Method for producing polyester film, polyester film, and laminated film

Abstract

The present invention aims to provide a method for producing a polyester film capable of further suppressing uneven thickness of a functional layer provided on the surface of the polyester film, as well as a polyester film and a laminated film capable of further suppressing uneven thickness of a functional layer provided on the surface. The method for producing a polyester film of the present invention comprises: an extrusion molding step of extruding a molten resin containing polyester into a film shape to form an unstretched polyester film; a longitudinal stretching step of stretching the unstretched polyester film in a conveying direction; a transverse stretching step of stretching a uniaxially oriented polyester film in a widthwise direction; a heat setting step of heating and heat setting the biaxially oriented polyester film; a heat relaxation step of heating and heat relaxing the heat-set polyester film at a temperature lower than that in the heat setting step; a cooling step of cooling the heat-relaxed polyester film; an expansion step of expanding the heat-relaxed polyester film in the widthwise direction during the cooling step; and a particle-containing layer forming step of providing a particle-containing layer containing particles on at least one surface of a polyester substrate, wherein the cooling rate V of the polyester film in the cooling step is 2200 to 3500°C / min and the following specific condition 1 is satisfied.

Description

Technical Field

[0001] The present invention relates to a method for producing a polyester film, a polyester film and a laminated film. Background Art

[0002] Biaxially oriented polyester films are widely used from the perspectives of processability, mechanical properties, electrical properties, dimensional stability, transparency, and chemical resistance. They are used in a variety of applications, such as decorative films, supports and protective films for dry film photoresists, magnetic tapes, and release films used in the production of ceramic green sheets for the manufacture of multilayer ceramic capacitors.

[0003] On the other hand, in the production process of a biaxially oriented polyester film, a technique of providing a particle-containing layer on the surface is known as a technique for suppressing the occurrence of wrinkles (conveying wrinkles) generated during the conveyance of the polyester film.

[0004] For example, Patent Document 1 discloses a polyester film for photoresist, which is a biaxially oriented polyester film having a lubricant resin layer containing no particles having an average particle size greater than 40 nm and having an average thickness of 3 to 80 nm laminated on the side opposite to the resist coating surface. The 10-point average roughness (SRz), haze, static friction coefficient (μs), and thermal shrinkage stress at 150°C of the lubricant resin layer side of the polyester film were determined.

[0005] Previous technical literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2004-361446 Summary of the Invention

[0008] Technical issues to be solved by the invention

[0009] The present inventors referred to the technology described in Patent Document 1 and further studied the method for manufacturing a polyester film having a particle-containing layer. As a result, they found that when a functional layer is formed on a biaxially oriented polyester film to manufacture a laminated film, even if no bumps or wrinkles are visually recognized before the functional layer is formed, uneven thickness of the functional layer may sometimes occur in the laminated film after a liquid composition (e.g., a coating liquid) is applied to the surface of the biaxially oriented polyester film and heat-treated to form the functional layer.

[0010] Uneven thickness of these functional layers, for example, can manifest as uneven color in a decorative film that also includes a decorative layer as a functional layer, reducing the visibility of the decorative film. Furthermore, if uneven thickness also occurs in other functional layers, it can affect the properties and appearance of the functional laminated film.

[0011] In view of the above circumstances, an object of the present invention is to provide a method for producing a polyester film capable of further suppressing unevenness in the thickness of a functional layer provided on the surface of the polyester film.

[0012] Furthermore, an object of the present invention is to provide a polyester film and a laminated film capable of further suppressing unevenness in the thickness of a functional layer provided on the surface.

[0013] Means for solving technical problems

[0014] The present inventors have conducted intensive studies on the above-mentioned problems and have found that the above-mentioned problems can be solved by the following configuration.

[0015] [1]

[0016] A method for producing a polyester film comprises: an extrusion molding step of extruding a molten resin containing polyester in a film shape to form an unstretched polyester film containing at least a polyester base material; a longitudinal stretching step of stretching the unstretched polyester film in a conveying direction to form a uniaxially oriented polyester film; a transverse stretching step of stretching the uniaxially oriented polyester film in a width direction to form a biaxially oriented polyester film; a heat setting step of heating the biaxially oriented polyester film to heat set it; a heat relaxing step of heating the polyester film heat set in the heat setting step at a temperature lower than that in the heat setting step to heat relax it; a cooling step of cooling the polyester film heat relaxed in the heat relaxing step; and an expansion step of expanding the heat relaxed polyester film in the width direction in the cooling step, wherein the polyester film comprises a polyester base material and a particle-containing layer containing particles located on at least one surface of the polyester base material, wherein a cooling rate V of the polyester film in the cooling step is 2200 to 3500° C. / min and the polyester film satisfies the condition 1 described below.

[0017] [2]

[0018] The manufacturing method according to [1], wherein the value D calculated by the formula (3) described later based on the above-mentioned A, the above-mentioned B and the above-mentioned cooling rate V is 1 to 10000.

[0019] 〔3〕

[0020] The production method according to [1] or [2], wherein the polyester film has a thickness of less than 50 μm.

[0021] [4]

[0022] A manufacturing method according to any one of [1] to [3], wherein, between the above-mentioned longitudinal stretching step and the above-mentioned transverse stretching step, there is also a step of forming the above-mentioned particle-containing layer using a coating liquid containing the above-mentioned particles, or there is also a step of forming the above-mentioned particle-containing layer by simultaneously extruding a second melt containing the above-mentioned particles and the adhesive and the above-mentioned molten resin in the above-mentioned extrusion molding step.

[0023] 〔5〕

[0024] The production method according to any one of [1] to [4], wherein the surface temperature T2 of the polyester film in the heat relaxation step is 210° C. or lower.

[0025] [6]

[0026] The production method according to any one of [1] to [5], wherein a cooling rate V of the polyester film in the cooling step is 2200 to 3000° C. / min.

[0027] [7]

[0028] The production method according to any one of [1] to [6], wherein the above-mentioned b exceeds 0% and is 1.2% or less.

[0029] 〔8〕

[0030] A polyester film comprising a polyester substrate and a particle-containing layer containing particles located on at least one surface of the polyester substrate, wherein the thickness of the polyester film is less than 50 μm, and after the polyester film is conveyed at a conveying speed of 30 m / min and a tension in the conveying direction of 100 N / m and subjected to a heat treatment for 20 seconds at a film surface temperature of 90° C., the total area of ​​streak-like defect regions observed in the polyester film is less than 40% of the total area of ​​the observed region.

[0031] 〔9〕

[0032] The polyester film according to [8], wherein the expansion rate of the polyester film in the width direction at 90°C is -0.15 to 0.15% relative to the dimension of the polyester film in the width direction at 30°C.

[0033]

[10]

[0034] The polyester film according to [8] or [9], wherein the density of the polyester film is 1.39 to 1.41 g / cm 3 .

[0035]

[11]

[0036] The polyester film according to any one of [8] to

[10] , wherein the polyester base has a thickness of 3 to 40 μm, and the particle-containing layer has a thickness of 0.001 to 2.5 μm.

[0037]

[12]

[0038] The polyester film according to any one of [8] to

[11] , wherein the particle-containing layer contains particles P having an average particle diameter of 10 nm or more and less than 1 μm.

[0039]

[13]

[0040] The polyester film according to

[12] , wherein the average particle size of the particles P is larger than the thickness of the particle-containing layer.

[0041]

[14]

[0042] The polyester film according to any one of [8] to

[13] , wherein the particle-containing layer contains particles P1 having an average particle diameter of 10 to 100 nm.

[0043]

[15]

[0044] The polyester film according to any one of [8] to

[14] , wherein the particle-containing layer contains particles P2 having an average particle diameter exceeding 100 nm and not more than 400 nm.

[0045]

[16]

[0046] The polyester film according to any one of [8] to

[15] , wherein the particles contained in the particle-containing layer are resin particles, or the particles contained in the particle-containing layer are inorganic particles, and the maximum peak height Rp of at least one surface of the polyester film is 5 to 200 nm.

[0047]

[17]

[0048] The polyester film according to any one of [8] to

[16] , wherein the polyester substrate contains substantially no particles.

[0049]

[18]

[0050] A laminated film comprising: a polyester film produced by the production method described in any one of [1] to [7] or the polyester film described in any one of [8] to

[17] , and having a particle-containing layer only on one surface of a polyester substrate; and a functional layer located on the surface of the polyester substrate opposite to the particle-containing layer and selected from a decorative layer, a photosensitive resin layer, and a release layer.

[0051]

[19]

[0052] The laminated film according to

[18] , wherein the functional layer is a decorative layer and the laminated film is a decorative film.

[0053] 〔20〕

[0054] The laminated film according to

[18] , wherein the functional layer is a photosensitive resin layer, and the laminated film is a photosensitive transfer film.

[0055] 〔twenty one〕

[0056] The laminated film according to

[18] , wherein the functional layer is a release layer, and the laminated film is a release film for producing a ceramic green sheet.

[0057] Effects of the Invention

[0058] According to the present invention, it is possible to provide a method for producing a polyester film capable of further suppressing unevenness in the thickness of a functional layer provided on the surface of the polyester film.

[0059] Furthermore, according to the present invention, it is possible to provide a polyester film and a laminated film capable of further suppressing unevenness in the thickness of the functional layer provided on the surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 This is an observed image of a polyester film having streak-shaped defect areas.

[0061] Figure 2 This is a plan view showing an example of a stretching machine for producing a polyester film. DETAILED DESCRIPTION

[0062] Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments and can be implemented with appropriate modifications within the scope of the purpose of the present invention.

[0063] In the present invention, the numerical range represented by "to" refers to a range including the numerical values ​​recorded before and after "to" as the lower limit and the upper limit. In the numerical ranges recorded in stages in the present invention, the upper limit or lower limit recorded in a certain numerical range can be replaced by the upper limit or lower limit of another numerical range recorded in stages. Furthermore, in the numerical ranges recorded in the present invention, the upper limit or lower limit recorded in a certain numerical range can be replaced by the values ​​shown in the Examples.

[0064] In the present invention, when a plurality of substances corresponding to each component are present in the composition, unless otherwise specified, the amount of each component in the composition refers to the total amount of the plurality of substances present in the composition.

[0065] In the present invention, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes as long as the intended purpose of the process can be achieved.

[0066] In the present invention, a combination of two or more preferred aspects is a more preferred aspect.

[0067] In the present invention, the term "polyester film" alone includes both a polyester base material alone and a laminate of a polyester base material and a particle-containing layer.

[0068] In the present invention, the “longitudinal direction” refers to the longitudinal direction of the polyester film when the polyester film is produced, and has the same meaning as the “conveying direction” and the “machine direction”.

[0069] In the present invention, "width direction" refers to a direction perpendicular to the longitudinal direction. In the present invention, "perpendicular" is not limited to strictly perpendicular, and includes substantially perpendicular. "Substantially perpendicular" means intersecting at 90°±5°, preferably at 90°±3°, and more preferably at 90°±1°.

[0070] Furthermore, in the present invention, the "film width" refers to the distance between both ends of the polyester film in the width direction.

[0071] 〔Polyester film〕

[0072] The polyester film of the present invention (hereinafter also referred to as "the present film") comprises at least a polyester substrate and a particle-containing layer located on at least one surface of the polyester substrate and containing particles.

[0073] In one embodiment of the present film, the polyester film has a thickness of less than 50 μm, and the area of ​​streak-shaped defect regions observed in the polyester film subjected to a heat treatment described below is 40% or less of the total area of ​​the observed region.

[0074] 〔structure〕

[0075] As described above, the present film comprises a polyester substrate and a particle-containing layer located on at least one surface of the substrate. The particle-containing layer may be formed on only one surface of the polyester substrate or on both surfaces of the polyester substrate.

[0076] The polyester substrate and the particle-containing layer are described in more detail below.

[0077] <Polyester base material>

[0078] The polyester substrate is a film-shaped object containing polyester as a main polymer component. Here, the "main polymer component" refers to the polymer with the largest content (mass) among all the polymers contained in the film.

[0079] The polyester base may contain one type of polyester alone or two or more types of polyesters.

[0080] (Polyester)

[0081] Polyester is a polymer having an ester bond in its main chain. Polyester is generally formed by polycondensing a dicarboxylic acid compound and a diol compound, which will be described later.

[0082] The polyester is not particularly limited, and known polyesters can be used. Examples of the polyester include polyethylene terephthalate (PET), polyethylene 2,6-naphthalate (PEN), polypropylene terephthalate (PPT), polybutylene terephthalate (PBT), and copolymers thereof. Among them, at least one selected from polyethylene terephthalate (PET), polyethylene 2,6-naphthalate (PEN), and copolymers thereof is preferred, with PET being more preferred.

[0083] The intrinsic viscosity of the polyester is preferably 0.50 dl / g or more and less than 0.80 dl / g, more preferably 0.55 dl / g or more and less than 0.70 dl / g.

[0084] The melting point (Tm) of the polyester is preferably 220 to 270°C, more preferably 245 to 265°C.

[0085] The glass transition temperature (Tg) of the polyester is preferably 65 to 90°C, more preferably 70 to 85°C.

[0086] The method for producing polyester is not particularly limited, and a known method can be used. For example, polyester can be produced by polycondensing at least one dicarboxylic acid compound and at least one diol compound in the presence of a catalyst.

[0087] -catalyst-

[0088] The catalyst used for producing polyester is not particularly limited, and any known catalyst that can be used for synthesizing polyester can be used.

[0089] Examples of the catalyst include alkali metal compounds (e.g., potassium compounds, sodium compounds), alkaline earth metal compounds (e.g., calcium compounds, magnesium compounds), zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, germanium compounds, and phosphorus compounds. Among these, titanium compounds are preferred from the viewpoint of catalytic activity and cost.

[0090] The catalyst may be used alone or in combination of two or more. Preferably, at least one metal catalyst selected from potassium compounds, sodium compounds, calcium compounds, magnesium compounds, zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, and germanium compounds and a phosphorus compound are used in combination, and more preferably, a titanium compound and a phosphorus compound are used in combination.

[0091] As the titanium compound, an organic chelate titanium complex is preferred. The organic chelate titanium complex is a titanium compound having an organic acid as a ligand.

[0092] Examples of the organic acid include citric acid, lactic acid, trimellitic acid, and malic acid.

[0093] As the titanium compound, the titanium compounds described in paragraphs 0049 to 0053 of Japanese Patent No. 5575671 can also be used, and the contents of the above publication are incorporated into this specification.

[0094] -Dicarboxylic acid compound-

[0095] The dicarboxylic acid compound is preferably a dicarboxylic acid or a dicarboxylic acid ester, and examples thereof include aliphatic dicarboxylic acid compounds, alicyclic dicarboxylic acid compounds, aromatic dicarboxylic acid compounds, and methyl esters or ethyl esters thereof. Among them, aromatic dicarboxylic acids or aromatic dicarboxylic acid methyl esters are more preferred.

