Polyester film and production method therefor

Abstract

Provided is a polyester film which contains particles having an average particle diameter of 0.03-0.80 μm and which has an antimony element content of 3 ppm or less, and the total content of the titanium element, the phosphorus element, and the magnesium element is 5-100 ppm.　The polyester film is usable in applications where the presence of foreign matter in the film is extremely undesirable.

Description

Polyester film and method for producing the same

[0001] The present invention relates to a polyester film and a method for producing the same.

[0002] BACKGROUND ART Polyester films have traditionally been used widely as materials for various applications, such as magnetic tapes, ferromagnetic thin film tapes, photographs, packaging, electronic components, electrical insulation, and metal laminates, due to their excellent mechanical properties and chemical resistance.

[0003] Some applications of polyester films require the extreme tolerance of foreign matter in the film. For example, dry film resist formation is one example. Dry film resists are widely used as resists for forming wiring patterns on electronic circuit boards, and typically have a three-layer structure consisting of a support film (also called a "carrier film"), a photoresist layer made of a photosensitive resin material, and a protective film (also called a "cover film").

[0004] A method for manufacturing an electronic circuit board using the dry film resist includes, for example, first peeling off the protective film from the dry film resist to expose the photoresist layer, then laminating the photoresist layer on the surface of a copper layer of an epoxy resin substrate, for example, on the surface of which a copper layer is laminated, and attaching the dry film resist. Then, a support film is placed on a glass plate with a printed circuit to adhere the dry film resist, and light is irradiated from the glass plate side. This light passes through the transparent portions of the printed circuit image on the glass plate and the support film layer, and then irradiates the photoresist layer, curing the irradiated areas of the photoresist layer. Next, after removing the glass plate and support film, the uncured portions of the photoresist layer are removed and etched using acid or the like. Removal of the uncured portions of the photoresist layer exposes the copper layer in the corresponding areas, and the exposed copper layer is removed from the epoxy resin substrate by etching, forming a circuit on the epoxy resin substrate. The cured photoresist layer is then removed to manufacture an electronic circuit board.

[0005] Regarding polyester films used in forming dry film resists, for example, Patent Document 1 discloses a biaxially oriented laminated polyester film containing particles having an average particle diameter of 0.01 to 3.0 μm in the outermost layer on at least one side, in which the outermost layer has a center line average roughness Ra of 0.005 μm or more, a maximum height Rt of less than 1.5 μm, and a haze value of 1.5% or less.

[0006] Patent Document 2 describes a laminated polyester film for dry film resist that has excellent winding properties, can more reliably prevent the occurrence of circuit defects, and is compatible with high resolution. The film is made up of at least two polyester layers, and has a density of 5 / 10 cm of metal-containing aggregates with a major axis of 10 μm or more. ２ The document discloses a laminated polyester film for dry film resist, which is as follows: at least one outermost layer of the film contains particles having an average particle diameter of 0.01 to 3.0 μm, and the surface has a center line average roughness Ra of 0.002 to 0.030 μm and a maximum height Rt of 0.05 to 1.0 μm.

[0007] Japanese Patent Laid-Open No. 7-333853 Japanese Patent Laid-Open No. 2005-77646

[0008] In dry film resists, light is irradiated onto the photoresist layer through a support film for exposure, so if aggregates (foreign matter) are present in the support film, this can inhibit the curing of the resist and cause circuit defects. For example, in order to improve the handling and winding properties of the film, particles are generally contained in the film to form fine protrusions on the surface, but these particles can aggregate and become foreign matter, and metals contained in the polymerization catalyst of the resin that makes up the film can also aggregate and become foreign matter, causing inhibition of the curing of the resist.

[0009] In recent years, the miniaturization of electronic devices has led to extremely complex circuits, and resist line widths have become even thinner, from 5 μm to 2 μm. This has created demands for dry film resists to have higher reproducibility in image formation and higher resolution, and the size of problematic aggregates (foreign matter) has become increasingly smaller.

[0010] Therefore, the present invention provides a polyester film that can be used in applications where the presence of foreign matter in the film is extremely unacceptable, such as for forming dry film resists and for producing ceramic green sheets.

[0011] In view of the above circumstances, the present inventors have conducted extensive research and discovered that the above problems can be easily solved by using a film having a specific configuration, and have thus completed the present invention. That is, the present invention provides the following [1] to

[18] .

[0012] [1] A polyester film containing particles with an average particle size of 0.03 to 0.80 μm, in which the antimony content in the film is 3 ppm or less, and the total content of titanium, phosphorus, and magnesium in the film is 5 to 100 ppm. [2] The number of protrusions in the film with a major axis of 1 μm or more and less than 3 μm is 350 / cm. ２ [3] The polyester film according to the above [1], wherein the number of protrusions protruding from the film surface and having a maximum peak height (Sp) of 0.3 μm or more is 2.7 / cm. ２[4] The polyester film according to any one of [1] to [3] above, which is a multilayer film comprising a polyester layer B and a polyester layer A on at least one surface thereof. [5] The polyester film according to any one of [1] to [4] above, which has a titanium content of 1 ppm or more and 30 ppm or less. [6] The polyester film according to any one of [1] to [4] above, which has a phosphorus content of 5 ppm or more and 35 ppm or less. [7] The polyester film according to any one of [1] to [5] above, which has a magnesium content of 5 ppm or more and 35 ppm or less. [8] The polyester film according to any one of [4] to [7] above, which has all polyester layers constituting the polyester film containing titanium. [9] The polyester film according to any one of [4] to [8] above, wherein the polyester layer A contains particles having an average particle size of 0.03 to 0.80 μm and a maximum particle size of 1.0 μm or less.

[10] The polyester film according to any one of [4] to [9] above, wherein the particle content in the polyester layer A is 10 to 6,000 ppm.

[11] The polyester film according to any one of [4] to

[10] above, wherein the polyester layer A contains two types of particles having different average particle sizes.

[12] The polyester film according to any one of [4] to

[11] above, wherein the polyester layer A contains particles Y having an average particle size of 0.30 to 0.80 μm and a maximum particle size of 1.0 μm or less.

[13] The polyester film according to any one of [1] to

[12] above, wherein another resin layer is provided on at least one surface of the polyester film.

[14] A method for producing a polyester film according to any one of [1] to

[13] above, comprising: a production step 1 in which a melt of polyester resin chips containing a titanium compound, which has been previously masterbatched, is filtered through a filter medium containing a powdered sintered body and a filter medium containing a fibrous sintered body with a filtration accuracy of 5 μm or less; and a production step 2 in which a polyester film is produced using the polyester resin melt obtained in the production step 1.

[15] The polyester film according to any one of [1] to

[13] above, which is used for producing a dry film resist.

[16] The polyester film according to any one of [1] to

[13] above, which is used for producing a ceramic green sheet.

[17] The polyester film according to any one of [1] to

[13] above, which is used for forming an interlayer insulating layer.

[18] The polyester film according to any one of [1] to

[13] above, which is used for optical purposes.

[0013] According to the present invention, it is possible to provide a polyester film suitable for applications in which the presence of foreign matter in the film is extremely undesirable, such as for forming a dry film resist, producing a ceramic green sheet, etc. More specifically, the polyester film of the present invention has the advantage of reducing the generation of aggregates (foreign matter) of particles, metals, etc., while maintaining the flatness, handleability, and winding properties of the film.

[0014] The present invention will now be described based on embodiments, although the present invention is not limited to the embodiments described below.

[0015] <Polyester Film> The polyester film of the present invention is characterized in that it contains particles with an average particle size of 0.03 to 0.80 μm, the antimony content in the film is 3 ppm or less, and the total content of titanium, phosphorus, and magnesium in the film is 5 to 100 ppm. In addition, the number of foreign particles in the film with a major axis of 1 μm or more and less than 3 μm is 350 particles / cm. ２ Furthermore, it is preferable that the number of protrusions having a maximum height (Sp) of 0.3 μm or more protruding from the film surface is 2.7 / cm. ２ It is preferable that:

[0016] The content of titanium in the film is preferably 1 ppm to 30 ppm, the content of phosphorus in the polyester film is preferably 5 ppm to 35 ppm, and the content of magnesium in the polyester film is preferably 5 ppm to 35 ppm.

[0017] The polyester film of the present invention is preferably a multilayer film comprising a polyester layer B and a polyester layer A on at least one side thereof. The polyester layer A preferably contains particles having an average particle size in the range of 0.03 to 0.80 μm and a maximum particle size of 2.0 μm or less, more preferably 1.0 μm or less. This embodiment can reduce the generation of particle aggregates (foreign matter) while maintaining the flatness, handleability, and winding properties of the film. The polyester film of the present invention also contains titanium element. More specifically, for example, by using a polyester raw material containing a titanium compound as a polymerization catalyst, the generation of metal aggregates (foreign matter) derived from the polymerization catalyst can be reduced. When the polyester film of the present invention is multilayered, it is preferable that all of the polyester layers contain titanium element.

[0018] <Polyester> The polyester used as the raw material for the polyester layer A and the polyester layer B is not particularly limited, and may be any polyester obtained from aromatic dicarboxylic acid or its ester and glycol as the main starting materials. Among these, polyesters having ethylene terephthalate units or ethylene-2,6-naphthalate units in 60% or more of the repeating structural units are preferred. Furthermore, the polyester may contain a third component other than ethylene terephthalate units and ethylene-2,6-naphthalate units as a copolymerization component or a mixed component. For example, a resin compatible with polyester-based resins such as polycarbonate may be mixed.

[0019] Examples of the aromatic dicarboxylic acid component include terephthalic acid, dimethyl terephthalate, 2,6-naphthalenedicarboxylic acid, isophthalic acid, phthalic acid, adipic acid, sebacic acid, etc. Terephthalic acid or dimethyl terephthalate is particularly preferred.

[0020] Examples of the glycol component include one or more of ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, etc. Ethylene glycol is particularly preferred.

[0021] When the polyester is a copolymer polyester, examples of the dicarboxylic acid component include one or more of isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, sebacic acid, and the like, and examples of the glycol component include one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, and the like.

[0022] The intrinsic viscosity of the polyester is not particularly limited, but from the viewpoint of film-forming properties and particle dispersibility in the polyester, it is preferably 0.45 to 1.0 dl / g, more preferably 0.50 to 0.90 dl / g, and even more preferably 0.60 to 0.80 dl / g.

[0023] In the present invention, it is preferable to use a polyester containing a titanium compound as a polymerization catalyst. Titanium compounds have high catalytic activity and can be polymerized in small amounts. By using a polyester polymerized using a titanium compound as a catalyst as a raw material, the amount of metal remaining in the film is reduced, and there is little risk of agglomerates (foreign matter) forming.

[0024] (Other Compounds) Examples of additives other than titanium compounds include phosphorus compounds, manganese compounds, aluminum compounds, magnesium compounds, and calcium compounds.

[0025] (Phosphorus Compound) The content of the phosphorus compound in the film is preferably 5 ppm to 35 ppm, more preferably 5 ppm to 25 ppm, and particularly preferably 5 ppm to 15 ppm, in terms of elemental phosphorus. By using the phosphorus compound in combination, the thermal stability of the polyester resin can be expected to be improved.

