Semi-aromatic polyamide film and manufacturing method thereof

Abstract

The present invention provides a semi-aromatic polyamide film with sufficiently small relaxation amount. The semi-aromatic polyamide film of the present invention is a rectangular semi-aromatic polyamide film having an edge along the MD direction and an edge along the TD direction. The refractive index difference nD calculated from the following formula (1) is -0.0010 to 0.0045, refractive index difference nD={(nC-nL)-(nC-nR)} / 2 (1) where nC is the refractive index of the central part of the film in the MD direction, nL is the refractive index of the position 10% inside the left end of the film in the MD direction, and nR is the refractive index of the position 10% inside the right end of the film in the MD direction.

Description

Technical Field

[0001] This invention relates to a semi-aromatic polyamide film with suppressed relaxation, a method for manufacturing the same, and electronic materials or optical components having the aforementioned semi-aromatic polyamide film. Prior Technology

[0002] Semi-aromatic polyamide films stretched along the MD direction (long side direction) and TD direction (width direction) are used in various fields due to their excellent heat resistance and mechanical properties. Among the semi-aromatic polyamides that constitute semi-aromatic polyamide films, polyamide 9T, which is composed of an aliphatic diamine with 9 carbon atoms and terephthalic acid, or polyamide 10T, which is composed of an aliphatic diamine with 10 carbon atoms and terephthalic acid, exhibits particularly excellent heat resistance and mechanical properties.

[0003] Patent Document 1 discloses a film made of semi-aromatic polyamide resin, which is a biaxially stretched film obtained by biaxially stretching an unstretched film with specific crystallization heat. However, the film disclosed in Patent Document 1 has a large relaxation amount, which sometimes forms wrinkles during winding or serpentine during travel.

[0004] On the other hand, Patent Document 2 discloses a membrane made of aliphatic polyamide resin, the relaxation amount of which can be controlled by the cooling rate of the biaxially stretched and heat-fixed membrane; as the cooling rate decreases, the relaxation amount decreases. However, the membrane disclosed in Patent Document 2 sometimes deforms when exposed to high temperatures. [Previous Technical Documents] [Patent Literature]

[0005] [Patent Document 1] Japanese International Publication No. 2020 / 230806 [Patent Document 2] Japanese Patent Application Publication No. 2008-297415 Summary of the Invention

[0006] [The problem that the invention aims to solve] Furthermore, the inventors applied the method described in Patent Document 2 in order to control the relaxation amount of the semi-aromatic polyamide film disclosed in Patent Document 1, but the relaxation amount could not be sufficiently reduced.

[0007] In addition, in recent years, optical films for display components have been required to maintain dimensional stability without deformation even when exposed to high temperatures during transportation or thermal processing.

[0008] The purpose of this invention is to provide a semi-aromatic polyamide film with sufficiently small relaxation amount. Another object of the present invention is to provide a semi-aromatic polyamide film with sufficiently small relaxation amount and excellent dimensional stability under high temperature conditions. Another object of the present invention is to provide a method for manufacturing a semi-aromatic polyamide film with a sufficiently small relaxation amount. Another object of the present invention is to provide an electronic material or optical component having the aforementioned semi-aromatic polyamide film. [Technical means used to solve the problem]

[0009] To address the aforementioned issues, the inventors conducted meticulous research and discovered that by preheating an unstretched film or a uniaxially stretched film in the MD direction at a specific temperature followed by stretching, and then cooling it at a specific temperature after stretching, the refractive index in the MD direction of the resulting film at the central, left, and right ends in the TD direction can be adjusted to a specific range, thereby significantly reducing the relaxation amount. Furthermore, by preheating an unstretched film or a uniaxially stretched film in the MD direction at a specific temperature followed by stretching, then heat-fixing it at a specific temperature, and further cooling it at a specific temperature, the relaxation amount of the resulting film can be significantly reduced, and the dimensional stability under high-temperature conditions can be improved. This invention was made based on the foregoing findings.

[0010] That is, the present invention provides a semi-aromatic polyamide film, which is a rectangular semi-aromatic polyamide film having an edge along the MD direction and an edge along the TD direction. The refractive index difference nD calculated from the following equation (1) is -0.0010 to 0.0045. Refractive index difference nD={(nC-nL)-(nC-nR)} / 2 (1) In the formula, nC is the refractive index of the central part of the film in the MD direction, nL is the refractive index of the position 10% inside the left end of the film in the MD direction, and nR is the refractive index of the position 10% inside the right end of the film in the MD direction; the aforementioned central part, left end, and right end are located on a line parallel to the TD direction of the film.

[0011] Furthermore, the present invention provides the aforementioned semi-aromatic polyamide film, wherein the average refractive index nAv calculated from the following formula (2) is between 1.5985 and 1.6045. The average refractive index is nAv = (nC + nL + nR) / 3 (2) In the formula, nC, nL, and nR are the same as those mentioned above.

[0012] Furthermore, the present invention provides the aforementioned semi-aromatic polyamide film, wherein the relaxation amount measured by the following method is 3.0‰ or less. <Methods for determining relaxation amount> Starting from one end along one side of the TD direction and extending to the other end, the length along the MD direction is measured in 50mm increments. The relaxation amount is then calculated from the maximum and minimum values ​​of the aforementioned length using the following formula (3). Relaxation amount (‰) = (maximum value - minimum value) ÷ maximum value × 1000 (3).

[0013] Furthermore, the present invention provides the aforementioned semi-aromatic polyamide film, wherein after being placed in a gas environment at 250°C for 5 minutes, and then placed in a gas environment at 23°C and 50%RH for 2 hours, the heat shrinkage rate SMD in the MD direction and the heat shrinkage rate STD in the TD direction, which are obtained by dimensional determination, are measured to be -1.0 to 1.5%, respectively.

[0014] Furthermore, the present invention provides a method for manufacturing a semi-aromatic polyamide film, which obtains the aforementioned semi-aromatic polyamide film through the steps described in [1] or [2] below. [1] The steps of preheating the unstretched film of semi-aromatic polyamide at a temperature of (Tg-9)℃ to (Tg+5)℃ based on the glass transition temperature Tg of semi-aromatic polyamide, the steps of stretching simultaneously in the MD direction and TD direction, and the steps of cooling at a temperature of (Tm-260)℃ to (Tm-170)℃ based on the melting point Tm of semi-aromatic polyamide; [2] The steps of preheating the semi-aromatic polyamide uniaxially stretched film in the MD direction at a temperature of (Tg-9)℃ to (Tg+5)℃ based on the Tg of the semi-aromatic polyamide, the steps of stretching in the TD direction, and the steps of cooling at a temperature of (Tm-260)℃ to (Tm-170)℃ based on the melting point Tm of the semi-aromatic polyamide.

[0015] Furthermore, the present invention provides an electronic material having the aforementioned semi-aromatic polyamide film.

[0016] Furthermore, the present invention provides an optical component having the aforementioned semi-aromatic polyamide film. [Effects of the Invention]

[0017] According to the present invention, a semi-aromatic polyamide film with sufficiently small relaxation amount (or sufficiently small relaxation amount and excellent dimensional stability even at high temperature of 250°C) can be provided.

