Optical laminate and image display device including optical film of optical laminate

Abstract

To provide an optical laminate in which peeling failure is remarkably suppressed when a surface protective film is peeled from a deformed processed part.SOLUTION: An optical laminate according to an embodiment of the present invention includes an optical film, a surface protective film temporarily bonded in a peelable manner to one side of the optical film, a pressure-sensitive adhesive layer arranged on the other side of the optical film, and a separator temporarily bonded in a peelable manner to the pressure-sensitive adhesive layer. The optical laminate has an irregular shape other than a rectangular shape. An upper end of the surface-protection film extends outward from a lower end thereof, a length of a straight line connecting outer edges of the optical laminate in a direction orthogonal to a peeling direction at a position 1mm away in the peeling direction from a peeling start point when the surface-protection film is peeled from the irregular shape is 2mm or more, and a bending load of the surface-protection film is 2. 5g or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical laminate and an image display device including an optical film of the optical laminate. [Background technology]

[0002] Various optical laminates (e.g., polarizing plates) are used in image display devices such as mobile phones and notebook personal computers to realize image display and / or improve the performance of the image display. Typically, an optical laminate has a pressure-sensitive adhesive layer as its outermost layer, allowing it to be attached to an image display cell. In practice, a separator is temporarily and releasably attached to the pressure-sensitive adhesive layer to protect the pressure-sensitive adhesive layer until actual use. Furthermore, in practice, a surface protection film is temporarily and releasably attached to the side of the optical laminate opposite the pressure-sensitive adhesive layer to protect the optical laminate during manufacturing, transportation, etc. In recent years, there have been cases where optical films are desired to be processed into shapes other than rectangular (deformed shapes: for example, rounded corner chamfering, notches, and / or through-holes). However, peeling the surface protection film from the deformed portion can result in poor peeling. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-022140 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-203167 Summary of the Invention [Problem to be solved by the invention]

[0004] A primary object of the present invention is to provide an optical laminate in which peeling failure when peeling a surface protection film from a contoured portion is significantly suppressed. [Means for solving the problem]

[0005] An optical laminate according to an embodiment of the present invention includes an optical film, a surface protection film releasably attached to one side of the optical film, a pressure-sensitive adhesive layer disposed on the other side of the optical film, and a separator releasably attached to the pressure-sensitive adhesive layer. The optical laminate has an irregular shape other than a rectangular shape. The upper end of the surface protection film extends outward beyond the lower end, and the length of a straight line connecting the outer edges of the optical laminate in a direction perpendicular to the peel direction at a position 1 mm away from the peel start point in the peel direction when peeling the surface protection film from the irregular shape is 2 mm or more, and the bending load of the surface protection film is 2.5 g or less. In one embodiment, the contour includes rounded corners. In one embodiment, the initial peel force required to peel off the surface protection film is 2.0 N or less. In one embodiment, the surface protection film has a thickness of 100 μm or less. In one embodiment, the extension length of the upper end of the surface protection film is 1 μm to 70 μm. In one embodiment, the optical film comprises a polarizer. According to another aspect of the present invention, there is provided an image display device, which includes the optical film of the optical laminate. [Effects of the Invention]

[0006] According to an embodiment of the present invention, in an optical laminate having a surface protection film, an optical film, and a separator, and having an irregularly shaped portion, when the upper end of the surface protection film extends outward more than the lower end, and the length of a straight line connecting the outer edge of the optical laminate in a direction perpendicular to the peeling direction at a position 1 mm away from the peeling starting point when peeling the surface protection film from the irregularly shaped portion is 2 mm or more, by setting the bending load of the surface protection film to 2.5 g or less, an optical laminate can be realized in which peeling defects when peeling the surface protection film from the irregularly shaped portion are significantly suppressed. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. [Figure 2] 1 is a schematic plan view illustrating an example of an irregularly shaped or irregularly processed portion in an optical laminate according to an embodiment of the present invention. [Figure 3] 10A and 10B are schematic plan views illustrating modified examples of irregularly shaped or irregularly shaped processed portions in the optical laminate according to the embodiment of the present invention. [Figure 4] 10A and 10B are schematic plan views illustrating further modified examples of irregularly shaped or irregularly shaped processed portions in the optical laminate according to the embodiment of the present invention. [Figure 5] 1 is a schematic diagram for explaining the relationship between an irregular shape or irregularly processed portion and peel characteristics in an optical laminate according to an embodiment of the present invention. [Figure 6] FIG. 2 is a schematic diagram illustrating a method for measuring the bending load of a surface protection film that can be used in an optical laminate according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

