JPH04115991A - Ink sheet for thermal transfer recording - Google Patents

Abstract

PURPOSE:To enhance preservability, to prevent the fusion with an image receiving sheet for thermal transfer recording or the background staining of the image receiving sheet and to suppress the lowering of image density by laminating an ink layer containing a heat-diffusible dye, an acetal resin and nitrocellulose to a support. CONSTITUTION:An ink sheet fundamentally has such a structure that an ink layer 2 is laminated to a support 1. The ink layer 2 fundamentally contains a heat-diffusible dye, an acetal resin and nitrocellulose. As the heat-diffusible dye, a cyan dye, a magenta dye and a yellow dye are designated and, as the cyan dye, a naphthoquinone type dye, an anthraquinone type dye or an azomethine type dye is designated. As the magenta dye, an anthraquinone type dye, an azo dye or an azomethine type dye is designated and, as the yellow dye, a methine type dye, an azo type dye, a quinophthalone type dye or an anthraisothiazole type dye is designated. As the acetal resin, polyvinyl acetoacetal or polyvinyl butyral can be designated.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an ink sheet for thermal transfer recording, and more specifically, it improves storage stability and prevents scumming and fusion of an image-receiving sheet for thermal transfer recording. The present invention relates to an ink sheet for thermal transfer recording, which can prevent the occurrence of image density and suppress a decrease in image density.

[Prior Art and Problems to be Solved by the Invention] Color recording techniques such as inkjet, electrophotography, and thermal transfer are being considered as methods for obtaining color hard copies.

Among these, the thermal transfer method in particular has advantages such as easy operation and maintenance, miniaturization of the device, and low cost.

There are two types of this thermal transfer method:

That is, a method in which a transfer sheet having a meltable ink layer on a support is heated imagewise (imagewise) by a laser or a thermal head, and the meltable ink layer is melt-transferred onto an image-receiving sheet for thermal transfer recording. and thermal diffusion transfer, in which the heat-diffusible dye is diffusely transferred to an image-receiving sheet for heat-sensitive transfer recording using an ink sheet for heat-sensitive transfer recording having an ink layer containing a heat-diffusible dye (sublimable dye) on a support. There are two types:

Among these, the thermal diffusion transfer method can control the gradation of the image by changing the amount of dye transferred according to changes in the thermal energy of the thermal head.
By overlapping magenta and yellow recording,
In recent years, this method has attracted attention as a method for obtaining color images with continuous changes in color shading.

However, the first problem with this thermal diffusion transfer method is that the ink sheet used for thermal transfer recording has poor storage stability. When stored after being rolled up, the heat-diffusible dye is released from the binder over time and accumulates on the ink layer surface, and also migrates to the back side of the sheet that is in contact with it. The entire transfer sheet may be stained with dye (background stain).

The second problem is that in a thermal transfer recording ink sheet in which the heat-diffusible dye has been released from the binder, the dye density decreases, and the density of the image source (transfer density) also decreases.

The third problem is that during thermal transfer, the entire ink layer from the ink sheet for thermal transfer recording is fused to the image receiving sheet for thermal transfer recording.

The present invention has been made to solve the various problems mentioned above.

That is, an object of the present invention is to improve storage stability, prevent fusion with an image-receiving sheet for thermal transfer recording, prevent background smearing on the image-receiving sheet, and suppress a decrease in image density. An object of the present invention is to provide an ink sheet for thermal transfer recording.

[Means for solving the above-mentioned problems] The present invention for achieving the above-mentioned objects is characterized in that an ink layer containing a heat-diffusible dye, an acetal resin, and nitrocellulose is laminated on a support. This is an ink sheet for thermal transfer recording.

The present invention will be explained in detail below.

(I) Ink sheet for thermal transfer recording The ink sheet for thermal transfer recording of the present invention basically has a structure in which an ink layer 2 is laminated on a support 1, as illustrated in FIG.

-Ink layer- The ink layer in the present invention basically contains a heat-diffusible dye, an acetal resin, and nitrocellulose. Moreover, this ink layer is not limited to a single layer, but may be composed of multiple layers.

(2) Heat-diffusible dye The heat-diffusible dye used in the present invention is not particularly limited as long as it is heat-diffusible or sublimable.

Examples of heat-diffusible dyes include cyan dyes, magenta dyes, and yellow dyes.