[0026] (Magnesium Compound) The content of the magnesium compound of the phosphorus compound in the film is preferably 5 ppm to 35 ppm, more preferably 5 ppm to 25 ppm, and particularly preferably 5 ppm to 15 ppm, in terms of magnesium element. The combined use of the magnesium compound can impart an effect of improving adhesion when electrostatically adhering a polyester resin sheet to a casting drum.

[0027] Furthermore, in addition to satisfying the above range, it is preferable to satisfy the following additional requirement: (titanium element amount + magnesium element amount) / phosphorus element amount ≥ 1.3 Titanium compounds are expected to be primarily effective in suppressing the by-production of 1 μm-sized foreign matter during the polymerization reaction of polyester resin. Meanwhile, magnesium compounds contribute to improving adhesion when melting polyester resin and adhering it to a casting drum, thereby contributing to the formation of a highly smooth sheet surface. By satisfying the above formula, it becomes possible to mold a film having a highly smooth surface while reducing, in particular, the amount of 1 μm-sized micro-foreign matter.

[0028] In the present invention, it is preferable that the content of the compounds derived from the metal elements be as low as possible, particularly from the viewpoint of reducing minute aggregates (foreign matter) with a major axis of 1 μm or more but less than 3 μm in the film. These compounds derived from metal elements tend to be recognized as minute foreign matter in the film. Therefore, the total content of titanium compounds, phosphorus compounds, and magnesium compounds (Ti + P + Mg) in the polyester film must be 5 ppm or more and 100 ppm or less in terms of elemental content. Preferably, it is 5 ppm or more and 90 ppm or less, more preferably 5 ppm or more and 75 ppm or less, particularly 10 ppm or more and 50 ppm or less, and most preferably 15 ppm or more and 40 ppm or less.

[0029] (Method for Producing Masterbatch) The polyester film of the present invention can be produced by preparing a masterbatch containing a polyester resin and particles in advance and using this masterbatch. The method for producing the masterbatch of the present invention may include a step of blending and melt-kneading the polyester resin and particles, or the particles may be added during polymerization of the polyester resin. First, the polyester and the particles, and, if necessary, any other components that are raw material components, are blended in various forms such as bulk, pellets, or chips to a predetermined blend ratio, and then, after premixing if necessary, the mixture is placed in a melt-kneader and heated to or above the melting point of the polyester resin to melt-knead.

[0030] The embodiment of the melt-kneaded product is not particularly limited as long as it does not impair the effects of the present invention. Preferably, the diluent polyester resin is added directly to the molten product, extruded into a strand, and then cut into granules such as pellets or chips. In the melt-kneading step, the premixing is not particularly limited as long as it does not impair the effects of the present invention. Examples include dry blending using a ribbon blender, Henschel mixer, V-blender, etc. In addition, the melt-kneading machine is not particularly limited as long as it does not impair the effects of the present invention. Examples include melt-kneaders equipped with a heating mechanism such as a Banbury mixer, mixing roll, single-screw or twin-screw extruder, and kneader. The melt-kneading machine used in the above step may be equipped with a filter having a mesh size of 100 μm or less, preferably 50 μm or less, and more preferably 30 μm or less.

[0031] The content of the polyester in each of the polyester layer A and the polyester layer B is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. When the amount of the polyester is equal to or more than the lower limit, flexibility, strength, etc. of the polyester film can be ensured.

[0032] <Polyester Layer A> The polyester layer A is preferably a layer containing particles (hereinafter, sometimes referred to as "particles P") having an average particle size in the range of 0.03 to 0.80 μm and a maximum particle size of 1.0 μm or less. Furthermore, the polyester layer A is provided on at least one surface of the polyester layer B described below, constituting the polyester film of the present invention, which is a multilayer film. The inclusion of the particles P in the polyester layer A provides good handling properties and prevents numerous scratches from being formed on the film surface during the polyester film formation process. As described above, the resist layer is irradiated and exposed to light through the support film. Therefore, if there is any foreign matter or scratch on the support film of the dry film resist, that portion will not be exposed, resulting in circuit defects. Therefore, when the present polyester film is used as the support film for a dry film resist, it is particularly preferable that the layer A forming the polyester film surface contains particles. Furthermore, the use of the particles P makes it less likely that the particles will form agglomerates (foreign matter) and inhibit the curing of the resist.

[0033] The average particle size of the particles P contained in the polyester layer A is preferably in the range of 0.03 μm to 0.80 μm. If the average particle size of the particles P is 0.80 μm or less, the transparency of the film is not impaired, while if the average particle size of the particles is 0.03 μm or more, the film surface can be made moderately rough, which not only improves handling but also can be expected to prevent scratches on the film surface during the polyester film production process. From this perspective, the average particle size of the particles contained in the polyester layer A is preferably 0.10 μm to 0.75 μm, more preferably 0.15 μm to 0.70 μm, and particularly preferably 0.30 μm to 0.60 μm.

[0034] The average particle size of the particles P in the polyester layer A is determined by measuring the diameters of 10 or more particles using a scanning electron microscope and averaging the diameters. In the case of non-spherical particles, the average of the longest and shortest diameters can be measured as the diameter of each particle.

[0035] Furthermore, the maximum particle size of the particles contained in the polyester layer A is preferably 2.0 μm or less. Within this range, inhibition of resist curing due to particle agglomeration (foreign matter) can be suppressed. From this viewpoint, the maximum particle size of the particles contained in the polyester layer (A) is more preferably 1.0 μm or less, even more preferably 0.80 μm or less, and even more preferably 0.60 μm or less. Note that, when the particles exist as aggregates, the maximum particle size refers to the particle size of the primary particles constituting the aggregates.

[0036] Furthermore, the polyester layer A preferably contains particles P having an average particle size of 0.03 μm to 0.80 μm in a mass proportion (also referred to as "concentration") of 10 to 6000 ppm. If the content (particle concentration) of particles P having an average particle size of 0.03 μm to 0.80 μm in the polyester layer A is 6000 ppm or less, the transparency of the film can be further improved. On the other hand, if the content (particle concentration) of particles P having an average particle size of 0.03 μm to 0.80 μm in the polyester layer A is 10 ppm or more, the film surface can be made moderately rough, which not only improves handleability but also can be expected to prevent scratches on the film surface during the polyester film production process. From this viewpoint, the polyester layer A more preferably contains particles P having an average particle size of 0.03 μm to 0.80 μm in a mass ratio of 100 ppm to 5000 ppm, even more preferably 500 ppm to 4500 ppm, and particularly preferably 1000 ppm to 4000 ppm.

[0037] The particles P contained in the polyester layer A are not particularly limited as long as they have an average particle size of 0.03 to 0.80 μm, and examples thereof include inorganic particles such as calcium carbonate, calcium phosphate, silica, kaolin, talc, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, and molybdenum sulfide, and organic particles such as ion exchange resins, crosslinked polymers, and calcium oxalate. From the viewpoints of effectively improving the film surface roughness and production costs, inorganic particles are preferred, and alumina and silica are more preferred. On the other hand, from the viewpoint of efficiently imparting lubricity and air release properties to the film surface, organic particles are preferred, and crosslinked polymers such as crosslinked polystyrene particles and crosslinked acrylic particles are more preferred.

[0038] The polyester layer A may contain one type of particle P, two or more types, or particles of the same type but different particle diameters or particle shapes may be used simultaneously. The shape of the particles is not particularly limited and may be any of spherical, blocky, rod-like, flat, and other shapes. Furthermore, the polyester layer A preferably contains at least two types of particles with different particle diameters in order to effectively impart surface lubricity. The two types of particles are referred to as particles X and particles Y, and will be described below. From the viewpoint of suppressing the occurrence of scratches on the film surface during processing, it is preferable to use particles X in combination with particles Y, which have an average particle diameter larger than that of particles X.

[0039] The average particle size of the particles X is preferably in the range of 0.03 μm to 0.20 μm, more preferably in the range of 0.04 μm to 0.15 μm, and particularly preferably in the range of 0.05 μm to 0.10 μm, within the particle size range of 0.03 μm to 0.80 μm of the particles P. If the average particle size of the particles X is 0.20 μm or less, the particles are less likely to form aggregates (foreign matter), and if the average particle size of the particles is 0.03 μm or more, the particles can contribute to improving the slipperiness of the film surface.

[0040] The mass proportion of particles X in polyester layer A is preferably in the range of 100 to 5000 ppm within the range of 10 to 6000 ppm, which is the content of particles P, and more preferably in the range of 500 ppm to 4000 ppm, and particularly preferably in the range of 1000 ppm to 3000 ppm. If the mass proportion of particles X in polyester layer A is 100 ppm or more, it can contribute to improving the slipperiness of the film surface, and if the mass proportion of particles X is 5000 ppm or less, it can maintain the light transmittance of the polyester film.

[0041] The average particle size of the particles Y is preferably in the range of 0.30 μm to 0.80 μm within the particle size range of 0.03 μm to 0.80 μm of the particles P, more preferably in the range of 0.35 μm to 0.70 μm, and particularly preferably in the range of 0.40 μm to 0.60 μm. If the average particle size of the particles Y is 0.80 μm or less, the resist curing is less likely to be inhibited, and if the average particle size of the particles is 0.30 μm or more, the slipperiness of the film surface and the winding properties when the film is wound (rolled) are improved.

[0042] The mass proportion of particles Y in polyester layer A is preferably in the range of 10 to 3000 ppm within the range of 10 to 6000 ppm, which is the content of particles P, and more preferably in the range of 100 ppm to 2500 ppm, and particularly preferably in the range of 200 ppm to 2000 ppm. When the mass proportion of particles Y in polyester layer A is 10 ppm or more, slipperiness and air release properties can be imparted to the film surface, and when the mass proportion of particles Y is 3000 ppm or less, the light transmittance of the polyester film can be maintained.

[0043] The average particle size of particles Y is preferably larger than the average particle size of particles X, and the maximum particle size is preferably 1.0 μm or less. Furthermore, particles Y preferably have a narrow particle size distribution. Specifically, the value obtained by dividing the average particle size of particles Y by the maximum particle size of particles Y (average particle size of particles Y / maximum particle size of particles Y) is preferably 0.4 or more, more preferably 0.6 or more, and even more preferably 0.8 or more. The upper limit is usually 1.0 or less. If the value obtained by dividing the average particle size of particles Y by the maximum particle size of particles Y (average particle size of particles Y / maximum particle size of particles Y) is 0.4 or more, the maximum particle size of particles is below a certain value, which can prevent particles from forming aggregates (foreign matter) and inhibiting the curing of the resist. Furthermore, since particles Y with a relatively large average particle size are contained in the polyester layer A, the film surface can be roughened without increasing the mass proportion (concentration) of particles in the polyester layer A. Therefore, not only is the handling property improved without reducing the transparency of the film, but scratches on the film surface during the polyester film production process are suppressed, and the film has excellent winding properties when wound into a roll.

[0044] In one preferred embodiment of the polyester layer A containing particles X and particles Y, the average particle size of particles X is in the range of 0.03 μm to 0.19 μm, the average particle size of particles Y is in the range of 0.20 μm to 0.80 μm, the mass proportion of particles X in the polyester layer A is in the range of 100 to 5000 ppm, and the mass proportion of particles Y is in the range of 10 to 3000 ppm. This embodiment provides excellent slip properties on the film surface, can prevent scratches, and provides excellent winding properties when the film is wound into a roll.

