Oriented polyester film roll and method for manufacturing oriented polyester film roll

Abstract

To provide an oriented polyester film roll that has a good winding appearance when rolled up while suppressing defects (coating hash) when used as a process film.SOLUTION: An oriented polyester film roll obtained by rolling up an oriented polyester film is configured such that, in a range of 0.5 mm to 100 mm in the inner direction of the width direction from the edge of the film in the width direction, when the oriented polyester film is sized to the average value of the horizontal Feret's diameter and vertical Feret's diameter obtained by the cross-Nicol inspection, the number Fe of foreign particles of size 10 to 200 μm is 1 to 10 pieces per 10 m2 .SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to an oriented polyester film roll with excellent winding stability. [Background technology]

[0002] Polyester film is used in a wide variety of industrial applications due to its mechanical and thermal properties, stiffness, and cost-effectiveness. Recently, in particular, it has been used as a process film for electronic components, such as separators and protective films for liquid crystal polarizing plates, release substrates for interlayer insulating resins, and product protection materials. With the recent proliferation of smart devices, electric vehicles, autonomous driving, connected cars, and the Internet of Things, demand for electronic components is expected to remain strong even in the post-smartphone era. Furthermore, as smart devices become more detailed and miniaturized, there is a growing demand for higher quality process films.

[0003] Foreign matter on the film can lead to scratches, poor coating application, and contamination of subsequent processes. Examples of foreign matter adhering to the film include oligomers, amides, and film chips. Technologies aimed at reducing oligomers and film chips, which are typical foreign matter in polyester films, have been disclosed (Patent Documents 1-3). Furthermore, technologies specifying winding length, roll width, thickness, hardness, and slitting conditions for film rolls have been disclosed (Patent Documents 4 and 5). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2009-154252 [Patent Document 2] Japanese Patent Publication No. 2014-211561 [Patent Document 3] Japanese Patent Publication No. 2009-12242 [Patent Document 4] Japanese Patent Publication No. 2020-12086 [Patent Document 5] Japanese Patent Publication No. 2012-46736 [Overview of the project] [Problems that the invention aims to solve]

[0005] The inventors of this invention conducted thorough research on foreign matter adhering to the film surface and found that reducing the amount of specific foreign matter adhering to the film surface at the widthwise ends of the polyester film roll too much deteriorates the winding appearance of the film roll. On the other hand, they found that if the amount of foreign matter is too large, defects (coating repellency) when used as a process film worsen. Therefore, the objective of this invention is to provide an oriented polyester film roll that has good winding appearance when wound, while suppressing defects (coating repellency) when used as a process film. [Means for solving the problem]

[0006] In view of the above circumstances, the inventors conducted diligent studies and found that it is possible to obtain an oriented polyester film roll that is excellent in maintaining its rolled shape while suppressing problems when used as a process film, thus leading to the present invention.

[0007] In other words, a preferred embodiment of the present invention is as follows: (1) An oriented polyester film roll formed by winding an oriented polyester film, wherein the oriented polyester film has an average value of 10 to 200 μm for the horizontal and vertical ferret diameters obtained by cross-nicol inspection in the inward direction of the width direction from the end of the width direction, and the number of foreign objects Fe is 1 to 10 per 10m 2 An oriented polyester film roll. (2) The orientation polyester film roll according to (1), wherein the width of the orientation polyester film roll is 500 mm or more and 2000 mm or less. (3) The orientation polyester film roll according to (1) or (2), wherein the orientation angles at both ends in the width direction of the orientation polyester film are 7.0 degrees or less. (4) The orientation polyester film roll according to any one of (1) to (3), wherein the foreign matter includes polyester powder. (5) The oriented polyester film roll according to (4), wherein the polyester powder is polyester film chips generated when slitting a polyester film roll. (6) The number of foreign objects with a size of 10 to 200 μm present in the range from the center in the width direction to the 50 mm at both ends in the width direction of the oriented polyester film Fc (pieces / 10 m 2 An oriented polyester film roll according to any of (1) to (5), wherein, when this is the case, Fc / Fe is less than 1.0. (7) An oriented polyester film roll according to any of (1) to (6) used for release purposes. (8) An oriented polyester film roll according to any of (1) to (7) used for polarizing plate release applications. (9) A method for manufacturing an oriented polyester film roll, comprising the step of cutting an oriented polyester film with a circular blade, wherein when the radius of the circular blade is r, the angle at a position r / 100 from the cutting edge of the circular blade is θ1, and the angle at a position r / 30 from the cutting edge is θ2, the method for manufacturing an oriented polyester film roll according to any one of (1) to (8), satisfying 5° < θ2 < 20 < θ1 < 50°. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an oriented polyester film roll that has excellent winding stability while suppressing defects as a process film. [Brief explanation of the drawing]

[0009] [Figure 1] A top view of an example of a circular blade. [Figure 2] A cross-sectional view of the cutting edge of an example of a circular blade. [Figure 3]Schematic diagram showing the evaluation area during cross-Nicol inspection in the embodiment.

