Optical laminate and image display device comprising the optical laminate

Abstract

This invention provides an optical laminate that significantly suppresses peeling defects when peeling a surface protective film from a shaped processing section. The optical laminate according to an embodiment of the invention comprises: an optical film, a surface protective film temporarily peelably adhered to one side of the optical film, an adhesive layer disposed on the other side of the optical film, and a release film temporarily peelably adhered to the adhesive layer. The optical laminate has an irregular shape other than a rectangle. The upper end of the surface protective film extends further outward than the lower end, and the length of the straight line connecting the outer edge of the optical laminate in a direction orthogonal to the peeling direction at a position 1 mm away from the peeling start point when peeling the surface protective film from the irregular shape is 2 mm or more, and the bending load of the surface protective film is 2.5 g or less.

Description

Technical Field

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

[0002] In image display devices such as mobile phones and laptop computers, various optical laminates (e.g., polarizers) are used to achieve image display and / or improve the performance of that image display. Typically, an adhesive layer is provided as the outermost layer on the optical laminate, which is then formed to adhere to the image display unit. In practical applications, a release film is peelably and temporarily adhered to this adhesive layer to protect it until actual use. Furthermore, in practical applications, a surface protective film is peelably and temporarily adhered to the opposite side of the optical laminate from the adhesive layer to protect the optical laminate during manufacturing processes and transport. In recent years, it has sometimes been desirable to process the optical film into shapes other than rectangular (irregular shapes: for example, chamfering of R-shaped corners, notches, and / or the formation of through-holes). However, peeling the surface protective film from the irregularly shaped portion sometimes results in poor peeling.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-022140

[0006] Patent Document 2: Japanese Patent Application Publication No. 2017-203167 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] The main objective of this invention is to provide an optical laminate in which peeling defects are significantly suppressed when peeling a surface protective film from a non-shaped processing part.

[0009] Methods for solving problems

[0010] An optical laminate according to an embodiment of the present invention comprises: an optical film, a surface protective film temporarily and peelably adhered to one side of the optical film, an adhesive layer disposed on the other side of the optical film, and a release film temporarily and peelably adhered to the adhesive layer. The optical laminate has an irregular shape other than a rectangle. The upper end of the surface protective film extends further outward than the lower end, and the length of the straight line connecting the outer edge of the optical laminate in a direction orthogonal to the peeling direction at a position 1 mm away from the peeling start point when the surface protective film is peeled from the irregular shape is 2 mm or more. The bending load of the surface protective film is 2.5 g or less.

[0011] In one embodiment, the aforementioned irregular shape includes an R-shaped chamfer at the corner.

[0012] In one embodiment, the initial peeling force when peeling off the surface protective film is 2.0 N or less.

[0013] In one embodiment, the thickness of the surface protective film is less than 100 μm.

[0014] In one embodiment, the upper end of the surface protective film extends to a length of 1 μm to 70 μm.

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

[0016] According to another aspect of the present invention, an image display device is provided. This image display device includes the aforementioned optical film of the aforementioned optical laminate.

[0017] Invention Effects

[0018] According to an embodiment of the present invention, in an optical laminate having a surface protective film, an optical film, and a release film, and having a shaped processing section, when the upper end of the surface protective film extends further outward than the lower end, and the length of the straight line connecting the outer edge of the optical laminate is set to 2 mm or more in a direction orthogonal to the peeling direction at a position 1 mm away from the peeling start point when peeling the surface protective film from the shaped processing section, and the bending load of the surface protective film is set to 2.5 g or less, it is possible to achieve an optical laminate in which peeling defects when peeling the surface protective film from the shaped processing section are significantly suppressed. Attached Figure Description

[0019] Figure 1 This is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention.

[0020] Figure 2 This is a schematic top view illustrating an example of an irregularly shaped or irregularly shaped processing section in an optical laminate according to an embodiment of the present invention.

[0021] Figure 3 This is a schematic top view illustrating a modified example of an irregularly shaped or irregularly shaped processed part in an optical laminate according to an embodiment of the present invention.

[0022] Figure 4 This is a schematic top view illustrating yet another variation of the irregular or irregularly shaped processing portion in the optical laminate according to an embodiment of the present invention.

[0023] Figure 5 This is a schematic diagram illustrating the relationship between irregular or irregularly shaped processed parts and peeling characteristics in an optical laminate according to an embodiment of the present invention.

[0024] Figure 6This is a schematic diagram illustrating a method for measuring the bending load of a surface protective film that can be used in an optical laminate according to an embodiment of the present invention. Detailed Implementation

[0025] 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. It should be noted that, for ease of observation, the drawings are schematic representations, and therefore, the proportions such as length, width, and thickness, as well as the angles, in the drawings differ from the actual figures.

