Optical film cutting end mill and optical film manufacturing method using said end mill

Abstract

Provided is an endmill capable of suppressing napping during an optical film cutting process. This endmill for cutting optical film has a main body that rotates about a rotation axis, and n number of cutting blades that protrude from the main body so as to constitute the most radially outward part thereof. The endmill also satisfies any one of the following conditions (1)-(3): (1) n is 1; (2) n is 2 or greater and the maximum value of the difference between the blade lengths of all the cutting blades is 0.12% or less with respect to a reference blade length; or (3) n is 2 or more and the minimum value of the difference between the blade length of the longest cutting blade and the blade length of the other cutting blades is 0.60% or more with respect to the reference blade length.

Description

[Technical Field]

[0001] The present invention relates to an end mill for cutting an optical film and a method for producing an optical film using the end mill. [Background technology]

[0002] It is known to cut the end surface of an optical film (e.g., a polarizing plate). In such cutting, typically, a workpiece is formed by stacking multiple optical films, and the outer peripheral surface of the workpiece is cut. In such cutting, a cutting tool having multiple cutting blades may be used. However, in cutting using such cutting tools, preventing or suppressing burrs (defective cutting or remaining cut portions) remains a continuous challenge. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2016-182658 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been made to solve the above-mentioned problems of the prior art, and its main object is to provide an end mill that can suppress fuzziness during cutting of optical films. [Means for solving the problem]

[0005] An end mill for cutting optical films according to an embodiment of the present invention has a main body that rotates around a rotation axis and n cutting blades that protrude from the main body and form the outermost diameter, and satisfies any of the following (1) to (3): (1) n is 1; (2) n is 2 or more, and the maximum difference in blade length among all cutting blades is 0.12% or less of the reference blade length; or (3) n is 2 or more, and the minimum difference between the blade length of the longest cutting blade and the blade length of the other cutting blades is 0.60% or more of the reference blade length. In one embodiment, the standard blade length is 0.5 mm to 10 mm. In one embodiment, the cutting edge has a helix angle of 0°. In one embodiment, the cutting blade is affixed to the body. In one embodiment, the end mill for cutting optical films has an outer diameter of less than 10 mm and a length in the direction of the rotation axis of 15 mm or more. According to another aspect of the present invention, there is provided a method for manufacturing an optical film, which includes stacking a plurality of optical films to form a workpiece, and cutting the outer peripheral surface of the workpiece using the optical film cutting end mill described above. In one embodiment, the cutting includes a rough cut and a finish cut. In one embodiment, the rough cut has a depth of cut of 0.2 mm or less, the finish cut has a depth of cut of 0.1 mm or less, and the total depth of cut of the cuts is 0.3 mm or less. In one embodiment, the feed speed of the end mill for cutting optical films during the cutting is 2000 mm / min or less, and the rotation speed is 8000 rpm to 20000 rpm. In one embodiment, the number of times that the cutting blade of the optical film cutting end mill comes into contact with the 100 mm workpiece during the cutting is 1800 to 5000 times. [Effects of the Invention]

[0006] According to an embodiment of the present invention, an end mill that can suppress fuzziness during cutting of optical films can be realized by limiting the number of cutting blades to one, by making the maximum difference in blade length of all cutting blades in an end mill with multiple cutting blades a predetermined percentage or less of a reference blade length, or by making the minimum difference between the blade length of one cutting blade and the blade lengths of other cutting blades in an end mill with multiple cutting blades a predetermined percentage or more of a reference blade length. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1(a) is a schematic plan view seen from the axial direction to explain the structure of an end mill according to one embodiment of the present invention; FIG. 1(b) is a schematic perspective view of the end mill of FIG. 1(a). [Figure 2] FIG. 10 is a schematic plan view, viewed from the axial direction, illustrating the structure of an end mill according to another embodiment of the present invention. [Figure 3] FIG. 10 is a schematic plan view, viewed from the axial direction, for explaining the structure of an end mill according to yet another embodiment of the present invention. [Figure 4] FIG. 10 is a schematic plan view, viewed from the axial direction, for explaining the structure of an end mill according to yet another embodiment of the present invention. [Figure 5] FIG. 10 is a schematic plan view, viewed from the axial direction, for explaining the structure of an end mill according to yet another embodiment of the present invention. [Figure 6] FIG. 10 is a schematic plan view, viewed from the axial direction, for explaining the structure of an end mill according to yet another embodiment of the present invention. [Figure 7] 1 is a schematic plan view showing an example of the shape of a nonlinearly processed optical film that can be obtained by a method for manufacturing an optical film using an end mill according to an embodiment of the present invention. [Figure 8] FIG. 2 is a schematic perspective view illustrating cutting of an optical film using an end mill according to an embodiment of the present invention. [Figure 9]9(a) to 9(e) are schematic plan views illustrating a series of steps in non-linear cutting, which is an example of cutting an optical film using an end mill according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] Specific embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. Note that the drawings are schematic for clarity, and the ratios of length, width, thickness, etc., as well as angles, etc., in the drawings may differ from the actual ones.

