JP3009416B2 - Thermal transfer method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer method and a combination of a thermal transfer sheet and an image receiving sheet used in the method.

BACKGROUND ART In thermal transfer recording, the receiving layer surface of an image receiving sheet is
A heating means such as a thermal head which is superposed on a thermal transfer sheet provided with a dye layer containing a heat transferable dye in a state where the thermal transfer sheet is opposed to the dye layer, and is controlled by an electric signal according to image information from the back of the thermal transfer sheet. Is performed by transferring the dye in the dye layer to the receptor layer by heating the thermal transfer sheet.

However, in the conventional thermal transfer method, it is difficult to obtain good print image storability and obtain a high recording density.

Generally, the dye used in the dye layer on the thermal transfer sheet is selected in consideration of parameters such as recording sensitivity, storage stability, hue, and solubility of the dye in the ink or the binder resin. Among these parameters, it is known that the recording sensitivity and the storage stability have a large correlation with the molecular weight of the dye and the sublimation temperature.
For example, it has been considered that the recording sensitivity is higher as the molecular weight of the dye is smaller and the sublimation temperature is lower, while the storage stability is better as the molecular weight of the dye is larger and the sublimation temperature is higher. From such a viewpoint, conventionally, in consideration of the balance between the two, the molecular weight is about 150 to 800, more preferably 350 to 700
A degree of dye is often selected as desirable.

However, in practice, even if the dye has a molecular weight in the range of 350 to 700, the number of dyes that produce good recording sensitivity is unexpectedly small, and screening from a large number of dye candidates is repeated to obtain the desired dye. At present, dyes having high performance are selected and used.

Further, the recording sensitivity when actually performing thermal transfer was selected as described above because it was greatly affected by any combination of the thermal transfer sheet and the image receiving sheet, that is, the combination of the dye layer and the receiving layer. In order to determine what kind of receiving layer is most suitable to combine with the dye, a material having a better recording sensitivity is selected by repeating screening from among many materials for forming the receiving layer. is the current situation.

Thus, in the development of conventional thermosensitive recording materials,
The selection criterion based on the dye molecular weight for judging the quality of the recording sensitivity is extremely vague, and a good combination of materials cannot be obtained unless the screening is repeated many times as described above and actual printing is performed. Therefore, there have been many difficulties in the development of thermal recording materials.

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the related art, and has as its object to provide a thermal transfer method which has good storability and guarantees image formation with good print density.

The present inventor has conducted intensive studies on factors that determine the combination in which the recording sensitivity is optimal when combining the thermal transfer sheet and the image receiving sheet, and particularly as a result of the dye diffusion coefficient in the receiving layer of the image receiving sheet and the dye of the thermal transfer sheet. It has been found that two factors of the saturation transfer rate of the dye from the layer to the receiving layer of the image receiving sheet are important factors in improving the recording sensitivity.

The thermal transfer method of the present invention is based on the above-mentioned findings, and more specifically, (a) a thermal transfer sheet in which a dye layer comprising a dye and a binder is formed on a substrate, and (b) A) an image receiving sheet having a receiving layer made of a resin for receiving a dye migrating from the dye layer of the thermal transfer sheet formed on a base material, and stacking the image receiving sheet so that the dye layer and the receiving layer face each other. A method for performing thermal transfer recording by transferring a dye to the receiving layer by performing heating according to image information from the back surface of the image receiving sheet, wherein the dye constituting the dye layer of the thermal transfer sheet is contained in the receiving layer of the image receiving sheet. The dye diffusion coefficient in the receiving layer when transferred to and diffused at 120 ° C. is 5 × 10 ⁻⁹ cm ² / min or more, more preferably 1 × 10 ⁻⁸ cm ² / min or more,
An image receiving sheet and a thermal transfer sheet wherein the saturation transfer rate of the dye from the dye layer to the receiving layer is at least 40% at 120 ° C when the dye constituting the dye layer of the thermal transfer sheet is transferred to the receiving layer of the image receiving sheet. Are used in combination.