[0026] A. Optical laminate

[0027] A-1. Overview of Optical Laminates

[0028] Figure 1 This 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 protective film 20 temporarily and peelably adhered to one side of the optical film 10, an adhesive layer 30 disposed on the other side of the optical film 10, and a release film 40 temporarily and peelably adhered to the adhesive layer 30. When the optical laminate is applied to an image display device, typically, the release film 40 is disposed on the image display unit side. During actual use of the optical laminate (essentially, the optical film), the release film 40 is peeled off, and the adhesive layer 30 is used to bond the optical laminate (essentially, the optical film) to the image display device (essentially, the image display unit). The surface protective film 20 typically includes a substrate 21 and an adhesive layer 22. It should be noted that, to distinguish it from the adhesive layer 30, the adhesive layer 22 of the surface protective film is sometimes referred to as the "PF adhesive layer." The surface protective film 20 is also peeled off during actual use of the optical laminate.

[0029] In embodiments of the present invention, the optical laminate has an irregular shape other than a rectangle. In this specification, "having an irregular shape other than a rectangle" means that the top view shape of the optical laminate has a shape other than a rectangle. An irregular shape is typically a shaped processing section. Therefore, "an optical laminate with an irregular shape other than a rectangle" (hereinafter, sometimes referred to as "an irregular optical laminate") includes not only cases where the entire irregular optical laminate (i.e., the outer edge defining the top view shape of the optical laminate) is not rectangular, but also cases where shaped processing sections are formed at intervals from the outer edge of a rectangular optical laminate inwards. If a surface protective film is to be peeled off from such a shaped processing section, peeling defects are likely to occur. According to embodiments of the present invention, such peeling defects can be significantly suppressed. For example, an irregular shape (shaped processing section) is... Figure 2As shown, examples include areas obtained by chamfering corners into an R-shape, through holes, and machined areas that appear concave when viewed from above. Representative examples of concave areas include shapes approximating a boat shape (not shown), rectangles, R-shapes approximating a bathtub shape, V-shaped notches, and U-shaped notches. Other examples of irregular shapes (irregularly machined areas) include... Figure 3 and Figure 4 As shown, examples of shapes corresponding to a car's dashboard can be listed. This shape includes a portion whose outer edge is formed as an arc along the direction of rotation of the instrument needle, and whose outer edge convex inwards in the planar direction, forming a V-shape (including an R-shape). Needless to say, the shape of the irregular shape (irregularly shaped processing part) is not limited to the example shown. For example, the shape of a through hole, besides the approximately circular shape shown in the example, can be any suitable shape (e.g., ellipse, triangle, quadrilateral, pentagon, hexagon, octagon) depending on the purpose. Furthermore, the through hole can be provided at any suitable location depending on the purpose. Through holes are as follows... Figure 2 As shown, it can be disposed approximately at the center of the longitudinal end of the rectangular optical laminate, at a predetermined position at the longitudinal end, or at a corner of the optical laminate; although not shown, it can also be disposed at the short side end of the rectangular optical laminate; Figure 3 or Figure 4 As shown, it can also be located at the central part of the irregularly shaped optical laminate. Multiple through holes can also be provided. Furthermore, the shapes illustrated in the figure can be appropriately combined according to the purpose. For example, it can also be... Figure 3 or Figure 4 A V-shaped notch and / or a U-shaped notch are formed at any suitable location on the outer edge of the irregularly shaped optical laminate. Such irregularly shaped optical laminates are suitable for use in image display devices such as automotive dashboards, smartphones, tablet PCs, or smartwatches.

[0030] When the irregular shape includes an R-shape, its radius of curvature is, for example, 0.2 mm or more, or for example, 1 mm or more, or for example, 2 mm or more, or for example, 3 mm or more, or 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, or for example, 25 mm or less, or for example, 20 mm or less, or for example, 15 mm or less, or for example, 10 mm or less. When the irregular shape is a portion obtained by chamfering a corner into an R-shape, the radius of curvature of the corner portion is, for example, 3 μm to 30 μm, or for example, 5 μm to 25 μm, or for example, 10 μm to 25 μm. The radius of curvature of the corner portion can also be, for example, 5 μm to 15 μm. In optical laminates with irregularly shaped processed portions having such radii of curvature, the effects of the embodiments of the present invention can be significant. It should be noted that when the irregular shape includes an R-shape, it may also include multiple R-shapes. Furthermore, an R-shape may also be a combination of multiple curvatures.

