JPH09300518A - Laminated film and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance tear resistance and mechanical characteristics by selecting polymers constituting the respective layers of a film laminated at least as two layers in its thickness direction from either one of at least two kinds of different thermoplastic resins and providing at least one layer of which the longitudinal refractive index is larger than a lateral refractive index. SOLUTION: The polymers constituting the respective layers of a film laminated in at least two layers in its thickness direction are selected from either one of at least two kinds of different thermoplastic resins. At least one layer wherein a refractive index in a longitudinal direction is larger than that in a lateral direction is provided to the laminated film. Herein, a layer wherein the refractive index in the longitudinbal direction of the laminated film is larger than that in the laterial direction thereof is a layer wherein the refractive index in the flow direction of the film is larger than that in the right-angled direction when the thermoplastic resin constitution that layer is biaxially stretched as a single film. By this constitution, tear strength and mechanical characteristics can be enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated film and a method for producing the same, and more specifically to a laminated film having a structure in which multiple layers are laminated in the film thickness direction and having excellent mechanical properties such as strength, particularly tear resistance, and the like. The present invention relates to a manufacturing method.

[0002]

2. Description of the Related Art In recent years, films of various thermoplastic resins have been industrially produced and used in fields suited to their respective characteristics. In particular, the biaxially stretched polyester film represented by polyethylene terephthalate or polyethylene naphthalate has excellent mechanical properties, thermal properties,
It is used in various fields due to its electrical properties and chemical resistance. Generally, these films have a problem of low tear resistance because of their high elastic modulus and creep resistance. However, it is required to have these characteristics which seem to be contradictory at first glance, in applications such as a glass shatterproof film and a photographic film.

Conventionally, as a method for obtaining a film having high strength and excellent tear resistance, a method of alternately laminating a film having high strength in the machine direction and a laminated film having high strength in the transverse direction is known. . For example, Japanese Patent Laid-Open No. 47-1
Japanese Patent No. 1394 proposes a laminated film obtained by laminating a film stretched in the machine direction and a film stretched in the transverse direction. However, in this method, since the stretching steps are separate from each other, the size of the apparatus becomes large and it is practically difficult to laminate three or more layers industrially.

Further, Japanese Patent Publication No. 6-88384 proposes an obliquely oriented cross film in which two films having a molecular orientation in a certain oblique direction are laminated so that the molecular orientations intersect each other. In this case as well, it is difficult to obtain two films in a continuous process because a process of bonding the two films with an adhesive is required.

Further, Japanese Patent Publication No. 8-22568 discloses that
When melt-extruding the thermotropic liquid crystalline polymer from the slit of the T-die by one extruder, shear stress is applied in the slit portion in a direction perpendicular to the extrusion direction, so that at least one of the front and back layer portions is laterally moved. Films have been proposed which are oriented and the center of the film is oriented in the machine direction by shearing by extrusion. This utilizes the property that a liquid crystalline polymer acts on shear stress to orient, and general thermoplastic resins widely used industrially are not suitable because they do not have liquid crystallinity.

Further, in JP-A-6-190995 and JP-A-6-190997, a laminate made of a film made of a rigid polyester and a film made of a ductile copolyester is laminated to improve tear resistance. A film has been proposed.

[0007]

Although attempts have been made to achieve tear resistance by a laminated film,
In such a laminated film, even if the tear resistance can be improved to some extent, depending on the purpose of use, it may be required to have a higher tear resistance and also have other mechanical properties, in order to widely meet the needs, Further study was needed. The present invention solves the above problems, and particularly provides a laminated film made of a thermoplastic resin suitable for glass shattering prevention applications and the like, which is further excellent in mechanical properties such as strength while further improving tear resistance. It is in.

Another object of the present invention is to provide various machines in which a layer having a refractive index in the vertical direction larger than that in the horizontal direction and a layer having a refractive index in the horizontal direction larger than that in the vertical direction are laminated in the thickness direction. The object is to provide a laminated film having excellent physical properties.

Still another object of the present invention is to industrially and economically perform in a continuous process without using a special material.
It is to provide a method for producing a laminated film in which a layer having high strength in the machine direction and a layer having high strength in a direction other than the machine direction are laminated in the thickness direction.