Further, the combination for thermal transfer according to the present invention comprises: (a) a thermal transfer sheet having a dye layer comprising a dye and a binder formed on a substrate; and (b) a dye of the thermal transfer sheet on a substrate. An image receiving sheet formed with a receiving layer made of a resin for receiving a dye transferred from the layer, and superimposing the dye layer and the receiving layer such that the dye layer and the receiving layer are opposed to each other, and apply heating according to image information from the back of the thermal transfer sheet. A combination of the thermal transfer sheet and the image receiving sheet for performing thermal transfer recording by transferring the dye to the receiving layer by performing the dye transfer, wherein the dye constituting the dye layer of the thermal transfer sheet is a receiving layer of the image receiving sheet. The dye diffusion coefficient in the receiving layer when it migrates and diffuses into
0 ^-9 cm ² / min or more, and the saturation transfer rate of the dye from the dye layer to the receiving layer when the dye constituting the dye layer of the thermal transfer sheet is transferred to the receiving layer of the image receiving sheet is 120 ° C.
Wherein the image receiving sheet and the thermal transfer sheet having a ratio of not less than 40% are combined.

BEST MODE FOR CARRYING OUT THE INVENTION As described above, in the thermal transfer method of the present invention, only two parameters, the dye diffusion coefficient in the receiving layer of the image receiving sheet and the saturation transfer rate of the dye in the dye layer of the thermal transfer sheet, are used. It is characterized in that the recording sensitivity can be optimized by using a combination in which these parameters satisfy certain conditions.

As the dye diffusion coefficient in the present invention, a value measured at 120 ° C. by the following method (A) or (B) is used.

Measuring Method of Dye Diffusion Coefficient (A): First, a resin composition for forming a receptor layer is coated on a release substrate, dried, and then, the separated resin film of the receptor layer (thickness: about 3 to 10 μm) is removed. A receiving layer is formed by laminating 3 to 10 sheets, and the receiving layer is placed on a substrate (synthetic paper having a thickness of 150 μm), and a dye layer film and a protective film (25
A polyethylene terephthalate film having a thickness of μm is laminated in this order. From above the protective film, a plate of a foil stamping machine whose surface temperature is set to a predetermined temperature is pressed and heated for a predetermined time (for example, hot namer type SW-II).
(Use a 35 mm ² plate manufactured by Yamadai Bisho Co., Ltd., and operate at a gauge pressure of 5 kgf / cm ² ). Then, peel off the laminated receiving layer resin film one by one, and extract the dye for each with toluene. Then, the dyeing amount is measured by an absorbance method.
The above data, determine the dye concentration distribution curve in a depth direction of the receiving layer, Matano (Jap.J.Phys 8 .109 (1
932) The diffusion coefficient is calculated based on the above method.

Method for measuring dye diffusion coefficient (B): A resin composition for forming a receptor layer is coated on a substrate so that the film thickness when dried becomes 100 to 500 μm to form a receptor layer. A thermal transfer sheet is placed on the receiving layer such that the dye layer overlaps the receiving layer. A foil-pressing machine whose surface temperature is set at 110 ° C. from above the thermal transfer sheet (for example, using a 35 mm ² plate manufactured by Hot Namer Type SW-II, Yamadai Bisho Co., Ltd., and using a gauge pressure of 5 kgf / cm ^2). ) And heated by pressing for a predetermined time. By using a microspectrophotometer (Olympus Optical Industries, Ltd., for example, AH2-STK) that creates a slice sliced in a direction perpendicular to the surface of the receptor layer, the absorbance at a predetermined position of the slice is measured to determine the depth of the receptor layer. The concentration distribution curve of the dye in the vertical direction was determined and the result was obtained using Matano (Jap. J. Phys. 8 .
109 (1932)), the dye diffusion coefficient in the receptor layer is determined.

By using the method (A) or (B), the diffusion coefficient of the receiving layer under any conditions can be determined. However, in this method, the dye diffusion coefficient tends to vary in the surface layer portion of the receiving layer and in the deepest portion of the dyed region. Therefore, the value obtained in the intermediate portion where the dye diffusion coefficient is substantially constant in the dyed area in the receiving layer is defined as the dye diffusion coefficient obtained by the method (A) or (B).

Method for Measuring Saturation Transfer Ratio of Dye: On the other hand, the saturation transfer ratio of the dye in the present invention is based on a value measured at 120 ° C. by the following method.

A base material is coated with a resin composition for forming a receptor layer and dried to form an image receiving sheet, on which a dye layer film and a protective film (2.5-thick polyethylene terephthalate film) are laminated in this order. From above the protective film, a plate of a foil stamping machine having a surface temperature set at a predetermined temperature is pressed for a predetermined time and heated (for example, a hot-namer type SW-II, manufactured by Yamadai Misho Co., Ltd., 35 mm ² Using a plate and operating at a gauge pressure of 5 kgf / cm ² ), the dye dyed in the receiving layer is extracted with toluene, and the dye dyeing amount is measured by an absorbance method. The dye remaining from the dye layer after the transfer is extruded with toluene, and the amount of the remaining dye is measured by an absorbance method. From the above data and the above data, the saturation transfer rate (%) of the dye is calculated by the following formula.