[0031] In embodiments of the present invention, such as Figure 1 As shown, the upper end of the surface protective film 20 extends further outward than the lower end. Therefore, the cross-sectional shape of the surface protective film can be a trapezoidal shape with the upper base longer than the lower base. The inventors have discovered that such a protruding portion formed in the surface protective film due to irregular processing can affect the peeling characteristics when the surface protective film is peeled off from the irregular processing part. Furthermore, the inventors conducted an in-depth study on the relationship between the structure of the optical laminate and the peeling characteristics of the protruding portion and the surface protective film, and found that by setting the bending load of the surface protective film (described later) to below a specified value, poor peeling when peeling the surface protective film off from the irregular processing part can be significantly suppressed, thereby completing the present invention. It should be noted that the upper end of the surface protective film 20 is substantially as follows: Figure 1 As shown, it extends outward from the lower end of the PF adhesive layer 22. In this specification, "the extension length L of the surface protective film" refers to... Figure 1 The length L is shown as starting from the lower end of the PF adhesive layer 22. The protrusion length L is, for example, 1 μm to 70 μm, or 5 μm to 70 μm, or 6 μm to 55 μm, or 7 μm to 45 μm.

[0032] Irregular shape machining can be performed using any suitable method. Specific examples include laser irradiation, cutting with end mills, and punching with Thomson cutters or PINNACLE (registered trademark) cutters. Figure 1 The protruding portion shown can be formed, for example, by laser irradiation from the release film side of the optical laminate, or by machining the surface protective film of the optical laminate with the surface facing upward using an end mill.

[0033] In embodiments of the present invention, such as Figure 5 As shown, the length of the straight line AB connecting the outer edge of the optical laminate is 2 mm or more, located 1 mm away from the peeling start point when the surface protective film is peeled from the irregularly shaped processing section, in a direction orthogonal to the peeling direction. The length of the straight line AB is, for example, 3 mm or more, or 4 mm or more, or 5 mm or more, or 6 mm or more. On the other hand, the length of the straight line AB is, for example, 100 mm or less, or 50 mm or less, or 30 mm or less, or 20 mm or less, or 18 mm or less, or 15 mm or less. The length of the straight line AB can also be, for example, 5.5 μm to 9.5 μm, or 5.8 μm to 9.0 μm. A length of the straight line AB exceeding a specified value means it is difficult to ensure the start point when peeling the surface protective film from the irregularly shaped processing section. For example... Figure 3 and Figure 4 As shown, irregularly shaped optical laminates are very difficult to peel because the force required for peeling, i.e., the stress, is dispersed during the peeling of the surface protective film. According to an embodiment of the present invention, even with such a configuration, the surface protective film can be easily peeled from the irregularly shaped processing section without causing peeling defects.

[0034] In embodiments of the present invention, the bending load of the surface protective film is 2.5g or less. If the bending load of the surface protective film is 2.5g or less, even for irregularly shaped processing sections with difficult-to-peel designs, poor peeling when peeling the surface protective film from such sections can be significantly suppressed. As described above, the surface protective film has a substrate and an adhesive layer. Even if the substrate thickness, adhesive layer thickness, overall thickness, elastic modulus of the substrate, elastic modulus of the adhesive layer, etc., are individually adjusted, poor peeling cannot be comprehensively suppressed. That is, even if the individual components of the surface protective film are changed, a clear correlation cannot be obtained regarding under what conditions poor peeling can be suppressed and under what conditions poor peeling will occur. The inventors have discovered that by setting the bending load of the surface protective film to 2.5g or less, poor peeling when peeling the surface protective film from irregularly shaped processing sections can be comprehensively suppressed. It should be noted that the bending load can be measured as follows. Figure 6 As shown, a U-shaped clamp is prepared and positioned 30 mm away from the weighing table, covering it. A sample obtained by punching a dumbbell-shaped multifunctional test piece (150 mm in total length) according to JIS K 7139-A1 is placed on the weighing table after being folded in half. The load applied to the weighing table due to the constraint of the clamp on the upper part when the surface protective film wants to return to its original shape is measured as the bending load.

[0035] In one embodiment, the bending load of the surface protective film is, for example, 2.0g or less, or even, 1.5g or less, or even, 1g or less, or even, 0.8g or less, or even, 0.5g or less, or even, 0.3g or less, or even, 0.1g or less, or even, 0.05g or less, or even, 0.03g or less. The lower limit of the bending load can be, for example, 0.005g. If the bending load of the surface protective film is within such a range, poor peeling during the removal of the surface protective film can be prevented very well. In another embodiment, the bending load of the surface protective film can be, for example, from 0.5g to 2.0g. If the bending load of the surface protective film is within such a range, poor peeling can be appropriately suppressed, and dents can be well suppressed.

