JP2001138640A - Laser heat transfer recording ink sheet and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat transfer film, in which no ununiform laser scanning develops and a stable color reproducibility is obtained even under wide range environmental temperature and humidity in a laser heat transfer recording system with high output and multi-channel laser. SOLUTION: In laser heat transfer recording ink sheet having at least a photothermal conversion layer and an ink layer, the adhesion between the ink layer and a layer adjacent to the ink layer is set to be 0.8 to 1.1 in the ratio of that under the environment of 19 deg.C and 30% RH to that under the environment of 27 deg.C and 70% RH.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer film used for a heat mode laser recording method for obtaining a high-definition image using a laser beam. In particular, the present invention relates to a thermal transfer film useful for making DDCP (Direct Digital Color Proof).

[0002]

2. Description of the Related Art In the field of graphic arts,
With the introduction of CTP (Computer-to-Plate), DDC that outputs high-definition images by laser light as a digital color proof that can obtain output equivalent to printing by directly inputting digital data
P has been proposed. Among them, the laser thermal transfer recording method using the same pigment as printing is attracting attention as a high-precision proof because it can obtain the same color tone as printing on the actual printing paper, can be calibrated, and can reproduce halftone dots Have been.

Conventionally, a film used in a laser thermal transfer recording system includes a photothermal conversion layer capable of absorbing a laser beam having an oscillation wavelength in an infrared region, and an ink layer containing a coloring material and a thermal transferable binder. Laser thermal transfer films having thereon are known.

[0004] In the heat mode laser recording system, in order to increase the output speed, a multi-beam laser and an increase in the output have been recently made. There is a demand for a transfer film that does not cause laser scanning unevenness even when using a multi-beam. As means for increasing the heat resistance of the light-to-heat conversion layer, Japanese Patent Application Laid-Open No. 8-267916 discloses a method of increasing the thermal decomposition temperature of the binder used for the light-to-heat conversion layer.

For applications used as DDCP, it is desired that stable color reproduction be obtained even at various environmental temperatures and humidity. In the laser thermal transfer method of transferring the ink layer, the entire ink layer is transferred at a certain temperature or higher, so the solid color reproduction is stable. The width sensitivity fluctuates and the dot gain fluctuates.
Also, in the multi-channel laser scanning method, it is difficult to completely flatten the beam intensity, so that the transfer energy varies in the sub-scanning direction, and the image tends to be uneven with laser scanning. .

[0006] As described above, a method of obtaining stable color reproducibility even when the laser scanning unevenness corresponding to the multi-channel beam and the environmental temperature and humidity fluctuates has not been found at present.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a laser thermal transfer recording system using a high-power multi-channel laser without uneven laser scanning and stable color reproducibility even over a wide range of environmental temperature and humidity. An object of the present invention is to provide an obtained thermal transfer film.

[0008]

According to the study of the present inventors, the adhesive force between the ink layer and the layer adjacent to the ink layer (light-to-heat conversion layer, release layer, etc.), the 0.8 mm needle of the ink layer,
By setting the fluctuations in the scratch line width at 0 g load and the breaking elongation of the ink layer in different environments within a preferable range, the thermal transfer sensitivity of the ink layer from a low temperature / low humidity environment to a high temperature / high humidity environment can be improved. It is possible to stabilize,
Even in a wide usage environment, stable color reproduction and dot gain values can be obtained. The present invention preferably has the following aspects.

(1) In a laser thermal transfer recording ink sheet having at least a photothermal conversion layer and an ink layer on a support, the adhesive strength between the ink layer and a layer adjacent to the ink layer is 19 ° C. and 30% RH. (Relative humidity) environment and 27 ℃
An ink sheet for laser thermal transfer recording having a ratio of 0.8 to 1.1 in a 70% RH environment.

(2) In a laser thermal transfer recording ink sheet having at least a light-to-heat conversion layer and an ink layer on a support, the ink layer has a scratch line width of 19 ° C./30 under a 0.8 mm needle and a load of 100 g. % RH environment and 27
An ink sheet for laser thermal transfer recording having a ratio of 0.8 to 1.2 in an environment of 70 ° C. and 70% RH.

(3) In an ink sheet for laser thermal transfer recording having at least a photothermal conversion layer and an ink layer on a support, the ink layer has a breaking elongation of 19 ° C. and 30% R
0.5% in the ratio between H environment and 27 ℃ ・ RH70% environment
1.2. An ink sheet for laser thermal transfer recording which is 1.2.

(4) In the thermal decomposition measurement of the main binder used in the light-to-heat conversion layer by the TGA method, the weight loss rate under a condition of a temperature rise rate of 10 ° C./min in a nitrogen stream is 50%.
(1), (2) or (3), wherein the ink sheet has a temperature of 360 ° C. or higher.

(5) The ink sheet for laser thermal transfer recording according to (1), (2) or (3), wherein the ink layer contains a thermoplastic resin having a softening point of 40 to 150 ° C.

