Laminate, method for manufacturing laminate, and method for manufacturing optical member

Abstract

The present invention addresses the problem of providing a laminate by which a member can be peeled in a desired peeling order, a method for manufacturing the laminate, and a method for manufacturing an optical member. The laminate of the present invention has a first member, a second member, and a third member in this order, and when the adhesive force at a contact surface between the first member and the second member is denoted by C1, the adhesive force at a central portion of a contact surface between the second member and the third member is denoted by C21, and the adhesive force of at least a portion of an outer perimeter portion positioned further outward than the central portion of the contact surface between the second member and the third member is denoted by C22, the laminate satisfies the requirement of expression (1). Expression (1): C22 > C1 > C21

Description

Laminate, laminate manufacturing method, and optical member manufacturing method

[0001] The present invention relates to a laminate, a method for manufacturing a laminate, and a method for manufacturing an optical member.

[0002] Optical components are known that are obtained by bonding a component such as a lens, a display, or a light guide plate to a laminate including a protective layer, etc. Patent Document 1 discloses, as a laminate used in producing such optical components, "a laminate comprising: a first film substrate and a reinforcing film including a first pressure-sensitive adhesive layer firmly laminated on a first main surface of the first film substrate; a separator temporarily attached to the first pressure-sensitive adhesive layer; and a surface protective film temporarily attached to a second main surface of the first film substrate, wherein the first pressure-sensitive adhesive layer has a property that its adhesive strength increases upon heating or light irradiation, and the adhesive strength between the first pressure-sensitive adhesive layer and the separator is smaller than the adhesive strength between the surface protective film and the first film substrate" (Claim 1 of Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2020-033400

[0004] As shown in Patent Document 1, when peeling components using a laminate having contact surfaces with high adhesion between components and contact surfaces with low adhesion between components, peeling typically occurs first at the contact surface with the lower adhesion between the components. Specifically, in a laminate obtained by simply laminating a first component, a second component, and a third component in this order, if the adhesion between the second component and the third component is lower than the adhesion between the first component and the second component, the third component typically peels before the first component. However, depending on the application of the laminate, as described above, a laminate is required that allows the first component, which would normally peel after the third component, to peel before the third component. In this specification, a "laminate that allows the first component, which would normally peel after the third component, to peel before the third component in a desired peeling order" is also referred to as a "laminate that allows components to be peeled in a desired peeling order."

[0005] Therefore, an object of the present invention is to provide a laminate that allows members to be peeled off in a desired peeling order, a method for manufacturing a laminate, and a method for manufacturing an optical member.

[0006] As a result of intensive research to solve the above-mentioned problems, the present inventors discovered that in a laminate having a first member, a second member, and a third member in this order, if the adhesion forces at predetermined locations on the contact surfaces of the members satisfy a predetermined relationship, the members can be peeled in a desired peel order, i.e., starting with the first member that is to be peeled first, and completed the present invention. That is, the present inventors discovered that the above-mentioned problems can be solved by the following configuration.

[0007] [1] A laminate having a first member, a second member, and a third member in this order, wherein when an adhesion strength at a contact surface between the first member and the second member is C1, an adhesion strength at a central portion of the contact surface between the second member and the third member is C21, and an adhesion strength at at least a part of a periphery positioned outside the central portion of the contact surface between the second member and the third member is C22, the requirement of the following formula (1) is satisfied: C22>C1>C21 Formula (1) [2] The first member includes a first protective film and an adhesive layer, the second member includes a substrate and a liquid crystal layer, the third member includes a second protective film, the adhesive layer of the first member is disposed closer to the second member than the first protective film of the first member, and the liquid crystal layer of the second member is disposed closer to the third member than the substrate of the second member. [3] A method for producing a laminate, comprising the step of cutting a laminate sheet having a first member, a second member, and a third member in this order with a laser to obtain the laminate according to [1] or [2], wherein when the adhesion strength at the contact surface between the first member and the second member in the laminate sheet is C1 and the adhesion strength at the contact surface between the second member and the third member in the laminate sheet is C2, the relationship of the following formula (2) is satisfied: Formula (2) C1>C2 [4] A method for producing an optical member, comprising the steps of: Step 1 of peeling the first member from the laminate according to [1] or [2] to obtain a laminate member in which the second member and the third member are laminated in this order; Step 2 of bonding the laminate member and an object to be bonded such that the object to be bonded and the second member face each other to obtain a bonded product; and Step 3 of peeling the third member from the bonded product to obtain an optical member.

[0008] According to the present invention, it is possible to provide a laminate in which members can be peeled off in a desired peeling order, a method for manufacturing a laminate, and a method for manufacturing an optical member.

[0009] Fig. 1 is a schematic partial cross-sectional view showing an example of a laminate of the present invention; Fig. 2 is a schematic cross-sectional view showing an example of a laminate sheet used in a method for manufacturing the present laminate; Fig. 3 is a schematic cross-sectional view of a sheet used in manufacturing the laminate sheet; Fig. 4 is a schematic cross-sectional view for explaining a step of irradiating a laser onto a laminate sheet to obtain a laminate; Fig. 5 is a view for explaining an example of a method for manufacturing an optical member of the present invention.

