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

Abstract

The invention provides an optical film capable of suppressing winding misalignment. The optical film (1A) has a long shape, and is wound from a starting end (11a) to a terminal end (11b) in the longitudinal direction of the long shape to form a film roll. In the optical film (1A), a plurality of embossments (20) are formed in the longitudinal direction between a starting end (11a) and a terminal end (11b), and the plurality of embossments (20) have the same height in a predetermined range. In the optical film (1A), when a first range (12a) is defined from a first intermediate portion (11c) to a second intermediate portion (11d) between a starting end portion (11a) and a terminal portion (11b), a second range (12b) is defined from the second intermediate portion (11d) to the terminal portion (11b), and the number of embossments (20) per unit angle of a film roll is defined as the embossing density, the first range (12a) is 50-1000 m from the first end portion, and the first range (12a) has a portion having an embossing density higher than that of the second range (12b).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an optical film formed with embossing, a film roll wound with the optical film, a method for manufacturing the optical film, and a method for manufacturing the film roll. BACKGROUND

[0002] It is known that, when a film used for optical use or the like is wound in a roll shape, an embossed (knurled) region is formed at the end portion in the short side direction. The embossed region functions to prevent the film from being misaligned in winding, in order to prevent the film from being misaligned in winding.

[0003] The embossing is formed by so-called die pressing, which is a method of pressing a convex shape formed on a roller against a film while conveying the film while rotating the roller (Patent Literature 1).

[0004] In the case where the embossing is formed by die pressing, the interval of the embossing along the long side direction of the film is constant. Thus, the density of the embossing per unit length in the long side direction of the film is constant.

[0005] In contrast, a technique of forming embossing by coating with a resin has been proposed (Patent Literature 2). In the method of forming embossing by coating with a resin, the height of the embossing can be further increased. In addition, compared with embossing formed by die pressing, the embossing damage can be suppressed.

[0006] PRIOR ART DOCUMENTS

[0007] PATENT LITERATURE

[0008] Patent Literature 1: Japanese Patent Application Laid-Open No. 2007-070514

[0009] Patent Literature 2: Japanese Patent No. 7125995 SUMMARY

[0010] However, if the embossing density is constant, misalignment in winding in the short side direction can occur between the films radially overlapping in the film roll.

[0011] In addition, in a configuration in which the coating embossing and the die pressing embossing are mixed, the height of the coating embossing is relatively high with respect to the die pressing embossing, and the coating embossing mainly supports the film. However, since the embossing density of the coating embossing is constant, misalignment in winding of the film can occur.

[0012] The present disclosure was made to solve such a problem, and aims to provide an optical film and a film roll in which misalignment in winding can be suppressed. In addition, the present disclosure aims to provide a method for manufacturing an optical film and a method for manufacturing a film roll.

[0013] To solve the above problems, the present disclosure provides an optical film that is long and has a plurality of embossments formed along a long side direction between a first end portion and a second end portion along the long side direction, the plurality of embossments being of the same height in a prescribed range, the first range being set from a first intermediate portion to a second intermediate portion between the first end portion and the second end portion, the second range being set from the second intermediate portion to the second end portion, the number of embossments per unit angle of the film roll being set as an embossment density, the first range being 50 m to 1000 m from the first end portion, and the first range having a portion with a higher embossment density than the second range.

[0014] In addition, the present disclosure provides a film roll in which an optical film is wound from a first end portion to a second end portion, the optical film being long and having a plurality of embossments formed along a long side direction between the first end portion and the second end portion along the long side direction, the plurality of embossments being of the same height in a prescribed range, the first range being set from a first intermediate portion to a second intermediate portion between the first end portion and the second end portion, the second range being set from the second intermediate portion to the second end portion, the number of embossments per unit angle of the film roll being set as an embossment density, the first range being 50 m to 1000 m from the first end portion, and the first range having a portion with a higher embossment density than the second range.

[0015] Furthermore, the present disclosure provides a method of manufacturing an optical film that is long and has a plurality of embossments formed along a long side direction between a first end portion and a second end portion along the long side direction, the method including setting a first range from a first intermediate portion to a second intermediate portion between the first end portion and the second end portion, setting a second range from the second intermediate portion to the second end portion, setting the number of embossments per unit angle of the film roll as an embossment density, forming the embossments by applying a resin such that the first range is 50 m to 1000 m from the first end portion and the first range has a portion with a higher embossment density than the second range.

[0016] In addition, the present disclosure provides a method of manufacturing a film roll in which an optical film is wound from a first end portion to a second end portion, the optical film being long and having a plurality of embossments formed along a long side direction between the first end portion and the second end portion along the long side direction, the method including setting a first range from a first intermediate portion to a second intermediate portion between the first end portion and the second end portion, setting a second range from the second intermediate portion to the second end portion, setting the number of embossments per unit angle of the film roll as an embossment density, forming the embossments by applying a resin such that the first range is 50 m to 1000 m from the first end portion and the first range has a portion with a higher embossment density than the second range, and winding the optical film having the embossments formed thereon on a core.

[0017] According to the present disclosure, in an optical film in which the optical film is wound in a radial direction of the film roll, the winding misalignment in the short side direction can be suppressed. Attached Figure Description

[0018] Figure 1 This is a top view showing an example of an optical film.

[0019] Figure 2 This is a top view of the main part, representing an example of an optical film.

[0020] Figure 3 This is a side view showing an example of a membrane roll.

[0021] Figure 4 It is an illustrative diagram that schematically shows the relationship between a unit angle and the number of embossed flowers.

[0022] Figure 5 This is a side view showing the details of the embossing.

[0023] Figure 6 This is a graph showing the relationship between embossing density and film winding length.

[0024] Figure 7 This is an illustrative diagram illustrating an example of an evaluation method for misalignment.

[0025] Symbol Explanation

[0026] 1A···Optical film, 2···Embossed area, 3···Non-embossed area, 10···Film roll, 11a···Starting end, 11b···Ending end, 11c···First intermediate section, 11d···Second intermediate section, 12a···First range, 12b···Second range, 20··Embossed Detailed Implementation

[0027] Hereinafter, an example of the optical film and film roll of this embodiment will be described with reference to the accompanying drawings. Additionally, an example of the manufacturing method of the optical film and the manufacturing method of the film roll of this embodiment will be described.

[0028] <Examples of the composition of optical films and film rolls>

[0029] Figure 1 This is a top view showing an example of an optical film. Figure 2 This is a top view of the main part of an example of an optical film. Figure 3 This is a side view showing an example of a membrane roll.

