Optical film, film roll, method for manufacturing optical film, and method for manufacturing film roll

Abstract

To provide an optical film capable of suppressing winding slippage. [Solution] The optical film 1A is long and is wound from a starting end 11a along the longitudinal direction of the long film to a terminal end 11b to form a film roll. The optical film 1A has a plurality of embossments 20 formed along the longitudinal direction between the starting end 11a and the terminal end 11b, the embossments 20 being of the same height within a predetermined range. In the optical film 1A, a first region 12a extends from the starting end 11a to an intermediate region 11c between the starting end 11a and the terminal end 11b, and a second region 12b extends from the intermediate region 11c to the terminal end 11b. The embossing density is the number of embossments 20 per unit length along the longitudinal direction. The embossing density of the embossments 20 formed in the second region 12b is higher than the embossing density of the embossments 20 formed in the first region 12a.

Description

[Technical Field]

[0001] The present invention relates to an embossed optical film, a film roll around which the optical film is wound, a method for manufacturing an optical film, and a method for manufacturing a film roll. [Background technology]

[0002] It is widely known that when films for optical applications are wound into rolls, embossed (knurled) areas are formed on the short edges of the films. The embossed areas act as anti-slip areas to prevent the film from slipping during winding.

[0003] The embossing is performed by pressing a convex shape formed on a roller against the film while the roller is rotated and the film is transported (Patent Document 1).

[0004] When the embossments are formed by stamping, the intervals between the embossments along the longitudinal direction of the film are constant, which results in a constant embossment density per unit length along the longitudinal direction of the film.

[0005] In response to this, a technique for forming embossments by applying resin has been proposed (Patent Document 2). The technique for forming embossments by applying resin makes it possible to increase the height of the embossments. Furthermore, compared to embossments formed by stamping, the embossments can be prevented from collapsing. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-070514 [Patent Document 2] Patent No. 7125995 Summary of the Invention [Problem to be solved by the invention]

[0007] However, if the embossing density is constant, as the winding length of the film roll increases, there is a possibility that winding misalignment in the short direction may occur between films overlapping in the radial direction of the film roll.

[0008] In addition, in a configuration in which coated embossing and embossing are mixed, the height of the coated embossing is relatively high compared to the embossing, and the coated embossing mainly supports the film. However, since the embossing density of the coated embossing is constant, there is a possibility that the film will slip during winding.

[0009] The present invention has been made to solve these problems, and has an object to provide an optical film and a film roll that can suppress winding slippage, as well as a method for manufacturing an optical film and a method for manufacturing a film roll. [Means for solving the problem]

[0010] In order to solve the above-mentioned problems, the present invention provides an optical film that is long and forms a film roll that is wound from a first end to a second end along the longitudinal direction of the long film, and has multiple embossments formed along the longitudinal direction between the first end and the second end, the multiple embossments being the same height within a predetermined range, where the first range is from the first end to an intermediate portion between the first end and the second end, and the second range is from the intermediate portion to the second end, and the number of embossments per unit length along the longitudinal direction is defined as the embossing density, and the embossing density of the embossments formed in the second range is higher than the embossing density of the embossments formed in the first range.

[0011] The present invention also provides a film roll comprising an optical film having a long shape, a plurality of embossments formed along the longitudinal direction between a first end and a second end along the longitudinal direction of the long shape, the plurality of embossments being of the same height within a predetermined range, and the film roll being wound from the first end to the second end, wherein the first range is from the first end to an intermediate portion between the first end and the second end, the second range is from the intermediate portion to the second end, and the number of embossments per unit length along the longitudinal direction is defined as the embossing density, and the embossing density of the embossments formed in the second range is higher than the embossing density of the embossments formed in the first range.

[0012] Furthermore, the present invention relates to a method for manufacturing an optical film that is long and has multiple embossments formed along the longitudinal direction between a first end and a second end along the longitudinal direction of the long film, wherein the embossments are formed by applying a resin such that, when a first range is from the first end to an intermediate portion between the first end and the second end, and a second range is from the intermediate portion to the second end, and the number of embossments per unit length along the longitudinal direction is defined as the embossing density, the multiple embossments have the same height within a predetermined range, and the embossing density of the embossments formed in the second range is higher than the embossing density of the embossments formed in the first range.

[0013] The present invention also provides a method for manufacturing a film roll, which includes forming multiple embossments along the longitudinal direction of a long optical film between a first end and a second end along the longitudinal direction, and winding the optical film from the first end to the second end, wherein the embossments are formed by applying a resin so that, when a first range is from the first end to an intermediate portion between the first end and the second end, and a second range is from the intermediate portion to the second end, and the number of embossments per unit length along the longitudinal direction is defined as the embossing density, the multiple embossments have the same height within a predetermined range, and the embossing density of the embossments formed in the second range is higher than the embossing density of the embossments formed in the first range, and the method for manufacturing a film roll includes winding the embossed optical film around a core. [Effects of the Invention]

[0014] According to the present invention, even if the winding length of the film roll is increased, it is possible to suppress winding misalignment in the short-side direction in optical films overlapping in the radial direction of the film roll. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a plan view illustrating an example of an optical film. [Figure 2] FIG. 2 is a plan view of a main portion illustrating an example of an optical film. [Figure 3] FIG. 2 is a side view illustrating an example of a film roll. [Figure 4] FIG. 10 is a side view showing the details of the embossment. [Figure 5] FIG. 10 is a side view showing the details of the embossment. [Figure 6] FIG. 2 is an explanatory diagram schematically illustrating the relationship between the magnitude of the embossing angle and the angle at which the embossing supports the optical film. [Figure 7] 1 is a graph showing the relationship between embossing density and film winding length. [Figure 8] 1 is a graph showing the relationship between embossing density and film winding length. [Figure 9] FIG. 10 is an explanatory diagram showing an example of a method for evaluating the amount of deviation. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an example of the optical film and the film roll according to the present embodiment will be described with reference to the drawings. Also, an example of a method for manufacturing the optical film and the film roll according to the present embodiment will be described.

[0017] <Configuration examples of optical films and film rolls> FIG. 1 is a plan view showing an example of an optical film, FIG. 2 is a plan view showing a main part of the example of the optical film, and FIG. 3 is a side view showing an example of a film roll.

