Film roll

Abstract

To provide a film roll that experiences few winding failures during transport or extended storage and retains its quality.SOLUTION: A film roll consists of a wound optical film. The film roll has fine irregularities solely in the area outside the circumference of a circle extending outward from the center of the side in the width direction of the film roll, with a radius equal to 70% of the maximum radius.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a film roll, and more particularly to a film roll that is less prone to winding failures during transportation or long-term storage and that can maintain its quality. [Background technology]

[0002] 2. Description of the Related Art Resin films containing cycloolefin resins, (meth)acrylic resins, or the like as their main components have good transparency and dimensional stability, and are therefore used as optical films such as polarizing plate protective films.

[0003] From the viewpoint of ease of handling and manufacturing efficiency, optical films are usually stored or transported in a rolled state. In that case, if the film roll is significantly deformed, or the optical films are significantly stuck to each other or scratched, the quality of the optical films will deteriorate, and waste will increase in the polarizing plate manufacturing process, and the number of steps such as quality inspection will increase, leading to an increase in product prices.

[0004] In order to suppress deterioration in quality due to deformation of the film roll, etc., fine concave-convex portions are sometimes formed on both ends in the width direction of the optical film. For example, Patent Document 1 discloses forming fine concave-convex portions by processing using embossing, and Patent Documents 2 and 3 disclose forming fine concave-convex portions by processing using coating.

[0005] When the fine unevenness is formed by the above-mentioned method, an air layer is taken in when the optical film is wound up, and the sticking of the optical film is suppressed. However, during product transportation or over time, the air in the air layer taken in the film roll is released, causing the film to sag. In addition, when sticking occurs at the winding core of the film roll, the optical film stuck to the winding core cannot be used and becomes a waste.

[0006] In response to this, a technique has been disclosed in which the average maximum height difference in the film thickness of the optical film is controlled within a predetermined range, rather than forming fine irregularities at both widthwise ends of the optical film as in Patent Document 4. This technique optimizes the air layer trapped in the film roll, and creates appropriate microcontact on the entire contact surfaces where the optical films face each other, to the extent that sticking is not noticeable.

[0007] However, when using a film roll produced by using the above-mentioned technology, white powder may adhere to the outer surface of the film roll after transportation. This phenomenon can also occur in Patent Documents 1, 2, and 3. This phenomenon can occur even if the film roll is transported carefully. Although this white powder adheres to the outer surface of the film roll, if the film roll is used in the next process, the white powder causes process contamination, so this is not a problem that is limited to the outer surface of the film roll.

[0008] For these reasons, there is room for improvement in preventing process contamination by suppressing the adhesion of the above-mentioned white powder and eliminating foreign matter that appears on the film. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2016-89110 A [Patent Document 2] JP 2012-206312 A [Patent Document 3] JP 2010-58311 A [Patent Document 4] International Publication No. 2022 / 153785 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been made in consideration of the above problems and circumstances, and an object of the present invention is to provide a film roll that is less susceptible to winding failures during transportation or long-term storage and that can maintain its quality. [Means for solving the problem]

[0011] In order to solve the above problems, the present inventors have investigated the causes of the above problems, and have found that the above problems can be solved by providing a fine concave-convex portion only in an area outside the circumference of a circle that is 70% of the maximum radius from the center of the side surface of a film roll in the width direction of the wound optical film toward the outside, thereby arriving at the present invention. That is, the above problems according to the present invention are solved by the following means.

[0012] 1. A film roll on which an optical film is wound, The film roll has fine irregularities only in an area outside the circumference of a circle that is 70% of the maximum radius from the center of the side surface in the width direction toward the outside. A film roll comprising:

[0013] 2. The ratio Rc / Re of the outer diameter Rc of the center of the film roll in the width direction to the outer diameter Re of the end portions is within the range of 0.96 to 1.01. 2. The film roll according to claim 1,

[0014] 3. The average maximum height difference (PV) of the film thickness other than the fine unevenness portion within a range of 1000 mm in diameter centered on any point in the optical film ave1 is in the range of 0.15 to 0.40 μm 2. The film roll according to claim 1,

[0015] 4. The fine concave-convex portion has fine concave-convex portions only at the ends in the width direction, including an area outside the outer circumference of a circle that is 90% of the maximum radius from the center of the side surface portion toward the outside. 2. The film roll according to claim 1,

[0016] 5. The fine concave-convex portion is provided over a length in the range of 150 to 1500 m in the longitudinal direction of the film roll. 2. The film roll according to claim 1,

[0017] 6. The fine concave-convex portion is provided over a length in the range of 500 to 1000 m in the longitudinal direction of the film roll. 2. The film roll according to claim 1,

[0018] 7. The main component of the optical film is a cycloolefin resin. 2. The film roll according to claim 1,

[0019] 8. The optical film is a single layer. 2. The film roll according to claim 1,

[0020] 9. The fine concave-convex portion is teardrop-shaped, and the relationship between the maximum width T2 in the long axis direction and the maximum width T1 in the short axis direction of the teardrop shape satisfies the following formula (1): Formula (1): 1.15≦T2 / T1≦1.90 2. The film roll according to claim 1,

[0021] 10. The long axis direction is the longitudinal direction of the optical film. 2. The film roll according to claim 1,

[0022] 11. The optical film has the fine concave-convex portions only at both ends in the width direction. 2. The film roll according to claim 1, Effect of the Invention

[0023] According to the above-mentioned means of the present invention, it is possible to provide a film roll which has few winding failures during transportation or long-term storage and can maintain its quality. Although the mechanism of expression or action of the effects of the present invention is not clear, it is speculated as follows.

[0024] The film roll of the present invention is a film roll having an optical film wound thereon, and is characterized in that the film roll has a fine concave-convex portion only in an area outside the outer periphery of a circle that is 70% of the maximum radius from the center of the side surface in the width direction toward the outside.

[0025] Generally, film rolls are transported over several days, and are therefore subject to vibrations as well as temperature differences throughout the day. This creates a temperature difference between the temperature during transport (outside air temperature) and the temperature inside and outside the roll, which is thought to cause the outside of the roll to loosen. In severe cases, this loosening can extend over a length of several tens to several hundred meters. This causes the outside of the roll to rub against the wrapping paper repeatedly, which is thought to be the source of the white powder.

[0026] Even if the outer winding did not loosen during transportation, it is assumed that the outer winding would loosen due to temperature changes when the film roll was stored in a warehouse in the factory from the winter transportation environment, and when the film roll was set at the start of production, the outer winding of the film roll would shift significantly. This could result in the production not even being able to start.

[0027] In the present invention, the above problem can be solved by providing an end fine unevenness on the outside of the winding, that is, by providing a fine unevenness only in the region outside the outer circumference of a circle that is 70% of the maximum radius from the center of the side surface in the width direction of the film roll on which the optical film is wound. This is presumably because, compared to the case where a fine unevenness is provided in the entire region from the inner circumference to the outer circumference of the film roll, the air layer (air layer) taken into the film roll is made appropriate, and moderate microcontact is generated on the entire contact surface where the optical films face each other to the extent that sticking is not noticeable, while there are few winding failures during transportation or long-term storage, and the quality can be maintained. [Brief description of the drawings]

[0028] [Figure 1] Schematic diagram of a side surface in the width direction of a film roll including a winding core [Diagram 2] An example of a schematic configuration diagram of a side surface portion in the width direction of the film roll of the present invention [Diagram 3] Relationship between convex parts and film thickness profile in the width direction [Figure 4] FIG. 1 is a schematic diagram illustrating a center portion and an end portion of a side portion in a longitudinal direction of a film roll. [Diagram 5] 1 is an enlarged plan view of an example of a teardrop shape formed on a film base according to the present invention; [Figure 6] 1B-1B line cross-sectional view of the teardrop-shaped object of FIG. 5. [Figure 7] FIG. 1 is a schematic plan view showing the distance between teardrop-shaped objects according to the present invention; [Figure 8] An example of a plan view of a teardrop-shaped object having multiple protrusions [Figure 9] An example of a plan view of a teardrop-shaped object with continuous dots [Figure 10] (a) An example of a schematic diagram of the hot pressing method (b) An example of the film base after the formation of the convex portion DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] The film roll of the present invention is a film roll having an optical film wound thereon, and is characterized in that the film roll has a fine concave-convex portion only in an area outside the outer periphery of a circle that is 70% of the maximum radius from the center of the side surface in the width direction toward the outside. This feature is a technical feature common to or corresponding to each of the following embodiments (aspects).

[0030] As an embodiment of the present invention, it is preferable that the ratio Rc / Re of the length of the outer diameter Rc of the center part in the width direction of the film roll to the outer diameter Re of the end part is within the range of 0.96 to 1.01, from the viewpoint of suppressing stress concentration due to sticking caused by contact between optical films and making the stress in the width direction uniform.

[0031] The average maximum height difference (PV) of the film thickness other than the fine unevenness portion within a range of 1000 mm in diameter centered on any point in the optical filmave1 From the viewpoint of preventing the optical films from sticking to each other, it is preferable that the thickness is within the range of 0.15 to 0.40 μm.

[0032] From the viewpoint of realizing the effects of the present invention, it is more preferable that the fine unevenness is present only at the ends in the width direction, including the area outside the outer periphery of a circle that is 90% of the maximum radius from the center of the side portion toward the outside.

[0033] From the viewpoints of thinning and productivity, it is preferable that the fine concave-convex portion is provided over a length in the range of 150 to 1500 m in the longitudinal direction of the film roll.

[0034] From the viewpoints of thinning and productivity, it is more preferable that the fine concave-convex portion is provided over a length in the range of 500 to 1000 m in the longitudinal direction of the film roll.

[0035] The main component of the optical film is preferably a cycloolefin resin from the viewpoints of stretchability, ease of control of crystallinity, and adhesive permeability.

[0036] From the viewpoint of exerting the effects of the present invention, it is preferable that the optical film is a single layer.

[0037] From the viewpoint of suppressing deformation of the film roll, it is preferable that the fine concave-convex portion is teardrop-shaped, and the relationship between the maximum width T2 in the major axis direction and the maximum width T1 in the minor axis direction of the teardrop shape satisfies the above formula (1).

[0038] It is more preferable that the long axis direction is the longitudinal direction of the optical film, from the viewpoint of suppressing deformation of the film roll.

[0039] It is preferable that the optical film has the fine irregularities only at both ends in the width direction from the viewpoints of thinning and productivity.

[0040] 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 the symbol "to" are included as the lower limit and upper limit.

[0041] [Outline of the film roll of the present invention] The film roll of the present invention is a film roll having an optical film wound thereon, and is characterized in that the film roll has a fine uneven portion only in a region outside the outer circumference of a circle that is 70% of the maximum radius from the center of the side surface of the film roll in the width direction toward the outside. Note that "the center of the side surface of the film roll in the width direction" refers to the center of a circle that is the maximum radius that appears approximately circular when the side surface of the film roll is observed from a direction perpendicular to the width direction of the film roll, i.e., the center point of the maximum diameter.