Mode for Carrying Out the Invention

[0010] Hereinafter, the present invention will be described in more detail.

[0011] The polyester in the oriented polyester film roll of the present invention is a polyester having dibasic acid and glycol as constituent components. As the aromatic dibasic acid, terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenyletherdicarboxylic acid, diphenylketonedicarboxylic acid, phenylindanedicarboxylic acid, sodium sulfoisophthalic acid, dibromoterephthalic acid, etc. can be used. As the alicyclic dibasic acid, oxalic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, dimer acid, etc. can be used. As the glycol, as the aliphatic diol, ethylene glycol, propylene glycol, tetramethylene glycol, propylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, diethylene glycol, etc. can be used, and as the aromatic diol, naphthalenediol, 2,2-bis(4-hydroxydiphenyl)propane, 2,2-bis(4-hydroxyethoxyphenyl)propane, bis(4-hydroxyphenyl)sulfone, hydroquinone, etc. can be used, and as the alicyclic diol, cyclohexanedimethanol, cyclohexanediol, etc. can be used.

[0012] The above polyester can be produced by known methods. It is preferable to use a polyester film having an intrinsic viscosity of 0.50 dl / g or more and 0.70 dl / g or less. The intrinsic viscosity of the polyester film is more preferably 0.55 dl / g or more and 0.64 dl / g or less. By setting the intrinsic viscosity of the polyester film within the above range, it becomes easy to provide a polyester powder on the surface of the end portion in the width direction of the film in the production method described later. The measurement of the intrinsic viscosity uses the value calculated by the following formula from the solution viscosity measured at 25°C in orthochlorophenol.

[0013] ηsp / C = [η] + K[η]2·C Here, ηsp = (solution viscosity / solvent viscosity) - 1, C is the mass of the dissolved polymer per 100 ml of the solvent (g / 100 ml, usually 1.2), and K is the Huggins constant (assumed to be 0.343). The solution viscosity and the solvent viscosity are measured using an Ostwald viscometer. The unit is shown as [dl / g].

[0014] The oriented polyester film in the oriented polyester film roll of the present invention is preferably a film oriented by biaxial stretching. The stretching method may be simultaneous biaxial stretching or sequential biaxial stretching. However, the oriented polyester film wound around the oriented polyester film roll of the present invention preferably has an orientation angle at both end portions in the width direction of 7.0 degrees or less, more preferably 5.0 degrees or less. By setting it within this range, in the cross Nicol inspection performed when using the polyester film of the present invention for the purpose of releasing a polarizing plate, the noise of the detected bright spot defect can be reduced and the inspection property becomes good. The orientation angles at both end portions in the width direction are determined by the method described in the examples.

[0015] The thickness of the oriented polyester film wound onto the oriented polyester film roll of the present invention is preferably 12 μm or more, more preferably 20 μm or more, and even more preferably 25 μm or more. It is also preferably 188 μm or less, more preferably 150 μm or less, and even more preferably 140 μm or less. A thickness of 12 μm or more provides sufficient stiffness during peeling, which can suppress film breakage when used as a process film. On the other hand, a thickness of 188 μm or less can suppress damage to the object to be peeled when used as a process film. Furthermore, the thickness variation is preferably 1.5 μm or less along the entire width of the oriented polyester film roll and 2.0 μm or less in the flow direction over 10 m. Note that the thickness variation refers to the maximum-minimum measurement.

[0016] The oriented polyester film wound onto the oriented polyester film of the present invention may contain particles. In this case, the volume-average particle size of the contained particles is preferably 1.3 μm or less. The particles used in this invention can be inorganic particles such as spherical silica, aggregated silica, calcium carbonate, aluminum oxide, barium titanate, and titanium oxide, or organic particles such as cross-linked polystyrene resin particles, cross-linked silicone resin particles, cross-linked acrylic resin particles, cross-linked styrene-acrylic resin particles, cross-linked polyester particles, polyimide particles, and melamine resin particles. It is desirable to select the type of particle as well as its particle size. Preferably, organic particles with high particle elasticity are used. Among the organic particles mentioned above, organic particles selected from cross-linked polystyrene resin particles, cross-linked silicone resin particles, cross-linked acrylic resin particles, cross-linked styrene-acrylic resin particles, and cross-linked polyester particles are particularly preferred. Among inorganic particles, spherical silica and aluminum oxide are particularly preferred.

[0017] The inventors' research revealed that when winding a film into a roll, if the film surface is too slippery, contact between the films becomes stronger, leading to a tendency for wrinkles and scratches to occur. They also found that blocking can occur between films when stored in a roll for a long period of time. The oriented polyester film roll of the present invention suppresses the occurrence of wrinkles, scratches, and blocking during winding by intentionally introducing foreign matter to the surface of the film's widthwise ends when winding the oriented polyester film into a roll, thereby achieving a good winding appearance. On the other hand, if there is too much foreign matter on the surface of the film's widthwise ends, problems may occur when using it as a process film (coating repellency, dents, process contamination).

