TWI851658B - Method for manufacturing optical thin film - Google Patents

Abstract

The present invention provides a method for manufacturing an optical film, which can suppress the generation of unnecessary recesses in the end portion even when an end milling cutter is used.

A method for manufacturing a cut optical film comprises the following steps: overlapping a plurality of optical films to form a workpiece; and cutting the workpiece with an end milling cutter, wherein the manufacturing method comprises the following steps: when cutting starts, the end milling cutter moves in a direction inclined to the workpiece in a plane viewing angle while the end milling cutter contacts the workpiece; or when cutting ends, the end milling cutter moves in a direction inclined to the workpiece in a plane viewing angle while the end milling cutter moves away from the workpiece.

Description

Method for manufacturing optical thin films

The present invention relates to a method for manufacturing an optical film.

In image display devices such as mobile phones and notebook personal computers, various optical films (such as polarizing plates) are used in order to realize image display and/or improve the performance of the image display. In recent years, it has been highly expected to use optical laminated bodies in dashboards of automobiles, smart watches, and the like, and it is also desirable to process the shape of the optical laminated bodies into a desired shape. When processing like this, the end face is sometimes cut with an end mill. In the cutting process performed by the end mill, on the one hand, high-precision cutting can be performed, but on the other hand, there is the following situation: when the end mill is brought into contact with the work surface at the beginning of cutting, a small amount of In the recessed part, or at the end of cutting, when the end mill is removed from the work surface, a slight drop or fluff will occur. In recent years, optical films have been increasingly required to have higher shape accuracy, and to suppress the generation of such concave portions, steps, and fuzz.

Prior art literature Patent Literature

Patent document 1: Japanese Patent Publication No. 2007-187781

Patent document 2: Japanese Patent Publication No. 2018-022140

The present invention is made to solve the above-mentioned previous problems, and its main purpose is to provide a method for manufacturing an optical film, which can suppress the generation of unnecessary concave parts, step differences, fuzz, etc. at the cutting start point and/or cutting end point even when using an end mill.

A method for manufacturing an optical film by cutting includes the following steps: overlapping a plurality of optical films to form a workpiece; and cutting the workpiece with an end milling cutter. The manufacturing method also includes the following steps: when cutting starts, the end milling cutter moves in a direction inclined to the workpiece in a plane viewing angle while the end milling cutter contacts the workpiece; and/or when cutting ends, the end milling cutter moves in a direction inclined to the workpiece in a plane viewing angle while the end milling cutter moves away from the workpiece.

In one embodiment, the travel trajectory ts of the end milling cutter at the start of cutting is curved.

In one embodiment, the radius of curvature of the travel trajectory ts of the end milling cutter at the start of the cutting is greater than 1/2 of the outer diameter of the end milling cutter.

In one embodiment, the curvature radius of the travel trajectory ts of the end milling cutter at the start of the cutting is larger than the outer diameter of the end milling cutter.

In one embodiment, the travel trajectory te of the end milling cutter at the end of the cutting is curved.

In one embodiment, the curvature radius of the travel trajectory te of the end milling cutter at the end of the cutting is greater than 1/2 of the outer diameter of the end milling cutter.

In one embodiment, the curvature radius of the travel trajectory te of the end milling cutter at the end of the cutting is larger than the outer diameter of the end milling cutter.

In one embodiment, the speed of the end milling cutter when the end milling cutter contacts the workpiece is slower than the feed speed of the end milling cutter when the end milling cutter cuts the outer peripheral surface of the workpiece.

In one embodiment, the speed of the end milling cutter when the end milling cutter is moved away from the workpiece is slower than the feed speed of the end milling cutter when the end milling cutter is cutting the outer peripheral surface of the workpiece.

In one embodiment, cutting is performed on the entire circumference of the outer peripheral surface of the workpiece, and the cutting start point a and the cutting end point b are set at different positions, and the cutting end point b is set closer to the front of the end milling cutter's travel direction than the cutting start point a.

In one embodiment, the outer diameter of the end milling cutter is less than 10 mm.

In one embodiment, the helix angle of the end mill is 0°.

According to the present invention, a method for manufacturing an optical film can be provided, which can suppress the generation of unnecessary recesses, steps, fuzz, etc. at the cutting start point and/or cutting end point even when using an end mill.