[0045] Examples of particles X and particles Y include inorganic particles, organic particles, and the like, as described above. For particles X having a relatively small average particle size, inorganic particles are preferred from the viewpoint of effectively improving dispersibility and film surface roughness, with alumina being more preferred. On the other hand, for particles Y having a relatively large average particle size, organic particles are preferred from the viewpoints of resistance to aggregation, ease of adjusting particle size distribution, and prevention of scratches on the film surface, with crosslinked polymers such as crosslinked polystyrene particles and crosslinked acrylic particles, ion exchange resins, and the like being more preferred. Furthermore, from the viewpoints of production cost and ease of handling, inorganic particles are preferred, with silica particles being more preferred.

[0046] The polyester constituting the polyester layer A can be any of the polyesters described above. However, from the viewpoint of suppressing the generation of aggregates (foreign matter) in the polyester film, it is preferable to use a polyester containing a titanium compound as a polymerization catalyst. Polymerization catalysts made of titanium compounds have high catalytic activity and can be polymerized in small amounts. By using polyester polymerized using a titanium compound as a catalyst as a raw material, the amount of metal remaining in the film is small, thereby reducing the risk of forming aggregates (foreign matter). From the viewpoint of reducing aggregates (foreign matter), it is further preferable that the film is substantially free of antimony compounds. "Substantially free" means that the film is not intentionally contained, and the content is 3 ppm or less, preferably 2 ppm or less, more preferably 1 ppm or less, and particularly 0 ppm.

[0047] From the viewpoint of transparency and the like, the thickness of the polyester layer A is preferably 0.1 to 20.0 μm, more preferably 0.3 to 10.0 μm, and even more preferably 0.5 to 5.0 μm.

[0048] <Polyester Layer B> The polyester film of the present invention preferably includes a polyester layer B and the polyester layer A on at least one side thereof. In order to improve the handling and winding properties of the film while maintaining the transparency of the film, the polyester layer B preferably does not substantially contain particles or contains particles at a concentration at least lower than that of the polyester layer (A). The above-mentioned "substantially does not contain" means that particles are not intentionally contained, and specifically refers to a particle content (particle concentration) of 200 ppm or less, more preferably 150 ppm or less.

[0049] When the polyester layer B contains particles, in order to reduce costs and increase transparency, the average particle size of the particles contained in the polyester layer B is preferably smaller than the average particle size of the particles contained in the polyester layer A, and is preferably in the range of 0.010 μm to 0.200 μm, more preferably in the range of 0.012 μm to 0.100 μm, and particularly preferably in the range of 0.015 μm to 0.080 μm. Furthermore, when the polyester layer (B) contains particles, from the viewpoints of maintaining light transmittance during exposure and eliminating circuit defects after exposure, it is preferable that the maximum particle size of the particles in the polyester layer B is 1.0 μm or less, similar to the polyester layer (A).

[0050] Furthermore, as described above, in order to enhance transparency, the particle concentration in the polyester layer B is preferably at least lower than the particle concentration in the polyester layer A. Specifically, the particle concentration is preferably 0 to 2500 ppm by mass, more preferably 2000 ppm or less, even more preferably 1000 ppm or less, even more preferably 500 ppm or less, and most preferably 100 ppm or less.

[0051] The type and shape of the particles contained in the polyester layer B are the same as those of the particles in the A layer.

[0052] The polyester constituting the polyester layer B can be any of the polyesters described above, but from the viewpoint of suppressing the generation of aggregates (foreign matter) in the film, it is preferable to use a polyester containing a titanium compound as a polymerization catalyst, i.e., the polyester layer B preferably contains titanium element.

[0053] From the viewpoints of increasing transparency and improving the handling and winding properties of the film, the thickness of the polyester layer B is preferably adjusted so that the ratio of the thickness of the polyester layer A to the thickness of the polyester layer B is 0.1 to 40.0%, more preferably 1.0% to 20.0%, and even more preferably 3.0% to 10.0%.

[0054] <Polyester Layer C> When the polyester film of the present invention includes a polyester layer other than the polyester layer A and the polyester layer B (hereinafter, sometimes referred to as "polyester layer C"), the polyester layer C is preferably made from the above-mentioned polyester and contains particles at a concentration at least lower than that of the polyester layer A. Alternatively, the polyester layer C may contain particles similar to those of the polyester layer A but have a different thickness from that of the polyester layer A. The type and shape of the particles in the polyester layer C are the same as those in the polyester layer A.

[0055] From the viewpoints of increasing transparency and reducing costs, the thickness of the polyester layer C is preferably 1 to 300%, more preferably 10 to 200%, and even more preferably 20 to 150% of the thickness of the polyester layer A.

[0056] <Polyester Film> The polyester film of the present invention is a film comprising a polyester layer B and a polyester layer A on at least one side thereof. The polyester layer A may be provided on both sides of the polyester layer B, or the polyester layer A may be provided on one side of the polyester layer B and a polyester layer C on the other side. Specific examples of the configuration include polyester layer A / polyester layer B, polyester layer A / polyester layer B / polyester layer A, etc. Further examples include polyester layer A / polyester layer B / polyester layer C, and polyester layer A / polyester layer B / polyester layer C / polyester layer A, etc. However, the configuration is not limited to these.

[0057] The polyester film of the present invention may have an intrinsic viscosity of 0.65 dl / g or more. As described below, an intrinsic viscosity of 0.65 dl / g or more allows stretching without breakage, even when the stretching ratio, particularly in the width direction (transverse direction), is increased to 4.0 times or more. This reduces thickness unevenness, particularly in the width direction, and suppresses air accumulation and wrinkle formation during winding into a roll. As an additional effect, during melt extrusion of each polyester layer, the shear stress applied to the raw materials of each polyester layer is increased, improving the dispersibility of particles contained in the raw materials and suppressing the generation of particle aggregates (foreign matter). From this perspective, the intrinsic viscosity of the polyester film is preferably 0.65 dl / g or more, more preferably 0.65 dl / g to 0.90 dl / g, and even more preferably 0.66 dl / g to 0.80 dl / g. The intrinsic viscosity of the polyester film can be adjusted by appropriately changing the polymerization conditions of the polyester raw material. For example, the intrinsic viscosity can be increased by increasing the molecular weight by extending the polymerization time or by employing solid-state polymerization. Note that the intrinsic viscosity mentioned above refers to the intrinsic viscosity of the entire polyester film layer.

[0058] The polyester film of the present invention may be an unstretched film (sheet) or a stretched film. A stretched film is preferred, and a biaxially stretched film is more preferred. When the polyester film of the present invention is a biaxially stretched film, it may be a sequentially stretched film or a simultaneous biaxially stretched film.

[0059] From the viewpoint of ease of handling and economic efficiency, the thickness of the polyester film is preferably 4 μm to 50 μm, more preferably 9 μm to 38 μm, and even more preferably 12 μm to 25 μm.

[0060] In the polyester film of the present invention, the number of foreign matter or aggregates having a major axis of 1 μm or more and less than 3 μm is 350 / cm ２ It is preferable that the number of particles is 300 or less. More preferably, it is 300 particles / cm. ２ More preferably, 200 pieces / cm or less ２ Below, among them, 100 pieces / cm ２ The following is preferable. According to the inventor's investigations, agglomerates (foreign matter) are formed when catalysts added during polyester production precipitate and aggregate, remaining in the film, or when particles added to the polyester layer aggregate. Furthermore, particles with large particle diameters (e.g., particles exceeding 2 μm) are counted as agglomerates (foreign matter). Among such agglomerates (foreign matter), agglomerates (foreign matter) with a major axis of 2 μm or more inhibit the curing of the resist, leading to circuit defects in the manufactured electronic circuit board. For example, when antimony trioxide, an antimony compound, is used as a polymerization catalyst in the production of polyester, the remaining antimony precipitates and aggregates, forming antimony-containing agglomerates (foreign matter) in the polyester. Therefore, agglomerates (foreign matter) exist in a polyester film, and are expanded in the film plane by biaxial stretching. Therefore, the number of agglomerates (foreign matter) that lead to circuit defects, i.e., agglomerates with a major axis of 1 μm or more but less than 3 μm, is set to 350 / cm. ２ It needs to be as follows:

[0061] Here, the width of the circuit formed by the dry film resist is, for example, 5 μm or less, but with the progress of higher resolution, 2 μm or less may be required. The irradiated light for curing a resist of 2 μm or less passes through the polyester film with a width of, for example, 2 μm or less. Therefore, even for aggregates (foreign matter) with a major axis of less than 2 μm, there is a concern that the risk of blocking light passing through the polyester film with a width of 2 μm or less is increased. Therefore, in order to suppress the occurrence of circuit defects caused by aggregates (foreign matter) of 1 μm or more and less than 3 μm, it has been necessary to manage the number of aggregates (foreign matter). Therefore, in the present invention, the number of aggregates (foreign matter) with a major axis of 1 μm or more and less than 3 μm in the film is set to 350 / cm. ２ The present inventors have found that the following has the effect of suppressing the occurrence of circuit defects, and have completed the present invention.

[0062] The aggregates (foreign matter) can be observed using an optical microscope or the like, and the maximum diameter of the aggregates (foreign matter) can be measured. Therefore, the number of aggregates (foreign matter) in the film having a major axis of 1 μm or more and less than 3 μm can be determined using an optical microscope or the like. In the present invention, the term "aggregates (foreign matter)" does not necessarily mean that some substance has aggregated. In other words, any substance that is confirmed in the polyester film as having the major axis described above is considered to be an aggregate, regardless of whether it is aggregated or not.

[0063] As described above, the aggregates (foreign matter) include aggregates of particles, particles with large particle diameters, aggregates of metal compounds used as catalysts, or aggregates of reduced metals. According to the studies of the present inventors, among the metal elements contained in polyester polymerization catalysts, antimony, titanium, and germanium, and among them, antimony has a higher light-shielding property than other metals, and therefore, if these metal elements are contained in a certain amount or more, it has been found that the performance of high-definition dry film resists is affected.

[0064] The titanium element content of the polyester film of the present invention is preferably 1 ppm or more and 30 ppm or less. If the titanium element content is 30 ppm or less, the number of titanium element-containing aggregates (foreign matter) in the polyester film can be reduced, the proportion of transmitted light blocked by titanium-containing aggregates (foreign matter) can be lowered, and a decrease in resolution can be suppressed, thereby reducing circuit defects occurring in electronic circuit boards. Furthermore, if the titanium element content is 1 ppm or more, it is appropriate as a catalyst amount for polyester, and polyester production efficiency can be maintained. From the above viewpoints, the titanium element content in the polyester film is more preferably 2 ppm or more and 25 ppm or less, and even more preferably 5 ppm or more and 20 ppm or less.

[0065] The content of titanium element in the polyester film can be determined by fluorescent X-ray analysis or the like.