[0018] The optical film 1A is configured in a long shape. The optical film 1A is, for example, a polymer film. Arrow LL indicates the longitudinal direction of the long optical film 1A. Arrow LS indicates the lateral direction of the long optical film 1A. The optical film 1A has embossed regions 2 on both ends in the lateral direction, and has non-embossed regions 3 between the embossed regions 2. The embossed regions 2 and non-embossed regions 3 are stretched along the longitudinal direction of the optical film 1A.

[0019] The optical film 1A has embossments 20 in each embossed region 2. The embossments 20 protrude from the surface of the optical film 1A in a predetermined shape. For example, the embossments 20 have a triangular cross-sectional shape along the longitudinal direction of the optical film 1A. The embossments 20 are arranged in a row at predetermined intervals along the longitudinal direction of the optical film 1A. Alternatively, the embossments 20 may be arranged in a row at predetermined intervals along the longitudinal direction of the optical film 1A, and may also be arranged in multiple rows along the lateral direction of the optical film 1A.

[0020] The optical film 1A is wound up to form a film roll 10 with the embossed portion 20 facing outwards.

[0021] The optical film 1A starts to be wound around the film roll 10 from the first end. The winding start point of the optical film 1A around the film roll 10 is referred to as the starting end 11a. The winding end point of the optical film 1A around the film roll 10 is referred to as the second end. The winding end point of the optical film 1A around the film roll 10 is referred to as the terminal end 11b.

[0022] Furthermore, the optical film 1A will be referred to as a first region 12a from the starting end 11a to the intermediate region 11c between the starting end 11a and the terminal end 11b, and as a second region 12b from the intermediate region 11c to the terminal end 11b.

[0023] The optical film 1A has a length L from the starting end 11a to the terminal end 11b of, for example, 3000 m or more. The optical film 1A also has a length L1 of a first region 12a from the starting end 11a to the middle region 11c of, for example, 900 m or more and 1100 m or less. The optical film 1A preferably has a length L2 of the first region 12a of, for example, 1000 m. The first region 12a is also referred to as a winding core.

[0024] The number of embossments 20 per unit length along the longitudinal direction of the optical film 1A is referred to as the embossing density. The optical film 1A is configured such that the embossing density in areas other than the first area 12a is higher than the embossing density in the first area 12a. That is, the optical film 1A is configured such that the embossing density in the second area 12b is higher than the embossing density in the first area 12a.

[0025] 4 and 5 are side views showing the details of the embossment. First, the height of the embossment 20 will be described.

[0026] When the height of the embossments 20 from the surface of the optical film 1A is H (mm), all of the embossments 20 have a constant height H. Note that the embossments 20 are said to have a constant height H when, for example, the average height H per meter of the optical film 1A falls within a range of −0.05% to +0.05%.

[0027] Next, the embossing density will be described. When the number of embossments 20 in a unit length (1 mm) is the embossing density d (pieces / mm) and the spacing between the embossments 20 is L (mm), the embossing density d is calculated by the following formula (1).

[0028] d=1 / L (1)

[0029] Next, the size of the embossments 20 will be described. The size of the embossments 20 along the longitudinal direction of the optical film 1A is expressed as the angle θ (°) with the center O of the film roll 10A as the vertex. The angle θ is also referred to as the emboss angle. In this case, if the length of the embossments 20 along the longitudinal direction of the optical film 1A is s (mm) and the radius of the film roll 10 is r (mm), the angle θ can be calculated using the following formula (2):

[0030] θ=180s / πr (2)

[0031] When the length s of the embossment 20 is constant, the embossing angle θ becomes smaller when the radius r of the film roll 10 is larger than when the radius r of the film roll 10 is small.

[0032] The radius r of the film roll 10 increases as the winding length of the film roll 10 increases. Therefore, the embossing angle θ decreases as the winding length of the film roll 10 increases. In FIG. 5, the embossing angle θ when the radius r of the film roll 10 is r1 is defined as θ1. Also, the embossing angle θ when the radius r of the film roll 10 is r2 is defined as θ2. If r2>r1, then θ1>θ2.

[0033] FIG. 6 is an explanatory diagram that schematically shows the relationship between the magnitude of the embossing angle and the angle at which the embossing supports the optical film.

[0034] The force f that each embossment 20 supports on the optical film 1A overlapping in the radial direction of the film roll 10 can be determined by the angle with the center O of the film roll 10 as the vertex. This angle corresponds to the embossing angle θ. The force f that each embossment 20 supports is schematically shown in FIG. 6 as a range indicated by dashed hatching, depending on the size of the embossing angle θ.

[0035] 6, when the embossing angle is θ1, the force with which each embossing 20 supports the optical film 1A is denoted by f1. When the embossing angle is θ2, the force with which each embossing 20 supports the optical film 1A is denoted by f2.

[0036] As the radius r of the film roll 10 increases, the embossing angle θ decreases. A smaller embossing angle θ means that the angle at which each embossing 20 supports the optical film 1A decreases. This corresponds to a relatively smaller force f with which each embossing 20 supports the optical film 1A. Therefore, if θ1 > θ2, then f1 > f2.

[0037] In this way, when the winding length of the film roll 10 increases, the force applied by lamination to the outer side along the radial direction of the film roll 10 becomes weaker.

[0038] Therefore, as the winding length of the film roll 10 increases, the optical film 1A overlapping the film roll 10 in the radial direction tends to shift in the lateral direction on the radially outer side. Such a shift is called winding shift.

[0039] Therefore, the embossing density d of the optical film 1A increases as the winding length of the film roll 10 increases. This is equivalent to configuring the embossing density of the second region 12b of the optical film 1A to be higher than the embossing density of the first region 12a. The embossing density d of the optical film 1A is changed by changing the spacing L of the embossings 20 without changing the size of the embossings 20.

[0040] Next, the amount of change Δd in the embossing density d between the first range 12a and the second range 12b will be defined.

[0041] First, consider the case where the embossing density d is constant from the starting end 11a where the film roll 10 begins to wind to the terminal end 11b where the film roll 10 ends. In this case, the product (d × θ) of the embossing density d and the embossing angle θ is used as a reference. The embossing angle θ decreases as the winding length of the film roll 10 increases. Therefore, if the embossing density d is constant, d × θ decreases as the winding length of the film roll 10 increases.

