Method for manufacturing optical laminate with adhesive layer having through holes

Abstract

The present application provides a method of manufacturing an optical laminate with an adhesive layer having a through-hole, which is suppressed from having a lack of adhesive and a relief of a surface protective film and a separation member, at low cost and with ease. The method of manufacturing an optical laminate with an adhesive layer having a through-hole according to an embodiment of the present application includes: laminating a plurality of optical laminates with an adhesive layer to form a workpiece; and forming a through-hole at a predetermined position of the workpiece by cutting using an end mill. The optical laminate with an adhesive layer includes an optical film, an adhesive layer disposed on one side of the optical film, a separation member temporarily adhered to the adhesive layer in a peelable manner, and a surface protective film temporarily adhered to the other side of the optical film in a peelable manner. The forming of the through-hole includes moving the end mill upward and downward in either direction while abutting the end mill against an end surface of the hole and cutting.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an optical laminate with an adhesive layer having through holes. Background Technology

[0002] In image display devices such as mobile phones and laptops, various optical laminates (e.g., polarizers) are used to achieve image display and / or improve the performance of that image display. These optical laminates typically include an adhesive layer to form an optical laminate with an adhesive layer, allowing them to be attached to the image display unit. In recent years, due to the rapid proliferation of smartphones and touch-panel information processing devices, image display devices equipped with cameras have become widely used. Correspondingly, optical laminates with adhesive layers that have through-holes at positions corresponding to the camera unit are also widely used. Such through-holes can be formed, for example, by using an end mill for drilling.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: International Publication No. 2017 / 047510 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] However, in the opening process of optical laminates with adhesive layers, so-called missing adhesive (the phenomenon of missing ends of the adhesive layer) and / or protrusions in the surface protective film and / or separators used in the manufacturing process sometimes occur. The present invention was made to solve such problems, and its main objective is to provide a method for easily and inexpensively manufacturing optical laminates with adhesive layers and through holes that suppresses missing adhesive and protrusions in the surface protective film and separators.

[0008] Solution for solving the problem

[0009] A method for manufacturing an optical laminate with a through hole and an adhesive layer according to an embodiment of the present invention includes: stacking multiple optical laminates with adhesive layers to form a workpiece; and forming a through hole at a predetermined position in the workpiece by cutting with an end mill. The optical laminate with adhesive layer includes an optical film, an adhesive layer disposed on one side of the optical film, a release element temporarily bonded to the adhesive layer in a peelable manner, and a surface protective film temporarily bonded to the other side of the optical film in a peelable manner. Forming the through hole includes: simultaneously cutting with an end mill against the end face of the hole, and simultaneously moving the end mill in either an upward or downward direction while cutting.

[0010] In one embodiment, the formation of the through hole includes: forming a pre-drilled hole; while the end mill abuts against the end face of the pre-drilled hole and performs cutting, the end mill moves along the end face of the pre-drilled hole and moves from a predetermined position at the start of cutting in either upward or downward direction and circles around it to form a next hole with a diameter greater than the diameter of the pre-drilled hole; returning the end mill to the predetermined position, while the end mill abuts against the end face of the next hole and performs cutting, the end mill moves along the end face of the next hole and moves from the predetermined position in either upward or downward direction and circles around it to form a next hole with a diameter greater than the diameter of the next hole; and repeating the cutting along the end face of the hole by the circling of the end mill a predetermined number of times to form a through hole with a predetermined diameter.

[0011] In one embodiment, the formation of the through hole includes: forming the pre-drilled hole using an end mill in a cantilevered state, and forming the next hole and subsequent holes using an end mill in a fixed-end state.

[0012] In one embodiment, the end mill has a helical cutting edge, and the up-and-down movement direction of the end mill in forming the through hole is the chip discharge direction.

[0013] In one embodiment, the end mill used to form the pre-drilled hole is the same end mill used to form the next hole and subsequent holes, and the direction of vertical movement of the end mill used to form the next hole and subsequent holes is upward.

[0014] In one embodiment, the thickness of the workpiece is 10 mm or more.

[0015] In one embodiment, the optical thin film includes a polarizer or a polarizer.

[0016] The effects of the invention

[0017] According to an embodiment of the present invention, in the formation of the through hole in an optical laminate with an adhesive layer having a through hole, by cutting while moving an end mill in either the upward or downward direction, it is possible to suppress adhesive defects and the protrusion of the surface protective film and the separator. Attached Figure Description

[0018] Figure 1 This is a schematic cross-sectional view illustrating an example of an optical laminate with an adhesive layer that can be used in the manufacturing method of an embodiment of the present invention.

[0019] Figure 2A This is a schematic cross-sectional view illustrating an example of a through-hole in an optical laminate with an adhesive layer that can be used in the manufacturing method of an embodiment of the present invention.

[0020] Figure 2B This is a schematic cross-sectional view illustrating other examples of through holes in an optical laminate with an adhesive layer that can be used in the manufacturing method of an embodiment of the present invention.

[0021] Figure 3 This is a schematic perspective view illustrating the general details of the formation of the through hole in the manufacturing method according to an embodiment of the present invention.

[0022] Figure 4 This is a schematic diagram illustrating the structure of an end mill with a helical cutting edge that can be used to form a through hole in the manufacturing method of an embodiment of the present invention.