[0010] The present invention will be described in detail below. The following description of the constituent elements may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the upper and lower limits. In numerical ranges described in stages in this specification, the upper or lower limit described in a certain numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in numerical ranges described in this specification, the upper or lower limit described in a certain numerical range may be replaced with a value shown in the Examples. In this specification, each component may be a single substance corresponding to the component, or two or more substances may be used. When two or more substances are used for each component, the content of that component refers to the total content of the two or more substances, unless otherwise specified. In this specification, a combination of two or more preferred embodiments is a more preferred embodiment. In this specification, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved. In this specification, the thickness of the laminate and each member (layer) constituting the laminate refers to the arithmetic mean value of the thicknesses measured at 10 different positions corresponding to the thickness of the object to be measured, after obtaining a cross-sectional image of the laminate using a scanning electron microscope (SEM).

[0011] [Laminate] The laminate of the present invention (hereinafter also referred to as "the laminate") has a first member, a second member, and a third member in this order, and satisfies the requirements of formula (1) when the adhesion force at the contact surface between the first member and the second member is C1, the adhesion force at the center of the contact surface between the second member and the third member is C21, and the adhesion force at at least a part of the outer periphery located outside the center of the contact surface between the second member and the third member is C22. Formula (1) C22>C1>C21

[0012] By using this laminate, the components of the laminate can be peeled in the desired order, i.e., the first component can be peeled off first from the laminate. The reason for this is presumed to be as follows: When peeling components from the laminate, force is likely to be applied to the outer periphery of the contact surface of each component, causing the outer periphery of the contact surface to start peeling. In this laminate, the adhesion force at the outer periphery of the contact surface between the second component and the third component is greater than the adhesion force at the contact surface between the first component and the second component (the entire contact surface), which is presumed to prevent the third component from peeling off before the first component.

[0013] Fig. 1 is a schematic partial cross-sectional view showing an example of the present laminate. The laminate 100 shown in Fig. 1 represents a cross-section near the center when the laminate 100 is viewed in plan. The laminate 100 shown in Fig. 1 has a first protective film 11, a first adhesive layer 12, a substrate 21, an adhesion layer 22, a liquid crystal layer 23, a second adhesive layer 24, a release layer 31, and a second protective film 32, in this order, stacked so that adjacent members are in contact with each other. The first member 10 includes the first protective film 11 and the first adhesive layer 12. The second member 20 includes the substrate 21, the adhesion layer 22, the liquid crystal layer 23, and the second adhesive layer 24. The third member 30 includes the release layer 31 and the second protective film 32.

[0014] The shape of the laminate 100 when observed from the stacking direction of each member is not particularly limited, and examples thereof include polygonal, circular, elliptical, and irregular shapes, among which polygonal shapes are preferred, and rectangular shapes are more preferred. The circle-equivalent diameter of the shape when observed from the stacking direction of each member of the laminate 100 is preferably 5 to 100 mm, more preferably 10 to 70 mm, and even more preferably 30 to 60 mm.

[0015] The thickness of the laminate 100 is preferably 50 to 500 μm, more preferably 100 to 200 μm.

[0016] Each of the components of the laminate 100 will be described in detail below.

[0017] <First Member> The first member 10 is disposed on the opposite side of the second member 20 from the side on which the third member 30 is disposed. In the production of the optical member (described later), the first member 10 is peeled off from the laminate 100 before the third member 30. In the example of Fig. 1 , the first member 10 includes a first protective film 11 and a first adhesive layer 12. The thickness of the first member 10 is preferably 20 to 120 µm, and more preferably 40 to 70 µm.

[0018] (First Protective Film) The first protective film 11 is bonded to the second member 20 via the first adhesive layer 12. By including the first protective film 11 in the laminate 100, damage to one surface of the second member 20 is suppressed. Specific examples of materials constituting the first protective film include polyolefins (e.g., polyethylene, polypropylene), cyclic polyolefins (e.g., norbornene-based polymers), polyvinyl alcohol, polyesters (e.g., polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate), polymethacrylates, polyacrylates, cellulose esters (e.g., triacetyl cellulose (TAC), diacetyl cellulose, cellulose acetate propionate), and polycarbonates. Among these, polyesters and cellulose esters are preferred because of their excellent strength.

[0019] The thickness of the first protective film 11 is preferably 10 to 100 μm, more preferably 30 to 50 μm, from the viewpoint of excellent strength and processability.

[0020] (First adhesive layer) The first adhesive layer 12 bonds the first protective film 11 and the second member 20. In this specification, the adhesive layer refers to a layer made of an adhesive. The first adhesive layer 12 may be formed on the entire one surface of the first protective film 11, or may be formed on at least a portion of the one surface of the first protective film 11.

[0021] Specific examples of adhesives constituting the first adhesive layer 12 include rubber-based adhesives, acrylic-based adhesives, silicone-based adhesives, urethane-based adhesives, vinyl alkyl ether-based adhesives, polyvinyl alcohol-based adhesives, and cellulose-based adhesives, and acrylic-based adhesives are preferred because they provide better effects of the present invention.

[0022] The thickness of the first adhesive layer 12 is not particularly limited, but is preferably 5 to 30 μm, more preferably 10 to 20 μm, in terms of achieving better effects of the present invention.

[0023] <Second Member> The second member 20 has the first member 10 disposed on one surface thereof and the third member 30 disposed on the other surface thereof. The second member 20 is a member to be bonded to an object to be attached in the manufacture of an optical member (described later). In the example of FIG. 1 , the second member 20 includes a substrate 21, an adhesion layer 22, a liquid crystal layer 23, and a second adhesive layer 24. The thickness of the second member 20 is preferably 10 to 90 μm, more preferably 30 to 70 μm. The shape and size of the contact surface between the first member 10 and the second member 20 are preferably the same as the shape and size when observed from the stacking direction of each member of the laminate 100.