[0096] Examples of the aliphatic dicarboxylic acid compound include malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, dimer acid, eicosanedioic acid, pimelic acid, azelaic acid, methylmalonic acid, and ethylmalonic acid.

[0097] Examples of the alicyclic dicarboxylic acid compound include adamantane dicarboxylic acid, norbornene dicarboxylic acid, cyclohexane dicarboxylic acid, and decalin dicarboxylic acid.

[0098] Examples of the aromatic dicarboxylic acid compound include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, 1,8-naphthalene dicarboxylic acid, 4,4'-diphenyl dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, sodium sulfoisophthalate, phenylindanedicarboxylic acid, anthracene dicarboxylic acid, phenanthrene dicarboxylic acid, 9,9'-bis(4-dicarboxyphenyl)fluorene acid, and methyl esters thereof.

[0099] Among them, terephthalic acid or 2,6-naphthalene dicarboxylic acid is preferred, and terephthalic acid is more preferred.

[0100] The dicarboxylic acid compound may be used alone or in combination of two or more. When terephthalic acid is used as the dicarboxylic acid compound, it may be used alone or copolymerized with other aromatic dicarboxylic acids such as isophthalic acid or aliphatic dicarboxylic acids.

[0101] -Diol compound-

[0102] Examples of the diol compound include aliphatic diol compounds, alicyclic diol compounds, and aromatic diol compounds, and aliphatic diol compounds are preferred.

[0103] Examples of the aliphatic diol compound include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, and neopentyl glycol, with ethylene glycol being preferred.

[0104] Examples of the alicyclic diol compound include cyclohexanedimethanol, spirodiol, and isosorbide.

[0105] Examples of the aromatic diol compound include bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, and 9,9'-bis(4-hydroxyphenyl)fluorene.

[0106] The diol compounds may be used alone or in combination of two or more.

[0107] -Capping agent-

[0108] In the production of polyester, a terminal blocking agent may be used as needed. By using the terminal blocking agent, a structure derived from the terminal blocking agent is introduced into the terminal of the polyester.

[0109] The terminal blocking agent is not limited, and a known terminal blocking agent can be used. Examples of the terminal blocking agent include oxazoline compounds, carbodiimide compounds, and epoxy compounds.

[0110] As the terminal blocking agent, reference can also be made to the contents described in paragraphs 0055 to 0064 of Japanese Patent Application Laid-Open No. 2014-189002, the contents of which are incorporated into this specification.

[0111] -Manufacturing conditions-

[0112] The reaction temperature is not limited and can be appropriately set according to the raw materials. The reaction temperature is preferably 260 to 300°C, more preferably 275 to 285°C.

[0113] The pressure is not limited and can be set appropriately according to the raw materials. The pressure is preferably 1.33×10 -3 ~1.33×10 - 5 MPa, more preferably 6.67×10 -4 ~6.67×10 -5 MPa.

[0114] As a method for synthesizing polyester, the method described in paragraphs 0033 to 0070 of Japanese Patent No. 5575671 can also be used, and the contents of the above publication are incorporated into this specification.

[0115] The content of the polyester in the polyester substrate is preferably 85% by mass or more, more preferably 90% by mass or more, further preferably 95% by mass or more, and particularly preferably 98% by mass or more, based on the total mass of the polymer in the polyester substrate.

[0116] The upper limit of the polyester content is not limited and can be appropriately set within the range of 100% by mass or less relative to the total mass of the polymer in the polyester substrate.

[0117] When the polyester substrate contains polyethylene terephthalate, the content of polyethylene terephthalate is preferably 90 to 100% by mass, more preferably 95 to 100% by mass, further preferably 98 to 100% by mass, and particularly preferably 100% by mass, relative to the total mass of the polyester in the polyester substrate.

[0118] The polyester substrate may contain components other than polyester (for example, a catalyst, unreacted raw material components, water, etc.).

[0119] The polyester substrate is preferably substantially particle-free. "Substantially particle-free" is defined as a particle content of 50 ppm by mass or less, preferably 10 ppm by mass or less, and more preferably below the detection limit, relative to the total mass of the polyester substrate, when both the polyester substrate and the particle-containing layer are quantitatively analyzed for particle-derived elements by fluorescent X-ray analysis. This is because even if particles are not actively added to the substrate film, contaminants from foreign matter or dirt adhering to production lines or equipment during the raw resin or film manufacturing process may peel off and enter the film.

[0120] From the perspective of suppressing an increase in haze value, the thickness of the polyester substrate is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 40 μm or less. The lower limit of the thickness is not particularly limited, but from the perspective of improving strength and processability, it is preferably 3 μm or more, more preferably 4 μm or more, and even more preferably 10 μm or more.

[0121] The thickness of the polyester substrate is measured according to the method for measuring the thickness of the polyester film described later.

[0122] <Layer with particles>

[0123] The particle-containing layer is a layer containing particles and is formed on at least one surface of the polyester substrate. The particle-containing layer improves the transportability of this film. More specifically, it improves winding quality (prevents blocking), suppresses scratches and defects during transport, and reduces transport wrinkles.

[0124] The particle-containing layer may be provided directly on the surface of the polyester substrate or through another layer. However, from the viewpoint of better adhesion, it is preferably provided directly on the surface of the polyester substrate.

[0125] Examples of the particles contained in the particle-containing layer include organic particles and inorganic particles. Among them, inorganic particles are preferred from the viewpoint of further improving film winding quality, haze, and durability (for example, thermal stability).

[0126] As organic particles, resin particles are preferred. As the resin constituting the resin particles, for example, acrylic resins, polyester resins, silicone resins, and styrene-acrylic resins such as polymethyl methacrylate resin (PMMA) can be cited. The resin particles preferably have a cross-linked structure. As the resin particles having a cross-linked structure, for example, divinylbenzene cross-linked particles (for example, divinylbenzene / styrene copolymer cross-linked particles) having a cross-linked structure derived from divinylbenzene can be cited. From the viewpoint of suppressing transfer marks, resin particles are preferred.

[0127] Examples of the inorganic particles include silica particles, titania particles, calcium carbonate, barium sulfate, and aluminum oxide particles. Of these, silica particles are preferred from the perspective of further improving haze and durability.

[0128] The shape of the particles is not particularly limited, and examples thereof include rice grains, spheres, cubes, spindles, scales, aggregates, and irregular shapes. Aggregates refer to a state in which primary particles are aggregated. The shape of the aggregated particles is not particularly limited, but preferably spherical or irregular shapes.

[0129] The particle-containing layer is preferably formed by an in-line coating method with a coating liquid containing at least one of agglomerated particles and non-agglomerated particles. Here, agglomerated particles refer to particles in an agglomerated state in the coating liquid, and non-agglomerated particles refer to particles in an unagglomerated state in the coating liquid.

[0130] Preferred examples of the aggregated particles include fumed silica particles, and examples of commercially available products include the AEROSIL series from NIPPON AEROSIL CO., LTD.

[0131] Preferred examples of non-aggregated particles include colloidal silica particles, and commercially available products include, for example, the SNOWTEX series manufactured by Nissan Chemical Industries, Ltd.

[0132] The particle-containing layer may contain a single type of particles, or may contain two or more types of particles.

[0133] From the viewpoint of improving film winding quality and suppressing transfer defects, the content of the particles is preferably 0.01 to 20 mass %, more preferably 0.5 to 15 mass %, and even more preferably 1 to 10 mass % relative to the total mass of the particle-containing layer.

[0134] Furthermore, the content of the particles is preferably 0.0001 to 0.01% by mass, more preferably 0.0005 to 0.005% by mass, based on the total mass of the polyester film.

[0135] (Particle P)

[0136] From the viewpoint of improving winding quality and suppressing transfer failure, the particle-containing layer preferably contains particles P having an average particle diameter of 10 μm or more and less than 1 μm.

[0137] From the viewpoint of further improving the winding quality, the average particle size of the particles P is preferably 0.03 μm or more. From the viewpoint of further suppressing transfer failure, the average particle size of the particles P is preferably 0.4 μm or less, and more preferably 0.25 μm or less.

[0138] Furthermore, in certain embodiments, from the perspective of improving conveyability and winding quality, the average particle size of the particles P is preferably greater than the thickness of the particle-containing layer. In other words, the particle-containing layer preferably contains particles P having an average particle size of 10 nm or greater and less than 1 μm, and having an average particle size greater than the thickness of the particle-containing layer.

[0139] When the particle-containing layer contains two or more particles with different particle sizes, it is preferred that at least one of the two or more particles with different particle sizes is particle P. From the perspective of further improving transfer defects and winding quality, it is more preferred that the particle-containing layer contains two or more particles P with different particle sizes.

[0140] The average particle size of the particles contained in the particle-containing layer is determined using a scanning electron microscope (SEM) or a transmission electron microscope (TEM) by the following method. Specifically, a cross-section of the particle-containing layer is observed using the SEM or TEM. The area of ​​each particle is measured using imaging software for all particles present in a 3 μm x 4 μm field of view. The diameter of a circle having the same area (area-equivalent circle diameter) is calculated, and the arithmetic mean of the obtained area-equivalent circle diameters is taken as the average particle size.

[0141] In the measurement of the average particle size, the particle size of secondary particles in an aggregated state (secondary particle size) is measured for aggregated particles.

[0142] And, when the particle-containing layer contains the situation that particle diameter is different from two or more, observe the peak value that particle diameter is different from more than 2 in the distribution of area circle equivalent diameter measured by the above-mentioned measuring method.Like this, when the distribution of area circle equivalent diameter measured by the above-mentioned measuring method has the situation that particle diameter is different from more than 2 peak values, calculate the mean value of area circle equivalent diameter to each peak value, calculate average particle size to each particle different from particle diameter.

[0143] The particle-containing layer may contain particles P of one type alone, or may contain particles P of two or more types.

[0144] The content of the particles P, including preferred embodiments thereof, may be the same as the content of the above-mentioned particles.

[0145] In certain embodiments, from the perspective of transparency and poor transfer, the particle-containing layer preferably contains particles with a small average particle size (hereinafter also referred to as "particles P1"). Specifically, the particle-containing layer preferably contains particles with an average particle size of 100 nm or less as particles P1, and more preferably contains particles with an average particle size of 70 nm or less. The lower limit of the particle P1 is not particularly limited, but is preferably 10 nm or more from the perspective of further improving winding quality.

[0146] The particles P1 may be used alone or in combination of two or more.

[0147] The content of the particles P1 varies depending on the purpose and / or application of the polyester film, but is preferably 0.01 to 20 mass %, more preferably 0.5 to 15 mass %, and even more preferably 1 to 10 mass % relative to the total mass of the particle-containing layer.

[0148] In certain embodiments, from the perspective of improving winding quality, the particle-containing layer preferably contains particles with a large average particle size (hereinafter also referred to as "particles P2"). Specifically, the particle-containing layer preferably contains particles with an average particle size exceeding 100 nm as particles P2. The upper limit of particles P2 is not particularly limited, but is preferably less than 1 μm. From the perspective of further improving transfer defects and winding quality, it is more preferably 400 nm or less, and even more preferably 250 nm or less.

[0149] The particles P2 may be aggregated particles or non-aggregated particles, but aggregated particles are preferred from the viewpoint of poor transfer.

[0150] The aggregated particles serving as particles P2 preferably have an average secondary particle size exceeding 100 nm. Furthermore, the aggregated particles preferably contain particles having an average primary particle size of 100 nm or less. If aggregated particles having an average secondary particle size exceeding 100 nm, formed by agglomerating particles having an average primary particle size of 100 nm or less, are used, then, particularly when forming a particle-containing layer by an in-line coating method, a desired Rp can be achieved, further improving transfer failure and winding quality.

[0151] The particles P2 may be used alone or in combination of two or more.

[0152] The content of the particles P2 varies depending on the purpose and / or application of the polyester film, but is preferably 0.01 to 15 mass %, more preferably 0.05 to 10 mass %, and even more preferably 0.1 to 5 mass % relative to the total mass of the particle-containing layer.

[0153] From the viewpoint of further improving transfer defects and winding quality, the particle-containing layer preferably contains at least one type of particles P1 and at least one type of particles P2.

[0154] The particles contained in the particle-containing layer can be appropriately selected according to the purpose and / or application.

[0155] When used as a support for a dry film resist for forming a fine pattern, if the particles scatter light during exposure through the support, it may cause pattern defects. Therefore, the support is required to have high transparency. From the perspective of further improving transparency, the content of particles P1 is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, relative to the total content of all particles contained in the particle-containing layer.

[0156] In this case, it is preferable that the remainder be particles P2.

[0157] On the other hand, when higher speed transport is required for the purpose of improving productivity, high transportability is required. From the viewpoint of further improving transportability, the content of particles P2 is preferably 10 to 100% by mass, more preferably 10 to 50% by mass, and even more preferably 10 to 30% by mass relative to the total content of all particles contained in the particle-containing layer.

[0158] In this case, it is preferable that the remainder be particles P1.

[0159] (Adhesive)

[0160] The particle-containing layer preferably contains a binder. As the binder, a resin binder is preferred. Examples of the resin binder include polyacrylic acid, polyurethane, polyester, and polyolefin.

[0161] The polyacrylic acid is not limited as long as it is a polymer having structural units derived from at least one compound selected from acrylates and methacrylates, and known polyacrylic acids can be used. The polyacrylic acid may have structural units derived from compounds other than acrylates and methacrylates (for example, olefin compounds and styrene compounds).

[0162] The polyurethane is not limited as long as it is a polymer having a urethane bond, and known polyurethanes can be used. Polyurethane is generally produced by reacting an isocyanate compound with a polyol compound.

[0163] As the polyester, the polyesters described in the above-mentioned item "Polyester" can be applied, and the preferred types are also the same.

[0164] The polyolefin is not limited, and known polyolefins can be used. Examples of the polyolefin include polyethylene and polypropylene.

[0165] The particle-containing layer may contain a single type of binder, or may contain two or more types of binders.

[0166] From the viewpoint of durability of the particle-containing layer and / or dispersibility of the particles, the content of the binder is preferably 30 to 99.8% by mass, more preferably 50 to 99.5% by mass, relative to the total mass of the particle-containing layer.

[0167] (additive)

[0168] The particle-containing layer may contain additives other than the above-mentioned particles and binder.

[0169] Examples of the additives contained in the particle-containing layer include surfactants, waxes, crosslinking agents, antioxidants, ultraviolet absorbers, colorants, reinforcing agents, plasticizers, antistatic agents, flame retardants, rust preventives, and mildew preventives.

[0170] The surfactant is not particularly limited, and examples thereof include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants.

[0171] The surfactant may be used alone or in combination of two or more.

[0172] The content of the surfactant is preferably 0.1 to 10% by mass relative to the total mass of the particle-containing layer.

