JPH10272847A - Thermal transfer sheet and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thermal transfer sheet having an excellent dot quality and giving an image approximate to a print, and an image forming method using this sheet. SOLUTION: A thermal transfer sheet having on a substrate an ink layer which contains a pigment of 20-35 wt.% and amorphous resin of 50-80 wt.% of which the softening point measured by a ring and ball method (JIS K2207) is in a temperature range of 50-150 deg.C, and which has a layer thickness in the range of 3-1.0 μm and satisfies the following conditions. The sheet is made a single sheet of a film thickness 200 μm and it is broken in the range of 60-120 deg.C when it is extended, being heated at a speed of temperature rise of 2 deg.C/min., under the conditions of a static tension 20 g and a forced vibration frequency 9.8 Hz.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer sheet having an ink layer on a support and an image forming method using the thermal transfer sheet. More particularly, the present invention relates to a thermal head printer or a laser beam for receiving an image on an ink layer. On the sheet,
The present invention relates to a heat-sensitive transfer sheet useful for forming a high-quality multi-tone image by transferring an image by area gradation recording and an image forming method using the same.

[0002]

2. Description of the Related Art Conventionally, as a thermal transfer recording system for forming an image using a thermal head printer, there are known a sublimation dye transfer system and a heat melting type transfer system. Sublimation type dye transfer method, a transfer sheet having a transfer layer composed of a sublimation type dye and a binder provided on a support is superimposed on an image receiving sheet,
In this method, heat is applied imagewise from the back side of the support of the transfer sheet by a thermal head to sublimate the sublimation dye and transfer it to the image receiving sheet, thereby forming an image on the image receiving sheet. In this method, by using a transfer sheet having a sublimation dye of each of yellow, magenta, and cyan,
A color image can be formed. However, the sublimation dye system has the following disadvantages.

(1) Since the gradation expression of an image mainly uses a density gradation which controls the kind or amount of a dye, it is suitable for obtaining a continuous multi-tone image similar to a photograph.
For example, it is not suitable for area gradation recording used in the printing industry.

(2) Since the image formation utilizes dye sublimation, the edge sharpness of the finished image tends to be insufficient, the solid density of thin lines tends to be low, and the quality of character images is low.

(3) Since the image formation utilizes the sublimation of the dye, the formed dye image easily sublimates due to environmental temperature, and the light resistance of the dye itself is lower than that of the pigment.
Use in fields requiring heat resistance and light resistance is limited.

(4) Since the thermal recording sensitivity is lower than that of the heat melting type transfer system, it is not suitable as a high-speed recording material.

(5) The transfer material is more expensive than the hot-melt transfer material. On the other hand, in the hot-melt transfer method, a heat-sensitive transfer sheet having a heat-meltable ink transfer layer formed of a coloring material such as a pigment or a dye and a binder such as wax on a support is superimposed on an image receiving sheet, and the transfer sheet is formed. In this method, heat is applied imagewise from the back side of the support by a thermal head, the transfer layer is melted and transferred and fused onto an image receiving sheet to form an image.

[0008] The hot-melt type transfer system has advantages such as higher sensitivity to heat, lower cost of materials, and superior image light fastness as compared with the sublimation type dye transfer system. Has disadvantages. That is, a major drawback of the thermal fusion transfer method is that the gradation of an image is inferior to that of the sublimation dye transfer method. This is because this method is not suitable for density gradation recording as in a sublimation dye transfer method, but rather suitable for binary recording. Conventionally, image formation using a thermal head involves controlling the amount of energy applied to the heat-sensitive sheet by controlling the amount of power applied to the head, thereby changing the amount of the transfer layer that melts in a continuous tone.
Various proposals have been made to improve the ink transfer layer to achieve density gradation recording. However, the concept of these improvements is based on the fact that the binder in the ink layer is melted by heating by the thermal head and the viscosity is reduced. Controlling the temperature rise of the ink layer to control the cohesion and destruction inside the ink layer, thereby controlling the transfer amount of the ink layer, that is, performing multi-tone printing by softening the gamma characteristic of thermal transfer recording. is there. However, even when such a method is used, the thermal fusion transfer method is inferior in multi-gradation property to the sublimation dye transfer method. In addition, it is generally said that the reproducibility of the image density of a thin line or the like is inferior to the thermal fusion transfer system.

Further, in the conventional hot-melt transfer method, since a crystalline wax having a low melting point is mainly used as a binder for the ink layer, the ink easily bleeds in the image receiving sheet during thermal printing, and the resolution is low. Is one factor that tends to decrease. Another problem is that the fixing strength of the transferred image tends to be insufficient. Furthermore, crystalline waxes have the disadvantage that it is difficult to obtain a transparent image due to light scattering of the crystalline phase. This is not a problem for forming black images such as documents and line drawings, but color images,
In particular, when forming a full-color image as a multi-color overlapping image such as a yellow image, a magenta image, and a cyan image, it is difficult to obtain color reproduction of the overlapping portion, which is a major drawback.
Further, in order to obtain transparency, the ratio of the pigment to the total amount of the ink layer is also limited. As described in JP-B-63-65029, the colorant is usually 20 parts by weight or less based on 100 parts by weight of the total amount of the ink layer. It was used in. Various proposals have been made in order to improve the color reproduction of a color image of a hot-melt transfer system. For example, JP-A-61-24459
No. 2 (Japanese Examined Patent Publication No. 5-13072) discloses that 65% by weight or more of an amorphous polymer is used for the purpose of improving transparency, fixed image strength, etc. while maintaining continuous gradation (density gradation). A heat-sensitive transfer sheet having a heat-sensitive ink layer composed of an ink, a release material and a colorant (dye or pigment) has been proposed. According to this specification, when the amount of the amorphous polymer is less than 65% by weight, the transparency of the thermal transfer sheet is remarkably deteriorated, and good color reproducibility cannot be obtained. It is stated that the content of amorphous polymer needs to be 70% by weight. The colorant contained in the heat-sensitive ink layer for maintaining transparency is limited to 20% by weight, and the layer thickness of the heat-sensitive ink layer is required to obtain a practically required image density and image strength. Usually, the thickness is preferably from 1 to 20 μm, and in the examples, 3 μm is adopted as the thickness of the heat-sensitive ink layer. This suggests that the heat-sensitive transfer sheet (heat-sensitive recording material) of the invention can be used for binary recording and multi-value recording. However, according to the study of the present inventor, continuous tone recording using the thermal transfer sheet described in the above specification cannot be said to be sufficiently satisfactory in terms of continuity and stability of the density tone. . On the other hand, in a multi-valued transfer image or a binary transfer image obtained using the above heat-sensitive transfer sheet, it is difficult to obtain a sufficient density gradation, and the transparency, particularly the transparency of a full-color image, is not sufficient. Also, the edge sharpness cannot be said to be sufficiently satisfactory. On the other hand, in the thermal transfer method, multi-level recording using area gradation, that is, image formation in which recording is performed using dots having various areas, and multi-gradation full-color image is obtained by a variable dot system VDS. The method is already known. In recent years, the technical progress of thermal head printers as a means of supplying heat to thermal transfer sheets has been remarkable, and as a printing method that enables high resolution of the thermal head itself and enables multi-tone recording with area gradation. And Japanese Patent Application Laid-Open Nos. Hei 4-19163 and Hei 5-155057.
2/7/6 Preliminary Proceedings ", and a heat-concentration type system has been proposed. In recent years, a method using laser light, that is, a digital image forming method, has been developed as a method for forming a multi-tone transfer image having an area gradation using a thermal transfer sheet. In this method, an image receiving sheet is superimposed on the ink layer of the thermal transfer sheet, and a laser beam modulated by a digital signal is irradiated from the back of the thermal transfer sheet or the back of the image receiving sheet, and the light energy of the laser light is converted into heat energy. Then, a transfer image is formed on the image receiving sheet. This transfer image can be obtained by retransferring the image formed on the image receiving material onto another sheet. In this case, it is also common to provide a light-to-heat conversion layer made of a carbon black layer, a metal thin film, etc. between the ink layer and the support in order to convert the light energy of the laser light into heat energy with high efficiency. It is being done. Further, in order to improve the image quality of the transferred image, in particular, the image density uniformity and the edge sharpness, etc., the ink layer is locally peeled or separated and transferred to the image receiving sheet without using melt transfer, so-called, Ablation has also been used.

Such an area gradation type recording method is particularly suitable for recording an area gradation color image such as a color proof for simulating a printed image. , Has filed numerous applications. Then, it has become clear that it is desirable that the heat-sensitive transfer sheet to be used for multi-value recording utilizing this area gradation has the following characteristics.

That is, (1) excellent in area gradation reproducibility, (2) excellent in edge sharpness of a line or point image, and (3) each color has a predetermined image density and is homogeneous. (4) high transparency of the transferred ink layer and excellent color reproduction by overlapping color images; (5) high sensitivity; and (6) application of color proof to printing paper. The image transferred to
High similarity to the printed matter in terms of texture, glossiness of the image, etc., in particular, approximation of the reproduction of a specific phenomenon called dot gain, (7) no occurrence of image defects due to causes other than data, (8) And (4) a material that can be produced stably with little change in recording characteristics due to aging or environmental change.