[0024] (Substrate) One surface of the substrate 21 is bonded to the first protective film 11 via the first adhesive layer 12, and the other surface is bonded to the liquid crystal layer 23 via an adhesive layer 22. The substrate 21 is used, for example, as a support that supports the liquid crystal layer 23, or as a protective layer that protects the liquid crystal layer 23 after the first member 10 is peeled off from the laminate 100.

[0025] Materials that can be used to form the substrate 21 include the materials exemplified as materials that can form the first protective film 11, and among these, polymethacrylic acid ester, polyacrylic acid ester, and cellulose ester are preferred from the standpoint of light transmittance.

[0026] The substrate 21 is preferably transparent. In this specification, "transparent" refers to an average visible light transmittance of 80% or more, preferably 90% or more, and more preferably 95% or more. In this specification, an average visible light transmittance of X% or more means that when the transmittance is calculated in 1-nm increments in the wavelength range of 380 to 780 nm, the transmittance at each wavelength is X% or more.

[0027] The thickness of the substrate 21 is not particularly limited, but is preferably 10 to 100 μm, more preferably 20 to 40 μm, in order to obtain better effects of the present invention.

[0028] In the example of FIG. 1, the laminate 100 has the substrate 21 , but the laminate 100 does not necessarily have to have the substrate 21 .

[0029] (Adhesion Layer) The adhesion layer 22 bonds the substrate 21 and the liquid crystal layer 23. In this specification, the term "adhesion layer" encompasses the concept of an adhesive layer and the above-mentioned pressure-sensitive adhesive layer. The adhesive layer refers to a layer obtained using an adhesive. The adhesion layer 22 is preferably an adhesive layer, since it can more firmly bond the substrate 21 and the liquid crystal layer 23. When observed from the stacking direction of the components of the laminate 100, the adhesion layer 22 may be formed in the entire area where the substrate 21 and the liquid crystal layer 23 overlap, or may be formed in at least a part of the area where the substrate 21 and the liquid crystal layer 23 overlap.

[0030] When the adhesive layer 22 is an adhesive layer, examples of adhesives used to form the adhesive layer include polyvinyl alcohol (PVA)-based adhesives and curing adhesives. As curing adhesives, active energy ray-curing adhesives are preferred, and ultraviolet (UV)-curing adhesives are more preferred. Examples of UV-curing adhesives include radical polymerization-curing adhesives and cationic polymerization-curing adhesives. Examples of radical polymerization-curing adhesives include (meth)acrylate-based adhesives. Examples of curable components in (meth)acrylate-based adhesives include compounds having a (meth)acryloyl group and compounds having a vinyl group. Examples of cationic polymerization-curing adhesives include compounds having an epoxy group or an oxetanyl group. The compound having an epoxy group is not particularly limited as long as it has at least two epoxy groups in its molecule, and various commonly known curing epoxy compounds can be used. Specific examples of compounds having an epoxy group include compounds having at least two epoxy groups and at least one aromatic ring in the molecule (aromatic epoxy compounds), and compounds having at least two epoxy groups in the molecule, at least one of which is formed between two adjacent carbon atoms constituting an alicyclic group (alicyclic epoxy compounds).

[0031] When the adhesive layer 22 is an adhesive layer, specific examples of the adhesive constituting the adhesive layer are the same as the adhesives exemplified in the description of the first adhesive layer, and preferred embodiments are also the same.

[0032] The thickness of the adhesive layer 22 is not particularly limited, but is preferably 5 to 30 μm, more preferably 10 to 20 μm, in order to bond the substrate 21 and the liquid crystal layer 23 more firmly.

[0033] In the example of Figure 1, the laminate 100 has an adhesive layer 22, but if the laminate 100 does not have a substrate 21, the laminate 100 does not need to have an adhesive layer 22.

[0034] (Liquid Crystal Layer) One surface of the liquid crystal layer 23 is bonded to the substrate 21 via the adhesive layer 22 , and the other surface is bonded to the third member 30 via the second adhesive layer 24 and the release layer 31 .

[0035] The liquid crystal layer 23 may have any configuration, as long as it is a layer formed using a liquid crystal compound. The liquid crystal layer 23 is preferably, for example, a layer formed by fixing an aligned liquid crystal compound, and more preferably a layer formed by fixing a liquid crystal compound having a polymerizable group through polymerization. In other words, the liquid crystal layer 23 is preferably a so-called optically anisotropic layer. In this specification, the "fixed" state refers to a state in which the alignment of the liquid crystal compound is maintained. Specifically, it is preferable that the layer has no fluidity, and can stably maintain the fixed alignment state without causing any change in the alignment state due to an external field or external force, usually within a temperature range of 0 to 50°C, or, under more severe conditions, within a temperature range of -30 to 70°C.

[0036] The type of liquid crystal compound is not particularly limited, and liquid crystal compounds can generally be classified into rod-shaped liquid crystal compounds and discotic liquid crystal compounds based on their shape. Furthermore, each type is further divided into low-molecular-weight and high-molecular-weight types. High-molecular-weight compounds generally refer to compounds with a degree of polymerization of 100 or more (see "Polymer Physics / Phase Transition Dynamics," by Masao Doi, page 2, Iwanami Shoten, 1992). While any liquid crystal compound can be used in the present invention, rod-shaped liquid crystal compounds or discotic liquid crystal compounds (discotic liquid crystal compounds) are preferred. Furthermore, liquid crystal compounds that are monomers or have a relatively low molecular weight with a degree of polymerization of less than 100 are preferred.