The dye transfer rate thus determined shows the following temporal change at a constant temperature. That is, while the heating time is short, the dye transfer rate increases as the heating time increases, and when the heating time is sufficiently long, the dye transfer rate reaches a constant value.
The dye transfer rate at this time is considered to indicate the affinity between the dye used and the receiving layer. That is, the value of the dye transfer rate when the dye transfer rate reaches a certain value indicates the distribution ratio of the dye when the dye layer reaches an equilibrium state between the binder and the receiving layer. Therefore, if the binder of the dye layer is the same, the higher the value of the dye transfer rate when the binder reaches a certain value, the higher the affinity between the dye and the receptor layer. Therefore, the value of the dye transfer rate when the value reaches a certain value is referred to as the saturated transfer rate of the dye.

The time-dependent change of the dye transfer rate was measured using various types of resins for forming a receiving layer as exemplified later. As a result, it was found that the dye transfer rate became almost constant within 1 minute of the heating time. Therefore, the dye transfer rate measured over a heating time of 3 minutes was defined as the saturation transfer rate of the dye. The measurement condition of the heating time of 3 minutes is for convenience. Since the saturation transfer rate of the dye is a value when the dye transfer rate reaches a constant value, when the measurement is performed by changing the dye, the resin for forming the binder receiving layer of the dye layer, etc., the heating time is deliberately fixed. No need to do.

The transfer method of the present invention is based on the measurement method as described above.
The dye diffusion coefficient and the dye at ℃ are performed by appropriately combining a thermal transfer sheet and an image receiving sheet such that the saturation transfer rate is a value within a specific range, whereby high-sensitivity thermal transfer can be performed. .

Thermal transfer sheet A thermal transfer sheet having a dye layer satisfying the conditions of the dye diffusion coefficient and the dye saturation transfer rate as described above has, for example, the following configuration.

It is composed of a substrate sheet conventionally used as a substrate sheet of this type of thermal transfer sheet, and a dye layer provided on the sheet. The dye layer is composed of a dye and a binder that are transferred by melting or sublimation by heating.

The dye is preferably a sublimable disperse dye, a sublimable oil-soluble dye, or a sublimable basic dye, and has a molecular weight of
It is 150-800, preferably 350-700. These dyes are selected in consideration of sublimation temperature, hue, weather resistance, solubility in ink or binder resin, and the like.

CI (short for Chemical Index, the same applies hereinafter) Disperse Yellow 51, 3, 54, 79, 6
0, 23, 7, 141, CI Disperse Blue 24, 56, 14, 14, 301, 3
34, 165, 19, 72, 87, 287, 154, 26, CI Disperse Red 135, 146, 59, 1, 1
73, 60, 167, CI Disperse Violet 4, 13, 36, 5
6, 31; CI Solvent Violet 13 CI Solvent Black 3 CI Solvent Green 3 CI Solvent Yellow 56, 14, 14, 16, 29, CI Solvent Blue 70, 35, 63, 36, 50,
Same 49, Same 111, Same 105, Same 97, Same 11, CI Solvent 135, Same 81, Same 18, Same 25, Same 19,
23, 24, 143, 146, and 182.

As a binder of the dye layer, ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, cellulose triacetate, cellulose diacetate, cellulose resin such as cellulose acetate butyrate, polyvinyl alcohol, polyvinyl acetal, polyvinyl pyrrolidone,
Vinyl resins such as polyester, polyvinyl acetate and polyacrylamide can be used. Examples of more preferred binders are not the ordinary vinyl acetal resins described above, but have a molecular weight of 60,000 to 200,000 and a weight percentage of the vinyl alcohol portion of 10 to 40 in the polyvinyl acetoacetal resin.
%, Preferably 15-30%, with a glass transition point of 60-110 ° C,
Preferably, a special polyvinyl butyral resin at 70 to 110 ° C is used. When the glass transition point is lower than 60 ° C., the phenomenon that the dye aggregates or precipitates with the passage of time occurs. On the other hand, when the glass transition point exceeds 110 ° C., the dye does not sufficiently sublimate, which is not preferable. If the molecular weight is less than 60,000, the binding power as a binder is insufficient, and if it exceeds 200,000, the viscosity at the time of application becomes too high, which hinders application. If the vinyl alcohol portion is less than 10%, the stability over time of the dye layer is insufficient,
For this reason, aggregation and precipitation of the dye and bleeding to the surface are inevitable. Conversely, if it exceeds 40%, the sublimation of the dye is hindered due to the affinity of the polyvinyl alcohol portion for the dye, and the print density decreases.