[0030] The optical film 1A is configured in a long strip shape. The optical film 1A is, for example, a polymer film. An arrow LL indicates a long side direction of the long strip-shaped optical film 1A. An arrow LS indicates a short side direction of the long strip-shaped optical film 1A. The optical film 1A has embossed regions 2 at both ends in the short side direction, and has non-embossed regions 3 between the embossed regions 2. The embossed regions 2 and the non-embossed regions 3 extend in the long side direction of the optical film 1A.

[0031] The optical film 1A has embossings 20 in each of the embossed regions 2. The embossings 20 protrude in a prescribed shape from a surface of the optical film 1A. The embossings 20 are, for example, triangular in cross-sectional shape along the long side direction of the optical film 1A. The embossings 20 are arranged in a row at prescribed intervals in the long side direction of the optical film 1A. Alternatively, the embossings 20 can be arranged in a plurality of rows in the short side direction of the optical film 1A at prescribed intervals in the long side direction of the optical film 1A.

[0032] The optical film 1A is wound to form a film roll 10 with the embossings 20 facing outward.

[0033] The optical film 1A is wound to form the film roll 10 from the first end portion. In the optical film 1A, a position at which winding of the film roll 10 is started is referred to as a start end portion 11a. In the optical film 1A, winding of the film roll 10 is ended at the second end portion. In the optical film 1A, a position at which winding of the film roll 10 is ended is referred to as an end end portion 11b.

[0034] Further, in the optical film 1A, a range from a first intermediate portion 11c to a second intermediate portion 11d between the start end portion 11a and the end end portion 11b is referred to as a first range 12a. In the optical film 1A, a range from the second intermediate portion 11d to the end end portion 11b is referred to as a second range 12b.

[0035] In the optical film 1A, a length L from the start end portion 11a to the end end portion 11b is, for example, 2000 m or more. In the optical film 1A, a length from the start end portion 11a to the first intermediate portion 11c is, for example, 50 m. Further, in the optical film 1A, a length from the start end portion 11a to the second intermediate portion 11d is, for example, 1000 m. The range from the start end portion 11a to the second intermediate portion 11d is also referred to as a core. The second range 12b from the second intermediate portion 11d to the end end portion 11b is also referred to as an outer portion.

[0036] The optical film 1A has a portion in the first range 12a between the first intermediate portion 11c and the second intermediate portion 11d in which the number of embossings 20 per unit length is larger than in the second range 12b. The number of embossings 20 per unit length of the optical film 1A can be expressed as the number of embossings 20 per unit angle with the center O of the film roll 10 as a vertex. The number of embossings 20 per unit angle of the film roll 10 is referred to as embossing density.

[0037] If the increase or decrease in the number of embossments 20 per unit length of the optical film 1A described above is expressed in terms of embossing density, the following is obtained. That is, the optical film 1A has a portion in which the embossing density becomes higher in the first range 12a between the first intermediate portion 11c and the second intermediate portion 11d than in the second range 12b. This indicates that there is a portion in which the embossing density is higher in a region at a distance of 50 m to 1000 m from the start end portion 11a of the optical film 1A than in a region from 1000 m to the end end portion 11b.

[0038] Figure 4 is a diagram schematically showing the relationship between unit angle and the number of embossments. In the case where the radius r of the film roll 10 is rl, for example, an arbitrary angle including one embossment 20 is set as a unit angle θref.

[0039] In the case where the number of embossments 20 per unit length is constant, the number of embossments 20 per unit angle θref becomes larger as the winding length of the film roll 10 increases. That is, the radius r of the film roll 10 becomes larger as the winding length of the film roll 10 increases. In the film roll 10, the length in the circumferential direction per unit angle θref becomes longer as the radius r of the film roll 10 becomes larger. When the radius r of the film roll 10 is r2, the number of embossments 20 per unit angle θref is larger than when the radius r of the film roll 10 is rl (r2 > rl).

[0040] Therefore, if the number of embossments 20 per unit length is constant, the number of embossments 20 per unit angle θref of the core becomes smaller than that of the outer portion. Thus, the force with which the embossments 20 of the core support the radially overlapping optical films 1A of the film roll 10 becomes weaker than that of the outer portion. On the other hand, due to the layering of the optical films 1A, the force applied to each embossment 20 of the core is larger than that of the outer portion.

[0041] Therefore, the core is more likely than the outer portion to have a misalignment at a position in the short side direction of the radially overlapping optical films 1A of the film roll 10. Such a misalignment is referred to as a winding misalignment. If a winding misalignment occurs, the possibility that the winding shape cannot be guaranteed becomes high. In addition, if a winding misalignment occurs, the possibility that the optical films 1A are deteriorated due to friction with the embossments 20 becomes high.

[0042] Therefore, in the film roll 10, the number of embossments 20 per unit angle θref of the core is increased compared to that of the outer portion.

[0043] Figure 5 is a side view showing the details of an embossment. Next, the embossing density and the size of the embossment 20 prescribed in the present disclosure are described.

[0044] In the film roll 10, the number of embossments 20 per unit angle Θref is set as the embossment density d (pieces / °). In the embossment density d thus defined, the embossment density d at an arbitrary position in the first range 12a at a distance of 50 m to 1000 m from the start end portion 11a is set as dbefore (pieces / °). In contrast, the changed embossment density d in the first range 12a is set as dafter (pieces / °). In addition, the difference between the changed embossment density d and the unchanged embossment density d, that is, the difference between dafter and dbefore is set as Δd.

[0045] As described above, the optical film 1A is provided with a portion in which the embossment density d in the first range 12a is higher than in the second range 12b. In this case, the difference Δd between the changed embossment density dafter and the unchanged embossment density dbefore in the first range 12a satisfies the following equation (1).

[0046] 4.1 > Δd > 0.17 ··· (1)

[0047] Figure 6 is a graph showing the relationship between the embossment density and the winding length of the film. In the first range 12a, one example of the range in which the changed embossment density dafter can be obtained is shown by a solid line within the range defined by equation (1). In addition, one example of the unchanged embossment density dbefore in the first range 12a is shown by a broken line. The embossment density d outside the first range 12a is shown by a solid line.

[0048] The difference Δd between the changed embossment density and the unchanged embossment density in the first range 12a can suppress the winding misalignment of the film roll 10 by satisfying equation (1).

[0049] As described above, in the case where the number of embossments 20 per unit length is constant, the number of embossments 20 per unit angle increases as the winding length of the film roll 10 increases. Therefore, in the first range 12a, the embossment density d is maximum at a position at a winding length of 1000 m in the case where the embossment density d is not changed. Therefore, the changed embossment density dafter of the first range 12a is based on the embossment density d at a position at a winding length of 1000 m in the case where the embossment density d is not changed.