[0037] The liquid crystal compound preferably has a polymerizable group. That is, the liquid crystal compound is preferably a polymerizable liquid crystal compound. Examples of the polymerizable group that the polymerizable liquid crystal compound has include an acryloyl group, a methacryloyl group, an epoxy group, and a vinyl group. By polymerizing such a polymerizable liquid crystal compound, the orientation of the liquid crystal compound can be fixed. Note that after the liquid crystal compound is fixed by polymerization, it no longer needs to exhibit liquid crystallinity.

[0038] Examples of orientation states that a liquid crystal compound can assume include homogeneous orientation, homeotropic orientation, hybrid orientation, twisted orientation, and tilted orientation. The twisted orientation refers to an orientation state in which the liquid crystal compound is twisted from one main surface of the optically anisotropic layer to the other main surface, with the thickness direction of the optically anisotropic layer as the rotation axis. In twisted orientation, the twist angle of the liquid crystal compound (the twist angle of the orientation direction of the liquid crystal compound) is usually greater than 0° and often less than 360°. Examples of liquid crystal layers with orientation states other than those described above include liquid crystal layers having a liquid crystal orientation pattern in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane. The configuration of a liquid crystal layer having the above liquid crystal orientation pattern is specifically disclosed, for example, in International Publication No. WO 2019 / 189809.

[0039] The thickness of the liquid crystal layer 23 is not particularly limited, but is preferably 1 to 50 μm, and more preferably 1 to 10 μm.

[0040] (Second Adhesive Layer) The second adhesive layer 24 functions to bond the liquid crystal layer 23 to the third member 30 (protective film 32). Specific examples of the adhesive constituting the second adhesive layer 24 are the same as those exemplified in the description of the first adhesive layer 12, and preferred embodiments are also the same. Here, it is preferable that the second adhesive layer 24 uses an adhesive having higher adhesive strength than the first adhesive layer 12. Specifically, when the adhesive constituting the first adhesive layer 12 is a silicone-based adhesive, the adhesive constituting the second adhesive layer 24 is preferably an acrylic-based adhesive. When observed from the stacking direction of the components of the laminate 100, the second adhesive layer 24 may be formed over the entire overlapping area between the liquid crystal layer 23 and the second protective film 32, or may be formed over at least a portion of the overlapping area between the liquid crystal layer 23 and the second protective film 32. However, it is preferable that the second adhesive layer 24 be formed over the entire overlapping area between the liquid crystal layer 23 and the second protective film 32.

[0041] The thickness of the second adhesive layer 24 is not particularly limited, but is preferably 5 to 40 μm, more preferably 5 to 20 μm, in terms of achieving better effects of the present invention.

[0042] <Third Member> The third member 30 is disposed on the opposite side of the second member 20 from the side on which the first member 10 is disposed. The third member 30 is peeled off from the laminate 100 after the first member 10 during the production of the optical member (described below). In the example of FIG. 1 , the third member 30 includes a release layer 31 and a second protective film 32. The thickness of the third member 30 is preferably 10 to 100 μm, more preferably 30 to 50 μm. The shape and size of the contact surface between the second member 20 and the third member 30 are preferably the same as the shape and size when observed from the stacking direction of the members of the laminate 100.

[0043] (Release Layer) The release layer 31 is a layer that facilitates peeling of the third member 30 during the manufacture of the optical member (described later). Including the release layer 31 may make the third member 30 more likely to peel off before the first member 10. This problem can be resolved, for example, by disposing the release layer 31 in the center of the contact surface between the second member 20 (particularly the liquid crystal layer 23) and the third member 30 (particularly the second protective film 32), and not disposing the release layer 31 in at least a portion of the periphery located outside the center of the contact surface, and bonding the liquid crystal layer 23 and the second protective film 32 via the second adhesive layer 24. In other words, even when a laminate 100 having the release layer 31 is used, the adhesion between the liquid crystal layer 23 and the second protective film 32 is improved by the action of the second adhesive layer 24 at the periphery of the contact surface, allowing the first member 10 to peel off before the third member 30. Therefore, in the laminate 100, if the release layer 31 is disposed in the center of the contact surface, and the release layer 31 is not disposed in at least a portion of the periphery of the contact surface, and the liquid crystal layer 23 and the second protective film 32 are joined via the second adhesive layer 24, a laminate satisfying the relationship of the above-mentioned formula (1) is easily obtained. As described below, to obtain a laminate having the above-mentioned configuration, a laminate sheet of a predetermined configuration is prepared and the laminate sheet is cut with a laser. By cutting the laminate sheet with a laser, the release layer is decomposed and deteriorated by the heat of the laser around the laser irradiated area of ​​the laminate sheet, and at least a portion of the release layer is removed, resulting in the above-mentioned laminate. Note that, in the periphery of the contact surface, it is sufficient that the release layer 31 is not disposed at the location where peeling of the third member 30 begins during the manufacturing of the optical member (described below), and the second adhesive layer 24 is disposed at the location where peeling of the third member 30 begins. However, it is preferable that the release layer 31 is not disposed over the entire periphery, and the second adhesive layer 24 is disposed over the entire periphery.