[0042] As described above, in the past, in order to prevent deterioration of quality during storage or transportation of optical films wound in a roll, fine unevenness was formed on both ends in the width direction of the optical film, or the average maximum height difference of the film thickness of the optical film was controlled within a predetermined range. This traps air in the air layer trapped in the film roll, preventing the air from escaping, and suppresses sticking of optical films to each other.

[0043] However, since white powder may adhere to the outer surface of the film roll after transportation, there is room for improvement in terms of preventing process contamination by suppressing the adhesion of the white powder and eliminating foreign matter that appears on the film.

[0044] In the present invention, the end fine unevenness is provided outside the winding, that is, the fine unevenness is provided only in the region outside the circumference of a circle that is 70% of the maximum radius from the center of the side surface of the film roll on which the optical film is wound in the width direction toward the outside. This makes it possible to make the air layer (air layer) taken into the film roll appropriate, and to generate an appropriate amount of microcontact on the entire contact surface where the optical films face each other so that sticking is not noticeable, while reducing winding failures during transportation and long-term storage and maintaining quality. Each component of the film roll of the present invention and the manufacturing method will be described below in order.

[0045] 1. Film roll (Side part in width direction) FIG. 1 is a schematic diagram of the side surface in the width direction of a film roll including a winding core, and FIG. 2 is an example of a schematic diagram of the side surface in the width direction of a film roll of the present invention.

[0046] In FIG. 1, 30c is a side surface of the winding core, R 0 is the center of the side of the core, r c is the radius of the side of the core, r p is the radius of the side of the film roll including the core at any point, r max represents the maximum radius of the side of the film roll, including the core. rayer is a layer of optical film from the outer periphery of the side of the core to the maximum radius. The typical size of the core is 150 to 300 mm in diameter.

[0047] In FIG. 2, 30c is a side surface of the winding core, R 0 is the center point of the side surface in the width direction of the film roll, and this point is 0% of the maximum radius from the center of the side surface outward. 70 represents the circumference of a circle that is 70% of the maximum radius from the center of the side part outward, and R 100 is the maximum radius (r max ) and is the circumference of a circle that is 100% of the maximum radius. rayer1is a layer of an optical film extending from the center of the side portion outward to the outer periphery of a circle that is 70% of the maximum radius.

[0048] F rayer2 is a layer of the optical film in the region outside the circumference of a circle that is 70% of the maximum radius from the center of the side surface portion toward the outside, and the film roll of the present invention is rayer2 In view of the effect of the present invention, it is more preferable that the fine unevenness is present only in the region outside the circumference of a circle that is 90% of the maximum radius from the center of the side surface portion toward the outside.

[0049] From the viewpoints of thinning and productivity, the fine irregularities are preferably provided over a length in the longitudinal direction of the film roll within a range of 150 to 1500 m, and more preferably within a range of 500 to 1000 m.

[0050] From the viewpoints of thinning and productivity, it is preferable that the optical film according to the present invention wound into a film roll has the fine irregularities only at both ends in the width direction.

[0051] (1.1) Fine irregularities The microrelief structure according to the present invention is formed on a film base. In this specification, the term "film base" refers to a film in a state in which the microrelief structure according to the present invention is not formed, or a portion of the film that does not include the microrelief structure after the microrelief structure is formed.

[0052] In the present invention, the "fine uneven structure" refers to a structure in which recesses and protrusions exist in a fine range. The recesses and protrusions exist repeatedly over at least 1000 mm in the longitudinal direction. The "fine range" refers to a range of 0.1 to 30 mm square. A plurality of recesses and protrusions exist within this range.

[0053] In the present invention, the term "depression" refers to a portion of the peaks and valleys of the unevenness of the thickness of an optical film measured and observed by film thickness measurement, the height of which is lower than the average film thickness, i.e., a thin portion. The depth of the depression is within a range of 0.05 to 30 μm, and preferably within a range of 0.1 to 5 μm. The concave portion of the fine irregularities in the present invention includes a so-called curl. The fine area is a 0.1 to 30 mm square area. The curl is a state in which the film is bent. The depth of the curl is within a range of 0.2 to 20 μm, and preferably within a range of 1 to 5 μm.

[0054] In the present invention, the term "convex portion" refers to a portion in which the height of the peaks and valleys of the uneven shape of the thickness of an optical film measured and observed by film thickness measurement is higher than the average film thickness, i.e., a thick portion. Details are as described below.

[0055] The condition of the uneven parts is measured and evaluated by measuring the film thickness at a random position on the edge of the film, then measuring the film thickness at a position moved 10 mm in the width direction and 30 mm in the length direction from the random position for each measurement, and repeating this process up to the other edge of the film.Noise is removed by Gaussian filter processing to obtain a film thickness profile in the width direction, and the condition of the uneven parts is measured and evaluated based on this profile.

[0056] FIG. 3 shows the relationship between the unevenness and the film thickness profile in the width direction. 1 " is the height of the convex part, and "h 2 " is the depth of the recess. The average thickness is determined by averaging the measured values ​​of each thickness in the width direction obtained by the above operation, and the part where the thickness profile in the width direction is thicker than the average thickness and continues for 50 mm or more in the width direction as shown in Figure 3 is regarded as a convex part, and the number of such parts is the number of convex parts. If the number of convex parts is too many, each mountain becomes sharp and deformation of the film occurs, and if the number is too few, too much stress is concentrated on a few convex parts during film winding, resulting in twisting, etc. Therefore, it is preferable to set the number of convex parts within the range of 1 to 10 per 1 m in the width direction.

[0057] In addition, the position where the maximum value was obtained for each convex portion determined by the above method was taken as the position of the convex portion, and the value obtained by subtracting the average film thickness in the width direction from the maximum value of the convex portion was taken as the height h of each convex portion. 1 If the height of the convex portions is too high, a chain shape will form at the foot of the mountain after the film roll is left for a long time, and if the height of the convex portions is too low, the film thickness spreading effect will be lost. Therefore, it is preferable that the height of the convex portions is within the range of 0.05 to 0.50 μm. In addition, the positions of the convex portions are adjusted so that they move continuously in the longitudinal direction of the film surface, so that the convex portions do not overlap each other when the film is wound up, thereby further enhancing the effect of adjusting the number and height of the convex portions.

[0058] The above film thickness can be measured using an in-line retardation / film thickness measuring device RE-200L2T-Rth+film thickness (manufactured by Otsuka Electronics Co., Ltd.).

[0059] 4 is an example of a schematic diagram illustrating the center and end of a side surface of a film roll in the longitudinal direction. Re represents the outer diameter of the end of the side surface, and Rc represents the outer diameter of the center of the side surface. It is preferable that the ratio Rc / Re of the outer diameter Rc of the center to the outer diameter Re of the end of the film roll in the width direction of the present invention is within the range of 0.96 to 1.01, from the viewpoint of suppressing stress concentration due to sticking caused by contact between optical films and making the stress in the width direction uniform.

[0060] The term "end" refers to a region within a range of 0 to 30 mm inside from the end in the width direction of the optical film (roll). The term "center" refers to a region excluding both ends in the width direction of the optical film. The term "outer diameter" refers to the diameter of a circle formed at the outermost circumference of a film roll when the cross section perpendicular to the central axis (core) of the film roll is taken as a circle. Therefore, the term "outer diameter of the end" refers to the diameter of a circular cross section observed in the end region (the average value of diameters measured at least at three randomly selected points). The term "outer diameter of the center" refers to the diameter of a circular cross section observed at the center point of the center.

[0061] The outer diameter of the film roll in the width direction can be measured, for example, by measuring the outer diameter at any position from both ends of the film roll using a tape measure. Other methods can also be used, such as measuring the outer diameter by installing a laser displacement meter (Keyence LK-G5000) so that the laser is irradiated to the outer diameters of multiple (at least three) predetermined positions in both end regions of the film roll in the width direction and the central position of the center part. The outer diameter of the end portion is the average value as described above.

[0062] (Shape of fine unevenness) [Teardrop shape] The shape of the fine unevenness according to the present invention is not particularly limited, but it is preferable that the fine unevenness is teardrop-shaped. Fig. 5 is an enlarged plan view of an example of a teardrop-shaped object according to the present invention formed on a film base, and Fig. 6 is a cross-sectional view of the teardrop-shaped object of Fig. 5 taken along line 1B-1B. In Fig. 5, M is the intersection of the long axis LA and short axis SA of the teardrop-shaped object. T1 is the maximum width in the short axis direction, T2 is the maximum width in the long axis direction, t is the height of the teardrop-shaped object, x is the width direction of the film, and y is the length direction of the film.

[0063] The term "teardrop shape" refers to a shape having a major axis LA and a minor axis SA, and the intersection M of the major axis LA and the minor axis SA of the teardrop-shaped object 12 is offset from the center of the major axis LA (does not overlap with the center of the major axis LA) (see FIG. 5).

[0064] The long axis LA is preferably along the length direction (y direction) of the film base, and more preferably parallel to the length direction (y direction) of the film base. The short axis SA is preferably along the width direction (x direction) of the film base, and more preferably parallel to the width direction (x direction) of the film base. The y direction is also the transport direction (travel direction) of the film when wound up.

[0065] The major axis LA and the minor axis SA are preferably perpendicular to each other. The outline of the teardrop shape may be a straight line, a curved line, or a combination thereof, but is preferably a curved line.

[0066] In this embodiment, from the viewpoint of suppressing deformation of the film roll, it is preferable that the teardrop-shaped objects 12 are arranged at both ends of the surface of the film base in the width direction so as to be aligned along the length direction of the film base, i.e., the longitudinal direction of the optical film (see FIG. 5). It is also preferable that each of the teardrop-shaped objects 12 is arranged so that its major axis LA direction is aligned along the length direction of the film base (see FIG. 5). The teardrop-shaped objects 12 may be integrated with the film base or may be separate.

[0067] From the viewpoint of suppressing deformation of the film roll, it is preferable that the relationship between the maximum width T2 in the long axis direction and the maximum width T1 in the short axis direction of the teardrop shape satisfies the following formula (1). In the following formula, "T1" represents the average value of the maximum widths in the short axis direction of the multiple teardrop shapes when there are multiple teardrop-shaped objects 12. In addition, "T2" represents the average value of the maximum widths in the long axis direction of the multiple teardrop shapes when there are multiple teardrop-shaped objects 12.

[0068] Formula (1): 1.15≦T2 / T1≦1.90

[0069] If the value of (T2 / T1) is 1.15 or more, even if an oblique force is applied from the front during winding, the teardrop-shaped objects 12 can come into uniform contact with the film after winding, so deformation of the film roll can be suppressed. If the value of (T2 / T1) is 1.9 or less, uniform contact with the film can be achieved, so the suppression effect of the film roll is unlikely to be impaired. From the same viewpoint, the value of (T2 / T1) is more preferably 1.3 to 1.6.