[0050] In the first range 12a, the embossment density d at a position at a winding length of 1000 m in the case where the embossment density d is not changed is set as embossment density d 1000. The changed embossment density dafter in the first range 12a satisfies the following equation (2).

[0051] dafter - d 1000 > 0 ··· (2)

[0052] Note that formula (2) is synonymous with d after > d 1000.

[0053] By satisfying formula (2) with the changed embossing density d after in the 1st range 12a, a portion where the embossing density d is higher in the 1st range 12a than in the 2nd range 12b is provided.

[0054] In addition, the interval of the embossing 20 along the longitudinal direction of the optical film 1A is set to L (mm), and the length of the embossing 20 is set to s (mm). The interval L of the embossing 20 and the length s of the embossing 20 satisfy the following formula (3).

[0055] L > s · · · (3)

[0056] In a case where the interval L of the embossing 20 and the length s of the embossing 20 do not satisfy formula (3), a gap between the embossings 20 arranged in the longitudinal direction of the optical film 1A disappears. In this case, air between the optical films 1A radially overlapping in the film roll 10 is difficult to escape, and winding misalignment is likely to occur.

[0057] On the other hand, in a case where the interval L of the embossing 20 and the length s of the embossing 20 satisfy formula (3), a gap is formed between the embossings 20 arranged in the longitudinal direction of the optical film 1A. In this case, air between the optical films 1A radially overlapping in the film roll 10 is likely to escape, and the occurrence of winding misalignment can be suppressed.

[0058] Note that the embossing density d, the difference Δd between the changed embossing density d after and the embossing density d before the change are calculated as follows.

[0059] The interval L of the embossing 20 is expressed by an angle θ (°) with the center O of the film roll 10 as a vertex. The angle θ is also referred to as an embossing angle. The embossing density d is calculated from the embossing angle θ by the following formula (4). In addition, the embossing angle θ is calculated by the following formula (5).

[0060] d = 1 / θ · · · (4)

[0061] θ = 180L / πr · · · (5)

[0062] In addition, the difference Δd between the changed embossing density d after and the embossing density d before the change is calculated by the following formula (6).

[0063] Δd = d after - d before · · · (6)

[0064] Next, the height of the emboss 20 is described. When the height of the emboss 20 from the surface of the optical film 1A is set as H (mm), the height H of all the embosses 20 is constant. Note that, for the emboss 20, a case where the average of the height H per 1 m of, for example, the optical film 1A is limited to a range of -0.05% to +0.05% is referred to as the height H being constant.

[0065] Example

[0066] Hereinafter, the present disclosure is specifically described with examples, but the present disclosure is not limited to these. Note that, in the following examples, operations are performed at room temperature (25°C) unless otherwise specified. In addition, unless otherwise specified, "%" and "parts" each refer to "mass %" and "mass parts", respectively.

[0067] Composition of Resin Constituting Film

[0068] The optical film can use a film composed of a publicly known resin. As a specific example of the resin, an acrylic resin, a cellulose ester resin, a cyclic olefin resin, and the like can be given. Hereinafter, specific examples of the resin are described.

[0069] [Acrylic Resin (A)]

[0070] As the acrylic resin (A), the following acrylic resins Al to A3 are used. Note that the acrylic resin Al is a commercially available product. In addition, the acrylic resins A2 and A3 are prepared by the following methods.

[0071] (Acrylic Resin Al)

[0072] The acrylic resin Al is DIANAL BR85 (manufactured by Mitsubishi Chemical Corporation).

[0073] (Preparation of Acrylic Resin A2)

[0074] The mass ratio (MMA:MA) of methyl methacrylate (MMA) to methyl acrylate (MA) was set to 98:2. Synthesis was performed in accordance with the method described in paragraphs

[0130] to

[0135] of Japanese Patent Application Publication No. 2006-241263. As a result, the acrylic resin A2 having a weight average molecular weight (Mw) of 80000 was obtained.

[0076] (Preparation of Acrylic Resin A3)

[0077] The mass ratio (MMA:MA) of methyl methacrylate (MMA) to methyl acrylate (MA) was set to 97:3. The synthesis was performed according to the method described in paragraphs

[0130] to

[0135] of Japanese Patent Application Publication No. 2006-241263. As a result, an acrylic resin A3 having a weight average molecular weight (Mw) of 930,000 was obtained.

[0079] [Cellulose ester resin (CE)]

[0080] As the cellulose ester resin (CE), the following cellulose ester resins CE1 to CE4 were used.

[0081] (Preparation of cellulose ester resin CE1)

[0082] A mixture of sulfuric acid (7.8 parts by mass relative to 100 parts by mass of cellulose) as a catalyst and carboxylic anhydride was cooled to -20°C. Then, it was added to cellulose from deciduous tree pulp, and acylation was performed at 40°C. At this time, the types and substitution ratios of acyl groups were adjusted by adjusting the types and amounts of carboxylic anhydride. In addition, the total substitution degree was adjusted by performing curing at 40°C after acylation. As a result, a cellulose ester resin CE1 having a weight average molecular weight of 200,000 was obtained. In the cellulose ester resin CE1, the total substitution degree (T) of acyl groups was 2.75, the substitution degree of acetyl groups (Ac) was 0.19, and the substitution degree of propionyl groups (Pr) was 2.56.

[0083] (Preparation of cellulose ester resin CE2)

[0084] In the preparation of the cellulose ester resin CE1, the types and substitution ratios of acyl groups were adjusted by appropriately adjusting the types and amounts of carboxylic anhydride. In addition, the total substitution degree was adjusted by performing curing at 40°C after acylation. As a result, a cellulose ester resin CE2 having a weight average molecular weight of 200,000 was obtained. In the cellulose ester resin CE2, the total substitution degree (T) of acyl groups was 2.1, the substitution degree of acetyl groups (Ac) was 0.8, and the substitution degree of propionyl groups (Pr) was 1.3.

[0085] (Preparation of cellulose ester resin CE3)

[0086] In the preparation of the cellulose ester resin CE1, the types and substitution ratios of acyl groups were adjusted by appropriately adjusting the types and amounts of carboxylic anhydride. In addition, the total substitution degree was adjusted by performing curing at 40°C after acylation. As a result, a cellulose ester resin CE3 having a weight average molecular weight of 200,000 was obtained. In the cellulose ester resin CE3, the total substitution degree (T) of acyl groups was 2.8. In addition, in the cellulose ester resin CE3, the substitution degree of acetyl groups (Ac) was 0.5, the substitution degree of propionyl groups (Pr) was 1.15, and the substitution degree of butyryl groups (Bu) was 1.15.

