrafine particles may be used not only under the same kind of conditions but also with different kinds.
As the colloidal inorganic pigment ultrafine particles, alumina sol is preferably used because it can increase the printing density and prevent abnormal transfer.

The size of the colloidal inorganic pigment ultrafine particles is 100 nm or less, preferably 50 nm or less in terms of average particle size, and particularly preferably 3 to 30 nm, whereby the function of the primer layer can be sufficiently exhibited.
The shape of the colloidal inorganic pigment ultrafine particles in the present invention may be any shape such as a spherical shape, a needle shape, a plate shape, a feather shape, or an amorphous shape.

The colloidal inorganic pigment ultrafine particles are preferably 50% by mass or less in the primer layer.
If it exceeds 50% by mass, there is a possibility that a problem of kogation occurs in printing. From the viewpoint of suppressing abnormal transfer, the lower limit of the content of the colloidal inorganic pigment ultrafine particles is more preferably 3% by mass, and the upper limit is 40% by mass from the viewpoint of suppressing kogation problems. preferable.

The primer layer comprises a primer layer composition obtained by mixing the cationic aqueous dispersion or cationic aqueous emulsion resin and, if necessary, the colloidal inorganic pigment ultrafine particles and an aqueous solvent. It can be formed by applying on a material and drying.

The aqueous solvent is not particularly limited, and examples thereof include water; a mixture of alcohols such as ethanol and propanol and water. Furthermore, as the aqueous solvent, cellosolves such as methyl cellosolve and ethyl cellosolve; organic solvents such as ketones such as acetone and methyl ethyl ketone and water can be used, but water or water and alcohols can be used. It is preferable that it is a mixture.

Examples of the coating method include conventionally known methods such as a gravure coating method, a roll coating method, a screen printing method, and a reverse roll coating method using a gravure plate.

The coating amount of the primer layer is greater than 0.03 g / ^{m 2,} is preferably 0.50 g / ^m of less than ² (dry). If it is 0.03 g / m ² or less, a sufficient print density cannot be obtained at the time of thermal transfer, and adhesion may be deteriorated. If it is 0.50 g / m ² or more, there is a possibility that the phenomenon of kogation occurs. The lower limit is more preferably 0.05 g / ^{m 2,} and more preferable upper limit is 0.40 g / ^{m 2.}

The primer layer formed as described above is mainly composed of the cationic aqueous dispersion or cationic aqueous emulsion resin in the primer layer composition and the colloidal inorganic pigment ultrafine particles, and other components. It is preferable that the solvent is not present or that the solvent remains a little.
Thus, the thermal transfer sheet having a primer layer made of a composition containing a cationic aqueous dispersion or a cationic aqueous emulsion resin has a high thermal transfer image sharpness, even after being stored under high temperature and high humidity. It is possible to suitably prevent the occurrence of kogation (black solid blur) in the black high density area where three dyes of yellow, magenta, and cyan are sequentially stacked, and the transfer sensitivity in thermal transfer printing is high and high-speed printing. In this case, a high-density print can be obtained.

(Dye layer)
In the thermal transfer sheet of the present invention, a dye layer is provided on one surface of a substrate via the primer layer.
The dye layer can be composed of a single layer of one color, or a plurality of dye layers containing dyes having different hues can 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 an arbitrary binder.
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. Selection can be made in consideration of printing sensitivity, light resistance, storage stability, solubility in a binder, and the like.

Examples of the dye include methine series such as diarylmethane series, triarylmethane series, thiazole series, merocyanine, pyrazolone methine, indoaniline, acetophenone azomethine, pyrazoloazomethine, imidazolazomethine, imidazoazomethine, and pyridone azomethine. Azomethine series, xanthene series, oxazine series, dicyanostyrene, cyanomethylene series represented by tricyanostyrene, thiazine series, azine series, acridine series, benzeneazo series, pyridoneazo, thiophenazo, isothiazoleazo, pyrroleazo, pyralazo, imidazole Azo, thiadiazole azo, triazole azo, diazo, etc., azo, spiropyran, indolinospiropyran, fluoran, rhodamine lactam, naphthoquinone Anthraquinone include the quinophthalone like.

As the binder for the dye layer, any conventionally known resin binder can be used, and preferable examples include ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxy cellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate propionate, cellulose acetate butyrate. Examples thereof include cellulose resins such as rate, cellulose acetate, and cellulose butyrate, vinyl resins such as polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, polyvinyl pyrrolidone, and polyacrylamide, polyester resins, and phenoxy resins.