[0070] The value of (T2 / T1) can be adjusted by the film conveying speed, drying conditions (drying method, drying temperature), resin concentration of the second resin composition (to form teardrop-shaped objects), drop height, surface condition of the film, etc. The value of (T2 / T1) can be increased by increasing the film conveying speed, lowering the drying temperature, and using hot air drying as the drying method. The value of (T2 / T1) can also be increased by appropriately lowering the resin concentration of the second resin composition and increasing the drop height.

[0071] The value of the maximum width T1 in the minor axis direction is not particularly limited, but may be within the range of, for example, 0.9 to 1.5 mm, and preferably within the range of 1.0 to 1.2 mm.

[0072] Fig. 7 is a schematic plan view showing the distance between teardrop-shaped objects according to the present invention. In Fig. 7, T2 represents the maximum width of the teardrop-shaped objects in the long axis direction, and Th represents the distance between the teardrop-shaped objects in the longitudinal direction (y direction) of the film base. When the average distance calculated from the distances Th between multiple teardrop-shaped objects is T3, it is preferable that T3 and T2 satisfy the following formula (2).

[0073] Formula (2): T3 <T2

[0074] By satisfying the above formula (2), the performance of absorbing diagonal forces can be improved in the front part of the teardrop-shaped object 12 (the region centered on the intersection M of the long axis LA and the short axis SA) when the film is transported and wound up, thereby further preventing the teardrop-shaped object 12 from being crushed unevenly due to diagonal forces.

[0075] The difference between T2 and T3 (T2-T3) is not particularly limited, but may be, for example, 0.1 mm or more, preferably 0.6 mm or more. In addition, when the length of the base of the film in the width direction is X, it is more preferable that the following formulas (3) and (4) are satisfied.

[0076] Formula (3): 0.0003≦T1 / X≦0.0063 Formula (4): 2400mm≦X≦2950mm

[0077] From the viewpoint of easily suppressing deformation of the film roll, it is preferable that the value of (T1 / X) is large. In addition, when the film is widened, the film is more likely to flutter during film transport than before. If the value of (T1 / X) is within the above range, T1 is not too large, so that it is possible to suppress the occurrence of transport scratches such as wrinkles and roll scratches caused by excessive restricting force on the film. From the same viewpoint, it is more preferable that the value of (T1 / X) is within the range of 0.0004 to 0.00051.

[0078] Furthermore, when the average distance between the teardrop-shaped structures 12 in the length direction (y direction) of the film base is T3 and the length of the film base is Y, it is more preferable that the following formulas (5) and (6) are satisfied.

[0079] Formula (5): 1.0×10 6 ≦Y / T3≦9.0×10 6 Formula (6): 6000m≦Y≦9000m

[0080] From the viewpoint of easily preventing the films from sticking to each other, it is preferable that T3 is small, and it is preferable that the value of (Y / T3) is large. On the other hand, if T3 is too small, the uniformity of the winding shape is easily lost. If the value of (Y / T3) is within the above range, it is possible to highly prevent the films from sticking (contacting) to each other while maintaining the uniformity of the winding shape. From the same viewpoint, the value of (Y / T3) is 3.0×10 3 ~8.0×10 3 It is more preferable that the range is within the range.

[0081] As described above, the length X of the film base in the width direction is preferably within the range of 2000 to 3500 mm, and more preferably within the range of 2400 to 2950 mm. As described above, the length Y of the film base is preferably within the range of 500 to 15000 m, and more preferably within the range of 6000 to 9000 m.

[0082] The average spacing T3 of the multiple teardrop-shaped structures 12 in the longitudinal direction (y direction) of the film base is not particularly limited as long as it is within a range that satisfies the above ratio, but is preferably within the range of 0.5 to 4 mm, and more preferably within the range of 1 to 3 mm.

[0083] When the average spacing T3 of the multiple teardrop-shaped objects 12 is equal to or greater than the lower limit, it is easier to appropriately adjust the amount of air contained between the film when it is wound into a roll, and when it is equal to or less than the upper limit, it is easier to prevent the films from sticking together due to the average spacing T3 of the multiple teardrop-shaped objects 12 being too wide.

[0084] The average spacing T3 of the teardrop-shaped structures 12 refers to the minimum distance between the ends of adjacent teardrop-shaped structures 12 in the length direction (y direction) of the film base. The ends of the teardrop-shaped structures 12 refer to the ends of the long axis LA.

[0085] In a cross section passing through the apex (highest point) of the teardrop-shaped object 12 along the width direction (x direction) of the film base, the height t of the teardrop-shaped object is within a range of 0.5 to 3 μm (see FIG. 6). If the height t of the teardrop-shaped object is 0.1 μm or more, the film bases can be sufficiently prevented from sticking to each other when the film 10 is wound into a roll. If the height t of the teardrop-shaped object is 3 μm or less, the absolute amount of crushing of the teardrop-shaped object 12 is small when the film 10 is wound into a roll, and the film roll can be made less likely to deform. From the same viewpoint, the height t of the teardrop-shaped object 12 is preferably within a range of 0.1 to 0.8 μm. The height t of the teardrop-shaped object 12 is the height from the surface of the film base to the apex of the teardrop-shaped object 12. The height t of the teardrop-shaped object 12 is preferably within a range of 0.2 to 10% of the thickness of the film base, and more preferably within a range of 0.3 to 5%.

[0086] In a cross section passing through the apex of the teardrop-shaped object 12 along the width direction (x direction) of the film base, the width w of the teardrop-shaped object 12 is not particularly limited, but is preferably in the range of 500 to 2000 μm. If the width w of the teardrop-shaped object 12 is 500 μm or more, the support area can be increased, so that the teardrop-shaped object 12 is less likely to be crushed, and if it is 2000 μm or less, the teardrop-shaped object 12 is more likely to dry when formed by solution application, and is more likely to cool when formed by melting, so that the film of the present invention can be produced efficiently. From the same viewpoint, the width w of the teardrop-shaped object 12 is more preferably in the range of 700 to 1500 μm. The width w of the teardrop-shaped object 12 is the maximum width of the teardrop-shaped object 12 in the cross section.

[0087] The height t and width w of the teardrop-shaped object 12 can be measured using a laser microscope. For example, a laser microscope VK-X1000 manufactured by Keyence Corporation can be used as the laser microscope. The height t and width w of the teardrop-shaped object are measured over an area of ​​100 mm in the longitudinal direction (y direction) of the film base in the area where multiple teardrop-shaped objects 12 are arranged, and the average values ​​of these are defined as the "height t and width w of the teardrop-shaped object."

[0088] In a cross section passing through the apex of the teardrop-shaped object 12 along the width direction (x direction) of the film base, the shape of the teardrop-shaped object 12 is not particularly limited, but may usually be a circular segment. A circular segment is a shape in which both ends of a circular or elliptical arc are connected by a straight line, and examples thereof include a semicircular shape and a semielliptical shape.

[0089] The teardrop-shaped objects 12 are preferably arranged such that the intersection M of the major axis LA and the minor axis SA is located upstream in the winding direction from the center of the major axis LA. This can prevent the teardrop-shaped objects 12 from being crushed unevenly even if an oblique force is applied to the teardrop-shaped objects 12, thereby preventing deformation of the film roll and sticking of the films together.

[0090] The teardrop-shaped object 12 includes a second resin composition containing a thermoplastic resin. The thermoplastic resin contained in the teardrop-shaped object 12 may be the same type as the thermoplastic resin contained in the film base, or may be a different type, but from the viewpoint of improving adhesion to the film base, it is preferable that the thermoplastic resin be the same type. For example, when the thermoplastic resin contained in the film base is a cycloolefin resin, the resin contained in the teardrop-shaped object 12 is also preferably a cycloolefin resin.

[0091] When the thermoplastic resin contained in the film base and the thermoplastic resin contained in the teardrop-shaped object 12 are the same type, the adhesion between the teardrop-shaped object 12 and the film base can be improved. The same type of thermoplastic resin refers to a thermoplastic resin having the same main component monomer (the component contained in the largest amount), but the type and content of the copolymerization component monomer, and physical properties such as the weight average molecular weight (Mw) and glass transition temperature (Tg) of the resin may be different. The content of the resin is not particularly limited, but is preferably 60% by mass or more, and more preferably 70 to 100% by mass, of the second resin composition constituting the teardrop-shaped object 12.

[0092] The teardrop-shaped object 12 may further contain the same components as the film base (e.g., fine particles, etc.) as necessary. However, from the viewpoint of preventing slippage between the teardrop-shaped object 12 and the back surface of the film base when the film is wound up and facilitating appropriate adhesion between them, the content of fine particles in the teardrop-shaped object 12 is preferably less than the content of fine particles in the film base, and more preferably does not contain fine particles.

[0093] [Modifications] The teardrop-shaped object 12 is not limited to the shape shown in Fig. 5. Fig. 8 is an example of a plan view of a teardrop-shaped object having a plurality of protrusions, and Fig. 9 is an example of a plan view of a teardrop-shaped object having successive impact points. In Figs. 8 and 9, T1 is the maximum width of the teardrop-shaped object in the minor axis direction, T2 is the maximum width of the teardrop-shaped object in the major axis direction, and M is the intersection of the major axis LA and minor axis SA of the teardrop-shaped object.

[0094] The teardrop-shaped objects 12 may be disposed on both surfaces of the film base, not only on one surface. The second resin composition for forming the teardrop-shaped objects 12 may not be a solution containing a resin and a solvent, but may be a melt. That is, when the film roll of the present invention is produced by the melt casting method described later, the roll body may be formed by casting a molten first resin composition, cooling and solidifying it to obtain a strip-shaped film base, applying droplets of the molten second resin composition to the strip-shaped film base, and cooling and solidifying it to form a plurality of teardrop-shaped objects.

[0095] (1.2) Film Thickness From the viewpoint of realizing the effects of the present invention, it is preferable that the wound optical film is a single layer. The effects of the present invention are more valuable in the thin film region. The thickness of the optical film according to the present invention 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 thickness is 5 μm or more, the rigidity of the film roll is high and it is easy to maintain the roll shape. If the thickness is 80 μm or less, the mass does not increase too much, and it is easy to produce a long film roll.

[0096] The average maximum height difference (PV) of the film thickness other than the fine unevenness portion within a range of 1000 mm in diameter centered on any point in the optical film ave1 From the viewpoint of preventing the optical films from sticking to each other, it is preferable that the thickness is within the range of 0.15 to 0.40 μm.

[0097] Average maximum height difference of film thickness (PV) ave1 However, by having a slight difference in height in the longitudinal direction of 0.15 to 0.40, it is defined as an optical film having minute stress-relieved and non-stress-relieved parts in adjacent regions, and it is presumed that due to the characteristics of this optical film, in the event of localized sticking, the non-stress-relieved parts perform local relaxation, thereby suppressing localized sticking.