[0087] (Preparation of cellulose ester resin CE4)

[0088] In the preparation of cellulose ester resin CE1, the kind and substitution ratio of acyl group were adjusted by appropriately adjusting the kind and amount of carboxylic anhydride. In addition, the total substitution degree was adjusted by performing aging at 40°C after acylation. As a result, cellulose ester resin CE4 having a weight average molecular weight of 76,000 was obtained. In cellulose ester resin CE4, the total substitution degree (T) of acyl group was 2.75, the substitution degree of acetyl group (Ac) was 0.19, and the substitution degree of propionyl group (Pr) was 2.56.

[0089] (Cycloolefin resin (COP))

[0090] As the cycloolefin resin, the following commercially available cycloolefin resin COP was used.

[0091] Cycloolefin resin COP: ARTON (registered trademark) G7810 (manufactured by JSR Corporation)

[0092] [Production of film]

[0093] An optical film was produced using the following conditions, and a film roll was produced by winding the optical film. Examples in which the conditions such as the composition of the resin and the film production method were changed, comparative examples are shown in Table I below.

[0094]

[0095] (Production of optical film using acrylic resin and cellulose ester resin)

[0096] Optical films of Examples 1A to 6A were produced using the above-described acrylic resins A1 to A3 and cellulose ester resins CE1 to CE4.

[0097] Example 1A: Acrylic resin A1 + cellulose ester resin CE1

[0098] Example 2A: Acrylic resin A1 + cellulose ester resin CE2

[0099] Example 3A: Acrylic resin A1 + cellulose ester resin CE3

[0100] Example 4A: Acrylic resin A1 + cellulose ester resin CE4

[0101] Example 5A: Acrylic resin A2 + cellulose ester resin CE1

[0102] Example 6A: Acrylic resin A3 + cellulose ester resin CE1

[0103] (Composition of coating liquid)

[0104] (1) Example 1A

[0105] Acrylic resin A1: 160 parts by mass

[0106] Cellulose ester resin CE1: 86 parts by mass

[0107] Rubber particles (Kane Ace M210, manufactured by KANEKA Corporation): 2.5 parts by mass

[0108] Methylene chloride: 550 parts by mass

[0109] Ethanol: 100 parts by mass

[0110] (2) Example 2A

[0111] Acrylic resin A1: 160 parts by mass

[0112] Cellulose ester resin CE2: 86 parts by mass

[0113] Rubber particles (Kane Ace M210, manufactured by KANEKA Corporation): 2.5 parts by mass

[0114] Methylene chloride: 550 parts by mass

[0115] Ethanol: 100 parts by mass

[0116] (3) Example 3A

[0117] Acrylic resin A1: 160 parts by mass

[0118] Cellulose ester resin CE3: 86 parts by mass

[0119] Rubber particles (Kane Ace M210, manufactured by KANEKA Corporation): 2.5 parts by mass

[0120] Methylene chloride: 550 parts by mass

[0121] Ethanol: 100 parts by mass

[0122] (4) Example 4A

[0123] Acrylic resin A1: 160 parts by mass

[0124] Cellulose ester resin CE4: 86 parts by mass

[0125] Rubber particles (Kane Ace M210, manufactured by KANEKA Corporation): 2.5 parts by mass

[0126] Methylene chloride: 550 parts by mass

[0127] Ethanol: 100 parts by mass

[0128] (5) Example 5A

[0129] Acrylic resin A2: 160 parts by mass

[0130] Cellulose ester resin CE1 : 86 parts by mass

[0131] Rubber particles (Kane Ace M210, manufactured by KANEKA Corporation): 2.5 parts by mass

[0132] Methylene chloride: 550 parts by mass

[0133] Ethanol: 100 parts by mass

[0134] (6) Example 6A

[0135] Acrylic resin A3: 160 parts by mass

[0136] Cellulose ester resin CE1 : 86 parts by mass

[0137] Rubber particles (Kane Ace M210, manufactured by KANEKA Corporation): 2.5 parts by mass

[0138] Methylene chloride: 550 parts by mass

[0139] Ethanol: 100 parts by mass

[0140] While heating the above composition, it was made to sufficiently dissolve, and a coating liquid was prepared.

[0141] (Making of optical film and first-stage stretching)

[0142] Using a belt casting apparatus, the coating liquid of each of the above examples was uniformly cast at a temperature of 22°C and a width of 2 m on a stainless steel belt support. On the stainless steel belt support, the solvent was evaporated to a residual solvent amount of 40 mass%, and was peeled from the stainless steel belt support at a peeling tension of 150 N / m.

[0143] The peeled acrylic resin roll was left to evaporate the solvent at 35°C and was cut to a width of 1.6 m. Then, the rotation speed of the stainless steel belt support and the speed of the stretching apparatus were adjusted, and stretching was performed in the longitudinal direction, i.e., the MD direction (first stretching). The first stretching ratio was calculated from the rotation speed of the stainless steel belt support and the speed of the stretching apparatus, and was 1.2 times. Here, the first stretching ratio in the above MD direction was defined as (transport speed of the film after stretching) / (transport speed of the film before stretching). In addition, the stretching temperature of the first stretching was 50°C.

[0144] Then, the stretching apparatus was heated to 135°C while being stretched to 1.1 times in the width direction (TD direction) (second stretching). Here, the second stretching ratio in the above TD direction was defined as (width of the film after stretching) / (width of the film before stretching). At this time, the residual solvent amount at the start of stretching in the stretching apparatus was 10 mass%.

[0145] After the stretching by the stretching device, the film was transported through a drying zone at 1100C to complete drying, and the stretching speed and the winding speed were adjusted to stretch in the MD direction (3rd stretching). The 3rd stretching ratio was calculated from the stretching speed and the winding speed, and the result was 1.2 times. Here, the 3rd stretching ratio in the MD direction described above was defined as (transportation speed of the film after stretching) / (transportation speed of the film before stretching).

[0146] The film after the 3rd stretching was wound on a core having an inner diameter of 15.24 cm with an initial tension of 220 N / m and a final tension of 110 N / m to obtain a film 1-1.

[0147] The residual solvent amount of the film 1-1 was 0.3 mass%, the film thickness was 47 μm, and the winding length was 12000 m.

[0148] (2nd stage stretching)

[0149] Then, the film 1-1 was subjected to the 2nd stage stretching (4th stretching) at a stretching ratio of 1.35 times. The 4th stretching was performed by unwinding the film 1-1 from its roll, and stretching in the width direction (TD direction) while heating to 1400C in a stretching device.