As the cyan dye, JP-A-59-78896;
No. 59-227948, No. 60-24966, No. 6
No. 0-53563, No. 60-130735, No. 60-
No. 131292, No. 60-239289, No. 61-1
9:196, 61-22993, 61-312
No. 92, 61-31467, 61-35994, 61-49893, 61-148269, the same! i2-191191, 63-91288, 6
Examples include naphthoquinone dyes, anthraquinone dyes, and azomethine dyes described in publications such as No. 3-91287 and No. 63-290793.

Examples of the magenta dye include JP-A-59-78896, JP-A-60-30392, and JP-A-60-30394.
No., JP-A-60-253595, JP-A-61-262
No. 190, JP-A-63-5992, JP-A-63-20
No. 5288, JP-A-64-159, JP-A-64-63
Examples include anthraquinone dyes, azo dyes, and azomethine dyes described in various publications such as No. 194.

As yellow pigments, JP-A-59-78896, JP-A-60-27594, JP-A-60-31560,
JP-A-60-53565, JP-A-61-12:194
Examples include methine dyes, azo dyes, quinophthalone dyes, and anthrisothiazole dyes, which are described in various publications such as JP-A No. 63-122594.

Further, as the heat-diffusible dye, an azomethine dye obtained by a coupling reaction of a compound having an open-chain or closed-chain active methylene group with an oxidized product of a p-phenylenediamine derivative or an oxidized product of a p-aminophenol derivative; and phenol or naphthol derivatives or p-
An indoaniline dye obtained by a coupling reaction with an oxidized product of a phenylenediamine derivative or an oxidized product of a p-aminophenol derivative can also be suitably used.

The heat-diffusible dye may be a yellow dye, a magenta dye, or a cyan dye, as long as the image to be formed is monochromatic.

Furthermore, depending on the tone of the image to be formed, it may contain two or more of the three types of heat-diffusible dyes or other colors.

The amount of the heat-diffusible dye used in the present invention is as follows:
Usually 0.1 to 2 (Ig, preferably 0.2 to 2) per m2
It is 5g.

(2) Binder In the present invention, it is important to use an acetal resin and nitrocellulose as the binder for the ink layer.

There are various compounds depending on the content of cetyl groups, etc., and typical examples include polyvinyl acetoacetal and polyvinyl butyral.

Among acetal resins, preferred for the purpose of the present invention are those with a polymerization degree of 300 to 2400 and an acetalization degree of 60.
It is an acetal resin having a mol% or more, an acetyl group content of 10 mol% or less, and a glass transition point (Tg) of 50°C or more.

The product names of acetal resins that meet these conditions include KS-1, KS-5, KS-8, BL-1, B
L-2, BL-3, BL-3, BM-1, BM-2, 8
Examples include M-5, BM-3, BH-3, and BX-1 [all manufactured by Building Block Chemical Industry Co., Ltd.]. These resins are not limited to one type alone, and two or more types can be used in combination.

Also, preferred nitrocellulose for the purpose of the present invention is a nitrogen content of 1007 to 12.2% and a polymerization degree of 35 to 1%, based on the test method of JIS K-6703.
10, viscosity is 1.0 to 6.2 seconds (solid content 25.
0%), 3 to 8 seconds (measured at 20.0% solids),
1.5 to 500 seconds (measured at solid content 12.2%), 1.1
~5.2 seconds (measured at 30% solids), 100-14
It is a nitrocellulose having a value of 0 c p s (measured by dissolving 1.5 g of dry nitrocellulose in 1 cc of butyl acetate).

The product names of nitrocellulose that meet these conditions are HIGI/16, HIGI/8, and HIGI/4.
,HIGI/2,HIGI,HIO2,HIO2,HI
O20, HIO60, HIO120, HIO500, L
IGI/8, LIGI/4, LIGI/2. 5L-
1, HIlooO, HI200 mouth, clear H1/4,
There are chips such as H1/2 [all manufactured by Asahi Kasei ■].

These resins are not limited to a single type, but two or more types can be used in combination.

The weight ratio of the acetal resin and nitrocellulose in the ink layer is usually in the range of 20:8Q to 90:10, preferably in the range of 5Q:5G to 85:15.

In the present invention, in addition to the above two types of resins, the following resins can be used as arbitrary binder components.