[0042] In contrast, consider the case where the embossing density d in the second region 12b is increased to embossing density d' (d'>d), in which case the difference Δd×θ between d'×θ and d×θ satisfies the relationship of the following equation (3).

[0043] 0.0013<Δd×θ<0.3034 (3)

[0044] 7 and 8 are graphs showing the relationship between embossing density and film winding length. The hatched area in Fig. 7 indicates the range of embossing densities that can be changed after changing the embossing density within the range defined by formula (3) relative to the reference embossing density. Fig. 8 also shows an example in which the embossing density is further changed in the second area 12b outside the winding core.

[0045] When the change Δd in the embossing density d between the first region 12a and the second region 12b satisfies the formula (3), the winding deviation of the film roll 10 can be suppressed.

[0046] The interval L of the embossments 20 and the length s of the embossments 20 are set to satisfy the relationship of the following formula (4):

[0047] L>s···(4)

[0048] If the spacing L and length s of the embossments 20 do not satisfy the relationship of formula (4), there will be no gaps between the embossments 20 aligned along the longitudinal direction of the optical film 1A. In this case, in the film roll 10, it becomes difficult for air to escape between the optical films 1A overlapping in the radial direction, making it more likely that misalignment will occur during winding.

[0049] In contrast, when the spacing L and length s of the embossments 20 satisfy the relationship of formula (4), gaps are formed between the embossments 20 aligned along the longitudinal direction of the optical film 1A. In this case, air can easily escape between the optical films 1A overlapping in the radial direction in the film roll 10, suppressing the occurrence of winding slippage. [Example]

[0050] <Creating film rolls> Optical films were prepared under the conditions shown in Tables I and II below, and these optical films were wound up to prepare film rolls.

[0051] [Table 1]

[0052] [Table 2]

[0053] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the following examples, unless otherwise specified, operations were carried out at room temperature (25°C). Furthermore, unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass," respectively.

[0054] The optical film may be made of a known resin. Specific examples of the resin include acrylic resin, cellulose ester resin, and cycloolefin resin. Specific examples of the resin are described below.

[0055] [Acrylic resin (A)] The following acrylic resins A1 to A4 are used as the acrylic resin (A). The acrylic resin A1 is a commercially available product. The acrylic resins A2 to A4 are prepared by the following methods.

[0056] (Acrylic resin A1) The acrylic resin A1 is Dianall BR85 (manufactured by Mitsubishi Chemical Corporation).

[0057] (Preparation of Acrylic Resin A2) The mass ratio (MMA:MA) of methyl methacrylate (MMA) to methyl acrylate (MA) was set to 98:2. This was synthesized in accordance with the method described in paragraphs

[0130] to

[0135] of JP 2006-241263 A. As a result, acrylic resin A2 having a weight average molecular weight (Mw) of 80,000 was obtained.

[0058] (Preparation of acrylic resin A3) The mass ratio (MMA:MA) of methyl methacrylate (MMA) to methyl acrylate (MA) was 97:3. This was synthesized in accordance with the method described in paragraphs

[0130] to

[0135] of JP 2006-241263 A. As a result, acrylic resin A3 having a weight average molecular weight (Mw) of 930,000 was obtained.

[0059] (Preparation of acrylic resin A4) A reactor was charged with 19 parts by mass of 2-hydroxypropyl methacrylate (HPMA) and 76 parts by mass of methyl methacrylate (MMA). Furthermore, 97 parts by mass of toluene was charged as a polymerization solvent. The reactor was equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen inlet tube. The temperature was raised to 105°C while nitrogen was passed through the reactor. Subsequently, solution polymerization was carried out under reflux at 105-110°C for 1 hour to obtain acrylic resin A4. The molecular weight of the obtained acrylic resin A4 was determined to be a weight-average molecular weight (Mw) of 281,000, a number-average molecular weight (Mn) of 133,000, and a molecular weight distribution (Mw / Mn) of 2.1.

[0060] [Cellulose ester resin (CE)] As the cellulose ester resin (CE), the following cellulose ester resins CE1 to CE4 are used.

[0061] (Preparation of Cellulose Ester Resin CE1) A mixture of sulfuric acid (7.8 parts by mass per 100 parts by mass of cellulose) as a catalyst and carboxylic acid anhydride was cooled to -20°C. It was then added to cellulose derived from hardwood pulp, and acylation was carried out at 40°C. The type and amount of carboxylic acid anhydride were adjusted to control the type and substitution ratio of acyl groups. After acylation, the mixture was aged at 40°C to adjust the total degree of substitution. As a result, cellulose ester resin CE1 with a weight-average molecular weight of 200,000 was obtained. The cellulose ester resin CE1 has a total degree of substitution (T) of acyl groups of 2.75, a degree of substitution of acetyl groups (Ac) of 0.19, and a degree of substitution of propionyl groups (Pr) of 2.56.

[0062] (Preparation of Cellulose Ester Resin CE2) In preparing cellulose ester resin CE1, the type and amount of carboxylic acid anhydride were appropriately adjusted to control the type and substitution ratio of acyl groups. Furthermore, after acylation, the mixture was aged at 40°C to adjust the total degree of substitution. As a result, cellulose ester resin CE2 with a weight-average molecular weight of 200,000 was obtained. Cellulose ester resin CE2 had a total degree of acyl substitution (T) of 2.1, a degree of acetyl group (Ac) substitution of 0.8, and a degree of propionyl group (Pr) substitution of 1.3.

[0063] (Preparation of Cellulose Ester Resin CE3) In preparing cellulose ester resin CE1, the type and amount of carboxylic acid anhydride were appropriately adjusted to control the type and substitution ratio of acyl groups. Furthermore, after acylation, the resin was aged at 40°C to adjust the total degree of substitution. As a result, cellulose ester resin CE3 with a weight-average molecular weight of 200,000 was obtained. Cellulose ester resin CE3 had a total degree of acyl substitution (T) of 2.8. Furthermore, cellulose ester resin CE3 had a degree of substitution of acetyl groups (Ac) of 0.5, a degree of substitution of propionyl groups (Pr) of 1.15, and a degree of substitution of butyryl groups (Bu) of 1.15.