(6) The ink layer of the laser thermal transfer recording ink sheet and the image receiving layer of the image receiving sheet are brought into close contact with each other, and then the ink layer is transferred to the image receiving layer by irradiating a laser beam from the back of the ink sheet. An image forming method using the laser thermal transfer recording ink sheet according to any one of (1) to (5), wherein the image forming method forms an image on the image receiving layer by peeling the ink sheet.

Hereinafter, the present invention will be described in more detail. The ink sheet for laser thermal transfer recording according to the present invention (hereinafter, also simply referred to as “ink sheet”) is a film having a light-to-heat conversion function and an ink (coloring material) transfer function. It has a light-to-heat conversion layer and an ink layer having a conversion function, but it is also possible to provide both functions to the same layer. If necessary, a cushion layer or an easily adhesive layer, a release layer, or the like may be provided between these layers and the support, and a back coat layer may be provided on the surface opposite to these layers.

As the support, any material can be used as long as it has rigidity, good dimensional stability, excellent smoothness, transmits laser light used for recording, and withstands heat during image formation.
Specifically, paper, coated paper, synthetic paper (polypropylene,
Various kinds of papers such as polystyrene or a composite material obtained by laminating them with paper), a vinyl chloride resin sheet, an ABS resin sheet, a polyethylene terephthalate (PET) film, a polybutylene terephthalate film, a polyethylene naphthalate (PEN) film, Polyacrylate film, polycarbonate (PC) film, polyetherketone film, polysulfone film, polyethersulfone film, polyetherimide film, polyimide film, polyethylene (PE) film, polypropylene (PP) film, polystyrene (PS) film, Shinji Tactic polystyrene (SPS) film, stretched nylon film, polyacetate film, polymethyl methacrylate (PMM
A) A single layer of a film or the like, or various plastic films or sheets obtained by laminating two or more layers thereof, films or sheets formed of various metals, films or sheets formed of various ceramics, further, aluminum, Examples thereof include a metal plate made of stainless steel, chromium, nickel, or the like, and a metal thin film laminated or deposited on a resin-coated paper.

These supports may be subjected to various processes such as dimensional stabilization and antistatic. Examples of the antistatic agent include cationic surfactants, anionic surfactants, nonionic surfactants, polymer antistatic agents, conductive fine particles, and “11290 Chemical Products”, Chemical Daily, 87
The compounds described on pages 5 to 876 and the like are widely used.

Further, these supports may be subjected to a conventionally known surface modification treatment. These surface modification treatments include flame radiation treatment, sulfuric acid treatment, corona discharge treatment, plasma treatment, glow discharge treatment and the like. In addition, an adhesive layer may be provided on the support so that each layer described below can be favorably applied to the support.

As the adhesive layer, conventionally known ones can be used without any particular limitation. Examples of the method for providing the adhesive layer include aqueous resin coating, solvent resin coating, aqueous latex coating, and hot melt coating. In general, it is advantageous to provide an adhesive layer at the time of producing a support from the viewpoint of cost and stability, and from this point, for example, acrylic resin, polystyrene resin, polyester resin, urethane resin, polyethylene / vinyl acetate resin However, a method of applying a latex such as a styrene-based resin is preferable, but not particularly limited thereto. Base films with such an adhesive layer are sold by various companies, and these can be suitably used.

When an image is formed by irradiating a laser beam from the ink sheet side, the support of the ink sheet is preferably transparent.

The thickness of the support of the ink sheet is preferably thinner than that of the image receiving sheet, and is generally preferably about 30 to 150 μm, and more preferably 50 to 100 μm, for ease of superposition.

Examples of the binder used for the back coat layer include gelatin, polyvinyl alcohol, methyl cellulose, nitrocellulose, acetyl cellulose, aromatic polyamide resin, silicone resin, epoxy resin, alkyd resin, phenol resin, melamine resin, fluorine resin, and polyimide. Resin, urethane resin, acrylic resin, urethane-modified silicone resin, polyethylene resin, polypropylene resin, polyester resin, Teflon resin, polyvinyl butyral resin, vinyl chloride resin, polyvinyl acetate, polycarbonate, organic boron compounds, aromatic esters, fluoride General-purpose polymers such as polyurethane and polyethersulfone can be used.

The use of a crosslinkable water-soluble binder as the binder of the back coat layer for crosslinking is effective in preventing the mat material from falling off and improving the scratch resistance of the back coat. It is also highly effective in blocking during storage.
As the crosslinking means, any one or combination of heat, actinic rays, and pressure can be employed without particular limitation depending on the characteristics of the crosslinking agent used.

In some cases, an optional adhesive layer may be provided on the side of the support on which the back coat layer is provided, in order to impart adhesiveness to the support.

It is preferable that the back coat layer contains a mat material. As the mat material preferably added, organic or inorganic fine particles can be used. Examples of the organic matting material include fine particles of PMMA, PS, PE, PP, and other radical polymerizable polymers, and fine particles of condensation polymers such as polyester and polycarbonate.

