RU2786076C1 - Semi-aromatic polyamide film and method for obtaining the film - Google Patents

Abstract

FIELD: semi-aromatic polyamide film.

SUBSTANCE: the invention relates to a method for obtaining semi-aromatic polyamide film and to the electronic material and the optical component that include this film. A semi-aromatic polyamide film has a thermal shrinkage coefficient in the longitudinal direction of the film, S_MD, from - 0,1 up to 1,5% and thermal shrinkage coefficient in width direction, S_TD, from - 0,1 up to 1,5% when measured in conditions of 250°C for 5 minutes, tensile elongation to break 70% or more in the longitudinal direction and the direction of the width, muddiness 14% or less. The method for producing said film includes biaxial stretching of an unstretched film of semi-aromatic polyamide having a crystallization enthalpy of 20 J/g or more. Stretch ratio is 2-3,5 times longitudinally and 2-4 times in the width direction. Tensile strain rate in the longitudinal and width directions is over 400%/min and 12000%/min or less. The tensile temperature is the glass transition temperature of the semi-aromatic polyamide or more and the glass transition temperature of the semi-aromatic polyamide +50°C or less. After biaxial stretching the film is heat-fixed at a temperature of 260-280°C, and then the film is subjected to relaxation treatment at the relaxation rates of 1-10% in the longitudinal direction and 1-12% in the width direction.

EFFECT: resulting film of semi-aromatic polyamide has a significantly reduced coefficient of thermal shrinkage in the longitudinal direction and greatly improved elongation at break in the direction of the film width.

5 cl, 6 tbl, 38 ex

Description

The technical field to which the invention belongs

[0001] The present invention relates to a semi-aromatic polyamide film with reduced thermal shrinkage.

State of the art

[0002] Films of semi-aromatic polyamide stretched in the longitudinal direction (length direction) and in the width direction (transverse direction) of the films have excellent heat resistance and mechanical characteristics, and therefore find application in various fields. Among the semi-aromatic polyamides constituting the semi-aromatic polyamide films, especially 9T polyamide including an aliphatic diamine having 9 carbon atoms and terephthalic acid as constituents, and 10T polyamide including an aliphatic diamine having 10 carbon atoms and terephthalic acid as constituents , have excellent mechanical performance and thermal performance.

[0003] For example, Patent Document 1 discloses a biaxially stretched film including a semi-aromatic polyamide resin obtained by performing biaxial stretching, then by performing a heat-setting treatment, and further by performing a relaxation treatment in the film width direction.

List of cited literature

Patent Literature

[0004] Patent Document 1: International Publication No. WO 2012/067172

The essence of the invention

Technical task

[0005] At present, for optical films such as elements of display devices, there is a great demand that deformation and the like do not occur during transportation and during processing.

The film disclosed in Patent Document 1 has a significantly reduced thermal shrinkage ratio at 200°C and 15 minutes. However, when the temperature is 250°C, the thermal shrinkage ratio in the longitudinal direction of the film may increase significantly even under the condition of 5 minutes, and depending on the temperature conditions during processing, deformation due to stresses accompanied by thermal shrinkage may be unavoidable.

In addition, the film disclosed in Patent Document 1 exhibits a high elongation at break in the longitudinal direction, but may have a low elongation at break in the width direction, and the film can be torn without being able to follow an applied external stress. .

The object of the invention is to provide a semi-aromatic polyamide film having a significantly reduced thermal shrinkage coefficient in the film length direction and having a significantly improved elongation at break in the film width direction.

The solution of the problem

[0006] As a result of extensive research, the present inventors have found that the object can be achieved by a semi-aromatic polyamide film obtained by adjusting the crystalline state of the film before stretching, stretching conditions, heat setting conditions, and relaxation conditions, and thereby completed the present invention.

[0007] The semi-aromatic polyamide film of the present invention has

thermal shrinkage ratio in the film length direction, S _MD , from -1.0 to 1.5%, and thermal shrinkage ratio in the film width direction, S _TD , from -1.0 to 1.5%, when measured at 250ºC and 5 minutes, an elongation at break of 70% or more in the longitudinal direction and in the width direction, and a haze of 14% or less.

According to the semi-aromatic polyamide film of the present invention, the absolute value of the difference between S _MD and S _TD (|S _MD -S _TD |) is preferably less than 1.2.

The method for producing a semi-aromatic polyamide film according to the present invention includes:

biaxially stretching an unstretched semi-aromatic polyamide film, wherein the biaxial stretching uses an unstretched film having an enthalpy of crystallization of 20 J/g or more.

According to the process for producing a semi-aromatic polyamide film according to the present invention, in biaxial stretching, the unstretched film is preferably stretched 2.0 to 3.5 times in the longitudinal direction, and stretched 2.0 to 4.0 times in the width direction.

According to the method for producing a semi-aromatic polyamide film according to the present invention, the film after biaxial stretching is preferably subjected to a heat-setting treatment at a temperature of 260 to 280°C, and subjected to a relaxation treatment at relaxation rates from 1.0 to 10.0% in the longitudinal direction, and from 1.0 up to 12.0% in the direction of the width.

The semi-aromatic polyamide film is used in the electronic material according to the present invention.

A semi-aromatic polyamide film is used in an optical component according to the present invention.

Advantageous results of the invention

[0008] The present invention can provide a semi-aromatic polyamide film having a low thermal shrinkage ratio in the film width direction and a small thermal shrinkage ratio in the film length direction at 250°C and 5 minutes, having excellent dimensional stability, and having a greatly improved tensile elongation. to break in the longitudinal direction of the film and a significantly improved elongation at break in the width direction.

Even if the semi-aromatic polyamide film of the present invention contains a lubricant to improve the slipperiness, the increase in haze is suppressed so that transparency remains excellent.

The semi-aromatic polyamide film of the present invention can be preferably used as an electronic material of films such as film substrates and cover films for flexible printed circuit boards (FPC), optical films used as substrates for display device materials, heat-resistant tapes, and the like.

Description of embodiments of the invention

[0009] The semi-aromatic polyamide film of the present invention has a thermal shrinkage ratio in the film longitudinal direction, S _MD , from -1.0 to 1.5%, and a thermal shrinkage ratio in the film width direction, S _TD , from -1.0 to 1.5%, when measured at 250ºC and 5 minutes, elongation at break of 70% or more, and haze of 14% or less.

[0010] <Semi-aromatic polyamide>

The semi-aromatic polyamide constituting the semi-aromatic polyamide film of the present invention includes an aromatic dicarboxylic acid component and an aliphatic diamine component.

[0011] The aromatic dicarboxylic acid component preferably contains 60 mol% or more, more preferably 70 mol% or more, and even more preferably 85 mol% or more of terephthalic acid. When the content of terephthalic acid is less than 60 mol%, heat resistance and low hygroscopicity may deteriorate.

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 in a range that does not impair the effects of the present invention. 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 includes an aliphatic diamine having 6 to 12 carbon atoms as a main component, more preferably includes an aliphatic diamine having 9 to 12 carbon atoms as a main component, and even more preferably includes an aliphatic diamine , having from 9 to 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. One aliphatic diamine having 6 to 12 carbon atoms may be used alone, or two or more aliphatic diamines having 6 to 12 carbon atoms may be used in combination. When two or more aliphatic diamines having 6 to 12 carbon atoms are used in combination, the content is the total content of aliphatic diamines having 6 to 12 carbon atoms.

[0013] Examples of an aliphatic diamine having 6 to 12 carbon atoms include linear aliphatic diamines, 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 aliphatic diamines other than aliphatic diamines 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 different diamine component than the aliphatic diamine component, as a diamine component in a range that does not adversely affect the effects of the present invention. Examples of other diamines include alicyclic diamines such as isophorone diamine, norbornane dimethylamine, and tricyclodecane dimethylamine, and aromatic diamines such as meta-xylylenediamine, para-xylylenediamine, meta-phenylenediamine, and para-phenylenediamine.

[0016] In a semi-aromatic polyamide, a lactam such as ε-caprotactam, ζ-enanolactam, η-capryllactam, or ω-laurolactam can be copolymerized in an amount that does not impair the effect of the present invention.

[0017] The types and copolymerization ratio of the monomers constituting the semi-aromatic polyamide are preferably selected such that the melting point (Tm) of the resulting semi-aromatic polyamide is in the range of 270 to 350°C. When the semi-aromatic polyamide has a Tm value in this range, pyrolysis can be effectively prevented when the semi-aromatic polyamide is processed into a film. When the Tm value is less than 270°C, the resulting film may not have sufficient heat resistance. On the other hand, when the Tm value is more than 350° C., pyrolysis may occur during film formation.

[0018] The intrinsic viscosity of the semi-aromatic polyamide is preferably 0.8 to 2.0 dL/g, more preferably 0.9 to 1.8 dL/g. When the semi-aromatic polyamide has an IV of 0.8 dL/g or more, a film with excellent mechanical strength can be obtained, but when the semi-aromatic polyamide has an IV of more than 2.0 dL/g, film formation may be difficult.

