JP7848165B2 - compound cutting tools - Google Patents

Description

This invention relates to a composite cutting tool and a method for manufacturing a resin sheet using the same.

Various types of resin sheets are widely used depending on the application. After the resin sheet is cut to a predetermined shape, the outer edge may be subjected to finishing. In such finishing processes, cutting with an end mill is sometimes performed. End mill cutting is typically performed on workpieces consisting of multiple layers of resin sheets. Considering manufacturing efficiency, it is preferable to cut on thick workpieces. However, when cutting on thick workpieces, if the end mill is tilted, there may be areas where the end mill does not contact the workpiece. Therefore, there are problems such as the need to precisely adjust the holding position of the end mill on the machine tool, and the fact that the thickness of the workpiece must be kept below a certain value, resulting in insufficient manufacturing efficiency.

Japanese Patent Publication No. 2009-196015

This invention was made to solve the above-mentioned conventional problems, and its main objective is to provide a composite cutting tool capable of cutting even thick workpieces without defects, and a method for efficiently and simply manufacturing resin sheets using such a composite cutting tool.

A composite cutting tool according to an embodiment of the present invention comprises: a body that rotates about a rotation axis; a cutting blade provided on the outer circumference of the body, having a cutting edge, a rake face, and a relief face; and a polishing portion provided as a protrusion having a file-like surface on a part of the relief face of the cutting blade.
In one embodiment, the protrusion height H of the polishing portion is 0.1 μm to 150 μm. Here, the protrusion height H is expressed as H = R2 - R1, where R1 is the distance from the rotation axis to the cutting edge and R2 is the distance from the rotation axis to the surface of the protrusion.
In one embodiment, the distance L from the cutting edge to the wall surface facing the rotation direction of the polishing section and R1 satisfy the following formula (1):
L ≥ 0.1 × R1 ... (1).
In one embodiment, the composite cutting tool has a remaining material height Ph of 0.03 μm to 280 μm per pitch. Here, the pitch P is expressed by the following formula (2), and the remaining material height Ph per pitch is expressed by the following formula (3):
P=F/(S×N)...(2)
Ph=arcsin(P/2×R1)...(3)
In equation (2), F is the feed rate of the composite cutting tool (mm/min), S is the rotational speed of the composite cutting tool (rpm), and N is the number of cutting edges of the composite cutting tool.
In one embodiment, the polishing portion includes diamond particles.
In one embodiment, the composite cutting tool has a rake angle θ1 of -30° to 45° and a cutting edge angle θ2 of 20° to 100°. Here, the rake angle is the angle between a line connecting the rotation axis and the cutting edge and a line extending from the cutting edge along the rake face in a cross section perpendicular to the rotation axis; the cutting edge angle is the angle between a line extending from the cutting edge along the rake face and a line extending from the cutting edge along the relief face in a cross section perpendicular to the rotation axis.
According to another aspect of the present invention, a method for manufacturing a resin sheet is provided. The manufacturing method includes stacking a plurality of resin sheets to form a workpiece, and cutting the outer surface of the workpiece with the composite cutting tool described above.
In one embodiment, the thickness of the workpiece is 30 mm or more.
In one embodiment, the resin sheet includes an adhesive layer and/or a tack layer.
In one embodiment, the resin sheet includes an optical film. In one embodiment, the optical film includes a polarizer.

According to embodiments of the present invention, a composite cutting tool capable of cutting even thick workpieces without problems can be realized. By using such a composite cutting tool, a method for manufacturing resin sheets efficiently and simply can be realized.

This is a schematic plan view of a composite cutting tool according to one embodiment of the present invention, as seen from the direction of the rotation axis. Figure 1A is a schematic perspective view of the composite cutting tool. This is a schematic plan view of the main parts showing the detailed structure of a composite cutting tool according to one embodiment of the present invention. This is a schematic cross-sectional view of a key part illustrating the depth and pitch of the surface irregularities of the polished portion in a composite cutting tool according to one embodiment of the present invention. Figures 4(a) to 4(e) are schematic plan views of key parts showing modified examples of the polishing section in a composite cutting tool according to an embodiment of the present invention. This is a schematic perspective view illustrating the outline of the edge processing of a resin sheet in the manufacturing method according to an embodiment of the present invention. Figures 6(a) and 6(b) are schematic plan views illustrating an example of edge processing when the resin sheet contains a polarizer in the manufacturing method according to an embodiment of the present invention.

The following describes specific embodiments of the present invention with reference to the drawings, but the present invention is not limited to these embodiments. Note that the drawings are schematic representations for clarity, and the ratios of lengths, widths, thicknesses, angles, etc., shown in the drawings may differ from actual dimensions. Furthermore, in order to facilitate understanding of detailed shapes and the meaning of symbols in the drawings, the shapes may not precisely correspond between drawings.

