JPH02107485A - Image receiving sheet for thermal transfer and thermal transfer method - Google Patents

Abstract

PURPOSE:To obtain a clear and fast image by providing a dye-receiving layer of an image receiving sheet for thermal transfer by use of an acidic resin. CONSTITUTION:An image receiving sheet for thermal transfer comprises a base sheet and an dye-receiving layer provided at least one side of the base sheet. The dye-receiving layer is provided by use of a resin having an acidic group, e.g., a carboxyl group or a sulfonyl group, in the molecule thereof, and may be provided by use of a mixture of the resin with a resin not having an acidic resin. Particularly when the acid value of the acidic resin is 2 or more, an excellent dye-receiving property is exhibited. A preferable range of the acid value is 2-20. If the acid value is less than 2, the receiving layer obtained is insufficient in resistance to bleeding of comparatively low molecular wight dyes or in contamination resistance, whereas if the acid value exceeds 20, receptivity for comparatively high molecular weight dyes becomes unsatisfactory. The acidic resins which can be used include acid-modified resins, among which a polyester resin is particularly preferred. A sublimable dye to be used is preferably a dye having at least one primary to tertiary amino group.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a thermal transfer image-receiving sheet and a thermal transfer method, and more specifically to a thermal transfer image-receiving sheet and a thermal transfer method capable of forming recorded images with excellent color density, clarity, and various fastness properties. An object of the present invention is to provide an image receiving sheet and a thermal transfer method.

(Prior Art) Various thermal transfer methods have been known in the past, but among them, a sublimation dye is used as a recording agent, this is carried on a base sheet such as paper to form a thermal transfer sheet, and the dye is dyed with a sublimation dye. The thermal transfer sheet is layered on a transferable material such as polyester woven cloth, and thermal energy is applied in a pattern from the back side of the thermal transfer sheet.
A sublimation transfer method is used in which a sublimable dye is transferred to a transfer material.

(Problems to be Solved by the Invention) In the above-mentioned sublimation printing method, in which the material to be transferred is, for example, a polyester woven fabric, heat energy is applied for a relatively long time, so the material to be transferred is As a result, relatively good dye migration is achieved as a result of the heat applied to the dye.

However, with advances in recording methods, delicate characters and graphics can be printed onto these materials at high speeds using thermal heads, etc., for example, using polyester sheets or paper with a dye-receiving layer. When forming a photographic image, it is required that the application of thermal energy be extremely short, on the order of seconds or less. Since it is not heated, it is not possible to form an image with sufficient density.

Therefore, in order to cope with such high-speed recording, sublimable dyes with excellent sublimation properties were developed, but dyes with excellent sublimation properties generally have small molecular weights, so they do not dissolve in the transferred material after transfer. Problems arise in that the dye migrates over time or bleeds onto the surface, resulting in the well-formed image becoming distorted or unclear, or contaminating surrounding articles.

In order to avoid such problems, if a sublimable dye with a relatively large molecular weight is used, the sublimation speed will be poor in the high-speed recording method as described above, so it will not be possible to form an image with a satisfactory density as described above. Met.

Therefore, an object of the present invention is to provide a clear image with sufficient density in a thermal transfer method using a sublimable dye by applying thermal energy in an extremely short period of time as described above.
Moreover, it is an object of the present invention to provide a thermal transfer image-receiving sheet in which the formed image exhibits excellent fastness properties.

(Means for solving problems) The above objects are achieved by the present invention as described below.

That is, the present invention provides a thermal transfer method comprising a base sheet and a dye-receiving layer formed on at least one surface of the base sheet, the dye-receiving layer comprising an acidic resin having an acid value of 2 or more. An image-receiving sheet and a thermal transfer method using the image-receiving sheet.

(Function) By forming the receptor layer of the thermal transfer image-receiving sheet from an acidic resin with an acid value of 2 or more, the bleed resistance of the received dye is improved even when a relatively low molecular weight dye is used. Images with excellent clarity, density, storage stability, etc. can be formed. or,
Even when a relatively high molecular weight dye is used, since the dye receptivity is excellent, it is possible to form an image which is also excellent in sharpness, density, storage stability, etc.