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

[0020] <Semi-aromatic polyamide film>

The semi-aromatic polyamide film of the present invention should have a thermal shrinkage ratio in the film length direction, S _MD , from -1.0 to 1.5%, and a thermal shrinkage ratio in the film width direction, S _TD , from -1.0 to 1. 5%, as measured at 250ºC and 5 minutes, and preferably has a thermal shrinkage ratio in the film length direction, S _MD , from -0.8 to 1.3%, and a thermal shrinkage ratio in the film width direction, S _TD , from -0.8 to 1.3%, more preferably a thermal shrinkage ratio in the film longitudinal direction, S _MD , from -0.6 to 1.0%, and a thermal shrinkage ratio in the film width direction, S _TD , from -0, 6 to 1.0%. The semi-aromatic polyamide film has improved dimensional stability and excellent heat resistance, having a thermal shrinkage ratio of 1.5% or less. On the other hand, when the semi-aromatic polyamide film has a thermal shrinkage ratio of over 1.5%, dimensional change increases when the semi-aromatic polyamide film is processed at a high temperature. Therefore, there are processing difficulties that create problems.

[0021] In the semi-aromatic polyamide film of the present invention, the absolute value of the difference between the thermal shrinkage ratio S _MD in the longitudinal direction and the thermal shrinkage ratio S _TD in the width direction, (|S _MD -S _TD |), measured at 250ºC and 5 minutes, preferably less than 1.2, more preferably less than 1.1, and even more preferably less than 1.0. When the value of (|S _MD -S _TD |) is less than 1.2 in a semi-aromatic polyamide film, the thermal shrinkage ratios in the longitudinal direction and in the width direction become the same, and the anisotropy is reduced, and even when heat is applied to the film during reflow soldering for processing with layering on another material or the like, the occurrence of deformation and buckling can be prevented.

[0022] In addition, the semi-aromatic polyamide film of the present invention should have an elongation at break of 70% or more in the longitudinal direction and in the width direction, as measured according to JIS K7127, and preferably has an elongation at break of 70 up to 150%, more preferably from 80 to 140%. When the semi-aromatic polyamide film has an elongation to break of 70% or more, the semi-aromatic polyamide film exhibits excellent ability to follow deformation changes, and therefore does not break when subjected to an external load, and is a deformable film. On the other hand, when the semi-aromatic polyamide film has an elongation at break of less than 70%, the semi-aromatic polyamide film cannot withstand an external load and breaks. In the semi-aromatic polyamide film of the present invention, the elongation at break values in the longitudinal direction and in the width direction need not be equal. Even if the elongation at break values in the longitudinal direction and in the width direction are not balanced with each other, the values of elongation at break in the longitudinal direction and in the width direction are acceptable as long as the preferred range of numerical values for elongation at break is satisfied. elongation at break in the longitudinal direction is 140%, and the elongation at break in the width direction is 80%, or the elongation at break in the longitudinal direction is 80%, and the elongation at break when stretched to break in the direction of the width is 140%.

[0023] In addition, the semi-aromatic polyamide film of the present invention should have a haze of 14% or less when measured according to JIS K7105, and preferably has a haze of 12% or less, more preferably 10% or less. In addition, the semi-aromatic polyamide film having a thickness of 25 µm or less preferably has a haze of 7% or less, more preferably 6% or less, and even more preferably 5% or less. The semi-aromatic polyamide film provides excellent visibility with a haze of 14% or less. On the other hand, a semi-aromatic polyamide film having a haze of more than 14% exhibits poor visibility.

[0024] The semi-aromatic polyamide film of the present invention preferably has a moisture absorption elongation in the film longitudinal direction, N _MD , of 1% or less and a moisture absorption elongation in the width direction, N _TD , of 1% or less, more preferably an elongation at film length, N _MD , 0.8% or less and width direction water absorption elongation, N _TD , 0.8% or less, and even more preferably, film longitudinal water absorption elongation, N _MD , 0.5% or less, and an elongation at moisture absorption in the width direction, N _TD , 0.5% or less, when measured under conditions of 20ºC and 90% relative humidity (RH).

Absolute value of the difference between the moisture absorption elongation N _MD in the film longitudinal direction and the moisture absorption elongation N _TD in the width direction, (|N _MD -N _TD |), measured at 20ºC and 90% relative humidity (RH) , preferably less than 0.3, more preferably less than 0.2, and even more preferably less than 0.1. When (|N _MD -N _TD |) is less than 0.3 in the semi-aromatic polyamide film, the elongation in the longitudinal direction and in the width direction under moisture absorption conditions are equal, and the occurrence of deformation and warpage can be prevented.

[0025] The semi-aromatic polyamide film of the present invention has a thermal shrinkage ratio in the film longitudinal direction, S _MD , and a thermal shrinkage ratio in the width direction, S _TD , in a predetermined range as measured under conditions of 250ºC and 5 minutes, and thus can be dimensional stability is improved when the semi-aromatic polyamide film is subjected to dynamic temperature changes during film processing and the like. In addition, the semi-aromatic polyamide film of the present invention has a moisture absorption elongation in the above range, and thereby dimensional change due to moisture during film processing and the like can be prevented. In other words, the dimensional stability of the film can be improved, and not only the positioning during lamination on another material and the dimensional accuracy during perforation can be improved, but also the risk of curling and deformation after lamination on another material can be reduced.

[0026] <Method for producing semi-aromatic polyamide film>

The semi-aromatic polyamide film of the present invention can be obtained by using an unstretched film having a crystallization enthalpy of 20 J/g or more, and, for example, by stretching the unstretched film to a value of 2.0 to 3.5 times in the longitudinal direction of the film and to a value of 2.0 to 4.0 times in the width direction, in the step of biaxially stretching an unstretched semi-aromatic polyamide film, subjecting the film after biaxial stretching to a heat setting treatment at a temperature of 260 to 280°C, and subjecting the film to a relaxation treatment at relaxation rates of 1.0 to 10 .0% in the longitudinal direction, and from 1.0 to 12.0% in the width direction.

[0027] (Semi-aromatic polyamide)

As the semi-aromatic polyamide, a commercially available product can preferably be used to obtain the semi-aromatic polyamide film. Examples of such industrial product include "Genestar (registered trademark)" manufactured by KURARAY CO., LTD., "XecoT (registered trademark)" manufactured by UNITIKA LTD., "Reny (registered trademark)" manufactured by Mitsubishi Engineering- Plastics Corporation, "ARLEN (registered trademark)" from Mitsui Chemicals, Inc., and "Ultramid (registered trademark)" from BASF.

[0028] The semi-aromatic polyamide can be obtained using a method known as the crystalline polyamide production method. Examples of the method include a solution polymerization method or an interfacial polymerization method using an acid chloride and a diamine component as raw materials (method A), an oligomer production method using a dicarboxylic acid component and a diamine component as raw materials, and polymerizing the oligomer by melt polymerization or solid-state polymerization (method B), a method for forming a ground mixture of salt and an oligomer using a dicarboxylic acid component and a diamine component as raw materials, and a solid-state polymerization of a ground mixture (method C), and a method for forming a salt using a dicarboxylic acid component and the diamine component as starting materials, by solid-state salt polymerization (method D). More specifically, method C and method D are preferred, and method D is more preferable. water during the formation of a ground mixture of salt and oligomer or salt. Therefore, the formation of a gel mass can be reduced, and fisheye defects can be reduced.

[0029] For example, in method B, an oligomer can be obtained by mixing a diamine component, a dicarboxylic acid component, and a polymerization catalyst simultaneously to obtain a nylon salt, and hot polymerizing the nylon salt at a temperature of 200 to 250°C. The intrinsic viscosity of the oligomer is preferably 0.1 to 0.6 dL/g. The advantage of adjusting the intrinsic viscosity of the oligomer in this range is that in the subsequent solid phase or melt polymerization, the molar balance between the carboxyl groups in the dicarboxylic acid component and the amino groups in the diamine component is not disturbed, and the polymerization rate can be increased. When the intrinsic viscosity of the oligomer is less than 0.1 dL/g, the polymerization time becomes long and the productivity may be poor. On the other hand, when the intrinsic viscosity of the oligomer is more than 0.6 dL/g, the resulting semi-aromatic polyamide can be dyed.

The solid state polymerization of the oligomer is preferably carried out under reduced pressure or in an inert gas stream. The solid state polymerization temperature is preferably 200 to 280°C. By controlling the solid state polymerization temperature in this range, coloring and gelation of the resulting semi-aromatic polyamide can be prevented. When the solid state polymerization temperature is below 200°C, the polymerization time becomes long, and therefore there may be poor performance. On the other hand, when the solid state polymerization temperature is above 280° C., coloring and gelation of the resulting semi-aromatic polyamide can occur.

The melt polymerization of the oligomer is preferably carried out at a temperature of 350° C. or less. When the polymerization temperature is over 350ºC, decomposition and thermal damage of the semi-aromatic polyamide can be promoted. Therefore, a film made from such a semi-aromatic polyamide may have poor strength and appearance. Melt polymerization also includes melt polymerization using a melt extruder.

[0030] For example, in Method C, a slurry comprising a molten aliphatic diamine and a solid aromatic dicarboxylic acid is agitated and mixed to form a liquid mixture. Then, in this liquid mixture, a salt formation reaction is carried out by reacting an aromatic dicarboxylic acid and an aliphatic diamine, and an oligomer formation reaction by polymerization of the salt formed is carried out at a temperature lower than the melting temperature of the final formed semi-aromatic polyamide to obtain a mixture of salt and oligomer. In this case, the grinding may be carried out while the reactions are taking place, or the grinding may be carried out after the reaction product has been isolated at the completion of the reactions. Then, the resulting reaction product is subjected to solid-state polymerization at a temperature lower than the melting point of the final formed semi-aromatic polyamide to raise the molecular weight to a predetermined molecular weight to obtain a semi-aromatic polyamide. The solid state polymerization is preferably carried out in a flow of an inert gas such as nitrogen at a polymerization temperature of 180 to 270° and a reaction time of 0.5 to 10 hours.

