Thermoplastic resin film

Abstract

A thermoplastic resin film having a haze of not more than 13%, said thermoplastic resin film being characterized by having a loop stiffness value, as measured by a loop stiffness tester, of not less than 140 mN / cm in at least one direction on a surface of the film.

Description

Thermoplastic resin film

[0001] The present invention relates to a thermoplastic resin film that is excellent in transparency and flex resistance and has sufficient flexural rigidity as a supporting substrate.

[0002] Traditionally, glass has been used as a substrate for mounting LED elements in image display devices such as organic electroluminescence (EL) displays and liquid crystal displays (LCDs) that use LED elements as a backlight source. However, in recent years, glass substrates have faced serious problems, such as increased weight due to the larger screen sizes of these devices and breakage due to thinner films. Therefore, there is a demand for plastic substrates that are lighter, more flexible, and easier to mold. Flexible plastic substrates enable flexible displays that can be bent or rolled for storage, and are expected to become even more popular in the future. Furthermore, with the widespread use of LED displays in recent years, there has been an increasing demand for displays that transmit light to the substrate side, such as bottom-emission displays, and therefore transparency is also required for LED mounting substrates.

[0003] Patent Document 1 discloses a thermoplastic resin film having excellent flex resistance that can be suitably used in flexible image display devices.

[0004] Japanese Patent Application Laid-Open No. 2019-099626

[0005] However, the thermoplastic resin film disclosed in Patent Document 1 has excellent bending resistance but sometimes has insufficient bending rigidity, and in an image display device equipped with an LED element, the entire device may not stand upright and may bend, thereby impairing the aesthetic appeal of the image display device. An object of the present invention is to provide a film that has sufficient transparency as an optical film and sufficient bending rigidity as a supporting substrate.

[0006] The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result have found that a thermoplastic resin film produced by controlling conditions such as the stretch ratio and temperature during film production can solve the above-mentioned problems, and have thus completed the present invention.

[0007] The thermoplastic resin film of the present invention having a haze of 13% or less is characterized in that the loop stiffness value in at least one direction of the film surface, as measured by a loop stiffness tester, is 140 mN / cm or more. The thermoplastic resin film of the present invention preferably has a thickness of 40 μm or more. The thermoplastic resin film of the present invention preferably has a glass transition temperature of 60°C or higher of the thermoplastic resin constituting the thermoplastic resin film. The thermoplastic resin film of the present invention preferably has a crystallinity of 0.1 or higher of the surface layer. The thermoplastic resin film of the present invention preferably has a semi-aromatic polyamide. The thermoplastic resin film of the present invention preferably has a breakage occurrence test count of 400,000 or more in a bending test conducted using a clamshell-type bending tester. The thermoplastic resin film of the present invention preferably contains 0.01 to 0.4 mass% of fine particles. The thermoplastic resin film of the present invention preferably has a dynamic friction coefficient of 0.8 or less, as measured in accordance with JIS K7125. The laminate of the present invention comprises the above-described thermoplastic resin film and an easy-adhesion layer laminated on at least one surface thereof. The LED mounting substrate of the present invention uses the above-described laminate. The flexible LED display of the present invention uses the LED mounting substrate. The method for producing a thermoplastic resin film of the present invention includes a step of biaxially stretching an unstretched thermoplastic resin film and then subjecting it to a cooling treatment.

[0008] The thermoplastic resin film of the present invention has sufficient transparency as an optical film and sufficient bending rigidity as a supporting substrate, and therefore can be suitably used as an LED mounting substrate for a flexible LED display, an optical substrate for an organic EL or the like, an electronic substrate material such as a flexible printed wiring board or a flexible flat cable, a coverlay film for a flexible printed wiring, etc.

[0009] The thermoplastic resin film of the present invention is a thermoplastic resin film having a haze of 13% or less and characterized in that the loop stiffness value in at least one direction of the film surface, as measured by a loop stiffness tester, is 140 mN / cm or more.

[0010] <Thermoplastic Resin> The resin constituting the film of the present invention must be a thermoplastic resin. A thermoplastic resin film makes the film easy to mold and also improves durability against bending. The thermoplastic resin constituting the film is preferably a polyamide resin, more preferably a semi-aromatic polyamide resin. Semi-aromatic polyamides are obtained by polycondensation of an aromatic dicarboxylic acid component (e.g., terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid) and an aliphatic diamine component.

[0011] The aromatic dicarboxylic acid component constituting the semi-aromatic polyamide resin preferably contains 60 mol% or more, more preferably 70 mol% or more, and even more preferably 85 mol% or more, of terephthalic acid. If the terephthalic acid content is less than 60 mol%, the heat resistance and low water absorption of the resulting film may be reduced. Examples of aromatic dicarboxylic acid components other than terephthalic acid include isophthalic acid and naphthalenedicarboxylic acid (1,2-isomer, 1,3-isomer, 1,4-isomer, 1,5-isomer, 1,6-isomer, 1,7-isomer, 1,8-isomer, 2,3-isomer, 2,6-isomer, and 2,7-isomer). The semi-aromatic polyamide may contain a dicarboxylic acid component other than the aromatic dicarboxylic acid component as long as the effects of the present invention are not impaired. Examples of other dicarboxylic acids include aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid, and octadecanedioic acid.

[0012] The aliphatic diamine component preferably contains an aliphatic diamine having 6 to 12 carbon atoms as the main component, more preferably an aliphatic diamine having 9 to 12 carbon atoms as the main component, and even more preferably an aliphatic diamine having 9 or 10 carbon atoms as the main component. The content of the aliphatic diamine having 6 to 12 carbon atoms in the aliphatic diamine component is preferably 60 mol% or more, more preferably 75 mol% or more, and even more preferably 90 mol% or more. When the content of the aliphatic diamine having 6 to 12 carbon atoms is 60 mol% or more, the resulting film can achieve both heat resistance and productivity. The aliphatic diamine having 6 to 12 carbon atoms may be used alone or in combination with two or more. When two or more types are used in combination, the content is the total of their contents.

[0013] Examples of aliphatic diamines having 6 to 12 carbon atoms include linear aliphatic diamines such as 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,11-undecanediamine, and 1,12-dodecanediamine, and branched aliphatic diamines such as 2-methyl-1,8-octanediamine, 4-methyl-1,8-octanediamine, 5-methyl-1,9-nonanediamine, 2,2,4- / 2,4,4-trimethyl-1,6-hexanediamine, 2-methyl-1,5-pentanediamine, 2-methyl-1,6-hexanediamine, and 2-methyl-1,7-heptanediamine.

[0014] Examples of the aliphatic diamine other than the aliphatic diamine having 6 to 12 carbon atoms include linear aliphatic diamines such as 1,4-butanediamine and 1,5-pentanediamine.