The back coat layer is preferably provided at a coverage of about 0.5 to 5 g / m ² . If the amount is less than 0.5 g / m ² , the coating property is unstable, and problems such as powder removal of the mat material are likely to occur. Also, if the coating is applied in excess of 5 g / m ² , the particle size of the suitable mat material becomes very large, and the ink layer surface is embossed by the back coat during storage,
In particular, in thermal transfer in which a thin ink layer is transferred, missing or unevenness of a recorded image tends to occur.

The mat material preferably has a number average particle size that is larger by 1 to 20 μm than the thickness of the binder alone in the back coat layer. Among the mat materials, particles having a particle size of 2 μm or more are required to be 1 mg / m ² or more, and preferably 2 to 6 μm.
00 mg / m ² . This particularly improves foreign object failure.

Further, a material having a narrow particle size distribution such that the value σ / rn (= coefficient of variation of the particle size distribution) obtained by dividing the standard deviation of the particle size distribution by the number average particle size is 0.3 or less is used. As a result, defects caused by particles having an abnormally large particle size can be improved, and desired performance can be obtained with a smaller amount of addition.
More preferably, the coefficient of variation is 0.15 or less.

In order to prevent foreign matter from adhering to the back coat layer due to frictional electrification with the transport roll during sheet supply,
It is preferable to add an antistatic agent. As antistatic agents, cationic surfactants, anionic surfactants,
In addition to nonionic surfactants, polymer antistatic agents and conductive fine particles, "11290 Chemical Products" (supra), 875-
The compounds described on page 876 and the like are widely used. As the antistatic agent that can be added, among the above substances, conductive fine particles such as metal oxides such as carbon black, zinc oxide, titanium oxide and tin oxide, and organic semiconductors are preferably used. In particular, the use of conductive fine particles is preferable because the antistatic agent does not dissociate from the back coat layer and a stable antistatic effect can be obtained regardless of the environment.

Further, in order to impart coating properties and release properties to the back coat layer, various activators, release agents such as silicone oil and fluorine-based resins can be added.
The back coat layer is the TMA of the cushion layer and the image receiving layer.
(Thermomechanical Analysis
It is particularly preferred if the softening point measured according to s) is below 70 ° C. The TMA softening point is determined by raising the temperature of a measurement object at a constant heating rate while applying a constant load, and observing the phase of the measurement object. In the present invention, the TMA softening point is defined as the temperature at which the phase of the measurement object starts to change. The measurement of the softening point by TMA is performed by using Rigaku Denki's The
This can be performed using an apparatus such as rmoflex.

Between the support and the light-to-heat conversion layer, there is provided a cushion layer for improving the adhesion between the ink sheet (recording medium) and the image receiving sheet (image receiving medium) at the time of exposure, or a support having a cushioning property. It is preferable to use The cushion layer is a layer having thermal softness or elasticity, and may be made of a material which can be sufficiently softened and deformed by heating, a material having a low elastic modulus, or a material having rubber elasticity.
The cushion layer is a layer having a cushioning property, and the elasticity or the penetration can be used as a guideline indicating the cushioning property here. For example, the elastic modulus at 25 ° C. is about 1 to 250 kg / mm ² , or JIS K253
It has been confirmed that a layer having a penetration of 0 to 1976 and having a penetration of 15 to 500, more preferably about 30 to 300 exhibits a cushioning property suitable for forming a color proof image for color proofing. Since the required degree varies depending on the intended use of the image, it may be appropriately selected.

The softening point of the cushion layer is preferably 70 ° C. or lower, more preferably 60 ° C. or lower. Although the preferable characteristics of the cushion layer cannot always be defined only by the type of the material, the characteristics of the material itself are preferable as polyolefin resin, ethylene-
Vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, polybutadiene resin, styrene-butadiene copolymer (SBR), styrene-ethylene-butene-styrene copolymer (SEBS), acrylonitrile-butadiene copolymer (NBR) , Polyisoprene resin (I
R), styrene-isoprene copolymer (SIS), acrylate copolymer, polyester resin, polyvinyl chloride resin, polyurethane resin, acrylic resin, butyl rubber,
Polynorbornene and the like can be mentioned. Among them, those having a relatively low molecular weight easily satisfy the requirements of the present invention, but are not necessarily limited in relation to the material.

The cushion layer can be provided by applying a solvent, but can also be applied and formed in the form of an aqueous dispersion such as latex or emulsion. In addition, a water-soluble resin can also be used. These resins can be used alone or in combination as necessary.

[0034] Even with materials other than those described above, favorable characteristics can be imparted to the cushion layer by adding various additives. Examples of such additives include low-melting substances such as wax, and plasticizers. Specific examples include phthalic acid ester, adipic acid ester, glycol ester, fatty acid ester, phosphoric acid ester, chlorinated paraffin, and the like. In addition, various additives described in, for example, "Practical Handbook of Additives for Plastics and Rubber" and Chemical Industries, Ltd. (issued in 1970) can be added. The amount of these additives to be added may be selected in an amount necessary for developing preferable physical properties in combination with the cushion layer material serving as a base, and is not particularly limited. It is preferably at most 5 mass%, more preferably at most 5 mass%.