1,1’: Workpiece

1a, 1b, 1c, 1d: peripheral surface (cutting surface)

11: Hole

20: End milling cutter

21: Rotation axis

22: Cutting edge

22a: Blade tip

22b: Slope

22c: Clearance surface

A: Side

a: Cutting starting point

B,B’: tangent

b: Cutting end point

te: The path of the end milling cutter at the end of cutting

ts: The path of the end milling cutter at the beginning of cutting

ue: Tangent of the walking trajectory at the cutting end point

us: Tangent of the walking trajectory at the starting point of cutting

x: The travel angle of the end milling cutter at the beginning of cutting

y: The travel angle of the end milling cutter at the end of cutting

FIG1 is a schematic three-dimensional diagram for illustrating an example of cutting processing of the optical film of the present invention.

FIG2 is a schematic three-dimensional diagram for explaining an example of an end milling cutter used in the cutting process in the optical film manufacturing method of the present invention.

FIG. 3(a) is a schematic cross-sectional view viewed from the axial direction for illustrating another example of a cutting mechanism used in the cutting process in the optical film manufacturing method of the present invention; FIG. 3(b) is a schematic three-dimensional view of the cutting mechanism of FIG. 3(a).

Figures 4(a) and 4(b) are schematic plan views illustrating a cutting process according to one embodiment of the present invention.

Figures 5(a) and 5(b) are schematic plan views illustrating a cutting process according to one embodiment of the present invention.

FIG6 is a schematic plan view of a workpiece in one embodiment of the present invention.

Figures 7(a) and 7(b) are schematic plan views illustrating a cutting process according to one embodiment of the present invention.

Figures 8(a) and 8(b) are schematic plan views illustrating a cutting process according to one embodiment of the present invention.

The form used to implement the invention

Although the specific implementation forms of the present invention are described below with reference to the drawings, the present invention is not limited to these implementation forms. Furthermore, the drawings are shown schematically for ease of viewing. In addition, the length, width, thickness, etc. ratios and angles in the drawings are different from the actual ones.

The manufacturing method of the optical film processed by cutting of the present invention includes the following steps: overlapping multiple sheets of optical film to form a workpiece; and cutting the outer peripheral surface of the workpiece with an end milling cutter.

FIG1 is a schematic three-dimensional diagram for explaining a cutting process, and a workpiece 1 is shown in this figure. As shown in FIG1, a workpiece 1 can be formed by overlapping a plurality of optical films. When the workpiece is formed, the optical film can be representatively cut into any appropriate shape. Specifically, the optical film can be cut into a rectangular shape, or a shape similar to a rectangular shape, or a shape appropriate for the purpose (e.g., a circle). In the example shown in the figure, the optical film is cut into a rectangular shape, and the workpiece 1 has mutually opposing peripheral surfaces (cutting surfaces) 1a, 1b, and peripheral surfaces (cutting surfaces) 1c, 1d that are orthogonal thereto. Preferably, the workpiece 1 is clamped from above and below by a clamping mechanism (not shown). The total thickness of the workpiece is, for example, 8 mm to 100 mm, preferably 8 mm to 50 mm, more preferably 8 mm to 20 mm, further preferably 9 mm to 15 mm, and further preferably about 10 mm. Such a thickness can prevent damage caused by pressing by a clamping mechanism or impact during cutting. The optical film is overlapped to give the workpiece such a total thickness. The number of optical films constituting the workpiece can be, for example, 10 to 500 sheets (10 to 300 sheets in one embodiment; 10 to 50 sheets in another embodiment). The clamping mechanism (such as a jig) can be made of a soft material or a hard material. When made of soft material, its hardness (JIS A) is preferably 20°~80°, more preferably 60°~80°, and its thickness is, for example, 0.3mm~5mm. When the hardness is too high, there will be residual clamping mechanism pressure marks. When the hardness is too low or too thick, the position will be offset due to the deformation of the jig, and the cutting accuracy may become insufficient.

Next, the outer circumference of the workpiece 1 is cut by the end mill 20. Cutting is performed by bringing the cutting edge of the end mill into contact with the outer circumference of the workpiece 1. Cutting can be performed over the entire circumference of the outer circumference of the workpiece or only at a predetermined position. In addition, for a workpiece having a hole, the cutting edge of the end mill can be brought into contact with the inner circumference of the hole to cut the inner circumference. As the end mill 20, a straight end mill can be used representatively. During the cutting process, only the end mill can be moved, only the workpiece can be moved, or both the end mill and the workpiece can be moved.