[0098] "Average maximum height difference (PV) of optical film thickness 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 the film thickness measurement 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 called (PV) ave1 The method for measuring the film thickness is not particularly limited, but for example, the film thickness can be measured using an in-line retardation / film thickness measuring device RE-200L2T-Rth+film thickness (manufactured by Otsuka Electronics Co., Ltd.).

[0099] (1.3) Resin that constitutes the film (1.3.1) Thermoplastic resin The thermoplastic resin used in the film according to the present invention is not limited as long as it can be handled as a film roll after film formation. For example, thermoplastic resins used for polarizing plate applications include cellulose ester resins such as triacetyl cellulose (TAC), cellulose acetate propionate (CAP), and diacetyl cellulose (DAC), cyclic olefin resins such as cycloolefin polymers (cycloolefin resins (COP)) (hereinafter also referred to as cycloolefin resins), polypropylene resins such as polypropylene (PP), acrylic resins such as polymethyl methacrylate (PMMA), and polyester resins such as polyethylene terephthalate (PET).

[0100] In particular, in a film with a low modulus of elasticity, for example, a resin with a modulus of elasticity of less than 3.0 GPa, it is difficult to relax the stress at multiple locations of the film when it is formed into a film roll, so it is difficult for the film to expand and contract in the width direction and length direction, and when the film is in a rolled state, the stress cannot be fully absorbed by the surface, and winding slippage is likely to occur. Also, from another perspective, when the above-mentioned low modulus film is viewed from the viewpoint of low elasticity, if there is a difference in height between the length and length directions of the film, the difference between the expansion and contraction of the high points and the low points of the film becomes large.

[0101] Therefore, in an embodiment of the present invention, it is preferable to control the maximum height difference (PV) of the longitudinal average film thickness to within a range of 0.02 to 0.40 μm, and it is effective to apply this to a film roll using a low elastic modulus resin such as cycloolefin polymer (cycloolefin resin (COP)) or polymethyl methacrylate (acrylic resin (PMMA)) as a thermoplastic resin.

[0102] However, it is preferable to use a cycloolefin resin (COP) in terms of ease of control of stretchability and crystallinity, ease of penetration of an adhesive, and ability to ensure better adhesion to the polarizer layer. The above-mentioned film may be subjected to a surface modification treatment after production.

[0103] (Cycloolefin resin) The cycloolefin resin contained in the film roll according to the present invention is preferably a polymer of a cycloolefin monomer, or a copolymer of a cycloolefin monomer and another copolymerizable monomer.

[0104] 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).

[0105] [ka]

[0106] 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.

[0107] 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, 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.

[0108] In general formula (A-1), R 1 ~R 4 Examples of the polar group represented by the formula (I) include a carboxy group, a hydroxy group, an alkoxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amide group, and a cyano group. Among them, a carboxy group, a hydroxy group, an alkoxycarbonyl group, and an aryloxycarbonyl group are preferred, and an alkoxycarbonyl group and an aryloxycarbonyl group are preferred from the viewpoint of ensuring solubility during solution casting.

[0109] In terms of improving the heat resistance of the film, p in general formula (A-1) is preferably 1 or 2. When p is 1 or 2, the obtained polymer becomes bulky and the glass transition temperature is likely to be improved.

[0110] [ka]

[0111] In general formula (A-2), R 5 R 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. 6represents 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.

[0112] 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.

[0113] R in general formula (A-2) 6 preferably 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.

[0114] In terms of improving the heat resistance of the film, p in general formula (A-2) preferably represents 1 or 2. When p represents 1 or 2, the obtained polymer becomes bulky and the glass transition temperature is likely to be improved.

[0115] The cycloolefin monomer having the structure represented by the general formula (A-2) is preferable from the viewpoint of improving the solubility in an organic solvent. In general, the crystallinity of an organic compound decreases by breaking the symmetry, and therefore the solubility in an organic solvent increases.

[0116] R in general formula (A-2) 5 and R 6 is substituted only on the ring carbon atoms on one side of the axis of symmetry of the molecule, so that 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 a film by a solution casting method.

[0117] The content ratio of the cycloolefin monomer having the structure represented by general formula (A-2) in the polymer of the cycloolefin monomer can be, for example, 70 mol% or more, preferably 80 mol% or more, more preferably 100 mol% relative to the total of all the cycloolefin monomers constituting the cycloolefin resin. If the cycloolefin monomer having the structure represented by general formula (A-2) is contained at a certain level or more, the orientation of the resin is increased, so that the retardation value is likely to increase.

[0118] Specific examples of cycloolefin monomers having a structure represented by general formula (A-1) are shown in Exemplary Compounds 1 to 14 below, and specific examples of cycloolefin monomers having a structure represented by general formula (A-2) are shown in Exemplary Compounds 15 to 34 below.

[0119] [ka]

[0120] 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.

[0121] Examples of copolymerizable monomers capable of ring-opening copolymerization include cycloolefins such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, and dicyclopentadiene.

[0122] Examples of the copolymerizable monomer capable of addition copolymerization include an unsaturated double bond-containing compound, a vinyl-based cyclic hydrocarbon monomer, and a (meth)acrylate.

[0123] Examples of the unsaturated double bond-containing compound include olefin-based compounds having 2 to 12 carbon atoms (preferably 2 to 8), and examples thereof include ethylene, propylene, and butene.

[0124] Examples of the vinyl-based cyclic hydrocarbon monomer include vinylcyclopentene-based monomers such as 4-vinylcyclopentene and 2-methyl-4-isopropenylcyclopentene.

[0125] 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.

[0126] 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 %, based on the total of all monomers constituting the copolymer.

[0127] 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). Examples of the cycloolefin resin include the following polymers (1) to (7).

[0128] (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 product of the 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 thereto. (5) Saturated copolymers of cycloolefin monomers and compounds containing unsaturated double bonds (6) Addition copolymers of cycloolefin monomers with vinyl cyclic hydrocarbon monomers and their hydrogenated products (7) Alternating copolymer of cycloolefin monomer and (meth)acrylate

[0129] The above polymers (1) to (7) can all be obtained by known methods, for example, the methods described in JP-A-2008-107534 and JP-A-2005-227606.

[0130] For example, the catalyst and solvent used in the ring-opening copolymerization (2) above can be, for example, those described in paragraphs 0019 to 0024 of JP-A-2008-107534. The catalyst used in the hydrogenated products (3) and (6) above can be, for example, those described in paragraphs 0025 to 0028 of JP-A-2008-107534. The acidic compound used in the Friedel-Crafts reaction (4) above can be, for example, those described in paragraph 0029 of JP-A-2008-107534. The catalyst used in the addition polymerization (5) to (7) above can be, for example, those described in paragraphs 0058 to 0063 of JP-A-2005-227606. The alternating copolymerization reaction (7) above can be carried out by, for example, the method described in paragraphs 0071 and 0072 of JP-A-2005-227606. Among these, the above polymers (1) to (3) and (5) are preferred, and the above polymers (3) and (5) are more preferred.

[0131] That is, the cycloolefin 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), from the viewpoint of increasing the glass transition temperature and light transmittance of the resulting cycloolefin resin, and more preferably contains only a structural unit represented by general formula (B-2) or contains both a structural unit represented by general formula (B-1) and a structural unit represented by general formula (B-2).

[0132] The structural unit represented by general formula (B-1) is a structural unit derived from a 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 a cycloolefin monomer represented by the above-mentioned general formula (A-2).

[0133] [ka]

[0134] In the general formula (B-1), X is -CH=CH- or -CH 2 CH 2 - stands for R 1 ~R 4 and p are each R in general formula (A-1). 1 ~R 4 and p.

[0135] [ka]

[0136] In the general formula (B-2), X is -CH=CH- or -CH 2 CH 2 - stands for R 5 ~R 6 and p are each R in general formula (A-2). 5 ~R 6 and p.

[0137] The cycloolefin resin according to the present invention may be a commercially available product. Examples of commercially available cycloolefin resins include Arton G (e.g., G7810, etc.), Arton F, Arton R (e.g., R4500, R4900, and R5000, etc.), and Arton RX, all of which are manufactured by JSR Corporation.

[0138] 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 More preferably, the range is 0.4 to 1.5 cm / g. 3 It is more preferable that the molecular weight is in the range of / g.

[0139] The number average molecular weight (Mn) of the cycloolefin resin is preferably within the range of 8,000 to 100,000, more preferably within the range of 10,000 to 80,000, and further preferably within the range of 12,000 to 50,000.

[0140] 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 further preferably within a range of 40,000 to 200,000.

[0141] The number average molecular weight and weight average molecular weight of the cycloolefin resin can be measured by gel permeation chromatography (GPC) in terms of polystyrene.

[0142] (Gel Permeation Chromatography) Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Showa Denko K.K., three columns connected together) 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.

[0143] 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.

[0144] 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. If 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 also easily suppressed.

[0145] 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.

[0146] (Acrylic resin) The acrylic resin according to the present invention is a polymer of an acrylic acid ester or a methacrylic acid ester, and includes copolymers with other monomers. Therefore, the acrylic resin according to the present invention also includes a methacrylic resin.

[0147] The resin is not particularly limited, but is preferably one containing 50 to 99% by mass of methyl methacrylate units and 1 to 50% by mass of other monomer units copolymerizable therewith.

[0148] 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, isobornyl methacrylate, hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate, α,β-unsaturated acids such as acrylic acid and methacrylic acid, acrylamides such as acryloylmorpholine and N-hydroxyphenylmethacrylamide, unsaturated group-containing divalent carboxylic 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, etc. Copolymerizable monomers forming units excluding glutarimide and glutaric anhydride from these units include monomers corresponding to the above units.

[0149] That is, examples of monomers include alkyl methacrylates having an alkyl number of 2 to 18 carbon atoms, alkyl acrylates having an alkyl number of 1 to 18 carbon atoms, 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 divalent carboxylic 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.

[0150] The glutarimide unit can be formed, for example, by reacting an intermediate polymer having a (meth)acrylic acid ester unit with a primary amine (imidizing agent) to form an imidization (see JP 2011-26563 A).The glutaric anhydride unit can be formed, for example, by heating an intermediate polymer having a (meth)acrylic acid ester unit (see JP 4961164 A).

[0151] Of the above-mentioned structural units, it is particularly preferable 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.

[0152] From the viewpoint of controlling dimensional changes due to changes in the environmental temperature and humidity atmosphere, and from the viewpoint of improving releasability from metal supports during film production, drying properties from organic solvents, heat resistance and mechanical strength, 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. 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 releasability from metal supports and drying properties from organic solvents are excellent.

[0153] 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.