[0064] (Preparation of Cellulose Ester Resin CE4) In preparing cellulose ester resin CE1, the type and amount of carboxylic acid anhydride were appropriately adjusted to control the type and substitution ratio of acyl groups. Furthermore, after acylation, the mixture was aged at 40°C to adjust the total degree of substitution. As a result, cellulose ester resin CE4 with a weight-average molecular weight of 76,000 was obtained. Cellulose ester resin CE4 had a total degree of acyl substitution (T) of 2.75, a degree of acetyl group (Ac) substitution of 0.19, and a degree of propionyl group (Pr) substitution of 2.56.

[0065] (Cycloolefin resin (COP)) As the cycloolefin resin, the following commercially available cycloolefin resin COP is used. Cycloolefin resin COP: ARTON (registered trademark) G7810 (manufactured by JSR Corporation)

[0066] [Optical film fabrication] The acrylic resin A1 and the cellulose ester resin CE1 were used to prepare optical films of Examples and Comparative Examples.

[0067] (Dope liquid composition) Acrylic resin A1: 160 parts by mass Cellulose ester resin CE1: 86 parts by mass Rubber particles (Kane Ace M210, manufactured by Kaneka Corporation): 2.5 parts by mass Methylene chloride: 550 parts by mass Ethanol: 100 parts by mass The above composition was thoroughly dissolved under heating to prepare a dope solution.

[0068] (Optical film production and first stage stretching) The dope solution was uniformly cast onto a stainless steel band support with a width of 2 m at a temperature of 22° C. The solvent was evaporated on the stainless steel band support until the residual solvent amount became 40% by mass, and the stainless steel band support was peeled off with a peeling tension of 150 N / m.

[0069] The solvent was evaporated from the peeled acrylic resin web at 35°C, and the web was slit to a width of 1.6 m. The rotation speed of the stainless steel band support and the speed of the stretching device were then adjusted, and the web was stretched in the MD direction (longitudinal direction) (first stretching). The first stretching ratio was calculated to be 1.2 times from the rotation speed of the stainless steel band support and the speed of the stretching device. Here, the first stretching ratio in the MD direction is defined as (the conveying speed of the film after stretching) / (the conveying speed of the film before stretching). The stretching temperature in the first stretching was 50°C.

[0070] The film was then stretched 1.1 times in the width direction (TD direction) while heated to 135°C in a stretching device (second stretching). The second stretching ratio in the TD direction was defined as (film width after stretching) / (film width before stretching). The residual solvent content was 10% by mass when stretching was started in the stretching device.

[0071] After stretching in the stretching device, the film was conveyed through a drying zone at 110°C to complete drying, and the stretching speed and take-up speed were adjusted to stretch the film in the MD direction (third stretching). The third stretching ratio was calculated from the tenter speed and take-up speed to be 1.2 times. Here, the third stretching ratio in the MD direction is defined as (the conveying speed of the film after stretching) / (the conveying speed of the film before stretching).

[0072] The film after the third stretching was wound around a core with an inner diameter of 15.24 cm at an initial tension of 220 N / m and a final tension of 110 N / m to obtain Film 1-1.

[0073] The residual solvent amount of Film 1-1 was 0.3% by mass, the film thickness was 47 μm, and the roll length was 12,000 m.

[0074] (Second stage extension) Thereafter, the wound-up film 1-1 was subjected to a second-stage stretching (fourth stretching) so that the stretching ratio became 1.35. In the fourth stretching, the film 1-1 was unwound from the roll, and then stretched in the width direction (TD) while being heated to 140°C in a stretching device.

[0075] Both ends of this stretched film were cut to a width of 2260 mm to obtain Film 1-2 used in Examples 1 to 3, 6-9, 12-20 and Comparative Example 4. Both ends of this stretched film were cut to a width of 1330 mm to obtain Film 1-2 used in Examples 4 and 11 and Comparative Example 1. Both ends of this stretched film were cut to a width of 3000 mm to obtain Film 1-2 used in Examples 5 and 10 and Comparative Example 2. Both ends of this stretched film were cut to a width of 1500 mm to obtain Film 1-2 used in Comparative Example 3.

[0076] The thickness of the film 1-2 used in Examples 1 to 3, 6 to 11, 14 to 17, 18, and 19, and Comparative Example 4, was 35 μm. The thickness of the film 1-2 used in Examples 5 and 13, and Comparative Example 1, was 15 μm. The thickness of the film 1-2 used in Examples 6 and 12, and Comparative Example 2, was 100 μm. The thickness of the film 1-2 used in Example 18, was 30 μm. The thickness of the film 1-2 used in Comparative Example 1, was 40 μm.

[0077] (Preparation of coating embossing solution) The acrylic resin was dissolved in a solvent containing dichloromethane and cyclopentanone to a concentration of 5% by mass to obtain a coating and embossing solution.

[0078] (Formation of coated embossment) The coating embossing solution was applied to the surface of Film 1-2 using a dispenser, SUPER HI JET, manufactured by Musashi Engineering Co., Ltd. The film was then dried using an IR heater until the film temperature reached 80°C, forming multiple coating embossments. The film temperature was confirmed using a thermal camera.

[0079] In Examples 1 to 3 and 6, a plurality of coated embossments each having a height H of 0.1 μm and a length s of 1 mm were formed in a row on both widthwise ends of the surface of film 1-2. In Examples 4 and 7, a plurality of coated embossments each having a height H of 0.1 μm and a length s of 0.883 mm were formed in a row on both widthwise ends of the surface of film 1-2. In Examples 9 to 14, 19 and 20, a plurality of coated embossments each having a height H of 0.1 μm and a length s of 1 mm were formed in a row on both widthwise ends of the surface of film 1-2.

[0080] In Example 5, multiple coated embossments with a height H of 0.4 μm and a length s of 0.3 mm were formed in rows on both widthwise ends of the surface of Film 1-2.In Example 8, multiple coated embossments with a height H of 0.4 μm and a length s of 1 mm were formed in rows on both widthwise ends of the surface of Film 1-2.

[0081] In Example 15, two rows of multiple coated embossments, each with a height H of 0.1 μm and a length s of 1 mm, were formed on both widthwise ends of the surface of film 1-2. In Example 16, three rows of multiple coated embossments, each with a height H of 0.1 μm and a length s of 1 mm, were formed on both widthwise ends of the surface of film 1-2. In Example 17, four rows of multiple coated embossments, each with a height H of 0.1 μm and a length s of 1 mm, were formed on both widthwise ends of the surface of film 1-2.