A. Compound Cutting Tool Figure 1A is a schematic plan view of a compound cutting tool according to one embodiment of the present invention as seen from the direction of the rotation axis; Figure 1B is a schematic perspective view of the compound cutting tool of Figure 1A. The illustrated compound cutting tool 20 includes: a main body 22 that rotates about a rotation axis 21; a cutting blade 23 provided on the outer circumference of the main body 22, having a cutting edge 23a, a rake face 23b, and a relief face 23c; and a polishing portion 24 provided as a protrusion having a file-like surface on a part of the relief face of the cutting blade 23.

The composite cutting tool 20 is integrally formed from a hard metal material such as cemented carbide or high-speed tool steel, and has a roughly cylindrical shaft shape centered on the rotation axis 21. In the illustrated example of the composite cutting tool, one end (the upper end in the illustrated example) where no cutting edge is formed is a cylindrical shank portion 25. Both ends of the composite cutting tool may also be shank portions. The shank portion 25 of the composite cutting tool is held on the spindle of a machine tool such as a machining center, and rotated around the rotation axis 21, causing the cutting edge that contacts the workpiece to cut the workpiece. When one end is a shank portion, the composite cutting tool is held in a cantilevered position on the machine tool; when both ends are shank portions, the composite cutting tool is held in a double-supported position on the machine tool.

As described above, the cutting blade 23 is provided on the outer circumference of the main body 22. The cutting blade 23 has a cutting edge 23a, a rake face 23b, and a relief face 23c. The rake face 23b is a wall surface facing the rotation direction T of the cutting blade 23. In the illustrated example, the rake face 23b defines a circular arc that is concave on the opposite side of the rotation direction T in a cross section perpendicular to the rotation axis, and extends toward the opposite side of the rotation direction T as it approaches the outer circumference. The relief face 23c is the outer surface of the cutting blade 23 and intersects with the rake face 23b to define the cutting edge 23a. The relief face 23c is also substantially the outer surface of the composite cutting tool 20. The relief face 23c is preferably roughened. Any appropriate roughening treatment can be used. A typical example is blasting. By roughening the relief surface, when the workpiece (typically a resin sheet) contains an adhesive layer and/or bonding layer, the adhesion of the adhesive and/or bonding agent to the cutting blade is suppressed, and as a result, blocking can be suppressed. In this specification, "blocking" refers to the phenomenon where resin sheets in a workpiece adhere to each other due to the adhesive on their edges, and the adhesive residue adhering to the edges contributes to the adhesion between the resin sheets.

The number of cutting edges (the number of edges in a composite cutting tool) can be any appropriate number depending on the purpose. The number of edges may be one, two, three, four (as shown in the illustrated example), or five or more. Preferably, the number of edges is two or four. With such a configuration, the rigidity of the edges is ensured, and pockets are secured to effectively discharge chips. When there are multiple edges (two or more), the multiple cutting edges may be formed at equal intervals in the circumferential direction, as shown in the illustrated example, or they may be formed at unequal intervals in the circumferential direction (not shown). Furthermore, when there are multiple edges (two or more), the rotational trajectories of the multiple cutting edges around the rotation axis 21 are typically aligned.

The cutting edge may have a helix angle Θ of 0° or a specific helix angle, depending on the purpose. That is, the cutting edge may be a straight edge or a helical edge, depending on the purpose. The helix angle Θ of the cutting edge may be, for example, 0° to 65°, 10° to 55°, 20° to 50°, or 30° to 45°. In this specification, "helix angle of 0°" means that the cutting edge 23a extends in a direction substantially parallel to the rotation axis 21. Note that "0°" means substantially 0° and includes cases where there is a slight angle of twist due to machining errors, etc.