[0018] The semi-aromatic polyamide film of the present invention can be suitable for use as a base film or cover film for flexible printed circuit boards and other electronic materials; as a substrate for displays and other optical materials; as a heat-resistant tape and the like. Simple Explanation of the Diagram

[0019] Figure 1 illustrates the method for measuring the amount of relaxation using the case of end relaxation as an example. Implementation

[0020] [Semi-aromatic polyamide film] The semi-aromatic polyamide film of the present invention is a rectangular semi-aromatic polyamide film having an edge along the MD direction and an edge along the TD direction, and is a film containing at least semi-aromatic polyamide as a resin component.

[0021] Semi-aromatic polyamides Semi-aromatic polyamides contain dicarboxylic acid components (i.e., components derived from dicarboxylic acid) and diamine components (i.e., components derived from diamine) as monomer components (i.e., components derived from monomers). Furthermore, the dicarboxylic acid component contains at least an aromatic dicarboxylic acid component, and the diamine component contains at least an aliphatic diamine component.

[0022] In addition to dicarboxylic acid and diamine, semi-aromatic polyamides may also contain other components. However, in order to obtain a film with excellent heat resistance and low water absorption, the total content of dicarboxylic acid and diamine 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.

[0023] In addition to aromatic dicarboxylic acid components and aliphatic diamine components, semi-aromatic polyamides may also contain other components. However, in order to obtain a film with excellent heat resistance and low water absorption, the total content of aromatic dicarboxylic acid components and aliphatic diamine 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.

[0024] The dicarboxylic acid that forms the aforementioned dicarboxylic acid component contains at least an aromatic dicarboxylic acid, and the diamine that forms the aforementioned diamine component contains at least an aliphatic diamine.

[0025] In terms of excellent heat resistance and low water absorption, the aforementioned aromatic dicarboxylic acid preferably contains more than 60 mol% terephthalic acid, more preferably more than 70 mol%, and even more preferably more than 85 mol%.

[0026] Aromatic dicarboxylic acids other than terephthalic acid include isophthalic acid and naphthalene dicarboxylic acid. In addition, naphthalene dicarboxylic acids include 1,2-, 1,3-, 1,4-, 1,5-, 1,6-, 1,7-, 1,8-, 2,3-, 2,6-, and 2,7- compounds.

[0027] In addition to aromatic dicarboxylic acids, other dicarboxylic acids may be included without impairing 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, dodecanoic acid, tetradecanoic acid, and octadecanoic acid.

[0028] The aforementioned aliphatic diamine preferably contains an aliphatic diamine with 6 to 12 carbon atoms as its main component. The content of aliphatic diamines with 6 to 12 carbon atoms in the total aliphatic diamine content is preferably 60 mol% or more, particularly 75 mol% or more, and even more preferably 90 mol% or more. When the content of aliphatic diamines with 6 to 12 carbon atoms is 60 mol% or more, the resulting membrane possesses both heat resistance and workability. One type of aliphatic diamine with 6 to 12 carbon atoms can be used alone or in combination of two or more. When two or more types are used in combination, the aforementioned content refers to the total content of these components.

[0029] Aliphatic diamines with 6 to 12 carbon atoms include: straight-chain 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-chain 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.

[0030] Among the aforementioned aliphatic diamines with 6 to 12 carbon atoms, it is particularly preferred that the aliphatic diamine with 9 to 12 carbon atoms is used as the main component, and more preferably that it is polyamide 9T with aliphatic diamine with 9 carbon atoms as the main component or polyamide 10T with aliphatic diamine with 10 carbon atoms as the main component.

[0031] In addition to aliphatic diamines with 6 to 12 carbon atoms, the aforementioned aliphatic diamines may also contain linear aliphatic diamines with 6 or fewer carbon atoms, such as 1,4-butanediamine and 1,5-pentanediamine.

[0032] Before forming the diamine component, the aforementioned diamines may contain other diamines besides aliphatic diamines, without impairing the effects of the present invention. Examples of other diamines include: alicyclic diamines such as isophorone diamine, norbornene dimethylamine, and tricyclodecane dimethylamine; and aromatic diamines such as m-xylene diamine, p-xylene diamine, m-phenylenediamine, and p-phenylenediamine.

[0033] Semi-aromatic polyamides may also contain endorphin components such as ε-caprolactam, ζ-heptylactam, η-octylactam, and ω-laurylactam as monomeric components, without impairing the effects of the present invention.

[0034] The types and copolymerization ratios of the monomer components constituting the semi-aromatic polyamide are preferably selected in a manner that allows the melting point (Tm) of the resulting semi-aromatic polyamide to be in the range of 270 to 350°C. By setting the Tm of the semi-aromatic polyamide to below 350°C, thermal decomposition during film processing can be effectively suppressed. Furthermore, by setting the Tm to above 270°C, a film with excellent heat resistance can be formed.

[0035] The limiting viscosity of semi-aromatic polyamide is preferably 0.8 to 2.0 dL / g, and more preferably 0.9 to 1.8 dL / g. When the limiting viscosity of semi-aromatic polyamide is above 0.8 dL / g, the membrane exhibits excellent productivity and can be manufactured with excellent mechanical strength.

[0036] <Other Ingredients> The semi-aromatic polyamide film of the present invention contains at least semi-aromatic polyamide as a resin component. Although the semi-aromatic polyamide film of the present invention may contain resins other than semi-aromatic polyamide as resin components, from the viewpoint of improving heat resistance and transparency, the proportion of semi-aromatic polyamide in the total amount of resin components is preferably, for example, 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, more preferably 80% by mass or more, particularly preferably 90% by mass or more, and most preferably 95% by mass or more.

[0037] In addition to the resin component, the semi-aromatic polyamide film of the present invention may also contain other components as needed. Other components may include, for example, polymerization catalysts (phosphoric acid, phosphorous acid, hypophosphoric acid, or salts thereof), end-capping agents (acetic acid, lauric acid, benzyl acid, octylamine, cyclohexylamine, aniline, etc.), and additives described later.

[0038] Semi-aromatic polyamide membrane The refractive index difference nD of the semi-aromatic polyamide film of the present invention, calculated from the following formula (1), is -0.0010 to 0.0045. From the viewpoint of suppressing relaxation, the aforementioned refractive index difference nD is preferably -0.0005 to 0.0040, more preferably 0.0000 to 0.0035, and most preferably 0.0010 to 0.0029. Refractive index difference nD={(nC-nL)-(nC-nR)} / 2 (1) In the formula, nC is the refractive index of the central part of the film in the MD direction, nL is the refractive index of the position 10% inside the left end of the film in the MD direction, and nR is the refractive index of the position 10% inside the right end of the film in the MD direction; the aforementioned central part, left end, and right end are located on a line parallel to the TD direction of the film.

[0039] Furthermore, from the viewpoint of suppressing relaxation, the average refractive index nAv of the semi-aromatic polyamide film of the present invention, calculated from the following formula (2), is preferably 1.5985 to 1.6045, more preferably 1.5989 to 1.6040, and particularly preferably 1.5993 to 1.6036. The average refractive index is nAv = (nC + nL + nR) / 3 (2) In the formula, nC, nL, and nR are the same as those mentioned above.