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

[0009] A. Optical laminate A-1. Overview of optical laminate FIG. 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. The illustrated optical laminate 100 includes an optical film 10, a surface protection film 20 releasably and temporarily attached to one side of the optical film 10, a pressure-sensitive adhesive layer 30 disposed on the other side of the optical film 10, and a separator 40 releasably and temporarily attached to the pressure-sensitive adhesive layer 30. When the optical laminate is used in an image display device, the separator 40 is typically disposed on the image display cell side. When the optical laminate (substantially an optical film) is actually used, the separator 40 is peeled off and removed, and the pressure-sensitive adhesive layer 30 is used to attach the optical laminate (substantially an optical film) to the image display device (substantially an image display cell). The surface protection film 20 typically includes a substrate 21 and a pressure-sensitive adhesive layer 22. The pressure-sensitive adhesive layer 22 of the surface protection film is sometimes referred to as a "PF pressure-sensitive adhesive layer" to distinguish it from the pressure-sensitive adhesive layer 30. The surface protection film 20 is also peeled off and removed when the optical laminate is actually used.

[0010] In an embodiment of the present invention, the optical laminate has an irregular shape other than rectangular. In this specification, "having an irregular shape other than rectangular" means that the planar shape of the optical laminate is other than rectangular. The irregular shape is typically an irregularly processed portion. Therefore, an "optical laminate having an irregular shape other than rectangular" (hereinafter, sometimes referred to as an "irregularly processed optical laminate") includes not only an irregularly shaped optical laminate in which the entire optical laminate (i.e., the outer edge defining the planar shape of the optical laminate) is other than rectangular, but also an irregularly processed portion formed in a portion spaced inward from the outer edge of the rectangular optical laminate. Peeling a surface protective film from such an irregularly processed portion is likely to result in poor peeling. However, according to an embodiment of the present invention, such poor peeling can be significantly suppressed. Examples of irregular shapes (irregularly processed portions) include those with rounded chamfered corners, through holes, and machined portions that form recesses in plan view, as shown in FIG. 2. Typical examples of recesses include a boat-like shape (not shown), a rectangle, a bathtub-like R-shape, a V-notch, and a U-notch. Another example of the irregular shape (irregularly processed portion) is a shape corresponding to an automobile meter panel, as shown in FIGS. 3 and 4. This shape includes a portion in which the outer edge is formed in an arc shape along the rotation direction of the meter needle and the outer edge forms a V-shape (including a rounded shape) that protrudes inward in the planar direction. Needless to say, the shape of the irregular shape (irregularly processed portion) is not limited to the illustrated example. For example, the shape of the through hole may be any appropriate shape (e.g., ellipse, triangle, square, pentagon, hexagon, octagon) depending on the purpose, in addition to the approximately circular shape shown in the illustrated example. Furthermore, the through hole may be provided in any appropriate position depending on the purpose. The through hole may be provided in approximately the center of the longitudinal end of the rectangular optical laminate, as shown in FIG. 2, at a predetermined position of the longitudinal end, or at a corner of the optical laminate; or, although not shown, at the lateral end of the rectangular optical laminate; or, as shown in FIG. 3 or 4, at the center of the irregularly shaped optical laminate. Multiple through holes may be provided. Furthermore, the shapes of the illustrated examples may be appropriately combined depending on the purpose. For example, a V-shaped notch and / or a U-shaped notch may be formed at any appropriate position on the outer edge of the irregular optical laminate of FIG. 3 or FIG.Such irregular optical laminates can be suitably used in image display devices such as automobile meter panels, smartphones, tablet PCs, and smart watches.

[0011] When the irregular shape includes a rounded shape, the radius of curvature is, for example, 0.2 mm or more, for example, 1 mm or more, for example, 2 mm or more, for example, 3 mm or more, for example, 5 mm or more, or for example, 10 mm or more. On the other hand, the radius of curvature is, for example, 30 mm or less, for example, 25 mm or less, for example, 20 mm or less, for example, 15 mm or less, or for example, 10 mm or less. When the irregular shape includes rounded corners, the radius of curvature of the corners is, for example, 3 μm to 30 μm, for example, 5 μm to 25 μm, or for example, 10 μm to 25 μm. The radius of curvature of the corners may be, for example, 5 μm to 15 μm. The effects of the embodiments of the present invention can be significant in an optical laminate having a rounded processed portion with such a curvature radius. When the irregular shape includes a rounded shape, it may include multiple rounded shapes. Furthermore, one rounded shape may be a combination of multiple curvatures.