[0154] Here, as the polymerization initiator, a normal peroxide-based or azo-based one can be used, and a redox-based one can also be used. The polymerization temperature can be within the range of 30 to 100°C in suspension or emulsion polymerization, and within the range of 80 to 160°C in bulk or solution polymerization. In order to control the reduced viscosity of the obtained copolymer, the polymerization can also be carried out using an alkyl mercaptan or the like as a chain transfer agent.

[0155] 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.

[0156] The acrylic resin according to the present invention may be a commercially available product. For example, Delpet 60N, 80N, 980N, SR8200 (all manufactured by Asahi Kasei Chemicals Corporation), Dianale BR52, BR80, BR83, BR85, BR88, EMB-143, EMB-159, EMB-160, EMB-161, EMB-218, EMB-229, EMB-270, EMB-273 (all manufactured by Mitsubishi Rayon Co., Ltd.), KT75, TX400S and IPX012 (all manufactured by Denki Kagaku Kogyo Co., Ltd.), etc. Two or more types of acrylic resins may be used in combination.

[0157] The acrylic resin according to the present invention preferably contains an additive. One example of the additive is acrylic particles (rubber elastomer particles) described in WO 2010 / 001668, which are preferably contained in order to improve the mechanical strength of the film and adjust the dimensional change rate.

[0158] Commercially available examples 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.

[0159] 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 more than a certain value, the film can be easily stretched under heating, and if the particle size is equal to or less than a certain value, the transparency of the obtained film is not easily impaired.

[0160] From the viewpoint of flexibility, the film according to 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. This flexural modulus varies depending on the type and amount of the acrylic resin and rubber elastomer particles in the film, and for example, the higher the content of the rubber elastomer particles, the smaller the flexural modulus generally becomes. Furthermore, the flexural modulus generally becomes smaller when a copolymer of alkyl methacrylate and alkyl acrylate is used as the acrylic resin than when a homopolymer of alkyl methacrylate is used.

[0161] (Cellulose ester resin) In the film roll according to the present invention, it is also preferable to use a cellulose ester resin. 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 2-, 3- and 6-positions in the β-1,4-bonded glucose units constituting cellulose are substituted with acyl groups.

[0162] 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.

[0163] Examples include cellulose esters in which the hydrogen atom of the hydroxy group 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.

[0164] 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 acyl group in the cellulose ester may be a single type or a combination of multiple acyl groups.

[0165] 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 alone or in combination.

[0166] (Type of acyl group / degree of substitution) By adjusting the type and substitution degree of the acyl group of the cellulose ester, the humidity fluctuation of the retardation can be controlled within a desired range, and the uniformity of the film thickness can be improved. The smaller the substitution degree of the acyl group of the cellulose ester, the better the retardation expression, and therefore the thinner the film can be. On the other hand, if the substitution degree of the acyl group is too small, the durability may deteriorate, which is not preferable.

[0167] On the other hand, the higher the substitution degree of the acyl group of the cellulose ester, the less retardation is expressed, so it is necessary to increase the stretching ratio during film formation, but it is difficult to stretch uniformly at a high stretching ratio, which results in greater (worsened) film thickness variation. In addition, the Rt humidity fluctuation, which is retardation in the thickness direction (retardation), occurs when water molecules coordinate to the carbonyl groups of cellulose, so the higher the substitution degree of the acyl group, i.e., the more carbonyl groups there are in the cellulose, the worse the Rt humidity fluctuation tends to be.

[0168] The total degree of substitution of the cellulose ester is preferably within the range of 2.1 to 2.5. By setting the degree of substitution within 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, the degree of substitution is within 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.

[0169] More specifically, the cellulose ester satisfies both of the following formulae (a) and (b): In the following formulae (a) and (b), X is the degree of substitution of an acetyl group, and Y is the degree of substitution of a propionyl group or a butyryl group, or the degree of substitution of a mixture thereof.

[0170] Formula (a): 2.1≦X+Y≦2.5 Formula (b): 0≦Y≦1.5

[0171] 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 terms of reducing film thickness variation.

[0172] Particularly preferably used cellulose acetate is cellulose diacetate (DAC) having a molecular weight of 2.1≦X≦2.5 (more preferably 2.15≦X≦2.45) in terms of achieving desired ranges for retardation expression, Rt humidity fluctuation, and film thickness variation.

[0173] 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.

[0174] 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.

[0175] The degree of substitution of acyl groups indicates the average number of acyl groups per glucose unit, and indicates how many hydrogen atoms of hydroxyl 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 hydrogen atoms of hydroxyl groups at the 2nd, 3rd and 6th positions are substituted with acyl groups. These acyl groups may be substituted evenly at the 2nd, 3rd and 6th positions of the glucose unit, or may be substituted with a distribution. The degree of substitution is determined by the method specified in ASTM-D817-96.

[0176] In order to obtain desired optical properties, cellulose acetates having different degrees of substitution may be mixed together, and the mixing ratio of the different cellulose acetates is not particularly limited.

[0177] 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 Within the range of 4×10 4 ~8×10 4 It is preferable that the number average molecular weight Mn of the cellulose ester is within the range from the viewpoint of increasing the mechanical strength of the obtained film roll. 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.

[0178] 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 Within the range of 4×10 4 ~8×10 4 It is preferable for the thickness to be within this range in view of increasing the mechanical strength of the resulting film roll.

[0179] The raw cellulose for the cellulose ester is not particularly limited, but examples thereof include cotton linters, wood pulp, kenaf, etc. Furthermore, the cellulose esters obtained from these can be mixed and used in any desired ratio.

[0180] Cellulose esters such as cellulose acetate and cellulose acetate propionate can be produced by known methods.

[0181] Generally, the raw material cellulose is mixed with a specified organic acid (acetic acid, propionic acid, etc.), an acid anhydride (acetic anhydride, propionic acid, etc.), and a catalyst (sulfuric acid, etc.) to esterify the cellulose and allow the reaction to proceed until a cellulose triester is produced.

[0182] In triesters, the three hydroxy groups of the glucose unit are replaced by acyl groups of organic acids. By using two kinds of organic acids at the same time, mixed ester type cellulose esters, such as cellulose acetate propionate and cellulose acetate butyrate, can be prepared.

[0183] Next, the cellulose triester is hydrolyzed to synthesize a cellulose ester resin having a desired degree of acyl substitution. After that, the cellulose ester resin is completed through processes such as filtration, precipitation, washing with water, dehydration, and drying. Specifically, the synthesis can be performed with reference to the method described in JP-A-10-45804.

[0184] (1.3.2) Other additives The material used for the film according to the present invention may contain the following additives in addition to the above-mentioned thermoplastic resin.

[0185] (Plasticizer) The optical film according to the present invention preferably contains at least one plasticizer for the purpose of imparting processability to, for example, a polarizing plate protective film. The plasticizer is preferably used alone or in combination of two or more. Among the plasticizers, it is preferable to contain at least one plasticizer selected from the group consisting of sugar esters, polyesters, and styrene-based compounds, from the viewpoint of effectively controlling moisture permeability and achieving high compatibility with base resins such as cellulose esters.

[0186] From the viewpoint of achieving both improved wet heat resistance and compatibility with base resins such as cellulose ester, the plasticizer preferably has a molecular weight of 15,000 or less, more preferably 10,000 or less. When the compound having a molecular weight of 10,000 or less is a polymer, the weight average molecular weight (Mw) is preferably 10,000 or less. The weight average molecular weight (Mw) is preferably in the range of 100 to 10,000, more preferably 400 to 8,000.

[0187] In particular, in order to obtain the effects of the present invention, the compound having a molecular weight of 1500 or less is preferably contained in an amount within a range of 6 to 40 parts by mass, more preferably 10 to 20 parts by mass, relative to 100 parts by mass of the base resin. By containing the compound within the above range, it is possible to effectively control the moisture permeability and to ensure compatibility with the base resin, which is preferable.

[0188] [Sugar esters] In order to prevent hydrolysis, a sugar ester compound may be contained as a plasticizer. 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 a part of the OH groups of the structure are esterified.

[0189] 〔polyester〕 Polyester can also be contained as a plasticizer. The polyester is not particularly limited, but for example, a polymer (polyester polyol) having a terminal hydroxyl group that can be obtained by condensation reaction of dicarboxylic acid or its ester-forming derivative with glycol, or a polymer (terminal-capped polyester) in which the terminal hydroxyl group of the polyester polyol is capped with monocarboxylic acid can be used. The ester-forming derivative here refers to an esterified product of dicarboxylic acid, a dicarboxylic acid chloride, or an anhydride of dicarboxylic acid.

[0190] [Styrene-based compounds] As a plasticizer, in addition to or instead of the sugar ester and polyester, a styrene-based compound can be used for the purpose of improving the water resistance of the film. 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. In order to ensure that the molecular structure has a certain level of bulkiness, the content of the structural unit derived from the styrene-based monomer in the styrene-based compound may be preferably within the range of 30 to 100 mol%, more preferably within the range of 50 to 100 mol%.

[0191] Examples of styrene 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. vinyl benzoates 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 used alone or in combination of two or more kinds.

[0192] (optional ingredient) The optical film according to the present invention may contain other optional components such as antioxidants, colorants, UV absorbers, matting agents, acrylic particles, hydrogen bonding solvents, and ionic surfactants, etc. These components may be added in an amount of 0.01 to 20 parts by mass relative to 100 parts by mass of the base resin.

[0193] [Antioxidants] The film roll according to the present invention can use any commonly known antioxidant, and in particular, lactone-based, sulfur-based, phenol-based, double bond-based, hindered amine-based, and phosphorus-based compounds can be preferably used.

[0194] These antioxidants are added in the range 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 film. A synergistic effect can be obtained by using several different types of compounds in combination rather than using only one type of these antioxidants. For example, it is preferable to use lactone-based, phosphorus-based, phenol-based and double bond-based compounds in combination.

[0195] [Coloring Agent] The film roll according to 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. The colorant means a dye or pigment, and in the present invention, refers to a colorant that has the effect of making the color tone of the liquid crystal screen blue, adjusting the yellow index, and reducing haze. As the colorant, various dyes and pigments can be used, and anthraquinone dyes, azo dyes, phthalocyanine pigments, etc. are effective.

[0196] [Ultraviolet absorber] The film roll according to the present invention may contain an ultraviolet absorbing agent for the purpose of imparting an ultraviolet absorbing function, since it can be used on the viewing side or backlight side of a polarizing plate. The ultraviolet absorbing agent is not particularly limited, but examples thereof include benzotriazole-based, 2-hydroxybenzophenone-based, and salicylic acid phenyl ester-based ultraviolet absorbing agents.

[0197] Examples of the ultraviolet absorbent 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 ultraviolet absorbent can be used alone or in combination of two or more kinds.

[0198] The amount of the UV absorber used varies depending on the type of UV absorber, the 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.