[0040] The semi-aromatic polyamide film of the present invention, because its refractive index difference nD is within the aforementioned range (preferably, the refractive index difference nD and the average refractive index nAv are within the aforementioned range), can suppress the generation of relaxation, thereby setting the relaxation amount of the film to 3.0‰ or less. This suppresses the formation of wrinkles during winding onto the take-up roller, and suppresses defects caused by wrinkles when the film wound onto the roller is pulled out and subjected to secondary processing. The relaxation amount of the semi-aromatic polyamide film of the present invention is, for example, 3.0‰ or less, preferably 2.5‰ or less, even more preferably 2.0‰ or less, more preferably 1.5‰ or less, and most preferably 1.0‰ or less.

[0041] The aforementioned relaxation amount is determined by the following measurement method. In this invention, when the relaxation occurs at a position (i.e., the position where the length in the MD direction is the maximum) within 80% of the center of the membrane in the TD direction, it is called "intermediate relaxation"; when it occurs at a position within 10% of both ends of the membrane in the TD direction, it is called "end relaxation".

[0042] <Methods for determining relaxation amount> When the semi-aromatic polyamide film is in the form of a film roll formed by winding the film, a circumference of the surface layer is cut from the film roll with an outer diameter of 300 mm or more, and this is used as a sample. Starting from one end of the sample along one side of the TD direction to the other end, the length in the MD direction is measured with a 50 mm scale, and the relaxation amount is obtained from the maximum and minimum values ​​of the aforementioned length by the following formula (3). When the semi-aromatic polyamide film is in the form of a single sheet, the length in the MD direction is measured from one end along one side of the TD direction to the other end using a 50mm scale, and the relaxation amount is obtained from the maximum and minimum values ​​of the aforementioned length by the following formula (3). Relaxation amount (‰) = (maximum value - minimum value) ÷ maximum value × 1000 (3)

[0043] Furthermore, the semi-aromatic polyamide film of the present invention exhibits excellent dimensional stability under high-temperature conditions. After placing the semi-aromatic polyamide film of the present invention in a 250°C gas environment for 5 minutes, and then in a 23°C and 50%RH gas environment for 2 hours, the thermal shrinkage rates SMD in the MD direction and STD in the TD direction, as determined by dimensional analysis, were measured. Preferably, these rates were -1.0% to 1.5%, more preferably -0.8% to 1.3%, and even more preferably -0.6% to 1.0%. When the thermal shrinkage rates of the semi-aromatic polyamide film in the MD and TD directions are below 1.5%, processing obstacles caused by dimensional changes can be suppressed during high-temperature processing.

[0044] Furthermore, from the viewpoint of excellent viewing quality, the haze of the semi-aromatic polyamide film of the present invention, as measured according to JIS K7105, is preferably 14% or less, more preferably 12% or less, and even more preferably 10% or less. Furthermore, in a semi-aromatic polyamide film 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.

[0045] [Manufacturing method of semi-aromatic polyamide film] The semi-aromatic polyamide film of the present invention can be produced by: simultaneously biaxially stretching an unstretched film; or by first stretching the unstretched film in the MD direction, and then stretching the resulting uniaxially stretched film in the MD direction in the TD direction in a phased biaxial stretching method.

[0046] The semi-aromatic polyamide film of the present invention is preferably manufactured by the steps described in [1] or [2] below. [1] The steps of preheating the unstretched semi-aromatic polyamide film, simultaneously stretching it in the MD and TD directions, and cooling it. [2] The steps of preheating the semi-aromatic polyamide uniaxially stretched film in the MD direction, stretching it in the TD direction, and cooling it.

[0047] In addition, a heat-fixing step or a loosening step can be set between the stretching step and the cooling step.

[0048] In this invention, it is preferred to manufacture the membrane using a staged biaxial stretching method. Compared to synchronous biaxial stretching, the staged biaxial stretching method has a simpler apparatus configuration and can reduce equipment investment costs. Furthermore, the stretching conditions in the MD and TD directions can be adjusted independently, and easing treatments can be applied to each direction separately. Therefore, the directionality of mechanical strength, etc., can be appropriately set according to different applications.

[0049] The semi-aromatic polyamide used in this invention has extremely high crystallinity. Therefore, when using the staged biaxial stretching method, orientation crystallization is easily caused during the initial stretching in the MD direction, and it is sometimes difficult to continue stretching in the TD direction.

[0050] On the other hand, when the thickness of the semi-aromatic polyamide film exceeds 50 μm, the force required to stretch the film in the simultaneous biaxial stretching method becomes too strong, sometimes making stretching difficult. In this case, the staged biaxial stretching method is preferred.

[0051] (Unstretched film of semi-aromatic polyamide) Unstretched films of semi-aromatic polyamide can be manufactured by melt-blending and forming a film material containing at least semi-aromatic polyamide in an extruder.

[0052] Semi-aromatic polyamides can be commercially available. Examples of such commercially available products include: Genestar (registered trademark) manufactured by Kuraray Co., Ltd., XecoT (registered trademark) manufactured by Unitika Co., Ltd., Reny (registered trademark) manufactured by Mitsubishi Engineering Plastic Co., Ltd., Arlen (registered trademark) manufactured by Mitsui Chemicals Co., Ltd., and Ultramid (registered trademark) manufactured by BASF.

[0053] Furthermore, semi-aromatic polyamides can be manufactured using methods known for producing crystalline polyamides. Examples include: solution polymerization or interfacial polymerization using chlorohydrin and diamine as raw materials (Method A); methods for producing oligomers using dicarboxylic acids and diamine as raw materials, and then performing melt polymerization or solid-state polymerization on these oligomers to achieve higher molecular weights (Method B); methods for generating a broken mixture of salt and oligomer using dicarboxylic acids and diamine as raw materials, and then performing solid-state polymerization on this mixture (Method C); and methods for generating a salt using dicarboxylic acids and diamine as raw materials, and then performing solid-state polymerization on this mixture (Method D), etc.

[0054] In method B, a nylon salt prepared by mixing diamines, dicarboxylic acids, and a polymerization catalyst is heated and polymerized at a temperature of 200 to 250°C to obtain oligomers. The limiting viscosity of the oligomers is preferably 0.1 to 0.6 dL / g. By setting the limiting viscosity of the oligomers to a range of 0.1 dL / g or higher, it is advantageous to maintain the molar balance between the carboxyl groups of the dicarboxylic acid and the amino groups of the diamine during subsequent solid-state polymerization or melt polymerization, thereby increasing the polymerization rate. Furthermore, by setting the limiting viscosity of the oligomers to a range of 0.6 dL / g or lower, coloring of the resulting semi-aromatic polyamide can be prevented.

[0055] Solid-state polymerization of oligomers is preferably carried out under reduced pressure or with the passage of an inert gas. Furthermore, the preferred temperature for solid-state polymerization is 200 to 280°C. By setting the temperature within this range, the polymerization rate can be increased, and semi-aromatic polyamides can be rapidly formed. Additionally, the coloring or gelation of the resulting semi-aromatic polyamide can be suppressed.

[0056] Regarding the ability to suppress the decomposition or thermal degradation of semi-aromatic polyamides to obtain semi-aromatic polyamides with high strength and excellent appearance, the melt polymerization of oligomers is preferably carried out at a temperature below 350°C. The aforementioned melt polymerization also includes melt polymerization using a melt extruder.