[0012] In an embodiment of the present invention, as shown in FIG. 1 , the upper end of the surface protection film 20 extends outward beyond the lower end. Therefore, the cross-sectional shape of the surface protection film may be a trapezoid with the upper base longer than the lower base. The inventors discovered that such an extended portion is formed in the surface protection film due to the contouring process, and that this extended portion can affect the peeling characteristics when the surface protection film is peeled from the contoured portion. Furthermore, the inventors thoroughly investigated the relationship between the configuration of the optical laminate, the extended portion, and the peeling characteristics of the surface protection film. As a result, they discovered that by setting the bending load of the surface protection film (described below) to a predetermined value or less, peeling failures when the surface protection film is peeled from the contoured portion can be significantly suppressed, thereby completing the present invention. Note that the upper end of the surface protection film 20 essentially extends outward from the lower end of the PF pressure-sensitive adhesive layer 22, as shown in FIG. 1 . In this specification, the "extension length L of the surface protection film" refers to the length starting from the lower end of the PF pressure-sensitive adhesive layer 22, as shown in FIG. 1 . The extension length L is, for example, 1 μm to 70 μm, or, for example, 5 μm to 70 μm, or, for example, 6 μm to 55 μm, or, for example, 7 μm to 45 μm.

[0013] The contouring can be performed in any suitable manner. Specific examples include laser light irradiation, cutting with an end mill, and punching with a Thomson blade or Pinnacle (registered trademark) blade. The extended portion shown in FIG. 1 can be formed, for example, by irradiating the optical laminate with laser light from the separator side, or by cutting the optical laminate with an end mill with the surface protection film facing up.

[0014] In an embodiment of the present invention, as shown in Fig. 5, the length of a straight line AB connecting the outer edges of the optical laminate in a direction perpendicular to the peeling direction at a position 1 mm away from the peeling start point in peeling the surface protection film from the contoured portion is 2 mm or more. The length of the straight line AB is, for example, 3 mm or more, or, for example, 4 mm or more, or, for example, 5 mm or more, or, for example, 6 mm or more. On the other hand, the length of the straight line AB is, for example, 100 mm or less, or, for example, 50 mm or less, or, for example, 30 mm or less, or, for example, 20 mm or less, or, for example, 18 mm or less, or, for example, 15 mm or less. The length of the straight line AB may be, for example, 5.5 µm to 9.5 µm, or, for example, 5.8 µm to 9.0 µm. The length of the straight line AB being equal to or greater than a predetermined value means that it is difficult to secure an opening for peeling the surface protection film from the contoured portion. For example, in the case of an irregular optical laminate such as that shown in Figures 3 and 4, the force, i.e., stress, required for peeling is dispersed when peeling off the surface protective film, making peeling extremely difficult. According to an embodiment of the present invention, even with such a configuration, the surface protective film can be easily peeled off from the irregularly processed portion without causing peeling problems.

[0015] In an embodiment of the present invention, the bending load of the surface protection film is 2.5 g or less. Even if the contoured portion has a shape that makes peeling difficult, peeling defects can be significantly suppressed when peeling the surface protection film from the contoured portion. As described above, the surface protection film has a substrate and a pressure-sensitive adhesive layer. However, even if the substrate thickness, pressure-sensitive adhesive layer thickness, overall thickness, elastic modulus of the substrate, elastic modulus of the pressure-sensitive adhesive layer, etc. are individually adjusted, peeling defects cannot be comprehensively suppressed. In other words, even if each component of the surface protection film is individually changed, a clear correlation cannot be obtained between the cases in which peeling defects are suppressed and the cases in which peeling defects occur. The present inventors have found that by setting the bending load of the surface protection film to 2.5 g or less, peeling defects can be comprehensively suppressed when peeling the surface protection film from the contoured portion. The bending load can be measured as follows. As shown in FIG. 6, a jig with a U-shaped cross section is prepared and placed 30 mm away from the weighing platform so as to cover the weighing platform. A sample of a surface protection film punched into a dumbbell-shaped multipurpose test piece (total length 150 mm) according to JIS K 7139-A1 is folded exactly in half and placed on a weighing platform, and the load applied to the weighing platform due to the surface protection film attempting to return to its original shape being restricted by the upper jig can be measured as the bending load.

[0016] In one embodiment, the bending load of the surface protection film is, for example, 2.0 g or less, for example, 1.5 g or less, for example, 1 g or less, for example, 0.8 g or less, for example, 0.5 g or less, for example, 0.3 g or less, for example, 0.1 g or less, for example, 0.05 g or less, or for example, 0.03 g or less. The lower limit of the bending load may be, for example, 0.005 g. When the bending load of the surface protection film is within this range, peeling failure when peeling the surface protection film can be extremely effectively prevented. In another embodiment, the bending load of the surface protection film may be, for example, 0.5 g to 2.0 g. When the bending load of the surface protection film is within this range, peeling failure can be appropriately prevented and dents can be effectively prevented.