As shown in Fig. 2 and Fig. 3, the end milling cutter 20 has: a rotation axis 21 extending in the stacking direction (lead vertical direction) of the workpiece 1, and a cutting blade 22 which is formed as the outermost diameter of the main body rotating around the rotation axis 21. The cutting blade 22 may be formed as the outermost diameter twisted along the rotation axis 21 as shown in Fig. 2 (it may also have a predetermined helix angle), or may be formed to extend in a direction substantially parallel to the rotation axis 21 as shown in Fig. 3 (the helix angle may also be 0°). Furthermore, "0°" means substantially 0°, and also includes the case where the angle is slightly twisted due to processing errors, etc. When the cutting edge has a predetermined helix angle, the helix angle is preferably less than 70°, more preferably less than 65°, and further preferably less than 45°. The cutting edge 22 includes a blade tip 22a, a chamfer 22b, and a clearance surface 22c. The number of blades of the cutting edge 22 can be appropriately set within a range that can obtain the desired number of contacts described later. Although the number of blades in Figure 2 is 3 blades and the number of blades in Figure 3 is 2 blades, the number of blades may be 1 blade, 4 blades, or more than 5 blades. Preferably, the number of blades is 2 blades. As long as it is such a structure, the rigidity of the blade can be ensured, and a pocket can be ensured so that the chips can be discharged well. In one embodiment, an end milling cutter with a helix angle of 0° can be used. In the present invention, even if an end milling cutter with a helix angle of 0° is used, which is easy to form an unnecessary recess when contacting the workpiece, the formation of the recess can still be prevented.

In one embodiment, the outer diameter of the end mill is less than 10 mm, preferably 3 mm to 9 mm, and more preferably 4 mm to 6 mm. In this specification, "the outer diameter of the end mill" refers to the distance from the rotation axis to the tip of one blade multiplied by 2.

The cutting conditions can be appropriately set according to the required shape. For example, the end milling cutter rotation speed is preferably 1000rpm~60000rpm, and more preferably 10000rpm~40000rpm. The feed speed of the end milling cutter is preferably 500mm/min~10000mm/min, and more preferably 500mm/min~2500mm/min. Furthermore, in this manual, the speed of the end milling cutter is the relative speed to the workpiece.

In one embodiment, at the start of cutting, the end milling cutter is moved in a direction inclined relative to the workpiece in a plane view while the end milling cutter is brought into contact with the workpiece. In this specification, the "direction inclined relative to the workpiece" at the start of cutting means the following direction: with the cutting start point a (the place where the end milling cutter is initially brought into contact with the workpiece), the angle x (angle x in FIG. 4 ) formed with the side A of the workpiece including the cutting start point a or the tangent B of the workpiece at the cutting start point a behind the moving direction of the end milling cutter after the start of cutting is less than 60°. In addition, the "direction inclined relative to the workpiece" means a direction that does not include a direction perpendicular to the workpiece or a direction close to perpendicular, that is, it also includes a direction in which the above-mentioned angle x is 0°. Furthermore, in this specification, the above-mentioned angle x is referred to as the moving angle x of the end milling cutter at the start of cutting. When the cutting starting point a exists on a straight line, the travel angle x of the end milling cutter at the start of the cutting can be determined by the side A of the workpiece including the cutting starting point a and the travel trajectory of the end milling cutter (Figure 4). When the cutting starting point a exists on a curve, the travel angle x of the end milling cutter at the start of the cutting can be determined by the tangent line B of the workpiece at the cutting starting point a and the travel trajectory of the end milling cutter (Figure 5).

Fig. 4(a) and Fig. 4(b) are schematic plan views for explaining a cutting process according to one embodiment of the present invention. Fig. 5(a) and Fig. 5(b) are schematic plan views for explaining a cutting process according to another embodiment of the present invention. In Fig. 4(a) and Fig. 4(b), and Fig. 5(a) and Fig. 5(b), the movement of the end milling cutter at the start of cutting (relative movement to the workpiece 1) is shown as a travel trajectory ts in a plane view. In Fig. 4(a) and (b), the workpiece 1 is roughly rectangular. Furthermore, in Fig. 5(a) and (b), the contour of the workpiece 1 includes a curve. The travel trajectory ts of the end milling cutter at the start of cutting may be a curve as shown in Fig. 4(a) and Fig. 5(a), or may be a straight line as shown in Fig. 4(b) and Fig. 5(b). As mentioned above, the travel angle x of the end milling cutter at the start of cutting is less than 60°, and is preferably greater than 0° and less than 60°, more preferably greater than 0° and less than 45°, further preferably greater than 0° and less than 40°, and particularly preferably greater than 0° and less than 35°. In the present invention, the generation of unnecessary recesses at the start point of cutting can be prevented by making the end milling cutter contact the workpiece while making it travel in a direction inclined relative to the workpiece. The closer the travel angle x of the end milling cutter at the start of cutting is to 0°, the better. In one embodiment, the travel angle x is less than 5° (preferably less than 3°, more preferably less than 1°, and further preferably less than 0.5°). Furthermore, the travel trajectory ts only needs to satisfy the above travel angle x at the start of cutting, and the end milling cutter can also be moved with any trajectory before the start of cutting (for example, before 2 seconds before the end milling cutter contacts the workpiece).

