JPH09175029A - Thermal ink transfer sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal ink transfer sheet which is highly sensitive and generates a high-quality image for the use as a masking film, a printing plate or a color proof. SOLUTION: This thermal ink transfer sheet consists of a coloring material capable of absorbing a semiconductor laser beam, a light/heat converting layer containing a binder and an imaging layer provided sequentially in this order on a support. In this case, the ratio of the absorptive area strength in a wavelength range of ±30nm of a a semiconductor laser beam to be used is set to 35% or higher for the total absorptive area strength in a wavelength range of 500-900nm of the light/heat converting layer.

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 which is advantageously used in an image forming method of irradiating a laser beam to form a high resolution image. In particular, the present invention uses a laser recording from a digital image signal to perform color proof (DDCP: direct digital color proof) in a printing field, a mask image forming film,
Alternatively, it relates to a thermal transfer sheet useful for producing a printing plate or the like.

[0002]

2. Description of the Related Art In the field of graphic arts, a set of color separation films is made from a color original by a lith film, and a printing plate is printed using the film, but the main printing (actual printing work) is performed. In general, a color proof is created from a color separation film, an error is checked in a color separation process, a necessity of color correction is checked, and the like. As a material for this color proof, it is said that it is preferable to use actual printing paper because of its closeness to an actual printed matter, and it is preferable to use a pigment as a coloring material. Further, it is desired to realize high resolution that enables high reproducibility of halftone images and high process stability.
Further, there is a strong demand for a dry proofing method that does not use a developing solution.

Recent pre-printing process (prepress field)
With the spread of computerized systems in Japan, there is an increasing demand for materials and recording systems for making color proofs directly from digital signals. In such an electronic system, it is necessary to create a high-quality color proof, and it is generally necessary to reproduce a halftone dot image of 150 lines / inch or more. In order to record a high-quality proof from a digital signal, it is necessary to use a laser beam that can be modulated by the digital signal and can narrow down the recording light as a recording head. For this reason, it is necessary to develop a recording material that exhibits high recording sensitivity to laser light and high resolution capable of reproducing high-definition halftone dots.

Conventionally, as a recording material used in a transfer image forming method using laser light, a photothermal conversion layer which absorbs laser light to generate heat, a heat-melting wax and a binder are provided on a support. A heat-melt transfer sheet having an image forming layer composed of a pigment dispersed in this order in this order, or a support, a photothermal conversion layer that absorbs laser light to generate heat, and a binder dispersed in a binder. A sublimable dye transfer sheet having an image forming layer made of a sublimable dye formed in this order is known. In the image forming method using these recording materials, heat generated in the photothermal conversion layer in the region irradiated with the laser beam causes the image forming layer corresponding to the region to be melted by heat in the former case, and in the latter case, to be melted. By sublimation of the sublimable dye, the dye is transferred onto the image receiving sheet laminated on the transfer sheet, and a transfer image is formed on the image receiving sheet.

In recent years, a thermal transfer sheet in which a photothermal conversion layer containing a photothermal conversion substance, a thermal peeling layer, and an image forming layer containing a coloring material are provided in this order on a support, and an image receiving layered on the thermal transfer sheet. An image forming method using so-called "ablation" using a sheet has also been developed (JP-A-6-21).
9052 publication). In this image forming method, the heat release layer is partially decomposed by the heat generated in the photothermal conversion layer in the area irradiated with the laser beam and vaporized, so that the area between the image forming layer and the photothermal conversion layer in the area is decomposed. This is a method of utilizing a phenomenon in which the bonding force is weakened and the image forming layer in that region is transferred to the image receiving sheet laminated thereon. It is possible to use a printing original paper provided with an image receiving layer (adhesive layer) as an image receiving sheet material,
Further, there are many advantages such that images of different colors can be created and successively superimposed on the image-receiving sheet, so that a multicolor image can be easily obtained and a high-definition image can be easily obtained. . Especially color proof (DDC
P: direct digital color proof), or a method useful for creating a high-definition mask image.

The photothermal conversion layer of the thermal transfer sheet is generally composed of a binder and a photothermal conversion substance dispersed therein (a coloring material such as a dye or a pigment capable of absorbing laser light). Examples of coloring materials capable of absorbing laser light include black pigments such as carbon black, phthalocyanines, pigments of macrocyclic compounds having absorption in the visible to near infrared region such as naphthalocyanine, or cyanine dyes, anthraquinone dyes, Organic dyes such as azulene-based dyes and phthalocyanine-based dyes, and dyes such as organometallic compounds such as dithiol-nickel complexes are used. On the other hand, as laser light used for laser recording, light obtained from various light sources can be used. For example, argon laser light, helium neon laser light, gas laser light such as helium cadmium laser light, solid-state laser light such as YAG laser light, semiconductor laser light, dye laser light, and direct laser light such as excimer laser light are used. It Alternatively, light obtained by converting these laser lights into a half wavelength through a second harmonic element can also be used. Above all, a semiconductor laser is advantageously used in terms of price, output power, easiness of modulation, and the like. A laser light absorbing coloring material having a high absorption peak for such a laser wavelength is usually used. For example, as described in the above publication, a semiconductor laser often uses 830 nm, but for this wavelength, a cyanine dye (absorption peak wavelength: 830 nm) represented by the following formula
Is commonly used. Since this dye is water-soluble, a water-soluble binder such as polyvinyl alcohol is advantageously used as the binder so that a good dispersion state can be maintained in the photothermal conversion layer.

[0007]

Embedded image

[0008]

The present inventor has examined the performance of the photothermal conversion layer containing a coloring material capable of absorbing semiconductor laser light as described above. As a result, for example, when a gas laser such as an argon laser was used, there was no problem, but when a semiconductor laser is used, the semiconductor laser generally has a lasing wavelength due to variations in its manufacturing conditions and operating temperature. Therefore, it was found that the conventional transfer sheet does not necessarily achieve efficient energy conversion with respect to the semiconductor laser light used, and therefore the obtained recording sensitivity is still insufficient. Further, since the photothermal conversion layer is affected by the dispersibility of the binder and the coloring material used, its absorption spectrum is likely to be broad absorption accompanied by secondary absorption. Therefore, from this point as well, the conventional transfer sheet is sufficient. It was found that recording sensitivity was difficult to obtain.

Due to the insufficient recording sensitivity as described above, for example, when a conventional thermal transfer sheet is used for manufacturing a mask film (lith film) or a printing plate, image transfer (image transfer) of a portion corresponding to laser recording is performed. Forming layer, or the photothermal conversion layer and the image forming layer) may not be sufficiently performed,
As a result, in the case of a mask film, the contrast of the image obtained by using it may not be sufficient, and in the case of a printing plate, the density of the image (printed matter) obtained may not rise sufficiently uniformly. I realized that.

It is conceivable to increase the addition amount of the laser light absorbing coloring material in order to increase the recording sensitivity. However, in this case, the heat resistance of the light-heat converting layer itself is lowered, and the light-heat converting layer is placed on the image receiving sheet side. Defects in transfer are likely to occur.
Further, in general, the laser light absorbing color material contained in the photothermal conversion layer has a problem that during storage, it migrates to the upper image forming layer to cause color material fog. The occurrence of fogging does not cause any particular problem in the use of the mask film or printing plate as described above, but in the use of color proof, it becomes a large obstacle because it appears as color turbidity in the transferred image obtained. The addition amount is preferably small. In addition, an increase in the amount of the laser light absorbing coloring material added causes a cost increase, which is also undesirable from this point of view.

It is an object of the present invention to provide a thermal transfer sheet which has higher sensitivity and which can give an image of good quality even in applications such as mask films, printing plates and color proofs.

