Film roll, and method of manufacturing film roll

Abstract

To provide a film roll that can reduce winding troubles during transportation and during long-term storage and hold quality, and to provide a method of manufacturing the film roll, that enhances production yield and largely reduces also inspection load.SOLUTION: A film roll according to the present invention, in which a single layer optical film has been wound up, has an average maximum height difference (P-V)ave1 of a film thickness measured in a range of a diameter of 1000 mm using an arbitrary point in the optical film as a center is 0.15 to 0.40 μm, and a ratio (Dc / De) of an outer diameter Dc of a central portion of the film roll to an outer diameter De of an end portion is 0.98 to 1.02.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a film roll and a method for manufacturing a film roll. More specifically, the present invention relates to a film roll that is less prone to winding problems during transportation or long-term storage and that can maintain its quality. The present invention also relates to a method for producing the film roll, which has a high production yield and significantly reduces the inspection load. [Background technology]

[0002] Recently, there has been a demand for thinner image display devices, and optical protective films and optical functional films provided in image display devices such as liquid crystal displays (LCDs), organic electroluminescent displays (ELDs), and electronic paper are usually supplied to the next process in rolls, so there is also a demand for thinner optical films. Furthermore, optical films are also required to be longer and wider in order to improve production efficiency.

[0003] Since optical films are usually wound into a roll after production and stored or transported as a film roll, the following techniques are generally known as techniques for winding a film into a roll. (1) A technology for winding up optical film together with a protective film that prevents sticking. (2) A technology for winding optical films with an anti-blocking layer on one side to prevent sticking. (3) A technology that prevents the optical film from sticking to product components by winding up optical film that has been knurled in advance at the edge, and by incorporating an air layer when winding up the optical film.

[0004] Regarding the technology (1) above, there is a problem in that waste is generated by the protective film in the manufacturing process of products to which customers who use film rolls apply optical films. Furthermore, since the protective film is provided with an anti-blocking function using particles or the like, there is a problem in that the particles or the like can press into the product, causing dents or scratches in the optical film.

[0005] Regarding the technology (2) above, as with the protective film, there is a problem in that particles or the like can press into the product, causing dents or scratches in the optical film. In addition to the above, customers who use film rolls are also facing the problem of process contamination during transportation in the manufacturing process of products to which optical films are applied.

[0006] Regarding technology (3), there are problems such as the air layer trapped in the film roll escaping during product transportation or over time, causing warping, or the film roll core sticking, which makes the film roll core unusable and becomes waste, resulting in a large environmental impact.

[0007] Since the winding techniques (1) to (3) above have problems, various improvements are required for film rolls. In relation to the above problem, an invention has been disclosed in which the edges of an optical film are knurled to incorporate an air layer, thereby improving the uniformity within the optical film surface, thereby suppressing variations in retardation and improving display quality (see Patent Document 1). However, in the above invention, the knurling processing is applied to the ends of the film roll, which means that the roll diameter at the ends is larger than the roll diameter at the center. This means that the air layer escapes during product transportation and over time, and the knurling acts as a support, causing the roll to bend, resulting in a difference in the stress in the circumferential direction (longitudinal direction) of the roll and a deterioration in quality.

[0008] Given the above, there is a demand for film rolls that are resistant to external environments such as vibration degradation caused by transportation by truck or ship and the passage of time, can be supplied with almost the same quality as at the time of product shipment, can be procured with long-term product storage in mind, keep logistics costs down, and are of high quality from the core to the outside of the roll. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-254699 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention was made in consideration of the above problems and circumstances, and aims to provide a film roll that has few winding problems during transportation or long-term storage and can maintain quality, as well as a method for manufacturing such a film roll that has a high production yield and significantly reduces the inspection load. [Means for solving the problem]

[0011] In order to solve the above problem, the inventors have investigated the causes of the above problem and have come to the following conclusions. The inventors have found that the problem can be solved by controlling the film thickness and surface reflectance of the optical film within specific ranges, which led to the present invention. That is, the above-mentioned problems of the present invention are solved by the following means.

[0012] 1. A film roll in which a single-layer optical film is wound, The average maximum height difference (PV) of the film thickness within a 1000 mm diameter range centered on any point in the optical film ave1 is 0.15 to 0.40 μm, The ratio of the diameter of the center to the diameter of the end of the film roll (outer diameter of the center / outer diameter of the end) is 0.98 to 1.02. A film roll characterized by:

[0013] 2. A film roll in which a single-layer optical film is wound, The average maximum height difference (PV) of the film thickness within a 1000 mm diameter range centered on any point in the optical film ave1 is 0.15 to 0.40 μm, In addition, the reflectance of the central and end surfaces of the film roll is calculated based on CIE1976L * a * b * a defined by the color system * value and b * The value satisfies the following formula (1): Formula (1): -1.0<(end a * -Central part a * )+(end b * -Central part b * )<1.0 A film roll characterized by:

[0014] 3. The average maximum height difference (PV) of the film thickness measured in a direction oblique to the width direction of the optical film in the following order of steps 1 to 3 ave2 is 0.15 to 0.40 μm 3. The film roll according to claim 1 or 2. Step 1: After measuring the film thickness at any position on the end, measure the film thickness at a position moved 50 mm in the width direction and 620 mm in the length direction from the arbitrary position for each measurement, and repeat this process up to the other end to calculate the maximum height difference in each of the film thicknesses in the diagonal direction relative to the width direction of the optical film. Step 2: After completion of step 1, measurements similar to step 1 are carried out until the total distance of the longitudinal movement positions reaches 1000 m, and the maximum height difference of each film thickness in the diagonal direction relative to the width direction of the optical film is further calculated. Step 3: The average maximum difference in thickness (PV) of the optical film in the diagonal direction relative to the width direction from the maximum difference in thickness of the optical film in the diagonal direction relative to the width direction obtained in steps 1 and 2 ave2 Calculate.

[0015] 4. The average differential orientation angle θ within a 1000 mm diameter range centered on any point in the optical film ave ° and average differential film thickness d ave When μm is calculated, the average differential orientation angle θ ave ° and average differential film thickness d ave μm satisfies the following formula (2) Formula (2): 800<|average difference orientation angle θ ave / average differential film thickness d ave x10 -3 |<10000 4. The film roll according to any one of items 1 to 3, characterized in that:

[0016] 5. The optical film contains inorganic fine particles 5. The film roll according to any one of items 1 to 4, characterized in that:

[0017] 6. The width of the optical film is 2400 to 3000 mm. 6. The film roll according to any one of items 1 to 5,

[0018] 7. The length of the film roll is 7,500 to 10,000 m. 7. The film roll according to any one of items 1 to 6,

[0019] 8. A method for producing a film roll according to any one of items 1 to 7, The method includes at least a stretching step of stretching an optical film in a stretching furnace and a flattening treatment step, In the flattening treatment step, flattening is performed at a temperature 50 to 200° C. higher than the temperature in the drawing furnace. A method for producing a film roll, comprising:

[0020] 9. In the stretching step, the flattening treatment is performed using an infrared (IR) heater, and The heat quantity A at the center of the infrared (IR) heater at a distance of 100 mm and the average heat quantity B at the end satisfy the following formula (3): Formula (3): 0.2<(B / A)<0.6 9. The method for producing a film roll according to claim 8. [Effects of the Invention]

[0021] According to the above-mentioned means of the present invention, it is possible to provide a film roll that is less prone to winding failure during transportation or long-term storage and that can maintain its quality. It is also possible to provide a method for manufacturing the film roll, which has a high production yield and requires a significantly reduced inspection load.

[0022] The mechanism by which the effects of the present invention are manifested or the mechanism of action is not clear, but is speculated as follows.

[0023] Conventionally, as disclosed in Patent Document 1, when a person skilled in the art produces a film roll, from the viewpoint of industrial productivity, cost, etc., a method has been adopted in which the end of the optical film is knurled and the optical film is wound up while an air layer is trapped in the end.

[0024] The main functions of the knurling section are thought to be to prevent the optical film from sticking by trapping an air layer, and to prevent the film roll from slipping due to physical irregularities. Immediately after the knurled film roll is wound up (immediately after production), the aforementioned air layer prevents the optical films from sticking together. However, over time, the air in the air layer escapes during transportation by sea or truck, or when stored in a customer's warehouse, causing problems with the two functions mentioned above.

[0025] Not only during transportation, but also in rare cases, customers do not immediately start production using rolls stored in the warehouse, and in some cases the rolls are stored in the warehouse for long periods of time, which made it difficult to predict when the rolls would stick together, which was a problem.

[0026] FIG. 1A is a schematic diagram of a conventional film roll with knurled edges immediately after winding (immediately after production). FIG. 1B is an enlarged view of a portion A of the end of the film roll in FIG. 1A. FIG. 1C is an enlarged cross-sectional view of a portion B of the film having the uneven shape of the knurling process in FIG. 1B.

[0027] FIG. 2 is a schematic diagram showing the state of deflection of the film roll after a certain period of time has elapsed. Here, the inventors analyzed the steps in which optical films with knurled edges are stuck together. They found that in a film roll with knurled edges as shown in Figure 1A, the optical film is stacked in multiple layers during winding, increasing the knurling height (see Figure 1B), causing the edges to protrude as shown in Figure 1C, making the roll diameter at the edges larger than the roll diameter in the center. On the outer surface of the roll, as shown in Figure 2, the air in the air layer gradually escapes over time, but friction between the knurled edges prevents slippage during winding. However, it was found that under such an environment, the weight of the film roll itself causes deflection at the top and bottom of the film roll, and sticking begins to occur.

[0028] Next, FIG. 3 is a schematic diagram showing the core side of the film roll of FIG. 2 after a certain time has elapsed. When a film is rolled, the air in the air layer gradually escapes over time on the surface of the film that comes into contact with the core (hereinafter referred to as the core-side surface), causing several overlapping sticking areas (sticking failure; part D in Figure 3) as shown in Figure 3. In order to release the force, in addition to the micro-wrinkles (wrinkles) in the width direction as shown in Figure 3, sticking in the width direction with a longitudinal period (gradual failure; see part C in Figure 3) occurs.

[0029] Furthermore, in optical films with knurled edges, if priority is given to the function of preventing the optical film from sticking by incorporating an air layer, or the function of preventing misalignment due to physical unevenness, the air layer will have a strong impact on the film roll when subjected to vibrations that occur during transportation by truck, etc., making the film roll more susceptible to misalignment and being susceptible to seasonal fluctuations, which is thought to have made it extremely difficult to control and resulted in the problem not being solved.

[0030] On the other hand, in the present invention, an air layer is appropriately incorporated into a film roll on which a single-layer optical film is wound, and knurling is not performed on the edges, but rather, appropriate and minute contact is generated over the entire contact surface where the optical films face each other (to the extent that sticking is not noticeable), thereby dispersing the function of winding misalignment, which is an idea that is the opposite of conventional technology and has led to a solution to the problem.

[0031] That is, the optical film of the present invention has an average maximum peak-to-valley (PV) value of the film thickness measured within a range of 1000 mm in diameter centered on any point in the optical film. ave1 is 0.15 to 0.40 μm, and the ratio (Dc / De) of the outer diameter Dc of the central part of the film roll to the outer diameter De of the end part is 0.98 to 1.02, and the problem can be solved by this means.

[0032] That is, as shown in FIG. 4, the film roll of the present invention is not knurled at the edges, and the average maximum difference in film thickness across the entire film roll, that is, the film thickness difference, is small. This makes the air layer between the optical films uniform, and the upper side of the film roll is flat. Although the lower side of the film roll is also affected by its own weight, the sagging of the lower side is suppressed by eliminating the sagging of the upper side in the width direction.

[0033] Furthermore, on the surface of the optical film facing the core, stress is uniform in the circumferential direction (longitudinal direction) of the film roll, and in the width direction, stress concentration due to sticking caused by optical films coming into contact with each other around the convex portions of the optical films is suppressed.

[0034] Furthermore, unlike conventional optical films, which use an air layer taken in during winding to prevent contact across the entire width of the product, the optical film does not undergo knurling at the edges, and instead takes into account variations in the longitudinal direction, the average maximum peak-to-valley (PV) difference in film thickness in the diagonal direction relative to the width of the optical film is ave2 It is presumed that by controlling the amount of winding within a specific range, the function of preventing winding slippage can be distributed, thereby providing a film roll that has fewer winding problems during transportation and long-term storage and can maintain its quality. It is also believed that a method for manufacturing the film roll has been provided that has a high production yield and significantly reduces the inspection load.

[0035] The average maximum difference in film thickness (PV) in the diagonal direction relative to the width direction of the optical film ave2 However, if it is less than 0.15, sticking becomes noticeable immediately after winding, and if it is 0.40 or more, minute sticking occurs due to variations, and the problem is not solved. [Brief explanation of the drawings]

[0036] [Figure 1A] Schematic diagram of a film roll with knurled edges immediately after being wound up (immediately after production) [Figure 1B] An enlarged view of a portion A of the end of the film roll in FIG. 1A. [Figure 1C]Enlarged cross-sectional view of the film at part B of the knurled uneven shape in Figure 1B [Figure 2] Schematic diagram showing the deflection of a film roll after a certain period of time has passed [Figure 3] Schematic diagram showing how stress is applied to the core side of a film roll after a certain period of time has passed. [Figure 4] Schematic diagram of a film roll of the present invention [Figure 5] Flowchart showing the manufacturing process of the solution casting film-forming method [Figure 6] Schematic diagram of an apparatus for manufacturing optical films using the solution casting method [Figure 7] FIG. 1 is a plan view schematically illustrating the internal configuration of a tenter stretching device. [Figure 8] Side view of the three zones within the tenter stretching unit [Figure 9] Plan view of the three zones within the tenter stretching unit [Figure 10] Schematic diagram of the nozzle and heater installation area when viewing the three zones inside the tenter stretching machine from the front [Figure 11] 1 is a schematic diagram showing a process of winding an optical film and a cross section of the film roll of the present invention after winding. [Figure 12] Flowchart showing the manufacturing process of the melt casting film manufacturing method [Figure 13] Schematic diagram of an apparatus for manufacturing optical films by the melt-casting film-forming method DETAILED DESCRIPTION OF THE INVENTION

[0037] The film roll of the present invention is a film roll in which a single-layer optical film is wound, and has an average maximum peak-to-valley (PV) of the film thickness within a range of a diameter of 1000 mm from an arbitrary point in the optical film as a center. ave1 is 0.15 to 0.40 μm, and the ratio of the outer diameter of the center to the outer diameter of the end of the film roll (outer diameter of the center / outer diameter of the end) is 0.98 to 1.02. The above features enable the problem of the present invention to be solved.

[0038] In addition to the above characteristics, the film roll of the present invention has a reflectance of 1000 nm or less in accordance with CIE1976L, which is determined from the reflectance of the surface of the center and end portions of the film roll. * a * b * a defined by the color system * value and b * The value satisfies the above formula (1). The above-mentioned features not only solve the problems of the present invention but also improve the applicability of the optical film to display devices, particularly improving the contrast and the like.

[0039] The above two features are technical features common to or corresponding to the following embodiments.

[0040] In an embodiment of the present invention, the average maximum height difference (PV) of the film thickness measured in the order of steps 1 to 3 in a direction oblique to the width direction of the optical film is ave2 However, it is preferable that the thickness is 0.15 to 0.40 μm from the viewpoint of realizing the effects of the present invention.

[0041] The average differential orientation angle θ within a range of 1000 mm in diameter centered on any point in the optical film ave ° and average differential film thickness d ave When μm is calculated, the average differential orientation angle θ ave ° and average differential film thickness d ave It is preferable from the viewpoint of realizing the effects of the present invention that the above formula (2) be satisfied.

[0042] The optical film preferably contains inorganic fine particles from the viewpoints of adjusting the surface of the optical film to an appropriate uneven state and imparting low birefringence, and also from the viewpoints of improving heat-resistant storage properties and environmental stability.

[0043] The width of the optical film is preferably 2400 to 3000 mm from the viewpoint of thinning and productivity.

[0044] The length of the optical film is preferably 7500 to 10000 m from the viewpoint of thinning and productivity.

[0045] The method for producing a film roll of the present invention is a method for producing the film roll, and includes at least a stretching step of stretching an optical film in a stretching furnace, and a flattening step, wherein the flattening step is performed at a temperature that is 50 to 200°C higher than the temperature in the stretching furnace, and wherein the flattening step is performed using an infrared (IR) heater, and the heat amount A at the center and the average heat amount B at the ends, which are 100 mm apart from each other, preferably satisfy the formula (3) in terms of the flattening effect.

[0046] The present invention, its components, and embodiments for carrying out the present invention will be described in detail below. In this application, the symbol "to" is used to mean that the numerical values ​​before and after it are included as lower and upper limits.

[0047] 1. Overview of the film roll of the present invention The film roll of the present invention is a film roll in which a single-layer optical film is wound, and has an average maximum peak-to-valley (PV) of the film thickness within a range of a diameter of 1000 mm from an arbitrary point in the optical film as a center. ave1 The film roll is characterized in that the outer diameter is 0.15 to 0.40 μm, and the ratio of the outer diameter of the center to the outer diameter of the end of the film roll (outer diameter of the center / outer diameter of the end) is 0.98 to 1.02.

[0048] (Definition of terms) First, the meanings of the main terms used in the present invention will be explained below. Optical film thickness average maximum height difference (PV) ave1 " refers to the average value of the maximum height difference between the peaks and valleys of the unevenness of the thickness of the optical film measured and observed by film thickness measurement, which will be described later. By measuring the film thickness, the difference in height between the highest part of the convex structure and the lowest part of the concave structure of the optical film is calculated, and the average value is defined as (PV) ave1 It was decided.

[0049] The term "edge" refers to a region within a range of 15 to 30 mm inward from the end in the width direction of the optical film (roll).

[0050] The "central portion" refers to a region excluding both end portions in the width direction of the optical film.

[0051] The term "outer diameter" refers to the diameter of a circle formed at the outermost periphery of a film roll when the cross section perpendicular to the central axis (core) of the roll is taken as a circle. Therefore, the "outer diameter of the end portion" refers to the diameter (average value) of the circular cross section observed in the end portion region. The "outer diameter of the central portion" refers to the diameter of the circular cross section observed at the center point of the central portion.

[0052] In the examples of the present invention, the outer diameter of the film roll was measured with a tape measure at positions 30 mm from both ends in the width direction, and these were taken as the outer diameter of the end portions. The outer diameter of the end portion was determined as the average value of the outer diameters of both ends. Other methods can also be used to measure the outer diameter of the film roll. For example, the outer diameter can be measured by setting up a laser displacement meter (Keyence LK-G5000) so that the laser is irradiated onto the outer diameter at positions 30 mm from both ends of the film roll in the width direction and at the center position of the center.

[0053] (1.1) Shape of the Optical Film of the Present Invention The optical film of the present invention has an average maximum peak-to-valley (PV) value of the film thickness measured within a range of 1000 mm in diameter centered on any point in the optical film. ave1 However, it is 0.15 to 0.40 μm. The ratio (Dc / De) of the outer diameter Dc at the center of the film roll to the outer diameter De at the end is 0.98 to 1.02.

[0054] That is, as shown in FIG. 4, the film roll of the present invention is not knurled at the edges, and the average maximum difference in film thickness across the entire film roll, that is, the film thickness difference, is small. This makes the air layer between the optical films uniform, and the upper side of the film roll is flat. Although the lower side of the film roll is also affected by its own weight, the sagging of the lower side is suppressed by eliminating the sagging of the upper side in the width direction.

[0055] Furthermore, on the surface of the optical film facing the core, stress is uniform in the circumferential direction (longitudinal direction) of the film roll, and in the width direction, stress concentration due to sticking caused by optical films coming into contact with each other around the convex portions of the optical films is suppressed.

[0056] The average maximum difference in thickness (PV) of the film thickness measured in a diagonal direction relative to the width direction of the optical film in the following order of steps 1 to 3. ave2 From the viewpoint of solving the problems according to the present invention through the above-mentioned mechanism of action, it is preferable that the thickness of the film is 0.15 to 0.40 μm. Step 1: After measuring the film thickness at any position on the edge, measure the film thickness at a position moved 50 mm in the width direction and 620 mm in the length direction from the arbitrary position for each measurement, and repeat this process up to the other edge to calculate the maximum height difference in the diagonal direction. Step 2: After the end of step 1, measurements similar to step 1 are carried out until the total distance of the movement positions in the longitudinal direction reaches 1000 m, and the maximum height difference in the diagonal direction is further calculated. Step 3: The average maximum height difference (PV) of the film thickness in the diagonal direction from the maximum height difference in each diagonal direction obtained from steps 1 and 2 ave2 Calculate.

