Semi-aromatic polyamide film and method for producing the same

Abstract

To provide a semi-aromatic polyamide film with a sufficiently small amount of sag. 【Solution means】The semi-aromatic polyamide film of the present invention is a rectangular semi-aromatic polyamide film having sides along the MD direction and sides along the TD direction, and the refractive index difference n R , C , L calculated from the following formula (1) is -0.0010 to 0.0045. Refractive index difference n D ={(n C -n L )-(n C -n R )} / 2 (1) (In the formula, n C is the refractive index in the MD direction at the central part of the film, n L is the refractive index in the MD direction at a position 10% inside the film width from the left end of the film, n R is the refractive index in the MD direction at a position 10% inside the film width from the right end of the film)

Description

Technical Field

[0001] The present invention relates to a semi-aromatic polyamide film with suppressed sag, a method for producing the same, and electronic materials and optical components including the semi-aromatic polyamide film.

Background Art

[0002] Semi-aromatic polyamide films stretched in the MD direction (longitudinal direction) and TD direction (width direction) of the film are used in various fields because of their excellent heat resistance and mechanical properties. Among the semi-aromatic polyamides constituting the semi-aromatic polyamide film, in particular, polyamide 9T composed of an aliphatic diamine having 9 carbon atoms and terephthalic acid, and polyamide 10T composed of an aliphatic diamine having 10 carbon atoms and terephthalic acid are excellent in heat resistance and mechanical properties.

[0003] Patent Document 1 discloses a biaxially stretched film obtained by biaxially stretching an unstretched film having a specific heat of crystallization, which is a film made of a semi-aromatic polyamide resin. However, the film disclosed in Patent Document 1 has a large amount of sag, and wrinkles may occur during winding or meandering may occur during running.

[0004] On the other hand, Patent Document 2 discloses that, for a film made of an aliphatic polyamide resin, the amount of sag can be controlled by the cooling rate of the film heat-fixed after biaxial stretching, and the amount of sag decreases when the cooling rate is lowered. However, the film disclosed in Patent Document 2 may generate distortion under conditions of being exposed to high temperatures.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] When the inventor applied the method described in Patent Document 2 to control the sag amount of the semi-aromatic polyamide film disclosed in Patent Document 1, the sag amount could not be made sufficiently small.

[0007] In recent years, optical films such as display members are also required to have dimensional stability such that no distortion occurs even under conditions of being exposed to high temperatures during transportation or heat processing.

[0008] An object of the present invention is to provide a semi-aromatic polyamide film having a sufficiently small sag amount.

[0009] Another object of the present invention is to provide a semi-aromatic polyamide film having a sufficiently small sag amount and excellent dimensional stability under high temperature conditions.

[0010] Another object of the present invention is to provide a method for producing a semi-aromatic polyamide film having a sufficiently small sag amount.

[0011] Another object of the present invention is to provide an electronic material or an optical component including the semi-aromatic polyamide film.

Means for Solving the Problems

[0012] As a result of intensive studies to solve the above problems, the present inventors have found that when an unstretched film or a film uniaxially stretched in the MD direction is preheated at a specific temperature and then stretched, and cooled at a specific temperature after stretching, the refractive index in the MD direction in each of the central portion, the left end portion, and the right end portion in the TD direction of the obtained film can be adjusted within a specific range, and the sag amount can be made sufficiently small. Further, when an unstretched film or a film uniaxially stretched in the MD direction is preheated at a specific temperature and then stretched, heat-fixed at a specific temperature after stretching, and further cooled at a specific temperature, it has been found that the sag amount of the obtained film can be made sufficiently small, and the dimensional stability under high temperature conditions can be improved.

[0013] The present invention has been completed based on the above findings.

[0014] That is, the present invention is a rectangular semi-aromatic polyamide film having sides along the MD direction and sides along the TD direction, The refractive index difference n D calculated from the following formula (1) is -0.0010 to 0.0045, and provides a semi-aromatic polyamide film.

[0015] Refractive index difference n D = {(n C - n L ) - (n C - n R )} / 2 (1) (In the formula, n C is the refractive index in the MD direction at the central portion of the film, n L is the refractive index in the MD direction at a position within 10% of the film width from the left end of the film, n R is the refractive index in the MD direction at a position within 10% of the film width from the right end of the film. The central portion, the left end portion, and the right end portion are located on a straight line parallel to the TD direction of the film) The present invention also provides the above semi-aromatic polyamide film, wherein the average refractive index value n Av calculated from the following formula (2) is 1.5985 to 1.6045.

[0016] Average refractive index n Av =(n C +n L +n R ) / 3 (2) (In the formula, n C , n L , and n R (This is the same as above.) The present invention also provides the semi-aromatic polyamide film having a sag amount of 3.0‰ or less, as measured by the following measurement method. <Method for measuring sagging amount> The length in the MD direction is measured in 50 mm increments from one end to the other of one side along the TD direction, and the amount of sag is calculated from the maximum and minimum values ​​of the said length using the following formula (3).

[0017] Sagging amount (‰) = (Maximum value - Minimum value) ÷ Maximum value × 1000 (3) The present invention also relates to the thermal shrinkage rate S in the MD direction, which is determined by measuring the dimensions after leaving the material in a 250°C atmosphere for 5 minutes, followed by leaving it in a 23°C and 50% RH atmosphere for 2 hours. MD and thermal shrinkage coefficient S in the TD direction TD The present invention provides the semi-aromatic polyamide film, wherein each of these concentrations is -1.0 to 1.5%.

[0018] The present invention also provides a method for producing a semi-aromatic polyamide film, comprising the steps of [1] or [2] below. [1] A step of preheating an unstretched semi-aromatic polyamide film at a temperature of (Tg-9)°C to (Tg+5)°C, based on the glass transition temperature Tg of the semi-aromatic polyamide; a step of simultaneously stretching the film in the MD direction and the TD direction; and a step of cooling the film at a temperature of (Tm-260)°C to (Tm-170)°C, based on the melting point Tm of the semi-aromatic polyamide. [2] A uniaxially stretched film of semi-aromatic polyamide in the MD direction is preheated at a temperature of (Tg-9)°C to (Tg+5)°C based on the Tg of the semi-aromatic polyamide, stretched in the TD direction, and cooled at a temperature of (Tm-260)°C to (Tm-170)°C based on the melting point Tm of the semi-aromatic polyamide. The present invention also provides an electronic material comprising the semi-aromatic polyamide film.

[0019] The present invention also provides an optical component comprising the semi-aromatic polyamide film. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide a semi-aromatic polyamide film that has a sufficiently small amount of sag (or has a sufficiently small amount of sag and exhibits excellent dimensional stability even under high temperature conditions of 250°C).

[0021] The semi-aromatic polyamide film of the present invention can be suitably used as an electronic material such as a base film or coverlay film for flexible printed circuit boards; an optical material such as a substrate for displays; and a heat-resistant tape. [Brief explanation of the drawing]

[0022] [Figure 1] Figure 1 illustrates a method for measuring the amount of sag, using the case of edge sag as an example. [Modes for carrying out the invention]

[0023] [Semi-aromatic polyamide film] The semi-aromatic polyamide film of the present invention is a rectangular semi-aromatic polyamide film having sides aligned along the MD direction and sides aligned along the TD direction, and is a film containing at least a semi-aromatic polyamide as a resin component. <Semi-aromatic polyamide> Semi-aromatic polyamides contain, as monomer components (in other words, monomer-derived components), dicarboxylic acid components (in other words, dicarboxylic acid-derived components) and diamine components (in other words, diamine-derived components). Furthermore, the dicarboxylic acid components contain at least aromatic dicarboxylic acid components, and the diamine components contain at least aliphatic diamine components.