[0012]

According to the research of the present inventors,
By adjusting the photothermal conversion layer to have absorption characteristics with relatively little side absorption in the laser light wavelength vicinity region,
That is, by using a photothermal conversion layer such that the ratio of the absorption area intensity in the wavelength range of the wavelength of the semiconductor laser light used ± 30 nm to the total absorption area intensity in the laser wavelength range accounts for 35% or more. The present inventors have found that a highly sensitive thermal transfer sheet can be produced more than ever before, and arrived at the present invention. Therefore, when a mask film or a printing plate is manufactured using such a high-sensitivity heat transfer sheet, sufficient image transfer (image forming layer corresponding to the photothermal conversion layer in the laser irradiation region, or photothermal conversion in the laser irradiation region) is performed. Since both the layer and the image forming layer corresponding thereto are realized, the image quality defect of the image obtained by using the mask film or the printing plate produced by using the thermal transfer sheet of the present invention can be improved. Further, since highly efficient energy conversion is achieved for the semiconductor laser light used, it is possible to reduce the addition amount of the laser light absorbing coloring material, and thus when the thermal transfer sheet of the present invention is used for a color proof, It is possible to obtain a high quality image with less fogging (turbidity).

The present invention provides a thermal transfer sheet comprising a support, on which a photothermal conversion layer containing a coloring material capable of absorbing semiconductor laser light and a binder, and an image forming layer are provided in this order, in the range of 500 nm to 900 nm of the photothermal conversion layer. The ratio of the area intensity of absorption in the wavelength region of the semiconductor laser light used of ± 30 nm to the area intensity of total absorption in 3 is 3
The thermal transfer sheet is characterized by being 5% or more.

The present invention preferably has the following aspects. (1) The binder contained in the photothermal conversion layer is mainly composed of polyamic acid. (2) The layer thickness of the photothermal conversion layer is 0.05 to 2.0 μm (more preferably 0.03 to 0.8 μm, particularly 0.05).
.About.0.3 .mu.m). (3) The coloring material capable of absorbing the semiconductor laser light is represented by the following formula (I).
Is represented by

[0015]

Embedded image In formula (I), R ¹ and R ² each independently represent an alkyl group or an alkoxyalkyl group, and R ⁴ is
Represents a hydrogen atom, a halogen atom, an alkyl group or an amino group, and R ³ and R ⁵ each independently represent a hydrogen atom or an alkyl group (provided that R ³ and R ⁵ together with an adjacent carbon atom form a 5-membered ring; Or a 6-membered ring may be formed), A ¹ and A ² each independently represent an atomic group necessary for forming an aromatic ring, and X ⁻ represents an anion for maintaining charge balance. . (4) A coloring material capable of absorbing semiconductor laser light is represented by the following formula (I-
It is represented by 1).

[0016]

Embedded image

(5) The image forming layer is a layer mainly containing a thermoplastic resin, a layer mainly containing a thermoplastic resin and a pigment or a dye, or a layer mainly containing a thermoplastic resin and a sublimable dye. . (6) A heat-sensitive peeling layer is further provided between the photothermal conversion layer and the image forming layer. (7) The wavelength of the semiconductor laser light is 830 nm.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The thermal transfer sheet of the present invention will be described in detail below with reference to the accompanying drawings. The thermal transfer sheet of the present invention includes three types. That is, FIG.
On the support 11, as described in 1.
2, and a heat-melt transfer sheet (first type) having a structure in which the image forming layer 14 is laminated in this order, a photothermal conversion layer 22, a heat-sensitive peeling layer on a support 21 as shown in FIG. The layer 23 and the image forming layer 24 are laminated in this order to form a thermal transfer sheet utilizing so-called ablation (second type), and a photothermographic material on the support 31 as shown in FIG. This is a sublimable dye transfer sheet (third type) in which a conversion layer 32 and a sublimable dye-containing image forming layer 34 are laminated in this order. The support and the photothermal conversion layer featured in the present invention can be composed of the same material and the same layer constitution in any type.

The materials constituting the thermal transfer sheet of the present invention will be described below. The material for the support of the thermal transfer sheet is not particularly limited, and various support materials can be used according to the purpose. Preferred examples of such a support material include polyethylene terephthalate, polyethylene-
Examples thereof include a sheet formed of a synthetic resin material such as 2,6-naphthalate, polycarbonate, polyethylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, and styrene-acrylonitrile copolymer. In particular, biaxially stretched polyethylene terephthalate is preferable in consideration of mechanical strength and dimensional stability against heat.
When the thermal transfer sheet of the present invention is used for producing a color proof, since the image receiving sheet support is generally an opaque sheet material such as a printing paper sheet, the support of the thermal transfer sheet is a transparent synthetic material that transmits laser light. It is preferably formed from a resin material.

The support of the thermal transfer sheet may be surface-activated and / or provided with one or two or more undercoat layers in order to improve the adhesion to the photothermal conversion layer provided thereon. Is preferred. Examples of the surface activation treatment include glow discharge treatment and corona discharge treatment. It is preferable that the material of the undercoat layer has high adhesiveness to both surfaces of the support and the photothermal conversion layer, has low thermal conductivity, and has excellent heat resistance. Examples of the material of the undercoat layer include styrene, styrene-butadiene copolymer, gelatin and the like. The thickness of the undercoat layer is usually 0.01 to
It is chosen to be in the range of 2 μm. If necessary, various functional layers such as an antireflection layer may be attached to the surface of the image recording sheet on the side opposite to the side on which the light-heat converting layer is attached, or surface treatment may be performed.

The light-heat conversion layer of the heat transfer sheet of the present invention comprises 5
The ratio of the absorption area intensity in the vicinity of the wavelength of the semiconductor laser light (wavelength of the semiconductor laser light ± 30 nm) to the area intensity of total absorption represented by the absorption spectrum in the wavelength range of 00 nm to 900 nm is 35% or more. Is formed in. That is, the photothermal conversion layer according to the present invention is formed so that the absorption spectrum thereof has a characteristic that the secondary absorption is extremely small with respect to the wavelength of the semiconductor laser light. Examples of the semiconductor laser light that can be used in the present invention include 620 nm, 780 nm, 790 nm,
797.5 nm, 807.5 nm, 817.5 nm, 8
Mention may be made of those having wavelengths of 30 nm, 835 nm, 850 nm and 855 nm. In the present invention,
Particularly, it is preferable to use semiconductor laser light having a wavelength of 830 nm. In the thermal transfer sheet of the present invention, it is preferable to use a coloring material represented by the following formula (I) as a coloring material capable of absorbing semiconductor laser light.

[0022]

[Chemical 6]

The above formula (I) will be described in more detail. R ¹
Examples of the alkyl group or the alkoxyalkyl group represented by R ² and R ² include an alkyl group having 1 to 10 carbon atoms (preferably 1 to 6 carbon atoms), or an alkoxyalkyl group. These may be linear or branched. Specific examples of these include methyl, ethyl, propyl, isopropyl, n-butyl,
s-Butyl, t-butyl, isobutyl, pentyl, hexyl, 2-methoxyethyl, 2-ethoxyethyl, 2-
Propoxyethyl and 2-butoxyethyl may be mentioned. Both R ¹ and R ² are preferably methyl.

The alkyl group represented by R ³ and R ⁵ has, for example, 1 to 10 carbon atoms (preferably 1 carbon atom).
To 6) alkyl groups can be mentioned. Specific examples thereof include methyl, ethyl, propyl, isopropyl, n-butyl, s-butyl, t-butyl, and isobutyl. R ³ and R ⁵ are preferably both hydrogen atoms. R ³ and R ⁵ are R ³
It is also preferable that R ⁵ and R ⁵ are alkyl groups having 1 to 4 carbon atoms, and a 5-membered ring or 6-membered ring formed by these and an adjacent carbon atom. Examples of the 5-membered ring or 6-membered ring formed together with R ³ and R ⁵ and the carbon atom adjacent thereto are a cyclopentene ring and a cyclohexene ring.

The alkyl group represented by R ⁴ has 1 carbon atom.
An alkyl group having 10 to 10 (more preferably 1 to 4 carbon atoms) is preferable. Specifically, methyl, ethyl, propyl,
And butyl can be mentioned. Of these, methyl and ethyl are preferred. Examples of the halogen atom represented by R ⁴ include chlorine atom, bromine atom, fluorine atom and iodine atom. Particularly, a fluorine atom or a chlorine atom is preferable. R ⁴ is also preferably a hydrogen atom.