[0044] The peripheral portion located outside the center of the contact surface between the second member 20 (particularly, the liquid crystal layer 23) and the third member 30 (particularly, the second protective film 32) refers to a region within 100 μm from the outer edge of the contact surface between the second member 20 and the third member 30 toward the center of the contact surface. Furthermore, the central portion of the contact surface between the second member 20 (particularly, the liquid crystal layer 23) and the third member 30 (particularly, the second protective film 32) refers to a region on the contact surface other than the peripheral portion.

[0045] The release layer 31 is preferably a layer formed using a silicone resin, a fluororesin, an alkyd resin, various waxes, or an aliphatic olefin, and more preferably a layer formed using a silicone resin.

[0046] The silicone resin refers to a resin having a silicone structure in the molecule. Examples of the silicone resin include curable silicone resins, silicone graft resins, and modified silicone resins such as alkyl-modified silicone resins, with reactive curable silicone resins being preferred. Examples of the reactive curable silicone resin include addition reaction silicone resins, condensation reaction silicone resins, and ultraviolet or electron beam curable silicone resins. Among these, addition reaction silicone resins with low-temperature curing properties or ultraviolet or electron beam curable silicone resins are preferred because they allow the release layer 31 to be formed at low temperatures.

[0047] Examples of silicone resins based on addition reactions include those obtained by reacting and curing polydimethylsiloxanes with hydrogen siloxanes, each having a vinyl group introduced at the end or side chain, using a platinum catalyst. Examples of silicone resins based on condensation reactions include those having a three-dimensional crosslinked structure, formed by condensing polydimethylsiloxanes with terminal OH groups and polydimethylsiloxanes with terminal H groups using an organotin catalyst. Examples of silicone resins based on ultraviolet curing include those that utilize the same radical reaction as silicone rubber crosslinking, those that introduce unsaturated groups to be photocured, those that decompose onium salts with ultraviolet or electron beams to generate strong acids, and those that crosslink by cleaving epoxy groups, and those that crosslink via the addition reaction of thiols to vinyl siloxanes. More specifically, examples include acrylate-modified polydimethylsiloxanes and glycidoxy-modified polydimethylsiloxanes.

[0048] The thickness of the release layer 31 is preferably 5 to 100 nm, more preferably 20 to 70 nm, in order to achieve superior effects of the present invention. In particular, when the release layer 31 is disposed in the central portion of the contact surface between the second member 20 and the third member 30 and the second adhesive layer 24 is disposed on at least a portion of the periphery of the contact surface, a thickness of the release layer 31 of 100 nm or less shortens the distance between the second adhesive layer 24 and the second protective film 32 at the periphery of the contact surface. This improves the adhesion strength at the periphery of the contact surface. Furthermore, when the thickness of the release layer 31 is 100 nm or less and the thickness of the second adhesive layer 24 is 5 μm or more, the release layer at the periphery of the contact surface between the second member and the third member is more easily removed than the second adhesive layer at the periphery when the laminate sheet is cut with a laser in the laminate manufacturing method described below.

[0049] In the example of Figure 1, the laminate 100 has a release layer 31, but if the third member 30 can be peeled off after the first member 10 is peeled off during the production of the optical component (described later), the laminate 100 does not need to have a release layer 31.

[0050] (Second Protective Film) The second protective film 32 is bonded to the liquid crystal layer 23 via the release layer 31 and the second adhesive layer 24. The laminate 100 has the second protective film 32, which suppresses damage to the other surface of the second member 20 (particularly the liquid crystal layer 23). Specific examples of materials constituting the second protective film 32 are the same as the materials exemplified in the description of the first protective film 11, and preferred aspects are also the same.

[0051] The thickness of the second protective film 32 is preferably 10 to 100 μm, more preferably 30 to 50 μm, in terms of excellent strength and processability.

[0052] <Adhesion Strength> In the laminate 100, the requirement of formula (1) is satisfied when the adhesion strength at the contact surface between the first member 10 and the second member 20 is C1, the adhesion strength at the center of the contact surface between the second member 20 and the third member 30 is C21, and the adhesion strength at at least a part of the outer periphery located outside the center of the contact surface between the second member 20 and the third member 30 is C22. Formula (1) C22>C1>C21 In this specification, adhesion strength means the peel force (N / 25 mm) measured by a 180-degree peel test in accordance with JIS K6854-2:1999 at a gripping speed of 300 mm / min.

[0053] The adhesion force C1 is the adhesion force across the entire contact surface between the first member 10 and the second member 20, and is preferably 0.10 to 0.40 N / 25 mm, more preferably 0.10 to 0.30 N / 25 mm, and even more preferably 0.10 to 0.20 N / 25 mm. The adhesion force C21 is preferably 0.01 to 0.10 N / 25 mm, more preferably 0.01 to 0.07 N / 25 mm, and even more preferably 0.01 to 0.05 N / 25 mm. The adhesion force C22 is preferably 0.15 to 10.00 N / 25 mm, more preferably 0.20 to 5.00 N / 25 mm, and even more preferably 0.30 to 1.00 N / 25 mm.