Further, a silane coupling agent can be added to the dye layer. Examples of the silane coupling agent include those containing an isocyanate group such as γ-isocyanatopropyltriethoxysilane and γ-isocyanatopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropyltriethoxysilane, those containing an amino group such as γ-phenylaminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane and β- (3, Examples include 4-epoxycyclohexyl) ethyltrimethoxysilane and the like containing an epoxy group. These can be used alone or as a mixture of two or more.

In the present invention, the following releasable graft copolymer can be used as a release agent or binder instead of the resin binder. This releasable graft copolymer is obtained by graft polymerizing at least one releasable segment selected from a polysiloxane segment, a fluorocarbon segment, a fluorinated hydrocarbon segment, or a long-chain alkyl segment on the polymer main chain. It is. Among these, a graft copolymer obtained by grafting a polysiloxane segment to a main chain made of a polyvinyl acetal resin is particularly preferable.

In the thermal transfer sheet of the present invention, the binder as a constituent of the dye layer is mentioned above in that the adhesiveness between the primer layer and the dye layer can be maintained even after being left under high temperature and high humidity. Among them, a single or mixture of resins having high adhesion and hydroxyl groups such as polyvinyl butyral, polyvinyl acetal, polyvinyl acetate, and cellulose resins such as polyester resins, cellulose acetate and cellulose butyrate is preferably used. .

The dye layer may contain the above-mentioned dyes, binders, and other various conventional additives as required. As the additive, for example, organic fine particles such as polyethylene wax, inorganic fine particles, silicone oil, silicone modified resin, fatty acid amide, fatty acid ester, phosphoric acid ester, which improve releasability from an image receiving sheet and ink coating suitability Etc. 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 has a coating amount at the time of drying of about 0.2 to 6.0 g / m ² , preferably about 0.3 to 3.0 g / m ² .

Further, the thermal transfer sheet of the present invention is one in which a primer layer and a dye layer are sequentially formed on one surface of the above-described base material. However, the embodiment of the thermal transfer sheet of the present invention is limited to such a structure. For example, a protective layer, a color material layer such as a gold color layer, a silver color layer, or a hologram layer may be formed on the primer layer in the surface order with the dye layer. In addition, when several layers, such as the said dye layer, a protective layer, and a color material layer, are formed on a primer layer, the formation order of these each layer is not specifically limited.

(Heat resistant slipping layer)
The thermal transfer sheet of the present invention is provided with a heat-resistant slipping layer on the surface opposite to the surface on which the primer layer of the substrate is provided in order to prevent adverse effects such as sticking and printing wrinkles due to the heat of the thermal head. It may be.
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, polyol (polyalcohol polymer compound, etc.), 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, Examples thereof include a polyimide resin, a polyamideimide resin, a polycarbonate resin, and a chlorinated polyolefin resin.

The slipperiness imparting agent added to or overcoating the heat resistant slipping layer made of these resins includes phosphate ester, metal soap, silicone oil, graphite powder, silicone graft polymer, fluorine graft polymer, acrylic silicone graft polymer, acrylic. Examples thereof include silicone polymers such as siloxane and arylsiloxane.
The heat-resistant slipping layer may further contain a known additive such as a filler or a crosslinking agent.
The heat-resistant slip layer in the present invention is preferably a layer made of a polyol, for example, a polyalcohol polymer compound, a polyisocyanate compound and a phosphate ester compound, and more preferably a filler added.

The heat-resistant slipping layer is prepared by dissolving or dispersing the above-described resin, slipperiness-imparting agent, and further a filler or the like with an appropriate solvent on the base material sheet to obtain a heat-resistant slipping layer coating solution. It can be prepared and applied 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 to form. The coating amount of the heat resistant slipping layer is preferably 0.1 to 3.0 g / m ² in terms of solid content.

Since the thermal transfer sheet of the present invention has the above-described configuration, the thermal transfer image has high definition, and dyes of three colors of yellow, magenta, and cyan are stored even after storage under high temperature and high humidity. The phenomenon of kogation (black solid fading) can be suppressed in the high density portion of black that is sequentially stacked. In addition, the transfer sensitivity is high in thermal transfer printing, and high density printing can be obtained in high-speed printing.

The contents of the present invention will be described with reference to the following examples, but the contents of the present invention should not be construed as being limited to these embodiments. Unless otherwise specified, “part” and “%” are based on mass.