For the purpose of improving the sensitivity of the photothermal conversion type recording material,
JP-A-5-262039 discloses that it is effective to make the ink layer thinner. JP-A-7-117359 and JP-A-8-104063 also disclose 30 to 70 parts by weight of a pigment as a thin film hot-melt ink layer as an ink layer capable of reproducing high density suitable for area gradation. An ink layer containing 25 to 60 parts by weight (in the latter patent, 25 to 65 parts by weight) of an amorphous resin having a point of 40 to 150 ° C. and having a thickness of 0.2 to 1.0 μm is disclosed. Japanese Patent Application Laid-Open No. H8-104063 discloses that the ink layer is applied to light-heat conversion type recording. JP-A-8-290675 discloses a heat-sensitive transfer sheet suitable for area gradation recording, in which a pigment and a softening point are 40 ° C to 150 ° C.
Each of the amorphous organic high-molecular polymers in the temperature range of
0 to 70% by weight, and 25 to 65% by weight, having an ink layer having a layer thickness in the range of 0.2 to 1.0 μm, and a constituent material of the ink layer (a single sheet) having a film thickness of 200 μm.
m, a thermal transfer sheet made of a material that does not have self-supporting properties when formed into a sheet having a size of 3 cm × 5 cm is disclosed. The layer was very brittle, and it was revealed that problems such as background contamination due to unnecessary scattering of the ink layer were likely to occur particularly in recording by laser beam irradiation.

[0013]

SUMMARY OF THE INVENTION The present inventors have invented a heat-sensitive transfer sheet particularly suitable for a multi-tone transfer method using the above-mentioned area gradation, particularly for laser light recording, and have already filed numerous patent applications. Is going.

However, it is desirable to further improve the dot sharpness represented by, for example, the edge sharpness of a transferred image, the shape of dots to be formed, the dot% at the minimum reproducible point, and the tone reproducibility. I understood. In particular, in the case of proof use, etc., the finally obtained retransfer image formed by retransfer of the transfer image formed on the image receiving sheet using the above-described heat-sensitive transfer sheet to another printing paper, It was also found that it is desirable to have a high approximation to the proof of the sample made from the squirrel manuscript. Therefore, the present invention has been made in view of the above circumstances, and its object is to be suitable for a multi-tone transfer system, and
It is an object of the present invention to provide a heat-sensitive transfer sheet having excellent properties satisfying the requirements shown in (8).
An object of the present invention is to provide a heat-sensitive transfer sheet having good dot quality and giving an image similar to a printed matter, and an image forming method using the same.

[0015]

The present invention has been attained by the following constitutions.

(1) On a support, 20 to 35% by weight of a pigment and 50 to 150 ° C. of an amorphous resin having a softening point of 50 to 150 ° C. measured by a ring and ball method (JIS K2207).
A heat-sensitive transfer sheet comprising 80% by weight, having an ink layer having a layer thickness in the range of 0.3 to 1.0 μm, and wherein the ink layer satisfies the following conditions.

As a single sheet having a thickness of 200 μm, a static tension of 20 g, a forced vibration frequency of 9.8 Hz, and a temperature rising rate of 2 ° C. /
When the sheet is stretched while being heated in minutes, the sheet breaks in the range of 60 to 120 ° C.

(2) On a support, 20 to 35% by weight of a pigment and 50 to 50% of an amorphous resin having a softening point in a temperature range of 40 to 150 ° C. measured by a ring and ball method (JIS K2207).
A heat-sensitive transfer sheet comprising 80% by weight, having an ink layer having a layer thickness in the range of 0.3 to 1.0 μm, and wherein the ink layer satisfies the following conditions.

The storage modulus G 'at 50 ° C. is 1 × 10
It is in the range of ⁸ to 1 × 10 ¹¹ dyne / cm ² .

(3) An amorphous resin having a pigment content of 20 to 35% by weight and a softening point measured by a ring and ball method (JIS K2207) in a temperature range of 40 to 150 ° C.
A heat-sensitive transfer sheet comprising 80% by weight, having an ink layer having a layer thickness in the range of 0.3 to 1.0 μm, and wherein the ink layer satisfies the following conditions.

The peak of tan δ of the ink layer is 30 to 50.
In the range of 100 ° C. and below 100 ° C., the storage elastic modulus E ′ is 1 × 10 ⁷ N / m ² or more and the loss elastic modulus E ″ is 1 × 10 ⁶ N / m ² or more.

(4) Any one of the above (1) to (3)
The image receiving sheet is superimposed on the ink layer of the thermal transfer sheet described in (1), a thermal head is pressed from the back of the thermal transfer sheet, and a transfer image composed of area gradation is transferred onto the image receiving sheet. An image forming method comprising forming a transfer image composed of area gradations.

(5) Any one of the above (1) to (3)
The image receiving sheet is superimposed on the ink layer of the thermal transfer sheet described in (1), and a laser beam modulated by a digital signal is irradiated from the back of the thermal transfer sheet to form a transfer image composed of area gradation on the image receiving sheet. An image forming method.

(6) Any one of the above (1) to (3)
The image receiving sheet is superimposed on the ink layer of the thermal transfer sheet described in (1), a laser beam modulated by a digital signal is irradiated from the back of the thermal transfer sheet, and the image receiving sheet is formed with an area gradation on the image receiving sheet by an ablation method. An image forming method comprising forming a transfer image.

That is, the present inventors have conducted intensive studies in search of a heat-sensitive transfer sheet having the above-mentioned good performance, and as a result, the present invention has been compared with the conventional sublimation dye transfer method and melt transfer method. A method that should be called a thin film transfer method, that is,
By utilizing the method of peeling and transferring the thin thermal ink layer containing a high concentration of pigment and adjusting the brittleness and elasticity of the ink layer, the image quality in area gradation reproduction, especially dot quality, The inventors have found that the tone reproducibility can be improved, and have reached the present invention.

The present invention is preferably in the following modes.

(A) 90 to 100% by weight of the amorphous resin is selected from amorphous styrene resin, styrene / acrylic copolymer and acrylic acid copolymer.

(B) 3 to 10% by weight of the amorphous resin contained in the ink layer is an ethylene vinyl acetate copolymer.

(C) at least one glass transition point (Tg) of at least one selected from the above amorphous styrene resin, styrene / acrylic copolymer and acrylic acid-based copolymer is 30.
° C or higher.

(D) at least one of the amorphous styrene resin, styrene / acrylic copolymer and acrylic acid copolymer having a melt viscosity at 160 ° C. of 15
000 or more.

(E) The vinyl acetate component of the ethylene-vinyl acetate copolymer is at least 30% by weight.

(F) The tensile strength (ASTM D-882) of the ethylene-vinyl acetate copolymer is 4 MPa (Kg /
cm ² ) or more.

(G) Elongation (ASTM D-882) of the ethylene-vinyl acetate copolymer is 600 or more.

(H) The softening point of the ethylene-vinyl acetate copolymer is 100 ° C. or less as measured by the ring and ball method (JIS K2207) or 50 ° C. or less according to the VICAT method.

(I) The thickness of the ink layer is from 0.3 to
It is in the range of 0.8 μm.

(J) In an image forming method for forming a transfer image composed of area gradations on an image receiving sheet by irradiating a laser beam, a layer thickness of 0.1 to 1.
It has a photothermal conversion layer in the range of 0 μm.

(K) The transferred image on the image receiving sheet is
The image is re-transferred onto a separately prepared final support to form a transfer image composed of area gradations on the final support.

Hereinafter, the present invention will be described in detail.

[1] Thermal Transfer Sheet The thermal transfer sheet of the present invention can be roughly classified into three modes.

(Embodiment 1) As Embodiment 1, a support is provided on a support.
20 to 35% by weight of pigment, ring and ball method (JIS K220
7) containing 50 to 80% by weight of an amorphous resin having a softening point in a temperature range of 50 to 150 ° C. and a layer thickness of 0.3 to
A heat-sensitive transfer sheet having an ink layer in a range of 1.0 μm, and the ink layer satisfies the following conditions.

Conditions: When a single sheet having a thickness of 200 μm was stretched while being heated at a static tension of 20 g, a forced vibration frequency of 9.8 Hz, and a heating rate of 2 ° C./min, it was 60 to 1
The sheet breaks in the range of 20 ° C.

That is, the ink layer of the heat-sensitive transfer sheet of Embodiment 1 has extremely high brittleness in the temperature range in which heat transfer is performed. For this reason, by using a thermal transfer sheet having such an ink layer, the transfer image has good dot omission and a very sharp dot shape. The heat-sensitive transfer sheet of this embodiment 1 is advantageously used for forming a multi-tone image (especially a full-color image) by the heat-sensitive transfer, particularly by the area gradation, but it can also be used for binary recording. Of course. Further, the film thickness is 200 μm, 3c
In the case of a single sheet of mx 5 cm, 25
It is desired to have self-supporting properties at a temperature of not more than ℃.
“Has self-supporting property at a temperature of 25 ° C. or less” means that
This means that the sheet does not break when it is hooked down at the temperature of 5 ° C. or less across the corners of the sheet having the above dimensions, and its shape is maintained. That is, the ink layer of the heat-sensitive transfer sheet of the embodiment 1 has an appropriate hardness under a temperature environment where the heat transfer temperature is not reached and the sheet is normally stored, so that careless transfer does not occur and storage stability is improved. Is also excellent.