[0082] In Comparative Example 1, multiple coated embossments with a height H of 0.1 μm and a length s of 0.815 mm were formed in rows on both widthwise ends of the surface of Film 1-2.In Comparative Example 2, multiple coated embossments with a height H of 0.4 μm and a length s of 0.3 mm were formed in rows on both widthwise ends of the surface of Film 1-2.

[0083] (Spacing between embossed coatings) In Examples 1 to 3 and 7 to 17, coated embossments were formed at intervals of 5.3 mm from the starting end to 1000 m of Film 1-2. In Examples 1 to 3 and 7 to 17, the portion 1000 m from the starting end constituted the intermediate portion.

[0084] In Examples 1, 8 to 17, coated embossments were formed at intervals of 3.533 mm between 1,000 m and 12,000 m of Film 1-2. In Examples 1, 8 to 17, the end was 12,000 m from the starting end. In Examples 1, 8 to 17, the coated embossments were also spaced 3.533 mm apart at 2,000 m, 5,000 m, 8,000 m, and 10,000 m from the starting end.

[0085] In Example 2, coated embossments were formed at intervals of 1.767 mm from 1000 m to 12000 m of Film 1-2. In Example 2, the location 12000 m from the starting end was the terminal end. In Example 2, the coated embossments were also spaced 1.767 mm apart at locations 2000 m, 5000 m, 8000 m, and 10000 m from the starting end.

[0086] In Example 3, coated embossments were formed at intervals of 1.060 mm from 1000 m to 12000 m of Film 1-2. In Example 3, the location 12000 m from the starting end was the terminal end. In Example 3, the coated embossments were also formed at intervals of 1.060 mm at locations 2000 m, 5000 m, 8000 m, and 10000 m from the starting end.

[0087] In Examples 4 and 7, coated embossments were formed at intervals of 0.883 mm from 1,000 m to 12,000 m of Film 1-2. In Examples 4 and 7, the end was 12,000 m from the starting end. In addition, in Examples 4 and 7, the coated embossments were also spaced 0.883 mm apart at 2,000 m, 5,000 m, 8,000 m, and 10,000 m from the starting end.

[0088] In Examples 5 and 6, coated embossments were formed at intervals of 7.067 mm from 1,000 m to 12,000 m of Film 1-2. In Examples 5 and 6, the end was 12,000 m from the starting end. In addition, in Examples 5 and 6, the coated embossments were also spaced 7.067 mm apart at 2,000 m, 5,000 m, 8,000 m, and 10,000 m from the starting end.

[0089] In Examples 19 and 20, coated embossments were formed at intervals of 5.3 mm from the starting end to 1000 m of Film 1-2. In Examples 19 and 20, the portion 1000 m from the starting end constituted the first intermediate portion.

[0090] In Examples 19 and 20, coated embossments were formed at intervals of 3.533 mm between 1000 m and 5000 m of Film 1-2. In Examples 19 and 20, the section 5000 m from the starting end constituted the second intermediate section. In Examples 19 and 20, the coated embossments were also spaced 3.533 mm apart at the section 2000 m from the starting end.

[0091] In Example 19, coated embossments were formed at intervals of 2.650 mm from 5000 m to 12000 m of Film 1-2. In Example 19, the location 12000 m from the starting end was the terminal end. In Example 19, the coated embossments were also formed at intervals of 2.650 mm at locations 5000 m, 8000 m, and 10000 m from the starting end.

[0092] In Example 20, coated embossments were formed at intervals of 4.240 mm from 5,000 m to 12,000 m of Film 1-2. In Example 20, the location 12,000 m from the starting end was the terminal end. In Example 19, the coated embossments were also formed at intervals of 4.240 mm at locations 5,000 m, 8,000 m, and 10,000 m from the starting end.

[0093] In Comparative Examples 1 and 2, coated embossments were formed at intervals of 10.6 mm from the starting end to 1000 m of Film 1-2. In Comparative Examples 1 and 2, the portion 1000 m from the starting end constituted the intermediate portion.

[0094] In Comparative Example 1, coated embossments were formed at intervals of 0.815 mm from 1000 m to 12000 m of Film 1-2. In Comparative Example 1, the location 12000 m from the starting end was the terminal end. In Comparative Example 1, the coated embossments were also spaced 0.815 mm apart at locations 2000 m, 5000 m, 8000 m, and 10000 m from the starting end.

[0095] In Comparative Example 2, coated embossments were formed at intervals of 8.833 mm from 1000 m to 12000 m of Film 1-2. In Comparative Example 2, the location 12000 m from the starting end was the terminal end. In Comparative Example 2, the coated embossments were also spaced 8.833 mm apart at locations 2000 m, 5000 m, 8000 m, and 10000 m from the starting end.

[0096] (Laser embossing) In Example 18, a plurality of embossments each having a height H of 3 μm and a length s of 1.2 mm were formed in a row by laser on both ends of the surface of the film 1-2 in the width direction.

[0097] The laser used was a carbon dioxide laser, with an output of 20 W, a central wavelength of 9.4 μm, and a wavelength range of ±0.01 μm or less around the central wavelength.

[0098] The laser beam was irradiated onto the film by focusing a collimated beam emitted from a carbon dioxide laser onto the surface of the transported film through an fθ lens. The focal length of the fθ lens was 200 mm. The collimated beam emitted from the carbon dioxide laser was reflected by two galvanometer mirrors. 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 beam irradiation on the film surface.

[0099] (Laser embossing spacing) In Example 18, embossments were formed at intervals of 4.2 mm by laser from the starting end to 1000 m of Film 1-2. In Example 18, the portion 1000 m from the starting end constituted the intermediate portion.

[0100] In Example 18, embossments were formed at 3 mm intervals using a laser from 1000 m to 12000 m of Film 1-2. In Example 18, the end was 12000 m from the starting end. In Example 18, the embossments formed by the laser were also spaced 3 mm apart at 2000 m, 5000 m, 8000 m, and 10000 m from the starting end.