[0009] A. Optical film cutting end mill FIG. 1(a) is a schematic plan view, viewed from the axial direction, illustrating the structure of an end mill for cutting optical films (hereinafter, sometimes simply referred to as an end mill) according to one embodiment of the present invention; FIG. 1(b) is a schematic perspective view of the end mill of FIG. 1(a). The end mill 100 shown in the figure has a main body 20 that rotates about a rotation axis 22 extending vertically (the stacking direction of a workpiece 200; the workpiece is an object to be cut in which an optical film is laminated; details will be described later), and a cutting blade 10 that protrudes from the main body 20 and forms the outermost diameter. End mills are typically straight end mills. The cutting blade 10 may have a helix angle of 0° or may have a predetermined helix angle. In the example shown, the helix angle of the cutting blade 10 is 0°. With this configuration, optical films can be cut well. More specifically, when cutting (e.g., irregular or nonlinear machining) using a cutting blade with a helix angle, the cut surface may be tapered when viewed from the side. However, using a cutting blade with a 0° helix angle can prevent the cut surface from becoming tapered. This is particularly effective when performing fine nonlinear machining (irregular machining) on ​​an optical film using a small-diameter end mill. Note that, in this specification, a "0° helix angle" means that the cutting edge 10a extends in a direction substantially parallel to the rotation axis 22, in other words, that the blade is not twisted relative to the rotation axis. "0°" means that the angle is essentially 0° and also includes cases where the blade is twisted by a slight angle due to machining errors, etc. Also, in this specification, "cutting" may be referred to as "cutting processing."

[0010] The cutting blade 10 may be integral with the body 20 (i.e., the end mill may be machined from a solid piece of wood), or may be attached to the body 20 as a separate piece. When the cutting blade 10 is attached to the body 20 as a separate piece, it may be embedded in the body as shown in FIG. 1(a) or attached to the body as shown in FIG. 2. The cutting blade 10 typically includes a cutting edge 10a, a rake face 10b, and a relief face 10c. The rake face 10b and the body 20 may define a pocket 30. The relief face 10c may have a linear shape as shown in the illustrated example, a curved shape (may have two relief faces), or a smoothly curved shape in a plan view. The relief face 10c is preferably roughened. Any appropriate treatment may be used for the roughening treatment. A typical example is blasting. By roughening the relief surface, when the optical film includes an adhesive layer (for example, an adhesive layer or a pressure-sensitive adhesive layer), adhesion of the adhesive or pressure-sensitive adhesive to the cutting blade can be suppressed, and as a result, blocking can be suppressed. In this specification, "blocking" refers to a phenomenon in which, when the optical film includes an adhesive layer, optical films in the workpiece are adhered to each other by the adhesive or pressure-sensitive adhesive on the end surface, and shavings of the adhesive or pressure-sensitive adhesive adhering to the end surface contribute to the adhesion of the optical films to each other.

[0011] In one embodiment, the cutting blade 10 includes sintered diamond. With this configuration, fine cutting can be performed well using a small diameter end mill as described below.