[0036] In embodiments of the present invention, the initial peel force when peeling off the surface protective film is, for example, 2.0 N or less, and also, for example, 1.5 N or less, and also, for example, 1.2 N or less, and also, for example, 1.0 N or less, and also, for example, 0.8 N or less, and also, for example, 0.7 N or less, and also, for example, 0.6 N or less, and also, for example, 0.5 N or less. The lower limit of the initial peel force can be, for example, 0.05 N. If the initial peel force is within such a range, the surface protective film can be easily peeled off, and poor peeling can be significantly suppressed. The initial peel force can be measured, for example, according to JIS Z 0237. Specifically, a pick-up tape can be attached to the surface of the surface protective film of the test sample (optical laminate) along the peeling direction, and the peel force when peeling at a 90° stretching direction using the pick-up tape can be measured as the initial peel force. The width of the pick-up tape can be, for example, 10 mm, and the stretching speed can be, for example, 300 mm / min.

[0037] A-2. Optical film

[0038] The optical film 10 can 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 phase retardation films. Specific examples of optical films composed of a laminate include polarizers (typically, a laminate of a polarizer and a protective film), conductive films for touch panels, surface treatment films, and laminates obtained by appropriately stacking these single-layer optical films and / or optical films composed of a laminate according to the purpose (e.g., circular polarizers for anti-reflection, polarizers with conductive layers for touch panels).

[0039] A-3. Surface protective film

[0040] The surface protective film 20, as described above, typically comprises a substrate 21 and a PF 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 the constituent materials include polyester polymers such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene terephthalate (PBT); cellulose polymers such as diacetylcellulose and triacetylcellulose; polycarbonate polymers; (meth)acrylic polymers such as polymethyl methacrylate; and cyclic olefin polymers such as polynorbornene. These can be used individually or in combination of two or more. Polyester polymers are preferred, and materials with excellent optical properties (e.g., transparency), mechanical strength, thermal stability, moisture shielding, isotropy, flexibility, and dimensional stability are particularly advantageous. Polyester films with moderate stiffness 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 and polyol components. For example, polyethylene terephthalate and polybutylene terephthalate can be used in combination as constituent materials of the substrate.

[0041] Other examples of constituent materials used as substrates 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; aromatic ester-based polymers; polyoxymethylene-based polymers; and epoxy-based polymers. These can be used individually or in combination of two or more.

[0042] In one embodiment, the substrate may also have a laminated structure of resin layer / adhesive layer / resin layer. The constituent materials of the resin layer include those described above as constituent materials of the substrate. The constituent materials of the adhesive layer include adhesives, binders, and anchoring coatings. The adhesive layer may also have a laminated structure of an adhesive layer or a binder layer and an anchoring coating layer. By intercalating an adhesive layer with specified properties (e.g., elastic modulus) between the two resin layers, the elastic modulus (e.g., tensile elastic modulus) can be reduced to a desired degree corresponding to the purpose. As a result, the desired bending load described above can be easily achieved.

[0043] The tensile modulus of the substrate 21 is, for example, 2.3 × 10⁻⁶. 9 Pa below, preferably 1.5 × 10 Pa 9 Pa or less, more preferably 1.3 × 10 Pa. 9 Pa below, more preferably 1.0 × 10 Pa 7 Pa ~ 1.3 × 109 Pa, preferably 1.0 × 10 Pa. 8 Pa ~ 1.3 × 10 9 Pa. If the tensile modulus of elasticity of the substrate is within this range, the desired bending load described above can be easily achieved. It should be noted that the tensile modulus of elasticity is determined according to JIS K 7161.

[0044] In one embodiment, the thickness of the substrate is, for example, 20 μm to 100 μm, or even, 25 μm to 80 μm, or 30 μm to 50 μm. If the substrate thickness is within this range, poor peeling during the removal of the surface protective film can be prevented very well. In another embodiment, the substrate thickness can, for example, be 60 μm to 90 μm. If the substrate thickness is within this range, poor peeling can be appropriately suppressed, and dents can be well suppressed.

[0045] As the PF adhesive layer 22, any suitable composition can be adopted as long as the desired bending load can be achieved. Specific examples include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. By adjusting the type, number, combination, and proportion of monomers in the base resin forming the adhesive, as well as the amount of crosslinking agent, reaction temperature, and reaction time, an adhesive with desired properties corresponding to the purpose can be prepared. The base resin of the adhesive can be used alone or in combination of two or more. The base resin is preferably an acrylic resin (i.e., the PF adhesive layer is preferably composed of an acrylic adhesive). The adhesive constituting the PF adhesive layer has the characteristic that the base resin contains a polymer with a functional group containing active hydrogen (e.g., hydroxyl groups). If such a base resin is used, a PF adhesive layer with the desired storage modulus of elasticity can be obtained. Details of the adhesive constituting the PF adhesive layer are described, for example, in Japanese Patent Application Publication No. 2018-123281, the description of which is incorporated herein by reference.