[0018] In this invention, "foreign matter" refers to materials that are attached to and present on the film surface without being embedded in the film surface resin layer.

[0019] In this invention, the size of a foreign object refers to the average value of the vertical ferret diameter and horizontal ferret diameter of the detection image detected by cross-nicol examination.

[0020] The orientation polyester film roll of the present invention is an orientation polyester film roll formed by winding an orientation polyester film, wherein the orientation polyester film, in the range of 0.5 mm to 100 mm inward in the width direction from the end in the width direction, has an average value (size) of vertical and horizontal ferret diameters of the detection image detected by cross-nicol inspection of 10 to 200 μm, with the number of foreign objects Fe being 1 to 10 per 10 m. 2 This is an oriented polyester film roll. The number of Fe particles in this foreign matter will be determined by the method described in the examples.

[0021] By having a certain number of large foreign particles measuring 10 to 200 μm in size within a range of 0.5 mm to 100 mm from the widthwise edge of the oriented polyester film, it is possible to create a film roll that has excellent peeling function and excellent winding shape retention while suppressing defects (coating repulsion) when used as a process film. The number of foreign particles Fe measuring 10 to 200 μm is more preferably 2 to 10 particles / 10 m 2 And more preferably 5 to 8 pieces / m 2 That is the case.

[0022] The type of foreign matter on the oriented polyester film roll of the present invention is not particularly limited, but it is preferably a polyester powder and / or an amide compound, and more preferably a polyester powder. Since the polyester powder is the same material as the film, coating defects such as release layers are less likely to occur during coating, resulting in good coating properties.

[0023] There are no particular limitations on how the aforementioned polyester powder is present on the film, but it is preferable that it be polyester chips generated when the film is slit. By utilizing polyester chips generated when the film is slit, no special processes or equipment are required, resulting in low costs.

[0024] The oriented polyester film of the present invention has a number of foreign particles of size 10 to 200 μm present in the range from the center in the width direction to 50 mm on both sides in the width direction, Fc (particles / 10 m 2 When this is the case, a Fc / Fe ratio of less than 1.0 is preferable because it is excellent in maintaining the winding shape of the oriented polyester film roll of the present invention. By having the aforementioned large foreign matter at the widthwise end of the film, it is possible to improve air release from the film while mitigating the effects of film tightening. More preferably, Fc / Fe is 0.10 or more and 0.98 or less, and more preferably 0.20 or more and 0.95 or less. Fc shall be determined by the method (cross-nicol test) as described in the examples, similar to Fe.

[0025] The oriented polyester film roll of the present invention preferably has a film roll width of 500 to 2000 mm. More preferably, it is 600 to 1525 mm. This range makes it easier to achieve a good winding appearance. Furthermore, this range reduces losses in subsequent processes and reduces losses when used as a process film, which is preferable from the viewpoint of productivity and waste reduction.

[0026] Furthermore, the oriented polyester film wound onto the oriented polyester film roll of the present invention preferably has a winding length (length in the longitudinal direction of the film) of 3,000 to 15,000 m, and more preferably 5,000 m to 12,500 m. This range makes it easier to achieve a good winding appearance. Additionally, this range reduces losses in subsequent processes and reduces losses when used as a process film, which is preferable from the viewpoint of productivity and waste reduction.

[0027] Next, the method for producing the polyester film of the present invention will be described, but the present invention is not limited to such examples.

[0028] One method for incorporating particles into a polyester film is to disperse inert particles in a predetermined proportion in a slurry form in ethylene glycol, which is a diol component, and add this ethylene glycol slurry at any stage before the completion of polyester polymerization. When adding the particles, it is preferable to add the aqueous sol or alcohol sol obtained during synthesis without drying it first, as this improves particle dispersibility and suppresses the generation of coarse protrusions. Alternatively, a method of directly mixing the aqueous slurry of particles with a predetermined polyester pellet and supplying it to a vented twin-screw compounding extruder to knead it into polyester is also effective for the production of the present invention.

[0029] The particle-containing master pellets and pellets substantially free of particles, prepared in this manner, are mixed in a predetermined ratio, dried, and then supplied to a known melt lamination extruder. In the production of the polyester film of the present invention, single-screw or twin-screw extruders can be used. Furthermore, to eliminate the pellet drying process, a vented extruder equipped with a vacuum line can be used. In addition, a so-called tandem extruder can be used, in which the function of melting the pellets and the function of maintaining the molten pellets at a constant temperature are divided between the extruders.

[0030] The polymer, melted and extruded in the extruder, is filtered. Since even very small foreign particles can become large protrusion defects if they enter the film, it is effective to use a high-precision filter that captures more than 95% of foreign particles, for example, that are 3 μm or larger. Next, the polymer is extruded into a sheet through a slit-shaped slit die and cooled and solidified on a casting roll to create an unstretched film. For example, in the case of a three-layer lamination, three extruders and three manifolds or confluence blocks (for example, confluence blocks with a rectangular confluence section) are used to laminate the polymer into three layers, and the sheets are extruded from the die. The sheets extruded from the die are cooled on a casting roll to create an unstretched film.

