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. The optical film 1A has a first region 12a extending from a first intermediate region 11c between the starting end 11a and the terminal end 11b to a second intermediate region 11d, and a second region 12b extending from the second intermediate region 11d to the terminal end 11b. The embossing density is the number of embossments 20 per unit angle of the film roll. The first region 12a extends from 50 m to 1000 m from the first end, and the first region 12a has a portion with a higher embossing density than the second region 12b.

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 formed 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, there is a possibility that misalignment in the width direction of the film roll 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 a first range is from a first intermediate portion between the first end and the second end to a second intermediate portion, and a second range is from the second intermediate portion to the second end, and the number of embossments per unit angle of the film roll is defined as the embossing density, the first range is from 50 m to 1000 m from the first end, and the first range has a portion where the embossing density is higher than that of the second range.

[0011] The present invention also provides a film roll comprising an optical film having a long shape, with multiple embossments formed along the longitudinal direction between a first end and a second end along the longitudinal direction of the long shape, the multiple embossments being of the same height within a predetermined range, and wound from the first end to the second end, wherein the first range is from a first intermediate portion between the first end and the second end to a second intermediate portion, and the second range is from the second intermediate portion to the second end, and the number of embossments per unit angle of the film roll is defined as the embossing density, the first range is from 50 m to 1000 m from the first end, and the first range has a portion with a higher embossing density than the second 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 first range is from a first intermediate portion between the first end and the second end to a second intermediate portion, the second range is from the second intermediate portion to the second end, and the number of embossments per unit angle of the film roll is defined as the embossing density, the first range is from 50 m to 1000 m from the first end, and the embossments are formed by applying a resin so that there are parts in the first range that have a higher embossing density than the second 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 such that, when a first range is from a first intermediate portion between the first end and the second end to a second intermediate portion, and a second range is from the second intermediate portion to the second end, and the embossment density is the number of embossments per unit angle of the film roll, the first range is from 50 m to 1000 m from the first end, and there is a portion in the first range where the embossment density is higher than that in the second range, and the optical film with the embossments formed therein is wound around a core. [Effects of the Invention]

[0014] According to the present invention, it is possible to suppress winding misalignment in the short-side direction in optical films overlapping in the radial direction of a 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 an explanatory diagram schematically showing the relationship between the unit angle and the number of embossments. [Figure 5] FIG. 10 is a side view showing the details of the embossment. [Figure 6] 1 is a graph showing the relationship between embossing density and film winding length. [Figure 7] 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 first intermediate region 11c between the starting end 11a and the terminal end 11b to the second intermediate region 11d, and as a second region 12b from the second intermediate region 11d 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, 2000 m or more. The optical film 1A also has a length from the starting end 11a to the first intermediate portion 11c of, for example, 50 m. The optical film 1A also has a length from the starting end 11a to the second intermediate portion 11d of, for example, 1000 m. The region from the starting end 11a to the second intermediate portion 11d is also referred to as the winding core. The second region 12b from the second intermediate portion 11d to the terminal end 11b is also referred to as the winding outside.

[0024] In the optical film 1A, a first region 12a between the first intermediate portion 11c and the second intermediate portion 11d has a portion where the number of embossments 20 per unit length is greater than that in the second region 12b. The number of embossments 20 per unit length in the optical film 1A can be expressed as the number of embossments 20 per unit angle with the center O of the film roll 10 as the vertex. The number of embossments 20 per unit angle in the film roll 10 is referred to as the embossing density.

[0025] The above-mentioned optical film 1 The increase or decrease in the number of embossments 20 per unit length of A can be expressed as the embossing density as follows: In other words, the optical film 1A has a portion in the first region 12a between the first intermediate portion 11c and the second intermediate portion 11d where the embossing density is higher than that in the second region 12b. This indicates that the region of the optical film 1A from the starting end 11a to 50 m or more and 1000 m or less has a higher embossing density than the region from more than 1000 m to the terminal end 11b.

[0026] 4 is an explanatory diagram that schematically shows the relationship between the unit angle and the number of embossments. When the radius r of the film roll 10 is r1, for example, an arbitrary angle that includes one embossment 20 is defined as the unit angle θref.

[0027] When the number of embossments 20 per unit length is constant, the number of embossments 20 per unit angle θref increases as the winding length of the film roll 10 increases. In other words, the radius r of the film roll 10 increases as the winding length of the film roll 10 increases. The circumferential length of the film roll 10 per unit angle θref increases as the radius r of the film roll 10 increases. The number of embossments 20 per unit angle θref is greater when the radius r of the film roll 10 is r2 than when the radius r of the film roll 10 is r1 (r2>r1).