[0046] The thickness of the PF adhesive layer 22 is, for example, 5 μm to 50 μm, or, for example, 10 μm to 40 μm, or, for example, 10 μm to 30 μm. If the thickness of the PF adhesive layer is within such a range, the desired bending load described above can be easily achieved.

[0047] The storage elastic modulus G' of the PF adhesive layer 22 at 25°C can, for example, be 0.5 × 10⁻⁶. 6 (Pa)~3.0×10 6(Pa). If the storage modulus is within such a range, the desired bending load can be easily achieved. Furthermore, an adhesive layer with an excellent balance between adhesion and peelability (resulting in a surface protective film) can be obtained. It should be noted that the storage modulus can be determined, for example, by dynamic viscoelasticity measurement.

[0048] The thickness of the surface protective film 20 is, for example, less than 100 μm, or for example, 30 μm to 90 μm, or for example, 40 μm to 80 μm, or for example, 45 μm to 70 μm. If the thickness of the surface protective film is within such a range, the desired bending load described above can be easily achieved. Furthermore, poor peeling during the removal of the surface protective film can be prevented very well. The thickness of the surface protective film can also be, for example, 70 μm to 100 μm. If the thickness of the surface protective film is within such a range, poor peeling can be appropriately suppressed, and dents can be well suppressed. It should be noted that the thickness of the surface protective film refers to the combined thickness of the substrate and the PF adhesive layer.

[0049] A-4. Adhesive layer

[0050] The adhesive layer 30 can be of any suitable composition. 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 proportion of monomers in the base resin forming the adhesive, as well as the amount of crosslinking agent, reaction temperature, and reaction time, an adhesive with desired properties corresponding to the purpose can be prepared. 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. Details of the adhesive constituting the adhesive layer are described, for example, in Japanese Patent Application Publication No. 2014-115468, the description of which is incorporated herein by reference. The thickness of the adhesive layer 30 can be, for example, 10 μm to 100 μm. The storage modulus G' of the adhesive layer 30 at 25°C can be, for example, 1.0 × 10⁻⁶. 4 (Pa)~1.0×10 6 (Pa).

[0051] A-5. Release film

[0052] As the release film 40, any suitable release film can be used. Specific examples include plastic films, non-woven fabrics, or paper with a surface coating using a release agent. Specific examples of release agents 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 release film can be, for example, from 10 μm to 100 μm.

[0053] B. Image display device

[0054] The optical laminate (essentially, optical film) of the embodiments of the present invention is suitable for use in image display devices. Therefore, image display devices comprising optical laminates (essentially, optical films) are also included in the embodiments of the present invention. A typical image display device includes an image display unit and an optical film bonded to the image display unit via an adhesive layer. Examples of image display devices include liquid crystal displays, organic electroluminescent (EL) displays, and quantum dot displays.

[0055] Example

[0056] The present invention will now be specifically described through examples, but the present invention is not limited to these examples. The evaluation items in the examples are as follows. Furthermore, unless otherwise explicitly stated, "parts" and "%" in the examples are based on weight.

[0057] (1) Extension length L

[0058] The cross-sections of the optical laminates obtained in the examples and comparative examples were photographed using a scanning electron microscope, and measurements were performed from the obtained images.

[0059] (2) Bending load of surface protective film

[0060] like Figure 6 As shown, a U-shaped clamp is prepared and positioned 30 mm away from the weighing stage. The surface protective film used in the examples and comparative examples is punched into a dumbbell-shaped multifunctional test piece (150 mm in total length) according to JIS K7139-A1 to prepare a sample. The sample is folded in half and placed on the weighing stage. The load applied to the weighing stage when the sample (surface protective film) is expected to return to its original shape is measured as the bending load.

[0061] (3) Peelability and initial peel force

[0062] Measurements were performed according to JIS Z 0237. Specifically, a pickup tape was attached to the surface of the protective film of the optical laminate obtained in the examples and comparative examples, along the peel direction (orthogonal to the wiring relative to the R-shape), and the peel force when peeled at a 90° stretching direction using the pickup tape was measured as the initial peel force. The pickup tape used in this measurement was Nitto Denko Corporation's polyester adhesive tape No. 315. The width of the pickup tape was 10 mm, the length of the adhered portion was set to 10 mm, and the stretching speed was set to 300 mm / min. Measurements were performed with n=6, and the average value remaining after excluding obvious delamination was set as the initial peel force.

[0063] <Manufacturing Example 1: Preparation of Acrylic Polymer A1>

[0064] A monomer mixture containing 96 parts of 2-ethylhexyl acrylate and 4 parts of 2-hydroxyethyl acrylate was added to a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet pipe, and a cooler. Then, 0.1 parts of 2,2'-azobisisobutyronitrile (2,2'-ANOVA), acting as a polymerization initiator, were added along with 100 parts of ethyl acetate to 100 parts of the monomer mixture. After nitrogen purging by slowly stirring, the liquid temperature in the flask was maintained at approximately 55°C for 8 hours to prepare a solution of an acrylic polymer A1 with a weight-average molecular weight (Mw) of 540,000.