[0150] The film after the stretching was cut at both ends to make the film 2260 mm in width to obtain a film 1-2. The film thickness of the film 1-2 was 40 μm.

[0151] (Preparation of solution for coating and embossing)

[0152] The solution for coating and embossing was obtained by dissolving the acrylic resin in a solvent at a concentration of 5 mass%. The solvent used was dichloromethane and cyclopentanone.

[0153] (Formation of coating and embossing)

[0154] The solution for coating and embossing was applied to the surface of the film 1-2 using SUPER HI JET manufactured by Musashi Engineering Co. as a dispenser. Then, drying was performed using an IR heater to bring the film temperature to 800C, and a plurality of coating and embossing were formed. The film temperature was confirmed by a thermograph.

[0155] In Examples 1A, 2A, 3A, 4A, 5A, and 6A, one row of a plurality of coating and embossing each having a height H of 0.5 μm was formed at both ends in the width direction of the surface of the film 1-2. In each example, the coating and embossing were formed at intervals of 5.3 mm between 1000 m and the terminal end of the film 1-2. Also, in each example, the coating and embossing were formed at intervals of 2.65 mm between 50 m and 1000 m of the film 1-2.

[0156] (Production of optical film using cyclic olefin resin)

[0157] An optical film of Example 7A was produced using a cyclic olefin resin (COP).

[0158] (Film formation)

[0159] Particles of a cyclic olefin resin G7810 (manufactured by JSR Corporation) were supplied to an extruder under a nitrogen atmosphere, and melt-cast. Then, the melt-cast film was cooled with a cooling roll, and then peeled to obtain a film. The cyclic olefin resin was a cyclic olefin resin containing a structural unit derived from a norbornene-based monomer represented by the following formula, and had a Tg of 165°C.

[0160] [Chemical Formula 1]

[0161]

[0162] The obtained film was stretched to 2 times in the width direction at 175°C, and then heated to complete drying and transported at 100°C. Then, the end portion was cut, and a film 1-2 having a thickness of 40 μm, a width of 2260 mm, and a length of 12000 m was obtained. The film was transported at a speed of 20 m / minute.

[0163] (Preparation of solution for coating and embossing)

[0164] A solution for coating and embossing was prepared by dissolving the cyclic olefin resin G7810 (manufactured by JSR Corporation) at a concentration of 5 mass% in a solvent. The solvent used was dichloromethane and cyclopentanone.

[0165] (Formation of coating and embossing)

[0166] The surface of the above film was subjected to corona treatment and plasma treatment. Then, the solution for coating and embossing was applied to both end portions in the width direction of the treated surface of the film, and then dried to form a plurality of coating and embossing. The application of the solution for coating and embossing was performed using SUPER HI JET manufactured by Musashi Engineering Co., Ltd. as a dispenser. In addition, the solution for coating and embossing after application was dried using an IR heater so that the film temperature was 80°C. The film temperature was confirmed by a thermograph.

[0167] In Example 7A, a plurality of coating and embossing each having a height H of 0.5 μm were formed on both end portions in the width direction of the surface of the film 1-2. In addition, in Example 7A, the coating and embossing were formed at intervals of 5.3 mm between 1000 m and the terminal end portion of the film 1-2. Furthermore, in Example 7A, the coating and embossing were formed at intervals of 2.65 mm between 50 m and 1000 m of the film 1-2.

[0168] An optical film of Example 8A was produced using a cyclic olefin resin (COP).

[0169] (Preparation of the coating material)

[0170] First, dichloromethane was added to the pressurized dissolving tank at a flow rate of 400 kg / min, and ethanol was added at a flow rate of 20 kg / min. Three minutes after the start of solvent addition, the cyclic polyolefin resin was added to the pressurized dissolving tank while stirring. Next, 5 minutes after the start of solvent addition, the fine particle additive solution was added, and the solution was heated to 60°C while stirring to completely dissolve the solution. The heating temperature was increased from room temperature at 5°C / min, and after 30 minutes of dissolution, the temperature was decreased at 3°C / min. The solution was filtered at a filtration flow rate of 300 L / min 2 • h, filter pressure 1.0 x 10 6 Pa, to prepare a coating material of the following composition. The filtration used Advantec filter paper No. 244 (filtration accuracy 0.005 mm) manufactured by Advantec Toyo Kaisha, Ltd.

[0171] Cyclic olefin resin G7810 (manufactured by JSR Corporation): 100 mass%

[0172] Dichloromethane: 380 mass%

[0173] Ethanol: 20 mass%

[0174] (Film formation)

[0175] Next, the obtained coating material was uniformly cast on a stainless steel belt support at a temperature of 31°C and a width of 2300 mm using a cyclic belt casting device. The temperature of the stainless steel belt was adjusted to 28°C, and the conveyance speed of the stainless steel belt was 30 m / min. On the stainless steel belt support, the solvent was evaporated to a residual solvent amount of 30 mass% in the coating material after casting. Then, the film was peeled from the stainless steel belt support at a peel tension of 110 N / m to obtain a film-like material.

[0176] The obtained film-like material was stretched by 1.3 times in the conveyance direction (MD direction) by a roll method using a difference in circumferential speed of the conveyance rolls, while heating to 120°C. Next, the film-like material was stretched by 1.65 times in the TD direction by a tenter method, while heating to 130°C. The obtained film-like material was conveyed while heating to complete drying at 70°C, and the end portion was cut to obtain a film. The conveyance speed of the film was 20 m / min.

[0177] (Second stage stretching)

[0178] Then, the wound film 1-1 was stretched in the second stage (4th stretching) so that the elongation ratio became 1.35 times. The 4th stretching was performed by unwinding the film 1-1 from the roll body, and stretching in the width direction (TD direction) in a stretching device while heating to 140°C.

[0179] Then, the wound film was stretched in the second stage (4th stretching) so that the elongation ratio became 1.35 times. The 4th stretching was performed by unwinding the film from the roll body, and stretching in the width direction (TD direction) in a stretching device while heating to 180°C.

[0180] Example 8A was produced under the same conditions as Example 7A except that a plurality of coating embosses were formed at both ends in the width direction of the film.

[0181] (Formation of embosses by laser)

[0182] Example 9A was produced using a cyclic olefin resin (COP) by forming embosses by laser. In Example 9A, one row of a plurality of embosses each having a height H of 0.5 μm were formed at both ends in the width direction of the film 1-2 produced by the film forming method of Example 7A by laser.