The aromatic ring formed by A ¹ and A ² may be unsubstituted or may have a substituent. Examples of such an aromatic ring include a benzene ring and a naphthalene ring. Preferable examples of the above substituent include a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group,
Examples thereof include an alkoxyalkyl group, an acyl group, an acyloxy group, an alkenyl group and an aryl group. Among these, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group, an acyloxy group and an aryl group are more preferable. Specific examples of the substituent include a fluorine atom,
Chlorine atom, iodine atom, methyl, ethyl, propyl, isopropyl, methoxy, ethoxy, propoxy, isopropoxy, 2-methoxyethyl, 2-ethoxyethyl, 2
-Butoxyethyl, acetyl, propionyl, butanoyl, acetoxy, propionyloxy, vinyl, 1-propenyl, 1-butenyl, phenyl, tolyl (-o,-
m, -p), methoxyphenyl (-o, -m, -p),
Chlorophenyl (-o, -m, -p) can be mentioned. More preferably, fluorine atom, chlorine atom, bromine atom, methyl, ethyl, methoxy, acetoxy, propionyloxy, phenyl, tolyl (-o, -m, -p),
And methoxyphenyl (-o, -m, -p).

X ⁻ represents an organic or inorganic monovalent anion. Examples of these include chlorine ion, bromine ion, iodine ion, ClO ₄ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , methylsulfate ion, ethylsulfate ion, benzenesulfonate ion, and p-toluenesulfonate ion. You can Among these, bromine ion, iodine ion, C
_{^{lO 4 -, BF 4 -,}} PF 6 - and p- toluenesulfonic acid ion.

Specific preferred examples of the coloring material represented by the above formula (I) include coloring materials represented by the following formula (I-1).

[0029]

Embedded image

As described above, the absorption characteristics of the photothermal conversion layer are easily affected by the dispersion state of the coloring material capable of absorbing the semiconductor laser light in the photothermal conversion layer. Therefore, it is preferable to use a solvent that maintains a good dispersion state without aggregation of the coloring material, and the photothermal conversion layer uses a binder showing high solubility in this solvent. It is preferable to configure. Examples of the binder material that can be used for the light-heat conversion layer include homopolymers or copolymers of acrylic acid-based monomers such as acrylic acid, methacrylic acid, acrylic acid ester, and methacrylic acid ester, methyl cellulose, ethyl cellulose, and cellulose acetate. Cellulosic polymers such as, polystyrene, vinyl chloride-vinyl acetate copolymers, polyvinylpyrrolidone, polyvinyl butyral, copolymers of vinyl polymers and vinyl compounds such as polyvinyl alcohol, polyesters, condensation polymers such as polyamides, Examples thereof include rubber-based thermoplastic polymers such as butadiene-styrene copolymer, and polymers obtained by polymerizing and crosslinking a photopolymerizable or thermopolymerizable compound such as an epoxy compound.

As a binder other than the above, polyamic acid can be mentioned. The polyamic acid is obtained by reacting a tetracarboxylic dianhydride and a diamine, and the tetracarboxylic dianhydride is preferably, for example, an aromatic tetracarboxylic dianhydride. When forming the photothermal conversion layer, the polyamic acid is N, N-dimethylacetamide (DMAc).
A commercial product dissolved in a solvent such as can be used.
When the photothermal conversion layer is formed using polyamic acid, the polyamic acid may partially react with polyimide in the drying step. In this case, the photothermal conversion layer is formed mainly with a polyamic acid partially having an imide structure.

In the light-heat conversion layer, the color material and the binder are preferably in the range of 1:20 to 2: 1 (color material: binder) in terms of solid content weight ratio, and particularly in the range of 1:10 to 2: 1. Is preferred. If the amount of the binder is too small, the cohesive force of the light-heat conversion layer is reduced, and when the formed image is transferred to the image receiving sheet, part of the light-heat conversion layer is easily transferred together, which may cause color mixing in the image. Become. Further, if the amount of the binder is too large, it is necessary to increase the layer thickness of the photothermal conversion layer in order to achieve a constant light absorption rate, which tends to cause a decrease in sensitivity.
The layer thickness of the photothermal conversion layer composed of the above color material and binder is
0.05-2.0 μm (more preferably 0.03-
It is preferably in the range of 0.8 μm, particularly 0.05 to 0.3 μm. The photothermal conversion layer has a thickness of 700 nm to 2
The maximum absorbance (optical density) in the wavelength range of 000 nm is in the range of 0.1 to 1.3 (more preferably 0.2 to 1.
It is preferably in the range 1).

The photothermal conversion layer of the thermal transfer sheet rises to an extremely high temperature when irradiated with a laser in carrying out the image forming method. Then, for example, in the case of using the ablation method, the photothermal conversion layer having a high temperature becomes a heat-sensitive peeling layer (a layer containing a heat-sensitive material that generates gas by the action of heat generated in the photothermal conversion layer) thereon. Heat is transferred, and the heat-sensitive material of the heat-sensitive peeling layer decomposes due to the heat to generate a gas or releases adhering water or the like, thereby increasing the bonding strength between the photothermal conversion layer and the image forming layer. Acts to weaken. Therefore, when an independent heat-sensitive peeling layer is provided, it is desirable that the heat resistance of the binder of the photothermal conversion layer be higher than that of the heat-sensitive material of the heat-sensitive peeling layer. That is, the thermal deformation temperature and thermal decomposition temperature of the binder of the photothermal conversion layer are preferably higher than the thermal deformation temperature and thermal decomposition temperature of the heat sensitive material of the heat sensitive release layer.

Alternatively, when the light-heat conversion layer contains a heat-sensitive material and, as a result, the light-heat conversion layer itself also serves as a heat-sensitive peeling layer, the heat-sensitive material contained in the light-heat conversion layer which has reached a high temperature is decomposed by the heat. As a result, gas is generated or adhering water or the like is released, which has the function of weakening the bonding strength between the photothermal conversion layer and the image forming layer.

As described above, the laser light irradiation weakens the bonding strength between the photothermal conversion layer and the image forming layer, and as a result, the image forming layer corresponding to the laser light irradiation region is thermally transferred as a transfer image. The image is transferred to an image receiving sheet laminated on the sheet. However, the results of the research conducted by the present inventor have revealed that the photothermal conversion layer may be transferred to the image receiving sheet together with the image forming layer depending on the material of the image receiving sheet to be used, particularly the adhesiveness of the surface for receiving the transferred image. . That is, the irradiation of the laser beam weakens the bonding strength between the support of the thermal transfer sheet and the photothermal conversion layer in the region corresponding to this, and as a result, the photothermal conversion layer in that region is together with the image forming layer above it. It was also found that it may be transferred to the image receiving sheet.
This is because the heat generated in the photothermal conversion layer is difficult to be sufficiently transmitted to the image receiving sheet laminated on the thermal transfer sheet due to the structure of the image receiving sheet, and therefore peeling between the support and the photothermal conversion layer is preferential. It is thought to occur in. In the present invention, the image forming method utilizing the above phenomenon can be advantageously used. For example, when used as a mask image forming film (mask film), the photothermal conversion layer transferred together with the image forming layer functions as a mask, and when used as a printing plate, it is advantageous as an ink-accepting surface. Because it works. The above phenomenon is likely to occur when an aluminum substrate is used as an image receiving sheet for producing a printing plate.

The light-to-heat conversion layer may contain a heat-sensitive material which generates gas by the action of heat generated in the light-to-heat conversion layer. As such a heat-sensitive material, a compound (polymer or low-molecular compound) that itself decomposes or deteriorates by heat to generate gas, or a characteristic of the material is to absorb or adsorb a considerable amount of easily vaporizable gas such as water. Compounds (polymers or low molecular weight compounds) that are used can be used. Note that they can be used in combination. Examples of the polymer that decomposes or deteriorates due to heat to generate gas include self-oxidizing polymers such as nitrocellulose, chlorinated polyolefin, chlorinated rubber, polychlorinated rubber, polyvinyl chloride, halogen such as polyvinylidene chloride. Contained polymers, easily depolymerizable polymers such as polystyrene, acrylic polymers such as polyisobutylmethacrylate that adsorbs volatile compounds such as water, cellulose esters such as ethyl cellulose that adsorbs volatile compounds such as water, water Examples thereof include natural polymer compounds such as gelatin to which volatile compounds such as are adsorbed. 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. It should be noted that, as described above, the decomposition and alteration of the heat-sensitive material due to heat,
It is preferable that it occurs at 280 ° C or lower, particularly 230 ° C.
It preferably occurs in the following.