[0010]

The present invention is intended to achieve the above object, and the laminated film of the present invention comprises:
It is a film in which at least two layers are laminated in the thickness direction, the polymer constituting each layer is selected from at least two different thermoplastic resins, and the longitudinal refractive index is higher than the lateral refractive index. It is characterized by including at least one large layer (a layer). Such a laminated film, preferably, at least a layer (a layer) having a longitudinal refractive index greater than the lateral refractive index and a layer (b layer) having a lateral refractive index greater than or equal to the longitudinal refractive index. 1
It includes each layer.

The laminated film of the present invention is a substantially amorphous laminated film obtained by laminating at least two layers in the thickness direction by coextrusion of a thermoplastic resin, and is subjected to multi-stage stretching in two or more stages in the longitudinal direction, It can be produced by stretching in the transverse direction. Here, more preferably, the glass transition point Tga to Tga + 60 ° C. of the a layer.
At a temperature of 1.2 to 4 times, the first longitudinal stretching is performed, and subsequently, the second longitudinal stretching is performed in the same direction at a temperature lower than the first stretching temperature by 5 ° C. or more. After being carried out, it can be produced by being characterized by stretching in the transverse direction.

The present invention includes the following preferred embodiments.

A. In the laminated film, the tear propagation resistance EL (g / mm) in the longitudinal direction and the transverse direction is within a certain range (Equation 1 described later).

B. The strength F-5 value at 5% elongation of the laminated film in the machine direction and the transverse direction is 100 MPa or more.

C. The layers of the laminated film are adjacent to each other without an adhesive.

D. The polymer forming each layer is selected from at least two different polyesters.

E. ΔTcg [difference between cold crystallization temperature Tc (° C.) and glass transition temperature Tg (° C.)] of the thermoplastic resin forming the (a layer) and ΔT of the thermoplastic resin forming the b layer
Difference from cg [ΔTcg (a layer) -ΔTcg (b layer)]
Is above 20 ° C.

F. Glass transition temperature Tg of the thermoplastic resin forming the (a layer) and the thermoplastic resin forming the b layer
The difference in (° C) is 10 ° C or more.

G. The (a layer) is made of polyethylene terephthalate or polyethylene-2,6-naphthalate, and the (b layer) is made of polyester containing 50 to 100 mol% of terephthalic acid or naphthalenedicarboxylic acid as a dicarboxylic acid component.

H. The (b layer) contains at least isophthalic acid, sebacic acid, adipic acid as a dicarboxylic acid component,
A polyester containing 3 to 50 mol% of any one of dimer acids.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The layer in which the refractive index in the longitudinal direction of the laminated film in the present invention is larger than the refractive index in the lateral direction means that when the thermoplastic resin constituting the layer is biaxially stretched with a single film, the refractive index in the flow direction of the film is Is larger than the refractive index in the direction perpendicular to. Further, the layer having a refractive index in the lateral direction higher than that in the vertical direction means a layer having a refractive index in the flow direction of the film smaller than that in the perpendicular direction in the same manner. The refractive index in the vertical direction and the refractive index in the horizontal direction can be obtained with an Abbe refractometer. As a method of biaxial stretching, a cast film is first stretched in the longitudinal direction between rolls having a difference in peripheral speed, and then laterally stretched by a tenter that grips both ends of the film with clips, so-called sequential biaxial stretching in which heat treatment is performed. The method is most preferably used.

In the present invention, it is necessary that at least one layer (a layer) having a vertical refractive index higher than the horizontal refractive index exists. More preferably, at least one layer (a layer) having a vertical refractive index higher than the horizontal refractive index and one or more layers (b layer) having a horizontal refractive index higher than the vertical refractive index exist. And, more preferably, the layers a and b are alternately laminated in multiple layers. However, b
The layer is not limited to a layer having a refractive index in the horizontal direction higher than that in the vertical direction. A layer having the same refractive index in the vertical direction and the refractive index in the horizontal direction can also be the b layer. Further, there may be another layer of the third type (c layer) different from the a layer and the b layer. The film in which the layers having different directions of large refractive index are laminated has high strength and excellent tear resistance because layers having different directions of high strength are laminated.

In the laminated film of the present invention, at least two layers or more are laminated in the thickness direction, and more preferably 3 to 50 layers are laminated. And, more preferably, 7 to 25 layers are laminated. The thickness of each layer is not particularly limited, but in order to obtain a laminated film having high strength and excellent tear resistance, it is preferable that the thickness of the a layer be larger than the thickness of the b layer. About 5 times the thickness of layer b
It is more preferable that it is not less than 200 times and not more than 200 times. By the way a
The layer thickness is of the order of 1-100 microns.

