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

Abstract

To provide an end mill capable of inhibiting a crack, a yellow band, a lack of paste and fluff, when optical film cutting is performed.SOLUTION: An end mill for cutting an optical film has a body 20 that rotates around a rotating shaft 22, and a cutting blade 10 that is constituted as an outermost diameter in the state of protruding from the body. An angle of torsion of the cutting blade is 0°, and a rake angle α is in the range of 5° to 45°. An optical film manufacturing method includes cutting an end surface of the optical film by using the end mill for cutting the optical film.SELECTED DRAWING: Figure 1

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 edge of an optical film (e.g., a polarizing plate). In such cutting processes, a cutting tool configured such that the cutting blade extends in the direction of the rotation axis (e.g., parallel to the rotation axis) may be used (see, for example, Patent Document 1). However, cutting processes using such cutting tools have the following problems: (i) the optical film is prone to cracking; (ii) discoloration due to friction (so-called yellow bands are likely to occur); (iii) if the optical film has an adhesive layer (e.g., an adhesive layer or a pressure-sensitive adhesive layer), glue chipping (the adhesive or pressure-sensitive adhesive in the adhesive layer is scraped off by the cutting blade and removed); and (iv) fuzz (uncut areas) is likely to occur. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-72453 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been made to solve the above-mentioned conventional problems, and its main object is to provide an end mill that can suppress cracks, yellow bands, glue chipping, and fuzziness when cutting optical films. [Means for solving the problem]

[0005] The end mill for cutting optical films of the present invention has a main body that rotates around a rotation axis and a cutting blade that protrudes from the main body and forms the outermost diameter, and the cutting blade has a twist angle of 0° and a rake angle of 5° to 45°. In one embodiment, the cutting blade of the optical film cutting end mill has a clearance angle of 5° to 30°. In one embodiment, the cutting blade of the optical film cutting end mill has a cutting edge angle of 45° or more. In another embodiment, the cutting edge angle of the optical film cutting end mill is 55° or more. In another embodiment, the cutting edge angle of the optical film cutting end mill is 65° or less. In one embodiment, the end mill for cutting optical films has an outer diameter of less than 10 mm. In one embodiment, the cutting blade comprises sintered diamond. In one embodiment, the optical film cutting end mill cuts an optical film that includes a polarizer, a pressure-sensitive adhesive layer, a surface protective film, and a separator, and the peeling force of the separator is smaller than the peeling force of the surface protective film. According to another aspect of the present invention, there is provided a method for producing an optical film, which method includes cutting an edge surface of an optical film using the above-described end mill for cutting an optical film. In one embodiment, the optical film includes a polarizing plate. In one embodiment, the polarizing plate includes a polarizer, a pressure-sensitive adhesive layer, a surface protective film, and a separator, and the peel strength of the separator is smaller than the peel strength of the surface protective film. [Effects of the Invention]

[0006] According to the present invention, in an end mill for cutting optical films in which the helix angle of the cutting blade is 0°, by setting the rake angle of the cutting blade within a predetermined range, it is possible to suppress cracks, yellow bands, glue chipping, and fuzziness when cutting optical films. [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 for cutting an optical film according to one embodiment of the present invention; FIG. 1(b) is a schematic perspective view of the end mill for cutting an optical film of FIG. 1(a). [Figure 2] 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 optical film cutting end mill according to an embodiment of the present invention. [Figure 3] FIG. 1 is a schematic perspective view illustrating cutting of an optical film using an end mill for cutting an optical film according to an embodiment of the present invention. [Figure 4] 4(a) to 4(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 for cutting an optical film 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 are different 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 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. The end mill is typically a straight end mill. Furthermore, in this embodiment of the present invention, the helix angle of the cutting blade 10 is 0°. This configuration allows for good cutting of optical films. More specifically, when cutting (e.g., irregular or nonlinear cutting) using a cutting blade with a helix angle, the cutting surface may be tapered when viewed from the side. However, using a cutting blade with a helix angle of 0° can prevent the cutting surface from becoming tapered. In particular, significant effects can be obtained when performing fine nonlinear processing (irregular processing) on ​​optical films using a small-diameter end mill. In this specification, "a twist angle of 0°" 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 with respect to the rotation axis. Note that "0°" means that the angle is substantially 0°, and also includes cases where there is a slight angle of twist due to processing errors, etc.

