JP2002127618A - White laminated polyester film for thermal transfer recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a while laminated polyester film for thermal transfer recording, excellent in whiteness, printing property, antistatic properties, light resistance and adherence durability. SOLUTION: In the white laminated polyester film provided on at lest one side of a white polyester layer (B) containing fine bubbles with a white polyester layer (A), the white polyester layer (B) contains a light-resistant agent and a surface specific resistance of the same measured from the white polyester layer (A) side is 1012 Ω/(square) or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a white laminated polyester film. More specifically, the present invention is excellent in film-forming properties, whiteness, printability and antistatic properties, light resistance, image adhesion durability, and is optimal for heat-sensitive transfer as a receiving sheet substrate for heat-sensitive transfer recording. It relates to a white laminated polyester film for recording.

[0002]

2. Description of the Related Art As one of recording methods in a hard copy technique, a thermal transfer recording method, which has features such as non-impact, easy operation and maintenance, low cost and downsizing, has been attracting attention. This thermal transfer recording method is a method in which a transfer sheet (ink ribbon) having an ink layer, which is a color material-containing layer, and a receiving sheet are superimposed, and are transferred by melting or sublimation according to the heating of the thermal head from the ink ribbon side. In this method, the color material-containing component or color material to be transferred is transferred to the receiving sheet in the form of fine halftone dots (dots) and printed.
Conventionally, as a receiving sheet substrate used in such a thermal transfer recording method, a white polyester film containing an inorganic fine particle such as titanium oxide, calcium carbonate or barium sulfate or a resin incompatible with polyester in polyester is used. Has been applied. In general, a receiving sheet for thermal transfer recording is provided by providing a receiving layer for enhancing the printing function on these white polyester films. Further, there is a demand for a white polyester film having high whiteness, which improves the accuracy of printing and recording, enhances the sharpness of a printed image, and gives a more luxurious appearance. In response to such a demand, a white polyester film in which a plurality of the above-mentioned inorganic fine particles are added in combination, a white polyester film in which an inorganic fine particle and an incompatible resin are added in combination, and the like are known. As such a white polyester film, for example, JP-A-4-153232,
JP-A-6-322153 is disclosed.

[0003]

However, in recent years, in addition to the above-mentioned requirements, practical characteristics include (1) light resistance (a yellowing even when irradiated with sunlight, fluorescent light, etc. for a long period of time). And (2) antistatic properties (that is, the receiving sheets are not stuck together due to static electricity, and it is difficult for dust and the like to adhere to the receiving sheet surface). However, when the white polyester film exemplified above is used as the receiving sheet substrate, the film is colored yellow (yellowing) when subjected to long-term light irradiation because of poor light resistance and antistatic property, There is a problem that dirt and dust adhere to the surface of the receiving sheet and the quality of the printed image is reduced. In addition, there are many problems in the practical characteristics of the receiving sheet, such as the fact that the receiving sheets are stuck to each other to cause troubles such as paper jam during printing and recording.

[0004] As a method of solving the above-mentioned problem, a method of incorporating a light-fast agent and an antistatic agent into a film can be considered. However, in such a method, there is a problem of coloring by the light-proofing agent or the antistatic agent itself, a decrease in adhesion between the receiving layer and the film surface when a receiving layer is provided on the surface to enhance the printing function, Various problems such as deterioration of the light fastness and antistatic properties due to the mutual influence of the inhibitors and a rise in the cost of raw materials are likely to occur, and the above-mentioned requirements could not be satisfied. In addition, even when the light-resistant agent and the antistatic agent are separately contained as a two-layer laminated film, the light-resistance and the antistatic property are affected by each other over time, and the light-resistant agent and the antistatic agent are reduced. There was also a disadvantage that the adhesion between the layers was reduced. In the receiving sheet manufactured using such a film, for example, there is a practical problem that a printed image is easily peeled from a portion where adhesion is reduced.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, to maintain high light fastness and adhesion durability of an image, and to provide a thermal transfer recording having excellent whiteness, printability and antistatic properties. To provide a white laminated polyester film.

[0006]

In order to achieve this object, a white laminated polyester film for thermal transfer recording according to the present invention comprises a white polyester layer (B) containing fine bubbles and a white polyester layer on at least one surface thereof. (A)
A white laminated polyester film provided with
The white polyester layer (B) contains a light stabilizer,
A white laminated polyester film for thermal transfer recording, wherein the surface specific resistance measured from the white polyester layer (A) side is 10 ¹² Ω / □ or less.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The white laminated polyester film for thermal transfer recording of the present invention is basically composed mainly of polyester.

In the present invention, the polyester is a polymer obtained by condensation polymerization of a diol and a dicarboxylic acid. Further, dicarboxylic acids are terephthalic acid,
Isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, adipic acid, sebacic acid and the like, and diols are represented by ethylene glycol, trimethylene glycol, tetramethylene glycol, cyclohexane dimethanol, and the like. . Specific examples of such a polyester include, for example, polyethylene terephthalate, polyethylene-p-oxybenzoate, poly-1,4-cyclohexylene dimethylene terephthalate, polyethylene 2,6-naphthalenedicarboxylate (polyethylene naphthalate), and the like. Can be used.

Of course, these polyesters may be either homopolyesters or copolyesters. Examples of the copolymerization components of the copolyester include diol components such as diethylene glycol, neopentyl glycol, and polyalkylene glycol. Dicarboxylic acid components such as adipic acid, sebacic acid, phthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, and 5-sodium sulfoisophthalic acid can also be used. Also, in this polyester, if necessary, an appropriate additive in an amount that does not impair the effects of the present invention, for example, a heat stabilizer,
Oxidation-resistant stabilizer, organic lubricant, organic fine particles, filler,
A nucleating agent, a dye, a dispersant, a coupling agent and the like may be blended.

As the polyester used in the present invention, polyethylene terephthalate and polyethylene naphthalate are particularly preferably used because of their excellent strength, heat resistance, water resistance and chemical resistance.

The white laminated polyester film of the present invention has a white polyester layer (B) containing fine bubbles and at least one surface thereof having a white polyester layer (A).
The white polyester layer (B) needs to contain a light-proofing agent in particular. When the white polyester layer (B) contains a light-resistant agent, the light resistance of the white laminated polyester film of the present invention is remarkably improved, and even when used as a receiving sheet substrate for thermal transfer recording for a long period of time, its whiteness is improved. (Whiteness representing whiteness, color b value representing bluish color, etc.) can be maintained in the initial state, and an excellent white laminated polyester film can be obtained in which the printed image is always clear and full of luxurious feeling. Further, the white laminated polyester film of the present invention,
The adhesiveness of the image is excellent, and various properties such as antistatic properties can be excellent in stability over time.

In the present invention, the content of the light stabilizer is 0.0
It is preferably from 5 to 10% by weight, more preferably from 0.1 to 7% by weight, and most preferably from 0.2 to 5% by weight. When the content of the light stabilizer is less than 0.05% by weight, the light resistance becomes insufficient, and the film deteriorates during long-term use, and the whiteness tends to decrease. On the other hand, when the content of the light stabilizer exceeds 10% by weight, whiteness may be reduced due to coloring by the light stabilizer, which is not preferable.