The layers of the laminated film of the present invention are preferably adjacent to each other without an adhesive. For example, as a means for laminating each layer, vinyl-based, acrylic-based, polyamide-based, epoxy-based, rubber-based, urethane-based, etc. adhesives are usually used. In the practice of the present invention, a laminated film is obtained by continuous steps. Is difficult and costly, which is not preferable.

In the laminated film of the present invention, the polymer constituting each layer must be selected from at least two different thermoplastic resins.
For example, it can be selected from thermoplastic resins having different thermodynamic parameters such as crystallinity and stretchability. In the present invention, the polymer forming each layer is preferably selected from at least two different polyesters. The order of arrangement of the respective layers is arbitrary, but it is preferable that the layers made of different thermoplastic resins are adjacent to each other. Further, a hard coat layer, a coating layer, an adhesive layer, or the like can be provided on one side or both sides of the laminated film within the range that does not impair the object of the present invention.

The polyester used in the present invention is a polymer obtained by polycondensation of a dicarboxylic acid and a diol, and examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, adipic acid and sebacic acid. In addition, the diol is represented by ethylene glycol, trimethylene glycol, tetramethylene glycol, cyclohexanedimethanol, polyalkylene glycol and the like. Specific examples of the polyester include polymethylene terephthalate, polyethylene terephthalate, polytetramethylene terephthalate, polyethylene-p-oxybenzoate, poly-1,4-cyclohexylene dimethylene terephthalate, polyethylene-2,
6-naphthalate and the like can be mentioned. Of course, these polyesters may be a homopolymer or a copolymer, and examples of the copolymerization component in the copolymer include diol components such as diethylene glycol, neopentyl glycol and polyalkylene glycol, dimer acid, adipic acid, Sebacic acid, phthalic acid,
Examples include diphthalic acid components such as isophthalic acid and 2,6-naphthalenedicarboxylic acid. The proportion of the copolymer component is about 3 to 60%. Further, a flame retardant, a heat stabilizer, an antioxidant, an ultraviolet absorber, an antistatic agent, etc. may be blended as long as the effects of the present invention are not impaired.

To obtain the laminated film of the present invention, a
The difference between ΔTcg (° C) [difference between cold crystallization temperature Tc (° C) and glass transition temperature Tg (° C)] of the thermoplastic resin forming the layer and the thermoplastic resin forming the layer b is 20 ° C or more. Alternatively, the difference in Tg (° C.) between the thermoplastic resin forming the layer a and the thermoplastic resin forming the layer b is preferably 10 ° C. or more. Further, both conditions may be satisfied at the same time.

The difference in crystallinity and the difference in intermolecular force between the thermoplastic resins constituting the layers a and b have a great influence on the orientation by stretching, and the principal axes of the orientation of the layers a and b are The directions are different, that is, the direction with a large refractive index is different. Specific examples of the combination of the layers a and b include (a layer) polyethylene-2,6-naphthalate and (b layer) polyethylene terephthalate, (a layer).
(Layer) polyethylene terephthalate and (b layer) polyethylene terephthalate containing a plasticizer, (a layer) polyethylene terephthalate and (b layer) copolymer of ethylene terephthalate and ethylene isophthalate, (a)
Layer) polyethylene terephthalate and (b layer) copolymer of ethylene terephthalate and ethylene sebacate,
Alternatively, (a layer) polyethylene terephthalate and (b)
Layer) Examples include copolymers with ethylene terephthalate and ethylene adipate.

The plasticizer in the present invention is, for example, a phosphoric acid-based, phthalic acid-based, polyester-based, epoxy-based or polyether-based plasticizer. When each layer of the laminated film is composed of polyester, the plasticizer is preferably polyether. The polyether is not particularly limited, and examples thereof include polyethylene oxide, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and a polyether containing at least one kind of a copolymer of these polyethers. And, more preferably, an end-capped polyether is used. The end-capped polyether is not particularly limited, but is, for example, a polyether whose end hydroxyl group is end-capped with an alkyl ether, that is, a methoxy group or an ethoxy group. The orientation ratio of the plasticizer is about 1 to 20%.