That is, as this arbitrary binder component, for example, acrylic resin, methacrylic resin, polycarbonate,
Polyvinyl alcohol, polyvinyl formal, polyvinyl ether, polyvinylpyrrolidone, polystyrene,
Cellulose resins other than polystyrene copolymers, ionomer resins, and nitrocellulose (e.g., ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate, cellulose acetate, etc.)
etc. can be mentioned.

In that case, the content of the resin, which is an arbitrary binder component, is usually in the range of 50% by weight or less based on the total amount of resin in the ink layer.

If this content exceeds 50% by weight, the effects of the present invention may not be obtained.

Moreover, the weight ratio of the binder and the heat-diffusible dye in the ink layer is preferably 1:10 to 10:1.

In this way, when acetal resin and nitrocellulose are used as essential binders in the ink layer, the shelf life of the ink sheet for thermal transfer recording is improved, and the background smudge and image density of the image-receiving sheet for thermal transfer recording are reduced. At the same time, the occurrence of fusion with the image-receiving sheet for thermal transfer recording is also prevented.

(1) Additives In the present invention, various additives may be added to the ink layer.

The additives include silicone resin, silicone oil (reactive curing type is also available), silicone modified resin, fluororesin, surfactant, peeling compounds such as waxes, fine metal powder, silica gel, carbon black, fine resin powder. Fillers such as, binder components and curing agents (for example, radiation active compounds such as isocyanates, acrylics, and epoxies) can be mentioned.

Further, heat-melting substances for promoting transfer, such as wax and higher fatty acid esters, may be added to JP-A-59-10
The compounds described in No. 6997 may be mentioned.

The amount added cannot be determined unconditionally depending on the type of additive and the purpose of addition, but the amount of the additive as a whole is usually in the range of 20% by weight or less based on the binder resin.

■Formation of the ink layer The ink layer is prepared by dispersing or dissolving the above-mentioned ink layer and heat-diffusible dye, as well as optional components added as necessary, in a solvent to prepare a coating solution for forming the ink layer. It can be formed by applying a coating liquid onto a support and drying it.

Σ.The above binders are not limited to being used by dissolving one or more of them in a solvent, but may also be dispersed in a latex form.

The above solvents include water, alcohols (e.g. methanol, ethanol, propatool), esters (e.g. methyl acetate, ethyl acetate, isopropyl acetate, n-acetate).
butyl, amyl acetate, ethyl lactate, cellosolve lactate, etc.), cellosolves (such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, cello acetate, etc.),
Among aromatics (e.g., toluene, xylene, chlorobenzene, etc.), ketones (e.g., acetone, methyl ethyl ketone, etc.), ethers (e.g., tetrahydrofuran, dioxane, etc.), chlorinated solvents (e.g., chloroform, trichloroethylene, etc.), One type can be used alone, or two or more types can be used in an appropriate combination.

For the above-mentioned coating, commonly known surface sequential coating using a gravure roll, extrusion coating, wire bar coating, roll coating, etc. can be used.

The thickness of the ink layer is preferably 0.2 to 10 pm, more preferably 0.3 to 3 ILm.

In addition, the ink layer is formed by forming a yellow ink layer containing a binder and a yellow dye, a magenta ink layer containing a binder and a magenta dye, and a cyan ink layer containing a binder and a cyan dye. It is preferable that the structure is formed on the top.

In addition to the three ink layers arranged along the surface direction, a black ink layer containing a black image forming substance may be interposed between any two horizontally adjacent layers.

In particular, with respect to the black ink layer, clear characters can be obtained using diffusion transfer type or melt transfer type ink.

Support The support used in the present invention may be any material as long as it has good dimensional stability and can withstand the heat during recording with a heat-sensitive head, such as condenser paper, thin paper such as glassine paper, polyethylene terephthalate, etc. Heat resistant plastic films such as polybutylene terephthalate, polyethylene naphthalate, polyamide, polycarbonate, polysulfone, polystyrene, polyimide are suitable.

The thickness of the support is generally preferably 2 to 1107 mm.

-Other Layers- An undercoat layer may be provided between the ink layer and the support in order to improve adhesion and the like.

Furthermore, an anti-fusing layer can also be provided on the ink layer.

Its thickness is usually 0.01 to 5 μm, preferably 0.05 μm.
It is in the range of ~1 μm.

If the thickness is less than 0.01 gm, the effect of preventing fusion will not be sufficiently exhibited, and if it exceeds 5 ILm, the diffusion of the thermally diffusible dye from the ink layer to the image receiving layer will be inhibited, and sufficient image density will not be obtained. This is not preferable as it makes it difficult to get caught.