The cushion layer is formed by dissolving or dispersing the above-mentioned material in a solvent or in the form of a latex, using a coating method such as a blade coater, a roll coater, a bar coater, a curtain coater or a gravure coater, or extrusion lamination by hot melt. The law can be applied.
It is also possible to use a resin layer having a void structure obtained by foaming a thermo-softening or thermoplastic resin as a special cushion layer.

The thickness of the cushion layer is preferably from 0.5 to 10 μm, more preferably from 1 to 7 μm.

The light-to-heat conversion layer is a layer having a light-to-heat conversion function. The light-to-heat conversion layer is provided between the support and the ink layer,
More preferably, it is provided between the support or the cushion layer or the easily adhesive layer and the ink layer.

As the binder in the light-to-heat conversion layer,
High Tg and high thermal conductivity resin, such as polymethyl methacrylate, polycarbonate, polystyrene, ethyl cellulose, nitrocellulose, polyvinyl alcohol,
General heat-resistant resins such as polyvinyl chloride, polyamide, polyamic acid, polyimide, polyetherimide, polysulfone, polyethersulfone, and aramid; polythiophenes, polyanilines, polyacetylenes, polyphenylenes, polyphenylene sulfides, and polypyrrole Polymer compounds consisting of the compounds and their derivatives or mixtures thereof can be used.

Further, a water-soluble polymer can also be used. The water-soluble polymer has good releasability from the ink layer,
In addition, heat resistance during laser irradiation is good, and scattering is small even with excessive heating.

From the viewpoint of heat resistance, JP-A-8-26791
No. 6, as a heat-resistant light-to-heat conversion layer binder having a heat loss rate of 50% at a temperature rising rate of 10 ° C./min in a nitrogen stream in a pyrolysis measurement by a TGA (thermogravimetric analysis) method. Temperature (described as TGA ₅₀ ) is 360 ° C
It is preferable to use the binder described above. As such a binder, a part of polyvinyl alcohol and polyamic acid among various engineering plastics have good solubility in general-purpose solvents and are suitable for coating.

By incorporating various release agents into the light-to-heat conversion layer, the releasability between the light-to-heat conversion layer and the ink layer can be increased, and the sensitivity can be improved. Examples of the release agent include silicone-based release agents (polyoxyalkylene-modified silicone oil, alcohol-modified silicone oil, etc.), fluorine-based surfactants (perfluorophosphate ester-based surfactant, etc.), and various other surfactants. Is valid.

When a photothermal conversion material is used, it depends on the light source, but it is preferable to use 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 that has an absorption band in the near infrared. Is preferred. As a near-infrared light absorber, for example, carbon black or cyanine-based, polymethine-based, azurenium-based, squarium-based,
Organic compounds such as thiopyrylium-based, naphthoquinone-based, and anthraquinone-based dyes, and phthalocyanine-based, azo-based, and thioamide-based organic metal complexes are preferably used. Specifically, JP-A-63-139191 and JP-A-64-33547
No., JP-A-1-160683 and 1-280750
Nos. 1-293342, 2-2074, 3-
No. 26593, No. 3-30991, No. 3-34891
No. 3-36093, No. 3-36094, No. 3-
No. 36095, No. 3-42281, No. 3-97589
And the compounds described in JP-A Nos. 3-103476 and 3-103476. These can be used alone or in combination of two or more.

The thickness of the photothermal conversion layer is preferably 0.05 to 3 μm, more preferably 0.1 to 1.0 μm. The content of the light-to-heat conversion substance in the light-to-heat conversion layer is usually determined so that the absorption at the wavelength of the light source used for image recording becomes 0.3 to 3.0, more preferably 0.7 to 2.5. it can. When carbon black is used as the light-to-heat conversion layer, if the thickness of the light-to-heat conversion layer exceeds 1 μm, the sensitivity tends to decrease instead of the occurrence of burning due to overheating of the colorant layer. And it changes depending on the absorbance of the light-to-heat conversion layer.

As the light-to-heat conversion layer, a vapor-deposited layer can also be used in addition to carbon black, gold, silver, aluminum, chromium, nickel, antimony, tellurium described in JP-A-52-20842. , Bismuth, selenium, and other metal black deposited layers, as well as Ib of the periodic table,
Vapor deposition of Group IIb, IIIa, IVb, Va, Vb, VIa, VIb, VIIb and VIII metal elements and alloys thereof, or alloys of these elements with Ia, IIa and IIIb elements, or mixtures thereof Particularly preferred metals are Al, Bi, Sn, In or Zn and alloys thereof, or these metals and Ia, IIa and II of the periodic table.
Alloys with Group Ib elements, or mixtures thereof, are included. Suitable metal oxides or sulfides include Al, Bi, S
n, In, Zn, Ti, Cr, Mo, W, Co, Ir,
There is a compound of Ni, Pb, Pt, Cu, Ag, Au, Zr or Te, or a mixture thereof. Further, a vapor-deposited layer of metal phthalocyanines, metal dithiolenes, and anthraquinones may also be used. The thickness of the deposited layer is preferably within 500 °.