[0012] The number of blades of an end mill may be one, two, or three or more. The upper limit of the number of blades may be, for example, six. The number of blades is preferably one to three. In embodiments of the present invention, cutting blades having specific configurations can be adopted depending on the number of blades (a detailed explanation will be provided later). This is based on the following findings, which were discovered as a result of the inventors' extensive investigation into the causes of burrs during cutting using an end mill with multiple cutting blades. For simplicity, the case where there are two cutting blades will be described. When the trajectories of two cutting blades (hereinafter referred to as blade A and blade B) during cutting are examined in detail, if the blade lengths (the length of the protruding portion from the main body) of blade A and blade B are identical or the difference between the two blade lengths is very small, the trajectories of blade A and blade B will essentially match, so blade A and blade B will contact the workpiece evenly and the entire workpiece can be cut well. However, if there is a predetermined difference in the blade lengths of blade A and blade B (for example, if blade A is longer than blade B by a predetermined amount), the trajectories of blade A and blade B will intersect at a predetermined portion of the workpiece. As a result, the short blade B contacts the workpiece only at a specific portion, resulting in a difference in cutting state between that specific portion and other portions of the workpiece. This causes poor cutting or incomplete cutting, resulting in burrs. On the other hand, if the difference in blade length between blade A and blade B exceeds a specific amount (for example, if blade A is significantly longer than blade B), the trajectories of blade A and blade B become approximately concentric and do not intersect. As a result, the short blade B does not contact the workpiece during cutting, allowing the entire workpiece to be cut well using only blade A. This configuration is essentially equivalent to having one blade.

[0013] Based on the above findings, if the number of blades is one, it is possible to effectively suppress fuzz without adopting any other special configuration.

[0014] In one embodiment, when the number of blades is two or more, burrs can be effectively suppressed by setting the maximum difference in blade length among all cutting blades to 0.12% or less of the reference blade length. In this specification, "reference length" refers to the longest blade length among multiple cutting blades. For example, when the number of blades is two, as shown in FIG. 1(a), burrs can be effectively suppressed by setting the difference between L1 and L2 to 0.12% or less of the reference blade length (the longer of L1 or L2). Furthermore, when the number of blades is three, as shown in FIG. 4, burrs can be effectively suppressed by setting the maximum difference in all blade lengths (i.e., the maximum difference between L1 and L2, L1 and L3, and L1 and L3) to 0.12% or less of the reference blade length (the longest of L1, L2, or L3). The maximum difference in blade length is preferably 0.10% or less of the reference blade length, more preferably 0.08% or less, and ideally zero. In this embodiment, the difference in blade length among the multiple cutting blades is minimized. For example, if the reference blade length is 2.5 mm, the maximum difference in blade length is 3 μm or less. Therefore, precise measurement of the blade length is required, and such precise measurement makes this embodiment feasible. Precise measurement of the blade length can be achieved, for example, by a three-dimensional shape measuring device that combines time-of-flight and interferometry. Such three-dimensional shape measuring devices are commercially available, for example, from Optical Comb Corporation.

[0015] In another embodiment, when the number of blades is two or more, the minimum difference between the blade length of the longest cutting blade and the blade lengths of the other cutting blades can be set to 0.60% or more of the reference blade length, thereby effectively suppressing fuzziness. For example, as shown in FIG. 5 for a case in which the number of blades is two, fuzziness can be effectively suppressed by setting the difference between L1 and L2 to 0.60% or more of the reference blade length (L1). Furthermore, as shown in FIG. 6 for a case in which the number of blades is three, fuzziness can be effectively suppressed by setting the minimum difference between the blade length of the longest cutting blade and the blade lengths of the other cutting blades (i.e., the smaller of the differences between L1 and L2 and L1 and L3) to 0.60% or more of the reference blade length (L1). The minimum difference in blade length is preferably 1.0% or more, more preferably 2.0% or more, and even more preferably 3.0% or more. The minimum value is, for example, 95% or less, or, for example, 90% or less. If the minimum value is within this range, the eccentricity of the end mill is smaller than when the number of blades is one, and the end mill rotates better, resulting in an end mill with superior durability. Note that if the minimum value is 100%, the configuration is equivalent to when the number of blades is one.

[0016] The standard blade length may be the blade length of the cutting blade that is most involved in cutting. The standard blade length is preferably 0.5 mm to 10 mm, more preferably 0.7 mm to 7 mm, even more preferably 0.8 mm to 5 mm, and particularly preferably 1 mm to 3 mm. If the standard blade length is within this range, good cutting can be achieved.

[0017] The outer diameter of the end mill is preferably less than 10 mm, more preferably 3 mm to 9 mm, and even more preferably 4 mm to 7 mm. According to an embodiment of the present invention, for example, in fine cutting (particularly non-linear cutting or irregular cutting) using such a small-diameter end mill, it is possible to effectively suppress burrs. In this specification, the "outer diameter of the end mill" refers to twice the distance from the rotation axis 22 to the cutting edge 10a.