[0066] (Other Resin Layer) The polyester film may have another resin layer laminated on at least one side thereof to improve the handling and winding properties of the film. When the polyester film is composed of two layers, polyester layer A and polyester layer B, it is preferable to form the other resin layer (hereinafter sometimes simply referred to as "resin layer") on the side opposite to polyester layer A, i.e., on the polyester layer B side. On the other hand, when the polyester film is composed of three layers, polyester layer A, polyester layer B, and polyester layer C, it is preferable that the other resin layer be on the polyester layer A side. Specifically, a configuration of other resin layer / polyester layer A / polyester layer B / polyester layer C is preferable.

[0067] The other resin layer preferably contains particles having an average particle size of 0.005 to 0.150 μm. If the average particle size of the particles contained in the other resin layer is 0.005 μm or more, the slipperiness and windability of the film can be favorably maintained, and if the average particle size is 0.150 μm or less, the particles are less likely to fall off from the resin layer and the resin layer is less likely to be scraped. From this perspective, the other resin layer preferably contains particles having an average particle size of 0.010 μm to 0.120 μm, and more preferably contains particles having an average particle size of 0.030 μm to 0.100 μm.

[0068] As long as the average particle size of the particles contained in the other resin layer is within the above range, the other resin layer may contain particles having a particle size of less than 0.005 μm or may contain particles having a particle size of more than 0.150 μm.

[0069] The average particle size of the particles in the other resin layer can be determined by measuring the diameters of 10 or more particles using a scanning electron microscope and taking the average value. In this case, in the case of non-spherical particles, the average value of the longest and shortest diameters can be measured as the diameter of each particle.

[0070] The particle concentration in the other resin layer is preferably 1 to 10% by mass. A particle concentration of 1% by mass or more in the resin layer can provide smoothness and improved winding, while a particle concentration of 10% by mass or less makes the particles less likely to aggregate, reducing scraping of the resin layer due to particle shedding, making it less likely to impede light transmission in the film for dry film resist substrates and less likely to cause circuit defects. From this perspective, the particle concentration in the other resin layer is more preferably 2% to 7% by mass, and even more preferably 2% to 5% by mass. By ensuring that the particle concentration in the other resin layer satisfies the above range, the flatness and scratch resistance of the polyester layer (A) and the smoothness of the resin layer can be simultaneously satisfied, resulting in a more suitable film for dry film resist substrates.

[0071] The ratio of the particle concentration (mass %) in the other resin layer to the particle concentration (mass %) in the polyester layer (A) is preferably 1 to 10,000, more preferably 5 to 1,000, and even more preferably 10 to 100.

[0072] The types and shapes of particles in the other resin layers are the same as those described for the particles contained in the polyester layer (A).Among these, inorganic particles, especially silica particles, are preferred.

[0073] It is preferable that the other resin layer further contains an antistatic agent. When peeling off a support film laminated to a photoresist layer, static electricity generated by peeling electrification can attract and adhere foreign matter such as dirt and dust to the photoresist layer, causing irregularities in the circuit pattern, so it is preferable to impart antistatic properties when peeling off the support film. By including an antistatic agent in the other resin layer, the polyester film can be made into a film for use as a high-resolution dry film resist substrate, which has a highly flat surface in contact with the photoresist layer and exhibits releasability and antistatic properties.

[0074] Examples of antistatic agents used in other resin layers include ionically conductive polymer compounds such as ammonium group-containing compounds, polyether compounds, sulfonic acid compounds, and betaine compounds, as well as π-electron conjugated polymer compounds such as polyacetylene, polyphenylene, polyaniline, polypyrrole, polyisothianaphthene, and polythiophene. Among these, ionically conductive polymer compounds are preferred, and ammonium group-containing compounds are particularly preferred. Resin layers formed from coating solutions containing π-conjugated conductive polymers, such as polythiophenes and polyanilines, generally exhibit strong coloration. Because high transparency (low haze) is preferred for films used as dry film resist substrates, π-conjugated conductive polymers may not be suitable. Furthermore, π-conjugated conductive polymer coating materials are generally more expensive than ionically conductive coating materials, and ionically conductive antistatic agents are therefore preferred from the standpoint of production costs.

[0075] The ammonium group-containing compound is preferably a polymeric compound having an ammonium group, such as a polymer containing a monomer having an ammonium group and an unsaturated double bond as a component.

[0076] Specific examples of such polymers include polymers having, as repeating units, the constituent elements represented by the following formula (1): This homopolymer or a copolymer obtained by copolymerizing a plurality of other components may also be used.

[0077]

[0078] In the above formula (1), R １ , R ２ are each independently a hydrogen atom, an alkyl group, a phenyl group, or the like, and these alkyl groups and phenyl groups may be substituted with the groups shown below. Examples of the substitutable groups include a hydroxyl group, an amide group, an ester group, an alkoxy group, a phenoxy group, a naphthoxy group, a thioalkoxy group, a thiophenoxy group, a cycloalkyl group, a trialkylammonium alkyl group, a cyano group, and a halogen atom. １ and R ２ may be chemically bonded, for example, -(CH ２ ) ｍ -(m=an integer of 2 to 5), -CH(CH ２ ) CH(CH ３ )-, -CH=CH-CH=CH-, -CH=CH-CH=N-, -CH=CH-N=C-, -CH ３ OCH ２ -, -(CH ２ ) ２ O (CH ２ ) ２ - and others can be mentioned.

[0079] In the case of a polymer having the constituent element represented by the above formula (1) as a repeating unit, it is preferable that the polymer be copolymerized with other repeating units, from the viewpoint of increasing compatibility with other materials and improving the transparency of the resulting coating film. Examples of the other repeating units include alkyl acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate, alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate, and acrylamides such as n-methylolacrylamide.

[0080] X in the above formula (1) －The cations may be appropriately selected within the scope of the present invention, and examples thereof include halogen ions, sulfonates, phosphates, nitrates, alkylsulfonates, and carboxylates.

[0081] Furthermore, a polymer in which the constituent element represented by formula (1) and a polyethylene glycol-containing (meth)acrylate are copolymerized is preferred because it has a flexible structure and can provide a resin layer with excellent uniformity during in-line coating.

[0082] The number-average molecular weight of the antistatic agent contained in the other resin layer is preferably 1,000 to 500,000, more preferably 2,000 to 350,000, and even more preferably 5,000 to 200,000. When the number-average molecular weight of the antistatic agent is 1,000 or more, the strength of the coating film can be maintained, heat resistance stability can be maintained, and sufficient antistatic properties can be obtained. Furthermore, when the molecular weight is 500,000 or less, an increase in the viscosity of the coating solution can be prevented, and good handleability and coatability can be maintained, making the film suitable for use as a dry film resist substrate.

[0083] The other resin layer preferably contains a wax to enhance the film's lubricity. This may be contained together with the antistatic agent, or the wax may be contained without the antistatic agent. Examples of waxes that may be contained in the other resin layer include natural waxes such as vegetable wax, animal wax, mineral wax, and petroleum wax, as well as synthetic waxes such as synthetic hydrocarbons, modified wax, and hydrogenated wax. Among these, polyolefin compounds are preferred. Specifically, compounds having a basic skeleton such as a polyolefin compound composed of a polymer or copolymer of unsaturated hydrocarbons such as ethylene, propylene, 1-butene, and 4-methyl-1-pentene are dissolved or dispersed. Examples include polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene-propylene copolymer, ethylene-1-butene copolymer, and propylene-1-butene copolymer. More specifically, polyolefins having an acid value of 10 to 50 and terminal active hydrogen groups, and more specifically, oxidized polyethylene or oxidized polypropylene, are preferably used.

[0084] When a polymer-type wax is used, its number average molecular weight is preferably 2,000 to 20,000, and more preferably 3,000 to 15,000. Within these ranges, film-forming properties and mold-releasing properties can be maintained. Furthermore, its softening point is preferably 70 to 170°C, and more preferably 90°C or higher or 150°C or lower. Within these ranges, film-forming properties and mold-releasing properties can be maintained.

[0085] In order to improve the coating strength of the other resin layer and impart abrasion resistance to the film, the other resin layer preferably further contains a crosslinking agent.

[0086] Examples of crosslinking agents include melamine compounds, oxazoline compounds, epoxy compounds, isocyanate compounds, and carbodiimide compounds. Among these crosslinking agents, melamine compounds are preferred from the viewpoints of providing good coating film strength and excellent releasability of the resin layer. Two or more of these crosslinking agents may be used in combination.

[0087] The melamine compound refers to a compound having a melamine skeleton within the compound. Examples of suitable compounds include alkylolated melamine derivatives, compounds obtained by reacting alkylolated melamine derivatives with alcohols to partially or completely etherify them, and mixtures thereof. Suitable alcohols for etherification include methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, and isobutanol. The melamine compound may be a monomer or a dimer or higher polymer, or a mixture thereof. Furthermore, melamine may be partially co-condensed with urea or the like, and a catalyst may be used to increase the reactivity of the melamine compound.

[0088] As the oxazoline compound, a polymer containing an oxazoline group is particularly preferred, and can be prepared by polymerizing an addition-polymerizable oxazoline group-containing monomer alone or with other monomers. Examples of the addition-polymerizable oxazoline group-containing monomer include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline, and these can be used alone or in combination.

[0089] The other monomer is not limited as long as it is a monomer copolymerizable with the addition-polymerizable oxazoline group-containing monomer, and examples thereof include (meth)acrylic acid esters such as alkyl(meth)acrylate (the alkyl group can be a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a 2-ethylhexyl group, or a cyclohexyl group); unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrenesulfonic acid, and salts thereof (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); unsaturated nitriles such as acrylonitrile and methacrylonitrile; (meth)acrylamide, N-alkyl(meth)acrylate, N-methyl-N ... unsaturated amides such as N,N-dialkyl(meth)acrylamide (the alkyl group can be, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a 2-ethylhexyl group, or a cyclohexyl group); vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; halogen-containing α,β-unsaturated monomers such as vinyl chloride and vinylidene chloride; and α,β-unsaturated aromatic monomers such as styrene and α-methylstyrene. One or more of these monomers can be used.

[0090] Examples of the epoxy compounds include condensation products of epichlorohydrin with a hydroxyl group or an amino group of ethylene glycol, polyethylene glycol, glycerin, polyglycerin, bisphenol A, etc., and also include polyepoxy compounds, diepoxy compounds, monoepoxy compounds, glycidylamine compounds, etc.

[0091] Examples of the polyepoxy compounds include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris(2-hydroxyethyl)isocyanate, glycerol polyglycidyl ether, and trimethylolpropane polyglycidyl ether. Examples of the diepoxy compounds include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcinol diglycidyl ether, and ethylene glycol diglycidyl ether. Examples of monoepoxy compounds include allyl glycidyl ether, 2-ethylhexyl glycidyl ether, and phenyl glycidyl ether. Examples of glycidyl amine compounds include N,N,N',N'-tetraglycidyl-m-xylylenediamine and 1,3-bis(N,N-diglycidylamino)cyclohexane.

[0092] It is preferable to use a crosslinking agent in a design that allows it to react during the drying process or film-forming process to improve the performance of the resin layer. It is assumed that the finished resin layer contains unreacted crosslinking agents, reacted compounds, or a mixture thereof.