As mentioned above, although the travel angle x can also be 0°, for example, when the workpiece is rectangular, the vertex of the workpiece can be set as the starting point of cutting, and the end milling cutter can be moved in a direction parallel to one side of the workpiece while the end milling cutter contacts the workpiece, but it is better not to set the vertex of the workpiece as the starting point of cutting (that is, it is better to set the travel angle x larger than 0° when the workpiece is rectangular). When the vertex of the workpiece is set as the starting point of cutting, there is a risk of fuzzing at the starting point of cutting.

Preferably, the travel trajectory ts of the end milling cutter at the start of cutting is curved. By setting the travel trajectory ts of the end milling cutter at the start of cutting to be curved, the effect of the above-mentioned invention becomes more significant. In the case where the travel trajectory ts is curved, the travel angle x of the end milling cutter at the start of cutting can be determined by the tangent us of the travel trajectory ts at the starting point a of cutting and the edge A of the workpiece or the tangent B at the starting point a of cutting. In one embodiment, the end milling cutter is moved relative to the workpiece along the curved travel trajectory ts while the workpiece is rotated in-plane. When the end milling cutter is brought close to the workpiece, the workpiece can be brought close to the fixed end milling cutter, the end milling cutter can be moved linearly to bring the end milling cutter close to the workpiece, or the end milling cutter and the workpiece can be moved linearly to bring the end milling cutter close to the workpiece.

When the travel path ts of the end milling cutter at the start of cutting is curved, the radius of curvature of the travel path ts is preferably 1/2 or more of the outer diameter of the end milling cutter, more preferably larger than the outer diameter of the end milling cutter, further preferably 110% or more of the outer diameter of the end milling cutter, particularly preferably 130% or more of the outer diameter of the end milling cutter, and most preferably 150% or more of the outer diameter of the end milling cutter. By setting such a range, the generation of unnecessary concave parts at the starting point a of cutting can be prevented. Furthermore, when the travel trajectory ts of the end milling cutter at the beginning of cutting is curved, the radius of curvature of the travel trajectory ts is preferably greater than 4 mm, more preferably greater than 6 mm, and further preferably greater than 7.5 mm.

The speed of the end milling cutter when the end milling cutter contacts the workpiece is preferably slower than the feed speed of the end milling cutter during cutting (when the end milling cutter cuts the cut surface of the workpiece). By setting the speed of the end milling cutter at the start of cutting to be slower, the roughness of the workpiece can be suppressed. In one embodiment, the speed of the end milling cutter when the end milling cutter contacts the workpiece is preferably 400 mm/min to 1200 mm/min, and more preferably 500 mm/min to 900 mm/min. In one embodiment, for example, when cutting the inner peripheral surface of a workpiece having a hole, the speed of the end milling cutter when the end milling cutter contacts the workpiece is preferably 30 mm/min to 1200 mm/min, and more preferably 50 mm/min to 1000 mm/min.

The shape of the workpiece (i.e., the optical film) can be set to any appropriate shape. As the shape of the workpiece, in addition to the roughly rectangular shape as shown in, for example, FIG. 4, roughly polygonal shapes, roughly circular shapes, roughly elliptical shapes, etc. can also be listed. In addition, the shape of the workpiece can also be a shape that appropriately combines straight lines and curves, or a shape composed of multiple curves with different curvatures. Furthermore, the above-mentioned workpiece may not be a pure rectangular shape, polygonal shape, circular shape, elliptical shape, etc., but may be a shape in which irregular parts are added to these shapes. In this specification, for example, a rectangular shape with an irregular part added is included in the "roughly rectangular shape". As the irregular part, in addition to the recessed part as shown in, for example, FIG. 4, a convex part, a hole, etc. can also be listed. Furthermore, the workpiece may be in a shape such as a rectangular shape with curved corners.

