JP2002264542A - Heat transfer image receiving medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat transfer image receiving medium having a dye receiving layer using a plasticizer which shows a superb plasticizing efficiency and is capable of imparting satisfactory shelf stability to a photographic matter without the necessity to use a phthalate plasticizer and the like highly suspected to contain an endocrine disrupter, a mutagen, a carcinogen and the like. SOLUTION: In the heat transfer image receiving medium comprising a base material sheet and the dye receiving layer formed on the former, a citrate compound represented by formula (1) (wherein, R<1> is a hydrogen atom or a substitutable acyle group and R<2> , R<3> and R<4> are independently a substitutable alkyl group or cycloalkyl group) is used as a plasticizer of the dye receiving layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer image receiver used for thermal transfer recording.

[0002]

2. Description of the Related Art Using a heat diffusible dye such as a sublimable dye,
A sublimation type thermal transfer recording method for forming a full-color image with continuous gradation has been put to practical use. In sublimation type thermal transfer recording, for example, an ink ribbon and a thermal transfer image receiving body (photographic paper)
And a dye image is formed on the thermal transfer receiver by heating the ink ribbon according to an image signal such as a video image.

As such a thermal transfer image receiving body, a heat diffusible dye transferred from an ink ribbon by heating is received on a sheet-like substrate made of polypropylene or the like.
A dye-receiving layer for holding a dye image formed thereby is used.

As a resin constituting such a dye-receiving layer, a thermoplastic resin such as polyester or polyvinyl chloride which is easily dyed by a dye has been used. However, in order to obtain a clear image, the image sensitivity is increased. Various attempts have been made on resins constituting the dye-receiving layer from the necessity of increasing the weather resistance, light resistance and thermal stability of the image in order to increase the image stability and the storage stability of the formed image. For example, in order to improve the light resistance and weather resistance of an image, it has been attempted to form the dye receiving layer from a resin having a high glass transition temperature such as polycarbonate or cellulose ester.

However, when a resin having a relatively high glass transition temperature, such as polycarbonate or cellulose ester, is used as the dye receiving layer, a sufficient printing density cannot be obtained by using the resin alone. Therefore, it has been proposed to add a plasticizer to the dye receiving layer to improve its dyeing properties.
For example, Japanese Patent Publication No. 60-19138 proposes to add a phthalate plasticizer to a dye receiving layer composed of a polycarbonate resin. In addition, Japanese Unexamined Patent Application Publication No.
JP-A-80291 proposes to add an aryl ester or aralkyl ester of phthalic acid to a dye-receiving layer. It is proposed to add a kind. Phthalates and phosphates disclosed in these publications are preferably used because they have a large effect of improving dyeing properties.
Further, it has been attempted to add these plasticizers and adipic esters to the dye receiving layer in combination (Japanese Patent Laid-Open No. 2000-218947).

[0006]

However, among the phthalate ester plasticizers, phosphate ester plasticizers and adipate ester plasticizers described above, there are Endocrine Disruptors (endocrine disrupting substances, Suspicions of so-called environmental hormones, mutagenic substances, carcinogenic substances, etc. have been pointed out. In particular, it has been pointed out that phthalate ester-based plasticizers (dibutyl phthalate, diethylhexyl phthalate, dicyclohexyl phthalate, etc.) may be endocrine disruptors. It is strongly desired to provide a plasticizer which is suitable for the dye receiving layer and has high safety.

The present invention is intended to solve the problems of the prior art, and uses an endocrine disruptor, a phthalate plasticizer or the like which is highly suspicious of a mutagenic substance, a carcinogenic substance and the like. At least, it is an object of the present invention to provide a thermal transfer image receiver having a dye receiving layer using a plasticizer which is excellent in plasticization efficiency and can impart good storage stability to a printed material.

[0008]

Means for Solving the Problems The present inventor has found that endocrine disruptors, citrate compounds which are not recognized as mutagens or carcinogens are comparable to phthalate ester plasticizers. The present invention has been found to have a plasticizing efficiency and to impart good storage stability (for example, weather resistance) to a printed material, thereby completing the present invention.

