JP2002192608A - Manufacturing method of oriented film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the manufacturing method of an oriented film, which is capable of restraining completely the generation of void even when a non- compatible substance is dispersed. SOLUTION: In the manufacturing method of the oriented film, constituted of at least a thermoplastic resin A, another thermoplastic resin C compatible with the thermoplastic resin A and a substance B, non-compatible with the thermoplastic resin C, while the thermoplastic resin A forms a continuous layer, the thermoplastic resin C, having a softening temperature lower than that of the thermoplastic resin A, is selected upon orientation and heat treatment while the heat treatment is effected at a temperature, higher than the softening temperature of the thermoplastic resin C and lower than that of the resin A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a stretched film, and more particularly to a method for producing a stretched film capable of suppressing the generation of voids while adding a substance incompatible with a matrix resin. The present invention relates to a method for producing a stretched film suitable for optics requiring transparency, in particular.

[0002]

2. Description of the Related Art Conventionally, a stretched film mainly comprises a polyester resin such as polyethylene terephthalate and polyethylene naphthalate resin, a polyolefin resin such as polypropylene, a crystalline resin such as a nylon resin, a polystyrene resin and a polyphenylene sulfide resin. After being extruded into a shape, it is stretched and, if necessary, subjected to heat treatment to form a thin film with excellent mechanical strength, heat resistance, electrical properties, surface smoothness, etc. It is widely used as a material, a printing material, and a process material thereof.

[0003] The addition of fine particles to the interior of these stretched films is widely used for the purpose of improving or imparting the surface shape characteristics of the stretched film, the electrical properties of the stretched film, and the optical properties of the stretched film. Is being done.

[0004] At this time, a fine-grained substance to be added to the inside of the stretched film (hereinafter sometimes simply referred to as "fine-particles") is used as a base resin to be mixed in order to maintain the properties of the substance even after melt extrusion. (Hereinafter sometimes referred to as “matrix resin”), which is often insoluble, in other words, incompatible.

However, in general, when a matrix resin sheet to which fine particles are added is formed into a sheet and then stretched, the fine particles and the matrix resin are incompatible.
It is well known that separation occurs at the interface, and cavities are generated around the fine particles (hereinafter, these cavities may be referred to as “voids”).

[0006] When voids are generated, various characteristics are deteriorated. For example, in electrical insulation applications, the dielectric constant decreases, the dielectric breakdown strength decreases, and in the case of magnetic tapes, carrier tapes, release films, etc., defects or tensile strengths occur due to falling off of fine particles during running of the tape or film. And mechanical properties such as tensile elongation, and transparency for optical applications.

Various proposals have been made so far to suppress the generation of voids, and they can be roughly classified into the following methods.

A method in which only the surface of the fine particles is subjected to surface treatment or the like so as to have good adhesion to the matrix resin.

[0009] A method for suppressing the generation of voids by adjusting the production conditions of the stretched film such as the stretching conditions in various ways.

[0010]

However, it has not been possible to completely suppress the generation of voids by any of the above-mentioned methods that have been proposed up to now. Especially in optical applications where transparency is required, no matter how much the voids can be reduced, if the interface between the fine particles and the matrix resin is not in close contact, light reflection at the interface will be strong, so complete Although it is required to suppress the occurrence of voids or to suppress the generation of very small voids, it has not been possible to produce a stretched film that can meet the requirements of this application.

For this reason, in the field where high transparency is required, a non-stretched film mainly containing triacetyl cellulose resin, polycarbonate resin, acrylic resin, alicyclic polyolefin resin, etc. is often used. Since these films are non-stretched, they often have drawbacks such as low chemical resistance and low heat resistance.In the production, dope dissolved in an organic solvent is cast on a drum or belt. Since it is often manufactured by a so-called solution casting method in which drying is performed, there are problems such as production efficiency and enormous labor required for treating solvent vapor.

Furthermore, in the case of a resin that can be melt-extruded but is not stretched, a mirror surface with two spaces adjusted immediately before cooling and solidifying in order to obtain surface smoothness which is one of the important properties for optics. A so-called calendar cast, which guides the sheet between the drums, is required, but the calender cast requires the amount of resin to be supplied, its temperature control device, the drum gap adjusted with extremely high precision, its drive device, etc. As a result, it had to be extremely inefficient.