[0018] The length of the end mill (essentially, the cutting blade) in the direction of the rotation axis is preferably 15 mm or more, more preferably 20 mm or more. The length of the cutting blade in the direction of the rotation axis is, for example, 120 mm or less, preferably 100 mm or less, more preferably 50 mm or less. With such a length, when cutting an optical film, it is possible to cut a workpiece having a desired number of laminated optical films, thereby improving the efficiency of the cutting process. In this case, the cutting blade 10 is preferably a seamless, one-piece piece along the length of the main body 20 (the direction of the rotation axis). Having a seamless, one-piece cutting blade can further improve cutting ability, strength, and durability.

[0019] B. Optical Film Manufacturing Method A method for manufacturing an optical film according to an embodiment of the present invention includes cutting an end surface of an optical film using the end mill for cutting an optical film described above in Section A. More specifically, this manufacturing method includes stacking multiple optical films to form a workpiece, and cutting the outer peripheral surface of the workpiece to cut the end surface of the optical film that constitutes the workpiece. In one embodiment, the cutting includes non-linear machining (irregular machining).

[0020] Specific examples of optical films include polarizers, retardation films, polarizing plates (typically, laminates of a polarizer and a protective film), conductive films for touch panels, surface-treated films, and laminates obtained by appropriately laminating these films according to the purpose (for example, anti-reflection circular polarizing plates, polarizing plates with a conductive layer for touch panels). In one embodiment, the optical film includes an adhesive layer (for example, an adhesive layer, a pressure-sensitive adhesive layer). According to an embodiment of the present invention, even optical films including an adhesive layer can be successfully cut with reduced fuzzing.

[0021] Hereinafter, a manufacturing method will be described in which a pressure-sensitive adhesive layer-attached polarizing plate is used as an example of an optical film. Specifically, each step in the manufacturing method of a pressure-sensitive adhesive layer-attached polarizing plate having a planar shape as shown in Fig. 7 will be described. It will be obvious to those skilled in the art that the optical film is not limited to a pressure-sensitive adhesive layer-attached polarizing plate, and that the planar shape of the pressure-sensitive adhesive layer-attached polarizing plate is not limited to the planar shape shown in Fig. 7. In other words, the manufacturing method of the present invention can be applied to any optical film of any shape.

[0022] B-1. Formation of work FIG. 8 is a schematic perspective view illustrating the cutting process of an optical film, showing a workpiece 200. As shown in FIG. 8, the workpiece 200 is formed by stacking multiple optical films (adhesive-coated polarizing plates). Adhesive-coated polarizing plates can be manufactured by methods well known and commonly used in the industry, and detailed descriptions of the manufacturing methods will be omitted. When forming the workpiece, the adhesive-coated polarizing plate is typically cut into any appropriate shape. Specifically, the adhesive-coated polarizing plate may be cut into a rectangular shape, a shape similar to a rectangular shape, or an appropriate shape (e.g., a circle) depending on the purpose. In the illustrated example, the adhesive-coated polarizing plate is cut into a rectangular shape, and the workpiece 200 has opposing outer peripheral surfaces (cutting surfaces) 200a and 200b and outer peripheral surfaces (cutting surfaces) 200c and 200d perpendicular to the rectangular shapes. The workpiece 200 is preferably clamped from above and below by clamping means (not shown). The total thickness of the workpiece is preferably 10 mm to 50 mm, more preferably 15 mm to 25 mm, and even more preferably about 20 mm. Such a thickness can prevent damage due to pressing by the clamping means or impact during cutting. The pressure-sensitive adhesive layer-attached polarizing plates are stacked so that the workpiece has such a total thickness. The number of pressure-sensitive adhesive layer-attached polarizing plates constituting the workpiece can be, for example, 20 to 100. The clamping means (e.g., a jig) may be made of either a soft or hard material. When made of a soft material, its hardness (JIS A) is preferably 60° to 80°. If the hardness is too high, a mark of pressure from the clamping means may remain. If the hardness is too low, displacement may occur due to deformation of the jig, resulting in insufficient cutting precision.