[0054] Here, in the laminate 100, the contact surface between the first member 10 and the second member 20 is the interface between the first adhesive layer 12 and the substrate 21. The contact surface between the second member 20 and the third member 30 is preferably the interface between the second adhesive layer 24 and the release layer 31 in the central portion, and the interface between the second adhesive layer 24 and the second protective film 32 in the peripheral portion. As described above, if the release layer 31 is disposed in the central portion of the contact surface and the second adhesive layer 24 is disposed on at least a portion of the peripheral portion of the contact surface, a laminate that satisfies the relationship of the above-mentioned formula (1) is easily obtained.

[0055] [Method for manufacturing laminate] The method for manufacturing the laminate includes a step of cutting a laminate sheet having a first member, a second member, and a third member in this order with a laser to obtain the laminate, and the laminate sheet satisfies the relationship of the following formula (2) when the adhesion force at the contact surface between the first member and the second member is C1 and the adhesion force at the contact surface between the second member and the third member is C2. Formula (2) C1>C2

[0056] <Laminate Sheet> Figure 2 is a schematic cross-sectional view showing an example of a laminate sheet used in the present laminate manufacturing method. As shown in Figure 2, the laminate sheet 200 includes a first protective film 11A, a first adhesive layer 12A, a substrate 21A, an adhesion layer 22A, a liquid crystal layer 23A, a second adhesive layer 24A, a release layer 31A, and a second protective film 32A, in this order, stacked so that adjacent components are in contact with each other. The first component 10A includes the first protective film 11A and the first adhesive layer 12A. The second component 20A includes the substrate 21A, the adhesion layer 22A, the liquid crystal layer 23A, and the second adhesive layer 24A. The third component 30A includes the release layer 31A and the second protective film 32A. The laminate sheet 200 differs from the laminate 100 in that the release layer 31A is disposed over the entire surface of one side of the second protective film 32A. The materials constituting the members of the laminated sheet 200 are the same as the materials constituting the members with the same names in the laminated body 100 of FIG. 1, and therefore, the description thereof will be omitted.

[0057] (Adhesion Strength) When the adhesion strength at the contact surface between the first member 10A and the second member 20A is C1 and the adhesion strength at the contact surface between the second member 20A and the third member 30A is C2, the laminate sheet 200 satisfies the relationship of the following formula (2): C1>C2 Formula (2)

[0058] The adhesion force C1 in the laminate sheet 200 refers to the adhesion force across the entire contact surface between the first member 10A and the second member 20A, and is synonymous with the adhesion force C1 described in the laminate 100. The adhesion force C2 refers to the adhesion force across the entire contact surface between the second member 20A and the third member 30A, and the value of the adhesion force C2 is equal to the value of the adhesion force C21 described in the laminate 100. In other words, in the laminate sheet 200, the adhesion force at the center of the contact surface between the second member 20A and the third member 30A is the same as the adhesion force at the outer periphery of the contact surface between the second member 20A and the third member 30A. As shown in formula (2), in the laminate sheet 200, the third member 30A is more easily peeled off than the first member 10A.

[0059] (Method for manufacturing laminate sheet) An example of a method for manufacturing a laminate sheet will be described with reference to the drawings. Fig. 3 is a schematic cross-sectional view of a sheet 10B used to manufacture the laminate sheet 200, and Fig. 4 is a schematic cross-sectional view of a sheet 20B used to manufacture the laminate sheet 200.

[0060] Sheet 10B has, in this order, first protective film 11A, first adhesive layer 12A, substrate 21A, adhesion layer 22A, and release film 41. The materials constituting the members included in sheet 10B other than release film 41 are the same as the materials constituting the members with the same names in laminate 100, and therefore their description will be omitted. The material constituting release film 41 is the same as the material exemplified in the description of first protective film 11, and preferred embodiments are also the same.

[0061] Sheet 20B has, in this order, liquid crystal layer 23A, second adhesive layer 24A, release layer 31A, and second protective film 32A. The materials constituting each member included in sheet 20B are the same as the materials constituting the members with the same names in laminate 100, and therefore, description thereof will be omitted.

[0062] In the method for manufacturing the laminated sheet 200, the sheet 10B after the release film 41 has been peeled off and the sheet 20B are bonded together so that the adhesive layer 22A and the liquid crystal layer 23A face each other. This results in the laminated sheet 200 shown in FIG. 2. The bonding method is not particularly limited, and the sheets may simply be stacked on top of each other, or pressure may be applied with a roll or the like when stacking them. The bonding may also involve heating.

[0063] <Process> The present laminate is obtained by cutting the laminate sheet with a laser. Around the laser irradiated area of ​​the laminate sheet (i.e., corresponding to the periphery of the present laminate), areas where the adhesion strength changes compared to before laser irradiation are generated. FIG. 5 is a schematic cross-sectional view illustrating the process of irradiating the laminate sheet 200 with a laser to obtain the laminate 100. As shown in FIG. 5, when the laminate sheet 200 is irradiated with a laser, the laminate sheet 200 is cut at the laser irradiated area S to form the laminate 100. Here, at least a portion of the release layer 31A of the laminate sheet 200 is removed around the laser irradiated area R of the laminate 100. As a result, at the outer periphery of the contact surface between the second member 20 and the third member 30 in the laminate 100 (corresponding to the periphery R of the laser irradiated area), a portion where the liquid crystal layer 23 and the second protective film 32 are bonded by the second adhesive layer 24 without the release layer 31 interposed therebetween is generated. As a result, the adhesive strength at the outer periphery of the contact surface between the second member 20 and the third member 30 is improved, and a laminate 100 that satisfies the relationship of the above-mentioned formula (1) is obtained.