[0013] In order to solve the above-mentioned problems, the present invention makes it possible to completely suppress the generation of voids while using a stretched film such as polyethylene terephthalate having high productivity, chemical resistance and heat resistance. To provide a method for producing a stretched film.

[0014]

In order to achieve the above object, the present invention provides at least a thermoplastic resin A, a thermoplastic resin C compatible with the thermoplastic resin A, and a non-compatible thermoplastic resin C with the thermoplastic resin A. A method for producing a stretched film comprising a soluble substance B, wherein the thermoplastic resin A forms a continuous phase, wherein the thermoplastic resin C is mixed in advance with the thermoplastic resin C and an incompatible substance B. An intermediate raw material D in which the substance B is dispersed in a thermoplastic resin C is produced, and at least one of the intermediate raw material D and the thermoplastic resin A is joined in a molten state, so that the thermoplastic resin A is continuously formed. After forming into a sheet in the form of forming a phase, when the sheet is stretched and heat-treated, the thermoplastic resin C is assumed to have a softening temperature lower than the softening temperature of the thermoplastic resin A. Is the softening temperature of the thermoplastic resin C It is obtained by a method for producing a stretched film, characterized in that at a temperature below the softening temperature of the upper and the thermoplastic resin A.

[0015]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, thermoplastic resin A
Represents the continuous phase of the stretched film.

Here, "constituting a continuous phase" means that the stretched film forms a continuous phase when cut at an arbitrary point in the film thickness direction in a plane direction and observed. For example, a thermoplastic resin A in a layered form, a thermoplastic resin A as a matrix resin, and a thermoplastic resin C in a discontinuous phase may be mentioned. More specifically, when viewed from the cross section of the stretched film, a thermoplastic resin C (c in the figure) obtained by dispersing the substance B (b in the figure) in a matrix resin composed of the thermoplastic resin A (a in the figure) ) Are present in the form of islands (FIG. 1 (A)), and the thermoplastic resin C (c in the figure) obtained by dispersing the substance B on the layer composed of the thermoplastic resin A (a in the figure) (Fig. 1
(B)), a layer obtained by laminating a thermoplastic resin C (c in the figure) in which a substance B (b in the figure) is dispersed on a layer made of a thermoplastic resin A (a in the figure) ( (Fig. 1 (C) (D))
Is exemplified. In particular, FIGS. 1 (C) and 1 (C) in which a thermoplastic resin C (c in the figure) obtained by dispersing a substance B (b in the figure) on a layer made of a thermoplastic resin A (a in the figure) are laminated. D)
Is preferred.

Since the present invention is a method for producing a stretched film, the thermoplastic resin A is preferably a crystalline polymer compound.

For example, polyester resins such as polyethylene terephthalate and polyethylene naphthalate resins; polyolefin resins such as polypropylene;
Nylon resin, polystyrene resin, polyphenylene sulfide resin and the like can be mentioned.

Of these, polyester resins, especially polyethylene terephthalate resins, are preferably used because they balance, at a high level, various properties required for industrial films such as optical properties, heat resistance, chemical resistance, and electrical insulation. Can be

Conventionally, various additives have been added or copolymerized to modify the properties of the polyester resin or polyethylene terephthalate resin according to the application for which the properties are required. Does not exclude these measures.

The thermoplastic resin C used in the present invention has compatibility with the above-mentioned thermoplastic resin A, and the thermoplastic resin A
Is selected from resins having a softening temperature lower than the softening temperature.

Here, "has compatibility" means that after a sheet-like material or a stretched film having a thermoplastic resin A as a continuous phase, which will be described later, is produced, it is integrated with the thermoplastic resin A phase and mechanically. It means that the resin A cannot be separated from the resin A, and the difference in solubility parameter (hereinafter, sometimes referred to as “SP value”) from the thermoplastic resin A is 0.3 (MPa) ＾
0.5) or less.

The thermoplastic resin C needs to have a lower softening temperature than the thermoplastic resin A. Here, the “softening temperature” is a melting point of a crystal of the crystalline polymer compound in the case of a crystalline polymer compound, and is measured based on an ASTM-D648 test method in a case of an amorphous polymer compound. Heat deformation temperature.

It is preferable that the difference between the softening temperatures of the thermoplastic resin C and the thermoplastic resin A is not less than 20 ° C. in that the control of the heat treatment temperature described later becomes easy.