Figure 2 is a schematic plan view of the main parts showing the detailed structure of the composite cutting tool 20. As shown in Figure 2, the rake angle θ1 of the cutting blade is preferably -30° to 45°, more preferably -10° to 30°, and even more preferably 0° to 20°; the cutting edge angle θ2 is preferably 20° to 100°, more preferably 30° to 90°, and even more preferably 45° to 80°. When the rake angle θ1 and cutting edge angle θ2 of the cutting blade are within this range, the machined surface by the cutting blade is smoothed, which has the advantage of making subsequent machining by the polishing part even more uniform. In this specification, "rake angle" is the angle between the line connecting the rotation axis 21 and the cutting edge 23a and the line extending from the cutting edge 23a along the rake face 23b in a cross-section perpendicular to the rotation axis; "cutting edge angle" is the angle between the line extending from the cutting edge 23a along the rake face 23b and the line extending from the cutting edge 23a along the relief face 23c in a cross-section perpendicular to the rotation axis. Note that if the rake face is defined as an arc in a cross-section perpendicular to the rotation axis as shown in the illustrated example, the line extending along the rake face is the tangent to the rake face extending from the cutting edge. Furthermore, the relief face is the outer circumferential surface of the cutting edge and is defined as an arc in a cross-section perpendicular to the rotation axis; therefore, the line extending along the relief face is essentially the tangent to the relief face extending from the cutting edge. Furthermore, a negative (-) rake angle means that, in a cross-section perpendicular to the axis of rotation, the straight line extending from the cutting edge along the rake plane is located on the T-side of the rotation direction (left side in Figure 2) than the straight line connecting the axis of rotation and the cutting edge.

In the embodiment of the present invention, as described above, a polishing portion 24 is formed on a part of the relief surface 23c. The polishing portion 24 is provided as a protrusion having a file-like surface. The polishing portion 24 (substantially its surface) typically contains diamond particles. With such a configuration, a file-like surface with appropriate surface roughness and surface hardness can be formed. The polishing portion 24 can typically function as a rotating grinding wheel. When multiple cutting blades are provided, the polishing portion is typically provided on each cutting blade. That is, typically, the number of cutting blades and the number of polishing portions coincide. Furthermore, the polishing portion is typically provided at the corresponding position on each cutting blade. When multiple polishing portions are formed, similar to the case of cutting blades, the rotational trajectories of the multiple polishing portions around the rotation axis 21 are typically aligned with each other.

The protrusion height H of the polishing portion 24 is preferably 0.1 μm to 100 μm, more preferably 1 μm to 50 μm, and even more preferably 5 μm to 30 μm. When the protrusion height H of the polishing portion is within this range, there is an advantage that a uniform processed surface can be obtained without the resin sheet melting or being damaged on the processed surface by the polishing portion. Here, the protrusion height H of the polishing portion is expressed as H = R2 - R1. R1 is the distance from the rotation axis 21 to the cutting edge 23a, and R2 is the distance from the rotation axis 21 to the surface of the polishing portion (protrusion) 24. R1 is also the radius of the rotational trajectory of the cutting blade 23, and R2 is also the radius of the rotational trajectory of the polishing portion 24. Therefore, the protrusion height H of the polishing portion is the difference between the rotational radius of the polishing portion and the rotational radius of the cutting blade. In the illustrated example, the polishing section may have walls on both sides extending radially with respect to the rotation axis in a cross-section perpendicular to the rotation axis, or it may extend outward substantially perpendicular to the outer circumference (relief surface) of the cutting edge. Furthermore, in the illustrated example, the surface of the polishing section is substantially flat in a cross-section perpendicular to the rotation axis and approximately coincides with the rotational trajectory of the polishing section.

The width W (mm) of the polishing portion 24 along the outer circumference of the composite cutting tool 20 is preferably R1 (mm) or less, more preferably 0.5 × R1 (mm) or less, and even more preferably 0.3 × R1 (mm) or less. The lower limit of the polishing portion width W may be, for example, 0.01 × R1 (mm). When the polishing portion width W is within this range, there is an advantage in that clogging of the polishing portion with cutting debris is reduced, and the machining quality can be maintained consistently over a long period of time. In other words, the above advantages can be obtained by adjusting the width of the polishing portion according to the outer diameter of the composite cutting tool.

The position where the polishing portion 24 is provided on the relief surface 23c of the cutting blade 23 can be appropriately set according to the purpose. In one embodiment, the distance L (mm) from the cutting edge 23a to the wall surface of the polishing portion 24 facing the direction of rotation and the distance R1 (mm) from the rotation axis 21 to the cutting edge 23a satisfy the following formula (1):
L ≥ 0.1 × R1 ... (1).
The distance L is preferably 0.1 × R1 to 1.0 × R1, and more preferably 0.15 × R1 to 0.8 × R1. This relationship between distance L and distance R1 has the advantage of reducing debris accumulation on the polished surface and maintaining consistent machining quality over a long period. In other words, the above advantages can be obtained by defining the position where the polished portion is provided in this relationship according to the outer diameter of the composite cutting tool.