[0057] The average differential orientation angle θ within a range of 1000 mm in diameter centered on any point in the optical film ave ° and average differential film thickness d ave When μm is calculated, the average differential orientation angle θ ave ° and average differential film thickness d ave It is preferable from the viewpoint of exerting the effect that the thickness of the film and the thickness of the glass satisfy the following formula (2): Formula (2): 800<|average difference orientation angle θ ave / average differential film thickness d ave x10 -3 |<10000

[0058] Here, the average differential orientation angle θ ave " refers to the value obtained by measuring and calculating using the following method. That is, the orientation angle was measured at a position 5 mm in the width direction and 5 mm in the longitudinal direction from an arbitrary position at one end within a range of 1000 mm in diameter, with an arbitrary point within the optical film as the center, and this measurement was repeated up to the other end. Next, the average value of the absolute values ​​of the differences between adjacent orientation angles is calculated, and the average differential orientation angle θ ave °. The timing of the measurement was immediately before the winding process at room temperature in both the solution casting film-forming process and the melt casting film-forming process.

[0059] "Average differential film thickness d ave " refers to the value obtained by measuring and calculating using the following method. That is, with an arbitrary point within the optical film as the center, the film thickness was measured at a position moved 5 mm in the width direction and 5 mm in the length direction from an arbitrary position at one end within a range of a diameter of 1000 mm, and this measurement was repeated up to the other end. Next, the average of the absolute values ​​of the differences between adjacent film thicknesses is calculated, and the average difference film thickness d ave μm. The timing of the measurement was immediately before the winding process at room temperature in both the solution casting film-forming process and the melt casting film-forming process.

[0060] In the present invention, the average maximum height difference (PV) of the film thickness ave1 However, there is a slight difference in height in the longitudinal direction of 0.15 to 0.40, and |average differential orientation angle θ ave / average differential film thickness d ave x10 -3When the film roll has a relatively large value of | as described above, it is defined as an optical film having minute stress-relieved and non-stress-relieved portions in adjacent regions, and it can be inferred that, due to the properties of this optical film, when local sticking occurs, the non-stress-relieved portions perform local relaxation, thereby suppressing local sticking.

[0061] In addition, although the heat-treated portion reduces the average film thickness of the optical film, it also slightly disturbs the orientation angle, which is presumed to result in an optical film having minute stress-relieved portions and non-stress-relieved portions. Therefore, it is believed that some form of heat treatment will be necessary when a person skilled in the art prepares a film roll with reduced film thickness deviation. The process of keeping the above-mentioned predetermined range is called "flattening process," which will be described later.

[0062] The optical film preferably contains inorganic fine particles from the viewpoint of imparting low birefringence, improving heat-resistant storage stability, and improving environmental stability.

[0063] The width of the optical film is preferably within a range of 2400 to 3000 mm from the viewpoint of thinning and productivity.

[0064] From the viewpoint of thinning and productivity, it is preferable that the length of the film roll is within the range of 7500 to 10000 m.

[0065] (1.2) Color uniformity of optical film As another example of an embodiment of the film roll of the present invention, CIE1976L * a * b * a defined by the color system * value and b * The value satisfies the following formula (1). Satisfying these characteristics means that there is little difference in hue and saturation depending on the location on the optical film, and the color tone of the optical film is uniform overall, so the unevenness of the optical film surface is uniform, and when the optical film is applied to a display device, it is easy to obtain an image with good contrast, according to the perspective of solving the problem of the present invention.

[0066] Formula (1): -1.0<(end a * -Central part a * )+(end b * -Central part b * )<1.0 (In the above formula, a * The values ​​represent the hue and saturation in the color system and are coordinate values ​​that indicate the position of the red-green transition line. * The values ​​represent the hue and saturation in the color system and are coordinate values ​​that indicate the position of the yellow-blue transition line.

[0067] In addition, a * value and b * The value can be measured using a colorimeter, for example, Palette CUBE (manufactured by Palette Pty Ltd).

[0068] 2. Resins that make up optical films (2.1) Thermoplastic resin There are no limitations on the thermoplastic resin material used in the optical film of the present invention, as long as it can be handled as a film roll after film formation.

[0069] For example, thermoplastic resins used for polarizing plates include cellulose ester resins such as triacetyl cellulose (TAC), cellulose acetate propionate (CAP), and diacetyl cellulose (DAC); cyclic olefin resins (hereinafter also referred to as cycloolefin resins) such as cycloolefin polymers (cycloolefin resins (COP)); polypropylene resins such as polypropylene (PP); acrylic resins such as polymethyl methacrylate (PMMA); and polyester resins such as polyethylene terephthalate (PET).

[0070] In particular, in the case of optical films with a low elastic modulus, for example, resins with an elastic modulus of less than 3.0 GPa, it is difficult to relieve stress at multiple locations on the film when forming a film roll, making it difficult for the film to stretch and contract in the width direction and length direction.When the optical film is in a rolled state, the stress cannot be fully absorbed on the surface, making it prone to slippage during winding. Furthermore, from another perspective, when the optical film having the low elastic modulus is examined, if there is a difference in height between the longitudinal direction and the longitudinal direction of the optical film, the difference in the stretching and contracting of the optical film between the high points and the low points becomes large. Therefore, in the embodiment of the present invention, taking into consideration the variation in the longitudinal direction, the average maximum difference in thickness (PV) of the film thickness in the diagonal direction relative to the width direction of the optical film is ave1 It is preferable to control the modulus of elasticity within a specific range, and it is effective to apply this to a film roll using a low-elasticity resin, such as cycloolefin polymer (cycloolefin resin (COP)) or polymethyl methacrylate (acrylic resin (PMMA)), as the thermoplastic resin.

[0071] However, it is desirable to use a cycloolefin resin (COP) in terms of ease of control of stretchability and crystallinity, ease of penetration of adhesive, and ability to ensure better adhesion to the polarizer. The optical film may be subjected to a surface modification treatment after production.

[0072] Furthermore, the effect of the present invention is enhanced in the thin film region. The thickness of the optical film is preferably in the range of 5 to 80 μm, more preferably in the range of 10 to 65 μm, and even more preferably in the range of 10 to 45 μm. If the film thickness is 5 μm or more, the rigidity of the film roll is high, and it becomes easy to maintain the roll shape. If the film thickness is 80 μm or less, the mass does not increase too much, making it easier to produce a long film roll.

[0073] (2.1.1) Cycloolefin resin The cycloolefin resin contained in the film roll of the present invention is preferably a polymer of a cycloolefin monomer or a copolymer of a cycloolefin monomer and another copolymerizable monomer.

[0074] The cycloolefin monomer is preferably a cycloolefin monomer having a norbornene skeleton, and more preferably a cycloolefin monomer having a structure represented by the following general formula (A-1) or (A-2).

[0075] [ka]

[0076] In general formula (A-1), R 1 ~R 4 each independently represents a hydrogen atom, a hydrocarbon group having 1 to 30 carbon atoms, or a polar group, and p represents an integer of 0 to 2. 1 ~R 4 Not all of these represent hydrogen atoms at the same time, and R 1 and R 2 does not simultaneously represent a hydrogen atom, and R 3 and R 4 does not simultaneously represent a hydrogen atom.

[0077] In general formula (A-1), R 1 ~R 4 The hydrocarbon group having 1 to 30 carbon atoms represented by the formula (I) is preferably a hydrocarbon group having 1 to 10 carbon atoms, and more preferably a hydrocarbon group having 1 to 5 carbon atoms. The hydrocarbon group having 1 to 30 carbon atoms may further have a linking group containing, for example, a halogen atom, an oxygen atom, a nitrogen atom, a sulfur atom, or a silicon atom. Examples of such linking groups include divalent polar groups such as a carbonyl group, an imino group, an ether bond, a silyl ether bond, and a thioether bond. Examples of the hydrocarbon group having 1 to 30 carbon atoms include a methyl group, an ethyl group, a propyl group, and a butyl group.

[0078] In general formula (A-1), R 1 ~R 4 Examples of the polar group represented by the formula include a carboxy group, a hydroxy group, an alkoxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amido group, and a cyano group. Among these, a carboxy group, a hydroxy group, an alkoxycarbonyl group, and an aryloxycarbonyl group are preferred, and from the viewpoint of ensuring solubility during solution casting, an alkoxycarbonyl group and an aryloxycarbonyl group are more preferred.

[0079] In general formula (A-1), p is preferably 1 or 2 from the viewpoint of improving the heat resistance of the optical film. When p is 1 or 2, the resulting polymer becomes bulky and the glass transition temperature tends to be improved.

[0080] [ka]

[0081] In general formula (A-2), R 5 represents a hydrogen atom, a hydrocarbon group having 1 to 5 carbon atoms, or an alkylsilyl group having an alkyl group having 1 to 5 carbon atoms. 6 represents a carboxy group, a hydroxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amido group, a cyano group, or a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom). p represents an integer of 0 to 2.

[0082] R in general formula (A-2) 5 preferably represents a hydrocarbon group having 1 to 5 carbon atoms, and more preferably represents a hydrocarbon group having 1 to 3 carbon atoms.

[0083] R in general formula (A-2) 6preferably represents a carboxy group, a hydroxy group, an alkoxycarbonyl group or an aryloxycarbonyl group, and more preferably an alkoxycarbonyl group or an aryloxycarbonyl group from the viewpoint of ensuring solubility during solution casting.

[0084] In formula (A-2), p preferably represents 1 or 2, from the viewpoint of improving the heat resistance of the optical film. When p is 1 or 2, the resulting polymer becomes bulky and the glass transition temperature tends to be improved.

[0085] A cycloolefin monomer having a structure represented by general formula (A-2) is preferred from the viewpoint of improving solubility in organic solvents. In general, breaking the symmetry of an organic compound reduces its crystallinity, thereby improving its solubility in organic solvents. R in general formula (A-2) 5 and R 6 is substituted only on the ring-constituting carbon atoms on one side of the axis of symmetry of the molecule, and therefore the molecule has low symmetry. In other words, a cycloolefin monomer having a structure represented by general formula (A-2) has high solubility and is therefore suitable for producing an optical film by a solution casting method.

[0086] The content of the cycloolefin monomer having the structure represented by general formula (A-2) in the polymer of cycloolefin monomers can be, for example, 70 mol% or more, preferably 80 mol% or more, and more preferably 100 mol% relative to the total of all cycloolefin monomers constituting the cycloolefin resin. When the cycloolefin monomer having the structure represented by general formula (A-2) is contained in a certain amount or more, the orientation of the resin is enhanced, and the phase difference (retardation) value is likely to increase.

[0087] Specific examples of cycloolefin monomers having a structure represented by general formula (A-1) are shown below as exemplary compounds 1 to 14, and specific examples of cycloolefin monomers having a structure represented by general formula (A-2) are shown below as exemplary compounds 15 to 34.

[0088] [ka]

[0089] Examples of the copolymerizable monomer copolymerizable with the cycloolefin monomer include a copolymerizable monomer capable of ring-opening copolymerization with the cycloolefin monomer, and a copolymerizable monomer capable of addition copolymerization with the cycloolefin monomer.

[0090] Examples of copolymerizable monomers capable of ring-opening copolymerization include cycloolefins such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, and dicyclopentadiene.

[0091] Examples of copolymerizable monomers capable of addition copolymerization include unsaturated double bond-containing compounds, vinyl-based cyclic hydrocarbon monomers, and (meth)acrylates.

[0092] Examples of the unsaturated double bond-containing compound include olefinic compounds having 2 to 12 carbon atoms (preferably 2 to 8 carbon atoms), and examples thereof include ethylene, propylene, and butene.

[0093] Examples of the vinyl-based cyclic hydrocarbon monomer include vinylcyclopentene-based monomers such as 4-vinylcyclopentene and 2-methyl-4-isopropenylcyclopentene.

[0094] Examples of the (meth)acrylate include alkyl (meth)acrylates having 1 to 20 carbon atoms, such as methyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate.

[0095] The content of the cycloolefin monomer in the copolymer of a cycloolefin monomer and a copolymerizable monomer can be, for example, within the range of 20 to 80 mol %, preferably within the range of 30 to 70 mol %, relative to the sum of all monomers constituting the copolymer.

[0096] As described above, the cycloolefin resin is a polymer obtained by polymerizing or copolymerizing a cycloolefin monomer having a norbornene skeleton, preferably a cycloolefin monomer having a structure represented by general formula (A-1) or (A-2), and examples thereof include the following polymers (1) to (7).

[0097] (1) Ring-opening polymer of cycloolefin monomer (2) Ring-opening copolymers of cycloolefin monomers and copolymerizable monomers capable of ring-opening copolymerization with the cycloolefin monomers. (3) Hydrogenated ring-opening (co)polymer of (1) or (2) above (4) A (co)polymer obtained by cyclizing the ring-opening (co)polymer of (1) or (2) above by the Friedel-Crafts reaction and then adding hydrogen. (5) Saturated copolymer of cycloolefin monomer and unsaturated double bond-containing compound (6) Addition copolymers of cycloolefin monomers with vinyl cyclic hydrocarbon monomers and their hydrogenated products (7) Alternating copolymer of cycloolefin monomer and (meth)acrylate

[0098] The polymers (1) to (7) above can all be obtained by known methods, for example, the methods described in JP-A Nos. 2008-107534 and 2005-227606.

[0099] For example, the catalyst and solvent used in the ring-opening copolymerization (2) above may be those described in paragraphs 0019 to 0024 of JP-A No. 2008-107534. As the catalyst used for the hydrogenated products (3) and (6) above, for example, those described in paragraphs 0025 to 0028 of JP-A No. 2008-107534 can be used. The acidic compound used in the Friedel-Crafts reaction (4) above can be, for example, the one described in paragraph 0029 of JP-A No. 2008-107534. As the catalyst used in the addition polymerization of the above (5) to (7), for example, those described in paragraphs 0058 to 0063 of JP-A No. 2005-227606 can be used. The alternating copolymerization reaction (7) above can be carried out by, for example, the method described in paragraphs 0071 and 0072 of JP-A No. 2005-227606.

[0100] Among these, the polymers (1) to (3) and (5) are preferred, and the polymers (3) and (5) are more preferred.

[0101] That is, the cycloolefin-based resin preferably contains at least one of a structural unit represented by the following general formula (B-1) and a structural unit represented by the following general formula (B-2), in order to increase the glass transition temperature and light transmittance of the resulting cycloolefin-based resin, and more preferably contains only a structural unit represented by the general formula (B-2), or contains both a structural unit represented by the general formula (B-1) and a structural unit represented by the general formula (B-2).

[0102] The structural unit represented by general formula (B-1) is a structural unit derived from the cycloolefin monomer represented by the above-mentioned general formula (A-1), and the structural unit represented by general formula (B-2) is a structural unit derived from the cycloolefin monomer represented by the above-mentioned general formula (A-2).

[0103] [ka]

[0104] In the general formula (B-1), X represents -CH=CH- or -CH2CH2-. 1 ~R 4 and p are R in general formula (A-1), 1 ~R 4 and p.

[0105] [ka]

[0106] In the general formula (B-2), X represents -CH=CH- or -CH2CH2-. 5 ~R 6and p are R in general formula (A-2), 5 ~R 6 and p.

[0107] The cycloolefin resin according to the present invention may be a commercially available product. Examples of commercially available cycloolefin resins include Arton G (for example, G7810), Arton F, Arton R (for example, R4500, R4900, and R5000), and Arton RX, all manufactured by JSR Corporation.

[0108] The intrinsic viscosity [η]inh of cycloolefin resin is 0.2 to 5 cm when measured at 30°C. 3 / g, and 0.3 to 3 cm 3 / g, and more preferably in the range of 0.4 to 1.5 cm 3 It is more preferable that the content is in the range of / g.

[0109] The number average molecular weight (Mn) of the cycloolefin resin is preferably within a range of 8,000 to 100,000, more preferably within a range of 10,000 to 80,000, and even more preferably within a range of 12,000 to 50,000.

[0110] The weight average molecular weight (Mw) of the cycloolefin resin is preferably within a range of 20,000 to 300,000, more preferably within a range of 30,000 to 250,000, and even more preferably within a range of 40,000 to 200,000.

[0111] The number average molecular weight and weight average molecular weight of the cycloolefin resin can be measured in terms of polystyrene by gel permeation chromatography (GPC).

[0112] (Gel Permeation Chromatography) Solvent: methylene chloride Column: Shodex K806, K805, K803G (three columns connected together, manufactured by Showa Denko K.K.) Column temperature: 25℃ Sample concentration: 0.1% by mass Detector: RI Model 504 (GL Sciences) Pump: L6000 (Hitachi, Ltd.) Flow rate: 1.0ml / min Calibration curve: A calibration curve was used using 13 samples of standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) in the range of Mw=500 to 2,800,000. It is preferable to use the 13 samples at approximately equal intervals.

[0113] When the intrinsic viscosity [η]inh, number average molecular weight and weight average molecular weight are within the above ranges, the cycloolefin resin has good heat resistance, water resistance, chemical resistance, mechanical properties and moldability into a film.

[0114] The glass transition temperature (Tg) of the cycloolefin resin is usually 110°C or higher, preferably in the range of 110 to 350°C, more preferably in the range of 120 to 250°C, and even more preferably in the range of 120 to 220°C.

[0115] When the glass transition temperature (Tg) is 110°C or higher, deformation under high temperature conditions is easily suppressed. On the other hand, if the glass transition temperature (Tg) is 350° C. or lower, molding is easy and deterioration of the resin due to heat during molding is easily suppressed.

[0116] The content of the cycloolefin resin is preferably 70% by mass or more, and more preferably 80% by mass or more, based on the film.

[0117] (2.1.2) Acrylic resin The acrylic resin according to the present invention is a polymer of an acrylic acid ester or a methacrylic acid ester, and also includes copolymers with other monomers. Therefore, the acrylic resin according to the present invention also includes methacrylic resin.

[0118] The resin is not particularly limited, but is preferably one containing methyl methacrylate units in the range of 50 to 99% by mass and other monomer units copolymerizable therewith in the range of 1 to 50% by mass.

[0119] Other units constituting the acrylic resin formed by copolymerization include alkyl methacrylates having 2 to 18 carbon atoms in the alkyl group, alkyl acrylates having 1 to 18 carbon atoms in the alkyl group, hydroxyalkyl acrylates such as isobornyl methacrylate and 2-hydroxyethyl acrylate, α,β-unsaturated acids such as acrylic acid and methacrylic acid, acrylamides such as acryloylmorpholine and N-hydroxyphenylmethacrylamide, unsaturated group-containing dicarboxylic acids such as N-vinylpyrrolidone, maleic acid, fumaric acid, and itaconic acid, aromatic vinyl compounds such as styrene and α-methylstyrene, α,β-unsaturated nitriles such as acrylonitrile and methacrylonitrile, maleic anhydride, maleimide, N-substituted maleimide, glutarimide, and glutaric anhydride.

[0120] Examples of copolymerizable monomers that form units obtained by excluding glutarimide and glutaric anhydride from the above units include monomers corresponding to the above units.

[0121] That is, examples of the monomer include alkyl methacrylates having 2 to 18 carbon atoms in the alkyl group, alkyl acrylates having 1 to 18 carbon atoms in the alkyl group, hydroxyalkyl acrylates such as isobornyl methacrylate and 2-hydroxyethyl acrylate, α,β-unsaturated acids such as acrylic acid and methacrylic acid, acrylamides such as acryloylmorpholine and N-hydroxyphenylmethacrylamide, unsaturated group-containing dicarboxylic acids such as N-vinylpyrrolidone, maleic acid, fumaric acid, and itaconic acid, aromatic vinyl compounds such as styrene and α-methylstyrene, α,β-unsaturated nitriles such as acrylonitrile and methacrylonitrile, maleic anhydride, maleimide, and N-substituted maleimide.

[0122] Furthermore, glutarimide units can be formed, for example, by reacting an intermediate polymer having a (meth)acrylic acid ester unit with a primary amine (imidizing agent) to effect imidization (see JP-A No. 2011-26563).

[0123] The glutaric anhydride units can be formed, for example, by heating an intermediate polymer having (meth)acrylic acid ester units (see Japanese Patent No. 4961164).

[0124] Of the above structural units, it is particularly preferred that the acrylic resin according to the present invention contains isobornyl methacrylate, acryloylmorpholine, N-hydroxyphenylmethacrylamide, N-vinylpyrrolidone, styrene, hydroxyethyl methacrylate, maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride, or glutarimide, from the viewpoint of mechanical strength.

[0125] The acrylic resin according to the present invention preferably has a weight average molecular weight (Mw) in the range of 50,000 to 1,000,000, more preferably in the range of 100,000 to 1,000,000, and particularly preferably in the range of 200,000 to 800,000, from the viewpoint of controlling dimensional changes due to changes in the environmental temperature and humidity, and from the viewpoint of improving peelability from metal supports during film production, drying properties in organic solvents, heat resistance, and mechanical strength.