[0173] The wax is not particularly limited and may be a natural wax or a synthetic wax. Examples of natural waxes include palm wax, candelilla wax, beeswax, montan wax, paraffin wax, and petroleum wax. Furthermore, lubricants described in

[0087] of the specification of International Publication No. 2017 / 169844 may also be used.

[0174] The content of the wax is preferably 0 to 10% by mass relative to the total mass of the particle-containing layer.

[0175] The cross-linking agent is not particularly limited, and a known cross-linking agent can be used.

[0176] As a cross-linking agent, for example, melamine compounds, oxazoline compounds, epoxy compounds, isocyanate compounds and carbodiimide compounds can be mentioned, preferably oxazoline compounds and carbodiimide compounds. As a commercial product, for example, CARBODILITE V-02-L2 (Nisshinbo Holdings Inc. manufacture) and EPOCROS K-2020E (NIPPON SHOKUBAI CO., LTD. manufacture) can be mentioned. For details about epoxy compounds, isocyanate compounds and melamine compounds, reference can be made to the records of

[0081] to

[0083] of Japanese Patent Publication No. 2015-163457. It is also possible to preferably use the cross-linking agent described in

[0082] to

[0084] of International Publication No. 2017 / 169844 specification. As the carbodiimide compound, reference can be made to the descriptions in

[0038] to

[0040] of JP-A-2017-087421.

[0177] Regarding the oxazoline compound, the carbodiimide compound, and the isocyanate compound, the cross-linking agents described in

[0074] to

[0075] of the specification of International Publication No. 2018 / 034294 can also be preferably used.

[0178] The content of the crosslinking agent can be appropriately changed depending on the application, and is preferably 0 to 50% by mass relative to the total mass of the particle-containing layer. From the perspective of being suitable as a support for a dry film, the content of the crosslinking agent is preferably 0.1 to 10% by mass relative to the total mass of the particle-containing layer.

[0179] The thickness of the particle-containing layer may be 0.001 to 5 μm, preferably 0.001 to 2.5 μm, more preferably 0.005 to 2.0 μm, further preferably 0.01 to 0.18 μm, and particularly preferably 0.01 to 0.1 μm, from the viewpoint of the manufacturability of the particle-containing layer and reduction of haze.

[0180] The thickness of the particle-containing layer was set as the arithmetic mean of the thicknesses at five locations measured using a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0181] The method of forming the particle-containing layer will be described in detail in the “particle-containing layer forming step” described later.

[0182] The present film may have layers other than the polyester substrate and the particle-containing layer, but is preferably composed of the polyester substrate and the particle-containing layer. Furthermore, the present film preferably has only one particle-containing layer formed on one surface of the polyester substrate.

[0183] 〔Physical properties, etc.〕

[0184] Next, the physical properties of the present film will be described.

[0185] (Orientation)

[0186] This film is a biaxially oriented polyester film. In the present invention, "biaxially oriented" means a film having molecular orientation in two axial directions.

[0187] Molecular orientation is measured using a microwave transmission molecular orientation instrument (e.g., MOA-6004, manufactured by Oji Scientific Instruments). The angle formed by the biaxial directions is preferably 90°±5°, more preferably 90°±3°, and even more preferably 90°±1°. The film preferably has molecular orientation in both the longitudinal and width directions.

[0188] (Stripe-shaped defect area)

[0189] In the present film, the total area of ​​the streak-shaped defect regions observed in the polyester film subjected to the heat treatment described below is preferably 40% or less relative to the total area of ​​the observation region.

[0190] In the present invention, "stripe-like defects" refer to wrinkles that appear as stripes along the length of the film and appear as concave and convex in the width direction of the film. As described later, striation-like defects are defects that occur in the film after production and are therefore often irreversibly generated. Streak-like defects are not defects caused by heat treatment during film production, but rather result from wavy wrinkles that form during heat treatment of the film after production. These wrinkles solidify during cooling after heat treatment. Furthermore, a "stripe-like defect region" refers to the portion of the film surface where striation-like defects occur.

[0191] If streak-like defects appear (i.e., streak-like defects appear locally within the film surface), the thickness of the functional layer formed on the film will be uneven, which may affect the properties and appearance of the functional layer. In addition, when heating is performed while a tensile load is applied in the longitudinal direction of the film, streak-like defects tend to appear more prominently.

[0192] On the other hand, when the total area of ​​the streak-like defect regions observed after the biaxially oriented polyester film is subjected to the following heat treatment is equal to or less than the above range, the thickness unevenness of the functional layer formed on the film can be reduced.

[0193] In the present film, the ratio of the total area of ​​the streak-like defect regions that appear when heated at 90°C to the total area of ​​the observed area of ​​the polyester film (hereinafter also referred to as the "area ratio of the streak-like defect regions") is preferably 40% or less, more preferably 30% or less, and even more preferably 18% or less. The smaller the value of the area ratio of the streak-like defect regions, the better, and the lower limit thereof can be, for example, 0%.

[0194] Furthermore, in the present film, the area ratio of streak-shaped defect regions generated when heated at 120° C. is preferably 90% or less, more preferably 65% ​​or less, and even more preferably 40% or less.

[0195] When the area ratio of the stripe-shaped defect region is below the above range, the thickness unevenness of the functional layer formed on the present film can be reduced. The smaller the area ratio of the stripe-shaped defect region, the better. The lower limit is, for example, 0%.

[0196] The lower limit of the area ratio of the streak-like defect region is not particularly limited. The area ratio of the streak-like defect region appearing when heated at 90° C. or 120° C. is preferably small, and more preferably, there is no streak-like defect region, that is, 0%.

[0197] The area ratio of the streak-shaped defect region generated when heating at each of 90° C. and 120° C. was measured by the following method.

[0198] (1) Using a heating conveyor, a polyester film is conveyed at a conveying speed of 30 m / min and a tension of 100 N / m in the conveying direction, while being heated at a surface temperature of 90°C or 120°C for 20 seconds. The heating time during the heat treatment is calculated from the moment when the surface temperature of the film reaches the target temperature (90°C or 120°C), and heating is continued for 20 seconds from then on. Here, a non-contact thermometer (e.g., a radiation thermometer) can be used to measure the surface temperature of the film. Regarding the surface temperature of the film, the temperature of the central portion approximately equidistant from both ends in the width direction of the film is measured to see if it has reached the target temperature.

[0199] (2) The polyester film that has been subjected to heat treatment is placed on a black flat plate. The polyester film is then visually observed from the side while changing the viewpoint of light reflection from a fluorescent lamp (e.g., rupikae-su manufactured by Mitsubishi Electric Corporation (color temperature: 5000K, average color rendering index (Ra): 84)) installed on the ceiling of the room. The region where the image reflected by the fluorescent lamp on the surface of the polyester film, which is visually observed, fluctuates is defined as a streak-shaped defect region.

[0200] (3) Count the number of streak-like defect areas observed and mark the visually observed area of ​​the polyester film (area 1m 2The perimeter of each stripe-shaped defect region present in the region (often referred to as the region of interest). Next, the distance between two parallel tangent lines circumscribing the perimeter of each stripe-shaped defect region, selected so as to maximize the distance between the two tangent lines, is measured as the length L of the major axis. The distance between two parallel tangent lines circumscribing the perimeter of the stripe-shaped defect region, which are orthogonal to the two parallel tangent lines having the length L, is measured as the length S of the minor axis. Based on the obtained lengths L and S, the area of ​​each stripe-shaped defect region is calculated using the following formula. Based on these values, the ratio of the total area of ​​the stripe-shaped defect regions to the total area of ​​the observation region of the polyester film is calculated.

[0201] The length of the major axis of the stripe-shaped defect region L×the length of the minor axis of the stripe-shaped defect region S×π=the area of ​​the stripe-shaped defect region

[0202] Since the stripe-shaped defect region is often elliptical or circular as described above, the area of ​​the stripe-shaped defect region can be calculated by the calculation method (3) described above.

[0203] Figure 1 The image (photograph) of the polyester film observed in the streak-shaped defect region produced by the heat treatment of (1) above is shown in FIG. Figure 1 The area surrounded by solid lines in the figure is a stripe defect area. Figure 1 In the stripe-shaped defect area shown in , a concavo-convex shape stretched in the transport (MD) direction is observed. Figure 1 The images (photographs) shown in FIG. 1 only show a portion of the observed area.

[0204] Thus, the stripe-shaped defect region is often elliptical or circular in shape. Moreover, when a stripe-shaped defect region appears, it is often an elliptical stripe-shaped defect region with at least one major axis oriented along the conveying direction.

[0205] In the polyester film production method, the conditions of each step are set so that the cooling rate V of the polyester film in the cooling step is 2200-3500°C / min and the condition 1 described below is satisfied, thereby producing a biaxially oriented polyester film having an area ratio of streak-shaped defect regions within the above range.

[0206] (Expansion rate)

[0207] The expansion coefficient of the polyester film in the width direction at 90°C and 120°C is preferably -0.15 to 0.15%, more preferably -0.10 to 0.10%, further preferably 0 to 0.10%, and particularly preferably 0 to 0.05% relative to the film width at 30°C.

[0208] By adjusting the widthwise expansion coefficient of the polyester film at 90°C and 120°C within the above range, not only can the film's widthwise expansion during heating be suppressed, but also the unevenness of the expansion coefficient across the film surface can be reduced. As a result, the occurrence of streak-like defects caused by heating has been observed to be suppressed.

[0209] The expansion ratio in the width direction at each of 90° C. and 120° C. was measured using a thermomechanical analyzer by the following method.

[0210] (1) Prepare a sample whose size is adjusted to at least 20 mm in a direction parallel to the width direction of the biaxially oriented film and 4 mm in a direction perpendicular to the width direction of the biaxially oriented film.

[0211] (2) Using a thermomechanical analyzer (for example, TMA-60, manufactured by Shimadzu Corporation), a tensile load of 0.1 g is applied to a sample having a width of 4 mm and a length (distance between chucks) of 20 mm.

[0212] (3) The sample is heated from a temperature of 20°C or higher and lower than 30°C (preferably 25°C) to 150°C at a heating rate of 5°C / min, thereby obtaining the dimensional values ​​of the sample at each temperature (°C).

[0213] (4) Based on the sample dimensions at 30°C (L30), 90°C (L90), and 120°C (L120), the expansion coefficients in the width direction at 90°C and 120°C were calculated using the following formula. In the present invention, the expansion coefficients in the width direction at 90°C and 120°C are the arithmetic mean of the expansion coefficients obtained using five samples, respectively. A positive expansion coefficient indicates expansion, and a negative expansion coefficient indicates contraction.

[0214] Formula: Expansion rate (%) = [(L120 or L90) - L30] / L30 × 100

[0215] The ratio of the widthwise expansion coefficient (E120) at 120°C to the widthwise expansion coefficient (E90) at 90°C (E120 / E90) is preferably 0 to 1.5, more preferably 0 to 1.1, and even more preferably 0 to 1.05. When E120 / E90 is within this range, thickness unevenness of the functional layer can be further suppressed. The widthwise expansion coefficient (E90) at 90°C and the widthwise expansion coefficient (E120) at 120°C are each determined using the aforementioned thermomechanical analysis apparatus.

[0216] The expansion rate of the polyester film in the width direction can be adjusted by, for example, appropriately setting the stretching ratio, heat treatment temperature, and film width during cooling in the production process of the biaxially oriented film.

[0217] (Maximum peak height Rp on the surface)

[0218] From the viewpoint of further improving the winding quality, the maximum peak height Rp on the particle-containing layer surface of the polyester film is preferably 0.005 μm (5 nm) or more, more preferably 0.01 μm (10 nm) or more. From the viewpoint of further suppressing poor transfer, the maximum peak height Rp on the particle-containing layer surface of the polyester film is preferably 1 μm or less, more preferably 0.5 μm or less, further preferably 0.25 μm (250 nm) or less, and particularly preferably 0.2 μm (200 nm) or less. Wherein, when the particle-containing layer contains inorganic particles, the inhibitory performance of poor transfer is more significantly manifested, and therefore the maximum peak height Rp on the surface of the particle-containing layer is preferably set within the above range. When the particle-containing layer is formed by an online coating method, the maximum peak height Rp on the particle-containing layer surface can be adjusted by the average particle diameter of the particles possessed by the particle-containing layer and the thickness of the particle-containing layer.

[0219] The maximum peak height Rp of the polyester film surface can be determined by cutting out the polyester film to prepare a test piece, measuring the surface of the obtained test piece using the following micro-profile measuring device under the following conditions, and then performing particle analysis (multiple levels) using built-in analysis software.

[0220] The measuring instrument and measurement conditions are described below. For the above measurement, the slice level was set at equal intervals of 10 nm. The average diameter and density of each slice level were measured five times while changing the measurement position. The average value was calculated and used as the maximum peak height Rp measurement value. The test piece was fixed to the sample stage so that the X direction of the field of view measured was the width direction of the polyester film.

[0221] Measuring device: Surf-corder ET-4000A manufactured by Kosaka Laboratory Ltd.

[0222] Analysis software: i-Face model TDA31 Ver2.2.0.4 JSIS

[0223] Stylus tip radius: 0.5μm

[0224] Measurement field of view: X direction: 380μm, pitch: 1μm

[0225] Y direction: 280μm, pitch: 5μm

[0226] Needle pressure: 50μN

[0227] Measuring speed: 0.1mm / s

[0228] Cut-off value: low area - 0.8mm, high area - none

[0229] Leveling: the entire area

[0230] Filter: Gaussian filter (2D)

[0231] Magnification: 100,000 times

[0232] Particle analysis (multiple levels) conditions

[0233] Output content setting: Mountain particles

[0234] Hysteresis width: 5nm

[0235] Slice level interval: 10nm

[0236] (density)

[0237] From the viewpoint of further improving the effects of the present invention, the density of the polyester film is preferably 1.39 to 1.41 g / cm 3 , more preferably 1.395 to 1.405 g / cm 3 , more preferably 1.398 to 1.400 g / cm 3 .

[0238] The density of the polyester film can be measured using an electronic densitometer (product name "SD-200L", manufactured by Alfa Mirage Co., Ltd.).

[0239] (Haze)

[0240] When a polyester film is used as a support for a dry film resist, it is required to have high transparency. In particular, when forming fine patterns such as lines and spaces of 50 μm or less, it is required to have higher transparency. In this respect, the haze of the polyester film is preferably 1% or less, more preferably 0.5% or less, further preferably 0.4% or less, and particularly preferably 0.3% or less. The smaller the haze, the more preferred it is, so there is no restriction on the lower limit of the haze. If the lower limit of the haze is set for convenience, it is 0% or more. By setting the haze to below the above-mentioned upper limit, the scattering of ultraviolet light from the support of the resist layer, i.e., the polyester film, when the resist layer is laminated on the polyester film and exposed by irradiation with ultraviolet light can be reduced, and the state of the resist pattern wall, such as distortion and loss in the patterning of the resist after development, can be improved.