On the photothermal conversion layer of the thermal transfer sheet (second type) of the present invention, there is provided a heat-sensitive peeling layer containing a heat-sensitive material which generates gas by the action of heat generated in the photothermal conversion layer. As such a heat-sensitive material, a compound (polymer or low-molecular compound) that itself decomposes or deteriorates by heat to generate gas, or a characteristic of the material is to absorb or adsorb a considerable amount of easily vaporizable gas such as water. Compounds (polymers or low molecular weight compounds) that are used can be used. They can also be used in combination. Note that examples of the heat-sensitive material that is introduced into the heat-sensitive release layer and that generates gas by the action of heat generated in the light-heat conversion layer are the same as those mentioned above. When a low molecular weight compound is used as the heat sensitive material in the heat sensitive release layer, it is desirable to combine it with a binder. In this case, the binder may be a polymer which itself decomposes or denatures by heat to generate a gas, or a normal polymer binder having no such property.
When the heat-sensitive low molecular weight compound and the binder are used in combination, the weight ratio of the former to the latter may be in the range of 0.02: 1 to 3: 1 and particularly 0.05: 1 to 2: 1. preferable.
It is desirable that the heat-sensitive peeling layer covers the photothermal conversion layer over substantially the entire surface thereof, and the thickness thereof is generally 0.0
It is preferably in the range of 3 to 1 μm, particularly 0.05 to 0.5 μm.

In the case of a thermal transfer sheet (second type) in which a photothermal conversion layer, a heat-sensitive peeling layer, and an image forming layer are laminated in this order on a support, the heat-sensitive peeling layer is a light-sensitive layer. The heat transmitted from the conversion layer causes decomposition, deterioration, etc., and gas is generated. Due to this decomposition or generation of gas, the heat-sensitive peeling layer partially disappears, or cohesive failure occurs in the heat-sensitive peeling layer, and the binding force between the photothermal conversion layer and the image forming layer is reduced. Therefore, depending on the behavior of the heat-sensitive peeling layer, a part of the heat-sensitive peeling layer adheres to the image forming layer,
It appears on the surface of the finally formed image and may cause color mixing of the image. Therefore, even if such transfer of the heat-sensitive peeling layer occurs, the heat-sensitive peeling layer has small coloring (that is, high transparency to visible light so that color mixture does not appear visually in the formed image. Is desirable). Specifically, the heat-sensitive release layer has a light absorption rate of 50% or less, preferably 10% or less, with respect to visible light.

In the case of the second type in the thermal transfer sheet of the present invention, an image forming layer is provided on the photothermal conversion layer via a heat-sensitive peeling layer. Alternatively, in the case of the first type or the third type, the image forming layer is directly provided on the photothermal conversion layer. The first type or the second type image forming layer is usually configured as a layer containing a coloring material for visualizing a recorded image and a thermoplastic binder as main constituent materials. When used, in the first type of image-forming layer, the coloring material is not particularly necessary and is constituted as a layer containing a thermoplastic binder as a main constituent material. On the other hand, the image forming layer of the third type is a layer mainly composed of a sublimable dye for visualizing a recorded image and a thermoplastic binder. The image forming layer of the third type will be described later.

The dye or pigment contained in the first type or second type image forming layer can be appropriately selected and used from the dyes or pigments known in the related art in the heat-melt transfer sheet. Examples of such dyes include Disperse Red 1, Disperse Yellow 3, Di
Azo dyes such as sperse Yellow 23 and Disperse Yellow 60, Disperse Violet 28, Disperse Blue 1
4, Disperse Blue 26, Disperse Red 4, Disperse R
Anthraquinone dyes such as ed60 and Disperse Yellow 13, and Disperse Yellow 54, Disperse Yello
w 61, Disperse Yellow 82 and Disperse Blue 20
And the like.

The pigments are generally classified into organic pigments and inorganic pigments. The former is particularly excellent in transparency of the coating film, and the latter is generally excellent in hiding power. When the thermal transfer sheet of the present invention is used for printing color proofing, an organic pigment that has a color tone similar to or close to that of yellow, magenta, cyan and black generally used for printing ink is preferably used. In addition, metal powder, fluorescent pigment, etc. may also be used. Examples of suitable pigments include azo pigments, phthalocyanine pigments, antriquinone pigments, dioxazine pigments, quinacridone pigments, isoindolinone pigments, and nitro pigments. In addition, if representative pigments are described separately for each hue, they are as follows.

1) Yellow pigments Hansa Yellow G, Hansa Yellow 5G, Hansa Yellow 10G, Hansa Yellow A, Pigment Yellow L,
Permanent Yellow NCG, Permanent Yellow F
GL, Permanent Yellow HR. 2) Red pigment Permanent Red 4R, Permanent Red F2R,
Permanent Red FRL, Rake Red C, Rake Red D, Pigment Scarlet 3B, Bordeaux 5B,
Alizarin Rake, Rhodamine Rake B. 3) Blue pigments Phthalocyanine blue, Victoria blue lake, and fast sky blue. 4) Black pigment Carbon black.

Examples of the thermoplastic binder for the image forming layer include the following thermoplastic polymers. Cellulose derivatives such as methyl cellulose, ethyl cellulose, and cellulose triacetate, homopolymers or copolymers of acrylic acid-based monomers such as acrylic acid, methacrylic acid, acrylic acid ester, and methacrylic acid ester, polyvinyl chloride, vinyl acetate, polyvinyl butyral , Vinyl-based polymers such as polyvinyl formal, polystyrene, styrene-based polymers such as styrene-maleic acid copolymers, rubber-based polymers such as polybutadiene and polyisoprene, polyolefins such as polyethylene and ethylene-vinyl acetate copolymers and their copolymers Combined, phenolic resin, ionomer resin. Among the above resins, those having a Tg (glass transition temperature) in the range of 30 to 120 ° C. are preferable, and for example, polyvinyl butyral and acrylic polymers are preferable. The average molecular weight of the thermoplastic polymer is preferably in the range of 5,000 to 100,000. The weight ratio of the coloring material to the thermoplastic resin binder in the melt transfer type image forming layer is 0.5: 1 to 4:
It is preferably in the range of 1.

Next, the image forming layer of the third type (sublimable dye transfer sheet) will be described in detail. The image forming layer of the third type is basically also the image forming layer of the above-mentioned first type (heat melting transfer sheet) or second type (transfer sheet by ablation method), and a sublimable dye as a coloring material. The same configuration can be used except that a dye (solid state is vaporized by heating and a transfer image is formed by diffusion movement) is used. That is, it can be configured as a layer containing the thermoplastic resin binder and the sublimable dye as main constituent materials. The sublimable dye (dye) used in the present invention is
Any of yellow dye, magenta dye, and cyan dye can be used. Examples of yellow dyes include methine dyes, quinophthalone dyes, and azo dyes. Specific examples of these include Kayaset Yellow AG, Kayaset Yellow 963, MS Yellow VP,
Mention may be made of MS Yellow VPH, MS Yellow HSO-246, Macrolex Yellow 6G, Foram Brilliant Yellow S-6GL and SYS-1. Examples of magenta dyes include anthraquinone dyes, azomethine dyes, and azo dyes, and specific examples thereof include Kayaset Red TD-FB and MS.
Magenta VP, MS Magenta HM-1450, MS Magenta HSO-147, MS Magenta HM-1450, M
S Red G, Macrolex Red Violet R, Kayaset Red 130, SMS-2, SMS-3, SM
S-4 can be mentioned. Examples of cyan dyes include naphthoquine dyes, anthraquinone dyes, and azomethine dyes, and specific examples thereof include:
Kayaset Blue 714, Kayaset Blue FR, Kayaset Blue 136, Kayaset Blue 814, Kayaset Blue 778, MS Cyan VPG, MS Cyan HM
-1238, MS Cyan HSO-144, MS Cyan H
SO-16, ceres blue, and SCM-1 can be mentioned. The weight ratio of the sublimable dye and the thermoplastic resin binder in the third type image forming layer is also preferably in the same range as that of the coloring material and the thermoplastic resin binder.