[0017] In an embodiment of the present invention, the initial peel force when peeling the surface protection film is, for example, 2.0 N or less, for example, 1.5 N or less, for example, 1.2 N or less, for example, 1.0 N or less, for example, 0.8 N or less, for example, 0.7 N or less, for example, 0.6 N or less, or for example, 0.5 N or less. The lower limit of the initial peel force may be, for example, 0.05 N. When the initial peel force is within this range, the surface protection film can be easily peeled, and peel failure can be significantly suppressed. The initial peel force may be measured, for example, in accordance with JIS Z 0237. Specifically, a pickup tape is applied to the surface of the surface protection film of a test sample (optical laminate) along the peeling direction, and the peel force measured when the pickup tape is used to peel the film at a 90° tensile direction can be the initial peel force. The width of the pickup tape may be, for example, 10 mm, and the pulling speed may be, for example, 300 mm / min.

[0018] A-2. Optical film The optical film 10 may be a film composed of a single layer or a laminate. Specific examples of optical films composed of a single layer include window films, polarizers, and retardation films. Specific examples of optical films composed as laminates include polarizing plates (typically, laminates of a polarizer and a protective film), conductive films for touch panels, surface-treated films, and laminates in which optical films composed of these single layers and / or optical films composed as laminates are appropriately laminated depending on the purpose (e.g., anti-reflection circular polarizing plates, polarizing plates with a conductive layer for touch panels).

[0019] A-3.Surface protection film As described above, the surface protection film 20 typically includes a substrate 21 and a PF pressure-sensitive adhesive layer 22. The substrate 21 can be made of any suitable material as long as it can achieve the desired bending load. Specific examples of constituent materials include polyester-based polymers such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene terephthalate (PBT); cellulose-based polymers such as diacetyl cellulose and triacetyl cellulose; polycarbonate-based polymers; (meth)acrylic polymers such as polymethyl methacrylate; and cycloolefin-based polymers such as polynorbornene. These may be used alone or in combination of two or more. Polyester-based polymers are preferred, and among them, those with excellent optical properties (e.g., transparency), mechanical strength, thermal stability, moisture barrier properties, isotropy, flexibility, and dimensional stability are preferably used. In particular, polyester films that are not too stiff can easily achieve the desired bending load. The properties of the polyester film can be controlled by adjusting the type and combination of the polycarboxylic acid component and polyol component. For example, polyethylene terephthalate and polybutylene terephthalate may be used in combination as the constituent materials of the substrate.

[0020] Other examples of materials constituting the substrate include styrene-based polymers such as polystyrene and acrylonitrile-styrene copolymers; vinyl chloride-based polymers; amide-based polymers such as nylon 6, nylon 6,6, and aromatic polyamides; imide-based polymers; sulfone-based polymers; polyethersulfone-based polymers; polyetheretherketone-based polymers; polyphenylene sulfide-based polymers; vinyl alcohol-based polymers; vinylidene chloride-based polymers; vinyl butyral-based polymers; arylate-based polymers; polyoxymethylene-based polymers; and epoxy-based polymers. These may be used alone or in combination of two or more.

[0021] In one embodiment, the substrate may have a laminated structure of resin layer / adhesive layer / resin layer. Constituent materials for the resin layer include those described above as constituent materials for the substrate. Constituent materials for the adhesive layer include adhesives, pressure-sensitive adhesives, and anchor coating agents. The adhesive layer may have a laminated structure of an adhesive layer or pressure-sensitive adhesive layer and an anchor coating layer. By interposing an adhesive layer having predetermined properties (e.g., elastic modulus) between two resin layers, the elastic modulus (e.g., tensile elastic modulus) can be reduced to a desired degree depending on the purpose. As a result, the desired bending load can be easily achieved.

[0022] The tensile modulus of the substrate 21 is, for example, 2.3×10 9 Pa or less, preferably 1.5 × 10 9 Pa or less, and more preferably 1.3×10 9 Pa or less, and more preferably 1.0 × 10 7 Pa~1.3×10 9 Pa, and particularly preferably 1.0×10 8 Pa~1.3×10 9 The tensile modulus of elasticity is Pa. If the base material has a tensile modulus within this range, it is easy to achieve the desired bending load. The tensile modulus of elasticity is measured in accordance with JIS K 7161.

[0023] In one embodiment, the thickness of the substrate is, for example, 20 μm to 100 μm, for example, 25 μm to 80 μm, or for example, 30 μm to 50 μm. If the thickness of the substrate is within this range, peeling failure when peeling off the surface protective film can be extremely effectively prevented. In another embodiment, the thickness of the substrate can be, for example, 60 μm to 90 μm. If the thickness of the substrate is within this range, peeling failure can be appropriately prevented while dents can be effectively prevented.