When the thermoplastic resin A is a crystalline polymer compound and the thermoplastic resin C is an amorphous polymer compound, it is measured at a temperature 30 ° C. lower than the melting point of the thermoplastic resin A. The melt viscosity of the resin C is 100,000 poise or less, more preferably 1,000 poise or more and 50,000
It is preferably at most poise in view of film formability and mechanical properties of the obtained film.

In order to satisfy such compatibility and softening temperature, the thermoplastic resin C has a repeating unit similar to that of the thermoplastic resin A, but has a copolymer component different from the thermoplastic resin A introduced therein. Is preferably a main component.

For example, when the thermoplastic resin A is polyethylene terephthalate, the thermoplastic resin C is
Isophthalic acid copolymerized polyethylene terephthalate, aliphatic dicarboxylic acid copolymerized polyethylene terephthalate, naphthalenedicarboxylic acid copolymerized polyethylene terephthalate, glycol copolymerized polyethylene terephthalate having 3 or more carbon atoms, cyclohexane dimethanol copolymerized polyethylene terephthalate, and copolymers thereof And the like.

When the resin A is polyethylene naphthalate, the thermoplastic resin C may be polyethylene phthalate copolymerized with isophthalic acid, polyethylene naphthalate copolymerized with an aliphatic dicarboxylic acid, polyethylene terephthalate copolymerized with naphthalenedicarboxylic acid, Number of glycol copolymerized polyethylene naphthalate of 3 or more, cyclohexane dimethanol copolymerized polyethylene naphthalate, polyethylene terephthalate, isophthalic acid copolymerized polyethylene terephthalate, aliphatic dicarboxylic acid copolymerized polyethylene terephthalate, naphthalenedicarboxylic acid copolymerized polyethylene terephthalate, carbon number Glycol copolymer terephthalate, cyclohexane dimethanol copolymer polyethylene terephthalate having at least 3 And the like of the copolymer.

The substance B incompatible with the thermoplastic resin C used in the present invention is dispersed in fine particles in a sheet or a stretched film described later. This substance B has two aspects.

One embodiment of the substance B is an inorganic fine particle or a fine particle made of a non-thermoplastic resin.
Agglomerated silica, spherical silica, alumina,
Examples include ceramic particles such as calcium carbonate, titanium oxide, magnesium oxide, and barium titanate, glass beads, and metal particles such as iron and aluminum. The fine particles made of a non-thermoplastic resin include cross-linked polystyrene particles, cross-linked polyester particles, cross-linked acryl particles, cross-linked silicone resin particles, and the like.

Of these, glass beads, cross-linked polystyrene particles, cross-linked polyester particles, cross-linked acryl particles, cross-linked silicone resin particles, and the like are particularly preferably used in view of the great effect of the present invention.

The shape of the fine particles is preferably substantially spherical or elliptical spherical. In the case of amorphous fine particles, the suppression of void generation may not be perfect.

The size of the particles is variously selected depending on the properties of the stretched film to be obtained. In the case of optics where transparency is prioritized, the average particle size is preferably 0.01 μm or more and 5 μm or less. However, there is no problem if there is a particle deviating from this range due to the distribution of the particle diameter.

The second embodiment of the substance B is that the thermoplastic resin A, the substance B incompatible with the thermoplastic resin A, and the thermoplastic resin C are all thermoplastic resins.
In this case, the substance B may be melted once before being formed into a sheet, but it is sufficient that the substance B is dispersed in the form of fine particles at the stage of being formed into a sheet by a kneading effect of an extruder or the like.

Therefore, when the substance B is a thermoplastic resin, it must be incompatible with the thermoplastic resin C. Here, "incompatible" means that after manufacturing a sheet-like material or a stretched film, it is mechanically separable from the thermoplastic resin C without being integrated with the thermoplastic resin C phase. And the difference between the solubility parameter and the resin C is 0.7 (MP
a) It is preferable to select from those having ＾ 0.5) or more.

The use of the substance B as a thermoplastic resin is preferable because filtering in a molten state is facilitated and foreign matter can be prevented from being mixed.

