Semi-aromatic polyamide film and method for producing the same

Abstract

To provide a semi-aromatic polyamide film having a sufficiently small amount of sagging. The semi-aromatic polyamide film of the present invention is a rectangular semi-aromatic polyamide film having a side along the MD direction and a side along the TD direction, and has a refractive index difference n calculated by the following formula (1): D is -0.0010 to 0.0045. Refractive index difference n D ={(n C -n L )-(n C -n R )} / twenty one) (In the formula, n C is the refractive index in the MD direction at the center of the film, n L is the refractive index in the MD direction at a position 10% inside the film width from the left edge of the film, n R is the refractive index in the MD direction at a position 10% of the film width inward from the right edge of the film)

Description

[Technical Field]

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

[0002] Semi-aromatic polyamide films stretched in the MD (longitudinal) and TD (transverse) directions have excellent heat resistance and mechanical properties, making them useful in a variety of fields. Among the semi-aromatic polyamides that make up semi-aromatic polyamide films, polyamide 9T, which is made up of an aliphatic diamine with nine carbon atoms and terephthalic acid, and polyamide 10T, which is made up of an aliphatic diamine with ten carbon atoms and terephthalic acid, have particularly excellent heat resistance and mechanical properties.

[0003] Patent Document 1 discloses a biaxially stretched film made of a semi-aromatic polyamide resin, which is obtained by biaxially stretching an unstretched film having a specific heat of crystallization. However, the film disclosed in Patent Document 1 has a large amount of sagging, and may wrinkle when wound up or meander during running.

[0004] On the other hand, Patent Document 2 discloses that the amount of sagging of a film made of an aliphatic polyamide resin that has been biaxially stretched and then heat-set can be controlled by the cooling rate, and that the amount of sagging decreases when the cooling rate is reduced. However, the film disclosed in Patent Document 2 sometimes suffers from distortion when exposed to high temperatures. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2020 / 230806 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-297415 Summary of the Invention [Problem to be solved by the invention]

[0006] The inventors then applied the method described in Patent Document 2 to control the amount of sagging of the semi-aromatic polyamide film disclosed in Patent Document 1, but were unable to sufficiently reduce the amount of sagging.

[0007] Furthermore, in recent years, optical films for display members and the like are also required to have dimensional stability that prevents distortion even under conditions of exposure to high temperatures, such as during transportation or thermal processing.

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

[0009] Another object of the present invention is to provide a semi-aromatic polyamide film that has a sufficiently small amount of sagging 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 with a sufficiently small amount of sagging.

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

[0012] As a result of intensive research to solve the above problems, the present inventors have found that if an unstretched film or a uniaxially stretched film is preheated at a specific temperature, stretched, and then cooled at a specific temperature after stretching, the MD refractive index of the resulting film at the center, left edge, and right edge in the TD direction can be adjusted to a specific range, and the amount of sagging can be sufficiently reduced. Furthermore, they have found that if an unstretched film or a uniaxially stretched film is preheated at a specific temperature, stretched, heat-set at a specific temperature after stretching, and then cooled at a specific temperature, the amount of sagging of the resulting film can be sufficiently reduced and the dimensional stability under high temperature conditions can be improved.

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

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

[0015] Refractive index difference n D ={(n C -n L )-(n C -n R )} / twenty one) (In the formula, n C is the refractive index in the MD direction at the center of the film, n L is the refractive index in the MD direction at a position 10% inside the film width from the left edge of the film, n R is the refractive index in the MD direction at a position 10% of the film width inward from the right edge of the film. The center, left edge, and right edge are located on a line parallel to the TD direction of the film. The present invention also provides a method for manufacturing a glass having a refractive index average value n calculated from the following formula (2): Av The semi-aromatic polyamide film has a viscosity of 1.5985 to 1.6045.

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

[0017] Slack (‰) = (maximum value - minimum value) ÷ maximum value × 1000 (3) The present invention also provides a thermal shrinkage ratio S in the MD direction, which is determined by leaving the sheet in an atmosphere at 250°C for 5 minutes, and then leaving it in an atmosphere at a temperature of 23°C and a humidity of 50% RH for 2 hours, and then measuring the dimensions. MD and thermal shrinkage rate S in the TD direction TD and σ are each −1.0 to 1.5%.

[0018] The present invention also provides a method for producing a semi-aromatic polyamide film, which comprises the steps of [1] or [2] below to obtain the semi-aromatic polyamide film. [1] A step of preheating an unstretched film of semi-aromatic polyamide 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 step of preheating a uniaxially stretched film of semi-aromatic polyamide in the MD direction at a temperature of (Tg-9) ° C. to (Tg+5) ° C. based on the Tg of the semi-aromatic polyamide, a step of stretching the film in 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. 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 having a sufficiently small amount of sagging (or having a sufficiently small amount of sagging and 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 electronic materials such as base films and coverlay films for flexible printed circuit boards; optical materials such as substrates for displays; heat-resistant tapes; and the like. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a diagram illustrating a method for measuring the amount of sagging, taking the case of end sagging as an example. DETAILED DESCRIPTION OF THE INVENTION

[0023] [Semi-aromatic polyamide film] The semi-aromatic polyamide film of the present invention is a rectangular semi-aromatic polyamide film having a side along the MD direction and a side along the TD direction, and is a film containing at least a semi-aromatic polyamide as a resin component. <Semi-aromatic polyamide> The semi-aromatic polyamide contains, as monomer components (i.e., components derived from monomers), a dicarboxylic acid component (i.e., a component derived from dicarboxylic acid) and a diamine component (i.e., a component derived from diamine). The dicarboxylic acid component contains at least an aromatic dicarboxylic acid component, and the diamine component contains at least an aliphatic diamine component.