[0024] The PF pressure-sensitive adhesive layer 22 may have any suitable structure as long as it can achieve the desired bending load. Specific examples include acrylic pressure-sensitive adhesives, rubber pressure-sensitive adhesives, silicone pressure-sensitive adhesives, polyester pressure-sensitive adhesives, urethane pressure-sensitive adhesives, epoxy pressure-sensitive adhesives, and polyether pressure-sensitive adhesives. By adjusting the type, number, combination, and compounding ratio of the monomers forming the base resin of the pressure-sensitive adhesive, as well as the amount of cross-linking agent, reaction temperature, reaction time, and other factors, a pressure-sensitive adhesive with desired properties can be prepared. The base resin of the pressure-sensitive adhesive may be used alone or in combination of two or more types. The base resin is preferably an acrylic resin (i.e., the PF pressure-sensitive adhesive layer is preferably composed of an acrylic pressure-sensitive adhesive). The pressure-sensitive adhesive constituting the PF pressure-sensitive adhesive layer is characterized in that the base resin contains a polymer having an active hydrogen-containing functional group (e.g., a hydroxyl group). Using such a base resin, a PF pressure-sensitive adhesive layer with the desired storage modulus can be obtained. Details of the adhesive that constitutes the PF adhesive layer are described, for example, in JP 2018-123281 A, the disclosure of which is incorporated herein by reference.

[0025] The thickness of the PF pressure-sensitive adhesive layer 22 is, for example, 5 μm to 50 μm, for example, 10 μm to 40 μm, or for example, 10 μm to 30 μm. If the thickness of the PF pressure-sensitive adhesive layer is in this range, the desired bending load can be easily achieved.

[0026] The storage modulus G' of the PF pressure-sensitive adhesive layer 22 at 25°C is, for example, 0.5 × 10 6 (Pa) ~ 3.0 × 106 (Pa). If the storage modulus is within this range, the desired bending load can be easily achieved. Furthermore, a pressure-sensitive adhesive layer (and consequently a surface protection film) with an excellent balance between adhesion and releasability can be obtained. The storage modulus can be determined, for example, by dynamic viscoelasticity measurement.

[0027] The thickness of the surface protection film 20 is, for example, 100 μm or less, for example, 30 μm to 90 μm, for example, 40 μm to 80 μm, or for example, 45 μm to 70 μm. If the thickness of the surface protection film is within this range, the desired bending load can be easily achieved. Furthermore, peeling defects when peeling the surface protection film can be extremely effectively prevented. The thickness of the surface protection film may be, for example, 70 μm to 100 μm. If the thickness of the surface protection film is within this range, peeling defects can be appropriately suppressed while dents can be effectively suppressed. The thickness of the surface protection film refers to the total thickness of the substrate and the PF pressure-sensitive adhesive layer.

[0028] A-4.Adhesive layer The adhesive layer 30 may have any suitable structure. Specific examples of adhesives constituting the adhesive layer include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. By adjusting the type, number, combination, and compounding ratio of monomers constituting the adhesive base resin, as well as the amount of crosslinking agent, reaction temperature, reaction time, and the like, adhesives with desired properties can be prepared according to the intended purpose. The adhesive base resin may be used alone or in combination of two or more types. From the viewpoints of transparency, processability, durability, and the like, acrylic adhesives are preferred. Details of adhesives constituting the adhesive layer are described, for example, in JP 2014-115468 A, the disclosure of which is incorporated herein by reference. The thickness of the adhesive layer 30 may be, for example, 10 μm to 100 μm. The storage modulus G' of the adhesive layer 30 at 25°C is, for example, 1.0 × 10 4 (Pa) ~ 1.0 × 10 6(Pa).

[0029] A-5. Separator Any appropriate separator can be used as the separator 40. Specific examples include plastic films, nonwoven fabrics, and paper whose surfaces are coated with a release agent. Specific examples of release agents include silicone-based release agents, fluorine-based 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 separator can be, for example, 10 μm to 100 μm.

[0030] B. Image display device The optical laminate (substantially, an optical film) according to an embodiment of the present invention can be suitably applied to an image display device. Therefore, an image display device including the optical laminate (substantially, an optical film) is also included in the embodiment of the present invention. The image display device typically includes an image display cell and an optical film bonded to the image display cell via an adhesive layer. Examples of the image display device include a liquid crystal display device, an organic electroluminescence (EL) display device, and a quantum dot display device. [Example]

[0031] The present invention will be specifically described below using examples, but the present invention is not limited to these examples. The evaluation items in the examples are as follows. Unless otherwise specified, "parts" and "%" in the examples are by weight.