The weight ratio of the dye binder to the dye in the dye layer is desirably 0.3 or more, and if it is less than 0.3, the print density and heat sensitivity are insufficient. On the other hand, when the ratio of the dye / binder exceeds 2.3, the retention of the dye in the binder is insufficient, and the storage stability of the thermal transfer sheet is reduced. Accordingly, the dye / binder content is preferably 0.3 to 2.3, more preferably 0.55 to 1.5.

It is desirable that the dye is dissolved in the binder of the dye layer. In a conventional sublimation transfer paper for fabric, since the dye is dispersed in the binder, sublimation of the dye requires energy that overcomes the interaction between the dye molecules and the interaction between the dye molecule and the binder. As a result, the thermal sensitivity decreases. In this regard, the fact that the dye is dissolved in the binder is advantageous in terms of heat sensitivity.

The dye layer may be formed by selecting a dye so that a desired hue can be transferred when printing, and forming two or more dye layers having different dyes on a single thermal transfer sheet as needed. For example, when an image such as a natural color photograph is formed by repeating printing of each color according to a color separation signal, the hue at the time of printing is preferably each of cyan, magenta, and yellow. Three thermal transfer layers containing the dye giving Or cyan, magenta,
A thermal transfer layer containing a dye giving a black hue in addition to yellow may be added. In addition, if the position detection mark is provided simultaneously with the formation of any of the thermal transfer layers during the formation of these dye layers, ink different from the dye layer formation,
This is preferable because a printing step is not required.

Image-Receiving Sheet On the other hand, an image-receiving sheet having a receiving layer that satisfies the conditions for the dye diffusion coefficient and the dye transfer rate as described above has, for example, the following configuration. In this image receiving sheet, the receiving layer is formed of a resin for forming a receiving layer that satisfies the above conditions, and this becomes the image receiving sheet of the present invention. As examples of the resin for forming the receptor layer in the present invention, the following synthetic resins can be used alone or in combination of two or more.

(A) Those having an ester bond.

Polyester resin, polyacrylate resin, polycarbonate resin, polyvinyl acetate resin, styrene acrylate resin, vinyl toluene acrylate resin, etc.

(B) Those having a urethane bond.

 Polyurethane resin etc.

(C) Those having an amide bond.

 Polyamide resin etc.

(D) Those having a urea bond.

 Urea resin and the like.

(E) Others having a highly polar bond.

Polycaprolactone resin, styrene-maleic anhydride resin, polyvinyl chloride resin, polyacrylonitrile resin and the like.

In addition, a saturated polyester and a vinyl chloride / vinyl acetate copolymer are used as the resin for forming the receiving layer. Vinyl chloride / vinyl acetate copolymer contains vinyl chloride component
Those having 85 to 97% by weight and a degree of polymerization of about 200 to 800 are preferred. The vinyl chloride / vinyl acetate copolymer is not necessarily limited to a copolymer of only a vinyl chloride component and a vinyl acetate component, but may include a vinyl alcohol component, a maleic acid component, and the like.

The image receiving sheet may be such that the sheet itself can be used as a receiving layer, or may be one in which a receiving layer is provided on a sheet substrate. Examples of the sheet substrate include a plastic film, synthetic paper, and cellulose fiber paper. As a plastic film, a film made of a resin such as polyester, polyvinyl chloride, polypropylene, polyethylene, polycarbonate, or polyamide can be used, and a white film or fine foam formed by adding a filler to these films. Foamed films can also be used. As synthetic paper, a polyolefin resin or other synthetic resin as a resin component, to which inorganic fillers and the like are added, mixed and extruded,
Further, a film produced by coating an extender on the surface of a film of a polystyrene resin, a polyester resin, a polyolefin resin or the like is used. As cellulose fiber paper,
Fine paper, coated paper, cast coated paper, synthetic rubber latex or synthetic resin emulsion impregnated paper can be used.
Laminated paper in which a foamed film or synthetic paper is adhered to a cellulose fiber paper or film can also be used.