In particular, when a sublimable dye having a basic amino group is used, the dye is captured by acidic groups within the receptor layer, resulting in better bleed resistance.

(Preferred Embodiments) Next, the present invention will be described in more detail by citing preferred embodiments.

The thermal transfer image-receiving sheet of the present invention consists of a base sheet and a dye-receiving layer provided on at least one surface of the base sheet.

The base sheet used in the present invention includes synthetic paper (polyolefin type, polystyrene type, etc.), high quality paper, art paper,
Coated paper, cast coated paper, wallpaper, lined paper, synthetic resin or emulsion impregnated paper, synthetic rubber latex impregnated paper, synthetic resin internalized paper, paperboard, etc., cellulose fiber paper, polyolefin, polyvinyl chloride, polyethylene terephthalate, polystyrene, polyester Various plastic films or sheets such as methacrylate and polycarbonate can be used, and are not particularly limited.

Furthermore, a laminate made of any combination of the above base sheets can also be used. Typical examples of laminates include cellulose fiber paper and synthetic paper, or synthetic paper of cellulose fiber paper and plastic film or sheet.

The receptor layer formed on the surface of the base sheet is for receiving the sublimable dye transferred from the thermal transfer sheet and maintaining the formed image. The receiving layer is formed from various resins having acidic groups such as carboxyl groups or sulfonic acid groups in the molecule, but it may also be formed from a mixture of resins having these acidic groups and resins not having acidic groups. good. In particular, in the present invention, it has been found that excellent dye receptivity is exhibited when the acidic resin used has an acid value of 2 or more.

The preferred range of acid value is from 2 to 20; if the acid value is less than 2, the bleeding resistance and stain resistance of relatively low molecular weight dyes will be insufficient; on the other hand, if the acid value exceeds 20. This is not preferable because the receptivity for relatively high molecular weight dyes becomes insufficient.

Examples of the acidic resin used in the present invention include the following acid-modified resins.

(a) Those having ester bonds, such as polyester resins, polyacrylic acid ester resins, polycarbonate resins, polyvinyl acetate resins, styrene acrylate resins, vinyl toluene acrylate resins, etc.

(0) Those having urethane bonds, such as polyurethane resins.

(8) Those having an amide bond, such as polyamide resin (nylon).

(d) Those having urea bonds, such as urea resins.

(f) Others having highly polar bonds, such as polycaprolactone resin, polystyrene resin, polyvinyl chloride resin, polyacrylonitrile resin, etc.

Among the above synthetic resins, polyester resins are particularly preferred.

The above acidic resin can be obtained by modifying the resin with a polycarboxylic acid during or after synthesis. Modification methods include, for example, in the case of condensation resins such as polyester resins, polyurethane resins, and polyamide resins, method 1 in which polycarboxylic acid is used in excess during synthesis, or trivalent or higher acid is used; In the case of vinyl resin,
A resin having a desired acid value can be obtained by using a monomer having an acidic group as part of the monomers used.

In addition, in the case of modification after synthesis, a resin having groups such as a water group, an amino group, an amide group, an epoxy group, an isocyanate group, etc. can be modified with a polycarboxylic acid to obtain a resin with an arbitrary acid value. Can be done.

Examples of polycarboxylic acids used for resin modification include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, fumaric acid, maleic acid, methylmaleic acid, methylfumaric acid, itaconic acid, and citraconic acid. ,
Examples of aromatic polycarboxylic acids include di- or tricarboxylic acids such as mesaconic acid, acetylenic acid, malic acid, methylmalic acid, citric acid, isocitric acid, and tartaric acid, or anhydrides thereof; For example, phthalic acid, terephthalic acid, isophthalic acid, trimellitic acid,
1,2.3-benzenetricarboxylic acid, 1,3.5-benzenetricarboxylic acid, pyromellitic acid, benzenehexacarboxylic acid, naphthalenedicarboxylic acid, naphthalenetricarboxylic acid, naphthalenetetracarboxylic acid, diphenyltetracarboxylic acid, diphenyl ethertetracarboxylic acid Examples include acids, azobenzenetetracarboxylic acids, and anhydrides thereof. A particularly preferred aromatic polycarboxylic acid in the present invention is benzenetricarboxylic acid, particularly trimellitic acid or its anhydride.