In particular, when the stretched film is a light-diffusing film (a film that diffuses light while transmitting light), the fine particles serving as the light-diffusing element have a particle size of 3 μm.
Although fine particles having a particle size of at least 5 μm are required, contamination with foreign particles having a particle size of at least 5 μm may not be allowed. In such a case,
The effect of enabling filtering in a molten state is extremely large.

When the three materials of the thermoplastic resin A, the substance B, and the thermoplastic resin C have the same or similar refractive index, a film without light turbidity having excellent light transmittance and straight light transmittance is obtained. If the refractive index is different from that of the resin C, a film having excellent light transmission and light diffusion properties can be obtained.

As a preferable combination for obtaining a light diffusing film, a thermoplastic resin A is a polyester resin such as polyethylene terephthalate or polyethylene naphthalate (the refractive index is generally 1.52 depending on the composition.
To 1.65), examples of the thermoplastic resin used as the substance B include polyethylene, polypropylene, polymethylpentene, and alicyclic polyolefin resin (the refractive index is generally 1.49 to 1.5 depending on the composition.
5) can be mentioned as a preferred example.

The process for producing a stretched film according to the present invention comprises the steps of mixing a substance B with the thermoplastic resin C selected as described above and dispersing the substance B in fine particles in the thermoplastic resin C. Raw material D is produced.

The method of mixing the thermoplastic resin C with the substance B is not particularly limited. However, when the substance B is an inorganic particle or a non-thermoplastic resin particle, when the thermoplastic resin C is polymerized, A method of dispersing in a polymerization solvent in advance or during the progress of polymerization;
In the case where the substance B is a thermoplastic resin, there is a method in which the thermoplastic resin C and the substance B are simultaneously supplied to one extruder and melt-kneaded. It is preferably used.

Next, the intermediate raw material D and the thermoplastic resin A obtained as described above are joined together in a state where at least one of them is in a molten state, and the thermoplastic resin A is formed into a sheet form so as to form a continuous layer. (Hereinafter, the sheet-like material obtained at this stage may be simply referred to as a “sheet”).

The method and procedure for combining the thermoplastic resin A and the intermediate raw material D are not particularly limited.

That is, a method in which a molten intermediate material D is melt-extruded into a sheet shape on the surface of the thermoplastic resin A previously formed into a sheet shape, and a method in which the heat is melted on the surface of the intermediate material D formed into a sheet shape. There is a method in which the thermoplastic resin A is melt-extruded into a sheet, a method in which the intermediate raw material D and the thermoplastic resin A are combined in a feed block, a joining pipe, or a slit die while both being in a molten state.

Of these methods, two extruders are used to supply thermoplastic resin A to one and intermediate raw material D to the other,
The simplest and most productive method is to form a sheet by merging both in the molten state with a feed block or merging pipe, guiding it to a slit-shaped die, extruding it onto a rotating cooling drum, and cooling and solidifying it. It is preferred in that respect.

However, at this time, it is preferable that the thermoplastic resin A be guided to the die in a laminar flow state so as not to be kneaded after the merging so that the thermoplastic resin A maintains a continuous phase. For this purpose, a method of appropriately adjusting the melt viscosity and the flow rate of the thermoplastic resin A and the intermediate raw material D is preferably used.

Further, when it is assumed that the thermoplastic resin C also forms a continuous phase similarly to the thermoplastic resin A, if the addition amount of the substance B is as large as 3% or more with respect to the total weight of the stretched film. However, it is preferable in that a stretched film without voids can be obtained. If a continuous phase is formed at the stage of the sheet-like material, a continuous phase is finally formed also in the stretched film, and this continuous phase is destroyed in a subsequent stretching step and heat treatment step. Never.

In the method for producing a stretched film of the present invention, the sheet thus obtained is stretched. The stretching method, magnification, and stretching direction are appropriately selected depending on the physical properties of the stretched film to be obtained.

As an example of the stretching method, a method of stretching in the direction along the sheet longitudinal direction by rotating rolls having different peripheral speeds before and after, and grasping both ends of the sheet with clips and gradually increasing the speed of the clips. A method of stretching in the direction along the sheet longitudinal direction, similarly gripping both ends of the sheet with clips, running the clip on a rail that widens the sheet width, and stretching in a direction perpendicular to the longitudinal direction And a method in which a sheet is formed into a tube shape in advance, and pressure air is introduced into the sheet to expand and stretch like a balloon, and a method in which these are combined.