[0028] For this reason, if the number of embossments 20 per unit length is constant, the number of embossments 20 per unit angle θref is smaller on the winding core than on the outer side of the winding. As a result, the force with which the embossments 20 support the optical film 1A overlapping in the radial direction of the film roll 10 is weaker on the winding core than on the outer side of the winding. On the other hand, due to the stacking of optical films 1A, the force applied to each embossment 20 is greater on the winding core than on the outer side of the winding.

[0029] Therefore, the position of the optical film 1A overlapping in the radial direction of the film roll 10 is more likely to shift in the short-side direction at the core than at the outside of the roll. This type of shift is called winding shift. When winding shift occurs, the winding shape is more likely to be lost. Furthermore, when winding shift occurs, the optical film 1A rubs against the embossments 20, which increases the likelihood of deterioration.

[0030] Therefore, in the film roll 10, the number of embossments 20 per unit angle θref is increased on the core compared to the outside of the roll.

[0031] 5 is a side view showing the details of the embossments. Next, the embossing density and the size of the embossments 20 specified in the present invention will be described.

[0032] In the film roll 10, the number of embossments 20 per unit angle θref is defined as the embossment density d (pieces / °). With the embossment density d defined in this way, an arbitrary embossment density d in the first range 12a from the starting end 11a, which is 50 m or more and 1000 m or less, is defined as dbfore (pieces / °). In contrast, the embossment density d after the change in the first range 12a is defined as dafter (pieces / °). Furthermore, the difference between dafter and dbfore, which is the difference between the embossment density d before and after the change, is defined as Δd.

[0033] As described above, the optical film 1A has a portion in the first region 12a where the embossing density d is higher than that in the second region 12b. In this case, the difference Δd between the embossing density dafter after the change and the embossing density dbfore before the change in the first region 12a satisfies the following formula (1):

[0034] 4.1>Δd>0.17 (1)

[0035] Figure 6 is a graph showing the relationship between embossing density and film winding length. In the first range 12a, the solid line shows an example of the range that the changed embossing density dafter can take within the range defined by formula (1). The dashed line shows an example of the original embossing density dbfore within the first range 12a. The solid line shows the embossing density d outside the first range 12a.

[0036] When the difference Δd between the embossing density before and after the change in the first range 12a satisfies the formula (1), it is possible to suppress winding deviation of the film roll 10.

[0037] As described above, when 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, if the embossing density d in the first region 12a is not changed, the embossing density d will be maximum at a winding length of 1000 m. Therefore, the embossing density dafter after the change in the first region 12a is based on the embossing density d at a winding length of 1000 m when the embossing density d is not changed.

[0038] In the first region 12a, the embossing density d at a wound length of 1000 m when the embossing density d is not changed is defined as embossing density d1000. The embossing density dafter after the change in the first region 12a satisfies the following formula (2).

[0039] dafter-d1000>0···(2) Note that equation (2) is equivalent to dafter>d1000.

[0040] When the changed embossing density dafter in the first region 12a satisfies the formula (2), a portion in the first region 12a where the embossing density d is higher than that in the second region 12b is provided.

[0041] The interval between the embossments 20 along the longitudinal direction of the optical film 1A is L (mm), and the length of the embossments 20 is s (mm). The interval L between the embossments 20 and the length s of the embossments 20 satisfy the relationship of the following formula (3).

[0042] L>s···(3)

[0043] If the spacing L and length s of the embossments 20 do not satisfy the relationship of formula (3), 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.

[0044] In contrast, when the spacing L and length s of the embossments 20 satisfy the relationship of formula (3), 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 radially overlapping optical films 1A in the film roll 10, suppressing the occurrence of winding slippage.

[0045] The emboss density d and the difference Δd between the emboss density after the change dafter and the emboss density before the change dbfore can be calculated as follows.

[0046] The spacing L of the embossments 20 is expressed as the angle θ (°) with the center O of the film roll 10 as the vertex. The angle θ is also referred to as the emboss angle. The emboss density d is calculated from the emboss angle θ using the following equation (4). The emboss angle θ is also calculated using the following equation (5).