The light stabilizer used in the present invention has excellent heat resistance, has good compatibility with the above-mentioned polyester, can be uniformly dispersed, has little coloring, and adversely affects the properties of the resin used and the whiteness of the film. It is desirable not to affect. There is no particular limitation as long as it is a light stabilizer that satisfies the above conditions.For example, various kinds of ultraviolet absorbers such as salicylic acid type, benzophenone type, benzotriazole type, cyanoacrylate type and ultraviolet stabilizers such as hindered amine type are applicable. It is. More specific examples of the light stabilizer are as follows.

(Ultraviolet absorber) (a) Salicylic acid: pt-butylphenyl salicylate, p-octylphenyl salicylate (b) Benzophenone: 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2 -Hydroxy-4-methoxy-5-sulfobenzophenone, 2,2'-4,4'-tetrahydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'- Dimethoxybenzophenone, bis (2-methoxy-4-hydroxy-5-benzoylphenyl) methane (c) Benzotriazole: 2- (2'-hydroxy-
5′-methylphenyl) benzotriazole, 2-
(2′-hydroxy-5′-t-butylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5 ′)
-Di-t-butylphenyl) benzotriazole, 2-
(2′-hydroxy-3′-t-butyl-5′-methylphenyl) -5-chlorobenzotriazole, 2-
(2′-hydroxy-3 ′, 5′-di-t-butylphenyl) -5-chlorobenzotriazole, 2- (2′-
(Hydroxy-5'-t-octylphenol) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-t-amylphenyl) benzotriazole, 2,2'
-Methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2 (2'hydroxy-5'-methacryloxyphenyl) -2H -Benzotriazole, 2
-[2'-hydroxy-3 '-(3 ", 4", 5 ",
6 ″ -tetrahydrophthalimidomethyl) -5′-methylphenyl] benzotriazole cyanoacrylate: ethyl-2-cyano-3,3 ′
-Diphenyl acrylate Other than the above: 2-ethoxy-2'-ethyloxazac acid bisanilide, 2- (4,6-diphenyl-1,2
3,5-triazin-2-yl) -5-[(hexyl)
Oxy] -phenol.

(Ultraviolet stabilizer) (d) Hindered amine type: bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, dimethyl succinate-1- (2-hydroxyethyl) -4-hydroxy- 2,2,6,6-tetramethylpiperidine polycondensate (e) Other than the above: nickel bis (octylphenyl) sulfide, [2-thiobis (4-t-octylphenolate)]-n-butylamine nickel, nickel complex -3,5-di-t-butyl-4-hydroxybenzyl-phosphate monoethylate, nickel dibutyldithiocarbamate, 2,4-di-t-butylphenyl-
3 ', 5'-di-t-butyl-4'-hydroxybenzoate, 2,4-di-t-butylphenyl-3', 5 '
-Di-t-butyl-4'-hydroxybenzoate.

Among these light stabilizers, 2,2 ', 4,4'-tetrahydroxy-benzophenone and bis (2-methoxy-4-hydroxy-5-benzoylphenyl) methane, which have excellent compatibility with polyester, , 2'-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2- (4,6-diphenyl-1,3, 5-
Triazin-2-yl) -5-[(hexyl) oxy]
-Application of phenol is preferred. The above-mentioned light stabilizers may be used alone or in combination of two or more.

As described above, the white laminated polyester film of the present invention has a laminated structure of two or more layers having the white polyester layer (A) on at least one surface of the white polyester layer (B). It is necessary that the polyester layer (B) be a layer containing fine bubbles. That is, by containing fine bubbles inside, a heat insulating effect against the heating of the thermal head at the time of thermal transfer recording can be obtained, and heat can be efficiently transmitted to the printed portion. Furthermore, the adhesion between the thermal head and the printing surface is enhanced by the development of the cushioning property, and the heat transfer to the printing portion becomes more uniform and more efficient.

The method for incorporating fine bubbles into a polyester film is as follows: (1) A foaming agent is added to polyester and foamed by heating during extrusion or film formation, or foamed by chemical decomposition to form bubbles. Method, (2)
(3) a method of adding a gas or a vaporizable substance at the time of extruding a polyester; (3) adding a thermoplastic resin (incompatible resin) incompatible with the polyester to the polyester and stretching it uniaxially or biaxially to obtain fine particles; (4) A method of adding a large amount of bubble-forming inorganic fine particles instead of the incompatible resin is generally used. Any method may be used as long as it is within the range of the object of the present invention.However, film forming properties, ease of adjusting the amount of bubbles to be contained therein, formation of bubbles of finer and uniform size are formed. The use of the incompatible resin of the above (3) is particularly preferred from the viewpoints of easiness and lightness.

The fine bubbles in the present invention refer to those which can contribute to imparting heat insulating properties and cushioning properties to the film itself in order to improve printability, and specifically, include those in polyester. Most preferably, the resin is formed using the incompatible resin as a core. More specifically, when the cross section (thickness direction) of the white polyester layer (B) is observed by a scanning electron microscope (SEM) or a transmission electron microscope (TEM), the cross-sectional area of the bubble portion (however, the average value of the core incompatible resin portion is excluded) is preferably what is 1 to 25 m ^2, more preferably 1.5～20Myuemu ^2, further 2
Most preferably, it is in the range of 15 μm ² . The immiscible resin referred to in the present invention is a thermoplastic resin other than polyester, and a thermoplastic resin showing incompatibility with the polyester, preferably dispersed in the polyester in a particle form, It is a resin having a large effect of forming bubbles in a film by stretching. More specifically, the incompatible resin is preferably a differential scanning calorimeter (DS)
In a measurement by a known method using C) or the like, in a system in which a polyester and the above-mentioned incompatible resin are melted, in addition to the glass transition temperature (hereinafter abbreviated as Tg) corresponding to the polyester, It is a resin for which a corresponding Tg is observed.

The melting point of such an incompatible resin may be lower than the melting point of the polyester and higher than the temperature at which the film is heat-fixed and oriented during the film formation (heat treatment temperature). preferable. From this point, among the incompatible resins, polyethylene, polypropylene, polybutene, polyolefin resins such as polymethylpentene,
Polystyrene resins, polyacrylate resins, polycarbonate resins, polyacrylonitrile resins, polyphenylene sulfide resins, fluorine-based resins, and the like are preferably used. These incompatible resins may be a homopolymer or a copolymer, and two or more incompatible resins may be used in combination. Among these, polyolefin resins such as polypropylene and polymethylpentene having a small critical surface tension are preferable, and polymethylpentene is most preferable. Since polymethylpentene has a relatively large difference in surface tension from polyester and a high melting point, it has a feature that the effect of forming bubbles per addition amount is large, and is particularly preferable as an incompatible resin.

The content of the incompatible resin in the white polyester layer (B) is not particularly limited, but is preferably 1 to 35% by weight, more preferably 2 to 30% by weight, and further preferably 3 to 2% by weight.
Most preferably, it is in the range of 5% by weight. When the addition amount is less than the above range, it is difficult to improve the whiteness and the concealing property of the film. On the contrary, when the addition amount is larger than the above range, the film tends to be broken at the time of stretching, and the production is increased. Performance may be reduced.