In this case, when the method of stretching in the direction along the sheet longitudinal direction by rotating rolls having different peripheral speeds before and after is adopted, it is necessary that the front and back surfaces are coated with the thermoplastic resin A. This is preferable in that the sheet or film can be prevented from sticking to a roll heated for stretching, thereby preventing productivity from being deteriorated.

The film stretched as described above is
Subsequently, heat treatment is performed. At this time, the heat treatment needs to be performed at a temperature equal to or higher than the softening temperature of the thermoplastic resin C and equal to or lower than the softening temperature of the thermoplastic resin A. Heat treatment at a temperature adjusted to this range makes it possible to obtain a stretched film substantially free of voids.

The heat treatment is carried out by holding both ends of the film with clips and guiding the film into an oven, a method of contacting the film on a heated roll, and a method of blowing hot air from a number of nozzles formed on the surface. Examples include, but are not limited to, methods. The temperature of this heat treatment is the temperature to which the stretched film was actually exposed, and it is difficult to measure it accurately on the spot. However, when the thermoplastic resin A is a crystalline polymer, The stretched film thus obtained can be analyzed by measuring it with a scanning differential calorimeter (DSC).

The mechanism whereby a stretched film substantially free of voids can be obtained by the production method of the present invention is not clear, but it is thought to be based on the following principle.

That is, at the stage when the above-mentioned sheet is formed, the thermoplastic resin C exists around the substance B which becomes the fine particles. When this sheet is stretched, the thermoplastic resin C
It is considered that the substance B and the substance B are incompatible with each other, so that separation occurs at the interface, and voids are generated.

However, since the subsequent heat treatment is performed at a temperature higher than the softening temperature of the thermoplastic resin C, the thermoplastic resin C is softened. Here, if the voids generated earlier are in a vacuum state, the thermoplastic resin C softens and the elastic modulus is greatly reduced, so that the voids are crushed by the atmospheric pressure and the voids disappear. On the other hand, since the thermoplastic resin A forming the continuous phase does not soften even by this heat treatment, the shape as a film is maintained, and as a result, it is supposed that a stretched film without voids is obtained.

[Evaluation Method of Properties] (1) Total light transmittance and haze Fully automatic direct-reading haze computer HGM-2DP (Suga Test Instruments Co., Ltd.) based on Japanese Industrial Standard JIS K7105 “Testing method for optical properties of plastics” Manufactured).

(2) Capacitor Withstand Voltage Aluminum was vacuum-deposited on one side of a film to be a sample so that the surface resistance was 2 Ω / □. At that time, vapor deposition was carried out in a stripe shape having a margin portion running in the longitudinal direction (repeated of 58 mm in width of the vapor deposition portion and 2 mm in width of the margin portion). Next, a blade was inserted into the center of each vapor deposition section and the center of each margin section, and slit to form a tape-shaped take-up reel having a total width of 30 mm and a left or right margin of 1 mm.

Each of the left and right margins of the reel thus obtained was wound one on top of the other to obtain a capacitor element having a capacitance of 0.1 μF. This capacitor element is heated at 130 ° C., at a temperature and pressure of 20 kg / cm 2 for 5 minutes.
Pressed for minutes. Metallicon is sprayed on both ends to form external electrodes, lead wires are welded to the metallicon, and the exterior is cured with epoxy resin to form a wound capacitor.
The capacitor is subjected to a voltage treatment at 800 V DC for 30 seconds once, and the polarity of the electrodes applied to the two lead wires is reversed to perform another test, thereby obtaining a test capacitor.

A voltage was applied to 1000 test capacitors obtained in this manner while increasing the voltage at a rate of 100 V / sec. Breakdown voltage)
Is measured. The obtained breakdown voltage was converted per unit thickness of the polyester film used as the dielectric, and the withstand voltage of the capacitor was determined as an average value of 1,000 capacitor samples.

When the capacity of the capacitor is large and a current of 5 mA or more flows only by the charging current, the current value is set to an appropriate value capable of separating the charging current and the breakdown current.