[0047] d=1 / θ (4) θ=180L / πr (5)

[0048] The difference Δd between the emboss density after the change dafter and the emboss density before the change dbefore is calculated by the following equation (6).

[0049] Δd=dafter-dbefore···(6)

[0050] Next, the height of the embossments 20 will be described. 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%. [Example]

[0051] 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.

[0052] <Composition of resin that makes up the film> 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.

[0053] [Acrylic resin (A)] The following acrylic resins A1 to A3 are used as the acrylic resin (A). The acrylic resin A1 is a commercially available product. The acrylic resins A2 and A3 are prepared by the following methods.

[0054] (Acrylic resin A1) The acrylic resin A1 is Dianall BR85 (manufactured by Mitsubishi Chemical Corporation).

[0055] (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.

[0056] (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.

[0057] [Cellulose ester resin (CE)] As the cellulose ester resin (CE), the following cellulose ester resins CE1 to CE4 are used.

[0058] (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.

[0059] (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.

[0060] (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.

[0061] (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 resin 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.

[0062] (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)

[0063] [Film production] An optical film was prepared under the following conditions, and this optical film was wound up to prepare a film roll. Examples and comparative examples in which the resin composition, film formation method, and other conditions were changed are shown in Table I below.

[0064] [Table 1]

[0065] (Preparation of optical films using acrylic resin and cellulose ester resin) The above acrylic resins A1 to A3 and cellulose ester resins CE1 to CE4 were used to prepare optical films of Examples 1A to 6A. Example 1A: Acrylic resin A1 + cellulose ester resin CE1 Example 2A: Acrylic Resin A1 + Cellulose Ester Resin CE2 Example 3A: Acrylic Resin A1 + Cellulose Ester Resin CE3 Example 4A: Acrylic Resin A1 + Cellulose Ester Resin CE4 Example 5A: Acrylic Resin A2 + Cellulose Ester Resin CE1 Example 6A: Acrylic Resin A3 + Cellulose Ester Resin CE1

[0066] (Dope liquid composition) (1) Example 1A 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 (2) Example 2A Acrylic resin A1: 160 parts by mass Cellulose ester resin CE2: 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 (3) Example 3A Acrylic resin A1: 160 parts by mass Cellulose ester resin CE3: 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 (4) Example 4A Acrylic resin A1: 160 parts by mass Cellulose ester resin CE4: 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 (5) Example 5A Acrylic resin A2: 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 (6) Example 6A Acrylic resin A3: 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.

[0067] (Optical film production and first stage stretching) The dope solution of each example was uniformly cast onto a stainless steel band support at 22°C with a width of 2 m using a belt casting apparatus. The solvent was evaporated on the stainless steel band support until the residual solvent amount became 40 mass %, and the stainless steel band support was peeled off with a peeling tension of 150 N / m.

[0068] 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.

[0069] 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.

[0070] 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).

[0071] 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.

[0072] 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.

[0073] (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.

[0074] Both ends of this stretched film were cut to a width of 2260 mm to obtain Film 1-2, which had a thickness of 40 μm.

[0075] (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.

[0076] (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.

[0077] In Examples 1A, 2A, 3A, 4A, 5A, and 6A, a row of multiple coated embossments with a height H of 0.5 μm was formed on both widthwise ends of the surface of film 1-2. Furthermore, in each Example, coated embossments were formed at 5.3 mm intervals from 1000 m to the end of film 1-2. Furthermore, in each Example, coated embossments were formed at 2.65 mm intervals from 50 m to 1000 m of film 1-2.

[0078] (Creation of optical films using cycloolefin resins) The optical film of Example 7A was prepared using a cycloolefin resin (COP).

[0079] (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.

[0080] [ka]

[0081] The obtained film-like material was stretched twice in the width direction at 175°C, and then transported while being heated at 100°C until completely dried. The edges were then slit to obtain Film 1-2, 40 μm thick, 2260 mm wide, and 12000 m long. The film transport speed was 20 m / min.

[0082] (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.

[0083] (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 film 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.

[0084] In Example 7A, multiple coated embossments with a height H of 0.5 μm were formed in a row on both widthwise ends of the surface of film 1-2. Furthermore, in Example 7A, coated embossments were formed at 5.3 mm intervals from 1000 m to the end of film 1-2. Furthermore, in Example 7A, coated embossments were formed at 2.65 mm intervals from 50 m to 1000 m of film 1-2.

[0085] The optical film of Example 8A was prepared using a cycloolefin resin (COP).