Furthermore, the above-mentioned cutting method (specifically, the travel trajectory of the end milling cutter at the beginning of the above-mentioned cutting, and the travel trajectory of the end milling cutter at the end of the cutting described later) can also be applied when cutting the inner peripheral surface of the hole 11 of the workpiece 1' having the hole 11 as shown in FIG. 6.

In one embodiment, at the end of cutting, the end milling cutter is moved away from the workpiece while being moved in a direction tilted relative to the workpiece in a plane view. In this specification, the "direction tilted relative to the workpiece" at the end of cutting means the following direction: with the cutting end point b (the point at which the end milling cutter is moved away from the workpiece) as a reference, in front of the moving direction of the end milling cutter before the end of cutting, the angle y (angle y in FIG. 7 ) formed with the side A of the workpiece including the cutting end point b or the tangent B' of the workpiece at the cutting end point b is less than 60°. As mentioned above, the "direction tilted relative to the workpiece" means: a direction that does not include a direction perpendicular to the workpiece or a direction close to perpendicular, that is, a direction in which the above-mentioned angle y is 0°. Furthermore, in this specification, the above-mentioned angle y is referred to as the moving angle y of the end milling cutter at the end of cutting. When the cutting end point b exists on a straight line, the travel angle y of the end milling cutter at the end of the cutting can be determined by the side A of the workpiece including the cutting end point b and the travel trajectory of the end milling cutter (Figure 7). When the cutting end point b exists on a curve, the travel angle y of the end milling cutter at the end of the cutting can be determined by the tangent line B' of the workpiece at the cutting end point b and the travel trajectory of the end milling cutter (Figure 8).

Fig. 7(a) and Fig. 7(b) are schematic plan views for explaining a cutting process according to one embodiment of the present invention. Fig. 8(a) and Fig. 8(b) are schematic plan views for explaining a cutting process according to another embodiment of the present invention. In Fig. 7(a) and Fig. 7(b), and Fig. 8(a) and Fig. 8(b), the movement of the end milling cutter at the end of cutting (relative movement to the workpiece 1) is shown as a travel trajectory te in a plane view. In Fig. 7(a) and (b), the workpiece 1 is roughly rectangular. In Fig. 8(a) and (b), the outline of the workpiece 1 includes a curve. The travel trajectory te of the end milling cutter at the end of cutting may be a curve as shown in Fig. 7(a) and Fig. 8(a), or may be a straight line as shown in Fig. 7(b) and Fig. 8(b). As mentioned above, the travel angle y of the end milling cutter at the end of cutting is less than 60°, and is preferably greater than 0° and less than 60°, more preferably greater than 0° and less than 45°, further preferably greater than 0° and less than 40°, and particularly preferably greater than 0° and less than 35°. In the present invention, the formation of unnecessary drop and fuzz at the end point of cutting can be prevented by moving the end milling cutter in a direction inclined relative to the workpiece while moving the end milling cutter away from the workpiece. The closer the travel angle y of the end milling cutter at the end of cutting is to 0°, the better. In one embodiment, the travel angle y is less than 5° (preferably less than 3°, more preferably less than 1°, and further preferably less than 0.5°). Furthermore, the travel trajectory te only needs to satisfy the above travel angle y at the end of cutting, and the end milling cutter can also be moved along any trajectory after the end milling cutter has moved away from the workpiece by a predetermined distance.

As mentioned above, the travel angle y may also be 0°. For example, when the workpiece is rectangular, the vertex of the workpiece may be set as the cutting end point, and the end mill may be moved away from the workpiece in a direction parallel to one side of the workpiece. In one embodiment, when the workpiece is rectangular, the vertex of the workpiece is not set as the cutting end point (that is, when the workpiece is rectangular, the travel angle y is set larger than 0°).

Preferably, the travel trajectory te of the end milling cutter at the end of cutting is a curved line. By setting the travel trajectory te of the end milling cutter at the end of cutting to a curved line, the above effect becomes more significant. In the case where the travel trajectory te is a curved line, the travel angle y of the end milling cutter at the end of cutting can be determined by the tangent ue of the travel trajectory te at the cutting end point b and the edge A of the workpiece or the tangent B' at the cutting end point a. In one embodiment, the end milling cutter is moved away from the workpiece while the workpiece is rotated in the plane, and the end milling cutter is moved relative to the workpiece along the curved travel trajectory te. When the end milling cutter is moved away from the workpiece, the workpiece can be moved away from the fixed end milling cutter, the end milling cutter can be moved linearly to move the end milling cutter away from the workpiece, or the end milling cutter and the workpiece can be moved linearly to move the end milling cutter away from the workpiece.