[0015] The semi-aromatic polyamide may contain a diamine component other than the aliphatic diamine component as long as the effects of the present invention are not impaired. Examples of other diamine components include alicyclic diamines such as isophorone diamine, norbornane dimethylamine, and tricyclodecane dimethylamine, and aromatic diamines such as meta-xylylene diamine, para-xylylene diamine, meta-phenylene diamine, and para-phenylene diamine.

[0016] The semi-aromatic polyamide may be copolymerized with lactams such as ε-caprolactam, ζ-enantholactam, η-capryllactam, and ω-laurolactam, within the range that does not impair the effects of the present invention.

[0017] The types and copolymerization ratios of the monomers constituting the semi-aromatic polyamide are preferably selected so that the melting point (Tm) of the resulting semi-aromatic polyamide is in the range of 270 to 350°C. When the Tm of the semi-aromatic polyamide is in the above range, thermal decomposition during processing into a film can be efficiently suppressed. If the Tm is less than 270°C, the resulting film may have insufficient heat resistance. On the other hand, if the Tm exceeds 350°C, thermal decomposition may occur during film production.

[0018] The semi-aromatic polyamide preferably has an intrinsic viscosity of 0.8 to 2.0 dL / g, more preferably 0.9 to 1.8 dL / g. When the semi-aromatic polyamide has an intrinsic viscosity of 0.8 dL / g or more, a film having excellent mechanical strength can be produced. However, when the intrinsic viscosity exceeds 2.0 dL / g, it may be difficult to produce the film.

[0019] The semi-aromatic polyamide may contain a polymerization catalyst or an end-capping agent. Examples of end-capping agents include acetic acid, lauric acid, benzoic acid, octylamine, cyclohexylamine, and aniline. Examples of polymerization catalysts include phosphoric acid, phosphorous acid, hypophosphorous acid, and salts thereof.

[0020] <Thermoplastic Resin Film> The thermoplastic resin film of the present invention must have a loop stiffness value of 140 mN / cm or more in at least one direction of the film surface, preferably 145 mN / cm or more, and more preferably 150 mN / cm or more. By having a loop stiffness value of 140 mN / cm or more, the thermoplastic resin film has sufficient bending rigidity as a support substrate, and when used as an LED mounting substrate, the image display device has excellent aesthetics.

[0021] Furthermore, the thermoplastic resin film of the present invention must have a haze measured in accordance with JIS K7105 of 13% or less, preferably 10% or less, and more preferably 5% or less. When the haze of the thermoplastic resin film exceeds 13%, the visibility of the thermoplastic resin film is poor. When the thermoplastic resin film has a haze of 13% or less, the visibility is excellent. For example, when the thermoplastic resin film is used as a substrate for a bottom-emission display, light from a light source such as an LED element can be sufficiently extracted through the substrate. Furthermore, even when displays become larger and higher resolution increases the number of pixels, resulting in a decrease in aperture ratio, the thermoplastic resin film can be used as a substrate material while maintaining practical light extraction efficiency. On the other hand, when the display is a top-emission display, the light extraction efficiency can be further improved.

[0022] The thermoplastic resin film of the present invention preferably has a thickness of 40 μm or more, more preferably 45 μm or more, even more preferably 70 μm or more, and particularly preferably 75 μm or more. A thermoplastic resin film having a thickness of 40 μm or more can prevent the entire laminate from warping when an LED element is mounted thereon. Suppressing the warping of the laminate not only ensures flatness as a substrate material, but also makes the light extraction efficiency uniform when used in a display, thereby ensuring uniform brightness on the screen of a large display. Furthermore, the thermoplastic resin film preferably has a thickness of 200 μm or less, more preferably 160 μm or less, and even more preferably 90 μm or less. A thermoplastic resin film having a thickness of 200 μm or less facilitates handling during roll-to-roll processing and, when used in an image display device, can suppress an increase in the overall thickness of the image display device.

[0023] The thermoplastic resin constituting the thermoplastic resin film of the present invention preferably has a glass transition temperature of 60°C or higher, more preferably 100°C or higher. Having a glass transition temperature of 60°C or higher, the thermoplastic resin film can withstand the processing temperatures required for fabricating an LED mounting substrate and can prevent thermal expansion and deformation due to heat generated by the LED light source. Furthermore, when used in a display, this ensures long-term durability and improves reliability in maintaining quality. Furthermore, in connection with the suppression of deflection, this can uniformize light extraction efficiency and ensure uniform brightness on the screen of a large display.

[0024] The surface layer of the thermoplastic resin film of the present invention preferably has a crystallinity of 0.1 or more, more preferably 0.15 or more, and even more preferably 0.2 or more, as determined by infrared spectroscopy. If the crystallinity of the surface layer is less than 0.1, the thermoplastic resin film will have low bending rigidity, and an LED mounting substrate using the film may lack aesthetic appeal. On the other hand, the crystallinity of the surface layer of the thermoplastic resin film is preferably 0.4 or less, more preferably 0.3 or less, and even more preferably 0.25 or less. If the crystallinity of the surface layer exceeds 0.4, the thermoplastic resin film may have high haze and poor visibility. The crystallinity of the present invention was determined by measurement using a diamond prism using infrared spectroscopy ATR. That is, in the obtained infrared spectrum, the crystallinity of the surface layer of the thermoplastic resin film is less than 0.4, and the crystallinity of the surface layer of the thermoplastic resin film may be ... －１ Among the peaks in this range, the peak area present on the low wavelength side was designated P1 (a peak derived from crystallization), and the peak area present on the high wavelength side was designated P2 (a peak derived from an amorphous portion), and the area ratio calculated by P1 / (P1+P2) was defined as the degree of crystallinity.

[0025] The thermoplastic resin film of the present invention preferably has a fracture occurrence test count of 400,000 or more, more preferably 450,000 or more, and even more preferably 500,000 or more, in a bending test carried out using a clamshell-type bending tester. By having a fracture occurrence test count of 400,000 or more, the thermoplastic resin film can withstand long-term use when applied to foldable displays, etc.

[0026] The thermoplastic resin film of the present invention preferably has a dynamic friction coefficient of 0.8 or less, more preferably 0.7 or less, and even more preferably 0.5 or less, measured in accordance with JIS K 7125. When the thermoplastic resin film has a dynamic friction coefficient of 0.8 or less, scratches that occur during processing, such as scratches that occur between a roll and the film during roll transport, can be effectively suppressed.

[0027] The thermoplastic resin film of the present invention has a thermal shrinkage ratio S in the longitudinal direction of the film measured under conditions of 250°C x 5 minutes. ＭＤ and the thermal shrinkage rate S in the width direction ＴＤ are preferably -1.0 to 1.5%, more preferably -0.8 to 1.3%, and even more preferably -0.6 to 1.0%. When the heat shrinkage rate of a thermoplastic resin film is 1.5% or less, the dimensional stability is improved and the film has excellent heat resistance. On the other hand, when the heat shrinkage rate of a thermoplastic resin film exceeds 1.5%, dimensional change becomes large when the film is processed at high temperatures, which may result in processing problems.

