JPH1077355A - White polyester film and receiving paper for thermal transfer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a white polyester film excellent in low specific gravity, flexibility, cushionability, adhesivity and high-temperature compressive resistance, easy to dry, and having good printability and adhesivity inherent in the polyester, and to obtain a recelving paper for thermal transfer with the above polyester film as base material. SOLUTION: This white polyester film with an apparent specific gravity of 0.5-1.3 is composed of at least one layer (designated as A layer) consisting of a composition comprising a polyester (a) and a syndiotactic styrene-based polymer (b) and whitened by virtue of containing fine cells inside the A layer. The other objective receiving paper for thermal transfer is such one that the above white polyester film serves as base material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white polyester film and a heat-sensitive recording sheet having a low specific gravity, excellent solvent resistance, good printability and adhesiveness, and excellent compression resistance at high temperatures. .

[0002] Printing base materials, packaging, cards, labels,
The present invention relates to a white polyester film used as a base material for receiving paper for video printers, photographic paper, display boards, IC cards, and the like.

[0003]

2. Description of the Related Art It is well known that a white polyester is obtained by adding a large amount of titanium dioxide or calcium carbonate to a polyester. It is also well known that a white polyester film is obtained by adding a polyolefin to polyester. It is also well known that amorphous polyester is added to polyester to obtain a white polyester film.

[0004]

However, a film obtained by adding a large amount of an inorganic substance such as titanium dioxide or calcium carbonate to polyester (Japanese Patent Laid-Open No. 62-207337).
Japanese Patent Application Laid-Open No. Sho 62-204941) can impart whiteness, but it is difficult to reduce the specific gravity, and the film is hard, so that it is not suitable for applications such as receiving paper that requires cushioning properties.

In addition, when a polyolefin resin such as polypropylene is added (Japanese Patent Application Laid-Open Nos. 63-168441 and 63-193938), the hardness of the film itself is lower than that when an inorganic substance is added. There is a problem that the surface free energy of the polyester film is reduced due to the polyolefin resin to be added, but the adhesiveness of the film is reduced. This is because, for example, the surface free energy of polyester is 44-46.
(MN / m, 20 ° C), whereas polyethylene is 34-37 (mN / m, 20 ° C), polypropylene is 29 (mN / m, 20 ° C), and polymethylpentene is 25 (mN / m, 20 ° C). m, 20 ° C.), it is considered that the resin having a low surface free energy tends to segregate on the surface. For this reason, a polyester layer is further laminated thereon to improve adhesiveness and printability (Japanese Patent Publication No. 7-37098).
However, when the lamination thickness is small, there is a problem such as peeling from the lamination surface, and when the lamination thickness is large, there is a problem that it is difficult to reduce the cushioning property and the density.

Conventional polystyrene is industrially obtained by radical polymerization by a method such as bulk polymerization, solution polymerization, emulsion polymerization, or suspension polymerization. Polystyrene obtained by such radical polymerization is usually amorphous because it has an atactic structure and does not have stereoregularity.
In addition, since polystyrene having stereoregularity has not been industrially produced, the quantity of this amorphous polystyrene is overwhelmingly large. For this reason, amorphous polystyrene is usually called general-purpose polystyrene or general-purpose polystyrene. A white polyester film obtained by adding amorphous polystyrene (Japanese Patent Publication No. 54-29550) to polyester has a polystyrene surface free energy of about 40 (mN / m, 20 ° C.). It is smaller and has good adhesion and printability,
When mixing amorphous polystyrene with the heat-dried polyester, and when drying the mixed composition or recovered product, there is a problem in production such as fusion of the polystyrene to the polyester to a stiff state, Due to the low heat distortion temperature of the crystalline polystyrene, the compressibility at high temperatures is inferior, so that it is sometimes unsuitable for applications where heat is directly applied, such as thermal transfer receiving paper. In addition, when a solvent-based coating agent such as toluene or xylene is applied, amorphous polystyrene in the base film may be eluted, resulting in poor coatability.

[0007] Polystyrene resins having stereoregularity include those having an isotactic (it) structure,
Some have a syndiotactic structure. Polystyrene having an isotactic structure tends to have a lower melting point and lower crystallization rate than polystyrene having a syndiotactic structure. For this reason, when a solvent-based coating agent such as toluene or xylene is applied, the polystyrene component in the base film is eluted, resulting in poor coatability, which is not preferable.

That is, a white polyester film having excellent low specific gravity, flexibility, cushioning property, adhesiveness and high-temperature compressibility, no problem in productivity, good coatability and good polyester printability and adhesiveness. Did not exist.

[0009]

Means for Solving the Problems At least one layer (referred to as layer A), wherein the layer A is composed of a composition of a polyester (a) and a styrenic polymer (b) having a syndiotactic structure, The layer is whitened by containing fine bubbles inside, and has an apparent specific gravity of 0.5 or more and 1.3 or more.
The invention is based on the following white polyester film and a heat-sensitive recording receiving sheet based on the white polyester film.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Polyester (a) referred to in the present invention
Is a polymer obtained by condensation polymerization from a diol and a dicarboxylic acid, and examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid naphthalenedicarboxylic acid, adipic acid, sebacic acid, and dimethyl esters thereof. Things. The diol is represented by ethylene glycol, trimethylene glycol, tetramethylene glycol, cyclohexanedimethanol and the like. Specifically, for example, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene-p-oxybenzoate, poly-1,4-cyclohexylene dimethylene terephthalate (PCHDMT), polyethylene-
For example, 2,6-naphthalenedicarboxylate (PEN) is used. In the case of the present invention, PET and PEN are particularly preferred. Various additives such as an antioxidant, an antistatic agent, and organic or inorganic fine particles may be added to the polyester within a range that does not impair the effects of the present invention.

The styrenic polymer (b) having a syndiotactic structure referred to in the present invention is a phenyl polymer whose stereochemical structure is mainly a syndiotactic structure, that is, phenyl which is a side chain with respect to a main chain formed from carbon-carbon bonds. Groups and substituted phenyl groups have a steric structure in which they are alternately located in opposite directions, and their tacticity is quantified by nuclear magnetic resonance ( ^13C -NMR) using isotope carbon. ¹³ C-NM
Tacticity measured by the R method can be represented by the ratio of the presence of a plurality of continuous structural units, for example, a dyad for two, a triad for three, and a pentad for five. The styrene-based polymer having a syndiotactic structure referred to in the invention means 75% or more, preferably 85% or more in dyad, or 30% or more, preferably 50% in pentad (racemic pentad).
% Of syndiotacticity.

The syndiotactic styrene polymer (b) includes polystyrene, poly (alkyl styrene), poly (halogenated styrene, poly (halogenated styrene), poly (alkoxystyrene), poly (vinyl benzoate) Acid ester) and a mixture thereof, or a copolymer containing these as a main component, wherein poly (alkylstyrene) is poly (methylstyrene), poly (ethylstyrene), poly (isopropylstyrene) , Poly (t-butylstyrene) and the like,
Poly (halogenated styrene) includes poly (chlorostyrene), poly (bromostyrene), and poly (fluorostyrene). Examples of poly (alkoxystyrene) include poly (methoxystyrene) and poly (ethoxystyrene). Of these, preferred styrene polymers include polystyrene and poly (p-
Methylstyrene), poly (m-methylstyrene), poly (pt-butylstyrene), poly (p-chlorostyrene), poly (m-chlorostyrene), poly (p-fluorostyrene), and styrene Copolymers with p-meter styrene can be mentioned.

The molecular weight of the styrenic polymer having a syndiotactic structure used in the present invention is not limited, but preferably has a weight average molecular weight of 10,000 or more, and most preferably 50,000 or more. Further, the molecular weight distribution is not limited in its width, and various types can be selected. Here, the weight average molecular weight is 100
If it is less than 00, the high-temperature compressibility of the obtained white polyester film may be undesirably reduced.

It is preferable that such a styrenic polymer having a predominantly syndiotactic structure be polymerized using a compound or complex containing titanium, zirconium, palladium or nickel metal as a catalyst. More preferably, they are polymerized with a Ziegler-type catalyst. In particular, metallocene catalysts, those polymerized using cyclopentadienyl-based or metallocene-based metal coordination catalysts collectively referred to as Kaminsky catalysts, or a combination of a titanium compound such as titanium halide or alkoxytitanium with alkylaluminosane Those polymerized using a catalyst (JP-A-62-230826) are most preferred.

For example, in the presence or absence of an inert hydrocarbon solvent, a titanium compound and a condensation product of water and a trialkylaluminum are used as a catalyst to form a styrene monomer (a monomer corresponding to the styrene polymer). (Japanese Patent Application Laid-Open No. 62-187).
708). A specific example of the metallocene catalyst is disclosed in JP-A-62-257948.
Further, a styrene-based polymer having a higher syndiotactic structure is preferably used by a separation means using a solvent or the like, if necessary.

The styrenic polymer (b) having a syndiotactic structure is dispersed in the polyester by melt extrusion molding, and interfacial separation occurs at the interface of the polymer (b) dispersion in a subsequent stretching step to form voids. Has the effect of causing In the case of the present invention, the polyester is a dispersion medium (matrix).
The styrenic polymer (b) having a syndiotactic structure is a dispersion.

The amount of the styrene polymer having a syndiotactic structure used in the layer A is preferably 2 to 25% by weight, more preferably 4 to 15% by weight. If the addition amount is less than 2% by weight, not only is it difficult to obtain a white polyester film of the present invention having an apparent specific gravity of 1.3 or less, but also it may be difficult to obtain a opaque white polyester. . On the other hand, when the amount of the styrene-based polymer exceeds 25% by weight, the mechanical properties of the polyester film of the present invention are reduced, the ejection stability at the time of extrusion is poor, and the film is easily broken at the time of stretching. Problems may occur.

In the present invention, an additive for finely dispersing a styrene polymer having a syndiotactic structure dispersed in a polyester, that is, a so-called dispersant may be used. As the dispersant, either a low molecular type or a high molecular type can be used. As a specific example of the low molecular type, a surfactant used for an antistatic agent or the like is used. Among the low molecular types, nonionic surfactants are preferred. The polymer type is preferable because it does not easily bleed out to the surface and does not lower the adhesiveness, but a polyester polyether copolymer is particularly preferable. Specifically, the polyester used as the polyester polyether copolymer includes polyethylene terephthalate (PE).
T), polytetramethylene terephthalate (PBT),
Polyethylene-p-oxybenzoate, poly-1,4
-Cyclohexylene dimethylene terephthalate (PCH
DMT) and polyethylene-2,6-naphthalenedicarboxylate (PEN). As the polyether component to be copolymerized, for example, polyethylene glycol (PEG) having a molecular weight of 300 to 20,000, methoxypolyethylene glycol, polytetramethylene glycol (P
TMG) and polypropylene glycol (PPG). PET-PEG, PBT-PTMG, P as preferred polyester polyether copolymers
There is CHDMT-PPG. The copolymerization ratio of the polyester and the polyether is preferably from 1: 9 to 9: 1 by weight, more preferably from 4: 6 to 9: 1, even more preferably from 4: 6 to 6: 4. As a production method, a polyester polyether copolymer can be produced by adding a polyether at an optional stage in producing a polyester obtained by subjecting an acid component and a glycol component to polycondensation. The preferred range of the molecular weight of the polyether used is 400 to 20,000, more preferably 1,000 to 10,000.

The amount of the polyester polyether copolymer used in the layer A is preferably 0.05 to 20% by weight, more preferably 0.1 to 5% by weight.
When the addition amount is less than 0.05% by weight, the syndiotactic polystyrene-based polymer (b) is hardly finely dispersed,
The generated voids are large and the film is easily broken. Conversely, if the content exceeds 20% by weight, voids are less likely to be generated, and the specific gravity tends to increase.

The polyester as the main component in the layer A is 70%.
% By weight or more is good. If the content is less than 70% by weight, the mechanical strength and heat resistance, which are advantages of the polyester film, may not be exhibited.

Next, the whiteness of the present invention is desirably 35% or more. It is preferably at least 80%, more preferably at least 90%. If the whiteness is less than 35%, it may be difficult to make use of the special color as a white film.

The whiteness changes with the addition of the above-mentioned styrene-based polymer having a syndiotactic structure or a polyester polyether copolymer, but if necessary, a fluorescent whitening agent containing an inorganic fluorescent agent may be added. As the fluorescent whitening agent, "UBITEC" OB, MD (manufactured by Ciba Geigy), "OB-1" (manufactured by Eastman) and the like are used.

The cushion ratio of the present invention is desirably 5% or more. It is preferably at least 15%, more preferably at least 20%. When the cushion ratio is less than 5%, for example, when used as a receiving paper for a video printer or the like, the head contact with the heat-sensitive recording head becomes insufficient, resulting in missing dots and failing to transfer a clear image. There is.

In the present invention, the optical density of the white polyester film in terms of the thickness of 150 μm is preferably 0.2
It is 1.6 or more and 1.6 or less, more preferably 0.8 or more and 1.6 or less. When the optical density is less than 0.2, the concealing property of the film becomes insufficient and the back side becomes transparent, which may not be preferable.

The laminated structure of the white polyester film of the present invention may be, for example, a single film of only the A layer, or a two layer of the A layer / B layer.
It may have any of a three-layer structure of a layer structure, a B layer / A layer / B layer, and a C layer / A layer / B layer. In this case, A
The layer is a styrenic polymer having a syndiotactic structure and is a layer containing fine bubbles, and the layers B and C are films such as paper, nonwoven fabric, metal foil and resin, and are preferably polyester. Is a layer composed of a composition mainly composed of

Particularly, in order to improve the winding property of the white polyester film and to improve the optical characteristics of the surface,
It is preferable to add inorganic or organic particles to the layer. As the inorganic particles used in the B layer, those usually added to polyester can be used. For example, there are calcium carbonate, titanium dioxide, barium sulfate, silica, alumina and the like. As the organic particles, silicone resin particles, crosslinked acrylic particles, crosslinked polystyrene particles, and the like can be used.

The addition amount of the particles is not limited to the present invention, but is preferably 0.01 to 30% by weight, and more preferably 0.01 to 20% by weight. When the addition amount is less than 0.01% by weight, the slipperiness of the film may be reduced and handling may be deteriorated. Conversely, if the content exceeds 30% by weight, the inorganic particles may be shaved during stretching, and the roll may be soiled.

Although not limiting the invention, the average particle size of the inorganic particles is about 0.1 to 10 μm, preferably about 0.1 to 10 μm.
Desirably, the thickness is 5 to 5 μm.

The lamination ratio is preferably such that the thickness ratio of the layer A is 80% or more. It is more preferably at least 90%, most preferably at least 95%. The thickness composition ratio of the layer A is 80
%, The cushioning property may not be sufficient or a material having a low apparent specific gravity may not be obtained. With such a configuration, the desired high whiteness and hiding property can be obtained by the layer A, and the adhesion and printability can be further improved and the appearance can be improved by the other layers.

Next, without limiting the invention,
In the present invention, the dispersed form of the styrene polymer having a syndiotactic structure is desirably a shape close to a sphere in a white polyester film. That is, when the styrene-based polymer having a syndiotactic structure has a shape close to a sphere, that is, the void volume can be increased and the specific gravity can be reduced as compared with the case where the styrene-based polymer is dispersed in a layered or flat shape, and the cushion rate can be reduced. A film having high thermal dimensional properties can be obtained. The shape close to a sphere means that the shape factor of the incompatible polymer dispersed in the film, that is, the ratio of the major axis to the minor axis is 1 to 10, preferably 1 to 4.

The amount of xylene extracted in the present invention is desirably 1% by weight or less. It is preferably at most 0.1% by weight, more preferably at most 0.01% by weight. When the xylene extraction amount exceeds 1% by weight, when a solvent-type coating liquid (ink or the like) is applied, the coated surface may be rough and the finish may be poor.

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

A styrene polymer having a syndiotactic structure and a polytetramethylene terephthalate (PBT) -tetramethylene glycol (PTMG) copolymer as a polyester polyether copolymer are mixed with polyethylene terephthalate. The extruder A, which is sufficiently dried and heated to a temperature of 270 to 300 ° C., is supplied. Also, polyethylene terephthalate and CaCO ₃
The inorganic particles such as are mixed and supplied to the extruder B by a conventional method, and the polymer of the extruder B layer comes to one side or both surfaces of the A layer in the T die two-layer or three-layer die. B / A
/ B may be laminated in two or three layers. Here, the polymer mixture can be extruded with a vented twin-screw extruder while removing water during the extrusion.

The melted sheet is adhered and cooled and solidified while applying static electricity on a drum cooled to a drum surface temperature of 10 to 60 ° C.
Guided to a group of rolls heated to ~ 120 ° C,
５5 longitudinal stretching and cooling with a group of rolls at 20-50 ° C. In order to obtain a white polyester film having a desired cushion rate, it is preferable to generate voids in this step. The obtained uniaxially stretched film can be subjected to corona discharge treatment and coated. Next, the uniaxially stretched film is guided to a tenter while holding both ends of the film with clips, and is horizontally stretched in a direction perpendicular to the machine direction in an atmosphere heated to 90 to 140 ° C. Stretch ratio is 2 in each of vertical and horizontal
The film is stretched 5 times, and the area magnification is desirably 6 to 20 times. If the area magnification is less than 6 times, the degree of whiteness is insufficient, and if it exceeds 20 times, the film tends to be broken at the time of stretching and the film-forming property tends to be poor.

In order to impart the planarity and dimensional stability of the biaxially stretched film in this way, 150-150.degree.
After heat-setting at 230 ° C., the mixture is gradually cooled, cooled to room temperature, and wound. At the time of this heat fixing, it is possible to add a relaxation of 10% or less in order to reduce the heat shrinkage. Thus, the white polyester film of the present invention is obtained.

Further, as described above, a white polyester film may be first produced under the above conditions, and a laminated layer may be laminated thereon by melt extrusion or coating.
In the white polyester film of the present invention, calcium carbonate, amorphous zeolite particles, anatase type titanium dioxide, calcium phosphate, silica, kaolin, talc,
Fine particles such as clay may be used in combination. The amount of these additives is 0.005 to 100 parts by weight of the polyester composition.
Preferably it is 20 parts by weight. In addition to the fine particles, fine particles precipitated by the reaction between the catalyst residue and the phosphorus compound in the polyester polycondensation reaction system can be used in combination. As the precipitated particles, for example, calcium,
Those composed of lithium and phosphorus compounds or those composed of calcium, magnesium and phosphorus compounds are used, and the content of these particles in the polyester is 0.05 to 1 part by weight based on 100 parts by weight of the polyester. Is preferred.

The heat-sensitive receiving sheet used in the present invention can be obtained by providing a heat-sensitive receiving layer on the white polyester sheet obtained as described above by a known method.

Further, a coating layer may be provided on the surface layer of the white polyester film, or the white polyester film may be bonded to paper for use.

[0039]

[Measurement of physical properties and evaluation of effects]

(1) Specific gravity A film was cut into a 100 × 100 mm square, and a thickness of at least 10 points was measured by attaching a measuring element (No. 7002) having a diameter of 10 mm to a dial gauge (No. 2109-10 manufactured by Mitsui Manufacturing Co., Ltd.). Is measured, and the average thickness d (μ
m) is calculated. The film is weighed by a direct balance and the weight w (g) is read to the unit of 10 ⁻⁴ g.
At this time, specific gravity = w / d × 100.

(2) Mean Diameter (a) and Shape Factor of Dispersion The cross section of the unstretched film cut in the machine direction (MD) or its perpendicular direction (TD) is measured with a scanning electron microscope at 1000
Take a photograph magnified up to 5000 times and apply at least 100 or more incompatible polymer dispersions in the specified thickness range to an image analyzer to determine the distribution of the diameter of the circle corresponding to the area of the dispersion. The area average diameter of this distribution is defined as the average diameter (dispersion diameter) of the dispersion. The ratio of the major axis / minor axis of 100 pieces is defined as the shape factor of the dispersion.

(3) Heat Shrinkage The film was cut in the MD direction or the TD direction to a width of 10 mm and a length of 300 mm, marked at 200 mm intervals, fixed on a support plate under a constant tension (5 g), and then the original length a of the marking interval a (Mm) is measured. Next, a load is applied by using a 3 g clip, and processing is performed for 30 minutes while rotating in a hot air oven at 150 ° C., and the marking interval b (mm) is measured in the same manner as the original length measurement. The heat shrinkage is determined by the following equation, and the average value of five pieces is used.

Heat shrinkage (%) = (ab) / a

(4) Optical Density One or several films are stacked, and an optical densitometer (TR9
27, manufactured by Macbeth Co., Ltd.). The thickness of the film and the optical density are plotted, and the optical density corresponding to a thickness of 150 μm is determined by an interpolation method.

(5) Cushion rate (%) Dial gauge No. 2109-10
The standard gauge head 900030 is used for the dial gauge stand no. It is obtained from the following formulas from the thicknesses d ₅₀ and d ₅₀₀ of the respective films when a partial load of 50 g and 500 g is applied to the dial gauge press using 7001DGS-M.

Cushion rate = 100 × (d ₅₀ −d ₅₀₀ ) / d ₅₀

(6) Whiteness According to JIS-L-1015, U-manufactured by Shimadzu Corporation
When the reflectance at wavelengths of 450 nm and 550 nm is B% and G% using V-260, whiteness (%) = 4B + 3G.

[0047]

(7) Adhesion of Dye-Receiving Layer A solution having the following composition in which the dried coating film has a softening point of 50 ° C. is applied and dried to form a dye-receiving layer having a thickness of 2 μm.
A cellophane tape peel test was performed.

No abnormality in coating film: ○ Peeling off part of coating film: △ Peeling off coating film as a whole: ×

15 parts PVC resin (Electrochemical Co., Ltd., “DENKARAC” TF-300) 15 parts Titanium oxide (Furukawa Kikai Metals Co., Ltd., FA-55W, particle diameter 0.5 μm) 4 parts Silicone oil (Shin-Etsu) Chemical Industry Co., Ltd., KF-410) 2 parts Antistatic agent (Yoshimura Oil Chemical Co., Ltd., "Elique" PS-909) 2 parts Toluene 25 parts Ethyl acetate 25 parts Methyl ethyl ketone 20 parts Dimethylformamide 7 parts

(8) Curling property The film was cut into A4 size, and was cut into a “Xerox” copier VIVACE550 (manufactured by Fuji Xerox Co., Ltd.).
After passing through the film, the film after passing was placed on a flat surface and the degree of curl was observed.

There is no curl at all, and there is no problem in both times: ◎ There is a slight curl but no paper jam in both times (no problem in practical use): The sheet is significantly curled and slightly jams in the second time (problem in practical use) ): × Curl and paper jam: ××

(9) Xylene extraction amount 1 g of the film is put into a Soxhlet extraction tube and extracted with xylene (100 g). The extraction temperature was near the xylene boiling point (138-144 ° C), and the extraction time was 3 hours. The residual solvent was removed by vacuum-reducing the extracted film at 40 ° C. for one day. The amount of film loss at this time was expressed as a percentage, and was defined as the xylene extraction amount.

[0054]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described based on embodiments.

Example 1 95% by weight of polyethylene terephthalate (PET) and syndiotactic-polystyrene (SYN-PS,
5% by weight of "Zarek" S100 manufactured by Idemitsu Petrochemical Co., Ltd.) was mixed, and the mixture was removed with a vacuum pump from a twin-screw vented extruder heated to 270 to 300 ° C. so that the vent pressure became 10 (mmHg). It was formed into a sheet from an extruded T-die while air-drying. Further, the film is heated to a surface temperature of 2
Cooled and solidified with a cooling drum of 5 ° C., guided to a group of rolls heated to 80 to 100 ° C., stretched three times in the machine axis direction,
It cooled with the roll group of 25 degreeC. Subsequently, the longitudinally stretched film was guided to a tenter while holding both ends of the film with clips, and was transversely stretched 3.6 times in a direction perpendicular to the machine axis direction in an atmosphere heated to 115 ° C. Thereafter, the film was heat-set at 220 ° C. in a tenter, gradually cooled, and then cooled to room temperature to obtain a film having a winding thickness of 100 μm. The physical properties of the obtained film are as shown in Tables 1 and 2.

Example 2 PET and polytetramethylene glycol (P
PET produced by adding PTMG during the polymerization of PET so that the weight ratio with TMG (molecular weight 4000) becomes 1: 1.
-1% by weight of PTMG copolymer, 90% by weight of polyethylene terephthalate (PET) and syndiotactic-
Polystyrene (SYN-PS, manufactured by Idemitsu Petrochemical Co., Ltd.)
"Zarek" A100) 9% by weight was mixed and 270-3
It was extruded from a twin screw vented extruder heated to 00 ° C. while being deaerated and dried with a vacuum pump so that the vent pressure became 10 (mmHg). Further, this film was cooled and solidified by a cooling drum having a surface temperature of 25 ° C., guided to a group of rolls heated to 80 to 100 ° C., stretched three times in the machine axis direction, and cooled by a group of rolls of 25 ° C. Subsequently, the longitudinally stretched film was guided to a tenter while holding both ends of the film with clips, and was transversely stretched 3.6 times in a direction perpendicular to the machine axis direction in an atmosphere heated to 115 ° C. Thereafter, the film was heat-set at 220 ° C. and relaxed by 5% in a tenter. Table 1 shows the physical properties of the obtained film.

Example 3 In a composite extruder in which two extruders A and B were installed, PET was previously adjusted so that the weight ratio between PET and polytetramethylene glycol (PTMG, molecular weight 4000) was 1: 1. P produced by adding PTMG during polymerization
1% by weight of ET-PTMG copolymer, 90% by weight of polyethylene terephthalate (PET) and syndiotactic-polystyrene (SYN-PS, Idemitsu Petrochemical Co., Ltd.)
9% by weight of "Zarek" A100)
The extruder A with a twin screw vent heated to 300 ° C. was extruded while being degassed and dried with a vacuum pump so that the vent pressure became 10 (mmHg), and 90% by weight of PET and calcium carbonate (manufactured by Shiraishi Calcium Co., Ltd.) Softon 3
200) A 10% by weight mixed chip is vacuum-dried at 180 ° C. for 3 hours and extruded from an extruder B, and extruder A is co-extruded in an inner layer and extruder B is a three-layered outer layer (B / A / B). T
The sheet was formed from a die. Further, this film is cooled and solidified by a cooling drum having a surface temperature of 25 ° C.
It was led to a roll group heated to 0 ° C., stretched three times in the machine axis direction, and cooled by a roll group at 25 ° C. Subsequently, the longitudinally stretched film was guided to a tenter while holding both ends of the film with clips, and was transversely stretched 3.6 times in a direction perpendicular to the machine axis direction in an atmosphere heated to 115 ° C. Then 2 in the tenter
The film was heat-set at 20 ° C., gradually cooled, and then cooled to room temperature to obtain a film having a winding thickness of 100 μm. The thickness configuration was 5/90/5. Table 1 shows the physical properties of the obtained film.
It is as follows.

Comparative Examples 1 and 2 Instead of the syndiotactic polystyrene used in Example 1, 9 parts by weight of polypropylene (PP) or polystyrene for general use (amorphous, "Stylon" 666, manufactured by Asahi Kasei Kogyo KK). %, And a film was obtained in the same manner as in Example 2 below. The thickness was 100 μm. Table 1 shows the physical properties of the obtained film.

It can be seen that in the system to which PP was added, the dye adhesion was poor. Also, it can be seen that the xylene extractability is poor in the system to which general-purpose polystyrene is added.

Comparative Example 3 Syndiotactic used in Example 3 for Layer A
General-purpose polystyrene instead of polystyrene (amorphous,
The film was dried in a vacuum at 180 ° C. for 3 hours and extruded using “Stylon” 666 manufactured by Asahi Kasei Kogyo Co., Ltd. to obtain a film in the same manner as in Example 3. The thickness was 100 μm, and the thickness configuration was 3/44/3. Table 1 shows the physical properties of the obtained film. It can be seen that even if the dye adhesion on the surface is improved by using a laminated structure, the curl property is inferior due to deformation at a high temperature.

[0061]

[Table 1]

[Table 2]

[0062]

Industrial Applicability The present invention provides a white polyester film having low specific gravity, excellent flexibility, cushioning property, adhesiveness and high-temperature compressibility, easy drying, good polyester printability and good adhesion. A receiving paper for thermal transfer using a white polyester film as a base material having various characteristics can be obtained.

Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location B41M 5/40 B41M 5/26 H // C08L 67:02

Claims (7)

[Claims] 1. A layer comprising a composition of a polyester (a) and a styrenic polymer (b) having a syndiotactic structure, wherein the layer A has a fine particle inside the layer A. A white polyester film which is whitened by containing fine bubbles and has an apparent specific gravity of 0.5 or more and 1.3 or less. 2. The method according to claim 1, wherein the layer A comprises a composition comprising a polyester (a), a styrene-based polymer having a syndiotactic structure (b), and a polyester polyether copolymer (c). The white polyester film as described. 3. The white polyester film according to claim 1, wherein the white polyester film is a composite film, and layers other than the layer A are polyester. 4. The white polyester film according to claim 1, wherein the white polyester film is a composite film, and a layer other than the layer A is a composition comprising polyester and inorganic particles. 5. The white polyester film according to claim 1, wherein the styrenic polymer (b) having a syndiotactic structure is polymerized using a metallocene catalyst. . 6. The white polyester film according to claim 1, wherein the amount of xylene extracted is 1% by weight or less.
The white polyester film according to claim 5. 7. A heat-sensitive recording receiving sheet comprising the white polyester film according to claim 1 as a base material.