[0031] In method D, for example, the aromatic dicarboxylic acid powder is preheated to a temperature equal to or greater than the melting point of the aliphatic diamine, or equal to or less than the melting point of the aromatic dicarboxylic acid, and to the aromatic dicarboxylic acid powder at this temperature, an aliphatic diamine substantially free of water content, thereby keeping the aromatic dicarboxylic acid in a powdered state to form a salt. Then, the resulting salt is subjected to solid state polymerization at a temperature lower than the melting point of the final generated semi-aromatic polyamide to raise the molecular weight to a predetermined molecular weight to form a semi-aromatic polyamide. The solid state polymerization is preferably carried out in a flow of an inert gas such as nitrogen at a polymerization temperature of 180 to 270° C. and a reaction time of 0.5 to 10 hours.

[0032] The starting materials for the semi-aromatic polyamide film may be a mixture of raw pure raw materials, and may be custom films formed when the semi-aromatic polyamide was produced, a mixture of waste formed as trimmings, or a material obtained by adding raw pure raw materials to waste mixtures. The mixing can be carried out in a known manner, such as a dry mixing process using known equipment, or a kneading and mixing melt plasticizing process using a single screw or twin screw extruder.

[0033] (Additives)

The semi-aromatic polyamide film of the present invention includes a semi-aromatic polyamide and may contain additives such as a lubricant, a coloring agent such as a pigment such as titanium oxide or a dye, a stain-preventing agent, a heat stabilizer, an antioxidant such as a hindered phenol, an ester phosphoric acid or phosphorous acid ester, weathering agent such as benztriazole compound, bromine-based or phosphorus-based flame retardant, plasticizer, release agent, reinforcing agent such as talc, modifier, antistatic agent, ultraviolet absorber , an anti-fogging agent, and various polymer resins, if necessary, within a range that does not impair the various characteristics of the film, so as to further improve the various characteristics of the semi-aromatic polyamide film.

Examples of the slippery lubricant include inorganic particles such as silica, alumina, titanium dioxide, calcium carbonate, kaolin, and barium sulfate. Examples of organic fine particles may include acrylic resin particles, melamine resin particles, silicone resin particles, and crosslinked polystyrene particles. The average particle diameter of the lubricant is preferably 0.05 to 5.0 µm. The content of the lubricant is preferably 0.2% by mass or less, but may be selected according to friction characteristics, optical characteristics, and other characteristics required for the film.

[0034] As a method for enabling additives to be contained in the semi-aromatic polyamide film, various methods can be applied. Examples of typical ways to do this may include the following ways:

(A) a method for adding additives during the polymerization of a semi-aromatic polyamide;

(B) a masterbatch method, directly adding additives to semi-aromatic polyamide, and melting and kneading the mixture to obtain granules;

(C) a process for directly adding additives to semi-aromatic polyamide, and melting and kneading the mixture in an extruder during film formation;

(D) a method of directly adding additives to the extruder and melting and kneading the mixture during film formation.

[0035] (Extrusion)

In the process for producing a semi-aromatic polyamide film according to the present invention, the unstretched semi-aromatic polyamide film used in the biaxial stretching step should have a crystallization enthalpy of 20 J/g or more, and preferably has a crystallization enthalpy of 25 J/g or more. When the enthalpy of crystallization of the unstretched film is less than 20 J/g, in the semi-aromatic polyamide film obtained by biaxially stretching the unstretched film, crystallization occurs and therefore the elongation at break decreases and haze increases when the semi-aromatic polyamide film contains a lubricant such as silicon oxide. An unstretched film having an enthalpy of crystallization of less than 20 J/g is not stretched unstably, or cannot be stretched in some cases due to frequent shearing, and a larger stretching force is required in the initial stage of stretching, and therefore it becomes difficult to obtain a stretched film having a uniform thickness.

An unstretched semi-aromatic polyamide film having a crystallization enthalpy of 20 J/g or more can be obtained by melting and mixing the semi-aromatic polyamide in an extruder at a temperature of 280 to 340°C for 3 to 15 minutes, then extruding the semi-aromatic polyamide to form a sheet-like shape through a flat die. die (T-die), and applying this sheet-like material to a cooling drum having a temperature adjusted to 30 to 40ºC to cool the sheet-like material. When the temperature of the chill roll is over 40°C, the resulting unstretched film has a crystallization enthalpy of less than 20 J/g, and the above problems occur after stretching.

[0036] (stretch)

In a process for producing a semi-aromatic polyamide film, an unstretched film is biaxially stretched, and the semi-aromatic polyamide orients and crystallizes as a result of the stretch.

The stretching method is not particularly limited, and a planar sequential biaxial stretching method, a planar simultaneous biaxial stretching method, a sleeve method, or the like can be applied. More specifically, the in-plane simultaneous biaxial stretching method is optimal because it provides good film thickness accuracy, and the physical properties are uniform in the film width direction. Examples of stretching equipment suitable for the planar simultaneous biaxial stretching method include a screw-type tenter frame, a pantograph-type tenter frame, and a linear motor-driven clamp-type tenter frame.

[0037] The stretch ratios are preferably 2.0 to 3.5 times in the longitudinal direction, and 2.0 to 4.0 times in the width direction, more preferably 2.0 to 3.0 times in the longitudinal direction, and from 2.0 to 3.5 times in the direction of width.

In the case of successive biaxial stretching, when the stretching ratio in the longitudinal direction is more than 3.5 times, too much crystallization occurs in the stretched film obtained, and the stretchability in the width direction may be reduced. Even when stretching in the width direction can be performed, stretch unevenness in the resulting stretched film is very likely to occur, and thickness accuracy may decrease, elongation to break in the longitudinal direction may decrease, and transparency may deteriorate.

In the sequential biaxial stretching method, furthermore, the stretching ratios are preferably 2.3 to 2.5 times in the longitudinal direction, and 3.3 to 3.5 times in the width direction.

In the case of simultaneous biaxial stretching, when the stretching ratio in the longitudinal direction is more than 3.5 times, the thermal shrinkage ratio may increase and the dimensional stability in the resulting stretched film may decrease. On the other hand, when the stretch ratio in the width direction is more than 4.0 times, the thermal shrinkage ratio may increase, the dimensional stability in the resulting stretched film may decrease, and the elongation at break may also decrease.

In the simultaneous biaxial stretching method, when a biaxially stretched film having a thickness of 1 to 25 µm is obtained, the stretching ratios are preferably 2.5 to 3.0 times in the longitudinal direction, and 2.5 to 3.3 times in the width direction. , and when a biaxially stretched film having a thickness of 26 to 50 µm is obtained, the stretching ratios are preferably 3.0 to 3.5 times in the longitudinal direction, and 2.8 to 3.3 times in the width direction.

When the stretch ratios in the longitudinal direction and in the width direction are less than 2.0 times, stretching unevenness in the obtained stretched film is very likely to occur, and the accuracy of the thickness may decrease, and the planarity may deteriorate.

[0038] In terms of stretching rates, stretching strain rates in the longitudinal direction and in the width direction are preferably more than 400%/min, more preferably 800 to 12000%/min, and even more preferably 1200 to 6000%/min. When the strain rates are 400%/min or less, crystals grow during stretching and the film may break. On the contrary, when the strain rates are excessively high, the unstretched film cannot follow the strain and may be torn.

The tensile temperature is preferably the glass transition temperature (Tg) of the semi-aromatic polyamide or more, more preferably above the Tg, and (Tg+50°C) or less. When the stretching temperature is below Tg, the film may be easily broken and stable production cannot be performed. On the contrary, when the stretching temperature exceeds (Tg+50°C), stretch unevenness may occur in the film.

[0039] (Heatfixing)

After the semi-aromatic polyamide film has been stretched, it is preferably subjected to a heat-setting treatment, with the film held in the clamps used during the stretching. In the film obtained by subjecting the heat-setting treatment, heat-induced unevenness does not occur, and thermal shrinkage coefficients can be reduced. The heat setting temperature is preferably 260 to 280°C, more preferably 263 to 278°C, and even more preferably 265 to 275°C. When the heat setting temperature is less than 260ºC, heat shrinkage ratios increase in the obtained film. When the heat setting temperature is more than 280° C., the elongation to break decreases, and deterioration in appearance due to heat-induced wrinkling is very likely to occur, and in some cases, break occurs during the heat set treatment, and it becomes difficult to obtain a biaxially stretched film.

In the sequential biaxial stretching method, the heat setting temperature is preferably 260 to 275°C. In the simultaneous biaxial stretching method, when a biaxially stretched film having a thickness of 1 to 25 µm is obtained, the heat setting temperature is preferably 260 to 280°C, and when a biaxially stretched film having a thickness of 26 to 50 µm is obtained, the heat setting temperature is preferably is from 260 to 275ºC.

[0040] Examples of the fusing method include known methods such as hot air blowing method, infrared irradiation method, and microwave irradiation method. More specifically, a hot air blowing method is preferable because uniform heating can be carried out with good accuracy.

[0041] (Relaxation)

After the film has been heat-set, it is subjected to a relaxation treatment at relaxation rates of 1.0 to 10.0% in the longitudinal direction, and 1.0 to 12.0% in the width direction, at the same temperature as heat setting temperature, with film held in clamps. When the relaxation rates in the longitudinal direction and in the width direction are less than 1.0%, a film having sufficiently reduced thermal shrinkage ratios cannot be obtained. When the relaxation rates in the longitudinal direction are over 10.0%, sagging may occur in the film. By performing the relaxation treatment at relaxation rates of relaxation from 1.0 to 10.0% in the longitudinal direction, and from 1.0 to 12.0% in the width direction, a film having reduced thermal shrinkage coefficients and improved dimensional stability can be obtained.