[0010] The cutting blade 10 may be integral with the main body 20 (i.e., the end mill may be machined from a solid piece of wood), or may be attached to the main body 20 as a separate piece. 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 main body 20 may define a pocket 30. The relief face 10c may have a curved shape (including two relief faces) as shown in the illustrated example, a straight shape, or a smoothly curved shape in 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 face, adhesion of the adhesive or pressure-sensitive adhesive to the cutting blade is suppressed when the optical film includes an adhesive layer (e.g., an adhesive layer or a pressure-sensitive adhesive layer), thereby suppressing blocking. In this specification, "blocking" refers to a phenomenon in which optical films in a workpiece are bonded together by an adhesive or pressure-sensitive adhesive on the end surfaces when the optical film includes an adhesive layer, and shavings of the adhesive or pressure-sensitive adhesive adhering to the end surfaces contribute to the adhesion of the optical films together.

[0011] In an embodiment of the present invention, the rake angle α of the cutting blade 10 is 5° to 45°, preferably 5° to 30°. A rake angle α within this range ensures blade sharpness, appropriately reduces resistance during cutting, and allows the pocket 30 to be an appropriate size for efficient removal of cutting debris. As a result, cracks and yellow bands in the optical film can be effectively suppressed. Furthermore, if the optical film has an adhesive layer, glue chipping can be effectively suppressed. Note that if the rake angle α is too large, it may be difficult to manufacture the cutting blade (ultimately, the end mill), especially when the cutting blade is attached to the main body as a separate unit. The clearance angle β of the cutting blade 10 is preferably 5° to 30°, more preferably 5° to 25°. A clearance angle β within this range prevents contact between the relief surface 10c and the workpiece 200, thereby appropriately reducing resistance during cutting. Furthermore, it is possible to prevent the cutting edge angle γ from becoming excessively small. As a result, cracks and yellow bands in the optical film can be effectively suppressed, and further, when the optical film has an adhesive layer, glue chipping can be effectively suppressed. In addition, the life of the cutting blade can be extended. The cutting edge angle γ of the cutting blade 10 is preferably 45° or more, more preferably 55° or more. If the cutting edge angle γ is within this range, the life of the cutting blade can be extended. Taking into account the rake angle α and the clearance angle β, the cutting edge angle γ is less than 85°, preferably 80° or less, more preferably 75° or less. In another embodiment, the cutting edge angle γ is 65° or less. If the cutting edge angle γ is within this range, the generation of fuzz can be suppressed while maintaining a good life of the cutting blade (suppressing cracking of the cutting edge). In one embodiment, the rake angle α is preferably in the range of 5° to 15°, the clearance angle β is preferably in the range of 15° to 25°, and the cutting edge angle γ is preferably in the range of 55 to 65°. In this specification, the term "rake angle α" refers to the angle between the rake face 10b and a straight line connecting the cutting edge 10a and the rotation axis 22; the term "clearance angle β" refers to the angle between the cutting surface of the workpiece 200 and the clearance face 10c; and the term "cutting edge angle γ" refers to an angle defined with the cutting edge 10a as the vertex, and is calculated from the formula: 90° - rake angle α - clearance angle β.

[0012] The number of blades of the end mill can be any appropriate number depending on the purpose. The number of blades may be one as in the illustrated example, or two, or three or more. Preferably, the number of blades is one to three. With such a configuration, the spacing between the cutting blades is appropriately ensured, allowing for good discharge of cutting debris. More preferably, the number of blades is two. With such a configuration, the rigidity of the cutting blades is ensured, and pockets are secured, allowing for good discharge of cutting debris.