[0024] Semi-aromatic polyamides may contain other components besides dicarboxylic acid and diamine components, but in order to obtain films with excellent heat resistance and low water absorption, the total content of dicarboxylic acid and diamine components is preferably, for example, 50% by mass or more of all components constituting the semi-aromatic polyamide, more preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and most preferably 95% by mass or more.

[0025] Furthermore, while the semi-aromatic polyamide may contain other components besides the aromatic dicarboxylic acid component and the aliphatic diamine component, in order to obtain a film with excellent heat resistance and low water absorption, the total content of the aromatic dicarboxylic acid component and the aliphatic diamine component is preferably, for example, 50% by mass or more of the total components constituting the semi-aromatic polyamide, more preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and most preferably 95% by mass or more.

[0026] The dicarboxylic acid forming the dicarboxylic acid component includes at least an aromatic dicarboxylic acid, and the diamine forming the diamine component includes at least an aliphatic diamine.

[0027] The aromatic dicarboxylic acid preferably contains 60 mol% or more of terephthalic acid, more preferably 70 mol% or more, and even more preferably 85 mol% or more, in terms of excellent heat resistance and low water absorption.

[0028] Examples of aromatic dicarboxylic acids other than terephthalic acid include isophthalic acid and naphthalenedicarboxylic acid. Furthermore, naphthalenedicarboxylic acid includes the 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.

[0029] In addition to aromatic dicarboxylic acids, other dicarboxylic acids may be included in the present invention, as long as they do 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, dodecanediic acid, tetradecanediic acid, and octadecanediic acid.

[0030] The aliphatic diamine preferably contains aliphatic diamines having 6 to 12 carbon atoms as its main component. The content of aliphatic diamines having 6 to 12 carbon atoms in the total amount of aliphatic diamines is preferably 60 mol% or more, more preferably 75 mol% or more, and even more preferably 90 mol% or more. When the content of aliphatic diamines having 6 to 12 carbon atoms is 60 mol% or more, the resulting film can achieve both heat resistance and productivity. The aliphatic diamines having 6 to 12 carbon atoms may be used alone or in combination of two or more. When two or more are used in combination, the above content refers to their total content.

[0031] Examples of aliphatic diamines with 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.

[0032] The aliphatic diamine is more preferably composed mainly of aliphatic diamines having 9 to 12 carbon atoms, and even more preferably of polyamide 9T containing a 9-carbon aliphatic diamine as the main component, or polyamide 10T containing a 10-carbon aliphatic diamine as the main component.

[0033] The aliphatic diamine may include not only aliphatic diamines having 6 to 12 carbon atoms, but also (linear) aliphatic diamines having 6 or fewer carbon atoms, such as 1,4-butanediamine and 1,5-pentanediamine.

[0034] The diamine forming the diamine component may contain other diamines besides aliphatic diamines, as long as the effects of the present invention are not impaired. Examples of other diamines include alicyclic diamines such as isophorone diamine, norbornane dimethylamine, and tricyclodecane dimethylamine; and aromatic diamines such as metaxylylenediamine, paraxylylenediamine, metaphenylenediamine, and paraphenylenediamine.

[0035] The semi-aromatic polyamide may contain lactam components (in other words, lactam-derived components) such as ε-caprolactam, ζ-enanthractam, η-capryllactam, and ω-laurolactam as monomer components, to the extent that it does not impair the effects of the present invention.

[0036] The types of monomer components and copolymerization ratios 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. A Tm of 350°C or lower allows for efficient suppression of thermal decomposition during film processing. Furthermore, a Tm of 270°C or higher enables the formation of a film with excellent heat resistance.

[0037] The intrinsic viscosity of the semi-aromatic polyamide is preferably 0.8 to 2.0 dL / g, and more preferably 0.9 to 1.8 dL / g. When the intrinsic viscosity of the semi-aromatic polyamide is 0.8 dL / g or higher, it is possible to produce a film with excellent film productivity and mechanical strength.

[0038] <Other ingredients> The semi-aromatic polyamide film of the present invention contains at least a semi-aromatic polyamide as a resin component. The semi-aromatic polyamide film of the present invention may contain resins other than semi-aromatic polyamide as a resin component, but from the viewpoint of improving heat resistance and transparency, the proportion of semi-aromatic polyamide in the total amount of resin components is preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and most preferably 95% by mass or more.

[0039] Furthermore, the semi-aromatic polyamide film of the present invention may contain other components as needed, in addition to the resin component. Examples of other components include polymerization catalysts (such as phosphoric acid, phosphorous acid, hypophosphorous acid, or salts thereof), end-cap encapsulants (such as acetic acid, lauric acid, benzoic acid, octylamine, cyclohexylamine, aniline, etc.), and additives described later. <Semi-aromatic polyamide film> The semi-aromatic polyamide film of the present invention has a refractive index difference n calculated from the following formula (1). D The refractive index difference n is -0.0010 to 0.0045. D From the viewpoint of suppressing the occurrence of sagging, a value of -0.0005 to 0.0040 is preferred, 0.0000 to 0.0035 is more preferred, and 0.0010 to 0.0029 is most preferred.

[0040] Refractive index difference n D ={(n C -n L )-(n C -n R )} / twenty one) (In the formula, n C n is the refractive index in the MD direction at the center of the film. L n is the refractive index in the MD direction at a position 10% inward from the left edge of the film, n R This is the refractive index in the MD direction at a position 10% inward from the right edge of the film. (Note that the center, left edge, and right edge are located on a line parallel to the TD direction of the film.) Furthermore, the semi-aromatic polyamide film of the present invention has an average refractive index n calculated from the following formula (2) from the viewpoint of suppressing sagging. Av The ratio is preferably 1.5985 to 1.6045, more preferably 1.5989 to 1.6040, and particularly preferably 1.5993 to 1.6036.

[0041] Average refractive index n Av =(n C +n L +n R ) / 3 (2) (In the formula, n C , n L , and n R (This is the same as above.) The semi-aromatic polyamide film of the present invention has a refractive index difference n D Since it is within the above range (preferably, refractive index difference n D and the average refractive index n Av (Since the above range is maintained), the occurrence of sagging can be suppressed, and the amount of sagging of the film can be reduced to 3.0‰ or less. This makes it possible to suppress wrinkles when winding the film onto a winding roll, and to prevent problems caused by wrinkles when pulling out the film wound onto the roll for secondary processing. The amount of sagging of the semi-aromatic polyamide film of the present invention is, for example, 3.0‰ or less, preferably 2.5‰ or less, more preferably 2.0‰ or less, even more preferably 1.5‰ or less, and most preferably 1.0‰ or less.

[0042] The amount of slack is measured by the following measurement method. In this invention, when the position where slack occurs (i.e., the position where the length in the MD direction is maximum) is within 80% of the center in the TD direction of the film, it is called "center slack," and when it is within 10% of both ends in the TD direction of the film, it is called "end slack." <Method for measuring sagging amount> If the semi-aromatic polyamide film is in the form of a film roll formed by winding the film, a sample is taken from the entire circumference of the surface layer of a film roll with an outer diameter of 300 mm or more. The length in the MD direction is measured at 50 mm intervals from one end to the other of one side along the TD direction of the obtained sample, and the amount of slack is calculated from the maximum and minimum values ​​of the length using the following formula (3).