In the sequential biaxial stretching method, when a biaxially stretched film having a thickness of 1 to 50 µm is obtained, the relaxation rates are preferably 1.0 to 6.0% in the longitudinal direction, and 1.0 to 12.0% in the width direction. , and when a biaxially stretched film having a thickness of 51 to 150 µm is obtained, the relaxation rates are preferably 1.0 to 3.0% in the longitudinal direction, and 6.0 to 12.0% in the width direction.

In the simultaneous biaxial stretching method, the relaxation rates are preferably 1.0 to 6.0% in the longitudinal direction, and 1.0 to 12.0% in the width direction.

The relaxation treatments of the films in the longitudinal direction and/or in the width direction in each case are independently controlled during film production, and either in the simultaneous biaxial stretching method or in the sequential biaxial stretching method, the absolute value of the difference between the relaxation rate in the longitudinal direction and the relaxation rate along the width direction is preferably 2 or less. Thus, in the obtained biaxially stretched film, the moisture absorption elongation is reduced, and the absolute value of the difference between the moisture absorption elongation N _MD in the longitudinal direction and the moisture absorption elongation N _TD in the width direction is reduced, (|N _MD -N _TD |), and in a laminate having another layered material, curling is prevented from occurring during absorption of moisture.

[0042] In the simultaneous biaxial stretching method, the relaxation treatment may be performed in-line at the same time or separately in the longitudinal direction and the width direction. When the relaxation treatment is carried out separately, examples include a method of performing relaxation in the longitudinal direction and then performing relaxation in the width direction, and a method of performing relaxation in the width direction and then performing relaxation in the longitudinal direction.

On the other hand, in the sequential biaxial stretching method, the relaxation treatment can be (i) performed in-line simultaneously in the longitudinal direction and in the width direction after performing stretching in the length direction and stretching in the width direction, and heat-setting treatment is carried out, and (ii) also it is possible to perform stretching in the length direction, then to perform relaxation treatment in the longitudinal direction, then to perform transverse stretching, to perform heat setting treatment, and then to perform relaxation treatment in the width direction. In case (ii), when stretching in the length direction and relaxation treatment in the longitudinal direction are performed, and then the heat-setting treatment is performed, the obtained film is in a state that makes it difficult to cross-stretch, and therefore it is not preferable to carry out the heat-setting treatment in the step before the cross-stretching. In options (i) and (ii) of the sequential biaxial stretching methods, first stretching in the length direction, and then performing transverse stretching, but in the sequential biaxial stretching method, it is permissible to perform transverse stretching first, and then perform stretching in the length direction.

Alternatively, with respect to the relaxation treatment, it is also possible to stretch the film biaxially, then subject the film to relaxation treatment in a production line in the width direction, then wind the film once, and pass the film on separate equipment through a drying oven set to a predetermined temperature at low tension. for relaxation processing in the longitudinal direction.

[0043] The film thickness of the semi-aromatic polyamide of the present invention is appropriately selected according to the application and purpose, but is preferably 1 to 150 µm, more preferably 10 to 100 µm, and even more preferably 20 to 80 µm.

The semi-aromatic polyamide resin constituting the semi-aromatic polyamide film of the present invention has a very high crystallinity. Therefore, when the sequential biaxial stretching method is used, orientation and crystallinity are likely to occur when the film is stretched in the unstretched state in the longitudinal direction or in the width direction. It may be difficult to subject the oriented and crystallized film to subsequent stretching in the orthogonal direction. Therefore, it is desirable to implement the method of simultaneous biaxial stretching. On the other hand, when the semi-aromatic polyamide film of the present invention has a thickness of over 50 μm, the stretching force at the time of stretching is too high in the simultaneous biaxial stretching method, and therefore the difficulty of stretching is greatly increased. Therefore, when biaxially stretching such a film having a high tensile force, it is preferable to use a sequential biaxial stretching method rather than a simultaneous biaxial stretching method.

[0044] In the semi-aromatic polyamide film making equipment of the present invention, the surfaces of the cylinder, the melting section of the drum, the metering section, the single pipe, the filter, the T-die, and the like, are preferably subjected to a surface roughness treatment to prevent resin retention. Examples of a method for reducing surface roughness include a method for modifying surfaces with a material having a low polarity, or a method for vapor deposition of silicon nitride or diamond-like carbon on a surface.

[0045] The resulting semi-aromatic polyamide film may be formed as a single sheet, or in the form of a roll of film, being wound around a winding drum. For performance reasons in various applications, the semi-aromatic polyamide film is preferably formed as a roll of film. When the semi-aromatic polyamide film is in the form of a roll of film, the semi-aromatic polyamide film can be cut to a desired width.

[0046] The semi-aromatic polyamide film may be a single layer film composed of one layer, or may be a multilayer structure obtained by laminating two or more layers. When a multi-layer structure is formed, for example, the lubricant may be contained in any of the two layers in the film of the two-layer structure, and the lubricant may be contained in each of the layers on both surfaces among the three layers in the film with the three-layer structure. The type and content of the lubricant contained can be selected independently in each case. By forming such a multilayer structure, the surface roughness of each surface of the semi-aromatic polyamide film can be independently controlled.

[0047] The surface of the semi-aromatic polyamide film may be subjected to corona treatment, plasma treatment, acid treatment, flame treatment, or the like to make good adhesiveness with another material.

[0048] The semi-aromatic polyamide film of the present invention may be laminated with an inorganic material such as a metal or an oxide thereof, another polymer, paper, textile fabric, non-woven material, wood, or the like.

[0049] <Applications>

The semi-aromatic polyamide film of the present invention has excellent dimensional stability while having heat resistance, and therefore can be used for various electronic materials and optical components and other applications.

More specifically, the semi-aromatic polyamide film of the present invention can be used as films for home use and industrial materials such as drug packaging materials; packaging materials for foodstuffs, such as prepackaged meals; packaging materials for electronic components such as packages for semiconductor devices; electrical insulating materials for motors, transformers, cables, and the like; dielectric materials for use in capacitors and the like; materials for magnetic tapes such as cassette tapes, magnetic tapes for storing data in digital data storage devices, and video tapes; protective panels for solar cell substrates, liquid crystal panels, conductive films, display devices, and the like; electronic substrate materials for mounting light emitting device (LED) substrates, flexible printed circuit board substrates, flexible flat cables, and the like; heat-resistant tapes such as flexible printed circuit cover films, heat-resistant masking tapes, and industrial process tapes; heat-resistant barcode labels; insulating tapes; various separating films; heat-resistant carrier films; photographic films; molding materials; agricultural materials; medical supplies; materials for civil engineering and structures; and filtration materials.

In addition, the semi-aromatic polyamide film of the present invention has excellent characteristics, i.e., heat resistance, dimensional stability and transparency, and therefore can be used for applications such as screen materials for mobile devices and the like, and for display devices. More specifically, the semi-aromatic polyamide film of the present invention can be used as a carrier film material in various functional materials such as optical substrates, polarization panels, and phase difference panels, and the like, using elements such as liquid crystals, organic electroluminescent devices (EL), and protective and sealing films in light emitting devices and display devices.

Examples

[0050] The present invention will be more specifically described below in the Examples.

1. Assessment methods

(1) Intrinsic viscosity of semi-aromatic polyamide

Value obtained by measuring the intrinsic viscosity (η _inh ) of the resin in concentrated sulfuric acid at 30ºC at concentrations of 0.05, 0.1, 0.2, and 0.4 g/dL from the following formula, and extrapolating the intrinsic viscosity (η _inh ) to zero concentration is taken as the specific viscosity of the polymer solution [η].

η inh \ _u003d [ln (t ₁ / t ₀ )] / c

in which η _inh represents the inherent viscosity (dL/g), t ₀ represents the flow time (seconds) of the solvent, t ₁ represents the flow time (seconds) of the resin solution, and c represents the concentration (g/dL) of the resin in the solution.

[0051] (2) Melting point and glass transition temperature of semi-aromatic polyamide

Semi-aromatic polyamide is heated from 20°C to 350°C at a heating rate of 10°C/minute, and held for 5 minutes (1st scan), and then cooled from 350°C to 20°C at a cooling rate of 100°C/minute, and held for 5 minutes under nitrogen atmosphere , using a differential scanning calorimetry apparatus (manufactured by PerkinElmer Inc., DSC-7). The glass transition temperature during the subsequent further reheating of the semi-aromatic polyamide from 20° C. to 350° C. at a heating rate of 10° C./minute (2nd scan) is taken as the Tg of the semi-aromatic polyamide. Similarly, the maximum temperature peak as the crystal melting peak observed in the 2nd scan is taken as Tm.

[0052] (3) Enthalpy of crystallization of unstretched film

10 mg of an unstretched semi-aromatic polyamide sheet was heated from 40°C to 350°C at a heating rate of 20°C/minute (1st scan) under a nitrogen atmosphere using a differential scanning calorimeter (manufactured by PerkinElmer Inc., DSC-7), and the enthalpy associated with the obtained exothermic peak.