[0032] (1) Extension length L The cross sections of the optical laminates obtained in the examples and comparative examples were photographed with a scanning electron microscope, and measurements were made from the obtained images. (2) Bending load of surface protection film As shown in Figure 6, a jig with a U-shaped cross section was prepared and placed 30 mm away from the weighing table. The surface protection films used in the examples and comparative examples were punched out into dumbbell-shaped multipurpose test pieces (total length 150 mm) according to JIS K 7139-A1 to prepare samples. This sample was folded exactly in half and placed on the weighing table, and the load applied to the weighing table when the sample (surface protection film) tried to restore its original shape was measured as the bending load. (3) Peelability and initial peel strength Measurements were made in accordance with JIS Z 0237. Specifically, a pickup tape was attached to the surface of the surface protection film of the optical laminate obtained in the Examples and Comparative Examples along the peeling direction (a direction perpendicular to the tangent to the R-shape), and the peel force when the pickup tape was used to peel at a 90° tensile direction was measured as the initial peel force. The pickup tape used in this measurement was No. 315, a polyester adhesive tape manufactured by Nitto Denko Corporation. The width of the pickup tape was 10 mm, the length of the bonded portion was 10 mm, and the pulling speed was 300 mm / min. Measurements were made with n=6, and the average value excluding values ​​that clearly deviated was taken as the initial peel force.

[0033] <Production Example 1: Preparation of Acrylic Polymer A1> A four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser was charged with a monomer mixture containing 96 parts of 2-ethylhexyl acrylate and 4 parts of 2-hydroxyethyl acrylate. Furthermore, 0.1 parts of 2,2'-azobisisobutyronitrile as a polymerization initiator and 100 parts of ethyl acetate were charged to 100 parts of this monomer mixture. Nitrogen gas was introduced with gentle stirring to replace the atmosphere, and the temperature in the flask was maintained at around 55°C, allowing the polymerization reaction to proceed for 8 hours to prepare a solution of acrylic polymer A1 with a weight-average molecular weight (Mw) of 540,000.

[0034] <Production Example 2: Preparation of Acrylic Polymer A2> A solution of acrylic polymer A2 having a weight average molecular weight (Mw) of 540,000 was prepared in the same manner as in Production Example 1, except that a monomer mixture containing 91 parts of 2-ethylhexyl acrylate and 9 parts of 4-hydroxybutyl acrylate was used.

[0035] <Production Example 3: Preparation of Pressure-Sensitive Adhesive Composition PSA1> A solution of acrylic pressure-sensitive adhesive composition PSA1 was prepared by blending 5 parts of an isocyanate crosslinking agent (manufactured by Tosoh Corporation, product name "Coronate HX", an isocyanurate of hexamethylene diisocyanate) and 0.3 parts of a reactive surfactant (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., product name "Aqualon HS-10") with 100 parts of the solid content of the solution of acrylic polymer A1 obtained in Production Example 1.

[0036] <Production Example 4: Preparation of PSA2> A solution of acrylic pressure-sensitive adhesive composition PSA2 was prepared by blending 100 parts of the solids content of the solution of acrylic polymer A2 obtained in Production Example 2 with 3.5 parts of an isocyanate crosslinking agent (manufactured by Tosoh Corporation, product name "Coronate HX", an isocyanurate of hexamethylene diisocyanate), 0.2 parts of a polyether-modified (oxyalkylene chain-having) organopolysiloxane compound (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KF-353"), and 0.15 parts of a conductive agent (manufactured by Tokyo Chemical Industry Co., Ltd., lithium bis(trifluoromethanesulfonyl)imide: LiTFSI).

[0037] <Production Example 5: Preparation of PSA3> A solution of acrylic pressure-sensitive adhesive composition PSA3 was prepared by blending 12 parts of an isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, trade name "Coronate L", trimethylolpropane / tolylene diisocyanate adduct) with 100 parts of the solid content of the solution of acrylic polymer A2 obtained in Production Example 2.

[0038] <Production Example 6: Preparation of surface protection film SPV1> The pressure-sensitive adhesive composition PSA1 obtained in Production Example 3 was applied to a polyethylene terephthalate (PET) film (thickness 38 μm) so as to give a dried thickness of 10 μm, and then dried to produce a surface protection film SPV1 having a substrate (PET film: 38 μm) / pressure-sensitive adhesive layer (10 μm) configuration. The bending load of SPV1 was 0.025 g.

[0039] <Production Example 7: Preparation of surface protection film SPV2> A surface protection film SPV2 was produced in the same manner as in Production Example 6, except that the thickness of the pressure-sensitive adhesive layer was 20 μm. The bending load of SPV2 was 0.027 g.

[0040] <Production Example 8: Preparation of surface protection film SPV3> A surface protection film SPV3 was produced in the same manner as in Production Example 6, except that the thickness of the pressure-sensitive adhesive layer was 30 μm. The bending load of SPV3 was 0.022 g.