That is, according to the present invention, in a thermal transfer image receiver having a dye receiving layer formed on a substrate sheet, the dye receiving layer is represented by the formula (1)

[0010]

Embedded image (In the formula, R ¹ is a hydrogen atom or an optionally substituted acyl group, and R ² , R ³ and R ⁴ are each independently an optionally substituted alkyl group or cycloalkyl group.) The present invention provides a thermal transfer image receptor comprising a citrate ester compound represented by the formula:

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The thermal transfer image receptor of the present invention comprises a substrate sheet having a dye-receiving layer formed thereon, wherein the dye-receiving layer is a citrate ester of the formula (1) as a plasticizer for a dye-dyeable resin. It is characterized by containing a series compound. Citrate compounds are highly safe compounds that are recognized as not endocrine disruptors, mutagens or carcinogens, and have a plasticization efficiency comparable to phthalate ester plasticizers. And a compound that can impart good storage stability (for example, weather resistance) to a printed material. Therefore, the thermal transfer image receiving body of the present invention has good safety and the obtained printed matter has good storage stability.

The optionally substituted acyl group of R ¹ in the formula (1) is preferably a lower alkanoyl group such as an acetyl group. Preferred examples of the substituent include a halogen, a hydroxyl group and an alkoxy group. A particularly preferred acyl group is an acetyl group. Examples of the optionally substituted alkyl group or cycloalkyl group of R ² , R ³ and R ⁴ include:
Preferred examples include a methyl group, an ethyl group, a propyl group, a butyl group, and a cyclohexyl group. Preferred examples of the substituent include a halogen, a hydroxyl group, an alkoxy group and the like. Particularly preferred, as the optionally substituted alkyl group or cycloalkyl group, a butyl group,
Ethyl groups are mentioned.

Specific examples of the citrate ester compound include triethyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate. Among them, acetyl tributyl citrate is preferred.

The amount of the citrate compound is preferably 1 to 100 parts by weight, more preferably 3 to 50 parts by weight, based on 100 parts by weight of the resin constituting the dye receiving layer.

In the dye receiving layer, in addition to a plasticizer comprising a citrate ester compound, if necessary, conventional plasticizers (phthalates, phosphates, etc.) as long as no major safety problems are caused. ) May be used in combination.

The dye-dyeing resin used in the dye-receiving layer includes a relatively high glass transition temperature (8%) such as cellulose ester, polycarbonate, and polyvinyl acetal resin.
(0 to 150 ° C.) can be preferably used.

Here, as the cellulose ester, esters of cellulose with various organic acids can be used. For example, cellulose acetate butyrate (CA
B), cellulose acetate propionate (CA
Esters of cellulose and lower alkyl fatty acids such as P) and cellulose acetate (CA) can be used, and commercially available products can be used. Also, aromatic esters such as benzoic acid esters and toluic acid esters of cellulose, and fatty acid esters having 4 or more carbon atoms such as caproic acid esters and lauric acid esters can be used.

The molecular weight of such a cellulose ester varies depending on the type of the cellulose ester to be used.
10,000 to 80,000 for AP, 30,000 for CA
~ 60,000 is preferred.

The degree of esterification also varies depending on the type of the cellulose ester used.
30%, 0.5-3.0% for CAP, about 40 for CA
% Is preferred.

In the case of CAB, the degree of butyrylation is 17
-60% is preferred, and for CAP, the degree of propionylation is preferably about 50%.

Commercially available cellulose esters suitable for the present invention include, for example, cellulose acetate butyrate CAB551-0.01, manufactured by Eastman Chemical Company, Inc.
B551-0.1, CAB551-0.2, CAB53
1-1, CAB500-1, CAB500-5, CAB
553-0.4, CAB381-0.1, CAB381
-0.5, CAB381-0.5BP, CAB381-
2, CAB381-20, CAB381-20BP, C
AB171-15S, C in cellulose propionate
AP482-0.5, CAP482-20, CAP50
4-0.2, CA-394- in cellulose acetate
60S, CA-398-10, CA-398-30 and the like.