[0093] The other resin layer may contain, as a binder, thermoplastic resins such as polyesters, polyurethanes, acrylic resins, polyvinyl resins, and polyolefins, and / or thermosetting resins such as thermosetting acrylic resins, melamine resins, and epoxy resins, in order to improve adhesion to the polyester film, etc.

[0094] The mass ratio of the particles contained in the other resin layer to the antistatic agent, wax, binder, and crosslinking agent that the resin layer may further contain is preferably adjusted appropriately depending on the compounds selected, and is as follows as a guideline:

[0095] The particle content (particle concentration) in the other resin layer is preferably 1% by mass or more, and more preferably 2% by mass or more or 10% by mass or less. When the particle content (particle concentration) in the other resin layer is 1% by mass or more, the effect of making the dry film resist substrate film smooth and improving winding is easily obtained, and when it is 10% by mass or less, the particles are less likely to aggregate, which can reduce scraping of the resin layer due to particle dropout, and is less likely to inhibit light transmission of the dry film resist substrate film and cause circuit defects.

[0096] The content of the antistatic agent in the other resin layer is preferably 5% by mass or more, more preferably 10% by mass or more and 90% by mass or less. When the antistatic agent is a polymer of a compound having an ionic functional group, the content is preferably 15 to 90% by mass, more preferably 20% by mass or more and 90% by mass or less. By keeping the content of the antistatic agent within the above range, sufficient surface resistivity can be achieved, and the film for dry film resist substrates is less susceptible to electrostatic adhesion.

[0097] The wax content in the resin layer is preferably 1% by mass or more, and more preferably 2% by mass or more and 10% by mass or less, in order to easily achieve a sufficient lubrication effect and to prevent the adhesion to the polyester film from being impaired.

[0098] The content of the crosslinking agent in the resin layer-forming composition constituting the other resin layer is preferably 1% by mass or more, and more preferably 2% by mass or more or 50% by mass or less. A crosslinking agent content of 1% by mass or more is likely to provide the effect of improving the lubrication and winding of the film for dry film resist substrates, while a content of 50% by mass or less is unlikely to impede the light transmission of the film for dry film resist substrates and to cause circuit defects.

[0099] The content of the binder in the other resin layer is preferably 1% by mass or more, and more preferably 2% by mass or more or 60% by mass or less. By having the binder content in the above range, sufficient adhesion to the polyester film can be obtained.

[0100] The other resin layers may contain, if necessary, antifoaming agents, coating property improvers, thickeners, organic lubricants, antistatic agents, ultraviolet absorbers, antioxidants, foaming agents, dyes, pigments, etc.

[0101] The components of the other resin layers can be analyzed by, for example, TOF-SIMS, X-ray photoelectron spectroscopy (XPS), fluorescent X-ray analysis, or the like.

[0102] The thickness of the other resin layer is preferably 0.001 μm to 0.5 μm, more preferably 0.005 μm or more or 0.3 μm or less, and even more preferably 0.01 μm or more or 0.2 μm or less. If the thickness of the other resin layer is 0.5 μm or less, the coating film appearance and cured state can be maintained, and if the thickness is 0.001 μm or more, sufficient releasability can be obtained. Furthermore, if the thickness of the other resin layer is 0.001 to 0.5 μm, it does not affect the surface roughness of the polyester film. In other words, the surface roughness of the polyester film and the surface roughness of the polyester film laminated with the other resin layer can be considered to be the same.

[0103] <Method for Producing Polyester Film> The method for producing the polyester film of the present invention will be described. The production of the polyester film of the present invention includes the following production steps 1 and 2. Production step 1 is a step in which a melt of polyester resin chips containing a titanium compound, which has been previously masterbatched, is filtered through a filter medium containing a powdered sintered body and a filter medium containing a fibrous sintered body with a filtration accuracy of 5 μm or less. The polyester resin chips in production step 1 can be melted, for example, using an extruder. Production step 2 is a step in which a polyester film is produced using the polyester resin melt obtained in production step 1. The polyester resin melt obtained in production step 1 has been freed of foreign matter and is co-melt-extruded from all nozzles of a die (e.g., a T-die) onto a rotating cooling drum, quenched to produce an unstretched laminate film, which is then stretched in the longitudinal and transverse directions and heat-set as necessary. In this case, the stretch ratio in the transverse direction, in other words, the width direction, is preferably 4.0 times or more, and, if necessary, it is even more preferable that the stretch ratio in the longitudinal direction be 2.5 times or more.

[0104] (Foreign matter removal) From the viewpoint of removing foreign matter and additives (aggregates such as fine particles) in the polyester molten resin, it is preferable to provide a filter after melt extrusion to remove foreign matter. For filtration using a filter, for example, a filter device incorporating a breaker plate type or a leaf disk type filter is preferably used. Filtration may be performed in one stage, or multi-stage filtration of two or more stages may be performed. Stainless steel is preferred as the filter material. The filter material may be made of woven wire, sintered metal fiber or metal powder (sintered filter material), and among these, sintered filter material is preferred. In the present invention, by using a filter material containing a specific fibrous sintered body using sintered fiber and having a filtration accuracy of 5 μm or less, preferably 3 μm or less, and a filter material containing a powdered sintered body using sintered powder, it is possible to remove gel-like foreign matter in the polyester resin. In particular, in the present invention, it is preferable to use a filter made of a fibrous sintered body from the viewpoint of improving filtration accuracy. More preferably, a powdered sintered body using sintered powder is combined with the fibrous sintered body, which is effective in removing gel-like foreign matter. It is particularly preferable to use a filtration device equipped with at least one filter in which both are integrated. A leaf disk-type filter is preferred as a filter containing the above-mentioned filter material. The number and size of the filter containing the above-mentioned filter material are appropriately selected depending on the characteristics (type, viscosity, flow rate, etc.) of the polyester resin used. The filtration accuracy of the filter material containing the specific fibrous sintered body is preferably 2 μm or less. In the present invention, "filtration accuracy" is defined as "the minimum glass bead diameter that can capture 95% or more by using the filter material." In the present invention, the polyester resin melt that has undergone the filtration process using the filter has a number of agglomerates (foreign matter) with a major axis of 1 μm or more and less than 3 μm of 350 / cm. ２ It is preferable that the number of particles is 300 or less, and more preferably 300 particles / cm ２ More preferably, 200 particles / cm or less ２ Below, among them, 100 pieces / cm ２ The following is good:

[0105] Next, an example of a method for producing a polyester film consisting of three layers: polyester layer (A) / polyester layer (B) / polyester layer (A) will be described. The same applies to other laminate structures. First, the polyester forming polyester layer (A) and the polyester forming polyester layer (B) are fed into separate extruders and heated to a temperature above the melting point of each polyester to melt them. Next, the polyesters are extruded as a sheet from a T-die so that they are laminated in the order polyester layer (A) / polyester layer (B) / polyester layer (A). Subsequently, this sheet is quenched on a rotating cooling drum to below the glass transition temperature to obtain an amorphous unstretched film. At this time, in order to improve the flatness of the unstretched film, the adhesion between the unstretched film and the rotating cooling drum may be improved by an electrostatic application adhesion method, a liquid application adhesion method, or the like.

[0106] Next, a roll stretching machine is used to stretch the unstretched film in its longitudinal direction (longitudinal stretching) to obtain a uniaxially stretched film. The stretching temperature is above the glass transition temperature of the polyester, preferably 70 to 150°C, and more preferably 75 to 130°C. The longitudinal stretching ratio is 2.5 times or more, preferably 2.8 to 4.0 times, and even more preferably 3.0 to 3.5 times. In this case, longitudinal stretching may be performed in a single stage or in two or more stages. Next, a tenter stretching machine is used to stretch the uniaxially stretched film in its short direction (transverse stretching) to obtain a biaxially stretched film. The stretching temperature is preferably 75 to 150°C, and more preferably 80 to 140°C. The transverse stretching ratio is 4.0 times or more, preferably 4.2 to 6.0 times, and even more preferably 4.4 to 5.5 times, and even more preferably 4.5 to 5.0 times. In this case, the transverse stretching may be carried out in one stage only, or in two or more stages.

[0107] Subsequently, the biaxially stretched film is heat-treated at a temperature of, for example, 150 to 250° C. to produce a laminated film. When the biaxially stretched film is heat-treated, the biaxially stretched film may be relaxed by 30% or less. Then, if necessary, the biaxially stretched film may be wound into a roll.

[0108] The other resin layer may be formed by "in-line coating," which treats the film surface during the polyester film production process, or by "off-line coating," which applies a coating outside the system onto a polyester film that has already been produced.

[0109] In-line coating is a method of coating within the polyester film production process, specifically, at any stage from melt extrusion of polyester to stretching, heat setting, and winding up. Typically, coating is performed on any of the following: an unstretched sheet obtained by melting and quenching, a stretched uniaxially stretched film, a biaxially stretched film before heat setting, or a film after heat setting and before winding up.

[0110] For example, in sequential biaxial stretching, a method in which a uniaxially stretched film stretched in the longitudinal direction (machine direction) is coated and then stretched in the transverse direction is particularly advantageous. This method allows film formation and resin layer formation to be performed simultaneously, resulting in manufacturing cost advantages. Furthermore, because stretching is performed after coating, the film thickness of the resin layer can be changed by adjusting the stretching ratio, making it easier to achieve a thinner coating than offline coating. Furthermore, by providing a resin layer on a polyester film before stretching, the resin layer can be stretched together with the polyester film. This allows the resin layer to be firmly adhered to the polyester film. Furthermore, in the production of biaxially stretched polyester films, stretching while holding the film edges with clips or the like allows the film to be restrained in both the machine and transverse directions, allowing for high temperatures to be applied in the heat setting process while maintaining flatness and preventing wrinkles. Therefore, the heat treatment performed after coating can be performed at high temperatures not achievable by other methods, improving the film-forming properties of the resin layer and allowing for stronger adhesion between the resin layer and the film. Furthermore, a stronger resin layer can be formed, improving the performance and durability of the resin layer. Therefore, a preferred method for forming a resin layer on at least one surface of a polyester film is a production method in which a coating liquid is applied to a polyester film and then the polyester film is stretched in at least one direction.

[0111] The resin layer can be formed, for example, by dispersing or dissolving the particles and any other additives that the resin layer may further contain, such as an antistatic agent, a wax, a binder, a crosslinking agent, etc., in a solvent to prepare a solution for the resin layer, and then applying the solution to one side of the base polyester film.

[0112] The resin layer solution is preferably formed by coating one side of a polyester film as an aqueous coating liquid (a water-soluble or water-dispersible resin using water as a medium). However, it is also possible to form the layer by coating an aqueous coating liquid containing a small amount of organic solvent. Examples of such organic solvents include alcohols such as ethanol, isopropanol, ethylene glycol, and glycerin; ethers such as ethyl cellosolve, t-butyl cellosolve, propylene glycol monomethyl ether, and tetrahydrofuran; ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate; and amines such as dimethylethanolamine. These can be used alone or in combination. By appropriately selecting and incorporating these organic solvents into the aqueous coating liquid as needed, the stability, coatability, or coating film properties of the coating liquid can be improved.

[0113] The resin layer solution can be applied to the polyester film using a reverse roll coater, gravure coater, rod coater, air doctor coater, or other coating device, as described in "Coating Methods" by Yuji Harasaki, published by Maki Shoten in 1979.