[0024] The semi-aromatic polyamide may contain other components in addition to the dicarboxylic acid component and the diamine component. However, in order to obtain a film with excellent heat resistance and low water absorption, the total content of the dicarboxylic acid component and the diamine component is, for example, preferably 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, the semi-aromatic polyamide may contain other components in addition to the aromatic dicarboxylic acid component and the aliphatic diamine component. However, 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, for example, preferably 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.

[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, more preferably 70 mol% or more, and even more preferably 85 mol% or more of terephthalic acid, 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, including the 1,2-, 1,3-, 1,4-, 1,5-, 1,6-, 1,7-, 1,8-, 2,3-, 2,6-, and 2,7-isomers of naphthalenedicarboxylic acid.

[0029] In addition to aromatic dicarboxylic acids, the dicarboxylic acid may contain other dicarboxylic acids within the 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.

[0030] The aliphatic diamine preferably contains an aliphatic diamine having 6 to 12 carbon atoms as a main component. The content of the aliphatic diamine 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 the aliphatic diamine having 6 to 12 carbon atoms is 60 mol% or more, the obtained film can achieve both heat resistance and productivity. The aliphatic diamine having 6 to 12 carbon atoms may be used alone or in combination of two or more. When two or more types are used in combination, the above content is the total content thereof.

[0031] Examples of aliphatic diamines having 6 to 12 carbon atoms include linear aliphatic diamines such as 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,11-undecanediamine, and 1,12-dodecanediamine; and branched aliphatic diamines such as 2-methyl-1,8-octanediamine, 4-methyl-1,8-octanediamine, 5-methyl-1,9-nonanediamine, 2,2,4- / 2,4,4-trimethyl-1,6-hexanediamine, 2-methyl-1,5-pentanediamine, 2-methyl-1,6-hexanediamine, and 2-methyl-1,7-heptanediamine.

[0032] The aliphatic diamine preferably contains, as a main component, an aliphatic diamine having 9 to 12 carbon atoms among aliphatic diamines having 6 to 12 carbon atoms, and more preferably polyamide 9T containing, as a main component, an aliphatic diamine having 9 carbon atoms or polyamide 10T containing, as a main component, an aliphatic diamine having 10 carbon atoms.

[0033] The aliphatic diamine may include, in addition to aliphatic diamines having 6 to 12 carbon atoms, (straight-chain) aliphatic diamines having 6 or less carbon atoms, such as 1,4-butanediamine and 1,5-pentanediamine.

[0034] The diamine component may contain, in addition to aliphatic diamines, other diamines within the scope of the present invention, such as alicyclic diamines such as isophoronediamine, norbornanedimethylamine, and tricyclodecanedimethylamine; and aromatic diamines such as metaxylylenediamine, paraxylylenediamine, metaphenylenediamine, and paraphenylenediamine.

[0035] The semi-aromatic polyamide may contain, as a monomer component, a lactam component (in other words, a component derived from lactam) such as ε-caprolactam, ζ-enantholactam, η-capryllactam, or ω-laurolactam, within a range that does not impair the effects of the present invention.

[0036] The types and copolymerization ratios of the monomer components constituting the semi-aromatic polyamide are preferably selected so that the melting point (Tm) of the resulting semi-aromatic polyamide falls within the range of 270 to 350°C. When the semi-aromatic polyamide has a Tm of 350°C or less, thermal decomposition during processing into a film can be efficiently suppressed. Furthermore, when the Tm is 270°C or more, a film with excellent heat resistance can be formed.

[0037] The semi-aromatic polyamide preferably has an intrinsic viscosity of 0.8 to 2.0 dL / g, more preferably 0.9 to 1.8 dL / g. When the semi-aromatic polyamide has an intrinsic viscosity of 0.8 dL / g or more, it is possible to produce a film having excellent 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 a resin other than a semi-aromatic polyamide as a resin component. However, from the viewpoint of improving heat resistance and transparency, the proportion of the semi-aromatic polyamide in the total amount of the resin component is, for example, 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] The semi-aromatic polyamide film of the present invention may contain other components in addition to the resin component, as needed, such as a polymerization catalyst (such as phosphoric acid, phosphorous acid, hypophosphorous acid, or a salt thereof), an end-capping agent (such as acetic acid, lauric acid, benzoic acid, octylamine, cyclohexylamine, or aniline), and additives described below. <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 D From the viewpoint of suppressing the occurrence of sagging, is preferably −0.0005 to 0.0040, more preferably 0.0000 to 0.0035, and most preferably 0.0010 to 0.0029.