[0065] <Manufacturing Example 2: Preparation of Acrylic Polymer A2>

[0066] Except for using a monomer mixture containing 91 parts of 2-ethylhexyl acrylate and 9 parts of 4-hydroxybutyl acrylate, a solution of acrylic polymer A2 with a weight average molecular weight (Mw) of 540,000 was prepared by operating in the same manner as in Manufacturing Example 1.

[0067] <Manufacturing Example 3: Preparation of Adhesive Composition PSA1>

[0068] A solution of acrylic adhesive composition PSA1 was prepared by mixing 100 parts of the solid component of the acrylic polymer A1 solution obtained in Manufacturing Example 1 with 5 parts of an isocyanate crosslinking agent (Tosoh Corporation, trade name "Coronate HX", isocyanurate form of hexamethylene diisocyanate) and 0.3 parts of a reactive surfactant (Daiichi Kogyo Pharmaceutical Co., Ltd., trade name "Aqualon HS-10").

[0069] <Manufacturing Example 4: Preparation of Adhesive Composition PSA2>

[0070] A solution of acrylic adhesive composition PSA2 was prepared by combining 100 parts of the solid component of the acrylic polymer A2 solution obtained in Manufacturing Example 2 with 3.5 parts of an isocyanate crosslinking agent (Tosoh Corporation, trade name "Coronate HX", isocyanurate form of hexamethylene diisocyanate), 0.2 parts of a polyether-modified (oxyalkylene chain-containing) organopolysiloxane compound (Shin-Etsu Chemical Industry Co., Ltd., trade name "KF-353") and 0.15 parts of a conductive agent (Tokyo Chemical Industry Co., Ltd., lithium bis(trifluoromethanesulfonyl)imide: LiTFSI).

[0071] <Manufacturing Example 5: Preparation of Adhesive Composition PSA3>

[0072] A solution of acrylic adhesive composition PSA3 was prepared by mixing 100 parts of the solid component of the acrylic polymer A2 solution obtained in Manufacturing Example 2 with 12 parts of an isocyanate crosslinking agent (manufactured by Tosoh Corporation, trade name "Coronate L", trimethylolpropane / toluene diisocyanate adduct).

[0073] <Manufacturing Example 6: Fabrication of Surface Protective Film SPV1>

[0074] A surface protective film SPV1, consisting of a substrate (PET film: 38 μm thick) and an adhesive layer (10 μm thick), was prepared by coating and drying the adhesive composition PSA1 obtained in Manufacturing Example 3 onto a polyethylene terephthalate (PET) film (38 μm thick) to achieve a dried thickness of 10 μm. The bending load of SPV1 was 0.025 g.

[0075] <Manufacturing Example 7: Fabrication of Surface Protective Film SPV2>

[0076] Except that the thickness of the adhesive layer was set to 20 μm, the surface protective film SPV2 was manufactured in the same manner as in Manufacturing Example 6. The bending load of SPV2 was 0.027 g.

[0077] <Manufacturing Example 8: Fabrication of Surface Protective Film SPV3>

[0078] Except that the thickness of the adhesive layer was set to 30 μm, the surface protective film SPV3 was manufactured in the same manner as in Manufacturing Example 6. The bending load of SPV3 was 0.022 g.

[0079] <Manufacturing Example 9: Fabrication of Surface Protective Film SPV4>

[0080] Except that the thickness of the PET film was set to 50 μm, the surface protective film SPV4 was manufactured in the same manner as in Manufacturing Example 6. The bending load of SPV4 was 0.137 g.

[0081] <Manufacturing Example 10: Fabrication of Surface Protective Film SPV5>

[0082] Except that the thickness of the PET film was set to 75 μm, the surface protective film SPV5 was manufactured in the same manner as in Manufacturing Example 6. The bending load of SPV5 was 0.624 g.

[0083] <Manufacturing Example 11: Fabrication of Surface Protective Film SPV6>

[0084] Except that adhesive composition PSA2 was used instead of adhesive composition PSA1 to form an adhesive layer with a thickness of 15 μm, a surface protective film SPV6 was produced in the same manner as in Manufacturing Example 6. The bending load of SPV6 was 0.027 g.

[0085] <Manufacturing Example 12: Fabrication of Surface Protective Film SPV7>

[0086] The thickness of the PET film was set to 125 μm, and an adhesive layer with a thickness of 20 μm was formed by using adhesive composition PSA3 instead of adhesive composition PSA1. Otherwise, the surface protective film SPV7 was produced in the same manner as in Manufacturing Example 6. The bending load of SPV7 was 3.092 g.