[0057] In method C, a mixture is obtained by stirring and mixing, for example, a suspension composed of a molten aliphatic diamine and a solid aromatic dicarboxylic acid. Then, in this mixture, at a temperature below the melting point of the ultimately formed semi-aromatic polyamine, a reaction is carried out: the formation of a salt resulting from the reaction of the aromatic dicarboxylic acid and the aliphatic diamine, and the formation of oligomers resulting from the polymerization of the formed salt, yielding a mixture of salt and oligomers. In this case, the reaction can be carried out simultaneously with fragmentation, or the mixture can be removed after the reaction and then fragmented. The resulting reactants are then subjected to solid-state polymerization at a temperature below the melting point of the ultimately formed semi-aromatic polyamine, and the molecular weight is increased to a predetermined molecular weight to obtain the semi-aromatic polyamine. Solid-state polymerization is preferably carried out at a polymerization temperature of 180 to 270°C and a reaction time of 0.5 to 10 hours in an inert gas stream such as nitrogen.

[0058] In method D, an aromatic dicarboxylic acid powder is preheated to a temperature above the melting point of an 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 in a substantially anhydrous state, maintaining the powdered state of the aromatic dicarboxylic acid, to prepare a salt. The obtained salt is then subjected to solid-state polymerization at a temperature below the melting point of the final semi-aromatic polyamide, and the molecular weight is increased to a predetermined molecular weight to obtain the semi-aromatic polyamide. Solid-state polymerization is preferably carried out at a polymerization temperature of 180 to 270°C and a reaction time of 0.5 to 10 hours in an inert gas stream such as nitrogen.

[0059] In this invention, methods C and D are preferred, with method D being particularly preferred. Compared to method B, methods C and D can generate a broken mixture of salt and oligomers or salt at low temperatures. Furthermore, less water is required when generating the broken mixture of salt and oligomers or salt. Therefore, the formation of gel-like substances can be reduced, thus reducing fisheye.

[0060] Semi-aromatic polyamides can be produced using only virgin raw materials, or by recycling off-specification membranes or cut end-pieces (insulating end-pieces) generated during membrane manufacturing and mixing them with virgin raw materials. Commonly known methods for mixing raw materials include dry blending and melt blending using a uniaxial or biaxial extruder.

[0061] In addition to semi-aromatic polyamide, the aforementioned membrane raw materials may contain one or more additives as needed to further enhance various properties. Examples of additives include: smoothing agents, pigments (e.g., titanium) or dyes, colorants, anti-coloring agents, heat stabilizers, antioxidants (e.g., hindered phenols, phosphate esters, phosphites), weather resistance modifiers (e.g., benzotriazole compounds), flame retardants (e.g., brominated flame retardants, phosphorus flame retardants), plasticizers, release agents, reinforcing agents (e.g., talc), modifiers, antistatic agents, ultraviolet absorbers, anti-turbidity agents, and various polymer resins.

[0062] Examples of smoothing agents include inorganic particles such as silicon dioxide, alumina, titanium dioxide, calcium carbonate, kaolin, and barium sulfate; and organic microparticles such as acrylic resin particles, melamine resin particles, polysiloxane resin particles, and cross-linked polystyrene particles. The average particle size of the smoothing agent is, for example, 0.05 to 5.0 μm. The content of the smoothing agent can be selected according to the frictional properties, optical properties, and other required properties of the membrane, 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. Furthermore, the content of the smoothing agent is, for example, 0.05% by mass or more, preferably 0.1% by mass or more. In addition, by adding a smoothing agent to the aforementioned membrane raw material, the haze of the obtained membrane is suppressed.

[0063] Unstretched films containing semi-aromatic polyamide and the above-mentioned additives can be manufactured by, for example, the following methods. (A) A method of adding additives during the polymerization of semi-aromatic polyamides to generate semi-aromatic polyamides containing additives, and then melting and forming a film from this mixture. (B) A method for pre-preparing granules by melt-blending high-concentration additives with semi-aromatic polyamine, and then melt-blending the masterbatch with the original granules (i.e., unadded semi-aromatic polyamine granules) in an extruder during film formation (masterbatch method). (C) A method for forming a film by feeding a dry blend of semi-aromatic polyamide and additives into an extruder and performing melt mixing in the extruder. (D) A method of forming a film by separately feeding semi-aromatic polyamide and additives into an extruder and performing melt mixing in the extruder.

[0064] The heat of crystallization of the unstretched semi-aromatic polyamide film is preferably 20 J / g or more, and more preferably 25 J / g or more. Furthermore, the aforementioned heat of crystallization is preferably, for example, 35 J / g or less, and more preferably 30 J / g or less. When the heat of crystallization of the unstretched film is 20 J / g or more, stretching can be stably performed with a relatively small stretching force, thus obtaining a stretched film with uniform thickness. In addition, the resulting film has a high elongation at break, and even when stress is applied externally in the TD direction, it elongates along with the stress, thereby suppressing fracture.

[0065] Unstretched films of semi-aromatic polyamide with a crystallization heat of 20 J / g or higher 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 sheets through a T-die, and then cooling the extruded sheets on cooling rollers with the temperature adjusted to 30 to 40°C.

[0066] In the method for manufacturing the semi-aromatic polyamide film of the present invention, the unstretched semi-aromatic polyamide film is biaxially stretched. This allows the semi-aromatic polyamide to undergo orientation crystallization.

[0067] (MD direction uniaxial stretching procedure) In the step of biaxial stretching the unstretched membrane, this is the step of stretching the unstretched membrane in the MD direction to obtain a uniaxially stretched membrane in the MD direction.

[0068] The stretch ratio in the MD direction is preferably 2.0 to 4.5 times. The lower limit of the aforementioned stretch ratio is preferably 2.3 times, more preferably 2.4 times. The upper limit of the aforementioned 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.

[0069] When stretched in the MD direction at a stretching ratio of 4.5 times or less, crystallization proceeds appropriately, resulting in a uniaxially stretched film with excellent stretchability in the TD direction. Furthermore, by stretching the uniaxially stretched film in the MD direction obtained in the TD direction, the generation of stretching unevenness can be suppressed, resulting in a biaxially stretched film with excellent thickness accuracy and transparency, and high tensile elongation at break in the MD direction.

[0070] Furthermore, when the stretching ratio in the MD direction is 2.0 times or more, the generation of uneven stretching can be suppressed, resulting in a stretched film with uniform thickness and high planarity.

[0071] The preferred stretching speed is a stretching deformation rate in the MD direction exceeding 400% / min, particularly 800 to 12000% / min, and even more preferably 1200 to 6000% / min. When stretching is performed at a stretching deformation rate exceeding 400% / min, crystal growth can prevent film breakage during stretching. Furthermore, when stretching is performed at a stretching deformation rate below 12000% / min, the film can deform in accordance with the applied stress, thus preventing film breakage.

[0072] From the viewpoint of suppressing film breakage and manufacturing biaxially stretched films with good yield, the stretching temperature is based on the glass transition temperature (Tg) of semi-aromatic polyamide, preferably above (Tg-5)℃, and even more preferably above (Tg)℃. Furthermore, from the viewpoint of suppressing the generation of uneven stretching, the stretching temperature is preferably below (Tg+50)℃, even more preferably below (Tg+45)℃, and even more preferably below (Tg+35)℃.