[0043] Furthermore, if the semi-aromatic polyamide film is in the form of a single sheet, the length in the MD direction is measured at 50 mm intervals from one end to the other of one side along the TD direction, and the amount of sag is calculated from the maximum and minimum values ​​of the said length using the following formula (3).

[0044] Sagging amount (‰) = (Maximum value - Minimum value) ÷ Maximum value × 1000 (3) Furthermore, the semi-aromatic polyamide film of the present invention exhibits excellent dimensional stability under high-temperature conditions. The thermal shrinkage rate S in the MD direction is determined by measuring the dimensions of the semi-aromatic polyamide film of the present invention after leaving it in a 250°C atmosphere for 5 minutes, and then leaving it at a temperature of 23°C and a humidity of 50%RH for 2 hours. MD and thermal shrinkage coefficient S in the TD direction TD The thermal shrinkage rates of the semi-aromatic polyamide film in the MD and TD directions are preferably -1.0 to 1.5%, more preferably -0.8 to 1.3%, and even more preferably -0.6 to 1.0%. If the thermal shrinkage rates of the semi-aromatic polyamide film in the MD and TD directions are 1.5% or less, it is possible to suppress processing problems caused by dimensional changes when subjected to high-temperature processing.

[0045] Furthermore, from the viewpoint of excellent visibility, the semi-aromatic polyamide film of the present invention preferably has a haze of 14% or less, more preferably 12% or less, and even more preferably 10% or less, as measured in accordance with JIS K7105. Moreover, for semi-aromatic polyamide films with a thickness of 25 μm or less, the haze is preferably 7% or less, more preferably 6% or less, and even more preferably 5% or less.

[0046] [Method for manufacturing semi-aromatic polyamide film] The semi-aromatic polyamide film of the present invention can be produced by a method of simultaneously biaxially stretching an unstretched film, or by a method of sequential biaxial stretching in which an unstretched film is first stretched in the MD direction, and the resulting uniaxially stretched film in the MD direction is then stretched in the TD direction.

[0047] The semi-aromatic polyamide film of the present invention is preferably manufactured by following the steps [1] or [2] below. [1] A process of preheating an unstretched semi-aromatic polyamide film, stretching it simultaneously in the MD direction and the TD direction, and cooling it. [2] A process of preheating a uniaxially stretched film of semi-aromatic polyamide in the MD direction, stretching it in the TD direction, and cooling it. Furthermore, a heat-setting step or a relaxation step may be included between the stretching step and the cooling step.

[0048] In this invention, the sequential biaxial stretching method is preferred for film production. Compared to the simultaneous biaxial stretching method, the sequential biaxial stretching method has a simpler equipment configuration and can reduce the cost of capital investment. Furthermore, the stretching conditions in the MD direction and TD direction can be adjusted independently, and relaxation treatment can be applied in both the MD and TD directions. Therefore, directional properties such as mechanical strength can be appropriately set for each application.

[0049] The semi-aromatic polyamide used in this invention is highly crystalline. Therefore, when employing a sequential biaxial stretching method, orientation crystallization is likely to occur during the initial stretching in the MD direction, which can make subsequent stretching in the TD direction difficult.

[0050] On the other hand, when the thickness of the semi-aromatic polyamide film exceeds 50 μm, the force required to stretch the film becomes too strong in the simultaneous biaxial stretching method, making stretching difficult. In such cases, it is preferable to employ the sequential biaxial stretching method.

[0051] (Unstretched film of semi-aromatic polyamide) Unstretched films of semi-aromatic polyamides can be produced by melt-kneading film raw materials containing at least semi-aromatic polyamides in an extruder to form a film.

[0052] Commercially available semi-aromatic polyamides can be used. Examples of such commercially available products include "Genesta®" manufactured by Kuraray Co., Ltd., "Zecotto®" manufactured by Unitika Ltd., "Lenny®" manufactured by Mitsubishi Engineering Plastics Corporation, "Arlen®" manufactured by Mitsui Chemicals, Inc., and "Ultramid®" manufactured by BASF.

[0053] Furthermore, semi-aromatic polyamides can be produced using methods known for producing crystalline polyamides. Examples include solution polymerization or interfacial polymerization using acid chloride and diamine as raw materials (Method A), a method of producing low polymers using dicarboxylic acid and diamine as raw materials and increasing the molecular weight of the low polymers by melt polymerization or solid-phase polymerization (Method B), a method of producing a salt and a crushed mixture of low polymers using dicarboxylic acid and diamine as raw materials and solid-phase polymerization of this mixture (Method C), and a method of producing a salt using dicarboxylic acid and diamine as raw materials and solid-phase polymerization of this mixture (Method D).

[0054] In method B, for example, a nylon salt prepared by mixing a diamine, a dicarboxylic acid, and a polymerization catalyst can be heated and 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 to a range of 0.1 dL / g or higher has the advantage of accelerating the polymerization rate while maintaining the molar balance between the carboxyl groups of the dicarboxylic acid and the amino groups of the diamine during subsequent solid-phase polymerization or melt polymerization. Furthermore, setting the intrinsic viscosity of the low polymer to a range of 0.6 dL / g or lower can prevent the resulting semi-aromatic polyamide from becoming discolored.

[0055] Solid-phase polymerization of low polymers is preferably carried out under reduced pressure or under inert gas flow. The solid-phase polymerization temperature is preferably 200-280°C. By setting the solid-phase polymerization temperature within this range, the polymerization reaction rate can be increased, allowing for the rapid production of semi-aromatic polyamides. Furthermore, discoloration and gelation of the resulting semi-aromatic polyamides can be suppressed.

[0056] The melt polymerization of low polymers is preferably carried out at a temperature of 350°C or lower, as this suppresses the decomposition and thermal degradation of the semi-aromatic polyamide, resulting in a semi-aromatic polyamide with high strength and excellent appearance. The above-mentioned melt polymerization also includes melt polymerization using a melt extruder.

[0057] In method C, for example, a suspension consisting of a molten aliphatic diamine and a solid aromatic dicarboxylic acid is stirred and mixed to obtain a mixture. Then, in this mixture, at a temperature below the melting point of the final semi-aromatic polyamide, a reaction to produce a salt by the reaction of the aromatic dicarboxylic acid and the aliphatic diamine, and a reaction to produce a low polymer by polymerization of the produced salt are carried out to obtain a mixture of salt and low polymer. In this case, crushing may be carried out while the reaction is in progress, or crushing may be carried out after the reaction has been completed and the mixture has been removed. The resulting reaction product is then subjected to solid-phase polymerization at a temperature below the melting point of the final semi-aromatic polyamide to increase its molecular weight to a predetermined molecular weight and obtain a semi-aromatic polyamide. Solid-phase polymerization is preferably carried out in an inert gas stream such as nitrogen at a polymerization temperature of 180 to 270°C and a reaction time of 0.5 to 10 hours.