The anti-fusing layer can usually be formed from solid waxes such as polyethylene wax, amide wax, and Teflon powder, fluorine, phosphate ester surface active substances, silicone oil, silicone resin, fluororesin, and the like.

Further, the back surface of the support (the side opposite to the ink layer) may have an anti-sticking layer for the purpose of preventing the head from adhesion, sticking, or wrinkles on the support.

The thickness of this anti-sticking layer is preferably in the range of 0.1 to 1 m.

Furthermore, by forming perforations on the ink sheet for thermal transfer recording, or providing detection marks for detecting the positions of areas with different hues, convenience in use can be improved.

(II) Image-receiving sheet for thermal transfer recording The image-receiving sheet for thermal transfer recording can be composed of a base material and an image-receiving layer formed thereon.

In some cases, an image-receiving sheet for thermal transfer recording can be formed with a self-supporting image-receiving layer.

In this image-receiving sheet for thermal transfer recording consisting of a self-supporting image-receiving layer, since no base material is used,
The number of parts can be reduced.

Image-receiving layer: This image-receiving layer can be formed from an image-receiving layer binder and various additives.

In some cases, the image-receiving layer can be formed using only the binder for the image-receiving layer.

■Binders for image-receiving layers Examples of binders for image-receiving layers include polyvinyl chloride resins, copolymer resins of vinyl chloride and other polymers (such as vinyl acetate), chlorinated polyethylene, polypropylene, ethylene-vinyl acetate, etc. Polymer resin, ketone resin, alkyd resin, polyester resin, acrylic ester,
Polyvinylpyrrolidone, polycarbonate, cellulose triacetate, styrene acrylate resin, vinyltoluene acrylate resin, polyurethane resin, polyamide resin,
Examples include urea resin, polycaprolactone resin, styrene-maleic anhydride resin, and polyacrylonitrile resin. These can be used alone or in combination of two or more. Among these, preferred are vinyl chloride-vinyl acetate copolymer resin, polyvinyl chloride resin, and polyester resin.

The above various resins may be newly synthesized and used, but commercially available products may also be used.

For example, commercially available polyester resins include Vylon 2
00. Byron 290, Byron 600, etc. [manufactured by Toyobo ■], KA-1038C [manufactured by Arayo Kagaku ■]
, TP220, TP23S [all manufactured by Nippon Gosei ■], etc. can be used.

The vinyl chloride-vinyl acetate copolymer resin has a vinyl chloride component content of 50 to 100% by weight and a polymerization degree of 50%.
~2500 is preferred.

The vinyl chloride-vinyl acetate copolymer resin preferably used in the present invention does not necessarily need to be composed only of a vinyl chloride component and a vinyl acetate component; Ingredients: sulfonic acid component, epoxy component, glycyridyl component,
Examples of such vinyl chloride-vinyl acetate copolymers, which may contain carboxyl components, include S-LEC A, S-LEC C, S-LEC M [the above,
Made by Okisui Kagaku Kogyo ■], Vinyrite VACH, Vinylyte VYHH, Vinylyte VMCH.

Vinylite VYHD, Vinylite VYLF, Vinylite VYNS, Vinylite VMCC, Vinylai) YMCA,
Vinylite VACD, Vinylite VERR, Vinylite VROH (manufactured by Union Carbide), Denkabinir 100OG K T, Denkabinir 100OL,
Denkabinir 100OC, Denkabinir 100OA,
Denkabinir 100OLK, , Denkabinir 100O
A S, Denkabinir 10100O,, Denkabinir 1
00OCS K, Denkabinir 100OCS, Denkabinir 100OG K, Denkabinir 100OG SK,
Denkabinir 100OG S, Denkabinir 100OL
T3. Denkabinir 100OD, Denkabinir 100O
Examples include W [manufactured by Denki Kagaku Kogyo ■] and the like.

In any case, from the viewpoint of physical properties, the binder for the image-receiving layer has a glass transition point (Tg) of -20 to 15.
Resins having a temperature in the range of 0°C, particularly resins in the range of 30 to 120°C are preferable,5 and from the viewpoint of molecular weight, resins having an Mw in the range of 2000 to 100,000 are preferable.

In addition, when forming the image-receiving layer, the various resins mentioned above utilize their reactive active sites (if there are no reactive active sites, give them to the resin), and crosslink with radiation, heat, moisture, catalysts, etc. Alternatively, it may be hardened.