[0101] (Embossing by coating and stamping) In Comparative Example 3, multiple coated embossments were formed in rows at both widthwise ends of the surface of Film 1-2, with a height H of 10 μm and intervals of 2 mm. Also, in Comparative Example 3, embossments were formed at both widthwise ends of the surface of Film 1-2 by knurling. The knurling process was performed using the method described in paragraphs

[0583] to

[0629] of JP 2020-75482 A. The height H was adjusted to 5 μm and the intervals were adjusted to 1.4 mm.

[0102] (embossing by pressing) In Comparative Example 4, embossments were formed on both widthwise ends of the surface of Film 1-2 by knurling. The knurling was performed using the method described above. The height H was adjusted to 3 μm and the spacing was adjusted to 1.4 mm.

[0103] (film winding) The embossed films of Examples 1 to 4, 6 to 13, 15 to 17, 19, and 20 were wound around a core with a diameter of 153.5 mm at an initial tension of 60 N / m and a final tension of 25 N / m. This resulted in a roll film. The embossed films of Examples 5, 14, and 18 and Comparative Example 2 were wound around a core with a diameter of 83.5 mm at an initial tension of 60 N / m and a final tension of 25 N / m. This resulted in a roll film. The embossed films of Comparative Examples 1 and 4 were wound around a core with a diameter of 153.5 mm at an initial tension of 60 N / m and a final tension of 25 N / m. The embossed film of Comparative Example 3 was wound around a core with a diameter of 250 mm at an initial tension of 60 N / m and a final tension of 25 N / m.

[0104] [Other optical film manufacturing examples] The optical films of the Examples and Comparative Examples can also be produced by the above method using any of the acrylic resins A1 to A4 and any of the cellulose ester resins CE1 to CE4.

[0105] (Creation of optical films using cycloolefin resin (COP)) The optical films of the examples and comparative examples can also be produced using cycloolefin resin (COP).

[0106] (film formation) Pellets of cycloolefin resin G7810 (manufactured by JSR Corporation) were fed into an extruder under a nitrogen atmosphere and melt-cast. The melt-cast film was cooled with a cooling roll and then peeled off to obtain a film-like material. The cycloolefin resin is a cycloolefin resin containing a structural unit derived from a norbornene-based monomer represented by the following formula, and has a Tg of 165°C.

[0107] [ka]

[0108] The resulting film was stretched twice in the width direction at 175°C, and then heated at 100°C until completely dried. The edges were then slit to obtain a film with a thickness of 40µm, a width of 2260mm, and a length of 12000m. The film was transported at a speed of 20m / min.

[0109] (Preparation of coating embossing solution) A cycloolefin resin G7810 (manufactured by JSR Corporation) was dissolved in a solvent to a concentration of 5% by mass, to obtain a coating embossing solution. The solvents used were dichloromethane and cyclopentanone.

[0110] (Formation of coated embossment) The surface of the film was subjected to corona treatment and plasma treatment. Then, a coating embossing solution was applied to both widthwise ends of the treated surface of the film, and the applied embossing solution was dried to form multiple coating embossments. A SUPER HI JET dispenser manufactured by Musashi Engineering was used to apply the coating embossing solution. After application, the coating embossing solution was dried using an IR heater to bring the film temperature to 80°C. The film temperature was confirmed using a thermal camera. The size and spacing of the embossing were as described above.

[0111] As a film formation method using cycloolefin resin (COP), the following example can also be applied.

[0112] (Preparation of Dope) 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 solvent addition, cyclic polyolefin resin was added to the pressurized dissolution tank while stirring. Next, five minutes after the start of solvent addition, the microparticle-added liquid was added, heated to 60°C, and completely dissolved while stirring. The heating temperature was increased from room temperature at a rate of 5°C / min, dissolved over 30 minutes, and then cooled at a rate of 3°C / min. This was filtered at a flow rate of 300 L / m. 2 The mixture was filtered for 1.5 hours at a pressure of 1.0×10 6 Pa to prepare a dope having the following composition: Azumi filter paper No. 244 (filtration accuracy: 0.005 mm) manufactured by Azumi Filter Paper Co., Ltd.

[0113] Cycloolefin resin G7810 (manufactured by JSR Corporation): 100% by mass Dichloromethane: 380% by mass Ethanol: 20% by mass

[0114] (film formation) 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 content in the cast dope reached 30% by mass. The dope was then peeled off from the stainless steel belt support at a peeling tension of 110 N / m to obtain a film.

[0115] The obtained film-like material was stretched 1.3 times in the conveying direction (MD direction) while heated to 120°C using a roll method that utilizes the difference in peripheral speed of conveying rolls. It was then stretched 1.65 times in the TD direction while heated to 130°C using a tenter method. The obtained film-like material was conveyed while being heated at 70°C until completely dried, and the edge was slit to obtain a film. The film conveying speed was 20 m / min.

[0116] (Second stage extension) Thereafter, the wound-up film 1-1 was subjected to a second-stage stretching (fourth stretching) so that the stretching ratio became 1.35. In the fourth stretching, the film 1-1 was unwound from the roll, and then stretched in the width direction (TD) while being heated to 140°C in a stretching device.

[0117] The wound film was then stretched in a second stage (fourth stretching) to a stretch ratio of 1.35. In the fourth stretching, the film was unwound from the roll and then stretched in the width direction (TD) while heated to 180°C in a stretching device.

[0118] Except for the film-forming method, the optical film 1A can be produced by forming a plurality of embossed coatings on both widthwise ends of the film using the above-mentioned method.

[0119] <Evaluation of film roll misalignment> The winding slippage of the film roll thus prepared was examined.

[0120] (1) Evaluation conditions As described above, the length from the starting end 11a to the terminal end 11b of the optical films 1A in Examples 1 to 20 was 12,000 (m). In Comparative Examples 1 to 4, the length from the starting end to the terminal end of the optical films was also 12,000 (m).

[0121] In the optical films 1A of Examples 1 to 18, the length of the first region 12a from the starting end 11a to the intermediate portion 11c was 1000 (m). In the optical films 1A of Examples 19 and 20, the length of the first region 12a from the starting end 11a to the first intermediate portion 11c1 was 1000 (m).

[0122] In Examples 1 to 20, the embossing density d'1 in the second region 12b was set higher than the embossing density d in the first region 12a. In addition, in Examples 1 to 20, the product of the difference Δd1 between the changed embossing density d'1 and the reference embossing density d and the embossing angle θ each satisfies the formula (3) defined in the present invention.