[0064] The laser is irradiated in the stacking direction of each component of the laminate sheet so that the resulting laminate has the desired size. The laser irradiation can be carried out using a known laser cutting device. The type of laser is not particularly limited, but examples include a carbon dioxide laser, a YAG (yttrium-aluminum-garnet) laser, and an excimer laser. A YAG laser is preferred because it is easy to cut the laminate sheet and because it is easy to adjust the adhesion strength of each component so that it satisfies the relationship of formula (1).

[0065] The output of the laser (particularly when a YAG laser is used) is preferably 1 to 100 W, more preferably 1 to 10 W, and even more preferably 1 to 5 W. The scanning speed of the laser (particularly when a YAG laser is used) is preferably 0.01 to 5,000 mm / min, more preferably 0.1 to 5,000 mm / min, and even more preferably 1 to 5,000 mm / min. When at least one (preferably both) of the laser output and scanning speed is within the above range, the adhesion strength at the outer periphery of the contact surface between the second member 20 and the third member 30 of the laminate 100 can be improved, making it easy to adjust the adhesion strength of each member to satisfy the relationship of Equation (1). In particular, when a laminate sheet having a release layer and an adhesive layer between the second member and the third member is used, such as the laminate sheet 10B, adjusting at least one of the laser output and scanning speed to be within the above range facilitates selective removal of the release layer located around the laser irradiation area, while suppressing removal of the adhesive layer located around the laser irradiation area. Furthermore, by setting the laser output and scanning speed within the above ranges, the width of the outer periphery of the joint between the second member and the third member can be easily adjusted within a desired range.

[0066] [Method for manufacturing optical member] The method for manufacturing an optical member of the present invention includes: Step 1 of peeling the first member from the present laminate described above to obtain a laminated member in which the second member and the third member are laminated in this order; Step 2 of bonding the laminated member and an object to be bonded such that the object to be bonded and the second member face each other to obtain a bonded product; and Step 3 of peeling the third member from the bonded product to obtain an optical member. Since the method for manufacturing an optical member of the present invention uses the present laminate described above, the first member and the second member can be peeled in this order.

[0067] 6A to 6C are diagrams illustrating an example of a method for producing an optical member according to the present invention. Each step will be described below with reference to FIG.

[0068] In step 1, the first member 10 in the laminate 100 is peeled off. This results in a laminated member 50 in which the second member 20 and the third member 30 are laminated in this order, as shown in Fig. 6. The second member 20 and the third member 30 are the same as the members denoted by the same reference numerals in the laminate 100, and therefore a description thereof will be omitted.

[0069] In step 2, the object 60 to be bonded and the laminated member 50 are bonded together so that one surface of the object 60 contacts the second member 20 of the laminated member 50. As a result, a bonded product 70 is obtained in which the object 60 to be bonded, the second member 20, and the third member 30 are laminated in this order, as shown in Fig. 6. Specific examples of the object 60 to be bonded include a lens, a display, and a light guide plate.

[0070] In step 3, the third member 30 of the pasted material 70 is peeled off. As a result, an optical member 80 is obtained in which the pasted material 60 and the second member 20 are laminated in this order, as shown in Fig. 6. The optical member 80 can be used, for example, as a member for VR (Virtual Reality) glasses or a member for a liquid crystal display.

[0071] The present invention will be described in more detail below with reference to examples. The materials, amounts used, ratios, treatment details, and treatment procedures shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the examples shown below.

[0072] Example 1 First, a first sheet (corresponding to sheet 10B in FIG. 3) was prepared, which included, in this order, a first protective film (material: PET, thickness: 40 μm), a first adhesive layer (material: silicone-based adhesive, thickness: 20 μm), a substrate (material: TAC, thickness: 20 μm), an adhesion layer (material: acrylic-based adhesive, thickness: 20 μm), and a release film (material: PET, thickness: 40 μm). A second sheet (corresponding to sheet 20B in FIG. 4) was prepared, which included, in this order, a liquid crystal layer (material: liquid crystal compound, thickness: 10 μm), a second adhesive layer (material: acrylic-based adhesive, thickness: 5 μm), a release layer (material: silicone resin, thickness: 10 nm), and a second protective film (material: PET, thickness: 40 μm).

[0073] After peeling off the release film from the first sheet, the first sheet after peeling off the release film and the second sheet were laminated together so that the adhesive layer and the liquid crystal layer faced each other to obtain a 155 μm thick laminate sheet A1 (corresponding to laminate sheet 200 in FIG. 2). Next, using a laser irradiation device, the surface of laminate sheet A1 was irradiated with a YAG laser and cut to obtain laminate B1 (a rectangle measuring 25 mm long x 100 mm wide). The laser output was 1 W, and the laser scanning speed was 1 mm / min.

[0074] Furthermore, the laminate B1 was cut along the stacking direction of each component, and an image of the cut surface of the laminate B1 was observed using a scanning electron microscope (SEM). As a result, it was confirmed that, between the liquid crystal layer and the second protective film, in a region extending from the periphery of the liquid crystal layer to 100 μm toward the center line of the cut surface in the thickness direction, no release layer was present, but the second adhesive layer was present.