(Embodiment 2) In addition, a pigment is coated on a support in an amount of 20 to
35% by weight, 50-80% by weight of an amorphous resin having a softening point measured by a ring and ball method (JIS K2207) in a temperature range of 40 to 150 ° C., and a layer thickness of 0.3 to 1.0 μm. A heat-sensitive transfer sheet having a certain ink layer, wherein the ink layer satisfies the following conditions.

Condition: Storage elastic modulus G 'at 50 ° C. is 1
The range is from × 10 ⁸ to 1 × 10 ¹¹ dyne / cm ² .

The heat-sensitive transfer sheet having such an ink layer is particularly suitable for recording by laser light irradiation.
It has high stability against fluctuations in light quantity and is excellent in reproducing fine lines and dots.

(Embodiment 3) Further, on a support, 20 pigments were added.
50 to 80% by weight of an amorphous resin having a softening point measured by a ring and ball method (JIS K2207) in a temperature range of 40 to 150 ° C, and a layer thickness of 0.3 to 1.0 µm. Wherein the ink layer satisfies the following conditions.

Conditions: The peak of tan δ of the ink layer is 30.
The storage elastic modulus E ′ is 1 × 10 ⁷ N / m ² or more and the loss elastic modulus E ″ is 1 × 10 ⁶ N / m ² or more in a range of from 50 ° C. to 100 ° C.

The heat-sensitive transfer sheet having such an ink layer also has high stability against fluctuations in the amount of light when recording by laser light irradiation, and is excellent in reproducing fine lines and dots.

The thermal transfer sheet of the present invention has an ink layer containing at least a pigment and an amorphous resin on a support.
The brittle or viscoelastic ink layer as described above specifically uses an amorphous styrene resin or a styrene / acrylic copolymer as an amorphous resin as a component thereof. Can be achieved.

As a support for the heat-sensitive transfer sheet, various supports which are known as a conventional support for a melt transfer or a sublimation type dye transfer sheet are used. Treated, thickness 5μm
The front and rear polyester films are particularly preferred. In the case where laser beam irradiation is used as an image forming method, a film thick enough not to hinder sheet conveyance can be used depending on the structure of the image forming apparatus.
Films having excellent dimensional stability, such as biaxially stretched polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) having a thickness of about 200 μm, are more preferably used.

As the pigment contained in the ink layer of the thermal transfer sheet of the present invention, various known pigments can be used, such as carbon black, azo type, phthalocyanine type, quinacridone type, thioindigo type, anthraquinone type and isoindolinone. And the like. These can be used in combination of two or more kinds, and a known dye may be added for adjusting the hue. In the thermal transfer sheet of the present invention, in order to obtain a predetermined concentration in a thin film,
The content of the pigment in the ink layer is 20 to 35% by weight, preferably 20 to 30% by weight. Pigment ratio is 2
If the amount is less than 0% by weight, it is difficult to obtain a desired density with the thickness of the ink layer suitable for recording, and if the pigment ratio exceeds 35% by weight, the ink layer becomes too brittle. In the present invention, it is preferable that the particle diameter of the pigment in the state of the coating liquid for the ink layer is dispersed so that the average particle diameter is smaller than the thickness of the ink layer to be formed. If the average particle size of the pigment particles is larger than the thickness of the ink layer, the smoothness of the surface of the formed ink layer tends to be significantly impaired, and the transfer of heat energy to the ink layer becomes uneven. When finer recording is performed depending on the tone, transfer unevenness is likely to occur. More preferred average particle size of the pigment dispersion particles,
It is 0.5 μm or less. From the viewpoint of color reproducibility at the time of forming a color image, it is not preferable that a large number of large particles exist.

The optimum dispersed pigment particle size in terms of hue, transparency, gloss, and color density varies slightly depending on the type of pigment.
It is preferably in the range of 0.5 to 0.5 μm. Although various methods for measuring the particle size of pigment particles are known, measurement methods using light scattering, such as a Coulter counter and MICROTRAC, are widely used. Regarding the dispersion of the pigment in the amorphous resin, adding an appropriate solvent, as conventionally known, ball mill, kneading with a dispersant or binder resin by a sand mill, etc., various used in the paint field A dispersion method is applied. A release agent or the like is added to the obtained dispersion to prepare a coating, and the coating thus prepared is applied on a support by a known method to form an ink layer. In order to obtain a preferable particle size of the pigment contained in the ink layer, the average particle size of the pigment in the liquid should be 0.
When a pigment dispersion having a particle diameter of 5 μm or less and a binder solution were mixed and adjusted, it was possible to obtain a pigment dispersion having a small particle diameter in a short time. Unexpectedly, the storage stability of the pigment dispersion was also improved, and a liquid in which aggregation of the pigment and the like hardly occurred even during long-term liquid supply in the production process could be obtained. Dispersing a part of the binder used in the ink layer as a dispersant at the time of the initial dispersion of the pigment is effective particularly when it is necessary to use a pigment that is apparently incompatible with the binder of the ink layer. Also, when two or more resins are used as the ink layer binder,
It was effective. The amorphous resin having a softening point of 40 to 150 ° C. measured by the ring and ball method (JIS K2207) contained in the ink layer of the heat-sensitive transfer sheet of the present invention, as described above,
90-100% by weight of which is amorphous styrene resin,
It is preferable to be composed of a resin selected from at least one of a styrene / acrylic copolymer and an acrylic acid-based copolymer.

Examples of the resin selected from styrene resin, styrene / acrylic copolymer and acrylic acid-based copolymer which can be used in the present invention include polystyrene resin (Hymer ST95, ST120, SB1 manufactured by Sanyo Chemical Industries, Ltd.).
30, Toporex GP50 manufactured by Mitsui Toatsu Chemicals, Inc.
0, GP565, GP535, LightTac 100PC,
Lightac 200PC, Lightac 330PC, etc.),
ABS resin (Santak UT- manufactured by Mitsui Toatsu Chemicals, Inc.)
61, UT-62, RT-22, etc.), low molecular weight styrene / acrylic copolymer (Hymer S manufactured by Sanyo Chemical Co., Ltd.)
BM100, SBM73F, etc.), partially crosslinked styrene /
Acrylic copolymer (Hymer TB1 manufactured by Sanyo Chemical Co., Ltd.)
000F), acrylic acid-based copolymer (Dianal BR60, BR64, BR9 manufactured by Mitsubishi Rayon Co., Ltd.)
0, BR101, BR105, BR108, BR113
Etc.). These can be used alone or in combination of two or more.

In the present invention, other amorphous resins which can be used in combination with the styrene resin or the styrene / acrylic copolymer include, for example, butyral resin, polyamide resin, polyethyleneimine resin, sulfonamide resin, polyester polyol resin, Styrene such as petroleum resin, vinylbenzoic acid, sodium vinylbenzenesulfonate and aminostyrene and derivatives thereof, homopolymers and copolymers of substituted products, dienes such as butadiene, isodiene and isoprene, acrylonitrile, vinyl ethers and maleic acid And maleic esters, maleic anhydride, copolymers of vinyl monomers such as cinnamic acid alone or other monomers, low molecular weight polyethylene, polypropylene, polybutylene such as polybutylene, ethylene vinyl acetate, etc. Can be mentioned . In particular, it is preferable to contain 3 to 10% by weight of an ethylene vinyl acetate copolymer.
Incidentally, specific examples of the ethylene-vinyl acetate copolymer include Evaflex EV-40W, EV-40Y, and EV-40.
LX, EV-45LX, and EV-47X (manufactured by Mitsui DuPont Polychemical Co., Ltd.) and the like. It was found that the addition of the ethylene vinyl acetate copolymer improved the abrasion resistance of the transferred image transferred to the image receiving sheet.

In the present invention, the amorphous resin is prepared by a ring and ball method (J
The softening point measured by IS K2207) is 40 to 150 ° C.
Is selected in the range. If the temperature exceeds 150 ° C., the thermal recording sensitivity tends to be low.

In the thermal transfer sheet of the present invention, the content of the amorphous resin in the ink layer is from 50 to 80% by weight. A surfactant can be added to the ink layer of the thermal transfer sheet of the present invention from the viewpoint of the stability of coating the ink layer. Examples of the activator include a cationic surfactant such as an ammonium salt having a long-chain aliphatic group and a pyridinium salt, or an anion having a long-chain aliphatic group, a nonionic surfactant, and a perfluorosurfactant. Can be mentioned. From the viewpoint of the storage stability of the ink layer, a perfluoro surfactant is preferable. The amount of the activator added is preferably about 2% by weight or less based on the solid content of the ink layer. These can be used alone or in combination of two or more.

The thickness of the ink layer of the heat-sensitive transfer sheet of the present invention is in the range of 0.3 to 1.0 μm, more preferably 0.3 to 0.8 μm. If the thickness is larger than 1.0 μm, shadow areas and fine lines are likely to be broken in area gradation reproduction, resulting in poor gradation reproduction. Also, the recording sensitivity is significantly reduced. This tendency is particularly remarkable in photothermal conversion recording using laser light. On the other hand, when the layer thickness is less than 0.3 μm, problems such as chipping of dots are likely to occur, and small dots are difficult to be properly transferred, so that highlight reproduction is insufficient and small characters are difficult to read. . When laser light recording is performed, background contamination due to scattering of the ink layer is likely to occur, and it goes without saying that it is difficult to obtain a target image density.