[0241] The haze is measured using a haze meter (for example, NDH-2000, manufactured by NIPPON DENSHOKU INDUSTRIES Co., LTD.) by a method in accordance with JIS K 7105.

[0242] (b * value)

[0243] When a polyester film is used as a support for a dry film resist, it is required to have high transparency. * a * b * b in the color system * The value is preferably 0 to 1, more preferably 0 to 0.8, further preferably 0 to 0.6, and particularly preferably 0 to 0.4. * a * b * b in the color system * A value of 0 to 1 can reduce the yellowness of the film, thereby making the hue of the film close to colorless. As a result, polyester films can be preferably used in applications requiring high visibility (for example, display devices).

[0244] For L * a * b * b in the color system * The values ​​are measured by a transmission method using a spectrocolorimeter (for example, SE-2000, manufactured by NIPPON DENSHOKU INDUSTRIES Co., LTD.).

[0245] (thickness)

[0246] From the perspective of suppressing an increase in haze value and improving lamination suitability, the thickness of the polyester film is preferably 100 μm or less, more preferably less than 50 μm, and even more preferably 40 μm or less. The lower limit of the thickness is not particularly limited, but from the perspective of improving strength and processability, it is preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more.

[0247] The thickness of the polyester film was taken as the arithmetic mean of the thicknesses at five locations measured using a scanning electron microscope (SEM).

[0248] [Manufacturing method]

[0249] As a method for producing the present film, for example, there is mentioned a method of biaxially stretching an unstretched polyester film.

[0250] Biaxial stretching may be simultaneous biaxial stretching in which longitudinal stretching and transverse stretching are performed simultaneously, or may be sequential biaxial stretching in which longitudinal stretching and transverse stretching are performed in two or more stages. Examples of sequential biaxial stretching methods include longitudinal stretching → transverse stretching, longitudinal stretching → transverse stretching → longitudinal stretching, longitudinal stretching → longitudinal stretching → transverse stretching, and transverse stretching → longitudinal stretching, with longitudinal stretching → transverse stretching being preferred.

[0251] <Stretching Machine>

[0252] The apparatus used for biaxial stretching is not particularly limited, and a known stretching machine can be used. An example of a stretching machine will be described below with reference to the drawings.

[0253] Figure 2 This is a plan view showing an example of a stretching machine for producing a polyester film.

[0254] Figure 2 The stretching machine 100 shown includes a pair of annular rails 60a and 60b, and gripping members 2a to 21 mounted on each annular rail and movable along the rails. The annular rails 60a and 60b are symmetrically arranged with the film 200 interposed therebetween. The stretching machine 100 grips the film 200 with the gripping members 2a to 21 and stretches the film 200 in the width direction by moving the gripping members 2a to 21 along the rails.

[0255] The stretching machine 100 includes a region composed of a preheating section 10 , a stretching section 20 , a heat setting section 30 , a heat relaxing section 40 , and a cooling section 50 in this order from the upstream side in the conveying direction.

[0256] The areas included in the stretching machine 100 are partitioned by wind curtains, and the temperature in each area can be adjusted by hot air or the like.

[0257] The preheating section 10 is a region for preheating the film 200 .

[0258] The stretching section 20 is a region where tension is applied to the preheated film 200 in the direction of the arrow TD (width direction) perpendicular to the direction of the arrow MD (length direction) to stretch it. Figure 2 As shown, in the stretching portion 20 , the film 200 is stretched from a width L0 to a width L1 .

[0259] The heat setting section 30 is a region that heats and heat-sets the film 200 to which tension is applied while applying tension.

[0260] The heat relaxation portion 40 is a region where the tension of the heat-set film 200 is thermally relaxed by heating the heat-set film 200 .

[0261] like Figure 2 As shown, in the thermal relaxation portion 40 , the film 200 is shrunk (relaxed) from the width L1 to the width L2 .

[0262] The cooling portion 50 is a region for cooling the thermally relaxed film 200. By cooling the film 200, the shape of the film 200 can be fixed.

[0263] Figure 2 1 and 2. In FIG. 2, the width of the film 200 fed into the cooling unit 50 is L2 and the width of the film 200 fed out of the cooling unit 50 is L3.

[0264] The gripping members 2a, 2b, 2e, 2f, 2i, and 2j are mounted on the annular guide rail 60a so as to be movable along the annular guide rail 60a. The gripping members 2c, 2d, 2g, 2h, 2k, and 2l are mounted on the annular guide rail 60b so as to be movable along the annular guide rail 60b.

[0265] Holding members 2a, 2b, 2e, 2f, 2i, and 2j hold one end of the film 200 in the direction of arrow TD. Holding members 2c, 2d, 2g, 2h, 2k, and 2l hold the other end of the film 200 in the direction of arrow TD. Holding members 2a to 2l are often referred to as chucks or clips.

[0266] The gripping members 2a, 2b, 2e, 2f, 2i, and 2j move counterclockwise along the annular guide rail 60a, and the gripping members 2c, 2d, 2g, 2h, 2k, and 2l move clockwise along the annular guide rail 60b.

[0267] The holding members 2a to 2d move along the annular guide rail 60a or 60b while holding the end of the film 200 in the preheating section 10, and advance to the cooling section 50 via the stretching section 20, the heat setting section 30, and the heat relaxation section 40. Then, the holding members 2a and 2b and the holding members 2c and 2d are moved to the cooling section 50 at their ends (for example, the ends on the downstream side of the cooling section 50 in the direction of the arrow MD in the conveying direction) in the preheating section 10. Figure 2 After leaving the end of the film 200 at the grip release point P and the grip release point Q in the preheating section, the film 200 moves along the annular guide rail 60a or 60b and returns to the preheating section 10. During the above process, the film 200 moves in the direction of arrow MD, and is preheated in the preheating section 10, stretched in the stretching section 20, heat-set in the heat-setting section 30, heat-relaxed in the heat-relaxing section 40, and cooled in the cooling section 50, thereby being stretched in the transverse direction.

[0268] By adjusting the moving speed of the gripping members 2a to 21, it is possible to adjust the conveying speed of the film 200. Furthermore, the moving speed of the gripping members 2a to 21 can be changed independently.

[0269] As described above, the stretching machine 100 can perform transverse stretching of the film 200 in the direction of arrow TD in the stretching section 20. Furthermore, the stretching machine 100 can also stretch the film 200 in the direction of arrow MD by varying the moving speed of the gripping members 2a to 2l. In other words, the stretching machine 100 can also perform simultaneous biaxial stretching.

[0270] In order to support the film 200 , the stretching machine 100 may further include other holding members (not shown) in addition to the holding members 2 a to 2 l .

[0271] Next, a method for producing a polyester film according to an example of an embodiment of the present invention (hereinafter also referred to as “the present production method”) will be described in detail.

[0272] The present production method is a method for producing a biaxially oriented polyester film, comprising: an extrusion molding step of extruding a molten resin containing a raw material polyester in a film shape to form an unstretched polyester film containing at least a polyester base material; a longitudinal stretching step of stretching the unstretched polyester film in a conveying direction to form a uniaxially oriented polyester film; a transverse stretching step of stretching the uniaxially oriented polyester film in a width direction to form a biaxially oriented polyester film; a heat setting step of heating the biaxially oriented polyester film to heat set it; a heat relaxation step of heating the polyester film heat set in the heat setting step at a temperature lower than that in the heat setting step to heat relax it; a cooling step of cooling the polyester film heat relaxed in the heat relaxation step; and an expansion step of expanding the heat relaxed polyester film in the width direction during the cooling step.

[0273] The present production method further includes a particle-containing layer forming step of providing a particle-containing layer containing particles on at least one surface of the polyester substrate.

[0274] <Extrusion molding process>

[0275] The extrusion molding step is a step of extruding a molten resin containing a raw material polyester into a film-like shape by an extrusion molding method to form an unstretched polyester film. The raw material polyester has the same meaning as the polyester described in the above section (Polyester). The unstretched polyester film formed by the extrusion molding step contains at least a polyester base material.

[0276] The extrusion molding method is a method of molding a raw material resin into a desired shape by, for example, extruding a melt of the raw material resin using an extruder.

[0277] The molten resin containing polyester is formed by, for example, heating the polyester to a temperature above its melting point using an extruder equipped with one or more screws, and then rotating the screws to perform melt kneading. The polyester is melted in the extruder by heating and kneading by the screws to form a melt.

[0278] The melt is extruded from an extrusion die through a gear pump and a filter. The extrusion die is also referred to as a "die" (see JIS B8650: 2006, a, extrusion molding machine, No. 134). For example, the extrusion die described in Japanese Patent Application Laid-Open No. 2005-297266, the extrusion die described in Japanese Patent Application Laid-Open No. 1-154720, and combinations thereof can also be used. The melt can be extruded in a single layer or in multiple layers.

[0279] During melt extrusion, the extruder is preferably purged with nitrogen from the viewpoint of suppressing thermal decomposition (eg, hydrolysis of polyester) in the extruder. Furthermore, from the viewpoint of suppressing the kneading temperature to a low level, the extruder is preferably a twin-screw extruder.

[0280] The melt extruded from the extrusion die is cooled and formed into a film. For example, the melt can be formed into a film by contacting the melt with a casting roll, where the melt is cooled and solidified. During the cooling of the melt, it is preferable to further blow air (preferably cold air) onto the melt.

[0281] The temperature of the casting roll is preferably higher than (Tg-10)°C and not higher than (Tg+30)°C, more preferably (Tg-7) to (Tg+20)°C, and further preferably (Tg-5) to (Tg+10)°C. The above-mentioned "Tg" refers to the glass transition temperature of the polyester constituting the film.

[0282] Here, the temperature of the polyester film and each component in this manufacturing method can be measured using a non-contact thermometer (e.g., a radiation thermometer). The surface temperature of the film is obtained by measuring the temperature of the center portion in the width direction of the film five times and calculating the average of the measured values.

[0283] When a casting roll is used in the extrusion molding process, it is preferable to improve the adhesion between the casting roll and the melt. Examples of methods for improving adhesion include electrostatic application, air knife, air chamber, vacuum nozzle, and touch roll.

[0284] The formed body (unstretched polyester film) cooled by the casting roll or the like is peeled off from the cooling member such as the casting roll using a peeling member such as a peeling roll.

[0285] <Longitudinal Stretching Process>

[0286] The longitudinal stretching step is a step of stretching the unstretched polyester film in the conveying direction (hereinafter also referred to as "longitudinal stretching"). A uniaxially oriented polyester film is formed by the longitudinal stretching step.

[0287] In the longitudinal stretching step, it is preferred to preheat the unstretched polyester film before longitudinal stretching. By preheating the unstretched polyester film, the polyester film can be easily stretched longitudinally.

[0288] The preheating temperature of the unstretched polyester film is preferably (Tg-30) to (Tg+40)° C., more preferably (Tg-20) to (Tg+30)° C. Specifically, the preheating temperature is preferably 60 to 100° C., more preferably 65 to 80° C.

[0289] As a method of preheating the unstretched polyester film, for example, a method of arranging a preheating roll having a function of preheating the film upstream of a stretching roll for longitudinal stretching and preheating the unstretched polyester film while conveying the film is mentioned.

[0290] Furthermore, the stretching roller may have a function of preheating the film. The preferred range of the preheating temperature of the film passing through the stretching roller is the same as the preferred range of the preheating temperature of the preheating roller described above.

[0291] Longitudinal stretching can be performed, for example, by stretching the unstretched polyester film in the longitudinal direction while applying tension between two or more pairs of stretching rollers arranged in the conveying direction. For example, when a pair of stretching rollers A is arranged upstream in the conveying direction and a pair of stretching rollers B is arranged downstream in the conveying direction, the rotation speed of the stretching rollers B is set faster than the rotation speed of the stretching rollers A during conveyance of the unstretched polyester film, thereby stretching the unstretched polyester film in the longitudinal direction.

[0292] Regarding the conveying speed (circumferential speed) of the film of a pair of stretching rollers A arranged on the upstream side of the conveying direction and a pair of stretching rollers B arranged on the downstream side of the conveying direction in the longitudinal stretching process, there is no special restriction as long as the conveying speed of the film of stretching roller A is slower than the conveying speed of the film of stretching roller B.

[0293] The film conveying speed of the stretching roller A is, for example, 5 to 60 m / min, preferably 10 to 50 m / min, and more preferably 15 to 45 m / min. The film conveying speed of the stretching roller B is, for example, 40 to 160 m / min, preferably 50 to 150 m / min, and more preferably 60 to 140 m / min.

[0294] The stretching ratio in the longitudinal stretching step is appropriately set depending on the intended use, and is preferably 2.0 to 5.0 times, more preferably 2.5 to 4.0 times, and even more preferably 2.8 to 4.0 times.

[0295] The stretching speed in the longitudinal stretching step is preferably 800 to 1500% / second, more preferably 1000 to 1400% / second, and even more preferably 1200 to 1400% / second. Here, the "stretching speed" refers to the value expressed as a percentage, which is the length Δd in the conveying direction of the polyester film stretched in one second in the longitudinal stretching step divided by the length d0 in the conveying direction of the polyester film before stretching.

[0296] In the longitudinal stretching step, it is preferred to heat the unstretched polyester film because heating facilitates longitudinal stretching.

[0297] The heating temperature in the longitudinal stretching step is preferably (Tg-20) to (Tg+50)°C, more preferably (Tg-10) to (Tg+40)°C, and even more preferably (Tg) to (Tg+30)°C. Specifically, the heating temperature in the longitudinal stretching step is preferably 70 to 120°C, more preferably 80 to 110°C, and even more preferably 85 to 100°C.

[0298] Examples of methods for heating the unstretched polyester film during the longitudinal stretching step include heating a roller such as a stretching roller that contacts the unstretched polyester film. Examples of methods for heating the roller include installing a heater inside the roller and installing piping inside the roller and flowing a heated fluid through the piping. In addition to the above, examples include blowing warm air onto the unstretched polyester film and heating the unstretched polyester film by bringing the unstretched polyester film into contact with a heat source such as a heater or passing the film near a heat source.

[0299] The longitudinal stretching step of longitudinally stretching the unstretched polyester film is not limited to the above-mentioned method.

[0300] In the above-mentioned longitudinal stretching process, the unstretched polyester film is longitudinally stretched by utilizing the difference in the conveying speeds of two pairs of stretching rollers. However, one or more high-speed stretching rollers arranged between the two stretching rollers and conveying the film at a faster conveying speed than these stretching rollers can also be used to longitudinally stretch the unstretched polyester film to produce a uniaxially oriented polyester film.

[0301] Furthermore, in the above-mentioned longitudinal stretching process, there is a structure in which the film is conveyed by clamping two rollers (a pair of rollers) facing each other, but the stretching rollers used in the longitudinal stretching process can also be composed of only one roller that contacts one surface of the polyester film without having opposing rollers.