[0028] The thermoplastic resin film of the present invention preferably has a longitudinal tensile strength of 110 MPa or more, more preferably 130 MPa or more, and even more preferably 140 MPa or more, as measured in accordance with JIS K7127. The widthwise tensile strength is preferably 200 MPa or more, more preferably 220 MPa or more, and even more preferably 230 MPa or more. When the tensile strength of the thermoplastic resin film is within the above range, it is less likely to break during molding or processing.

[0029] In order to further improve the various properties of the thermoplastic resin film of the present invention, as needed, additives such as lubricants, colorants such as pigments or dyes (e.g., titanium dioxide), color inhibitors, heat stabilizers, hindered phenols, antioxidants such as phosphate esters and phosphites, weather resistance improvers such as benzotriazole-based compounds, bromine-based and phosphorus-based flame retardants, plasticizers, release agents, reinforcing agents such as talc, modifiers, antistatic agents, ultraviolet absorbers, antifogging agents, and various polymer resins may be contained within limits that do not sacrifice the various properties of the film.

[0030] Examples of lubricants that improve the lubricity include inorganic particles such as silica, alumina, titanium dioxide, calcium carbonate, kaolin, and barium sulfate. Examples of organic particles include acrylic resin particles, melamine resin particles, silicone resin particles, and cross-linked polystyrene particles. Among these, silica particles and acrylic resin particles are preferred because of their good dispersibility in the substrate film and ease of handling.

[0031] From the viewpoints of slipperiness and bending rigidity, the thermoplastic resin film of the present invention preferably contains fine particles as a lubricant. The content of the fine particles in the thermoplastic resin film is preferably 0.01 to 0.4 mass%, more preferably 0.05 to 0.3 mass%, and even more preferably 0.1 to 0.3 mass%.

[0032] From the viewpoint of the slipperiness of the film, the fine particles preferably have a large average particle diameter, preferably 0.010 μm or more, more preferably 0.5 μm or more, and even more preferably 1.0 μm or more. On the other hand, from the viewpoint of the transparency and bending rigidity of the film, the average particle diameter is preferably small, preferably 5.0 μm or less, more preferably 4.0 μm or less, and even more preferably 3.0 μm or less. When the average particle diameter of the fine particles is small, the gaps generated between the resin constituting the film become small, so that the thermoplastic resin film has excellent transparency and bending rigidity. In addition, a small particle diameter is preferable because the fine particles are less likely to slide off. The thermoplastic resin film of the present invention may use two or more types of fine particles having different average particle diameters in combination, and by using them in combination, the balance between slipperiness, transparency, and bending rigidity can be adjusted.

[0033] Various methods can be used to incorporate the additives into a thermoplastic resin film. Representative methods include the following: (A) Addition during polymerization of the thermoplastic resin; (B) Masterbatch method in which the additive is directly added to the thermoplastic resin and melt-kneaded to prepare pellets; (C) Addition directly to the thermoplastic resin during film formation and melt-kneading in an extruder; (D) Addition directly to the extruder during film formation and melt-kneading

[0034] <Method for Producing Thermoplastic Resin Film> The thermoplastic resin film of the present invention can be produced by a method of increasing the crystallinity of the film by controlling production conditions such as the stretching ratio during film stretching and the subsequent temperature.

[0035] (Thermoplastic resin) As the thermoplastic resin for producing the thermoplastic resin film, commercially available products can be suitably used. Examples of such commercially available products include semi-aromatic polyamide resins such as "Genesta (registered trademark)" manufactured by Kuraray Co., Ltd., "Zecot (registered trademark)" manufactured by Unitika Ltd., "Reny (registered trademark)" manufactured by Mitsubishi Engineering Plastics Corporation, "Arlen (registered trademark)" manufactured by Mitsui Chemicals, Inc., and "Ultramid (registered trademark)" manufactured by BASF Corporation, and examples of polyamide 6 resins include "Novamid 1022 (registered trademark)" manufactured by Mitsubishi Plastics Inc. and "A1030BRF (registered trademark)" manufactured by Unitika Ltd.

[0036] Semi-aromatic polyamides can also be produced using methods known for producing crystalline polyamides. Examples include solution polymerization or interfacial polymerization (Method A) using an acid chloride and a diamine component as raw materials; a method in which a low-molecular-weight polymer is produced using a dicarboxylic acid component and a diamine component as raw materials and then polymerized by melt polymerization or solid-state polymerization (Method B); a method in which a salt and a low-molecular-weight polymer are produced using a dicarboxylic acid component and a diamine component as raw materials and then solid-state polymerized (Method C); and a method in which a salt is produced using a dicarboxylic acid component and a diamine component as raw materials and then solid-state polymerized (Method D). Among these, Methods C and D are preferred, with Method D being more preferred. Compared to Method B, Methods C and D can produce a salt and a low-molecular-weight polymer mixture at lower temperatures and do not require large amounts of water for the salt and low-molecular-weight polymer mixture or the salt. This reduces the occurrence of gels and reduces fisheyes.

[0037] In Method B, for example, a nylon salt prepared by mixing a diamine component, a dicarboxylic acid component, and a polymerization catalyst all at once is thermally polymerized at a temperature of 200 to 250°C to obtain a low polymer. The intrinsic viscosity of the low polymer is preferably 0.1 to 0.6 dL / g. Setting the intrinsic viscosity of the low polymer within this range has the advantage of preventing disruption of the molar balance between the carboxyl groups in the dicarboxylic acid component and the amino groups in the diamine component during subsequent solid-state polymerization or melt polymerization, thereby increasing the polymerization rate. If the intrinsic viscosity of the low polymer is less than 0.1 dL / g, the polymerization time may be prolonged, resulting in poor productivity. On the other hand, if it exceeds 0.6 dL / g, the resulting semi-aromatic polyamide may become discolored. The solid-state polymerization of the low polymer is preferably carried out under reduced pressure or in an inert gas flow. Furthermore, the temperature of the solid-state polymerization is preferably 200 to 280°C. Setting the solid-state polymerization temperature within this range can suppress discoloration and gelation of the resulting semi-aromatic polyamide. If the solid-state polymerization temperature is less than 200°C, the polymerization time will be long, which may result in poor productivity. On the other hand, if it exceeds 280°C, discoloration or gelation may occur in the resulting semi-aromatic polyamide. The melt polymerization of the oligomer is preferably carried out at a temperature of 350°C or less. If the polymerization temperature exceeds 350°C, decomposition or thermal degradation of the semi-aromatic polyamide may be accelerated. Therefore, films obtained from such semi-aromatic polyamides may have poor strength and appearance. The above-mentioned melt polymerization also includes melt polymerization using a melt extruder.