[0114] Regarding the drying and curing conditions when forming a resin layer on a polyester film, for example, when the resin layer is formed by off-line coating, it is generally recommended to carry out heat treatment at 80 to 200°C for 3 to 40 seconds, preferably at 100 to 180°C for 3 to 40 seconds. On the other hand, when the resin layer is formed by in-line coating, it is generally recommended to carry out heat treatment at 70 to 270°C for 3 to 200 seconds.

[0115] Regardless of whether off-line coating or in-line coating is used, heat treatment and irradiation with active energy rays such as ultraviolet light may be used in combination, if necessary. The surface of the polyester film may be previously subjected to a surface treatment such as a corona treatment or a plasma treatment.

[0116] Next, the characteristics of the polyester film of the present invention will be described.

[0117] (Surface Roughness) The average surface roughness Ra of the polyester film surface is preferably in the range of 0.001 to 0.020 μm, more preferably 0.002 μm to 0.010 μm, and even more preferably 0.003 μm to 0.005 μm. Having the surface roughness Ra of the polyester film within the above range prevents the transparency of the polyester film from being impaired and minimizes the increase in light scattering due to the unevenness of the film surface, thereby suppressing a decrease in the ultraviolet (UV) exposure dose and thus a decrease in resolution. When a resin layer is formed on only one side of the polyester film, it is preferably formed on the side opposite the side on which the photoresist layer is formed. Therefore, the average surface roughness Ra is preferably present on the surface of the polyester film on the polyester layer A side. The same applies to the maximum surface roughness Rt, which will be described next.

[0118] The maximum surface roughness Rt is preferably in the range of 0.010 to 0.400 μm, with 0.015 μm to 0.300 μm, more preferably 0.020 μm to 0.200 μm, and even more preferably 0.025 μm to 0.100 μm. An Rt of 0.400 μm or less can prevent irregularities from being transferred to the photoresist layer, eliminating the problem of circuit defects during fine-pitch circuit formation. On the other hand, an average surface roughness Ra of 0.001 μm or more or a maximum surface roughness Rt of 0.010 μm or more ensures process suitability, particularly the film formation process, by preventing scratches from occurring on the surface of the film for use as a dry film resist substrate. Furthermore, these are preferred because scratches are less likely to transfer to the photoresist layer or cause scattering of light exposure, thereby less likely to affect the fine-pitch circuit pattern.

[0119] (Film Haze) When used in a high-resolution dry film resist, the film haze is preferably 1.0% or less, and more preferably 0.1% or more and 0.7% or less, and even more preferably 0.2% or more and 0.5% or less, from the viewpoint that the exposure amount of ultraviolet light is unlikely to be insufficient, defects in the desired circuit are unlikely to occur, and a decrease in resolution can be suppressed.

[0120] (Number of aggregates (foreign matter) having a major axis of 1 μm or more and less than 3 μm in the polyester film) The number of aggregates (foreign matter) having a major axis of 1 μm or more and less than 3 μm in the polyester film was 350 / cm ２ It is necessary that the number of particles is 300 / cm. ２ More preferably, 200 particles / cm or less ２ Below, among them, 100 pieces / cm ２ The following is good:

[0121] (Number of protrusions having a maximum peak height (Sp) of 0.3 μm or more protruding from the film surface) The number of protrusions having a maximum peak height (Sp) of 0.3 μm or more protruding from the film surface was 2.7 / cm ２ It is preferable that the density is 2.2 particles / cm or less. ２ More preferably, 1.7 particles / cm or less ２ Below, among them, 1.0 pieces / cm ２ The following is good:

[0122] The maximum peak height (Sp) is one of the surface roughness parameters (ISO 25178), and represents the maximum value of the height from the mean plane of the surface, and is expressed by the following formula (2).

[0123]

[0124] In the present invention, by satisfying the above number of protrusions, it becomes possible to cope with the progress of further narrowing of resist line width from 5 μm or less to 2 μm or less.

[0125] <Method of Using Polyester Film> The polyester film of the present invention can be used as a support film for dry film resist, a support film for producing ceramic green sheets, a substrate film for optical applications, and the like.

[0126] (Film for dry film resist substrate) The polyester film of the present invention is useful as a film for producing a dry film resist. Specifically, a dry film resist can be formed by laminating a photoresist layer on the polyester film of the present invention, and then laminating a protective film on the photoresist layer.

[0127] In this case, when the resin layer is formed on only one side of the polyester film, it is preferable to laminate the polyester film to the photoresist layer so that the resin layer is located on the side opposite to the photoresist layer formation side when forming the dry film resist, in other words, so that the photoresist layer is adhered to the surface of the polyester film opposite to the resin layer. Dry film resists usually have a laminated structure of support film / photoresist layer / protective film. When the dry film resist is wound into a roll, the lower surface of the dry film resist, i.e., the support film, comes into contact with the upper protective film. Therefore, the presence of a resin layer on the surface that comes into contact with the protective film makes the effect of easy slippage more pronounced. Furthermore, the absence of a resin layer on the resist surface makes it less likely that the adhesion between the resist and the support film will change, and peeling problems will be less likely to occur when removing the support film from the resist.

[0128] Conventional compositions can be used as the photosensitive resin composition constituting the photoresist layer. Typically, a negative-type photosensitive resin is used as the photosensitive resin contained in a photosensitive resin composition for dry film resist, and is composed mainly of a monomer having a polymerizable unsaturated group, a polymer, a photopolymerization initiator, etc. Photosensitive resins are generally alkali-soluble, and in the dry film resist processing step, the exposed portions form a circuit by development, while the unexposed portions are removed by a developer.

[0129] The monomer having a polymerizable unsaturated group is not particularly limited, but examples thereof include a monomer having one polymerizable unsaturated group, a monomer having two polymerizable unsaturated groups, and a monomer having three or more polymerizable unsaturated groups, and these may be used alone or in appropriate combination.

[0130] Examples of the monomer having one polymerizable unsaturated group include methyl(meth)acrylate, ethyl(meth)acrylate, 2-hydroxyethyl(meth)acrylate, propyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, butyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, 2-phenoxy-2-hydroxypropyl(meth)acrylate, 2-(meth)acryloyloxy-2-hydroxypropyl phthalate, 3-chloro-2-hydroxypropyl(meth)acrylate, glycerin mono(meth)acrylate, 2-(meth)acryloyloxyethyl acid phosphate, half(meth)acrylate of a phthalic acid derivative, and N-methylol(meth)acrylamide.

[0131] Examples of the monomer having two polymerizable unsaturated groups include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethylene oxide-modified bisphenol A di(meth)acrylate, and propylene oxide-modified bisphenol A di(meth)acrylate. ester, ethylene oxide-propylene oxide-modified bisphenol A di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, glycerin di(meth)acrylate, pentaerythritol di(meth)acrylate, ethylene glycol diglycidyl ether di(meth)acrylate, diethylene glycol diglycidyl ether di(meth)acrylate, propylene glycol diglycidyl di(meth)acrylate, phthalic acid diglycidyl ester di(meth)acrylate, hydroxypivalic acid-modified neopentyl glycol di(meth)acrylate, etc. Among these, ethylene oxide-modified bisphenol A di(meth)acrylate and ethylene oxide-propylene oxide-modified bisphenol A di(meth)acrylate are particularly preferred.

[0132] Examples of the monomer having three or more polymerizable unsaturated groups include trimethylolpropane tri(meth)acrylate, trimethylolpropane tripropoxy(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, tri(meth)acryloyloxyethoxytrimethylolpropane, and glycerin polyglycidyl ether poly(meth)acrylate.

[0133] In addition to the above, epoxy (meth)acrylate compounds, urethane (meth)acrylate compounds, phosphorus-containing polymerizable compounds, and the like may also be used.

[0134] The monomer having a polymerizable unsaturated group is preferably one having two polymerizable unsaturated groups and a weight-average molecular weight of 1,500 or less, preferably 300 to 1,200, and among these, ethylene oxide-modified bisphenol A di(meth)acrylate and ethylene oxide / propylene oxide-modified bisphenol A di(meth)acrylate are particularly preferred. If the weight-average molecular weight exceeds 1,500, the distance between crosslinks becomes too long and sufficient curing may not be achieved, which may result in a decrease in resolution and a decrease in fine line adhesion.

[0135] The polymer contained in the photosensitive resin composition is not particularly limited, but examples thereof include polymers made of acrylic or methacrylic polymerizable monomers, which may be homopolymers or copolymers, or copolymers with polymerizable monomers other than acrylic or methacrylic monomers. Examples of the polymerizable monomer include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid, as well as anhydrides and half esters thereof; (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and glycidyl (meth)acrylate; acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, styrene, α-methylstyrene, vinyl acetate, and alkyl vinyl ethers.

[0136] The weight-average molecular weight of the polymer is preferably in the range of 5,000 to 250,000, more preferably 10,000 to 200,000. If the weight-average molecular weight is less than 5,000, the resin may become too soft and may bleed when processed into a roll form as a photoresist film, whereas if it exceeds 250,000, the resolution may decrease.

[0137] The glass transition temperature (Tg) of the polymer is preferably in the range of 30 to 150° C. If the glass transition temperature is less than 30° C., the resin may become too soft and may bleed when processed into a roll as a photoresist film, whereas if the glass transition temperature is more than 150° C., the conformability to the irregularities on the substrate surface may be reduced when used as a photoresist film.

[0138] As the photopolymerization initiator contained in the photosensitive resin composition, a conventionally known one can be used.

[0139] The photosensitive resin composition may further contain additives such as thermal crosslinking agents, such as amino resins such as melamine and isocyanate compounds, coloring dyes, such as crystal violet, malachite green, malachite green lake, brilliant green, patent blue, methyl violet, Victoria blue, rose aniline, parafuchsin, and ethylene violet, adhesion promoters, plasticizers, antioxidants, thermal polymerization inhibitors, solvents, surface tension modifiers, stabilizers, chain transfer agents, antifoaming agents, and flame retardants.

[0140] When a photosensitive resin composition is applied to a polyester film to form a photosensitive resin layer (photoresist layer), an example of the method is to mix an organic solvent with the photosensitive resin composition to a predetermined concentration. Examples of organic solvents include acetone, methyl ethyl ketone, methanol, ethanol, isopropyl alcohol, toluene, propylene glycol monoethyl ether, propylene glycol monomethyl ether acetate, ethyl acetate, and butyl acetate. These solvents may be used alone or in combination of two or more. A coating liquid containing a mixture of photosensitive resin compositions is uniformly applied to one side of a support film using a roll coater or bar coater method, and the coating is then dried, typically at 50 to 130°C or in an oven with gradually increasing temperatures, to form a photosensitive resin layer (photoresist layer). A protective film is then laminated onto the photosensitive resin layer and wound into a roll to produce a photosensitive resin laminate (dry film resist).

[0141] The protective film that constitutes the dry film resist is formed from a polyolefin such as polyethylene or polypropylene, or a polyester, and is laminated on the side of the photoresist layer opposite the support film side to protect the photoresist layer.