Further, the white polyester layer (B) of the present invention
In addition to the polyester and the incompatible resin described above,
Further, by adding a dispersing agent, the dispersion diameter of the immiscible resin becomes smaller, so that the bubbles generated by stretching can be made finer, and as a result, the whiteness and film forming property of the film can be improved. Is more preferable. Examples of the dispersant exhibiting the above effects include olefin polymers or copolymers having a polar group such as a carboxyl group or an epoxy group or a functional group reactive with polyester, polyalkylene glycol, a surfactant, An adhesive resin or the like can be used. Of course, these may be used alone or in combination of two or more. As a method of adding a dispersant, blending and mixing with polyester, random copolymerization,
Copolymerization such as block copolymerization can be employed. Further, partial copolymerization, which is an intermediate state between the two, may be used.

The amount of the dispersant added in the present invention is 0.0
It is preferably 5 to 10% by weight, more preferably 0.1 to 7% by weight.
%, Most preferably 0.2-5% by weight. When the addition amount is less than 0.05% by weight, the effect of making the air bubbles fine is reduced. On the other hand, when the addition amount is more than 10% by weight, the effect of adding the incompatible resin is reduced, and problems such as a decrease in whiteness and an increase in cost are likely to occur.

In the present invention, as a method for whitening the white polyester layer (A), a white dye, a white pigment,
Although a method of adding inorganic fine particles to the polyester layer is used, it is preferable to include inorganic fine particles in terms of surface glossiness, stability over time, and film forming properties. Even if the inorganic fine particles have bubble forming properties,
It does not have to have, for example, calcium carbonate, magnesium carbonate, zinc carbonate, titanium oxide, zinc oxide (zinc white), antimony oxide, cerium oxide, zirconium oxide, tin oxide, lanthanum oxide, magnesium oxide , Barium carbonate, zinc carbonate, basic lead carbonate (lead white), barium sulfate, calcium sulfate, lead sulfate, zinc sulfide, calcium phosphate, silica, alumina, mica, mica titanium, talc, clay, kaolin, lithium fluoride and fluorine Calcium iodide and the like can be used.

The bubble-forming properties of the inorganic fine particles depend not only on the difference in surface tension from the polyester but also on the average particle diameter and the cohesiveness. Typical examples of the inorganic fine particles having a bubble-forming property are as follows. , Calcium carbonate, barium sulfate, magnesium carbonate and the like. On the other hand, inorganic fine particles that do not have bubble-forming properties are those that whiten a film mainly due to the difference in refractive index from polyester, and typical examples thereof include titanium oxide, zinc sulfide, zinc oxide, and cerium oxide. It is. These inorganic fine particles may be used alone or in combination of two or more. The inorganic fine particles may be in the form of a porous or hollow porous material. Further, as long as the effects of the present invention are not impaired, the inorganic fine particles may be further subjected to a surface treatment in order to improve dispersibility in the resin. It may be.

The average particle diameter of the inorganic fine particles in the present invention in the polyester is preferably 0.05 to 3 μm, more preferably 0.07 to 1 μm. If the average particle diameter of the inorganic fine particles is outside the above range, the uniform dispersibility of the inorganic fine particles due to agglomeration or the like, or the gloss or smoothness of the film surface may be reduced by the particles themselves, is not preferable.

The addition amount of the inorganic fine particles in the white polyester layer (A) is not particularly limited.
It is preferably 35% by weight, more preferably 2 to 30% by weight, and most preferably 3 to 25% by weight. When the amount is less than the above range, it is difficult to improve the properties of the film such as whiteness and hiding power (optical density). Not only does the smoothness tend to be reduced, but inconveniences such as tearing of the film during stretching and generation of powder during post-processing may occur.

In the white laminated polyester film of the present invention, the surface specific resistance measured from the white polyester layer (A) side must be 10 ¹² Ω / □ or less,
This surface resistivity is more preferably 10 ¹¹ Ω / □ or less,
Most preferably, it is 10 ¹⁰ Ω / □ or less.
The smaller the surface resistivity, the better the antistatic properties and paper feeding properties. If the surface resistivity is greater than 10 ¹² Ω / □, the antistatic properties are inferior. In the case of a sheet, problems such as sticking of the receiving sheets due to static electricity, paper jam at the time of printing, and adhesion of dust and dust to the surface of the receiving sheet are likely to occur.

The surface specific resistance can be adjusted to 10 ¹² Ω / □ or less by a method in which an antistatic agent is contained in the white polyester layer (A) or an antistatic layer is provided on the white polyester layer (A). Although the method is used, the latter method is more preferably employed from the viewpoint that the effect of imparting the antistatic property is high, and the range of selection of the antistatic agent is wide because the antistatic agent is not used directly.

When an antistatic layer is provided on the white polyester layer (A), the antistatic layer may be either a single layer of an antistatic agent or a layer in which a binder resin is used in combination. This is more preferable because the effect of improving the adhesion to the receiving layer can be easily obtained when a receiving sheet for thermal transfer recording is provided by providing a receiving layer thereon.

The above-mentioned antistatic agent is not particularly restricted but includes, for example, ionic polymer compounds, surfactants,
Conductive inorganic fine particles, inorganic electrolytes, organic complex salts, and the like can be used. Among these, an ionic polymer compound is preferably used in terms of applicability, miscibility with a binder resin and other compositions, and the like. Here, the ionic polymer compound is a general term for a polymer compound having an ionic group as a pendant of a main chain, a side chain or a main chain.

Examples of the ionic group include anionic groups such as a sulfonate, a carboxylate, a phosphate, an alkyl sulfonate and an alkyl phosphate, an alkyltrimethylammonium salt, a lauryltrimethylammonium chloride, and an alkylpyrrolidium. A cationic group which is a compound mainly containing a quaternary ammonium salt such as a salt,
Nonionic groups, long-chain aliphatic groups, quaternary ammonium-type nitrogen and carboxyl groups, which are compounds containing polyethers, polyhydric alcohols, polyoxyethylene alkylamines, polyoxyethylene fatty acid esters, etc. as main components. Alternatively, an amphoteric ion group such as a compound having a sulfone group can be used.

Specific examples thereof include a polymer compound having an ionic group in its main chain, for example, a pyrrolidium ring,
A polymer compound having a piperidinium ring or the like in the main chain or a polymer compound containing a compound having an unsaturated bond as a copolymer component thereof can be used.

Examples of the high molecular compound having an ionic group in the side chain include a homopolymer of acrylic acid, methacrylic acid, styrene and the like and / or a saturated hydrocarbon such as polyethylene and polypropylene as other components. The main chain is a copolymer such as an unsaturated hydrocarbon such as polyacetylene or an alkylene oxide, and an ionic group such as a phosphate, a sulfonate, a vinyl sulfonate, a carboxylate, or a quaternary ammonium salt is used as a side chain. Can be used.