[0013] The thickness δ of the end mill blade is preferably 1.5 mm or less, more preferably 1.2 mm or less, and even more preferably 1.0 mm or less. The lower limit of the thickness is preferably 0.3 mm, more preferably 0.6 mm. By keeping the blade thickness within this range, cutting sharpness can be maintained. Furthermore, by adjusting the cutting edge angle, both good tool life and good cutting sharpness can be achieved.

[0014] 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 non-linear machining (irregular shape machining) using such a small-diameter end mill, cracks and yellow bands in the optical film can be effectively suppressed, and further, when the optical film has an adhesive layer, glue chipping can be effectively suppressed. 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.

[0015] In one embodiment, the cutting blade 10 includes sintered diamond. With this configuration, fine non-linear machining (irregular shape machining) using the small diameter end mill as described above can be performed well.

[0016] 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).

[0017] 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 (e.g., anti-reflection circular polarizing plates, polarizing plates with a conductive layer for touch panels). In one embodiment, the optical film includes an adhesive layer (e.g., an adhesive layer, a pressure-sensitive adhesive layer). According to an embodiment of the present invention, even optical films including an adhesive layer can suppress glue chipping during cutting.

[0018] In one embodiment, the optical film can be a polarizing plate with a pressure-sensitive adhesive layer, which includes, in this order, a surface protective film, a polarizer, a pressure-sensitive adhesive, and a separator. In one embodiment, the peel strength of the separator is smaller than that of the surface protective film. When an end mill is used on such a polarizing plate with a pressure-sensitive adhesive layer, the separator, which has a smaller peel strength than the surface protective film, tends to slip away from the blade of the end mill, which can result in the generation of fuzz. However, according to an embodiment of the present invention, by setting the cutting edge angle to 55° to 65°, good cutting sharpness is maintained, fuzz on the separator side is suppressed, and a long life of the cutting blade (suppression of cracks on the cutting edge) can be achieved.

[0019] 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. 2 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. 2. In other words, the manufacturing method of the present invention can be applied to any optical film having any shape.

[0020] B-1. Formation of work FIG. 3 is a schematic perspective view illustrating the cutting process of an optical film, showing a workpiece 200. As shown in FIG. 3, 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.

[0021] B-2. End mill processing Next, predetermined positions on the outer peripheral surface of workpiece 200 are 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 planar view shape as shown in FIG. 2, 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.

[0022] The cutting process of the workpiece 200 will be described in detail. First, as shown in FIG. 4(a), the portion where the chamfered portion 200E in FIG. 2 is to be formed is chamfered. Then, as shown in FIGS. 4(b) to 4(d), the portions where the chamfered portions 200F, 200G, and 200H are to be formed are successively chamfered. Finally, as shown in FIG. 4(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.

[0023] The conditions for the cutting process can be appropriately set depending on the configuration and desired shape of the pressure-sensitive adhesive layer-attached polarizing plate. For example, the rotation speed (number of rotations) of the end mill is preferably less than 25,000 rpm, more preferably 22,000 rpm or less, and even more preferably 20,000 rpm or less. The lower limit of the rotation speed of the end mill can be, for example, 10,000 rpm. Furthermore, for example, the feed rate of the end mill is preferably 500 mm / min to 10,000 mm / min, more preferably 500 mm / min to 2,500 mm / min, and even more preferably 800 mm / min to 1,500 mm / min. The number of times the end mill cuts the cutting area can be one cut, two cuts, three cuts, or more.

[0024] 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]

[0025] 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.