The surface roughness of the polishing section 24 surface is preferably #60 or higher, more preferably #100 or higher, and even more preferably #200 or higher, as expressed by the grit number of the file blade. The surface roughness may also preferably be #2000 or lower, more preferably #1200 or lower, and even more preferably #800 or lower, as expressed by the grit number of the file blade. When the surface roughness of the polishing section is within this range, the resin sheet does not melt or break on the processed surface due to the polishing section, and there is less clogging of the polishing section with cutting debris, which has the advantage of maintaining consistent processing quality over a long period of time. Note that a lower grit number of the file blade indicates a coarser grit. The grit number can be adjusted by the amount and size of the diamond particles, etc.

Figure 3 is a schematic cross-sectional view of the main part illustrating the uneven shape of the file-like surface of the polishing section 24. The depth D of the unevenness on the file-like surface of the polishing section 24 is, for example, 1 μm to 120 μm. The lower limit of the depth D is preferably 5 μm or more, more preferably 10 μm or more. The upper limit of the depth D is preferably 50 μm or less, more preferably 35 μm or less. The pitch p of the unevenness on the file-like surface of the polishing section 24 is, for example, 1 μm to 250 μm. The lower limit of the pitch p is preferably 5 μm or more, more preferably 10 μm or more. The upper limit of the pitch p is preferably 100 μm or less, more preferably 60 μm or less. With this configuration of unevenness on the surface of the polishing section, the resin sheet does not melt or break on the processed surface by the polishing section, and there is less clogging of cutting debris in the polishing section, allowing for consistent processing quality over a long period of time.

The outer diameter of the composite cutting tool can be appropriately set depending on the purpose. More specifically, the outer diameter of the composite cutting tool is preferably 0.5 mm to 30 mm, more preferably 0.8 mm to 25 mm, and even more preferably 1 mm to 20 mm. If the outer diameter of the composite cutting tool is within this range, it can be machined without problems using a machine tool capable of general end milling. Note that the outer diameter of the composite cutting tool is twice the above R2 (i.e., the diameter of the rotational trajectory of the grinding section).

In one embodiment, the remaining material height Ph for each pitch of the composite cutting tool is preferably 0.03 μm to 280 μm, more preferably 0.1 μm to 100 μm, and even more preferably 0.2 μm to 10 μm. When the remaining material height Ph is within this range, there is an advantage that a uniform machined surface can be obtained without the resin sheet melting or being damaged on the machined surface by the polishing portion. Here, the pitch P is represented by the following formula (2), and the remaining material height Ph for each pitch is represented by the following formula (3):
P=F/(S×N)...(2)
Ph=arcsin(P/2×R1)...(3)
In equation (2), F is the feed rate of the composite cutting tool (mm/min), S is the rotational speed of the composite cutting tool (rpm), and N is the number of cutting edges of the composite cutting tool.

The shape of the polishing section 24 as viewed from the direction of the rotation axis (the outer shape defining the surface of the polishing section) can be any appropriate shape depending on the purpose, etc. Figures 4(a) to 4(e) are schematic plan views of the main parts showing typical modified examples of the polishing section. In the polishing section of Figure 4(a), in a cross-section perpendicular to the rotation axis, the surface facing away from the direction of rotation is substantially flat along the outer circumference from the wall surface facing away from the direction of rotation to a predetermined portion facing the direction of rotation, and the protruding height gradually decreases from that predetermined portion to the wall surface facing the direction of rotation. In the polishing section of Figure 4(b), in a cross-section perpendicular to the rotation axis, the protruding height gradually decreases from the wall surface facing away from the direction of rotation to the wall surface facing the direction of rotation. In the polishing section of Figure 4(c), in a cross-section perpendicular to the axis of rotation, the protrusion height gradually decreases at a first inclination angle from the wall surface facing the opposite direction of rotation to a predetermined portion in the direction of rotation, and from that predetermined portion to the wall surface facing the direction of rotation, the protrusion height gradually decreases at a second inclination angle greater than the first inclination angle. In the polishing section of Figure 4(d), in a cross-section perpendicular to the axis of rotation, the wall surface facing the direction of rotation extends in the opposite direction of rotation as it moves outward (towards the protruding side). In the polishing section of Figure 4(e), in a cross-section perpendicular to the axis of rotation, the intersection of the line defining the surface of the polishing section and the line defining the wall surface facing the direction of rotation is chamfered. These modifications may be combined as appropriate. For example, in the modified forms shown in Figures 4(a) to 4(d), the intersection of the line defining the polishing surface and the line defining the wall surface facing the direction of rotation may be chamfered; also, for example, in the modified forms shown in Figures 4(a) to 4(c), the wall surface facing the direction of rotation may extend in the opposite direction to the direction of rotation as it moves outward (towards the protruding side). These modified forms can be appropriately selected depending on the protrusion height H of the polishing part, the position (distance L) where the polishing part is provided, the remaining material height Ph, etc. For example, the modified form in Figure 4(b) may be useful when the protrusion height H of the polishing part is large; the modified form in Figure 4(c) may be useful when the distance L is large; the modified form in Figure 4(d) may be useful when the remaining material height Ph is small; and the modified form in Figure 4(e) may be useful when the remaining material height Ph is large. Furthermore, the modified form in Figure 4(a) may be useful when the protrusion height H, distance L, and remaining material height Ph are all of intermediate size.