( Reference Example 1 )
As a base material, on a polyethylene terephthalate film (PET, corona treatment) having a thickness of 4.5 μm, a primer layer composition having the following composition is applied by gravure coating so that the dry coating amount is 0.15 g / m ^2. And dried to form a primer layer.
On the primer layer, a dye layer coating solution having the following composition is applied by gravure coating so that the dry coating amount is 0.7 g / m ² and dried to form a dye layer. Thermal transfer of Reference Example 1 A sheet 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 to a dry coating amount of 1.0 g / m ² , and heat resistant slipping was performed. A sex layer was formed.

<Composition for primer layer>
Alumina sol Solid content 2.5 parts Cationic urethane resin A Solid content 2.5 parts Water 47.5 parts Isopropyl alcohol 47.5 parts In addition, alumina sol 200 (manufactured by Nissan Chemical Industries, Ltd.) is used as the alumina sol, and the above As cationic urethane resin A, SF-600 (Daiichi Kogyo Seiyaku Co., Ltd.) was used.

<Dye layer coating solution>
C. I. Solvent Blue 63 4.5 parts Cellulose acetate propionate resin 3.5 parts (Eastman Chemical Co.)
Methyl ethyl ketone 46.0 parts Toluene 46.0 parts

<Heat resistant slipping layer coating solution>
13.6 parts of polyvinyl butyral resin (manufactured by Sekisui Chemical Co., Ltd.)
0.6 parts of polyisocyanate curing agent (Mitsui Chemical Polyurethane)
Phosphate ester 0.8 parts (Daiichi Kogyo Seiyaku Co., Ltd.)
Methyl ethyl ketone 42.5 parts Toluene 42.5 parts

(Examples 2-16, Reference Examples 2-3 , Comparative Examples 1-12)
In the thermal transfer sheet produced in Reference Example 1 , the alumina sol and the resin of the primer layer composition are the colloidal inorganic pigment ultrafine particles and the resin shown in Table 1 below, respectively, and the blending amount (solid content) and coating amount thereof are as follows. Except having carried out as shown in following Table 1, it carried out similarly to the reference example 1, and produced the thermal transfer sheet of Examples 2-16, Reference Examples 2-3 , and Comparative Examples 1-12. In addition, the commercially available colloidal inorganic pigment ultrafine particles and resins used are as follows.
<Ultrafine colloidal pigments>
Alumina sol 200 (trade name, solid content 10%, manufactured by Nissan Chemical Industries, Ltd.)
<Cationic resin>
Cationic urethane resin A: SF-600, Daiichi Kogyo Seiyaku Co., Ltd. Cationic urethane resin B: SF-620, Daiichi Kogyo Seiyaku Co., Ltd. Cationic urethane resin C: SF-650, Daiichi Kogyo Seiyaku Co., Ltd. Urethane resin D: CP-7020, DIC Corporation cationic urethane resin E: CP-7050, DIC Corporation cationic urethane resin F: CP-7060, DIC Corporation cationic acrylic resin A: AC-117N, Shin-Nakamura Chemical Co., Ltd. Cationic Acrylic Resin B: AC-13, Shin-Nakamura Chemical Co., Ltd. Cationic Acrylic Resin C: Viniblanc 2647, Nissin Chemical Industry Co., Ltd. Cationic Acrylic Resin D: UW-319SX, Taisei Fine Chemical Co., Ltd. Polyvinylpyrrolidone: K-90, IS Japan Polyvinylpyrrolidone modified with vinyl acetate: E-335, anionic urethane resin A: AP-40N, anionic polyester resin DIC Corporation: MD-1245, manufactured by Toyobo Co., Ltd. Urethane resin B: SF-460, Daiichi Kogyo Seiyaku Co., Ltd. hydroxyethyl cellulose: SP-200, Daicel Chemical Industries, Ltd.

(Evaluation)
The following evaluation was performed about each thermal transfer sheet obtained above in the following procedure. The results are shown in Table 1.

<Ink conversion>
When the composition for the primer layer was prepared according to Table 1, those that could be inked were evaluated as ◯, and those that could not be inked due to aggregation or the like were evaluated as x.

(Printing suitability)
<Abnormal transcription evaluation>
The thermal transfer sheet prepared above is stored for one week in an environment of 40 ° C. and 90% RH, and then left at room temperature for 1 hour, and then attached to the Cy portion of a genuine ribbon for CW-01 printer manufactured by Citizen Systems. In combination with Citizen Systems' CW-01 postcard size genuine thermal transfer image-receiving sheet, in increments of 15 gradations in 3 environments of 25 ° C 50% RH, 35 ° C 80% RH, 40 ° C 90% RH (0, 15, 30 ... 240, 255/255) is printed, and the dye layer of the thermal transfer sheet is transferred to the thermal transfer image-receiving sheet and visually examined to see if so-called abnormal transfer occurs. evaluated.
(Evaluation criteria)
A: Abnormal transfer cannot be confirmed in any environment.
◯: Abnormal transfer is observed in an environment of 40 ° C. and 90% RH, but abnormal transfer cannot be visually confirmed by printing in an environment of 35 ° C. and 80% RH and 25 ° C. and 50% RH.
(Triangle | delta): Although abnormal transcription | transfer is recognized in 40 degreeC90% RH environment and 35 degreeC80% RH environment, abnormal transcription | transfer cannot be confirmed visually in printing in 25 degreeC50% RH environment.
X: Abnormal transcription is observed in any environment.