[0183] As the laser device, a carbon dioxide laser device was used. In addition, the output of the laser device was set to 20 W, the center wavelength of the emission wavelength was set to 9.4 μm, and the emission wavelength range was set to ±0.01 μm or less from the center wavelength.

[0184] The irradiation of the laser to the film was performed by condensing the parallelized light beam emitted from the carbon dioxide laser device onto the surface of the film being conveyed through a fθ lens. The focal length of the fθ lens was 200 mm. The parallelized light beam emitted from the carbon dioxide laser device was reflected by two galvanometer mirrors. By controlling the angles of the galvanometer mirrors, the condensing position was moved in the film plane direction, and thus the track of the laser irradiation onto the film surface was controlled.

[0185] In Example 9A, the coating embosses were formed at intervals of 5.3 mm between 1000 m and the terminal end of the film 1-2. In addition, in Example 9A, the coating embosses were formed at intervals of 2.65 mm between 50 m and 1000 m of the film 1-2.

[0186] (Winding of film)

[0187] The film 1-2 on which the embosses were formed was wound on a core having a diameter of 153.5 mm at an initial tension of 60 N / m and a final tension of 25 N / m. At the time of winding the film, the tension at the winding lengths of 50 m, 100 m, 200 m, 500 m, and 1000 m was half the tension at the time of starting the winding contact roller. Thus, a film roll was obtained.

[0188] An optical film of Comparative Example 1A was produced using a cyclic olefin resin (COP). Comparative Example 1A is a film 1-2 produced by the film forming method of Example 7A. In Comparative Example 1A, a plurality of coating embossments each having a height H of 0.5 μm were formed at each of the widthwise end portions of the surface of the film 1-2. In addition, in Comparative Example 1A, the coating embossments were formed at intervals of 5.3 mm between the start end portion and the end end portion of the film 1-2.

[0189] An optical film of Comparative Example 2A was produced using a cyclic olefin resin (COP) by forming embossments by molding. In Comparative Example 2A, a film 1-2 was produced by the film forming method of Example 7A. In Comparative Example 2A, one row of embossments each having a height H of 3 μm and an interval of 1.4 mm were formed at each of the widthwise end portions of the surface of the film 1-2 by knurling. The knurling was performed using the method described in paragraphs

[0583] to

[0629] of Japanese Patent Application Publication No. 2020-75482.

[0190] An optical film of Comparative Example 3A was produced using triacetyl cellulose (TAC) by forming embossments by coating and by molding. In Comparative Example 3A, a plurality of coating embossments each having a height H of 10 μm and an interval of 2 mm were formed at each of the widthwise end portions of the surface of the film 1-2. In addition, in Comparative Example 3A, one row of embossments each having a height H of 5 μm and an interval of 1.4 mm were formed at each of the widthwise end portions of the surface of the film 1-2 by knurling. The knurling was performed using the method described above.

[0191] Next, the examples and comparative examples in which the conditions such as the embossment density d, the embossment interval L, and the embossment height H were changed are shown in Table II below.

[0192]

[0193] Examples 1B and 2B changed the embossment density d of the first range 12a in such a manner that the difference Δd between the embossment densities d before and after the change satisfied Equation (1) with respect to Example 1A shown in Table I, Table II. In Example 1B, the interval L of the embossments 20 was narrowed by the same value at each of the winding lengths of 50 m, 100 m, 200 m, 500 m, and 1000 m from the start end portion 11a. In Example 2B, the interval L of the embossments 20 was narrower in the range of the winding lengths of 100 m to 1000 m from the start end portion 11a than in the range of 50 m from the start end portion 11a.

[0194] Examples 3B to 6B widened the interval L of the embossments 20 before the change with respect to Example 1A shown in Table I, Table II. In Examples 3B to 6B, the interval L of the embossments 20 before the change satisfied the upper limit. In addition, Examples 3B and 4B lowered the height H of the embossments 20 with respect to Example 1A shown in Table I, Table II.

[0195] In Examples 3B and 5B, the difference Δd in the embossing density d before and after the change of the first range 12a and the second range 12b satisfies the upper limit of the formula (1). Therefore, in Examples 3B and 5B, the interval L of the embossing 20 after the change of the first range 12a is narrowed in a manner that the difference Δd in the embossing density d before and after the change satisfies the upper limit of the formula (1).

[0196] In addition, in Examples 4B and 6B, the difference Δd in the embossing density d before and after the change of the first range 12a and the second range 12b satisfies the lower limit of the formula (1). Therefore, in Examples 4B and 6B, the interval L of the embossing 20 after the change of the first range 12a is narrowed in a manner that the difference Δd in the embossing density d before and after the change satisfies the lower limit of the formula (1).

[0197] Examples 7B and 8B narrow the interval L of the embossing 20 before the change, relative to Example 1A shown in Table I and Table II. In Examples 7B and 8B, the interval L of the embossing 20 before the change satisfies the lower limit.

[0198] In Examples 7B and 8B, the difference Δd in the embossing density d before and after the change of the first range 12a and the second range 12b satisfies the formula (1). Therefore, in Examples 7B and 8B, the interval L of the embossing 20 after the change of the first range 12a is narrowed in a manner that the difference Δd in the embossing density d before and after the change satisfies the formula (1).

[0199] Examples 9B and 10B increase the height H of the embossing 20, relative to Example 1A shown in Table I and Table II. The height H of the embossing 20 of Examples 9B and 10B satisfies the upper limit.

[0200] Examples 11B and 12B decrease the height H of the embossing 20, relative to Example 1A shown in Table I and Table II. The height H of the embossing 20 of Examples 11B and 12B satisfies the lower limit.

[0201] In Examples 9B to 12B, the difference Δd in the embossing density d before and after the change of the first range 12a and the second range 12b satisfies the formula (1). Therefore, in Examples 9B to 12B, the interval L of the embossing 20 after the change of the first range 12a is narrowed in a manner that the difference Δd in the embossing density d before and after the change satisfies the formula (1).

[0202] In Example 13B, the film thickness of the film is increased, and the embossing density d of the first range 12a is changed within a range satisfying the formula (1). The film thickness of the film of Example 13B satisfies the upper limit. In Examples 14B and 15B, the film thickness of the film is decreased, and the embossing density d of the first range 12a is changed within a range satisfying the formula (1). The film thickness of the film of Example 14B satisfies the lower limit.

[0203] In Examples 16B and 17B, the width of the film is increased, and the embossing density d of the first range 12a is changed within the range satisfying formula (1). The width of the film in Examples 16B and 17B satisfies the upper limit. In Examples 18B and 19B, the width of the film is decreased, and the embossing density d of the first range 12a is changed within the range satisfying formula (1). The width of the film in Examples 18B and 19B satisfies the lower limit.