[0058] In method D, for example, aromatic dicarboxylic acid powder is heated to a temperature above the melting point of the aliphatic diamine and below the melting point of the aromatic dicarboxylic acid. An aliphatic diamine is then added to the aromatic dicarboxylic acid powder at this temperature, without substantially containing water, in order to maintain the powder state of the aromatic dicarboxylic acid, to produce a salt. The resulting salt is then subjected to solid-phase polymerization at a temperature below the melting point of the final semi-aromatic polyamide to increase its molecular weight to a predetermined level, thereby obtaining a semi-aromatic polyamide. Solid-phase polymerization is preferably carried out in an inert gas stream such as nitrogen at a polymerization temperature of 180 to 270°C for a reaction time of 0.5 to 10 hours.

[0059] In this invention, methods C and D are preferred, with method D being more preferred. Compared to method B, methods C and D can produce the crushed mixture of salt and low polymer, and the salt, at low temperatures, and do not require a large amount of water during the production of the crushed mixture of salt and low polymer, or the salt. Therefore, the generation of gel-like material can be reduced, and fish eyes can be reduced.

[0060] As the semi-aromatic polyamide, only virgin raw materials may be used, or off-spec film and cut-off trim (edge ​​trim) produced as by-products during film manufacturing may be recovered and mixed with the virgin raw materials. Examples of methods for mixing the raw materials include known methods such as the dry blending method and the melt mixing method, which uses a single-screw or twin-screw extruder to obtain the compound.

[0061] In addition to the semi-aromatic polyamide, the aforementioned film raw material may contain one or more additives as needed to further improve its properties. Examples of additives include lubricants, colorants such as pigments (e.g., titanium) and dyes, color inhibitors, heat stabilizers, antioxidants (e.g., hindered phenols, phosphate esters, phosphite esters), weather resistance modifiers (e.g., benzotriazole compounds), flame retardants (e.g., brominated flame retardants, phosphorus-based flame retardants), plasticizers, mold release agents, reinforcing agents (e.g., talc), modifiers, antistatic agents, ultraviolet absorbers, antifogging agents, and various polymer resins.

[0062] Examples of lubricants include inorganic particles such as silica, alumina, titanium dioxide, calcium carbonate, kaolin, and barium sulfate; and organic fine particles such as acrylic resin particles, melamine resin particles, silicone resin particles, and cross-linked polystyrene particles. The average particle size of the lubricant is, for example, 0.05 to 5.0 μm. The lubricant content can be selected according to the required properties of the film, such as friction characteristics, optical characteristics, and other properties, and is, for example, 0.5% by mass or less, preferably 0.4% by mass or less, particularly preferably 0.3% by mass or less, and most preferably 0.2% by mass or less. Alternatively, the lubricant content can be, for example, 0.05% by mass or more, preferably 0.1% by mass or more. Furthermore, adding a lubricant to the film raw material can suppress haze in the resulting film.

[0063] An unstretched film containing a semi-aromatic polyamide and the above-mentioned additive can be produced, for example, by the following method. (A) A method of adding an additive during polymerization of a semi-aromatic polyamide to produce a semi-aromatic polyamide containing the additive, melting it, and forming a film. (B) A method in which pellets are prepared by melt-kneading a high concentration of additives and semi-aromatic polyamide, and then the masterbatch and natural pellets (i.e., additive-free semi-aromatic polyamide pellets) are melt-kneaded in an extruder during film formation (masterbatch method). (C) A method of forming a film by feeding a dry blend of semi-aromatic polyamide and additives into an extruder, melting and kneading it in the extruder. (D) A method of forming a film by charging semi-aromatic polyamide and an additive into an extruder, melting and kneading them in the extruder, and then forming the film. The unstretched film of semi-aromatic polyamide preferably has a crystallization heat of 20 J / g or more, and more preferably 25 J / g or more. Furthermore, the crystallization heat is preferably 35 J / g or less, and more preferably 30 J / g or less. When the crystallization heat of the unstretched film is 20 J / g or more, it can be stably stretched with a small stretching force, so a stretched film with uniform thickness can be obtained. The resulting film has a high tensile elongation at break, and even when stress is applied from the outside in the TD direction, it stretches in response to the stress, thus suppressing breakage.

[0064] Unstretched films of semi-aromatic polyamides with a crystallization heat of 20 J / g or more can be manufactured by melting and mixing the semi-aromatic polyamide in an extruder at a temperature of 280 to 340°C for 3 to 15 minutes, extruding it into a sheet through a T-die, and then cooling the extruded sheet by bringing it into close contact with a cooling roll whose temperature is controlled to 30 to 40°C.

[0065] In the method for producing a semi-aromatic polyamide film of the present invention, the unstretched semi-aromatic polyamide film is biaxially stretched. As a result, the semi-aromatic polyamide undergoes oriented crystallization. (MD direction uniaxial stretching process) In the process of sequentially biaxially stretching an unstretched film, this is a step in which the unstretched film is stretched in the MD direction to obtain a uniaxially stretched film in the MD direction.

[0066] The stretch ratio in the MD direction is preferably 2.0 to 4.5 times. The lower limit of the stretch ratio is preferably 2.3 times, more preferably 2.4 times. The upper limit of the stretch ratio is preferably 3.5 times, more preferably 3.0 times, even more preferably 2.8 times, particularly preferably 2.7 times, and most preferably 2.6 times.

[0067] When stretched in the MD direction at a stretching ratio of 4.5 times or less, a uniaxially oriented MD film is obtained with moderate crystallization and excellent stretchability in the TD direction. Then, by stretching the obtained uniaxially oriented MD film in the TD direction, stretching unevenness can be suppressed, and a biaxially oriented film can be obtained with excellent thickness accuracy and transparency, as well as high tensile elongation at break in the MD direction.

[0068] Furthermore, if the stretching ratio in the MD direction is 2.0 times or higher, the occurrence of stretching unevenness can be suppressed, and a stretched film with uniform thickness and high flatness can be obtained.

[0069] The stretching speed is preferably such that the stretching strain rate in the MD direction exceeds 400% / min, more preferably 800 to 12000% / min, and even more preferably 1200 to 6000% / min. Stretching at a stretching strain rate exceeding 400% / min prevents the film from breaking during stretching due to crystal growth. Furthermore, stretching at a stretching strain rate of 12000% / min or less allows the film to deform in response to the applied stress, thus preventing the film from breaking.

[0070] From the viewpoint of suppressing film breakage and producing biaxially oriented films with good yield, the stretching temperature is preferably (Tg-5)°C or higher, and more preferably (Tg)°C or higher, based on the glass transition temperature (Tg) of the semi-aromatic polyamide. Furthermore, from the viewpoint of suppressing the occurrence of stretching irregularities, the stretching temperature is preferably (Tg+50)°C or lower, more preferably (Tg+45)°C or lower, and even more preferably (Tg+35)°C or lower.

[0071] For example, in the case of polyamide 9T film (Tg = 125°C for polyamide 9T), the stretching temperature is preferably 120 to 175°C, more preferably 120 to 170°C, and even more preferably 125 to 160°C. (Preheating process) The preheating step is a step of preheating the film (unstretched film in the case of simultaneous biaxial stretching, and uniaxially stretched film in the MD direction in the case of sequential biaxial stretching) before the stretching step. From the viewpoint of suppressing the amount of sagging, the preheating temperature T1 of the film is preferably in the range of (Tg-9)°C to (Tg+5)°C, based on the glass transition temperature (Tg) of the semi-aromatic polyamide. The lower limit of the preheating temperature T1 is preferably (Tg-6)°C, more preferably (Tg-5)°C. The upper limit of the preheating temperature T1 is preferably (Tg+4)°C, more preferably (Tg+1)°C, even more preferably (Tg)°C, and particularly preferably (Tg-1)°C.