[0023] Figure 5 This is a schematic diagram illustrating a representative example of the structure of an end mill with a helical cutting edge that can be used in the manufacturing method of an embodiment of the present invention, and the relationship between the chip discharge direction and the rotation direction.

[0024] Figure 6 This is a schematic top view illustrating the detailed process of forming a through hole in the manufacturing method according to an embodiment of the present invention.

[0025] Figure 7 (a) is a schematic cross-sectional view illustrating the formation of the pre-drilled hole in the formation of the through hole. Figure 7 (b) is a schematic cross-sectional view illustrating the formation of the next hole and subsequent holes.

[0026] Figure 8 This is a schematic top view illustrating the cutting process using an end mill in the formation of a through hole.

[0027] Figure 9 (a) is a schematic top view illustrating the in-plane path of the end mill during the formation of the through hole. Figure 9 (b) is a schematic diagram illustrating the upward movement accompanying the in-plane movement of the end mill;

[0028] Figure 9 (c) is a schematic diagram illustrating the downward movement accompanying the in-plane movement of the end mill.

[0029] Figure 10 This is a schematic diagram illustrating the vertical movement of the end mill in the plane accompanying the movement of the end mill in Comparative Example 4. Detailed Implementation

[0030] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited to these embodiments. Furthermore, for ease of viewing, the drawings are shown schematically, and the proportions of length, width, thickness, and angles in the drawings differ from the actual figures.

[0031] A method for manufacturing an optical laminate with a through-hole and an adhesive layer according to an embodiment of the present invention includes: stacking multiple optical laminates with adhesive layers to form a workpiece; and forming a through-hole at a predetermined position on the workpiece by cutting with an end mill. The optical laminate with an adhesive layer includes an optical film, an adhesive layer disposed on one side of the optical film, a release element temporarily bonded to the adhesive layer in a peelable manner, and a surface protective film temporarily bonded to the other side of the optical film in a peelable manner. In an embodiment of the present invention, forming the through-hole includes cutting while moving the end mill in either upward or downward direction. For convenience, firstly, a specific structure of an optical laminate with an adhesive layer that can be used in the manufacturing method of an embodiment of the present invention will be described, and then, a method for manufacturing an optical laminate with a through-hole and an adhesive layer according to an embodiment of the present invention will be described.

[0032] A. Optical laminate with adhesive layer

[0033] Figure 1 This is a schematic cross-sectional view illustrating an example of an optical laminate with an adhesive layer that can be used in the manufacturing method of an embodiment of the present invention. The example optical laminate 100 with an adhesive layer includes an optical film 10, an adhesive layer 20 disposed on one side of the optical film 10, a release member 30 temporarily bonded to the adhesive layer 20 in a peelable manner, and a surface protective film 40 temporarily bonded to the other side of the optical film 10 in a peelable manner. In the case where the optical laminate with the adhesive layer is applied to an image display device, the release member 30 is typically disposed on the image display unit side. In actual use of the optical laminate with the adhesive layer, the release member 30 is peeled off, and the adhesive layer 20 can be used to adhere the optical laminate with the adhesive layer to the image display device (essentially the image display unit). The surface protective film 40 typically has a substrate 41 and an adhesive layer 42. Furthermore, to distinguish it from the adhesive layer 20, the adhesive layer 42 of the surface protective film is sometimes referred to as the "PF adhesive layer." Additionally, the surface protective film 40 is also peeled off during actual use of the optical laminate with the adhesive layer.

[0034] In an embodiment of the invention, the optical laminate with an adhesive layer has a through-hole 50 at a predetermined location. The through-hole 50 can be as follows: Figure 2A As shown, one can be formed, or as shown in the diagram. Figure 2B As shown, two holes can be formed, but more than three can also be formed (not shown). For example, when two through holes are formed, it can be done as follows: Figure 2BThe through-holes can be formed side-by-side along the short side, or side-by-side along the long side, or randomly. The location of the through-holes can be appropriately set according to the purpose. Through-holes are typically formed at or near the end of the optical laminate with the adhesive layer, preferably at the corner as shown in the example. By forming the through-holes at or near the end of the optical laminate with the adhesive layer, the impact on image display can be minimized when the optical laminate with the adhesive layer is applied to an image display device. In one embodiment, the through-hole can be formed at a position corresponding to the camera section of the image display device. The top view shape of the through-hole can be any suitable shape depending on the purpose and the desired structure of the image display device. As a representative example, a roughly circular shape as shown in the example can be used. The size of the through-hole (diameter in the example) is, for example, 5 mm or less, preferably 1 mm to 5 mm, more preferably 2 mm to 4 mm. Furthermore, in Figure 1 The depiction of the through hole is omitted. According to an embodiment of the present invention, as described later, during the formation of the through hole, cutting is performed while moving the end mill in either the upward or downward direction, thereby suppressing insufficient adhesive and protrusion of the surface protective film and the separator. That is, according to an embodiment of the present invention, the unique problems in the manufacturing method of an optical laminate with an adhesive layer, including an adhesive layer, a separator, and a surface protective film, can be solved.

[0035] As the optical thin film 10, any suitable optical thin film for applications requiring through holes can be cited. The optical thin film can be a thin film composed of a single layer or a laminate. Specific examples of optical thin films composed of a single layer include polarizers and phase difference films. Specific examples of optical thin films configured as laminates include polarizers (representatively a laminate of a polarizer and a protective film), conductive films for touch panels, surface-treated films, and laminates formed by appropriately stacking the above-mentioned optical thin films composed of single layers and / or optical thin films configured as laminates according to the purpose (e.g., circular polarizers for anti-reflection, polarizers with conductive layers for touch panels).