Tear propagation resistance EL of the laminated film of the present invention
(G / mm) preferably satisfies the following expression (1). It can be said that the laminated film of the present invention satisfying the following formula (1) has significantly improved tear resistance as compared with the conventional polyester film.

[0031] EL: Tear propagation resistance (g / mm) of the laminated film ELn: Tear propagation resistance (g / mm) Tn of the thermoplastic resin film (thickness is the same as the laminated film) constituting the n-th layer Tn : Thickness of n-th layer T: thickness of the laminated film i: number of layers constituting the laminated film Further, F in the longitudinal direction and the transverse direction of the laminated film of the present invention.
The -5 value (strength at 5% elongation) is preferably 100 MPa or more. More preferably, the F-5 value in the machine direction or the transverse direction is 150 MPa or more, and the laminated film has high strength.

Next, a method for producing the laminated film of the present invention will be described. The thermoplastic resin that constitutes each sufficiently dried layer is supplied to each extruder, and after passing through a filter selected as necessary, a known technique such as a multi-manifold die method, a feed block method or a static mixer method is used. The layers are laminated using a pressing method and melt coextruded from a die. The multi-manifold method uses a die having a plurality of manifolds. In this method, the resin flows into the manifold corresponding to each layer from the inflow port, the flow is widened over the entire die width in the manifold, and then the resin is discharged through the joining slit. The feed block method is to form a combined flow in a feed block before feeding a plurality of resins into a die, and then feed the resin into a normal single manifold die to widen and extrude the flow. In addition, the static mixer method is a method in which several kinds of resins combined in a certain arrangement are divided into multiple layers by a mixer, and is suitable for a case where the laminated arrangement is a repetition of a simple arrangement. The film-like laminate obtained by any one of these methods is rapidly cooled and solidified on a casting drum controlled at a temperature of 20 to 60 ° C. to be in an amorphous state. At this time, it is more preferable to improve the adhesion between the drum and the film by using a known static electricity applying device.

Next, the obtained amorphous laminated film is first stretched and oriented in the longitudinal direction. The laminated film is passed through a sufficiently heated roll and preheated, and the stretching temperature in the longitudinal direction is the glass transition temperature (Tga) to (Tga + 60) ° C. of the thermoplastic resin constituting the layer a, preferably (Tga
Within the temperature range of +20) to (Tga + 50) ° C, 1.2
After the first stage stretching of 4 to 4 times, preferably 1.5 to 3 times, the second stage stretching of 2.5 to 4 times is performed at a temperature 5 ° C. or more lower than the first stage stretching temperature. When such a two-step stretching is carried out, since the direction of the principal axis of the orientation of the layer a is the longitudinal direction even after the lateral stretching, a laminate including a layer having a refractive index in the longitudinal direction higher than that in the lateral direction. It is particularly suitable for obtaining films.

The longitudinally stretched film thus obtained is subsequently guided to a tenter which holds clips at both ends of the film, and laterally stretched and heat-treated. The transverse stretching ratio is preferably set in the range of 3 to 6 times. The transverse stretching temperature depends on the transverse stretching ratio, but is 80 to
It is preferable to set in the range of 200 ° C. According to the longitudinal stretching method described above, the main axis of orientation of the layer a is still in the longitudinal direction even after transverse stretching, so that the refractive index in the longitudinal direction is larger than the refractive index in the lateral direction. However, in the b layer, as in the result of sequential biaxial stretching performed in the order of normal longitudinal stretching and transverse stretching, the main axis of orientation after transverse stretching is the transverse direction, and therefore the refractive index in the transverse direction is It becomes larger than the refractive index.

The biaxially stretched laminated film is continuously subjected to 120 to 120% in order to impart flatness and thermal dimensional stability.
Heat treatment is performed in the temperature range of 250 ° C. In order to further improve the thermal dimensional stability in the lateral direction, it is also preferable to perform a so-called relaxation treatment in which the widthwise length of the tenter is reduced from the latter half of the heat treatment chamber to the cooling chamber. The evaluation methods of various physical property values in the present invention are as follows.