B. Resin Sheets Any suitable resin sheet that can be subjected to edge processing can be used as the resin sheet. The resin sheet may be a film composed of a single layer or a laminate. Specific examples of resin sheets include optical films, heat insulating sheets, resin windows, surface protection films, fiber-reinforced plastic (FRP) sheets, packaging films, and food films. In one embodiment, the resin sheet includes an optical film. Optical films require more precise edge processing than other resin sheets or films, and the effects of the embodiments of the present invention are particularly noticeable in this regard. Specific examples of optical films include polarizers, phase difference films, polarizing plates (typically laminates of polarizers and protective films), conductive films for touch panels, surface treatment films, and laminates obtained by appropriately laminating these according to their purpose (e.g., anti-reflective circular polarizers, polarizers with conductive layers for touch panels). In one embodiment, the resin sheet includes an adhesive layer and/or a tack layer. Therefore, the resin sheet may be, for example, an optical film including an adhesive layer and/or a tack layer. In optical films including an adhesive layer and/or a tack layer, the effects of the embodiments of the present invention become even more pronounced.

C. Method for Manufacturing Resin Sheets Below, a method for manufacturing a resin sheet using a polarizing plate with an adhesive layer will be described as an example. It will be obvious to those skilled in the art that the planar shape of the polarizing plate with an adhesive layer is not limited to the planar shape shown in the illustration. It will also be obvious to those skilled in the art that the embodiments of the present invention can be applied to any suitable resin sheet other than a polarizing plate with an adhesive layer. That is, the embodiments of the present invention can be applied to the manufacture of any suitable resin sheet having any suitable shape.

C-1. Formation of the Workpiece Figure 5 is a schematic perspective view illustrating the outline of edge processing of a resin sheet (here, a polarizing plate with an adhesive layer) in a manufacturing method according to an embodiment of the present invention. A workpiece W is shown in this figure. As shown in Figure 5, the workpiece W is formed by stacking multiple polarizing plates with adhesive layers. When forming the workpiece, the polarizing plates with adhesive layers are typically cut from a raw roll to any appropriate size and shape. Specifically, the polarizing plates with adhesive layers may be cut into a rectangular shape, into a shape similar to a rectangular shape, or into an appropriate shape depending on the purpose (for example, a circle). In the illustrated example, the polarizing plates with adhesive layers are cut into a rectangular shape, and the workpiece W has outer peripheral surfaces (cutting surfaces) 1a, 1b that face each other and outer peripheral surfaces (cutting surfaces) 1c, 1d that are perpendicular to them. Cutting is performed by any appropriate means. Specific examples of cutting means include punching with a punching blade (for example, a Thomson blade) and laser irradiation. In one embodiment, a release liner may be temporarily attached to the surface of the adhesive layer of the polarizing plate with an adhesive layer, and/or a surface protective film may be temporarily attached to the surface of the polarizing plate with an adhesive layer that is opposite to the adhesive layer.

The total thickness of the workpiece is, for example, 3 mm or more, preferably 5 mm or more, more preferably 10 mm or more, even more preferably 30 mm or more, and particularly preferably 60 mm or more. According to the embodiments of the present invention, by using a composite cutting tool as described in Section A above, even such thick workpieces can be cut (typically, end-face machining) without problems. As a result, resin sheets (here, polarizing plates with adhesive layers) can be manufactured efficiently and simply. On the other hand, the total thickness of the workpiece is preferably 150 mm or less, more preferably 100 mm or less. The upper limit of the total thickness of the workpiece may be mainly due to constraints on the configuration of the machine tool. It should be noted that while the effects of the embodiments of the present invention are particularly pronounced when the workpiece is thick, it goes without saying that it can also be implemented without problems even when the workpiece is of normal thickness (e.g., 10 mm or less).

The workpiece W is preferably clamped from above and below by clamping means (not shown). The clamping means (e.g., a jig) may be made of a soft material or a hard material. If made of a soft material, its hardness (JIS A) is preferably 60° to 80°. If the hardness is too high, indentations from the clamping means may remain. If the hardness is too low, deformation of the jig may cause misalignment, resulting in insufficient cutting accuracy.