[0086] (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.

[0087] Cycloolefin resin G7810 (manufactured by JSR Corporation): 100% by mass Dichloromethane: 380% by mass Ethanol: 20% by mass

[0088] (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.

[0089] 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.

[0090] (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.

[0091] 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.

[0092] In Example 8A, a plurality of coated embossments were formed on both widthwise ends of the film under the same conditions as in Example 7A except for the film-forming method.

[0093] (Laser embossing) The optical film of Example 9A was produced by laser embossing using a cycloolefin resin (COP). In Example 9A, multiple embosses with a height H of 0.5 μm were formed in rows by laser on both widthwise ends of Film 1-2 produced by the film formation method of Example 7A.

[0094] 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.

[0095] 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.

[0096] In Example 9A, coated embossments were formed at 5.3 mm intervals from 1000 m to the end of Film 1-2, and in Example 9A, coated embossments were formed at 2.65 mm intervals from 50 m to 1000 m of Film 1-2.

[0097] (film winding) The embossed film 1-2 was wound around a core with a diameter of 153.5 mm with an initial tension of 60 N / m and a final tension of 25 N / m. When winding the film, the tension of the touch roll was set to half that at the start of winding for winding lengths of 50 m, 100 m, 200 m, 500 m, and 1000 m. This resulted in film rolls.

[0098] An optical film of Comparative Example 1A was produced using a cycloolefin resin (COP). In Comparative Example 1A, film 1-2 was produced using the film formation method of Example 7A. In Comparative Example 1A, a plurality of coated embossments with a height H of 0.5 μm were formed in a row on both ends of the surface of film 1-2 in the width direction. In Comparative Example 1A, coated embossments were formed at intervals of 5.3 mm from the starting end to the terminal end of film 1-2.

[0099] An optical film of Comparative Example 2A was produced using cycloolefin resin (COP) by embossing. For Comparative Example 2A, film 1-2 was produced using the film-forming method of Example 7A. For Comparative Example 2A, embossments with a height H of 3 μm and intervals of 1.4 mm were formed in rows on both ends of the surface of film 1-2 in the width direction by knurling. The knurling process was performed using the method described in paragraphs

[0583] to

[0629] of JP 2020-75482 A.

[0100] An optical film of Comparative Example 3A was produced using cellulose triacetate (TAC) by embossing through coating and embossing through stamping. In Comparative Example 3A, multiple coated embossments were formed in rows on both ends of the surface of Film 1-2 in the width direction, with a height H of 10 μm and intervals of 2 mm. In Comparative Example 3A, embossments were formed in rows on both ends of the surface of Film 1-2 in the width direction, with a height H of 5 μm and intervals of 1.4 mm, by knurling. The knurling method described above was used.

[0101] Next, examples and comparative examples in which conditions such as embossing density d, embossing interval L, and embossing height H were changed are shown in Table II below.

[0102] [Table 2]

[0103] In Examples 1B and 2B, the embossing density d in the first region 12a was changed compared to Example 1A shown in Tables I and II so that the difference Δd between the embossing densities d before and after the change satisfied formula (1). In Example 1B, the spacing L between the embosses 20 was narrowed to the same value at winding lengths of 50 m, 100 m, 200 m, 500 m, and 1000 m from the starting end 11a. In Example 2B, the spacing L between the embossments 20 in the winding length range of 100 m to 1000 m from the starting end 11a was narrower than in the range of 50 m from the starting end 11a.

[0104] In Examples 3B to 6B, the spacing L of the embossments 20 before the change was wider than in Example 1A shown in Tables I and II. In Examples 3B to 6B, the spacing L of the embossments 20 before the change satisfies the upper limit. Furthermore, in Examples 3B and 4B, the height H of the embossments 20 was lower than in Example 1A shown in Tables I and II.

[0105] In Examples 3B and 5B, the difference Δd between the embossing density d before and after the change in the first range 12a and the second range 12b satisfies the upper limit of formula (1). Therefore, in Examples 3B and 5B, the spacing L of the embossments 20 after the change in the first range 12a was narrowed so that the difference Δd between the embossing density d before and after the change satisfies the upper limit of formula (1).

[0106] Furthermore, in Examples 4B and 6B, the difference Δd between the embossing density d before and after the change in the first range 12a and the second range 12b satisfies the lower limit of formula (1). Therefore, in Examples 4B and 6B, the spacing L of the embossments 20 after the change in the first range 12a was narrowed so that the difference Δd between the embossing density d before and after the change satisfies the lower limit of formula (1).