In the present invention, any of the above ionic high molecular compounds can be used without any particular limitation.
From the viewpoint of miscibility and applicability, a polymer compound in which the ionic group is an anionic group is particularly preferable. The above ionic polymer compounds may be used alone or in combination of two or more.

The binder resin is not particularly limited as long as it is a resin having miscibility with the antistatic agent, coatability, and adhesion to the receptor layer. Examples of the binder resin include polyester resins, polyacrylate resins, and polyurethane resins. Resins such as a resin, a polyvinyl alcohol resin, and a polyvinyl butyral resin can be used. Among these resins, polyester resins, polyacrylate resins, and polyurethane resins are more preferably used. Of course, these resins may be used alone, or two or more kinds may be used in combination or as a copolymer.

In the present invention, the binder resin may be used in combination with an antistatic agent or as a mixture of both. Because of the range and range of application,
More preferred. The ratio (weight ratio) of the binder resin to the antistatic agent is not particularly limited as long as it is within the range of the present invention. For example, 5/95 to 95/5 is preferable, and 10/90 to 90 is more preferable. / 10. When the amount is outside the above range, the film formability or the appearance of the film is likely to be deteriorated due to poor coatability, and dirt or dust is likely to adhere due to poor antistatic properties, and paper jams during printing. Trouble easily occurs.

In the antistatic layer, other additives such as a cross-linking agent, a surfactant, a defoaming agent, a leveling agent, a heat-resistant stabilizer, and an oxidation-resistant stabilizer may be used as long as the object of the present invention is not impaired. Agents, organic lubricants, organic or inorganic fine particles, fillers, nucleating agents, dyes, dispersants and the like.

In the present invention, the method for forming the antistatic layer is preferably a method in which a coating liquid for forming an antistatic layer is applied to the white polyester layer (A) side of the white laminated polyester film and dried. As a method of applying the antistatic layer forming coating solution, for example, reverse (roll) coating, gravure coating, knife coating, air knife coating, roll coating, blade coating, bead coating, rotating screen coating, slot orifice coating, rod coating, Bar coat, die coat, spray coat, curtain coat, die slot coat, champlex coat, brush coat, two coat, size press coat of metering blade type, bill blade coat, short dwell coat, gate roll coat, gravure reverse coat, ext A method such as a lug coat or an extrusion coat can be used.

In addition, the coating process of the antistatic layer forming coating solution may be a method of applying in a film forming process of a white laminated polyester film (in-line coating), or a method of applying and drying on a film after forming the film (off-line coating). ) May be used, but the in-line coating is a more excellent method in terms of uniform coating, thin film coating, economy, and the like. The film before coating may be preliminarily subjected to a pretreatment such as a corona discharge treatment or a plasma treatment for the purpose of improving coatability.

The liquid medium of the antistatic layer-forming coating liquid is as follows:
Any liquid medium of an aqueous system, a solvent system, or a mixture of both may be used.However, in the case where an antistatic layer is provided by an in-line coating method, an aqueous system or water is mainly used in terms of safety such as handleability and explosion proof. A mixed liquid medium of the above two types is preferably used.

The thickness of the antistatic layer is not particularly limited, but is preferably 0.01 to 10 μm, more preferably 0.02 to 5 μm. The thickness of the antistatic layer is 0.01
When the thickness is smaller than μm, the antistatic property tends to be insufficient. On the other hand, when the thickness of the antistatic layer is more than 10 μm, the coating properties of the antistatic layer forming coating liquid during coating may be reduced, or the cost may be increased, and the economical efficiency may be reduced.

In the present invention, the white polyester layer (A) and / or the white polyester layer (B) contains a fluorescent whitening agent in order to give the white laminated polyester film for thermal transfer recording a higher degree of whiteness. Is desirable.

In the present invention, a fluorescent whitening agent is a polymer that absorbs ultraviolet light in sunlight or artificial light, converts the ultraviolet light into visible light of purple to blue, and radiates the light. It is a compound that promotes whiteness without reducing the brightness of the substance. Examples of the fluorescent whitening agent include trade names "Ubitek" (Ciba-Geigy), "OB-1" (Eastman), "TBO" (Sumitomo Seika Co., Ltd.) and "Kay Coal" (Nippon Soda Co., Ltd.). , "Kayalite" (Nippon Kayaku Co., Ltd.), "Ryukopua" EGM (Client Japan Co., Ltd.) and the like can be used. The optical brightener is
There is no particular limitation.
More than one kind may be used in combination, but in the present invention, the selection of a fluorescent whitening agent which is particularly excellent in heat resistance, has good compatibility with the polyester described above, can be uniformly dispersed, and has little coloring and does not adversely affect the resin. Is desirable.

The content of the fluorescent whitening agent in the white polyester layer (A) or the white polyester layer (B) is as follows:
It is preferably 0.01 to 1.5% by weight, more preferably 0.03 to 1% by weight, furthermore 0.05 to 0.5% by weight.
Is most preferably within the range. If the content of the fluorescent whitening agent is less than the above range, it is difficult to obtain a sufficient whitening effect, and if the content exceeds the above range, the whiteness or light resistance is rather reduced due to a decrease in uniform dispersibility and coloring of the fluorescent whitening agent itself. Is liable to decrease.

The white laminated polyester film of the present invention must have a laminated structure of two or more layers in which a white polyester layer (A) is provided on at least one side of a white polyester layer (B). For example, when the effect of the present invention is intended to be obtained with a single-layer single film film, the film is likely to be broken and the film formation is unstable, so that the cost may be increased as a result. In addition, when an incompatible resin is added to contain fine bubbles, depending on the type, the dispersed incompatible resin in the form of particles is dropped off, and a film forming apparatus is used during a long-time film formation. Contacting parts (drums, rolls, coaters, etc.) may be contaminated. Problems such as the contamination adversely affecting the film characteristics and the periodic cleaning as a countermeasure tend to cause a decrease in productivity and an increase in cost. In addition, since the amount of the light-proofing agent for exhibiting the necessary light-fastness is increased, problems such as an increase in raw material cost and coloring are likely to occur. Therefore, the white polyester layer (A) is made to have whiteness, smoothness or luster, and the white polyester layer (B) is excellent in various properties such as light resistance, cushioning property and heat insulation property. With such a layer, it is possible to satisfy all of the necessary properties as a whole film.

Here, when the white laminated polyester film of the present invention has a two-layer laminated structure having a white polyester layer (A) on one side of a white polyester layer (B), this is used as a receiving sheet base for thermal transfer recording. When used as a material, it is preferable to provide a receiving layer on the white polyester layer (A).

Accordingly, when the white laminated polyester film of the present invention is formed by laminating the white polyester layer (A) on both sides of the white polyester layer (B) to form a three-layer laminated structure, the film-forming properties are further improved. It is more desirable from the viewpoint that practicality such as handleability can be improved, or bleed-out of the light-resistant agent with the lapse of time, and stability of various properties with the lapse of time.