[0053] (4) Thermal shrinkage coefficients of semi-aromatic polyamide film

Tape-shaped test specimens (10 mm wide×100 mm long) were cut in the longitudinal direction and along the width direction of the semi-aromatic polyamide film, respectively. The resulting test specimens were in each case treated in an atmosphere heated to 250°C for 5 minutes, and then allowed to cool at 23°C and 50% relative humidity (RH) for 2 hours. Then, the dimension in the length direction was measured, and the thermal shrinkage ratio of the test piece in the longitudinal direction, S _MD , and the thermal shrinkage ratio of the test piece in the width direction, S _TD , were determined by the following formula:

thermal shrinkage ratio (%)=[{original length-length after processing}/original length]×100

For Comparative Examples 1-4, in addition to measuring the thermal shrinkage coefficients when treated with an atmosphere heated to 250ºC for 5 minutes, the thermal shrinkage coefficients were also measured when treated with an atmosphere heated to 200ºC for 15 minutes.

The absolute value of the difference between the thermal shrinkage coefficient S _MD in the longitudinal direction and the thermal shrinkage coefficient S _TD in the width direction, (|S _MD -S _TD |), was also calculated, and the anisotropy of the thermal shrinkage coefficient was evaluated according to the following criteria:

Excellent: |S _MD -S _TD | is less than 0.4

Good: |S _MD -S _TD | is 0.4 or more and less than 0.8

Acceptable: |S _MD -S _TD | is 0.8 or more and less than 1.2

Bad: |S _MD -S _TD | is 1.2 or more

[0054] (5) Tensile elongation at break of semi-aromatic polyamide film

The elongation at break of the semi-aromatic polyamide film in the longitudinal direction and in the width direction was measured in accordance with JIS K7127.

[0055] (6) Semi-aromatic polyamide film haze

The haze of the semi-aromatic polyamide film was measured according to JIS K7105 using a turbidity meter (NDH 2000) manufactured by Nippon Denshoku Industries Co., Ltd.

[0056] (7) Water absorption elongation of semi-aromatic polyamide film

The semi-aromatic polyamide film was left to lie in an environment of 20ºC and 40% relative humidity (RH) for 2 days, and then a test piece (width 200 mm × length 300 mm) was cut out, and a base length of 100 mm was noted in the longitudinal direction and in the direction of the width. The test piece was subjected to a moisture absorption treatment in an environment of 20ºC and 90% relative humidity (RH) for 2 days, and then the base length in the longitudinal direction and the width direction were measured, and the moisture absorption elongation of the test piece in the longitudinal direction was determined. and in the direction of the width according to the following formula:

moisture absorption elongation (%)=[{length after moisture absorption treatment-original length}/original length]×100

The absolute value of the difference between the moisture absorption elongation N _MD in the longitudinal direction and the moisture absorption elongation N _TD in the width direction, (|N _MD -N _TD |), was also calculated, and the anisotropy of the moisture absorption relative elongation was evaluated according to the following criteria:

Excellent: |N _MD -N _TD | is less than 0.20

Good: |N _MD -N _TD | is 0.20 or more and less than 0.30

Acceptable: |N _MD -N _TD | is 0.30 or more

[0057] (8) Laminate deformation

An aqueous dispersion of an acid-based polyamide resin (manufactured by UNITIKA LTD., solids concentration 20% by mass) and an aqueous dispersion containing an oxazoline group-containing polymer (manufactured by NIPPON SHOKUBAI CO., LTD., EPOCROS WS-700, solids concentration 25% by weight) were mixed so that the respective solids levels were 100 parts by weight and 10 parts by weight, and stirred at room temperature for 5 minutes to obtain a coating agent.

A film fragment (width 200 mm×length 300 mm) was cut out from a semi-aromatic polyamide film in a completely dry state immediately after production, and a coating agent was applied to the film fragment with a thickness of 3 μm after drying, and dried under a temperature of 150ºC and for 30 seconds with the formation of an adhesive layer on a film fragment. In addition, electrolytic copper foil (manufactured by Furukawa Electric Co., Ltd., with CTS-treated surface, thickness 18 µm) with the same size as the film piece and the film piece were laminated with this adhesive layer placed therebetween, to obtaining a multilayer material. Lamination was carried out under a temperature of 180ºC, with a duration of 15 minutes, and at a pressure of 2 MPa using a hot pressing machine.

A test piece (100 mm wide x 100 mm long) was cut from the resulting laminate, heat treated for 15 seconds in a reflow oven set at 260ºC, then removed from the oven and allowed to cool to room temperature (23ºC) in within 1 hour. The deformation of the laminate after heat treatment was checked visually and evaluated according to the following criteria:

Excellent: the laminate is not deformed at all.

Good: planarity is not broken, but there is a slight deformation.

Acceptable: The laminate exhibits deformation, but without causing practical problems.

Bad: the multilayer material is severely deformed and unsuitable for practical use.

[0058] (9) Moisture Absorption Curling of Laminate

A test piece (100 mm wide x 100 mm long) was cut from the laminate obtained in section (8), placed on a flat table with the film side down, and left to stand in an environment of 20°C and 40% relative humidity (RH ) for 2 days to control humidity. The test piece was then left to stand in an environment of 20°C and 90% relative humidity (RH) for 2 days. The hygroscopicity of the film was evaluated by the degree of curl of the test piece, that is, by the height of the edges of the test piece raised on the table when the test piece was twisted due to moisture absorption and elongation of the semi-aromatic polyamide film only, since copper foil does not exhibit moisture absorption.

Excellent: the test piece does not curl.

Good: The test piece is slightly curled in the film length direction or in the width direction. No problem for practical application.

Acceptable: The test piece is twisted in the film length direction or in the width direction. The test sample does not pose a problem for practical use.

[0059] 2. Raw materials

(1) Semi-aromatic polyamide

The semi-aromatic polyamides A and B obtained in the following Production Examples 1 and 2 were used.

Example 1 receive

3289 parts by weight terephthalic acid (TA), 2533 parts by weight 1,9-nonanediamine (NDA), 633 parts by weight 2-methyl-1,8-octanediamine (MODA), 48.9 parts by weight benzoic acid (BA ), 6.5 parts by weight (0.1% by weight based on all of the four polyamide starting materials) of sodium hypophosphite monohydrate, and 2200 parts by weight of distilled water were placed in a reaction kettle and purged with nitrogen. The molar ratio of these starting materials (TA/BA/NDA/MODA) is 99/2/80/20.

The contents of the reaction kettle was stirred at 100°C for 30 minutes, and then the internal temperature was raised to 210°C for 2 hours. At this time, the pressure inside the reaction kettle increased to 2.12 MPa (22 kg/cm ² ). The reaction was continued for 1 hour in this state, and then the temperature was raised to 230°C. Then, the reaction was carried out for 2 hours and kept at 230°C, and in parallel, water vapor was gradually removed to maintain the pressure at 2.12 MPa (22 kg/cm ² ). Then, the pressure was reduced to 0.98 MPa (10 kg/cm ² ) over 30 minutes, and the reaction was further carried out for 1 hour to obtain a prepolymer. The prepolymer was dried at 100° C. under reduced pressure for 12 hours, and then crushed to a size of 2 mm or less.

Then, the crushed prepolymer was subjected to solid-state polymerization under a temperature of 230°C and a pressure of 13.3 Pa (0.1 mmHg) for 10 hours to obtain a polymer. The resin was sent to a twin screw extruder (manufactured by The Japan Steel Works, Ltd., TEX44C), melted and kneaded under barrel temperature conditions of 320°C, extruded, cooled, and cut to obtain semi-aromatic polyamide A pellets.

[0060] Obtaining Example 2

489 parts by weight terephthalic acid (TA), 507 parts by weight 1,10-decanediamine (DDA), 2.8 parts by weight benzoic acid (BA), 1.0 parts by weight (0.1% by weight calculated all of the three polyamide starting materials) sodium hypophosphite monohydrate, and 1000 parts by weight of distilled water were placed in a reaction kettle and purged with nitrogen. The molar ratio of these starting materials (TA/BA/DDA) is 99/2/100.

The contents of the reaction kettle was stirred at a speed of 28 rpm at 80ºC for 0.5 hours, and then heated to 230ºC. The contents were then heated at 230°C for 3 hours. The reaction product was then cooled and recovered.

The reaction product was pulverized and then heated in a dryer under a stream of nitrogen gas at 220° for 5 hours to perform solid state polymerization to form a polymer. The resin was sent to a twin screw extruder (manufactured by The Japan Steel Works, Ltd., TEX44C), melted and kneaded under barrel temperature conditions of 320°C, extruded, cooled, and cut to obtain semi-aromatic polyamide B pellets.

[0061] The melting points, glass transition temperature, and intrinsic viscosity of the resulting semi-aromatic polyamides are shown in Table 1.

[0062]

[Table 1]

Semi-aromatic polyamide type Molar ratio of starting materials of semi-aromatic polyamide Physical Properties Acid component Amine component Intrinsic viscosity [η] The melting temperature Glass transition temperature Terephthalic acid (TA) Benzoic acid (BA) 1,9-nonanediamine (NDA) 2-methyl-1,8-octanediamine (MODA) 1,10-decandiamine (DDA) dL/g ºС ºС A 99 2 80 twenty 0 1.17 290 125 B 99 2 0 0 100 1.24 316 150

[0063] (2) Silicon oxide

Used base samples from (M1) to (M3), containing 2% by weight of silicon oxide, obtained in the following Examples 3-5 production.

Receive Example 3

98 parts by weight of semi-aromatic polyamide A and 2 parts by weight of silica (manufactured by FUJI SILYSIA CHEMICAL LTD., SYLYSIA 310P, average particle diameter 2.7 µm) were melted and kneaded to obtain base samples (M1) containing 2% by weight silicon oxide.

[0064] Obtaining Example 4

98 parts by weight of semi-aromatic polyamide B and 2 parts by weight of silica (manufactured by FUJI SILYSIA CHEMICAL LTD., SYLYSIA 310P, average particle diameter 2.7 µm) were melted and kneaded to obtain base samples (M2) containing 2% by weight silicon oxide.