(3) Heat treatment temperature (Tmeta) and melting point (Tm) of a stretched film containing a crystalline polymer phase As a differential scanning calorimeter (DSC), a robot DSC “RDC220” manufactured by Seiko Electronics Industry Co., Ltd. was used. As a data analysis device, the company's disk station “SS”
Using C / 5200, 10 mg of a stretched oriented film was filled in an aluminum tray, and the temperature was raised from room temperature at a temperature rising rate of 20 ° C./min to obtain a temperature rising DSC curve. The highest peak temperature in this measurement curve is determined by the melting point (T
m), and a small endothermic peak temperature different from the melting point to a temperature lower than the melting point peak is set to the heat treatment temperature (Tmet).
a). When Tmeta is close to Tm, it may be recognized as a shoulder peak.

(4) Solubility parameter (SP value) This is a value calculated by the atomic group contribution method.
evelen, “Properties of Po
lymers ”, Third completely
Revised Edition, Elsevier
r (1990).
Various proposals have been made for the parameters of each atomic group, and they may be calculated by any method.
sizer-Van Krevelen, Hoy, S
Mall, Fedors et al.

(5) Refractive index of resin Measured according to the method specified in JIS K-7105 using an Abbe refractometer (manufactured by Atago) using sodium D line as a light source. The mounting liquid was measured using methylene iodide in an atmosphere of 25 ° C. and 65% RH. When anisotropy was found in the refractive index because the resin was oriented, the average value of the maximum refractive index and the minimum refractive index was used.

(6) Melt viscosity of resin L / D1 was measured using a Capillograph 1B manufactured by Toyo Seiki Seisaku-sho, Ltd.
The relationship between the shear rate and the melt viscosity was examined using a capillary having a diameter of 0 and a diameter of 1 mm, and the value obtained when the shear rate was zero was extrapolated from a graph of the shear rate and the melt viscosity.

[0065]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not necessarily limited to these.

Example 1 In a main extruder, a copolymerized polyester resin obtained by copolymerizing polyethylene terephthalate (PET) with 17 mol% of an isophthalic acid component as a thermoplastic resin C (crystalline resin, melting point 210 ° C., density 1. 3
5. Glass transition temperature 70 ° C, SP value 21.8 (MPa)
(0.5) 80% by weight, polymethylpentene as substance B (melting point: 235 ° C, density: 0.83, SP value: 15.1 (M
Pa) {0.5) of 20% by weight and polyethylene glycol of 0.5% by weight in a dry state are mixed and supplied. Separately, PET (melting point: 2) is used as a thermoplastic resin A in a sub-extruder.
65 ° C, density 1.35, SP value 21.8 (MPa) ＾
0.5), heated to 280 ° C., melt-extruded from both extruders, merged in a molten state by a feed block as it is, and extruded into the air from a slit-shaped die to remove the surface placed directly below. It is laminated in a three-layer structure of thermoplastic resin A / intermediate raw material D (a substance in which the substance B is dispersed in the thermoplastic resin C) / thermoplastic resin A by cooling and taking off by a rotating cast drum finished to a mirror surface. A sheet-like material was produced.

This sheet is guided to a group of heating rolls,
The film is stretched 3.3 times in the longitudinal direction at 90 ° C., and then passed through a 90 ° C. preheating zone using a tenter (a device in which clips holding both ends of the film run and lead to an oven).
At 3.5 ° C. in the width direction at 230 ° C.
Heat treatment was performed at 30 ° C. for 30 seconds to obtain a stretched film having a total thickness of 70 μm. When the cross section of the obtained stretched film was observed with a scanning electron microscope, the thickness of the PET (thermoplastic resin A) portion was 7 μm for both surface layers. In the intermediate layer, the copolyester resin (thermoplastic resin C) formed a continuous phase, in which polymethylpentene (substance B) was dispersed in a spherical shape having an average particle diameter of 10 μm. Furthermore, the stretched film was free from voids at the interface between the copolymerized polyester resin (thermoplastic resin C) and polymethylpentene (substance B) and had no voids.

The total light transmittance of this stretched film was measured to be 85% (haze was 92%) to confirm that there were no voids. The total light transmittance of the stretched film prepared from PET alone under the same conditions was measured. It exhibited a high light transmittance comparable to that of 89% (haze was 0.2%).

(Example 2) A copolymerized polyester resin obtained by copolymerizing the thermoplastic resin C with polyethylene terephthalate (PET) and 23 mol% of an isophthalic acid component (crystalline resin, melting point 190 ° C, density 1.3
5. Glass transition temperature 70 ° C, SP value 21.8 (MPa)
0.5) and a stretched film was obtained in the same manner as in Example 1 except that the substance B was polypropylene (melting point 170 ° C., density 0.90, SP value 19.0 (MPa) 0.5). .