The ink layer of the heat-sensitive transfer sheet of the present invention is mainly composed of a pigment and an amorphous resin (organic polymer), and has a higher pigment ratio than a conventional wax-melting type. In comparison, the viscosity at the time of thermal transfer does not become as low as 102 to 103 cps, and is at least higher than 15000 cps at a temperature of 160 ° C. For this reason, an image forming method by thermal transfer using the thermal transfer sheet of the present invention is a thin film peeling development type image utilizing thermal adhesiveness to an image receiving sheet, or thermal adhesiveness between ink layers when producing a color image. It can also be formed. This, combined with the effect of thinning the ink layer, enables a wide gradation reproduction from the shadow area to the highlight area while maintaining high resolution, improves the edge sharpness, and further increases the 100% Enables image transfer. This makes it possible to reproduce, for example, the uniformity of the density of small characters of 4 points and the solid portion.

[2] Image receiving sheet The image receiving sheet used in the image forming method of the present invention includes:
Thermosoftening synthetic paper or U.S. Pat. No. 4,482,625
No. 4,766,053, and No. 4,933,
For example, an image receiving sheet technology provided with a thermal adhesive layer containing an organic high molecular polymer described in JP-A-258-258 can be used. Paper or a plastic film such as a polyester film, a polycarbonate film, a polypropylene film, a polyvinyl chloride film, or the like can be used as a support of the image receiving sheet provided with the thermal adhesive layer containing at least the organic high molecular polymer. It is also possible to use a white PET film or the like. When used for proofing, a transfer image formed on a plastic film may be retransferred to the printing paper to form an image in order to form an image on the same paper as the printing paper. in this way,
When the transfer image is most transferred to the printing paper, a method is known in which the image receiving layer that receives the transfer image is heat and pressure transferable, and the image receiving layer and the transfer image are simultaneously transferred to the printing paper by heating and pressing using a laminator or the like. Have been. A support for such an image receiving sheet of the transfer system is required to have dimensional stability particularly against heat, and is preferably a biaxially stretched PET film or PEN.
Films and the like are particularly preferred. The thickness of the support is also 50-2
Those having a thickness of about 00 μm are preferred.

[3] Image Forming Method Next, the image forming method of the present invention will be described. An image forming method of the present invention includes a heat-sensitive transfer sheet having the above-described configuration,
Further, the present invention can be implemented by using a thermal head printer or a laser beam using the image receiving sheet as described above.

First, when a thermal head printer is used, the image receiving sheet as described above is overlaid on the ink layer of the thermal transfer sheet of the present invention, and the thermal head is pressed from behind the thermal transfer sheet to print. Thereafter, the transfer is achieved by peeling the support of the transfer sheet from the image receiving sheet, whereby a transfer image by area gradation can be formed on the image receiving sheet. Further, the transferred image on the image receiving sheet obtained as described above is further superimposed on a separately prepared white support serving as a printing paper, and in this state, pressure and heat treatment are performed to obtain an area on the white support. A retransfer image composed of gradations can be formed. Specifically, the above-described image forming method can be carried out by using a heat-sensitive transfer sheet and a method known as an image forming method using a thermal head printer.

When the image forming method of the present invention is carried out by using a laser beam, it can be carried out by irradiating a laser beam imagewise instead of the thermal head in the above-mentioned image forming method. As an image forming method using a laser beam, for example, Japanese Patent Application Laid-Open No. 49-15437
Discloses a method of transferring a sublimable dye by irradiating an infrared laser beam, and Japanese Patent Application Laid-Open No. 49-17743 discloses a method of performing a fusion type thermal transfer by irradiating an infrared laser beam. It has been devised. These methods have recently been reviewed as "heat mode" image forming methods,
The present inventors have also continued to develop more suitable materials and recording methods. JP-A-5-286257, JP-A-5-318
952, JP-A-5-338358, JP-A-6-11
No. 5263, JP-A-6-255271, JP-A-7-5
No. 2538 and JP-A-7-76164 specifically disclose a method in which a light-to-heat conversion layer that absorbs laser light and converts it into heat is provided between the support and the ink layer. Various improvements for improvement have been proposed. In recent studies by the present inventors, it is preferable that the photothermal conversion layer be provided adjacent to the ink layer. The light-to-heat conversion layer basically contains a light-to-heat conversion agent for converting laser light into heat energy and a binder. The light-to-heat conversion layer preferably has a large absorption per unit film thickness and is preferably as thin as possible in terms of sensitivity, but on the other hand, if the absorption per unit film thickness is too large, the temperature reached during exposure is locally high. That is, the heat resistance of the light-to-heat conversion layer is deteriorated, so that this setting is important. The highest temperature is the light incident surface of the light-to-heat conversion layer. If the heat resistance is poor, ablation of the light-to-heat conversion layer itself occurs from this light-incident interface, and the light-to-heat conversion layer receives the image simultaneously with the ink layer. It is transferred to a sheet, hindering color reproducibility and gradation reproducibility and causing unnecessary background stains. Further, even if the light-to-heat conversion layer is not completely transferred, heat conduction to the ink layer is partially hindered by generation of a pyrolysis gas, and transfer unevenness occurs. For this reason, although it depends on the exposure illuminance, the absorbance / μm at the exposure wavelength is preferably 3.0 or less, more preferably 1.5 or less.
It is as follows. If it is less than 0.3, the efficiency becomes too poor, which is not preferable. The ratio of the photothermal conversion material to the binder suitable for achieving this absorbance is 7: 3 to 1: 9,
Preferably it is in the range of 5: 5 to 2: 8. In order to avoid generation of a dilemma of sensitivity and heat resistance, for example, a light-to-heat conversion layer having small absorption per unit film thickness can be separately provided on the recording light incident surface. That is, the light incident surface is provided with a light-to-heat conversion layer having an absorbance / μm of 1.5 or less, and a second light-to-heat conversion layer having an absorbance / μm of 1.5 or more is provided between the light-incidence surface and the ink layer. A recording medium with higher sensitivity and high heat resistance can be manufactured. The absorbance per unit film thickness of the light-to-heat conversion layer depends on whether or not the layer is in close contact with an adjacent layer or an image receiving medium, etc., but is described in Journal of Imaging Science and Technology (Journa).
l of Imaging Science and
Technology) 36, 2 (1992) 18
As described on page 0, temperatures as high as 600 ° C. or more are reached. As described above, in the case of heat mode laser recording, the temperature reached by the light-to-heat conversion layer is extremely high, and the change is short-lived. It is clear from our consideration that this is not the case. That is, specifically, the exposure is performed under reduced pressure and close contact, and the temperature is increased / decreased in a very short time even if the ultimate temperature is high.
We examined various measurement methods and the recording characteristics corresponding to the heat resistance of the binder, and by dynamic pyrolysis measurement by TGA (thermogravimetric analysis) method, the thermal decomposition conditions were as follows: 5% weight loss under nitrogen flow
0% temperature (hereinafter referred to as TGA50 pyrolysis temperature)
It has been found that by measuring the heat resistance, it is possible to judge practically appropriate heat resistance. As the binder in the light-to-heat conversion layer, a resin having a TGA50 thermal decomposition temperature of 360 ° C. or higher, that is, various functional plastics and a water-soluble binder, preferably a water-soluble binder such as polyvinyl alcohol, polyvinyl acetal, polyvinyl pyrrolidone, and nylon , Polyacrylamide, polyalkylene oxide, gelatin, casein, methylcellulose,
Hydroxyethyl cellulose, carboxymethyl cellulose, hydroxyethyl starch, gum arabic, saccharose octaacetate, ammonium alginate, sodium alginate, polyvinylamine, polyethylene oxide, polyacrylic acid, etc., among which polyvinyl alcohol, polyvinyl acetal, nylon, polyacrylamide And polyalkylene oxides are preferred. As functional plastics, polyarylate,
Polyimide, polyether imide, polyether ether ketone, polycarbonate, polysulfone, polyethersulfone, polyamide sulfone, polyphenylene ether, polyphenylene sulfide, among the resin group,
A resin having a TGA50 thermal decomposition temperature of 360 ° C. or higher can be selected. Among these, a water-soluble binder is particularly preferred.

The light-to-heat conversion material varies depending on the light source, but is preferably a material that absorbs light and efficiently converts it to heat. For example, when a semiconductor laser is used as a light source, a material having an absorption band in the near infrared is preferable. Examples of near-infrared light absorbers include organic compounds such as carbon black, cyanine-based, polymethine-based, azurenium-based, squarylium-based, thiopyrylium-based, naphthoquinone-based, and anthraquinone-based dyes, phthalocyanine-based, azo-based, and thioamide-based organic metals. Complexes and the like are preferably used.
3-139191 and 64-33547, JP-A-1
-160683, 1-280750, 1-29
No. 3342, No. 2-2074, No. 3-26593,
3-30991, 3-34891, 3-36
Nos. 093, 3-36094, 3-36095,
3-42281, 3-97589, 3-10
No. 3476 and the like. These are 1
Species or a combination of two or more can be used. In particular, when carbon black is used, the stability is high, and by setting the dispersed particle size of carbon black to 0.5 μm or less, the efficiency becomes particularly high.