[0031] The film, which has been cooled while in close contact with the casting roll, is separated from the casting roll using a release roll and guided to the next stretching process. The stretching method may be simultaneous biaxial stretching or sequential biaxial stretching.

[0032] When manufacturing the polyester film of the present invention using sequential stretching, the initial stretching in the longitudinal direction is important for suppressing the occurrence of scratches and thickness unevenness in the longitudinal direction, and the stretching temperature is 90°C to 130°C, preferably 100°C to 120°C. If the stretching temperature is lower than 90°C, the film is prone to tearing, and if the stretching temperature is higher than 130°C, the film surface is prone to thermal damage. Furthermore, from the viewpoint of preventing stretching unevenness and scratches, it is preferable to perform stretching in two or more stages, and the total stretching ratio is 2.8 times to 5.0 times in the length direction, preferably 3.3 times to 4.0 times, and 3.5 times to 5 times in the width direction, preferably 4.0 times to 4.5 times. When setting the longitudinal stretching ratio to the above values, it is desirable to set multiple stretching sections to make it less likely for the stretching roll and the film to slip, in order to suppress fluctuations in stretching tension due to slippage. In this case, it is preferable to keep the stretching ratio in a single stretching section at 3.0 times or less, as this ensures appropriate stretching tension. If the temperature and stretching ratio fall outside this range, problems such as uneven stretching or film breakage will occur, making it difficult to obtain the film of the present invention.

[0033] In sequential stretching, the longitudinal stretching process is prone to damage when the film slips due to the difference in peripheral speed between the roll and the film during contact between the film and the roll, and can also cause uneven thickness in the longitudinal direction. Therefore, a drive system that allows the peripheral speed of each roll to be set individually is preferred. In the longitudinal stretching process, the material of the transport roll is selected by either heating the unstretched film to above its glass transition point before stretching, or transporting it to the stretching zone while maintaining a temperature below the glass transition point and then heating it all at once during stretching. When heating the unstretched film to above its glass transition point before stretching, adhesion due to heating can induce uneven stretching. To prevent this, it is preferable to select from non-stick silicone rolls, ceramics, or Teflon®.

[0034] Next, the unstretched film is transported to the stretching zone while being kept at a temperature below the glass transition point. When heating the film all at once during stretching, it is preferable to use metal rolls with a surface roughness Ra of 0.2 μm to 0.6 μm, which have been surface-treated with hard chromium or tungsten carbide, for the transport rolls in the preheating zone, in order to suppress adhesion that can cause heat wrinkles.

[0035] Next, the uniaxially oriented film stretched in the longitudinal direction is heated to 90°C or higher but less than 120°C in a transverse stretcher, and then stretched in the width direction by 3.0 times or more but less than 6.0 times to obtain a biaxially oriented (biaxially oriented) film. When the stretching temperature is lower than 90°C and the stretching ratio is higher than 6.0 times, the orientation angle tends to decrease, but the film becomes more prone to tearing. Furthermore, in order to lower the orientation angle, it is preferable that the stretching ratio in the width direction is higher than the stretching ratio in the longitudinal direction. If the stretching ratio in the width direction is higher than the stretching ratio in the longitudinal direction, the molecular orientation within the film tends to tilt towards the longitudinal direction, which can make it difficult to control the orientation angle. In manufacturing the oriented polyester film roll of the present invention, stretching in the width direction is performed after stretching in the longitudinal direction. This is because if stretching in the longitudinal direction is performed after stretching in the width direction, the molecules will mainly orient strongly in the width direction after stretching in the width direction, but if stretching in the longitudinal direction is performed afterward, they will also orient in the longitudinal direction, resulting in a high orientation angle. This transverse stretcher uses self-circulation in each oven chamber to blow hot air onto the film, thereby raising the film's temperature and performing stretching and heat fixing. To prevent oligomers and volatile components precipitated from the heat-treated film from cooling and adhering to the oven, it is advisable to replace the air by supplying and exhausting air within the oven. When the supplied air merges with the circulating air, if the air temperature remains close to that of the outside air, temperature unevenness may occur in the combined air, potentially worsening thickness uniformity in the longitudinal and width directions. Therefore, it is preferable to heat the supplied air to the same temperature as the circulating air, or to a temperature commensurate with the capacity of the heat exchanger that heats the circulating air.