The light-to-heat conversion substance may be the coloring material itself of the ink layer, and is not limited to the above-mentioned ones, and various substances can be used.

If the light-to-heat conversion layer has poor adhesion to the lower layer of the support, the film may peel off when the transfer material is peeled off from the image receiving sheet at the time of light irradiation or after thermal transfer. It is also possible to provide an adhesive layer between the support and the lower layer.

It is necessary to select a material for the adhesive layer such that the adhesive strength between the light-to-heat conversion layer and the adhesive layer and the lower layer of the support at the time of ink transfer is greater than the ink peel strength at the time of ink transfer. In general, conventionally known adhesives such as polyester, urethane and gelatin, and the materials mentioned for the cushion layer can be used. Further, in order to obtain the same effect, instead of providing an adhesive layer, a tackifier in the lower layer of the support,
An adhesive can also be added.

When the heat-softening property or the thermoplasticity of the adhesive layer is poor, the effect of the heat-softening property is reduced, so that the adhesive layer is preferably as thin as possible. The preferred film thickness is 0.5 μm or less, but is not limited as long as the adhesive layer can fulfill the purpose of the heat-softening layer.

The ink layer mainly comprises a coloring material and a thermoplastic binder. The ink layer is a layer that can be transferred to each layer containing a coloring material and a binder by melting or softening when heated, but it is not necessary to transfer the ink layer in a completely molten state. Examples of the coloring material include inorganic pigments (titanium dioxide, carbon black, graphite, zinc oxide, Prussian blue,
Cadmium sulfide, iron oxide and chromates of lead, zinc, barium and calcium, etc.) and organic pigments (azo,
Pigments such as thioindigo-based, anthraquinone-based, anthranthrone-based, triphenedioxazine-based pigments, vat dye pigments, phthalocyanine pigments and derivatives thereof, quinacridone pigments, and dyes (acidic dyes, direct dyes, disperse dyes, oil-soluble dyes); Metal-containing oil-soluble dyes or sublimable dyes). For example, when a color proof material is used, yellow, magenta, and cyan are respectively C.I. I. 21095 or C.I. I. 21090,
C. I. 15850: 1, C.I. I. 74160 pigments are preferably used.

The content of the coloring material in the ink layer is not particularly limited as long as it is adjusted so as to obtain a desired concentration at a desired coating film thickness, but is usually in the range of 5 to 70% by mass, preferably It is 10 to 60% by mass.

When used as DDCP, the same pigment as used in printing is selected, dispersed to the same dispersed particle size as the printing pigment, and a transparent thermoplastic binder is selected. This is preferable because reproducibility can be obtained. Japanese Patent Application Laid-Open No. Sho 62-158092 discloses that a high concentration can be obtained by adjusting the particle size of the pigment. However, in order to secure the dispersibility of the pigment and obtain good color reproduction, various dispersants are used. It is effective to use.

It is preferable to use an amorphous and transparent thermoplastic resin as a binder for the ink layer. As the thermoplastic resin, a resin having a melting point or a softening point within a range of 40 to 200 ° C is used. By imparting appropriate thermoplasticity, it is possible to perform heat-sensitive transfer to an object to be transferred during exposure and heating. In the present invention, the softening point is 40 to
It is preferable to contain a thermoplastic resin at 150 ° C.

Specifically, ethylene copolymers, polyamide resins, polyester resins, styrene resins, polyurethane resins, polyolefin resins, acrylic resins, vinyl chloride resins, cellulose resins, rosin resins, Examples thereof include a polyvinyl alcohol-based resin, a polyvinyl acetal-based resin, an ionomer resin, a petroleum-based resin, and a resin for an ink layer binder described in JP-A-6-325883.

In addition to the above thermoplastic resins, elastomers such as natural rubber, styrene butadiene rubber, isoprene rubber, chloroprene rubber, and diene copolymer;
Rosin derivatives such as ester gum, rosin maleic acid resin, rosin phenol resin, hydrogenated rosin; and high molecular compounds such as phenol resin, terpene resin, cyclopentadiene resin, and aromatic hydrocarbon resin, and waxes may also be used. it can.

Further, by using a binder having a high thermal decomposition property, an image can be formed by ablation transfer. Such binders include polymeric substances that undergo rapid acid-catalyzed partial decomposition desirably at temperatures below 200 ° C. when measured under equilibrium conditions, and specifically include nitrocellulose, polycarbonates and J.I. M. J. Frechet, F.C. Bouchard, J.M. M. Houlihan, B.A. Kryzuku
ke) and E.C. Eichler; Imaging Science
ce), 30 (2), pp. 59-64 (1986), polymers and polyurethanes;
It includes polyesters, polyorthoesters, and polyacetals, and copolymers thereof. These polymers, as well as their degradation mechanisms, are described in more detail in the above-mentioned report by Holyhan et al.