[0041] <Production Example 9: Preparation of surface protection film SPV4> A surface protection film SPV4 was produced in the same manner as in Production Example 6, except that the thickness of the PET film was 50 μm. The bending load of SPV4 was 0.137 g.

[0042] <Production Example 10: Preparation of surface protection film SPV5> A surface protection film SPV5 was produced in the same manner as in Production Example 6, except that the thickness of the PET film was 75 μm. The bending load of SPV5 was 0.624 g.

[0043] <Production Example 11: Preparation of Surface Protection Film SPV6> A surface protection film SPV6 was produced in the same manner as in Production Example 6, except that a 15 μm thick adhesive layer was formed using adhesive composition PSA2 instead of adhesive composition PSA1. The bending load of SPV6 was 0.027 g.

[0044] <Production Example 12: Preparation of Surface Protection Film SPV7> Surface protection film SPV7 was produced in the same manner as in Production Example 6, except that the thickness of the PET film was 125 μm and a 20 μm thick adhesive layer was formed using adhesive composition PSA3 instead of adhesive composition PSA1. The bending load of SPV7 was 3.092 g.

[0045] Example 1 1. Preparation of HC-coated TAC film A resin solution (DIC Corporation, product name: Unidic 17-806, solids concentration: 80%) containing a UV-curable resin monomer or oligomer primarily composed of urethane acrylate dissolved in butyl acetate was added with 5 parts of a photopolymerization initiator (BASF Ltd., product name: IRGACURE 907) and 0.1 parts of a leveling agent (DIC Corporation, product name: GRANDIC PC4100) per 100 parts of solids in the solution. A hard coat layer-forming material was prepared by adding cyclopentanone and propylene glycol monomethyl ether in a 45:55 ratio to the solution so that the solids concentration of the solution became 36%. This hard coat layer-forming material was applied to a TAC film (thickness: 25 μm) to form a coating film, resulting in a hard coat layer thickness of 7 μm after curing. The coating film was dried at 90°C for 1 minute and then further irradiated with a high-pressure mercury lamp at an integrated light intensity of 300 mJ / cm. 2 The coating film was cured by irradiating it with ultraviolet light to form a hard coat layer, and the resulting HC-added TAC film was then subjected to a saponification treatment.

[0046] 2. Preparation of Polarizing Plates A 30 μm-thick polyvinyl alcohol film was stretched 3 times between rolls with different speed ratios while dyeing in a 0.3% iodine solution at 30°C for 1 minute. It was then immersed in an aqueous solution containing 4% boric acid and 10% potassium iodide at 60°C for 0.5 minutes, resulting in a total stretch ratio of 6 times. The film was then washed by immersion in an aqueous solution containing 1.5% potassium iodide at 30°C for 10 seconds, and then dried at 50°C for 4 minutes to obtain a 12 μm-thick polarizer. A polarizing plate was fabricated by bonding the HC-attached TAC film obtained above to one side of the polarizer and a cycloolefin resin (COP) film (manufactured by Zeon Corporation, product name "ZF14") to the other side using a polyvinyl alcohol adhesive. The HC-attached TAC film was attached with the HC facing outward (opposite the polarizer).

[0047] 3. Fabrication of Optical Laminates The SPV1 obtained in Production Example 6 was bonded to the HC surface of the polarizing plate obtained above, via the adhesive layer of SPV1. Meanwhile, a 20 μm-thick acrylic adhesive layer was formed on the release-treated surface of a polyethylene terephthalate film (Mitsubishi Chemical Polyester Film Co., Ltd., product name "MRF38", separator film) treated with a silicone-based release agent. Next, the adhesive layer of a separator film / adhesive layer laminate was bonded to the COP film side of the polarizing plate obtained above. In this way, an optical laminate having a configuration of surface protective film / polarizing plate (optical film) / adhesive layer / separator was produced.

[0048] 4. Fabrication of Optical Laminates The obtained optical laminate was punched into a rectangle measuring 150 mm x 150 mm, and the four corners were chamfered into a rounded shape (deformed). The deformed shape was performed by irradiating with a laser beam. Specifically, the laser beam was irradiated from the separator side under the following conditions. The radius of curvature of the chamfered portion (R-shape) was 5 mm. Equipment used: TLSM-301 (Takei Electric Co., Ltd.) Oscillator wavelength and output: RF excited CO2 laser (9.4 μm) Machining speed: 500mm / sec Number of passes: 1 Processing power: as shown in Table 1 The surface protection film in the obtained optical laminate had an upper end extending outward beyond the lower end, and the extension length was 35.1 μm. The obtained optical laminate was subjected to the evaluation (3) above. The results are shown in Table 1.