[0107] In Examples 7B and 8B, the spacing L of the embossments 20 before the change was narrower than in Example 1A shown in Tables I and II. In Examples 7B and 8B, the spacing L of the embossments 20 before the change satisfied the lower limit.

[0108] In Examples 7B and 8B, the difference Δd between the embossing density d before and after the change in the first area 12a and the second area 12b satisfies formula (1). Therefore, in Examples 7B and 8B, the spacing L of the embossments 20 after the change in the first area 12a was narrowed so that the difference Δd between the embossing density d before and after the change satisfies formula (1).

[0109] In Examples 9B and 10B, the height H of the embossments 20 was increased compared to Example 1A shown in Tables I and II. In Examples 9B and 10B, the height H of the embossments 20 satisfies the upper limit.

[0110] In Examples 11B and 12B, the height H of the embossments 20 was lower than in Example 1A shown in Tables I and II. In Examples 11B and 12B, the height H of the embossments 20 satisfies the lower limit.

[0111] In Examples 9B to 12B, the difference Δd between the embossing density d before and after the change in the first area 12a and the second area 12b satisfies formula (1). Therefore, in Examples 9B to 12B, the spacing L of the embossments 20 after the change in the first area 12a was narrowed so that the difference Δd between the embossing density d before and after the change satisfies formula (1).

[0112] In Example 13B, the film thickness was increased, and the embossing density d in the first region 12a was changed within a range that satisfied formula (1). In Example 13B, the film thickness satisfied the upper limit. In Examples 14B and 15B, the film thickness was decreased, and the embossing density d in the first region 12a was changed within a range that satisfied formula (1). In Example 14B, the film thickness satisfied the lower limit.

[0113] In Examples 16B and 17B, the film width was increased, and the embossing density d in the first region 12a was changed within a range that satisfied formula (1). In Examples 16B and 17B, the film width satisfied the upper limit. In Examples 18B and 19B, the film width was decreased, and the embossing density d in the first region 12a was changed within a range that satisfied formula (1). In Examples 18B and 19B, the film width satisfied the lower limit.

[0114] In Examples 20B and 21B, the film winding length was increased, and the embossing density d in the first region 12a was changed within a range that satisfied formula (1). In Examples 20B and 21B, the film winding length satisfied the upper limit. In Examples 22B and 23B, the film winding length was decreased, and the embossing density d in the first region 12a was changed within a range that satisfied formula (1). In Examples 22B and 23B, the film winding length satisfied the lower limit.

[0115] In Example 24B, the diameter of the core around which the film is wound and the film width were reduced, and the embossing density d in the first region 12a was changed within a range that satisfied formula (1).

[0116] In Example 25B, the embossing was performed by the laser as described above, and the embossing density d in the first region 12a was changed within a range that satisfied the formula (1).

[0117] In Examples 26B to 31B, the number of embossing rows was increased, and the embossing density d in the first region 12a was changed within a range that satisfied the formula (1).

[0118] In Comparative Example 1B, the embossing density d was not changed throughout the entire winding length of the film. In Comparative Examples 2B to 5B, the embossing density d exceeded the upper limit or fell below the lower limit of formula (1). In Comparative Example 6B, the film thickness exceeded the upper limit.

[0119] <Evaluation of film roll misalignment> The winding slippage of the film roll thus prepared was examined. (1) Evaluation method 7 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.

[0120] (2) Evaluation criteria A deviation of 0 mm or more and 2 mm or less was rated as A, and a deviation of more than 2 mm was rated as B. A rating of A is preferable, and a rating of B is undesirable.

[0121] (3) Evaluation results The evaluation results of examples and comparative examples in which conditions such as resin composition and film formation method were changed are shown in Table III below. Furthermore, the evaluation results of examples and comparative examples in which conditions such as embossing density d, embossing interval L, and embossing height H were changed are shown in Table IV below.

[0122] [Table 3]

[0123] [Table 4]

[0124] In Comparative Example 1A, the spacing L between the embossments formed by coating is constant from the start to the end of the optical film. Therefore, in Comparative Example 1A, the embossing density d is constant from the start to the end of the optical film. Therefore, in Comparative Example 1A, the difference Δd between 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 11a. Thus, in Comparative Example 1A, the difference Δd between the embossing density d before and after the change does not satisfy the above formula (1). As a result, Comparative Example 1A was evaluated as B. This shows that if the embossing density d is constant between the winding core and the outside of the winding, winding misalignment occurs.