[0038] In Method C, for example, a suspension of molten aliphatic diamine and solid aromatic dicarboxylic acid is stirred and mixed to obtain a mixture. Then, in this mixture, a salt-forming reaction between the aromatic dicarboxylic acid and the aliphatic diamine and a oligomer-forming reaction between the resulting salt and the resulting oligomer are carried out at a temperature below the melting point of the semi-aromatic polyamide to be ultimately produced. Crushing may be carried out during the reaction, or the reaction mixture may be removed and crushed after the reaction. The resulting reaction product is then solid-phase polymerized at a temperature below the melting point of the semi-aromatic polyamide to obtain a predetermined molecular weight, thereby obtaining a semi-aromatic polyamide. Solid-phase polymerization is preferably carried out in a stream of inert gas such as nitrogen at a polymerization temperature of 180 to 270°C for a reaction time of 0.5 to 10 hours.

[0039] In Method D, for example, aromatic dicarboxylic acid powder is preheated to a temperature above the melting point of the aliphatic diamine but below the melting point of the aromatic dicarboxylic acid. The aliphatic diamine is then added to the aromatic dicarboxylic acid powder at this temperature, essentially without adding water, so as to maintain the aromatic dicarboxylic acid powder in a powder state. The resulting salt is then solid-state polymerized at a temperature below the melting point of the semi-aromatic polyamide to be ultimately produced, thereby increasing the molecular weight to a predetermined level, thereby obtaining a semi-aromatic polyamide. Solid-state polymerization is preferably carried out in a stream of inert gas such as nitrogen, at a polymerization temperature of 180 to 270°C for a reaction time of 0.5 to 10 hours.

[0040] The raw material for the semi-aromatic polyamide film may be a mixture of the above virgin raw materials, or may be a mixture of scraps generated during the production of semi-aromatic polyamide film, such as off-spec film or edge trimmings, or a mixture of such scraps with virgin raw materials. These may be mixed by known methods, such as dry blending using a known device or melt-kneading using a single-screw or twin-screw extruder.

[0041] (Extrusion) In the method for producing a thermoplastic resin film of the present invention, the unstretched film of the thermoplastic resin used in the biaxial stretching step can be produced by melt-mixing the thermoplastic resin in an extruder at a temperature of 280 to 340°C for 3 to 15 minutes, extruding the thermoplastic resin into a sheet through a T-die, and cooling the sheet by bringing it into close contact with a cooling roll whose temperature is adjusted to 30 to 40°C.

[0042] (Stretching) In the method for producing the thermoplastic resin film of the present invention, an unstretched film is biaxially stretched, and the thermoplastic resin is oriented and crystallized by stretching. The stretching method is not particularly limited, but flat-type sequential biaxial stretching, flat-type simultaneous biaxial stretching, tubular stretching, etc. can be used. Among them, flat-type sequential biaxial stretching and flat-type simultaneous biaxial stretching are optimal because they can produce films with good thickness accuracy. Examples of stretching devices for employing flat-type simultaneous biaxial stretching include screw-type tenters, pantograph-type tenters, and linear motor-driven clip-type tenters.

[0043] The stretching ratio is preferably 2.0 to 3.5 times in the longitudinal direction and 2.0 to 4.0 times in the width direction, and more preferably 2.0 to 3.0 times in the longitudinal direction and 2.0 to 3.5 times in the width direction. If the stretching ratio in the longitudinal direction exceeds 3.5 times, the resulting stretched film may undergo excessive crystallization, resulting in reduced stretchability in the width direction. Even if stretching in the width direction is successful, the resulting stretched film may be prone to stretching irregularities, resulting in reduced thickness accuracy, reduced longitudinal tensile strength, and reduced transparency. On the other hand, if the stretching ratio in the width direction exceeds 4.0 times, transparency may be reduced, the heat shrinkage rate may increase, dimensional stability may be reduced, and tensile strength may be further reduced. If the stretching ratios in the longitudinal and width directions are less than 2.0 times, the resulting stretched film may have reduced loop stiffness and tensile strength, and may be prone to stretching irregularities, resulting in thickness irregularities and reduced flatness.

[0044] The stretching speed is preferably such that the stretching strain rate in both the longitudinal and transverse directions exceeds 400% / min, more preferably 800 to 12,000% / min, and even more preferably 1,200 to 6,000% / min. If the strain rate is 400% / min or less, crystals may grow during stretching, causing the film to break. Conversely, if the strain rate is too fast, the unstretched film may be unable to keep up with the deformation and break. The stretching temperature is preferably equal to or higher than the glass transition temperature (Tg) of the thermoplastic resin, and more preferably above Tg but not higher than (Tg + 50°C). If the stretching temperature is lower than Tg, the film is prone to breakage and stable production is not possible. Conversely, if the stretching temperature exceeds (Tg + 50°C), stretching unevenness may occur in the film.

[0045] (Heat Setting) After the above-described stretching, the thermoplastic resin film is preferably heat-set while the film is still held by the clips used during stretching. By performing heat setting, the resulting film can have a reduced heat shrinkage without the occurrence of heat damage spots. The heat setting temperature is preferably 260 to 280°C, more preferably 263 to 278°C, and even more preferably 265 to 275°C. If the heat setting temperature is less than 260°C, the resulting film will have a high heat shrinkage. If the heat setting temperature exceeds 280°C, the resulting film will have a reduced tensile strength and be prone to poor appearance due to heat damage wrinkles, and in some cases will break during heat setting, making it difficult to obtain a biaxially stretched film.

[0046] Examples of the heat setting method include known methods such as a method of blowing hot air, a method of irradiating infrared rays, a method of irradiating microwaves, etc. Among these, a method of blowing hot air is preferred because it allows for uniform and precise heating.

[0047] (Relaxation) After heat setting, the film may be subjected to a relaxation treatment at the same temperature as the heat setting temperature while still being held by the clips. By performing the relaxation treatment, the thermal shrinkage rate can be reduced, and a film with improved dimensional stability can be obtained. The relaxation rate is preferably 10.0% or less in the longitudinal direction, and preferably 1.0 to 12.0% in the transverse direction. If the relaxation rate in the longitudinal direction exceeds 10.0%, sagging may occur in the film.