[0302] <Transverse Stretching Process>

[0303] The transverse stretching step is a step of transversely stretching the uniaxially oriented polyester film. The transverse stretching step is performed, for example, in the transverse stretching section 20 of the stretching machine 100 .

[0304] In the transverse stretching step, it is preferred to preheat the polyester film before transverse stretching. By preheating the polyester film, the polyester film can be easily stretched transversely.

[0305] The preheating temperature is preferably (Tg-10) to (Tg+60)° C., more preferably (Tg) to (Tg+50)° C. Specifically, the preheating temperature is preferably 80 to 120° C., more preferably 90 to 110° C.

[0306] The stretch ratio in the width direction of the uniaxially oriented polyester film in the transverse stretching step (transverse stretch ratio a) is not particularly limited, but is preferably greater than the stretch ratio in the longitudinal stretching step. The stretch ratio a in the transverse stretching step is preferably 3.0 to 6.0 times, more preferably 3.5 to 5.0 times, and even more preferably 3.5 to 4.5 times.

[0307] When the transverse stretching step is performed in the transverse stretching section 20 of the stretching machine 100 , the transverse stretching ratio a is determined from the ratio ( L1 / L0 ) of the film width L1 when the film is fed out of the transverse stretching section 20 to the film width L0 when the film is fed into the transverse stretching section 20 .

[0308] The area ratio, represented by the product of the stretch ratio in the longitudinal stretching step and the stretch ratio in the transverse stretching step, is preferably 12.8 to 15.5 times, more preferably 13.5 to 15.2 times, and even more preferably 14.0 to 15.0 times. When the area ratio is above the lower limit, molecular orientation in the film width direction is improved. Furthermore, when the area ratio is below the upper limit, the molecular orientation is easily maintained in a state where it is not easily relaxed during heat treatment.

[0309] The heating temperature in the transverse stretching step is preferably (Tg-10) to (Tg+80)°C, more preferably (Tg) to (Tg+70)°C, and even more preferably (Tg) to (Tg+60)°C. Specifically, the heating temperature in the transverse stretching step is preferably 100 to 140°C, more preferably 110 to 135°C, and even more preferably 115 to 130°C.

[0310] The stretching speed in the transverse stretching step is preferably 8 to 45% / second, more preferably 10 to 30% / second, and even more preferably 15 to 20% / second.

[0311] <Heat setting process>

[0312] In the present production method, a heat setting step and a heat relaxation step are performed as heat treatments on the polyester film stretched transversely in the transverse stretching step.

[0313] In the heat setting step, the biaxially oriented polyester film obtained in the transverse stretching step is heated and heat-set. The heat setting crystallizes the polyester, thereby suppressing shrinkage of the polyester film.

[0314] The heat setting step is performed, for example, in the heat setting section 30 of the stretching machine 100 .

[0315] The surface temperature of the polyester film in the heat-setting step (heat-setting temperature T1) is preferably 190 to 240°C, more preferably 200 to 240°C, and further preferably 210 to 230°C.

[0316] In the heat setting step, the heat treatment is performed while controlling the maximum temperature of the surface of the polyester film to the heat setting temperature T1.

[0317] During the heat setting step, the variation in the surface temperature in the film width direction is preferably 0.5 to 10.0° C., more preferably 0.5 to 7.0° C., further preferably 0.5 to 5.0° C., and particularly preferably 0.5 to 4.0° C. By controlling the variation in the surface temperature in the film width direction within the above range, the variation in crystallinity in the width direction can be suppressed.

[0318] Examples of the heating method include a method of blowing hot air onto the film and a method of radiantly heating the film. Examples of the device used in the radiant heating method include an infrared heater.

[0319] The heating time in the heat setting step is preferably 5 to 50 seconds, more preferably 5 to 30 seconds, and even more preferably 5 to 10 seconds.

[0320] <Heat Relaxation Process>

[0321] In the heat relaxation step, the polyester film heat-set in the heat setting step is heated at a temperature lower than that in the heat setting step to perform heat relaxation. The heat relaxation can relax the residual strain in the polyester film.

[0322] The heat relaxation step is performed, for example, in the heat relaxation unit 40 of the stretching machine 100 .

[0323] The surface temperature of the polyester film during the heat relaxation step (heat relaxation temperature T2) is preferably 5°C or higher, more preferably 15°C or higher, further preferably 25°C or higher, and particularly preferably 30°C or higher, lower than the heat setting temperature T1. Specifically, the heat relaxation temperature T2 is preferably 235°C or lower, more preferably 225°C or lower, further preferably 210°C or lower, and particularly preferably 200°C or lower.

[0324] The lower limit of the heat relaxation temperature T2 is preferably 100°C or higher, more preferably 110°C or higher, and further preferably 120°C or higher.

[0325] In the heat relaxation step, the heat treatment is performed while controlling the maximum temperature of the surface of the polyester film to the heat relaxation temperature T2.

[0326] Examples of the heating method include a method of blowing hot air onto the film and a method of radiantly heating the film. Examples of the device used in the radiant heating method include an infrared heater.

[0327] <Cooling process>

[0328] This production method includes a cooling step of cooling the thermally relaxed polyester film. The cooling step and the expansion step described below are performed in the cooling unit 50 of the stretching machine 100, for example.

[0329] Examples of a method for cooling the polyester film in the cooling step include a method of blowing air (preferably cold air) onto the film and a method of bringing the film into contact with a temperature-regulable member (for example, a temperature-controlled roll).

[0330] From the viewpoint of distinguishing from the heat relaxation step, the cooling temperature in the cooling step is preferably 130°C or lower. The cooling temperature is more preferably 30 to 120°C, further preferably 30 to 100°C, and particularly preferably 30 to 80°C.

[0331] In this production method, the cooling step is performed so that the polyester film reaches a cooling rate V of 2200 to 3500° C. / min. By adjusting the cooling rate V within the above range, the thickness unevenness of the functional layer laminated on the biaxially oriented film can be reduced.

[0332] Although the details of the mechanism for reducing the thickness unevenness of the functional layer by determining the range of the cooling rate V are not clear, it can be inferred that the reason is that by effectively lowering the temperature of the membrane surface and setting the cooling rate to a level that can suppress the temperature unevenness on the membrane surface, the inherent strain in the cooled membrane can be reduced and the generation of ripples associated with high-temperature treatment when the functional layers are stacked can be suppressed.

[0333] From the above viewpoints, the cooling rate V in the cooling step is preferably 2200 to 3000° C. / min, more preferably 2300 to 2600° C. / min.

[0334] The cooling rate V of the polyester film during the cooling process can be measured using a non-contact thermometer. For example, when the cooling process is performed in the cooling section 50 of the stretching machine 100, the surface temperature of the film 200 entering the cooling section 50 from the heat relaxation section 40 and the surface temperature of the film 200 exiting the cooling section 50 are measured to determine the temperature difference ΔT (°C). The cooling rate V is determined by dividing the obtained temperature difference ΔT (°C) by the residence time ta of the film 200 in the cooling section 50.

[0335] The cooling rate of the polyester film can be adjusted by the operating conditions of the cooling device and the conveying speed of the film.

[0336] In the present production method, the heat setting step, heat relaxation step, and cooling step are preferably performed sequentially and continuously. This is because the load (thermal history) on the polyester film due to repeated heating and cooling can be reduced, and the inherent strain in the film can be reduced, thereby suppressing the occurrence of streak-like defects.

[0337] <Expansion Process>

[0338] This production method includes an expanding step of expanding the polyester film, which has been thermally relaxed in the cooling step, in the width direction.

[0339] In the cooling process, "expanding the polyester film in the width direction" means applying tension to the polyester film in the width direction during the cooling process so that the film width ( Figure 2 L3 in the cooling process) is greater than the film width of the polyester film at the start of the cooling process ( Figure 2 L2) width.

[0340] There is no particular limitation on the method for expanding the polyester film in the width direction during the cooling process. For example, when a biaxially oriented polyester film is produced using the stretching machine 100, the film 200 held by the holding members can be expanded in the width direction during the cooling process by making the distance between the annular guide rails 60a and 60b at the end point (grip release point P and grip release point Q) of the cooling section 50 wider than the distance between the annular guide rails 60a and 60b at the start point of the cooling section 50.

[0341] As long as the film width is expanded before or after the cooling step, the expansion step may be performed continuously or intermittently from the start to the end of the cooling step, or may be performed only during one period of the cooling step.

[0342] The expansion step is preferably performed at 130°C or lower, more preferably 30 to 120°C, further preferably 30 to 100°C, and particularly preferably 30 to 80°C.

[0343] If the expansion rate of the polyester film in the width direction based on the expansion process, that is, the ratio of the film width at the end of the cooling process to the film width before the start of the cooling process is greater than 0, there is no particular restriction, but from the viewpoint of better effect of the present invention, the percentage b of the above expansion rate is preferably greater than 0.001%, more preferably greater than 0.01%.

[0344] While the upper limit is not particularly limited, the expansion ratio percentage b is preferably 1.3% or less, more preferably 1.2% or less, and even more preferably 1.0% or less. By setting the film width expansion ratio below the upper limit, even when high tension is applied in the conveying direction for high-speed conveyance during film production (for example, when the tension in the conveying direction is 100 N / m or greater), it is possible to suppress the occurrence of disturbances in the cut surface during the trimming step described later, and thus the resulting film breakage.

[0345] <Particle-Containing Layer Formation Step>

[0346] The present production method includes a particle-containing layer forming step of providing a particle-containing layer on at least one surface of a polyester substrate. The particle-containing layer formed by the particle-containing layer forming step has the same meaning as that of the particle-containing layer described in detail in the above section <Particle-containing layer>.

[0347] The formation of the particle-containing layer can be carried out at any stage in the present manufacturing method, for example, a method of forming a coating film on at least one surface of an unstretched or stretched polyester substrate using a coating liquid containing a material constituting the particle-containing layer, and drying it as needed; and a method of forming the particle-containing layer simultaneously with the formation of the polyester substrate by a co-extrusion method.

[0348] First, a method for forming a particle-containing layer using a particle-containing layer coating liquid will be described.

[0349] The particle-containing layer coating solution can be prepared by mixing the particles contained in the particle-containing layer, the binder and additives added as needed, and the solvent. As the solvent, for example, water, ethanol, toluene, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether can be mentioned. Among them, water is preferred from the viewpoints of environment, safety, and economy.

[0350] The particle-containing layer coating liquid may contain a single solvent or two or more solvents.

[0351] The content of the solvent is preferably 80 to 99% by mass, more preferably 90 to 98% by mass, based on the total mass of the particle-containing layer coating liquid.

[0352] That is, the total content of components (solid content) other than the solvent in the particle-containing layer coating liquid is preferably 0.5 to 20% by mass, more preferably 1 to 10% by mass, relative to the total mass of the particle-containing layer coating liquid.

[0353] The components other than the solvent in the particle-containing layer coating liquid, including this preferred embodiment, are the same as those described for the components contained in the particle-containing layer. Furthermore, the content of each component in the coating liquid is preferably adjusted so that the content of each component relative to the total mass of the solid components of the particle-containing layer coating liquid is the same as the preferred content of each component relative to the total mass of the particle-containing layer.

[0354] The average particle size of the particles contained in the particle-containing layer coating liquid is measured using a laser diffraction / scattering particle size distribution measuring apparatus ("LA-950", manufactured by HORIBA, Ltd.) When commercially available particles are used, the average particle size of the particles may be a catalog value.

[0355] The coating method of the particle-containing layer coating liquid is not particularly limited, and a known method can be used. Examples of the coating method include spray coating, slit coating, roll coating, knife coating, spin coating, bar coating, and dip coating.

[0356] As a method for forming a particle-containing layer using a coating liquid for a particle-containing layer, either a so-called online coating method in which the coating liquid is applied to at least one surface of a polyester substrate while the polyester substrate is being conveyed, or a so-called offline coating method in which the coating liquid is applied separately after a biaxially oriented polyester substrate is manufactured can be applied. However, from the perspective of greater efficiency and the perspective of imparting transparency, the online coating method is preferred.

[0357] In the in-line coating method, the polyester substrate to which the coating liquid for the particle-containing layer is applied may be an unstretched polyester substrate or a uniaxially oriented polyester substrate, and is preferably a uniaxially oriented polyester substrate.

[0358] Next, a method of forming the particle-containing layer simultaneously with the formation of the polyester substrate by a coextrusion method will be described.

[0359] The method for forming the particle-containing layer by coextrusion is not particularly limited. For example, the particle-containing layer can be formed by preparing a resin composition containing particles constituting the particle-containing layer, a binder, and additives added as needed, heating and melt-kneading the obtained resin composition according to the method described in the above-mentioned <Extrusion Molding Step> to produce a melt of the resin composition, and extruding the resin composition together with the polyester melt using an extruder.

[0360] As a particle-containing layer forming process, from the viewpoint of being able to shorten the heating time of the polyester substrate in the manufacturing process and to reduce the strain inside the polyester substrate, it is preferred to use an online coating method process to form the particle-containing layer using a coating liquid for the particle-containing layer between the longitudinal stretching process and the transverse stretching process, or to use a co-extrusion molding process in which a first melt containing polyester constituting the polyester substrate and a second melt containing particles and an adhesive are simultaneously formed with the polyester substrate and the particle-containing layer.

[0361] It is preferred to apply the above-mentioned in-line coating method to a uniaxially oriented polyester substrate between the longitudinal stretching step and the transverse stretching step to form the particle-containing layer. After the particle-containing layer is formed by applying the particle-containing layer coating liquid to at least one surface of the uniaxially oriented polyester substrate, the polyester substrate and the particle-containing layer are simultaneously stretched transversely, thereby improving the adhesion between the polyester substrate and the particle-containing layer. The specific method for transverse stretching at this time is as described in the transverse stretching step above.

[0362] The present production method may further include a winding step of obtaining a roll-shaped biaxially oriented polyester film by winding the biaxially oriented polyester film obtained through the above steps.

[0363] Furthermore, the present production method may further include a trimming step of continuously cutting the polyester film along the conveying direction to cut at least one end portion in the width direction of the polyester film before performing the winding step.

[0364] <Manufacturing Conditions>

[0365] This production method satisfies the following condition 1.

[0366] Condition 1: When the melting point of the polyester constituting the polyester substrate is Tm (°C), the heat setting temperature in the heat setting step is T1 (°C), the stretch ratio of the uniaxially oriented polyester film in the transverse stretching step is a, and the percentage of the expansion rate in the width direction of the heat-relaxed polyester film in the expansion step is b (%), the value C of the product (A×B) of A calculated by the following formula (1) and B calculated by the following formula (2) is -4.0 to 4.0. However, this does not apply to cases where only one of A and B is 0.

[0367] A=Tm-T1-30 (1)

[0368] B=a / 5-b (2).