[0126] If it is 50,000 or more, the heat resistance and mechanical strength are excellent, and if it is 1,000,000 or less, the peelability from the metal support and the drying property of the organic solvent are excellent.

[0127] The method for producing the acrylic resin according to the present invention is not particularly limited, and any of the known methods such as suspension polymerization, emulsion polymerization, bulk polymerization, and solution polymerization may be used.

[0128] Here, as the polymerization initiator, ordinary peroxide-based and azo-based initiators can be used, and also redox-based initiators can be used.

[0129] The polymerization temperature may be within a range of 30 to 100°C for suspension or emulsion polymerization, and within a range of 80 to 160°C for bulk or solution polymerization.

[0130] In order to control the reduced viscosity of the resulting copolymer, the polymerization may be carried out using an alkyl mercaptan or the like as a chain transfer agent.

[0131] The glass transition temperature (Tg) of the acrylic resin is preferably within the range of 80 to 120°C from the viewpoint of maintaining the mechanical strength of the film.

[0132] As the acrylic resin according to the present invention, commercially available products can also be used. Examples include Delpet 60N, 80N, 980N, and SR8200 (all manufactured by Asahi Kasei Chemicals Corporation), Dianal BR52, BR80, BR83, BR85, BR88, EMB-143, EMB-159, EMB-160, EMB-161, EMB-218, EMB-229, EMB-270, and EMB-273 (all manufactured by Mitsubishi Rayon Co., Ltd.), KT75, TX400S, and IPX012 (all manufactured by Denki Kagaku Kogyo Co., Ltd.), and the like. Two or more types of acrylic resins can also be used in combination.

[0133] The acrylic resin according to the present invention preferably contains an additive, and as an example of the additive, it is preferable to contain acrylic particles (rubber elastomer particles) described in WO 2010 / 001668 in order to improve the mechanical strength of the film and adjust the dimensional change rate.

[0134] Examples of commercially available products of such multilayered acrylic granular composites include "Metablen W-341" manufactured by Mitsubishi Rayon Co., Ltd., "Kane Ace" manufactured by Kaneka Corporation, "Paraloid" manufactured by Kureha Corporation, "Acryloid" manufactured by Rohm and Haas Company, "Staphyloid" manufactured by Aica Corporation, Chemisnow MR-2G, MS-300X (all manufactured by Soken Chemical & Engineering Co., Ltd.), and "Parapet SA" manufactured by Kuraray Co., Ltd., and these may be used alone or in combination.

[0135] The volume average particle size of the acrylic particles is 0.35 μm or less, preferably in the range of 0.01 to 0.35 μm, and more preferably in the range of 0.05 to 0.30 μm. If the particle size is equal to or larger than a certain level, the film can be easily stretched under heat, and if the particle size is equal to or smaller than a certain level, the transparency of the resulting film is less likely to be impaired.

[0136] From the viewpoint of flexibility, the optical film of the present invention preferably has a flexural modulus (JIS K7171) of 10.5 GPa or less. This flexural modulus is more preferably 1.3 GPa or less, and even more preferably 1.2 GPa or less. The flexural modulus varies depending on the type and amount of acrylic resin and rubber elastic particles in the film. For example, the greater the content of rubber elastic particles, the smaller the flexural modulus generally becomes.

[0137] Furthermore, when a copolymer of alkyl methacrylate and alkyl acrylate or the like is used as the acrylic resin, the flexural modulus is generally smaller than when a homopolymer of alkyl methacrylate is used.

[0138] (2.1.3) Cellulose ester resin In the film roll of the present invention, it is also preferable to use a cellulose ester resin.

[0139] The cellulose ester used in the present invention refers to a cellulose acylate resin in which some or all of the hydrogen atoms of the hydroxyl groups (-OH) at the 2nd, 3rd, and 6th positions in the β-1,4-bonded glucose units that constitute cellulose are substituted with acyl groups.

[0140] The cellulose ester used is not particularly limited, but is preferably an ester of a linear or branched carboxylic acid having about 2 to 22 carbon atoms. The carboxylic acid constituting the ester may be an aliphatic carboxylic acid, may form a ring, or may be an aromatic carboxylic acid.

[0141] Examples include cellulose esters in which the hydrogen atom of the hydroxy group portion of cellulose is substituted with an acyl group having 2 to 22 carbon atoms, such as an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, a valeryl group, a pivaloyl group, a hexanoyl group, an octanoyl group, a lauroyl group, or a stearoyl group.

[0142] The carboxylic acid (acyl group) constituting the ester may have a substituent. The carboxylic acid constituting the ester is preferably a lower fatty acid having 6 or less carbon atoms, more preferably a lower fatty acid having 3 or less carbon atoms. The cellulose ester may contain a single type of acyl group or a combination of multiple acyl groups.

[0143] Specific examples of preferred cellulose esters include cellulose acetates such as diacetyl cellulose (DAC) and triacetyl cellulose (TAC), as well as mixed fatty acid esters of cellulose to which a propionate group or a butyrate group is bonded in addition to an acetyl group, such as cellulose acetate propionate (CAP), cellulose acetate butyrate, and cellulose acetate propionate butyrate. These cellulose esters may be used singly or in combination of two or more kinds.

[0144] (Type of acyl group, degree of substitution) By adjusting the type and degree of substitution of the acyl group of the cellulose ester, it is possible to control the humidity fluctuation of the retardation within a desired range, and to improve the uniformity of the film thickness.

[0145] The smaller the substitution degree of the acyl group in the cellulose ester, the more improved the retardation is, and thus the thinner the film can be made. On the other hand, if the degree of substitution of the acyl group is too small, the durability may be deteriorated, which is undesirable.

[0146] On the other hand, the greater the substitution degree of the acyl group in the cellulose ester, the less retardation is exhibited, so it is necessary to increase the stretching ratio during film formation. However, it is difficult to achieve uniform stretching at a high stretching ratio, which results in greater (worsening) variation in film thickness. Furthermore, the Rt humidity fluctuation, which is the retardation (phase difference) in the thickness direction, occurs when water molecules coordinate with the carbonyl groups of cellulose, so the higher the degree of acyl group substitution, i.e., the more carbonyl groups there are in the cellulose, the worse the Rt humidity fluctuation tends to be.

[0147] The total degree of substitution of the cellulose ester is preferably within the range of 2.1 to 2.5. By setting the temperature in this range, environmental fluctuations (especially Rt fluctuations due to humidity) can be suppressed, and the uniformity of the film thickness can be improved. More preferably, it is in the range of 2.2 to 2.45, from the viewpoint of improving the flowability and stretchability during film formation and further improving the uniformity of the film thickness.

[0148] More specifically, the cellulose ester satisfies both of the following formulae (a) and (b): In the formulae (a) and (b), X is the degree of substitution of the acetyl group, and Y is the degree of substitution of the propionyl group or the butyryl group, or the degree of substitution of a mixture thereof.

[0149] Formula (a): 2.1≦X+Y≦2.5 Formula (b): 0≦Y≦1.5

[0150] The cellulose ester is preferably cellulose acetate (Y=0) or cellulose acetate propionate (CAP) (Y: propionyl group, Y>0), and more preferably cellulose acetate where Y=0 in order to reduce film thickness variations.

[0151] A particularly preferred cellulose acetate is cellulose diacetate (DAC) having a value of 2.1≦X≦2.5 (more preferably 2.15≦X≦2.45) in order to keep retardation expression, Rt humidity fluctuation, and film thickness variation within desired ranges.

[0152] When Y>0, cellulose acetate propionate (CAP) is particularly preferably used, where X satisfies 0.95≦X≦2.25, 0.1≦Y≦1.2, and 2.15≦X+Y≦2.45.

[0153] By using the above-mentioned cellulose acetate or cellulose acetate propionate, a film roll having excellent retardation, mechanical strength, and resistance to environmental changes can be obtained.

[0154] The degree of acyl substitution indicates the average number of acyl groups per glucose unit, and indicates how many hydrogen atoms of the hydroxy groups at the 2nd, 3rd, and 6th positions of one glucose unit are substituted with acyl groups. Therefore, the maximum degree of substitution is 3.0, which means that all of the hydrogen atoms of the hydroxy groups at the 2-, 3-, and 6-positions are substituted with acyl groups. These acyl groups may be substituted evenly at the 2-, 3- and 6-positions of the glucose units, or may be substituted with a distribution. The degree of substitution is determined by the method specified in ASTM-D817-96.

[0155] To obtain desired optical properties, cellulose acetates having different degrees of substitution may be mixed and used. In the above case, the mixing ratio of different cellulose acetates is not particularly limited.

[0156] The number average molecular weight (Mn) of cellulose ester is 2×10 4 ~3×10 5 in the range of 2×10 4 ~1.2×10 5 in the range of 4×10 4 ~8×10 4 Within this range, the mechanical strength of the resulting film roll is increased, which is preferable.

[0157] The number average molecular weight Mn of the cellulose ester is calculated by measurement using gel permeation chromatography (GPC) under the above-mentioned measurement conditions.

[0158] The weight average molecular weight (Mw) of the cellulose ester is 2 × 10 4 ~1×10 6 in the range of 2×10 4 ~1.2×10 5 in the range of 4×10 4 ~8×10 4 It is preferable that the thickness is within this range in view of increasing the mechanical strength of the resulting film roll.

[0159] The raw cellulose for the cellulose ester is not particularly limited, but examples thereof include cotton linter, wood pulp, and kenaf. The cellulose esters obtained from these materials can be mixed and used in any desired ratio.

[0160] Cellulose esters such as cellulose acetate and cellulose acetate propionate can be produced by known methods.

[0161] Generally, the raw material cellulose is mixed with a specific organic acid (acetic acid, propionic acid, etc.), an acid anhydride (acetic anhydride, propionic anhydride, etc.), and a catalyst (sulfuric acid, etc.), and the cellulose is esterified, and the reaction is continued until a cellulose triester is produced.

[0162] In triesters, the three hydroxy groups of the glucose unit are replaced with the acyl group of an organic acid.

[0163] When two kinds of organic acids are used at the same time, mixed ester type cellulose esters, such as cellulose acetate propionate and cellulose acetate butyrate, can be prepared.

[0164] Next, the cellulose triester is hydrolyzed to synthesize a cellulose ester resin having a desired degree of acyl substitution. Thereafter, the cellulose ester resin is completed through steps such as filtration, precipitation, washing with water, dehydration, drying, etc. Specifically, the cellulose ester resin can be synthesized by referring to the method described in JP-A-10-45804.

[0165] (2.2) Other additives The film roll of the present invention may contain the following additives in addition to the above-mentioned thermoplastic resin.

[0166] (2.2.1) Plasticizers The film roll of the present invention preferably contains at least one plasticizer for the purpose of imparting processability to, for example, a polarizing plate protective film. The plasticizers are preferably used alone or in combination.

[0167] Among plasticizers, it is preferable to include at least one plasticizer selected from the group consisting of sugar esters, polyesters, and styrene-based compounds, from the viewpoint of achieving both effective control of moisture permeability and high compatibility with base resins such as cellulose esters.

[0168] The molecular weight of the plasticizer is preferably 15,000 or less, more preferably 10,000 or less, from the viewpoint of achieving both improved resistance to moist heat and compatibility with base resins such as cellulose esters.

[0169] When the compound having a molecular weight of 10,000 or less is a polymer, it preferably has a weight average molecular weight (Mw) of 10,000 or less. The weight average molecular weight (Mw) is preferably in the range of 100 to 10,000, and more preferably in the range of 400 to 8,000.

[0170] In particular, to obtain the effects of the present invention, it is preferable to contain the compound having a molecular weight of 1500 or less in an amount within the range of 6 to 40 parts by mass, and more preferably within the range of 10 to 20 parts by mass, per 100 parts by mass of the base resin. By containing the component within the above range, it is possible to effectively control the moisture permeability and also to ensure compatibility with the base resin, which is preferable.

[0171] <Sugar ester> The film roll of the present invention may contain a sugar ester compound for the purpose of preventing hydrolysis. Specifically, the sugar ester compound may be a sugar ester having 1 to 12 of at least one kind of pyranose structure or furanose structure, in which all or part of the OH groups of the structure have been esterified.

[0172] <polyester> The film roll of the present invention may contain polyester.

[0173] The polyester is not particularly limited, but examples thereof include a polymer (polyester polyol) having a terminal hydroxy group that can be obtained by a condensation reaction between a dicarboxylic acid or an ester-forming derivative thereof and a glycol, and a polymer (terminal-capped polyester) in which the terminal hydroxy group of the polyester polyol is capped with a monocarboxylic acid. The ester-forming derivatives referred to here include esters of dicarboxylic acids, dicarboxylic acid chlorides, and dicarboxylic acid anhydrides.

[0174] <Styrene-based compounds> In the film roll of the present invention, a styrene-based compound may be used in addition to or instead of the sugar ester and polyester for the purpose of improving the water resistance of the optical film.

[0175] The styrene-based compound may be a homopolymer of a styrene-based monomer, or a copolymer of a styrene-based monomer and another copolymerizable monomer. The content of structural units derived from styrene monomers in the styrene compound is preferably within a range of 30 to 100 mol %, more preferably within a range of 50 to 100 mol %, so that the molecular structure has a certain level of bulkiness.

[0176] Examples of styrene-based monomers include styrene; alkyl-substituted styrenes such as α-methylstyrene, β-methylstyrene, and p-methylstyrene; halogen-substituted styrenes such as 4-chlorostyrene and 4-bromostyrene; hydroxystyrenes such as p-hydroxystyrene, α-methyl-p-hydroxystyrene, 2-methyl-4-hydroxystyrene, and 3,4-dihydroxystyrene; vinylbenzyl alcohols; alkoxy-substituted styrenes such as p-methoxystyrene, p-tert-butoxystyrene, and m-tert-butoxystyrene; 3-vinylbenzoic acid, 4-vinylbenzoic acid, and the like. vinylbenzoates such as benzoic acid; 4-vinylbenzyl acetate; 4-acetoxystyrene; amidostyrenes such as 2-butylamidostyrene, 4-methylamidostyrene, and p-sulfonamidostyrene; aminostyrenes such as 3-aminostyrene, 4-aminostyrene, 2-isopropenylaniline, and vinylbenzyldimethylamine; nitrostyrenes such as 3-nitrostyrene and 4-nitrostyrene; cyanostyrenes such as 3-cyanostyrene and 4-cyanostyrene; vinylphenylacetonitrile; arylstyrenes such as phenylstyrene, and indenes. The styrene-based monomer may be one type or a combination of two or more types.

[0177] (2.2.2) Optional components The film roll of the present invention may contain other optional ingredients such as antioxidants, colorants, ultraviolet absorbers, matting agents, acrylic particles, hydrogen-bonding solvents, and ionic surfactants. These components can be added in an amount of 0.01 to 20 parts by mass per 100 parts by mass of the base resin.

[0178] (antioxidant) In the film roll of the present invention, commonly known antioxidants can be used. In particular, lactone-based, sulfur-based, phenol-based, double bond-based, hindered amine-based, and phosphorus-based compounds can be preferably used.

[0179] These antioxidants and the like are added in an amount of 0.05 to 20% by mass, preferably 0.1 to 1% by mass, based on the resin that is the main raw material of the optical film. A synergistic effect can be obtained by using several different types of compounds in combination with these antioxidants rather than using only one type. For example, it is preferable to use lactone-based, phosphorus-based, phenol-based and double bond-based compounds in combination.

[0180] (coloring agent) The film roll of the present invention preferably contains a colorant for adjusting the color tone, within a range that does not impair the effects of the present invention.

[0181] The colorant means a dye or pigment, and in the present invention refers to a dye or pigment that has the effect of making the color tone of the liquid crystal screen blue, adjusting the yellow index, or reducing haze.

[0182] As the colorant, various dyes and pigments can be used, but anthraquinone dyes, azo dyes, phthalocyanine pigments, etc. are effective.

[0183] (ultraviolet absorber) The film roll of the present invention can be used on the viewing side or backlight side of a polarizing plate, and therefore may contain an ultraviolet absorber for the purpose of imparting an ultraviolet absorbing function.

[0184] The ultraviolet absorber is not particularly limited, but examples thereof include ultraviolet absorbers such as benzotriazole-based, 2-hydroxybenzophenone-based, and salicylic acid phenyl ester-based ultraviolet absorbers. Examples include triazoles such as 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole, and 2-(3,5-di-t-butyl-2-hydroxyphenyl)benzotriazole, and benzophenones such as 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, and 2,2′-dihydroxy-4-methoxybenzophenone. The above ultraviolet absorbents can be used alone or in combination of two or more.

[0185] The amount of ultraviolet absorber used varies depending on the type of ultraviolet absorber, conditions of use, etc., but is generally added in the range of 0.05 to 10 mass %, preferably 0.1 to 5 mass %, relative to the base resin.

[0186] (fine particles) The film roll of the present invention preferably contains fine particles that impart slipperiness to the film roll. In particular, the addition of fine particles is effective from the viewpoint of improving the lubricity of the surface of the optical film according to the present invention, improving the lubricity during winding, and preventing the occurrence of scratches and blocking.

[0187] The fine particles may be either inorganic or organic as long as they do not impair the transparency of the resulting film roll and are heat resistant when melted, but inorganic fine particles are more preferred. These fine particles can be used alone or in combination of two or more kinds.

[0188] By using particles with different particle sizes and shapes (for example, needle-like and spherical), it is possible to achieve both high transparency and lubricity.

[0189] Among the compounds constituting the above-mentioned fine particles, silicon dioxide is particularly preferably used because it has a refractive index close to that of the cycloolefin resin, acrylic resin, and cellulose ester resin and therefore has excellent transparency (haze).

[0190] Specific examples of silicon dioxide that can be preferably used include commercially available products with trade names such as Aerosil (registered trademark) 200V, Aerosil (registered trademark) R972V, Aerosil (registered trademark) R972, R974, R812, 200, 300, R202, OX50, TT600, and NAX50 (all manufactured by Nippon Aerosil Co., Ltd.), Seahoster (registered trademark) KEP-10, Seahoster (registered trademark) KEP-30, and Seahoster (registered trademark) KEP-50 (all manufactured by Nippon Shokubai Co., Ltd.), Silohorbic (registered trademark) 100 (manufactured by Fuji Silysia Co., Ltd.), Nipsil (registered trademark) E220A (manufactured by Nippon Silica Kogyo Co., Ltd.), and Admafine (registered trademark) SO (manufactured by Admatechs Co., Ltd.).

[0191] The shape of the particles is not particularly limited and may be irregular, acicular, flat, spherical, etc., but spherical particles are particularly preferred as they can improve the transparency of the resulting film roll.

[0192] If the particle size is close to the wavelength of visible light, the light will be scattered and transparency will be reduced, so the particle size is preferably smaller than the wavelength of visible light, and more preferably 1 / 2 or less of the wavelength of visible light.

[0193] If the particle size is too small, the lubricity may not be improved, so it is particularly preferable that the particle size is within the range of 80 to 180 nm. The particle size means the size of the aggregate when the particle is an aggregate of primary particles. When the particle is not spherical, the particle diameter means the diameter of a circle equivalent to the projected area of ​​the particle.

[0194] The fine particles are preferably added in an amount within a range of 0.05 to 10% by mass, and more preferably within a range of 0.1 to 5% by mass, relative to the base resin.

[0195] (Optical film applications) The optical film unwound from the film roll of the present invention is suitably used as an optical film, such as a protective film for a polarizing plate, and can be used in various optical measuring devices and display devices such as liquid crystal display devices and organic electroluminescence display devices.

[0196] 3. Film roll manufacturing method The method for producing a film roll of the present invention includes at least a stretching step of stretching an optical film in a stretching furnace, and a flattening step, wherein the flattening step involves flattening at a temperature in the range of 50 to 200°C higher than the temperature in the stretching furnace.

[0197] The term "film roll" as used herein refers to an optical film wound in a roll shape. The optical film according to the present invention can be produced by a conventional production method such as an inflation method, a T-die method, a calendar method, a cutting method, a casting method, an emulsion method, or a hot press method. From the viewpoints of suppressing coloration, foreign matter defects, and optical defects such as die lines, the solution casting method and the melt casting method are preferred, and the solution casting method is particularly preferred in order to obtain a uniform surface.

[0198] (3.1) Flattening the uneven surface of the optical film: a means of controlling film thickness Average maximum height difference (PV) of the film thickness of the optical film according to the present invention ave1 In order to adjust the ratio (Dc / De) of the outer diameter Dc at the center of the film roll to the outer diameter De at the end to a desired value, it is possible to consider a method for flattening the uneven shape of the optical film surface, and examples of such methods include the following flattening treatments 1 to 4. Moreover, they may be combined.

[0199] (Flattening process 1) The film thickness is controlled by controlling the pitch of the pump pulsation. The dope discharge amount is controlled by increasing the rotation speed by adjusting the gear ratio of the gear pump, and the pulsation during dope delivery (extrusion of resin in the case of melting) is controlled, thereby controlling the pitch of the pump pulsation.