[0048] (Cooling) One suitable method for producing the thermoplastic resin film of the present invention is to cool the film after heat setting, or after heat relaxation if heat relaxation has been performed, while the film is held by clips at a temperature lower than the temperature used in the heat setting or heat relaxation treatment. The cooling treatment prevents a sudden drop in temperature (rapid cooling) from the high temperature used in the heat setting or heat relaxation treatment to room temperature, thereby increasing the crystallinity and bending rigidity of the resulting thermoplastic resin film. That is, the method for producing a thermoplastic resin film of the present invention must include a step of biaxially stretching an unstretched thermoplastic resin film and then cooling it. The cooling temperature is preferably 110°C or higher, more preferably 120°C or higher. On the other hand, the cooling temperature is preferably 150°C or lower, more preferably 140°C or lower. If the cooling temperature exceeds 150°C, the temperature difference between the cooling temperature and room temperature becomes too large, resulting in rapid cooling to room temperature in the subsequent step. As a result, the crystallinity of the resulting thermoplastic resin film cannot be sufficiently increased. That is, the thermoplastic resin film of the present invention can be easily made to have a preferable crystallinity by maintaining the thermoplastic resin film at the predetermined cooling treatment temperature for a certain period of time, preferably 0.5 to 25 seconds, more preferably 1 to 20 seconds, and even more preferably 2 to 15 seconds.

[0049] In the apparatus for producing the thermoplastic resin film of the present invention, the surfaces of the cylinder, the melting section of the barrel, the metering section, the single pipe, the filter, the T-die, etc. are preferably treated to reduce the surface roughness in order to prevent the resin from stagnation. Examples of methods for reducing the surface roughness include a method of modifying the surface with a low-polarity substance. Alternatively, a method of vapor-depositing silicon nitride or diamond-like carbon on the surface can be used.

[0050] The obtained thermoplastic resin film may be cut into sheets or may be wound around a winding roll to form a film roll. From the viewpoint of productivity when used for various applications, the film roll is preferred. When the film roll is formed, it may be slit to a desired width.

[0051] <Laminate> The thermoplastic resin film may be a single-layer film consisting of one type of layer, or may have a multilayer structure consisting of two or more layers laminated together. In the case of a multilayer structure, for example, a two-layer film may contain a lubricant in any one of the two layers, and a three-layer film may contain a lubricant in each of the layers located on both surfaces of the three layers. The type and content of the lubricant to be contained can be designed independently. By using such a multilayer structure, the surface roughness of each surface of the thermoplastic resin film can be controlled independently.

[0052] At least one surface of the thermoplastic resin film may be laminated with an easy-adhesion layer or may be subjected to corona treatment, plasma treatment, acid treatment, flame treatment, or the like in order to improve adhesion to other materials.

[0053] The resin constituting the easy-adhesion layer is not particularly limited, and various resins can be used. Examples of the resin include polyamide-based resins, polyurethane-based resins, polyester-based resins, acrylic resins, and epoxy-based resins. Among them, polyamide-based resins, polyester-based resins, polyurethane-based resins, and acrylic resins are preferred because they have excellent adhesion to various functional layers, and polyamide-based resins, polyurethane-based resins, and acrylic resins are more preferred from the viewpoint of heat resistance.

[0054] (Polyamide-Based Resin) The polyamide-based resin constituting the easy-adhesion layer is not particularly limited, and examples thereof include aliphatic polyamides, alicyclic polyamides, and aromatic polyamides. Aromatic polyamides include semi-aromatic polyamides and wholly aromatic polyamides (aramids). From the viewpoint of improving adhesion to the semi-aromatic polyamide used as the substrate, the same type of semi-aromatic polyamide can also be used for the easy-adhesion layer. Among these polyamide-based resins, dimer acid polyamides are preferred from the viewpoint of achieving an excellent balance between heat resistance and adhesion. Furthermore, an aqueous dispersion of a polyamide resin can be used to form the easy-adhesion layer. Examples of commercially available aqueous dispersions of polyamide resins include Sepolsion PA-150 and PA-200 (manufactured by Sumitomo Seika Chemicals Co., Ltd.).

[0055] (Polyurethane Resin) The polyurethane resin constituting the easy-adhesion layer is not particularly limited, and examples thereof include various urethane resins such as polyester-based urethane resins, polyether-based urethane resins, and polycarbonate-based urethane resins. From the viewpoint of improving the adhesion between the substrate film and the functional layer and improving dispersibility in water, the polyurethane resin may be copolymerized with a compound having a sulfo group or a compound having a carboxyl group. To form the easy-adhesion layer, an aqueous dispersion of a polyurethane resin can be used. Examples of commercially available aqueous dispersions of polyurethane resins include the Hydran series (manufactured by DIC Corporation), the Superflex series (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), the Takelac series (manufactured by Mitsui Chemicals, Inc.), the Adeka Bontitor series (manufactured by Adeka Corporation), and U-Coat (manufactured by Sanyo Chemical Industries, Ltd.).

[0056] (Polyester-based resin) The polyester-based resin constituting the easy-adhesion layer is not particularly limited, and examples thereof include those composed of a polybasic acid component and a polyhydric alcohol component and produced by a known polymerization method. The polybasic acid component and the polyhydric alcohol component may be used alone or in combination of two or more types. Furthermore, an aqueous dispersion of a polyester resin can be used to form the easy-adhesion layer. Examples of commercially available aqueous dispersions of polyester resins include Elitel KA-5034, KZA-0134, and KZA-3556 (all manufactured by Unitika Ltd.), and Pluscoat Z-730 and RZ-142 (all manufactured by GOO Chemical Industry Co., Ltd.).

[0057] (Acrylic Resin) The acrylic resin constituting the easy-adhesion layer is not particularly limited, and may be a copolymer of ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, or the like as a main component with a vinyl compound such as styrene, methyl methacrylate, or acrylonitrile, and functional group monomers such as acrylic acid, methacrylic acid, itaconic acid, acrylamide, methylol acrylamide, hydroxyethyl acrylate, or hydroxyethyl methacrylate. To form the easy-adhesion layer, an aqueous dispersion of an acrylic resin can be used. Commercially available aqueous acrylic resin dispersions include the Nikasol series (manufactured by Nippon Carbide Corporation), the Nanocryl series, and the Liocryl series (all manufactured by Toyochem Co., Ltd.), the Ultrasol series (manufactured by Aica Kogyo Co., Ltd.), and the Boncoat series (manufactured by DIC Corporation).

[0058] The thermoplastic resin film of the present invention may be laminated with inorganic materials such as metals or oxides thereof, other polymers, paper, woven fabric, nonwoven fabric, wood, or the like.