C-2. End Face Machining with a Compound Cutting Tool Next, a predetermined position on the outer circumferential surface of the workpiece W is cut (end face machining) using a compound cutting tool 20. Typically, the compound cutting tool 20 is held in a machine tool (not shown) and rotated at high speed around its rotation axis, and is used by bringing the cutting blade into contact with the outer circumferential surface of the workpiece W while being fed in a direction intersecting the rotation axis. In other words, cutting is typically performed by bringing the cutting blade of the compound cutting tool into contact with the outer circumferential surface of the workpiece W and cutting into it. Furthermore, according to the embodiment of the present invention, following the cutting by the cutting blade, polishing (cutting) is performed by a polishing section whose rotational trajectory radius is larger than that of the cutting blade. By performing additional cutting by such a polishing section, end face machining can be performed without problems even with thick workpieces (more specifically, without any uncut areas due to the cutting blade not contacting the workpiece, and uniformly across the entire thickness direction of the workpiece). Furthermore, cracks in the adhesive-coated polarizing plate (typically a polarizer), blade contamination of the cutting blade, and blocking can be suppressed. In particular, it can effectively suppress the progression of cracks over time. In addition, if a release liner and/or surface protective film are temporarily attached to the polarizing plate with an adhesive layer, their lifting can be suppressed. Here, cutting blade contamination refers to the phenomenon in which the adhesive from the adhesive layer adheres to the cutting blade, causing the cutting performance (processing performance) to decrease beyond the acceptable range. Blocking is as described above.

The conditions for end-face machining using a composite cutting tool can be appropriately set according to the type of resin sheet, the desired shape, etc. For example, the rotational speed (rotational speed) of the composite cutting tool is preferably 100 rpm to 50,000 rpm, more preferably 1,000 rpm to 30,000 rpm, and even more preferably 2,000 rpm to 20,000 rpm. Also, for example, the feed rate of the composite cutting tool is preferably 100 mm/min to 5,000 mm/min, more preferably 200 mm/min to 4,000 mm/min, and even more preferably 300 mm/min to 3,000 mm/min. If the rotational speed and feed rate of the composite cutting tool are within these ranges, end-face machining can be performed without problems even on thick workpieces. The number of cuts performed on the end face of the workpiece (resin sheet) using the composite cutting tool may be one, two, three, or more cuts.

A composite cutting tool may be held in a cantilevered or double-supported position on the machine tool. Holding it in a cantilevered position facilitates the movement of the composite cutting tool in the plane and vertical directions. As a result, non-linear cutting (machining) becomes easier when required. Furthermore, the cantilevered position makes the composite cutting tool easier to manufacture. On the other hand, holding it in a double-supported position suppresses play in the cutting surface (irregularities when viewing the cutting surface from the side). Additionally, holding it in a double-supported position reduces the stress on the cutting edge of the composite cutting tool during cutting. As a result, the durability of the composite cutting tool can be improved, and therefore, the stability and reliability of end-face machining using the composite cutting tool can be improved.

The edge processing of the resin sheet using a composite cutting tool may be performed on the entire outer surface of the resin sheet or on a portion of the outer surface. When the resin sheet contains a polarizer (for example, when the resin sheet is a polarizing plate with an adhesive layer as shown in the illustration), the edge processing using the composite cutting tool is preferably performed only in the direction of the polarizer's absorption axis. Figures 6(a) and 6(b) are schematic plan views illustrating an example of a specific procedure for edge processing of a resin sheet containing a polarizer (here, a polarizing plate with an adhesive layer). In this embodiment, the polarizing plate with an adhesive layer is typically cut into a rectangular shape, as shown in Figure 6(a), such that the absorption axis A of the polarizer is in the direction of the shorter side.

Next, as shown in Figure 6(a), the end face of the short side is machined using an end mill. The end mill can be any appropriate configuration depending on the purpose and the type of resin sheet including the polarizer. The end mill may have the same configuration as a composite cutting tool except that it does not have a grinding section, or it may have a completely different configuration overall (for example, outer diameter, number of teeth, helix angle, rake angle, cutting edge angle). The conditions for end face machining with the end mill can be appropriately set depending on the purpose, etc. The outer diameter of the end mill may be, for example, 0.5 mm to 30 mm, or for example, 1 mm to 20 mm. The rotational speed (number of rotations) of the end mill may be, for example, 100 rpm to 50,000 rpm, or for example, 1,000 rpm to 35,000 rpm, or for example, 2,000 rpm to 20,000 rpm. Furthermore, the feed rate of the end mill may be, for example, 100 mm/min to 5,000 mm/min, or for example, 300 mm/min to 3,000 mm/min. The number of cuts made to the short edge of the workpiece (a resin sheet containing a polarizer, in this case a polarizing plate with an adhesive layer) by the end mill may be one, two, three, or more passes. The illustrated example schematically shows two passes for roughing and finishing. Roughing and finishing may be performed under the same conditions or under different conditions.