[0036] The adhesive layer 20 can have any suitable structure. Specific examples of adhesives constituting the adhesive layer include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, polyurethane adhesives, epoxy adhesives, and polyether adhesives. By adjusting the type, quantity, combination, and mixing ratio of the monomers in the base resin forming the adhesive, as well as the mixing amount of the crosslinking agent, reaction temperature, and reaction time, an adhesive with desired properties corresponding to the purpose can be formulated. The base resin of the adhesive can be used alone or in combination of two or more. From the viewpoints of transparency, processability, and durability, acrylic adhesives are preferred. Detailed information about the adhesive constituting the adhesive layer is described, for example, in Japanese Patent Application Publication No. 2014-115468, which is incorporated herein by reference. The thickness of the adhesive layer 20 is, for example, 10 μm to 100 μm.

[0037] The creep value of the adhesive layer 20 at 85°C is, for example, less than 500 μm, preferably 5 μm to 500 μm. In one embodiment, the creep value is preferably 200 μm to 450 μm, more preferably 220 μm to 420 μm. In other embodiments, the creep value is preferably 5 μm to 300 μm, more preferably 5 μm to 200 μm, and even more preferably 10 μm to 100 μm. If the creep value is within such a range, insufficient adhesive can be significantly suppressed when forming through-holes, and peeling under high temperature and high humidity conditions can be significantly suppressed. It is speculated that when the creep value is relatively large (e.g., above 200 μm), insufficient adhesive can also be suppressed by controlling the composition of the adhesive constituting the adhesive layer (e.g., the type of base polymer (polarity, Tg, softness), molecular weight) and crosslinking structure (e.g., the type of crosslinking agent, the distance between crosslinking points (molecular weight between crosslinking points), the crosslinking density, and the amount of uncrosslinked components (sol)). Furthermore, creep values ​​can be measured, for example, by attaching a test sample cut from an optical laminate with an adhesive layer to a support plate with a 10mm × 10mm joint surface. With the support plate containing the test sample fixed in place, a load of 500gf is applied vertically downwards. The offset relative to the support plate is measured 1 second after the load is applied and 3600 seconds later, denoted as Cr1 and Cr, respectively. 3600 Based on Cr1 and Cr 3600 The creep value is defined as ΔCr obtained from the following formula.

[0038] ΔCr=Cr 3600 -Cr1

[0039] The energy storage modulus of the adhesive layer 20 at 85°C is preferably 1.0 × 10⁻⁶. 4 Pa or higher, preferably 2.0 × 10 Pa. 4 Pa or higher, more preferably 5.0 × 10 Pa.4 Pa or higher, more preferably 1.0 × 10 Pa 5 Pa or higher. If the energy storage modulus is within this range, the desired creep value can be easily achieved. On the other hand, the energy storage modulus is, for example, 3.0 × 10⁻⁶ Pa. 6 Below Pa. Furthermore, the storage modulus can be determined, for example, by dynamic viscoelasticity measurements.

[0040] As the separating element 30, any suitable separating element can be used. Specific examples include plastic films, non-woven fabrics, or paper coated with a release agent. Specific examples of release materials include silicone-based release agents, fluorinated release agents, and long-chain alkyl acrylate-based release agents. Specific examples of plastic films include polyethylene terephthalate (PET) films, polyethylene films, and polypropylene films. The thickness of the separating element is, for example, 10 μm to 100 μm.

[0041] As described above, the surface protective film 40 typically comprises a substrate 41 and an adhesive layer 42. Examples of materials forming the substrate 41 include ester resins such as polyethylene terephthalate resins, cyclic olefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, and copolymers thereof. Ester resins (especially polyethylene terephthalate resins) are preferred. Using such a material provides the advantage of a sufficiently high elastic modulus, making it less prone to deformation even when tension is applied during transport and / or bonding.

[0042] The elastic modulus of substrate 41 is, for example, 2.2 kN / mm². 2 ~4.8kN / mm 2 If the elastic modulus of the substrate is within such a range, it has the advantage of not easily deforming even when tension is applied during transport and / or bonding. Furthermore, the elastic modulus is measured based on JIS K 6781.

[0043] The thickness of the substrate 41 is, for example, 30 μm to 70 μm.

[0044] As the adhesive layer (PF adhesive layer) 42, any suitable structure can be adopted. Specific examples include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, polyurethane adhesives, epoxy adhesives, and polyether adhesives. By adjusting the type, quantity, combination, and mixing ratio of the monomers of the base resin forming the adhesive, as well as the mixing amount of the crosslinking agent, reaction temperature, and reaction time, an adhesive with desired properties corresponding to the purpose can be formulated. The base resin of the adhesive can be used alone or in combination of two or more. The adhesive constituting the PF adhesive layer is characterized by the base resin containing a polymer having active hydrogen functional groups. Using such a base resin, a PF adhesive layer with a desired storage modulus can be obtained. Detailed information about the adhesive constituting the PF adhesive layer is described, for example, in Japanese Patent Application Publication No. 2018-123281, which is incorporated herein by reference. The thickness of the PF adhesive layer 42 is, for example, 10 μm to 100 μm. The storage modulus G' of PF adhesive layer 42 at 25°C is, for example, 0.5 × 10⁻⁶. 6 (Pa)~3.0×10 6 (Pa). If the storage modulus is within this range, an adhesive layer with an excellent balance between adhesion and peelability can be obtained (resulting in a surface protective film).