[0204] In Examples 20B and 21B, the winding length of the film is increased, and the embossing density d of the first range 12a is changed within the range satisfying formula (1). The winding length of the film in Examples 20B and 21B satisfies the upper limit. In Examples 22B and 23B, the winding length of the film is decreased, and the embossing density d of the first range 12a is changed within the range satisfying formula (1). The winding length of the film in Examples 22B and 23B satisfies the lower limit.

[0205] In Example 24B, the diameter of the core of the wound film, the width of the film is decreased, and the embossing density d of the first range 12a is changed within the range satisfying formula (1).

[0206] In Example 25B, the method of forming the embossing is changed to the above-described method using laser, and the embossing density d of the first range 12a is changed within the range satisfying formula (1).

[0207] In Examples 26B to 31B, the number of rows of the embossing is increased, and the embossing density d of the first range 12a is changed within the range satisfying formula (1).

[0208] In Comparative Example 1B, the embossing density d is not changed over the entire winding length of the film. In Comparative Examples 2B to 5B, the embossing density d exceeds the upper limit or is lower than the lower limit of formula (1). In Comparative Example 6B, the film thickness of the film exceeds the upper limit.

[0209] < Evaluation of Winding Misalignment of Film Roll >

[0210] The winding misalignment of the film roll produced above was verified.

[0211] (1) Evaluation Method

[0212] Figure 7 This is a diagram illustrating one example of the evaluation method of the misalignment amount. 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 is measured. This difference is taken as the misalignment amount.

[0213] (2) Evaluation Criteria

[0214] The misalignment amount of 0 mm to 2 mm is taken as A, and the misalignment amount exceeding 2 mm is taken as B. Evaluation of A is preferred, and evaluation of B is not preferred.

[0215] (3) Evaluation results

[0216] The evaluation results of the examples and comparative examples in which the conditions such as the composition of the resin, the film forming method were changed are shown in Table III below. In addition, the evaluation results of the examples and comparative examples in which the conditions such as the embossing density d, the embossing interval L, the embossing height H were changed are shown in Table IV below.

[0217]

[0218]

[0219] In Comparative Example 1A, the interval L of the embossing formed by coating is constant from the start end portion to the terminal end portion of the optical film. Therefore, in Comparative Example 1A, the embossing density d is constant from the start end portion to the terminal end portion of the optical film. Therefore, in Comparative Example 1A, the difference Δd in the embossing density d before and after the change is 0 at each of the winding lengths of 50 m, 100 m, 200 m, 500 m, and 1000 m from the start end portion 11a. Thus, in Comparative Example 1A, the difference Δd in the embossing density d before and after the change does not satisfy the above formula (1). As a result, the evaluation result of Comparative Example 1A is B. It is thus understood that if the embossing density d is constant in the core and outside of the roll, winding misalignment occurs.

[0220] Comparative Example 2A forms embossing by molding. Thus, in Comparative Example 1B, the embossing density d is also constant from the start end portion to the terminal end portion of the optical film. Therefore, in Comparative Example 2A, the difference Δd in the embossing density d before and after the change does not satisfy the above formula (1). As a result, the evaluation result of Comparative Example 2A is B. It is thus understood that if the embossing density d is constant, winding misalignment occurs. It is thus understood that even if the embossing density d is constant in the core and outside of the roll by forming embossing by molding, winding misalignment occurs.

[0221] In Comparative Example 3A, the coating embossing with a height H of 10 μm and the molding embossing with a height H of 5 μm are mixed, and the height H of the embossing 20 is not constant. In addition, in Comparative Example 3A, the embossing density d of the coating embossing is constant from the start end portion to the terminal end portion of the optical film. Furthermore, in Comparative Example 3A, the embossing density d of the molding embossing is constant from the start end portion to the terminal end portion of the optical film.

[0222] Therefore, in Comparative Example 3A, the difference Δd in the embossing density d before and after the change of the coating embossing does not satisfy the above formula (1). In addition, the difference Δd in the embossing density d before and after the change of the molding embossing does not satisfy the above formula (1). As a result, the evaluation result of Comparative Example 3A is B. In Comparative Example 3A, the height of the coating embossing is relatively high with respect to the molding embossing, and in the roll of the film, the coating embossing mainly supports the film. However, the embossing density d of the coating embossing is constant, and is not optimized in the core and outside of the roll. It is thus understood that winding misalignment occurs.

[0223] On the other hand, in Embodiments 1A to 9A, in the first range 12a of the optical film 1A, the embossed density d after the change is higher than the embossed density d before the change. Also, in Embodiments 1A to 9A, the difference Δd between the embossed densities d before and after the change is 0.17 to 4.1. This satisfies the above-described formula (1).

[0224] As a result, the evaluation results of Embodiments 1A to 9A are A. From this, it is known that, in the first range 12a of the optical film 1A, if the difference Δd between the embossed densities d before and after the change satisfies the formula (1), the winding misalignment can be sufficiently suppressed in the core portion. It should be noted that the winding misalignment can be sufficiently suppressed even in the outer portion. In addition, it is known that if the plurality of embossing heights H are constant, the winding misalignment can be sufficiently suppressed.

[0225] It should be noted that, regarding the composition of the optical film and the film formation method, it is known that the same effect can be obtained by satisfying the above-described conditions, regardless of which of the above-described examples. In addition, it is known that even if the embossing 20 is formed by a laser, the same effect can be obtained as long as the above-described conditions are satisfied.

[0226] In Comparative Example 1B, the interval L of the embossing formed by coating is constant from the start end portion to the end portion of the optical film, like Comparative Example 1A. Therefore, in Comparative Example 1B, the embossed density d is constant from the start end portion to the end portion of the optical film. Thus, in Comparative Example 1B, the difference Δd between the embossed densities d before and after the change is 0 at each of the winding lengths of 50 m, 100 m, 200 m, 500 m, and 1000 m from the start end portion 11a. In this way, in Comparative Example 1B, the difference Δd between the embossed densities d before and after the change does not satisfy the above-described formula (1). As a result, the evaluation result of Comparative Example 1B is B. From this, it is known that if the embossed density d is constant in the core and the outer portion of the roll, the winding misalignment occurs.

[0227] In Comparative Examples 2B to 6B, in the first range 12a of the optical film 1A, the embossed density d after the change is higher than the embossed density d before the change. However, in Comparative Example 2B, the difference Δd between the embossed densities d before and after the change does not satisfy the above-described formula (1) at the winding length of 1000 m from the start end portion 11a. In addition, in Comparative Examples 3B to 6B, there is a range in which the difference Δd does not satisfy the above-described formula (1) at each of the winding lengths of 50 m, 100 m, 200 m, 500 m, and 1000 m from the start end portion 11a.