Next, as shown in Figure 6(b), the long edge is machined using a composite cutting tool. The configuration of the composite cutting tool is as described in Section A above, and the conditions for edge machining using the composite cutting tool are as described above. By performing edge machining in this manner, even thick workpieces can be machined without problems. Furthermore, cracks in the adhesive-coated polarizing plate (typically the polarizer), blade contamination of the cutting edge, and blocking can be suppressed. In addition, if a release liner and/or surface protective film are temporarily attached to the adhesive-coated polarizing plate, their lifting can be suppressed. When the entire outer circumference of an adhesive-coated polarizing plate is edge-machined with an end mill, unmachined material often occurs due to the cutting edge not contacting the workpiece. When the entire outer circumference of an adhesive-coated polarizing plate is edge-machined with a composite cutting tool, the machined edge parallel to the absorption axis becomes vulnerable to impact due to thermal shock, and cracks may occur. However, if the resin sheet does not contain a polarizer, this problem does not substantially occur even if the entire outer circumference of the resin sheet is edge-machined with a composite cutting tool.

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:

(1) Cracks The polarizing plates with adhesive layers obtained in the examples, comparative examples, and reference examples were attached to a glass plate (thickness 1.1 mm) via the adhesive layer to be used as test samples.
(1-1) Cracking by heat shock test The above test samples were subjected to a heat shock test in which the samples were held at -40°C for 30 minutes and then at 85°C for 30 minutes, repeated 300 times. The state of crack formation after the test was observed using an optical microscope (magnification 5x). Specifically, the number and length (μm) of the cracks were examined and evaluated according to the following criteria.
A: Number of cracks is 10 or less, and the maximum length is 500 μm or less B: Number of cracks is 10 or less, but the maximum length exceeds 500 μm C: Number of cracks exceeds 10, and the maximum length exceeds 500 μm (1-2) Cracking by heating test The above test samples were subjected to a heating test at 105°C for 1000 hours and evaluated in the same manner as in (1-1).

(2) Lifting The amount of lifting of the surface protective film and release liner in the adhesive-coated polarizing plates obtained in the examples, comparative examples, and reference examples was measured using a magnifying glass or microscope. The maximum amount of lifting in one workpiece was defined as the amount of lifting and evaluated according to the following criteria.
A: Buoyancy of 300 μm or less B: Buoyancy of more than 300 μm but 500 μm or less C: Buoyancy of more than 500 μm

(3) Blade contamination The state of contamination by adhesive on the cutting blades of the composite cutting tool after end face machining in the example, and on the cutting blades of the end mill after end face machining in the comparative example and reference example was observed and evaluated according to the following criteria.
A: Substantially no contamination was observed. B: Contamination was observed, but no problems occurred during processing. C: Significant contamination was observed, and problems occurred during processing.

(4) Blocking The condition of the workpieces after end face machining in the examples, comparative examples and reference examples was observed and evaluated according to the following criteria.
A: Separation from the workpiece into individual polarizing plates with adhesive layers was easy. B: Separation from the workpiece into individual polarizing plates with adhesive layers was possible, but the separation operation was difficult. C: The workpiece was completely block-shaped, making separation into individual polarizing plates with adhesive layers impossible.