[0142] The dry film resist obtained by using the polyester film of the present invention as a support film, i.e., a film for a dry film resist substrate, has a reduced number of aggregates (foreign matter) in the support film and is less likely to suffer from inhibition of resist curing, thereby reducing circuit defects that occur on electronic circuit boards and making the dry film resist suitable for forming high-definition electronic circuits.

[0143] (Support for Producing Ceramic Green Sheets) The polyester film of the present invention is useful as a film for producing ceramic green sheets. Specifically, when producing ceramic green sheets, a ceramic slurry is applied to the release surface of a release film, dried and cured, and then peeled off from the release film. The ceramic green sheets are laminated to produce a ceramic capacitor. The release layer constituting the release film is not particularly limited as long as it contains a material with releasability. Among such materials, the use of a curable silicone resin is preferred because it provides particularly good releasability. It may be a type whose main component is a curable silicone resin, or a modified silicone type obtained by graft polymerization with an organic resin such as a urethane resin, epoxy resin, or alkyd resin. The curable silicone resin may be any type of curing reaction type, such as an addition type, condensation type, UV-curable type, electron beam-curable type, or solventless type. The coating amount of the release layer (after drying) is 0.01 to 5 g / m. ２ , and further 0.01 to 2 g / m ２ , particularly 0.01 to 1 g / m ２ The range is preferred.

[0144] When the polyester film of the present invention is used as a support for producing a ceramic green sheet, the film surface has high smoothness, and pinholes and the like are unlikely to occur when a ceramic slurry is applied, and the film can be used to form a thin ceramic green sheet having a thickness of, for example, 3 μm or less.

[0145] (Film for forming an interlayer insulating layer) The polyester film of the present invention is useful as a film for forming an interlayer insulating layer. Specifically, a laminate can be formed by laminating an interlayer insulating layer on the polyester film of the present invention, and then laminating a protective film on the interlayer insulating layer. The insulating layer resin composition constituting the insulating layer preferably contains an epoxy resin and an inorganic filler. The polyester film with an insulating layer in this embodiment can be obtained by applying a coating liquid consisting of the insulating layer resin composition to the surface of the resin layer (release layer) of the polyester film and curing it. The configuration of the protective film is not particularly limited as long as it can suppress damage or deformation of the insulating layer. A resin film is preferred as the protective film substrate, and more specifically, a film mainly composed of polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyimide, or polycarbonate is preferred.

[0146] When the polyester film of the present invention is used as a film for forming an interlayer insulating layer, the film surface has high smoothness and can be used for forming a highly smooth interlayer insulating layer.

[0147] (Optical film) The polyester film of the present invention is useful as an optical film. Specifically, when a pressure-sensitive adhesive sheet is produced by providing a pressure-sensitive adhesive layer on the polyester film of the present invention, the transparency is high, and the sheet has an advantage of being easy to work with, for example, allowing inspection for foreign matter in a state where the sheet is attached to an adherend.

[0148] <Explanation of Terms, etc.> Generally, a "sheet" is defined in JIS as a thin, flat product whose thickness is small relative to its length and width, and a "film" is generally a thin, flat product whose thickness is extremely small compared to its length and width and whose maximum thickness is arbitrarily limited, and is usually supplied in roll form (Japanese Industrial Standard JIS K6900). However, the boundary between sheet and film is unclear, and there is no need to distinguish between the two in the present invention. Therefore, in the present invention, when referring to a "film," it is intended to include a "sheet," and when referring to a "sheet," it is intended to include a "film." Furthermore, when referring to a "panel," such as an image display panel or a protective panel, it includes a plate, a sheet, and a film.

[0149] In this specification, when it is stated that "X to Y" (X and Y are any numbers), it means "X or more and Y or less" unless otherwise specified, and also includes the meaning of "preferably greater than X" or "preferably smaller than Y." Furthermore, when it is stated that "X or more" (X is any number), it means "preferably greater than X" unless otherwise specified, and when it is stated that "Y or less" (Y is any number), it also means "preferably smaller than Y" unless otherwise specified.

[0150] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded.

[0151] <Materials for Forming Polyester Film> In the examples and comparative examples, polyester films (polyester layer (A), polyester layer (B)) were prepared using the following polyesters.

[0152] <Polyester I> Polyethylene terephthalate homopolymer prepared using ethyl acid phosphate, magnesium acetate tetrahydrate, and tetra-n-butyl titanate as a polymerization catalyst. The intrinsic viscosity of Polyester I was 0.70 dL / g. (Ti element: 10 ppm) (P element: 15 ppm) (Mg element: 15 ppm)

[0153] <Polyester II> Polyethylene terephthalate homopolymer prepared using ethyl acid phosphate, magnesium acetate tetrahydrate, and tetra-n-butyl titanate as a polymerization catalyst. The intrinsic viscosity of Polyester II was 0.63 dL / g. (Ti element: 10 ppm), (P element: 15 ppm), (Mg element: 15 ppm)

[0154] <Polyester III> Polyethylene terephthalate homopolymer prepared using ethyl acid phosphate, magnesium acetate tetrahydrate, and antimony trioxide as a polymerization catalyst. The intrinsic viscosity of Polyester III was 0.63 dL / g. (Sb element: 310 ppm) (P element: 30 ppm) (Mg element: 30 ppm)

[0155] <Polyester IV> Polyethylene terephthalate homopolymer prepared using ethyl acid phosphate, magnesium acetate tetrahydrate, and tetra-n-butyl titanate and antimony trioxide as polymerization catalysts. The intrinsic viscosity of Polyester IV was 0.63 dL / g. (Ti: 6 ppm, Sb: 95 ppm), (P: 40 ppm), (Mg: 40 ppm)

[0156] <Polyester V> A polyethylene terephthalate homopolymer containing spherical alumina particles, prepared using ethyl acid phosphate, magnesium acetate tetrahydrate, and tetra-n-butyl titanate as a polymerization catalyst. The intrinsic viscosity of Polyester V was 0.61 dl / g, the spherical alumina particles had an average particle size of 0.05 μm and a maximum particle size of 0.20 μm, and the spherical alumina particle content was 1.5 mass% relative to the total amount of Polyester V. (Ti element: 10 ppm), (P element: 15 ppm), (Mg element: 15 ppm).

[0157] <Polyester VI> Polyethylene terephthalate homopolymer containing spherical silica particles, prepared using ethyl acid phosphate, magnesium acetate tetrahydrate, and tetra-n-butyl titanate as a polymerization catalyst. The intrinsic viscosity of the polyester VI was 0.61 dl / g, the spherical silica particles had an average particle size of 0.30 μm, a maximum particle size of 0.60 μm, and the spherical silica particle content was 1.0 mass% based on the total weight of the polyester VI. (Ti element: 10 ppm), (P element: 15 ppm), (Mg element: 15 ppm)

[0158] <Polyester VII> A polyethylene terephthalate homopolymer containing ion-exchange resin particles, prepared using ethyl acid phosphate, magnesium acetate tetrahydrate, and tetra-n-butyl titanate as a polymerization catalyst. The intrinsic viscosity of Polyester VII was 0.61 dl / g, the average particle size of the ion-exchange resin particles was 0.50 μm, the maximum particle size was 0.80 μm, and the content of the ion-exchange resin particles was 1.0 mass% based on the total weight of Polyester VII. (Ti element: 10 ppm), (P element: 15 ppm), (Mg element: 15 ppm)

[0159] <Polyester VIII> A polyethylene terephthalate homopolymer containing ion-exchange resin particles, prepared using ethyl acid phosphate, magnesium acetate tetrahydrate, and tetra-n-butyl titanate as a polymerization catalyst. The intrinsic viscosity of Polyester VIII was 0.61 dL / g, the average particle size of the ion-exchange resin particles was 0.8 μm, the maximum particle size was 1.5 μm, and the content of the ion-exchange resin particles was 0.5 mass% based on the total weight of Polyester VIII. (Ti element: 10 ppm), (P element: 15 ppm), (Mg element: 15 ppm)

[0160] <Polyester IX> Polyethylene terephthalate homopolymer containing silica particles, prepared using ethyl acid phosphate, magnesium acetate tetrahydrate, and tetra-n-butyl titanate as a polymerization catalyst. The intrinsic viscosity of Polyester IX was 0.61 dl / g, the average particle size of the silica particles was 2.7 μm, the maximum particle size was 4.0 μm, and the content of the spherical silica particles was 0.7 mass% based on the total weight of Polyester IX. (Ti element: 10 ppm), (P element: 15 ppm), (Mg element: 15 ppm)

[0161] <Polyester X> Polyethylene terephthalate homopolymer prepared using ethyl acid phosphate, magnesium acetate tetrahydrate, and tetra-n-butyl titanate as a polymerization catalyst. The intrinsic viscosity of Polyester X was 0.63 dL / g. (Ti element: 10 ppm), (P element: 60 ppm), (Mg element: 60 ppm)

[0162] <Composition for forming resin layer> In the following examples and comparative examples, the following raw materials were used and mixed in the mass ratios shown in Table 2 to prepare a coating liquid as a composition for forming a resin layer.

[0163] Antistatic agent (A1): Polydiallyldimethylammonium chloride (average molecular weight: approximately 30,000)

[0164] Wax (B1) 300 g of oxidized polyethylene wax having a melting point of 105°C, oxidation state of 16 mgKOH / g, density of 0.93 g / mL, and average molecular weight of 5000, 650 g of ion-exchanged water, 50 g of decaglycerin monooleate surfactant, and 10 g of 48% aqueous potassium hydroxide solution were added to a 1.5 L emulsification facility equipped with a stirrer, thermometer, and temperature controller, and the facility was purged with nitrogen, sealed, and stirred at high speed at 150°C for 1 hour. The resulting wax emulsion was then cooled to 130°C and passed through a high-pressure homogenizer at 400 atmospheres to obtain a wax emulsion cooled to 40°C.

[0165] Particles (C1): Silica particles having an average particle size of 0.05 μm Particles (C2): Silica particles having an average particle size of 0.08 μm The average particle sizes of particles (C1) to (C2) were determined using a transmission electron microscope (H7650, manufactured by Hitachi High-Technologies Corporation, accelerating voltage 100 kV).

[0166] Acrylic water dispersion (D1): A water dispersion of an acrylic resin polymerized with the following composition and having a glass transition temperature of 40°C: Emulsion polymer of ethyl acrylate / n-butyl acrylate / methyl methacrylate / N-methylolacrylamide / acrylic acid = 65 / 21 / 10 / 2 / 2 (mass%) (emulsifier: anionic surfactant).