[0045] The thickness of the surface protective film 40 is, for example, 40 μm to 120 μm. Furthermore, the thickness of the surface protective film refers to the total thickness of the substrate and the PF adhesive layer.

[0046] B. Method for manufacturing optical laminates with adhesive layers

[0047] The following describes a representative example of a method for manufacturing an optical laminate with an adhesive layer.

[0048] B-1. Formation of the workpiece

[0049] First, the workpiece is formed. Figure 3 This is a schematic perspective view illustrating the general details of the formation of a through hole in the manufacturing method according to an embodiment of the present invention. The workpiece W is shown in this view. Figure 3As shown, a workpiece W is formed by stacking multiple optical laminates with adhesive layers. During workpiece formation, the optical laminates with adhesive layers are typically cut into any suitable shape. Specifically, the optical laminates with adhesive layers can be cut into rectangular shapes, rectangular-like shapes, or suitable shapes corresponding to the purpose (e.g., circles). In one embodiment, the workpiece W has mutually opposing outer peripheral surfaces (cutting surfaces) 1a, 1b and orthogonal outer peripheral surfaces (cutting surfaces) 1c, 1d. The workpiece W is preferably held from above and below by a clamping member (not shown). The total thickness of the workpiece is preferably 3 mm or more, more preferably 5 mm to 40 mm, and even more preferably 10 mm to 30 mm. For example, when the diameter of the through hole is 2 mm to 3 mm, the total thickness of the workpiece is preferably 10 mm to 25 mm. According to embodiments of the present invention, as described later, in the formation of the through hole, the total thickness of the workpiece can be increased by cutting while moving the end mill in either the upward or downward direction. As a result, the manufacturing efficiency of optical laminates with through holes and adhesive layers can be significantly improved. Optical laminates with adhesive layers are stacked such that the workpiece has such a total thickness. The number of optical laminates with adhesive layers constituting the workpiece can vary depending on the thickness of the optical laminates with adhesive layers. The number of optical laminates with adhesive layers is preferably 50 or more, more preferably 50 to 200, and even more preferably 75 to 150. According to embodiments of the present invention, a workpiece can be formed by stacking a significantly larger number of optical laminates with adhesive layers than usual, resulting in a significant improvement in the manufacturing efficiency of optical laminates with through holes and adhesive layers. The clamping component (e.g., a jig) can be made of either a soft or hard material. In the case of a soft material, its hardness (JIS A) is preferably 60° to 80°. When the hardness is too high, indentations may sometimes be left on the clamping component. When the hardness is too low, positional displacement may sometimes occur due to deformation of the jig, resulting in insufficient cutting accuracy.

[0050] B-2. Formation of through holes

[0051] Next, through holes are formed in the workpiece (essentially an optical laminate with an adhesive layer). For example... Figure 3 As shown, a through hole can be formed by cutting with an end mill. Furthermore, in Figure 3 The diagram schematically illustrates the initial pre-drilled hole and the final through hole. Below, we will first describe the end mills that can be used to form the through hole, and then explain the specific steps involved in forming the through hole.

[0052] B-2-1. Structure of an end mill

[0053] The end mill 60 may have a helical cutting edge (which may have a predetermined cutting angle), or the cutting angle may be 0°. A representative example of the end mill 60 is... Figure 3 and Figure 4 As shown, it has a helical cutting edge. The effect of cutting (described later) by using an end mill with a helical cutting edge while moving the end mill in either upward or downward direction is significant. This is because it is easy to make the direction of chip removal consistent with the direction of end mill movement. For example... Figure 4 As shown, the end mill 60 with a helical cutting edge has: a rotation axis 61 extending along the stacking direction (vertical direction) of the workpiece W; and a cutting edge 62 configured as the outermost diameter of a main body rotating around the rotation axis 61. In the example shown, the cutting edge 62 is configured as the outermost diameter twisted along the rotation axis 61, and a right-hand helix is ​​shown in the example. The cutting edge 62 includes a tip 62a, a rake face 62b, and a flank face 62c. The number of cutting edges 62 can be appropriately set according to the purpose. The cutting edge in the example is a three-piece structure, but the number of cutting edges can be one consecutive piece, two pieces, four pieces, or more than five pieces. The cutting edge angle of the end mill (the helix angle θ of the cutting edge in the example) is preferably 10° to 40°, more preferably 20° to 30°. The rake angle is preferably 15° to 25°, and the clearance angle is preferably 25° to 35°. The flank face of the cutting edge is preferably roughened. As a roughening treatment, any suitable treatment can be adopted. Sandblasting is a representative example. By roughening the flank face, the adhesion of the adhesive to the cutting edge can be suppressed, and as a result, adhesion can be suppressed. The outer diameter of the end mill is preferably 0.5 mm to 10 mm, more preferably 0.8 mm to 5 mm, and even more preferably 1 mm to 3 mm. The effective length of the cutting edge of the end mill is preferably 10 mm to 50 mm, more preferably 20 mm to 40 mm. Furthermore, in this specification, "adhesion" refers to the phenomenon where optical laminates with adhesive layers in a workpiece adhere to each other due to the adhesive on their end faces; chips with adhesive adhering to the end faces can promote adhesion between the optical laminates with adhesive layers. Additionally, "outer diameter of the end mill" refers to twice the distance from the rotation axis 61 to the tip 62a.