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

[0041] Refractive index average value n Av =(n C +n L +n R ) / 3 (2) (In the formula, n C , n L , and n R is the same as above) The semi-aromatic polyamide film of the present invention has a refractive index difference of n D Since the refractive index difference n D and the average refractive index n Av is within the above range), the occurrence of sagging can be suppressed, and the amount of sagging of the film can be kept at 3.0‰ or less. This can prevent wrinkles from occurring when the film is wound onto a take-up roll, and can prevent problems caused by wrinkles from occurring when the film wound onto the roll is pulled out and subjected to 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 sagging is measured by the following method: In the present invention, when the position where sagging occurs (i.e., the position where the length in the MD direction is maximum) is within 80% from the center in the TD direction of the film, it is called "center sagging," and when it is within 10% from both ends in the TD direction of the film, it is called "end sagging." <Method for measuring sagging amount> When the semi-aromatic polyamide film is in the form of a wound film roll, a sample is cut out from a film roll having an outer diameter of 300 mm or more, covering one circumference of the surface layer. The length of the obtained sample in the MD direction is measured from one end of one side along the TD direction to the other end at 50 mm intervals, and the amount of sagging is calculated from the maximum and minimum values ​​of the length using the following formula (3).

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

[0044] Slack (‰) = (maximum value - minimum value) ÷ maximum value × 1000 (3) Furthermore, the semi-aromatic polyamide film of the present invention has excellent dimensional stability under high temperature conditions. The semi-aromatic polyamide film of the present invention is left in an atmosphere of 250°C for 5 minutes, and then left at a temperature of 23°C and a humidity of 50% RH for 2 hours, and the dimensions are measured. The thermal shrinkage ratio S in the MD direction is determined by measuring the dimensions of the semi-aromatic polyamide film. MD and thermal shrinkage rate S in the TD direction TD are preferably −1.0 to 1.5%, more preferably −0.8 to 1.3%, and even more preferably −0.6 to 1.0%. When the heat shrinkage rates of the semi-aromatic polyamide film in the MD and TD directions are 1.5% or less, the occurrence of processing problems due to dimensional changes when the film is subjected to high-temperature processing can be suppressed.

[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 K 7105. Furthermore, in a semi-aromatic polyamide film having 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 of 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 a method of sequential biaxial stretching in which an unstretched film is first stretched in the MD direction and the resulting MD-uniaxially stretched film is stretched in the TD direction.

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

[0048] In the present invention, the production of a film by the sequential biaxial stretching method is particularly preferred. The sequential biaxial stretching method has a simpler device configuration than the simultaneous biaxial stretching method, and can reduce capital investment costs. Furthermore, the stretching conditions in the MD and TD directions can be adjusted independently, and relaxation treatment can be performed in both the MD and TD directions. Therefore, the directionality of mechanical strength, etc. can be appropriately set for each application.

[0049] The semi-aromatic polyamide used in the present invention has very high crystallinity, so when the sequential biaxial stretching method is used, orientation crystallization tends to occur during the initial stretching in the MD direction, and subsequent stretching in the TD direction may become 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 adopt the sequential biaxial stretching method.

[0051] (Unstretched semi-aromatic polyamide film) The unstretched film of semi-aromatic polyamide can be produced by melt-kneading a film raw material containing at least a semi-aromatic polyamide in an extruder and forming the film.

[0052] Commercially available semi-aromatic polyamides can be used, such as "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)" manufactured by Mitsui Chemicals, Inc., and "Ultramid (registered trademark)" manufactured by BASF.

[0053] Semi-aromatic polyamides can be produced by known methods for producing crystalline polyamides, such as solution polymerization or interfacial polymerization using acid chloride and diamine as raw materials (Method A), a method in which a low polymer is produced using dicarboxylic acid and diamine as raw materials and the low polymer is then polymerized by melt polymerization or solid-state polymerization (Method B), a method in which a salt and a crushed mixture of low polymers are produced using dicarboxylic acid and diamine as raw materials and then solid-state polymerized (Method C), and a method in which a salt is produced using dicarboxylic acid and diamine as raw materials and then solid-state polymerized (Method D).

[0054] In Method B, for example, a nylon salt prepared by mixing a diamine, a dicarboxylic acid, and a polymerization catalyst is thermally polymerized at a temperature of 200 to 250°C to obtain a low polymer. The intrinsic viscosity of the low polymer is preferably 0.1 to 0.6 dL / g. By setting the intrinsic viscosity of the low polymer in the range of 0.1 dL / g or more, it is possible to increase the polymerization rate in the subsequent solid-state polymerization or melt polymerization while maintaining the molar balance between the carboxyl groups of the dicarboxylic acid and the amino groups of the diamine. Furthermore, by setting the intrinsic viscosity of the low polymer in the range of 0.6 dL / g or less, it is possible to prevent the resulting semi-aromatic polyamide from becoming discolored.