When the cross section of the obtained stretched film was observed with a scanning electron microscope, the polyolefin was dispersed in the copolymerized polyester resin, and the interface between the copolymerized PET (thermoplastic resin C) and the polyolefin (substance B) was observed. Had no peeling at all and had a void-free stretched film. The total light transmittance of this stretched film is 91%.
(Haze was 92%).

Example 3 A stretched film was obtained in the same manner as in Example 1, except that the substance B was a spherical crosslinked silicone resin having an average particle size of 3 μm. When the cross section of the obtained stretched film was observed with a scanning electron microscope, it was found that the stretched film had no peeling and no void at the interface between the copolymerized polyester resin (resin C) and the crosslinked silicone resin particles. The total light transmittance of the stretched film was 89%.

Comparative Example 1 A method similar to that of Example 1 was repeated except that the PET resin used as the thermoplastic resin A in Example 1 was used instead of the copolymerized polyester resin as the resin C in Example 1. To prepare a stretched film. Observation of the cross section of this stretched film revealed that flat cavities were generated around the polymethylpentene. Further, the total light transmittance of this stretched film was only 8% due to reflection by voids.

Comparative Example 2 A stretched film was prepared in the same manner as in Example 1 except that the heat treatment temperature was changed to 180 ° C. Observation of the cross section of this stretched film revealed that flat cavities were generated around the polymethylpentene. Further, the total light transmittance of this stretched film was only 12% due to reflection by voids.

(Comparative Example 3) In an extruder, polyethylene terephthalate (PET) was mixed with an isophthalic acid component of 17 mol.
1% copolymerized polyester resin (melting point 210
° C, density 1.35, glass transition temperature 70 ° C, SP value 2
1.8 (MPa) ＾ 0.5) 80% by weight, polymethylpentene as substance B (melting point 235 ° C., density 0.83, S
20% by weight (P value 15.1 (MPa) ＾ 0.5) and 0.5% by weight of polyethylene glycol are mixed and supplied in a dry state, and extruded from a circular hole having a diameter of 2 mm and guided into water.
After being formed into a gut shape, it was cut into a length of 6 mm to prepare a chip as an intermediate raw material D. 80% by weight of this chip and PET (melting point: 265 ° C., density: 1.35, SP value: 21.8)
(MPa) ＾ 0.5) 20% by weight was mixed in a dry state and supplied to an extruder, heated to 280 ° C. and extruded into air from a slit-shaped die, and the surface immediately below was mirror-finished. The sheet-like material in which PET and the intermediate raw material D were mixed was prepared by taking up with a finished rotating cast drum and cooling.

This sheet-like material uses exactly the same raw materials as in Example 1, except that PET which forms a continuous phase as the thermoplastic resin A in Example 1 is different from that of Example 1. Are different.

This sheet is guided to a group of heating rolls.
The film is stretched 3.3 times in the longitudinal direction at 90 ° C., and then passed through a 90 ° C. preheating zone using a tenter (a device in which clips holding both ends of the film run and lead to an oven).
At 3.5 ° C. in the width direction at 230 ° C.
When heat treated at 30 ° C. for 30 seconds, the film was broken in the tenter and a stretched film was not obtained. Then, when the heat treatment temperature was lowered to 180 ° C., a stretched film was obtained. However, this stretched film had voids and had a total light transmittance of only 15%.

(Example 4) A thermoplastic resin C was added to an extruder.
Polyethylene terephthalate (PET) is a copolymerized polyester resin obtained by copolymerizing cyclohexane dimethanol with 33 mol% (amorphous resin, heat deformation temperature 70 ° C,
30,000 poise at 235 ° C., density 1.3
5, SP value 21.8 (MPa) ＾ 0.5) 80% by weight,
As a substance B, 2% by weight of spherical silica particles (average particle size: 0.5 μm) are mixed and supplied in a dry state, extruded from a circular hole having a diameter of 2 mm, guided into water, and formed into a gut shape.
A chip as the intermediate raw material D was prepared by cutting into a length of 6 mm. This intermediate material was supplied to the main extruder and separately to the sub-extruder, and PET (melting point 265 ° C., density 1.35, SP value 21.8 (MPa) ＾ 0.5) was supplied as thermoplastic resin A, The extruder was heated to 280 ° C and melted and extruded from both extruders. Then, the extruders were joined together in a molten state using a feed block and a three-stage static mixer, and extruded into the air from a slit-shaped die, and the surface immediately below was mirror-finished. Sheets laminated in a 16-layer structure consisting of a thermoplastic resin A / intermediate raw material D (a substance in which the substance B is dispersed in the thermoplastic resin C) repeated (having the same thickness) by being taken up by a rotating cast drum and cooled. A product was prepared.