[0054] Next, we will explain the relationship between the structure of the end mill and the direction of chip discharge and rotation. Figure 5 This is a schematic diagram illustrating a representative example of the structure of an end mill with a helical cutting edge that can be used in the manufacturing method of an embodiment of the present invention. Figure 5 As shown, end mills with helical cutting edges can be broadly categorized into right-hand right-helical, right-hand left-helical, left-hand right-helical, and left-hand left-helical. Figure 5As shown, the right cutting edge refers to the structure that allows cutting when rotated clockwise as viewed from above (shank side); the left cutting edge refers to the structure that allows cutting when rotated counterclockwise as viewed from above (shank side). Figure 5 As further illustrated, a right-hand helix refers to a structure where the tool tip extends diagonally upwards to the right when viewed from the side; a left-hand helix refers to a structure where the tool tip extends diagonally upwards to the left when viewed from the side. The chip removal direction for right-hand right-hand helical cuts and left-hand left-hand helical cuts is upwards; the chip removal direction for right-hand left-hand helical cuts and left-hand right-hand helical cuts is downwards.

[0055] B-2-2. Formation of Through Holes

[0056] The following is for reference Figures 6-9 This section illustrates a representative example of forming a through hole using an end mill as described above.

[0057] First, such as Figure 6 As shown, a pre-drilled hole 51 is formed. In this specification, a "pre-drilled hole" refers to a hole that serves as a basis for forming a through hole in the correct location. A pre-drilled hole 51 is typically shown as... Figure 7 As shown in (a), the pre-drilled hole 51 can be formed by an end mill 60 in a cantilevered state (holding only one end). In the example shown, the end mill 60 with its upper end held is moved from top to bottom to form the pre-drilled hole 51, but the end mill 60 with its lower end held can also be moved from bottom to top to form the pre-drilled hole 51. The diameter of the pre-drilled hole 51 is substantially the same as the outer diameter of the end mill 60.

[0058] Next, as Figure 8 As shown, while the end mill 60 is pressed against the end face of the pre-drilled hole 51 and cutting, the end mill 60 is simultaneously moved around the end face of the pre-drilled hole 51. The result is as follows: Figure 6 and Figure 8 As shown, a next hole 52 is formed with a diameter P larger than the diameter of the pre-drilled hole 51. In an embodiment of the invention, the end mill 60 is moved from a predetermined position A at the start of cutting in either upward or downward direction, while circling the end face of the pre-drilled hole 51 to form the next hole 52. As an example, such as Figure 9 As shown in (a), the cutting start position A from the pre-drilled hole 51 S The following explanation will begin with the case of forming the next hole 52. In this case, the outermost part (tip) of the end mill 60 cuts the end face of the pre-drilled hole 51 while moving at A... S →A1→A2→A3→A4→A1→A S It moves in a certain way. Specifically, A S→A1 is the end mill's movement along a clockwise path when viewed from above to begin cutting at a predetermined interval. Then, the end mill completes a full circle along the end face of the pre-drilled hole 51 in the sequence A1→A2→A3→A4→A1. When it reaches A1 after completing one full circle, the end mill returns to A1 while continuing to cut along a clockwise path when viewed from above. S Here, when the end mill 60 (e.g., the midpoint M of the cutting edge as a positioning index) is located at a predetermined position T in the thickness direction (vertical direction) of the workpiece, as the end mill moves at A... S →A1→A2→A3→A4→A1→A S The end mill moves in a manner that causes it to move upwards, such as... Figure 9 The change is as shown in (b), where the end mill moves downwards as... Figure 9 The change is as described in (c). When cutting around a circle to form the next hole 52, at position A... S The end mill 60 returns to position T (at this time, no cutting is performed). Furthermore, in this specification, the predetermined amount P is sometimes referred to as the cutting distance.

[0059] Next, move the end mill 60 from position A. S Starting from position B of the next hole 53 along the horizontal direction. S Movement (no cutting during this movement). The following steps are similar to the cutting of the pre-drilled hole (formation of the next hole 52), in which the end mill 60 is moved in either upward or downward while cutting around the end face of the next hole 52. The result is as follows: Figure 6 As shown, a next hole 53 is formed, which has a diameter that is a predetermined amount P larger than the diameter of the next hole 52. More specifically, as... Figure 9 As shown in (a), the outermost edge (tip) of the end mill 60 cuts the end face of the next hole 52 while moving at a speed of B. S →B1→B2→B3→B4→B1→B S The end mill moves in a B-shape. S →B1→B2→B3→B4→B1→B S The end mill moves in a manner that causes it to move upwards, such as... Figure 9 The change is as shown in (b), where the end mill moves downwards as... Figure 9 The change is as described in (c). When cutting around a circle to form the next hole 53, at position B... S The end mill 60 returns to position T. Then, the end mill 60 is moved from position B. S The cutting start position C of the next hole along the horizontal direction. SMove the device and repeat the same steps to create a through hole with the desired diameter.