[0023] B-2. End mill processing Next, a predetermined position on the outer peripheral surface of workpiece 200 is cut using end mill 100. End mill 100 is typically held by a machine tool (not shown), rotated at high speed around the rotation axis of the end mill, and used by bringing a cutting blade into contact with the outer peripheral surface of workpiece 200 and cutting into it while being fed in a direction intersecting the rotation axis. That is, cutting is typically performed by bringing the cutting blade of the end mill into contact with the outer peripheral surface of workpiece 200 and cutting into it. When producing a pressure-sensitive adhesive layer-attached polarizing plate having a shape as shown in Fig. 7 in a plan view, chamfered portions 200E, 200F, 200G, and 200H are formed at four corners on the outer periphery of workpiece 200, and a recess 200I is formed in the center of the outer peripheral surface connecting chamfered portions 200E and 200H.

[0024] The cutting process of the workpiece 200 will be described in detail. First, as shown in FIG. 9(a), the portion where the chamfered portion 200E of FIG. 7 is to be formed is chamfered. Then, as shown in FIGS. 9(b) to 9(d), the portions where the chamfered portions 200F, 200G, and 200H are to be formed are successively chamfered. Finally, as shown in FIG. 9(e), the recess 200I is cut and formed. Note that in the illustrated example, the chamfered portions 200E, 200F, 200G, and 200H, and the recess 200I are formed in this order, but they may be formed in any appropriate order.

[0025] The conditions for the cutting process can be appropriately set depending on the configuration, desired shape, etc. of the pressure-sensitive adhesive layer-attached polarizing plate. In one embodiment, the cutting includes rough cutting and finish cutting. The cutting depth of the rough cutting is preferably 0.2 mm or less. In rough cutting, the number of cuts made by an end mill at the cutting location can be one, two, three, or more times. For example, when rough cutting is performed twice, the cutting depth per cut is preferably 0.1 mm or less; when rough cutting is performed three times, the cutting depth per cut is preferably 0.07 mm or less. The cutting depth of the finish cutting is preferably 0.1 mm or less. In finish cutting, the number of cuts can typically be one cut. The total cutting depth is preferably 0.3 mm or less. With the above configuration, fuzziness can be effectively suppressed when cutting the optical film.

[0026] The feed rate of the end mill during cutting is preferably 2000 mm / min or less, more preferably 500 mm / min to 1800 mm / min, and even more preferably 800 mm / min to 1500 mm / min. The rotational speed of the end mill is preferably 8000 rpm to 20000 rpm, and more preferably 10000 rpm to 18000 rpm.

[0027] The number of contacts of the cutting blade of the end mill with respect to 100 mm of the workpiece during cutting is preferably 1,800 to 5,000 times, more preferably 2,000 to 4,000 times. If the number of contacts is too low, the cutting resistance increases, which may result in a shortened lifespan of the cutting blade. If the number of contacts is too high, the effect of suppressing burrs may be insufficient. The number of contacts can be adjusted by appropriately setting the number of cutting blades of the end mill, the feed rate and the rotation speed, and the minimum value of the difference in blade length. In particular, according to an embodiment of the present invention, by setting the minimum value of the difference in blade length to a predetermined value or more, the number of contacts can be reduced to a level that can suppress burrs.

[0028] In this manner, a cut-processed pressure-sensitive adhesive layer-attached polarizing plate can be obtained. In the illustrated example, a pressure-sensitive adhesive layer-attached polarizing plate including a nonlinearly processed portion can be obtained. [Example]

[0029] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The evaluation items in the examples are as follows.

[0030] (1) Fringe The cross section of the workpiece (a laminate of polarizing plates with adhesive layers) obtained in the examples and comparative examples was photographed with a camera. The photographed data was subjected to image analysis, and the area of ​​the portion corresponding to the fluff was calculated and evaluated according to the following criteria. Specifically, (i) the photographed image was digitized using a grayscale (black 0 to white 255), (ii) a portion with a brightness of 100 or more and spanning four or more adjacent pixels, and a portion with a brightness of 150 or more and spanning two to three or more adjacent pixels, were recognized as fluff, and (iii) the fluff was quantified by the sum of the area (number of pixels) of the portion recognized as fluff. The total area of ​​the photographed data was 3360 mm 2 (area 525,000). Good: fluff area is 0.19 mm 2 (equivalent to area 30) or less Allowable: fluff area 0.19 mm 2 Beyond 0.45mm 2 Below (equivalent to area 30-70) Unacceptable: fluff area 0.45mm 2 Exceeding (exceeding 70 in area)