It is preferable that the content of the heat transferable thermoplastic binder is 40% by mass or more of the whole ink layer. If it is less than 40% by mass, it is difficult to provide sufficient thermal transferability.

In the present invention, the adhesive strength between the ink layer and the layer adjacent to the ink layer, the 0.8 mm needle of the ink layer,
The scratch line width at 0 g load and the breaking elongation of the ink layer are respectively 19 ° C / 30% RH environment / 27 ° C / 70% R
By appropriately determining the thermoplastic binder used for the ink layer so that the ratio is within a desired range in the H environment, it is possible to eliminate laser scanning unevenness and stabilize the color reproducibility of the halftone portion with respect to fluctuations in the recording environment. Become.

However, regarding the scratch line width, 10
In some cases, measurement cannot be performed with a load of 0 g. In this case, the load is appropriately reduced. In this case, the range of the ratio in a 19 ° C./30% RH environment / 27 ° C./70% RH environment also changes.

Other additives for the ink layer include the addition of a plasticizer for increasing the sensitivity, the addition of a surfactant for improving coating properties, and the addition of submicron to micron order particles (mat material) for preventing blocking. It is possible.

The preferable thickness of the ink layer is 0.2 to 2 μm.
m, more preferably 0.3 to 1.5 μm. In particular,
It has been confirmed that high sensitivity can be obtained by setting the thickness to 0.8 μm or less. However, since the thin film transferability of the ink layer varies depending on the type of binder and color material used, the mixing ratio, and the like, the optimum film thickness range Is selected according to the balance between sensitivity and resolution and other desired image reproduction performance.

In addition, between the light-to-heat conversion layer and the ink layer,
A release layer or the like may be provided. As the release layer, celluloses such as methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, and nitrocellulose, vinyl resins such as polyvinyl alcohol, polyvinyl acetal, and polyvinyl butyral, and water-soluble resins such as gelatin can be used. The film thickness is preferably as thin as possible so as not to lower the sensitivity.
0.5 μm is preferred.

Next, an image receiving sheet used together with the ink sheet of the present invention will be described. The image receiving sheet receives the ink layer peeled off imagewise from the ink sheet to form an image. Usually, it has a support and an image receiving layer, but it may be formed only from the support. Further, a cushion layer may be provided in order to improve the adhesion to the ink sheet.

Since the ink layer melted by heat is transferred to the image receiving sheet, it is desirable that the image receiving sheet has appropriate heat resistance and excellent dimensional stability so that an image can be formed properly. The image receiving layer formed on the support comprises a binder, various additives which are added as required, and a mat material. In some cases, it is formed only with a binder.

Examples of the binder for the image receiving layer having good image receiving properties include adhesives such as polyvinyl acetate emulsion adhesive, chloroprene adhesive, epoxy resin adhesive, natural rubber, chloroprene rubber, butyl rubber, and polyacrylic acid. Ester type, nitrile rubber type, polysulfide type,
Adhesives such as silicone rubber, rosin, vinyl chloride, petroleum resin and ionomer resin, recycled rubber, SB
R, polyisoprene, polyvinyl ether and the like can be mentioned.

When the image formed on the image receiving layer is retransferred to another recording medium by heating and / or pressurizing, a resin having a relatively small polarity (small SP value) is used as the image receiving layer. The use of is especially preferred. For example, polyethylene,
Examples include polypropylene, ethylene-vinyl chloride copolymer, polybutadiene resin, ethylene-acrylic copolymer, vinyl chloride-based resin, and various modified olefins.

The thickness of the image receiving layer is usually from 1 to 10 μm, but is not limited to the case where the cushion layer is used as the image receiving layer. As the cushion layer, the material described in the ink sheet is preferably provided in a thickness of 15 to 30 μm.

As the support for the image receiving sheet, the same as those described for the ink sheet can be used, but the thickness is preferably 30 to 200 μm, more preferably 50 to 1 μm.
25 μm.

In addition, if necessary, a release layer may be provided between the image receiving layer and the support, more preferably between the image receiving layer and the cushion layer, and a back coat layer, an antistatic layer and the like may be provided on the surface of the support opposite to the image receiving layer. Can be provided.

Next, an image forming method will be described. In the laser thermal transfer recording method of the present invention, the transfer of the ink layer may be any of a fusion type thermal transfer and an ablation type thermal transfer, convert the laser beam to heat, transfer the ink layer to the image receiving sheet using the thermal energy, An image is formed on an image receiving sheet. More specifically, the laser thermal transfer recording method of the present invention sequentially feeds out an image receiving sheet and an ink sheet wound in a roll from a feeding section,
The ink sheet is wound around an exposure drum in the order of the ink sheet and held by pressure contact, and a laser beam is irradiated from the back of the ink sheet according to image data, and the ink sheet absorbs the laser beam and converts it into heat. To transfer and form an image from the ink layer to the image receiving sheet.