The thermal transfer image-receiving sheet of the present invention has the above-mentioned acidic resin or a mixture thereof with a non-acidic resin dissolved in an appropriate organic solvent or dispersed in an organic solvent or water on at least one surface of the above-mentioned base sheet. A dye-receiving layer is obtained by coating and drying the dispersion obtained. When an acidic resin and a non-acidic resin are used as a mixture, the acidic resin is preferably 5% by weight or more, preferably 10% by weight or more in the total of both.

When forming the above-mentioned receptor layer, titanium oxide,
Pigments and fillers such as zinc oxide, kaolin clay, calcium carbonate, and finely powdered silica can be added. Further, in order to further increase the light resistance of the transferred image, an ultraviolet absorber and/or a light stabilizer can be added to the receiving layer.

Such a dye-receiving layer may be of any thickness, but numerically from 3 to 50 μm thick. Although such a dye-receiving layer is preferably a continuous coating, it may also be formed as a discontinuous coating using a resin emulsion or resin dispersion.

Although the thermal transfer image-receiving sheet of the present invention can basically be used satisfactorily with the above structure, it is possible to incorporate an inorganic powder for preventing adhesion into the dye-receiving layer. Even if the temperature at the time of thermal transfer is increased, adhesion between the thermal transfer sheet and the thermal transfer image-receiving sheet can be prevented, and even more excellent thermal transfer can be performed. Particularly preferred is finely powdered silica.

Further, a resin having good mold release properties may be added in place of or in combination with the above-mentioned inorganic powder such as silica. Particularly preferred release polymers include cured products of silicone compounds, such as cured products of epoxy-modified silicone oil and amino-modified silicone oil. It is preferable that such a dynamic agent accounts for about 0.5 to 30% by weight of the dye-receiving layer.

The thermal transfer sheet used when carrying out thermal transfer using the thermal transfer image-receiving sheet of the present invention as described above is one in which a dye layer containing a sublimable dye is provided on a sheet of paper or a polyester film, and conventionally known thermal transfer sheets are Any of them can be used as is in the present invention.

According to the research of the present inventor, it is preferable that the dye used in the thermal transfer sheet is a dye having at least one primary to tertiary amino group, and in particular, indoaniline represented by the following structural formula. It has been found that the best images can be formed when dyes are dyes such as cyanoacetyl, cyanoacetyl, or anthraquinone.

Dye number 1゜Dye number 6゜Dye number 2゜Dye number 7゜Dye number 3゜Dye number 4゜+12 Dye number 5゜(R1 to R4 in the above formula are CI to C6 alkyl group, cycloalkyl group, or phenyl R2 may be a hydrogen atom or an alkoxy group, and R3 and R4 may form a ring. X is a substituent such as a hydrogen atom, a halogen atom, a lower alkyl group, an alkoxy group, a nitro group ) Also, any conventionally known means for applying thermal energy during thermal transfer can be used, such as thermal printers (e.g., Video Printer V manufactured by Hitachi).
By controlling the recording time using a recording device such as Y-Zoo, the intended purpose can be fully achieved by applying thermal energy of about 5 to 100 mJ/mm1.

(Effects) According to the present invention as described above, by forming the dye-receiving layer of the thermal transfer image-receiving sheet from an acidic resin, high-density and clear images are formed, and in particular, these images have excellent bleed resistance, Since it has stain resistance, the sharpness of the image does not deteriorate even if the image is stored for a long period of time, and it does not contaminate other articles when it comes into contact with them, thus solving various problems of the prior art.

(Example) Next, the present invention will be explained in more detail by giving examples and comparative examples. In the text, parts or percentages are based on weight unless otherwise specified.