[0369] Although the details of the mechanism for reducing uneven thickness of the functional layer by setting the conditions of each process in a manner that satisfies the above-mentioned condition 1 are not clear, it is speculated that the reason is that excessive crystallization of the polyester is suppressed in the heat setting process, and expansion is carried out in the width direction at a specified expansion rate in the cooling process, thereby increasing the proportion of polyester molecular chains in the width direction, thereby reducing the dimensional change rate caused by heating in the subsequent process. As a result, the generation of ripples accompanying high-temperature treatment in the process of laminating the functional layer can be suppressed.

[0370] From the above viewpoints, the absolute value of the value C is preferably 0.1 to 0.7, and the absolute value of the value C is more preferably 0.1 to 0.5.

[0371] Furthermore, as described above, when only one of A and B is 0, condition 1 is not satisfied. However, when both A and B are 0, condition 1 is satisfied.

[0372] In the present manufacturing method, when the melting point of the polyester constituting the polyester substrate is set to Tm (°C), the heat setting temperature in the heat setting process is set to T1 (°C), the stretching ratio of the uniaxially oriented polyester film in the transverse stretching process is set to a, the percentage of the expansion rate in the width direction of the heat-relaxed polyester film in the expansion process is set to b (%), and the cooling rate in the cooling process is set to V (°C / minute), D calculated by the following formula (3) is preferably 1 to 10000 based on A calculated by the above formula (1), B calculated by the above formula (2) and the cooling rate V.

[0373] D = (A × B) 2 ×V (3).

[0374] Although the details of the mechanism for reducing thickness unevenness of the functional layer by setting the conditions of each process so that the above-mentioned value D is within the above-mentioned range are unclear, it is speculated that it is the same mechanism as the mechanism for reducing thickness unevenness by determining the range of the above-mentioned cooling rate V and the range of the value C.

[0375] From the above viewpoints, the value D is preferably 0.1 to 6000, more preferably 1 to 1500.

[0376] The conveyance speed of the polyester film in each step of the present production method, except for the longitudinal stretching step, is not particularly limited. However, when the stretching machine 100 is used to perform the transverse stretching step, heat setting step, heat relaxation step, cooling step, and expansion step, the conveyance speed of the polyester film is preferably 50 to 200 m / min, and more preferably 80 to 150 m / min, from the perspectives of productivity and quality. Furthermore, after the cooling step, the conveyance speed of the polyester film until it is wound up in the winding step is preferably 50 to 200 m / min, and more preferably 80 to 150 m / min. The conveyance speed of the polyester film in the longitudinal stretching step is as described above.

[0377] Furthermore, in each process other than the longitudinal stretching process, there is no particular restriction on the tension imparted to the polyester film in the conveying direction. When the above-mentioned stretching machine 100 is used to perform the transverse stretching process, the heat setting process, the heat relaxation process, the cooling process and the expansion process, the tension imparted to the polyester film in the conveying direction can be adjusted according to the stretching conditions.

[0378] Furthermore, after the cooling step is performed, the tension applied to the polyester film in the conveying direction until the film is wound up in the winding step is preferably 3 to 30 N / m, more preferably 5 to 20 N / m.

[0379] [Laminated film]

[0380] The use of the present film is not particularly limited, but it is preferred to further laminate a functional layer to produce a laminated film.

[0381] Examples of the functional layer laminated on the present film include a decorative layer, a photosensitive resin layer, a magnetic layer, a release layer, an adhesive layer, a conductive layer, a refractive index preparation layer, and a visibility layer.

[0382] In order to maintain the lubricity (transportability) of the particle-containing layer as a laminated film, it is preferred that the particle-containing layer be provided only on one surface of the polyester substrate and the functional layer be provided on the surface of the polyester substrate opposite to the particle-containing layer.

[0383] More specific examples of laminated films include the following: a decorative film whose functional layer is a decorative layer, a photosensitive transfer film whose functional layer is a photosensitive resin layer and is used as a support for a dry film resist, a release film whose functional layer is a release layer (a protective film for a dry film resist, a release film for manufacturing ceramic green sheets, a release film for manufacturing semiconductor processes), an adhesive film whose functional layer is an adhesive layer (an adhesive film for manufacturing semiconductor processes), a film for a transparent conductive substrate whose functional layer is a transparent conductive layer, a photosensitive transfer film for forming an etching resist film whose functional layers are a photosensitive resin layer and a visible layer, and a photosensitive transfer film for forming a protective film for a touch panel whose functional layers are a photosensitive resin layer and a refractive index preparation layer.

[0384] There is no particular limitation on the method of laminating a functional layer on the surface of the present film. It is preferred to apply a coating liquid containing a material constituting the functional layer to the surface of a biaxially oriented polyester film to form the functional layer. From the perspective of better productivity, it is more preferred to form the functional layer by applying a coating liquid for the functional layer to the surface of the present film while conveying the present film and then heating the coating film.

[0385] Even when the present film is subjected to a heat treatment in the step of forming the functional layer, the occurrence of streak-shaped defect regions in the biaxially oriented polyester film can be suppressed, and thickness unevenness of the laminated functional layer can be suppressed.

[0386] The laminated film may have layers other than the present film and the functional layer. Examples of layers other than the present film and the functional layer include a base layer containing a binder resin provided for the purpose of improving the adhesion between the present film and the functional layer.

[0387] This film is preferably used as a support for dry film resists. A photosensitive resin layer can be provided as a functional layer, and a decorative layer, a refractive index preparation layer, and / or a visibility layer can be further laminated. Multiple functional layers tend to be heated each time they are laminated, resulting in uneven thickness. However, using this film can resolve this issue.

[0388] The photosensitive resin layer is not particularly limited, but is preferably a negative-type layer. Specifically, preferred embodiments include the binder polymers, ethylenically unsaturated compounds, or photopolymerization initiators described in International Publication No. 2018 / 105313. More preferably, the photosensitive resin layer comprises an alkali-soluble acrylic resin containing a cyclic structure, a multifunctional acrylate, an oxime-based photopolymerization initiator, or a bisimidazole-based photopolymerization initiator.

[0389] When used to form a dry film resist support for a touch panel electrode protective film, a refractive index adjusting layer is preferably laminated separately from the photosensitive resin layer. A preferred embodiment of the refractive index adjusting layer includes the second curable transparent resin layer described in Japanese Patent Application Laid-Open No. 2014-108541. The refractive index adjusting layer preferably has a refractive index of 1.6 or greater, and preferably comprises metal oxide particles with a high refractive index, such as titanium oxide and zirconium oxide.

[0390] When used as a dry film resist support for forming a decorative pattern, the photosensitive resin layer is preferably colored. The colored photosensitive resin layer is preferably formed from a photosensitive resin composition described in International Publication No. 2017 / 208849. The colored photosensitive resin layer preferably contains a pigment as a colorant, and more preferably contains a pigment, a binder polymer, a multifunctional acrylate, and a photopolymerization initiator.

[0391] When used for forming a dry film resist support for an etching resist used in forming a fine pattern of 50 μm or less, a visibility layer is preferably laminated separately from the photosensitive resin layer. The visibility layer enables visual recognition in the process of confirming the pattern latent image.

[0392] The present film is also preferably used as a release film for producing ceramic green sheets. In the case of a release film, a release layer is often provided as a functional layer. A preferred embodiment of the release layer is a layer comprising a silicone resin.

[0393] Example

[0394] The present invention will be further described in detail with reference to the following examples. The materials, usage amounts, ratios, processing contents, and processing sequences shown in the following examples can be appropriately modified without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. In addition, unless otherwise stated, "parts" and "%" are by mass.

[0395] Hereinafter, in the present embodiment, the term "film" simply refers to not only the polyester substrate alone and both the polyester substrate and the particle-containing layer, but also all of the unstretched film, the uniaxially oriented film, and the biaxially oriented film.

[0396] In addition, in each process of this embodiment, a non-contact thermometer (AD-5616 (product name), manufactured by A&D Company, emissivity 0.95) is used to measure the temperature of the central part of the width direction of the film five times, and the arithmetic average of the obtained measurement values ​​is used as the measured value of the surface temperature of the film.

[0397] [Example 1]

[0398] <Extrusion molding process>

[0399] A titanium compound described in Japanese Patent No. 5575671 (citric acid chelate titanium complex, VERTEC AC-420, manufactured by Johnson Matthey Co.) was used as a polymerization catalyst to produce polyethylene terephthalate particles. Specifically, 390 kg of ethylene glycol was mixed with 1 ton (1000 kg) of terephthalic acid so that the amount of Ti atoms reached 9 mass ppm relative to the polyethylene terephthalate produced by the titanium compound. The resulting mixture was continuously supplied to a reaction apparatus to carry out an esterification reaction. In addition, magnesium acetate tetrahydrate (Mg atoms were in an amount of 81 mass ppm relative to the polyethylene terephthalate produced) and trimethyl phosphate (P atoms were in an amount of 73 mass ppm relative to the polyethylene terephthalate produced) were added to the mixture to carry out a polycondensation reaction to produce polyethylene terephthalate particles.

[0400] The pellets were dried to a moisture content of 50 ppm or less and then placed in the hopper of a 30 mm diameter uniaxial kneading extruder. The pellets were then melted and extruded at 280°C. The melt was passed through a filter (pore size 3 μm) and then extruded from a die onto a cooling drum at 25°C to produce an unstretched film made of polyethylene terephthalate. The extruded melt was then brought into close contact with the cooling drum using electrostatic application.

[0401] The polyethylene terephthalate constituting the unstretched film has a melting point (Tm) of 258°C and a glass transition temperature (Tg) of 80°C.

[0402] <Longitudinal Stretching Process>

[0403] The unstretched film was subjected to a longitudinal stretching step by the following method.

[0404] Under the following conditions, a preheated unstretched film was passed between two pairs of rolls having different peripheral speeds and stretched in the longitudinal direction (conveying direction), thereby producing a uniaxially oriented film.

[0405] (Longitudinal stretching conditions)

[0406] Preheating temperature: 75℃

[0407] Stretching temperature: 90℃

[0408] Stretching ratio: 3.4 times

[0409] Stretching speed: 1300% / second

[0410] <Particle-Containing Layer Formation Step>

[0411] The particle-containing layer coating solution described below was applied to one side of a longitudinally stretched uniaxially oriented film (polyester substrate) using a bar coater so that the weight of the solid content of the coating film relative to the surface area of ​​the uniaxially oriented film was 5.6 g / m 2 .

[0412] (Coating liquid for particle-containing layer)

[0413] A coating liquid for a particle-containing layer (coating liquid A) was prepared by mixing the following components. The prepared coating liquid A was filtered using a 6 μm filter (F20, manufactured by MAHLE Filter Systems Japan Corp.) and subjected to membrane degassing (2x6 radial flow super hydrophobic, manufactured by Polypore International Inc.). The resulting coating liquid was then applied to the surface of a uniaxially oriented film and dried in hot air at 100°C to form a slippery coating layer.

[0414] Acrylic resin (aqueous dispersion containing 27.5% by mass of a copolymer of methyl methacrylate, styrene, 2-ethoxyhexyl acrylate, 2-hydroxyethyl methacrylate, and acrylic acid (containing them in a mass ratio of 59:8:26:5:2) as a solid content): 167 parts

[0415] Nonionic surfactant ("NAROACTY (registered trademark) CL95", manufactured by Sanyo Chemical Industries, Ltd., polyoxyalkylene alkyl ether, solid content 100% by mass): 0.7 parts

[0416] Anionic surfactant ("RAPISOL (registered trademark) A-90", manufactured by NOF CORPORATION, solid content 1% by mass, diluted in water): 55.7 parts

[0417] Wax ("Cellosol (registered trademark) 524", manufactured by Chukyo Yushi Co., Ltd., ester wax dispersion, solid content 30% by mass): 7 parts

[0418] Cross-linking agent ("CARBODI IMIDE (registered trademark) V-02-L2", manufactured by Nisshinbo Chemical Inc., a carbodiimide compound, a 10% by mass solids diluted in water): 20.9 parts

[0419] Non-agglomerated particles ("SNOWTEX XL", average particle size 50 nm, colloidal silica, manufactured by Nissan Chemical Industries, Ltd., solid content 40% by mass aqueous dispersion): 2.8 parts

[0420] Agglomerated particles ("AEROSILOX 50", average secondary particle size 200 nm, agglomerated silica, average primary particle size 40 nm, manufactured by NIPPON AEROSIL CO., LTD., solid content 10% by mass aqueous dispersion): 2.95 parts

[0421] Water: 743 parts

[0422] <Transverse Stretching Process>

[0423] The film having undergone the longitudinal stretching step and the particle-containing layer forming step was stretched in the width direction using a tenter under the following conditions to produce a biaxially oriented film.

[0424] (Transverse stretching conditions)

[0425] Preheating temperature: 100°C

[0426] Stretching temperature: 120℃

[0427] Stretching ratio: 4.3 times

[0428] Stretching speed: 50% / second

[0429] <Heat setting process>

[0430] The biaxially oriented film subjected to the transverse stretching step was heated using a tenter under the following conditions to perform a heat-setting step of the heat-setting film.

[0431] (Heat setting conditions)

[0432] Heat setting temperature T1: 227℃

[0433] Heat setting time: 6 seconds

[0434] <Heat Relaxation Process>

[0435] Next, the heat-set film was heated under the following conditions to relax the film's tension. During the heat relaxation step, the distance between the tenter's gripping members (the tenter width) holding the film at both ends was narrowed, reducing the film width compared to the end of the heat-setting step. The heat relaxation rate ΔLr was calculated using the formula: Lr = (L1 - L2) / L1 × 100, based on the film width L2 at the end of the heat relaxation step relative to the film width L1 at the start of the heat relaxation step.

[0436] (Thermal relaxation conditions)

[0437] Thermal relaxation temperature T2: 190°C

[0438] Thermal relaxation rate Lr: 4%

[0439] <Cooling and Expansion Process>

[0440] The heat-relaxed film was subjected to a cooling step of cooling under the following conditions. In the cooling step, an expansion step of expanding the width of the tenter to increase the film width compared to the end of the heat-relaxing step was performed.

[0441] The residence time from the film being fed into the cooling section 50 of the stretching machine 100 to being fed out is set as the cooling time ta, and the following cooling rate V is calculated by dividing the cooling time ta by the temperature difference ΔT (°C) between the film surface temperature measured when it is fed into the cooling section 50 and the film surface temperature measured when it is fed out of the cooling section 50.

[0442] The following expansion ratio ΔL was determined from the film width L3 at the end of the cooling process relative to the film width L2 of the polyester film at the start of the cooling process using the formula ΔL=(L3-L2) / L2×100.

[0443] (cooling conditions)

[0444] Cooling rate V: 2500℃ / min

[0445] Cooling time ta: 3.1 seconds

[0446] (Expansion conditions)

[0447] Expansion rate ΔL: 0.6%

[0448] <Coiling process>

[0449] The film, cooled in the cooling step, was continuously cut along the conveying direction at 20 cm from both ends of the film's width using a trimming device to trim both ends. Next, the film was extruded (knurled) from both ends to a width of 10 mm, and then wound up at a tension of 40 kg / m.