In that case, radiation active monomers such as epoxies, acrylics, and crosslinking agents such as incyanates may be used.

■ Additives Release agents, antioxidants, UV absorbers, light stabilizers, fillers (inorganic fine particles, organic shelf particles), and pigments may be added to the image-receiving layer, and plasticizers and sensitizers may be added. A thermal solvent or the like may be added, and these are used as appropriate in consideration of compatibility with the binder, image storage stability, and the like.

The release agent can improve the releasability between the ink sheet for thermal transfer recording and the image receiving sheet for thermal transfer recording.

Examples of such a release agent include solid waxes such as silicone oil, polyethylene wax, amide wax, and Teflon powder; fluorine-based and phosphoric acid ester-based surfactants; among these, silicone oil is preferred.

There are two types of silicone oil: a type in which it is simply added (simple addition type) and a type in which it is cured or reacted (curing reaction type).

In the case of a simple addition type, it is preferable to use modified silicone oil as the silicone oil in order to improve compatibility with the binder.

As modified silicone oil, polyester modified silicone resin (or silicone modified polyester resin)
, acrylic-modified silicone resin (or silicone-modified acrylic resin), urethane-modified silicone resin (or silicone-modified urethane resin), cellulose-modified silicone resin (or silicone-modified cellulose resin), alkyd-modified silicone resin (or silicone-modified alkyd) resin), epoxy-modified silicone resin (or silicone-modified epoxy resin), and the like.

Namely, polyester-modified silicone resin containing polysiloxane resin in the main chain and copolymerizing polyester in block form, silicone-modified polyester resin having dimethylpolysiloxane moiety as a side chain bonded to the polyester main chain, dimethyl Block copolymers, alternating copolymers, graft copolymers, random copolymers, etc. of polysiloxane and polyester moieties can also be used as modified silicone oils or resins.

In particular, in the present invention, it is preferable to add a polyester-modified silicone resin.

Typical polyester-modified silicone resins include, for example, a copolymer of diol and dibasic acid, or a block copolymer of polyester, which is a ring-opening polymer of caprolactone, and dimethylpolysiloxane (both ends or one end of dimethylpolysiloxane). The terminal is blocked by the above polyester moiety (or conversely, it contains a copolymer blocked with the above polyester or dimethylpolysiloxane), or the above polyester is used as the main chain and (dimethyl)polysiloxane is bonded to the side chain. At least one copolymer can be mentioned.

Since the amount of these simple addition type silicone oils can vary depending on the type, it is not possible to uniformly determine the amount. The amount is 0.5 to 50% by weight, preferably 1 to 20% by weight.

Curing reaction type silicone oils include reaction curing type,
Examples include photocuring type and catalyst curing type.

Examples of reaction-curing silicone oils include those obtained by reaction-curing amino-modified silicone oil and epoxy-modified silicone oil.

In addition, as catalyst curing type or photo curing type silicone oil, KS-705F-PS, KS-705F-PS-
1. KS-770-PL-3 [Both catalyst-curing silicone oils: @Etsu Kagaku Kogyo ■], KS-720
, KS-774-PL-3 [all photocurable silicone oils: manufactured by Etsu Kagaku Kogyo], and the like.

The amount of these curable silicone oils added is preferably 0.5 to 30% by weight of the binder for the image-receiving layer.

Note that a release agent layer can also be provided by dissolving or dispersing the above-mentioned release agent in a suitable solvent and applying the solution to a part of the surface of the image-receiving layer, followed by drying.

Next, as the antioxidant, JP-A-59-18278
5, No. 60-130735, JP-A No. 1-127387, etc., and compounds known to improve image durability in photographs and other image recording materials.

As the U■ absorber and light stabilizer, JP-A-59-
158287, 63-74686, 63-1450
89, 59-196292. 62-229594.
63-122596, 61-283595, JP-A-1
-204788, and compounds known to improve image durability in photographs and other image recording materials.

Examples of the filler include inorganic fine particles and organic resin particles.

These inorganic fine particles include silica gel, calcium carbonate,
Examples of the organic particles include titanium oxide, acid clay, activated clay, and alumina. Examples of organic fine particles include resin particles such as fluorocarbon resin particles, guanamine resin particles, acrylic resin particles, and silicone resin particles. These inorganic/organic resin particles vary depending on their specific gravity, or from 0.1 to 70% by weight.
The addition of is preferred.