To the light-to-heat conversion layer, in addition to the above substances, a surfactant for improving coating properties, a release agent for promoting interfacial separation from the ink layer, and the like can be added. Particularly, it is preferable to add an olefin compound such as a silicone compound, a fluorine compound or a wax or a long-chain alkyl compound as a release agent. Preferred silicone compounds include polydimethylsiloxane and modified products thereof, for example, polyester-modified silicone, acrylic-modified silicone, urethane-modified silicone, alkyd-modified silicone, amino-modified silicone, epoxy-modified silicone, oil and resin such as polyether-modified silicone, or This cured product is exemplified. Preferred fluorine compounds include fluorinated olefins and perfluorophosphate compounds. Preferred olefin compounds include dispersions of polyethylene and polypropylene, and long-chain alkyl compounds such as polyethyleneimine octadecyl. Of these release agents, those having poor solubility can be used after being dispersed. Also, it can be added to other polymers similarly to the silicone compound.
It is also possible to add various crosslinking agents to crosslink the binder.

The amount of the additive to be added to the light-to-heat conversion layer is 0.01 to 20 of the total amount of the light-to-heat conversion substance and the binder.
% By weight is preferred. The light-to-heat conversion layer is preferably a thin film because the heat energy generated is easily transmitted to the ink layer effectively, so that the light-to-heat conversion layer has high sensitivity.

The present inventors have found that the sensitivity is dramatically improved when the layer thickness is 1.2 μm or less. 0.5 μm
If it is less than 3, the amount of the light-to-heat conversion material added to the binder for effective heat conversion increases, and the light-to-heat conversion layer as a whole becomes brittle, which tends to cause unnecessary transfer of the light-to-heat conversion layer itself.

As another image forming method using a laser beam, for example, US Pat. No. 5,352,562,
An image forming method using so-called "ablation" disclosed in JP-A-6-219052 and the like can be used. Specifically, the image forming method described in Japanese Patent Application Laid-Open No. 6-219052 specifically discloses a photothermal conversion layer which absorbs laser light between a support and an ink layer and converts it into heat and / or a photothermal conversion layer. Using a heat-sensitive transfer sheet provided with a layer containing a heat-sensitive material (heat-sensitive release layer) that generates a gas by the action of generated heat, and an image-receiving sheet laminated on an ink layer, light-to-heat conversion by laser light irradiation Ablation occurs due to alteration, melting, etc. of the conversion layer due to the temperature rise of the layer, and the heat-sensitive release layer is partially decomposed and vaporized, the bonding force between the ink layer and the light-to-heat conversion layer is weakened, and the ink layer in that region receives an image. This utilizes the phenomenon transferred to a sheet. By using the above-mentioned ablation method, it is also possible to form a transfer image composed of area gradations on the image receiving sheet. Further, by using the printing paper as the image receiving sheet, it is possible to form a transfer image composed of area gradation on the printing paper. In the image forming method using the above method, the ink layer is melted by the heat generated by the absorption of the laser light, and the area is melt-transferred to the image receiving sheet, so that the transferred image is formed on the image receiving sheet. It can also be formed. Hereinafter, the light-to-heat conversion layer and the heat-sensitive release layer provided on the heat-sensitive transfer sheet used in the ablation method will be described. The ink layer is that of the present invention.

In general, the light-to-heat conversion layer has a basic structure composed of a material such as a dye or a pigment capable of absorbing laser light and a binder. Examples of dyes and pigments that can be used include black pigments such as carbon black, pigments of macrocyclic compounds having absorption in the visible to near infrared region such as phthalocyanine and naphthalocyanine, and lasers for high-density laser recording such as optical disks. Organic dyes such as cyanine dyes such as indolenine dyes, anthraquinone dyes, azulene dyes, and phthalocyanine dyes, and organic metal compound dyes such as dithiol nickel complexes, which can be used as the absorbing material. The selection of these materials can be selected according to the wavelength of laser light used for image formation. In order to increase the recording sensitivity, the light-to-heat conversion layer is preferably as thin as possible. Therefore, it is desirable to use a cyanine-based dye or a phthalocyanine-based dye having a large extinction coefficient in the laser light wavelength region. Although there is no particular limitation on the material of the binder of the light-to-heat conversion layer, for example,
Acrylic acid, methacrylic acid, acrylic acid ester, methacrylic acid ester or other homopolymer or copolymer of acrylic acid monomer, methylcellulose, ethylcellulose, cellulosic polymer such as cellulose acetate, polystyrene, vinyl chloride-vinyl acetate copolymer Coalescing,
Vinyl-based polymers and copolymers of vinyl compounds such as polyvinylpyrrolidone, polyvinylbutyral, and polyvinyl alcohol; condensation-based polymers such as polyester and polyamide; rubber-based thermoplastic polymers such as butadiene-styrene copolymer; epoxy compounds; And a polymer obtained by polymerizing / crosslinking a photopolymerizable or thermopolymerizable compound. When the light-to-heat conversion layer is composed of a dye or a pigment and a binder, the weight ratio of the dye or the pigment to the binder is preferably 1: 5 to 10: 1,
In particular, it is preferable to set the ratio to 1: 3 to 3: 1. If the amount of the binder is too small, the cohesive force of the light-to-heat conversion layer decreases, and when the formed image is transferred to the image receiving sheet, it is easily transferred together, which causes color mixing of the image. On the other hand, if the amount of the binder is too large, it is necessary to increase the thickness of the light-to-heat conversion layer in order to achieve a constant light absorptivity. The layer thickness of the light-to-heat conversion layer comprising the above-mentioned dye and binder is generally 0.05 to 2 μm, preferably 0.1 to 2 μm.
１1 μm. Further, the light-to-heat conversion layer preferably exhibits a light absorption of 70% or more at the wavelength of laser light used for optical recording.

The heat-sensitive release layer is a layer containing a heat-sensitive material. As such a heat-sensitive material, a compound (a polymer or a low-molecular compound) that decomposes or degrades by heat to generate a gas, or a material that absorbs or adsorbs a considerable amount of an easily vaporizable gas such as moisture as a characteristic of the material. Compounds (polymers or low molecular weight compounds) can be used. These can be used in combination. Examples of the polymer that decomposes or degrades by heat to generate a gas include self-oxidizing polymers such as nitrocellulose, chlorinated polyolefins, chlorinated rubbers, halogens such as polyvinyl chloride, polyvinyl chloride, and polyvinylidene chloride. Containing polymers, acrylic polymers such as polyisobutyl methacrylate to which volatile compounds such as water are adsorbed, cellulose esters such as ethyl cellulose to which volatile compounds such as water are adsorbed, and volatile compounds such as water being adsorbed And natural polymer compounds such as gelatin. Examples of the low molecular weight compound which decomposes or degrades by heat to generate a gas include a compound which generates a gas upon exothermic decomposition such as a diazo compound or an azide compound. Decomposition, alteration, and the like by the heat-sensitive material as described above preferably occur at 280 ° C. or lower, and particularly preferably 230 ° C. or lower. When a low-molecular compound is used as a heat-sensitive material in the heat-sensitive peeling layer, it is desirable to combine it with a binder. In such a case, the binder may be a polymer which itself decomposes or degrades by heat to generate a gas, or a normal polymer binder having no such properties.

When a heat-sensitive low molecular weight compound and a binder are used in combination, the weight ratio of the former to the latter is 0.02: 1.
３3: 1, preferably 0.05: 1 to 2: 1. The heat-sensitive release layer desirably covers the light-to-heat conversion layer over substantially the entire surface thereof, and the thickness thereof is generally preferably in the range of 0.03 to 1 μm, particularly preferably 0.05 to 0.5 μm.

[0071]

EXAMPLES The present invention will be described below in detail with reference to examples, but embodiments of the present invention are not limited thereto. In addition, "part" shown below represents "part by weight".

Example 1 (Preparation of thermal transfer sheet) Pigment / amorphous resin dispersions A to C for three types of ink layers each having the following compositions
Was prepared.

(Dispersion A for Yellow Ink Layer) Amorphous resin Styrene acrylic resin (Hymer SBM-100, manufactured by Sanyo Kasei Co., Ltd.) 3.2 parts Ethylene vinyl acetate resin (Evaflex EV-40Y, DuPont Mitsui) 0.2 parts Yellow pigment (Disazo Yellow) 1.3 parts Dispersing aid Poly ε-caprolactone 0.3 parts Solvent Methyl ethyl ketone (MEK) 20 parts (Dispersion B for magenta ink layer) Amorphous Porous resin Hymer SBM-100 3.0 parts Ethylene vinyl acetate resin Evaflex EV-40Y 0.2 parts Magenta pigment (Brilliant Carmine 6B) 1.5 parts Dispersing aid poly ε-caprolactone 0.3 parts Solvent MEK 20 parts ( Dispersion C for cyan ink layer C) Amorphous resin Hymer SBM-100 3.5 parts Ethylene vinegar Vinyl resin Evaflex EV-40Y 0.2 parts Cyan pigment (phthalocyanine blue) 1.1 parts Solvent MEK 20 parts Surfactant (Megafac F-178K) And 0.05 parts of Dainippon Ink and Chemicals, Inc.), and diluted with 5 parts of MEK and 25 parts of cyclohexanone to obtain coating solutions A to C. A 6 μm-thick polyester film (diafoil) which was release-treated on the back surface Chemical Co., Ltd.) using a wire bar coating machine, the dry film thickness is 0.47μm coating solution A,
The coating solution B is 0.52 μm, and the coating solution C is 0.42 μm.
m, so that heat-sensitive transfer sheets (yellow, magenta, cyan) were prepared.

FIG. 1 shows the particle size distribution of the yellow pigment in the coating solution used, FIG. 2 shows the particle size distribution of the magenta pigment, and FIG. 3 shows the particle size distribution of the cyan pigment.