[0065] Obtaining Example 5

98 parts by weight of semi-aromatic polyamide A and 2 parts by weight of silica (manufactured by Tosoh Silica Corporation, NIPGEL AZ-200, average particle diameter 2.0 µm) were melted and kneaded to obtain base samples (M3) containing 2% by weight silicon oxide.

[0066] (3) Hindered phenol thermal stabilizer

GA starting material: 3,9-bis[2-{3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy}-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[ 5.5]undecane (manufactured by Sumitomo Chemical Co., Ltd., SUMILIZER GA-80, pyrolysis temperature 392ºC).

[0067] Example 1

Semi-aromatic polyamide A, GA, and base samples (M1) were mixed so that the content of GA was 0.2 parts by mass, and the content of silicon oxide was 0.1 parts by mass, based on 100 parts by mass of semi-aromatic polyamide A.

This mixture was loaded into a single screw extruder with a diameter of 65 mm, having a barrel temperature adjusted to 295ºC (first stage), 320ºC (middle stage), and 320ºC (last stage), melted, extruded through a T-die to form a sheet-like extrudate set to 320°C, electrostatically mounted on a chill roll having a surface temperature adjusted to 40°C, and cooled to produce a substantially non-oriented, unstretched sheet having a thickness of 250 µm.

As the chill roll, a chill roll having a ceramic material (Al ₂ O ₃ ) surface coating with a thickness of 0.15 mm was used. On the upstream side of the contact point of the drum surface with the film, two carbon brushes were placed and brought into contact with the cooling drum, and the carbon brush holder was grounded to remove the charge from the surface of the ceramic coating layer. A tungsten wire having a diameter of 0.2 mm was used as the electrode, and a voltage of 6.5 kV DC with a power of 300 W (15 kV×20 mA) was applied from a high voltage current generating device.

The resulting unstretched sheet was cut into 12×12 cm pieces, placed in a batch-type biaxial stretching machine (manufactured by Imoto machinery Co., LTD., ICM-18BE), and subjected to simultaneous biaxial stretching. With respect to stretching conditions, the preheating and stretching temperatures were 115ºC, the stretching strain rates in the longitudinal direction and in the width direction were 3200%/min, and the stretching ratios in the longitudinal direction and in the width direction were 3.0 times and 3.3 times, respectively.

After stretching, heat-setting treatment was carried out at 275° C. for 10 seconds, and relaxation treatment at relaxation rates of 1.0% in the longitudinal direction and 8.0% in the width direction, to obtain a semi-aromatic polyamide film having a thickness of 25 μm. The stretching treatment of the unstretched sheet and the relaxation treatment of the stretched film were carried out along the extrusion direction when the unstretched sheet was formed along the longitudinal direction, and along the direction perpendicular to the extrusion direction when formed along the width direction.

[0068] Examples 2-16 and 18, and Comparative Examples 1-15

A semi-aromatic polyamide film was obtained as in Example 1, except that the semi-aromatic polyamide type, chill roll surface temperature, stretch ratios, heat-setting temperature, and relaxation rates were changed as described in Table 2, 3, 5, or 6 In Example 18, base samples (M2) were used instead of base samples (M1). In Comparative Examples 1 and 3, base samples (M1) were not used, and a semi-aromatic polyamide film containing no silicon oxide was obtained.

[0069] Example 17

Semi-aromatic polyamide A and base samples (M1) were mixed so that the content of silicon oxide was 0.1 parts by mass. This mixture was loaded into extruder A, the barrel temperature was adjusted to 295°C (first stage), 320°C (middle stage) and 320°C (last stage), and the mixture was melt-extruded (hereinafter referred to as resin X).

On the other hand, the semi-aromatic polyamide A was loaded into the extruder B, the barrel temperature was adjusted to 295°C (first stage), 320°C (middle stage) and 320°C (last stage), and the semi-aromatic polyamide A was melt extruded (hereinafter referred to as resin Y).

Resins X and Y, melted in extruders A and B, respectively, were extruded into sheet-like extrudates from a T-die set at 320°C so as to obtain three-layer structures X/Y/X, electrostatically fixed on a cooling drum having a surface temperature of 40°C, and pre-cooled, and then further cooled on a chill roll having a surface temperature of 20°C to obtain an unstretched film having a total thickness of 500 µm with a ratio of X/Y/X=100/300/100 µm. The specifications of the chill rolls, voltage application method, and the like are the same as in Example 1.

The resulting unstretched sheet was cut into 12×12 cm pieces, placed in a batch-type biaxial stretching machine (manufactured by Imoto machinery Co., LTD., ICM-18BE), and subjected to simultaneous biaxial stretching. With respect to stretching conditions, the preheating and stretching temperatures were 115ºC, the stretching strain rates in the longitudinal direction and in the width direction were 3200%/min, and the stretching ratios in the longitudinal direction and in the width direction were 3.0 times and 3.3 times, respectively.

After stretching, heat-setting treatment was carried out at 275° C. for 10 seconds, and relaxation treatment was carried out at relaxation rates of 2.0% in the longitudinal direction and 8.0% in the width direction, to obtain a semi-aromatic polyamide film having a thickness of 50 μm and having a layer structure of X /Y/X=10/30/10 µm.

[0070] Example 19

A semi-aromatic polyamide film was obtained in the same manner as in Example 1, except that successive biaxial stretching was carried out with stretching ratios in the longitudinal direction and in the width direction of 2.5 times and 3.3 times, respectively, and the relaxation treatment was performed at speeds relaxation in the longitudinal direction and in the width direction, amounting to 2.0% and 4.0%, respectively.

[0071] Examples 20-38 and Comparative Examples 16-21

A semi-aromatic polyamide film was obtained in the same manner as in Example 19, except that the semi-aromatic polyamide type, chill roll surface temperature, stretch ratios, heat-setting temperature, and relaxation rates were changed as described in Tables 3-6. In Example 29, base samples (M3) were used instead of base samples (M1).

[0072] The semi-aromatic polyamide compositions, film formation conditions, and characteristics of the resulting semi-aromatic polyamide films are shown in Tables 2-6.

[0073]

[Table 2]

Examples one 2 3 4 five 6 7 eight nine 10 eleven 12 Semi-aromatic polyamide composition Type of AND AND AND AND AND AND AND AND AND AND AND AND Silica content (%) 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Conditions for obtaining a semi-aromatic polyamide film Extrusion Chilled drum surface temperature (ºC) 40 40 40 40 40 40 40 40 40 40 40 40 Enthalpy of Crystallization of Unstretched Film (J/g) 27 27 27 27 27 27 27 27 27 27 27 27 stretching Degrees of stretching (times) Longitudinal direction 3.0 3.0 3.0 3.0 3.0 3.0 3.5 3.0 3.0 3.0 3.0 3.0 Width Direction 3.3 3.3 3.3 3.3 3.3 3.3 2.8 3.3 3.3 3.3 3.3 3.3 Stretching method Simultaneously Thermal fixation Temperature (ºC) 275 275 275 275 275 260 275 275 275 275 275 275 Relaxation Relaxation rates (%) Longitudinal direction 1.0 2.0 6.0 2.0 2.0 2.0 2.0 1.0 2.0 6.0 10.0 10.0 Width Direction 8.0 8.0 8.0 1.0 12.0 8.0 8.0 8.0 8.0 8.0 8.0 2.0 Characteristics of semi-aromatic polyamide film Thickness (µm) 25 25 25 25 25 25 25 fifty fifty fifty fifty fifty Thermal shrinkage ratios (%) (200ºC×15 minutes) Longitudinal direction - - - - - - - - - - - - Width Direction - - - - - - - - - - - - (250ºC×15 minutes) Longitudinal direction (S _MD ) 1.3 0.8 -0.2 0.9 0.7 1.5 1.2 1.1 0.5 0.1 -0.2 -0.2 Width Direction (S _TD ) 0.7 0.7 0.6 1.5 -0.4 1.2 0.1 0.4 0.2 0.1 0.0 0.9 |S _MD -S _TD | 0.6 0.1 0.8 0.6 1.1 0.3 1.1 0.7 0.3 0.0 0.2 1.1 Grade Okay Fine Acceptable Okay Acceptable Fine Acceptable Okay Fine Fine Fine Acceptable Tensile elongation to break (%) Longitudinal direction 12 130 141 129 130 144 92 132 140 147 148 148 Width Direction 90 96 102 78 100 121 154 103 110 120 122 99 Turbidity (%) 5.1 5.1 5.2 5.0 5.3 4.8 5.1 8.1 8.0 7.9 8.1 8.0 Elongation at moisture absorption (%) 20ºC×90% RH Longitudinal direction (N _MD ) 0.32 0.37 0.59 0.37 0.39 0.31 0.34 0.42 0.39 0.50 0.63 0.64 Width Direction (N _TD ) 0.61 0.60 0.62 0.30 0.71 0.52 0.66 0.61 0.63 0.66 0.67 0.32 |N _MD -N _TD | 0.29 0.23 0.03 0.07 0.32 0.21 0.32 0.19 0.24 0.16 0.04 0.32 Grade Okay Okay Great Great Acceptable Okay Acceptable Great Okay Great Great Acceptable Characteristics of the laminate Deformation (260°C×15 sec) Okay Great Acceptable Okay Acceptable Great Acceptable Okay Great Great Great Acceptable Wet curl 20°C×90%RH Okay Okay Fine Fine Acceptable Okay Acceptable Fine Okay Fine Fine Acceptable