[0125] In Comparative Example 2A, the embossing is formed by embossing. As a result, in Comparative Example 1B as well, the embossing density d is constant from the start end to the end end of the optical film. For this reason, in Comparative Example 2A, the difference Δd between the embossing density d before and after the change does not satisfy the above formula (1). As a result, the evaluation result for Comparative Example 2A was B. This shows that when the embossing density d is constant, winding slippage occurs. This shows that winding slippage occurs even when the embossing density d is constant between the winding core and the outside of the winding due to the embossing being formed by embossing.

[0126] Comparative Example 3A has a mixture of coated embossments with a height H of 10 μm and embossed embossments with a height H of 5 μm, and the height H of the embossments 20 is not constant. Also, in Comparative Example 3A, the embossment density d of the coated embossments is constant from the start end to the end end of the optical film. Furthermore, in Comparative Example 3A, the embossment density d of the embossed embossments is constant from the start end to the end end of the optical film.

[0127] For this reason, in Comparative Example 3A, the difference Δd in the embossing density d before and after the change in the coated embossing does not satisfy the above formula (1). Furthermore, the difference Δd in the embossing density d before and after the change in the embossing pattern does not satisfy the above formula (1). As a result, Comparative Example 3A was evaluated as B. In Comparative Example 3A, the height of the coated embossing is relatively high compared to the embossing pattern, and in the film roll, the coated embossing mainly supports the film. However, the embossing density d of the coated embossing is constant and is not optimized between the winding core and the outside of the winding. This indicates that winding misalignment occurs.

[0128] In contrast, in Examples 1A to 9A, the embossing density dafter after the change is higher than the embossing density dbfore before the change in the first region 12a of the optical film 1A. Furthermore, in Examples 1A to 9A, the difference Δd between the embossing density d before and after the change is 0.17 or more and 4.1 or less. This satisfies the above formula (1).

[0129] As a result, Examples 1A to 9A were evaluated as A. This shows that, in the first region 12a of the optical film 1A, if the difference Δd between the embossing density d before and after the change satisfies formula (1), winding slippage can be sufficiently suppressed at the winding core. Furthermore, winding slippage can also be sufficiently suppressed outside the winding. Furthermore, it shows that, if the height H of the multiple embossments is constant, winding slippage can be sufficiently suppressed.

[0130] It is understood that the same effects can be obtained regardless of the composition of the optical film and the film-forming method, provided that the above conditions are met. It is also understood that the same effects can be obtained even when the embossments 20 are formed by a laser, provided that the above conditions are met.

[0131] In Comparative Example 1B, like Comparative Example 1A, the spacing L of the embossments formed by coating is constant from the start end to the end end of the optical film. Therefore, in Comparative Example 1B, the embossing density d is constant from the start end to the end end of the optical film. Therefore, in Comparative Example 1B, the difference Δd between 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 11a. Thus, in Comparative Example 1B, the difference Δd between the embossing density d before and after the change does not satisfy the above formula (1). As a result, Comparative Example 1B was evaluated as B. This shows that if the embossing density d is constant between the winding core and the outside of the winding, winding misalignment occurs.

[0132] In Comparative Examples 2B to 6B, the embossing density dafter after the change was higher than the embossing density dbfore in the first region 12a of the optical film 1A. However, in Comparative Example 2B, the difference Δd between the embossing density d before and after the change did not satisfy the above formula (1) for a winding length of 1000 m from the starting end 11a. Similarly, in Comparative Examples 3B to 6B, there are ranges in which the difference Δd does not satisfy the above formula (1) for winding lengths of 50 m, 100 m, 200 m, 500 m, and 1000 m from the starting end 11a.

[0133] As a result, the evaluation results for Comparative Examples 2B to 6B were B. This shows that even if the embossing density d of the winding core is increased compared to the outer side of the winding, if there is a range in which the difference Δd exceeds the upper limit or falls below the lower limit of the above formula (1), winding slippage will occur. Also, even if the film thickness is changed, it is clear that if there is a range in which the difference Δd does not satisfy the above formula (1), winding slippage will occur.

[0134] In contrast, in Examples 1B to 31B, the embossing density dafter after the change is higher than the embossing density dbfore before the change in the first region 12a of the optical film 1A. Furthermore, in Examples 1B to 31B, the difference Δd between the embossing density d before and after the change is 0.17 or more and 4.1 or less. This satisfies the above formula (1).