[0123] In Example 2, the embossing density d'1 after change was increased relative to Example 1 within a range that satisfied formula (3). In Example 3, the embossing density d'1 was increased relative to Example 2 within a range that satisfied formula (3). In Examples 1 to 3, the length s of the embossments 20 was the same, and the spacing L of the embossments 20 was varied to change the embossing density d.

[0124] In Example 4, the product of the difference Δd1 between the reference and changed embossing densities and the embossing angle θ is set as the upper limit of equation (3) defined in the present invention. In Example 5, the product of the difference Δd1 between the reference and changed embossing densities and the embossing angle θ is set as the lower limit of equation (3) defined in the present invention.

[0125] In Examples 6 and 7, the interval L of the embossments 20 was changed. In Example 6, the interval L of the embossments 20 was set to the upper limit value. In Example 7, the interval L of the embossments 20 was set to the lower limit value.

[0126] In Examples 8 and 9, the height H of the embossment 20 was changed. In Example 8, the height H of the embossment 20 was set to the upper limit value. In Example 9, the height H of the embossment 20 was set to the lower limit value.

[0127] In Examples 10 and 11, the width of the optical film 1A was changed. In Example 10, the width of the optical film 1A was set as the upper limit. In Example 11, the width of the optical film 1A was set as the lower limit.

[0128] In Examples 12 and 13, the film thickness of the optical film 1A was changed. In Example 12, the film thickness of the optical film 1A was set to the upper limit. In Example 13, the film thickness of the optical film 1A was set to the lower limit.

[0129] In Example 14, the diameter of the core of the film roll 10 was changed. In Examples 15 to 17, the number of rows of the embossments 20 was changed. In Example 18, the method of forming the embossments 20 was changed.

[0130] In Examples 19 and 20, the embossing density d' is further changed within the second range 12b. In Example 19, the embossing density d'2 is further increased within the second range 12b. In Example 20, the embossing density d'2 is reduced within the second range 12b. However, the reduced embossing density d'2 within the second range 12b is higher than the embossing density d in the first range 12a. In Examples 19 and 20, the product of the difference Δd2 between the changed embossing density d'2 and the reference embossing density d and the embossing angle θ also satisfies the formula (3) defined in the present invention.

[0131] (2) Evaluation method 9 is an explanatory diagram showing an example of a method for evaluating the amount of misalignment. The difference between the length a from one end of the film roll 10 to one end of the core 100 and the length b from the other end of the film roll 10 to the other end of the core 100 was measured. This difference was taken as the amount of misalignment.

[0132] (3) Evaluation criteria A deviation of 0 mm was rated as A, a deviation of more than 0 mm but 2 mm or less was rated as B, and a deviation of more than 2 mm was rated as C. A rating of A or B is preferable, A is more preferable, and a rating of C is undesirable.

[0133] (4) Evaluation results The evaluation results are shown in Table III below.

[0134] [Table 3]

[0135] In Examples 1 to 20, the embossing density d' (d'1) in the second region 12b of the optical film 1A is higher than the embossing density d in the first region 12a. In Examples 1 to 20, the product of the difference Δd (Δd1) between the changed embossing density d'1 and the reference embossing density d and the embossing angle θ is 0.0013 or more and 0.3034 or less. This satisfies the above formula (3).

[0136] Furthermore, in Examples 19 and 20, the embossing density d' is further changed from d'1 to d'2 within the second range 12b. In Examples 19 and 20, the product of the difference Δd (Δd2) between the changed embossing density d'2 and the reference embossing density d and the embossing angle θ is also 0.0013 or more and 0.3034 or less. This also satisfies the above formula (3).

[0137] Furthermore, in Examples 1 to 20, the height H of the embossments 20 was constant, falling within the range of −0.05% or more and +0.05% or less with respect to the average.

[0138] In Comparative Examples 1 and 2, the embossing density d' (d'1) in the second range is higher than the embossing density d in the first range of the optical film. In addition, in Comparative Examples 1 and 2, the embossing height H is constant, falling within the range of -0.05% to +0.05% of the average.

[0139] However, in Comparative Example 1, the product of the difference Δd (Δd1) between the changed embossing density d'1 and the standard embossing density d and the embossing angle θ exceeds 0.3034 in the winding core. Also, in Comparative Example 2, the product of the difference Δd (Δd1) between the changed embossing density d'1 and the standard embossing density d and the embossing angle θ is less than 0.0013 in areas other than the winding core. Neither of these examples satisfies the above formula (3).

[0140] In Comparative Example 3, coated embossments with a height H of 10 μm and stamped embossments with a height H of 5 μm are mixed, and the height H of the embossments 20 is not constant.

[0141] In Comparative Example 3, the embossing density d3 of the coated embossing is smaller than the embossing density d4 of the embossing with embossing embossing. Therefore, the embossing density of the embossing with a relatively high height is relatively smaller than the embossing density of the embossing with a relatively low height. Furthermore, the embossing density ranges both relatively low and high.

[0142] Furthermore, in Comparative Example 3, the embossing density d3 of the coated embossing is constant from the start to the end of the film roll. Also, in Comparative Example 3, the embossing density d4 of the embossed embossing is constant from the start to the end of the film roll.

[0143] In Comparative Example 3, for example, the embossing density d4 of the embossed embossing is set as the reference, and the embossing density d3 of the applied embossing is considered to be the changed embossing density. In this case, the product of the difference Δd3 between the changed embossing density d3 and the reference embossing density d4 and the embossing angle θ does not satisfy the above formula (3).

[0144] In Comparative Example 4, the embossing density d of the embossing is constant from the start end to the end end of the film roll, and the embossing height H is also constant.

[0145] In Comparative Example 1, the evaluation result for the winding core portion was C. This shows that when the product of the difference Δd1 between the changed embossing density d′1 and the reference embossing density d and the embossing angle θ exceeds 0.3034, winding deviation occurs.

[0146] In addition, in Comparative Example 2, the evaluation result for areas other than the winding core was C. This shows that if the product of the difference Δd1 between the changed embossing density d′1 and the reference embossing density d and the embossing angle θ is less than 0.0013, winding deviation occurs.