The corresponding heat-sensitive transfer sheets were prepared in the same manner except that the amorphous resin used in the preparation of the magenta heat-sensitive transfer sheet was changed as shown in Table 1 below. In addition, the particle size of the pigment in each dispersion at the time of producing each heat-sensitive transfer sheet showed almost the same distribution. Table 1 below summarizes the amorphous resins used for each of the obtained thermal transfer sheets.

[0076]

[Table 1]

With respect to each of the heat-sensitive transfer sheets obtained above, the ink layer was evaluated by the following method.

(Preparation of Ink Layer Only) A dispersion of the above composition was applied on a stainless steel plate and dried (25 ° C., 3 days, then 80 ° C., 2 hours) to form a sheet having a dry film thickness of 200 μm. Of the ink layer alone was formed.

(Evaluation of Breaking Temperature) The sheet obtained above was set on a Rheograph Solid L-1 (manufactured by Toyo Seiki Seisaku-sho, Ltd.), and a forced vibration frequency of 9.8 Hz and a static tension of 2 were applied.
The temperature at which the sheet broke when the temperature was raised at 0 g at a temperature rising rate of 2 ° C./min was determined.

(Evaluation of Self-Supporting Property) The sheet obtained above was cut into a size of 3 cm × 5 cm, and the corner was sandwiched between tweezers and hung in a thermostat at 25 ° C. to determine whether the sheet was broken. It was confirmed.

(Preparation of Image Receiving Sheet) A coating solution for forming an image receiving layer (a coating solution for an image receiving layer) having the following composition was prepared.

-Coating solution for image receiving layer- Styrene resin (Dianal BR-113, manufactured by Mitsubishi Rayon Co., Ltd.) 13.8 parts Mat material (Sylysia 320, manufactured by Fuji Silysia Chemical Ltd.) 0.2 parts MEK 39 Part methyl isobutyl ketone 30 parts isopropyl alcohol 17 parts 100 μm thick white PET film support (T-40
0W, Diafoil Hoechst Co., Ltd.), using a wire bar coating machine to apply the coating solution for the image receiving layer.
Dried in an oven at 100 ° C. for 2 minutes. The thickness of the obtained image receiving layer was 3 μm.

(Image formation and evaluation using thermal head) Using the heat-sensitive transfer sheet and the image receiving sheet obtained above,
Image formation was performed in the following procedure. First, a cyan heat-sensitive transfer sheet and an image receiving sheet were overlapped, and printing was performed by a thermal head recording apparatus using a sub-scanning division method. This principle is 75
micro head in 50 μm direction by micro feed 3 μm × 50 μm
This is a method of performing multi-stage modulation of only area gradation by turning on and off at a pitch of μm. The polyester film of the cyan thermal transfer sheet was peeled off, and an image consisting only of area gradation was formed on the image receiving sheet. Next, a magenta heat-sensitive transfer sheet is superimposed on the image receiving sheet on which the cyan image is formed, printed in the same manner with alignment, and a magenta image is formed on the image receiving sheet by peeling off the polyester film of the transfer sheet. did. Similarly, a yellow image was formed, and a color image (full color image) consisting only of area gradation was formed on the image receiving sheet. The obtained color images were evaluated for dot quality (shape, minimum dot%), print similarity, and abrasion resistance as described below. The evaluation was performed by the following relative evaluation.

(Dot Quality) -Dot Shape- A relative comparison was made by visual evaluation of 10 persons according to the following evaluation criteria.

A: No burrs around the dots and no deformation of the dot shape were observed.
Good B: Slight burrs and slight deformation of the dot shape are observed around the dots, but good C: Burr and the deformation of the dot shapes are observed around the dots, and bothersome D: Burr around the dots And dot shape collapse, and the impression of the image is poor.

-Minimum dot% The dot% at the minimum reproducible point was evaluated by observation with a 100-power loupe.

(Printed Product Similarity) The printed material similarity of the obtained color image was evaluated by comparing it with a proof print prepared from a squirrel manuscript prepared from the same image data.

A: Very similar B: Approximate C: Difference is observed in highlight and shadow parts D: Image is not reproduced.

(Scratch Resistance) A single-color solid image of 10 cm × 3 cm was formed on the image receiving sheet only from the magenta heat-sensitive transfer sheet, and 2 cm of printing paper (Torishi Art 127 g / m ² ) was formed on the solid image. ^{The two} cut-out pieces were rubbed 5 times at a load of 200 g / cm ² and a speed of 200 mm / sec, and the scratch resistance of the image was evaluated.

A: No scratch B: Almost no scratch C: Scratched D: Completely rub off.

The solid density was measured by Macbeth densitometer D-186.
(Manufactured by Macbeth Co., Ltd.) using a filter 47BP.

The results are shown in Table 2 below.

[0093]

[Table 2]

As is clear from the results shown in Table 2, the images obtained according to the present invention have improved dot quality, and are excellent in printed matter approximation and scratch resistance.

Example 2 A heat-sensitive transfer sheet for heat mode recording was obtained by the following method.

(Preparation of Thermal Transfer Sheet for Heat Mode Recording) -Preparation of Release Sheet- A coating solution having the following composition was applied by wire bar coating.
A wire bar was applied to a 38 μm-thick PET film (manufactured by Diafoil Hoechst Co., Ltd.), dried at 80 ° C. for 2 minutes, and then heated at 60 ° C. for 80 hours to obtain a thickness of 0.3 μm.
A release sheet having a 7 μm crosslinked release layer was obtained.

(Coating solution for release layer) Polyvinyl alcohol (Gohsenol EG-30, manufactured by Nippon Synthetic Chemical Co., Ltd.) 9 parts Fluorine-based resin (Sumireze resin FP-150, manufactured by Sumitomo Chemical Co., Ltd.) 1.4 Part Amine salt (Sumirez Resin ACX-P, manufactured by Sumitomo Chemical Co., Ltd.) 0.3 part Melamine resin (Sumirez Resin 613, manufactured by Sumitomo Chemical Co., Ltd.) 2.3 parts Water 78 parts Isopropyl alcohol 8 parts (separated) Coating of ink layer on mold layer) On the release layer, an ink layer coating solution having the following formulation is applied by wire bar coating.
After drying at 100 ° C. for 2 minutes, a thermal transfer sheet (yellow, magenta, cyan, and black) was formed.

(Yellow Ink Layer Coating Solution) 14.2 parts of yellow pigment dispersion (MHI yellow # 625, 10% MEK dispersion of disazo yellow, manufactured by Mikuni Dye Co., Ltd.) Amorphous resin Styrene acrylic resin (Hymer SBM) -73F) 7.8 parts of a 40% by weight MEK solution of ethylene vinyl acetate (Evaflex EV-40Y) 1.6 parts of a 10% by weight MEK solution Surfactant (Megafac F-178K) 0.3 part MEK 8. 6 parts Cyclohexanone 67.5 parts (Magenta ink layer coating liquid) Magenta pigment dispersion 10 parts (MHI magenta # 527, 15% MEK dispersion of brilliant carmine 6B, manufactured by Mikuni Pigment Co., Ltd.) Amorphous resin Hymer SBM- 7.4 parts of 40% by weight MEK solution of 73F 7.4 parts of ethylene vinyl acetate (Evaflex EV-40Y) 10% by weight MEK solution 1.9 parts Surfactant (Megafac F-178K) 0.3 parts MEK 23.8 parts Cyclohexanone 56.6 parts (Cyan ink layer coating liquid) Cyan pigment dispersion 4.2 parts (MHI) Cyan # 454, 30% MEK dispersion of phthalocyanine blue, manufactured by Mikuni Dyestuff Co., Ltd. Amorphous resin Hymer SBM-73F 40% by weight MEK solution 8.3 parts Ethylene vinyl acetate (Evaflex EV-40Y) 10 % By weight MEK solution 2.2 parts Surfactant (Megafac F-178K) 0.3 parts MEK 18.8 parts Cyclohexanone 66.2 parts (coating solution for black ink layer) Black pigment dispersion 4.1 parts (MHI black) # 220, 35% MEK dispersion of carbon black, manufactured by Mikuni Color Co., Ltd.) Cyan pigment dispersion (MHI Blue # 45) 0.7 part) Violet pigment dispersion 1.0 part (MHI violet # 735, 10% MEK dispersion of dioxazine violet, manufactured by Mikuni Color Co., Ltd.) Amorphous resin Hymer SBM-73F 40% by weight MEK solution 9.3 parts 10% by weight MEK solution of ethylene vinyl acetate (Evaflex EV-40Y) 2.6 parts Surfactant (Surflon S-382, manufactured by Asahi Glass Co., Ltd.) 1.3 parts MEK 54.1 parts Cyclohexanone 26 .9 parts The particle size distribution of the yellow pigment in the coating solution used is shown in FIG. 4, the particle size distribution of the magenta pigment is shown in FIG. 5, the particle size distribution of the cyan pigment is shown in FIG. 6, and the particle size distribution of the black pigment mixture is shown. FIG.
Shown in

(Coating solution for light-to-heat conversion layer) A carbon black dispersion was gradually added to a light-to-heat conversion layer having the following formulation and a solution of polyvinyl alcohol in a predetermined amount of water and isopropyl alcohol to adjust the particle size while suppressing an increase in particle size. .