Typical examples of the pigment include titanium white,
Examples include calcium carbonate, zinc oxide, barium sulfate, silica, talc, clay, kaolin, activated clay, and acid clay.

Examples of the plasticizer and heat solvent include phthalate esters (for example, dimethyl phthalate, dibutyl phthalate, dioctyl phthalate, didecyl phthalate, etc.), adipate esters (dioctyl adipate, methyl lauryl adipate, di-2 adipate, etc.). -ethylhexyl, ethyl lauryl adipate, etc.), other oleic acid esters, succinic acid esters, maleic acid esters, sepatic acid esters, citric acid esters, epoxy epoxy stearate, triphenyl phosphate, Examples include phosphoric acid esters such as tricresyl phosphate, and glycol esters such as ethyl phthalyl ethyl glycolate and butylphthalyl butyl glycolate.

In the present invention, the total amount of additives added is usually in the range of 0.1 to 50% by weight based on the binder for the image-receiving layer.

■Formation of the image-receiving layer The image-receiving layer is prepared by, for example, dispersing or dissolving the components forming the image-receiving layer in a solvent to prepare a coating solution for the image-receiving layer, and applying this coating solution for the image-receiving layer to the surface of the base material. The image-receiving layer can be formed by a coating method in which the image-receiving layer is dried, a lamination method in which a mixture containing the components forming the image-receiving layer is melt-extruded, and then laminated on the surface of a base material.

Examples of solvents used in the above coating method include ketones such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, aromatic solvents such as toluene and xylene, ethyl acetate,
Examples include ester-based solvents such as butyl acetate, ether-based solvents such as diethyl ether, tetrahydrofuran, and dioxane, alcohol-based solvents such as methyl alcohol, ethyl alcohol, and isopropanol, and halogen-based solvents such as dichloromethane and trichloroethylene. .

When employing the above lamination method, if the base material is a synthetic resin as described later, a coextrusion method may also be employed. The image receiving layer may be formed over the entire surface of the base material, or may be formed on a part of the surface.

The thickness of the image receiving layer is generally 3 to 50 μLm, preferably 3
~15 ILm.

On the other hand, when the image-receiving layer itself forms an image-receiving sheet for thermal transfer recording because the image-receiving layer is self-supporting, the thickness of the image-receiving layer is usually 60-200 pm, preferably 90-200 pm.
It is about 150 ILm.

-Substrate- Examples of this substrate include paper, coated paper, synthetic paper (polypropylene, polystyrene, or a composite material made of paper and paper), white polyethylene terephthalate base film, transparent polyethylene terephthalate base film, polyolefin coating. Examples include paper.

The thickness of the base material is usually 30~:]OOpm, preferably 8
0 to 200 m.

-Other layers- An overcoat layer may be laminated on the surface of the image-receiving sheet for thermal transfer recording for the purpose of preventing fusion with the ink layer and improving image storage stability. It can be formed by existing coating methods such as gravure coating, wire bar coating, roll coating, lamination method, etc.

The thickness of this layer is typically 0.05 to 5 Bm.

Further, between the base material and the image receiving layer of the image receiving sheet for thermal transfer recording, in order to reduce noise and transfer and record an image corresponding to image information with good reproducibility.

A cushion layer can also be provided.

Examples of the material constituting this cushion layer include urethane resin, acrylic resin, ethylene resin, butadiene rubber, and epoxy resin.

The thickness of the cushion layer is preferably 5 to 25 μm.

(m) Image formation To perform image formation, the ink layer surface of the ink sheet for thermal transfer recording of the present invention and the image-receiving layer surface of the image-receiving sheet for thermal transfer recording are brought into contact with each other, and then this interface is formed. imagewise adds thermal energy to.

Then, the heat-diffusible dye in the ink sheet for thermal transfer recording vaporizes or sublimates in an amount corresponding to the applied thermal energy, and migrates to the image-receiving sheet for thermal transfer recording.
It is fixed on the image-receiving layer to form an image there.

A thermal head is generally used as the heat source for providing the thermal energy, but other known heat sources such as a laser beam, an infrared flash, and a heat vent can also be used.

Thermal energy can be applied from the image receiving sheet for thermal transfer recording, from the ink sheet for thermal transfer recording, or from both sides.

However, from the point of view of effective use of thermal energy, it is better to perform this from the ink sheet side for thermal transfer recording.