[0060] The amount of upward or downward movement of the end mill during the formation of a through hole ( Figure 9 (b) of U or Figure 9 (c) of D) is preferably 1mm to 8mm, more preferably 2mm to 7mm, and even more preferably 3mm to 5mm. When this movement amount is too small, it may sometimes be insufficient to suppress insufficient adhesive, or the protrusion of the surface protective film or the separator. The larger this movement amount is, the more preferred, and the upper limit can be limited by the effective length of the cutting edge of the end mill. This movement amount relative to the effective length of the cutting edge of the end mill can be, for example, 6% to 15%.

[0061] The preferred direction of movement for the end mill is the direction of chip removal. That is, when the end mill is a right-handed right-handed helical cutter or a left-handed left-handed helical cutter, the direction of movement is upward; when the end mill is a right-handed left-handed helical cutter or a left-handed right-handed helical cutter, the direction of movement is downward. With such a structure, chip accumulation at the tip of the cutter face can be significantly suppressed, and chip removal is extremely efficient. Therefore, the indentation of the adhesive layer and / or surface protective film and / or separator by the chips can be significantly suppressed. As a result, insufficient adhesive and protrusion of the surface protective film and separator can be significantly suppressed.

[0062] In one embodiment, it is preferable that during the formation of the through hole (cutting process), air is supplied from the side opposite to the chip discharge side toward the discharge direction. With this structure, chip discharge is more efficient, thus better suppressing defects in the adhesive and the protrusion of the surface protective film and separator. The air supply pressure is, for example, 0.05 MPa to 1 MPa, the air velocity is, for example, 1500 m / min to 15000 m / min, and the air volume is, for example, 5 L / min to 1000 L / min.

[0063] The next hole 52 and subsequent holes are representative as follows: Figure 7 As shown in (b), it can be formed by an end mill 60 that is fixed at both ends (maintaining the state of both ends).

[0064] The end mill used for forming the next hole 52 and subsequent holes (hereinafter, sometimes referred to as cutting by circumferential movement) can be either the same as or different from the end mill used to form the pre-drilled hole 51. When the end mill used for cutting by circumferential movement is the same as the end mill used to form the pre-drilled hole, the vertical movement direction of this end mill during cutting by circumferential movement is preferably upward. More specifically, the pre-drilled hole is typically formed by moving the end mill in a cantilevered state (the upper end is held) downward, as described above. In this case, from the viewpoint of suppressing insufficient adhesive and the protrusion of the surface protective film and the separator, the chip discharge direction is preferably upward. Therefore, the vertical movement direction of this end mill during cutting by circumferential movement is preferably the chip discharge direction, i.e., upward. When the end mill used for cutting by circumferential movement is different from the end mill used to form the pre-drilled hole, the vertical movement direction of this end mill during cutting by circumferential movement can be either upward or downward, corresponding to the structure of the end mill (the chip discharge direction).

[0065] The cutting distance P can vary depending on the size of the through hole, the outer diameter of the end mill, and the number of times the end mill rotates. The number of times the end mill rotates can also vary depending on the size of the through hole, the outer diameter of the end mill, and the cutting distance P. The cutting distance is, for example, 5μm to 20μm, preferably 5μm to 10μm. For example, when the size of the through hole is 3mm, the outer diameter of the end mill is 2mm, and the cutting distance P is 10μm, the number of times the end mill rotates is 50.

[0066] The cutting conditions for forming the through hole can be appropriately set according to the size of the through hole, the outer diameter of the end mill, and the number of turns of the end mill. The rotational speed of the end mill is preferably 1000 rpm to 10000 rpm, more preferably 1500 rpm to 4000 rpm. The feed rate of the end mill is preferably 50 mm / min to 2000 mm / min, more preferably 70 mm / min to 1000 mm / min, and even more preferably 70 mm / min to 400 mm / min.

[0067] A through hole 50 with a predetermined diameter is formed by repeating the cutting along the end face of the hole with an end mill as described above a predetermined number of times (i.e., cutting with an end mill a predetermined number of times around the hole). The end face of the through hole may also be finely cut as needed.

[0068] As described above, an optical laminate with an adhesive layer and through-holes can be obtained. The optical laminate with an adhesive layer obtained by the manufacturing method of the present invention suppresses adhesive defects and protrusions in the surface protective film and separators.

[0069] Example

[0070] The present invention will now be described in detail through embodiments, but the present invention is not limited to these embodiments. The evaluation criteria for the embodiments are as follows.

[0071] (1) Lack of glue

[0072] Ten optical laminates with adhesive layers and through holes were extracted from the workpieces obtained in the Examples and Comparative Examples. These ten optical laminates with adhesive layers consisted of the top and bottom optical laminates with adhesive layers, one optical laminate with adhesive layers extracted from the top and bottom portions after dividing the workpiece into five equal parts along its thickness direction, and two optical laminates with adhesive layers randomly extracted from each of the three central portions. For each of these ten optical laminates with adhesive layers, the through-hole portions were observed for missing adhesive using a magnifying glass or microscope. If no missing adhesive greater than 50 μm was observed, the optical laminate with adhesive layers was counted as a "no missing adhesive" sample. The percentage (%) of the ten "no missing adhesive" samples was used as the evaluation criterion. For Examples 5 and Comparative Example 3, 50 sets of workpieces were prepared, and a total of 500 samples were evaluated.

[0073] A: Over 90% of the samples were "free of defective glue".