(1) Refractive index The refractive index in the machine direction and the transverse direction of the film was measured by Abbe refractometer type 4 manufactured by Atago Co., Ltd. using sodium D ray (wavelength 589 nm) as a light source. The thermoplastic resin constituting each layer was stretched as a single film under almost the same conditions as the laminated film, and the refractive indices in the longitudinal direction and the transverse direction were obtained. Methylene iodide was used as a mount solution for polyethylene terephthalate, a copolymer of ethylene terephthalate and ethylene isophthalate, and a copolymer of ethylene terephthalate and ethylene sebacate. Also, polyethylene-2,
For 6-naphthalate, sulfur methylene iodide was used as the mount solution.

(2) Tear propagation resistance An Elmendorf tear tester manufactured by Toyo Seiki Seisakusho is used. Sample film length 63.5 mm, width 50.8 m
Sampling into a rectangle of m, a 12.7 mm vertical cut is made at the center of both grips along the horizontal direction, and the tearing force (g) for the remaining 50.8 mm is obtained. Tear propagation resistance (g / m)
m).

(3) F-5 value A sample film having a width of 10 mm was placed on a tensile tester RTA-100 manufactured by Orientec Co., Ltd. and a length between chucks was 50 m.
m, and a tensile test was carried out at a tensile speed of 200 mm / min under the conditions of 23 ° C. and 65% RH, and the strength at 5% elongation of the film was measured to obtain an F-5 value (MP
a).

(4) Glass transition temperature and cold crystallization temperature Differential scanning calorimeter RDC220 manufactured by Seiko Denshi Kogyo KK
It was measured using a mold. The measurement conditions are as follows. That is, 5 mg of the sample is set in the DSC device, and the temperature is 300 ° C
After being melted at the temperature of 5 minutes, it was rapidly cooled. The temperature of this rapidly cooled sample is raised at 10 ° C./min, and the glass transition point Tg is detected. The temperature was further raised and the crystallization exothermic peak temperature was set to the cold crystallization temperature Tc. Further, when the cold crystallization peak Tc is difficult to detect because the crystallinity is particularly low, it is assumed that Tg = Tc.

[0040]

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

Examples 1 to 4 Polyethylene terephthalate (A) [Intrinsic viscosity 0.6
5, glass transition temperature 79 ° C., cold crystallization temperature 178 ° C., melting point 255 ° C., ΔTcg 99 ° C.] pellets were vacuum dried at 180 ° C. for 3 hours and then heated to 280 ° C. Extruder 1
Supplied. Further, a copolymer (B) comprising 90 mol% of ethylene terephthalate and 10 mol% of ethylene sebacylate [intrinsic viscosity 0.63, glass transition temperature 59 ° C.,
Cold crystallization temperature 151 ° C, melting point 233 ° C, ΔTcg92
C.] pellets were vacuum dried at 120.degree. C. for 2 hours, further vacuum dried at 150.degree. C. for 3 hours, and then fed to the extruder 2 heated to 280.degree. The polyesters A and B extruded from the extruders 1 and 2 were alternately laminated in the thickness direction in the mixer section in a total of 16 layers, and formed into a sheet from a T die. Further, this film was adhered and solidified on a cooling drum having a surface temperature of 25 ° C. by electrostatic force to obtain an unstretched cast film.

This unstretched film was introduced into a plurality of roll groups heated to 105 ° C. and preheated, and then the first longitudinal stretching was carried out at a draw ratio of 2.0 times, and subsequently, a plurality of roll groups was heated to 82 ° C. After cooling, the second stage longitudinal stretching was performed at a stretching ratio of 3 times. The obtained film was introduced into a tenter holding both ends with clips, laterally stretched 3.5 times at 85 ° C., and then heat treated at 140 ° C. Table 1 shows the tear propagation resistance, F-5 value, the direction in which the refractive index of the A layer and the B layer is large, and the ratio of the laminated thickness of the A layer and the B layer of the obtained laminated film. Also,
The thickness of the laminated films of Examples 1 to 4 was unified to about 20 μm.

[0043]

[Table 1] Comparative Example 1 The polyethylene terephthalate (A) of Examples 1 to 4 was dried in a single layer under the same conditions as in Examples 1 to 4 and extruded, and then stretched in the machine direction and subsequently stretched in the cross direction and heat-treated. The obtained film had a thickness of 20 μm and had a large refractive index in the longitudinal direction. The F-5 value is 185 MPa in the vertical direction and 100 MPa in the horizontal direction, and the tear propagation resistance is 2 in the vertical direction.
It was 00 g / mm and 650 g / mm in the lateral direction.