[0073] For example, in the case of polyamide 9T film (polyamide 9T has a Tg of 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.

[0074] (Preheating step) The preheating step is a process 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 staged biaxial stretching) before it is applied to the stretching step. From the viewpoint of suppressing relaxation, the preheating temperature T1 of the film is based on the glass transition temperature (Tg) of the semi-aromatic polyamide, and preferably falls within the range of (Tg-9)℃ to (Tg+5)℃. The lower limit of the aforementioned preheating temperature T1 is preferably (Tg-6)℃, more preferably (Tg-5)℃. The upper limit of the aforementioned preheating temperature T1 is preferably (Tg+4)℃, more preferably (Tg+1)℃, even more preferably (Tg)℃, and particularly preferably (Tg-1)℃.

[0075] When the preheating temperature of the membrane does not reach (Tg-9)℃, the resulting membrane tends to have large end relaxation. Furthermore, when the preheating temperature of the membrane exceeds (Tg+5)℃, the resulting membrane tends to have large intermediate relaxation.

[0076] When the preheating step involves gradually changing the temperature to preheat the film, the preheating temperature shortly before the stretching step is preferably within the aforementioned range.

[0077] For example, in the case of a polyamide 9T film (polyamide 9T with a Tg of 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 aforementioned preheating temperature T1 is preferably 119°C, more preferably 120°C. Furthermore, the upper limit of the aforementioned preheating temperature T1 is preferably 129°C, more preferably 126°C, even more preferably 125°C, and particularly preferably 124°C.

[0078] In this invention, relaxation is suppressed by preheating the membrane within the aforementioned specific temperature range. While the principle behind adjusting the membrane's preheating temperature to suppress relaxation is still unclear, it is believed to be achieved by controlling the bowing phenomenon.

[0079] When manufacturing film using a tenter frame stretching method, an arc-shaped warping phenomenon occurs at the interface between the stretching section and the heat-setting section due to the stress generated in the film. That is, when manufacturing stretched film using a tenter frame stretching method, the film passes through a preheating section, stretching section, heat-setting section, loosening section, and cooling section. However, near the end of the stretching section, i.e., at the position where the set stretch ratio is reached, the tensile stress becomes maximum. At this time, inside the tenter frame, because the two ends of the film are held by clamps, the central portion of the film is pulled towards the end of the stretching section. Then, the central portion of the film is pulled closer to the stretching section from the next heat-setting section. Therefore, when the film exits the tenter frame in a straight line perpendicular to its direction of travel before entering the stretching machine, an arc-shaped warping phenomenon occurs, depicting the central portion of the film protruding in the opposite direction to its direction of travel. As a result of this phenomenon, the actual stretch ratio of the membrane in the direction of travel becomes different in the central portion and at both ends of the membrane, which is considered to affect membrane relaxation. Furthermore, it is speculated that controlling the temperature of the preheating or cooling section within a specific range can suppress the occurrence of bow-shaped warping, thereby inhibiting relaxation.

[0080] (Stretching steps) The stretching step is a step of stretching the membrane to obtain a biaxially stretched membrane. In addition, when the membrane provided to this step is an unstretched membrane, the unstretched membrane is simultaneously biaxially stretched in the MD direction and TD direction. When the membrane provided to this step is a uniaxially stretched membrane in the MD direction, the uniaxially stretched membrane in the MD direction is stretched in the TD direction.

[0081] When a uniaxially stretched film in the MD direction is stretched in the TD direction (when performing staged 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, even more preferably 3.0 to 4.0 times, and particularly preferably 3.3 to 3.8 times.

[0082] When the stretch ratio in the TD direction is within the aforementioned range, uneven stretching can be suppressed, resulting in a biaxially stretched film with excellent thickness accuracy and transparency, and high tensile elongation at break in the TD direction.

[0083] When the unstretched film is simultaneously biaxially stretched, the stretch 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 stretch 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.

[0084] When stretched in the MD direction at a stretch ratio of 4.5 times or less, a stretched film with low heat shrinkage and excellent dimensional stability can be obtained. Furthermore, when stretched in the TD direction at a stretch ratio of 5.0 times or less, a stretched film with low heat shrinkage, excellent dimensional stability, and high tensile elongation at break can be obtained.

[0085] Furthermore, when the stretching ratio in the MD and TD directions is 2.0 times or more, the generation of uneven stretching can be suppressed, resulting in a stretched film with uniform thickness and high planarity.

[0086] In the simultaneous biaxial stretching method, when obtaining a biaxially stretched film with a thickness of 1 to 25 μm, the preferred stretching ratio is 2.5 to 3.0 times in the MD direction and 2.5 to 3.3 times in the TD direction. Furthermore, when obtaining a biaxially stretched film with a thickness of 26 to 50 μm, the preferred stretching ratio is 2.8 to 3.3 times in the MD direction and 3.0 to 3.5 times in the TD direction.

[0087] Regarding the stretching speed, the stretching deformation speed in both the MD and TD directions preferably exceeds 400% / min, particularly 800 to 12000% / min, and even more preferably 1200 to 6000% / min. When stretching at a stretching deformation speed exceeding 400% / min, crystal growth can prevent film breakage during stretching. Furthermore, when stretching at a stretching deformation speed below 12000% / min, the film can deform in response to the applied stress, thus preventing film breakage.

[0088] From the viewpoint of manufacturing biaxially stretched films with high yield while suppressing film breakage, the stretching temperature is based on the glass transition temperature (Tg) of semi-aromatic polyamide, preferably above (Tg-5)℃, and even more preferably above (Tg)℃. Furthermore, from the viewpoint of suppressing uneven stretching, the stretching temperature is preferably below (Tg+50)℃, even more preferably below (Tg+35)℃, and even more preferably below (Tg+30)℃.

[0089] For example, in the case of polyamide 9T film (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 step is divided into two zones, the stretching temperature in the first zone is preferably 120 to 140°C, and more preferably 125 to 135°C. In addition, the stretching temperature in 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.

[0090] (Heat-setting step) After the semi-aromatic polyamide film undergoes the aforementioned stretching, it is preferable to perform a heat-setting treatment while maintaining the film held in the same clamps used during stretching. By performing a heat-setting treatment, the resulting film does not suffer from uneven thermal damage, thus reducing the thermal shrinkage rate. The heat-setting temperature is based on the melting point (Tm) of the semi-aromatic polyamide, preferably within the range of (Tm-30)℃ to (Tm)℃, particularly within the range of (Tm-27)℃ to (Tm-3)℃, and even more preferably within the range of (Tm-24)℃ to (Tm-6)℃. When the heat-setting temperature is above (Tm-30)℃, a film with a low thermal shrinkage rate can be obtained. Furthermore, when the heat-setting temperature is below (Tm)℃, the generation of appearance defects such as thermal damage wrinkles or breakage during heat-setting can be suppressed, resulting in a biaxially stretched film with high tensile elongation at break.

[0091] For example, in the case of polyamide 9T film (Tm=290°C for polyamide 9T), the heat setting temperature is preferably 260 to 290°C, more preferably 263 to 287°C, and even more preferably 266 to 284°C.