[0074] B: The percentage of samples with "no defective glue" is between 60% and 90%.

[0075] C: Less than 60% of the samples were "without defective glue".

[0076] (2) Surface protective film or raised parts

[0077] Similar to (1) above, the surface protective film or the protrusion of the separator in the through hole portion was observed. If no protrusion greater than 50 μm was observed, the optical laminate with the adhesive layer was considered a "protrusion-free" sample. The percentage (%) of "protrusion-free" samples out of 10 pieces was used as the evaluation criterion. For Example 5 and Comparative Example 3, 50 sets of workpieces were prepared, and a total of 500 samples were evaluated.

[0078] A: Over 98% of the samples were "without raised bumps".

[0079] B: The percentage of samples with "no bulging" is over 60% but less than 98%.

[0080] C: Less than 60% of the samples are "without convexity".

[0081] (3) Cracks

[0082] Similar to (1) above, the through-hole portion was observed for cracks. If no cracks larger than 50 μm were observed, the optical laminate with the adhesive layer was considered a "crack-free" sample. The percentage (%) of "crack-free" samples out of 10 pieces was used as the evaluation criterion. For Example 5 and Comparative Example 3, 50 sets of workpieces were prepared, and a total of 500 samples were evaluated.

[0083] A: Over 98% of the samples were "crack-free".

[0084] B: More than 60% of the samples were "crack-free" but less than 98%.

[0085] C: Less than 60% of the samples were "crack-free".

[0086] <Example 1>

[0087] A polarizer with an adhesive layer was fabricated according to conventional methods, consisting of a surface protective film (58 μm), an HC-TAC protective film (32 μm), a polarizer (5 μm), an adhesive layer (15 μm), and a separator (38 μm) in sequence from the visible side. The HC-TAC protective film is a film with a 7 μm hard coating (HC) layer formed on a 25 μm cellulose triacetate (TAC) film, laminated with the TAC film on the polarizer side. As the surface protective film, a surface protective film with a structure of a 38 μm PET substrate and a 20 μm PF adhesive layer was used. The creep value of the adhesive layer was 73 μm. The resulting polarizer with the adhesive layer was punched to a 5.7-inch size (approximately 140 mm in length and 65 mm in width), and 120 of these punched polarizers were stacked to form a workpiece (total thickness approximately 18 mm). With the workpiece held in a fixture, a through hole with a diameter of 3 mm is formed at the corner using an end mill. More specifically, as described below. The end mill used to form the through hole has an outer diameter of 2.0 mm, an effective cutting edge length of 30 mm, a cutting edge angle of 25°, a rake angle of 20°, a clearance angle of 30°, and is a right-handed, right-hand helical cutter (chip discharge direction is upward). Using this end mill, firstly, a pre-drilled hole (diameter 2 μm) is formed by moving it downward from the surface protective film side (above) in a cantilevered position. Next, the end mill is set to a fixed-end position, as follows... Figure 9 As in (a), the end mill is positioned so that it abuts against the end face of the pre-drilled hole while cutting, and then circles around the end face of the pre-drilled hole once. The cutting distance is 10 μm. In this embodiment, the end mill is circled once and moved upwards by 4 mm. After circling, the end mill is returned to A. S After positioning, move the end mill downwards by 4mm (i.e., move it downwards by 4mm without cutting), and return it to its original position in the vertical direction. Next, move the end mill from position A... S To BS The end mill is moved and cut by the next circle of the end mill described above. This cutting by the circle of the end mill is repeated to form a through hole with a diameter of 3 mm. The horizontal movement speed of the end mill during the circle is 250 mm / min, and the rotation speed is 2500 rpm. The polarizer with adhesive layer and through hole obtained above (1) to (3) was evaluated. The results are shown in Table 1.

[0088] <Example 2>

[0089] In a cantilevered configuration, cutting was performed using an end mill. A polarizer with a through-hole and adhesive layer was fabricated in the same manner as in Example 1. The obtained polarizer with a through-hole and adhesive layer was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0090] <Comparative Example 1>

[0091] In the cutting process performed by surrounding the end mill, the end mill was not moved upwards (only horizontally), and otherwise, a polarizer with a through-hole and adhesive layer was obtained in the same manner as in Example 1. The obtained polarizer with a through-hole and adhesive layer was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0092] <Comparative Example 2>

[0093] In the cutting process performed by surrounding the end mill, the end mill was not moved upwards (only horizontally). Otherwise, a polarizer with a through-hole and adhesive layer was fabricated in the same manner as in Example 2. The obtained polarizer with a through-hole and adhesive layer was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0094] <Example 3>

[0095] A circular polarizer with an adhesive layer was fabricated using conventional methods, comprising, from the visible side, a surface protective film (58 μm) / an HC-TAC protective film (32 μm) / a polarizer (12 μm) / a TAC protective film (25 μm) / an adhesive layer (1 μm) / a first retardation layer (2.5 μm thick) / an adhesive layer (5 μm) / a second retardation layer (1.5 μm thick) / an adhesive layer (20 μm) / a separator (38 μm). Furthermore, both the first and second retardation layers are alignment-cured layers of a liquid crystal compound, with an in-plane phase difference of 240 nm for the first retardation layer and 120 nm for the second retardation layer. The angle between the slow axis of the first retardation layer and the absorption axis of the polarizer is 15°, and the angle between the slow axis of the second retardation layer and the absorption axis of the polarizer is 75°. The creep value of the adhesive layer is 73 μm. The obtained polarizer with adhesive layer was punched to a size of 5.7 inches (approximately 140 mm in length and 65 mm in width). Ninety punched polarizers were stacked to form a workpiece (total thickness approximately 18 mm). Hereinafter, circular polarizers with through holes and adhesive layers were fabricated in the same manner as in Example 1, except that the horizontal movement speed of the end mill was set to 70 mm / min. The obtained circular polarizers with through holes and adhesive layers were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0096] <Example 4>