[0200] Here, a supplementary explanation will be given regarding the liquid delivery capacity of the pump. In the casting process described later, if the length of the piping from the pump to the casting die is not too short, the pulsation due to the influence of the rotation speed of the pump will not increase, and if it is not too long, the pressure loss will not be too large, and it is possible to prevent the liquid delivery capacity of the pump from decreasing below the lower limit. Furthermore, if the rotation speed of the pump is not too slow, it is possible to prevent a decrease in the liquid delivery capacity, and if it is not too fast, it is possible to prevent the pressure loss from becoming too large and prevent a decrease in the liquid delivery capacity.

[0201] From the above viewpoints, it is preferable that the length of the piping from the pump to the casting die is set within the range of 50 to 100 m, and the gear ratio of the gear pump used for sending the dope (or extruding the resin in the case of melting) is adjusted to set the rotation speed of the pump within the range of 10 to 50 rpm.

[0202] <Definition of whether or not flattening process 1 is performed> In the examples and comparative examples of the present invention, the flattening treatment 1 means that in the casting process described later, the length of the piping from the pump to the casting die is set to 60 m, and the gear ratio of the gear pump used for feeding the dope is adjusted to set the rotation speed of the pump to 20 rpm. The flattening treatment 1 is not performed in the casting process described later. This means that the length of the pipe from the pump to the casting die is set to 30 m, which is outside the range of 50 to 100 m, and the gear ratio of the gear pump used for sending the dope is adjusted to 70 rpm, which is outside the range of 10 to 50 rpm.

[0203] (Flattening process 2) The initial film thickness is controlled by the heat bolt of the casting die. The casting die is provided with a mechanism for adjusting the width of a slit through which the dope is discharged (or the resin is extruded in the case of a melt).

[0204] Here, a method for controlling the initial thickness of the cast film by adjusting the width of the slit through which the dope is discharged using the heat bolt of the casting die will be described in more detail. In the casting step described later, if the width of the slit through which the dope is discharged by the heat bolt of the casting die is not too small, the preparation can be carried out relatively easily and does not take much time. If the width of the slit through which the dope is discharged is too large, the initial discharge thickness of the casting film cannot be made uniform.

[0205] From the above viewpoint, in the casting process described later, it is preferable to adjust the width of the slit through which the dope is discharged by the heat bolt of the casting die so that the film thickness deviation immediately after discharge is within the range of 1.0 to 5.0% for the entire casting film, thereby controlling the initial film thickness of the casting film.

[0206] <Definition of whether or not to perform flattening process 2> In the examples and comparative examples of the present invention, the flattening treatment 2 means that in the casting process described later, the width of the slit through which the dope is discharged is adjusted by a heat bolt of the casting die so that the film thickness deviation immediately after discharge is 1.5% for the entire casting film, thereby controlling the initial film thickness of the casting film. In addition, not performing the flattening treatment 2 means that in the casting process described later, the width of the slit for discharging the dope is adjusted by the heat bolt of the casting die to 5.5% of the film thickness deviation immediately after discharging, which is outside the range of 1.0 to 5.0% for the entire casting film, thereby controlling the initial film thickness of the casting film.

[0207] <Clarification of the definition of whether or not flattening process 2 is performed> However, the film thickness deviation immediately after ejection in the definition of whether or not the flattening treatment 2 is performed can be changed as appropriate depending on the desired film thickness of the optical film to be produced.

[0208] (Flattening process 3) Hot air is blown onto the casting film, and the heat flattens the protrusions, thereby controlling the film thickness. In the casting step (S2), the air may be blown onto the surface of the opposite side of the belt of the casting film while it is still a film, or immediately after the casting film is peeled off from the belt. At this time, since the inside of the casting film is soft due to the solvent, the projections are flattened, and the film thickness is controlled by measuring the non-uniformity of the casting film in the width direction online and adjusting the temperature, speed or volume of the drying air and the amount of residual solvent.

[0209] Here, a supplementary explanation will be given on the temperature, velocity or volume of the drying air, and the amount of residual solvent. If the temperature of the drying air is not too low, the air velocity is not too low, or the air volume is not too small, the film thickness can be controlled appropriately. Also, as long as the temperature is not too high, the wind speed is not too fast, or the air volume is not too large, the film thickness will not become uncontrollable locally.

[0210] If the amount of residual solvent is not too small, the film will be in a state closer to an optical film than a cast film, and will not become too soft and unable to be flattened. Also, if the amount is not too large, there will be no variation in film thickness when planarizing.

[0211] From these facts, by adjusting the residual solvent amount to an appropriate level, the planarization 3 can be carried out in a state where a thin film is formed on the surface layer.

[0212] From the above viewpoint, the temperature of the drying air is preferably within the range of 10 to 80° C., and the air velocity is preferably within the range of 5 to 40 m / sec. The amount of residual solvent is preferably 150 to 550% by mass.

[0213] If the above operation is carried out when the surface layer of the casting film on the side opposite to the belt is not in a film state, streaks will appear, and it is not preferable that the inside is dry. On the belt in the casting process (S2), the non-uniformity of the thickness deviation of the cast film in the width direction is measured online, and the film thickness is controlled by adjusting the temperature when blowing hot air to reduce the non-uniformity.

[0214] <Definition of whether or not to perform flattening process 3> In the examples and comparative examples of the present invention, the flattening treatment 3 refers to the flattening of protrusions by blowing hot air at a speed of 16 m / sec (40°C) onto the casting film on the belt after the casting process described later, which is carried out by drying the casting film on the belt until the amount of residual solvent reaches 200 mass % to form a coating on the surface. Furthermore, not carrying out the flattening treatment 3 means that in the casting process described below, after the casting film on the belt is dried until the residual solvent amount is 5 mass %, which is outside the range of 150 to 550 mass %, to form a coating on the surface, hot air is blown onto the casting film at a speed of 45 m / sec (40°C), which is outside the range of 5 to 40 m / sec, to flatten the protrusions.

[0215] (Flattening process 4) In the stretching step, the film thickness is controlled by changing the temperature inside the furnace of the tenter stretching device and the timing of the heat treatment. In the present invention, the heat treatment is carried out using an infrared (IR) heater, but the heat treatment may be carried out by other methods. Furthermore, the flattening treatment 4 can be carried out in a furnace other than the drawing process by changing the environmental temperature or the timing of the heat treatment in a different process. A tenter stretching device is a device that stretches an optical film by gripping both widthwise ends of the optical film with clips and widening the gap between the clips while running along with the optical film. It is usually divided into multiple zones (preheating zone, stretching zone, and heat-setting zone). In the present invention, the timing for applying heat treatment among the above zones is set to at least one of the following three: (1-1) when passing through the preheating zone in the tenter stretching device, (1-2) when passing through the stretching zone, and (1-3) when passing through the heat-setting zone.

[0216] Here, a supplementary explanation will be given regarding the temperature difference between the furnace temperature and the heat treatment temperature. The inside of the stretching furnace as defined in the present application refers to three zones: a preheating zone, a stretching zone, and a heat setting zone, and the temperature inside the furnace refers to the temperature inside the stretching furnace measured at a position 100 mm above the center of the optical film in the stretching zone immediately before stretching. If the temperature difference between the furnace temperature and the heat treatment temperature is neither too small nor too large, the flattening process can be easily controlled.

[0217] From the above viewpoint, the temperature difference between the furnace temperature and the heat treatment temperature is preferably within the range of 50 to 200°C.

[0218] <Definition of whether or not flattening process 4 is performed> In the examples and comparative examples of the present invention, carrying out the flattening treatment 4 means that a necessary number of infrared (IR) heaters are provided to carry out a heat treatment in the stretching step described below. Furthermore, not carrying out the flattening treatment 4 means that no heat treatment is carried out by installing an infrared (IR) heater in the stretching step described below.

[0219] (Infrared (IR) heater) The infrared (IR) heater used in the present invention will now be described in detail. Unlike general infrared (IR) heaters, infrared (IR) heaters that can be used in the practice of the present invention are preferably designed to be able to pinpoint and narrow the infrared irradiation range by using a mirror that reflects infrared rays. Examples of mirrors that reflect infrared rays include cold mirrors (manufactured by Sigma Koki Co., Ltd.) and infrared aluminum enhanced reflection mirrors (manufactured by Novo Optics). The mirror used in the practice of the present invention is an aluminum enhanced infrared mirror (manufactured by Novo Optics), which is an aluminum mirror. The infrared radiation range of a single currently available, general infrared (IR) heater is 500 mm in the width direction, for example, MCHNNS3, with an irradiation energy of 400 W (manufactured by Misumi Corporation), whereas the infrared radiation range of a single infrared (IR) heater used in the practice of the present invention is 100 to 150 mm in the width direction, with an irradiation energy of 550 W (manufactured by Heattech Co., Ltd.).

[0220] (Relationship between the heat quantity A in the center and the average heat quantity B at the edges) In the stretching step, the flattening treatment is performed using an infrared (IR) heater, and the heat quantity A at the center and the average heat quantity B at the ends, which are 100 mm apart from each other, of the infrared (IR) heater satisfy the formula (3), thereby enabling the flattening treatment to be effectively achieved. In the present invention, the heat quantity A at the center of the infrared (IR) heater and the average heat quantity B at the ends, both 100 mm apart, were calculated by measuring the temperature distribution with a thermoviewer (VIM-640G2ULC, manufactured by Vision Sensing Co., Ltd.) and taking the average value. However, if heat treatment was performed by another method, the calculation was made accordingly.

[0221] The principle and calculation method are explained in detail below. The optical film is heated by the infrared (IR) heater. The heated portion is integrated in the longitudinal direction, and the integrated value in the longitudinal direction of the center part is defined as heat quantity A. The integrated value in the longitudinal direction at a position 75 mm from the center is calculated on both sides of the edge of the optical film, and their average is defined as average edge heat quantity B. Calculate (B / A) from the above values. In this case, if (B / A) is too large, the infrared (IR) heater is not designed to pinpoint and narrow the infrared irradiation range, but if (B / A) is too small, the range of the (B / A) value can be controlled by increasing the number of infrared (IR) heaters installed across the width.

[0222] (3.2) Solution casting film roll manufacturing process FIG. 5 is a flowchart showing the flow of the manufacturing process by the solution casting film-forming method. FIG. 6 is a schematic diagram of an apparatus for producing an optical film by a solution casting film-forming method.

[0223] The solution casting film-forming method will be described below with reference to FIGS. The method for producing an optical film by the solution casting film-forming method includes a dope preparation step (S1), a casting step (S2), a peeling step (S3), a shrinking step (S4), a first drying step (S5), a first stretching step (S6), a first cutting step (S7), a second stretching step (S8), a second cutting step (S9), a second drying step (S10), a third cutting step (S11), and a winding step (S12).

[0224] It should be noted that the above manufacturing method does not necessarily include both the first drying step (S5) and the second drying step (S10), but may include at least one of these steps. Furthermore, it is only necessary to include the first stretching step (S6), the second stretching step (S8), and any one of the first cutting step (S7), the second cutting step (S9) and the third cutting step (S11).

[0225] (3.2.1) Dope preparation (stirring preparation) step (S1) In the dope preparation (stirring and preparation) step (S1), at least a resin and a solvent are stirred in a stirring tank 1a of a stirring device 1 to prepare a dope to be cast onto a support 3 (endless belt).

[0226] As the solvent, a mixed solvent of a good solvent and a poor solvent is used. Hereinafter, as one embodiment of the present invention, a dope preparation process will be described using a cycloolefin resin (hereinafter also referred to as COP) as a thermoplastic resin as an example, but the present invention is not limited thereto.

[0227] This process is a process of dissolving a cycloolefin resin (COP) and, if necessary, other compounds in a solvent mainly consisting of a good solvent for the COP in a dissolution vessel while stirring the COP and, if necessary, other compound solutions, to form a dope, or a process of mixing the COP solution with, if necessary, other compound solutions to form a dope, which is a main solution.

[0228] The concentration of the cycloolefin resin (COP) in the dope is preferably high because the drying load after casting on the support can be reduced. However, if the COP concentration is too high, the load during filtration increases and accuracy deteriorates. The concentration that satisfies both of these requirements is preferably in the range of 10 to 35% by mass, and more preferably in the range of 15 to 30% by mass.

[0229] The solvents used in the dope may be used alone or in combination of two or more kinds. However, it is preferable to use a mixture of a good solvent and a poor solvent for the cycloolefin resin (COP) in terms of production efficiency, and it is preferable to use a larger amount of the good solvent in terms of solubility of the COP.

[0230] The preferred range of the mixing ratio of the good solvent to the poor solvent is 70 to 98 mass % of the good solvent and 2 to 30 mass % of the poor solvent. A good solvent and a poor solvent are defined as those that can dissolve the cycloolefin resin (COP) used alone, and those that swell or do not dissolve the COP alone. Therefore, the average degree of substitution of COP determines whether a solvent is a good solvent or a poor solvent.

[0231] The good solvent used in the present invention is not particularly limited, but examples thereof include organic halogen compounds such as methylene chloride, dioxolanes, acetone, methyl acetate, and methyl acetoacetate. Particularly preferred are methylene chloride and methyl acetate.

[0232] The poor solvent used in the present invention is not particularly limited, but for example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone, etc. are preferably used. The dope preferably contains water in an amount of 0.01 to 2% by mass.

[0233] The solvent used to dissolve the cycloolefin resin (COP) is recovered after being removed from the film by drying in the optical film production process, and is then reused.

[0234] The recovered solvent may contain trace amounts of additives added to the COP, such as plasticizers, ultraviolet absorbers, polymers, and monomer components. However, even if these additives are contained, the recovered solvent can be preferably reused, and if necessary, it can be purified and reused.

[0235] As the method for dissolving COP when preparing the dope described above, a general method can be used. Specifically, preferred are methods carried out at normal pressure, at or below the boiling point of the main solvent, and methods carried out under pressure at or above the boiling point of the main solvent. Combining heating and pressure allows heating above the boiling point at normal pressure.

[0236] In addition, a method of stirring and dissolving while heating at a temperature above the boiling point of the solvent at normal pressure but within a range in which the solvent does not boil under pressure is also preferred, as this prevents the formation of lumpy undissolved matter called gel or lumps.

[0237] Also preferably used is a method in which a cycloolefin resin (COP) is mixed with a poor solvent to wet or swell it, and then a good solvent is added to dissolve it.

[0238] The pressure may be applied by injecting an inert gas such as nitrogen gas or by increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside, and for example, a jacket type is preferred because it is easy to control the temperature.

[0239] The heating temperature after adding the solvent is preferably higher from the viewpoint of the solubility of the cycloolefin resin (COP). However, if the heating temperature is too high, the required pressure increases, resulting in poor productivity.

[0240] The heating temperature is preferably within a range of 30 to 120°C, more preferably within a range of 60 to 110°C, and even more preferably within a range of 70 to 105°C. The pressure is also adjusted so that the solvent does not boil at the set temperature.

[0241] Alternatively, a cooling dissolution method is also preferably used, by which the cycloolefin resin (COP) can be dissolved in a solvent such as methyl acetate.

[0242] Next, it is preferable to filter the cycloolefin resin (COP) solution (dope during or after dissolution) using a suitable filter material such as filter paper.

[0243] It is preferable that the filter has a low absolute filtration accuracy in order to remove insoluble matters, but if the absolute filtration accuracy is too low, there is a problem that the filter is easily clogged. Therefore, a filter medium with an absolute filtration accuracy of 0.008 mm or less is preferred, a filter medium with an absolute filtration accuracy in the range of 0.001 to 0.008 mm is more preferred, and a filter medium with an absolute filtration accuracy in the range of 0.003 to 0.006 mm is even more preferred.

[0244] There are no particular restrictions on the material of the filter medium, and ordinary filter medium can be used, but filter medium made of plastic such as polypropylene or Teflon (registered trademark), or filter medium made of metal such as stainless steel is preferred as it does not cause fiber shedding.

[0245] It is preferable to remove or reduce impurities, particularly bright spot foreign matter, contained in the raw material cycloolefin resin (COP) by filtration.

[0246] Bright spot foreign matter is a point (foreign matter) that is visible as light leaking from the opposite side when two polarizing plates are placed in a cross-Nicol state, a film or the like is placed between them, and light is shone from one polarizing plate side and observed from the other polarizing plate side. The number of bright spots is 200 / cm and is 0.01 mm or more in diameter. 2 It is preferable that: More preferably 100 / cm 2 More preferably, it is 50 pieces / m or less. 2 or less, and more preferably 0 to 10 particles / cm 2 The following is the result. It is also preferable to have fewer bright spots of 0.01 mm or less.

[0247] The dope can be filtered by a conventional method. However, a method of filtering the dope while heating the solvent at a temperature above the boiling point of the solvent at normal pressure and within a range where the solvent does not boil under pressure is preferred because the increase in the difference in filtration pressure (referred to as differential pressure) before and after filtration is small.

[0248] The temperature is preferably in the range of 30 to 120°C, more preferably in the range of 45 to 70°C, and even more preferably in the range of 45 to 55°C.

[0249] A small filtration pressure is preferred. Specifically, it is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and even more preferably 1.0 MPa or less.

[0250] (3.2.2) Casting process (S2) In the casting step (S2), the casting film 5 formed from the dope cast on the support 3 is heated on the support 3 to evaporate the solvent until the casting film 5 can be peeled off from the support 3 by a peeling roll 4.

[0251] The evaporation is preferably carried out in an atmosphere within a range of 5 to 75°C. The solvent can be evaporated by blowing hot air onto the upper surface of the casting film and / or by transferring heat from the backside of the support 3 using a liquid, or by transferring heat from the front and backside using radiation heat. The method of transferring heat from the front and backside using radiation heat is preferred because of its high drying efficiency. A combination of these methods is also preferably used.

[0252] The casting width is preferably 1.3 m or more from the viewpoint of productivity. More preferably, it is in the range of 1.3 to 4.0 m. If the casting width does not exceed 4.0 m, no streaks will appear during the manufacturing process and the film will be more stable during the subsequent transport process. From the viewpoint of transportability and productivity, a range of 1.3 to 3.0 m is more preferable.

[0253] The support 3 in the casting step (S2) preferably has a mirror-finished surface, and the support 3 is preferably a stainless steel belt or a cast drum with a plated surface.

[0254] The surface temperature of the support 3 in the casting step (S2) is in the range of -50°C to the boiling point of the solvent, and a higher temperature is preferred because it increases the drying speed of the cast film.

[0255] The support temperature is preferably in the range of 0 to 55°C, more preferably in the range of 22 to 50°C.

[0256] There are no particular limitations on the method for controlling the temperature of the support 3, but examples include a method of blowing hot or cold air onto the support, or a method of bringing hot water into contact with the back side of the support. The use of warm water is preferable because heat is transferred more efficiently and the time required for the temperature of the support to become constant is shorter. When using hot air, the temperature may be higher than the desired temperature.

[0257] In the casting step (S2), the dope prepared in the dope preparation step (S1) is sent to a casting die 2 through a conduit via a pressure-type metering gear pump or the like, and the dope is cast from the casting die 2 onto a casting position on a support 3 made of a rotating stainless steel endless belt that is transported endlessly.

[0258] In order for those skilled in the art to improve the uniformity of the film thickness in the casting process, a method of controlling the slit gap at the lip of the casting die can be mentioned in both the solution casting film-forming method and the melt casting film-forming method. For example, when extruding a highly viscous dope (including melt), the width of the slit gap varies. To prevent this, multiple heat bolts are installed in the width direction to control the slit gap. However, this method has the problem that there is a physical limit to the number of heat bolts that can be installed. In order to suppress the pressure fluctuation in the width direction, which causes the variation in the width direction of the slit gap, there is a method of changing the internal structure of the casting die in the width direction. However, this method requires changing the casting die for each product type, which is time-consuming and costly.

[0259] (Pump pulsation pitch control) Controlling the pitch of the pump pulsation is one of the means for controlling the film thickness of the optical film according to the present invention (flattening process 1). It is known that a high-precision gear pump is used to transport the dope in the piping leading up to the casting die (to extrude the resin in the case of melting). The gear pump can control the pump pulsation pitch by controlling the pump rotation speed with its gear ratio. The pulsation during transport can control the film thickness in the longitudinal direction, i.e., the average maximum height difference (PV) of the film thickness. ave1 has a significant impact on

[0260] In this case, the length of the piping from the pump to the casting die is preferably within a range of 50 to 100 m in order to eliminate the influence of pressure loss and pump pulsation. The rotation speed of the pump is preferably within the range of 10 to 50 rpm from the viewpoint of preventing pressure loss.