[0074]

[Table 3]

Examples 13 fourteen fifteen 16 17 eighteen nineteen twenty 21 22 23 Semi-aromatic polyamide composition Type of AND AND AND AND AND AT AND AND AND AND AND Silica content (%) 0.1 0.1 0.1 0.1 0.1/0/0.1 0.1 0.1 0.1 0.1 0.1 0.1 Conditions for obtaining a semi-aromatic polyamide film Extrusion Chilled drum surface temperature (°C) 40 40 40 40 40 40 40 40 40 40 40 Enthalpy of Crystallization of Unstretched Film (J/g) 27 27 27 27 27 27 27 27 27 27 27 stretching Degrees of stretching (times) Longitudinal direction 3.0 3.0 3.0 3.5 3.0 2.5 2.5 2.3 2.3 2.3 2.3 Width Direction 3.3 3.3 3.3 2.8 3.3 2.5 3.3 3.5 3.5 3.5 3.5 Stretching method Simultaneously Consistently Thermal fixation Temperature (ºC) 275 275 260 275 275 280 275 275 275 275 275 Relaxation Relaxation rates (%) Longitudinal direction 2.0 2.0 2.0 2.0 2.0 2.0 2.0 1.0 2.0 6.0 2.0 Width Direction 1.0 12.0 8.0 8.0 8.0 8.0 4.0 8.0 8.0 8.0 1.0 Characteristics of semi-aromatic polyamide film Thickness (µm) fifty fifty fifty fifty fifty 25 25 25 25 25 25 Thermal shrinkage ratios (%) (200ºC×15 minutes) Longitudinal direction - - - - - - - - - - - Width Direction - - - - - - - - - - - (250ºC×15 minutes) Longitudinal direction (S _MD ) 0.6 0.5 1.2 1.0 0.5 0.3 0.8 1.1 0.8 -0.1 0.8 Width Direction (S _TD ) 1.3 -0.4 0.9 -0.1 0.2 0.0 0.9 0.5 0.4 0.2 1.5 |S _MD -S _TD | 0.7 0.9 0.3 1.1 0.3 0.3 0.1 0.6 0.4 0.3 0.7 Grade Okay Acceptable Fine Acceptable Fine Fine Fine Okay Okay Fine Okay Tensile elongation to break (%) Longitudinal direction 137 138 131 77 146 110 108 103 105 123 111 Width Direction 75 94 112 149 113 119 107 109 104 101 92 Turbidity (%) 8.1 8.0 7.8 8.0 5.0 6.7 3.9 4.0 4.0 3.9 3.9 Elongation at moisture absorption (%) 20ºC×90% RH Longitudinal direction (N _MD ) 0.34 0.38 0.33 0.43 0.39 0.47 0.37 0.35 0.37 0.54 0.37 Width Direction (N _TD ) 0.49 0.70 0.56 0.60.6 0.63 0.62 0.50 0.63 0.64 0.65 0.33 |N _MD -N _TD | 0.15 0.32 0.23 0.25 0.24 0.15 0.13 0.28 0.27 0.11 0.04 Grade Fine Acceptable Okay Okay Okay Fine Fine Okay Okay Fine Fine Laminate Characteristics Deformation (260ºC×15 sec) Okay Acceptable Fine Acceptable Fine Fine Fine Okay Okay Fine Okay Wet curl 20ºC×90% RH Fine Acceptable Okay Okay Okay Fine Fine Okay Okay Fine Fine

[0075]

[Table 4]

Examples 24 25 26 27 28 29 thirty 31 32 33 34 35 Semi-aromatic polyamide composition Type of AND AND AND AND AND AND AND AND AND AND AND AND Silica content (%) 0.1 0.1 0.1 0.1 0.1 0.2 0.1 0.1 0.1 0.1 0.1 0.1 Conditions for obtaining a semi-aromatic polyamide film Extrusion Chilled drum surface temperature (ºC) 40 40 40 40 40 40 40 40 40 40 40 40 Enthalpy of Crystallization of Unstretched Film (J/g) 27 27 27 27 27 27 27 27 27 27 27 27 stretching Degrees of stretching (times) Longitudinal direction 2.3 2.3 2.5 2.3 2.3 2.3 2.3 2.3 2.3 2.3 2.3 2.3 Width Direction 3.5 3.5 3.3 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 Stretching method Consistently Thermal fixation Temperature (ºC) 275 260 275 275 275 260 275 275 275 275 275 260 Relaxation Relaxation rates (%) Longitudinal direction 2.0 2.0 2.0 1.0 2.0 2.0 6.0 10.0 10.0 2.0 2.0 2.0 Width Direction 12.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 2.0 1.0 12.0 8.0 Characteristics of semi-aromatic polyamide film Thickness (µm) 25 25 25 fifty fifty fifty fifty fifty fifty fifty fifty fifty Thermal shrinkage ratios (%) (200ºC×15 minutes) Longitudinal direction - - - - - - - - - - - - Width Direction - - - - - - - - - - - - (250ºC×15 minutes) Longitudinal direction (S _MD ) 0.7 1.5 1.3 1.1 0.9 0.9 0.1 -0.2 -0.1 1.0 0.8 1.4 Width Direction (S _TD ) 0.7 0.7 0.6 1.5 -0.4 1.2 0.1 0.4 0.2 0.1 0.0 0.9 |S _MD -S _TD | 0.8 0.3 1.0 0.7 0.6 0.6 0.0 0.2 1.1 0.3 1.0 0.5 Grade Acceptable Fine Acceptable Okay Okay Okay Fine Fine Acceptable Fine Acceptable Okay Tensile elongation to break (%) Longitudinal direction 95 131 94 106 109 110 128 129 129 118 100 134 Width Direction 113 130 131 110 107 109 103 103 96 94 121 132 Turbidity (%) 4.1 3.6 4.4 7.2 7.3 12.8 7.2 7.3 7.3 7.3 7.4 6.6 Elongation at moisture absorption (%) 20°C×90%RH Longitudinal direction (N _MD ) 0.39 0.37 0.35 0.38 0.42 0.41 0.50 0.65 0.65 0.39 0.42 0.39 Width Direction (N _TD ) 0.66 0.49 0.61 0.64 0.66 0.66 0.67 0.70 0.35 0.36 0.71 0.52 |N _MD -N _TD | 0.27 0.12 0.26 0.26 0.24 0.25 0.17 0.05 0.30 0.03 0.29 0.13 Grade Okay Fine Okay Okay Okay Okay Fine Fine Acceptable Fine Okay Acceptable Characteristics of the laminate Deformation (260ºC×15 sec) Acceptable Fine Acceptable Okay Okay Okay Fine Fine Acceptable Fine Acceptable Okay Wet curl 20ºC×90% RH Okay Fine Okay Okay Okay Okay Fine Fine Acceptable Fine Okay Fine

[0076]

[Table 5]

Examples Comparative Examples 36 37 38 one 2 3 4 five 6 7 eight nine Semi-aromatic polyamide composition Type of AND AND AND AND AND AND AND AND AND AND AND AND Silica content (%) 0.1 0.1 0.1 - 0.1 - 0.1 0.1 0.1 0.1 0.1 0.1 Conditions for obtaining a semi-aromatic polyamide film Extrusion Chilled drum surface temperature (ºC) 40 40 40 fifty fifty fifty fifty fifty 60 70 70 80 Enthalpy of Crystallization of Unstretched Film (J/g) 27 27 27 nineteen nineteen nineteen nineteen nineteen 16 10 10 one stretching Degrees of stretching (times) Longitudinal direction 25 2.3 2.3 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 Width Direction 3.3 3.5 3.5 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3 Stretching method Consistently Simultaneously Thermal fixation Temperature (ºC) 275 275 275 270 270 270 270 275 275 275 275 - Relaxation Relaxation rates (%) Longitudinal direction 2.0 1.0 1.0 0.0 0.0 2.0 2.0 1.0 1.0 2.0 2.0 - Width Direction 8.0 8.0 8.0 5.0 5.0 5.0 5.0 8.0 8.0 8.0 8.0 - Characteristics of semi-aromatic polyamide film Thickness (µm) fifty 75 100 25 25 25 25 25 25 25 fifty - Thermal shrinkage ratios (%) (200ºC×15 minutes) Longitudinal direction - - - 0.4 0.4 0.0 0.0 - - - - - Width Direction - - - 0.1 0.1 -0.1 -0.1 - - - - - (250ºC×15 minutes) Longitudinal direction (S _MD ) 1.3 1.0 0.9 2.5 2.5 1.3 1.3 1.2 1.1 0.7 0.4 - Width Direction (S _TD ) 0.2 0.3 0.1 1.1 1.1 1.0 1.0 0.6 0.6 0.5 0.1 - |S _MD -S _TD | 1.1 0.7 0.8 1.4 1.4 0.3 0.3 0.6 0.5 0.2 0.3 - Grade Acceptable Okay Acceptable Badly Badly Fine Fine Okay Okay Fine Acceptable - Tensile elongation to break (%) Longitudinal direction 97 112 120 98 95 111 109 107 99 93 105 - Width Direction 134 113 118 64 62 69 67 65 61 60 75 - Turbidity (%) 7.1 10.3 13.6 1.5 7.1 1.5 7.1 7.2 8.6 11.1 14.4 - Elongation at moisture absorption (%) 20ºC×90% RH Longitudinal direction (N _MD ) 0.36 0.40 0.43 0.21 0.22 0.31 0.31 0.33 0.36 0.27 0.43 - Width Direction (N _TD ) 0.64 0.67 0.69 0.54 0.53 0.55 0.55 0.61 0.60 0.55 0.68 - |N _MD -N _TD | 0.28 0.27 0.26 0.33 0.31 0.24 0.24 0.28 0.24 0.28 0.25 - Grade Okay Okay Okay Acceptable Acceptable Okay Okay Okay Okay Okay Okay - Laminate Characteristics Deformation (260ºC×15 sec) Acceptable Okay Acceptable Badly Badly Fine Fine Okay Okay Fine Fine - Wet curl 20ºC×90% RH Okay Okay Okay Acceptable Acceptable Okay Okay Okay Okay Okay Okay -