[0031] <Production Example 1> Preparation of a polarizing plate with an adhesive layer The polarizer used was a film (thickness 12 μm) obtained by incorporating iodine into a long polyvinyl alcohol (PVA)-based resin film and uniaxially stretching it in the longitudinal direction (MD). An optically functional film (COP film with an antistatic layer) was attached to one side of this polarizer. The COP film with an antistatic layer was a film in which an antistatic layer (5 μm) was formed on a cycloolefin (COP) film (25 μm), and the COP film was attached so that it faced the polarizer. A surface protective film was attached to the antistatic layer side of the resulting laminate of polarizer / COP film / antistatic layer. Meanwhile, a cycloolefin-based resin retardation film (manufactured by Zeon Corporation, product name "ZB-12," in-plane retardation Re(550)=50 nm, thickness 40 μm) was attached to the polarizer side of the laminate. Furthermore, a pressure-sensitive adhesive layer (thickness 20 μm) was formed on the outer side of the retardation film, and a separator was attached to the pressure-sensitive adhesive layer. In this way, a polarizing plate with a pressure-sensitive adhesive layer was produced, which had a structure of surface protective film / antistatic layer / COP film / polarizer / retardation film / pressure-sensitive adhesive layer / separator.

[0032] Example 1 The pressure-sensitive adhesive layer-attached polarizing plate obtained in Production Example 1 was punched out to a size of 5.7 inches (approximately 140 mm long and 65 mm wide), and several punched polarizing plates were stacked to form a workpiece (total thickness approximately 20 mm). Polystyrene (PS) sheets were placed on both sides of the obtained workpiece as backing materials, and while the workpiece was held in a clamp (jig), chamfers were formed at the four corners of the periphery of the workpiece by cutting using an end mill. Furthermore, a recess was formed in the center of one of the four outer peripheral surfaces, resulting in a nonlinearly processed pressure-sensitive adhesive layer-attached polarizing plate as shown in Figure 7. The end mill had two blades, a twist angle of 0°, and an outer diameter of 5 mm. The end mill's feed rate was 1200 mm / min, and its rotation speed was 15000 rpm. Furthermore, in this example, the blade length (reference blade length) L1 of the longer of the two cutting blades was set to 2.5 mm, and the difference between the reference blade length L1 and the blade length L2 of the other cutting blade was set to 1.7 μm (0.07% of the reference blade length). The fluff of the obtained pressure-sensitive adhesive layer-attached polarizing plate (workpiece) was calculated using the procedure (1) above. The results are shown in Table 1.

[0033] <Comparative Example 1> A nonlinearly processed polarizing plate with a pressure-sensitive adhesive layer was obtained in the same manner as in Example 1, except that the difference between L1 and L2 was 3.7 μm (0.15% of the standard blade length). The fluff of the obtained polarizing plate with a pressure-sensitive adhesive layer (workpiece) was calculated using the procedure in (1) above. The results are shown in Table 1.

[0034] <Comparative Example 2> A nonlinearly processed polarizing plate with a pressure-sensitive adhesive layer was obtained in the same manner as in Example 1, except that the difference between L1 and L2 was 10.7 μm (0.43% of the standard blade length). The fluff of the obtained polarizing plate with a pressure-sensitive adhesive layer (workpiece) was calculated using the procedure in (1) above. The results are shown in Table 1.

[0035] <Comparative Example 3> A nonlinearly processed polarizing plate with a pressure-sensitive adhesive layer was obtained in the same manner as in Example 1, except that the difference between L1 and L2 was 11.7 μm (0.47% of the standard blade length). The fluff of the obtained polarizing plate with a pressure-sensitive adhesive layer (workpiece) was calculated using the procedure in (1) above. The results are shown in Table 1.

[0036] <Example 2> A nonlinearly processed polarizing plate with a pressure-sensitive adhesive layer was obtained in the same manner as in Example 1, except that the difference between L1 and L2 was 127.7 μm (5.11% of the standard blade length). The fluff of the obtained polarizing plate with a pressure-sensitive adhesive layer (workpiece) was calculated using the procedure in (1) above. The results are shown in Table 1.

[0037] Example 3 A nonlinearly processed polarizing plate with a pressure-sensitive adhesive layer was obtained in the same manner as in Example 1, except that the number of blades of the end mill was three. In this example, the blade length (reference blade length) L1 of the longest cutting blade among the three cutting blades was 2.5 mm, and the blade lengths of the two cutting blades were each L2 (the same length), with the difference between L1 and L2 being 1.7 μm (0.07% of the reference blade length). In other words, a configuration corresponding to Figure 6 was used. The fluff of the obtained polarizing plate with a pressure-sensitive adhesive layer (workpiece) was calculated using the procedure (1) above. The results are shown in Table 1.