Further, the dye-receiving layer of the thermal transfer image receptor of the present invention is formed by improving the whiteness of the dye-receiving layer to enhance the sharpness of the image, and further to provide the surface of the thermal transfer image receptor with writability and formed. In order to prevent retransfer of an image, a fluorescent whitening agent or a white pigment can be contained. Commercially available fluorescent whitening agents and white pigments can be used. For example, Ubitex OB manufactured by Ciba Specialty Chemicals can be used as the fluorescent whitening agent. Also,
As white pigments, titanium oxide, zinc oxide, kaolin,
Clay, calciulum carbonate, finely divided silica and the like can be mentioned, and these can be used alone or in combination of two or more.

In order to improve the light fastness of the transferred image, one or more additives such as an ultraviolet absorber, a light stabilizer and an antioxidant can be added to the dye receiving layer as needed. . The amounts of these fluorescent whitening agents, white pigments, ultraviolet absorbers, and light stabilizers can be appropriately adjusted depending on the use of the thermal transfer image receptor. Parts by weight.

In the dye receiving layer, a releasing agent can be contained in order to improve releasability from the ink ribbon sheet. Examples of the release agent include solid waxes such as polyethylene wax, amide wax, and Teflon (registered trademark) powder, fluorine-based surfactants, phosphate-based surfactants, silicone oil, and high-melting silicone wax. Among them, liquid silicone oil is preferred. Here, the silicone oil may be of a reaction (curing) type depending on the intended use of the thermal transfer image receiving body. As the reaction (curing) type silicone, alcohol-modified silicone oil and isocyanate are reacted, epoxy-modified silicone oil (epoxy / polyether-modified silicone oil) and carboxy-modified silicone oil (carboxy-polyether-modified silicone oil)
And a reaction-cured product of an amino-modified silicone oil (amino-polyether-modified silicone oil) and a carboxy-modified silicone oil (carboxy-polyether-modified silicone oil).

Further, an antistatic agent can be used in the dye receiving layer in order to prevent generation of static electricity during running in the printer. Examples of the antistatic agent include cationic surfactants (quaternary ammonium salts, polyamine derivatives, etc.), anionic surfactants (alkylbenzene sulfonate, alkyl sulfate sodium salt, etc.), zwitterionic surfactants, Alternatively, various surfactants such as a nonionic surfactant can be used. These antistatic agents may be contained in the dye receiving layer, or may be applied to the surface of the dye receiving layer by a method such as coating.

The thickness of the dye receiving layer is usually 0.01 to 5 μm.
m.

The thermal transfer image receptor of the present invention is characterized by having the above-mentioned dye receiving layer, and other configurations can be the same as those of the conventional thermal transfer image receptor. For example, as the substrate sheet, papers such as high-quality paper and coated paper, various types of plastic sheets, or a laminated sheet obtained by combining them can be used as in the case of the conventional thermal transfer image receiving member.

Further, a lubricating layer or the like may be provided on the surface of the substrate sheet opposite to the dye receiving layer, if necessary.

The thermal transfer image receiving body of the present invention can be manufactured by a known method.
A dye-dyeing resin, a citrate compound, and other additives are dissolved or dispersed in a solvent, and a dye-receiving layer-forming coating liquid composition is applied by a wire bar coater or the like, and is manufactured by drying. be able to.

The thermal transfer image receiving body of the present invention described above can be preferably applied as photographic paper used in conventional sublimation thermal transfer recording.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

Example (1A, 1A ', 1A ", 2A, 2A', 2A", 3
6) and reference (1A, 2A, 1B, 2B) The coating liquid composition for forming a receiving layer of compositions 1 to 8 shown in Table 1 was prepared using synthetic paper [trade name YUPO FPG-150 (Oji Oil Chemical Synthetic Paper)]. )], Coated with a wire bar so that the coating amount at the time of drying was 5 g / m ² , dried at 120 ° C. for 2 minutes, and kept at 50 ° C. for 48 hours to produce photographic paper.

The amount of the citric acid ester used as a plasticizer used in Examples and Comparative Examples was determined by adding dicyclohexyl phthalate as a plasticizer to the dye receiving layer resin at 20 PHR.
(60 mmol / 100 g of dye-receiving layer resin) was used as a reference, and the amount of addition was such that print density characteristics equivalent to the reference (print density difference of each gradation was within ± 0.03 of the reference ratio) were obtained.