[0097] The horizontal movement speed of the end mill during its circumduction was set to 125 mm / min. Otherwise, a circular polarizer with a through-hole and adhesive layer was fabricated in the same manner as in Example 3. The obtained circular polarizer with a through-hole and adhesive layer was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0098] <Example 5>

[0099] The horizontal movement speed of the end mill during its circumduction was set to 250 mm / min. Otherwise, a circular polarizer with a through-hole and adhesive layer was fabricated in the same manner as in Example 3. The obtained circular polarizer with a through-hole and adhesive layer was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0100] <Comparative Example 3>

[0101] In the cutting process performed by surrounding the end mill, the end mill was not moved upwards (only horizontally), and the cutting was performed by surrounding the end mill in a cantilevered state. Otherwise, a circular polarizer with a through-hole and adhesive layer was fabricated in the same manner as in Example 5. The obtained circular polarizer with a through-hole and adhesive layer was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0102] <Comparative Example 4>

[0103] In cutting operations performed by surrounding the end mill, such as Figure 10 As shown, the end mill was moved vertically in a sinusoidal manner. Specifically, during one complete revolution of the end mill, it was moved 2 mm vertically and horizontally. In addition, a circular polarizer with a through-hole and adhesive layer was fabricated in the same manner as in Comparative Example 3. The obtained circular polarizer with a through-hole and adhesive layer was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0104] [Table 1]

[0105]

[0106] <Evaluation>

[0107] As shown in Table 1, according to an embodiment of the present invention, in the formation of the through hole of the optical laminate with the adhesive layer, when the end mill is surrounded, the end mill is moved in either the upward or downward direction, thereby significantly suppressing the lack of adhesive and the protrusion of the surface protective film or the separator.

[0108] Industrial availability

[0109] The manufacturing method of the present invention is suitable for manufacturing optical laminates with adhesive layers that require through holes. The optical laminates with adhesive layers obtained according to the manufacturing method of the present invention are suitable for use in automotive dashboards, smartwatches, and image display units with through holes, such as image display devices with camera units.

[0110] Explanation of reference numerals in the attached figures

[0111] W, workpiece; 10, optical film; 20, adhesive layer; 30, separator; 40, surface protective film; 60, end mill; 100, optical laminate with adhesive layer.

Claims

1. A method for manufacturing an optical laminate with an adhesive layer having through holes, wherein, The manufacturing method includes: To form a workpiece by stacking multiple optical laminates with adhesive layers; and A through hole is formed at a predetermined position on the workpiece by using an end mill. The optical laminate with an adhesive layer includes an optical film, an adhesive layer disposed on one side of the optical film, a release element temporarily bonded to the adhesive layer in a peelable manner, and a surface protective film temporarily bonded to the other side of the optical film in a peelable manner. The formation of the through hole includes: simultaneously bringing the end mill against the end face of the hole and cutting, and simultaneously moving the end mill in either upward or downward direction and cutting. When the end mill is a right-hand helical cutter or a left-hand helical cutter, the end mill moves upward; when the end mill is a right-hand helical cutter or a left-hand helical cutter, the end mill moves downward.

2. The manufacturing method according to claim 1, wherein, The formation of the through hole includes: Pre-drilled holes were formed; While the end mill is brought into contact with the end face of the pre-drilled hole and cutting is performed, the end mill is moved along the end face of the pre-drilled hole and moves from a predetermined position at the start of cutting in either the upward or downward direction and around the hole to form a next hole with a diameter that is a predetermined amount larger than the diameter of the pre-drilled hole. The end mill is returned to the predetermined position, while simultaneously abutting the end mill against the end face of the next hole and cutting. At the same time, the end mill is moved along the end face of the next hole and from the predetermined position in either upward or downward direction, completing a full circle to form a next hole with a diameter predetermined amount larger than the diameter of the previous hole; and A through hole with a predetermined diameter is formed by repeating the cutting along the end face of the hole a predetermined number of times by using an end mill to encircle it.

3. The manufacturing method according to claim 2, wherein, The formation of the through hole includes: forming the pre-drilled hole using an end mill in a cantilevered state; and forming the next hole and subsequent holes using an end mill in a fixed state at both ends.

4. The manufacturing method according to claim 2 or 3, wherein, The end mill used to form the pre-drilled hole is the same end mill used to form the next hole and subsequent holes, and the direction of vertical movement of the end mill used to form the next hole and subsequent holes is upward.

5. The manufacturing method according to any one of claims 1 to 3, wherein, The thickness of the workpiece is 10 mm or more.

6. The manufacturing method according to any one of claims 1 to 3, wherein, The optical thin film includes a polarizer.

7. The manufacturing method according to any one of claims 1 to 3, wherein, The optical thin film includes a polarizer.

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