The first and second type image forming layers may further contain a plasticizer. That is, particularly when an operation of repeatedly superposing a large number of image layers (image forming layers on which images are formed) on the same image-receiving sheet image in order to create a multicolor image, the adhesion between the image layers is increased. It is preferable to add a plasticizer to the image forming layer in order to improve the image quality.
Examples of such plasticizers include phthalates such as dibutyl phthalate, di-n-octyl phthalate, di (2-ethylhexyl phthalate, dinonyl phthalate, dilauryl phthalate, butyl lauryl phthalate, butyl benzyl phthalate). Acid diesters, aliphatic dibasic acid esters such as di (2-ethylhexyl) adipate, di (2-ethylhexyl) sebacate, tricresyl phosphate, phosphate triesters such as tri (2-ethylhexyl) phosphate,
Examples include polyol polyesters such as polyethylene glycol ester and epoxy compounds such as epoxy fatty acid ester. In addition to the above-mentioned general plasticizers, polyethylene glycol dimethacrylate, 1,2,4-butanetriol trimethacrylate, trimethylolethane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dimethacrylate, etc. Acrylic acid esters such as pentaerythritol-polyacrylate are also preferably used in combination depending on the type of binder used. Two or more plasticizers may be used in combination.

The plasticizer is generally used in the image forming layer.
The weight ratio of the total amount of colorant and binder to the plasticizer is 100: 1.
˜100: 3, preferably 100: 2 to 100: 15. In addition to the above-mentioned components, a surfactant, a thickener, etc. are added to the image forming layer, if necessary. The layer thickness (dry layer thickness) of the image forming layer can be changed depending on the purpose, but generally does not exceed 10 μm, and is usually 0.1 to 2 μm (preferably 0.1 to 1.5 μm).
(μm).

Next, the image receiving sheet will be described. The image-receiving sheet is an ordinary sheet-shaped base material such as a plastic sheet, a metal sheet, a glass sheet, a paper, etc., and is usually used with one or more image-receiving layers attached to the surface thereof. Examples of plastic sheets include polyethylene terephthalate sheet, polycarbonate sheet,
A polyethylene sheet, a polyvinyl chloride sheet, a polyvinylidene chloride sheet, a polystyrene sheet, a styrene-acrylonitrile sheet, etc. can be mentioned. Further, as the paper, actual printing paper, coated paper, or the like can be used. The thickness of the base material of the image receiving sheet is usually 10 to 400.
μm, particularly 25 to 200 μm. The surface of the image receiving sheet may be subjected to surface treatment such as corona discharge treatment or glow discharge treatment in order to improve the adhesiveness with the image receiving layer or the image forming layer of the thermal transfer sheet.

The image receiving sheet has one or more image receiving layers on the surface of the image receiving sheet, as described above, in order to help the recorded portion of the image forming layer to be easily transferred and fixed by transfer and abrasion. It is preferable to provide two or more layers. The image receiving layer is a layer formed mainly of an organic high molecular polymer binder. The binder is preferably a thermoplastic resin, examples of which include acrylic acid,
Methacrylic acid, acrylic acid esters, homopolymers of acrylic monomers such as methacrylic acid esters and copolymers thereof, cellulosic polymers such as methyl cellulose, ethyl cellulose, cellulose acetate, polystyrene, polyvinylpyrrolidone, polyvinyl butyral, polyvinyl alcohol, etc. Examples thereof include homopolymers and copolymers of vinyl monomers, condensation polymers such as polyesters and polyamides, and rubber polymers such as butadiene-styrene copolymers. The binder of the image receiving layer is preferably a polymer having a glass transition temperature (Tg) of lower than 90 ° C. in order to obtain a proper adhesive force with the image forming layer. It is also preferable to use the above-mentioned plasticizer in combination in order to adjust the glass transition temperature of the image receiving layer.

When producing a color proof, a first image-receiving layer (cushion layer) and a second image-receiving layer (adhesive layer) thereon
It is preferable to use an image-receiving sheet having an image-receiving layer having a two-layer structure. Among the above thermoplastic resins, the first image-receiving layer is a high-molecular polymer having a degree of polymerization of 200 to 2000 (for example, polyvinyl chloride, a copolymer of vinyl chloride and vinyl acetate, vinyl chloride and vinyl alcohol). Copolymer,
A copolymer of vinyl chloride, vinyl acetate and maleic acid) is preferable. The reason for this is that polyvinyl chloride and vinyl chloride copolymers have almost no adhesiveness at room temperature, have a relatively low elastic modulus, and can easily follow the irregularities of the transferred image during thermal transfer. It is possible to easily control the interlayer adhesion force by the effect of the hydroxyl group or the carboxyl group, and particularly to easily control the elastic modulus by the plasticizer.

The thickness of the cushion layer is 1 μm to 50 μm.
(More preferably 5 μm to 30 μm). The reason is that when transferring the image transferred on the image-receiving sheet to the permanent support, it is necessary to make it thicker than the unevenness on the surface of the permanent support, and it is necessary to make the relief step at the portion where the four color images overlap. In order to obtain sufficient cushioning properties, it is necessary to have a thickness capable of absorbing dust, and to have sufficient cushioning properties so that image defects due to dust do not occur even if dust adheres during image formation (absorption of dust) It can be mentioned that such thickness is required.

The cushion layer is 200 kg · f / cm ²
It is preferably formed with the following elastic modulus. By reducing the elastic modulus, cushioning properties are generated in the second image receiving layer, and recording sensitivity, dot quality, and gradation reproducibility are improved. Further, even if foreign matter such as dust exists between the thermal transfer sheet and the image receiving sheet during thermal transfer recording, there is an advantage that image defects are less likely to occur because of the cushioning property of the intermediate layer. In addition, when the image transferred to the image receiving sheet is retransferred to the actual printing paper such as paper under heat and pressure,
Since the cushion layer is embedded according to the unevenness of the paper,
High adhesion to paper is obtained, and even after the second image-receiving layer is peeled off and the surface is not subjected to a special treatment such as matting, the surface gloss becomes an image similar to that of a printed matter.

When a vinyl chloride resin is used as the high molecular weight polymer, a butyl tin stabilizer or an octyl tin stabilizer generally known as a stabilizer for polyvinyl chloride and vinyl chloride copolymers, etc. It is also effective to add the above organic tin stabilizer.

The purpose of the second image-receiving layer is to be able to receive an image by thermal transfer, and when the image-receiving sheet is peeled off at the time of retransfer to a permanent support, the interlayer is peeled off between the cushion layer and the second image-receiving layer to provide a permanent support. By leaving only the thin second image-receiving layer on the image on the body, the unevenness of the permanent support allows you to obtain an image similar to the gloss of the actual printed matter without applying a special matting treatment, and also to improve the scratch resistance of the image. To improve.

The second image-receiving layer is preferably composed of polyvinyl butyral and an alkyl acrylate / acrylamide copolymer. The coating solvent used for the second image receiving layer should not dissolve or swell the resin used for the cushion layer in order to prevent the cushion layer and the second image receiving layer from being mixed with each other due to the penetration of the coating solvent into the lower layer during coating. It is preferable to use a different coating solvent. For example, when a vinyl chloride resin having a relatively good solubility in various solvents is used for the cushion layer, it is preferable to use an alcohol-based or water-based coating solvent.

The thickness of the second image receiving layer is 0.1 μm to 10 μm.
It is preferably in the range of m (more preferably 0.5 μm to 5 μm). If the film thickness is too thick, the unevenness of the surface of the permanent support will be impaired, and the glossiness will be too high and the approximation of the printed matter will tend to be reduced.

Next, an image forming method using the thermal transfer sheet of the present invention will be described. The image forming method using the thermal transfer sheet of the present invention, an image receiving sheet is laminated on the surface of the image forming layer of the thermal transfer sheet, the surface of the laminate is irradiated with a laser beam imagewise in a time series, and then an image receiving sheet and By peeling off the thermal transfer sheet, the image forming layer (or
It is carried out by obtaining an image receiving sheet to which the laser light irradiation area of both the photothermal conversion layer and the image forming layer) is transferred.
The above-mentioned laminated body can be easily obtained by superposing the image forming layer side of the thermal transfer sheet and the image receiving side (image receiving layer side) of the image receiving sheet and passing them through a pressure heating roller. In this case, the heating temperature should be 130 ° C or lower.
Particularly, it is preferably 100 ° C. or lower. The thermal transfer sheet and the image receiving sheet may be joined to each other immediately before the laser light irradiation operation, or the laminated body may be formed in advance before the laser light irradiation operation. The laser light irradiation operation is usually performed by vacuuming the image receiving sheet side of the image forming laminate on the surface of the recording drum (a rotary drum having a vacuum forming mechanism inside and a large number of minute openings on the surface). It is carried out by a method of bringing them into close contact with each other and irradiating laser light from the outside, that is, from the side of the laser image recording and transfer sheet in this state. Irradiation with laser light is scanned so as to reciprocate in the width direction of the drum, and the drum is rotated at a constant angular velocity during the irradiation operation.