<Evaluation of koge (solid black)>
Next, the thermal transfer sheet prepared above was stored for one week in an environment of 40 ° C. and 90% RH, and left at room temperature for 1 hour, and then the genuine ribbon Ye for Citizen Systems printer CW-01 In combination with Citizen Systems' CW-01 post card size genuine thermal transfer image-receiving sheet, in 3 environments of 25 ° C, 50% RH, 35 ° C, 80% RH and 40 ° C, 90% RH The original Ye part, the original Mg part, and the original Cy part were sequentially overlapped to perform solid printing (255/255 gradation), and the solid prints were visually checked for kogation and evaluated according to the following criteria.
(Evaluation criteria)
A: Kogation cannot be visually confirmed in any printing environment.
○: Kogation is observed in printing in a 40 ° C. and 90% RH environment, but kogation cannot be visually confirmed in printing in a 25 ° C., 50% RH environment and a 35 ° C., 80% RH environment.
Δ: Kogation is observed in printing in an environment of 35 ° C. and 80% RH and 40 ° C. and 90% RH, but kogation cannot be visually confirmed in printing in an environment of 25 ° C. and 50% RH.
X: Koge is visually recognized in any printing environment.
However, koge means that poor image quality and hue fluctuations occur in the solid high-density area when a thermal transfer image is formed by printing the dye layers one after the other, resulting in the matte surface of the printed material and loss of glossiness. It is a phenomenon.

<Print density>
Next, using the thermal transfer sheet produced above, it is attached to the Cy part of the genuine ribbon for Citizen Systems printer CW-01 and combined with the postcard size genuine thermal transfer image receiving sheet for CW-01 manufactured by Citizen Systems. The printing pattern of cyan solid (gradation 255/255) was printed, and the maximum density (cyan) of the printing portion was measured with SpectroLino (manufactured by Gretag Macbeth). Then, using the ribbon (hereinafter referred to as a reference ribbon) to which the thermal transfer sheet according to Comparative Example 8 was attached as a reference, the ratio of the highest density with respect to the reference ribbon was evaluated according to the following criteria.
(Evaluation criteria)
○: Maximum density is 95 to 105% compared to the standard ribbon
Δ: Maximum density is 90 to 95% compared to the standard ribbon
×: The maximum density is less than 90% compared to the reference ribbon

From Table 1, the thermal transfer sheet of each example was excellent in both printability (abnormal transfer, burnt) and print density.
On the other hand, the thermal transfer sheet of the comparative example did not give excellent results in both printability (abnormal transfer, burnt) and print density.

Since the thermal transfer sheet of the present invention has the above-described configuration, the thermal transfer image has high definition, and even after being stored under high temperature and high humidity, a black color in which three dyes of yellow, magenta, and cyan are sequentially stacked. The present invention provides a thermal transfer sheet that can suitably prevent the occurrence of kogation (black solid blur) in a high density portion of the image, has high transfer sensitivity in thermal transfer printing, and can obtain high density printing in high-speed printing. it can.

Claims (4)

A thermal transfer sheet in which a primer layer and a dye layer are sequentially formed on one surface of a substrate,
The primer layer is composed of a composition containing a cationic aqueous dispersion or a cationic aqueous emulsion resin,
The solids content of from cationic aqueous dispersion or cationic aqueous emulsion resin, Ri entire solid content from 65 to 100% by mass of the composition,
The thermal transfer sheet, wherein the cationic aqueous dispersion or the cationic aqueous emulsion resin is a dispersion or emulsion made of a cationic acrylic resin or a cationic urethane resin . The thermal transfer sheet according to claim 1, wherein the primer layer contains 50 mass% or less of colloidal inorganic pigment ultrafine particles. The thermal transfer sheet according to claim 2, wherein the colloidal inorganic pigment ultrafine particles are alumina sol. The thermal transfer sheet according to claim 1, 2 or 3, wherein the substrate is subjected to an adhesion treatment.