[0038] <Comparative Example 4> A nonlinearly processed polarizing plate with a pressure-sensitive adhesive layer was obtained in the same manner as in Example 3, except that the difference between L1 and L2 was 10.7 μm (0.43% of the standard blade length). The fluff of the obtained polarizing plate with a pressure-sensitive adhesive layer (workpiece) was calculated using the procedure in (1) above. The results are shown in Table 1.

[0039] Example 4 A nonlinearly processed polarizing plate with a pressure-sensitive adhesive layer was obtained in the same manner as in Example 3, except that the difference between L1 and L2 was 127.7 μm (5.11% of the standard blade length). The fluff of the obtained polarizing plate with a pressure-sensitive adhesive layer (workpiece) was calculated using the procedure in (1) above. The results are shown in Table 1.

[0040] <Example 5> A nonlinearly processed pressure-sensitive adhesive layer-attached polarizing plate was obtained in the same manner as in Example 1, except that the number of blades of the end mill was one. The fluff of the obtained pressure-sensitive adhesive layer-attached polarizing plate (workpiece) was calculated using the procedure in (1) above. The results are shown in Table 1.

[0041] [Table 1]

[0042] As is clear from Table 1, according to the embodiments of the present invention, in an end mill having multiple cutting blades, the maximum difference in blade length between all cutting blades is set to a predetermined percentage or less of the reference blade length, or the minimum difference between the blade length of one cutting blade and the blade length of another cutting blade is set to a predetermined percentage or more of the reference blade length, thereby effectively suppressing fuzziness during cutting of optical films. [Industrial Applicability]

[0043] The end mill of the present invention can be suitably used for cutting optical films. Optical films cut by the end mill of the present invention can be used for irregularly shaped image display units, such as those used in automobile instrument panels and smart watches. [Explanation of symbols]

[0044] 10 cutting blade 10a cutting edge 10b Rake face 10c Relief surface 20 Main Unit 22 Rotation axis 30 pockets 100 end mill 200 Work

Claims

1. An end mill for cutting optical films, comprising a main body that rotates around a rotation axis and n cutting blades that are integral, seamless pieces protruding from the main body and configured as the outermost diameter, and which satisfies the following (1) or (2): (1) n is 2 or more, and the maximum difference in the cutting edge lengths of all cutting edges is 0.07% or more and 0.12% or less with respect to the reference cutting edge length; or (2) n is 2 or more, and the minimum difference between the blade length of the longest cutting blade and the blade length of the other cutting blades is 5.11% or more and 95% or less of the reference blade length: Here, the blade length of a cutting blade is the length of the portion protruding from the main body in the radial direction of the main body, and the reference blade length is the longest blade length among the blade lengths of the n cutting blades.

2. 2. The end mill for cutting optical films according to claim 1, wherein the standard blade length is 0.5 mm to 10 mm.

3. The end mill for cutting optical films according to claim 1 or 2, wherein the helix angle of the cutting blade is 0°.

4. The end mill for cutting optical films according to claim 1 , wherein the cutting blade is attached to the main body.

5. 5. The end mill for cutting an optical film according to claim 1, wherein the outer diameter is less than 10 mm and the length in the direction of the rotation axis is 15 mm or more.

6. A method for manufacturing an optical film, comprising: stacking a plurality of optical films to form a workpiece; and cutting the outer peripheral surface of the workpiece using the end mill for cutting optical films according to any one of claims 1 to 5.

7. The method for producing an optical film according to claim 6 , wherein the cutting comprises rough cutting and finish cutting.

8. The method for producing an optical film according to claim 7 , wherein the rough cutting has a cutting depth of 0.2 mm or less, the finish cutting has a cutting depth of 0.1 mm or less, and the total cutting depth is 0.3 mm or less.

9. 9. The method for producing an optical film according to claim 6, wherein the feed speed of the optical film cutting end mill during the cutting is 2000 mm / min or less, and the rotation speed is 8000 rpm to 20000 rpm.

10. 10. The method for producing an optical film according to claim 6, wherein the number of contacts of the cutting blade of the optical film cutting end mill with the 100 mm workpiece during the cutting is 1800 to 5000 times.

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