[0072] If the preheating temperature of the film is below (Tg-9)°C, the resulting film tends to have a large amount of sag at the edges. Conversely, if the preheating temperature of the film exceeds (Tg+5)°C, the resulting film tends to have a large amount of sag in the middle.

[0073] If the preheating process involves preheating the film while gradually changing the temperature, it is preferable that the preheating temperature immediately before the stretching process is within the aforementioned range.

[0074] For example, in the case of polyamide 9T film (Tg of polyamide 9T = 125°C), the preheating temperature T1 of the polyamide 9T film is preferably in the range of 116 to 130°C. The lower limit of the preheating temperature T1 is preferably 119°C, more preferably 120°C. The upper limit of the preheating temperature T1 is preferably 129°C, more preferably 126°C, even more preferably 125°C, and particularly preferably 124°C.

[0075] In this invention, sagging can be suppressed by preheating the film within the specified temperature range. The principle by which sagging is suppressed by adjusting the preheating temperature of the film is not clear, but it is thought that sagging is suppressed by controlling the bowing phenomenon.

[0076] When manufacturing film using the tenter stretching method, a bowing phenomenon occurs due to the stress generated in the film at the boundary between the stretching section and the heat-setting section. Specifically, when manufacturing stretched film using the tenter stretching method, the film passes through the preheating section, stretching section, heat-setting section, relaxation section, and cooling section, but the stretching stress is maximum near the end of the stretching section, that is, at the point where the set stretching ratio is reached. At this time, since both ends of the film are held by clips inside the tenter, a phenomenon occurs in which the central part of the film is pulled towards the end of the stretching section. Then, the central part of the film is pulled from the heat-setting section following the stretching section towards the stretching section, so when a straight line drawn perpendicular to the direction of film travel before entering the stretching machine comes out of the stretching machine, a bowing phenomenon occurs in which the central part of the film draws an arc in the opposite direction to the direction of film travel. Due to this phenomenon, the effective stretching ratio in the direction of film travel differs between the central part of the film and both ends, and this is thought to affect the slack of the film. Furthermore, it is hypothesized that controlling the temperatures of the preheating and cooling sections within a specific range can suppress the occurrence of the Boeing phenomenon, thereby reducing sagging. (Stretching process) The stretching process involves stretching a film to obtain a biaxially oriented film. If the film used in this process is an unstretched film, the process involves simultaneously biaxially stretching the unstretched film in the MD and TD directions. If the film used in this process is a uniaxially oriented film in the MD direction, the process involves stretching the uniaxially oriented film in the MD direction in the TD direction.

[0077] When a uniaxially oriented film in the MD direction is stretched in the TD direction (sequentially biaxially oriented), the stretching ratio in the TD direction is preferably 2.0 to 5.0 times, more preferably 2.0 to 4.0 times, even more preferably 3.0 to 4.0 times, and particularly preferably 3.3 to 3.8 times.

[0078] When the stretching ratio in the TD direction is within the aforementioned range, it is possible to suppress the occurrence of stretching unevenness, obtain a biaxially oriented film that has excellent thickness accuracy and transparency, and high tensile elongation at break in the TD direction.

[0079] When an unstretched film is simultaneously biaxially stretched, the stretching ratio in the MD direction is preferably 2.0 to 4.5 times, more preferably 2.0 to 3.5 times, even more preferably 2.5 to 3.5 times, and particularly preferably 2.5 to 3.3 times. Furthermore, the stretching ratio in the TD direction is preferably 2.0 to 5.0 times, more preferably 2.0 to 4.0 times, even more preferably 3.0 to 4.0 times, and particularly preferably 3.3 to 3.8 times.

[0080] Stretching in the MD direction at a stretching ratio of 4.5 times or less yields a stretched film with low thermal shrinkage and excellent dimensional stability. Furthermore, stretching in the TD direction at a stretching ratio of 5.0 times or less yields a stretched film with low thermal shrinkage, excellent dimensional stability, and even higher tensile elongation at break.

[0081] Furthermore, if the stretching ratio in the MD and TD directions is 2.0 times or higher, the occurrence of stretching unevenness can be suppressed, and a stretched film with uniform thickness and high flatness can be obtained.

[0082] In simultaneous biaxial stretching, when obtaining a biaxially oriented film with a thickness of 1 to 25 μm, the stretching ratio in the MD direction is preferably 2.5 to 3.0 times, and the stretching ratio in the TD direction is preferably 2.5 to 3.3 times. Furthermore, when obtaining a biaxially oriented film with a thickness of 26 to 50 μm, the stretching ratio in the MD direction is preferably 2.8 to 3.3 times, and the stretching ratio in the TD direction is preferably 3.0 to 3.5 times.

[0083] The stretching speed is preferably such that the stretching strain rate in both the MD direction and the TD direction exceeds 400% / min, more preferably between 800 and 12000% / min, and even more preferably between 1200 and 6000% / min. Stretching at a stretching strain rate exceeding 400% / min prevents the film from breaking during stretching due to crystal growth. Furthermore, stretching at a stretching strain rate of 12000% / min or less allows the film to deform in response to the applied stress, thus preventing the film from breaking.

[0084] From the viewpoint of suppressing film breakage and producing biaxially oriented films with good yield, the stretching temperature is preferably (Tg-5)°C or higher, and more preferably (Tg)°C or higher, based on the glass transition temperature (Tg) of the semi-aromatic polyamide. Furthermore, from the viewpoint of suppressing the occurrence of stretching irregularities, the stretching temperature is preferably (Tg+50)°C or lower, more preferably (Tg+35)°C or lower, and even more preferably (Tg+30)°C or lower.

[0085] For example, in the case of polyamide 9T film (polyamide 9T Tg = 125°C), the stretching temperature is preferably 120 to 160°C, and more preferably 125 to 155°C. Furthermore, when the heating temperature of the stretching process is divided into two zones, the stretching temperature for the first zone is preferably 120 to 140°C, and more preferably 125 to 135°C. Furthermore, the stretching temperature for the second zone is preferably above 135°C and below 160°C, more preferably 140 to 160°C, and particularly preferably 145 to 155°C. (heat setting process) After the stretching of the semi-aromatic polyamide film, it is preferable to perform a heat-setting treatment while holding the film with the clips used during stretching. By performing a heat-setting treatment, the resulting film can have its thermal shrinkage rate reduced without the occurrence of heat-induced unevenness. The heat-setting treatment temperature is preferably in the range of (Tm-30)°C to (Tm)°C, more preferably in the range of (Tm-27)°C to (Tm-3)°C, and even more preferably in the range of (Tm-24)°C to (Tm-6)°C, based on the melting point (Tm) of the semi-aromatic polyamide. If the heat-setting treatment temperature is (Tm-30)°C or higher, a film with low thermal shrinkage rate can be obtained. Furthermore, if the heat-setting treatment temperature is (Tm)°C or lower, it is possible to suppress appearance defects such as heat-induced wrinkles and breakage during the heat-setting treatment, and a biaxially oriented film with high tensile elongation at break can be obtained.

[0086] For example, in the case of polyamide 9T film (Tm of polyamide 9T = 290°C), the heat-fixing treatment temperature is preferably 260 to 290°C, more preferably 263 to 287°C, and even more preferably 266 to 284°C.