[0092] Examples of heat-fixing methods include, for instance, blowing hot air, irradiating with infrared radiation, and irradiating with microwaves. Among these, blowing hot air is preferred because it provides uniform and precise heating.

[0093] (Relaxation steps) After heat curing, the film is preferably loosened in both the MD and TD directions while being held in a fixture at the same temperature as the heat curing temperature.

[0094] The loosening rate in the MD direction is, for example, 1.0 to 10.0%. The loosening rate in the TD direction is, for example, 1.0 to 12.0%. When loosening treatment is performed in the MD and TD directions with the aforementioned loosening rates, relaxation can be suppressed and thermal shrinkage can be reduced, thereby obtaining a film with improved dimensional stability.

[0095] In the staged biaxial stretching method, when obtaining a biaxially stretched film with a thickness of 1 to 50 μm, the loosening rate 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 stretched film with a thickness of 51 to 150 μm, the loosening rate is preferably 1.0 to 3.0% in the MD direction and 1.0 to 10.0% in the TD direction.

[0096] In the synchronous biaxial stretching method, the optimal loosening rate is 1.0 to 6.0% in the MD direction and 1.0 to 12.0% in the TD direction.

[0097] In the synchronous biaxial stretching method, the above-mentioned loosening treatment can be performed continuously in the MD direction and TD direction simultaneously or individually. When performed individually, it can be done by loosening in the MD direction first and then loosening in the TD direction, or by loosening in the TD direction first and then loosening in the MD direction.

[0098] On the other hand, in the staged biaxial stretching method, the aforementioned loosening treatment can be (i) performed continuously and synchronously in the MD and TD directions after stretching in the MD direction, stretching in the TD direction, and heat-fixing treatment; or (ii) performed in the MD direction after stretching in the MD direction, followed by stretching in the TD direction, and then loosening treatment in the TD direction after heat-fixing treatment. In (ii), when performing heat-fixing treatment after stretching in the MD direction and loosening treatment in the MD direction, the resulting film is in a state where it is difficult to stretch in the TD direction, so performing heat-fixing treatment in the stage before stretching in the TD direction is not ideal. Furthermore, in the staged biaxial stretching methods of (i) and (ii) above, stretching in the MD direction is performed first, followed by stretching in the TD direction; however, the staged biaxial stretching method can also perform stretching in the TD direction first, followed by stretching in the MD direction. Alternatively, after biaxial stretching, the aforementioned loosening treatment can be continuously performed in the TD direction, followed by winding, and then discontinuously passed through a drying oven set to a predetermined temperature under low tension to perform loosening treatment in the MD direction.

[0099] (Cooling Step) The cooling step involves cooling the stretched film. The cooling temperature T2 is based on the melting point (Tm) of the semi-aromatic polyamide, and preferably falls within the range of (Tm-260)℃ to (Tm-170)℃. From the viewpoint of suppressing relaxation, the lower limit of the cooling temperature T2 is preferably (Tm-245)℃, more preferably (Tm-240)℃, even better (Tm-235)℃, more preferably (Tm-230)℃, particularly preferably (Tm-225)℃, and most preferably (Tm-220)℃. The upper limit of the cooling temperature T2 is preferably (Tm-180)℃, more preferably (Tm-185)℃, more preferably (Tm-190)℃, particularly preferably (Tm-195)℃, and most preferably (Tm-200)℃.

[0100] For example, in the case of polyamide 9T film (Tm = 290°C), the cooling temperature T2 is, for example, 30 to 120°C. From the viewpoint of suppressing relaxation, the lower limit of the cooling temperature T2 is preferably 45°C, more preferably 50°C, even more preferably 55°C, more preferably 60°C, particularly preferably 65°C, and best preferably 70°C. The upper limit of the cooling temperature T2 is preferably 110°C, more preferably 105°C, more preferably 100°C, particularly preferably 95°C, and best preferably 90°C.

[0101] When manufacturing the semi-aromatic polyamide film of the present invention by the staged biaxial stretching method, from the viewpoint of adjusting the refractive index of the obtained film in the central part, left end and right end in the MD direction to a specific range, the preheating temperature T1 (°C) and the 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). 1073≦10×T1-T2≦1211 (4) 1085≦10×T1-T2≦1200 (4-1) 1096≦10×T1-T2≦1188 (4-2)

[0102] Although the thickness of the semi-aromatic polyamide film of the present invention may be appropriately varied according to the application and purpose, it is preferably 1 to 150 μm, more preferably 10 to 100 μm, and even more preferably 20 to 80 μm.

[0103] The semi-aromatic polyamide film of this invention can be manufactured using planar staged biaxial stretching, planar synchronous biaxial stretching, tubular stretching, etc. Examples of stretching devices used to implement the planar synchronous biaxial stretching method include: screw-type tenter frame, pantograph-type tenter frame, and linear motor-driven clamp-type tenter frame.

[0104] In the apparatus for manufacturing the semi-aromatic polyamide film of the present invention, in order to prevent resin retention, it is preferable to treat the surfaces of the pressure cylinder, the melting section of the cylinder body, the metering section, the single tube, the filter, the T-die, etc., to reduce the surface roughness. Methods for reducing surface roughness include, for example, modifying the surface with a low-polarity substance, or depositing silicon nitride or cobalt-like carbon onto the surface.

[0105] The resulting semi-aromatic polyamide film can be in the form of a single sheet or in the form of a film roller wound onto a take-up roller. Furthermore, the film roller can be in the form of a preform roller that winds the film obtained after preheating, stretching and cooling steps onto a take-up roller, or a cutting roller that cuts the preform roller into pieces of the desired width.

[0106] Semi-aromatic polyamide films can be single-layer films or multi-layer structures consisting of two or more layers.

[0107] When the semi-aromatic polyamide film is a multilayered film, at least one layer may contain a smoothing agent. For example, in a two-layer film, it is preferable that one layer contains a smoothing agent; in a three-layer film, it is preferable that the layers located on both surfaces each contain a smoothing agent. This allows for easy control of the surface roughness of the semi-aromatic polyamide film. The type or content of the smoothing agent can be appropriately adjusted according to the application.

[0108] To achieve good adhesion with other materials, the surface of the semi-aromatic polyamide film can be subjected to corona treatment, plasma treatment, acid treatment, flame treatment, etc.

[0109] On the semi-aromatic polyamide film of the present invention, layers composed of inorganic substances such as metals or their oxides, other types of polymers, paper, woven fabrics, non-woven fabrics, wood, etc., may also be deposited.

[0110] <use> The semi-aromatic polyamide film of this invention has heat resistance and excellent dimensional stability under high temperature conditions. Therefore, it can be used in various electronic materials, optical components, and other applications.

[0111] Specifically, the semi-aromatic polyamide film of this invention can be used as: packaging material for pharmaceuticals; packaging material for prepared foods; packaging material for electronic components such as semiconductor packaging; electrical insulation material for motors, transformers, wires, etc.; dielectric material for capacitors, etc.; magnetic tape material for cassette tapes, digital data storage magnetic tapes, videotapes, etc.; protective board for solar cell substrates, liquid crystal panels, conductive films, display machines, etc.; electronic substrate material for LED packaging substrates, flexible printed wiring substrates, flat flexible wires, etc.; heat-resistant tapes such as flexible printed wiring cover films, heat-resistant shielding tapes, and industrial engineering tapes; heat-resistant barcode labels; heat-resistant reflective sheets; insulating tapes; various release films; heat-resistant base films; photographic films; molding materials; agricultural materials; medical materials; civil engineering and construction materials; and membranes for household and industrial use such as filter membranes.