[0026] (1) Crack The pressure-sensitive adhesive layer-attached polarizing plates obtained in the Examples and Comparative Examples (all pressure-sensitive adhesive layer-attached polarizing plates constituting the workpiece) were visually inspected for cracking and evaluated according to the following criteria: The cracks were observed enlarged using an optical microscope. ◎: No cracks were observed ○: Slight cracks were observed, but to an extent that did not pose a problem in practical use. ×: Cracks were observed (2) Yellow Band The pressure-sensitive adhesive layer-attached polarizing plates obtained in the Examples and Comparative Examples (all pressure-sensitive adhesive layer-attached polarizing plates constituting the workpiece) were visually inspected for the occurrence of yellow bands and evaluated according to the following criteria: The yellow bands were observed enlarged under an optical microscope. ◎: No yellow band was observed ○: A slight yellow band was observed, but it was not a problem for practical use. ×: Yellow bands were observed (3) Missing glue The adhesive layer-attached polarizing plates obtained in the examples and comparative examples (all adhesive layer-attached polarizing plates constituting the workpiece) were visually inspected for glue chipping in the adhesive layer (the adhesive layer being scraped off by the cutting blade and missing), and evaluated according to the following criteria. ◎: No glue chipping was observed ○: A small amount of adhesive chipping was observed, but it was not a problem for practical use. ×: Glue chipping was observed (4) Cutting blade life The state of the cutting blades used in the examples and comparative examples after cutting was confirmed. ◎: The blade had no scratches or chips and was durable. ○: Slight scratches were found on the blade (5) Fringe The workpieces cut in the examples and comparative examples were fixed in a bundle, and the edges were observed by reflection under a fluorescent lamp. Workpieces containing samples with fuzz could be visually confirmed to have white discoloration on the edge surface. The size of the fuzz in the white discolored part of one bundle of workpieces was visually confirmed, and the fuzz was evaluated according to the following criteria. ◎: No fuzz was observed 〇: There was a very slight white discoloration in the area, and when the size of the fuzz was checked, a slight fuzz was found, but it was not a problem for practical use. △: There was a slight white discoloration in the area, and when the size of the fluff was checked, fluff was found, but it was within the standard range. ×: Fuzziness was observed

[0027] <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 manner, a polarizing plate 1 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.

[0028] <Production Example 2> Preparation of a polarizing plate with an adhesive layer A polarizer was produced in the same manner as in Production Example 1, and a brightness-enhancing film (manufactured by 3M, product name "DBEF") was attached to one side of this polarizer. A surface protective film was attached to the brightness-enhancing film side of the obtained polarizer / brightness-enhancing film. Meanwhile, a saponified 40 μm thick acrylic resin film 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 acrylic resin film, and a separator was attached to the pressure-sensitive adhesive layer. In this way, a polarizing plate 2 with an adhesive layer was produced, having a configuration of surface protective film / brightness-enhancing film / polarizer / acrylic resin film / pressure-sensitive adhesive layer / separator.

[0029] Example 1 The pressure-sensitive adhesive layer-attached polarizing plate 1 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 of approximately 20 mm). The obtained workpiece was clamped (jig) and subjected to cutting using an end mill with a 0° helix angle to form chamfers at the four corners of the outer periphery of the workpiece. Furthermore, a recess was formed in the center of one of the four outer periphery surfaces, resulting in a nonlinearly processed pressure-sensitive adhesive layer-attached polarizing plate as shown in FIG. 2. The end mill had one blade, an outer diameter of 5 mm, a cutting blade rake angle of 5°, a clearance angle of 15°, and a cutting edge angle of 70°. The end mill's feed rate was 1200 mm / min, and its rotation speed was 15,000 rpm.

[0030] The finally obtained nonlinearly processed polarizing plate with a pressure-sensitive adhesive layer was subjected to the evaluations (1) to (3) above. Furthermore, the cutting blade was evaluated in (4) above. Furthermore, the polarizing plate with a pressure-sensitive adhesive layer after cutting was evaluated in (5) above. The results are shown in Table 1.

[0031] <Examples 2 to 6 and Comparative Example 1> A nonlinearly processed pressure-sensitive adhesive layer-attached polarizing plate was produced in the same manner as in Example 1, except that the rake angle, clearance angle, and cutting edge angle of the cutting blade of the end mill were changed as shown in Table 1. The obtained nonlinearly processed pressure-sensitive adhesive layer-attached polarizing plate was subjected to the evaluations (1) to (3) above. Furthermore, the cutting blade used was subjected to the evaluation (4) above. Furthermore, the pressure-sensitive adhesive layer-attached polarizing plate after cutting was subjected to the evaluation (5) above. The results are shown in Table 1.