Examples of the laser light source for image recording include a semiconductor laser, a YAG laser, a carbon dioxide laser, and a helium neon laser. Among semiconductor lasers, it is preferable to use a so-called single-mode laser diode as it is easy to narrow the 1 / e ² diameter to several to several tens μm at the focal point without significantly lowering the optical efficiency.

Light sources other than lasers include light emitting diodes (LEDs). Although a multi-channel laser light source is used in the present invention, LEDs and semiconductor lasers that are easy to use as an integrated array of a plurality of light emitting elements are used.

In the present invention, it is preferable to first record an image on an ink sheet having a color set so as to maximize the absorption of the ink sheet. In laser thermal transfer recording, laser exposure is performed image-wise by bringing the ink sheet and the image-receiving sheet into close contact (for example, under reduced pressure). If the absorption is large, the amount of gas generated during laser exposure (regardless of the presence or absence of ablation) , The transferability is likely to deteriorate. In the case where a single color image is repeatedly recorded and a plurality of colors are superimposed, it is preferable to transfer the color with a large amount of generated gas in order to stabilize the adhesion at the time of exposure and the sensitivity of the second and subsequent colors.

As the laser scanning method, the outer surface scanning of the cylinder and the inner surface scanning of the cylinder are easier to improve the precision of the optical system.
Suitable for high density recording. In the case of multi-channel exposure in which a plurality of light-emitting elements are used at the same time, cylindrical outer surface scanning is most suitable.

[0074]

EXAMPLES The present invention will be described below with reference to examples.
Embodiments of the invention are not limited to this. In particular,
Unless otherwise noted, “parts” in the examples are “mass” of the effective solids.
Part ". (Production of ink sheet 1) Polyethylene having a thickness of 75 μm
Terephthalate (PET) film (Dupont: 7
05), apply the following back coat layer coating solution to a wire bar
1.0g / m at ^TwoApply and dry to the dry weight of
After that, apply the following cushion to the surface opposite to the back coat layer.
Coating and drying with a reverse roll coater.
To form a cushion layer having a thickness of 1 μm after drying.
On the cushion layer, apply the following photothermal conversion layer coating solution 1
Coating and drying were carried out with a yaver to form a light-to-heat conversion layer.
The drying weight of the light-to-heat conversion layer is 0.67 g / m^TwoMet.

Next, the following ink layer coating liquid 1 was applied on the light-to-heat conversion layer by a wire bar and dried to form an ink layer having a dry coverage of 0.72 g / m ² , thereby producing an ink sheet 1. .

The prepared ink sheet was wound around a 3-inch outer diameter paper tube so that the ink layer surface was inwardly wound. Backcoat layer coating solution Polyester resin (Byron 200: manufactured by Toyobo Co., Ltd.) 8.64 parts PMMA resin particles (MX-500H: manufactured by Soken Chemical Co., Ltd.) 0.36 parts Methyl ethyl ketone 54.6 parts Toluene 27.3 parts Cyclohexanone 9. 1 part Cushion layer coating liquid Styrene-isoprene copolymer (Clayton D-1117: manufactured by Shell Chemical Co., Ltd.) 4.0 parts Methyl ethyl ketone 57.0 parts Toluene 38.0 parts Light-to-heat conversion layer coating liquid 1 polyvinyl alcohol (EG-30: 6 parts Carbon black dispersion (SD-9020, concentration 40%: manufactured by Dainippon Ink) 4 parts Fluorinated surfactant (FT-251: manufactured by Neos) 0.05 part Water 490 parts Ink Layer Coating Liquid 1 Cyan Pigment Dispersion (MHI Cyan # 454: Cyan Pigment ME, manufactured by Mikuni Dyestuffs Co., Ltd.) K dispersion, pigment content 30%) 7.61 parts Styrene resin (Hymer ST-95, Tg = 42, Mw = 40000: manufactured by Sanyo Chemical Industries, Ltd.) 9.31 parts Fluorinated surfactant (MegaFac F178K: DIC) 0.10 part Methyl ethyl ketone 21.38 parts Cyclohexanone 61.60 parts (Preparation of ink sheets 2 to 9) The binder of the coating liquid for the photothermal conversion layer and the binder of the coating liquid for the ink layer were changed as shown in Table 1. Except for the above, ink sheets 2 to 9 were prepared in the same manner as ink sheet 1.

[0077]

[Table 1]

(Image Formation and Performance Evaluation) Using the ink sheets 1 to 9, the following image performance was evaluated. The exposure machine used was Konica EV-laser-proofer, and Konica Color Decision CD-2R was used as an image receiving sheet.

The exposure conditions are such that the exposure surface power is 100 mW /
ch, the number of rotations was 400 to 600 rpm. After the exposure, the image was transferred to Mitsubishi special art paper by an EV-laminator to obtain an evaluation image. Gretag-D186
Using a densitometer (manufactured by GRETAG), black backing was performed, and density measurement and dot gain measurement of 50% were performed. << Laser Scanning Unevenness >> Solid exposure was performed, and the result was visually determined.