[0049] <Examples 2 and 3> A profiled optical laminate was obtained in the same manner as in Example 1, except that the radius of curvature of the chamfered portion (R-shape) was changed as shown in Table 1. The upper end of the surface protection film in the obtained optical laminate extended further outward than the lower end. The extension length is shown in Table 1. Furthermore, the obtained optical laminate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0050] Example 4 An optical laminate was obtained in the same manner as in Example 1. The obtained optical laminate was punched into a rectangle measuring 150 mm × 150 mm, and the four corners were chamfered into a rounded shape (deformed). The deformed shape was performed by cutting with an end mill. More specifically, the optical laminates were stacked to a height of 50 mm with the surface protection film facing up, and the stack was fixed with a clamp and cut using an end mill with a blade diameter of 5.0 mm and a helix angle of 45°. The cutting was performed at a blade rotation speed of 38,000 rpm and a feed rate of 1,250 mm / min. The radius of curvature of the chamfered portion (R-shape) was 6.5 mm. The upper end of the surface protection film in the obtained optical laminate extended outward beyond the lower end, and the extension length was 7.2 μm. The obtained optical laminate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0051] <Examples 5 to 19 and Comparative Examples 1 to 3> A deformed optical laminate was obtained in the same manner as in Example 1, except that the surface protection film shown in Table 1 was used, the chamfered portion (R-shape) was deformed to the radius of curvature shown in Table 1, and the laser processing power was changed as shown in Table 1. The upper end of the surface protection film in the obtained optical laminate extended outward more than the lower end. The extension length is shown in Table 1. Furthermore, the obtained optical laminate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0052] <Comparative Examples 4 to 6> Deformed optical laminates were obtained in the same manner as in Examples 17 to 19, except that the laser beam was irradiated from the surface protection film side during deformed processing and the laser processing power was changed as shown in Table 1. The surface protection film in the obtained optical laminate had a lower end that extended outward beyond the upper end. The extension length is shown in Table 1. Note that the symbol "-" for the extension length in Table 1 indicates that the extension direction was opposite to that in Examples 1 to 19 and Comparative Examples 1 to 3, and that the lower end extended outward beyond the upper end. Furthermore, the obtained optical laminates were subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0053] [Table 1]

[0054] The abbreviations in Table 1 are as follows. The blending amount of each component in Table 1 is the number of parts per 100 parts of polymer. Furthermore, "poor peeling" in Table 1 means that when an attempt was made to peel the surface protection film using a pick-up tape, the surface protection film did not peel off, and only the pick-up tape was peeled off, making it impossible to peel. 2EHA: 2-ethylhexyl acrylate HEA: 2-hydroxyethyl acrylate 4HBA: 4-hydroxybutyl acrylate C / HX: Isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, product name "Coronate HX", isocyanurate of hexamethylene diisocyanate) C / L: Isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, product name "Coronate L", trimethylolpropane / tolylene diisocyanate adduct) Aqualon HS-10: reactive surfactant (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., product name "Aqualon HS-10") KF-353: Polyether-modified (oxyalkylene chain-containing) organopolysiloxane compound (manufactured by Shin-Etsu Chemical Co., Ltd., product name "KF-353") LiTFSI: Conductive agent (Tokyo Chemical Industry Co., Ltd., lithium bis(trifluoromethanesulfonyl)imide)

[0055] <Evaluation> As is clear from Table 1, according to the examples of the present invention, in an optical laminate having a predetermined irregularly processed portion, by setting the bending load of the surface protection film to 2.5 g or less, it is possible to significantly suppress peeling defects when peeling the surface protection film from the irregularly processed portion. Furthermore, as is clear from Comparative Examples 4 to 6, it is found that good peelability of the surface protection film can be achieved by extending the upper end of the surface protection film outward beyond the lower end. [Industrial Applicability]

[0056] The optical laminate of the present invention can be suitably used in image display devices, and in particular, can be suitably used in image display devices having irregularly shaped parts, such as automobile instrument panels, smartphones, tablet PCs, or smart watches. [Explanation of symbols]

[0057] 10 Optical Film 20 Surface protection film 21 Base material 22 PF adhesive layer 30 adhesive layer 40 Separator 100 Optical laminate

Claims

[Claim 1] An optical laminate comprising an optical film, a surface protective film releasably and temporarily attached to one side of the optical film, a pressure-sensitive adhesive layer disposed on the other side of the optical film, and a separator releasably and temporarily attached to the pressure-sensitive adhesive layer, The optical laminate has an irregular shape other than a rectangle, The upper end of the surface protection film extends outward beyond the lower end thereof, when peeling the surface protective film from the irregular shape, the length of a straight line connecting the outer edges of the optical laminate in a direction perpendicular to the peeling direction at a position 1 mm away from the peeling start point in the peeling direction is 2 mm or more; The bending load of the surface protection film is 2.5 g or less. Optical laminate.

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