[0199] [Fine particles] The film roll according to the present invention is preferably added with fine particles that impart slipperiness to the film roll. In particular, the addition of fine particles is effective from the viewpoints of improving the slipperiness of the film surface according to the present invention, improving the slipperiness during winding, and preventing the occurrence of scratches and blocking.

[0200] As the fine particles, either inorganic or organic fine particles may be used as long as they do not impair the transparency of the obtained film roll and have heat resistance during melting, but inorganic fine particles are more preferable. These fine particles can be used alone or in combination of two or more kinds. By using particles with different particle sizes and shapes (e.g., needle-shaped and spherical, etc.), it is also possible to achieve both high transparency and slipperiness.

[0201] Among the compounds constituting the above 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).

[0202] Specific examples of silicon dioxide include Aerosil (registered trademark) 200V, Aerosil (registered trademark) R972V, Aerosil (registered trademark) R972, R974, R812, 200, 300, R202, OX50, TT600, NAX50 (all manufactured by Nippon Aerosil Co., Ltd.), Sea Hoster (registered trademark) KEP-10, Sea Hoster (registered trademark) KEP-30, Sea Hoster (registered trademark) KEP-50 (all manufactured by Nippon Shokubai Co., Ltd.), Silo Hobic (registered trademark) 100 (manufactured by Fuji Silysia Co., Ltd.), Nipsil (registered trademark) E220A (manufactured by Nippon Silica Industry Co., Ltd.), and Adma Fine (registered trademark) SO (manufactured by Admatechs Co., Ltd.).

[0203] The shape of the particles is not particularly limited and may be any shape, such as amorphous, acicular, flat, or spherical. In particular, spherical particles are preferred because they can provide a film roll with good transparency.

[0204] The particle size is preferably smaller than the wavelength of visible light, and more preferably less than 1 / 2 the wavelength of visible light, since light scattering occurs when the particle size is close to the wavelength of visible light, resulting in poor transparency. If the particle size is too small, the slipperiness may not be improved, and therefore the particle size is particularly preferably within the range of 80 to 180 nm. Note that the particle size means the size of the aggregate when the particle is an aggregate of primary particles. In addition, when the particle is not spherical, the particle size means the diameter of a circle equivalent to the projected area of ​​the particle.

[0205] 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.

[0206] (1.4) Uses of the film The optical film unwound from the film roll according to the present invention is suitably used 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.

[0207] 2. Film roll manufacturing method The film roll of the present invention can be manufactured by a solution casting film forming method or a melt casting film forming method, for example, by the methods described in WO 2022 / 259668, WO 2022 / 153785, and WO 2022 / 224635. In particular, the teardrop shape of the fine unevenness described above can be formed by the method described in WO 2022 / 224635.

[0208] The film roll of the present invention can be produced through a film-forming step, a fine concave-convex portion forming step, and a winding step.

[0209] (2.1) Film forming process In the film-forming process, the first resin composition is prepared, cast, dried, peeled, and dried and stretched to prepare a strip-shaped film base. The casting of the first resin composition may be performed by a melt casting method or a solution casting method. Among them, from the viewpoint of being able to use a high molecular weight resin, it is preferable to cast the first resin composition by a solution casting method. That is, the film base can be prepared through a dope preparation process, a casting, drying, peeling process, and a drying and stretching process.

[0210] (2.1.1) Dope preparation step: First resin composition preparation step In the film-forming process, first, a first resin composition for producing a film base is prepared.

[0211] (First resin composition) Examples of resins that can be used to prepare the first resin composition include the above-mentioned cellulose ester resins, cycloolefin resins (COP), polypropylene resins, acrylic resins, and polyester resins.

[0212] The solvent includes an organic solvent (good solvent) capable of dissolving at least the resin. Examples of the good solvent include chlorine-based organic solvents such as dichloromethane, as well as non-chlorine-based organic solvents such as methyl acetate, ethyl acetate, acetone, and tetrahydrofuran. Among them, methylene chloride is preferable.

[0213] The solvent may further include a poor solvent. Examples of the poor solvent include linear or branched aliphatic alcohols having 1 to 4 carbon atoms. When the ratio of alcohol in the dope is high, the film-like material is likely to gel and is likely to be easily peeled off from the metal support. Examples of linear or branched aliphatic alcohols having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Among them, methanol and ethanol are preferred from the viewpoints of stability and drying property.

[0214] (2.1.2) Casting, drying and peeling process Next, the first resin composition prepared in the dope preparation step is cast onto a support. The first resin composition can be cast by discharging it from a casting die. The temperature of the first resin composition during casting is usually within a range of 15 to 30°C, and is preferably room temperature (23°C).

[0215] Next, after the solvent in the first resin composition cast on the support is appropriately evaporated (after drying), the first resin composition after the solvent evaporation is peeled off from the support to obtain a film-like material of the first resin composition. The residual solvent amount of the film-like material of the first resin composition is, for example, preferably 25% by mass or more, more preferably in the range of 30 to 37% by mass, and even more preferably in the range of 30 to 35% by mass. If the residual solvent amount of the film-like material of the first resin composition at the time of peeling is 25% by mass or more, the solvent is easily evaporated from the film-like material after peeling at once. In addition, if the residual solvent amount of the film-like material of the first resin composition at the time of peeling is 37% by mass or less, the film-like material can be prevented from being stretched too much due to peeling.

[0216] The residual solvent amount in the film of the first resin composition at the time of peeling is defined by the following formula. The same applies hereinafter. In the following formula, "heat treatment when measuring the residual solvent amount" refers to heat treatment at 140°C for 15 minutes.

[0217] Residual solvent amount (mass%)=(mass of first resin composition before heat treatment−mass of first resin composition after heat treatment) / mass of first resin composition after heat treatment×100

[0218] (2.1.3) Drying / stretching process The film of the first resin composition thus obtained is then dried. Drying may be performed in one step or multiple steps. Furthermore, drying may be performed while stretching as necessary. Stretching may be performed according to the desired optical properties, and stretching is preferably performed in at least one direction, and stretching may be performed in two mutually perpendicular directions (for example, biaxial stretching in the width direction (x direction) of the film and the transport direction (y direction) perpendicular thereto).

[0219] The stretching ratio can be within the range of 1.01 to 2.00, for example, from the viewpoint of use as a retardation film. The stretching ratio is defined as (size of film in stretching direction after stretching) / (size of film in stretching direction before stretching). When performing biaxial stretching, it is preferable to set the above stretching ratios for each of the x direction and the y direction. The in-plane slow axis direction of the film (the direction in which the refractive index is maximum in the plane) is usually the direction in which the stretching ratio is maximum.

[0220] When the glass transition temperature of the resin is Tg, the drying temperature (stretching temperature) during stretching is preferably within the range of (Tg-65)° C. to (Tg+60)° C., and more preferably within the range of (Tg-50)° C. to (Tg+50)° C. If the stretching temperature is above a certain level, the solvent is easily volatilized appropriately, making it easy to adjust the stretching tension to an appropriate range, while if the temperature is below a certain level, the solvent does not volatilize too much, making it difficult for stretchability to be impaired.

[0221] It is preferable that the amount of residual solvent in the film of the first resin composition at the start of stretching is approximately the same as the amount of residual solvent in the film of the first resin composition at the time of peeling, for example, preferably in the range of 20 to 30 mass%, and more preferably in the range of 25 to 30 mass%.

[0222] The film of the first resin composition can be stretched in the x direction (TD direction) by, for example, fixing both ends of the film of the first resin composition with clips or pins and widening the distance between the clips or pins in the traveling direction (tenter method).The film of the first resin composition can be stretched in the y direction (MD direction) by, for example, applying a peripheral speed difference between multiple rolls and utilizing the roll peripheral speed difference therebetween (roll method).

[0223] From the viewpoint of further reducing the amount of residual solvent in the film of the first resin composition, it is preferable to further dry (post-dry) the film of the first resin composition obtained after stretching. For example, it is preferable to further dry the film of the first resin composition obtained after stretching while conveying it with a roll or the like (with a certain tension applied).

[0224] The drying temperature after stretching is preferably within the range of (Tg-30) to (Tg+30)° C., and more preferably within the range of (Tg-20) to Tg° C., where Tg is the glass transition temperature of the resin. If the drying temperature after stretching is equal to or higher than a certain level, the evaporation rate of the solvent from the film of the first resin composition after stretching is likely to be increased, and therefore the drying efficiency is likely to be improved, whereas if the temperature is equal to or lower than a certain level, deformation due to stretching of the film of the first resin composition is likely to be suppressed.

[0225] In this manner, the film base made of the first resin composition is produced.

[0226] (2.2) Fine unevenness formation process The method of forming the fine unevenness according to the present invention is not particularly limited as a method of forming the fine unevenness after preparing the second resin composition, and examples thereof include a method of applying the second resin composition onto the film base and then drying to form the fine unevenness, a method of forming the fine unevenness by embossing the second resin composition onto the film base, and a method of forming the fine unevenness by subjecting the film base and the second resin composition to laser processing. Among these, a method of applying the fine unevenness onto the film base and then drying to form the fine unevenness is particularly preferred. Examples of methods of forming fine unevenness by embossing or laser include the methods described in JP 2021-056302 A. Hereinafter, a method of applying the second resin composition onto the film base and then drying to form the fine unevenness, that is, a method of forming the fine unevenness through a second resin composition preparation step, a second resin composition application step, and a second resin composition drying step will be described.

[0227] (2.2.1) Second resin composition preparation step In the second resin composition preparation step, a resin is dissolved in a solvent to prepare a second resin composition.

[0228] (Second resin composition) The resin that can be used to prepare the second resin composition is the same as that of the first resin composition. The solvent contained in the second resin composition includes at least an organic solvent (good solvent) capable of dissolving the resin. Examples of the good solvent include chlorine-based organic solvents such as methylene chloride; and non-chlorine-based organic solvents such as methyl acetate, ethyl acetate, acetone, tetrahydrofuran, cyclopentanone, and toluene. Among them, methylene chloride, cyclopentanone, and toluene are preferable from the viewpoint of easily dissolving the cycloolefin-based resin. The solvent contained in the second resin composition may further include a poor solvent. As the poor solvent, the same poor solvent as that contained in the dope can be used.

[0229] The resin concentration of the second resin composition is preferably lower than that of the first resin composition, and is preferably 50% by mass or less of the resin concentration of the first resin composition. Specifically, the resin concentration of the second resin composition is preferably more than 2% by mass and 10% by mass or less, and more preferably in the range of 3 to 7% by mass. The height of the teardrop-shaped object can be adjusted by adjusting the resin concentration and amount of the second resin composition. For example, the height of the teardrop-shaped object can be increased by increasing the resin concentration and amount of the second resin composition.