：: No laser scanning unevenness Δ: Slight laser scanning unevenness ×: Laser operation unevenness << Stability due to environmental fluctuation >> 19 as a low temperature / low humidity environment
℃ ・ 30% RH 、 27 ℃ ・ 70 in high temperature and high humidity environment
% RH, exposure and 175 after controlling the temperature and humidity for 12 hours or more for the exposure machine, ink sheet, and image receiving sheet.
The dot gain of 50% of the halftone dot image was measured, and the dot gain difference between low temperature and low humidity and high temperature and high humidity was obtained. Note that this difference is evaluated by taking the same value of exposure energy (rotation speed) under both environments. (Measurement of TGA ₅₀ thermal decomposition temperature)
SC-220, measuring conditions were 10 ° C./min. ,
Temperature rising start temperature 30 ° C., nitrogen flow 100 ml / min. ,
The test was performed with a sample amount of 5 to 10 mg. << Adhesiveness of light-to-heat conversion layer and ink layer >> A double-sided tape is adhered to the glass surface, and an adhesive tape (Nichiban cellophane tape 25.4 mm width) is separately adhered to the ink layer surface of the ink sheet. The surface was adhered to the adhesive tape surface. The ink sheet was folded upward by 90 degrees, and the peel strength between the ink layer and the light-to-heat conversion layer was measured with a tensile tester (push-pull gauge) at a moving speed of 300 mm / min. Under 19 ℃ ・ 30% RH environment,
The measurement was performed under an environment of 27 ° C. and 70% RH, and the ratio was determined. << Scratch line width of ink layer >> HEIDO manufactured by Shinto Kagaku
An N scratch tester was used. A sapphire needle having a tip diameter of 0.8 mm is vertically pressed against the ink layer of the ink sheet of the present example and the comparative example, and a load of 100 g is applied to the sapphire needle at a scratching speed of 1000 mm / min to scratch the ink layer. Was. The line width due to the scratch was measured under a 19 ° C./30% RH environment and under a 27 ° C./70% RH environment, and the ratio was determined. << Elongation at break of ink layer >> An ink layer coating liquid was applied to a 75 μm-thick PET film (described above: 705) with a wire bar and dried, and the applied amount was 0.72 g / m2.
^{The second} ink layer was formed, and an ink layer film sample was prepared. The measurement of the elongation at break of the ink layer is made by T
Using ENSILON, under 19 ℃ ・ 30% RH environment
The measurement was performed under an environment of 27 ° C. and 70% RH, and the ratio was determined.

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[Table 2]

[0082]

As is clear from the results shown in Table 2, according to the present invention, it is possible to obtain a high-quality image without laser scanning unevenness, and even if the environment changes during recording, a stable image can be obtained. An ink sheet for laser thermal transfer recording that maintains color reproducibility can be obtained.

Claims (6)

[Claims] In a laser thermal transfer recording ink sheet having at least a light-to-heat conversion layer and an ink layer on a support, the adhesive strength between the ink layer and a layer adjacent to the ink layer is 19 ° C. and 30% RH ( Relative humidity) environment and 27 ℃
An ink sheet for laser thermal transfer recording, wherein the ratio is 0.8 to 1.1 in a 70% RH environment. 2. A laser thermal transfer recording ink sheet having at least a light-to-heat conversion layer and an ink layer on a support, wherein the ink layer has a scratch line width of 19 ° C./30% under a 0.8 mm needle and a load of 100 g. RH environment and 27 ℃
A laser thermal transfer recording ink sheet having a ratio of 0.8 to 1.2 in a 70% RH environment. 3. An ink sheet for laser thermal transfer recording having at least a light-to-heat conversion layer and an ink layer on a support, wherein the elongation at break of the ink layer is 19 ° C./30% RH environment and 27 ° C./RH 70%. 0.5-1.
2. An ink sheet for laser thermal transfer recording, wherein 4. A method for measuring the thermal decomposition of a main binder used in a light-to-heat conversion layer by a TGA method in a nitrogen stream,
4. The ink sheet for laser thermal transfer recording according to claim 1, wherein the temperature at which the rate of weight loss at a temperature rising rate of 10 ° C./min becomes 50% is 360 ° C. or higher. 5. The ink sheet for laser thermal transfer recording according to claim 1, wherein the ink layer contains a thermoplastic resin having a softening point of 40 to 150 ° C. 6. The ink layer of the laser thermal transfer recording ink sheet and the image receiving layer of the image receiving sheet are brought into face-to-face contact with each other, and then the ink layer is transferred to the image receiving layer by irradiating a laser beam from the back side of the ink sheet. An image forming method for forming an image on an image receiving layer by peeling a sheet, wherein the ink sheet for laser thermal transfer recording according to any one of claims 1 to 5 is used.