In the case where the image receiving sheet is required to be transparent, a transparent receiving layer may be provided on a transparent sheet substrate.

For applications requiring transparency as a sheet substrate (such as for overhead projectors) or applications where heat is transferred to an article such as a card or cloth, an adhesive or the like may be applied to the side opposite to the transparent plastic film receiving layer. A white film, a foamed film, a synthetic or cellulose fiber paper can also be laminated as the applied support or the material for imparting shielding properties. Further, a sheet substrate in which plastic films, synthetic papers, or cellulose fiber papers are bonded together with an adhesive can be used.

In forming the receiving layer, the ink for forming the receiving layer prepared by preparing the resin for forming the receiving layer with a solvent or the like is applied onto a sheet substrate by a conventionally well-known coating means, and dried. The thickness of the receiving layer is preferably 1 to 50 μm. When the image receiving sheet is composed of the receiving layer alone, the thickness is
Those having a thickness of 30 μm or more are preferred.

The image receiving sheet of the present invention can be provided with an intermediate layer composed of a cushion layer, a porous layer, and the like between the sheet base material and the receiving layer. Good transfer recording is possible. Examples of the material constituting the intermediate layer include urethane resin, acrylic resin, ethylene-based resin, butadiene rubber, and epoxy resin. The thickness of the intermediate layer is 2
It is preferably about 20 μm.

In the image receiving sheet of the invention, a releasing agent may be contained in the receiving layer in order to improve the releasability from the thermal transfer sheet. Examples of the release agent include solid waxes such as polyethylene wax, amide wax and Teflon powder; fluorine-based and phosphoric acid ester-based surfactants; silicone oil; and silicone oil is preferred.

As the silicone oil, an oily oil can be used, but a curable oil is preferable. Examples of the curable silicone oil include a reaction curable type, a photocurable type, and a catalyst curable type, and a reaction curable type silicone oil is particularly preferable. As the reaction-curable silicone oil, those obtained by reacting and curing an amino-modified silicone oil and an epoxy-modified silicone oil are preferable. Examples of the amino-modified silicone oil include X-22-3050C (manufactured by Shin-Etsu Chemical Co., Ltd.). Examples of the epoxy-modified silicone oil include X-22-3000E (manufactured by Shin-Etsu Chemical Co., Ltd.). As the catalyst-curable or light-curable silicone oil, KS-705F-PS (catalyst-curable silicone oil, manufactured by Shin-Etsu Chemical Co., Ltd.), KS-705F-PS
720 (photo-curable silicone oil, Shin-Etsu Chemical Co., Ltd.)
Manufactured). The addition amount of these curable silicone oils is 0.5 to 100 parts by weight of the resin constituting the receiving layer.
About 30 parts by weight is preferred.

In the present invention, the release agent layer may be provided by dissolving or dispersing the above release agent in an appropriate solvent on the surface of the receptor layer, applying the solution, followed by drying. As the release agent constituting the release agent layer, the above-mentioned cured product of the amino-modified silicone oil and the epoxy-modified silicone oil is particularly preferable. The thickness of the release agent layer is 0.01 to 5 μm, particularly 0.1 μm.
05 to 2 μm is preferred.

Further, the image receiving sheet of the present invention may have a slip layer on the back surface of the sheet substrate. In some cases, image receiving sheets are stacked and sent one by one to perform transfer. In this case, if a slip layer is provided, the slip between the sheets becomes smooth, and
It can be sent out one sheet at a time. Examples of the material of the lubricating layer include a methacrylate resin such as methyl methacrylate or a corresponding acrylate resin, and a vinyl resin such as a vinyl chloride-vinyl acetate copolymer.

Further, the image receiving sheet may contain an antistatic agent. The incorporation of an antistatic agent has the effect of preventing dust from adhering to the image receiving sheet. The antistatic agent may be contained in the sheet substrate or the receiving layer,
Alternatively, it can be provided as an antistatic agent layer on the back surface of the sheet substrate or the like, but is preferably provided as an antistatic layer on the back surface of the sheet substrate.

Further, it is also possible to provide a detection mark on the image receiving sheet. The detection mark is extremely convenient when positioning the thermal transfer sheet and the heat transfer target sheet. For example, a detection mark that can be detected by the photoelectric tube detection position can be provided on the back surface of the sheet base by printing or the like.