[0112] Furthermore, the semi-aromatic polyamide film of this invention has excellent heat resistance, dimensional stability, and transparency, and therefore can be used in display materials and display devices in portable machines. Specifically, it can be used as a substrate film, protective film, or sealing film for light-emitting elements or display devices in various functional materials such as optical substrates, polarizing plates, and retardation plates of various displays such as liquid crystals and organic ELs.

[0113] [Electronic Materials] The electronic material of the present invention has at least the above-mentioned semi-aromatic polyamide film.

[0114] The aforementioned electronic materials include, for example: packaging materials for electronic components such as semiconductor packaging; electrical insulation materials for motors, transformers, wires, etc.; dielectric materials for capacitors, etc.; magnetic tape materials such as cassette tapes, magnetic tapes for digital data storage, and videotapes; heat-resistant shielding tapes, heat-resistant reflective sheets, insulating tapes, release films, etc.

[0115] [Optical Components] The optical component of the present invention has at least the aforementioned semi-aromatic polyamide film.

[0116] The aforementioned optical components include, for example: protective plates or protective films used in solar cell substrates, liquid crystal panels, conductive films, display machines, etc.; electronic substrate materials such as LED displays, OLED displays, LED mounting substrates, substrates for flexible printed wiring, and flat flexible wires; and protective films, insulating tapes, release films, polarizing plates, substrate films, protective films for light-emitting elements or display devices, etc., used in flexible printed wiring.

[0117] The various components and combinations thereof described above are merely examples. Without departing from the spirit of the invention, appropriate additions, omissions, substitutions, and modifications can be made to the components. Furthermore, the invention is not limited to any particular embodiment. [Example]

[0118] The present invention will be specifically illustrated by way of examples below.

[0119] 1. Evaluation Methods (1) Limiting viscosity of semi-aromatic polyamide The intrinsic viscosity (ηinh) of the resin in concentrated sulfuric acid at 30°C at concentrations of 0.05, 0.1, 0.2, and 0.4 g / dL is obtained from the following formula, and the value extrapolated to concentration 0 is set as the limiting viscosity [η]. ηinh=[ln(t1 / t0)] / c In the formula, ηinh represents the intrinsic viscosity (dL / g), t0 represents the solvent flow time (seconds), t1 represents the resin solution flow time (seconds), and c represents the resin concentration in the solution (g / dL).

[0120] (2) Melting point Tm and glass transition temperature Tg of semi-aromatic polyamide Using a differential scanning calorimeter (Perkin Elmer DSC-7), the semi-aromatic polyamide was heated from 20°C to 350°C at a rate of 10°C / min under nitrogen atmosphere and held for 5 minutes (1st Scan). It was then 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 process of heating again 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 temperature of the crystallization melting peak observed in the 2nd Scan was defined as Tm.

[0121] (3) Heat of crystallization of the unstretched film Using a differential scanning calorimeter (Perkin Elmer DSC-7), 10 mg of unstretched semi-aromatic polyamide sheets were heated from 40 °C to 350 °C at a rate of 20 °C / min under nitrogen atmosphere (1st Scan), and the heat of the resulting peak heating value was determined.

[0122] (4) Heat shrinkage rate of semi-aromatic polyamide film Test pieces in the MD direction (100mm length in the MD direction × 10mm width in the TD direction) and TD direction (100mm length in the TD direction × 10mm width in the MD direction) were cut from a semi-aromatic polyamide film. The obtained test pieces were subjected to a treatment process: placing them in a 250°C gas environment for 5 minutes, followed by a treatment process at 23°C and 50%RH for 2 hours. The dimensions in the length direction after treatment were then measured, and the heat shrinkage rate SMD in the MD direction and the heat shrinkage rate STD in the TD direction were calculated using the following formulas. Heat shrinkage rate (%) = [{length before treatment - length after treatment} / length before treatment] × 100

[0123] (5) Refractive index of semi-aromatic polyamide film One circumference of the surface layer was cut from the 400 mm diameter film roller obtained in the examples and comparative examples and used as a sample. For the obtained samples, the refractive index n in the MD direction at three points on a line parallel to the TD direction was determined using the Abbe Refractometer DR-M2 (manufactured by Atago Corporation) according to the JIS K7142 method. Sodium D-rays were used as the light source, and a test piece with a refractive index of 1.74 was used. Diiodomethane was used as the intermediate solution.

[0124] More specifically, the refractive index nC of the central part of the sample in the MD direction is measured, the refractive index nL of the position 10% inside the left end of the sample in the MD direction is measured, and the refractive index nR of the position 10% inside the right end of the sample in the MD direction is measured.

[0125] Then the refractive index difference nD is obtained from the following equation (1). Refractive index difference nD={(nC-nL)-(nC-nR)} / 2 (1) In addition, the average refractive index nAv is obtained from the following equation (2). The average refractive index is nAv = (nC + nL + nR) / 3 (2)

[0126] (6) Relaxation amount Cut a portion of the surface layer from a 400mm diameter film roller and use it as a sample. Release the obtained sample from the tension during winding and spread it on a plane. Then, starting from one end along one side of the TD direction and extending to the other end, measure the length in the MD direction at 50mm scales. From the maximum value Lmax and the minimum value Lmin of the aforementioned length, calculate the relaxation amount using the following formula (3) (see Figure 1). Relaxation amount (‰) = (Lmax - Lmin) ÷ Lmax × 1000 (3)

[0127] 2.Raw materials (1) Semi-aromatic polyamide The semi-aromatic polyamide A obtained in the manufacturing example 1 below is used.

[0128] Manufacturing Example 1 (Manufacturing of Semi-Aromatic Polyamide A) 3289 parts by weight of terephthalic acid (TPA), 2533 parts by weight of 1,9-nonanediamine (NDA), 633 parts by weight of 2-methyl-1,8-octanediamine (MODA), 48.9 parts by weight of benzyl acid (BA), 6.5 parts by weight of sodium hypophosphite monohydrate (0.1 parts by weight relative to the total of the four polyamide raw materials mentioned above), and 2200 parts by weight of distilled water were charged into a reactor and subjected to nitrogen substitution. The molar ratio (TPA / BA / NDA / MODA) of these raw materials was 99 / 2 / 80 / 20.

[0129] After stirring the contents of the reactor at 100°C for 30 minutes, the internal temperature was raised to 210°C over 2 hours. At this point, the internal pressure of the reactor was increased to 2.12 MPa. The reaction was continued under this condition for 1 hour, followed by raising the temperature to 230°C. This temperature was then maintained at 230°C for 2 hours, with water vapor slowly removed while the pressure was maintained at 2.12 MPa. The pressure was then reduced to 0.98 MPa over 30 minutes, and the reaction was continued for another hour to obtain the prepolymer. After drying at 100°C under reduced pressure for 12 hours, the prepolymer was pulverized to a size of less than 2 mm.