[0228] As a result, the evaluation results of Comparative Examples 2B to 6B were B. It was thus found that even if the embossing density d of the core was increased compared with the outer portion, if the difference Δd was in a range exceeding the upper limit or falling below the lower limit of the above formula (1), winding misalignment occurred. In addition, it was found that even if the film thickness of the film was changed, if the difference Δd was not in a range satisfying the above formula (1), winding misalignment occurred.

[0229] On the other hand, in Examples 1B to 31B, the embossing density d after the change was higher than the embossing density d before the change in the first range 12a of the optical film 1A. Furthermore, in Examples 1B to 31B, the difference Δd between the embossing densities d before and after the change was 0.17 to 4.1. This satisfied the above formula (1).

[0230] As a result, the evaluation results of Examples 1B to 31B were A. It was thus found that in the first range 12a of the optical film 1A, if the difference Δd between the embossing densities d before and after the change satisfied the formula (1), winding misalignment could be sufficiently suppressed in the core portion. Note that winding misalignment could also be sufficiently suppressed in the outer portion. In addition, it was found that if the plurality of embossing heights H were constant, winding misalignment could be sufficiently suppressed.

[0231] Note that in Examples 3B to 8B, it was found that even if the interval L of the embossing 20 was changed, as long as the above conditions were satisfied, winding misalignment did not occur.

[0232] In addition, in Examples 3B, 4B, 9B to 12B, it was found that even if the height H of the embossing 20 was changed, as long as the above conditions were satisfied, winding misalignment did not occur.

[0233] Furthermore, in Examples 13B to 15B, it was found that even if the film thickness of the optical film 1A was changed, as long as the above conditions were satisfied, winding misalignment did not occur.

[0234] In addition, in Examples 16B to 19B, it was found that even if the width of the optical film 1A was changed, as long as the above conditions were satisfied, winding misalignment did not occur.

[0235] Furthermore, in Examples 20B to 23B, it was found that even if the winding length of the optical film 1A was changed, as long as the above conditions were satisfied, winding misalignment did not occur.

[0236] In addition, in Example 24B, it was found that even if the diameter of the core of the film roll 10 was changed, as long as the above conditions were satisfied, winding misalignment did not occur.

[0237] Furthermore, in Example 25B, it was found that even if the embossing 20 was formed using a laser, as long as the above conditions were satisfied, winding misalignment did not occur.

[0238] In addition, in Embodiments 26B to 31B, it was found that even if the number of rows of the embossing 20 was changed, as long as the above conditions were satisfied, the winding misalignment did not occur.

Claims

1. An optical film which is long and formed into a roll wound from a first end portion to a second end portion in a longitudinal direction of the long shape, a plurality of embossments are formed in the longitudinal direction between the first end portion and the second end portion, and the plurality of embossments are of the same height in a prescribed range, when a first range from a first intermediate portion to a second intermediate portion between the first end portion and the second end portion is set as the first range, a second range from the second intermediate portion to the second end portion is set as the second range, and a number of embossments per unit angle of the roll is set as an embossment density, the first range is 50 m to 1000 m from the first end portion, the first range has a portion with a higher embossment density than the second range.

2. The optical film of claim 1, wherein, when an arbitrary embossment density of the first range before the change is set as d before, and an embossment density of the first range after the change is set as d after, a difference Δd between the embossment density after the change d after and the embossment density before the change d before satisfies the following formula (1): 4.1 > Δd > 0.17 ··· (1).

3. The optical film of claim 1, wherein, when an embossment density at a position 1000 m from the first end portion is set as d 1000, the embossment density after the change d after at an arbitrary position of the first range and the embossment density before the change d 1000 satisfy the following formula (2): d after - d 1000 > 0 ··· (2).

4. The optical film of claim 1, wherein, when an interval of the embossments in the longitudinal direction of the optical film is set as L, and a length of the embossments in the longitudinal direction of the optical film is set as s, the interval L of the embossments and the length s of the embossments satisfy the following formula (3): L > s ··· (3).

5. The optical film of claim 4, wherein, when an angle at which the interval L of the embossments is possessed is set as an embossment angle θ, and a radius of the roll is set as r, the embossment density d is obtained by the following formula (4), and the embossment angle θ is obtained by the following formula (5): d = 1 / θ ··· (4), θ = 180L / πr ··· (5).

6. The optical film of claim 1, wherein, the height of the embossments is in a range of -0.05% to +0.05% with respect to an average of the height of the embossments contained in a unit length in the longitudinal direction.

7. The optical film of claim 1, wherein, the embossments are formed by coating of a resin.

8. A roll of an optical film which is long and formed into a roll wound from a first end portion to a second end portion in a longitudinal direction of the long shape, a plurality of embossments being formed in the longitudinal direction between the first end portion and the second end portion, and the plurality of embossments being of the same height in a prescribed range, when a first range from a first intermediate portion to a second intermediate portion between the first end portion and the second end portion is set as the first range, a second range from the second intermediate portion to the second end portion is set as the second range, and a number of embossments per unit angle of the roll is set as an embossment density, the first range is 50 m to 1000 m from the first end portion, the first range has a portion with a higher embossment density than the second range.

9. A method of manufacturing an optical film which is long and formed into a roll wound from a first end portion to a second end portion in a longitudinal direction of the long shape, when a first range from a first intermediate portion to a second intermediate portion between the first end portion and the second end portion is set as the first range, a second range from the second intermediate portion to the second end portion is set as the second range, and the number of embossments per unit angle of the film roll is set as an embossing density, the embossing is formed by coating of resin in a manner that the first range is 50 m to 1000 m from the first end portion, and the first range has a portion with a higher embossing density than the second range.

10. A method of manufacturing a film roll, the method of manufacturing a film roll in which a plurality of embossings are formed in a longitudinal direction between a first end portion and a second end portion in the longitudinal direction of an optical film in a long strip shape, and the optical film is wound into a film roll from the first end portion toward the second end portion, when a first range from a first intermediate portion to a second intermediate portion between the first end portion and the second end portion is set as the first range, a second range from the second intermediate portion to the second end portion is set as the second range, and the number of embossments per unit angle of the film roll is set as an embossing density, the embossing is formed by coating of resin in a manner that the first range is 50 m to 1000 m from the first end portion, and the first range has a portion with a higher embossing density than the second range, the optical film on which the embossing is formed is wound around a core.

Images