[0261] (Initial film thickness control by heat bolts on the casting die) The control of the initial extrusion film thickness by the heat bolt of the casting die is the means for controlling the film thickness of the optical film according to the present invention. The casting die is provided with a mechanism for adjusting the width of a slit through which the dope is discharged (or the resin is extruded in the case of melting). It is preferable to adjust the width of the slit through which the dope is discharged by the heat bolt of the casting die so that the thickness deviation immediately after discharge is within the range of 1.0 to 5.0% for the entire casting film, thereby controlling the initial film thickness of the casting film.

[0262] (others) Here, the part of the casting die slit from which the dope comes out is called a lip. A casting die is preferred in which the slit shape of the lip can be adjusted and the film thickness can be easily made uniform. Casting dies include coat hanger dies and T-dies, and any of these is preferably used. In the present invention, the casting film refers to the dope film cast from the lip portion. In order to increase the film-forming speed of the optical film according to the present invention, two or more of the above-mentioned casting dies may be provided on the support, and the dope may be divided and layered. Alternatively, it is also preferable to obtain a film roll having a laminated structure by a co-casting method in which a plurality of dopes are simultaneously cast. To increase the film-forming speed, two or more casting dies may be provided on the support, and the dope may be divided and layered.

[0263] The slit can be narrowed by manually turning and pushing the heat bolt to make the film thinner, or opened to make it thicker. A common method is to apply voltage to a heat bolt to press it in place using heat, but these methods are usually used in combination. It is also possible to use a push-pull system. This is the average maximum height difference (PV) of the film thickness measured in the order of steps 1 to 3 in the diagonal direction to the width direction.ave2 has a significant impact on However, the pitch of the bolts may not be narrow due to the mechanism of the casting die. In the case of a highly viscous dope (including a molten dope), the pressure load on the lip when the dope is discharged from the casting die is large, and the pressure drops suddenly after the discharge, resulting in an increase in the film thickness (balance effect), which may cause variations in the film thickness across the width. Therefore, it is necessary to design the casting die so that the lip of the casting die is not subjected to excessive load due to the internal structure of the casting die.

[0264] In the casting step (S2), the cast dope is dried on the support 3 to form a cast membrane 5. In this case, the inclination of the casting die 2, i.e., the direction of the dope discharged from the casting die 2 to the support 3, may be set appropriately so that the angle with respect to the normal to the surface of the support 3 (the surface onto which the dope is cast) falls within the range of 0 to 90°.

[0265] The support 3 is made of, for example, a stainless steel belt, and is held by a pair of rolls 3a and 3b and a plurality of rolls positioned between them. In this case, the surface of the support is preferably a mirror surface.

[0266] One or both of the rolls 3a and 3b is provided with a drive device that applies tension to the support 3, so that the support 3 is used in a tensioned state. The support 3 may be a drum.

[0267] (3.2.3) Peeling process (S3) In this process, in the casting process (S2), the solvent is evaporated until the cast film 5 on the support 3 has a film strength that allows it to be peeled off, and after drying and solidifying or cooling and solidifying, the optical film is peeled off from the support 3 before it makes a full revolution around the support 3. That is, this step is a step of peeling off the optical film from which the solvent has evaporated on the support 3 at the peeling position. At this time, from the viewpoints of surface quality, moisture permeability, and releasability, it is preferable to peel the optical film from the support within a range of 30 to 600 seconds. The position where the optical film is peeled from the support is called a peeling point, and the roll that assists the peeling is called a peeling roll. In the peeling step (S3), the optical film is peeled off by a peeling roll 4 while maintaining its self-supporting property. The temperature at the peeling position on the support is preferably within the range of -50 to 40°C, more preferably within the range of 10 to 40°C, and most preferably within the range of 15 to 30°C.

[0268] (Residual solvent amount) The amount of solvent remaining in the optical film on the support 3 at the time of peeling is appropriately adjusted depending on the strength of the drying conditions, the length of the support 3, and the like. Although it depends on the thickness of the optical film, if the amount of residual solvent at the peeling point is too large, the optical film may become too soft and difficult to peel, which may impair flatness or make it more susceptible to horizontal steps, wrinkles, or vertical streaks due to peeling tension. Conversely, if the amount of residual solvent is too small, the optical film may be partially peeled off during the process. In order for the optical film to exhibit good flatness, it is desirable that the amount of residual solvent is within the range of 10 to 50% by mass, from the viewpoint of balancing economic speed and quality.

[0269] In the flattening process 3 according to the present invention, when a coating is formed on the surface of the casting film on the belt with the residual solvent amount being in the range of 150 to 550 mass %, it is preferable to flatten the protrusions by blowing dry air having a temperature in the range of 10 to 80°C and a speed of 5 to 40 m / sec onto the casting film, in order to prevent the generation of streaks.

[0270] One method to increase the film production speed (to increase the film production speed by peeling while the residual solvent content is still as high as possible) is the gel casting method, which allows peeling even when the residual solvent content is high. The methods include adding a poor solvent for cycloolefin resin (COP) to the dope, and gelling the cast film after casting the dope, and cooling the support to gel the cast film and peeling it off in a state where it contains a large amount of residual solvent. There is also a method of adding a metal salt to the dope. As described above, the cast film is gelled on the support to strengthen the film, thereby facilitating peeling and increasing the film production rate.

[0271] The amount of residual solvent is defined by the following formula: Residual solvent amount (mass%) = {(MN) / N} × 100 Here, M is the mass of a sample taken at any time during or after the production of the cast membrane or optical film, and N is the mass of M after heating at 115° C. for 1 hour.

[0272] (peel tension) The peel tension when peeling the optical film from the support is preferably 300 N / m or less. A more preferable range is 196 to 245 N / m, but if wrinkles are likely to occur during peeling, peeling is preferably performed with a tension of 190 N / m or less.

[0273] (3.2.4) Shrinkage process (S4) The shrinking step is a step of shrinking the optical film in-plane. This shrinking step is carried out by stretching the optical film after peeling it from the support in the machine direction (hereinafter also referred to as "MD direction"). In this case, the optical film shrinks in the transverse direction (hereinafter also referred to as "TD direction") perpendicular to the MD direction within the plane of the optical film.

[0274] The shrinkage process promotes entanglement between polymer molecules (matrix molecules) in the thickness direction of the optical film, so that even when the optical film is bonded to a polarizer via an adhesive during polarizing plate production, the adhesive can easily penetrate into the optical film through the entangled parts (crosslinked parts) between the matrix molecules. As a result, the optical film can be firmly fixed to the polarizer via the adhesive, and the peel strength of the optical film from the polarizer can be improved. That is, good adhesion between the optical film and the polarizer can be ensured.

[0275] (Definition of shrinkage rate) In the present invention, the shrinkage rate is defined by the following formula.

[0276] Formula: Shrinkage rate [%] = Optical film width at the end of the shrinking process [mm] / Optical film width at the start of the shrinking process [mm] x 100

[0277] Here, if the shrinkage rate of the optical film in the shrinking step is too small, the effect of promoting entanglement between matrix molecules will be insufficient, and if it is too large, there is a concern that the production efficiency of the optical film (stretched film) will decrease. Therefore, the shrinkage rate of the optical film in the shrinking step is preferably within a range of 1 to 40%, and more preferably within a range of 5 to 20%.

[0278] (Method of measuring and calculating shrinkage rate) In the present invention, the width of the optical film was measured using LS-9000 manufactured by Keyence Corporation. The shrinkage factor of the optical film according to the present invention was determined by measuring the width of the optical film every second for 5 minutes (300 seconds) using the above-mentioned measuring device, taking the average of the measured values ​​as the width of the optical film, and substituting it into the above formula. However, the method is not limited to the above, and for example, the width of the optical film may be read from a ruler, which may be used as the width of the optical film, and then substituted into the above formula.

[0279] In the shrinking step (S4), the optical film F is shrunk in the width direction. Methods for shrinking an optical film include, for example, (1) treating the optical film at a high temperature without holding the width of the film to increase the density of the optical film, (2) applying tension to the optical film in the transport direction (MD direction) to shrink the optical film in the width direction (TD direction), and (3) rapidly reducing the amount of residual solvent in the optical film.

[0280] (3.2.5) First drying step (S5) The drying step is a step in which the optical film is heated on the support to evaporate the solvent.

[0281] In the drying device 6 in FIG. 6, the optical film is transported by a plurality of transport rolls arranged in a staggered pattern when viewed from the side, and the optical film is dried during this transport. The drying method in the drying device 6 is not particularly limited, and the optical film is generally dried using hot air, infrared rays, a heated roll, microwaves, etc., but from the standpoint of simplicity, a method of drying the optical film with hot air is preferred. A combination of these methods is also preferred. The first drying step (S5) may be carried out as needed.

[0282] If the optical film is thin, it dries quickly, but if it dries too quickly, the flatness of the finished optical film is likely to be impaired. When drying at high temperatures, the amount of residual solvent must be taken into consideration, but failure due to foaming of the solvent can be prevented by ensuring that the amount of residual solvent is not too large. It is preferable to start drying when the amount of the residual solvent is about 30% by mass or less, and the drying is generally carried out in the range of 30 to 250°C throughout. It is particularly preferable to dry within the range of 35 to 200°C, and it is preferable to increase the drying temperature stepwise. The amount of residual solvent in the optical film on the support 3 at the time of peeling in the peeling step (S3) is adjusted appropriately depending on the strength of the drying conditions, the length of the support 3, etc., and the amount of residual solvent in the shrinking step (S4) is significantly affected by the film thickness, resin, etc., so there is an overlapping range of the preferred ranges of residual solvent amount in the peeling step (S3) and the shrinking step (S4).

[0283] The temperature of the support may be the same throughout or may vary depending on the position. In the first drying step (S5), the optical film is peeled off from the support by a drying device 6 and further dried.

[0284] The drying process for optical films generally involves the roll drying method (a method in which the optical film is dried by passing it alternately through multiple rolls arranged above and below) or the tenter method, in which the optical film is dried while being transported.

[0285] When a tenter stretching apparatus is used, it is preferable to use an apparatus that can independently control the gripping length (the distance from the start of gripping to the end of gripping) of the optical film on the left and right sides by the left and right gripping means of the tenter stretching apparatus in the stretching step described below. It is also preferable to intentionally create zones with different temperatures in the stretching process to improve flatness.

[0286] It is also preferable to provide a neutral zone between the different temperature sections to prevent interference between the sections.

[0287] (3.2.6) First stretching process (S6) The stretching step may be a step of stretching the optical film only in the MD direction within the plane of the optical film, a step of stretching only in the TD direction, a step of stretching in both the MD and TD directions, or a step of stretching in an oblique direction. There is no limitation on the stretching direction, but from the viewpoint of obtaining a wide optical film, it is preferable to include a step including stretching at least in the width direction. Such stretching can be carried out using a stretching device 7.

[0288] In order to ensure a high retardation, a wide width, and to promote penetration of an adhesive when adhering to a polarizer, it is preferable to stretch the optical film at a high magnification in the stretching step. However, if the stretching ratio is too high, crazes may occur in the optical film due to the stretching stress, or the entanglement between matrix molecules that maintain the strength of the optical film may be dissociated, resulting in weakening of the optical film.

[0289] Therefore, the stretching ratio in the stretching step is preferably within the range of 1.1 to 5.0 times, and more preferably within the range of 1.3 to 3.0 times.

[0290] When the stretching is carried out multiple times, it is preferable that the stretching at the highest magnification, which poses the highest risk of dissociation of the matrix molecules, is carried out in the final stretch. For example, in FIG. 5, the highest stretching ratio is preferably performed in the second stretching step. In this case, the entanglement of the matrix molecules can be strengthened before the maximum stretching ratio, so that even when the film is stretched to the maximum stretching ratio, dissociation of the entanglement of the matrix molecules can be suppressed, thereby suppressing cohesive failure.

[0291] In the first stretching step (S6), the optical film F is stretched by a tenter stretching device . In this case, the stretching method is preferably a method in which a difference in peripheral speed between rolls is used to stretch in the transport direction (longitudinal direction of the optical film; film-forming direction; casting direction; MD direction), or a tenter method in which both side edges of the optical film F are fixed with clips or the like and stretched in the width direction (direction perpendicular to the plane of the optical film; TD direction), in order to improve the performance, productivity, flatness, and dimensional stability of the film.

[0292] In the case of the so-called tenter method, it is preferable to drive the clip portion by a linear drive system, since this allows smooth stretching and reduces the risk of breakage.

[0293] The width holding or transverse stretching in the film-forming process is preferably carried out by a tenter stretching device, which may be a pin tenter or a clip tenter. In addition to stretching, drying may be carried out in the tenter stretching device 7.

[0294] (Tenter stretching device) Hereinafter, the device used as the tenter stretching device 7 will be described with reference to FIGS. FIG. 7 is a plan view schematically illustrating the internal configuration of a tenter stretching apparatus, and is a cross-sectional view of the tenter stretching apparatus viewed from above along a plane perpendicular to the plane of the optical film. FIG. 7 shows a state in which the cover has been removed, and the cover is indicated by a two-dot chain line.

[0295] The tenter stretching device 40 is equipped with a large number of clips 42 that grip both widthwise ends of the optical film F, and the clips 42 are attached to an endless chain 48 at regular intervals. The endless chains 48 are arranged on both sides of the optical film F, and are respectively stretched between a driving sprocket 50 on the entrance side and a driven sprocket 52 on the exit side. The driving sprocket 50 is connected to a motor (not shown), and the driving sprocket 50 is rotated by driving this motor. As a result, the endless chain 48 travels around between the driving sprocket 50 and the driven sprocket 52, causing the clips 42 attached to the endless chain 48 to travel around.

[0296] Between the driving sprocket 50 and the driven sprocket 52, a rail 54 is provided to guide the endless chain 48 (or the clip 42). The rails 54 are arranged on both sides of the optical film F, and the distance between the rails 54 is configured to be wider on the downstream side in the transport direction of the optical film F than on the upstream side. As a result, when the clips 42 travel around, the intervals between the clips 42 are widened, so that the optical film F held by the clips 42 can be transversely stretched in the width direction.

[0297] The driving sprocket 50 and the driven sprocket 52 each have a release member 56 attached thereto. The opening member 56 is a device that displaces a flapper (not shown) of the clip 42 (described later) from a gripping position to an open position, and the opening member 56 automatically performs the gripping and release operations of the optical film F.

[0298] As shown in FIG. 7, the tenter stretching device 40 is provided with a preheating zone, a (transverse) stretching zone, and a heat setting zone inside. The zones are separated from each other by windshield curtains (not shown). In each zone, hot air is supplied to the optical film F from above, below, or both. The hot air is blown out uniformly in the width direction of the optical film F while being controlled at a predetermined temperature for each zone. This allows the interior of each zone to be controlled to a desired temperature. Each zone will now be described.

[0299] The preheating zone is a zone where the optical film F is preheated, and the optical film F is heated without widening the gap between the clips 42.

[0300] The optical film F preheated in the preheating zone moves to the transverse stretching zone. The transverse stretching zone is a zone in which the optical film F is transversely stretched in the width direction by widening the gap between the clips 42 . The stretching ratio in this transverse stretching treatment is preferably in the range of 1.0 to 2.5 times, more preferably in the range of 1.05 to 2.3 times, and even more preferably in the range of 1.1 to 2 times.

[0301] The optical film F that has been transversely stretched in the transverse stretching zone moves to the heat setting zone.

[0302] In this embodiment, the interior of the tenter 40 is divided into a preheating zone, a (transverse) stretching zone, and a heat-setting zone, but the types and arrangement of the zones are not limited to this, and for example, a cooling zone for cooling the optical film F may be provided after the transverse stretching zone. A heat relaxation zone may also be provided within the heat setting zone.

[0303] In this embodiment, only transverse stretching is carried out by the tenter 40, but stretching in the machine direction may also be carried out simultaneously. In this case, the pitch of the clips 42 (the distance between the clips 42 in the conveying direction) may be changed when the clips 42 are moved. As a mechanism for changing the pitch of the clip 42, for example, a pantograph mechanism or a linear guide mechanism can be used.

[0304] Methods for stretching optical films include stretching in the longitudinal (length) direction (longitudinal stretching), stretching in the transverse (width) direction (transverse stretching), sequential stretching in the longitudinal direction and transverse direction (sequential biaxial stretching), and simultaneous stretching in the longitudinal direction and transverse direction (simultaneous biaxial stretching). Of these, transverse stretching and simultaneous biaxial stretching (including diagonal stretching) use a tenter stretching apparatus. The tenter stretching device is a device that holds both widthwise ends of an optical film with clips and stretches the optical film by widening the gap between the clips while running the clips together with the optical film.

[0305] (Heat treatment timing) A tenter stretching apparatus is usually divided into multiple zones, such as a preheating zone for heating the optical film, a transverse stretching zone for stretching the optical film in the transverse direction, a heat setting zone for crystallizing the optical film, and a relaxation zone for removing thermal stress from the optical film, as shown in Figure 7.

[0306] The timing of the heat treatment (flattening treatment 4 according to the present invention) in the stretching process in the tenter stretching apparatus is determined by whether the heat treatment is applied when the optical film passes through any of the following zones, and is used as a means of controlling the film thickness in conjunction with the furnace temperature. (1-1) When passing through the preheating zone in the tenter stretching device (1-2) When passing through the stretching zone in the tenter stretching device (1-3) When passing through the heat setting zone in the tenter stretching device Infrared (IR) heaters are used for the heat treatment in the above three zones, and the necessary number of infrared (IR) heaters are installed in each zone. As an example of an infrared (IR) heater installed in each zone, a side view of three zones in a tenter stretching apparatus in which an infrared (IR) heater is installed in the preheating zone is shown in FIG.

[0307] (Furnace temperature) Generally, the temperature inside the furnace is preferably in the range of 120 to 200°C, more preferably in the range of 120 to 180°C. Here, the furnace temperature in the present invention refers to the temperature measured at a position 100 mm above the center of the film immediately before stretching in the stretching zone of a tenter stretching device described below (see Figure 8), and is calculated by measuring each temperature value every minute for one hour and calculating the average value of these. Generally, the temperature inside the furnace is preferably in the range of 120 to 200°C, more preferably in the range of 120 to 180°C. Here, when a temperature gradient is applied longitudinally in a plurality of compartments, the compartment to be heat-treated is the subject of the term. In the present invention, the furnace temperature differs depending on whether or not heat treatment is performed in the stretching zone. However, when heat treatment is performed in the stretching zone, the furnace temperature refers to the furnace temperature in the stretching zone before heat treatment is performed.

[0308] (Residual solvent amount) The amount of residual solvent in the optical film during stretching is preferably 20% by mass or less, and more preferably 15% by mass or less.

[0309] FIG. 9 is a plan view of the three zones in the tenter stretching apparatus, and FIG. 10 is a schematic diagram of the nozzles and heaters installed in the three zones in the tenter stretching apparatus as viewed from the front. As shown in FIG. 10, the infrared (IR) heater is disposed only above the nozzle so that the optical film does not come into contact with the infrared (IR) heater when the optical film is broken. Furthermore, since the radiant energy from the infrared (IR) heater can be concentrated in a narrower area by placing the infrared (IR) heater closer to the optical film, the infrared (IR) heater should be placed as close as possible to the optical film as long as it does not interfere with the width adjustment operation using the clips.

[0310] FIG. 10 shows heat treatment mainly from the central nozzle, and heat treatment from the end nozzles is not performed in this example, but they can be used together in this embodiment.

[0311] In a stretching device, an infrared (IR) heater coming out of the nozzle gap as shown in Figure 8 can transmit radiant energy to the optical film without waste. As shown in FIG. 9, infrared (IR) heaters were arranged in a row so that the entire width of the optical film before stretching could be heated. The heaters may be arranged in a staggered pattern in the longitudinal direction.

[0312] (3.2.7) First cutting process (S7) In the first cutting step (S7), a cutting unit 8 made of a slitter cuts both widthwise ends of the optical film F stretched in the first stretching step (S6). In the optical film F, the portions remaining after cutting both ends constitute product portions that will become optical film products. On the other hand, the portion cut from the optical film F may be collected and reused as part of the raw material for producing an optical film.

[0313] (3.2.8) Second stretching process (S8) In the second stretching step (S8), the optical film F is stretched by the stretching device 9 in the same manner as in the first stretching step (S6). As a stretching method for this purpose, a stretching method in the conveying direction (MD) by setting a difference in peripheral speed between rolls, or a tenter method in which both side edges of the optical film F are fixed with clips or the like and stretched in the width direction (TD) is preferred in order to improve the performance, productivity, flatness, and dimensional stability of the film. In addition to stretching, drying may also be carried out in the stretching device 9.

[0314] (3.2.9) Second cutting process (S9) In the second cutting step (S9), the cutting unit 10 made of a slitter cuts both ends of the formed optical film F in the width direction, similar to the first cutting step (S7). The portions of the optical film gripped by the clips at both ends are usually cut off because the optical film is deformed and cannot be used as a product. If the material is not degraded by heat, it can be recovered and reused. In the optical film F, the portions remaining after cutting both ends constitute product portions that will become optical film products. On the other hand, the portion cut off from the optical film F is collected and reused as part of the raw material for producing the optical film.