[0059] <Applications> A laminate obtained by laminating the above-mentioned easy-adhesion layer on at least one surface of the thermoplastic resin film of the present invention can be used for an LED-mounted substrate, and the LED-mounted substrate can be used for a flexible LED display. Furthermore, the thermoplastic resin film of the present invention has heat resistance and excellent dimensional stability, and therefore can be used for various electronic materials, optical components, and other applications. Specifically, the thermoplastic resin film of the present invention can be used as a packaging material for pharmaceuticals; a packaging material for food such as retort pouch foods; a packaging material for electronic components such as semiconductor packages; an electrical insulating material for motors, transformers, cables, etc.; a dielectric material for capacitors; a magnetic tape material such as cassette tapes, magnetic tapes for digital data storage, and video tapes; a protective plate for solar cell substrates, liquid crystal panels, conductive films, and display devices; an electronic substrate material such as a substrate for flexible printed wiring and a flexible flat cable; a heat-resistant tape such as a coverlay film for flexible printed wiring, a heat-resistant masking tape, and an industrial process tape; a heat-resistant barcode label; a heat-resistant reflector; an insulating tape; various release films; a heat-resistant base film; a photographic film; a molding material; an agricultural material; a medical material; a civil engineering and construction material; a filter membrane; and other films for household and industrial materials. Furthermore, because the thermoplastic resin film of the present invention has the above-mentioned properties, i.e., excellent heat resistance, dimensional stability, and transparency, it can be used as a display material for mobile devices, a display device, etc. Specifically, it can be used as an optical substrate in various displays such as liquid crystal and organic EL displays, a base film in various functional materials such as polarizing plates and retardation plates, a protective film in light-emitting elements and display devices, and a sealing film.

[0060] The present invention will be specifically described below with reference to examples. 1. Evaluation method

[0061] (1) Intrinsic Viscosity of Thermoplastic Resin In concentrated sulfuric acid at 30°C, the intrinsic viscosity (ηinh) of the resin at concentrations of 0.05, 0.1, 0.2, and 0.4 g / dL was calculated using the following formula, and the value extrapolated to a concentration of 0 was taken as the intrinsic viscosity [η]: ηinh = [ln(t1 / t0)] / c (where ηinh is the intrinsic viscosity (dL / g), t0 is the flow time of the solvent (seconds), t1 is the flow time of the resin solution (seconds), and c is the concentration of the resin in the solution (g / dL).)

[0062] (2) Melting point and glass transition temperature of thermoplastic resin Using a differential scanning calorimeter (PerkinElmer DSC-7), the thermoplastic resin was heated from 20 ° C. to 350 ° C. at 10 ° C. / min under a nitrogen atmosphere and held for 5 minutes (1st scan), then cooled from 350 ° C. to 20 ° C. at 100 ° C. / min and held for 5 minutes. The glass transition temperature in the process of further heating from 20 ° C. to 350 ° C. at 10 ° C. / min (2nd scan) was taken as Tg of the thermoplastic resin. Similarly, the peak top temperature of the crystalline melting peak observed in the 2nd scan was taken as Tm.

[0063] (3) Crystallinity of Thermoplastic Resin Film The front and back surfaces of the thermoplastic resin film obtained by stretching were subjected to FT-IR ATR measurement using an infrared spectrophotometer (FT / IR-6100 infrared spectrophotometer manufactured by JASCO Corporation). The ATR prism was diamond, the incident angle was 45°, and the resolution was 4 cm. －１ The measurement was carried out under the condition of 128 cumulative cycles. The crystallinity was 1100 to 1250 cm －１ Among the peaks in this range, the peak area present on the low wavelength side was designated P1 (a peak derived from crystallization), and the peak area present on the high wavelength side was designated P2 (a peak derived from an amorphous portion), and the area ratio calculated by P1 / (P1+P2) was defined as the degree of crystallinity.

[0064] (4) Haze of Thermoplastic Resin Film The haze of the thermoplastic resin film was measured according to JIS K7105 using a haze meter (NDH 2000) manufactured by Nippon Denshoku Industries Co., Ltd.

[0065] (5) Dynamic Friction Coefficient of Thermoplastic Resin Film The dynamic friction coefficient of the thermoplastic resin film was measured in accordance with JIS K7125.

[0066] (6) Heat Shrinkage of Thermoplastic Resin Film Strip-shaped test pieces (10 mm wide x 100 mm long) were cut out from the thermoplastic resin film in the longitudinal and transverse directions. The test pieces were each treated in an atmosphere of 250°C for 5 minutes, and then left at a temperature of 23°C and a humidity of 50% RH for 2 hours, after which the dimension in the longitudinal direction was measured. The heat shrinkage of the test piece in the longitudinal direction, S, was calculated by the following formula: ＭＤ and the thermal shrinkage rate S of the test piece in the width direction ＴＤ Heat shrinkage rate (%) = [{original length - length after treatment} / original length] x 100

[0067] (7) Tensile Strength of Thermoplastic Resin Film The tensile strength of the thermoplastic resin film in the longitudinal direction and width direction was measured in accordance with JIS K7127.

[0068] (8) Loop Stiffness Value of Thermoplastic Resin Film After conditioning a thermoplastic resin film for 1 day in an environment of a temperature of 23°C and a humidity of 50% RH, a test piece (10 mm wide x 200 mm long) was cut out in an arbitrary direction, and the loop stiffness value was measured using a Loop Stiffness Tester DA manufactured by Toyo Seiki Co., Ltd. The measurement was performed under conditions of a loop length of 60 mm, a crushing amount of 15 mm, and a compression speed of 3.3 mm / s, and the average value of n = 5 was taken as the loop stiffness value.

[0069] (9) Evaluation of Stiffness of Thermoplastic Resin Film A thermoplastic resin film was cut into a width of 20 mm and a length of 120 mm, and copper foil was laminated on the surface of the cut-out test piece by sputtering to obtain a metal laminate. An etching mask patterned in the shape of a wiring pattern was formed on the metal foil surface of the obtained metal laminate. Thereafter, the metal foil not covered by the etching mask was removed using an immersion solution, and then the etching mask was removed using an alkaline stripping solution. Finally, an LED element was soldered onto the metal foil with the obtained wiring pattern to produce a simple LED mounting module. The sample was fixed on a horizontal surface plate so that its tip protruded 100 mm, and the amount of deflection of the tip from the surface of the surface plate was measured, and stiffness was evaluated according to the following criteria. Practically, A to C are preferable, with A and B being more preferable, and A being even more preferable. A: 25 mm or less B: More than 25 mm and 30 mm or less C: More than 30 mm and 35 mm or less D: More than 35 mm

[0070] (10) Flexibility Test pieces cut into 30 mm x 200 mm were thoroughly conditioned at a temperature of 20°C and a humidity of 65% RH and then mounted in a clamshell-type flex tester (Yuasa System Co., Ltd., Model DR11MR-CS-m). Under the above-mentioned atmosphere, flex tests were performed with n = 5 each under the following conditions: a bend radius of 1.0 mm, a bend angle of 0° to 180°, and a test speed of 60 r / min. Test pieces were removed every 50,000 cycles (300,000 cycles, 350,000 cycles, 400,000 cycles, etc.) and visually inspected for fracture. If fracture was detected, the number of tests at that time was recorded and the test was terminated. If fracture was not detected, the flex test was continued. All tests were completed at 500,000 cycles. Unbroken test pieces were visually evaluated for whitening and bending marks according to the following criteria, with the lowest evaluation result recorded. <Whitening> ○: No whitening at the bent portion. △: Decreased transparency at the bent portion. ×: The bent portion turned white. <Bending marks> ○: No bending marks remained. △: Bending wrinkles occurred. ×: Bending marks remained.