Polyvinyl alcohol (Gohsenol EG-30) 5.2 parts Water 69.5 parts Isopropyl alcohol 18.3 parts Carbon black dispersion (SD-9020, manufactured by Dainippon Ink and Chemicals, Inc.) 7 parts (ink layer) Coating of a light-to-heat conversion layer on the ink layer formed on the release sheet by the method described above, the light-to-heat conversion layer was coated with a wire bar to have a transmittance and absorption of 0.8 at a wavelength of 830 nm.
It was formed to become. The thickness of the coating layer was 0.58 μm.

(Formation of Intermediate Layer) Separately, a 100 μm-thick PET film (Diafoil Hoechst Co., Ltd.) was coated with an intermediate layer coating solution having the following composition by a reverse roll coater and dried to obtain a dried layer having a dry thickness of 7 μm. A layer was formed.

(Intermediate Layer Coating Solution) SEBS (Clayton G1657, manufactured by Shell Chemical Co., Ltd.) 14 parts Tackifier (Super Ester A100, Arakawa Chemical Co., Ltd.) 6 parts MEK 10 parts Toluene 80 parts The two were bonded together by roll touch in accordance with the light-to-heat conversion layer, and then the release sheet was peeled off to obtain a heat transfer sheet for heat mode recording. Subsequently, a heat-sensitive transfer sheet was prepared in the same manner except that the amorphous resin of the magenta ink layer coating liquid was changed as shown in Table 1 below. still,
The particle size of the pigment in each dispersion when preparing each thermal transfer sheet of Example 2 showed almost the same distribution as in Example 1. Table 3 below summarizes the amorphous resins used for each of the obtained thermal transfer sheets.

[0103]

[Table 3]

For each of the heat-sensitive transfer sheets obtained above, the breaking temperature and self-supporting property of the ink layer were evaluated in the same manner as in Example 1. The storage elastic modulus G 'for the ink layer of the heat-sensitive transfer sheet (yellow, magenta, cyan, and black), and t for the black sheet.
The peak of an δ, the storage elastic modulus E ′ and the loss elastic modulus E ″ in the range of 100 ° C. or less were also measured.
Shown in

(Measurement of Storage Elastic Modulus G ') MR-500
The dynamic viscoelasticity of each ink layer was measured using (manufactured by Rheology Co., Ltd.). A solid ink layer component obtained by sufficiently drying each ink layer coating solution is formed into a tablet having a predetermined shape, and the solid ink layer component is formed into a tablet.
℃ ~ 150 ℃ temperature range, frequency 1Hz, weight control 0,
The measurement was performed under the condition without distortion control.

(Measurement of tan δ peak, storage elastic modulus E ′, loss elastic modulus E ″) An ink layer was formed to a thickness of 250 μm, and was set on Rheograph Solid L-1 (manufactured by Toyo Seiki Seisaku-sho, Ltd.). , Forced vibration frequency 9.8 Hz, static tension 2
The temperature was measured at 0 g at a heating rate of 2 ° C./min.

[0107]

[Table 4]

(Preparation of Image Receiving Sheet) P having a thickness of 100 μm
A back coat layer having the following formulation was applied to an ET film so as to have a dry film thickness of 0.6 μm, and an acrylic latex (Yodosol AD92K, Kanebo NSC) was applied on the back surface.
(Manufactured by Co., Ltd.) was dried and applied with an applicator to a thickness of about 35 μm, followed by drying to form a cushion layer. A release layer coating solution having the following composition was applied on the cushion layer by wire bar coating and dried to form a release layer having a thickness of about 1.8 μm.

(Back Coat Layer Coating Solution) Polyvinyl Alcohol (Gohsenol EG-30) 9.4 parts Mat material (synthetic PMMA particles having an average particle size of 5.6 μm) 0.6 parts Water 90 parts (Release layer coating solution) ethyl cellulose (Ethocel 10, manufactured by Dow Chemical Co., Ltd.) 10 parts Isopropyl alcohol 85 parts MEK 5 parts On the release layer, an image receiving layer having the following formulation was applied. To obtain an image receiving sheet.

(Coating solution of image receiving layer) Acrylic acid latex (Iodozol A5805, manufactured by Kanebo NSC) 30.4 parts Mat material (MX-300, manufactured by Soken Chemical Co., Ltd.) 0.5 parts Fluorinated resin (FP) -150) 5.7 parts Water 61.5 parts Isopropyl alcohol 1.9 parts (Image formation by laser beam irradiation) The image receiving sheet produced by the above method is brought into contact with the surface of the drum provided with the suction holes on the back coat side. The heat-sensitive transfer sheet, which was cut slightly larger than the image-receiving sheet, was wound around the image-receiving layer surface with light suction and fixed, and was adhered at a reduced pressure of 200 mmHg from atmospheric pressure.
The drum was rotated, and exposure recording was performed from the back of the ink sheet with a 32ch laser diode having an oscillation wavelength of 830 nm. The exposure illuminance was 0.15 mW / cm ² , and the exposure beam diameter for one channel was 6 μm. After exposure, the heat-sensitive transfer sheet and the image-receiving sheet are released from suction by releasing the suction, and the heat-sensitive transfer sheet is removed from the image-receiving sheet. . As described above, the image receiving sheet on which the color image has been formed is printed on printing paper (Tokushi Art, 125 g /
m ² ), pressure 3 kg, roll temperature 1 on image receiving sheet side
35 ° C, roll temperature 110 ° C, roll peripheral speed 2
Heating was performed at 0 mm / sec, the support of the image receiving sheet was peeled off, and an image in which the recorded image and the image receiving layer were transferred onto printing paper was obtained. For the obtained color image, dot quality (shape, minimum dot%), solid density, and print similarity were evaluated according to the first embodiment.
Was evaluated in the same way as The results are shown in Table 5 below.

[0111]

[Table 5]

As is evident from Table 5, even when an image is formed by using a laser beam, a transfer image with good dot quality can be obtained, and a transfer image with excellent printed matter approximation can be obtained.

Example 3 (Production of Thermal Transfer Sheet for Ablate Recording) An image receiving sheet was produced, and the image receiving layer side of the image receiving sheet was superimposed on each ink layer of the thermal transfer sheet to produce respective laminates. Then, this laminate is irradiated with laser light by the following method,
A transfer image was formed on the image receiving sheet. The ink layer of the thermal transfer sheet used was the same as that of the magenta ink sheet of Example 2.

(Preparation of heat-sensitive transfer sheet) 1) Preparation of coating solution for forming photothermal conversion layer The following components were mixed with stirring with a stirrer to prepare a coating solution for forming a photothermal conversion layer.

Infrared absorbing cyanine dye 0.3 g 5% aqueous solution of polyvinyl alcohol (Poval, Type 205, manufactured by Kuraray Co., Ltd.) 6 g Isopropyl alcohol 5 g Pure water 20 g Infrared absorbing dye (IR-820, Nippon Kayaku 1.7 g Polyamic acid varnish (PAA-A, manufactured by Mitsui Toatsu Chemicals, Inc.) 13 g 1-methoxy-2-propanol 60 g MEK 88 g Surfactant (MegaFac F-177, Dainippon Ink & Chemicals, Inc.) 0.05 g

[0116]

Embedded image

2) Formation of a light-to-heat conversion layer on the surface of a support On one surface of a PET film having a thickness of 75 μm, a styrene / butadiene copolymer undercoat layer (0.5 μm thickness) and a gelatin undercoat layer (thickness (0.1 μm) in this order to produce a support. Next, after applying the above-mentioned coating solution on the undercoat layer of the support by using a rotary coater (whiter), the coated product is dried in an oven at 100 ° C. for 2 minutes, and is then coated on the support. A light-to-heat conversion layer (thickness: 0.2 μm: measured by a stylus-type film thickness meter;
4) was formed.

3) Preparation of coating solution for forming heat-sensitive release layer The following components were mixed with stirring with a stirrer to prepare a coating solution for forming a heat-sensitive release layer.

Nitrocellulose (Type HIG120, manufactured by Asahi Kasei Corporation) 1.3 g MEK 26 g Propylene glycol monomethyl ether acetate 40 g Toluene 92 g Surfactant (MegaFac-177, manufactured by Dainippon Ink and Chemicals, Inc.) 01g 4) Formation of a heat-sensitive release layer on the surface of the light-to-heat conversion layer After the above-mentioned coating solution was applied to the surface of the light-to-heat conversion layer provided on the above-mentioned support using a wheyer, the coated material was placed in an oven at 100 ° C for 2 hours. After drying for one minute, a heat-sensitive release layer (thickness: 0.1 μm: the same coating solution was applied to the flat surface of the hard sheet under the same conditions) Value measured by a meter).

5) Formation of coating solution for heat-sensitive ink layer The coating solution for the magenta ink layer of Example 2 was used.

6) Formation of an ink layer on the surface of the heat-sensitive release layer The above-mentioned coating solution was applied to the surface of the heat-sensitive release layer using a wooler, and the coated material was dried in an oven at 100 ° C for 2 minutes. Ink layer (thickness 0.3μ) on the heat-sensitive release layer
m: The same coating solution was applied to the flat surface of the hard sheet under the same conditions and dried under the same conditions to form a layer obtained by measuring with a stylus-type film thickness meter. The optical density of the obtained image forming layer was 0.7 (measured by a green filter and a Macbeth densitometer). Through the above steps, a heat-sensitive transfer sheet was obtained in which the light-to-heat conversion layer, the heat-sensitive release layer, and the magenta image forming layer were laminated on the support in this order.