<Example 1>
A polarizing plate with an adhesive layer was fabricated using a conventional method, having the following configuration from the viewing side: surface protective film (60 μm) / cycloolefin-based protective film (47 μm) / polarizer (5 μm) / cycloolefin-based protective film (24 μm) / adhesive layer (20 μm) / release liner. The surface protective film used was a PET substrate (50 μm) / adhesive layer (10 μm). This polarizing plate with an adhesive layer was punched out to a size of 5.7 inches (approximately 140 mm in length and 65 mm in width). Here, the punching was performed so that the absorption axis direction of the polarizer was in the horizontal direction (short side direction). Multiple punched polarizing plates with adhesive layers were stacked to form a workpiece. The total thickness of the workpiece was 45 mm. With the obtained workpiece clamped (jig), the end face was machined on the short side (along the absorption axis direction of the polarizer) using an end mill. Specifically, an end mill with an outer diameter of 9 mm, two blades, and a helix angle of 45° was used to perform two end face machining processes on each short side: rough machining and finish machining. The amount of material removed during rough machining was 0.2 mm, and the amount of material removed during finish machining was 0.1 mm. In both rough machining and finish machining, the feed rate of the end mill was 1,000 mm/min and the rotational speed was 35,000 rpm. Next, the end face of the long side (in the direction perpendicular to the absorption axis of the polarizer) was machined using a composite cutting tool according to an embodiment of the present invention. The composite cutting tool used was one in which a polishing section with a protrusion height of 20 μm was provided on the relief surface of the cutting edge of the end mill. The protrusion surface of the polishing section was file-like (or rotary grinding wheel-like) containing diamond particles. The distance L from the cutting edge of the cutting edge to the wall surface of the polishing section facing the rotational direction was 0.9 mm, and the relationship L = 0.167 × R1 was found with respect to the distance R1 from the rotational axis to the cutting edge. The end face machining of the long side was performed twice under identical conditions. Specifically, the feed rate of the composite cutting tool was 1,000 mm/min, the rotational speed was 8,000 rpm, and the amount of material removed per pass was 0.1 mm. In this way, a polarizing plate with an adhesive layer was obtained. In the end face machining, it was not necessary to precisely adjust the holding state of the end mill and composite cutting tool on the machine tool, and uniform cutting was achieved throughout the entire thickness direction of the workpiece. The obtained polarizing plate with an adhesive layer was evaluated according to (1) to (4) above. The results are shown in Table 1.

<Example 2>
A polarizing plate with an adhesive layer was obtained in the same manner as in Example 1, except that the thickness of the workpiece was set to 60 mm. In the end face machining, it was not necessary to precisely adjust the holding state of the end mill and composite cutting tool on the machine tool, and uniform cutting was achieved throughout the entire thickness direction of the workpiece. The obtained polarizing plate with an adhesive layer was evaluated in the same manner as in Example 1. The results are shown in Table 1.

<Comparative Example 1>
The entire outer surface of a workpiece formed in the same manner as in Example 1 was machined using only an end mill. Specifically, the entire outer surface of the workpiece was subjected to two end-face machining processes, rough and finish, in a single continuous motion. The conditions for rough and finish machining were the same as in Example 1. Next, only the long sides were machined using a rotary grinding wheel (#400). The rotation speed of the rotary grinding wheel was 1,000 rpm, and the feed rate was 500 mm/min. In this way, a polarizing plate with an adhesive layer was obtained. During end-mill end-face machining, cutting defects occurred in a part of the workpiece (the upper or lower end in the thickness direction). The cutting defects were particularly pronounced on the long sides. The obtained polarizing plate with an adhesive layer was evaluated in the same manner as in Example 1. The results are shown in Table 1.

<Reference example 1>
A polarizing plate with an adhesive layer was obtained in the same manner as in Comparative Example 1, except that the thickness of the workpiece was set to 15 mm. No cutting defects were observed during end face machining. The obtained polarizing plate with an adhesive layer was evaluated in the same manner as in Example 1. The results are shown in Table 1.

<Evaluation>
As is clear from Table 1, the composite cutting tool of the embodiment of the present invention can cut even thick workpieces without any problems.

The composite cutting tool according to the embodiment of the present invention can be suitably used in the manufacture of resin sheets (particularly in edge processing during manufacturing). The resin sheet may be, for example, an optical film.

W Workpiece 20 Compound cutting tool 21 Rotating shaft 22 Body 23 Cutting blade 23a Cutting edge 23b Rake face 23c Relief face 24 Polishing section

Claims (4)

A composite cutting tool for processing the edge faces of optical films,
A main body that rotates around a rotation axis;
A cutting blade having a cutting edge, a rake face, and a relief face is provided on the outer circumference of the main body;
A polishing portion provided as a protrusion integrally formed with the main body on a part of the relief surface of the cutting blade, having a file-like surface;
It has,
The cutting blade is a twisted blade,
The cutting blade is configured to cut the edge of the optical film by contacting and rotating against the outer surface of a workpiece consisting of multiple stacked optical films.
A composite cutting tool for processing the edge face of an optical film , wherein the polishing portion is formed as a relief surface over the entire area along the rotation axis of the cutting blade . The polishing section is configured such that the file-like surface rotates in a circular orbit when the main body rotates around its axis of rotation, as described in claim 1, for the composite cutting tool for processing the edge face of an optical film. The composite cutting tool for processing the edge face of an optical film according to claim 2, wherein the depth D of the unevenness of the abrasive surface is 1 μm to 120 μm, and the pitch p of the unevenness is 1 μm to 250 μm. The composite cutting tool for processing the edge face of an optical film according to claim 2, wherein the surface roughness of the abrasive surface is between #60 and #2000 as the grit number of the abrasive blade.