[0055] The solid-state polymerization of the oligomer is preferably carried out under reduced pressure or in an inert gas flow. The temperature of the solid-state polymerization is preferably 200 to 280°C. By setting the temperature of the solid-state polymerization within this range, the polymerization reaction rate can be increased, and the semi-aromatic polyamide can be rapidly produced. Furthermore, coloration and gelation of the resulting semi-aromatic polyamide can be suppressed.

[0056] The melt polymerization of the oligomer is preferably carried out at a temperature of 350° C. or less, since this suppresses decomposition and thermal degradation of the semi-aromatic polyamide and allows the production of a semi-aromatic polyamide having 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 of molten aliphatic diamine and solid aromatic dicarboxylic acid is stirred and mixed to obtain a mixture. Then, in this mixture, a salt-forming reaction between the aromatic dicarboxylic acid and the aliphatic diamine and a oligomer-forming reaction between the salt and the oligomer are carried out at a temperature below the melting point of the semi-aromatic polyamide to be ultimately produced. Crushing may be carried out during the reaction, or the reaction mixture may be removed and then crushed after the reaction. The resulting reaction product is then solid-phase polymerized at a temperature below the melting point of the semi-aromatic polyamide to obtain a predetermined molecular weight, thereby obtaining a semi-aromatic polyamide. Solid-phase polymerization is preferably carried out in a stream of inert gas such as nitrogen at a polymerization temperature of 180 to 270°C for a reaction time of 0.5 to 10 hours.

[0058] In Method D, for example, aromatic dicarboxylic acid powder is preheated to a temperature above the melting point of the aliphatic diamine but below the melting point of the aromatic dicarboxylic acid. The aliphatic diamine is then added to the aromatic dicarboxylic acid powder at this temperature, essentially without adding water, so as to maintain the aromatic dicarboxylic acid powder in powder form. The resulting salt is then solid-state polymerized at a temperature below the melting point of the semi-aromatic polyamide to obtain a desired molecular weight, yielding a semi-aromatic polyamide. Solid-state polymerization is preferably carried out in a stream of inert gas such as nitrogen, at a polymerization temperature of 180-270°C for a reaction time of 0.5-10 hours.

[0059] In the present invention, methods C and D are preferred, with method D being more preferred. Compared with method B, methods C and D can produce a crushed mixture of salt and oligomers or a salt at a lower temperature, and do not require a large amount of water when producing a crushed mixture of salt and oligomers or a salt. Therefore, the occurrence of gel-like bodies can be reduced, and fisheyes can be reduced.

[0060] As the semi-aromatic polyamide, only virgin raw materials may be used, or off-spec film and offcuts (edge ​​trims) produced as by-products during film production may be collected and mixed with the virgin raw materials. Examples of methods for mixing the raw materials include known methods such as a dry blending method and a melt mixing method in which a compound is obtained using a single-screw extruder or a twin-screw extruder.

[0061] In addition to the semi-aromatic polyamide, the film raw material may contain one or more additives as needed to further improve various properties. Examples of additives include lubricants, colorants such as pigments (e.g., titanium dioxide) and dyes, color inhibitors, heat stabilizers, antioxidants (e.g., hindered phenols, phosphate esters, and phosphites), weather resistance improvers (e.g., benzotriazole compounds), flame retardants (e.g., bromine-based flame retardants and phosphorus-based flame retardants), plasticizers, release agents, reinforcing agents (e.g., talc), modifiers, antistatic agents, UV 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 content of the lubricant can be selected depending on the frictional properties, optical properties, and other properties required for the film, 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. The content of the lubricant is, for example, 0.05% by mass or more, preferably 0.1% by mass or more. Adding a lubricant to the film raw materials can also reduce the haze of the resulting film.

[0063] The unstretched film containing the semi-aromatic polyamide and the above-mentioned additives can be produced, for example, by the following method. (A) A method in which an additive is added during polymerization of a semi-aromatic polyamide to produce a semi-aromatic polyamide containing the additive, which is then melted and formed into a film. (B) A method in which a high concentration of additives and semi-aromatic polyamide are melt-kneaded to prepare pellets, and then, at the time of film production, the masterbatch and natural pellets (i.e., additive-free semi-aromatic polyamide pellets) are melt-kneaded in an extruder to produce a film (masterbatch method). (C) A method in which a dry blend of semi-aromatic polyamide and additives is charged into an extruder, melt-kneaded in the extruder, and formed into a film. (D) A method in which the semi-aromatic polyamide and the additives are separately charged into an extruder, melt-kneaded in the extruder, and then formed into a film. The unstretched semi-aromatic polyamide film preferably has a heat of crystallization of 20 J / g or more, more preferably 25 J / g or more. The heat of crystallization is preferably, for example, 35 J / g or less, more preferably 30 J / g or less. When the heat of crystallization of the unstretched film is 20 J / g or more, it can be stably stretched with a small stretching force, resulting in a stretched film with a uniform thickness. Furthermore, the resulting film has a high tensile elongation at break, and even when external stress is applied in the TD direction, it stretches in response to the stress, thereby preventing breakage.