[0315] (3.2.10) Second drying process (S10) In the second drying step (S10), the optical film F is dried in the drying device 11 in the same manner as in the first drying step (S5). In the drying device 11, the optical film F is transported by a plurality of transport rolls arranged in a staggered pattern when viewed from the side, and the optical film F is dried during this transport. The drying method in the drying device 6 is not particularly limited, and typical methods include hot air, infrared rays, a heated roll, and microwaves. Among the above drying methods, the method of drying the optical film F with hot air is preferred from the viewpoint of simplicity. The second drying step (S10) may be carried out as needed.

[0316] (3.2.11) Third cutting process (S11) In the third cutting step (S11), similarly to the first cutting step (S7) and the second cutting step (S9), the cutting unit 12 made of a slitter cuts both ends of the formed optical film F in the width direction. In the optical film F, the portions remaining after cutting both ends constitute product portions that will become optical film products. On the other hand, the portion cut off from the optical film F is collected and reused as part of the raw material for producing the optical film.

[0317] (3.2.12) Winding process (S12) Finally, in the winding step (S12), the optical film F is wound by a winding device 13 to obtain a film roll. That is, in the winding step, the optical film F is wound around a core while being transported, thereby producing a film roll. The initial tension when winding the optical film in the winding step is preferably in the range of 20 to 300 N / m.

[0318] (Residual solvent amount) More specifically, this is a process in which the optical film is wound up by a winding device 12 after the amount of residual solvent in the optical film has reached 2% by mass or less, and by reducing the amount of residual solvent to 0.4% by mass or less, an optical film with good dimensional stability can be obtained. In particular, it is preferable to wind the film when the amount of residual solvent is in the range of 0.00 to 0.20% by mass.

[0319] (Winding method) The optical film F can be wound using a commonly used winder, and various tension control methods, such as the constant torque method, constant tension method, taper tension method, and program tension control method with constant internal stress, can be used appropriately.

[0320] Before being wound up, the ends may be slit and cut to the width of the product, and a surface modification treatment may be applied to both ends of the optical film to prevent sticking or scratches during winding.

[0321] (After winding) The film roll of the present invention is preferably a long film, specifically within the range of about 100 to 10,000 m, and is usually provided in a roll form.

[0322] <Details of optical film winding method> The optical film according to the present invention is preferably wound up by the following winding method. The winding method preferably includes a straight winding step of winding the optical film around a winding core so that the side edges of the optical film are aligned, and an oscillating winding step of, after the straight winding step, periodically vibrating the optical film or the winding core in the width direction of the optical film so that the side edges are periodically misaligned within a certain range with respect to the width direction of the optical film, thereby winding the optical film around the winding core.

[0323] In particular, it is preferable to switch from the straight winding process to the oscillating winding process when the winding length of the optical film reaches a predetermined switching winding length within a range of 1 to 30% of the total winding length of the optical film.

[0324] The optical film winding device preferably includes an optical film winding unit that rotates the winding core to wind the optical film onto the winding core, an oscillating unit that vibrates the optical film or the winding core in the width direction of the optical film in conjunction with the winding of the optical film so that the optical film is oscillated on the winding core in a manner that periodically shifts within a certain range in the width direction of the optical film, and a switching unit that switches the winding of the optical film from the straight winding to the oscillating winding when the winding length of the optical film reaches a predetermined switching winding length. Details of the oscillatory winding will be omitted below.

[0325] FIG. 11 is a schematic diagram showing the process of winding up an optical film and a cross section of the film roll of the present invention after winding up. In FIG. 11, the formed optical film 31 is wound around a roll 32 and a touch roll 33 and taken up as a film roll 30.

[0326] (3.3) Film roll manufacturing process using the melt casting method The optical film according to the present invention can also be produced by a melt casting method. The "melt film-forming method" refers to a method in which a composition containing a thermoplastic resin and the above-mentioned additives is heated to a temperature at which it exhibits fluidity and melted, and then the melt containing the fluid thermoplastic resin is cast.

[0327] Molding methods involving heating and melting can be specifically classified into melt extrusion molding, press molding, inflation molding, injection molding, blow molding, stretch molding, and the like. Among these molding methods, the melt extrusion method is preferred from the viewpoints of mechanical strength and surface precision.

[0328] FIG. 12 is a flowchart showing the flow of the manufacturing process of the melt-casting film-forming method. FIG. 13 is a schematic diagram of an apparatus for producing an optical film by a melt-casting film-forming method. The solution casting film-forming method will be described below with reference to FIGS. The method for producing a film roll by the melt-casting film-forming method includes an extrusion step (M1), a casting / molding step (M2), a first stretching step (M3), a first cutting step (M4), a second stretching step (M5), a second cutting step (M6), and a winding step (M7).

[0329] It is not necessary for the above-mentioned production method to include both the first stretching step (M3) and the second stretching step (M5), but it is sufficient to include at least one of these steps. Similarly, it is sufficient that the first cutting step (M4) and the second cutting step (M6) include at least one of the steps.

[0330] (3.3.1) Extrusion process (M1) In the extrusion step (M1), at least a resin is melt-extruded in an extruder 14 and molded onto a cast drum 16. The resins that can be used in the present invention will be described in detail below.

[0331] It is also preferable that the resin be kneaded and pelletized in advance. The pelletization may be carried out by a known method.

[0332] For example, dry resin, plasticizer, and other additives are fed into an extruder using a feeder, kneaded using a single-screw or twin-screw extruder, extruded in the form of strands from a casting die, cooled with water or air, and cut into pellets.

[0333] The additives may be mixed with the resin before being fed to the extruder, or the additives and the resin may be fed to the extruder using separate feeders. Furthermore, it is preferable to mix small amounts of additives such as particles and antioxidants into the resin in advance in order to mix them uniformly.

[0334] When the pellets are introduced into the extruder from the supply hopper, it is preferable to prevent oxidative decomposition by drying, under vacuum, reduced pressure or in an inert gas atmosphere.

[0335] It is preferable that the extruder be operated at a temperature as low as possible that allows pelletization and prevents deterioration of the resin (reduction in molecular weight, coloration, gel formation, etc.) by suppressing shearing force.

[0336] For example, in the case of a twin-screw extruder, it is preferable to use deep-groove type screws and rotate them in the same direction. In view of uniformity of kneading, the intermeshing type is preferred. When the resin pellets are melted, it is preferable to filter them using a leaf disc type filter or the like to remove foreign matter.

[0337] The pellets obtained as described above are used to form a film. Of course, it is also possible to feed the raw material resin (powder, etc.) directly to an extruder using a feeder without pelletizing, and to form a film directly from the resin.

[0338] (3.3.2) Casting / forming process (M2) In the casting and molding process (M2), the resin pellets melted in the extrusion process are passed through a pressure-type metering gear pump or the like and cast into a film form from the casting die 15 through a conduit, and then cast from the casting die 15 onto the casting position on the endless cast drum 16 made of stainless steel and rotated to transport the resin pellets endlessly. The cast molten resin pellets are then molded on a cast drum 16 to form a cast film 18 .

[0339] The inclination of the casting die 15, i.e., the direction of the molten resin / pellets being discharged from the casting die 15 to the support 16, may be set appropriately so that the angle relative to the normal to the surface of the cast drum 16 (the surface onto which the molten resin / pellets are cast) falls within the range of 0 to 90°.

[0340] The optical film F may be formed by using a touch roll 16a or a cooling drum 17 that assists the casting drum 16, either alone or in combination.

[0341] A person skilled in the art would know how to improve the film thickness uniformity in the casting / molding step (M2), such as controlling the pump pulsation pitch, controlling the initial film thickness by using a heat bolt of the casting die, and other matters, which are similar to those in the casting step (S2) in the manufacturing process of the film roll by the solution casting film-forming method described above. Also, the description of the amount of residual solvent in the peeling step (S3), the shrinkage rate in the shrinking step (S4), and the drying method in the drying step (S5) are omitted here to avoid redundancy.

[0342] (3.3.3) First stretching process (M3) In the first stretching step (M3), the optical film F is stretched by a stretching device 19. As the stretching method in this case, a stretching method in the MD direction by setting a difference in peripheral speed between rolls, or a tenter method in which both side edges of the optical film F are fixed with clips or the like and stretched in the TD direction is preferred in order to improve the performance, productivity, flatness, and dimensional stability of the optical film. In addition to stretching, drying may also be carried out in the stretching device 19.

[0343] The description of the tenter stretching device, heat treatment timing, furnace temperature, stretching temperature, temperature inside the stretching furnace, and amount of residual solvent will be omitted because they overlap with the first stretching step (S6) in the film roll manufacturing process by the solution casting film-forming method.

[0344] (3.3.4) First cutting process (M4) In the first cutting step (M4), a cutting unit 20 made of a slitter cuts both ends of the formed optical film F in the width direction. In the optical film F, the portions remaining after cutting both ends constitute product portions that will become optical film products. On the other hand, the portion cut from the optical film F may be collected and reused as part of the raw material for producing an optical film.

[0345] (3.3.5) Second stretching process (M5) In the second stretching step (M5), the optical film F is stretched by the stretching device 21 in the same manner as in the first stretching step (M3). As the stretching method in this case, a stretching method in the MD direction by setting a difference in peripheral speed between rolls, or a tenter method in which both side edges of the optical film F are fixed with clips or the like and stretched in the TD direction is preferred in order to improve the performance, productivity, flatness, and dimensional stability of the optical film. In addition to stretching, drying may also be carried out in the stretching device 21.

[0346] (3.3.6) Second cutting process (M6) In the second cutting step (M6), the cutting unit 22 made of a slitter cuts both ends of the formed optical film F in the width direction, similar to the first cutting step (M4). In the optical film F, the portions remaining after cutting both ends constitute product portions that will become optical film products. On the other hand, the portion cut from the optical film F may be collected and reused as part of the raw material for producing an optical film.

[0347] (3.3.7) Winding process (M7) Finally, in the winding step (M7), the optical film F is wound by a winding device 23 to obtain a film roll. That is, in the winding step, the optical film F is wound around a core while being transported, thereby producing a film roll. The optical film F can be wound using a commonly used winder, and various tension control methods, such as the constant torque method, constant tension method, taper tension method, and program tension control method with constant internal stress, can be used appropriately. [Example]

[0348] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the examples, the terms "parts" and "%" are used, but unless otherwise specified, they represent "parts by mass" or "% by mass."

[0349] <Preparation of film roll> (Production of film roll No. 101) The optical film was formed by a solution casting method.

[0350] (Dope preparation step (S1)) <Synthesis of cyclic polyolefin polymer P-1> 100 parts by mass of purified toluene and 100 parts by mass of norbornenecarboxylic acid methyl ester were placed in a stirrer. Next, 25 mmol % (based on the monomer mass) of ethylhexanoate-Ni dissolved in toluene, 0.225 mol % (based on the monomer mass) of tri(pentafluorophenyl)boron, and 0.25 mol % (based on the monomer mass) of triethylaluminum dissolved in toluene were added to the stirring device. The reaction was carried out at room temperature with stirring for 18 hours. After the reaction was completed, the reaction mixture was poured into an excess of ethanol to precipitate a polymer. The precipitate was purified, and the resulting polymer (P-1) was dried in a vacuum oven at 65° C. for 24 hours.

[0351] <Preparation of Dope D-1> The following composition 1 was charged into a mixing tank and stirred to dissolve each component, and then filtered through a filter paper having an average pore size of 34 μm and a sintered metal filter having an average pore size of 10 μm to prepare a dope.

[0352] (Composition 1) Cyclic polyolefin polymer (P-1) 150 parts by mass Dichloromethane 380 parts by mass Methanol 70 parts by mass Next, the following composition 2 containing the cyclic polyolefin solution (dope) prepared by the above method was charged into a disperser to prepare a fine particle dispersion (M-1) as an additive.

[0353] (Composition 2) Fine particles (Aerosil R812: manufactured by Nippon Aerosil Co., Ltd., primary average particle size: 7 nm, apparent specific gravity 50 g / L) 4 parts by mass Dichloromethane 76 parts by mass Methanol 10 parts by mass Cyclic polyolefin solution (Dope D-1) 10 parts by mass 100 parts by mass of the cyclic polyolefin solution and 0.75 parts by mass of the fine particle dispersion were mixed to prepare a film-forming dope (resin composition cycloolefin resin COP1).

[0354] (Casting process (S2)) The dope (resin composition cycloolefin resin COP1) prepared in the dope preparation step (S1) was sent to a casting die through a conduit via a pressure-type metering gear pump, and the dope was cast from the casting die to a casting position on a support consisting of an endless rotating stainless steel belt in an 1800 mm width on a film production line. The dope was heated on the support until it became self-supporting, and dried by evaporating the solvent until the cast film could be peeled off from the support with a peel roll, thereby forming a cast film.

[0355] The length of the piping from the pump to the casting die was set to 30 m, and the gear ratio of the gear pump used for sending the dope was adjusted to set the rotation speed of the pump to 70 rpm (flattening treatment 1 was not performed).

[0356] The width of the slit through which the dope was discharged was adjusted by the heat bolt of the casting die so that the film thickness deviation immediately after discharge was 5.5% relative to the entire cast film, thereby controlling the initial film thickness of the cast film (flattening treatment 2 was not performed).

[0357] After the casting film on the belt was dried until the residual solvent amount reached 5% by mass, forming a coating on the surface, hot air was blown onto the film at a speed of 45 m / sec (40°C) to flatten the protrusions (flattening treatment 3 not performed).

[0358] (Peeling step (S3)) In the casting step (S2), after forming the cast film, the cast film was peeled off from the support by a peeling roll while maintaining its self-supporting property.

[0359] (Shrinkage process (S4)) The optical film was treated at a high temperature without being held in the width direction, and the density of the optical film was increased, thereby causing the optical film to shrink in the width direction at a shrinkage rate of 7%.

[0360] (1st drying step (S5)) Thereafter, the optical film was heated on the support to evaporate the solvent. The amount of residual solvent in the optical film was measured by the following method and was found to be 5% by mass or less.

[0361] (Measurement of residual solvent amount) The amount of residual solvent was determined by mass spectrometry using gas chromatography as follows. That is, a piece of film was taken from any location, and in order to prevent the solvent remaining in the film from volatilizing, it was quickly placed in a vial and sealed. Next, a needle was inserted into the vial and mass spectrometry was performed using a gas chromatograph (Agilent Technologies, Inc.).

[0362] The amount of residual solvent is defined by the following formula: Residual solvent amount (mass%) = {(MN) / N} × 100 In the above formula, M is the mass (g) of a sample taken at any time during or after the production of the cast membrane or film, and N is the mass (g) of the sample after heating at 115°C for 1 hour.

[0363] (1st stretching process (S6)) Thereafter, the optical film was transported in a tenter stretching device and stretched transversely. Under the conditions shown in Table I, a required number of infrared (IR) heaters were installed to perform heat treatment (implementation of flattening treatment 4).

[0364] (1st cutting process (S7)) Both ends in the width direction of the stretched optical film were cut.

[0365] (Second stretching process (S8)) As in the first stretching step, the optical film was stretched by a tenter stretching device. The amount of residual solvent in the optical film was measured by the following method and was found to be 1 to 5% by mass.

[0366] (Second cutting process (S9)) Similar to the first cutting step, both ends in the width direction of the stretched optical film were cut.

[0367] (Second drying step (S10)) As in the first drying step, the optical film was heated on the support to evaporate the solvent. The amount of residual solvent in the optical film was measured and found to be 0.1 to 2% by mass.

[0368] (Third cutting process (S11)) Similar to the first cutting step and the second cutting step, both ends in the width direction of the stretched optical film were cut.

[0369] (Winding process (S12)) The optical film was wound up. The initial tension was 50 N, the taper was 70%, and the corners were 25%. Using a touch roll (TR), the average thickness of the air layer contained in the film roll was reduced to 0.8 μm. The film roll width was 2000 mm and the roll length was 3900 m. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 101 was produced through the above steps.

[0370] (Production of film roll No. 102) The optical film was formed by a solution casting method.

[0371] (Dope preparation step (S1)) A film-forming dope (resin composition: cycloolefin resin COP1) was prepared in the same manner as in the film roll No. 101.

[0372] (Casting process (S2)) The casting process was carried out in the same manner as in the case of film roll No. 101. In the casting process, the length of the piping from the pump to the casting die was set to 60 m, and the gear ratio of the gear pump used for sending the dope was adjusted to 20 rpm (planarization treatment 1). Planarization treatments 2 and 3 were not performed.

[0373] (Peeling step (S3) to first drying step (S5)) The peeling step (S3) to the first drying step (S5) were carried out in the same manner as in the film roll No. 101. The amount of residual solvent in the optical film after the first drying step (S5) was measured and found to be 5% by mass or less.

[0374] (1st stretching process (S6)) Thereafter, the optical film was transported in a tenter stretching device and stretched transversely. The temperature inside the furnace was 175°C, and no infrared (IR) heater was installed on the optical film, so no heat treatment was performed (flattening treatment 4 not performed: no heat treatment).

[0375] (1st cutting process (S7)) ~ (3rd cutting process (S11)) The first cutting step (S7) to the third cutting step (S11) were carried out in the same manner as for film roll No. 101.

[0376] (Winding process (S12)) The optical film was wound up. The initial tension was 50 N, the taper was 70%, and the corners were 25%. A touch roll (TR) was used to reduce the average thickness of the air layer contained in the film roll to 0.6 μm. The film roll width was 2000 mm and the roll length was 3900 m. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 102 was produced through the above steps.

[0377] (Production of film roll No. 103) The optical film was formed by a solution casting method. (Dope preparation step (S1)) A film-forming dope (resin composition: cycloolefin resin COP1) was prepared in the same manner as in the film roll No. 101.

[0378] (Casting process (S2)) The casting process was carried out in the same manner as in the case of film roll No. 101. The thickness deviation of the film thickness immediately after the casting was adjusted to 1.5% in the width direction of the slit through which the dope was discharged by the heat bolt of the casting die, thereby controlling the initial film thickness of the cast film (implementation of flattening treatment 2). Planarization treatments 1 and 3 were not performed.

[0379] (Peeling step (S3) to first drying step (S5)) The peeling step (S3) to the first drying step (S5) were carried out in the same manner as in the film roll No. 101. The amount of residual solvent in the optical film after the first drying step (S5) was measured and found to be 5% by mass or less.

[0380] (1st stretching process (S6)) Thereafter, the optical film was transported in a tenter stretching device and stretched transversely. The temperature inside the furnace was 175°C, and no infrared (IR) heater was installed on the optical film, so no heat treatment was performed (flattening treatment 4 not performed: no heat treatment).

[0381] (1st cutting process (S7)) ~ (3rd cutting process (S11)) The first cutting step (S7) to the third cutting step (S11) were carried out in the same manner as for film roll No. 101.

[0382] (Winding process (S12)) The optical film was wound up. The initial tension was 50 N, the taper was 70%, and the corners were 25%. A touch roll (TR) was used to reduce the average thickness of the air layer contained in the film roll to 0.4 μm. The film roll width was 2000 mm and the roll length was 3900 m. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 103 was produced through the above steps.

[0383] (Production of film roll No. 104) The optical film was formed by a solution casting method. (Dope preparation step (S1)) A film-forming dope (resin composition: cycloolefin resin COP1) was prepared in the same manner as in the film roll No. 101.

[0384] (Casting process (S2)) The casting process was carried out in the same manner as in the case of film roll No. 101. After the casting film on the belt was dried until the residual solvent amount reached 200% by mass, forming a coating on the surface, hot air was blown onto the film at a speed of 16 m / sec (40°C) to flatten the protrusions (flattening treatment 3). Planarization treatments 1 and 2 were not performed.

[0385] (Peeling step (S3) to first drying step (S5)) The peeling step (S3) to the first drying step (S5) were carried out in the same manner as in the film roll No. 101. The amount of residual solvent in the optical film after the first drying step (S5) was measured and found to be 5 to 15% by mass.

[0386] (1st stretching process (S6)) Thereafter, the optical film was transported in a tenter stretching device and stretched transversely. The temperature inside the furnace was 175°C, and no infrared (IR) heater was installed on the optical film, so no heat treatment was performed (flattening treatment 4 not performed: no heat treatment).

[0387] (1st cutting process (S7)) ~ (3rd cutting process (S11)) The first cutting step (S7) to the third cutting step (S11) were carried out in the same manner as for film roll No. 101.

[0388] (Winding process (S12)) The optical film was wound up. The initial tension was 50 N, the taper was 70%, and the corners were 25%. A touch roll (TR) was used to reduce the average thickness of the air layer contained in the film roll to 0.5 μm. The film roll width was 2000 mm and the roll length was 3900 m. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 104 was produced by the above steps.