In the present invention, the kind of polyester used for each of the white polyester layer (A) and the white polyester layer (B) may be the same or different. Particularly when different polyester combinations are used, for example, when the polyester used for the white polyester layer (A) is polyethylene naphthalate and the polyester used for the white polyester layer (B) is polyethylene terephthalate, the light resistance, rigidity, etc. are improved. Is more preferable. The polyester used for the white polyester layer (A) is a copolyester,
It is more preferable that the polyester used for the white polyester layer (B) is a homopolyester, since the effect of improving the adhesion to the receptor layer or the antistatic layer can be obtained.

In the present invention, as a method of laminating the white polyester layer (A) and the white polyester layer (B), a method of compounding by coextrusion during melt film formation or a method of separately forming each film is used. Any of laminating methods may be used, but the former method is more preferable in terms of cost and the like.

When the white laminated polyester film of the present invention is used as a receiving sheet substrate for thermal transfer recording, it may be used alone or in combination with other materials. Examples of the material include plain paper, high quality paper, medium quality paper, coated paper, art paper, cast coated paper, resin impregnated paper, emulsion impregnated paper, latex impregnated paper, synthetic resin internal paper, glassine paper, laminated paper, and the like. Paper, synthetic paper,
Non-woven fabrics or other types of films can be used. However, when laminating the white laminated polyester film of the present invention with another material, it is preferable to laminate it on the surface opposite to the surface on which the receiving layer is provided.

As described above, the white laminated polyester film of the present invention is a laminated structure of two or more layers in which the white polyester layer (B) is provided with the white polyester layer (A) on at least one side of the white polyester layer (B). It is necessary to whiten by the means described above, but the preferable level of whitening (whiteness) is substantially determined after the film is formed into a laminated film.

That is, as for the whiteness of the white laminated polyester film for thermal transfer recording of the present invention, the whiteness measured from the white polyester layer (A) side is preferably 70% or more, more preferably 80% or more. And most preferably 90% or more. When the whiteness is less than 70%, the printed image is likely to have a dark impression due to insufficient whiteness, which is not preferable.

On the other hand, the color tone b value measured from the white polyester layer (A) side is preferably 2 or less, more preferably 1 or less, and most preferably 0 or less. When the color tone b value is larger than 2, the printed image tends to have an old impression because the film itself has a yellowish color even if the light resistance is satisfied, which is not preferable.

As another film property in the present invention, the specific gravity of the film is preferably 0.4 or more and less than 1.3, more preferably 0.45 or more and 1.2 or less, further preferably 0.5 or less. More preferably, it is 1.1 or less. When the specific gravity is smaller than 0.4, a large amount of bubbles must be contained for lowering the specific gravity, and therefore, the film strength is reduced, and the film is easily broken at the time of film formation, and the productivity is reduced. May be undesirable. On the other hand, when the specific gravity is 1.3 or more, the cushioning property and the heat insulating property are reduced to deteriorate the printability, and the whiteness of the film is insufficient, and the printed image tends to have a dark impression, which is not preferable.

Further, the glossiness of the white laminated polyester film of the present invention measured from the white polyester layer (A) side is preferably at least 40%, more preferably at least 50%, most preferably at least 55%. is there. When the glossiness is less than 40%, the smoothness of the film surface is reduced, and unevenness or chipping may occur in a printed image, resulting in poor printing.

Although the thickness of the white laminated polyester film of the present invention is not particularly limited, it is usually 10 to 500 μm,
More preferably 15 to 400 μm, further preferably 20 to 30
It is preferable that the thickness is in the range of about 0 μm because the whiteness and the handleability in practical use are excellent. Further, when the white laminated polyester film of the present invention is laminated with another material,
The upper limit of the thickness is preferably 200 μm or less, more preferably 150 μm or less, from the viewpoint of handleability. Further, the ratio of the white polyester layer (B) to the total thickness (the thickness of the white polyester layer (B) / the total thickness) is 0.55 to 0.55.
0.99, more preferably 0.6
０．９0.97, most preferably 0.65 to 0.95. If the above ratio is less than 0.55, it is difficult to obtain sufficient light resistance. On the other hand, when it is larger than 0.99, the film-forming property may be poor.

Next, an example of the method for producing a white laminated polyester film of the present invention will be described, but the present invention is not limited to only such an example.

In a composite film forming apparatus having an extruder (A) and an extruder (B), in order to form a white polyester layer (B), vacuum-dried polyester chips and a light-proofing agent master chip are used, if necessary. And a vacuum-dried chip of an incompatible resin are mixed so that the incompatible resin is 1 to 35% by weight and the light stabilizer is 0.05 to 10% by weight, and the mixture is heated to 260 to 300 ° C. The extruder (B) is melted and introduced into a T-die composite die. If necessary, a dispersant may be added to this raw material in an amount of 0.05 to 10% by weight. The addition of the immiscible resin may be performed by vacuum-drying a master chip which has been used in advance. on the other hand,
In order to laminate the white polyester layer (A), polyester chips and a master chip of inorganic fine particles are mixed so that the inorganic fine particles become 1 to 35% by weight, and sufficiently vacuum-dried. If necessary, a fluorescent whitening agent may be added to this raw material in an amount of 0.01 to 1.5% by weight. next,
The dried raw material is supplied to an extruder (A) heated to 260 to 300 ° C., melted and introduced into a T-die composite die, and the polymer of the extruder (A) is changed to the extruder (B). The polymer is laminated so as to be on the surface layer (one surface) or both surface layers (both surfaces) and co-extruded into a sheet to obtain a melt-laminated sheet.

The molten laminated sheet was subjected to a surface temperature of 10 to 6
It is tightly cooled and solidified by static electricity on a drum cooled to 0 ° C. to produce an unstretched laminated film. The unstretched laminated film is guided to a group of rolls heated to 70 to 120 ° C., and has a length of 2 to 5 in a longitudinal direction (longitudinal direction, that is, a traveling direction of the film).
The film is double-stretched and cooled with a group of rolls at 20 to 30 ° C.

Subsequently, after the corona discharge treatment is performed on the white polyester layer (A) side of the film stretched in the longitudinal direction, a coating solution for forming an antistatic layer is applied to the treated surface. The film coated with the antistatic layer-forming coating solution is guided into a tenter while gripping both ends of the film with clips, and is moved in a direction perpendicular to the longitudinal direction (lateral direction) in an atmosphere heated to 90 to 150 ° C.
Stretch up to 5 times.

The stretching ratio is 2 to 5 times each in the vertical and horizontal directions, and the area ratio (longitudinal stretching ratio × lateral stretching ratio) is 6 to 5 times.
Preferably it is 20 times. When the area magnification is less than 6 times, the whiteness and film strength of the obtained film become insufficient, and when the area magnification exceeds 20 times, the film tends to be easily broken during stretching.

In order to complete the crystal orientation of the biaxially stretched laminated film thus obtained and to impart flatness and dimensional stability, the biaxially stretched laminated film is subsequently heated at 150 to 230 ° C. in a tenter.
, And then uniformly cooled, then cooled to room temperature and rolled up, whereby the white laminated polyester film of the present invention can be obtained. During the heat treatment step, a 3 to 12% relaxation treatment may be performed in the horizontal or vertical direction as necessary. Further, the biaxial stretching may be either sequential stretching or simultaneous biaxial stretching, and may be re-stretched in either the longitudinal or transverse direction after the biaxial stretching.