[0450] A biaxially oriented film was produced using the above method. The resulting biaxially oriented film had a thickness of 31 μm, a width of 1.5 m, and a roll length of 7,000 m. Furthermore, the particle-containing layer of the resulting biaxially oriented film had a thickness of 40 nm. Furthermore, measurements using the above method confirmed that the particle-containing layer of the resulting biaxially oriented film contained particles with an average particle size of 50 nm and particles with an average particle size of 200 nm.

[0451] [Example 2]

[0452] A biaxially oriented film was produced in the same manner as in Example 1 except that coating liquid B having the same composition as coating liquid A was used as the coating liquid for the particle-containing layer, except that the non-aggregated particles were not contained.

[0453] [Examples 3 to 11]

[0454] A biaxially oriented film was produced according to the method described in Example 1 except that the heat setting temperature T1 in the heat setting step, the cooling rate V in the cooling step, and the expansion ratio ΔL in the expansion step were controlled to the values ​​described in Table 1 below.

[0455] [Examples 12 to 17]

[0456] A biaxially oriented film was produced according to the method described in Example 1, except that the aggregated particles were not contained, the particles listed in Table 1 were used as the non-aggregated particles, and the thickness of the particle-containing layer was adjusted to the value listed in Table 1.

[0457] The details of the particles described in Table 1 are shown below.

[0458] 450nm non-agglomerated particles: SNOWTEX MP-4540M, manufactured by Nissan Chemical Industries, Ltd., average particle size 450nm, colloidal silica

[0459] 200nm non-agglomerated particles: SNOWTEX MP-2040, manufactured by Nissan Chemical Industries, Ltd., average particle size 200nm, colloidal silica

[0460] 100nm non-agglomerated particles: SNOWTEX ZL, manufactured by Nissan Chemical Industries, Ltd., average particle size 100nm, colloidal silica

[0461] 50nm non-agglomerated particles: SNOWTEX XL, manufactured by Nissan Chemical Industries, Ltd., average particle size 50nm, colloidal silica

[0462] 300nm non-agglomerated particles: divinylbenzene / styrene copolymer cross-linked particles, average particle size 300nm

[0463] [Example 18]

[0464] Instead of the extrusion molding process implemented in Example 1, the melt produced by coextrusion molding in the extrusion molding process of Example 1 and the melt of the following resin H are coextruded onto a cooling drum at 25°C, thereby producing an unstretched film composed of polyethylene terephthalate and a particle-containing layer. In addition, a biaxially oriented film is produced according to the method described in Example 1.

[0465] Pellets of Resin H containing non-agglomerated particles were produced according to the method for producing polyethylene terephthalate pellets in Example 1, except that divinylbenzene / styrene copolymer crosslinked particles having an average particle size of 300 nm were mixed. The pellets were dried until the moisture content reached 50 ppm or less, then charged into the hopper of a 30 mm diameter uniaxial kneading extruder and melted at 280°C to produce a melt of Resin H.

[0466] The obtained biaxially oriented film had a thickness of 31 μm, and the particle-containing layer had a thickness of 2 μm.

[0467] [Examples 19 to 21]

[0468] A biaxially oriented film was produced according to the method described in Example 1, except that the thickness of the unstretched film made of polyethylene terephthalate was adjusted in the extrusion molding step so that the thickness of the produced biaxially oriented polyester film would be the value described in Table 1.

[0469] In Example 20, the coating liquid F described above was used as the coating liquid for the particle-containing layer.

[0470] [Example 22]

[0471] A biaxially oriented film was produced according to the method described in Example 1, except that the heat setting temperature T1 was controlled to the value described in Table 1 in the heat setting step.

[0472] [Comparative Examples 1 to 5]

[0473] The heat setting temperature T1 in the heat setting process, the cooling rate V in the cooling process, and the expansion rate ΔL in the expansion process were controlled to the values ​​described in Table 1 described later, and the above-mentioned coating liquid B was used as the coating liquid for the particle-containing layer in Comparative Examples 1 to 4. Except for this, a biaxially oriented film was produced according to the method described in Example 1.

[0474] 〔Physical Property Measurement〕

[0475] The following physical properties were measured for each of the biaxially oriented films of Examples 1 to 25 and Comparative Examples 1 to 6. The measurement results are shown in Table 1.

[0476] Furthermore, the thickness of the particle-containing layer and the average particle size of the particles contained in the particle-containing layer were measured for each of the biaxially oriented films of Examples 2 to 25 and Comparative Examples 1 to 6 according to the above-mentioned measurement method.

[0477] <density>

[0478] The density (g / cm2) of the biaxially oriented film was measured using an electronic densitometer (product name "SD-200L", manufactured by Alfa Mirage Co., Ltd.). 3 ).

[0479] <Stripe-shaped defect area (90°C, 120°C)>

[0480] A heated conveyor was used to convey the biaxially oriented film at a conveying speed of 30 m / min and a tension of 100 N / m in the conveying direction, while heat-treating it at 90°C or 120°C for 20 seconds. The heating temperature during the heat treatment refers to the surface temperature of the film. The heating time during the heat treatment was calculated from the moment when the surface temperature of the film reached the target temperature (90°C or 120°C). The biaxially oriented film after the heat treatment was placed on a black flat plate, and then, while changing the viewpoint of light reflection from a fluorescent lamp [rupikae-su manufactured by Mitsubishi Flectric Corporation (color temperature: 5000K, average color rendering rating (Ra): 84)] installed on the ceiling of the room, the biaxially oriented film was visually observed from the side. By visually observing an area of ​​1 m×1 m, the area where the reflected image of the fluorescent lamp on the surface of the biaxially oriented film was undulating was set as a stripe-shaped defect area. Next, the ratio of the total area of ​​the observed streak-like defect regions to the total area of ​​the observed region of the biaxially oriented film (area ratio) was calculated by the method described above (see the item "streak-like defect regions").

[0481] <Expansion rate (90℃, 120℃)>

[0482] The expansion ratio of the biaxially oriented film in the width direction at 90° C. and 120° C. was measured using a thermomechanical analyzer (TMA-60, manufactured by Shimadzu Corporation) according to the above-described method (see the item “Expansion ratio”).

[0483] <Maximum peak height Rp>

[0484] A test piece of the manufactured biaxially oriented film was cut out and the surface of the obtained test piece was measured using the described micro-shape measuring device under the described conditions. Then, particle analysis (multiple levels) was performed using the built-in analysis software to determine the maximum peak height Rp of the surface of the biaxially oriented film.

[0485] For the maximum peak height Rp measurement, the slices were set at equal intervals of 10 nm. The average diameter and density of each slice were measured five times while changing the measurement position. The average value was calculated and used as the maximum peak height Rp value. The test piece was fixed to the sample stage so that the X direction of the field of view measured was the width direction of the polyester film.

[0486] [evaluate]

[0487] The following evaluations were performed on each of the biaxially oriented films of Examples 1 to 22 and Comparative Examples 1 to 5. The evaluation results are shown in Table 1.

[0488] Uneven thickness

[0489] While the biaxially oriented films produced in each of the Examples and Comparative Examples were being conveyed, a base layer coating liquid having the following formulation A was applied to the surface of the biaxially oriented film using a slit nozzle. The coated film was then dried at 90°C to form a base layer. Subsequently, while the biaxially oriented film having the base layer formed thereon was being conveyed, a black layer coating liquid having the following formulation B was applied to the base layer. The coated film was then dried at 90°C to form a black layer. The conveyance speed of the biaxially oriented film during the formation of the base layer and the black layer was 70 m / min.

[0490] The biaxially oriented film provided with the base layer and the black layer was placed on a light table, and color unevenness of the black layer was visually observed at a position 1 m away from the biaxially oriented film.

[0491] A biaxially oriented film provided with a base layer and a black layer was formed according to the above method except that the drying temperature conditions during the formation of the base layer and the formation of the black layer were both changed to 120° C., and visual observation was performed.

[0492] Based on the observation results of each biaxially oriented film produced by setting the drying temperature condition of the coating film to 90° C. or 120° C., the thickness unevenness of the biaxially oriented film was evaluated according to the following criteria.

[0493] (Formula A: coating solution for base layer)

[0494] PVA205 (polyvinyl alcohol, manufactured by KURARAY CO., LTD., saponification degree 88%, polymerization degree 550): 32.2 parts by mass

[0495] Polyvinyl pyrrolidone (K-30, manufactured by Information System Products Co., Ltd.): 14.9 parts

[0496] Distilled water: 524 parts by mass

[0497] Methanol: 429 parts by mass

[0498] (Formula B: Coating liquid for black layer)

[0499] 13.1 parts by mass of resin-coated carbon black prepared according to paragraphs 0036 to 0042 of Japanese Patent No. 5320652

[0500] Dispersant: 10.65 parts by mass of the dispersant described in paragraph

[0103] of International Publication No. 2017 / 208849

[0501] Polymer (random copolymer of benzyl methacrylate / methacrylic acid = 72 / 28 molar ratio, weight average molecular weight 37,000): 6.72 parts by mass

[0502] Propylene glycol monomethyl ether acetate: 79.53 parts by mass

[0503] (Evaluation Criteria)

[0504] A: In both cases where the drying temperature conditions were 90° C. and 120° C., no color unevenness of the black layer was observed.

[0505] B: In either case of the drying temperature condition being 90° C. or 120° C., slight color unevenness of the black layer was observed.

[0506] C: Color unevenness of the black layer was observed only when the drying temperature was 120°C.

[0507] D: In both cases where the drying temperature conditions were 90° C. and 120° C., color unevenness of the black layer was clearly observed.

[0508] [Poor transfer]

[0509] The biaxially oriented film having a base layer and a black layer produced in the above-described thickness unevenness evaluation was trimmed at both ends to a width of 45 cm. The trimmed biaxially oriented film was then wound onto an ABS (acrylonitrile-butadiene-styrene) resin core with a diameter of 3 inches (1 inch = 2.54 cm) while being pressed against a touch roll at a tension of 11.5 kg / m. The longitudinal length of the wound biaxially oriented film was 100 m.

[0510] The obtained sample was left to stand for 30 days under conditions of 25°C and 50% RH. After 30 days, the surface of the black layer of the biaxially oriented film wound around the core was observed under a fluorescent lamp (Rupikae-su manufactured by Mitsubishi Electric Corporation (color temperature: 5000K, average color rendering index (Ra): 84)). The film surface was visually observed for irregularities using reflected light from the fluorescent lamp, and transfer failure was evaluated according to the following criteria.

[0511] (Evaluation Criteria)

[0512] A: The surface is completely free of bumps and is in excellent condition.

[0513] B: Some surface irregularities can be visually recognized, but they are very slight.

[0514] C: Slight surface irregularities can be visually recognized.

[0515] Table 1 shows the evaluation results of each example and comparative example.

[0516] In Table 1, the “Formation Method” column of “Particle-Containing Layer” in each Example and Comparative Example means that the particle-containing layer was formed by the following method as the particle-containing layer forming step.

[0517] A: It is formed by applying a coating liquid on a uniaxially oriented film after the longitudinal stretching step and before the transverse stretching step (in-line coating method).

[0518] B: Formed simultaneously with an unstretched film by co-extrusion molding.

[0519] [Table 1]

[0520]

[0521] [Table 2]

[0522]

[0523] Table 1 shows that the cooling rate V of the polyester film in the cooling step is within the range of 2200 to 3500° C. / min and that Examples 1 to 22 satisfying Condition 1 can suppress thickness variations of the laminated functional layer compared to Comparative Examples 1 to 5.

[0524] Furthermore, Table 1 shows that, after the specific heat treatment, Examples 1 to 22, in which the area of ​​the streak-like defect region observed in the polyester film was 40% or less relative to the total area of ​​the observed region, can suppress the thickness unevenness of the laminated functional layer compared to Comparative Examples 1 to 5.

[0525] Among them, a comparison of Examples 1 to 5 and 9 to 11 confirmed that when the absolute value of the value C of the product of A calculated by formula (1) and B calculated by formula (2) is 0.1 to 0.7, the uneven thickness of the stacked functional layer can be further suppressed, and it was confirmed that when the above-mentioned value C is 0.1 to 0.5, the uneven thickness of the stacked functional layer can be further suppressed.

[0526] Furthermore, a comparison of Examples 1 and 6 to 8 confirms that when the cooling rate V in the cooling process is 2200 to 3000°C, the uneven thickness of the stacked functional layers can be further suppressed, and when it is 2300 to 2600°C / minute, the uneven thickness of the stacked functional layers can be further suppressed.

[0527] Furthermore, from the comparison between Examples 1 and 12 to 17, it was confirmed that when the maximum peak height Rp of the surface of the particle-containing layer was 0.2 μm or less, transfer failures could be further suppressed.

[0528] Furthermore, from the comparison between Example 12 and Example 18, it was confirmed that when the particles contained in the particle-containing layer are resin particles, transfer failure can be further suppressed.

[0529] Furthermore, from the comparison between Examples 1 and 12 to 17, it was confirmed that when the particles have an average particle size of 0.4 μm or less, transfer failures can be further suppressed.

[0530] [Example 23]

[0531] The biaxially oriented film produced in Example 1 was used as a support, and a decorative transfer film was produced by the following procedure.

[0532] The thermoplastic (non-photosensitive) resin layer coating liquid described in

[0106] of the specification of International Publication No. 2017 / 208849 is applied to the surface of the biaxially oriented film produced in Example 1 on the side opposite to the particle-containing layer, and dried at 80°C to form a thermoplastic (non-photosensitive) resin layer. Subsequently, a base layer coating liquid consisting of the above-mentioned formula A is applied and dried at 120°C to form a base layer. A photosensitive resin layer-forming composition consisting of the following formula C is applied thereon and dried at 90°C to form a photosensitive resin layer. The thickness of the base layer is 1.6 μm, and the thickness of the photosensitive resin layer is 2.0 μm. Finally, a decorative transfer film is produced by crimping a polypropylene film with a thickness of 12 μm on the surface of the photosensitive resin layer as a protective film.

[0533] The obtained decorative transfer film exhibited excellent properties, with no color unevenness or transfer defects. Furthermore, the obtained decorative transfer film was used to form a decorative pattern according to the description in

[0109] of the specification of International Publication No. 2017 / 208849, resulting in a good pattern.