[0075] <Measurement of Adhesion Force> The above-mentioned adhesion forces C1, C21, and C22 were measured using the laminate B1. The adhesion force C1 was measured by attaching the surface of the laminate B1 facing the third member (i.e., the second protective film) to a substrate with strong adhesive tape, and then measuring the peel force (N / 25 mm) when peeling at the interface between the first adhesive layer and the substrate. The peel force was measured using an in-house manufactured device by a 180-degree peel test in accordance with JIS K6854-2:1999, at a gripping movement speed of 300 mm / min. The adhesion forces C21 and C22 were measured as follows. First, peeling was performed at the interface between the first adhesive layer and the substrate in the laminate B1, to obtain a laminate in which the first member (i.e., the first protective film and the first adhesive) was peeled from the laminate B1. The surface of the obtained laminate facing the second member (i.e., the substrate) was fixed to a substrate with strong adhesive tape, and the peel force (N / 25 mm) was measured when peeling at the interface between the release layer or second protective film and the second adhesive layer. Here, the adhesion force C21 is the peel force in the region extending from the outer edge of the contact surface between the second member and the third member to the center of the contact surface (i.e., the central portion of the contact surface). The adhesion force C22 is the peel force in the region extending from the outer edge of the contact surface between the second member and the third member to the center of the contact surface (i.e., the outer periphery of the contact surface). The apparatus and conditions used to measure the adhesion force C21 and the adhesion force C22 were the same as those used to measure the adhesion force C1.

[0076] In the laminate B1, the adhesion force C1 was 0.10 N / 25 mm, the adhesion force C21 was 0.05 N / 25 mm, and the adhesion force C22 was 0.35 N / 25 mm, satisfying the relationship of the above-mentioned formula (1). Furthermore, when the members corresponding to the first member and the third member were peeled off using the laminate B1 before the adhesion force measurement, it was confirmed that the first member peeled off first.

[0077] [Example 2] A laminate B2 was obtained in the same manner as in Example 1, except that the second adhesive layer included in the second sheet was replaced with a second adhesive layer having a thickness of 15 μm. The adhesion forces C1, C21, and C22 were measured in the same manner as in Example 1, except that laminate B2 was used. For laminate B2, the adhesion forces C1 were 0.10 N / 25 mm, C21 were 0.05 N / 25 mm, and C22 were 0.35 N / 25 mm, satisfying the relationship of formula (1) described above. Furthermore, when laminate B2 before adhesion force measurement was used to peel the members corresponding to the first and third members, it was confirmed that the first member peeled first.

[0078] Comparative Example 1 The laminate sheet A1 obtained in Example 1 was cut with a cutter blade to obtain a laminate B3 (size: length 25 mm x width 100 mm).

[0079] The above-mentioned adhesion forces C1, C21, and C22 were measured using laminate B3. Here, the measurement of adhesion force C1 using laminate B3 was the same as the measurement of adhesion force C1 for laminate B1, except that a laminate obtained by peeling the third member from laminate B3 was used, and a sample was used in which the second member side was fixed to a substrate. Furthermore, the measurement of adhesion forces C21 and C22 using laminate B3 was the same as the measurement of adhesion forces C21 and C22 for laminate B1, except that a sample was used in which the surface of laminate B3 facing the first member was fixed to a substrate.

[0080] In laminate B3, the adhesion force C1 was 0.10 N / 25 mm, the adhesion force C21 was 0.05 N / 25 mm, and the adhesion force C22 was 0.05 N / 25 mm, which did not satisfy the relationship of the above-mentioned formula (1). Furthermore, when laminate B3 before the adhesion force measurement was used to peel off the members corresponding to the first member and the third member, it was confirmed that the third member peeled off first.

[0081] REFERENCE SIGNS LIST 10 First member 10B, 20B Sheet 11, 11A First protective film 12, 12A First adhesive layer 12 20, 20A Second member 21, 21A Base material 22, 22A Adhesion layer 23, 23A Liquid crystal layer 24, 24A Second adhesive layer 30, 30A Third member 31, 31A Release layer 32, 32A Second protective film 41 Peel-off film 50 Laminated member 60 Bonded object 70 Bonded object 80 Optical member S Irradiated area R Surroundings of irradiated area

Claims

1. The device has a first member, a second member, and a third member in this order, When the adhesion force at the contact surface between the first member and the second member is C1, the adhesion force at the center of the contact surface between the second member and the third member is C21, and the adhesion force at at least a part of the outer periphery located outside the center of the contact surface between the second member and the third member is C22, the requirement of the following formula (1) is satisfied, Formula (1) C22>C1>C21 The first member includes a first protective film and an adhesive layer, the second member includes a base material and a liquid crystal layer, the third member includes a second protective film, the adhesive layer of the first member is disposed closer to the second member than the first protective film of the first member, A laminate, wherein the liquid crystal layer in the second member is disposed closer to the third member than the base material in the second member.

2. A method for producing a laminate, comprising a step of cutting a laminate sheet having a first member, a second member, and a third member in this order with a laser to obtain the laminate according to claim 1, A method for manufacturing a laminate, wherein when the adhesion strength at a contact surface between the first member and the second member in the laminate sheet is C1 and the adhesion strength at a contact surface between the second member and the third member is C2, the relationship of the following formula (2) is satisfied. Formula (2) C1>C2

3. A step 1 of peeling off a first member from the laminate according to claim 1 to obtain a laminated member in which a second member and a third member are laminated in this order; A step 2 of bonding the laminated member and the object to be bonded so that the object to be bonded and the second member face each other to obtain a bonded product; and a step 3 of peeling the third member from the bonded product to obtain an optical member.