Example An ink composition for forming a dye-carrying layer having the following composition was prepared, and it was applied and dried on a 6 μm thick polyethylene terephthalate film whose back surface had been heat-resistant treated so that the dry coating amount was 1.0 g/♂. A thermal transfer sheet shown in Table 1 below was obtained.

Dye of the above structural formula 3.0 parts Polyvinyl butyral resin 4.5 parts Methyl ethyl ketone 46.25 parts Toluene
46.25 parts However, if the dye mixture is insoluble in the above composition, DMF, dioxane,
Chloroform etc. were used as appropriate.

J-1 d -CH.

-C21+5 -CH.

-CH3 CH3 CH3 -cd+t CH3 -(:)13 -CH,t C2115 Cl3 -C3H? C2H5 C.L. CH3 -C3) 1st floor -C,O.

C4H9 -(:2H.

I"C)13 I-(:H3 Next, synthetic paper (Yubo FP manufactured by Tamago Yuka Co., Ltd.) was used as a base sheet.
G#150), apply a coating liquid with the following composition to one side at a rate of 10.0g/ba when dry,
The sheets were dried at .degree. C. for 30 minutes to obtain thermal transfer image-receiving sheets of the present invention shown in Table 2 below.

Acidic resin shown in Table 2 below: 11.5 parts Vinyl chloride/vinyl acetate copolymer (VY, manufactured by UCC) 5.0 parts Amino-modified silicone (F-393, manufactured by Shin-Etsu Chemical Co., Ltd.) 1.2 parts Epoxy-modified Silicone (X-22-: +43, manufactured by Shin-Etsu Chemical)
1.2 parts methyl ethyl ketone/toluene/cyclohexanone (weight ratio 4:4:2)
102.0 copies? -z 2 - No, 1 Polyester resin (# value 0.6) modified with trimellitic anhydride Acid value 4.8 No, 2 Same as above, acid value 2 No, 3 Same as above, acid value 5 No. 14 Same as above No. 5 with acid value 6 No. 6 Same as above with acid value 9 No. 6 Same as above modified with phthalic anhydride Acid value 4
．． 7 NO67 same t modified with maleic anhydride Acid value: 4.
4 NO18 Same as above modified with succinic anhydride Acid value 4.7 No. 9 Unmodified (comparative example) Acid value 0.6 The above thermal transfer sheet and the thermal transfer image receiving sheet of the present invention were
The respective dye layers and the dye-receiving surface were stacked facing each other, and recording was performed from the back side of the thermal transfer sheet using a thermal head under the conditions of an applied head voltage of 10 v1 and a printing time of 0 m5 ec, and the results shown in Table 3 below were obtained. Ta.

'7. 3. When the white paper was colored, it was marked as △, and when the image became unclear and the white paper was markedly colored, it was marked as ×.

1 1 1.20 ◎
2 2 1.20 ◎3
3 1.30 ◎4
4 1.50 ◎5
5 1.40 ◎6
6 1.02 ◎7
7 1.10 ◎1
8 1.05 ◎1
9 1.00 0 The color density was measured using a densitometer RD-9 manufactured by Maches, USA.
This is the value measured at 18.

Claims (6)

[Claims] (1) A thermal transfer image-receiving sheet comprising a base sheet and a dye-receiving layer formed on at least one surface of the base sheet, the dye-receiving layer comprising an acidic resin having an acid value of 2 or more. (2) The thermal transfer image-receiving sheet according to claim 1, wherein the acidic resin is an acid-modified polyester resin. (3) In a thermal transfer method in which a thermal transfer sheet having a sublimable dye layer and a thermal transfer image-receiving sheet having a dye-receiving layer are stacked and heated in an imagewise manner to form an image on the dye-receiving layer, the dye-receiving layer has an acid value of A thermal transfer method characterized by comprising an acidic resin having two or more. (4) The thermal transfer method according to claim 3, wherein the acidic resin is an acid-modified polyester resin. (5) The thermal transfer method according to claim 3, wherein the sublimable dye is a dye having an amino group. (6) The thermal transfer method according to claim 3, wherein the sublimable dye is an indoaniline dye, a cyanoacetyl dye, or an anthraquinone dye.