[0534] <Formulation C: Photosensitive Resin Layer-Forming Composition>

[0535] 180.9 parts of the black pigment dispersion described above

[0536] 3.29 parts of A-NOD-N (Shin-Nakamura Chemical Co., Ltd., bifunctional, molecular weight 226)

[0537] 9.9 parts of A-DCP (Shin-Nakamura Chemical Co., Ltd., bifunctional, molecular weight 304)

[0538] 8UX-015A (TAISEI FINE CHEMICAL CO., LTD., 15-functional) 6.59 parts

[0539] 2.20 parts of A-DPH (Shin-Nakamura Chemical Co., Ltd., hexafunctional, molecular weight 578)

[0540] 141.2 parts of adhesive (benzyl methacrylate / methacrylic acid copolymer, 70 / 30 mass %, weight average molecular weight (Mw) = 5000, solid content = 40.5 mass %)

[0541] 6.75 parts of polymerization initiator OXE-02 (BASF, IRGACURE OXE 02, acetone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(0-acetoxime))

[0542] 250 parts of propylene glycol monomethyl ether acetate

[0543] 404.2 parts of methyl ethyl ketone

[0544] [Example 24]

[0545] The biaxially oriented film produced in Example 21 was used as a support, and a dry film for forming a touch panel protective film was produced by the following procedure.

[0546] A coating liquid for forming a second transparent transfer layer, consisting of the following formula D, was applied to the surface of the biaxially oriented film produced in Example 21 on the side opposite to the particle-containing layer and dried at 90°C to form a second transparent transfer layer. Next, a coating liquid for forming a first transparent transfer layer, consisting of the following formula E, was applied to the second transparent transfer layer and dried at 70°C to form a first transparent transfer layer. The thickness of the second transparent transfer layer was 5.0 μm, and the thickness of the first transparent transfer layer was approximately 80 nm. Finally, a 16 μm thick polyethylene terephthalate film was press-bonded to the surface of the first transparent transfer layer as a protective film to produce a transfer film for forming a touch panel protective film.

[0547] The resulting transfer film showed no changes in refractive index due to thickness variations, and no transfer defects, demonstrating excellent properties. The contact hole formation results for the resulting transfer film, referring to

[0122] to

[0128] of International Publication No. 2018 / 186428, demonstrated that a good pattern could be formed.

[0548] <Formulation D: Coating Liquid for Forming the Second Transparent Transfer Layer>

[0549] ARONIX TO-2349 (TOAGOSEI CO., LTD., carboxylic acid-containing monomer) 0.93 parts

[0550] 5.6 parts of A-DCP (Shin-Nakamura Chemical Co., Ltd., bifunctional, molecular weight 304)

[0551] 8UX-015A (TAISEI FINE CHEMICAL CO., LTD., polyurethane acrylate) 2.80 parts

[0552] 15.59 parts of binder (copolymer of cyclohexyl methacrylate / methyl methacrylate / methacrylic acid / methacrylic acid glycidyl methacrylate adduct, 51.5 / 2 / 26.5 / 20%, weight average molecular weight (Mw) = 29,000, acid value = 95 mgKOH)

[0553] 0.11 parts of polymerization initiator IRGACURE OXE-02 (BASF)

[0554] 0.21 parts of polymerization initiator IRGACURE 907 (BASF, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one)

[0555] 0.03 parts of N-phenylglycine

[0556] 3.63 parts of blocked isocyanate (Asahi Kasei Chemicals Co., Ltd., Duranate WT32-B75P)

[0557] 0.09 parts of benzimidazole

[0558] 0.02 parts of surfactant (DIC Corporation, MEGAFACE F-551)

[0559] 31.08 parts of 1-methoxy-2-propyl acetate

[0560] 40.0 parts of methyl ethyl ketone

[0561] <Formulation E: Coating Liquid for Forming the First Transparent Transfer Layer>

[0562] 4.34 parts NanoUse OZ-S30M (ZrO2 particle methanol dispersion, Nissan Chemical Industries, Ltd., nonvolatile content 30.5%)

[0563] 7.82 parts of ammonia water (25%)

[0564] 0.02 parts of monoisopropanolamine

[0565] 0.24 parts of binder (allyl methacrylate / methacrylic acid copolymer, 40 / 60 mol%, weight average molecular weight (Mw) = 38,000)

[0566] ARONIX TO-2349 (TOAGOSEI CO., LTD.) 0.03 parts

[0567] 0.03 parts of benzotriazole

[0568] Surfactant (DIC Corporation, MEGAFACE F-444) 0.01 part

[0569] 21.5 parts ion exchange water

[0570] 66.0 parts of methanol

[0571] [Example 25]

[0572] The biaxially oriented film produced in Example 21 was used as a support, and a dry film for forming an etching resist was produced by the following procedure.

[0573] A coating liquid for forming a thermoplastic resin layer composed of the following formula F was applied to the surface of the biaxially oriented film produced in Example 21 on the side opposite to the particle-containing layer, and dried at 80°C to form a thermoplastic resin layer. Next, a coating liquid for forming a water-soluble resin layer composed of the following formula G was applied to the thermoplastic resin layer and dried at 80°C to form a water-soluble resin layer. In addition, a coating liquid for forming a photosensitive resin layer composed of the following formula H was applied to the water-soluble resin layer and dried at 80°C to form a photosensitive resin layer. The thickness of the thermoplastic resin layer was 2μm, the thickness of the water-soluble resin layer was 1μm, and the thickness of the photosensitive resin layer was 2μm. Finally, a polyethylene terephthalate film with a thickness of 16μm was pressed onto the surface of the photosensitive resin layer as a protective film to produce a transfer film for forming an etching resist.

[0574] The obtained transfer film was exposed with reference to

[0429] to

[0430] of the specification of International Publication No. 2019 / 151534, and the visibility was confirmed. As a result, the line and space pattern could be clearly visually recognized.

[0575] <Formulation F: Coating Liquid for Forming Thermoplastic Resin Layer>

[0576] Benzyl methacrylate / methacrylic acid / acrylic acid polymer (75 / 10 / 15 mass %, molecular weight 30,000, solid content 30%) 22.7 parts

[0577] 0.12 parts of 3,6-bis(diphenylamino)fluoran

[0578] 0.2 parts of A-1 described in paragraph 0227 of JP-A-2013-047765 and an oxime sulfonate-type photoacid generator

[0579] 3.32 parts of tricyclodecane dimethanol diacrylate

[0580] 8UX-015A (TAISEI FINE CHEMICAL CO., LTD., 15-functional) 1.66 parts

[0581] ARONIX TO-2349 (TOAGOSEI CO., LTD.) 0.55 parts

[0582] Surfactant (DIC Corporation, MEGAFACE F-552) 0.02 parts

[0583] <Formulation G: Coating liquid for forming a water-soluble resin layer>

[0584] Polyvinyl alcohol (KURARAY POVAL4-88LA, manufactured by Kuraray Co., Ltd.) 3.22 parts

[0585] Polyvinyl pyrrolidone (manufactured by NIPPON SHOKUBAI CO., LTD., K-30) 1.49 parts

[0586] Surfactant (MEGAFACE F-444, manufactured by DIC Corporation) 0.0035 parts

[0587] Methanol (manufactured by MITSUBISHI GAS CHEMICAL COMPANY, INC.) 57.1 parts

[0588] 38.12 parts ion exchange water

[0589] <Formulation H: Coating Liquid for Forming Photosensitive Resin Layer>

[0590] 25.2 parts of a polymer of styrene / methacrylic acid / methyl methacrylate (52 / 29 / 19 mass %, molecular weight 60,000, solids concentration 30%)

[0591] 0.06 parts of colorless crystal violet

[0592] 1.03 parts of photopolymerization initiator (2-(2-chlorophenyl)-4,5-diphenylimidazole dimer)

[0593] 0.04 parts of 4,4'-bis(diethylamino)benzophenone

[0594] 0.02 parts of N-phenylcarbamoylmethyl-N-carboxymethylaniline

[0595] 5.61 parts of ethoxylated bisphenol A dimethacrylate NK ESTER BPE-500 (manufactured by Shin-Nakamura Chemical Co., Ltd.)

[0596] ARONIX M-270 (manufactured by TOAGOSEI CO., LTD.) 0.58 parts

[0597] 0.04 parts of phenothiazine

[0598] 0.002 parts of 4-hydroxymethyl-4-methyl-1-phenyl-3-pyrazolone

[0599] Surfactant (DIC Corporation, MEGAFACE F-552) 0.048 parts

[0600] 19.7 parts of propylene glycol monomethyl ether acetate

[0601] 43.8 parts of methyl ethyl ketone

[0602] [Example 26]

[0603] The biaxially oriented film produced in Example 1 was used as a support, and a release film for producing a ceramic green sheet was produced by the following procedure.

[0604] The peeling layer-forming coating liquid composed of the following formula J was applied to the surface of the biaxially oriented film produced in Example 1 on the side opposite to the particle-containing layer, and dried at 20°C to form a peeling layer. The thickness of the peeling layer was 0.1 μm. Next, a ceramic slurry composed of the following formula K was applied to the peeling layer to a thickness of 0.5 μm after drying, and then dried at 90°C. The slurry surface was overlapped with the particle-containing layer surface, and a pressure of 1 kg / cm 2 After 10 minutes of loading, the release film was peeled off to obtain a ceramic green sheet.

[0605] The obtained ceramic green sheet had no thickness unevenness and no transfer failure and had excellent characteristics.

[0606] <Formulation J: Coating liquid for forming a release layer>

[0607] 10 parts of silicone resin (SRX-345, addition reaction type silicone, manufactured by Dow Corning Toray Co., Ltd.)

[0608] 0.1 part of platinum catalyst (SRX-212 manufactured by Dow Corning Toray Co., Ltd.)

[0609] 490 parts of toluene / methyl ethyl ketone mixed solvent

[0610] <Formula K: Ceramic slurry>

[0611] 5 parts of polyvinyl butyral (S-LEC BH-3 manufactured by SEKISUI CHEMICAL CO., LTD.)

[0612] 50 parts of barium titanate (HPBT, manufactured by Fuji Titanium Industry Co., Ltd.)

[0613] 45 parts of toluene / ethanol mixed solvent

[0614] Explanation of symbols

[0615] 2a~21-holding parts, 10-preheating section, 20-stretching section, 30-heat setting section, 40-heat relaxation section, 50-cooling section, 60a, 60b-annular guide rails, 100-stretching machine, 200-film, P, Q-holding release point, MD-transmission direction (length direction), TD-width direction, L0, L1, L2, L3-film width.

Claims

1. A method for producing a polyester film, comprising: An extrusion molding step of extruding a molten resin containing polyester in a film shape to form an unstretched polyester film containing at least a polyester base material; a longitudinal stretching step of stretching the unstretched polyester film along a conveying direction to form a uniaxially oriented polyester film; a transverse stretching step of stretching the uniaxially oriented polyester film in the width direction to form a biaxially oriented polyester film; a heat setting step of heating the biaxially oriented polyester film to heat set it; a heat relaxation step of heating the polyester film heat-set in the heat setting step at a temperature lower than that in the heat setting step to heat relax the film; a cooling step of cooling the polyester film heat-relaxed in the heat-relaxing step; and an expansion step of expanding the thermally relaxed polyester film in the cooling step in the width direction, The polyester film comprises a polyester substrate and a particle-containing layer containing particles located on at least one surface of the polyester substrate. The cooling rate V of the polyester film in the cooling step is 2200°C / min to 3000°C / min, and The method for producing the polyester film satisfies the following condition 1: Condition 1: When the melting point of the polyester is set to Tm, the heat setting temperature in the heat setting step is set to T1, the stretching ratio of the uniaxially oriented polyester film in the transverse stretching step is set to a, and the percentage of the expansion rate in the width direction of the heat-relaxed polyester film in the expansion step is set to b, the value C of the product of A calculated by the following formula (1) and B calculated by the following formula (2) is -4.0 to 4.0, except when either A or B is 0, the units of Tm and T1 are ° C, and the unit of b is %. A=Tm-T1-30 (1) B=a / 5-b (2) In the method for producing a polyester film, the value D calculated by the following formula (3) based on A, B, and the cooling rate V is 1 to 1500. D=(A×B) 2 ×V (3)。 2. The manufacturing method according to claim 1, wherein The polyester film has a thickness of less than 50 μm.

3. The manufacturing method according to claim 1 or 2, wherein: A step of forming the particle-containing layer using a coating liquid containing the particles is further included between the longitudinal stretching step and the transverse stretching step, or The method further comprises forming the particle-containing layer by simultaneously extruding a second melt containing the particles and the binder together with the molten resin in the extrusion molding step.

4. The manufacturing method according to claim 1 or 2, wherein: The surface temperature T2 of the polyester film in the heat relaxation step is 210° C. or lower.

5. The manufacturing method according to claim 1 or 2, wherein: The above b is more than 0% and is 1.2% or less.

6. A polyester film comprising: Polyester substrate; and a particle-containing layer containing particles located on at least one surface of the polyester substrate, The particles contained in the particle-containing layer are inorganic particles, and the maximum peak height Rp of at least one surface of the polyester film is 5 nm to 200 nm, The thickness of the polyester film is less than 50 μm, The polyester film is conveyed at a conveying speed of 30 m / min and a tension in the conveying direction of 100 N / m, and is heated for 20 seconds at a surface temperature of 90° C., and the total area of ​​the stripe-like defect regions observed in the polyester film is less than 40% relative to the total area of ​​the observation area.

7. The polyester film according to claim 6, wherein The expansion rate of the polyester film in the width direction at 90° C. is −0.15% to 0.15% relative to the dimension of the polyester film in the width direction at 30° C.

8. The polyester film according to claim 6 or 7, wherein The density of the polyester film is 1.39 g / cm 3 ~1.41g / cm 3 .

9. The polyester film according to claim 6 or 7, wherein The thickness of the polyester substrate is 3 μm to 40 μm, The particle-containing layer has a thickness of 0.001 μm to 2.5 μm.

10. The polyester film according to claim 6 or 7, wherein The particle-containing layer contains particles P having an average particle diameter of 10 nm or more and less than 1 μm. The polyester film according to claim 10 , wherein The average particle size of the particles P is greater than the thickness of the particle-containing layer.

12. The polyester film according to claim 6 or 7, wherein The particle-containing layer contains particles P1 having an average particle diameter of 10 nm to 100 nm.

13. The polyester film according to claim 6 or 7, wherein The particle-containing layer contains particles P2 having an average particle diameter exceeding 100 nm and not more than 400 nm.

14. The polyester film according to claim 6 or 7, wherein The polyester substrate is substantially free of particles.

15. A laminated film comprising: A polyester film produced by the production method according to any one of claims 1 to 5 or the polyester film according to any one of claims 6 to 14, and having a particle-containing layer only on one surface of a polyester substrate; and The functional layer is located on the surface of the polyester substrate opposite to the particle-containing layer and is selected from a decorative layer, a photosensitive resin layer, and a release layer.

16. The laminated film according to claim 15, wherein The functional layer is a decorative layer, and the laminated film is a decorative film.

17. The laminated film according to claim 15, wherein The functional layer is a photosensitive resin layer, and the laminated film is a photosensitive transfer film.

18. The laminated film according to claim 15, wherein The functional layer is a release layer, and the laminated film is a release film for producing ceramic green sheets.

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