[0036] The polyester film of the present invention may be further re-stretched once or more times in each direction, or it may be re-stretched simultaneously in two axes. In this case, the transport rolls before re-stretching in the longitudinal direction may be heated to a temperature of 80°C to 100°C, or the film may be transported using unheated rolls. Furthermore, the re-stretching process may be passed without applying a stretching ratio. After re-stretching, transverse stretching is performed, and the film is heat-treated after stretching. This heat treatment can be performed in an oven, on heated rolls, or any other conventionally known method. The heat treatment temperature can usually be any temperature between 180°C and 230°C, preferably between 185°C and 210°C. If the heat treatment temperature is below 180°C, the heat treatment will be insufficient, and it will be difficult to control the thermal shrinkage rate. If the heat treatment temperature is higher than 230°C, bowing is likely to occur, making it difficult to control the orientation angle within the above range, which is undesirable. The heat treatment time is usually preferably between 1 second and 60 seconds. The heat treatment may be carried out while relaxing the film in its longitudinal and / or widthwise directions. After the heat treatment, it is preferable to relax the film in the widthwise direction by 0% to 10% at a temperature lower than the heat treatment temperature, between 0°C and 180°C.

[0037] After heat treatment, the film can be modified by providing, for example, an intermediate cooling zone or a slow cooling zone to adjust its dimensional change rate and flatness. In particular, to impart a specific thermal shrinkage property, the film may be relaxed in the longitudinal and / or transverse directions during or after the heat treatment in the intermediate cooling zone or slow cooling zone.

[0038] After biaxial stretching, the film is cooled in a conveying process, then the edges are cut and the film is wound to obtain an intermediate product. During this conveying process, the film thickness in the width direction is measured, and this data is used as feedback to adjust the film thickness by adjusting the die thickness, etc., and foreign matter can also be detected using a defect detector.

[0039] The intermediate product is slit to the appropriate width and length in a slitting process and wound onto a core to obtain a roll of polyester film. In this cutting process, 3 to 10 locations are simultaneously cut in the width direction of the intermediate product. Methods used for this cutting include cutting by shearing with a lower and upper blade, cutting using a razor blade in the air between pass lines, and cutting using a roll with an annular groove and a circular blade with the cutting edge inserted into the annular groove. From the viewpoint of having a small amount of polyester powder on the surface of the widthwise end of the polyester film, a method consisting of a grooved roll with an annular groove and a circular blade with the cutting edge inserted into the annular groove, which cuts the film conveyed on the grooved roll, is preferred (Japanese Patent Publication No. 2002-220153). With a razor blade, force is always applied to one location during cutting, so the blade deteriorates quickly and tends to generate a large amount of polyester powder. Therefore, in order to keep the amount of foreign matter at the end within the range of the present invention, it may be necessary to include a step to remove the foreign matter after cutting with a razor blade.

[0040] A preferred embodiment of the present invention relates to a method for manufacturing an oriented polyester film, comprising the step of cutting an oriented polyester film roll with a circular blade, wherein the method satisfies 5°<θ2<20°<θ1<50° when the radius of the circular blade is r, the angle at a position r / 100 from the cutting edge of the circular blade is θ1, and the angle at a position r / 30 from the cutting edge is θ2. In other words, it is preferable to use a circular blade for slitting the film. An example of a circular blade is shown in Figure 1. Since the circular blade rotates in accordance with the film being conveyed, it is less prone to deterioration and the amount of chips generated is less varied compared to a laser blade. In particular, it is preferable to have a circular blade that satisfies 5°<θ1<20°<θ2<50° when the angle at a position r / 100 from the cutting edge of a circular blade with radius r is θ1, and the angle at a position r / 30 from the cutting edge is θ2. In other words, it is preferable to have a circular blade with progressively different angles from the cutting edge. An example of the angles indicated by θ1 and θ2 is shown in Figure 2. If the θ2 at the tip of the blade is greater than 50°, the circular blade becomes thicker and there is a higher possibility that the circular blade will slip out of the film being transported, causing slitting defects, which may make it unsuitable for slitting. If θ2 is 20° or less, the blade may chip easily during slitting, and the amount of chips generated may increase. It is preferable that the circular blade is double-edged (i.e., the cross-section of the blade is symmetrical). It is also preferable that the r of the circular blade is between 10 and 100 mm.

[0041] The film slitting is preferably performed at a speed of 350 m / min or less, and the slitting blade depth is preferably 1.5 mm to 2.5 mm. The slitting blade depth refers to the distance from the cutting edge of the slitting blade inserted into the annular groove of the grooved roll to the insertion position. Preferably, the slitting speed is 150 m / min to 330 m / min, and the slitting blade depth is 1.5 mm to 2.0 mm. Setting the slitting blade depth to be greater than the above range can suppress the blade from slipping out of the film during slitting, resulting in poor cuts. Setting the slitting blade depth to be less than the above range can suppress deterioration of the winding shape due to an increased contact surface between the film and the blade or an increased accompanying airflow. Furthermore, setting the slitting blade depth to the above range makes it easy to apply the aforementioned size and amount of polyester powder to the surface of the widthwise end of the polyester film wound onto the polyester film roll.