[0064] An unstretched film of semi-aromatic polyamide having a heat of crystallization of 20 J / g or more can be produced by melt-mixing the semi-aromatic polyamide in an extruder at a temperature of 280 to 340°C for 3 to 15 minutes, extruding the polyamide into a sheet through a T-die, and cooling the extruded sheet by placing it in close contact with a cooling roll whose temperature is adjusted to 30 to 40°C.

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

[0066] The stretching ratio in the MD direction is preferably 2.0 to 4.5 times. The lower limit of the stretching ratio is preferably 2.3 times, more preferably 2.4 times. The upper limit of the stretching 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] Stretching in the MD direction at a draw ratio of 4.5 times or less results in a uniaxially stretched MD film with moderate crystallization and excellent stretchability in the TD direction. Stretching the resulting uniaxially stretched MD film in the TD direction suppresses the occurrence of stretching irregularities, resulting in a biaxially stretched film with excellent thickness precision and transparency and high tensile elongation at break in the MD direction.

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

[0069] The stretching speed is preferably a stretching strain rate in the MD direction of more than 400% / min, more preferably 800 to 12,000% / min, and even more preferably 1,200 to 6,000% / min. Stretching at a stretching strain rate of more than 400% / min can prevent the film from breaking during stretching due to crystal growth. Stretching at a stretching strain rate of 12,000% / min or less allows the film to deform in response to the applied stress, preventing the film from breaking.

[0070] From the viewpoint of suppressing film breakage and producing a biaxially stretched film with a high 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 a polyamide 9T film (Tg of polyamide 9T=125°C), 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, or MD-uniaxially stretched film in the case of sequential biaxial stretching) before it is subjected to 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 less than (Tg-9)°C, the resulting film tends to have a large amount of edge sagging. If the preheating temperature of the film is more than (Tg+5)°C, the resulting film tends to have a large amount of center sagging.

[0073] When the preheating step is a step in which the film is preheated while the temperature is changed stepwise, the preheating temperature immediately before the stretching step is preferably within the above range.

[0074] For example, in the case of a 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 the present invention, sagging can be suppressed by preheating the film within the above-mentioned specific temperature range. Although the mechanism by which sagging is suppressed by adjusting the preheating temperature of the film is not clear, it is thought that sagging can be suppressed by controlling the bowing phenomenon.

[0076] When a film is produced using the tenter-type stretching method, bowing occurs due to stress generated in the film at the boundary between the stretching section and the heat-setting section. Specifically, when a stretched film is produced using the tenter-type stretching method, the film passes through the preheating section, stretching section, heat-setting section, relaxation section, and cooling section. The stretching stress reaches its maximum near the end of the stretching section, i.e., the point where the set stretch ratio is reached. At this time, because both ends of the film are held by clips in the tenter, the central portion of the film is pulled toward the end of the stretching section. Since the central portion of the film is pulled toward the stretching section from the heat-setting section following the stretching section, a bowing phenomenon occurs in which the central portion of the film forms an arc protruding in the opposite direction to the film's direction of travel when it emerges from the stretching machine, rather than a straight line drawn perpendicular to the film's direction of travel before entering the stretching machine. This phenomenon results in a difference in the effective stretch ratio in the film's direction of travel between the central portion and both ends, which is thought to affect film sagging. It is presumed that the occurrence of bowing can be suppressed by controlling the temperatures of the preheating section and the cooling section within a specific range, thereby suppressing sagging. (Stretching process) The stretching step is a step of stretching a film to obtain a biaxially stretched film. When the film to be subjected to this step is an unstretched film, the unstretched film is simultaneously biaxially stretched in the MD and TD directions. When the film to be subjected to this step is an MD-uniaxially stretched film, the MD-uniaxially stretched film is stretched in the TD direction.

[0077] When a MD uniaxially stretched film is stretched in the TD direction (sequential biaxial stretching), the stretching ratio in the TD direction is preferably 2.0 to 5.0 times, more preferably 2.0 to 4.0 times, still 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 above range, the occurrence of stretching irregularities can be suppressed, and a biaxially stretched film having excellent thickness precision and transparency and high tensile elongation at break in the TD direction can be obtained.

[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, and 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 draw ratio of 4.5 or less can produce a stretched film with low heat shrinkage and excellent dimensional stability, while stretching in the TD direction at a draw ratio of 5.0 or less can produce a stretched film with low heat shrinkage, excellent dimensional stability, and high tensile elongation at break.

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

[0082] In the simultaneous biaxial stretching method, when a biaxially stretched film having a thickness of 1 to 25 μm is obtained, 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. When a biaxially stretched film having a thickness of 26 to 50 μm is obtained, 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 and TD directions exceeds 400% / min, more preferably 800 to 12,000% / min, and even more preferably 1,200 to 6,000% / min. Stretching at a stretching strain rate of more than 400% / min can prevent the film from breaking during stretching due to crystal growth. Stretching at a stretching strain rate of 12,000% / min or less allows the film to deform in response to the applied stress, preventing the film from breaking.