The thus obtained white laminated polyester film of the present invention has not only excellent cushioning properties and heat insulating properties, but also very good light resistance, image adhesion durability, whiteness, printability and antistatic properties. Are better. Further, the receiving sheet for thermal transfer recording using the white laminated polyester film of the present invention as a base material has no paper feeding trouble at the time of printing and has a clear printed image. Further, since dust and dirt do not easily adhere and have durability against light irradiation for a long period of time, the sharpness of a printed image can be maintained for a long period of time. Furthermore, the image can have excellent adhesion durability. Therefore, the white laminated polyester film of the present invention is a film having optimal characteristics as a receiving sheet substrate for thermal transfer recording.

[Method of Measuring and Evaluating Characteristics] The characteristic values of the present invention are determined by the following evaluation methods and evaluation criteria.

(1) Average Particle Diameter of Particles and Thickness of Antistatic Layer The average particle diameter of the particles was determined by observing a cross section of a white laminated polyester film containing the particles. That is, the cross section of the white polyester layer (A) was observed at a magnification of 3,000 to 200,000 times using a transmission electron microscope type HU-12 (manufactured by Hitachi, Ltd.), and a cross-sectional photograph was taken. Next, the particle portion of this cross-sectional photograph is marked, and the marked portion is subjected to image processing using a Hi-Vision image analysis processing device PIAS-IV (manufactured by Pierce Co., Ltd.), and a total of 100 particles in the measurement visual field are obtained. Was converted to a perfect circle, and the average diameter was calculated and used as the average particle diameter of the particles.

The thickness of the antistatic layer is determined by measuring the length in the thickness direction of the antistatic layer in a cross-sectional photograph taken in the same manner as above for the white laminated polyester film provided with the antistatic layer, The thickness was calculated by back calculation. In determining the thickness of the antistatic layer, a total of five cross-sectional photographs arbitrarily selected from different measurement fields of view were used, and the average value was used as the thickness of the antistatic layer.

(2) Fine Bubbles Inside the Film and Thickness of White Polyester Layer The cross section of the film was magnified 500 to 5,000 times using a scanning electron microscope S-2100A type (manufactured by Hitachi, Ltd.). From the cross-sectional photograph taken and observed, the presence or absence of fine bubbles was examined. (Additional description of bubbles in Example 1 and Comparative Example 1) The determination of the presence / absence of bubbles is made by averaging when the cross-sectional area of the bubble portion of the cross-sectional photograph is converted to a perfect circle in the same manner as in the method (1). When the value is 1 μm ² or more, “bubble exists”, and when it is less than 1 μm ² , “no bubble.” However, when two or more adjacent bubbles are connected, one bubble Further, the length in the thickness direction of each white polyester layer was measured from the cross-sectional photograph, and the thickness of each layer was determined by back calculation from the magnification. In determining the cross-sectional area of the bubble portion and the thickness of each white polyester layer, a total of five cross-sectional photographs arbitrarily selected from different measurement visual fields were used, and the average value was calculated.

(3) Film-forming properties The following three-stage evaluation was carried out with respect to occurrence of troubles such as film breakage and contamination of the film-forming apparatus during film-forming.
○ was determined to be good. ：: The film formation is stable and good. Δ: Film is sometimes broken, or the drum and / or roll of the film forming apparatus becomes dirty, resulting in poor film forming property. X: The film is frequently torn and the film-forming properties are completely poor.

(4) Whiteness The white laminated polyester film was measured from the white polyester layer (A) side using a spectral colorimeter SE-2000 (manufactured by Nippon Denshoku Industries Co., Ltd.) according to JIS Z-8722. X value, Y value, Z which are tristimulus values of color under optical conditions
The whiteness was calculated by the following formula. Whiteness (%) = 4 × 0.847 × Z value−3 × Y value (5) Color b value Measured under the apparatus and optical conditions described in the above item (4).
It was determined according to -8730.

(6) Light fastness UV deterioration promotion tester I-Super UV tester SUV
Using -W131 (manufactured by Iwasaki Electric Co., Ltd.), a forced light resistance test was performed for 3 hours under ultraviolet irradiation under the following conditions. “Ultraviolet irradiation conditions” Illuminance: 100 mW / cm ² , temperature: 60 ° C., relative humidity:
50% RH The test was performed by irradiating ultraviolet rays from the white polyester layer (A) side. Next, for the irradiated surface, the color tone b value before and after the ultraviolet irradiation was measured according to the apparatus and optical conditions in the above item (4), and the absolute value of the difference (| color tone b value before irradiation−color tone b value after irradiation) The following four-level evaluation was performed for |). ◎ or ○ was determined to be good. ◎: less than 3 ：: 3 or more and less than 5 Δ: 5 or more and less than 7 ×: 7 or more.

(7) Glossiness Digital angle change glossmeter UGV-5B (Suga Test Instruments Co., Ltd.)
JIS) from the white polyester layer (A) side
It measured according to Z-8741. The measurement conditions were an incident angle = 60 ° and a light receiving angle = 60 °.

(8) Specific Gravity A sample sample obtained by cutting a film into a size of 50 mm × 60 mm was used as a high-precision electronic specific gravity meter SD-120L.
(Made by Mirage Trading Co., Ltd.) using JIS K-71
The measurement was carried out according to Method A (Substitution method in water) of No. 12. The measurement was performed under the conditions of a temperature of 23 ° C. and a relative humidity of 65%.

(9) Surface specific resistance After the humidity was controlled by leaving the substrate at a temperature of 23 ° C. and a relative humidity of 65% for 24 hours, a digital ultra-high resistance microammeter R834 under the same conditions.
0 (manufactured by Advantest Co., Ltd.) and an applied voltage of 100
Measured in V. The smaller the value, the better the antistatic property.

(10) Printability On a white laminated polyester film of the present invention, the following coating liquid for forming a receptor layer was applied by a gravure coater, and then applied to a gravure coater.
After drying at 0 ° C. for 1 minute, a receiving sheet for thermal transfer recording having a receiving layer thickness of 0.1 μm was obtained.

[Coating Liquid for Forming Receptor Layer] An aqueous dispersion of urethane-modified polyethylene (urethane-modified ratio = 20% by weight, emulsified by heating in an aqueous ammonia solution to form an aqueous dispersion) was diluted with water and solidified. The partial concentration was 3%.

Next, "Professi" is used as a color printer.
onal Color Point 2 "(manufactured by Seiko Electronic Industry Co., Ltd.) and CH705 (yellow, magenta, cyan) manufactured by Seiko I Supply Co., Ltd. as an ink ribbon. 8 on the surface
A gradation test pattern was printed. Next, the printed test pattern was evaluated for print density, print dot shape, and image clarity by the following method, and printability was determined.