[0042] During slitting, it is preferable to have a dust removal device for the slitting blade and a dust removal device for scattered foreign matter. By installing such dust removal devices, the number of foreign matter present on the surface of the widthwise end of the polyester film wound onto the polyester film roll can be controlled. The suction air velocity of the dust removal device for the slitting blade is preferably 10 m / s to 20 m / s. The suction air velocity of the dust removal device for scattered foreign matter is preferably 30 m / s to 50 m / s.

[0043] In the manufacturing process of the oriented polyester film roll of the present invention, it is preferable to include a step of bringing a cloth into contact with the surface of the film being conveyed at any given step. Including such a step makes it possible to wipe away and remove minute foreign matter adhering to the film surface. It is preferable that the film cleaning cloth be composed of long fibers. General rags and bleached cloths are composed of short fibers, and the fibers tend to fall off. Therefore, this can cause fiber dust to adhere to the film, potentially increasing the total number of minute foreign matter. Using long fibers as the cleaning cloth is preferable because it reduces the amount of fiber that falls off, and the fallen fibers remain on the film surface as relatively large foreign matter. Furthermore, it is preferable that the cleaning cloth be a woven fabric because it reduces the amount of fiber that falls off, and the fallen fibers remain on the film surface as relatively large foreign matter.

[0044] Furthermore, using a cloth with high-fiber fibers as a cleaning cloth may scrape off particles present on the film surface, leading to the accumulation of particle-aggregated dust on the film and potentially increasing the total number of foreign objects. Therefore, by using microfibers with low fiber density as a film cleaning cloth, it is possible to simultaneously reduce film adhesion and prevent the generation of fiber dust and particle-aggregated dust. This film cleaning cloth contact process can be applied at any stage of film manufacturing after the molten polymer has been formed into a sheet.

[0045] One factor determining the efficiency of foreign matter removal is the pressure applied to the cloth. For example, when this process is applied during slitting and before film winding, a pressure of 0.1 to 100 Pa, preferably 10 to 50 Pa, is highly efficient. Of course, these are not the only possible pressures, and they can be appropriately selected depending on the film formation speed, film thickness, application location, etc. [Examples]

[0046] The present invention will be described in detail below with reference to examples.

[0047] The measurement and evaluation methods related to the present invention are as follows.

[0048] (1) Orientation angle measurement Measurements were performed using a Nomura Trading Co., Ltd. orientation measuring instrument (SST-4000). A4-sized samples were cut from both ends of the film roll in the width direction where the inclination of the orientation axis was greatest relative to the width of the film roll. The longer side (297 mm) was cut parallel to the flow direction. The midpoint (105 mm) of the cut A4-sized sample was measured, and the orientation angle was defined as 0 degrees when the orientation axis was parallel to the film width direction. A clockwise inclination relative to the film width direction was defined as +, and a counterclockwise inclination as -, and the absolute value was taken as the measurement result. If the orientation angle values ​​differed at both ends, the larger value was recorded in the table.

[0049] (2) Cross-nicol test As equipment for evaluating the number of foreign particles adhering to the film surface, a cross-nicol inspection machine was used, which is equipped with a 550,000 Lux White LED as the illumination means and multiple cameras (Teledyne e2v Eliixa 16K CXP) with a resolution of 15 μm as the light receiving means.

[0050] In the camera's image sensor, the amount of light received was evaluated in 256 steps, with the darkest detectable state being 0 and the brightest detectable state being 255. The light source and each camera unit were equipped with angle-adjustable polarizing plates. The angle of the polarizing plates was changed in advance according to the orientation angle of the raw material to adjust the amount of light received in a state free of foreign matter across the entire inspection width. The angle of each polarizing plate was adjusted to minimize the amount of light received by each camera, so that the value of the amount of light received output from the image sensor was 20 or less in all cases. This value of the amount of light received was used as the base amount of light received.

[0051] Furthermore, the camera's aperture value is set so that it is in focus with the thickness of the film being inspected, and the inspection is performed at a film transport speed that provides a flow direction resolution of 15 μm.

[0052] To distinguish defects caused by internal foreign matters, the detection sensitivity of the camera was set as a constant value, and a filter was applied to the detected defects. Defects with a brightness of base light reception amount +30 or more and a size of 10 μm or more and 200 μm or less were counted as foreign matters. Here, the size is the average value of the vertical Feret diameter and the horizontal Feret diameter of the detected foreign matter. The inspection was carried out for 5900 m of the film from 100 m to 6000 m. That is, for Fe, 99.5 mm (from 0.5 mm from the outermost end in the width direction to 100 mm from the outermost end in the width direction) × 2 (both ends respectively) × 5900 m = 1174.1 m 2 was obtained from the area of. For Fc, 100 mm (50 mm on both sides in the width direction from the center in the width direction) × 5900 m = 59*.0 m 2 was obtained from the area of. The obtained values were rounded to the first decimal place.