[0084] From the viewpoint of suppressing film breakage and producing a biaxially stretched film with a high 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 a polyamide 9T film (Tg of polyamide 9T=125°C), the stretching temperature is preferably 120 to 160°C, more preferably 125 to 155°C. When the heating temperature in the stretching step is divided into two zones, the stretching temperature in the first half is preferably 120 to 140°C, more preferably 125 to 135°C. The stretching temperature in the second half is preferably above 135°C but not higher than 160°C, more preferably 140 to 160°C, and particularly preferably 145 to 155°C. (heat setting process) After the stretching, the semi-aromatic polyamide film is preferably heat-set while the film is still held by the clips used during stretching. By performing heat-setting, the resulting film can be prevented from developing heat-induced spots and have a reduced heat shrinkage rate. The heat-setting temperature, based on the melting point (Tm) of the semi-aromatic polyamide, 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. A heat-setting temperature of (Tm-30)°C or higher can provide a film with a low heat shrinkage rate. Furthermore, a heat-setting temperature of (Tm)°C or lower can prevent poor appearance such as heat-induced wrinkles and breakage during heat-setting, resulting in a biaxially stretched film with a high tensile elongation at break.

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

[0087] Examples of the heat setting method include known methods such as a method of blowing hot air, a method of irradiating infrared rays, a method of irradiating microwaves, etc. Among these, a method of blowing hot air is preferred because it allows for uniform and precise heating. (Relaxation process) After the heat setting treatment, the film is preferably subjected to a relaxation treatment in the MD and TD directions at the same temperature as the heat setting temperature while being held by the clips.

[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%. When the relaxation treatment is performed in the MD direction and the TD direction at the above relaxation rates, the occurrence of sagging is suppressed, the heat shrinkage rate is reduced, and a film with improved dimensional stability can be obtained.

[0089] In the sequential biaxial stretching method, when a biaxially stretched film having a thickness of 1 to 50 μm is obtained, the relaxation rate is preferably 1.0 to 6.0% in the MD direction and 1.0 to 12.0% in the TD direction, and when a biaxially stretched film having a thickness of 51 to 150 μm is obtained, the relaxation rate 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 treatment can be carried out in-line in the MD and TD directions simultaneously or separately. When the treatments are carried out separately, the relaxation can be carried out by a method in which the MD direction is relaxed first and then the TD direction, or by a method in which the TD direction is relaxed first and then the MD direction.

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

[0093] Alternatively, the relaxation treatment can be carried out in-line in the TD direction after biaxial stretching, and then taken up, followed by passing the film offline through a drying oven set at a predetermined temperature under low tension to perform relaxation treatment in the MD direction. (cooling process) The cooling step is a step of cooling the stretched film. 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 the amount of 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 the amount of 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] When producing the semi-aromatic polyamide film of the present invention by a sequential biaxial stretching method, from the viewpoint of adjusting the MD refractive index at the center, left end, and right end of the obtained film in the TD direction within a specific range, it is preferable that the preheating temperature T1 (°C) and the cooling temperature T2 (°C) satisfy the following formula (4), more preferably the following formula (4-1), and even more preferably 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 may 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 produced by a flat-type sequential biaxial stretching method, a flat-type simultaneous biaxial stretching method, a tubular method, etc. Examples of stretching devices for carrying out the flat-type simultaneous biaxial stretching method include a screw-type tenter, a pantograph-type tenter, and a linear motor-driven clip-type tenter.

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

[0099] The obtained semi-aromatic polyamide film may be in the form of a sheet or a film roll wound around a take-up roll, and the film roll form includes a raw roll obtained by winding the film obtained through the preheating, stretching, and cooling steps around a take-up roll, and a slit roll obtained by slitting the raw roll to a desired width.

[0100] The semi-aromatic polyamide film may be a single-layer film or may have a multi-layer structure in which two or more layers are laminated.

[0101] When the semi-aromatic polyamide film is a multilayer film, a lubricant can be contained in at least one layer. For example, in a two-layer film, a lubricant is preferably contained in one layer, and in a three-layer film, a lubricant is preferably contained 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 and amount of lubricant to be contained can be adjusted appropriately 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, etc. in order to improve adhesion to other materials.

[0103] The semi-aromatic polyamide film of the present invention may be laminated with a layer made of an inorganic material such as a metal or its oxide, another type of polymer, paper, woven fabric, nonwoven fabric, wood, or the like. <Application> The semi-aromatic polyamide film of the present invention has heat resistance and excellent dimensional stability under high temperature conditions, and therefore can be used for various electronic materials, optical parts, and other applications.