[0087] Examples of known heat-setting methods include blowing hot air, irradiating with infrared rays, and irradiating with microwaves. Among these, blowing hot air is preferred because it allows for uniform and precise heating. (Relaxation process) After heat-setting, it is preferable to perform a relaxation treatment in the MD and TD directions at the same temperature as the heat-setting treatment while the film is still held in place by the clip.

[0088] The relaxation rate in the MD direction is, for example, 1.0 to 10.0%. The relaxation rate in the TD direction is, for example, 1.0 to 12.0%. By performing relaxation treatment in the MD and TD directions at the aforementioned relaxation rates, it is possible to obtain a film with reduced thermal shrinkage and improved dimensional stability while suppressing sagging.

[0089] In the sequential biaxial stretching method, when obtaining a biaxially oriented film with a thickness of 1 to 50 μm, the relaxation ratio is preferably 1.0 to 6.0% in the MD direction and 1.0 to 12.0% in the TD direction. When obtaining a biaxially oriented film with a thickness of 51 to 150 μm, the relaxation ratio is preferably 1.0 to 3.0% in the MD direction and 1.0 to 10.0% in the TD direction.

[0090] In the simultaneous biaxial stretching method, the relaxation rate is preferably 1.0 to 6.0% in the MD direction and 1.0 to 12.0% in the TD direction.

[0091] In the simultaneous biaxial stretching method, the relaxation process can be performed in-line, simultaneously or separately, for the MD and TD directions. When performed separately, it can be done by relaxing the MD direction first, followed by the TD direction, or by relaxing the TD direction first, followed by the MD direction.

[0092] On the other hand, in the sequential biaxial stretching method, the relaxation treatment can be performed simultaneously in line in the MD and TD directions after (i) stretching in the MD direction and then stretching in the TD direction, followed by a heat-setting treatment, or (ii) stretching in the MD direction, followed by a relaxation treatment in the MD direction, then stretching in the TD direction, followed by a heat-setting treatment, and then a relaxation treatment in the TD direction. However, in (ii), if the heat-setting treatment is performed after stretching in the MD direction and the relaxation treatment in the MD direction, the resulting film will be difficult to stretch in the TD direction, so it is not desirable to perform the heat-setting treatment before stretching in the TD direction. Furthermore, in the sequential biaxial stretching methods described in (i) and (ii) above, stretching in the MD direction is performed first, followed by stretching in the TD direction, but in the sequential biaxial stretching method, stretching in the TD direction is also acceptable.

[0093] Alternatively, the relaxation process described above can also be performed by relaxing the material in the TD direction in-line after biaxial stretching, winding it up, and then passing it through a drying oven set to a predetermined temperature under low tension offline, thereby performing relaxation in the MD direction. (cooling process) The cooling step is a step of cooling the film after stretching. The cooling temperature T2 is preferably in the range of (Tm-260)°C to (Tm-170)°C, based on the melting point (Tm) of the semi-aromatic polyamide. From the viewpoint of suppressing sagging, the lower limit of the cooling temperature T2 is preferably (Tm-245)°C, more preferably (Tm-240)°C, more preferably (Tm-235)°C, even more preferably (Tm-230)°C, particularly preferably (Tm-225)°C, and most preferably (Tm-220)°C. The upper limit of the cooling temperature T2 is preferably (Tm-180)°C, more preferably (Tm-185)°C, even more preferably (Tm-190)°C, particularly preferably (Tm-195)°C, and most preferably (Tm-200)°C.

[0094] For example, in the case of a polyamide 9T film (Tm of polyamide 9T = 290°C), the cooling temperature T2 is, for example, 30 to 120°C. From the viewpoint of suppressing sagging, the lower limit of the cooling temperature T2 is preferably 45°C, more preferably 50°C, more preferably 55°C, even more preferably 60°C, particularly preferably 65°C, and most preferably 70°C. The upper limit of the cooling temperature T2 is preferably 110°C, more preferably 105°C, even more preferably 100°C, particularly preferably 95°C, and most preferably 90°C.

[0095] In manufacturing the semi-aromatic polyamide film of the present invention by sequential biaxial stretching, from the viewpoint of adjusting the refractive index in the MD direction at the central part, left end, and right end in the TD direction of the obtained film to a specific range, the preheating temperature T1 (°C) and cooling temperature T2 (°C) preferably satisfy the following formula (4), more preferably satisfy the following formula (4-1), and even more preferably satisfy the following formula (4-2).

[0096] 1073 ≤ 10 × T1 - T2 ≤ 1211 (4) 1085 ≤ 10 × T1 - T2 ≤ 1200 (4-1) 1096 ≤ 10 × T1 - T2 ≤ 1188 (4-2) The thickness of the semi-aromatic polyamide film of the present invention can be appropriately changed depending on 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.

[0097] The semi-aromatic polyamide film of the present invention can be manufactured using methods such as flat sequential biaxial stretching, flat simultaneous biaxial stretching, and tubular stretching. Examples of stretching equipment for implementing flat simultaneous biaxial stretching include screw type tenters, pantograph type tenters, and linear motor driven clip type tenters.

[0098] Furthermore, in the apparatus for manufacturing the semi-aromatic polyamide film of the present invention, it is preferable that the surfaces of the cylinder, barrel melting section, metering section, single pipe, filter, T-die, etc., are treated to reduce surface roughness in order to prevent resin accumulation. Methods for reducing surface roughness include, for example, modifying the surface with a low-polarity substance or depositing silicon nitride or diamond-like carbon onto the surface.

[0099] The resulting semi-aromatic polyamide film may be in the form of a single sheet or in the form of a film roll wound onto a winding roll. The film roll form may also include a raw material roll obtained by winding a film obtained through preheating, stretching, and cooling processes onto a winding roll, and a slit roll obtained by slitting a raw material roll to a desired width.

[0100] The semi-aromatic polyamide film may be a single-layer film or a multilayer structure consisting of two or more layers.

[0101] When a semi-aromatic polyamide film has a multilayer structure, a lubricant can be included in at least one layer. However, in a two-layer film, it is preferable to include a lubricant in one of the layers, and in a three-layer film, it is preferable to include a lubricant in each of the layers located on both surfaces. This makes it easier to control the surface roughness of the semi-aromatic polyamide film. The type of lubricant and the amount of lubricant included can be adjusted as appropriate depending on the application.

[0102] The surface of the semi-aromatic polyamide film may be subjected to corona treatment, plasma treatment, acid treatment, flame treatment, or the like to improve adhesion with other materials.

[0103] The semi-aromatic polyamide film of the present invention may have layers laminated on it made of inorganic materials such as metals and their oxides, other polymers, paper, woven fabrics, nonwoven fabrics, wood, and the like. <Application> The semi-aromatic polyamide film of the present invention has heat resistance and excellent dimensional stability under high-temperature conditions. Therefore, it can be used in various applications such as electronic materials and optical components.

[0104] The semi-aromatic polyamide film of the present invention can be used specifically as a packaging material for pharmaceuticals; a packaging material for food products such as retort foods; a packaging material for electronic components such as semiconductor packages; an electrical insulating material for motors, transformers, cables, etc.; a dielectric material for capacitor applications, etc.; a material for magnetic tapes such as cassette tapes, magnetic tapes for digital data storage, and video tapes; a protective board for solar cell substrates, liquid crystal panels, conductive films, and display devices; an electronic circuit board material such as LED mounting substrates, flexible printed circuit boards, and flexible flat cables; a heat-resistant tape such as coverlay film for flexible printed circuit boards, heat-resistant masking tape, and 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 filtration membrane, and other films for household and industrial use.