[0077]

[Table 6]

Comparative Examples 10 eleven 12 13 fourteen fifteen 16 17 eighteen nineteen twenty 21 Semi-aromatic polyamide composition Type of AND AND AND AND AND AND AND AND AND AND AND AND Silica content (%) 0.1 0.1 0.1 0.1 0.1 0.2 0.1 0.1 0.1 0.1 0.1 0.2 Conditions for obtaining a semi-aromatic polyamide film Extrusion Chilled drum surface temperature (ºC) 40 40 40 40 40 40 40 40 fifty fifty 70 40 Enthalpy of Crystallization of Unstretched Film (J/g) 27 27 27 nineteen nineteen nineteen nineteen nineteen nineteen nineteen 10 27 stretching Degrees of stretching (times) Longitudinal direction 3.0 3.0 3.0 3.0 3.0 3.0 2.3 2.8 2.3 2.3 2.5 2.3 Width Direction 3.3 3.3 3.3 3.3 3.3 3.3 3.5 3.5 3.5 3.5 3.3 3.5 Stretching method Simultaneously Consistently Thermal fixation Temperature (ºC) 275 275 250 290 275 275 250 275 275 275 275 275 Relaxation Relaxation rates (%) Longitudinal direction 0.0 2.0 2.0 - 1.0 2.0 2.0 2.0 2.0 2.0 - 2.0 Width Direction 8.0 0.0 0.0 - 8.0 8.0 8.0 8.0 8.0 8.0 - 8.0 Characteristics of semi-aromatic polyamide film Thickness (µm) 25 25 25 - 75 fifty 25 fifty 75 100 - fifty Thermal shrinkage ratios (%) (200ºC×15 minutes) Longitudinal direction - - - - - - - - - - - - Width Direction - - - - - - - - - - - - (250ºC×15 minutes) Longitudinal direction (S _MD ) 2.0 1.0 4.5 - - 0.7 4.3 1.5 0.5 0.3 - 0.9 Width Direction (S _TD ) 0.8 2.2 3.2 - - 0.2 3, 0.6 0.2 0.0 - 0.5 |S _MD -S _TD | 1.2 1.2 1.3 - - 0.5 1.2 0.9 0.3 0.3 - 0.4 Grade Badly Badly Badly - - Okay Badly Acceptable Fine Fine - Okay Tensile elongation to break (%) Longitudinal direction nineteen 122 150 - - 129 131 100 100 106 - 100 Width Direction 86 73 128 - - 99 133 65 67 69 - 97 Turbidity (%) 5.2 5.0 4.5 - - 17.5 3.6 14.6 15.1 18.3 - 15.2 Elongation at moisture absorption (%) 20ºC×90% RH Longitudinal direction (N _MD ) 0.24 0.37 0.08 - - 0.33 0.09 0.29 0.40 0.45 - 0.42 Width Direction (N _TD ) 0.57 0.23 0.16 - - 0.63 0.16 0.61 0.65 0.69 - 0.62 |N _MD -N _TD | 0.33 0.14 0.08 - - 0.30 0.07 0.32 0.25 0.24 - 0.20 Grade Acceptable Fine Fine - - Acceptable Fine Acceptable Okay Okay - Okay Laminate Characteristics Deformation (260ºC×15 sec) Badly Badly Badly - - Okay Badly Acceptable Fine Fine - Okay Wet curl 20ºC×90% RH Acceptable Fine Fine - - Acceptable Fine Acceptable Okay Okay - Okay

[0078] The semi-aromatic polyamide films of Examples 1-38 satisfied all of the performance values defined in the present invention and had low thermal shrinkage ratios, low haze, and sufficiently high elongation at break.

In other words, in the production of a semi-aromatic polyamide film, by lowering the surface temperature of the chill roll, an unstretched film having an increased enthalpy of crystallization was obtained, and, with respect to a semi-aromatic polyamide film, by using an unstretched film having an increased enthalpy of crystallization, the elongation at break increased and decreased haze, and as a result of performing relaxation treatment in the longitudinal direction and in the width direction, thermal shrinkage coefficients in the longitudinal direction and in the width direction were reduced, and an increase in elongation at break was stimulated.

[0079] In Comparative Example 1, as in Example 2 of Patent Document 1, a semi-aromatic polyamide containing no silicon oxide was used, and an unstretched film was obtained using a chill roll having a surface temperature of 50°C, followed by stretching 3.0 times in the longitudinal direction and 3.3 times in the width direction, heat setting at 270ºС, and then relaxation at a relaxation rate of 5.0% only in the longitudinal direction.

The unstretched film obtained using a chill roll having a surface temperature of 50° C. had a crystallization enthalpy of 19 J/g.

As for the semi-aromatic polyamide film obtained from this unstretched film, the thermal shrinkage ratios measured under conditions of 200°C and 15 minutes were low, 0.4% in the longitudinal direction and 0.1% in the width direction, but the thermal shrinkage ratio in the longitudinal direction was increased to 2.5% when the measurement was carried out under conditions with a temperature of 250°C and 5 minutes. The elongation at break was 98% in the longitudinal direction, but in the width direction was low at 64%.

With respect to the semi-aromatic polyamide film of Comparative Example 2 obtained as in Comparative Example 1, except that a semi-aromatic polyamide containing silicon oxide was used, an increase in haze was observed.

[0080] Semi-aromatic polyamide films of Comparative Examples 3 and 4 were prepared as in Comparative Examples 1 and 2, except that relaxation was also carried out at a relaxation rate of 2.0% in the longitudinal direction. The thermal shrinkage ratio in the longitudinal direction decreased to 1.3%, but the elongation at break in the width direction did not change, and was low, ranging from 67 to 69%.

[0081] In Comparative Examples 5 to 9, a semi-aromatic polyamide containing silicon oxide was used, and an unstretched film was obtained using a chill roll having a surface temperature of 50° C. or more. The films of Comparative Examples 5-7 using this unstretched film had a low elongation at break in the width direction, as in Comparative Examples 1-4. With respect to the film of Comparative Example 8, the increase in elongation at break was suppressed, but haze was high. In Comparative Example 9, a tear occurred during stretching of the film, and no biaxially stretched film was obtained.

With regard to the films of Comparative Examples 10-11, relaxation treatment in a given direction was not carried out, and therefore the thermal shrinkage coefficient was high in this direction. With respect to the film of Comparative Example 12, the temperature in the fusing step was low, and therefore the thermal shrinkage coefficients were high. Dimensional stability was poor in all cases.

In Comparative Example 13, tearing occurred during the fusing treatment, and in Comparative Example 14, simultaneous biaxial stretching was attempted using a thick unstretched film, but no biaxially stretched film was obtained in both cases.

With respect to the film of Comparative Example 15, the silica content was high, and therefore the haze was high.

[0082] Also with respect to the film of Comparative Example 16 using the serial biaxial stretching method, the temperature in the fusing step was low, and therefore the thermal shrinkage coefficients were high, and the dimensional stability was poor. With respect to the film of Comparative Example 17, the stretching rates were outside the preferred ranges, and therefore the elongation at break was less than 70% and haze was high. With respect to the films of Comparative Examples 18 and 19, the enthalpy of crystallization of the unstretched film was small, and therefore the elongation at break was less than 70%, and the haze was high. In Comparative Example 20, a break occurred during transverse stretching, and no biaxially stretched film was obtained. With respect to the film of Comparative Example 21, the silica content was high, and therefore the haze was high.

Claims (14)

1. Semi-aromatic polyamide film having a thermal shrinkage ratio in the film longitudinal direction, S _MD , from -0.1 to 1.5%, and a thermal shrinkage ratio in the width direction, S _TD , from -0.1 to 1.5% , when measured at 250ºC and 5 minutes, an elongation at break of 70% or more in the longitudinal direction and in the width direction, and turbidity 14% or less. 2. The film of claim. 1, in which the absolute value of the difference between S _MD and S _TD (|S _MD -S _TD |) is less than 1.2. 3. A method for producing a semi-aromatic polyamide film according to claim 1, including: biaxial stretching of an unstretched film of semi-aromatic polyamide, and in biaxial stretching: using an unstretched film having a crystallization enthalpy of 20 J/g or more, the degree of stretching is 2.0 to 3.5 times in the longitudinal direction and 2.0 to 4.0 times in the width direction, tensile strain rates in the longitudinal direction and in the width direction are more than 400%/min and 12000%/min or less, and the tensile temperature is the glass transition temperature (Tg) of the semi-aromatic polyamide or more and (Tg+50°C) or less; thermosetting treatment of the film after biaxial stretching at a temperature of 260 to 280ºС, and relaxation processing of the film after thermosetting treatment at relaxation rates from 1.0 to 10.0% in the longitudinal direction and from 1.0 to 12.0% in the width direction. 4. An electronic material comprising a semi-aromatic polyamide film according to claim 1 or 2. 5. An optical component comprising a semi-aromatic polyamide film according to claim 1 or 2.