[0104] The semi-aromatic polyamide film of the present invention can be used, specifically, as a packaging material for pharmaceuticals; packaging material for food such as retort foods; packaging material for electronic components such as semiconductor packages; electrical insulating materials for motors, transformers, cables, etc.; dielectric materials for capacitors, etc.; magnetic tape materials such as cassette tapes, magnetic tapes for data storage in digital data storage, and video tapes; solar cell substrates, liquid crystal panels, conductive films, protective plates for display devices, etc.; electronic substrate materials such as LED mounting substrates, substrates for flexible printed wiring, and flexible flat cables; heat-resistant tapes such as cover lay films for flexible printed wiring, heat-resistant masking tapes, and industrial process tapes; heat-resistant barcode labels; heat-resistant reflectors; insulating tapes; various release films; heat-resistant base films; photographic films; molding materials; agricultural materials; medical materials; civil engineering and construction materials; and filtration membranes, as well as films for household and industrial materials.

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

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

[0107] Examples of the electronic materials include packaging materials for electronic components such as semiconductor packages; electrical insulating materials for motors, transformers, cables, etc.; dielectric materials for capacitor applications, etc.; magnetic tape materials for cassette tapes, magnetic tapes for storing data in digital data storage, video tapes, etc.; heat-resistant masking tapes, heat-resistant reflectors, insulating tapes, release films, etc.

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

[0109] Examples of the optical components include solar cell substrates, liquid crystal panels, conductive films, protective plates and 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, and sealing films.

[0110] The above-described configurations and combinations of the present invention are merely examples, and the configurations may be added, omitted, substituted, or modified as appropriate within the scope of the gist of the present invention. Furthermore, the present invention is not limited to the embodiments. [Example]

[0111] The present invention will be specifically described below with reference to examples. 1. Evaluation Method (1) Intrinsic viscosity of semi-aromatic polyamide Intrinsic viscosity (η) of resin at concentrations of 0.05, 0.1, 0.2, and 0.4 g / dL in concentrated sulfuric acid at 30°C inh ) was calculated using the following formula, and the value extrapolated to a concentration of 0 was taken as the limiting viscosity [η].

[0112] η inh =[ln(t1 / t0)] / c (In the formula, η inhis the intrinsic viscosity (dL / g), t0 is the flow time of the solvent (seconds), t1 is the flow time of the resin solution (seconds), and c is the concentration of the resin in the solution (g / dL). (2) Melting point Tm and glass transition temperature Tg of semi-aromatic polyamide Using a differential scanning calorimeter (PerkinElmer DSC-7), the semi-aromatic polyamide was heated from 20°C to 350°C at 10°C / min under a nitrogen atmosphere and held for 5 minutes (first scan), then cooled from 350°C to 20°C at 100°C / min and held for 5 minutes. The glass transition temperature during the second scan, during which the temperature was raised again from 20°C to 350°C at 10°C / min, was taken as Tg of the semi-aromatic polyamide. Similarly, the peak top temperature of the crystalline melting peak observed in the second scan was taken as Tm. (3) Heat of crystallization of unstretched film Using a differential scanning calorimeter (DSC-7 manufactured by PerkinElmer), 10 mg of an unstretched sheet of semi-aromatic polyamide was heated from 40°C to 350°C at a rate of 20°C / min (1st scan) under a nitrogen atmosphere, and the calorific value of the resulting exothermic peak was determined. (4) Heat shrinkage rate of semi-aromatic polyamide film A MD test piece (MD length 100 mm × TD width 10 mm) and a TD test piece (TD length 100 mm × MD width 10 mm) were cut out from the semi-aromatic polyamide film. The obtained test pieces were left in an atmosphere of 250°C for 5 minutes, and then left at a temperature of 23°C and a humidity of 50% RH for 2 hours. The length of the test pieces after the treatment was measured, and the thermal shrinkage ratio S of the test pieces in the MD direction was calculated using the following formula: MD and the thermal shrinkage of the test piece in the TD direction S TD asked for.

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

[0114] The refractive index n in the MD direction of the obtained sample at three points located on a line parallel to the TD direction was determined using an Abbe refractometer DR-M2 (manufactured by Atago Co., Ltd.) in accordance with a method conforming to JIS K7142. 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 liquid.

[0115] More specifically, the refractive index n C , the refractive index n in the MD direction at a position 10% of the sample width inside from the left end of the sample L , and the refractive index n in the MD direction at a position 10% of the sample width inside from the right end of the sample R was measured.

[0116] Then, from the following formula (1), the refractive index difference n D asked for.

[0117] Refractive index difference n D ={(n C -n L )-(n C -n R )} / twenty one) Furthermore, the average refractive index n Av asked for.

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

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

[0120] Production Example 1 (Production of Semi-Aromatic Polyamide A) 3,289 parts by mass of terephthalic acid (TPA), 2,533 parts by mass of 1,9-nonanediamine (NDA), 633 parts by mass of 2-methyl-1,8-octanediamine (MODA), 48.9 parts by mass of benzoic acid (BA), 6.5 parts by mass of sodium hypophosphite monohydrate (0.1% by mass relative to the total of the four polyamide raw materials), and 2,200 parts by mass of distilled water were placed in a reactor and purged with nitrogen. The molar ratio of these raw materials (TPA / BA / NDA / MODA) was 99 / 2 / 80 / 20.