[0230] (2.2.2) Second resin composition application step In the second resin composition application step, droplets of the second resin composition are applied (dropped) to both ends in the width direction of the surface of the formed film base to form a plurality of fine irregularities. In this case, it is preferable that the fine irregularities are teardrop-shaped, and that the relationship between the maximum width T2 in the major axis direction and the maximum width T1 in the minor axis direction of the teardrop shape satisfies the following formula (1) from the viewpoint of suppressing deformation of the film roll.

[0231] Formula (1): 1.15≦T2 / T1≦1.90

[0232] The second resin composition may be a melt or a solution, but is preferably a solution from the viewpoint of easy adjustment of shape and dimensions. That is, the teardrop-shaped object can be formed by applying droplets of the second resin composition (knurling solution) containing a resin and a solvent to both ends in the width direction of the film base and then drying.

[0233] The second resin composition can be applied by any method, such as a dispenser method or an inkjet method, and is more preferred from the viewpoint of easier adjustment of the teardrop shape. The temperature of the second resin composition at this time is, for example, within a range of 10 to 30°C, and is preferably room temperature (23°C).

[0234] (2.2.3) Second resin composition drying step The second resin composition drying step can be carried out by any drying method, such as air blowing (including hot air drying) or heating and drying by electromagnetic waves (for example, heating and drying by an infrared (IR) heater). In particular, when the fine unevenness is teardrop-shaped, hot air drying is preferred from the viewpoint of adjusting the relationship between the maximum width T2 in the major axis direction and the maximum width T1 in the minor axis direction of the teardrop-shaped object so as to satisfy the formula (1). In addition, in the case of air blowing and drying (hot air drying), the air blowing direction is preferably parallel to the surface of the film, and more preferably opposite to the transport direction of the film.

[0235] The drying temperature is preferably within a range that satisfies the above formula (1). The drying temperature is preferably high from the viewpoint of increasing the value of (T2 / T1), and specifically, when the glass transition temperature of the resin contained in the second resin composition is Tg, the drying temperature is preferably within a range of 40 to (Tg-20)°C, and more preferably within a range of 80 to (Tg-10)°C. Specifically, the drying temperature is preferably within a range of 40 to 115°C, and more preferably within a range of 80 to 100°C.

[0236] The value of (T2 / T1) can be adjusted by the film conveying speed, drying conditions (drying method, drying temperature), resin concentration of the second resin composition (for forming teardrop-shaped objects), dropping height, surface condition of the film, etc.

[0237] The value of (T2 / T1) can be increased by increasing the film conveying speed, decreasing the drying temperature, and using hot air drying as the drying method. In addition, the value of (T2 / T1) can be increased by appropriately decreasing the resin concentration of the second resin composition and increasing the drip height.

[0238] When the fine concave-convex portion is teardrop-shaped, the average distance T3 between the plurality of teardrop-shaped objects can be adjusted by the discharge frequency of the droplets of the second resin composition, etc. The height of the teardrop-shaped objects can be adjusted by, for example, the droplet concentration and discharge amount of the second resin composition.

[0239] (2.3) Winding process The film produced by forming a fine concave-convex portion on the film base is wound in the length direction of the film using a winding machine. This makes it possible to produce a film roll in which the strip-shaped film is wound around a winding core. The winding method is not particularly limited, and may be a constant torque method, a constant tension method, a taper tension method, or the like. The winding tension when winding the film is not particularly limited, and may be about 50 to 170 N.

[0240] (2.4) Other (Effect of teardrop-shaped objects on film rolls) As described above, when the optical film to be wound into the film roll of the present invention has a plurality of teardrop-shaped objects formed as the fine unevenness in the manufacturing process, it is preferable that the optical film has a plurality of teardrop-shaped objects 12 arranged at both ends in the width direction such that the intersection M of the major axis LA and the minor axis SA is located upstream in the winding direction. As a result, even if an oblique force is applied from the front in the traveling direction during winding, the teardrop-shaped objects 12 are unlikely to be crushed unevenly while mitigating the oblique force, and can be wound in a state of uniform contact with the film (in an ideal convex shape). Therefore, deformation of the film roll can be suppressed while the amount of air is uniformly taken in.

[0241] (Application) When the optical film is used, the teardrop-shaped portions are removed from the film roll produced by the above-mentioned manufacturing method, and the film is used as an optical film for a display device such as a liquid crystal display device or an organic EL display device. Examples of the optical film include a polarizing plate protective film (including a retardation film and a brightness enhancing film), a transparent substrate film, and a light diffusion film. Among these, the film 10 is preferably used as a polarizing plate protective film. EXAMPLES

[0242] The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. In the examples, the terms "parts" and "%" are used, but they represent "parts by mass" or "% by mass" unless otherwise specified.

[0243] A. Preparation of film rolls (A.1) Preparation of film roll 1 (A.1.1) Film formation First, dichloromethane was added to the pressurized dissolution tank at a flow rate of 400 kg / min and ethanol at a flow rate of 20 kg / min. Three minutes after the start of the solvent addition, the cyclic polyolefin resin was added to the pressurized dissolution tank while stirring. Next, five minutes after the start of the solvent addition, the fine particle additive liquid was added, heated to 60°C, and completely dissolved while stirring. The heating temperature was raised from room temperature at 5°C / min, dissolved in 30 minutes, and then cooled at 3°C / min.

[0244] This was filtered using Asaka Filter Paper No. 244 (filtration accuracy 0.005 mm) manufactured by Asaka Filter Paper Co., Ltd., with a filtration flow rate of 300 L / m. 2 ·h, filtration pressure 1.0×10 6 The mixture was filtered at 1000 Pa to prepare a dope having the following composition.

[0245] <Composition> Cycloolefin resin "G7810" (JSR Corporation) 100% by mass Dichloromethane 380% by mass Ethanol 20% by weight

[0246] The obtained dope was then uniformly cast onto a stainless steel belt support at a temperature of 31° C. and a width of 2300 mm using an endless belt casting apparatus. The temperature of the stainless steel belt was adjusted to 28° C., and the conveying speed of the stainless steel belt was 30 m / min. The solvent was evaporated on the stainless steel belt support until the residual solvent amount in the cast dope became 30 mass %, and then the dope was peeled off from the stainless steel belt support at a peeling tension of 110 N / m to obtain a film-like material.

[0247] The obtained film-like material was stretched 1.3 times in the transport direction (MD direction) while heated to 120°C by a roll method utilizing the difference in peripheral speed of the transport roll, and then stretched 1.65 times in the TD direction while heated to 130°C by a tenter method. The obtained film-like material was transported while heated at 70°C until it was completely dried, and the end was slit to form a film base with an average thickness of 30 μm, a width of 2260 mm, and a length of 6000 m. The transport speed was 20 m / min.

[0248] (Film thickness and average maximum height difference of film thickness (PV) ave1 (Measurement and calculation) The film thickness was measured at 1612 points using an in-line retardation film thickness measuring device RE-200L2T-Rth + film thickness (manufactured by Otsuka Electronics Co., Ltd.). The traverse speed was 100 mm / sec. From the film thickness measurements, the difference in height between the highest and lowest points of the uneven structure formed on the surface of the film base was calculated, and the average value was taken as (PV). ave1 It was decided.

[0249] (Measurement of thermal expansion coefficient) Using the same film base as above, a measurement plate of 3 mm square × 15 mm long was prepared. Next, a thermomechanical tester (TMA device) TM-9500 manufactured by ULVAC-RIKO, Inc. was used as the measurement device, and measurements were performed with a tensile load of 2 g. The temperature range was 25 to 100°C (heating rate 5°C / min, measurement environment: 25°C, 50% RH). The thermal expansion coefficient was calculated by measuring 10 measurement plates, approximating the temperature-elongation relationship to a straight line in the above temperature range using the TMA device, and averaging the results.

[0250] Specifically, the measurement plate is placed in the device and the temperature is raised at a constant rate until the temperature T 0 From T 1 Length A during the rise to 0 From A 1 The change in temperature was measured and the thermal expansion coefficient [ / °C] was calculated according to the following formula. The thermal expansion coefficient of the base film was 80×10 -6 / ℃ (80 ppm / ℃).

[0251] Thermal expansion coefficient [ / ℃] = (A 1 -A 0 ) / (T 1 -T 0 ) / L o

[0252] (A.1.2) Formation of uneven parts (teardrop-shaped objects) A cycloolefin resin G7810 (manufactured by JSR Corporation) was dissolved in a solvent to a concentration of 2% by mass to obtain a solution for teardrop-shaped objects. The solvent used was dichloromethane.

[0253] After the surface of the film base was corona-treated and plasma-treated, a solution for teardrop-shaped objects was applied to both ends of the treated surface of the film base in the width direction. A dispenser "SUPER HI JET" (manufactured by Musashi Engineering Co., Ltd.) was used for application. Then, the film was dried with an IR heater so that the film temperature reached 80°C, and multiple teardrop-shaped objects were formed on the film base. The temperature of the film was confirmed with a thermo camera. As a result, multiple teardrop-shaped objects having a height of approximately 0.4 μm were formed in a row on both ends of the film base surface in the width direction, and an optical film 1 was produced. The teardrop-shaped objects were formed up to 1500 m when the end of the optical film 1 in the longitudinal direction was set to 0 m, so that the uneven area of ​​the side surface in the width direction was only 90 to 100% when the optical film 1 was wound up.

[0254] Specifically, the teardrop-shaped objects were formed so that M in FIG. 5 was located 3 mm from the edge of the optical film in the width direction (x direction in FIG. 5 and FIG. 7). The planar shape of the teardrop-shaped objects was as shown in FIG. 5, and the maximum width T1 of the short axis SA was 1.00 mm, the maximum width T2 of the long axis LA was 1.89 mm, and the value of T2 / T1 was 1.89. The average distance T3 between the multiple teardrop-shaped objects was 1.5 mm. The height of the teardrop-shaped objects was adjusted by the amount of coating by the dispenser and was set to 0.4 μm. Then, the optical film on which the multiple teardrop-shaped objects were formed was wound around a core (a winding core with a diameter of 280 mm) to prepare a film roll 1. At this time, the initial tension during winding was 150 N, the taper was 70%, and the corners were 25%.

[0255] (A.2) Preparation of film rolls 2, 3 and 6-19 (A.2.1) Film formation The base film was formed in the same manner as in the preparation of film roll 1, and the film thickness and the average maximum height difference (PV) of the film thickness were ave1 and the thermal expansion coefficient were calculated.

[0256] (A.2.2) Formation of uneven parts (teardrop-shaped objects) Each optical film was produced by forming a plurality of teardrop-shaped objects in the same manner as in film roll 1, except that the height and "T2 / T1" value of the plurality of nearly hill-shaped teardrop-shaped objects formed in a row at both ends in the width direction of the film base surface were changed to the values ​​shown in Table I, and the length from the end in the longitudinal direction of each optical film was formed to be within the range shown in Table II so that the uneven area of ​​the side surface in the width direction would be within the range shown in Table II when each optical film was wound up. Film rolls 2, 3, and 6 to 19 were produced by winding each optical film under the same conditions as film roll 1. The average distance (T3) between the plurality of teardrop-shaped objects and the value of T2 / T1 were adjusted by the drying conditions (method, temperature).