[0105] Furthermore, because the semi-aromatic polyamide film of the present invention has excellent heat resistance, dimensional stability, and transparency, it can be used in applications such as display materials and display devices in mobile devices. Specifically, it can be used as a base film for various functional materials such as optical substrates, polarizing plates, and phase difference plates for various displays such as liquid crystal displays and organic EL displays, as well as a protective film and sealing film for light-emitting elements and display devices.

[0106] [Electronic materials] The electronic material of the present invention comprises at least the above-mentioned semi-aromatic polyamide film.

[0107] The aforementioned electronic materials include, for example, packaging materials for electronic components such as semiconductor packages; electrical insulating materials for motors, transformers, cables, etc.; dielectric materials for capacitor applications, etc.; materials for magnetic tapes such as cassette tapes, magnetic tapes for digital data storage, and video tapes; and heat-resistant masking tapes, heat-resistant reflectors, insulating tapes, release films, etc.

[0108] [Optical components] The optical component of the present invention comprises at least the above-mentioned semi-aromatic polyamide film.

[0109] The optical components include, for example, solar cell substrates, liquid crystal panels, conductive films, protective plates and protective films for display devices, etc.; electronic substrate materials such as LED displays, OLED displays, LED mounting substrates, substrates for flexible printed wiring, and flexible flat cables; coverlay films for flexible printed wiring, insulating tapes, release films, polarizing plates, base films, protective films for light-emitting elements and display devices, sealing films, etc.

[0110] The configurations and combinations thereof described above are merely examples, and additions, omissions, substitutions, and modifications to the configurations are permitted as appropriate, without departing from the spirit of the present invention. Furthermore, the present invention is not limited by its embodiments. [Examples]

[0111] The present invention will be specifically described below with reference to examples. 1. Evaluation Method (1) Intrinsic viscosity of semi-aromatic polyamides The intrinsic viscosity (η) of the resin at concentrations of 0.05, 0.1, 0.2, and 0.4 g / dL in concentrated sulfuric acid at 30°C. inh The intrinsic viscosity [η] was obtained by calculating the following formula and extrapolating it to a concentration of 0.

[0112] η inh =[ln(t1 / t0)] / c (In the formula, η inh(where is the intrinsic viscosity (dL / g), t0 is the solvent flow time (seconds), t1 is the resin solution flow time (seconds), and c is the concentration of the resin in the solution (g / dL)) (2) Melting point Tm and glass transition temperature Tg of semi-aromatic polyamides Using a differential scanning calorimeter (PerkinElmer DSC-7), a semi-aromatic polyamide was heated from 20°C to 350°C at a rate of 10°C / min under a nitrogen atmosphere and held for 5 minutes (1st Scan). Then, it was cooled from 350°C to 20°C at a rate of 100°C / min and held for 5 minutes. The glass transition temperature during the subsequent reheating from 20°C to 350°C at a rate of 10°C / min (2nd Scan) was defined as the Tg of the semi-aromatic polyamide. Similarly, the peak top temperature of the crystal melting peak observed in the 2nd Scan was defined as Tm. (3) Heat of crystallization of unstretched film A 10 mg unstretched sheet of semi-aromatic polyamide was heated from 40°C to 350°C at a rate of 20°C / min under a nitrogen atmosphere using a differential scanning calorimeter (PerkinElmer DSC-7) (1st Scan), and the heat energy of the resulting exothermic peak was determined. (4) Thermal shrinkage rate of semi-aromatic polyamide film From the semi-aromatic polyamide film, MD-direction test specimens (100 mm length in the MD direction × 10 mm width in the TD direction) and TD-direction test specimens (100 mm length in the TD direction × 10 mm width in the MD direction) were cut out. Each of the obtained test specimens was left in a 250°C atmosphere for 5 minutes, then subjected to a treatment at 23°C and 50% RH humidity for 2 hours. The length dimensions after treatment were measured, and the thermal shrinkage rate S of the MD-direction test specimen was calculated using the following formula. MD and the thermal shrinkage rate S of the test specimen in the TD direction TD They sought it.

[0113] Thermal shrinkage rate (%) = [{length before treatment - length after treatment} / length before treatment] × 100 (5) Refractive index of semi-aromatic polyamide film A sample was obtained by cutting out one full circle of the surface layer from a 400 mm diameter film roll obtained in the examples and comparative examples.

[0114] The refractive index n in the MD direction at three points located on a line parallel to the TD direction of the obtained sample was determined using an Abbe refractometer DR-M2 (manufactured by Atago Co., Ltd.) in accordance with JIS K7142. A sodium D line was used as the light source, a test piece with a refractive index of 1.74 was used, and methylene iodide was used as the intermediate solution.

[0115] More specifically, the refractive index n in the MD direction of the central part of the sample C , the refractive index n in the MD direction at a position 10% inward from the left edge of the sample width L , and the refractive index n in the MD direction at a position 10% inward from the right edge of the sample width R We measured the following.

[0116] Then, from equation (1) below, the refractive index difference n D They sought it.

[0117] Refractive index difference n D ={(n C -n L )-(n C -n R )} / twenty one) Furthermore, the average refractive index n can be obtained from equation (2) below. Av They sought it.

[0118] Average refractive index n Av =(n C +n L +n R ) / 3 (2) (6) Amount of sagging A sample was taken from the entire surface of a 400mm diameter film roll. The obtained sample was released from the tension of winding and spread out on a flat surface. The length in the MD direction was measured at 50mm intervals from one end to the other of one side along the TD direction, and the maximum value L of the length was measured. max and minimum value L min Therefore, the amount of sagging was calculated using the following formula (3) (see Figure 1).

[0119] Sagging amount (‰) = (L max -L min )÷L max×1000 (3) 2. Raw materials (1) Semi-aromatic polyamides The semi-aromatic polyamide A obtained in Production Example 1 below was used.

[0120] Manufacturing Example 1 (Production of semi-aromatic polyamide A) 3289 parts by mass of terephthalic acid (TPA), 2533 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 hypophosphate monohydrate (0.1% by mass relative to the total of the four polyamide raw materials), and 2200 parts by mass of distilled water were placed in a reaction vessel and purged with nitrogen. The molar ratio of these raw materials (TPA / BA / NDA / MODA) was 99 / 2 / 80 / 20.

[0121] The contents of the reaction vessel 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 internal pressure of the reaction vessel was raised to 2.12 MPa. The reaction continued for 1 hour, then the temperature was raised to 230°C, and the temperature was maintained at 230°C for 2 hours, during which the reaction was carried out while gradually releasing the water vapor and maintaining the pressure at 2.12 MPa. Next, the pressure was reduced to 0.98 MPa over 30 minutes, and the reaction was continued for another hour to obtain a prepolymer. This was dried under reduced pressure at 100°C for 12 hours, and then pulverized to a size of 2 mm or less.