Comparative Example 2 The copolymer (B) of 90 mol% ethylene terephthalate and 10 mol% ethylene sebacylate of Examples 1 to 4 was dried and extruded in a single layer under the same conditions as in Examples 1 to 4, Stretching was carried out in the machine direction, followed by stretching in the transverse direction and heat treatment. The obtained film had a thickness of 20 μm and had a large refractive index in the lateral direction. The F-5 value was 81 MPa in the vertical direction and 90 MPa in the horizontal direction, and the tear propagation resistance was 11 in the vertical direction.
It was 20 g / mm and the lateral direction was 880 g / mm.

Comparative Examples 3 to 6 The polyethylene terephthalate (A) pellets of Examples 1 to 4 were vacuum dried at 180 ° C. for 3 hours and then fed to the extruder 1 heated to 280 ° C. Further, the copolymer (B) consisting of 90 mol% of ethylene terephthalate and 10 mol% of ethylene sebacylate of Examples 1 to 4 was vacuum dried for 2 hours and further vacuum dried at 150 ° C. for 3 hours.
It was fed to the extruder 2 heated to 0 ° C. The polyesters A and B extruded from the extruders 1 and 2 were alternately laminated in the thickness direction in the mixer section in a total of 16 layers, and formed into a sheet from a T die. Further, this film was adhered and solidified on a cooling drum having a surface temperature of 25 ° C. by electrostatic force to obtain an unstretched cast film.

This unstretched film was introduced into a plurality of roll groups heated to 95 ° C. and preheated, and then longitudinally stretched at a stretch ratio of 4.0. The obtained film was introduced into a tenter holding both ends with clips, laterally stretched 4.5 times at 100 ° C., and then heat-treated at 140 ° C. Table 2 shows the tear propagation resistance, the F-5 value, the direction in which the refractive index of the A layer and the B layer is large, and the ratio of the laminated thickness of the A layer and the B layer of the obtained film.
The thickness of the laminated film was unified to about 20 μm.

[0047]

[Table 2] Examples 5 to 8 The polyethylene terephthalate (A) pellets of Examples 1 to 4 were vacuum dried at 180 ° C for 3 hours and then fed to the extruder 1 heated to 280 ° C. Further, a copolymer (C) consisting of 75 mol% of ethylene terephthalate and 25 mol% of ethylene isophthalate [intrinsic viscosity 0.65, glass transition temperature 77 ° C, cold crystallization temperature 77 ° C, melting point 190
[° C, ΔTcg0 ° C] pellets were vacuum dried at 120 ° C for 2 hours and further at 150 ° C for 3 hours.
It was fed to the extruder 2 heated to 0 ° C. The polyesters A and C extruded from the extruders 1 and 2 were alternately laminated in the thickness direction in the mixer section in a total of 16 layers, and formed into a sheet from a T die. Further, this film was adhered and solidified on a cooling drum having a surface temperature of 25 ° C. by electrostatic force to obtain an unstretched cast film.

This unstretched film was introduced into a plurality of roll groups heated to 105 ° C. and preheated, and then the first longitudinal stretching was carried out at a draw ratio of 2.0 times, and subsequently to a plurality of roll groups at 82 ° C. After cooling, the second stage longitudinal stretching was performed at a stretching ratio of 3 times. The obtained laminated film was introduced into a tenter which holds both ends with clips, laterally stretched 3.5 times at 85 ° C., and then heat-treated at 140 ° C. Table 3 shows the tear propagation resistance of the obtained film, the F-5 value, the direction in which the refractive index of the A layer and the C layer are large, and the ratio of the laminated thickness of the A layer and the C layer. The thickness of the laminated films of Examples 5 to 8 was unified to about 20 μm.

[0049]

[Table 3] Comparative Example 7 Copolymer (C) of 75 mol% ethylene terephthalate and 25 mol% ethylene isophthalate of Examples 5-8
Was dried in a single layer under the same conditions as in Examples 5 to 8 and extruded,
Stretching was carried out in the machine direction, followed by stretching in the transverse direction and heat treatment.
The thickness of the obtained laminated film was 20 μm, and the refractive index was large in the lateral direction. The F-5 value is 80MP in the vertical direction.
a, the horizontal direction was 95 MPa, and the tear propagation resistance was 992 g / mm in the vertical direction and 902 g / mm in the horizontal direction.