Hereinafter, the present invention will be described in more detail with reference to examples.
The following "parts" indicate parts by weight.

Examples 1 and 2 and Comparative Examples 1 and 2 (Preparation of Thermal Transfer Sheet) Formation of a heat-resistant lubricating layer having the following composition on a 4.5-μm-thick polyethylene terephthalate film (manufactured by Toray: Lumirror 5A-F53) The ink composition for application is applied with a wire bar so that the thickness when dried is 1 μm,
The resultant was dried and cured at 72 ° C. for 72 hours to form a heat-resistant lubricating layer.

Ink composition for forming heat-resistant lubricating layer Polyvinyl butyral resin ... 1.8 parts (Sekisui Chemical: Esrec BX-1) Isocyanate (45% solution) ... 7.9 parts (Dainippon Ink Chemical: Burnock D-750) Phosphate ester ... 1.3 parts (Daiichi Kogyo Seiyaku: Plysurf A-208S) Phosphate sodium salt ... 0.54 parts (Toho Chemical: Gaffa RD-720) Talc ... 0.36 parts (Nippon Talc: Microace L-1) Toluene ... 44.04 parts Methyl ethyl ketone ... 44.04 parts Then, on the opposite surface of the base material, the ink composition 1 for forming a dye layer having the following composition was dried to a thickness of 1 using a miller bar # 10.
The dye was applied to a thickness of .mu.m and dried at 80.degree. C. for 5 minutes to form a dye layer, whereby a thermal transfer sheet 1 was obtained. The coating was performed so as to have a thickness of 5 μm for measuring the dye diffusion coefficient.

Ink composition for forming dye layer 1 Magenta dye: No.13 (the following structural formula) 3.00 parts Polyvinyl acetoacetal resin (BV-5, Sekisui Chemical) 3.20 parts Polyvinyl acetoacetal resin (BV-1, Sekisui Chemical) 0.30 parts Toluene 46.75 parts Methyl ethyl ketone 46.75 parts (Preparation of image receiving sheet) Each of the ink compositions for forming a receiving layer having the following composition was applied to a synthetic paper having a thickness of 150 μm by wire bar coating so that the thickness after drying became 6 μm, and dried at 100 ° C. for 15 minutes to obtain an image receiving sheet. Using this, the saturation transfer rate of the dye, the reflection color density, and the relative print density were measured.

In addition, the same ink composition for forming each receptor layer as described above was applied to a stretched polypropylene film having a thickness of 60 μm instead of the synthetic paper and dried, and then peeled off from the substrate to measure a dye diffusion coefficient described below. An image receiving sheet having a thickness of 6 μm was obtained. Seven dyes were superimposed and the dye diffusion coefficient was measured by the measurement method (A).

Further, the same ink composition for forming a receiving layer as described above,
A 100 μm-thick polyethylene terephthalate film (manufactured by Toray Industries, Inc.) was applied and dried so as to have a thickness of 100 to 500 μm after drying to obtain an image receiving sheet for measuring the dye diffusion coefficient by the measurement method (B).

Ink composition for forming receiving layer (Example 1) Resin for forming receiving layer Vinyl chloride-vinyl acetate copolymer ... 20 parts (Electrochemical: 1000A) Amino-modified silicone oil ... 2 parts (Shin-Etsu Chemical: X- 22-3050C) Epoxy-modified silicone oil ... 2 parts (Shin-Etsu Chemical: X-22-3000E) Toluene ... 38 parts Methyl ethyl ketone ... 38 parts Ink composition for forming receiving layer (Example 2) Resin for forming receiving layer Polyester resin … 20 parts (Arakawa Chemical: KA-1039U18) Amino-modified silicone oil… 2 parts (Shin-Etsu Chemical: X-22-3050C) Epoxy-modified silicone oil… 2 parts (Shin-Etsu Chemical: X-22-3000E) Toluene 38 parts Methyl ethyl ketone 38 parts Ink composition for forming a receiving layer (Comparative Example 1) Resin for forming a receiving layer Polymethyl methacrylate resin 15 parts (Mitsubishi Rayon: Dianal BR-85) Amino Silicone oil: 1.5 parts (Shin-Etsu Chemical: X-22-3050C) Epoxy-modified silicone oil: 1.5 parts (Shin-Etsu Chemical: X-22-3000E) Toluene: 40 parts Methyl ethyl ketone: 40 parts Ink for forming receiving layer Composition (Comparative Example 2) Receptive Layer Forming Resin SBR… 20 parts (Shell Chemical: Kaliflex TR1101) Amino-modified silicone oil… 2 parts (Shin-Etsu Chemical: X-22-3050C) Epoxy-modified silicone oil… 2 (Shin-Etsu Chemical Co., Ltd .: X-22-3000E) Toluene: 38 parts Methyl ethyl ketone: 38 parts The saturation transfer rate of the dye was measured using the above-mentioned sheet, and the dye diffusion coefficient was measured using the above-mentioned image-receiving sheet prepared using a stretched propylene film as a substrate. Measured by (A), also was measured dye diffusion coefficient (B) with each image-receiving sheet was prepared PET film as a substrate. The results are shown in Table 1.