[0032] Example 7 A nonlinearly processed pressure-sensitive adhesive layer-attached polarizing plate as shown in FIG. 2 was produced in the same manner as in Example 1, except that the pressure-sensitive adhesive layer-attached polarizing plate 2 obtained in Production Example 2 was used. The nonlinearly processed pressure-sensitive adhesive layer-attached polarizing plate obtained was subjected to the evaluations (1) to (3) above. Furthermore, the cutting blade used was evaluated in (4) above. Furthermore, the pressure-sensitive adhesive layer-attached polarizing plate after cutting was evaluated in (5) above. The results are shown in Table 1.

[0033] <Examples 8 to 12 and Comparative Example 2> A nonlinearly processed pressure-sensitive adhesive layer-attached polarizing plate was produced in the same manner as in Example 7, except that the rake angle, clearance angle, and cutting edge angle of the cutting blade of the end mill were changed as shown in Table 1. The obtained nonlinearly processed pressure-sensitive adhesive layer-attached polarizing plate was subjected to the evaluations (1) to (3) above. Furthermore, the cutting blade used was subjected to the evaluation (4) above. Furthermore, the pressure-sensitive adhesive layer-attached polarizing plate after cutting was subjected to the evaluation (5) above. The results are shown in Table 1.

[0034] <Comparative Example 3> We tried to make an end mill with a rake angle of 50°, but were unable to do so.

[0035] [Table 1]

[0036] <Evaluation> As is clear from Table 1, according to the examples of the present invention, by setting the rake angle of the cutting blade of the end mill within a predetermined range, cracks, yellow bands, and glue chipping can be suppressed during cutting of an optical film (here, a polarizing plate with a pressure-sensitive adhesive layer). Furthermore, by setting the lower limit of the rake angle to a predetermined value or more, the sharpness of the blade can be further improved, resulting in further suppression of cracks, yellow bands, and glue chipping (comparison between Example 1 and Examples 2 to 6, and comparison between Example 7 and Examples 8 to 12). Furthermore, by setting the upper limit of the rake angle to a predetermined value or less, pockets of an appropriate size can be secured, resulting in reduced friction caused by cutting debris and further suppression of yellow bands (comparison between Example 6 and Examples 2 to 5, and comparison between Example 12 and Examples 8 to 11). Furthermore, by setting the cutting edge angle to a predetermined value or more, the life of the cutting blade can be extended. Furthermore, by setting the cutting edge angle to a predetermined value or less, the cutting sharpness can be improved, and as a result, fuzziness can be suppressed (comparison of Examples 4-6 with Examples 1-3, and comparison of Examples 10-12 with Examples 7-9). Furthermore, by setting the cutting edge angle within a predetermined range, fuzziness can be suppressed while maintaining a good lifespan of the cutting blade (suppression of cracks on the cutting edge) (comparison of Examples 3-4 with Examples 1-2 and 5-6, and comparison of Examples 9-10 with Examples 7-8 and 11-12). [Industrial Applicability]

[0037] 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]

[0038] α Rake angle β Clearance angle γ Edge angle δ Blade thickness 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. The cutting tool has a main body that rotates around a rotation axis and a cutting blade that protrudes from the main body and is configured as an outermost diameter, The cutting edge has a helix angle of 0°, a rake angle of 5° to 30°, a relief angle of 25° to 30°, and a cutting edge angle of 45° to 65°; The thickness of the cutting blade is 0.6 mm to 1.2 mm. End mill for cutting optical film.

2. The end mill for cutting optical films according to claim 1 , wherein the outer diameter is less than 10 mm.

3. The end mill for cutting optical films according to claim 1 or 2, wherein the cutting blade comprises sintered diamond.

4. A method for producing an optical film, comprising cutting an end surface of an optical film using the end mill for cutting an optical film according to claim 1 .

5. The method of claim 4 , wherein the optical film comprises a polarizing plate.

6. The method according to claim 5 , wherein the polarizing plate comprises a polarizer, a pressure-sensitive adhesive layer, a surface protective film, and a separator, and the peel strength of the separator is smaller than the peel strength of the surface protective film.

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