(Print Density) Determined from the optical density (reflection density) in the reflection system. That is, the reflection density of the magenta portion was measured using an optical densitometer TR927 (manufactured by Macbeth Co., Ltd.).
Grading was performed. ◎ or ○ was determined to be good. ：: 0.13 ≦ OD _min , 0.85 ≦ OD _max ○: 0.1 ≦ OD _min <0.13, 0.7 ≦ OD _max <
0.85 Δ: 0.07 ≦ OD _min <0.1, 0.5 ≦ OD _max <
0.7 ×: OD _min <0.07, OD _max <0.5 where OD _min and OD _max represent the reflection density of the print portion of the lowest gradation and the highest gradation, respectively.

(Dot Shape) Each of the three colors of yellow, magenta and cyan on the printing surface was observed at a magnification of 100 to 300 times using a reflection type optical microscope. An evaluation was performed. ◎ or ○ was determined to be good. ：: For all three colors, a beautiful circular shape and extremely good. ：: Good, although slight chipping was observed. Δ: “Chip” or “crush” is observed. Or the dots are small. X: "Chip" and "crush" are remarkable. Or the dots are extremely small.

(Image Clarity) The printed surface was visually observed, and the brightness and impression of the printed image were evaluated in the following four grades. ◎ or ○ was determined to be good. A: The whole image is very clear and extremely good. ：: clear image, good Δ: The image itself is thin, or the non-printed surface is slightly yellowish, so the image has a dark impression, and the image sharpness is poor. X: The image itself was very thin, or the non-printed surface was yellowish, so that the overall image impression was very dark and completely poor.

(11) Paper feedability According to the method described in the above item (10), the receiving sheet prepared by using the white laminated polyester film of the present invention is cut into A4 size sheets, and 50 sheets are stacked, and then the sheets are stacked. Continuous printing was performed in the same manner as in the above method. At this time, the following three-stage evaluation was performed on the paper feedability based on the number of paper feed errors such as paper jams. ○ was determined to be good. ：: 0 to 1 time Δ: 2 times ×: 3 times or more

(12) Image Adhesion Durability A receiving sheet prepared and printed using the white laminated polyester film of the present invention according to the method described in (10) above was placed in a hot air oven at a temperature of 60 ° C. The mixture was left for 5 days and subjected to forced heating. "S" is printed on the printing surface of this receiving sheet.
The following three-level evaluation was performed by attaching a “cotch” mending tape (manufactured by Sumitomo 3M Limited) and visually observing the persistence of the printed image after the T-peeling. ○: Image on the mending tape Is almost not transferred Δ: The image is partially peeled ×: The image is peeled in a planar manner

[0083]

The present invention will be described with reference to the following examples.
The present invention is not limited to these.

(Example 1) Extruder (A) and extruder (B)
In order to form the white polyester layer (A) in a composite film forming apparatus having a mean particle size of 0.2%, a polyethylene terephthalate (hereinafter abbreviated as PET) chip is used.
The raw material to which 7% by weight of anatase type titanium oxide fine particles of 7 μm is added is vacuum-dried at 180 ° C. for 3 hours, then supplied to the extruder (A) side, melted at 285 ° C. by a conventional method, and introduced into a T-die composite die. did.

On the other hand, in order to form the white polyester layer (B), 10% by weight of polymethylpentene (hereinafter abbreviated as “PMP”) was added to the PET chip, and a benzophenone-based ultraviolet absorber “ADK STAB” LA-5 was used as a light-resistant agent.
1 (manufactured by Asahi Denka Kogyo KK) in an amount of 1.2% by weight, and 1% by weight of polyethylene glycol having a molecular weight of 4,000 (hereinafter abbreviated as PEG) as a dispersant, and vacuum added at 180 ° C. for 3 hours. After drying, it was supplied to the extruder (B) side, melted at 285 ° C. by a conventional method, and similarly introduced into a T-die composite die. Next, the white polyester layer (A) was merged so as to be laminated on both surface layers of the white polyester layer (B) in the die, and then co-extruded into a sheet to obtain a melt laminated sheet. Then, the molten laminated sheet was tightly cooled and solidified by an electrostatic method on a cooling drum maintained at a surface temperature of 25 ° C. to obtain an unstretched laminated film. Subsequently, the unstretched laminated film was stretched 3.2 times in the longitudinal direction (longitudinal direction) using a group of rolls heated to 95 ° C. in a conventional manner, and
It was cooled by a group of rolls at 5 ° C. to obtain a uniaxially stretched film. Subsequently, the uniaxially stretched film was subjected to a corona discharge treatment in air, and the following antistatic layer forming coating solution was applied to the treated surface by a bar coating method using a metaling bar. While holding both ends of the uniaxially stretched film coated with the antistatic layer forming coating liquid with a clip, the film is led to a preheating zone in a tenter, preheated and dried at 110 ° C., and then continuously dried.
The film was stretched 3.4 times in a direction (lateral direction) perpendicular to the longitudinal direction in a heating zone at 5 ° C. Subsequently, a heat treatment at 220 ° C. is performed in a heat treatment zone in the tenter to complete the crystal orientation, and then the film is gradually cooled and then wound up. The white polyester layer (A) is 10 μm on one side and the white polyester layer (B) is
Was obtained in which a 0.15 μm-thick antistatic layer was provided on a 120 μm-thick polyester film having a structure of 100 μm. In addition, the cross section of the white laminated polyester film was enlarged and observed with a SEM to confirm that the white polyester layer (B) contained fine air bubbles. These fine bubbles are formed around PMP dispersed in the form of particles as a nucleus, and the major axis has an elliptical shape in the stretching direction, and the minor axis has an elliptical shape in the film thickness direction. It was 4 μm ² .

The properties of the white laminated polyester film thus obtained are as shown in Table 1, which indicates that the white laminated polyester film is excellent in whiteness and light resistance. In addition, the printability and the paper feedability are at a high level, and it can be seen that they are extremely excellent as a receiving sheet base material for thermal transfer recording.

[Coating solution for forming antistatic layer] (A) Antistatic agent: aqueous dispersion of ammonium polystyrene sulfonate (molecular weight = about 70,000) (B) Binder resin: acrylic emulsion (acryl component: methyl methacrylate / butyl acrylate /
Acrylic acid / N-methylolacrylamide = 60/3
8/1/1 (wt%) copolymer) A mixture of the above (A) / (B) at a solid content weight ratio of 35/65 and dilution with water to a solid content concentration of 6% by weight. It is.

(Example 2) Except that 0.12% by weight of an optical brightener "OB-1" (manufactured by Eastman Co.) was further added as a raw material to be supplied to the extruder (A) of Example 1. A white laminated polyester film was obtained in the same manner as in Example 1. The same fine bubbles as in Example 1 were contained inside the white polyester layer (B) of this white laminated polyester film. The properties of this white laminated polyester film were excellent as shown in Table 1, and particularly excellent in whiteness (whiteness and color b value) and image clarity.

(Examples 3 and 4) Extruder (B) of Example 2
, A white laminated polyester film was obtained in the same manner as in Example 2, except that the amounts of the light stabilizers added were 0.3 wt% and 2.5 wt%, respectively. The same fine bubbles as in Example 1 were contained inside the white polyester layer (B) of these white laminated polyester films. Each characteristic was excellent as shown in Table 1. In particular, Example 3 was excellent in whiteness and image clarity, and Example 4 was excellent in light resistance.