[0087] <Example 1>

[0088] 1. Preparation of TAC membranes with HC

[0089] A resin solution (manufactured by DIC Corporation, trade name: UNIDIC17-806, solids concentration: 80%) containing UV-curable resin monomers or oligomers with urethane acrylate as the main component, dissolved in butyl acetate, was supplemented with 5 parts of a photopolymerization initiator (manufactured by BASF Corporation, trade name: IRGACURE907) and 0.1 parts of a leveling agent (manufactured by DIC Corporation, trade name: GRANDIC PC4100) per 100 parts of the solids in the solution. Cyclopentanone and propylene glycol monomethyl ether were added to the solution at a ratio of 45:55, with the solids concentration in the solution being 36%. This prepared a hard coating forming material. The hard coating forming material was then coated onto a TAC film (thickness: 25 μm) to form a coating film with a hardened coating thickness of 7 μm. The coating film was dried at 90°C for 1 minute and then further irradiated with a high-pressure mercury lamp with a cumulative light intensity of 300 mJ / cm². 2 Ultraviolet light was used to harden the coating, forming a hard coating layer, thus producing a TAC film with HC. The obtained TAC film with HC was then subjected to a saponification treatment.

[0090] 2. Fabrication of Polarizing Films

[0091] A 30 μm thick polyvinyl alcohol (PVA) film was dyed for 1 minute in a 0.3% iodine solution at 30°C between rollers with different speed ratios, and stretched to 3 times its original length. Then, it was immersed in an aqueous solution containing 4% boric acid and 10% potassium iodide at 60°C for 0.5 minutes, and stretched to a total stretch ratio of 6 times. Next, after washing by immersion in an aqueous solution containing 1.5% potassium iodide at 30°C for 10 seconds, it was dried at 50°C for 4 minutes to obtain a 12 μm thick polarizer. A TAC film with HC (contains cycloolefin resin) was bonded to one side of the polarizer using a PVA-based adhesive, and a cycloolefin resin (COP) film (manufactured by ZEON CORPORATION, trade name "ZF14") was bonded to the other side to create a polarizer. It should be noted that the TAC film with HC was bonded with HC facing outwards (opposite to the polarizer).

[0092] 3. Fabrication of optical laminates

[0093] The SPV1 obtained in Manufacturing Example 6 is bonded to the HC surface of the polarizer obtained above via an adhesive layer of SPV1. On the other hand, an acrylic adhesive layer with a thickness of 20 μm is formed on the release-treated surface of a polyethylene terephthalate film (Mitsubishi Chemical Polyester Film, trade name "MRF38", release film) treated with a silicone-based release agent. Next, the adhesive layer of the release film / adhesive layer laminate is bonded to the COP film side of the polarizer obtained above. By operating in this way, an optical laminate having a structure of surface protective film / polarizer (optical film) / adhesive layer / release film is produced.

[0094] 4. Fabrication of optical laminates

[0095] The resulting optical laminate was punched into a rectangle measuring 150mm × 150mm, and the four corners were chamfered (irregular shaping) into an R-shape. Irregular shaping was performed by laser irradiation. Specifically, the laser was irradiated from the release film side under the following conditions: The radius of curvature of the chamfered portion (R-shape) was 5mm.

[0096] Device used: TLSM-301 (manufactured by Takei Electric Industry Co., Ltd.)

[0097] Oscillator wavelength and output power: RF-excited CO2 laser (9.4μm)

[0098] Processing speed: 500mm / second

[0099] Number of passes: 1

[0100] Processing power: as shown in Table 1

[0101] The upper end of the surface protective film in the obtained optical laminate extends further outward than the lower end, with an extension length of 35.1 μm. The obtained optical laminate was subjected to the evaluation described in (3) above. The results are shown in Table 1.

[0102] <Examples 2-3>

[0103] Except for changing the radius of curvature of the chamfered portion (R shape) as shown in Table 1, the same procedure as in Example 1 was followed to obtain an irregularly shaped optical laminate. The upper end of the surface protective film in the obtained optical laminate extends 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.