[0135] As a result, Examples 1B to 31B were evaluated as A. This shows that, in the first region 12a of the optical film 1A, if the difference Δd between the embossing density d before and after the change satisfies formula (1), winding slippage can be sufficiently suppressed at the winding core. Furthermore, winding slippage can also be sufficiently suppressed outside the winding. Furthermore, it shows that, if the height H of the multiple embossments is constant, winding slippage can be sufficiently suppressed.

[0136] It is noted that in Examples 3B to 8B, even if the interval L of the embossments 20 is changed, as long as the above conditions are met, no winding deviation occurs.

[0137] Furthermore, in Examples 3B, 4B, and 9B to 12B, even if the height H of the embossments 20 is changed, by satisfying the above conditions, it is understood that no winding deviation occurs.

[0138] Furthermore, it is clear that in Examples 13B to 15B, even if the film thickness of the optical film 1A is changed, by satisfying the above conditions, no winding slippage occurs.

[0139] Furthermore, it is clear that in Examples 16B to 19B, even if the width of the optical film 1A is changed, by satisfying the above conditions, no winding deviation occurs.

[0140] Furthermore, it is clear that in Examples 20B to 23B, even if the winding length of the optical film 1A is changed, by satisfying the above conditions, winding deviation does not occur.

[0141] Furthermore, in Example 24B, 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.

[0142] Furthermore, in Example 25B, even if the embossments 20 are formed by laser, it is understood that by satisfying the above conditions, no winding slippage occurs.

[0143] Furthermore, it is understood that in Examples 26B to 31B, even if the number of rows of the embossments 20 is changed, as long as the above conditions are met, no winding deviation occurs. [Explanation of symbols]

[0144] 1A optical film, 2 embossed region, 3 non-embossed region, 10 film roll, 11a starting end, 11b end, 11c first intermediate portion, 11d second intermediate 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 a first intermediate portion to a second intermediate portion between the first end and the second end, and a second range from the second intermediate portion to the second end; When the number of embossments per unit angle of the film roll is defined as the embossing density, the first range is 50 m or more and 1000 m or less from the first end, The first area has a portion with a higher embossing density than the second area. Optical film.

2. When an arbitrary emboss density before the change in the first range is dbefore and an emboss density after the change in the first range is dafter, the difference Δd between the emboss density after the change dafter and the emboss density before the change dbefore satisfies the following formula (1): The optical film according to claim 1 . 4.1>Δd>0.17...(1)

3. When the embossing density at a point 1000 m from the first end is d1000, the embossing density dafter after the change and the embossing density d1000 before the change at any point in the first range satisfy the following formula (2): The optical film according to claim 1 . dafter-d1000>0...(2)

4. When the interval between the embossments along the longitudinal direction of the optical film is L and the length of the embossments along the longitudinal direction of the optical film is s, the interval between the embossments L and the length of the embossments s satisfy the relationship of the following formula (3): The optical film according to claim 1 . L>s... (3)

5. When the angle of the embossing interval L is defined as an embossing angle θ and the radius of the film roll is defined as r, the embossing density d can be calculated by the following formula (4), and the embossing angle θ can be calculated by the following formula (5). The optical film according to claim 4 . d=1 / θ...(4) θ=180L / πr...(5)

6. 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 .

7. The embossment is formed by applying a resin. 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 a first intermediate portion to a second intermediate portion between the first end and the second end, and a second range from the second intermediate portion to the second end; When the number of embossments per unit angle of the film roll is defined as the embossing density, the first range is 50 m or more and 1000 m or less from the first end, The first area has a portion with a higher embossing density than the second 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 a first intermediate portion to a second intermediate portion between the first end and the second end, and a second range from the second intermediate portion to the second end; When the number of embossments per unit angle of the film roll is defined as the embossing density, the first range is 50 m or more and 1000 m or less from the first end, The embossments are formed by applying a resin so that the first area has a portion with a higher embossing density than the second area. 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 a first intermediate portion to a second intermediate portion between the first end and the second end, and a second range from the second intermediate portion to the second end; When the number of embossments per unit angle of the film roll is defined as the embossing density, the first range is 50 m or more and 1000 m or less from the first end, forming the embossments by applying a resin so that the first area has a portion with a higher embossing density than the second area; 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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