(Example 5) The same as Example 2 except that among the raw materials supplied to the extruder (A) of Example 2, anatase type titanium oxide fine particles were changed to calcium carbonate fine particles having an average particle diameter of 1 µm. A white laminated polyester film was obtained by the technique. As shown in Table 1, fine white cells similar to those in Example 1 were contained inside the white laminated polyester film. Moreover, the characteristics were excellent in each characteristic.

(Comparative Example 1) A white laminated polyester film was obtained in the same manner as in Example 1 except that the light-proofing agent was removed from the raw materials supplied to the extruder (B) of Example 1.
The white laminated polyester film contains fine bubbles therein, and as shown in Table 1, the white laminated polyester film shows good values for whiteness, printability, antistatic property, etc. Was inferior.

(Comparative Example 2) Except that the light-fastening agent was removed from the raw material supplied to the extruder (B) of Example 1, and the light-proofing agent was further added to the raw material supplied to the extruder (A) by 2% by weight. ,
A white laminated polyester film was obtained in the same manner as in Example 1. This white laminated polyester film contains fine bubbles therein, and as shown in Table 1, the whiteness, printability and antistatic properties of the white laminated polyester film show good values. The adhesion durability was poor.

Comparative Example 3 Of the raw materials supplied to the extruder (B) of Example 1, 14% by weight of anatase type titanium oxide fine particles having an average particle diameter of 0.2 μm instead of removing PMP and PEG. A white laminated polyester film was obtained in the same manner as in Example 1 except that the above addition was performed. SE
From the observation of the M cross section, no fine air bubbles were contained inside the white laminated polyester film (cross-sectional area of the air bubble portion = 0.04 μm ² ). In addition, as shown in Table 1, the light resistance and antistatic properties were good, but the printability was poor.

Comparative Example 4 Extruder (A) of Example 1
The raw materials to be supplied to (B) are all
10% by weight of P, 1% by weight of PEG, average particle size 1 μm
5% by weight of anatase-type titanium oxide fine particles of Example 1 and 1% by weight of a benzophenone-based ultraviolet absorber “ADK STAB” LA-51 (manufactured by Asahi Denka Kogyo KK) as a light stabilizer. A white polyester film was obtained in the same manner as in Example 1. Although fine bubbles were contained in the inside of this film, substantially 1
This was a single layer film. Further, as shown in Table 1, the film has good light resistance and antistatic properties (surface resistivity), but easily breaks during film formation. The film was inferior in film-forming properties, for example, the part gradually became dirty.

Comparative Example 5 A white laminated polyester film was obtained in the same manner as in Example 1, except that the film was formed without providing an antistatic layer. The white laminated polyester film contains fine bubbles therein, and as shown in Table 1, the film has good anti-light properties and whiteness, but has antistatic properties (surface resistivity). And poor paper feedability.

[0096]

[Table 1]

[0097]

The white laminated polyester film for thermal transfer recording of the present invention is a white laminated polyester film having a white polyester layer (A) provided on at least one surface of a white polyester layer (B) containing fine bubbles. Since the white polyester layer (B) contains a light-resistant agent and the surface resistivity measured from the white polyester layer (A) side is 10 ¹² Ω / □ or less, Excellent in printing properties, printing properties, antistatic properties, and also excellent in light resistance. Therefore, the receiving sheet for thermal transfer recording using the white laminated polyester film as a base material can obtain a clear printed image without trouble such as paper jam. Furthermore, since it shows excellent whiteness even after long-term use and excellent image adhesion durability, the durability as a receiving sheet can be remarkably improved. Therefore, the white polyester film for thermal transfer recording of the present invention can be suitably used as a receiving sheet substrate in any of the thermal transfer recording systems of the fusion type and the sublimation type.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 3/00 C08L 23/00 5/00 67/00 C08L 23/00 B41M 5/26 H 67/00 101H F-term (reference) 2H111 AA01 AA08 AA26 AA27 CA02 CA03 CA25 CA31 CA33 CA37 CA38 CA41 CA49 4F006 AA35 AB16 AB43 BA07 CA10 DA04 EA03 4F071 AA02 AA14 AA21 AA43 AA51 AB01 AB18 AC07 AE05 AE18 AE12 AF32 A00 A39 AB01A00 AA21H AK01A AK03A AK41A AK41B AK41C AK42 AK62A AK66A AL05A AR00D AR00E BA02 BA03 BA05 BA06 BA07 BA10B BA10C BA10D BA10E BA13 BA16 CA22 CA30A CA30B CA30C DE01B DE01C DJ01A EH20 EJ38 EJ55 GB90 HB00A HB00B HB00C JB04A JB16A JG03 JG03D JG03E JG04 JG04B JG04C JK06 JL00 JL01 JL10A JL10B JL10C JN21 JN21B JN21C JN30 JN30B JN30C YY00 YY00A YY00B YY00C 4J002 BB012 BB032 BB122 BB172 BC032 B D122 BG022 CF001 CN012 DD037 DE077 DE097 DE107 DE127 DE137 DE147 DE237 DE247 DG027 DG047 DG057 DH047 DJ017 DJ037 DJ047 DJ057 EE036 EJ066 EN006 EU176 EZ006 FD017 FD046 FD056 FD208 GK03 GQ00

Claims (10)

[Claims] 1. A white laminated polyester film comprising a white polyester layer (A) provided on at least one side of a white polyester layer (B) containing fine bubbles, wherein the white polyester layer (B) is a light-resistant agent. And a surface specific resistance measured from the white polyester layer (A) side of 10 ¹² Ω / □ or less, a white laminated polyester film for thermal transfer recording. 2. The white laminated polyester film for thermal transfer recording according to claim 1, wherein the content of the light stabilizer in the white polyester layer (B) is 0.05 to 10% by weight. 3. The method according to claim 1, wherein the whiteness measured from the white polyester layer (A) side is 70% or more, the color tone b value is 2 or less, and the glossiness is 40% or more. A white laminated polyester film for thermal transfer recording according to the above. 4. The white polyester layer (A) contains 1 to 35% by weight of inorganic fine particles.
4. The white laminated polyester film for thermal transfer recording according to any one of items 1 to 3. 5. The thermal transfer recording method according to claim 1, wherein the white polyester layer (A) and / or the white polyester layer (B) contains a fluorescent whitening agent. White laminated polyester film. 6. The white laminated polyester for thermal transfer recording according to claim 1, wherein the white polyester layer (B) contains a thermoplastic resin incompatible with the polyester. the film. 7. The white laminated polyester film for thermal transfer recording according to claim 7, wherein the thermoplastic resin incompatible with the polyester is a polyolefin resin. 8. The white laminated polyester film for thermal transfer recording according to claim 1, wherein a white polyester layer (A) is provided on both sides of the white polyester layer (B). 9. The white laminated polyester film for thermal transfer recording according to claim 1, wherein an antistatic layer is provided on the white polyester layer (A). 10. The white laminated polyester film for thermal transfer recording according to claim 9, wherein the antistatic layer is the outermost layer.