In carrying out the image forming method using the thermal transfer sheet of the present invention, the laser beam is irradiated under the condition that the beam diameter on the photothermal conversion layer is in the range of 5 to 50 μm (particularly 6 to 30 μm). The scanning speed is preferably 1 m / sec or more (particularly 3 m / sec or more).

The image forming method using the thermal transfer sheet of the present invention can be used for producing a printing plate or a lith film, or for producing a color proof (either a single color image or a multicolor image).

[0059]

The present invention will be described more specifically with reference to the following Examples and Comparative Examples. [Example 1] (Preparation of thermal transfer sheet) 1) Preparation of coating liquid for forming light-to-heat conversion layer The following components were mixed with stirring with a stirrer to prepare a coating liquid for forming light-to-heat conversion layer.

Composition of coating liquid: parts by weight Infrared absorbing dye represented by the following formula (I-1) (NK-2014, manufactured by Nihon Sensitive Dye Co., Ltd.) 6.47

[0061]

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Binder 132.0 (Polyamic acid PAA-A, manufactured by Mitsui Toatsu Chemicals, Inc.) 1-Methoxy-2-propanol 525.0 Methyl ethyl ketone 885.0 Methanol 90.0 Surfactant (MegaFac F-177) Manufactured by Dainippon Ink and Chemicals, Inc. 1.65 In addition, the polyamic acid PAA-A (obtained by reacting an aromatic tetracarboxylic dianhydride and a diamine) is N, N- 25% by weight of dimethylacetamide
It is a solution.

2) Formation of a photothermal conversion layer on the surface of a support On one surface of a polyethylene terephthalate film having a thickness of 75 μm, an undercoat layer of styrene-butadiene copolymer (thickness of 0.5 μm) and a gelatin undercoat layer (0.5 μm). Thickness 0.
1 μm) was formed in this order to prepare a support. The above coating solution was applied on the undercoat layer of this support by a spin coater (whirler) to a film thickness of 0.1 μm, and the coated product was dried in an oven at 110 ° C. for 2 minutes to give the support. A photothermal conversion layer was formed on the body. The obtained photothermal conversion layer has 8
There was an absorption maximum at 10 nm, and the absorbance at a wavelength of 830 nm was measured and found to be 0.9. When the cross section of the photothermal conversion layer was observed with a scanning electron microscope, the film thickness was 0.07 μm on average.

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

Composition of coating liquid: parts by weight nitrocellulose (type HIG120, manufactured by Asahi Kasei Corporation) 1.3 methyl ethyl ketone 26 propylene glycol monomethyl ether acetate 40 toluene 92 surfactant (MegaFac F-177PF, Dainippon Ink and Chemicals, Inc.) ) Made 0.01

4) Formation of a heat-sensitive peeling layer on the surface of the light-heat converting layer: The surface of the light-heat converting layer provided on the above-mentioned support was coated with the above coating solution for 1 minute using a whiler, and then the coated product was heated to 100 ° C. In the oven for 2 minutes, and a heat-sensitive release layer (thickness 0.1 μm: the same coating solution was applied to a hard sheet flat surface under the same conditions on the support and dried under the same conditions) to obtain a layer. (Measured by a stylus type film thickness meter).

5) Preparation of Magenta Image Forming Layer Forming Coating Liquid Each of the following components was applied to a paint shaker (Toyo Seiki Co., Ltd.).
Dispersion) for 2 hours to prepare a magenta pigment dispersion mother liquor. When the obtained dispersion mother liquor was diluted with n-propyl alcohol and measured with a particle size measuring device (laser light scattering method), the particle size distribution of the pigment was such that 70% by weight or more of the particles were in the range of 180 to 300 nm. . Pigment dispersion mother liquor composition parts by weight Polyvinyl butyral 12.6 (Denka Butyral # 2000-L, manufactured by Denki Kagaku Kogyo Co., Ltd.) Coloring material (magenta pigment, Lionol Red 6B4290G, CIPigment Red 57: 1, manufactured by Toyo Ink Co., Ltd.) ) 18 Dispersion aid (Solspers S-20000, manufactured by ICI Corporation) 0.8 n-propyl alcohol 110 Glass beads 100

The following components were mixed with a stirrer under stirring to prepare a coating solution for forming an image forming layer for magenta. Composition of coating liquid Part by weight of the above pigment dispersion mother liquor 6 n-Propyl alcohol 60 Surfactant (Megafuck F-176PF, Dainippon Ink and Chemicals, Inc.) 0.01

4) Formation of Magenta Image Forming Layer on Surface of Heat-Sensitive Release Layer After coating the above-mentioned coating solution on the surface of the heat-sensitive release layer for 1 minute using a whiler, the coated product was dried in an oven at 100 ° C. for 2 minutes. After drying for a minute, a magenta image forming layer (thickness: 0.3 μm; film thickness was measured using a stylus type film thickness meter as described above) was formed on the heat-sensitive peeling layer. The absorbance of the obtained image forming layer was 0.7 (measured by a green filter and a Macbeth densitometer). Through the above steps, a thermal transfer sheet was prepared in which the photothermal conversion layer, the heat-sensitive peeling layer, and the magenta image forming layer were laminated in this order on the support.

Comparative Example 1 (Preparation of Thermal Transfer Sheet) In the same manner as in Example 1 except that the photothermal conversion layer was formed using the coating solution for forming a photothermal conversion layer having the following composition. A thermal transfer sheet was prepared in which a photothermal conversion layer, a heat-sensitive peeling layer, and a magenta image forming layer were laminated in this order on a support.

Composition of coating liquid: parts by weight Infrared absorbing dye represented by the following formula: 1.0

[0072]

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Binder (polyvinyl alcohol) (5% solution / water) 25 (PVA-205, manufactured by Kuraray Co., Ltd.) Methanol 8.0 Ion-exchanged water 20.0

The photothermal conversion layer of the above-mentioned thermal transfer sheet had an absorption maximum at 830 nm, and its absorbance was measured and found to be 1.1. The film thickness was 0.1 μm on average when measured by the same method as above.

[Comparative Example 2] (Preparation of thermal transfer sheet) In the same manner as in Example 1 except that the photothermal conversion layer was formed using the coating solution for forming a photothermal conversion layer having the following composition. A thermal transfer sheet was prepared in which a photothermal conversion layer, a heat-sensitive peeling layer, and a magenta image forming layer were laminated in this order on a support.

Composition of coating liquid: parts by weight Infrared absorbing dye represented by the following formula (IR-820B, manufactured by Nippon Kayaku Co., Ltd.) 16.5

[0077]

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Binder 132.0 (Polyamic acid PAA-A, manufactured by Mitsui Toatsu Chemicals, Inc.) 1-Methoxy-2-propanol 605.0 Methyl ethyl ketone 880.0 Surfactant (MegaFac F-177, Dainippon Ink and Chemicals, Inc.) Chemical Industry Co., Ltd.) 1.65 The polyamic acid PAA-A (obtained by reacting an aromatic tetracarboxylic dianhydride with a diamine) is N, N-dimethylacetamide 25. weight%
It is a solution. The photothermal conversion layer of the thermal transfer sheet had an absorption maximum at 835 nm, and the absorbance at a wavelength of 830 nm was measured and found to be 0.9. The film thickness was measured by the same method as described above and found to be 0.1 on average.
μm.