When the running track te of the end milling cutter at the end of cutting is curved, the curvature radius of the running track te is preferably 1/2 or more of the outer diameter of the end milling cutter, more preferably larger than the outer diameter of the end milling cutter, further preferably 110% or more of the outer diameter of the end milling cutter, particularly preferably 130% or more of the outer diameter of the end milling cutter, and most preferably 150% or more of the outer diameter of the end milling cutter. By setting such a range, the generation of unnecessary drop and fuzz at the cutting end point b can be prevented. Furthermore, when the travel trajectory te of the end milling cutter at the end of cutting is curved, the curvature radius of the travel trajectory te is preferably greater than 4 mm, more preferably greater than 6 mm, and further preferably greater than 7.5 mm.

The speed of the end milling cutter when the end milling cutter is moved away from the workpiece is preferably slower than the feed speed of the end milling cutter during cutting (when the end milling cutter cuts the cut surface of the workpiece). By setting the speed of the end milling cutter at the end of cutting to be slower, the roughness of the workpiece can be suppressed. In one embodiment, the speed of the end milling cutter when the end milling cutter is moved away from the workpiece is preferably 400 mm/min to 1200 mm/min, and more preferably 500 mm/min to 900 mm/min. In one embodiment, when cutting the inner circumference of a workpiece having a hole, the speed of the end milling cutter when the end milling cutter is moved away from the workpiece is preferably 30 mm/min to 1200 mm/min, more preferably 50 mm/min to 1000 mm/min.

When cutting is performed over the entire periphery of the outer circumference of the workpiece or the inner circumference of the hole, the cutting start point a and the cutting end point b may be at the same position, or the cutting start point a and the cutting end point b may be set at different positions, and the cutting end point b may be set to be closer to the end milling cutter's travel direction than the cutting start point a. Preferably, the cutting start point a and the cutting end point b are set to be different positions, and the cutting end point b is set to be closer to the end milling cutter's travel direction than the cutting start point a. In this way, as long as the travel trajectory of the end milling cutter during cutting is partially overlapped to end the cutting, unnecessary drop and fuzzing at the end of cutting can be better prevented. As mentioned above, when the cutting end point b is set closer to the front of the end milling cutter's travel direction than the cutting start point a, the distance between the cutting start point a and the cutting end point b is preferably 0.1mm~5mm, more preferably 0.3mm~4mm, and further preferably 0.5mm~2mm.

In one embodiment, the end milling cutter is moved as described above at the beginning of cutting, and is moved as described above at the end of cutting. In another embodiment, the end milling cutter is moved as described above at the beginning of cutting, and is moved by an arbitrary method at the end of cutting. In yet another embodiment, the end milling cutter is moved by an arbitrary method at the beginning of cutting, and is moved as described above at the end of cutting.

In one embodiment, the optical film includes a polarizer.

The optical film including the polarizer may be a single polarizer or a film including the polarizer and other layers. Examples of other layers include: a protective layer for protecting the polarizer, a layer composed of any appropriate optical functional layer, etc. In one embodiment, a polarizing plate may be used as the optical film including the polarizer. The polarizing plate may include a polarizer and a protective layer disposed on at least one side of the polarizer. Furthermore, as the film including the polarizer, a laminate may be used, and the laminate is a laminate of a polarizing plate, a surface protection film and/or a separator. The surface protection film or the separator is releasably laminated on the polarizing plate via any appropriate adhesive. In this manual, "surface protection film" refers to a film that temporarily protects the polarizing plate, and has a different structure from the protective layer (layer that protects the polarizer) possessed by the polarizing plate.

Polarizers are typically obtained by subjecting resin films (such as polyvinyl alcohol-based resin films) to various treatments, such as swelling treatment, stretching treatment, dyeing treatment with dichroic substances (such as iodine, organic dyes, etc.), crosslinking treatment, washing treatment, and drying treatment. Generally speaking, although polarizers obtained by stretching treatment have the characteristic of easily generating cracks, according to the present invention, it is possible to prevent cracks and cut optical films including polarizers.

The thickness of the optical film including the polarizer is not particularly limited, and an appropriate thickness, such as 20μm~200μm, can be adopted according to the purpose. The thickness of the polarizer is also not particularly limited, and an appropriate thickness can be adopted according to the purpose. The thickness of the polarizer is typically about 1μm~80μm, preferably 3μm~40μm.