Also, it is used for the purpose of controlling thermal energy to express the gradation of light and shade in images, or promoting the diffusion of dyes into image-receiving sheets for thermal transfer recording to ensure the expression of continuous gradations in images. It is preferable to apply thermal energy from the side of the image-receiving sheet for thermal transfer recording.

Furthermore, in the sense that the advantages of the above two methods can be enjoyed at the same time, it is preferable to carry out the process from the side of the ink sheet for thermal transfer recording and the side of the image receiving sheet for thermal transfer recording.

When a thermal head is used as a heat source for providing thermal energy, the applied thermal energy can be varied continuously or in multiple stages by modulating the voltage or pulse width applied to the thermal head.

When laser light is used as a heat source for providing thermal energy, the amount of heat energy provided can be varied by changing the amount of laser light and the irradiation area.

If a tod generator with a built-in acousto-optic element is used, thermal energy can be applied depending on the size of the halftone dot.

When using a laser beam as a heat source, it is desirable that the ink sheet for thermal transfer recording and the image receiving sheet for thermal transfer recording be brought into close contact with each other, and that the surface to be irradiated with the laser beam absorbs the laser beam well. It is a good idea to color it black, for example.

When an infrared flash lamp is used as a heat source for providing thermal energy, irradiation from the lamp is preferably performed through a colored layer such as black, as in the case of using laser light.

In addition, irradiation with this lamp can be performed through a pattern or a halftone dot pattern that continuously expresses the shading of an image such as black, and a colored layer such as black on the - side and a negative of the above pattern. It can also be done in combination with a negative pattern.

When thermal energy is applied in this way, an amount of dye corresponding to the amount of energy is thermally transferred from the ink sheet for thermal transfer recording to the image receiving layer of the image receiving sheet for thermal transfer recording.
It is possible to record a one-color image there, or by replacing the ink sheet for thermal transfer recording, a color photographic color image can be obtained.

For example, by sequentially replacing the yellow, magenta, cyan, and, if necessary, black thermal transfer recording ink sheets and performing thermal transfer according to each color, it is possible to obtain a photographic color image that is a combination of each color. .

Incidentally, instead of using ink sheets for thermal transfer recording of each color as described above, the following method can also be used.

That is, an ink sheet for thermal transfer recording is prepared in which areas are formed by coating each color in advance.

First, the yellow area is used to thermally transfer the yellow color separation image, then the magenta area is used to exclusively heat transfer the magenta color separation image, and thereafter, by sequentially repeating this operation, yellow, magenta, cyan, and If necessary, thermally transfer the black and separated color images.

This method has the advantage that there is no need to replace the ink sheet for thermal transfer recording.

[Example] Next, the present invention will be explained in more detail based on Examples.

Note that in the following, "parts" represent "parts by weight."

(Example 1) On the corona-treated surface of a polyethylene terephthalate film with a thickness of 9 ILm as a support, a coating solution for forming an ink layer having the following composition was applied by wire bar coating method so that the thickness after drying was 1pm. After drying, use a dropper to drop 1.2 drops of silicone oil [X-41°4003A, manufactured by Shin-Etsu Silicone ■] on the back surface that has not been corona treated, spread it over the entire surface, apply a back treatment coat, and apply thermal transfer recording ink. Got a sheet.

Coating liquid for ink layer formation Dispersed dye [manufactured by Nippon Kayaku ■...4 parts Kayaset Blue 136] Nitrocellulose......1.5 parts [viscosity 3
．． 0 to 4.9 seconds, desired element content 11.5 to 12.2%, degree of polymerization 80 to 95, trade name HIGI/2, manufactured by Asahi Kasei ■ Polyvinyl butyral 3.5 parts [polymerization Degree of acetalization: 300, degree of acetalization: 63±3 mol% or more, acetyl group: 3 mol% or less, T g 59.2°C, product name: BL-1゜manufactured by Hosui Kagaku Kogyo ■] Toluene... ...40 parts Methyl ethyl ketone...40 parts Dioxane...
・・・・・・・・・・・・1 part Next, as a base material, thickness 15
A coating solution for forming an image-receiving layer having the following composition was coated on 0 pm synthetic paper [trade name Yubo FPG-150; made by Tamago Oil Synthetic Paper ■] using a wire bar coating method, and then temporarily dried with a hair dryer. In the oven at a temperature of 100℃ 1
The mixture was dried for a period of time to obtain an image-receiving sheet for thermal transfer recording in which an image-receiving layer with a thickness of about 10 pm was formed on synthetic paper.