[0389] (Production of film roll No. 105) The optical film was formed by a solution casting method. (Dope preparation step (S1)) A film-forming dope (resin composition: cycloolefin resin COP1) was prepared in the same manner as in the film roll No. 101.

[0390] (Casting process (S2)) The casting process was carried out in the same manner as in the case of film roll No. 101. In the casting process, the length of the piping from the pump to the casting die was set to 60 m, and the gear ratio of the gear pump used for sending the dope was adjusted to 20 rpm (planarization treatment 1). The width of the slit through which the dope was discharged was adjusted by the heat bolt of the casting die so that the film thickness deviation immediately after discharge was 1.5% for the entire casting film, thereby controlling the initial film thickness of the casting film (implementation of flattening treatment 2).

[0391] Planarization process 3 was not performed.

[0392] (Peeling step (S3) to first drying step (S5)) The peeling step (S3) to the first drying step (S5) were carried out in the same manner as in the film roll No. 101. The amount of residual solvent in the optical film after the first drying step (S5) was measured and found to be 5% by mass or less.

[0393] (1st stretching process (S6)) Thereafter, the optical film was transported in a tenter stretching device and stretched transversely. The temperature inside the furnace was 175°C, and no infrared (IR) heater was installed on the optical film, so no heat treatment was performed (flattening treatment 4 not performed: no heat treatment).

[0394] (1st cutting process (S7)) ~ (3rd cutting process (S11)) The first cutting step (S7) to the third cutting step (S11) were carried out in the same manner as for film roll No. 101.

[0395] (Winding process (S12)) The optical film was wound up. The initial tension was 50 N, the taper was 70%, and the corners were 25%. A touch roll (TR) was used to reduce the average thickness of the air layer contained in the film roll to 0.4 μm. The film roll width was 2000 mm and the roll length was 3900 m. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 105 was produced through the above steps.

[0396] (Production of film roll No. 106) The optical film was formed by a solution casting method. (Dope preparation step (S1)) A film-forming dope (resin composition: cycloolefin resin COP1) was prepared in the same manner as in the film roll No. 101.

[0397] (Casting process (S2)) The casting process was carried out in the same manner as in the case of film roll No. 101. In the casting process, the length of the piping from the pump to the casting die was set to 60 m, and the gear ratio of the gear pump used for sending the dope was adjusted to 20 rpm (planarization treatment 1). The width of the slit through which the dope was discharged was adjusted by the heat bolt of the casting die so that the film thickness deviation immediately after discharge was 1.5% for the entire casting film, thereby controlling the initial film thickness of the casting film (implementation of flattening treatment 2). The casting film on the belt was dried until the residual solvent amount reached 200% by mass, forming a coating on the surface. After that, hot air was blown onto the casting film at a speed of 16 m / sec (40°C) to flatten the protrusions (flattening treatment 3).

[0398] (Peeling step (S3) to first drying step (S5)) The peeling step (S3) to the first drying step (S5) were carried out in the same manner as in the film roll No. 101. The amount of residual solvent in the optical film after the first drying step (S5) was measured and found to be 5 to 15% by mass.

[0399] (1st stretching process (S6)) Thereafter, the optical film was transported in a tenter stretching device and stretched transversely. The temperature inside the furnace was 175°C, and the optical film was heat-treated by installing the required number of infrared (IR) heaters in the preheating zone so that the temperature difference between the furnace and the optical film was 60°C (planarization process 4 was performed: the heat treatment was performed in the preheating zone).

[0400] The first cutting step (S7) to the third cutting step (S11) were carried out in the same manner as for film roll No. 101.

[0401] (Winding process (S12)) The optical film was wound up. The initial tension was 50 N, the taper was 70%, and the corners were 25%. A touch roll (TR) was used to reduce the average thickness of the air layer contained in the film roll to 0.4 μm. The film roll width was 2000 mm and the roll length was 3900 m. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 106 was produced through the above steps.

[0402] (Production of film roll No. 107) The optical film was formed by a solution casting method. (Dope preparation step (S1)) A film-forming dope (resin composition: cycloolefin resin COP1) was prepared in the same manner as in the film roll No. 101.

[0403] (Casting process (S2)) The casting process was carried out in the same manner as in the case of film roll No. 101. As with film roll No. 106, all of the flattening treatments 1 to 3 were carried out.

[0404] (Peeling step (S3) to first drying step (S5)) The peeling step (S3) to the first drying step (S5) were carried out in the same manner as in the film roll No. 101. The amount of residual solvent in the optical film after the first drying step (S5) was measured and found to be 5 to 15% by mass.

[0405] (1st stretching process (S6)) Thereafter, the optical film was transported in a tenter stretching device and stretched transversely. The temperature inside the furnace was 175°C, and the optical film was heat-treated by installing the required number of infrared (IR) heaters in the preheating zone so that the temperature difference between the furnace and the optical film was 190°C (planarization process 4 was performed: the heat treatment was performed in the preheating zone).

[0406] (1st cutting process (S7)) ~ (3rd cutting process (S11)) The first cutting step (S7) to the third cutting step (S11) were carried out in the same manner as for film roll No. 101.

[0407] (Winding process (S12)) The optical film was wound up. The initial tension was 50 N, the taper was 70%, and the corners were 25%. A touch roll (TR) was used to reduce the average thickness of the air layer contained in the film roll to 0.2 μm. The film roll width was 2000 mm and the roll length was 3900 m. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 107 was produced through the above steps.

[0408] (Production of film roll No. 108) The optical film was formed by a solution casting method. (Dope preparation step (S1)) A film-forming dope (resin composition: cycloolefin resin COP1) was prepared in the same manner as in the film roll No. 101.

[0409] (Casting process (S2)) The casting process was carried out in the same manner as in the case of film roll No. 101. As with film roll No. 106, all of the flattening treatments 1 to 3 were carried out.

[0410] (Peeling step (S3) to first drying step (S5)) The peeling step (S3) to the first drying step (S5) were carried out in the same manner as in the film roll No. 101. The amount of residual solvent in the optical film after the first drying step (S5) was measured and found to be 5 to 15% by mass.

[0411] (1st stretching process (S6)) Thereafter, the optical film was transported in a tenter stretching device and stretched transversely. The temperature inside the furnace was 175°C, and the optical film was heat-treated by installing the required number of infrared (IR) heaters in the stretching zone so that the temperature difference between the furnace and the optical film was 60°C (flattening treatment 4 was performed: the heat treatment was performed in the stretching zone).

[0412] (1st cutting process (S7)) ~ (3rd cutting process (S11)) The first cutting step (S7) to the third cutting step (S11) were carried out in the same manner as for film roll No. 101.

[0413] (Winding process (S12)) The optical film was wound up. The initial tension was 50 N, the taper was 70%, and the corners were 25%. A touch roll (TR) was used to reduce the average thickness of the air layer contained in the film roll to 0.2 μm. The film roll width was 2000 mm and the roll length was 3900 m. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 108 was produced through the above steps.

[0414] (Production of film roll No. 109) The optical film was formed by a solution casting method. (Dope preparation step (S1)) A film-forming dope (resin composition: cycloolefin resin COP1) was prepared in the same manner as in the film roll No. 101.

[0415] (Casting process (S2)) The casting process was carried out in the same manner as in the case of film roll No. 101. As with film roll No. 106, all of the flattening treatments 1 to 3 were carried out.

[0416] (Peeling step (S3) to first drying step (S5)) The peeling step (S3) to the first drying step (S5) were carried out in the same manner as in the film roll No. 101. The amount of residual solvent in the optical film after the first drying step (S5) was measured and found to be 5 to 15% by mass.

[0417] (1st stretching process (S6)) Thereafter, the optical film was transported in a tenter stretching device and stretched transversely. The temperature inside the furnace was 175°C, and the optical film was heat-treated by installing the required number of infrared (IR) heaters in the heat-setting zone so that the temperature difference between the furnace and the optical film was 60°C (planarization treatment 4 was performed: the heat treatment was performed in the heat-setting zone).

[0418] (1st cutting process (S7)) ~ (3rd cutting process (S11)) The first cutting step (S7) to the third cutting step (S11) were carried out in the same manner as for film roll No. 101.

[0419] (Winding process (S12)) The optical film was wound up. The initial tension was 50 N, the taper was 70%, and the corners were 25%. A touch roll (TR) was used to reduce the average thickness of the air layer contained in the film roll to 0.3 μm. The film roll width was 2000 mm and the roll length was 3900 m. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 109 was produced through the above steps.

[0420] (Production of film roll No. 110) The optical film was formed by a solution casting method.

[0421] (Dope preparation step (S1) to third cutting step (S11)) The dope preparation step (S1) to the third cutting step (S11) were carried out in the same manner as in the film roll No. 106, except that some conditions were changed when performing the flattening treatment 2, such as increasing the width of the casting die or the thickness at the casting die.

[0422] (Winding process (S12)) The optical film was wound up. The initial tension was 50 N, the taper was 70%, and the corners were 25%. A touch roll (TR) was used to reduce the average thickness of the air layer contained in the film roll to 0.4 μm. The film roll width was 2900 mm and the roll length was 3900 m. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 110 was produced through the above steps.

[0423] (Production of film roll No. 111) The optical film was formed by a solution casting method.

[0424] (Dope preparation step (S1) to third cutting step (S11)) The dope preparation step (S1) to the third cutting step (S11) were carried out in the same manner as in the film roll No. 106.

[0425] (Winding process (S12)) The optical film was wound up. The test was carried out with an initial tension of 50 N, a taper of 70%, and a corner of 25%. A touch roll (TR) was used to reduce the average thickness of the air layer contained in the film roll to 0.3 μm. The film roll width was 2000 mm and the roll length was 9100 m. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 111 was produced through the above steps.

[0426] (Production of film roll No. 112) The optical film was formed by a solution casting method. (Dope preparation step (S1)) A film-forming dope (resin composition: cycloolefin resin COP1) was prepared in the same manner as in the film roll No. 101.

[0427] (Casting process (S2)) The casting process was carried out in the same manner as in the case of film roll No. 101. As with film roll No. 106, all of the flattening treatments 1 to 3 were carried out.

[0428] (Peeling step (S3) to first drying step (S5)) The peeling step (S3) to the first drying step (S5) were carried out in the same manner as in the film roll No. 101. The amount of residual solvent in the optical film after the first drying step (S5) was measured and found to be 5 to 15% by mass.

[0429] (1st stretching process (S6)) Thereafter, the optical film was transported in a tenter stretching device and stretched transversely. The temperature inside the furnace was 175°C, and the optical film was heat-treated by installing the required number of infrared (IR) heaters in the preheating zone so that the temperature difference between the furnace and the optical film was 140°C (planarization process 4 was performed: the heat treatment was performed in the preheating zone).

[0430] (1st cutting process (S7)) ~ (3rd cutting process (S11)) The first cutting step (S7) to the third cutting step (S11) were carried out in the same manner as for film roll No. 101.

[0431] (Winding process (S12)) The optical film was wound up. The initial tension was 50 N, the taper was 70%, and the corners were 25%. A touch roll (TR) was used to reduce the average thickness of the air layer contained in the film roll to 0.3 μm. The film roll width was 2000 mm and the roll length was 3900 m. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 112 was produced through the above steps.

[0432] (Production of film roll No. 113) The optical film was formed by a solution casting method. (Dope preparation step (S1)) A film-forming dope (resin composition: cycloolefin resin COP1) was prepared in the same manner as in the film roll No. 101.

[0433] (Casting process (S2)) The casting process was carried out in the same manner as in the case of film roll No. 101. As with film roll No. 106, all of the flattening treatments 1 to 3 were carried out.

[0434] (Peeling step (S3) to first drying step (S5)) The peeling step (S3) to the first drying step (S5) were carried out in the same manner as in the film roll No. 101. The amount of residual solvent in the optical film after the first drying step (S5) was measured and found to be 5 to 15% by mass.

[0435] (1st stretching process (S6)) Thereafter, the optical film was transported in a tenter stretching device and stretched transversely. The temperature inside the furnace was 165°C, and the optical film was heat-treated by installing the required number of infrared (IR) heaters in the preheating zone so that the temperature difference between the furnace and the optical film was 30°C (planarization process 4 was performed: the heat treatment was performed in the preheating zone).

[0436] (1st cutting process (S7)) ~ (3rd cutting process (S11)) The first cutting step (S7) to the third cutting step (S11) were carried out in the same manner as for film roll No. 101.

[0437] (Winding process (S12)) The optical film was wound up. The initial tension was 50 N, the taper was 70%, and the corners were 25%. A touch roll (TR) was used to reduce the average thickness of the air layer contained in the film roll to 0.5 μm. The film roll width was 2000 mm and the roll length was 3900 m. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 113 was produced through the above steps.

[0438] (Production of film roll No. 114) The optical film was formed by a solution casting method. (Dope preparation step (S1)) A film-forming dope (resin composition cycloolefin resin COP1) was prepared in the same manner as in film roll No. 101, except that fine particles (Aerosil R812: manufactured by Nippon Aerosil Co., Ltd., primary average particle diameter: 7 nm, apparent specific gravity: 50 g / L) were not used as an additive.

[0439] (Casting process (S2)) The casting process was carried out in the same manner as in the case of film roll No. 101. As with film roll No. 106, all of the flattening treatments 1 to 3 were carried out.

[0440] (Peeling step (S3) to first drying step (S5)) The peeling step (S3) to the first drying step (S5) were carried out in the same manner as in the film roll No. 101. The amount of residual solvent in the optical film after the first drying step (S5) was measured and found to be 5 to 15% by mass.

[0441] (1st stretching process (S6)) Thereafter, the optical film was transported in a tenter stretching device and stretched transversely. The temperature inside the furnace was 165°C, and the optical film was heat-treated by installing the required number of infrared (IR) heaters in the preheating zone so that the temperature difference between the furnace and the optical film was 30°C (planarization process 4 was performed: the heat treatment was performed in the preheating zone).

[0442] (1st cutting process (S7)) ~ (3rd cutting process (S11)) The first cutting step (S7) to the third cutting step (S11) were carried out in the same manner as for film roll No. 101.

[0443] (Winding process (S12)) The optical film was wound up. The initial tension was 50 N, the taper was 70%, and the corners were 25%. A touch roll (TR) was used to reduce the average thickness of the air layer contained in the film roll to 0.5 μm. The film roll width was 2000 mm and the roll length was 3900 m. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 114 was produced through the above steps.

[0444] (Production of film roll No. 115) The optical film was formed by a melt casting method. (Extrusion process (M1)) A resin (resin composition cycloolefin resin COP2) was prepared using the same procedure as for film roll No. 101. The resin was pelletized and then fed into an extruder together with additives (fine particles (Aerosil R812: manufactured by Nippon Aerosil Co., Ltd., average primary particle diameter: 7 nm, apparent specific gravity: 50 g / L)). The pellets were melted in the extruder and extruded into a film form from a casting die onto a casting drum through a pressure-type metering gear pump.

[0445] (Casting / forming process (M2)) In the extrusion process, the length of the piping from the pump to the casting die was set to 60 m, and the gear ratio of the gear pump used for feeding the liquid was adjusted to set the rotation speed of the pump to 20 rpm (implementation of flattening treatment 1).

[0446] The width of the slit through which the dope was discharged was adjusted by the heat bolt of the casting die so that the film thickness deviation immediately after discharge was 1.5% for the entire casting film, thereby controlling the initial film thickness of the casting film (implementation of flattening treatment 2).

[0447] Planarization process 3 was not performed. The extruded resin was cooled on a cooling drum and molded to form a cast film.

[0448] (1st stretching process (M3)) Thereafter, the optical film was transported in a tenter stretching device and stretched transversely. The temperature inside the furnace was 150°C, and the optical film was heat-treated by installing the required number of infrared (IR) heaters in the preheating zone so that the temperature difference between the furnace and the optical film was 100°C (planarization process 4 was performed: the heat treatment was performed in the preheating zone).

[0449] (1st cutting process (M4)) Both ends in the width direction of the stretched optical film were cut.

[0450] (Second stretching process (M5)) As in the first stretching step, the optical film was stretched by a tenter stretching device.

[0451] (Second cutting process (M6)) Similar to the first cutting step, both ends in the width direction of the stretched optical film were cut.

[0452] (Winding process (M7)) The optical film was wound up. The initial tension was 50 N, the taper was 70%, and the corners were 25%. A touch roll (TR) was used to reduce the average thickness of the air layer contained in the film roll to 0.5 μm. The film roll width was 2000 mm and the roll length was 3900 m. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 115 was produced through the above steps.

[0453] (Production of film roll No. 116) The optical film was formed by a melt casting method. (Extrusion process (M1) to second cutting process (M6)) The extrusion process (M1) to the second cutting process (M6) were carried out in the same manner as for film roll No. 115, except that fine particles (Aerosil R812: manufactured by Nippon Aerosil Co., Ltd., primary average particle diameter: 7 nm, apparent specific gravity 50 g / L) were not used as an additive.

[0454] (Winding process (M7)) The optical film was wound up. The initial tension was 50 N, the taper was 70%, and the corners were 25%. A touch roll (TR) was used to reduce the average thickness of the air layer contained in the film roll to 0.5 μm. The film roll width was 2000 mm and the roll length was 3900 m. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 116 was produced through the above steps.

[0455] (Production of film roll No. 117) The optical film was formed by a solution casting method. (Dope preparation step (S1)) A dope for film formation was prepared in the same manner as in the film roll No. 101, except that TAC was used instead of COP1 as the resin composition.

[0456] (Casting process (S2) ~ 1st drying process (S5)) The casting step (S2) to the first drying step (S5) were carried out in the same manner as in the optical film No. 106. The amount of residual solvent in the optical film after the first drying step (S5) was measured and found to be 5 to 15% by mass.

[0457] (1st stretching process (S6)) Thereafter, the optical film was transported in a tenter stretching device and stretched transversely. The temperature inside the furnace was 150°C, and the optical film was heat-treated by installing the required number of infrared (IR) heaters in the preheating zone so that the temperature difference between the furnace and the optical film was 140°C (planarization process 4 was performed: the heat treatment was performed in the preheating zone).

[0458] (1st cutting process (S7)) ~ (3rd cutting process (S11)) The first cutting step (S7) to the third cutting step (S11) were carried out in the same manner as for film roll No. 101.

[0459] (Winding process (S12)) The optical film was wound up. The initial tension was 50 N, the taper was 70%, and the corners were 25%. A touch roll (TR) was used to reduce the average thickness of the air layer contained in the film roll to 0.5 μm. The film roll width was 2000 mm and the roll length was 3900 m. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 117 was produced through the above steps.

[0460] (Production of film roll No. 118) The optical film was formed by a solution casting method. (Dope preparation step (S1)) A dope for film formation was prepared in the same manner as in Film Roll No. 101, except that polymethyl methacrylate (PMMA) was used instead of COP1 as the resin composition.

[0461] (Casting process (S2) ~ 1st drying process (S5)) The casting step (S2) to the first drying step (S5) were carried out in the same manner as in the optical film No. 106. The amount of the remaining solvent in the casting membrane after the first drying step (S5) was measured and found to be 5 to 15% by mass.

[0462] (1st stretching process (S6)) Thereafter, the optical film was transported in a tenter stretching device and stretched transversely. The temperature inside the furnace was 115°C, and the optical film was heat-treated by installing the required number of infrared (IR) heaters in the preheating zone so that the temperature difference between the furnace and the optical film was 120°C (planarization process 4 was performed: the heat treatment was performed in the preheating zone).

[0463] The first cutting step (S7) to the third cutting step (S11) were carried out in the same manner as for film roll No. 101.

[0464] (Winding process (S12)) The optical film was wound up. The initial tension was 50 N, the taper was 70%, and the corners were 25%. A touch roll (TR) was used to reduce the average thickness of the air layer contained in the film roll to 0.3 μm. The film roll width was 2000 mm and the roll length was 3900 m. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 118 was produced through the above steps.

[0465] (Production of film roll No. 119) In the winding step (S12), the same procedure as for film roll No. 106 was followed, except that the film roll width was set to 2400 mm. A touch roll (TR) was used to limit the average thickness of the air layer contained in the film roll to 0.4 μm. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 119 was produced through the above steps.

[0466] (Production of film roll No. 120) The winding process was carried out in the same manner as for film roll No. 106, except that the winding length in (S12) was 7,500 m. A touch roll (TR) was used to reduce the average thickness of the air layer contained in the film roll to 0.3 μm. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 120 was produced by the above steps.

[0467] (Production of film roll No. 121) The optical film was formed by a solution casting method.

[0468] (Dope preparation step (S1) to first drying step (S5)) The dope preparation step (S1) to the first drying step (S5) were carried out in the same manner as in the film roll No. 101. The residual solvent amount in the cast film was measured and found to be 5% by mass or less.