(Preparation of Image Receiving Sheet) (Preparation of First Image Receiving Layer Coating Solution) The following components were mixed with stirring with a stirrer to prepare a first image receiving layer coating solution.

Polyvinyl chloride (Zeon 25, manufactured by Nippon Zeon Co., Ltd.) 9 g Surfactant (Megafac F-177P, manufactured by Dainippon Ink and Chemicals, Inc.) 0.1 g MEK 130 g Toluene 35 g Cyclohexanone 20 g Dimethylformamide 20 g (Formation of the first image receiving layer on the surface of the support)
m PET film), the above coating solution is applied using a wheyer, and the coated material is dried in an oven at 100 ° C. for 2 minutes to form a first image receiving layer (thickness) on the support. 1 μm).

(Preparation of Coating Solution for Second Image Receiving Layer) The following components were mixed with stirring with a stirrer to prepare a coating solution for the second image receiving layer.

Methyl methacrylate / ethyl acrylate / methacrylic acid copolymer (Dianal BR-77, manufactured by Mitsubishi Rayon Co., Ltd.) 17 g Alkyl acrylate / alkyl methacrylate copolymer (Dianal BR-64, manufactured by Mitsubishi Rayon Co., Ltd.) 17 g Pentaerythritol tetraacrylate (A-TMMT, manufactured by Shin-Nakamura Chemical Co., Ltd.) 22 g Surfactant (Megafac F-177P, manufactured by Dainippon Ink and Chemicals, Inc.) 0.4 g MEK 100 g Hydroquinone monomethyl ether 05 g 2,2-dimethoxy-2-phenylacetophenone 1.5 g (Formation of the second image receiving layer on the surface of the first image receiving layer) The above coating solution was coated on the surface of the first image receiving layer on the support using a wheyer. After drying, the coating is dried in an oven at 100 ° C. for 2 minutes, A second image receiving layer (26 μm thick) was formed. Through the above steps, an image receiving sheet in which two image receiving layers were laminated on a support was produced.

(Preparation of Laminate for Image Forming) After leaving the thermal transfer sheet and the image receiving sheet prepared as described above at room temperature for one day, the image receiving sheet was placed on the magenta image forming layer of the thermal transfer sheet. Were passed through a heat roller having a surface temperature of 70 ° C. and a pressure of 4.5 kg / cm ^{2 at} a speed of 200 cm / sec to integrate them to produce a laminate. The temperature at which the heat-sensitive transfer sheet and the image-receiving sheet reached each other when they passed through the heat roller was measured by a thermocouple and found to be about 50 ° C.

(Mounting of Image-forming Laminate in Image Recording Forming Apparatus) The above-obtained laminate was left at room temperature for about 10 minutes to be sufficiently cooled. Next, the laminate is wound around a rotary drum provided with a suction hole for vacuum suction, so that the image receiving sheet surface side is in contact with the drum surface,
The laminate was fixed to the drum surface by applying a vacuum to the inside of the drum.

(Image Recording on Image Forming Laminate) The drum was rotated, and the surface of the image forming laminate on the drum was irradiated with a semiconductor laser beam having a wavelength of 830 nm from the outside in the same manner as in Example 2. Image recording was performed.

(Formation of Transferred Image) The laminate on which the above laser image recording was performed was removed from the drum, and the image receiving sheet and the transfer sheet were peeled off by hand. The image was transferred from the thermal transfer sheet to the image receiving sheet at 5.0 μm.

(Formation of Retransferred Image) As described above,
The image receiving sheet on which the color image was formed was overlapped with printing paper (Tokushi Art, 125 g / m ² ), and a retransferred color image was formed on the art paper in the same manner as in Example 2.

(Evaluation of Image by Image Formation Using Laser Light) The dot quality (dot shape, dot% of minimum point) was obtained for the various retransferred color images thus obtained in the same manner as in Example 1. ) And print similarity. The obtained optical reflection densities on the monochromatic art paper were almost the same as those in Example 2. Table 6 shows the results.

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[Table 6]

As is evident from Table 6, even when image formation using laser light is performed, a transfer image with good dot quality can be obtained, and a transfer image with excellent printed matter approximation can be obtained.

[0134]

According to the present invention, there is provided a heat-sensitive transfer sheet capable of obtaining a transfer image of good dot quality even when an image is formed using a laser beam, and obtaining a transfer image having excellent closeness to printed matter. And an image forming method corresponding thereto can be provided.

[Brief description of the drawings]

FIG. 1 is a graph showing a particle size distribution of a yellow pigment.
The horizontal axis of the graph indicates the particle diameter (μm), and the vertical axis indicates the percentage of particles of each particle diameter.

FIG. 2 is a graph showing a particle size distribution of a magenta pigment.
The horizontal axis and vertical axis of the graph are the same as in FIG.

FIG. 3 is a graph showing a particle size distribution of a cyan pigment. The horizontal axis and vertical axis of the graph are the same as in FIG.

FIG. 4 is a graph showing a particle size distribution of a yellow pigment.
The horizontal axis and vertical axis of the graph are the same as in FIG.

FIG. 5 is a graph showing a particle size distribution of a magenta pigment.
The horizontal axis and vertical axis of the graph are the same as in FIG.

FIG. 6 is a graph showing a particle size distribution of a cyan pigment. The horizontal axis and vertical axis of the graph are the same as in FIG.

FIG. 7 is a graph showing a particle size distribution of a black pigment mixture. The horizontal axis and vertical axis of the graph are the same as in FIG.

Claims (11)

[Claims] (1) 20 to 35% by weight of a pigment on a support,
Softening point of 50 measured by the ring and ball method (JIS K2207)
It has an ink layer containing 50 to 80% by weight of an amorphous resin having a temperature in the range of up to 150 ° C. and a layer thickness in the range of 0.3 to 1.0 μm, and the ink layer satisfies the following conditions. A heat-sensitive transfer sheet. (A single sheet having a thickness of 200 μm, a static tension of 20 g and a forced vibration frequency of 9.8
When the sheet is stretched while heating at a rate of 2 ° C./min at a rate of 2 ° C./minute, the sheet breaks in the range of 60 to 120 ° C. ) 2. The ink layer having a thickness of 200 μm, 3 cm
The heat-sensitive transfer sheet according to claim 1, wherein when a single sheet having a size of 5 cm is used, the sheet has a self-supporting property at a temperature of 25 ° C or less. 3. On a support, 20 to 35% by weight of a pigment,
Softening point measured by the ring and ball method (JIS K2207) is 40
It has an ink layer containing 50 to 80% by weight of an amorphous resin having a temperature in the range of up to 150 ° C. and a layer thickness in the range of 0.3 to 1.0 μm, and the ink layer satisfies the following conditions. A heat-sensitive transfer sheet. (The storage modulus G ′ at 50 ° C. is in the range of 1 × 10 ⁸ to 1 × 10 ¹¹ dyne / cm ^2. ) 4. On a support, 20 to 35% by weight of a pigment,
Softening point measured by the ring and ball method (JIS K2207) is 40
It has an ink layer containing 50 to 80% by weight of an amorphous resin having a temperature in the range of up to 150 ° C. and a layer thickness in the range of 0.3 to 1.0 μm, and the ink layer satisfies the following conditions. A heat-sensitive transfer sheet. (Tanδ of ink layer
Exists in the range of 30 to 50 ° C., and in the range of 100 ° C. or lower, the storage elastic modulus E ′ is 1 × 10 ⁷ N / m ² or more and the loss elastic modulus E ″ is 1 × 10 ⁶ N / m ^2. That's it.) 5. 90 to 100% by weight of the amorphous resin
5. The heat-sensitive transfer sheet according to claim 1, wherein is selected from an amorphous styrene resin, a styrene / acrylic copolymer, and an acrylic acid-based copolymer. 6. The heat-sensitive transfer sheet according to claim 1, wherein 3 to 10% by weight of the amorphous resin is an ethylene vinyl acetate copolymer. 7. The amorphous styrene resin, styrene /
7. The heat-sensitive transfer sheet according to claim 5, wherein at least one glass transition point (Tg) selected from an acrylic copolymer and an acrylic acid-based copolymer is 30 ° C. or higher. 8. An image receiving sheet is superimposed on the ink layer of the heat-sensitive transfer sheet according to claim 1, and a thermal head is pressed from the back of the heat-sensitive transfer sheet to form an area gradation on the image receiving sheet. An image forming method comprising: transferring a transfer image composed of: and forming a transfer image composed of area gradations on the image receiving sheet. 9. An image receiving sheet is superimposed on the ink layer of the thermal transfer sheet according to any one of claims 1 to 7, and a laser beam modulated by a digital signal is irradiated from the back of the thermal transfer sheet to receive an image. An image forming method, wherein a transfer image composed of area gradations is formed on a sheet. 10. An ablation method, wherein an image receiving sheet is superimposed on the ink layer of the thermal transfer sheet according to claim 1, and a laser beam modulated by a digital signal is irradiated from the back of the thermal transfer sheet to perform ablation. An image forming method, wherein a transfer image composed of area gradations is formed on an image receiving sheet by a method. 11. The transfer image on the image receiving sheet is re-transferred onto a separately prepared final support to form a transfer image composed of area gradations on the final support. The image forming method according to any one of claims 8 to 10.