[0053] (3) Collection of foreign matters by an adhesive roll The collection of foreign matters for elemental analysis described later in (4) was carried out using an adhesive roll. The adhesive roll (p-type adhesive roll manufactured by Teknek) was brought into contact with the polyester film for 1000 m in length to collect the adhered foreign matters on the film surface. The adhesive roll was rotated 10 times back and forth on a transfer film (dust sampler manufactured by NTT-ATCR) to transfer the adhered foreign matters from the adhesive roll to the transfer film. The transfer film with the adhered foreign matters was observed using a shape analysis laser microscope (VK-X250 manufactured by KEYENCE). The observation conditions were to automatically observe 81 fields at a measurement area of *00 μm × 530 μm using a 20-fold objective lens. This was repeated 9 times, and a total of 729 fields (= 280.7 mm 2 ) were observed. The center line of each field was calculated with 1024 × 768 pixels, the total number of measured pixels per field. Using a multi-file analysis application (VK-Xseries manufactured by KEYENCE), for each field, the threshold value (height of foreign matter) was set to 0.5 μm or more and the size (area of foreign matter) was set to 75 μm 2 or more, and for the detected protrusions, those with an average value of the vertical Feret diameter and the horizontal Feret diameter of *0 to 200 μm were collected as foreign matters.

[0054] (4) Elemental analysis (Fourier transform microscopic infrared spectroscopy (microscopic FT-IR method)) (3) The type of foreign substance was identified using a Fourier transform infrared spectrometer (Thermo Fisher Scientific Nicolet 6700).

[0055] (5) Rolled up For rolls wound under the conditions of the example, the determination is made based on the amount of displacement of the roll surface and end face as described below. ◎: Less than 1mm ○: 1mm or more and less than 3mm ×: 3mm or more.

[0056] (6) Applicability of the release layer A coating solution containing a cross-linked primer layer (BY24-846, manufactured by Toray Dow Corning Silicone Co., Ltd.) adjusted to a solid content of 1% by mass was applied and dried to the surface of a polyester film. The coating was then applied using a gravure coater to a dry coating thickness of 0.1 μm and dried and cured at 100°C for 20 seconds. Within one hour thereafter, a coating solution containing 100 parts by mass of addition-reaction type silicone resin (LTC750A, manufactured by Toray Dow Corning Silicone Co., Ltd.) and 2 parts by mass of platinum catalyst (SRX212, manufactured by Toray Dow Corning Silicone Co., Ltd.) adjusted to a solid content of 5% by mass was applied using a gravure coat to a dry coating thickness of 0.1 μm. After drying and curing at 120°C for 30 seconds, the film was wound up to obtain a release film.

[0057] The release film wound up as described above was unwound and visually inspected to check the coating condition. The area to be observed was 500 mm inward from the edge in the width direction of the film, and 500 mm in length. The release film was illuminated from the front with a 1,000 lux backlight unit, and the coating repellency was observed and evaluated as follows. ◎: No coating defects were observed within the observation area. ○: One to two instances of coating repellency were observed within the observed area. ×: Three or more coating defects were observed within the observation area.

[0058] (7) Bright spot Regarding bright spot defects obtained by crossed nicols examination The following criteria were used for evaluation. ◎: 0.01 bright spots / m² with a size of 100μm or larger. 2 The following applies: ○: 0.01-0.15 bright spots / m² with a size of 100 μm or larger. 2 That is the case. ×: 0.15 bright spots / m² with a size of 100 μm or larger. 2 That's all.

[0059] (8) Bent The oriented polyester film roll was unfurled at 2000m intervals from the surface and dents were visually inspected. The area observed was 500mm inward in the width direction from the edge of the film in the width direction, and 500mm in length. The number of small protruding defects observed on the film surface was evaluated as follows. ◎: One or fewer impact marks were observed within the observed area. ○: Two to three impact marks were observed within the observed area. ×: Four or more impact marks were observed within the observed area.

[0060] (Example 1) To 100 parts by mass of dimethyl terephthalate (DMT), 61 parts by mass of ethylene glycol (1.9 moles per mole of DMT), 0.05 parts by mass of magnesium acetate tetrahydrate, and 0.015 parts by mass of phosphoric acid were added and heated transesterified. Subsequently, 0.025 parts by mass of antimony trioxide was added, and the mixture was heated, the temperature was increased, and a polycondensation reaction was carried out under vacuum to obtain polyester pellets with an intrinsic viscosity of 0.62 that were substantially free of particles.

[0061] Next, the true specific gravity is 2.71 g / cm³. 3 Calcium carbonate with an average particle size of 1.0 μm was prepared and mixed with a 10% by mass ethylene glycol slurry. This slurry was dispersed using a jet agitator for one hour and then filtered with high precision using a filter with a collection efficiency of 95% and a particle size of 5 μm or larger. This slurry was added after transesterification, and the polycondensation reaction was carried out in the same manner as above to obtain a calcium carbonate-containing master pellet with an intrinsic viscosity of 0.62 and containing 1% calcium carbonate with an average particle size of 1.0 μm.