[Use of Thermal Transfer Sheet as Color Proof and Evaluation thereof] In the manufacturing process of each thermal transfer sheet as described above, the absorption spectrum of the photothermal conversion layer of each thermal transfer sheet was measured. For the measurement, a spectrophotometer (UV-
240, manufactured by Shimadzu Corporation. Then, from the obtained absorption (area intensity) of the total absorption spectrum in the range of 500 to 900 nm, the laser light wavelength 830
The ratio of absorption (area intensity) in the region of nm ± 30 nm was calculated. The performance of each of the obtained thermal transfer sheets was evaluated. The evaluation was performed by performing image formation (use for color proof) by laser using the image receiving sheet prepared as described below, and examining the sensitivity and fogging of the obtained transferred image. The evaluation method is as follows. (1) Sensitivity When recording at the same output in an atmosphere at room temperature, the recording line width of the obtained transferred image is measured with a microscope, and the energy (mJ / cm ² ) required to record a unit area is used. displayed. (2) Fogging For fogging, color turbidity generated in a transferred image was visually observed according to the following criteria. A: Fogging hardly occurs. B: Slight fogging occurred, but it was within the allowable range. C: Fogging occurs and is outside the allowable range (not suitable for use as a curler proof). The results are summarized in Table 1.

(Preparation of Image Receiving Sheet) 1) Preparation of First Image Receiving Layer Forming Coating Liquid The following components were mixed with stirring with a stirrer to prepare a first image receiving layer forming coating liquid.

Composition of coating liquid Polyvinyl chloride / vinyl acetate copolymer (MPR-TSL, manufactured by Nissin Chemical Co., Ltd.) 44 parts Acrylic rubber (RS-08, manufactured by Nissin Chemical Co., Ltd.) 22 parts Plasticizer ( Polycizer W20, manufactured by Dainippon Ink and Chemicals, Inc. 22 parts Dioctyl mercaptotin (KS-2000A, manufactured by Kyodo Pharmaceutical Co., Ltd.) 0.33 parts Surfactant (MegaFac F-177PF, 0.6 parts large) Nippon Ink Chemical Co., Ltd.) Methyl ethyl ketone 135 parts Toluene 11 parts N, N-dimethylformamide 0.4 parts

2) Formation of the first image-receiving layer on the surface of the support: The above coating solution was applied onto one surface of the support (polyethylene terephthalate film having a thickness of 100 μm) using a whiler, and then the coated product was heated to 100 ° C. On the support for 5 minutes in the first image-receiving layer (film thickness 2
3 μm) was formed.

3) Preparation of Second Image Receiving Layer Forming Coating Solution The following components were mixed with a stirrer under stirring to prepare a second image receiving layer forming coating solution.

Coating liquid composition Polyvinyl butyral 12.5 parts (Denka Butyral # 2000-L, manufactured by Denki Kagaku Kogyo Co., Ltd.) N, N-Dimethylacrylamide / butyl acrylate 3.2 parts Copolymer (copolymerization composition ratio: 50/50) Surfactant (Megafac F-177PF, manufactured by Dainippon Ink and Chemicals, Inc.) 0.07 parts n-propyl alcohol 164 parts 1-methoxy-2-propanol 10 parts N, N-dimethylformamide 0 4 parts 4) Second image-receiving layer formation on the surface of the first image-receiving layer After coating the above-mentioned coating solution on the surface of the first image-receiving layer on the support using a whiler, the coated product was placed in an oven at 100 ° C. And dried for 5 minutes to form a second image-receiving layer on the surface of the first image-receiving layer (film thickness 2 μm). Through the above steps, an image-receiving sheet having a two-layer image-receiving layer on the support was prepared.

(Preparation of image-forming laminate) The thermal transfer sheet and the image-receiving sheet prepared as described above were allowed to stand at room temperature for one day, and then the image-receiving sheet was imaged on the magenta image-forming layer of the thermal transfer sheet. The layer sides were overlapped, and in this state, they 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 / min to integrate them to form a laminate. The temperature reached by each of the thermal transfer sheet and the image receiving sheet when passing through the heat roller was measured by a thermocouple and was about 50 ° C. The pressure was measured through a roller at room temperature using a pressure-sensitive color-developing material (prescale) for pressure measurement manufactured by Fuji Photo Film Co., Ltd.

(Image Recording on Laminate for Image Formation) The laminate obtained above was left to stand at room temperature for about 10 minutes to be sufficiently cooled. Next, the laminated body is wound around a rotary drum provided with suction holes for vacuum suction so that the image receiving sheet surface side is in contact with the drum surface, and the inside of the drum is evacuated to form a drum. It was fixed on the surface. The above-mentioned drum is rotated, and semiconductor laser light having a wavelength of 830 nm is condensed from the outside onto the surface of the image forming laminate on the drum so as to form a spot having a diameter of 7 μm on the surface of the photothermal conversion layer. While moving in the direction perpendicular to the rotation direction (main scanning direction) (sub-scanning), laser image (image line) recording was performed on the laminate. The laser irradiation conditions are as follows. Laser power: 110 mW Main scanning speed: 10 m / sec Sub-scanning pitch (sub-scanning amount per rotation): 5 μm

(Formation of Transfer Image and Observation of Transfer Image)
When the laminated body on which the laser image recording was performed was removed from the drum and the image receiving sheet and the thermal transfer sheet were peeled off by hand, only the laser irradiation portion of the image (image line) forming layer had a recording line width of 5.0 μm. It was transferred from the transfer sheet to the image receiving sheet.

[0088]

[Table 1] Table 1 ──────────────────────────────────── 830nm for the total absorption of the photothermal conversion layer Performance evaluation Dye / binder weight ratio ± 30nm absorption ratio Sensitivity fog ───────────────────────────────────── Example 1 0.20 37.6% 170 A ───────────────────────────────────── Comparative Example 1 0.80 32.6% 170 C Comparative example 2 0.50 27.1% 170 B ───────────────────────────── ────────

From the results shown in Table 1 above, a sample having an absorption property such that the area intensity of absorption in the vicinity of the laser light wavelength (830 nm ± 30 nm) with respect to the area intensity of absorption in the total absorption spectrum is 35% or more. By providing the photothermal conversion layer according to the invention, fogging is reduced,
A good transferred image can be obtained. Further, by selecting and using such a dye capable of absorbing semiconductor laser light, it is possible to reduce the amount of the dye added to the binder while maintaining high sensitivity. That is, by using the semiconductor laser light absorbing dye represented by the formula (I), a photothermal conversion layer with less secondary absorption can be formed as compared with the conventional one, and therefore, even if added in a small amount, efficient energy conversion can be achieved. It is clear.

Example 2 (Preparation of Thermal Transfer Sheet) 1) Preparation of Coating Solution for Photothermal Conversion Layer Formation A coating solution for photothermal conversion layer formation was prepared in the same manner as in Example 1 above.

2) Formation of a photothermal conversion layer on the surface of a support: The above coating solution was applied onto one surface of a polyethylene terephthalate film having a thickness of 25 μm by using a spin coater (whirler) to form a coated product at 110 It was dried in an oven at 0 ° C. for 2 minutes to form a photothermal conversion layer on the support.
The obtained photothermal conversion layer has an absorption maximum at 810 nm,
When the absorbance at a wavelength of 830 nm was measured, it was found to be 0.
55. In addition, the film thickness can be measured by a scanning electron microscope.
When the cross section of the photothermal conversion layer was observed, the average was 0.1 μm.
Met.

3) Preparation of coating liquid for forming black image forming layer Each of the following components was applied to a paint shaker (Toyo Seiki Co., Ltd.).
Dispersion) for 2 hours to prepare a magenta pigment dispersion mother liquor. Pigment dispersion mother liquor composition parts by weight Polyvinyl butyral 12.6 (Denka Butyral # 2000-L, manufactured by Denki Kagaku Kogyo KK) Coloring material (carbon black, MA-100, 24 Mitsubishi Kasei Co., Ltd.) 18 Dispersion aid ( Sols Perth S-20000, manufactured by ICI Corporation 0.8 n-propyl alcohol 110 Glass beads 100

The following components were mixed with a stirrer with stirring to prepare a coating liquid for forming a black image forming layer. Coating liquid composition parts by weight Pigment dispersion mother liquor 20 n-Propyl alcohol 60 Surfactant (Megafuck F-177P, Dainippon Ink and Chemicals, Inc.) 0.05

4) Formation of Black Image Forming Layer on Photothermal Conversion Layer Surface The above coating solution was coated on the surface of the above photothermal conversion layer by using a whiler for 1 minute, and then the coated product was dried in an oven at 100 ° C. for 2 minutes. After drying for a minute, a black image forming layer (thickness (average) 1.1 μm: film thickness was measured using a stylus type film thickness meter in the same manner as above) was formed. The optical density of the obtained image forming layer was 3.6 (measured value by Macbeth densitometer). Through the above steps, a thermal transfer sheet was prepared in which the photothermal conversion layer and the black image forming layer were laminated in this order on the support.