[0147] Furthermore, the evaluation result for Comparative Example 3 was C. In Comparative Example 3, the embossing density d3 of the coated embossing and the embossing density d4 of the embossed embossing are both constant from the start to the end of the film roll. The height of the coated embossing is relatively high compared to the embossed embossing, and in the film roll, the coated embossing is mainly responsible for supporting the film. However, the embossing density of the coated embossing is constant and is not optimized outside the winding core. Therefore, even if there are a mixture of relatively low and high embossing density ranges, the presence of embossings of different heights can cause winding misalignment.

[0148] Furthermore, the evaluation result for Comparative Example 4 was C. This shows that when the embossing density d is constant, winding deviation occurs even if the embossing height H is constant.

[0149] In contrast, in Examples 1 to 20, the evaluation results were A or B in the winding core portion and the entire area other than the winding core portion. This shows that if the product of the difference Δd1 between the changed embossing density d'1 and the reference embossing density d and the embossing angle θ satisfies the above formula (3), winding slippage does not occur. Alternatively, it shows that winding slippage can be sufficiently suppressed. In addition, it shows that if the multiple embossing heights H are constant, winding slippage does not occur.

[0150] Furthermore, in Examples 8 and 9, even if the height H of the embossment 20 is changed, it is understood that by satisfying the above conditions, no winding deviation occurs.

[0151] Furthermore, in Examples 10 and 11, even if the width of the optical film 1A is changed, by satisfying the above conditions, it is understood that no winding deviation occurs.

[0152] Furthermore, in Examples 12 and 13, even if the film thickness of the optical film 1A is changed, by satisfying the above conditions, it is understood that no winding slippage occurs.

[0153] Furthermore, in Example 14, it is understood that even if the diameter of the core of the film roll 10 is changed, by satisfying the above conditions, winding deviation does not occur.

[0154] Furthermore, in Examples 15 to 17, even if the number of rows of the embossments 20 is changed, by satisfying the above conditions, it is understood that no winding deviation occurs.

[0155] Furthermore, in Example 18, even if the embossments 20 are formed by laser, it is understood that by satisfying the above conditions, no winding deviation occurs.

[0156] Furthermore, in Examples 19 and 20, even if the embossing density is further changed within the second range 12b, it is understood that the above conditions are satisfied and no winding deviation occurs.

[0157] Regardless of the composition and manufacturing method of the optical film, similar effects can be obtained as long as the above conditions are met. [Explanation of symbols]

[0158] 1A Optical film, 2 Embossed region, 3 Non-embossed region, 10 Film roll, 11a Starting end, 11b Ending end, 11c Middle portion, 12a First region, 12b Second region, 20 Embossed

Claims

1. The film roll is long and wound from a first end to a second end along the longitudinal direction of the long film roll, an optical film having a plurality of embossments formed along a longitudinal direction between the first end and the second end, the plurality of embossments having the same height within a predetermined range, a first range from the first end to an intermediate portion between the first end and the second end; a second range from the intermediate portion to the second end portion; When the number of embossments per unit length along the longitudinal direction is defined as the embossing density, The embossing density of the embossments formed in the second area is made higher than the embossing density of the embossments formed in the first area. Optical film.

2. The length from the first end to the second end is 3000 m or more, The length of the first region from the first end to the middle portion is 900 m or more and 1100 m or less. The optical film according to claim 1 .

3. The embossing density d is calculated by the following formula (1), where d is the embossing density and L is the interval between the embosses along the longitudinal direction of the optical film: When the length of the embossment along the longitudinal direction of the optical film is s, the radius of the film roll is r, the size of the embossment along the longitudinal direction of the optical film is represented by an angle with the center of the film roll as the vertex, and an embossing angle representing the size of the embossment is θ, the embossing angle θ can be calculated by the following formula (2): If the product of the embossing density d in the first range and the embossing angle θ is d×θ, and the product of the embossing density d′ (d′>d) in the second range and the embossing angle θ is d′×θ, the difference Δd×θ between d×θ and d′×θ satisfies the relationship of the following formula (3): The optical film according to claim 1 . d=1 / L...(1) θ=180s / πr...(2) 0.0013<Δd×θ<0.3034 (3)

4. The height of the embossment is in the range of −0.05% to +0.05% of the average height of the embossment included in a unit length along the longitudinal direction. The optical film according to claim 1 .

5. The embossment is formed by applying a resin. The optical film according to claim 1 .

6. The height of the embossment is determined by the amount of resin applied. The optical film according to claim 1 .

7. The embossing density is changed according to the length from the first end. The optical film according to claim 1 .

8. A film roll is provided, the film roll being an elongated optical film having a plurality of embossments formed along the longitudinal direction between a first end and a second end along the longitudinal direction of the elongated film, the plurality of embossments having the same height within a predetermined range, the film roll being wound from the first end to the second end, a first range from the first end to an intermediate portion between the first end and the second end; a second range from the intermediate portion to the second end portion; When the number of embossments per unit length along the longitudinal direction is defined as the embossing density, The embossing density of the embossments formed in the second area is made higher than the embossing density of the embossments formed in the first area. Film roll.

9. A method for manufacturing an optical film having a long shape, the method including forming a plurality of embossments along the longitudinal direction between a first end and a second end along the longitudinal direction of the long shape, the method comprising: a first range from the first end to an intermediate portion between the first end and the second end; a second range from the intermediate portion to the second end portion; When the number of embossments per unit length along the longitudinal direction is defined as the embossing density, The embossments are formed by applying a resin so that the plurality of embossments have the same height within a predetermined range and the embossing density of the embossments formed in the second range is higher than the embossing density of the embossments formed in the first range. A method for manufacturing an optical film.

10. A method for manufacturing a film roll, comprising forming a plurality of embossments along a longitudinal direction of a long optical film between a first end and a second end along the longitudinal direction of the film, and winding the optical film from the first end to the second end, a first range from the first end to an intermediate portion between the first end and the second end; a second range from the intermediate portion to the second end portion; When the number of embossments per unit length along the longitudinal direction is defined as the embossing density, forming the embossments by applying a resin so that the plurality of embossments have the same height within a predetermined range and the embossing density of the embossments formed in the second range is higher than the embossing density of the embossments formed in the first range; The optical film on which the embossing is formed is wound around a core. A method for manufacturing a film roll.

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