[0167] Crosslinking agent (E1): hexamethoxymethylolmelamine

[0168] Example 1 As the polyester layer A, polyester I and polyester V were blended in a mass ratio of 80:20, melted in an extruder, and supplied to the polyester layer A of the lamination die, and as the polyester layer B, 100% by mass of polyester I was melted in an extruder and supplied to the polyester layer B of the lamination die. Regarding the two-kind three-layer laminated polyester resin having a structure of A layer / B layer / A layer, 100 sheets of laminated filters equipped with a filter material containing a powdered sintered body and a filter material containing a fibrous sintered body with a filtration accuracy of 3 μm or less were set, and after a manufacturing process of filtering, the laminated filter was co-extruded into a film, cast onto a cooling drum at 35 ° C, and adhered to the surface of the cooling drum by an electrostatic adhesion method, and rapidly cooled and solidified to produce an unstretched film. Next, the unstretched film was preheated with a heating roll at 75°C, and then stretched 3.2 times in the longitudinal direction between rolls at 85°C using a combination of an infrared heater and a heating roll. One side of this longitudinally stretched film was in-line coated with a coating liquid as a resin layer-forming composition prepared with the formulation shown in Table 2. The film was then guided into a tenter while holding the edges with clips, and stretched 4.5 times in the transverse direction while heated at 95°C. Heat treatment was then performed at 225°C for 10 seconds to produce a polyester film (sample) having a thickness of 16.0 μm (A layer / B layer / A layer = 1.0 μm / 14.0 μm / 1.0 μm), a width of 1580 mm, and a surface with a resin layer having a thickness of 0.030 μm.

[0169] Examples 2 to 4, Comparative Examples 1 to 4 Polyester films (samples) were produced in the same manner as in Example 1, except that the raw materials of the polyester film were changed as shown in Table 2, or the polyester raw materials were not filtered, the filtering mesh was changed, or a resin layer was not provided.

[0170] <Measurement and Evaluation Methods> The methods for measuring and evaluating the physical properties of the materials and polyester films (samples) used in the above examples and comparative examples are as follows.

[0171] (1) Thickness of Polyester Film The thickness of the polyester film (sample) was measured with a micrometer.

[0172] (2) Thickness of Each Layer of the Polyester Film and Resin Layer Thickness The thickness of each layer of the polyester film (polyester layer A and polyester layer B) and the resin layer thickness were measured by observing the film cross section using a transmission electron microscope (TEM). Specifically, a small piece of the film sample was first embedded in a resin containing an epoxy resin, a curing agent, and an accelerator, and then 200 nm-thick sections were prepared using an ultramicrotome to serve as the observation sample. The obtained sample was observed using a transmission electron microscope (H-9000) manufactured by Hitachi High-Technologies Corporation. In the observed cross section, the interface between polyester layer A and polyester layer B, and the interface between the polyester film surface and the resin layer were observed by light and dark, approximately parallel to the polyester film. The distance from these interfaces to the film surface was measured for 50 transmission electron microscope photographs, and the 10 largest and 10 smallest measurements were removed to average the remaining 30 measurements. The thickness of each layer and the resin layer was calculated from the average value. The transmission electron microscope was set at an acceleration voltage of 300 kV and a magnification ranging from 1 to 100,000 times depending on the layer thickness.

[0173] (3) Contents of Antimony and Titanium in Polyester Film In each of the Examples and Comparative Examples, the amounts of elements in the film were determined by single-sheet measurement using an X-ray fluorescence analyzer (manufactured by Shimadzu Corporation, model "XRF-1800") under the conditions shown in Table 1. In the case of a film, the film was melted and molded into a disk shape, and then the contents of antimony (Sb) and titanium (Ti) relative to the entire film were measured.

[0174]

[0175] (4) Number of aggregates (foreign matter) in polyester film with a major axis of 1 μm or more and less than 3 μm In each example and comparative example, the inside of the polyester film was observed using an optical microscope. The obtained images were binarized using image processing software (manufactured by Nireco Corporation, "LUZEX"). The aggregates (foreign matter) in the film were observed in black, and the aggregates (foreign matter) were extracted by binarizing the obtained images. 1.3 cm ２ The number of agglomerates (foreign matter) with a major axis of 1 μm or more and less than 3 μm in the area of ​​1 cm was counted. ２ was converted to.

[0176] (5) The number of protrusions having a maximum peak height (Sp) of 0.3 μm or more protruding from the film surface was measured using a white light interferometer "NewView" (registered trademark) manufactured by Ametec Co., Ltd. Using a 10x lens and a 0.5x zoom, the maximum peak height Sp value per field of view = 1.83 mm × 1.83 mm area was measured, and the measurement was repeated sequentially so that the measurement points were adjacent to each other without overlapping, for a total of 180 times (total measurement area = 602.8 mm ２ The maximum peak height (Sp) value of 0.3 μm or more was counted from the 180 Sp values ​​(number / 602.8 mm ２ ) and the number of protrusions of 0.3 μm or more (pieces / cm ２ ) was converted.

[0177] (6) Average Surface Roughness (Ra) of Film Surface When a resin layer is present, the average surface roughness (Ra) of the film surface opposite the resin layer, i.e., the surface on the polyester layer (A) side, was determined using a surface roughness measuring instrument (SE-3F) manufactured by Kosaka Laboratory Co., Ltd., as follows. That is, a section of reference length L (2.5 mm) was cut out from the film cross-sectional curve obtained by measurement in the direction of its center line. When the center line of this cutout section was taken as the x-axis and the direction of longitudinal magnification as the y-axis, and the roughness curve was expressed as y = f(x), the value given by the following formula was expressed in μm. The center-line average roughness was expressed as the average value of the center-line average roughnesses of the cutout sections obtained from 10 cross-sectional curves obtained from the sample film surface. The tip radius of the stylus was 2 μm, the load was 30 mg, and the cutoff value was 0.08 mm.

[0178] (7) Maximum Height (Rt) of Film Surface The maximum height (Rt) of a film surface, similar to the average surface roughness (Ra), was measured as follows. A sampled portion of the cross-sectional curve obtained during Ra measurement was sandwiched between two straight lines parallel to the average line, and the distance between these two straight lines was measured in the longitudinal direction of the cross-sectional curve. This value, expressed in micrometers (μm), was taken as the maximum height Rt of the sampled portion. Ten cross-sectional curves were measured from the surface of the sample film, and the maximum height was expressed as the average value of the maximum heights of the sampled portions measured from these cross-sectional curves.

[0179] (8) Average particle size of particles The average particle size of particles in each layer was determined by observing 10 or more particles with a scanning electron microscope, measuring the diameters of the particles, and calculating the average value. In this case, in the case of non-spherical particles, the average value of the longest and shortest diameters was measured as the diameter of each particle.

[0180] (9) Particle Content (Particle Concentration) of Polyester Layer A and Polyester Layer B A sample was scraped off from a layer of a polyester film (sample) for which the particle concentration was to be measured, and the sample was subjected to a dissolution treatment using a selected solvent that dissolves polyester but does not dissolve particles. The particles were then centrifuged from the solution, and the ratio (ppm) of the particles to the total mass of the particles was measured as the particle concentration.

[0181] (10) Intrinsic Viscosity Approximately 0.25 g of a freeze-pulverized polyester film was dissolved in approximately 25 mL of a mixed solvent of phenol / 1,1,2,2-tetrachloroethane (1 / 1 by mass) at 120°C for 30 minutes to a concentration of 1.00 g / dL, and then cooled to 30°C. The number of seconds it took for the sample solution and the solvent alone to fall was measured at 30°C using a fully automatic solution viscometer (DT553, manufactured by Sentec Co., Ltd.), and the intrinsic viscosity was calculated by the following formula (3): Intrinsic viscosity = ((1 + 4K Ｈ η ＳＰ ) ０．５ -1) / (2K Ｈ C) ...Equation (3) where η ｓｐ =η / η ０ -1, η is the number of seconds the sample solution falls, η ０ is the number of seconds for the solvent to fall, C is the concentration of the sample solution (g / dL), K Ｈ is Huggins' constant.Ｈ was set to 0.33.

[0182] (11) Film Haze The haze of a polyester film (sample) was measured in accordance with JIS K 7105:1981 using an integrating sphere turbidity meter NDH-20D manufactured by Nippon Denshoku Industries Co., Ltd.

[0183]

[0184] From the results of the above Examples and Comparative Examples, it is clear that the polyester film contains titanium element, and by filtering during melt extrusion, the number of aggregates (foreign matter) with a major axis of 1 μm or more and less than 3 μm in the film is reduced to 350 pieces / cm ２ While suppressing the number of protrusions with a maximum peak height (Sp) of 0.3 μm or more protruding from the film surface to 2.7 / cm ２ This makes it possible to keep the thickness below 2 μm, for example, even when dry film resists are thinned from the 5 μm level to 2 μm or less. The present invention achieves this by utilizing titanium catalytic activity to suppress particle aggregation in the film, while also combining this with a physical method of removing foreign matter by filtration using a specially configured filter.

[0185] The polyester film of the present invention has the advantage of maintaining the flatness, handling properties, and winding properties of the film while reducing the generation of aggregates (foreign matter) of particles, metals, etc. Therefore, it is applicable to applications where the presence of foreign matter in the film is extremely unacceptable, such as for forming dry film resists and producing ceramic green sheets, and is an industrially valuable invention.

Claims

1. A polyester film containing particles with an average particle size of 0.03 to 0.80 μm, containing 3 ppm or less of antimony, and containing 5 to 100 ppm of titanium, phosphorus and magnesium in total.

2. The number of foreign objects with a major axis of 1 μm or more and less than 3 μm in the film is 350 / cm ２ 2. The polyester film according to claim 1, wherein:

3. The number of protrusions with a maximum peak height (Sp) of 0.3 μm or more protruding from the film surface is 2.7 / cm ２ 2. The polyester film according to claim 1, wherein:

4. The polyester film according to claim 1, which is a multi-layer film comprising a polyester layer B and a polyester layer A on at least one side of the polyester layer B.

5. The polyester film according to claim 1, wherein the titanium element content in the polyester film is 1 ppm or more and 30 ppm or less.

6. The polyester film according to claim 1, wherein the content of phosphorus in the polyester film is 5 ppm or more and 35 ppm or less.

7. The polyester film according to claim 1, wherein the magnesium element content in the polyester film is 5 ppm or more and 35 ppm or less.

8. The polyester film according to claim 4, wherein all of the polyester layers constituting the polyester film contain titanium element.

9. The polyester film according to claim 4, wherein the polyester layer A contains particles having an average particle size in the range of 0.03 to 0.80 μm and a maximum particle size of 1.0 μm or less.

10. The polyester film according to claim 4, wherein the particle content in the polyester layer A is in the range of 10 to 6,000 ppm.

11. The polyester film according to claim 4, wherein the polyester layer A contains two types of particles having different average particle sizes.

12. The polyester film according to claim 4, wherein the polyester layer A contains particles Y having an average particle size in the range of 0.30 to 0.80 μm and a maximum particle size of 1.0 μm or less.

13. The polyester film according to claim 1, further comprising another resin layer on at least one surface of the polyester film.

14. A method for producing a polyester film according to any one of claims 1 to 13, comprising: a production step 1 in which a melt of polyester resin chips containing a titanium compound, which has been converted into a master batch in advance, is filtered through a filter medium containing a powdered sintered body and a filter medium containing a fibrous sintered body having a filtration accuracy of 5 μm or less; and a production step 2 in which a polyester film is produced using the melt of polyester resin obtained in the production step 1.

15. The polyester film according to any one of claims 1 to 13, which is used for producing a dry film resist.

16. The polyester film according to any one of claims 1 to 13, which is used for producing a ceramic green sheet.

17. The polyester film according to any one of claims 1 to 13, which is used for forming an interlayer insulating layer.

18. The polyester film according to any one of claims 1 to 13, which is for optical use.

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