The size of the optical film including the polarizer is not particularly limited and can be set to an appropriate size according to the purpose. In one embodiment, the optical film including the polarizer is rectangular and includes a side parallel to the absorption axis of the polarizer, and the length of the side parallel to the absorption axis of the polarizer is 10mm~400mm, and the length of the other sides is 10mm~500mm. In this specification, "parallel" means substantially parallel, specifically, the angle between the two directions is 0°~5°.

The optical film obtained by the manufacturing method of the present invention can be used in liquid crystal image display devices, organic EL image display devices, etc. In addition, the optical film can be suitably used in: rectangular image display parts represented by the above-mentioned personal computers (PCs) or tablet computer terminals, and/or irregular image display parts represented by automobile dashboards or smart watches.

Implementation example

Although the present invention is specifically described below through embodiments, the present invention is not limited to these embodiments.

[Implementation Example 1]

An optical film (polarizing plate) is produced according to conventional methods. The optical film has a structure of surface protection film (48μm)/hard coating layer (5μm)/cycloolefin protective film (47μm)/polarizer (5μm)/cycloolefin protective film (24μm)/adhesive layer (20μm)/separator in order from the visual identification side. The adhesive layer is produced in accordance with [0121] and [0124] of Japanese Patent Publication No. 2016-190996. The obtained optical film is punched into a shape similar to Figure 4 (approximate size of about 140mm × about 65mm). Multiple sheets of the punched optical film are overlapped to produce a workpiece (total thickness of about 10mm). The obtained workpiece is clamped by a fixture (jig), and the outer circumference of the workpiece is cut by the end milling cutter. At the beginning of cutting, the end milling cutter is moved in a direction inclined to the workpiece from a plane perspective (the walking trajectory ts of the end milling cutter at the beginning of cutting: a curve with a curvature radius of 7.5mm, the walking angle x of the end milling cutter at the beginning of cutting: 13°, and the speed of the end milling cutter at the beginning of cutting: 700mm/min), while the end milling cutter is brought into contact with the workpiece. In addition, the outer diameter of the end milling cutter is 5mm, the number of blades is 2, and the helix angle is 0°. In addition, the feed speed of the end milling cutter (the feed speed when cutting the straight part) is 1000mm/min, and the number of rotations is 25000rpm.

By the above-mentioned cutting process, a cut optical film can be obtained without generating unnecessary concave portions at the starting point of cutting.

[Example 2]

The cutting is started in the same manner as in Example 1. At the end of cutting, the end mill moves away from the workpiece while the end mill moves in a direction inclined to the workpiece in a plane view (the walking trajectory te of the end mill at the end of cutting: a curve with a curvature radius of 7.5 mm, the walking angle y of the end mill at the end of cutting: 0°, and the speed of the end mill at the end of cutting: 700 mm/min). Furthermore, the cutting end point b is set to be closer to the front of the walking direction of the end mill than the cutting start point a, and the distance between the cutting start point a and the cutting end point b is set to 1 mm.

By the above-mentioned cutting process, a cut optical film can be obtained without generating unnecessary concave parts at the cutting start point and without generating unnecessary step and fuzz at the cutting end point.

[Implementation Example 3]

At the beginning of cutting, except that the vertex of the workpiece is set as the starting point of cutting, the end milling cutter is moved in a direction parallel to the long side of the workpiece (the moving track ts of the end milling cutter at the beginning of cutting: straight line, the moving angle x of the end milling cutter at the beginning of cutting: 0°, the speed of the end milling cutter at the beginning of cutting: 700mm/min), and the end milling cutter is brought into contact with the workpiece, it is set the same as Example 1 and the cutting process is performed.

Although the above-mentioned cutting process can obtain a cut optical film without generating unnecessary concave portions at the cutting starting point, the generation of fuzz is observed at the cutting starting point.

[Implementation Example 4]

According to conventional methods, an optical film (polarizing plate) is produced. The optical film has the following structure from the visual identification side: surface protection film (48μm)/hard coating layer (5μm)/cycloolefin protective film (47μm)/polarizer (5μm)/cycloolefin protective film (24μm)/adhesive layer (20μm)/separator. The adhesive layer is produced in accordance with [0121] and [0124] of Japanese Patent Publication No. 2016-190996. The obtained optical film is punched into a shape similar to that of FIG. 4 (approximate size is about 140 mm × about 65 mm). Multiple sheets of the punched optical film are overlapped to form a workpiece (total thickness is about 10 mm). The obtained workpiece is clamped by a fixture (jig), and the outer circumference of the workpiece is cut by the end milling cutter. At the end of cutting, the end milling cutter is moved away from the workpiece while moving in a direction inclined to the workpiece in a plane view (the walking trajectory te of the end milling cutter at the end of cutting: a curve with a curvature radius of 7.5mm, the walking angle y of the end milling cutter at the end of cutting: 30°, and the speed of the end milling cutter at the end of cutting: 700mm/min). In addition, the outer diameter of the end milling cutter is 5mm, the number of blades is 2, and the helix angle is 0°. In addition, the feed speed of the end milling cutter (the feed speed when cutting the straight part) is 1000mm/min, and the number of rotations is 25000rpm.