As shown in Table 1, when the citrate ester agent was used, the same printing characteristics were obtained with a smaller amount of addition as compared with the case where dicyclohexyl phthalate was used, and the plasticization efficiency was higher than that of dicyclohexyl phthalate. Is excellent.

(Printing Test) Each photographic paper obtained from the coating liquid composition for forming a dye receiving layer having compositions 1 to 8 was applied to a color printer (U.
P-D8800 (manufactured by Sony)), and 16 gradation prints of yellow, magenta and cyan were performed using an ink ribbon (UPC-8840 (manufactured by Sony)). In addition, when the self-lamination layer (protective layer) applied following yellow, magenta, and cyan of the ink ribbon is not transferred, and in the two cases where the transfer is performed, the light resistance test and the dark discoloration test are performed on the prints. went. Tables 2 and 3 show the obtained results.

[0037] For light resistance test paper to form indicia images of printed matter, a xenon arc lightfastness tester (Atlas Ci35A-UV weatherometer, manufactured by Atlas) Xenon arc exposure with (integrated irradiation dose = 90 kJ / ^{m 2} Irradiance = 0.35 W / m ² , black panel temperature = 64 ° C., dry-bulb humidity = 43 ° C., relative humidity = 25%), and the residual ratio defined by the following equation was determined by the printing density before and after irradiation. .

## EQU1 ## Residual rate (%) = (reflection density after irradiation / reflection density before irradiation) × 100

Test for Dark Fading of Printed Material The printed material was allowed to stand at 60 ° C. and 85% RH for 2 weeks, and the residual ratio (preservation ratio) of the dye defined by the following formula was determined from the change in the printing density before and after standing. At the same time, the degree of bleeding of the image after the test was also examined.

## EQU2 ## Residual rate (%) = (reflection density after standing / reflecting density before standing) × 100

As can be seen from Tables 2 and 3, when the protective layer was transferred after image formation, Examples 1B, 2B and 3 to 3 were used.
6, it can be seen that storage performance equivalent to that in the case of using dicyclohexyl phthalate of Reference 1B and Reference 2B is obtained irrespective of the type of citrate ester.

When the protective layer was not transferred after image formation, the results of Examples 1A ', 1A ", 2A' and 2A" using triethyl citrate or acetyl triethyl citrate were used. Also, it can be seen that the results of Examples 1A and 2A using tributyl acetylcitrate are excellent. Moreover, in the case of Example 1A and Example 2A using tributyl acetyl citrate, reference 1
A and a storage performance equivalent to the use of dicyclohexyl phthalate of Reference 2A are obtained. Therefore, when the protective layer is not transferred after printing, tributyl acetyl citrate is particularly useful as a citrate plasticizer to be added to the dye receiving layer of the thermal transfer image receptor.

[Table 1]

[Table 2]

[Table 3]

[0041]

According to the present invention, an endocrine disrupter, a citrate ester compound which is recognized as not a mutagenic substance or a carcinogenic substance is used as a plasticizer for a dye receiving layer of a thermal transfer image receptor. It can be suitably used as a substitute for the phthalic acid ester and the like conventionally used. As a result, it is possible to provide photographic paper with higher safety.

Claims (4)

[Claims] In a thermal transfer image receiver having a dye receiving layer formed on a base sheet, the dye receiving layer is represented by the formula (1): (In the formula, R ¹ is a hydrogen atom or an optionally substituted acyl group, and R ² , R ³ and R ⁴ are each independently an optionally substituted alkyl group or cycloalkyl group.) A thermal transfer image receptor comprising a citrate compound of formula (I). 2. A dye-receiving layer comprising the citrate compound in an amount of 1 to 100 parts by weight of a resin constituting the dye-receiving layer.
2. The thermal transfer image receptor according to claim 1, wherein the thermal transfer image receptor is contained in an amount of from 100 to 100 parts by weight. 3. The thermal transfer image receptor according to claim 1, wherein said citrate compound is acetyl tributyl citrate. 4. The thermal transfer image receiver according to claim 1, wherein the resin constituting the dye receiving layer contains a cellulose ester.