[0121] The contents of the reactor were stirred at 100°C for 30 minutes, and then the internal temperature was increased to 210°C over two hours. At this time, the pressure inside the reactor rose to 2.12 MPa. The reaction was continued for one hour, then the temperature was increased to 230°C and maintained at 230°C for two hours, while the water vapor was gradually released to maintain the pressure at 2.12 MPa. The pressure was then reduced to 0.98 MPa over 30 minutes, and the reaction continued for another hour, yielding a prepolymer. This was then dried under reduced pressure at 100°C for 12 hours and then crushed to a size of 2 mm or less.

[0122] The ground prepolymer was then subjected to solid-state polymerization at 230°C and 13.3 Pa for 10 hours to obtain a polymer. The resulting polymer was fed into a twin-screw extruder, melt-kneaded and extruded at a cylinder temperature of 320°C, cooled, and cut to produce pellets of semi-aromatic polyamide A. The resulting 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 the following Production Example 2 was used.

[0123] Manufacturing Example 2 (Manufacturing of Master Chip (M1)) 98 parts by mass of the semi-aromatic polyamide A obtained in Production Example 1 and 2 parts by mass of silica (Sylysia 310P, manufactured by Fuji Silysia Chemical Ltd., average particle size 2.7 μm) were melt-kneaded to prepare a master chip (M1) containing 2% by mass of silica.

[0124] Example 1 A mixture was obtained by mixing semi-aromatic polyamide A, a heat stabilizer (Sumitomo Chemical Co., Ltd., Sumilizer GA-80), and a master chip (M1) so that the amounts were 100 parts by mass of semi-aromatic polyamide A, 0.2 parts by mass of heat stabilizer, and 0.1 parts by mass of silica.

[0125] The resulting mixture was melted in a 65 mm single-screw extruder with cylinder temperatures set to 295°C (front stage), 320°C (middle stage), and 320°C (rear stage), extruded into a sheet from a T-die set at 320°C, and cooled by electrostatically adhering it to a cooling roll set at a surface temperature of 40°C, yielding a substantially unoriented, unstretched sheet with a thickness of 230 μm (crystallization heat of 27 J / g).

[0126] Next, the resulting unstretched sheet was biaxially stretched using a flat-type sequential stretching machine.

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

[0128] The MD uniaxially stretched film was then introduced into a TD stretching machine while both ends were held with clips. The MD uniaxially stretched film was preheated in the preheating section of the TD stretching machine at a preheating temperature (T1) of 123°C and stretched in the TD stretching section at a stretching temperature of 130°C and a stretch ratio of 3.4.

[0129] After stretching, the film was heat-set at 279°C in the heat-setting section.

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

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

[0132] This resulted in a semi-aromatic polyamide film having a thickness of 27 μm, which was then wound up into a film roll having a width of 1200 mm and a diameter of 400 mm.

[0133] Examples 2 to 8, Comparative Examples 1 to 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] From Examples 1 to 7, it was found that when the film was preheated at a predetermined temperature before stretching and cooled at a predetermined temperature after stretching, the refractive index difference n D It can be seen that the refractive index difference n can be adjusted to a predetermined range, and a semi-aromatic polyamide film with excellent dimensional stability under high temperature conditions and sufficiently small sagging can be obtained. In addition, by controlling the cooling temperature after stretching to a more preferable range, D It can be seen that a semi-aromatic polyamide film having the most preferable range can be obtained, and the amount of sagging can be further reduced.

[0135] Furthermore, a comparison of Examples 1 to 7 with Example 8 reveals that by adjusting the heat setting temperature, a semi-aromatic polyamide film with little 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 had a refractive index difference of n D did not satisfy the range specified in the present invention, the amount of sagging was large.

Claims

1. A rectangular semi-aromatic polyamide film having a side along the MD direction and a side along the TD direction, The refractive index difference n calculated from the following formula (1) Ｄ A semi-aromatic polyamide film having a refractive index of -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 center 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% of the film width inward from the right end of the film. The center, left end, and right end are located on a 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 tensile strength is 1.5985 to 1.6045. Refractive index average value n Ａｖ = (n Ｃ +n Ｌ +n Ｒ ) / 3 (2) (In the formula, n Ｃ , n Ｌ , and n Ｒ is the same as above)

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

4. The heat shrinkage ratio S in the MD direction is determined by leaving the sample in an atmosphere at 250°C for 5 minutes, and then leaving it in an atmosphere at a temperature of 23°C and a humidity of 50% RH for 2 hours, and then measuring the dimensions. ＭＤ and the thermal shrinkage rate S in the TD direction ＴＤ and , respectively, are -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 according to any one of claims 1 to 4. [1] A step of preheating an unstretched film of semi-aromatic polyamide 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 and TD directions; 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 step of preheating a semi-aromatic polyamide uniaxially stretched film in the MD direction at a temperature of (Tg-9) ° C. to (Tg+5) ° C. based on the Tg of the semi-aromatic polyamide, a step of stretching the film in 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.

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

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

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