[0122] Next, the pulverized prepolymer was solid-phase polymerized for 10 hours under conditions of 230°C and 13.3 Pa. The obtained polymer was fed into a twin-screw extruder, melt-kneaded and extruded under conditions of 320°C cylinder temperature, cooled, and cut to produce pelletized semi-aromatic polyamide A. The obtained semi-aromatic polyamide A had an intrinsic viscosity of 1.17 dL / g, a melting point (Tm) of 290°C, and a glass transition temperature (Tg) of 125°C. (2) Silica master chip (MI) of semi-aromatic polyamide A The master chip (MI) obtained in Manufacturing Example 2 below was used.

[0123] Manufacturing Example 2 (Manufacturing of Master Chip (M1)) A master tip (M1) containing 2% by mass of silica was prepared by melt-kneading 98 parts by mass of semi-aromatic polyamide A obtained in Production Example 1 with 2 parts by mass of silica (Silysia 310P, manufactured by Fuji Silysia Chemical Co., Ltd., average particle size 2.7 μm).

[0124] Example 1 A mixture was obtained by mixing semi-aromatic polyamide A, a heat stabilizer (Sumitomo Chemical Co., Ltd., Sumirizer GA-80), and a master chip (M1) in an amount of 100 parts by mass of semi-aromatic polyamide A, 0.2 parts by mass of heat stabilizer (Sumitomo Chemical Co., Ltd., Sumirizer GA-80), and 0.1 parts by mass of silica.

[0125] The obtained mixture was fed into a 65 mm single-screw extruder with the cylinder temperature set to 295°C (initial stage), 320°C (middle stage), and 320°C (final stage) to melt it. It was then extruded into a sheet through a T-die set to 320°C, and cooled by electrostatic adhesion onto a cooling roll set to a surface temperature of 40°C to obtain a substantially unoriented, unstretched sheet with a thickness of 230 μm (crystallization heat of 27 J / g).

[0126] Next, the obtained unstretched sheet was biaxially stretched using a flat-type sequential stretcher.

[0127] First, using a heating roll and an infrared heater, the heating roll was heated to 110°C, and then, while heating the space to 150°C with the infrared heater, the unstretched film was stretched in the MD direction at a stretching ratio of 2.5 times to obtain a uniaxially oriented film in the MD direction.

[0128] Next, the uniaxially oriented film in the MD direction was guided to the TD direction stretching machine while both ends were held with clips. The uniaxially oriented film in the MD direction was then preheated at a preheating temperature (T1) of 123°C in the preheating section inside the TD direction stretching machine, and stretched in the TD direction at a stretching temperature of 130°C and a stretching ratio of 3.4 times in the stretching section.

[0129] After stretching, the heat-fixed portion was heat-set at 279°C.

[0130] Subsequently, in the relaxed section, a relaxation treatment was performed at the same temperature as the heat-fixed section, with a relaxation rate of 3% in the MD direction and a relaxation rate of 2.7% in the TD direction.

[0131] Subsequently, the system was cooled in the cooling section at a cooling temperature (T2) of 80°C.

[0132] This resulted in a semi-aromatic polyamide film with a thickness of 27 μm. The obtained film was then wound up to produce a film roll with a width of 1200 mm and a diameter of 400 mm.

[0133] Examples 2-8, Comparative Examples 1-5 A semi-aromatic polyamide film and a film roll were obtained in the same manner as in Example 1, except that the preheating temperature, stretching method, stretching ratio, relaxation rate, and cooling temperature were changed as shown in Table 1.

[0134] [Table 1] Examples 1 to 7 show that when the film is preheated to a predetermined temperature before stretching and cooled to a predetermined temperature after stretching, the refractive index difference n of the resulting semi-aromatic polyamide film is D It is possible to adjust the ratio to a predetermined range, and it is found that a semi-aromatic polyamide film with excellent dimensional stability under high-temperature conditions and sufficiently small sag can be obtained. Furthermore, by controlling the cooling temperature after stretching to a more favorable range, the refractive index difference n can be adjusted. D This yields a semi-aromatic polyamide film within the most desirable range, and it can be found that the amount of sagging can be further reduced.

[0135] Furthermore, a comparison of Examples 1-7 and Example 8 shows that by adjusting the heat-setting treatment temperature, a semi-aromatic polyamide film with less sagging and excellent dimensional stability under high-temperature conditions can be obtained.

[0136] On the other hand, the semi-aromatic polyamide films obtained in Comparative Examples 1 to 5 have a refractive index difference n D Because it did not meet the range defined in this invention, the amount of sagging was large.

Claims

1. A rectangular semi-aromatic polyamide film having sides aligned along the MD direction and sides aligned along the TD direction, The refractive index difference n calculated from the following formula (1) Ｄ A semi-aromatic polyamide film having a coefficient of -0.0010 to 0.0045. Refractive index difference n Ｄ = {(n Ｃ -n Ｌ ) - (n Ｃ -n Ｒ )} / 2 (1) (where n Ｃ is the refractive index in the MD direction at the central part of the film, n Ｌ is the refractive index in the MD direction at a position within 10% of the film width from the left end of the film, n Ｒ is the refractive index in the MD direction at a position within 10% of the film width from the right end of the film. The central part, the left end part, and the right end part are located on the same straight line parallel to the TD direction of the film)

2. The average refractive index n calculated from the following formula (2) Ａｖ The semi-aromatic polyamide film according to claim 1, wherein the ratio is 1.5985 to 1.6045. Average refractive index n Ａｖ = (n Ｃ +n Ｌ +n Ｒ ) / 3 (2) (In the formula, n Ｃ , n Ｌ , and n Ｒ (This is the same as above.)

3. The semi-aromatic polyamide film according to claim 1, wherein the amount of sag measured by the measurement method described below is 3.0‰ or less. <Method for measuring sagging amount> The length in the MD direction is measured in 50 mm increments from one end to the other of one side along the TD direction, and the amount of sag is calculated from the maximum and minimum values ​​of the said length using the following formula (3). Sagging amount (‰) = (Maximum value - Minimum value) ÷ Maximum value × 1000 (3)

4. The thermal shrinkage rate S in the MD direction is determined by measuring the dimensions after leaving the material in a 250°C atmosphere for 5 minutes, followed by leaving it in a 23°C and 50% RH atmosphere for 2 hours. ＭＤ and the thermal shrinkage coefficient S in the TD direction ＴＤ The semi-aromatic polyamide film according to claim 1, wherein each of these is -1.0 to 1.5%.

5. A method for producing a semi-aromatic polyamide film, comprising the steps of [1] or [2] below to obtain the semi-aromatic polyamide film described in any one of claims 1 to 4. [1] A step of preheating an unstretched semi-aromatic polyamide film at a temperature of (Tg-9)°C to (Tg+5)°C, based on the glass transition temperature Tg of the semi-aromatic polyamide; a step of simultaneously stretching the film in the MD direction and the TD direction; and a step of cooling the film at a temperature of (Tm-260)°C to (Tm-170)°C, based on the melting point Tm of the semi-aromatic polyamide. [2] A uniaxially stretched film of semi-aromatic polyamide in the MD direction is preheated to a temperature of (Tg-9)°C to (Tg+5)°C based on the Tg of the semi-aromatic polyamide, stretched in the TD direction, and cooled to a temperature of (Tm-260)°C to (Tm-170)°C based on the melting point Tm of the semi-aromatic polyamide.

6. An electronic material comprising a semi-aromatic polyamide film according to any one of claims 1 to 4.

7. An optical component comprising a semi-aromatic polyamide film according to any one of claims 1 to 4.

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