(Printing test) First, an image receiving sheet made of the synthetic paper as a base material prepared in Example 1 was used and combined with the above-mentioned thermal transfer sheet 1, and a thermal head (manufactured by Kyocera: KMT-85-6MPD2-STV)
The printing is performed under the following printing conditions, and the value of the printing pulse width at which the reflected color density of magenta measured by a color densitometer (RD-918, manufactured by Macbeth) becomes approximately 1.0 is obtained.

Printing conditions Printing speed 33.3 msec / line Applied pulse width 1 to 16 msec Head applied voltage 12.0 V Feed pitch 0.167 mm Dot density 6 dots / mm The value of the applied pulse width at which the reflected color density determined above is approximately 1.0. The printing was performed with the image receiving sheet and the thermal transfer sheet 1 of other examples and comparative examples based on the above printing conditions.

The magenta reflection color densities of the other examples and comparative examples were measured under these printing conditions, and the measured values were used as relative printing densities (reflection color density / Example 1) based on the measurement values of Example 1. (Reflection color density), and the results are shown in Table 1.

On the other hand, the transfer sheets 2 to 2 prepared in the same manner as the ink composition 1 for forming a dye layer using the image receiving sheets prepared in Examples 1 and 2 and the ink compositions 2 to 6 for forming a dye layer described below. 6 and the saturated dye transfer rate at 120 ° C., the reflection color density, and the relative print density were determined by the above method. The results are shown in Table 2.

As for the reflection color density, the color density of yellow was measured for the combination with the thermal transfer sheet 2, the color density of magenta was measured for the thermal transfer sheet 3, and the cyan color density was measured for the combination with the thermal transfer sheets 4, 5, and 6.

Ink composition for forming dye layer 2 Dye: FORON BRILLIANT YELLOW S-6GL 3.00 parts (manufactured by SANDOZ) Polyvinyl acetoacetal resin (manufactured by Sekisui Chemical: BV-5) 3.20 parts polyvinyl acetoacetal resin (manufactured by Sekisui Chemical: BV-1) 0.30 parts Toluene 46.75 parts Methyl ethyl ketone 46.75 parts Ink composition for forming dye layer 3 Disperse dye CISOLVENT RED 19 3.00 parts Polyvinyl acetoacetal resin (Sekisui Chemical: BV-5) 3.20 parts Polyvinyl acetoacetal resin (Sekisui Chemical: BV-) 1) 0.30 parts Toluene 46.75 parts Methyl ethyl ketone 46.75 parts Dye layer forming ink composition 4 Disperse dye CISOLVENT BLUE 63 3.00 parts Polyvinyl acetoacetal resin (Sekisui Chemical: BV-5) 3.20 parts Polyvinyl acetoacetal resin (Sekisui Chemical: BV) -1) 0.30 part Toluene 46.75 parts Methyl ethyl ketone 46.75 parts Ink composition for forming dye layer 5 Shea Dye: No.15 (the following structural formula) 3.00 parts Polyvinyl acetoacetal resin (Sekisui Chemical: BV-5) 3.20 parts Polyvinyl acetoacetal resin (Sekisui Chemical: BV-1) 0.30 parts Toluene 46.75 parts Methyl ethyl ketone 46.75 parts Ink composition for forming dye layer 6 Cyan dye: No. 4 (Structural formula below) 3.00 parts Polyvinyl acetoacetal resin (Sekisui Chemical: BV-5) 3.20 parts Polyvinyl acetoacetal resin (Sekisui Chemical: BV-1) 0.30 parts Toluene 46.75 parts Methyl ethyl ketone 46.75 parts As is clear from the above Examples and Comparative Examples, according to the thermal transfer method of the present invention, the dye diffusion coefficient in the receiving layer at 120 ° C. becomes 5 × 10 ⁻⁹ cm ² / min or more and the dye at 120 ° C. Since the transfer is performed by combining the thermal transfer sheet and the image receiving sheet so that the saturation transfer rate is 40% or more, the desired print density can be obtained in a short time without prolonging the print time even with relatively small applied energy. Transfer can be performed, and good transfer can be performed with a small amount of printing energy, so that power consumption and the like can be reduced.