This sheet-like material was used at 95 ° C. 3.6 times in the longitudinal direction and at the same time in the width direction by using a tenter capable of expanding the width of the clip in the oven at the same time as the width of the clip. Stretched 8 times, followed by 220 ° C
For 30 seconds to obtain a stretched film having a total thickness of 1.8 μm. Observation of the cross section of the obtained stretched film with a scanning electron microscope reveals that the stretched film has no voids and no voids at the interface between the copolymerized polyester resin (thermoplastic resin C) and the spherical silica particles (substance B). I was A test capacitor was prepared from this stretched film, and the withstand voltage of the capacitor was measured to be 465 V / μm.
And a good value.

(Comparative Example 4) A stretched film was prepared in the same manner as in Example 4, except that the PET used as the resin A in Example 4 was used instead of the copolymerized polyester resin. When observing the cross section of this stretched film, it was observed that cavities were generated around the spherical silica particles. A test capacitor was prepared from this stretched film, and the withstand voltage of the capacitor was measured to be 442 V / μm.
It is considered that the withstand voltage decreased due to the void.

[0080]

As described above, according to the present invention, it is possible to obtain a stretched film free of voids due to stretching, even if the stretched film is added with an incompatible substance.
A stretched film that maintains transparency and an insulating film that does not decrease in withstand voltage can be obtained.

[Brief description of the drawings]

FIG. 1 shows a cross-sectional view of a stretched film obtained according to the present invention.

[Explanation of symbols]

 a: thermoplastic resin A b: substance B c: thermoplastic resin C

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B29K 101: 12 B29K 101: 12 105: 16 105: 16 B29L 7:00 B29L 7:00 F term ( Reference) 4F070 AA12 AA15 AA47 AA71 AB09 AB11 AB23 AC06 AC11 AC84 AC88 AC92 FA04 FA17 FB07 4F071 AA02 AA85 AB00 AD02 AF30 AF39 AH12 BB07 BC01 4F210 AA12 AA24 AB11 AG01 AG03 AR06 QC06 QG01 QG15 QG02B02 BC02B02B02B02B CF06W CF06X CF08W CF08X CL00W CN01W CP03Y DA086 DA096 DE076 DE136 DE146 DE186 DE236 DJ016 DL006 FA08Y FA086 GQ01

Claims (5)

[Claims] 1. A thermoplastic resin comprising at least a thermoplastic resin A, a thermoplastic resin C compatible with the thermoplastic resin A, and a substance B incompatible with the thermoplastic resin C, wherein the thermoplastic resin A has a continuous phase. A method for producing a stretched film to be formed, comprising mixing a thermoplastic resin C and a substance B incompatible with the thermoplastic resin C in advance, and mixing the intermediate material D in which the substance B is dispersed in the resin C. After the production, the intermediate raw material D and the thermoplastic resin A are merged in a state where at least one of them is in a molten state, and the thermoplastic resin A is formed into a sheet so as to form a continuous phase. During stretching and heat treatment, the thermoplastic resin C is assumed to have a softening temperature lower than the softening temperature of the thermoplastic resin A, and the heat treatment is performed at a temperature equal to or higher than the softening temperature of the thermoplastic resin C and the softening temperature of the thermoplastic resin A. Characterized to be performed at a temperature lower than Method for producing a stretched film to be. 2. The method according to claim 1, wherein the substance B is an inorganic fine particle or a fine particle made of a non-thermoplastic resin. 3. The method according to claim 1, wherein the substance B is a thermoplastic resin. 4. The method for producing a stretched film according to claim 1, wherein the thermoplastic resin C forms a continuous phase. 5. The method according to claim 1, wherein the thermoplastic resin A is a crystalline polymer compound.