[0071] 2. Raw Materials (1) Thermoplastic Resins Thermoplastic Resin A: Thermoplastic resin A produced by the following method was used. 3,289 parts by mass of terephthalic acid (TA), 2,533 parts by mass of 1,9-nonanediamine (NDA), 633 parts by mass of 2-methyl-1,8-octanediamine (MODA), 48.9 parts by mass of benzoic acid (BA), 6.5 parts by mass of sodium hypophosphite monohydrate (0.1% by mass relative to the total of the four polyamide raw materials), and 2,200 parts by mass of distilled water were placed in a reactor and purged with nitrogen. The molar ratio of these raw materials (TA / BA / NDA / MODA) was 99 / 2 / 80 / 20. The contents of the reactor were stirred at 100°C for 30 minutes, and then the internal temperature was raised to 210°C over 2 hours. At this time, the inside of the reactor was pressurized to 2.12 MPa (22 kg / cm). ２ The reaction was continued for 1 hour, and then the temperature was raised to 230°C. The temperature was then maintained at 230°C for 2 hours, and the steam was gradually released to reduce the pressure to 2.12 MPa (22 kg / cm). ２ The reaction was carried out while maintaining the pressure at 0.98 MPa (10 kg / cm) over 30 minutes. ２ ) and reacted for another hour to obtain a prepolymer. This was dried at 100°C under reduced pressure for 12 hours and then pulverized to a size of 2 mm or less. The pulverized prepolymer was then solid-state polymerized for 10 hours at a temperature of 230°C and a pressure of 13.3 Pa (0.1 mmHg) to obtain a polymer. This was fed into a twin-screw extruder (TEX44C manufactured by The Japan Steel Works, Ltd.), melt-kneaded and extruded at a cylinder temperature of 320°C, cooled, and cut to produce pellets of thermoplastic resin A. Thermoplastic resin A had a melting point of 290°C, a glass transition temperature of 125°C, and an intrinsic viscosity of 1.17 dL / g.

[0072] Thermoplastic resin B: A resin produced by the following method was used. 489 parts by mass of terephthalic acid (TA), 507 parts by mass of 1,10-decanediamine (DDA), 2.8 parts by mass of benzoic acid (BA), 1.0 part by mass of sodium hypophosphite monohydrate (0.1% by mass relative to the total of the three polyamide raw materials), and 1,000 parts by mass of distilled water were placed in a reactor and purged with nitrogen. The molar ratio of these raw materials (TA / BA / DDA) was 99 / 2 / 100. The contents of the reactor were stirred at 80°C for 0.5 hours at 28 revolutions per minute, then heated to 230°C. The mixture was then heated at 230°C for 3 hours. The mixture was then cooled, and the reaction product was removed. The reaction product was pulverized and then heated in a dryer under a nitrogen stream at 220°C for 5 hours to undergo solid-state polymerization, yielding a polymer. This was fed into a twin-screw extruder (TEX44C manufactured by The Japan Steel Works, Ltd.), melt-kneaded and extruded under conditions of a cylinder temperature of 320°C, cooled, and cut to produce pellets of thermoplastic resin B. Thermoplastic resin B had a melting point of 316°C, a glass transition temperature of 150°C, and an intrinsic viscosity of 1.24 dL / g.

[0073] Thermoplastic resin C: Polyamide 6 resin (manufactured by Unitika Ltd., A1030BRF, monomer content 1.0% or less, melting point 223°C, glass transition temperature 52°C, intrinsic viscosity 3.10 dL / g) Thermoplastic resin D: Polyethylene terephthalate resin (manufactured by Nippon Ester Co., Ltd., UT-CBR, melting point 255°C, glass transition temperature 78°C, intrinsic viscosity 0.67 dL / g)

[0074] (2) Microparticles Master chips (M1) to (M13) containing 2% by mass of silica, prepared by the following method, were used. Master chip (M1): 98 parts by mass of thermoplastic resin A and 2 parts by mass of silica As (NIPGEL AZ-204, average particle size 1.7 μm, manufactured by Tosoh Silica Corporation), were melt-kneaded. Master chip (M2): 98 parts by mass of thermoplastic resin A and 2 parts by mass of silica Bs (NIPGEL AZ-200, average particle size 2.0 μm, manufactured by Tosoh Silica Corporation), were melt-kneaded. Master chip (M3): 98 parts by mass of thermoplastic resin A and 2 parts by mass of silica Cs (Fuji Silysia Chemical Ltd., average particle size 2.3 μm), were melt-kneaded. Master chip (M4): 98 parts by mass of thermoplastic resin A and 1 part by mass of silica As and 1 part by mass of silica Bs were melt-kneaded. Master Chip (M5) 98 parts by mass of thermoplastic resin A and 2 parts by mass of acrylic Da (ENEOS Liquid Crystal Corporation, NMB-0220C, average particle size 2.0 μm) were melt-kneaded. Master Chip (M6) 98 parts by mass of thermoplastic resin A and 2 parts by mass of acrylic Ea (ENEOS Liquid Crystal Corporation, NMB-0320C, average particle size 3.0 μm) were melt-kneaded. Master Chip (M7) 98 parts by mass of thermoplastic resin A and 1 part by mass of acrylic Da and 1 part by mass of acrylic Ea were melt-kneaded. Master Chip (M8) 98 parts by mass of thermoplastic resin A and 2 parts by mass of acrylic Fa (ENEOS Liquid Crystal Corporation, NMB-0520C, average particle size 5.0 μm) were melt-kneaded. Master chip (M9): 98 parts by mass of thermoplastic resin A, 1 part by mass of acrylic Da, and 1 part by mass of acrylic Fa were melt-kneaded. Master chip (M10): 98 parts by mass of thermoplastic resin B and 2 parts by mass of acrylic Da were melt-kneaded. Master chip (M11): 98 parts by mass of thermoplastic resin C and 2 parts by mass of acrylic As were melt-kneaded. Master chip (M12): 98 parts by mass of thermoplastic resin D and 2 parts by mass of acrylic As were melt-kneaded. Master chip (M13): 98 parts by mass of thermoplastic resin D, 1 part by mass of acrylic Ea, and 1 part by mass of acrylic Fa were melt-kneaded.