Through the above-mentioned cutting process, a cut optical film can be obtained without generating a drop or fuzz at the cutting end point.

[Comparison Example 1]

When cutting starts, the cutting process is performed in the same manner as in Example 1, except that the end milling cutter is moved perpendicularly to the workpiece in a plane view and the end milling cutter is brought into contact with the workpiece.

According to the above-mentioned cutting process, an unnecessary concave portion is observed at the starting point of cutting.

Industrial availability

The cut optical film of the present invention can be suitably used in: a rectangular image display represented by a personal computer (PC) or a tablet terminal, and/or an irregular image display represented by a car dashboard or a smart watch.

1: Workpiece

A: Side

a: Cutting starting point

ts: The path of the end milling cutter at the beginning of cutting

us: Tangent of the walking trajectory at the starting point of cutting

x: The travel angle of the end milling cutter at the beginning of cutting

Claims (12)

A method for manufacturing an optical film by cutting, comprising the following steps: overlapping a plurality of optical films to form a workpiece; and cutting the outer peripheral surface of the workpiece with an end milling cutter, wherein the manufacturing method further comprises the following steps: at the beginning of cutting, the end milling cutter is moved in a direction inclined to the workpiece in a plane viewing angle while the end milling cutter is in contact with the workpiece; and/or at the end of cutting, the end milling cutter is moved away from the workpiece in a direction inclined to the workpiece in a plane viewing angle while the end milling cutter is moved in a direction inclined to the workpiece in a plane viewing angle, and the angle x formed by the moving direction of the end milling cutter after the beginning of cutting and the side A of the workpiece including the cutting starting point a or the tangent line B of the workpiece at the cutting starting point a is less than 5°. The method for manufacturing an optical film by cutting as claimed in claim 1, wherein the travel trajectory ts of the aforementioned end milling cutter at the beginning of cutting is curved. A method for manufacturing an optical film by cutting as in claim 2, wherein the radius of curvature of the travel trajectory ts of the end milling cutter at the beginning of the cutting is greater than 1/2 of the outer diameter of the end milling cutter. A method for manufacturing an optical film by cutting as in claim 2, wherein the radius of curvature of the travel trajectory ts of the end milling cutter at the beginning of the cutting is larger than the outer diameter of the end milling cutter. A method for manufacturing an optical film by cutting as claimed in claim 1, wherein the travel trajectory te of the end milling cutter is curved at the end of cutting. A method for manufacturing an optical film by cutting as claimed in claim 5, wherein the radius of curvature of the travel path te of the end milling cutter at the end of the cutting is greater than 1/2 of the outer diameter of the end milling cutter. A method for manufacturing an optical film by cutting as claimed in claim 5, wherein the radius of curvature of the travel trajectory te of the end milling cutter at the end of the cutting is larger than the outer diameter of the end milling cutter. The method for manufacturing a cut optical film as claimed in claim 1 is to make the speed of the end milling cutter when it contacts the workpiece slower than the feed speed of the end milling cutter when it cuts the outer peripheral surface of the workpiece. A method for manufacturing a cut optical film as claimed in claim 1, wherein the speed of the end milling cutter when the end milling cutter is moving away from the workpiece is slower than the feed speed of the end milling cutter when the end milling cutter is cutting the outer peripheral surface of the workpiece. The method for manufacturing an optical film by cutting as claimed in claim 1 is to cover the entire circumference of the outer peripheral surface of the aforementioned workpiece for cutting, and set the cutting start point a and the cutting end point b to different positions, and set the cutting end point b to be closer to the front of the moving direction of the end milling cutter than the cutting start point a. A method for manufacturing an optical film by cutting as claimed in claim 1, wherein the outer diameter of the end milling cutter is less than 10 mm. A method for manufacturing optical thin films by cutting as in claim 1, wherein the helix angle of the end mill is 0°.