Comparative Examples 8 to 11 The polyethylene terephthalate (A) pellets of Examples 1 to 4 were vacuum dried at 180 ° C. for 3 hours and then fed to the extruder 1 heated to 280 ° C. Further, the copolymer (C) consisting of 75 mol% of ethylene terephthalate and 25 mol% of ethylene isophthalate of Examples 5 to 8 was vacuum dried for 2 hours, further vacuum dried at 150 ° C. for 3 hours, and then 2
It was supplied to the extruder 2 heated to 80 ° C. Extruders 1 and 2
The polyesters A and C extruded from the above were alternately laminated in the thickness direction in the mixer section for a total of 16 layers and formed into a sheet from a T die. Further, this film was adhered and solidified on a cooling drum having a surface temperature of 25 ° C. by electrostatic force to obtain an unstretched cast film.

This unstretched film was introduced into a plurality of roll groups heated to 95 ° C. and preheated, and then longitudinally stretched at a stretching ratio of 4.0. The obtained film was introduced into a tenter holding both ends with clips, laterally stretched 4.5 times at 100 ° C., and then heat-treated at 140 ° C. Table 4 shows the tear propagation resistance, the F-5 value, the direction in which the refractive index of the A layer and the C layer are large, and the ratio of the laminated thickness of the A layer and the C layer of the obtained laminated film. The thickness of the laminated film was unified to about 20 μm.

[0052]

[Table 4] Examples 9 to 12 Polyethylene naphthalate (D) [intrinsic viscosity 0.75,
Pellets having a glass transition temperature of 124 ° C., a cold crystallization temperature of 224 ° C., a melting point of 266 ° C., ΔTcg of 100 ° C.] were vacuum dried at 120 ° C. for 2 hours, further vacuum dried at 180 ° C. for 3 hours, and then extruded at 280 ° C. Supplied to machine 1. Further, the polyethylene terephthalate (A) of Examples 1 to 4
After vacuum drying the pellets of
It was fed to the extruder 2 heated to 0 ° C. Polyesters D and A extruded from the extruders 1 and 2 were alternately laminated in the thickness direction in the mixer section for a total of 16 layers, and formed into a sheet from a T die. Further, this film was adhered and solidified on a cooling drum having a surface temperature of 25 ° C. by electrostatic force to obtain an unstretched cast film.

This unstretched film was introduced into a plurality of roll groups heated to 165 ° C. and preheated, and then the first longitudinal stretching was carried out at a draw ratio of 2.0 times, and subsequently the plurality of roll groups was heated to 130 ° C. After cooling, the second stage longitudinal stretching was performed at a stretching ratio of 3 times. The obtained film was introduced into a tenter holding both ends with clips, laterally stretched 3.5 times at 140 ° C., and then heat-treated at 200 ° C. Table 5 shows the tear propagation resistance, the F-5 value, the direction in which the refractive index of the D layer and the A layer is large, and the ratio of the laminated thickness of the D layer and the A layer of the obtained laminated film. The thickness of the laminated films of Examples 9 to 12 is about 20 μm.
Unified.

[0054]

[Table 5] Comparative Example 12 The polyethylene naphthalate (D) of Examples 9 to 12 was dried in a single layer under the same conditions as in Examples 9 to 12, extruded, and then stretched in the machine direction, and subsequently stretched in the cross direction and heat-treated. The obtained film had a thickness of 20 μm and had a large refractive index in the longitudinal direction. The F-5 value is 380 MPa in the vertical direction,
The transverse direction was 170 MPa, and the tear propagation resistance was 312 g / mm in the longitudinal direction and 481 g / mm in the lateral direction.

Comparative Examples 13 to 16 Polyethylene naphthalate (D) pellets of Examples 9 to 12 were vacuum dried at 120 ° C. for 2 hours, and further 180 ° C.
After vacuum drying for 3 hours, it was fed to the extruder 1 heated to 280 ° C. Further, the polyethylene terephthalate (A) pellets of Examples 1 to 4 were vacuum dried at 180 ° C. for 3 hours and then fed to the extruder 2 heated to 280 ° C. Polyesters D and A extruded from the extruders 1 and 2
Was alternately laminated in the thickness direction in the mixer section for a total of 16 layers and formed into a sheet from a T die. Further, this film was adhered and solidified on a cooling drum having a surface temperature of 25 ° C. by electrostatic force to obtain an unstretched cast film.