[0257] Specifically, film rolls 2, 3, 6 to 9, and 11 to 19 were dried by heating at 90°C (Tg-70°C) using an infrared heater. Film roll 10 was dried at a drying temperature of 30°C by blowing hot air at 40°C in the film transport direction.

[0258] The resin type of film roll No. 8 was an acrylic resin. The acrylic resin used as the resin of film roll No. 8 was a methacrylic resin with a composition ratio of methyl methacrylate:N-phenylmaleimide of 95:5, a weight average molecular weight (Mw) of 500,000, and a glass transition temperature (Tg) of 110° C. The weight average molecular weight (Mw) and glass transition temperature (Tg) were measured by the following method.

[0259] (Measurement of weight average molecular weight) The weight average molecular weight (Mw) of the methacrylic resin was measured using gel permeation chromatography (HLC8220GPC manufactured by Tosoh Corporation) and a column (TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL in series manufactured by Tosoh Corporation). 20 mg ± 0.5 mg of the sample was dissolved in 10 ml of tetrahydrofuran and filtered through a 0.45 mm filter. 100 ml of this solution was injected into the column (temperature 40°C), and the measurement was performed with a detector RI temperature of 40°C, and the value converted into styrene was used.

[0260] (Measurement of glass transition temperature) The glass transition temperature of the methacrylic resin was measured using DSC (Differential Scanning Colorimetry) in accordance with JIS K 7121-2012.

[0261] (A.3) Preparation of film roll 4 (Preparation of film roll by embossing) (A.3.1) Film formation The base film was formed in the same manner as in the preparation of film roll 1, and the film thickness and the average maximum height difference (PV) of the film thickness were ave1 and the thermal expansion coefficient were calculated.

[0262] (A.3.2) Formation of uneven parts After the surface of the film base was corona-treated and plasma-treated, a plurality of uneven portions were formed by embossing at intervals of 1.5 mm on both ends of the width direction of the treated surface of the film (at a position 3 mm from the edge of the film in the width direction of the film). In addition, the length from the end of the longitudinal direction of the optical film was formed within the range shown in Table II so that the uneven portion area of ​​the side surface in the width direction would be within the range shown in Table II when the optical film was wound up. As a result, a plurality of approximately hill-shaped uneven portions with a height of 2.5 μm were formed in a row at both ends of the width direction of the film surface. The plurality of uneven portions were formed as shown in (a) and (b) of FIG. 10. (a) and (b) of FIG. 10 are schematic diagrams showing a heat pressing method for forming a convex portion 8 on the film base 1 by embossing.

[0263] FIG. 10(a) is an example of a schematic diagram of embossing by the hot pressing method, and is a schematic diagram showing the "hot pressing method" in which a metal roll (not shown) having a convex shape formed on the metal roll is pressed against the film base 1 while being heated by an embossing ring 4, and the back roll is a metal roll 5. Since the back roll is made of metal, the stress generated when the embossing ring 4 is pressed into the film base 1 is directed toward the inside of the film base 1 and the periphery of the embossing ring 4, and a convex portion 8 is formed in the shape shown in FIG. 10(b). The processing conditions for the convex portion 8 were as follows:

[0264] <Convex part processing conditions> Processing temperature: 250℃ Processing pressure: 0.5MPa Metal back roll

[0265] Then, the optical film having the plurality of protrusions 8 formed thereon was wound around a core under the same conditions as in the film roll 1 to prepare a film roll 4.

[0266] (A.4) Preparation of film roll 5 (preparation of film roll by laser) (A.4.1) Film formation The base film was formed in the same manner as in the preparation of film roll 1, and the film thickness and the average maximum height difference (PV) of the film thickness were ave1 and the thermal expansion coefficient were calculated.

[0267] (A.4.2) Formation of uneven parts After the surface of the base film was corona-treated and plasma-treated, multiple uneven portions were formed by laser at intervals of 1.5 mm on both ends of the treated surface of the film in the width direction (at positions 3 mm from the edges of the film in the width direction of the film). The length from the end of the longitudinal direction of the optical film was also formed within the range shown in Table II so that the uneven portion area on the side surface in the width direction would be within the range shown in Table II when the optical film was wound up. As a result, multiple approximately hill-shaped uneven portions with a height of 1.5 μm were formed in a row on each end of the film surface in the width direction.

[0268] A carbon dioxide gas laser was used as the laser device, with an output of 20 W, a central wavelength of the emitted light of 9.4 μm, and a range of the emitted light wavelengths of ±0.01 μm or less around the central wavelength.

[0269] The film was irradiated with laser light by reflecting a collimated beam emitted from a carbon dioxide laser device with two galvanometer mirrors and focusing it on the surface of the transported film via an fθ lens (focal length 200 mm). By controlling the angle of the galvanometer mirrors, the focusing position was moved in the film plane direction, thereby controlling the trajectory of the laser light irradiation on the film surface.

[0270] Then, the optical film having a plurality of concave and convex portions formed thereon was wound around a core under the same conditions as those for the film roll 1, to prepare a film roll 5.

[0271] [Table 1]

[0272] B. Measuring the outer diameter of the center and the outer diameter of the end of the film roll and calculating Rc / Re After storing each film roll at 40℃ and 80% RH for one week, the outer diameters of each film roll were measured with a tape measure at positions 30 mm from both ends in the width direction and at the center of the center, and these were recorded as the outer diameters of the ends and center, respectively. The outer diameter of the ends was taken as the average of the outer diameters of both ends. The results are shown in Table II.

[0273] C. Evaluation (C.1) Adhesion of film fragments (Evaluation method) A vibration test ("Sine wave sweep vibration test" JIS Z 0232) was performed on each film roll so that an impact of 8G was instantly applied to each film roll. After that, the optical film was unwound from each film roll, the end of the optical film was cut, and the cross section of the optical film was observed visually and with an optical microscope (50x) to see if white powder was observed. The white powder is small fragments of transparent film.

[0274] (Evaluation Criteria) A: No white powder was detected by visual inspection or detailed analysis. B: No white powder is visible to the naked eye, but detailed analysis reveals white powder. C: White powder is visible to the naked eye, but only in very small amounts. D: White powder is clearly visible to the naked eye.

[0275] (C.2) Outer winding misalignment (Evaluation method) After conducting the same vibration test as in the evaluation of adhesion of film fragments, the movement in the width direction was measured with a tape measure by how many mm, assuming that the portion of the film where the end face in the longitudinal direction of the optical film wound on the film roll contacts the winding core (winding core) is 0. Note that the winding core does not shift because it is fixed to the film with tape, and this portion is used as the reference, so the portion of the film where it contacts the winding core was set to 0.

[0276] (Evaluation Criteria) A: 0 mm in the width direction, i.e. no movement. B: There is movement in the width direction, but the distance moved is less than 2 mm. C: There is movement in the width direction, but the distance of movement is 2 mm or more and less than 5 mm. D: There is movement in the width direction, but the distance moved is 5 mm or more.

[0277] (C.3) Feeding performance (Evaluation method) For payout performance, after conducting the same vibration test as in the evaluation of adhesion of film fragments, the optical film was paid out from the roll and conveyed while shining reflected light on the optical film, and if any abnormality was found, the line was stopped and visually confirmed for sticking or other failures. In this way, the state of sticking (hereinafter, blocking) between overlapping optical films was visually observed and evaluated based on the following criteria.

[0278] (Evaluation Criteria) A: No blocking. B: Weak blocking is occasionally observed, but does not cause any problems in practical use. C: Blocking is at a weak level, but is not a problem in practical use. D: The blocking level is other than the above and users may complain.

[0279] [Table 2]

[0280] D. Overall Evaluation From the above, it is clear that the Examples do not have a "D" in the evaluation items and are therefore problem-free in practice, and are generally superior to the Comparative Examples. This also shows that the film rolls of the Examples have fewer winding problems during transportation and long-term storage, and can maintain their quality. [Explanation of symbols]

[0281] 1 Film Base 4 Embossed Rings 5 Metal Roll 8 Convex 30c Side of the core R 0 Center of the side of the core, center point of the side of the film roll in the width direction R 70 The circumference of a circle that is 70% of the maximum radius from the center of the side part outward R 100 Maximum radius (r max ) the circumference of the circle r cCore side radius r p The radius of the side of a film roll, including the core, at any point r max Maximum radius of the side of the film roll including the core F rayer A layer of optical film from the outer periphery of the side of the core to the maximum radius F rayer1 A layer of optical film extending from the center of the side surface to the outer circumference of a circle that is 70% of the maximum radius. F rayer2 A layer of optical film in the area outside the circumference of a circle that is 70% of the maximum radius from the center of the side surface outward h 1 Height of the protrusion h 2 Recess depth Re: Outside diameter of end at side Rc Outside diameter of the center of the side LA Long axis of teardrop shape SA Minor axis of teardrop shape M Intersection of the long and short axes of the teardrop-shaped object T1 Maximum width in the minor axis direction T2 Maximum width in the longitudinal direction Th Teardrop-shaped object spacing t Height of teardrop-shaped object x Width of film y Longitudinal direction of the film w Width of teardrop shape t Height of teardrop-shaped object

Claims

1. A film roll on which an optical film is wound, The film roll has a fine concave-convex portion only in a region outside the outer periphery of a circle that is 70% of the maximum radius from the center of the side surface in the width direction toward the outside, The ratio Rc / Re of the outer diameter Rc of the central portion of the film roll in the width direction to the outer diameter Re of the end portion is within a range of 0.96 to 1.

01. A film roll characterized by:

2. The fine irregularities are formed only at the end portions in the width direction, including an area outside the outer periphery of a circle that is 90% of the maximum radius from the center of the side surface portion outward.

2. The film roll according to claim 1.

3. The fine concave-convex portion is provided over a length in the range of 150 to 1500 m in the longitudinal direction of the film roll.

2. The film roll according to claim 1.

4. The fine concave-convex portion is provided over a length in the range of 500 to 1000 m in the longitudinal direction of the film roll.

2. The film roll according to claim 1.

5. The main component of the optical film is a cycloolefin resin.

2. The film roll according to claim 1.

6. The optical film is a single layer.

2. The film roll according to claim 1.

7. The minute concave-convex portion has a teardrop shape, and the relationship between the maximum width T2 in the major axis direction and the maximum width T1 in the minor axis direction of the teardrop shape satisfies the following formula (1): Formula (1): 1.15≦T2 / T1≦1.90 2. The film roll according to claim 1.

8. The long axis direction is the longitudinal direction of the optical film.

8. The film roll according to claim 7.

9. The optical film has the fine concave-convex portions only at both ends in the width direction.

2. The film roll according to claim 1.

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