[0469] (1st stretching process (S6)) Thereafter, the optical film was transported in a tenter stretching device and stretched transversely. The temperature inside the furnace was 165°C, and the optical film was heat-treated by installing the required number of infrared (IR) heaters in the preheating zone so that the temperature difference between the furnace and the optical film was 60°C (planarization process 4: the heat treatment was performed in the preheating zone).

[0470] The first cutting step (S7) to the third cutting step (S11) were carried out in the same manner as for film roll No. 101.

[0471] (Winding process (S12)) The optical film was wound up. The initial tension was 50 N, the taper was 70%, and the corners were 25%. A touch roll (TR) was used to reduce the average thickness of the air layer contained in the film roll to 0.5 μm. The film roll width was 2000 mm and the roll length was 3900 m. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 121 was produced through the above steps.

[0472] (Production of film roll No. 122) The optical film was formed by a solution casting method.

[0473] (Dope preparation step (S1) to first drying step (S5)) The dope preparation step (S1) to the first drying step (S5) were carried out in the same manner as in the film roll No. 101. The residual solvent amount in the cast film was measured and found to be 5% by mass or less.

[0474] (1st stretching process (S6)) Thereafter, the optical film was transported in a tenter stretching device and stretched transversely. The temperature inside the furnace was 175°C, and the optical film was heat-treated by installing the required number of infrared (IR) heaters in the preheating zone so that the temperature difference between the furnace and the optical film was 140°C (planarization process 4 was performed: the heat treatment was performed in the preheating zone).

[0475] The first cutting step (S7) to the third cutting step (S11) were carried out in the same manner as for film roll No. 101.

[0476] (Winding process (S12)) The optical film was wound up. The initial tension was 50 N, the taper was 70%, and the corners were 25%. Using a touch roll (TR), the average thickness of the air layer contained in the film roll was reduced to 0.8 μm. The film roll width was 2000 mm and the roll length was 3900 m. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 122 was produced through the above steps.

[0477] (Production of film roll No. 123) The optical film was formed by a solution casting method.

[0478] (Dope preparation step (S1) to first drying step (S5)) The dope preparation step (S1) to the first drying step (S5) were carried out in the same manner as in the film roll No. 101. The residual solvent amount in the cast film was measured and found to be 5% by mass or less.

[0479] (1st stretching process (S6)) Thereafter, the optical film was transported in a tenter stretching device and stretched transversely. The temperature inside the furnace was 165°C, and the optical film was heat-treated by installing the required number of infrared (IR) heaters in the preheating zone so that the temperature difference between the furnace and the optical film was 60°C (planarization process 4: the heat treatment was performed in the preheating zone).

[0480] The first cutting step (S7) to the third cutting step (S11) were carried out in the same manner as for film roll No. 101.

[0481] (Winding process (S12)) The optical film was wound up. The initial tension was 50 N, the taper was 70%, and the corners were 25%. A touch roll (TR) was used to reduce the average thickness of the air layer contained in the film roll to 0.5 μm. The film roll width was 2000 mm and the roll length was 3900 m. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 123 was produced through the above steps.

[0482] (Production of Film Roll No. 124) (For Comparative Example 1) The optical film was formed by a solution casting method.

[0483] (Dope preparation step (S1) to first drying step (S5)) The dope preparation step (S1) to the first drying step (S5) were carried out in the same manner as in the film roll No. 101. The residual solvent amount in the cast membrane was measured and found to be 5 to 15% by mass.

[0484] (1st stretching process (S6)) Thereafter, the optical film was transported in a tenter stretching device and stretched transversely. The temperature inside the furnace was 175°C, and no infrared (IR) heater was installed on the optical film, so no heat treatment was performed (flattening treatment 4 not performed: no heat treatment).

[0485] (1st cutting process (S7) ~ 3rd cutting process (S11)) The first cutting step (S7) to the third cutting step (S11) were carried out in the same manner as for film roll No. 101.

[0486] (Winding process (S12)) The optical film was wound up. The initial tension was 50 N, the taper was 70%, and the corners were 25%. Using a touch roll (TR), the average thickness of the air layer contained in the film roll was reduced to 1.9 μm. The film roll width was 2000 mm and the roll length was 3900 m. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 124 was produced through the above steps.

[0487] (Production of Film Roll No. 125) (For Comparative Example 2) The optical film was formed by a solution casting method.

[0488] (Dope preparation step (S1) to third cutting step (S11)) The dope preparation step (S1) to the third cutting step (S11) were carried out in the same manner as in the film roll No. 101.

[0489] (Knurling process) Thereafter, the optical film was irradiated with laser light to form a knurled portion (area A).

[0490] The width of the knurling process on both ends was 15 mm from the film edge. The line speed for transporting the optical film was set to 60 m / min.

[0491] A carbon dioxide gas laser was used as the laser device, with an output of 20 W, a central wavelength of the emitted light wavelength of 9.4 μm, and a wavelength range of the emitted light of ±0.01 μm or less around the central wavelength.

[0492] The laser light was irradiated onto the optical film by reflecting a collimated beam emitted from a carbon dioxide laser device with two galvanometer mirrors and focusing it onto the surface of the optical film being transported via an fθ lens (focal length 200 mm). By controlling the angle of the galvanometer mirror, the focusing position was moved in the plane direction of the optical film, thereby controlling the trajectory of the laser light irradiation on the surface of the optical film.

[0493] (Atmospheric pressure plasma treatment process: surface modification treatment) A Kasuga Electric AGP-500 was installed on the back side of the knurled part of the optical film, and 0.5 kW of light was applied. The distance between the probe generating atmospheric pressure plasma and the optical film was set to 5 mm. The atmospheric pressure plasma was positioned so that it could be irradiated over a width that was 110% of the knurling width on the back side of the optical film facing the knurling processed area.

[0494] (Winding process (S12)) The optical film was wound up. The initial tension was 50 N, the taper was 70%, and the corners were 25%. Using a touch roll (TR), the average thickness of the air layer contained in the film roll was reduced to 1.7 μm. The film roll width was 2000 mm and the roll length was 3900 m. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 125 was produced through the above steps.

[0495] (Production of Film Roll No. 126) (For Comparative Example 3: with protective film) The optical film was formed by a solution casting method.

[0496] (Dope preparation step (S1) to third cutting step (S11)) The dope preparation step (S1) to the third cutting step (S11) were carried out in the same manner as in the film roll No. 101.

[0497] (Manufacturing process of optical film with protective film) The optical film obtained above was continuously transported through an expander roll, and a long protective film (Toray Processing Film Co., Ltd., Toretek 7832C, total thickness: 30 μm) was also continuously transported. These were stacked and passed between laminating rolls, whereby the laminate of the protective film and the optical film was pressed from above and below and laminated together to produce a laminate film with protective film.

[0498] (Winding process (S12)) The laminated film was wound up. The initial tension was 50 N, the taper was 70%, and the corners were 25%. Using a touch roll (TR), the average thickness of the air layer contained in the film roll was reduced to 0.7 μm. The film roll width was 2000 mm and the roll length was 3900 m. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 126 was produced through the above steps.

[0499] (Preparation of Film Roll No. 127) (For Comparative Example 4: Anti-blocking Film) The optical film was formed by a solution casting method.

[0500] (Dope preparation step (S1) to third cutting step (S11)) The dope preparation step (S1) to the third cutting step (S11) were carried out in the same manner as in the film roll No. 101.

[0501] (Process for producing optical film with anti-blocking layer) The following materials were used to form the anti-blocking layer.

[0502] Binder resin: Arrowbase SE1030N manufactured by Unitika Ltd.: Aqueous dispersion of modified polyolefin resin (modified polyethylene) Crosslinker: Epocross WS700 (manufactured by Nippon Shokubai Kagaku Kogyo Co., Ltd.): Aqueous dispersion of polyoxazoline compound Particle B: Seahoster KE-P30 manufactured by Nippon Shokubai Co., Ltd.: silica particle powder, number average particle size of primary particles: 300 nm Dispersion medium: water

[0503] <Preparation of particle B dispersion> Seahoster KE-P30 was mixed with water and ultrasonically dispersed to prepare an aqueous dispersion with a dispersion concentration of 5% by mass.

[0504] <Preparation of Antiblocking Layer Composition> An anti-blocking layer composition was prepared by combining Arrowbase SE1030N, Epocross WS700, a particle B dispersion, and pure water. The solids concentration in the composition was 2.5% by mass, and the proportions of each component in the solids were 91% by mass for the binder resin, 5.0% by mass for the crosslinker, and 4.0% by mass for the particle B.

[0505] <Preparation of Laminated Film> One surface of the optical film prepared above was subjected to a corona discharge treatment. The electron irradiation dose in corona discharge is 500W / m 2 / min. The prepared antiblocking layer composition was applied to the corona-treated portion of the obtained optical film using a bar coater so that the thickness of the binder resin after drying would be 100 nm, and then dried at 100°C for 3 minutes to form a functional layer. As a result, a laminated film including the optical film and the antiblocking layer was obtained.

[0506] (Winding process (S12)) The laminated film was wound up. The initial tension was 50 N, the taper was 70%, and the corners were 25%. Using a touch roll (TR), the average thickness of the air layer contained in the film roll was reduced to 0.7 μm. The film roll width was 2000 mm and the roll length was 3900 m. The line speed for transporting the optical film was set to 60 m / min. Film roll No. 127 was produced through the above steps.

[0507] (Various measurements and evaluations) The methods for measuring, calculating and evaluating the properties of the above-mentioned various film rolls, such as the outer diameter, are shown below.

[0508] A. Outer diameter of film roll <Measurement method> After storing the prepared film roll at 40°C and 80% RH for one week, the outer diameter was measured with a tape measure at positions 30 mm from both ends of the film roll in the width direction and at the center of the center, and these were taken as the outer diameters of the ends and center, respectively. The outer diameter of the end portion was determined as the average value of the outer diameters of both ends.

[0509] B. Average maximum height difference of film thickness (height of peaks and valleys of uneven surface) (PV) ave1 and (PV)ave2 was measured as follows:

[0510] (B.1) Average maximum height difference (PV) of film thickness ave1 <Measurement and calculation methods> The film thickness was measured at 1612 locations using an in-line retardation / film thickness measuring device RE-200L2T-Rth+film thickness (manufactured by Otsuka Electronics Co., Ltd.). At this time, the traverse movement speed was 100 mm / sec.

[0511] From the above film thickness measurement values, the difference in height between the highest and lowest points of the uneven structure formed on the surface of the optical film is calculated, and the average value is (PV) ave1 It was decided.

[0512] (B.2) Average maximum height difference (PV) of film thickness ave2 <Measurement and calculation methods> Average maximum height difference of film thickness (PV) ave2 The measurement was carried out using an in-line retardation / film thickness measurement system RE-200L2T-Rth+film thickness (manufactured by Otsuka Electronics Co., Ltd.). At this time, the traverse movement speed was 100 mm / sec.

[0513] The measurements were carried out in the following order of steps 1 to 3 in a direction oblique to the width direction of the produced optical film. In step 3, the average maximum elevation difference (PV) ave2 The data used to calculate this is the measurement data for 1612 locations.

[0514] Step 1: After measuring the film thickness at any position on the end, measure the film thickness at a position moved 50 mm in the width direction and 620 mm in the length direction from the arbitrary position for each measurement, and repeat this process up to the other end to calculate the maximum height difference in the diagonal direction. Step 2: After step 1 is completed, measurements similar to step 1 are carried out until the total distance of the longitudinal movement positions reaches 1000 m, and the maximum elevation difference in the diagonal direction is further calculated. Step 3: The average maximum height difference (PV) of the film thickness in the diagonal direction from the maximum height difference in each diagonal direction obtained from steps 1 and 2 ave2 Calculate.

[0515] C. Evaluation of color uniformity of optical films CIE1976L calculated from the spectral reflectance of the surface at the center and edge of the film roll * a * b * a defined by the color system * value and b * The values ​​were calculated to evaluate the uniformity of the color tone of the film. In other words, the color tone of the film is L * a * b * a, which represents the hue and saturation of the edge and center of the optical film based on the color space chromaticity diagram. * value and b * The uniformity of the color tone was evaluated by calculating the difference between the

[0516] <Measurement method> Each value (L * , a * , b * ) and each value at the center position of the central part (L * , a * , b * ) was measured using a Palette CUBE (Palette Pty Ltd.) after storing the film roll at 40°C and 80% RH for one week. In addition, the end a * and b * The value was the average value of the values ​​at both ends.

[0517] <Calculation method> From the above measurements (end a * -Central part a * )+(end b * -Central part b* ) values ​​were calculated.

[0518] D. Average difference orientation angle The average differential orientation angle was measured and calculated by the following method. The timing of the measurement was immediately before the winding process at room temperature in both the solution casting film-forming process and the melt casting film-forming process.

[0519] <Measurement method> The orientation angle was measured at a position 5 mm in the width direction and 5 mm in the length direction from any position on the edge within a 1000 mm diameter range, with any point on the optical film as the center, and this measurement was repeated up to the other edge.

[0520] <Calculation method> The average of the absolute values ​​of the differences between adjacent orientation angles is calculated, and the average differential orientation angle θ ave °.

[0521] E. Average differential film thickness The detailed definition of the average differential film thickness is as described above.

[0522] <Measurement method> The film thickness was measured at a position 5 mm in the width direction and 5 mm in the length direction from any position on the edge within a range of 1000 mm in diameter, with any point on the optical film as the center, and this measurement was repeated up to the other edge. The timing of the measurement was immediately before the winding process at room temperature in both the solution casting film-forming process and the melt casting film-forming process.

[0523] <Calculation method> The average of the absolute values ​​of the differences between adjacent film thickness values ​​is calculated, and the average difference film thickness d ave μm.

[0524] F. Average air layer The average air layer thickness [μm] was calculated from the film roll diameter minus the core diameter and the value obtained by multiplying the film thickness of the optical film by the number of layers of the optical film and then multiplying by two.

[0525] G. Ratio of the heat quantity A at the center of the optical film to the average heat quantity B at the edge (B / A) The ratio (B / A) of the heat quantity A at the center of the optical film in the stretching zone to the average heat quantity B at the edges has been explained in (Relationship between the heat quantity A at the center and the average heat quantity B at the edges), so it will not be repeated here.

[0526] [evaluation] (Method for evaluating adhesion) For sticking failure, the film roll was stored at 40°C and 80% RH for one week, then the film was unwound from the roll and visually inspected for sticking between overlapping films (hereafter referred to as blocking), and evaluated based on the following criteria.

[0527] (Stickness evaluation criteria) ◎: No blocking ○: Weak blocking occurs occasionally, but is not a problem in practical use △: Blocking is weak, but there is no problem in practical use ×: Blocking is at a level other than those mentioned above (at a level where users may complain) (Note that a weak level in the above evaluation criteria refers to a level at which it is difficult to determine whether the adhesive is stuck or not.)

[0528] (Contrast evaluation method) The LCD display (8K, BRAVIA KJ-85Z9H (manufactured by Sony Corporation [85 inches]) was left in an environment of 23°C and 55% RH with the backlight turned on continuously for one week, and then the front contrast was measured. The front contrast was measured using a white display (500 cd / m 2 ) unevenness in brightness was visually evaluated from the normal direction.

[0529] (Contrast evaluation criteria) ◎: No occurrence Good: Occasional small unevenness with weak contrast ◇: Large unevenness with weak contrast occurs occasionally △: Occasional thin unevenness with low contrast ×: Unevenness other than those mentioned above occurs (at a level that will result in user complaints)

[0530] [Evaluation results of Examples 1 to 20 and Comparative Examples 1 to 4] Table I shows the film-forming means, resin composition, additives, surface roughness flattening treatment, and measurement results of the layer structure, width, length, etc. of the film roll of the optical film produced as described above. The values ​​calculated using the film rolls and the evaluation results for the Examples and Comparative Examples are shown in Table II.

[0531] [Table 1]

[0532] [Table 2]

[0533] As is clear from the conditions and evaluation results shown in Tables I and II, the examples of the present invention are superior to the comparative examples in sticking resistance and contrast when used in a display device. [Industrial Applicability]

[0534] It is possible to provide a film roll that has few winding problems during transportation or long-term storage and can maintain its quality. It is also possible to provide a method for manufacturing the film roll, which has a high production yield and requires a significantly reduced inspection load. [Explanation of symbols]

[0535] 1, 1a Stirring device (stirring tank) 2 Casting die 3 Support (endless belt, drum) 3a, 3b rolls 4 Peeling roll 5 Casting membrane 6 Drying equipment 7. Stretching device (tenter stretching device, diagonal stretching device) 8 Cut section 9 Stretching device (tenter stretching device) 10 Cut section 11 Drying equipment 12 Cut section 13 Winding device 14 Extruder 15 Casting die 16 Cast drum, support 16a Touch Roll 17 Cooling drum 19 Stretching device (tenter stretching device) 20 Cut section 21 Stretching device (tenter stretching device) 22 Cut section 23 Winding device 30 film rolls 31 Optical Film 32 rolls 33 Touch Roll 40 Tenter (stretching device) 42 clips 46 Cover 48 endless chain 50 driving sprocket 52 driven sprocket 54 Rail 56 Opening member 80 Temperature distribution sensor 101 Nozzle fixing part 102 nozzle 103 Casting membrane 104 End nozzle 105 Central nozzle 106 Clip Cover A Part of the end of the film roll B Part of the uneven shape of the knurling process C: Widthwise adhesion area D Longitudinal adhesive area F Optical Film H A , HB width Q Thermocouple, Infrared (IR) Heater

Claims

1. A film roll in which a single-layer optical film is wound, The average maximum difference in film thickness (P-V) within a range of 1000 mm in diameter centered on any point in the optical film. ａｖｅ１ is 0.15 to 0.40 μm, The ratio of the diameter of the center to the diameter of the end of the film roll (outer diameter of the center / outer diameter of the end) is 0.98 to 1.

02. A film roll characterized by:

2. A film roll in which a single-layer optical film is wound, The average maximum difference in film thickness (P-V) within a range of 1000 mm in diameter centered on any point in the optical film. ａｖｅ１ is 0.15 to 0.40 μm, The reflectance of the central and end surfaces of the film roll is calculated based on CIE 1976L ＊ a ＊ b ＊ a defined by the color system ＊ value and b ＊ The value satisfies the following formula (1): Formula (1): -1.0 < (end a) ＊ -Central Department a ＊ ) + (end b ＊ - Central Department b ＊ <1.0 A film roll characterized by:

3. The average maximum height difference (P-V) of the film thickness measured in a direction oblique to the width direction of the optical film in the following order of steps 1 to 3 ａｖｅ２ is 0.15 to 0.40 μm 3. The film roll according to claim 1 or 2. Step 1: After measuring the film thickness at any position on the end, the film thickness is measured at a position moved 50 mm in the width direction and 620 mm in the length direction from the arbitrary position for each measurement, and this is repeated up to the other end, to calculate the maximum height difference of the film thickness in each direction oblique to the width direction of the optical film. Step 2: After completion of step 1, measurements similar to step 1 are carried out until the total distance of the movement positions in the longitudinal direction reaches 1000 m, and the maximum height difference of each film thickness in the diagonal direction relative to the width direction of the optical film is further calculated. Step 3: The average maximum difference in thickness (P-V) of the optical film in the direction oblique to the width direction from the maximum difference in thickness of the optical film in the direction oblique to the width direction obtained in steps 1 and 2. ａｖｅ２ Calculate.

4. The average differential orientation angle θ within a range of 1000 mm in diameter centered on any point in the optical film ａｖｅ ° and average difference film thickness d ａｖｅ When μm is calculated, the average differential orientation angle θ ａｖｅ ° and average difference film thickness d ａｖｅ μm satisfies the following formula (2): Formula (2): 800 < | Average difference distribution angle θ ａｖｅ / Average differential film thickness d ａｖｅ ×10 －３ | <10000 The film roll according to any one of claims 1 to 3.

5. The optical film contains inorganic fine particles. The film roll according to any one of claims 1 to 4.

6. The optical film has a width of 2400 to 3000 mm. The film roll according to any one of claims 1 to 5.

7. The length of the film roll is 7,500 to 10,000 m. The film roll according to any one of claims 1 to 6.

8. A method for producing a film roll according to any one of claims 1 to 7, comprising: The method includes at least a stretching step of stretching an optical film in a stretching furnace and a flattening treatment step, In the flattening treatment step, flattening is performed at a temperature that is 50 to 200° C. higher than the temperature in the drawing furnace. A method for producing a film roll, comprising:

9. In the stretching step, the flattening treatment is performed using an infrared (IR) heater, and The heat quantity A at the center of the infrared (IR) heater at a position 100 mm away and the average value B of the heat quantity at the end satisfy the following formula (3): Formula (3): 0.2<(B / A)<0.6 The method for producing a film roll according to claim 8 .

Images