[0075] (3) Hindered phenol-based heat stabilizer GA: 3,9-bis[2-{3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy}-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane (Sumitomo Chemical Co., Ltd., Sumilizer GA-80, thermal decomposition temperature 392°C)

[0076] Example 1 Thermoplastic resin A, GA, and master chip (M1) were mixed so that GA was 0.2 parts by mass and silica As was 0.1 parts by mass per 100 parts by mass of thermoplastic resin A. This mixture was melted and fed into a 65 mm single-screw extruder with a cylinder temperature set to 320 ° C., extruded into a sheet from a T-die set to 320 ° C., and cooled by electrostatic contact on a cooling roll set to a surface temperature of 40 ° C. to obtain a substantially unoriented unstretched film with a thickness of 650 μm. Next, while holding both ends of this unstretched film with clips, it was introduced into a tenter-type sequential biaxial stretching machine and subjected to sequential biaxial stretching. The stretching conditions were: preheating section temperature 155 ° C., stretching section temperature 150 ° C., longitudinal and width direction stretching strain rate 3200% / min, longitudinal and width direction stretch ratio 3.0 times and 3.3 times, respectively. After stretching, the film was heat-set at 280°C for 5 seconds, relaxed in the width direction only at a relaxation rate of 3.0%, and cooled at 130°C for 3 seconds to obtain a thermoplastic resin film with a thickness of 75 µm. The film properties of the obtained thermoplastic resin film are shown in Table 1.

[0077] Examples 2 to 28, Comparative Examples 1 to 7 Thermoplastic resin films were obtained in the same manner as in Example 1, except that the type of thermoplastic resin, the type and content of the fine particles, the thickness of the unstretched film, the stretching ratio, and the cooling treatment temperature were changed as shown in Tables 1 and 2. In Comparative Example 1, no cooling treatment was performed.

[0078] Example 29 Thermoplastic resin C and master chip (M11) were mixed so that silica As was 0.1 parts by mass per 100 parts by mass of thermoplastic resin C. This mixture was melted and fed into a 65 mm single-screw extruder with a cylinder temperature set to 240 ° C., and then fed into a T-die set to 240 ° C. and extruded into a sheet. The film was then wound around a metal drum adjusted to a temperature of 20 ° C., cooled, and wound up to produce a substantially unoriented unstretched film with a thickness of 780 μm. Next, while holding both ends of this unstretched film with clips, it was introduced into a tenter-type sequential biaxial stretching machine and subjected to sequential biaxial stretching. The stretching conditions were: preheating section temperature 65 ° C., stretching section temperature 96 ° C., longitudinal and widthwise stretching strain rates 3200% / min, longitudinal and widthwise stretch ratios 2.8 times and 3.7 times, respectively. After stretching, the film was heat-set at 202°C for 5 seconds, relaxed at a relaxation rate of 3.0% in the width direction, and cooled at 130°C for 3 seconds to obtain a thermoplastic resin film with a thickness of 75 μm.

[0079] Example 30 Thermoplastic resin C and master chips (M12) were mixed so that silica As was 0.1 parts by mass per 100 parts by mass of thermoplastic resin D. This mixture was melted and fed into a 65 mm single-screw extruder with a cylinder temperature set to 280 ° C., and then fed into a T-die set to 280 ° C. to extrude into a sheet. The film was then wound around a metal drum adjusted to a temperature of 20 ° C., cooled, and wound up to produce a substantially unoriented unstretched film with a thickness of 780 μm. Next, while holding both ends of this unstretched film with clips, it was introduced into a tenter-type sequential biaxial stretching machine and subjected to sequential biaxial stretching. The stretching conditions were: preheating section temperature 75 ° C., stretching section temperature 85 ° C., longitudinal and widthwise stretching strain rates 3200% / min, and longitudinal and widthwise stretch ratios 2.8 times and 3.7 times, respectively. After stretching, the film was heat-set at 243°C for 5 seconds, relaxed at a relaxation rate of 3.0% in the width direction, and cooled at 130°C for 3 seconds to obtain a thermoplastic resin film with a thickness of 75 µm.

[0080] Example 31 A thermoplastic resin film was obtained in the same manner as in Example 30, except that the type and content of the fine particles and the thickness of the unstretched film were changed as shown in Table 2.

[0081] Example 32 A thermoplastic resin film was obtained in the same manner as in Example 1, except that the relaxation treatment was carried out at a relaxation rate of 3.0% in the width direction and 1.0% in the longitudinal direction.

[0082] Tables 1 and 2 show the structure of the thermoplastic resin film, the production conditions of the film, and the properties of the obtained thermoplastic resin film.

[0083]

[0084]

[0085] The thermoplastic resin films of Examples 1 to 32 satisfied all of the characteristic values ​​specified in the present invention, exhibiting low haze and excellent transparency, high loop stiffness values, sufficient stiffness, and excellent flex resistance. The thermoplastic resin films of Comparative Examples 1 to 5 had low loop stiffness values, and the thermoplastic resin films of Comparative Examples 6 and 7 had poor haze. Note that Comparative Example 1 was a thermoplastic resin film obtained under the same film-forming and stretching conditions as those in Patent Document 1 (Example 12), listed as a prior art document, but because no cooling treatment was performed after stretching and heat setting, the crystallinity was 0.06 and the loop stiffness value was less than 140 mN / cm.

Claims

1. The haze is 13% or less, A semi-aromatic polyamide film having a loop stiffness value of 140 mN / cm or more in at least one direction of the film plane, as measured by a loop stiffness tester.

2. 2. The semi-aromatic polyamide film according to claim 1, wherein the thickness is 40 μm or more.

3. A semi-aromatic polyamide film as described in claim 1 or 2, characterized in that the glass transition temperature of the semi-aromatic polyamide constituting the semi-aromatic polyamide film is 60°C or higher.

4. 4. The semi-aromatic polyamide film according to claim 1, wherein the crystallinity of the surface layer is 0.1 or more.

5. The semi-aromatic polyamide film according to any one of claims 1 to 4, characterized in that the number of times at which the film breaks in a bending test conducted using a clamshell-type bending tester is 400,000 or more.

6. The semi-aromatic polyamide film according to any one of claims 1 to 5, characterized in that it contains 0.01 to 0.4 mass % of fine particles.

7. 7. The semi-aromatic polyamide film according to claim 1, wherein the coefficient of dynamic friction measured in accordance with JIS K7125 is 0.8 or less.

8. A laminate comprising the semi-aromatic polyamide film according to any one of claims 1 to 7 and an easy-adhesion layer laminated on at least one surface of the semi-aromatic polyamide film.

9. An LED mounting substrate using the laminate according to claim 8.

10. A flexible LED display using the LED mounting substrate according to claim 9.

11. A method for producing the semi-aromatic polyamide film according to any one of claims 1 to 7, comprising the steps of: A method for producing a semi-aromatic polyamide film, comprising the steps of biaxially stretching an unstretched semi-aromatic polyamide film, holding the film at 110 to 150°C for 0.5 to 25 seconds, and then cooling the film to room temperature.