[Use of Thermal Transfer Sheet as Mask Image-Forming Film and Evaluation thereof] The thermal transfer sheet obtained above was measured for the absorption spectrum of the photothermal conversion layer in the same manner as in Example 1 to obtain the total absorption spectrum. The absorption (area intensity) in the region of the semiconductor laser light wavelength of 830 nm ± 30 nm was calculated from. As a result, it was 37.6%. An image was formed by a semiconductor laser using the image-receiving sheet prepared as described below to prepare a mask image-forming film.

(Preparation of image-receiving sheet) 1) Preparation of coating solution for forming image-receiving layer The following components were mixed with stirring with a stirrer to prepare a coating solution for forming image-receiving layer. Composition of coating liquid: parts by weight methyl methacrylate / ethyl acrylate / methacrylic acid copolymer 4.0 (Dianal BR-77, manufactured by Mitsubishi Rayon Co., Ltd.) alkyl acrylate / alkyl methacrylate copolymer 4.0 (Dianal BR-64) , Mitsubishi Rayon Co., Ltd.) 2.0 (Oxylac SH-128, manufactured by Co., Ltd.) Surfactant (Megafuck F-177P, manufactured by Dainippon Ink and Chemicals, Inc.) 0.1 Methyl ethyl ketone 50 plasticizer (Polysizer W-4000, 2 manufactured by Dainippon Ink and Chemicals, Inc.)

2) Formation of Image Receiving Layer on Support Surface The above coating solution was applied onto one surface of a support (polyethylene terephthalate having a thickness of 100 μm) using a whiler, and then the coated product was placed in an oven at 100 ° C. And dried for 5 minutes to form an image receiving layer (thickness: 5 μm) on the support.

(Preparation of Mask Image-Forming Film) 1) Preparation of Laminated Body The thermal transfer sheet and the image-receiving sheet prepared as described above were allowed to stand at room temperature for one day and then placed on the magenta image-forming layer of the thermal transfer sheet. , The image receiving layer side of the image receiving sheet is overlaid, and in this state, the surface temperature is 60 ° C. and the pressure is 2 kg / cm ^2.
It was passed through a heat roller of No. 1 at a speed of 200 cm / min to integrate them, and a laminate was prepared.

2) Image recording on laminated body Using the laminated body obtained above, this was mounted on a recording drum in the same manner as described above, and semiconductor laser image recording was performed under the same conditions. Then, the laminated body after recording was removed from the drum, and the image receiving sheet and the thermal transfer sheet were peeled off by hand, and a transfer image was formed on the image receiving sheet.

(Image formation using a mask image forming film) A photosensitive material was contact-exposed to light using the obtained image receiving sheet (mask image forming film), and then developed. The developed image on the light-sensitive material reproduced halftone dots of 3 to 98%, had good contrast, and was sufficiently equipped with the performance as a mask image forming film.

Example 3 (Preparation of Thermal Transfer Sheet) Same as Example 1 except that the heat-sensitive release layer was not provided and carbon black was used instead of the magenta pigment in the image forming layer. Then, a thermal transfer sheet was prepared.

[Use of Thermal Transfer Sheet as Printing Plate and Its Evaluation] (Preparation of Printing Plate) Semiconductor laser image recording was performed using the thermal transfer sheet obtained above and the following aluminum substrate as an image receiving sheet. Aluminum substrate Grained and then anodized, a substrate obtained by removing the photosensitive layer with a developer from an untreated PS plate (trade name: SNG, manufactured by Fuji Photo Film Co., Ltd.), thickness: 0.12 mm

Recording Method The aluminum substrate was adsorbed on a rotary drum having a vacuum adsorption groove on its surface, and the periphery of the substrate was fixed with an adhesive tape. Next, prepare a thermal transfer sheet with a size that is larger on all four sides than the aluminum substrate, stack so that the image forming layer and the aluminum anodized surface are in contact, and further reduce the pressure between the substrate and the thermal transfer sheet by vacuum adsorption to ensure even contact. Let Recording was performed by rotating the drum and irradiating the semiconductor laser light modulated by the image signal from above the sheet under the following conditions. Laser: (semiconductor laser: output 110 mW, wavelength 83
0 nm) Beam diameter: 7 μm (on image forming layer surface) Recording power: 110 mW (on image forming layer surface) Drum rotation (recording) speed: 4 m / sec Sub-scanning pitch (laser beam movement in the direction perpendicular to the rotation direction): 5 μm

When the thermal transfer sheet was peeled off from the aluminum substrate after laser recording, an image was formed on the aluminum substrate corresponding to the laser irradiation portion. The obtained image reproduced 3 to 98% of halftone dots on the 175 line. The color of the dye of the photothermal conversion layer was not observed in the portion of the thermal transfer sheet corresponding to the transferred image on the image receiving sheet, and it was confirmed that the photothermal conversion layer was also transferred to the image receiving sheet side.

(Printing) When the printing plate obtained above was mounted on a general offset printing machine and printing was carried out by a general method, it was possible to print 1000 or more sheets without stains on non-image areas. confirmed. Further, the printed matter was finished with a uniform density and had good image quality.

[0106]

Since the thermal transfer sheet of the present invention is provided with the photothermal conversion layer having the absorption characteristic with a relatively small amount of secondary absorption, it has a very high sensitivity. Therefore, a squirrel film or printing plate with stable quality can be manufactured. Further, when it is used for a color proof, the addition amount of a coloring material capable of absorbing the semiconductor laser light can be reduced, so that fogging due to this coloring material can be suppressed and a transferred image with good image quality can be obtained. Further, it is possible to reduce the cost by reducing the addition amount of the coloring material.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a cross-sectional structure of one example (first type) of a thermal transfer sheet of the present invention.

FIG. 2 is a diagram schematically showing a cross-sectional structure of one example (second type) of the thermal transfer sheet of the present invention.

FIG. 3 is a diagram schematically showing a cross-sectional structure of one example (third type) of the thermal transfer sheet of the present invention.

[Explanation of symbols]

 11 Support 12 Photothermal Conversion Layer 14 Image Forming Layer 21 Support 22 Photothermal Conversion Layer 23 Thermal Release Layer 24 Image Forming Layer 31 Support 32 Photothermal Conversion Layer 34 Sublimable Dye-Containing Image Forming Layer

Claims (5)

[Claims] 1. A thermal transfer sheet comprising a support, on which a photothermal conversion layer containing a colorant capable of absorbing semiconductor laser light and a binder, and an image forming layer are provided in this order, and the entire photothermal conversion layer having a thickness of 500 nm to 900 nm is provided. Wavelength of semiconductor laser light used ± 30n with respect to absorption area intensity
A thermal transfer sheet having a ratio of absorption area intensity in a wavelength range of m of 35% or more. 2. The thermal transfer sheet according to claim 1, wherein the binder contained in the photothermal conversion layer is composed mainly of polyamic acid. 3. The layer thickness of the photothermal conversion layer is 0.05 to 2.0.
The thermal transfer sheet according to claim 1, which is in the range of μm. 4. A coloring material capable of absorbing semiconductor laser light is represented by the following formula (I): In the formula (I), R ¹ and R ² each represent an alkyl group or an alkoxyalkyl group, R ⁴ represents a hydrogen atom, a halogen atom, an alkyl group or an amino group,
R ³ and R ⁵ each represent a hydrogen atom or an alkyl group (provided that R ³ and R ⁵ together with the adjacent carbon atom may form a 5-membered ring or a 6-membered ring), A ¹ and A Each ² represents an atomic group necessary for forming an aromatic ring, and X ⁻ represents an anion for maintaining charge balance. The thermal transfer sheet according to claim 1, represented by: 5. A coloring material capable of absorbing semiconductor laser light is represented by the following formula (I-1): The thermal transfer sheet according to claim 1, represented by: