JP2001260294A - White laminated polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a white polyester film suitable for use as an information recording/printing material having excellent concealability, whiteness and printability. SOLUTION: A white laminated polyester film comprises a polyester skin layer (layer A) containing a white pigment and a polyester layer (layer B) containing a white pigment or not containing the pigment. In this case, the layer A is provided on at least at one outermost layer. Its optical density is 1.0 or more in terms of a film thickness of 100 μm. A dynamic hardness of a surface of the layer A forming surface side is 49.0 to 98.0 mN/pm2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a white laminated polyester film. Specifically, the present invention relates to a white laminated polyester film suitable as an information recording / printing material having excellent concealing properties, whiteness and mechanical performance.

[0002]

2. Description of the Related Art Synthetic paper, which is a paper substitute using synthetic resin as a main raw material, is superior to natural paper in water resistance, moisture absorption dimensional stability, surface stability, mechanical performance, and the like. In recent years, application development utilizing these advantages has been promoted. As the main raw material of synthetic paper, polyester, polypropylene, polystyrene and the like are used.Among these, a film made of polyester represented by polyethylene terephthalate has heat resistance, gloss and sharpness of printing, and strength of stiffness. In particular, the range of use as printing materials and information recording materials is expanding.

When this polyester film is used as a paper substitute, as a method for imparting necessary hiding properties, whiteness, and mechanical performance, a method of dispersing fine cavities in the film and adding white particles. Methods have been considered. For example, Japanese Patent Application Laid-Open No. 4-44979 has examined the use of a film having whiteness and concealing properties by dispersing fine cavities in the film as a recording material. However, in the film obtained by this method, a decrease in mechanical performance such as a decrease in strength and generation of wrinkles due to the presence of cavities is inevitable, and the content of cavities naturally has an upper limit. For this reason, a film having sufficient hiding properties, whiteness and mechanical properties for use in printing and information recording has not been obtained by this method. In addition, the method of adding white particles can impart whiteness, but cannot control the dynamic hardness of the film surface, so that printability and surface strength are insufficient.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a white color suitable for use as an information recording / printing material which has excellent concealing properties, whiteness and mechanical properties. An object of the present invention is to provide a laminated polyester film.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, the polyester skin layer (A layer) containing white particles and the white particles containing or not containing them. A white laminated polyester film having a polyester layer (B layer) and having the A layer in at least one of the outermost layers has the following properties (1) and (2), whereby concealing properties are obtained. The present inventors have found that a white laminated polyester film excellent in whiteness and mechanical performance and suitable for use as an information recording / printing material can be obtained, thereby completing the present invention. (1) The optical density is 1.0 in terms of a film thickness of 100 μm.
That is all. (2) At least the dynamic hardness of the film surface on the layer A formation side is 49.0 to 98.0 mN / μm ² .

That is, the present invention comprises (1) a polyester skin layer (A layer) containing white particles and a polyester layer (B layer) containing or not containing white particles. 49. A white laminated polyester film having at least one outermost layer, the optical density of which is 1.0 or more in terms of a film thickness of 100 μm, and the dynamic hardness of at least the film surface on the A layer forming surface side is 49. 0 to 98.0 mN / μm ² , white laminated polyester film, (2) white color of the above (1), wherein the white particles are contained in the A layer in an amount of 10 to 45% by weight. (3) The white laminated polyester film according to the above (1) or (2), wherein the white particles in the layer A are titanium oxide. And (4) the white laminated polyester film according to (1) to (3), wherein the layer A further contains 100 to 10000 ppm by weight of a fluorescent whitening agent; The present invention relates to the white laminated polyester films of the above (1) to (4), wherein the prescribed apparent density is 1.30 g / cm ³ or more.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The white laminated polyester film of the present invention (hereinafter abbreviated as a laminated film) includes a polyester skin layer (A layer) containing white particles and a polyester layer (B layer) containing or not containing white particles. The layer A is disposed on at least one of the outermost layers, and the laminated film is required to have a specific optical density and a specific dynamic hardness at least on the film surface on the side where the layer A is formed. These features are essential requirements for obtaining an information recording / printing material having excellent concealing properties, whiteness and mechanical performance.

The A layer and the B layer in the present invention are each mainly composed of polyester. Examples of the polyester in the present invention include an aromatic dicarboxylic acid (for example, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, etc.) or an ester thereof; Polyesters obtained by polycondensing glycols (eg, ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, etc.) are preferred. The polyester may be a homopolymer or a copolymer of a third component. Representative examples of the polyester include polyethylene terephthalate, polyethylene butylene terephthalate, and polyethylene-2,6-naphthalate.

The preferred polyester in the present invention has at least one of ethylene terephthalate unit, butylene terephthalate unit and ethylene-2,6-naphthalate unit, and the unit is at least 70 mol% in the polyester. , Preferably 80 mol%
As mentioned above, more preferably, a polyester containing 90 mol% or more is exemplified.

The polyester can be prepared by directly reacting an aromatic dicarboxylic acid and a glycol, or by subjecting an alkyl ester of an aromatic dicarboxylic acid to a transesterification reaction with a glycol followed by polycondensation. It can be produced by a method of polycondensing a glycol ester.

The "polyester skin layer containing white particles (layer A)" in the present invention is a polyester skin layer containing the following white particles. The polyester in the A layer has a preferable intrinsic viscosity range depending on its type. For example, in the case of polyethylene terephthalate,
The lower limit of the intrinsic viscosity is preferably 0.40 or more,
If it is less than 40, the film strength is remarkably reduced and stretching becomes difficult. The upper limit is preferably 1.00 or less, and if it exceeds 1.00, the viscosity increases and extrusion becomes difficult.

The white particles contained in the layer A include titanium oxide, barium sulfate, zinc oxide, zinc sulfide, calcium carbonate and the like, and one or more of these may be used in combination. Among these, titanium oxide is particularly preferred because it has a high refractive index and can exhibit high concealing properties with a small amount, and among titanium oxides, anatase type titanium dioxide is most preferred. The white particles used in the present invention can be subjected to various organic and / or inorganic surface treatments for the purpose of improving dispersibility. It is also preferable to apply a high shear force in the step of extruding the molten resin using, for example, a twin-screw extruder.

In the layer A of the present invention, white particles are contained preferably in an amount of 10 to 45% by weight, more preferably 15 to 35% by weight, and further preferably 15 to 25% by weight. In particular, when the content of the white particles is less than 10% by weight, the optical density of the laminated film decreases (the light transmittance of the film increases), and a sufficient hiding effect cannot be obtained. When the content of the white particles exceeds 45% by weight, the film-forming stability of the laminated film decreases, and when the fluorescent whitening agent described later is used in combination, the ultraviolet absorption effect of the white particles causes
Ultraviolet light necessary for the fluorescent whitening agent to exert its effect is absorbed, so that the fluorescent whitening effect is significantly inhibited and the whiteness is reduced. The average particle size of the white particles is 0.1
To 3.0 μm, more preferably 0.1 to 0.1 μm.
6 μm. When the average particle diameter is less than 0.1 μm, the concealing property of the laminated film is hardly developed, and when it is more than 3.0 μm, the surface strength of the laminated film becomes low.

The “polyester layer (B layer) containing or not containing white particles” in the present invention may contain white particles. In view of the concealability of the laminated film, the polyester layer contains white particles. Is preferred. Examples of the white particles contained in the layer B include those similar to the white particles contained in the layer A. The content of the white particles in the B layer is preferably 35% by weight or less, more preferably 2% by weight.
It may be 0% by weight or less. The B layer may further contain a fluorescent whitening agent, a light-shielding agent, an antioxidant, an antistatic agent, and the like, as necessary, in addition to the white particles.

The laminated film of the present invention comprises the above-mentioned layers A and B. In order to further improve the concealing property and the like, any one of these layers may be formed of an inorganic or organic material other than the white particles. Particles may be contained as needed. However, when added to the layer A, it is necessary to select particles that do not impair the effects of the present invention. Examples of the particles that can be added to the layer A include silica, kaolinite, talc, zeolite, alumina, and carbon black, but are not particularly limited thereto.

Further, in the laminated film of the present invention,
For the purpose of improving the whiteness, it is possible to further add a fluorescent whitening agent, and it is particularly preferable to add the fluorescent brightening agent to the layer A located at the outermost layer of the laminated film. 10000 ppm of optical brightener. When the content of the fluorescent whitening agent is less than 100 ppm, the amount of emitted fluorescent light is reduced and the bluish component of reflected light is reduced, so that it is difficult to obtain a sufficient whiteness because the laminated film looks yellowish. . In addition, the content of the fluorescent whitening agent is 1
If it exceeds 0000 ppm, the discoloration when the fluorescent whitening agent is denatured under ultraviolet irradiation or high-temperature and high-humidity conditions becomes remarkable, and the weather resistance of the laminated film tends to be reduced.

In order to achieve the object of the present invention, the laminated film of the present invention comprising the layer A and the layer B has an optical density of 1.0 or more, preferably 1.5 or more in terms of a film thickness of 100 μm. When the ratio is less than 1.0, the concealing property of the film is reduced, and when the laminated film is used for printing, there arises a problem that the back surface is seen through.

In the present invention, the optical density of the laminated film includes the type, particle size and concentration of the white particles, the thickness of the A layer, the ratio of the thickness of the entire laminated film to the A layer, the dispersion state of the particles,
It depends on the presence or absence of the light-shielding agent in the layer and the amount thereof. Examples of a method for adjusting the optical density of the laminated film to 1.0 or more in terms of a film thickness of 100 μm include, for example, a method of adding an appropriate amount of the white particles (for example, titanium oxide) to the layer A,
A method of adding an appropriate amount of a light-shielding agent (for example, carbon black or the like) to the B layer is exemplified.

In order to achieve the object of the present invention, the dynamic hardness of the laminated film of the present invention on the film surface on the side of layer A is 49.0 to 98.0 mN / μm.
m ² , preferably 49.0 to 78.4
mN / μm ² . The dynamic hardness is 49.0.
If it is less than mN / μm ² , the strength of the film surface will be reduced, and if it is more than 98.0 mN / μm ² , the cushioning property of the surface will be reduced, making it unsuitable for use in printing applications. In a laminated film in which a coating layer described later is laminated on the layer A, the film surface on the side of the layer A on which the coating layer is laminated needs to have the above dynamic hardness.

The dynamic hardness of the laminated film in the present invention depends on the concentration of white particles, the size of micro-cavities appearing around the particles after the film is stretched, the ratio of the cavities, the density of the film surface layer, and the like. The dynamic hardness of the laminated film surface is 49.0-98.0 mN /
Examples of the method of setting the thickness to μm ² include a method of performing cold stretching when the film is longitudinally stretched. Specifically, cold stretching is performed until stretching becomes unstable (for example, stretching by an infrared heater, heating roll Stretching used). That is, the stretching tension is increased by lowering the output of the infrared heater or lowering the temperature of the heating roll to perform stretching, so that fine cavities are developed around the particles (titanium oxide) in the A layer, Dynamic hardness can be controlled.

The apparent density of the laminated film of the present invention is preferably 1.30 g / cm ³ or more, more preferably 1.30 g / cm ³ .
It is preferably at least 40 g / cm ³ . The apparent density is specified in the description in Examples. When the apparent density is less than 1.30 g / cm ³ , the stiffness of the laminated film becomes weak, and it cannot be said that the laminated film is suitable for the information recording material and the printing material as the object of the present invention.

The laminated film of the present invention comprises a metal-deposited film, a functional adhesion-imparting layer, a coating layer such as an antistatic layer, an adhesive layer, and a release layer on at least one outermost layer of the laminated film. It may be provided.

The laminated film of the present invention can improve the wettability and adhesiveness of an ink or a coating agent by providing an easy-adhesion layer on the outermost layer on the side of layer A. As the compound constituting the easy-adhesion layer, a polyester-based resin is preferable.In addition, a polyurethane resin, a polyester-urethane resin, an acrylic-based resin, and the like, are disclosed as means for improving the adhesiveness of a normal polyester-based film. And the like are applicable.

As the method for providing the coating layer, a commonly used method such as a gravure coating method, a kiss coating method, a dip method, a spray coating method, a curtain coating method, an air knife coating method, a blade coating method, and a reverse roll coating method can be applied. The application step can be performed at any stage such as before stretching the film, after longitudinal stretching, or after finishing the orientation treatment.

The method for producing the laminated film of the present invention is arbitrary and is not particularly limited. For example, it can be produced as follows. In order to impart the dynamic hardness of the present invention to the laminated film, the polyester layer containing ultrafine voids derived from white particles, that is, the layer A, is joined to the core layer B. The most suitable joining method is
A co-extrusion method in which the A layer and the B layer are supplied to separate extruders, laminated in a molten state, and extruded from the same die is used. The layers A and B thus extruded from separate extruders
The layers do not necessarily have the same properties. This is because even if the raw material compositions of the A layer and the B layer are the same, since the discharge amount of the molten resin is changed according to the thickness ratio of each layer of the laminated film using a separate extruder, each extrusion is performed. This is because the heat history and shear force in the machine do not become the same. The unstretched film obtained by laminating the layer A on the surface of the core layer (layer B) by coextrusion or the like is further stretched between rolls having different speeds (roll stretching), and gripped and spread by clips. Stretching (tenter stretching), stretching by air pressure (inflation stretching)
For example, biaxial orientation processing is performed.

The conditions for stretching and orienting the unstretched film are closely related to the physical properties of the film. In the following, the stretching / orienting conditions will be described by taking, as an example, a sequential biaxial stretching method most preferably used in the present invention, particularly a method of stretching an unstretched sheet in the longitudinal direction and then in the width direction. First, the first
In the vertical stretching step, stretching is performed between two or many rolls having different peripheral speeds. As a heating means at this time, a method using a heating roll or a method using a non-contact heating method may be used, and it is preferable to use both of them. When heating in combination, the temperature of the heating roll is (Tg-5) ° C ~
(Tg + 10) ° C., and the output of the infrared heater was lowered until just before the stretching became unstable.
Stretch 5 to 4.5 times. Next, the uniaxially stretched film is introduced into a tenter, and at a temperature of not less than Tg (the melting point of polyester (hereinafter, abbreviated as Tm) -10) ° C in the width direction and not more than 2.
Stretch 5 to 5 times. Here, Tg means the glass transition temperature of polyester. The biaxially stretched film thus obtained is further subjected to a heat treatment as needed. The heat treatment is preferably performed in a tenter,
(Tm-50) It is preferable to carry out in a temperature range of from C to Tm.

When used as an information recording / printing material,
The thickness of the layer A in the laminated film of the present invention is usually preferably about 10% of the whole laminated film, and the thickness of the whole laminated film is usually 10 to 300 μm.

[0028]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples. First, a measurement / evaluation method used in the present invention will be described. (1) Optical density (OD) Transmission density meter (Ihac-T5) manufactured by Ihara Electronics Industry Co., Ltd.
It measured using. However, it was converted to a film thickness of 100 μm. The higher the value of the optical density, the higher the concealing property. (2) Dynamic hardness Dynamic ultra-fine hardness tester (DUH-20) manufactured by Shimadzu Corporation
Using 1), at 25 ° C., a 115 ° triangular cone
A load of 96 mN was applied, and the load speed was 1.42 × 10
^It was pushed into the laminated film at ^-5 N / sec, and the dynamic hardness was determined from the load and the indentation depth of the indenter by the following formula, and was shown by three significant figures. DH = 370.81 P / h ² (where DH is the dynamic hardness and P is the test load (m
N) and h indicate the indentation depth (μm). (3) Color b value The color difference was measured using a color difference meter (Z-1001DP) manufactured by Nippon Denshoku. The whiteness of the film was evaluated using the b value. A larger value indicates a stronger yellow tint. As an information recording / printing material, a laminated film having a color b value of usually 2 to -6, preferably -2 to -5 is suitable. (4) Apparent density (g / cm ³ ) The film was cut into four squares of 5.00 cm square to obtain samples. Four samples were stacked, and the thickness at any 10 points on the stacked samples was measured using a micrometer with four significant figures, and the average of the measured values of the obtained 10 points was determined. Further, the average value was divided by 4 to obtain an average thickness per sheet (t: unit is μm) using three significant figures. Further, the weight (w: unit is g) of the four samples was measured using an automatic precision balance with four significant figures. The apparent density (unit: g / cm ³ ) of the sample was determined by three significant figures according to the following equation. Apparent density = (w × 10 ⁴ ) / (5.00 × 5.00 ×)
t × 4)

Production Example As a raw material, an intrinsic viscosity of 0.62 dl obtained by an ordinary method.
/ G of polyethylene terephthalate resin of 50% by weight and 50% by weight of anatase type titanium dioxide particles (TA-300, manufactured by Fuji Titanium Co., Ltd.) having an average particle diameter of 0.3 μm were supplied to a vented twin-screw extruder. Pre-kneaded. The molten resin was continuously supplied to a vent-type single-screw kneader, kneaded and extruded. The obtained strand is cooled and cut to obtain a titanium dioxide-containing master pellet (X).
Was prepared. Next, a benzoxazole-based fluorescent whitening agent (OB-manufactured by Eastman Chemical Company) was added to 95% by weight of a polyethylene terephthalate resin having an intrinsic viscosity of 0.62 dl / g.
1) A mixture obtained by mixing 5% by weight was supplied to a vented twin-screw extruder and preliminarily kneaded. Thereafter, the molten resin was continuously supplied to a vent-type single-screw kneader, and kneaded to prepare a fluorescent brightener-containing master pellet (Y). The titanium dioxide-containing master pellet (X) and the fluorescent brightener-containing master pellet (Y) thus obtained were used in Examples and Comparative Examples.

Example 1 60% by weight of a polyethylene terephthalate resin having an intrinsic viscosity of 0.62 dl / g and 40% by weight of a master pellet (X) containing titanium dioxide were subjected to vacuum drying at 140 ° C. for 8 hours, and these were mixed in a pellet. Film material (I)
And In addition, 59% by weight of a polyethylene terephthalate resin having an intrinsic viscosity of 0.62 dl / g, 40% by weight of a master pellet (X) containing titanium dioxide, and 1% by weight of a master pellet (Y) containing a fluorescent brightener were added at 140 ° C. for 8 hours. After vacuum drying, these were mixed with pellets to obtain a film raw material (II). Each of these film raw materials is supplied to a separate extruder, and a layer (layer B) composed of the raw material (I) and a layer (layer A) composed of the raw material (II) are formed using a feed block to form an A layer / B layer / The layers were laminated in the order of layer A. This was co-extruded from a T-die onto a cooling roll adjusted to 25 ° C. The discharge amount of each extruder was adjusted so that the thickness ratio of each layer became 1: 8: 1, and an unstretched film having a thickness of 570 μm was prepared.

The obtained unstretched film is uniformly heated to 65 ° C. using a heating roll, and two pairs of nip rolls having different peripheral speeds (low-speed roll = 2 m / min, high-speed roll = 6.2 m)
/ Min) during stretching 3.1 times. At this time, as an auxiliary heating device for the film, an infrared heater (a rated output: 74 W / cm) having a gold reflective film in the middle of the nip roll was installed at a position 1 cm from the film surface opposite to both surfaces of the film. Heated at 35%. The uniaxially stretched film thus obtained was guided to a tenter, heated to 150 ° C., and stretched transversely 3.7 times. After the transverse stretching, the width was fixed, heat treatment was performed at 230 ° C. for 5 seconds, and relaxation was performed at 200 ° C. in the width direction by 4% to obtain a white laminated polyester film having a thickness of about 50 μm.

Example 2 80% by weight of a polyethylene terephthalate resin having an intrinsic viscosity of 0.62 dl / g and 20% by weight of a master pellet (X) containing titanium dioxide were vacuum-dried at 140 ° C. for 8 hours, and these were mixed by pellet mixing. Film raw material (I) was obtained. Also, 78% by weight of a polyethylene terephthalate resin having an intrinsic viscosity of 0.62 dl / g, 20% by weight of a master pellet (X) containing titanium dioxide, and 2% by weight of a master pellet (Y) containing a fluorescent brightener were added at 40 ° C. for 8 hours. Vacuum-dried and pellet-mixed film raw material (II)
Used as

Each of these film raw materials is supplied to a separate extruder, and the raw material (I) is fed using a feed block.
(Layer B) and layer (layer A) composed of raw material (II)
Were laminated in the order of layer A / layer B / layer A. This was co-extruded from a T-die onto a cooling roll adjusted to 25 ° C. The discharge amount of each extruder was adjusted so that the thickness ratio of each layer became 1: 8: 1, and an unstretched film having a thickness of 570 μm was prepared.

The obtained unstretched film is uniformly heated to 65 ° C. using a heating roll, and two pairs of nip rolls having different peripheral speeds (low-speed roll = 2 m / min, high-speed roll = 6.2 m)
/ Min) during stretching 3.1 times. At this time, as an auxiliary heating device for the film, an infrared heater (a rated output: 74 W / cm) having a gold reflective film in the middle of the nip roll was installed at a position 1 cm from the film surface opposite to both surfaces of the film. Heated at 30%. The uniaxially stretched film thus obtained was guided to a tenter, heated to 150 ° C., and stretched transversely 3.7 times. After the transverse stretching, the width was fixed, heat treatment was performed at 230 ° C. for 5 seconds, and relaxation was performed at 200 ° C. in the width direction by 4% to obtain a white laminated polyester film having a thickness of about 50 μm.

Example 3 30% by weight of a polyethylene terephthalate resin having an intrinsic viscosity of 0.62 dl / g and 70% by weight of a titanium dioxide-containing master pellet (X) were vacuum-dried at 140 ° C. for 8 hours, mixed with pellets, and mixed with a film raw material ( I). 26% by weight of a polyethylene terephthalate resin having an intrinsic viscosity of 0.62 dl / g, 70% by weight of a master pellet (X) containing titanium dioxide, and 4% by weight of a master pellet (Y) containing a fluorescent whitening agent were added at 40 ° C. for 8 hours. The mixture obtained by vacuum drying and pellet mixing was used as a film raw material (II).

Each of these film raw materials is supplied to a separate extruder, and the raw material (I) is fed using a feed block.
(Layer B) and layer (layer A) composed of raw material (II)
Were laminated in the order of layer A / layer B / layer A. This was co-extruded from a T-die onto a cooling roll adjusted to 25 ° C. The discharge amount of each extruder was adjusted so that the thickness ratio of each layer became 1: 8: 1, and an unstretched film having a thickness of 570 μm was prepared.

The obtained unstretched film is uniformly heated to 65 ° C. using a heating roll, and two pairs of nip rolls having different peripheral speeds (low-speed roll = 2 m / min, high-speed roll = 6.2 m)
/ Min) during stretching 3.1 times. At this time, as an auxiliary heating device for the film, an infrared heater (a rated output: 74 W / cm) having a gold reflective film in the middle of the nip roll was installed at a position 1 cm from the film surface opposite to both surfaces of the film. At 40% of the temperature. The uniaxially stretched film thus obtained was guided to a tenter, heated to 150 ° C., and stretched transversely 3.7 times. After the transverse stretching, the width was fixed, heat treatment was performed at 230 ° C. for 5 seconds, and relaxation was performed at 200 ° C. in the width direction by 4% to obtain a white laminated polyester film having a thickness of about 50 μm.

Example 4 60% by weight of a polyethylene terephthalate resin having an intrinsic viscosity of 0.62 dl / g and 40% by weight of a titanium dioxide-containing master pellet (X) were vacuum-dried at 140 ° C. for 8 hours, mixed with pellets, and mixed with a film raw material ( I). Further, 58% by weight of a polyethylene terephthalate resin having an intrinsic viscosity of 0.62 dl / g, 40% by weight of a master pellet (X) containing titanium dioxide, and 2% by weight of a master pellet (Y) containing a fluorescent whitening agent were added at 40 ° C. for 8 hours. The mixture obtained by vacuum drying and pellet mixing was used as a film raw material (II).

Each of these film raw materials is supplied to a separate extruder, and the raw material (I) is fed using a feed block.
(Layer B) and layer (layer A) composed of raw material (II)
Were laminated in the order of layer A / layer B / layer A. This was co-extruded from a T-die onto a cooling roll adjusted to 25 ° C. The discharge amount of each extruder was adjusted so that the thickness ratio of each layer became 1: 8: 1, and an unstretched film having a thickness of 1140 μm was prepared.

The obtained unstretched film is uniformly heated to 65 ° C. using a heating roll, and two pairs of nip rolls having different peripheral speeds (low-speed roll = 2 m / min, high-speed roll = 6.2 m)
/ Min) during stretching 3.1 times. At this time, as an auxiliary heating device for the film, an infrared heater (a rated output: 74 W / cm) having a gold reflective film in the middle of the nip roll was installed at a position 1 cm from the film surface opposite to both surfaces of the film. At 40% of the temperature. The uniaxially stretched film thus obtained was guided to a tenter, heated to 150 ° C., and stretched transversely 3.7 times. After transverse stretching, the width was fixed, heat treatment was performed at 230 ° C. for 5 seconds, and relaxation was performed at 200 ° C. in the width direction by 4% to obtain a white laminated polyester film having a thickness of about 100 μm.

Comparative Example 1 90% by weight of a polyethylene terephthalate resin having an intrinsic viscosity of 0.62 dl / g and 10% by weight of a titanium dioxide-containing master pellet (X) were vacuum-dried at 140 ° C. for 8 hours, mixed with pellets, and mixed with a film raw material ( I). Further, 88% by weight of a polyethylene terephthalate resin having an intrinsic viscosity of 0.62 dl / g, 10% by weight of a master pellet (X) containing titanium dioxide, and 2% by weight of a master pellet (Y) containing a fluorescent brightener were added at 140 ° C. for 8 hours. The mixture obtained by vacuum drying and pellet mixing was used as a film raw material (II).

Each of these film raw materials is supplied to a separate extruder, and the raw material (I) is fed using a feed block.
(Layer B) and layer (layer A) composed of raw material (II)
Were laminated in the order of layer A / layer B / layer A. This was co-extruded from a T-die onto a cooling roll adjusted to 25 ° C. The discharge amount of each extruder was adjusted so that the thickness ratio of each layer became 1: 8: 1, and an unstretched film having a thickness of 570 μm was prepared.

The obtained unstretched film was uniformly heated to 65 ° C. using a heating roll, and two pairs of nip rolls having different peripheral speeds (low-speed roll = 2 m / min, high-speed roll = 6.2 m)
/ Min) during stretching 3.1 times. At this time, as an auxiliary heating device for the film, an infrared heater (a rated output: 74 W / cm) having a gold reflective film in the middle of the nip roll was installed at a position 1 cm from the film surface opposite to both surfaces of the film. Heated at 30%. The uniaxially stretched film thus obtained was guided to a tenter, heated to 150 ° C., and stretched transversely 3.7 times. After the transverse stretching, the width was fixed, heat treatment was performed at 230 ° C. for 5 seconds, and relaxation was performed at 200 ° C. in the width direction by 4% to obtain a white laminated polyester film having a thickness of about 50 μm.

Comparative Example 2 60% by weight of a polyethylene terephthalate resin having an intrinsic viscosity of 0.62 dl / g and 40% by weight of a titanium dioxide-containing master pellet (X) were vacuum-dried at 140 ° C. for 8 hours, mixed with pellets, and mixed with a film raw material ( I). In addition, 88% by weight of a polyethylene terephthalate resin having an intrinsic viscosity of 0.62 dl / g, 10% by weight of a master pellet (X) containing titanium dioxide, and 2% by weight of a master pellet (Y) containing a fluorescent whitening agent were added at 40 ° C. for 8 hours. The mixture obtained by vacuum drying and pellet mixing was used as a film raw material (II).

Each of these film raw materials is supplied to a separate extruder, and the raw material (I) is fed using a feed block.
(Layer B) and layer (layer A) composed of raw material (II)
Were laminated in the order of layer A / layer B / layer A. This was co-extruded from a T-die onto a cooling roll adjusted to 25 ° C. The discharge amount of each extruder was adjusted so that the thickness ratio of each layer became 1: 8: 1, and an unstretched film having a thickness of 570 μm was prepared.

The obtained unstretched film is uniformly heated to 65 ° C. using a heating roll, and two pairs of nip rolls having different peripheral speeds (low-speed roll = 2 m / min, high-speed roll = 6.2 m)
/ Min) during stretching 3.1 times. At this time, as an auxiliary heating device for the film, an infrared heater (a rated output: 74 W / cm) having a gold reflective film in the middle of the nip roll was installed at a position 1 cm from the film surface opposite to both surfaces of the film. Heated at 35%. The uniaxially stretched film thus obtained was guided to a tenter, heated to 150 ° C., and stretched transversely 3.7 times. After the transverse stretching, the width was fixed, heat treatment was performed at 230 ° C. for 5 seconds, and relaxation was performed at 200 ° C. in the width direction by 4% to obtain a white laminated polyester film having a thickness of about 50 μm.

Comparative Example 3 In Example 1, an infrared heater (rated output: 74 W / cm) having a gold reflection film in the middle of the nip roll was installed at a position 1 cm away from the film surface, facing both surfaces of the film. A white laminated polyester film was obtained in exactly the same manner as in Example 1, except that heating was performed at 25% of the rating.

[0048]

[Table 1]

The results of measuring the physical properties of the white laminated polyester film obtained by the above method are shown in Table 1. The hiding properties, whiteness and mechanical properties required for the laminated film of the present invention were confirmed by measuring the optical density, the color b value, and the dynamic hardness, respectively.
From Table 1, the following conclusions can be made. The laminated films obtained in Examples 1 to 4 satisfy all of the requirements specified in the present invention, have high whiteness / concealing properties and good mechanical performance in a well-balanced manner. It is suitable as. On the other hand, a laminated film that does not satisfy the requirements specified in the present invention as in the comparative example was insufficient as an information recording / printing material.

[0050]

The white laminated polyester film of the present invention has excellent concealing properties, whiteness and mechanical properties.
It is suitable as an information recording / printing material.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor, Mutsumi Nishi 2-1-1 Katata, Otsu-shi, Shiga Prefecture Toyobo Co., Ltd. Research Institute (72) Inventor Akira Takahashi 2-1-1 Katata, Otsu-shi, Shiga Prefecture F-term in Toyobo Co., Ltd. Research Laboratory (Reference) 4F100 AA21A AK41A AK41B AK42 AL05A AL05B BA02 BA15 CA30A DE01A DE01B HB00A HB00B JA13 JK12A JL10A JL10B JN02 JN30A YY00 YY00A 4J002 CF041 CF051

Claims (5)

[Claims] 1. A polyester skin layer (layer A) containing white particles and a polyester layer (layer B) containing or not containing white particles, wherein the A layer is at least one of the outermost layers. Wherein the optical density is 1.0 or more in terms of a film thickness of 100 μm and the dynamic hardness of at least the film surface on the A layer forming surface side is 4
A white laminated polyester film having a thickness of 9.0 to 98.0 mN / μm ² . 2. The white laminated polyester film according to claim 1, wherein the layer A contains 10 to 45% by weight of white particles. 3. The white laminated polyester film according to claim 1, wherein the white particles of the layer A are titanium oxide. 4. The white laminated polyester film according to claim 1, wherein the layer A further contains 100 to 10000 ppm by weight of a fluorescent whitening agent. 5. The apparent density specified in the text is 1.30.
and characterized in that g / cm ³ or more, the white laminated polyester film according to any one of claims 1 to 4.