INDUSTRIAL APPLICABILITY The present invention can be widely applied to a thermal recording system in which an image is formed using a point heating means such as a thermal head, an energizing head, and a laser beam.

Continuation of front page (56) References JP-A-61-237691 (JP, A) JP-A-61-283595 (JP, A) JP-A-62-176896 (JP, A) JP-A-1-125291 (JP) JP-A-2-70487 (JP, A) JP-A-63-7793 (JP, A) JP-A-63-42892 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) B41M 5/38-5/40

Claims (11)

(57) [Claims] 1. A thermal transfer sheet having a dye layer comprising a dye and a binder formed on a substrate, and (b) receiving a dye migrating from the dye layer of the thermal transfer sheet on a substrate. An image receiving sheet having a receiving layer made of a resin formed thereon is stacked so that the dye layer and the receiving layer face each other, and heating is performed in accordance with image information from the back side of the thermal transfer sheet to form a dye on the receiving layer. A method for performing thermal transfer recording by transferring the dye, wherein the dye constituting the dye layer of the thermal transfer sheet migrates and diffuses into the receiving layer of the image receiving sheet, the dye diffusion coefficient in the receiving layer is 120 ° C. 5 × 10 ^-9 cm ² /
Minutes or more, and the saturation transfer rate of the dye from the dye layer to the receiving layer when the dye constituting the dye layer of the thermal transfer sheet is transferred to the receiving layer of the image receiving sheet is 40% or more at 120 ° C. A heat-sensitive transfer method characterized by using an image receiving sheet and a thermal transfer sheet in combination. 2. The method according to claim 1, wherein the dye in the dye layer of the thermal transfer sheet is present in a state dissolved in a binder. 3. The method according to claim 1, wherein the dye layer of the thermal transfer sheet is formed by separately applying dye layers of a plurality of hues on a single substrate. 4. The method according to claim 1, wherein the dye constituting the dye layer of the thermal transfer sheet comprises a sublimable dye having a molecular weight of 150 to 800. 5. A thermal transfer sheet having a dye layer comprising a dye and a binder formed on a substrate, and (b) receiving a dye migrating from the dye layer of the thermal transfer sheet on a substrate. An image receiving sheet having a receiving layer made of a resin formed thereon is stacked so that the dye layer and the receiving layer face each other, and heating is performed in accordance with image information from the back side of the thermal transfer sheet to form a dye on the receiving layer. A combination of the thermal transfer sheet and the image receiving sheet for performing thermal transfer recording by transferring, wherein the dye constituting the dye layer of the thermal transfer sheet migrates and diffuses into the receiving layer of the image receiving sheet. dye diffusion coefficient in receiver layer at ^{120 ℃ 5 × 10 -9 cm 2} /
Min. Or more, and the dye transfer rate from the dye layer to the receiving layer when the dye constituting the dye layer of the thermal transfer sheet is transferred to the receiving layer of the image receiving sheet is 40% or more at 120 ° C. And a thermal transfer sheet. A combined body for thermal transfer. 6. The combination according to claim 5, wherein the dye in the dye layer of the thermal transfer sheet exists in a state dissolved in a binder. 7. The combination according to claim 5, wherein the dye layer of the thermal transfer sheet is formed by separately applying dye layers of a plurality of hues on a single substrate. 8. The combination according to claim 5, wherein the dye constituting the dye layer of the thermal transfer sheet comprises a sublimable dye having a molecular weight of 150 to 800. 9. The combination according to claim 5, wherein in the image receiving sheet, a base material also serves as an image receiving layer. 10. The dye diffusion coefficient is 1 × 1 at 120 ° C.
^2. The method according to claim 1, wherein the amount is ^0-8 cm2 / min or more. 11. The dye diffusion coefficient is 1 × 1 at 120 ° C.
0 ^-8 is cm ² / min or more, the combination product according to claim 5.