This unstretched film was introduced into a plurality of roll groups heated to 140 ° C. and preheated, and then longitudinally stretched at a stretching ratio of 3.0 times. The obtained film was introduced into a tenter holding both ends with clips, laterally stretched 4.5 times at 160 ° C., and then heat-treated at 200 ° C. Tear propagation resistance of the obtained film, F-5 value, orientation axis of D layer and A layer, D
Table 6 shows the ratio of the laminated thickness of the layer and the layer A. The thickness of the laminated film was unified to about 20 μm.

[0057]

[Table 6]

[0058]

INDUSTRIAL APPLICABILITY The laminated film of the present invention has excellent mechanical properties and tear resistance, and is suitable for applications such as a glass shatterproof film. Further, according to the production method of the present invention, a film in which the main axis of orientation and the horizontal layer are alternately laminated is manufactured industrially and economically in a continuous process without using a special thermoplastic resin. Obtainable.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location // B29K 67:00 B29L 9:00

Claims (13)

[Claims] 1. A film in which at least two layers are laminated in the thickness direction, and the polymer constituting each layer is at least two.
A layer (a which has a refractive index in the longitudinal direction larger than that in the lateral direction and is selected from any of different types of thermoplastic resins).
Laminated film comprising at least one layer). 2. A layer having at least one layer having a refractive index in the vertical direction larger than that in the horizontal direction (a layer) and a layer having a refractive index in the horizontal direction larger than or equal to that in the vertical direction (layer b), at least one layer each. The laminated film according to claim 1, comprising: 3. The laminated film according to claim 1, wherein the tear propagation resistance EL (g / mm) in the machine direction and the transverse direction satisfies the following expression (1). EL: Tear propagation resistance (g / mm) of the laminated film ELn: Tear propagation resistance (g / mm) Tn of the thermoplastic resin film (thickness is the same as the laminated film) constituting the n-th layer Tn : Thickness of n-th layer T: thickness of the laminated film i: number of layers constituting the laminated film 4. The laminated film according to claim 1, wherein the strength F-5 value at 5% elongation in the machine direction and the transverse direction is 100 MPa or more. 5. The laminated film according to claim 1, wherein the layers of the laminated film are adjacent to each other without an adhesive. 6. The polymer according to claim 1, wherein the polymer constituting each layer is selected from at least two different polyesters.
The laminated film according to any one of 1. 7. A ΔTc of a thermoplastic resin forming the layer a
g [cold crystallization temperature Tc (° C.) and glass transition temperature Tg
(° C.)] and ΔTcg of the thermoplastic resin forming the layer b
[ΔTcg (a layer) -ΔTcg (b layer)] is 2
It is 0 degreeC or more, Claim 1 to Claim 6 characterized by the above-mentioned.
The laminated film according to any one of 1. 8. The glass transition temperature Tg (° C.) difference between the thermoplastic resin forming the a layer and the thermoplastic resin forming the b layer is 10 ° C. or more. Item 8. The laminated film according to any one of item 7. 9. The laminated film according to claim 1, wherein the layer a is made of polyethylene terephthalate or polyethylene-2,6-naphthalate. 10. The laminated film according to claim 1, wherein the layer b is made of polyester containing 50 to 100 mol% of terephthalic acid or naphthalenedicarboxylic acid as a dicarboxylic acid component. 11. The layer b is made of a polyester containing 3 to 50 mol% of at least one of isophthalic acid, sebacic acid, adipic acid and dimer acid as a dicarboxylic acid component. The laminated film according to any one of 1 to 10. 12. A substantially amorphous laminated film obtained by laminating at least two layers in the thickness direction by coextrusion of a thermoplastic resin is subjected to multi-stage stretching in two or more stages in the longitudinal direction, and then stretched in the transverse direction, A method for producing a laminated film, comprising obtaining a laminated film containing at least one layer (a layer) having a refractive index in the longitudinal direction of the film higher than that in the lateral direction of the film. 13. The glass transition point Tga to (Tg of the a layer).
a + 60) ° C., the longitudinal stretching of the first step is performed at a draw ratio of 1.2 to 4 times, and subsequently, in the same direction, the second step is performed at a temperature lower than the stretching temperature of the first step by 5 ° C. or more. The method for producing a laminated film according to claim 12, wherein the film is stretched in the transverse direction after being longitudinally stretched.