Coating liquid for image-receiving layer formation Polyester resin: 10 parts [Vylon 103, manufactured by Toyobo ■, Tg: 47°C] Amino-modified silicone oil: 0.125 parts [KF39, Made by Shin-Etsu Silicone Binding] Epoxy-modified silicone oil...0.125 parts [X-
22-343, made by Shin-Etsu Silicone ■] Toluene...
・・・・・・・・・・57 parts・Xylene・・・・・・・
・・・・・・13 parts methyl ethyl ketone・・・・・・
・・6.3 parts 2-butanol・・・・・・・・・・1
4 parts Cyclohexanone 30 parts Next, the ink sheet for thermal transfer recording obtained as described above was stored at 60°C for 8 days, and then the sheet and the ink sheet for thermal transfer recording obtained as above were stored at 60°C for 8 days. The image-receiving sheets were overlapped so that the ink layer surface of the former was in contact with the image-receiving layer surface of the latter, and a thermal head was used from the support side of the ink sheet for thermal transfer recording to output 0.35 W/dot and dot density 8 dots/mm.
One image was recorded by heating under the following conditions.

After image recording, background stains on the unprinted area (white area) on the surface of the image-receiving layer of the image-receiving sheet for thermal transfer recording, the transfer density of the surface of the image-receiving layer, and the state of fusion between the ink sheet for thermal transfer recording and the image-receiving sheet for thermal transfer recording. was evaluated based on the following criteria.

The results are shown in Table 1.

Ground stains: O... ・・In the unprinted area on the surface of the image-receiving layer There was no contamination caused by the dye.

X: The unprinted area was contaminated with dye.

Transfer density: ○...The concentration was sufficient.

X: Concentration was low.

Fusion: Good: Only the dye was transferred to the image-receiving layer, and the ink thermal layer was difficult to peel off from the support.

X: The entire ink layer was transferred to the image receiving layer.

(Example 2) In Example 1, polyvinyl butyral, which is one of the components of the coating solution for forming an ink layer, was replaced with polyvinyl acetoacetal [degree of polymerization of about 2400. Degree of acetalization 70 mol% or more, acetyl group 3 mol% or less, 7g 110°C or more, KS-
5z, manufactured by Okisui Kagaku Kogyo Co., Ltd.], the same procedure as in Example 1 was carried out.

The results are shown in Table 1.

(Example 3) Example 1 was carried out in the same manner as in Example 1 except that the composition of the coating liquid for forming the image receiving layer was changed as follows.

Coating liquid for forming image-receiving layer Vinyl chloride-vinyl acetate copolymer resin 10 parts [degree of polymerization 410. V Y HH Union Carbide Co., Ltd.] Methyl ethyl ketone 100 parts Cyclohexanone 50 parts (Comparative Example 1) Coating for ink layer formation in Example 1 The same procedure as in Example 1 was carried out except that nitrocellulose, which was a component of the liquid, was replaced with polyvinyl butyral.

The results are shown in Table 1.

(Comparative Example 2) In Example 1, nitrocellulose, which is one of the components of the coating liquid for forming an ink layer, was replaced with ethylcellulose [trade name EC
The procedure was carried out in the same manner as in Example 1, except that the sample was replaced with N-14 (manufactured by Vercules).

The results are shown in Table 1.

The results are shown in Table 1.

(Comparative Example 3) The same procedure as in Example 1 was carried out except that polyvinyl butyral, which was a component of the coating liquid for forming an ink layer, was replaced with nitrocellulose (therefore, the total amount of nitrocellulose was There will be 5 parts.)

The results are shown in Table 1.

Note to Table 1) The transfer density in Comparative Examples 1 and 2 could not be measured due to fusion.

[Effects of the Invention] The ink sheet for thermal transfer recording of the present invention has reliably improved storage stability, prevents fusion with the image-receiving sheet for thermal transfer recording and the occurrence of scumming on the sheet, and improves image density. It is possible to suppress the decline.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of an ink sheet for thermal transfer recording of the present invention. 1...Support, 2...Ink layer.

Claims (1)

[Claims] (1) An ink sheet for thermal transfer recording, characterized in that it is formed by laminating an ink layer containing a thermally diffusible dye, an acetal resin, and nitrocellulose on a support.