[0062] Next, a calcium carbonate-containing master pellet and a polyester pellet without particles were mixed to obtain polyester A containing 0.5% by mass of calcium carbonate and polyester B containing 0.054% by mass of calcium carbonate. The average intrinsic viscosity of polyester A and polyester B was 0.62.

[0063] Polyesters A and B were each dried under reduced pressure at 160°C for 8 hours to a moisture content of 100 ppm. They were then fed into separate extruders and melt-extruded at 275°C. After filtration with a high-precision filter of 5 μm or larger with a collection efficiency of 95%, the layers were combined and laminated in a rectangular three-layer confluence block to form a three-layer laminate consisting of polyester A / polyester B / polyester A. Subsequently, an electrostatic casting method was used, in which electrostatic charge was applied to the entire width of the unstretched film through a slit die maintained at 285°C. The film was then wound onto a casting drum with a surface temperature of 25°C and cooled and solidified to obtain an unstretched laminated film.

[0064] This unstretched laminated film was subjected to sequential stretching (longitudinal and widthwise). First, it was stretched longitudinally, and then stretched 3.8 times to obtain a uniaxially oriented film.

[0065] This uniaxially oriented film was stretched 4.0 times in the transverse direction at 110°C in a stenter, then heat-set at 190°C, during which it was relaxed by 3% in the width direction and cooled in the conveying process. After that, knurling was performed on the edges, and the outside of the knurled section was cut and wound up to obtain an intermediate product of biaxially oriented film with a thickness of 38 μm.

[0066] (4) Manufacturing of polyester film rolls The aforementioned biaxially oriented film was slit with a slitting blade set to a depth of 1.5 mm, and a polyester film roll was obtained by winding it onto a roll with a width of 1,500 mm and a length of 6,000 m at a speed of 250 m / min. A film cleaning cloth (Toray Industries, Inc.'s "Toraysee" PW (long fiber woven type)) was placed on the film to cover the entire width of the film, and foreign matter was wiped away.

[0067] (Examples 2-9, 12, Comparative Examples 1-3, 5-7) An oriented polyester film roll was obtained by following the same procedure as in Example 1, except that the raw materials and film-forming conditions were changed as shown in the table.

[0068] (Example 10) In Example 10, the procedure was carried out in the same manner as in Example 1, except that a film cleaning cloth was not installed during the slitting process, and an oriented polyester film roll was obtained.

[0069] (Example 11) In Example 11, the procedure was the same as in Comparative Example 7, except that after wiping with a film cleaning cloth, a polyester powder was sprinkled separately onto the polyester film to obtain an oriented polyester film roll.

[0070] (Comparative Example 4) In Comparative Example 4, the procedure was carried out in the same manner as in Example 1, except that the slitting process was changed to a cutting method in which a laser blade was used to cut the slits in the air between the pass lines, and an oriented polyester film roll was obtained.

[0071] (Example 12, Comparative Example 8) Except for using slitting blades with different cutting edge angles in the slitting process, the procedure was carried out in the same manner as in Example 1 to obtain an oriented polyester film roll.

[0072] [Table 1]

[0073] [Table 2] [Explanation of symbols]

[0074] 1. Evaluation domain when determining Fe Evaluation domain when determining 2 Fc

Claims

1. An oriented polyester film roll obtained by winding an oriented polyester film, wherein the number of foreign matters Fe having an average horizontal Feret diameter and a vertical Feret diameter of 10 to 200 μm obtained by a crossed Nicol inspection in a range of 0.5 mm to 100 mm inward in the width direction from the end of the oriented polyester film is 1 to 10 per 10 m. ２ A roll of oriented polyester film.

2. 2. The oriented polyester film roll according to claim 1, wherein the oriented polyester film roll has a width of 500 mm or more and 2000 mm or less.

3. 3. The oriented polyester film roll according to claim 1, wherein the orientation angle at each of both ends in the width direction of the oriented polyester film is 7.0 degrees or less.

4. The oriented polyester film roll according to claim 1 or 2, wherein the foreign matter comprises polyester powder.

5. 5. The oriented polyester film roll according to claim 4, wherein the polyester powder is polyester film chips generated when the polyester film roll is slit.

6. The number of foreign matters having a size of 10 to 200 μm present within a range from the center in the width direction of the oriented polyester film to 50 mm at both ends in the width direction is determined as Fc (pieces / 10 m ２ 3. The oriented polyester film roll according to claim 1, wherein Fc / Fe is less than 1.

0.

7. The oriented polyester film roll according to claim 1 or 2, which is used for releasing purposes.

8. The oriented polyester film roll according to claim 1 or 2, which is used for releasing a polarizing plate.

9. 3. The method for producing an oriented polyester film roll according to claim 1, comprising a step of cutting an oriented polyester film with a circular blade, wherein the radius of the circular blade is r, the angle at a position r / 100 from the edge of the circular blade is θ1, and the angle at a position r / 30 from the edge of the circular blade is θ2, and the relationship 5°<θ2<20<θ1<50° is satisfied.

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