[0104] <Example 4>

[0105] The optical laminate was obtained by operating in the same manner as in Example 1. The obtained optical laminate was punched into a rectangle of 150mm × 150mm, and the four corners were chamfered (irregular shaping) into an R-shape. Irregular shaping was performed by cutting with an end mill. More specifically, the optical laminate was stacked with the surface protective film facing upwards, secured with a clamp to a height of 50mm, and cut using an end mill with a diameter of 5.0mm and a helix angle of 45°. Cutting was performed at a mill speed of 38,000 rpm and a feed rate of 1250mm / min. The radius of curvature of the chamfered portion (R-shape) was 6.5mm. The upper end of the surface protective film in the obtained optical laminate extended outwards compared to the lower end, with an extension length of 7.2μm. The obtained optical laminate was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0106] <Examples 5-19 and Comparative Examples 1-3>

[0107] Using the surface protective film shown in Table 1, irregular shaping was performed with the radius of curvature of the chamfered portion (R shape) shown in Table 1, and the laser processing power was varied as shown in Table 1. Otherwise, the operation was the same as in Example 1 to obtain an irregularly shaped optical laminate. The upper end of the surface protective film in the obtained optical laminate extends 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.

[0108] <Comparative Examples 4-6>

[0109] In the irregular shape processing, laser was irradiated from the surface protective film side, and the laser processing power was varied as shown in Table 1. Otherwise, the process was carried out in the same manner as in Examples 17-19 to obtain irregularly shaped optical laminates. The lower end of the surface protective film in the obtained optical laminates extends further outward than the upper end. The extension length is shown in Table 1. It should be noted that the symbol "-" for the extension length in Table 1 indicates that the extension direction is opposite to that in Examples 1-19 and Comparative Examples 1-3, with the lower end extending further outward than 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.

[0110]

[0111] The abbreviations in Table 1 are as follows. Furthermore, the proportions of each component in Table 1 are parts per 100 parts of the polymer. Moreover, "poor peeling" in Table 1 means that when attempting to peel off the protective film using pick-up tape, the protective film remains unpeeled, and only the pick-up tape is peeled off, thus preventing peeling.

[0112] 2EHA: 2-Ethylhexyl acrylate

[0113] HEA: 2-Hydroxyethyl acrylate

[0114] 4HBA: 4-Hydroxybutyl acrylate

[0115] C / HX: Isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, trade name "Coronate HX", isocyanurate form of hexamethylene diisocyanate).

[0116] C / L: Isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, trade name "Coronate L", trimethylolpropane / toluene diisocyanate adduct)

[0117] Aqualon HS-10: Reactive surfactant (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., trade name "Aqualon HS-10")

[0118] KF-353: Polyether-modified (with oxyalkylene chains) organopolysiloxane compound (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KF-353")

[0119] LiTFSI: Conductive agent (manufactured by Tokyo Chemical Industry Co., Ltd., lithium bis(trifluoromethanesulfonyl)imide)

[0120] <Evaluation>

[0121] As shown in Table 1, according to embodiments of the present invention, in an optical laminate having a defined irregularly shaped processing portion, by setting the bending load of the surface protective film to 2.5g or less, poor peeling when peeling the surface protective film from the irregularly shaped processing portion can be significantly suppressed. Furthermore, as shown in Comparative Examples 4-6, good peelability of the surface protective film can be achieved by making the upper end of the surface protective film extend further outward than the lower end.

[0122] Industrial availability

[0123] The optical laminate of the present invention is suitable for image display devices, and is particularly suitable for image display devices with irregularly shaped parts, such as car dashboards, smartphones, tablet PCs or smartwatches.

[0124] Explanation of symbols

[0125] 10 Optical film

[0126] 20 Surface protective film

[0127] 21 Substrate

[0128] 22 PF adhesive layer

[0129] 30 Adhesive layer

[0130] 40 Release film

[0131] 100 optical laminates

Claims

1. An optical laminate comprising: an optical film, a surface protective film temporarily and peelably adhered to one side of the optical film, an adhesive layer disposed on the other side of the optical film, and a release film temporarily and peelably adhered to the adhesive layer. This optical laminate has an irregular shape other than a rectangle. The surface protective film has a substrate and an adhesive, and the upper end of the surface protective film extends further outward than the lower end. The adhesive layer comprises a base resin, a crosslinking agent, and a reactive surfactant. The base resin is an acrylic resin with hydroxyl groups. In a direction orthogonal to the peeling direction, at a position 1 mm away from the peeling start point when the surface protective film is peeled from the irregular shape, the length of the straight line connecting the outer edge of the optical laminate is 6 mm or more. The bending load of this surface protective film is less than 2.5g. The initial peeling force when peeling off the surface protective film is less than 2.0N.

2. The optical laminate according to claim 1, wherein, The irregular shape includes an R-shaped chamfer at the corner.

3. The optical laminate according to claim 1 or 2, wherein, The thickness of the surface protective film is less than 100 μm.

4. The optical laminate according to claim 1 or 2, wherein, The upper end of the surface protective film extends from 1 μm to 70 μm.

5. The optical laminate according to claim 1 or 2, wherein, The optical film includes a polarizer.

6. An image display device comprising the optical film of the optical laminate according to any one of claims 1 to 5.

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