[0130] The pulverized prepolymer was then subjected to solid-state polymerization at 230°C and 13.3 Pa for 10 hours to obtain the polymer. The obtained polymer was fed into a biaxial extruder and melt-blended and extruded at a cylinder temperature of 320°C. After cooling and cutting, granular semi-aromatic polyamide A was produced. The obtained semi-aromatic polyamide A had a limiting viscosity of 1.17 dL / g, a melting point (Tm) of 290°C, and a glass transition temperature (Tg) of 125°C.

[0131] (2) Silicon dioxide masterbatch of semi-aromatic polyamide A (M1) The masterbatch (M1) obtained in Manufacturing Example 2 below is used.

[0132] Manufacturing Example 2 (Manufacturing of Masterbatch (M1)) 98 parts by mass of the semi-aromatic polyamide A obtained in Manufacturing Example 1 were melt-blended with 2 parts by mass of silicon dioxide (Sylysia 310P manufactured by Fuji Silysia Chemical Co., Ltd., with an average particle size of 2.7 μm) to produce a masterbatch (M1) containing 2% by mass of silicon dioxide.

[0133] Example 1 A mixture was obtained by mixing semi-aromatic polyamide A, heat stabilizer, and masterbatch (M1) with 0.2 parts by weight of heat stabilizer (Sumilizer GA-80 manufactured by Sumitomo Chemical Co., Ltd.) and 0.1 parts by weight of silicon dioxide in 100 parts by weight of semi-aromatic polyamide A.

[0134] The resulting mixture was fed into a 65mm uniaxial extruder with cylinder temperatures set at 295℃ (front section), 320℃ (middle section), and 320℃ (rear section) for melting. It was then extruded into a sheet from a T-die set at 320℃ and electrostatically bonded to a cooling roller set at a surface temperature of 40℃ for cooling, resulting in a substantially unoriented unstretched sheet with a thickness of 230μm (heat of crystallization 27J / g).

[0135] Next, the unstretched sheet was biaxially stretched using a planar stage stretching machine. First, a heating roller and an infrared heater are used, and the heating roller is set to 110°C. Then, while the space is heated to 150°C by the infrared heater, the unstretched film is stretched in the MD direction at a stretch ratio of 2.5 times to obtain a uniaxially stretched film in the MD direction. Next, the two ends of the MD-direction uniaxially stretched film are held by clamps while being continuously fed into the TD-direction stretching machine. The MD-direction uniaxially stretched film is then preheated in the preheating section of the TD-direction stretching machine at a preheating temperature (T1) of 123°C, and stretched in the stretching section at a stretching temperature of 130°C and a stretching ratio of 3.4 times in the TD direction. After stretching, it is heat-fixed at 279°C in the heat-fixing part. Then, in the loosening section, at the same temperature as the heat-fixed section, a loosening treatment is performed with a loosening rate of 3% in the MD direction and a loosening rate of 2.7% in the TD direction. Then it is cooled in the cooling section at a cooling temperature (T2) of 80°C. This yields a semi-aromatic polyamide film with a thickness of 27 μm. The resulting film is then wound up to obtain a film roller with a width of 1200 mm and a diameter of 400 mm.

[0136] Examples 2 to 8, Comparative Examples 1 to 5 Except for the changes in preheating temperature, stretching method, stretching ratio, loosening rate and cooling temperature as recorded in Table 1, the semi-aromatic polyamide film and film roller were obtained in the same manner as in Example 1.

[0137] [Table 1]

[0138] From Examples 1 to 7, it can be seen that by preheating at a predetermined temperature before stretching and cooling at a predetermined temperature after stretching, the refractive index difference nD of the obtained semi-aromatic polyamide film can be adjusted to a predetermined range, resulting in a semi-aromatic polyamide film with excellent dimensional stability under high-temperature conditions and sufficiently small relaxation. Furthermore, it can be seen that controlling the cooling temperature after stretching within an optimal range yields a semi-aromatic polyamide film with a refractive index difference nD within the optimal range, and further reduces the relaxation. Furthermore, from the comparison between Examples 1 to 7 and Example 8, it can be seen that by adjusting the heat-fixing treatment temperature, a semi-aromatic polyamide film with small relaxation amount and excellent dimensional stability under high temperature conditions can be obtained.

[0139] On the other hand, since the refractive index difference nD of the semi-aromatic polyamide films obtained in Comparative Examples 1 to 5 does not meet the range specified in this invention, the relaxation amount is large.

[0140] none

Claims

1. A semi-aromatic polyamide film, which is rectangular with an edge along the MD direction and an edge along the TD direction, and contains semi-aromatic polyamide as a resin component, wherein, The aforementioned semi-aromatic polyamide contains aromatic dicarboxylic acid components and aliphatic diamine components. The aforementioned aliphatic diamine components contain aliphatic diamines with 9 to 12 carbons accounting for more than 60 moles of the total aliphatic diamine components. The refractive index difference nD calculated from the following formula (1) is -0.0010 to 0.0045. The refractive index difference nD = {(nC-nL)-(nC-nR)} / 2 (1) Wherein, nC is the refractive index of the central part of the film in the MD direction, nL is the refractive index of the position 10% inside the left end of the film in the MD direction, and nR is the refractive index of the position 10% inside the right end of the film in the MD direction. The aforementioned central part, left end, and right end are located on a line parallel to the TD direction of the film.

2. The semi-aromatic polyamide film as claimed in claim 1, wherein the average refractive index nAv calculated from the following formula (2) is 1.5985 to 1.6045, the average refractive index nAv=(nC+nL+nR) / 3 (2) where nC, nL and nR are the same as described above.

3. The semi-aromatic polyamide film as described in claim 1, wherein the relaxation amount measured by the following method is 0.5‰ to 3.0‰, <Method for measuring relaxation amount> The length in the MD direction is measured from one end along one side of the TD direction to the other end with a 50mm scale, and the relaxation amount is obtained from the maximum and minimum values ​​of the aforementioned length by the following formula (3): Relaxation amount (‰) = (maximum value - minimum value) ÷ maximum value × 1000 (3).

4. The semi-aromatic polyamide film as described in claim 1, wherein after being placed in a gas environment at 250°C for 5 minutes, and then placed in a gas environment at 23°C and 50%RH for 2 hours, the heat shrinkage rate SMD in the MD direction and the heat shrinkage rate STD in the TD direction, which are determined by the size, are measured to be -1.0 to 1.5%.

5. A method for manufacturing a semi-aromatic polyamide film, wherein the semi-aromatic polyamide film as described in any one of claims 1 to 4 is obtained by the following steps [1] or [2]: [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 in the MD direction and the TD direction, and a step of cooling at a temperature of (Tm-260)°C to (Tm-170)°C based on the melting point Tm of the semi-aromatic polyamide; [2] The steps of preheating the semi-aromatic polyamide uniaxially stretched film in the MD direction at a temperature of (Tg-9)℃ to (Tg+5)℃ based on the Tg of the semi-aromatic polyamide, the steps of stretching in the TD direction, and the steps of cooling at a temperature of (Tm-260)℃ to (Tm-170)℃ based on the melting point Tm of the semi-aromatic polyamide.

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

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

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