Method for manufacturing an adhesive sheet and an adhesive sheet

Abstract

To provide a manufacturing method of an adhesive sheet easy to design, capable of preventing a decrease in productivity due to deterioration of curability and a difference in physical properties at front and back surfaces or a change in physical properties such as a change in a release force of a release sheet, even when an ultraviolet light absorber is mixed in a photocurable adhesive sheet, and also to provide an adhesive sheet obtained through the manufacturing method.SOLUTION: A manufacturing method of an adhesive sheet includes steps of: disposing an adhesive layer 10 formed of a transparent photocurable adhesive base material on a substrate S1; irradiating the adhesive layer 10 with ultraviolet light U to cure the adhesive layer; preparing a solution 12 of an ultraviolet light absorber 11; applying the solution 12 on one surface of the cured adhesive layer 10a; impregnating the ultraviolet light absorber 11 contained in the solution 12 in a thickness direction from the one surface of the adhesive layer 10a; and drying the adhesive layer 10a.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an adhesive sheet having a transparent adhesive layer and an adhesive sheet obtainable by the manufacturing method. In particular, the present invention relates to a method for manufacturing an adhesive sheet having a transparent adhesive layer that can be used for bonding a transparent optical member to another optical member and an adhesive sheet obtainable by the manufacturing method.

Background Art

[0002] An image display device such as a liquid crystal display device or an organic EL display device is composed of an optical member laminate in which transparent cover members such as a polarizing film, a retardation film, a cover glass, and various other transparent optical members are laminated. An adhesive sheet made of a transparent adhesive layer is used to bond between these optical members. That is, an adhesive sheet is disposed between two optical members to be joined, and the two optical members are joined by pressing them against each other to form an optical member laminate. Further, an adhesive sheet having an adhesive layer provided on one side of a base film is generally used in the manufacturing process of optical products as a surface protection film for preventing adhesion of scratches and dirt to the optical member.

[0003] In addition, in an image display device provided with a touch panel, a transparent and conductive printed layer such as patterned ITO (indium tin oxide) is formed on the surface of the optical member. Further, lead wiring of silver or copper is formed in the peripheral portion. Also, it is common to print a black concealment portion in a frame shape on the peripheral edge of the transparent cover member. An adhesive sheet for bonding an optical member having such a printed layer and wiring is required to have step absorptivity such that no bubbles remain in the printing step.

[0004] As such an adhesive sheet, a solventless photocurable adhesive sheet is widely used (for example, see Patent Document 1). The photocurable adhesive sheet has an advantage that, before curing, a part thereof is in an uncured (semi-cured) state and has high fluidity, so that it has high step absorptivity, and the adhesive reliability can be improved by subsequent photocuring by ultraviolet irradiation.

[0005] On the other hand, in an image display device, in order to suppress deterioration of components in the image display device due to incident ultraviolet rays, ultraviolet ray cut-off properties may be required. In particular, in an organic EL display device, since an organic compound is used as a light-emitting element, deterioration due to ultraviolet rays occurs earlier than in a liquid crystal display device. Furthermore, the thinning of optical members such as a polarizing film and a protective film has progressed, and the light resistance to ultraviolet rays has decreased, so it has become essential to provide an ultraviolet absorption layer. For example, it is known to use an adhesive sheet including an ultraviolet absorption layer containing an ultraviolet absorber (see, for example, Patent Document 2).

[0006] On the other hand, a double-sided adhesive sheet of a type without a base material (which may be referred to as a "base material-less adhesive sheet" in this specification) is used in a form in which both sides are protected by release sheets. When bonding an optical member using a base material-less adhesive sheet, first, after peeling off one-sided release sheet from the adhesive sheet, it is pasted onto the first member, then the remaining release sheet is peeled off, and the second member is bonded in a procedure of bonding. At that time, when the forces (peeling forces) required to peel off the two release sheets are similar, in the stage of peeling off the first release sheet, the release sheet on the opposite side (the second one) is also peeled off, and a so-called "weeping separation" problem occurs. Therefore, the peeling forces of the two release sheets provided in the base material-less adhesive sheet are designed to be different from each other.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] The pressure-sensitive adhesive sheet of Patent Document 2 is composed of an ultraviolet absorption layer in which an ultraviolet absorber is blended into a pressure-sensitive adhesive composition and uniformly dissolved. However, there is a problem that adding a sufficient amount of ultraviolet absorber to impart ultraviolet cut-off properties to the pressure-sensitive adhesive composition affects the physical properties and curability of the pressure-sensitive adhesive. In particular, when curing a photocurable pressure-sensitive adhesive sheet containing an ultraviolet absorber by ultraviolet irradiation, there is a problem that the ultraviolet rays are absorbed by the ultraviolet absorber, resulting in deteriorated curability and reduced productivity.

[0009] In addition, there is also a problem that in a photocurable pressure-sensitive adhesive sheet in which an ultraviolet absorber is uniformly dissolved, physical property differences such as adhesiveness and viscoelasticity occur between the front and back of the pressure-sensitive adhesive sheet. This is because the ultraviolet rays are absorbed by the ultraviolet absorber while passing through the inside of the pressure-sensitive adhesive layer, and the ultraviolet illuminance decreases as the depth from the ultraviolet irradiation side surface increases, resulting in a difference in curing speed between the front and back.

[0010] Furthermore, in a substrate-free pressure-sensitive adhesive sheet in which an ultraviolet absorber is uniformly dissolved in the pressure-sensitive adhesive layer, there is also a problem that the design of the difference in peel strength between the two release sheets changes. That is, as a countermeasure against the deterioration of curability due to the ultraviolet absorber, increasing the amount of polymerization initiator or the amount of ultraviolet irradiation light causes the peel strength of the release sheet on the irradiation side to become larger than the design value. As a result, problems such as difficulty in peeling with a peeling machine, the peel strengths of the two release sheets becoming close and causing separation, and the peel strengths of the two release sheets reversing may occur. Also, when the peel strength becomes heavy, when peeling the other release sheet remaining after pasting to the first member, a force is applied to the pressure-sensitive adhesive sheet, causing it to stretch and deform, resulting in a defect that it cannot be pasted neatly.

[0011] Therefore, when blending an ultraviolet absorber into a photocurable pressure-sensitive adhesive sheet, in order to maintain curability and reduce physical property changes such as physical property differences between the front and back and changes in the peel strength of the release sheet, it is necessary to start the design of the pressure-sensitive adhesive composition such as the blending amount of the ultraviolet absorber, the thickness of the pressure-sensitive adhesive sheet, and the curing conditions such as ultraviolet illuminance from scratch.

[0012] In particular, in recent years, due to the thinning of image display devices, there has been an increasing demand for thinning the adhesive layer and increasing the concentration of the ultraviolet absorber included in the adhesive composition, and the above problems have become more prominent.

[0013] The present invention has been conceived under the above circumstances, and even when an ultraviolet absorber is blended into a photocurable adhesive sheet, it is possible to prevent a decrease in productivity due to deterioration of curability, physical property differences between the front and back, and changes in the peel strength of the release sheet. The purpose is to provide a method for manufacturing an adhesive sheet that is easy to design without causing physical property changes such as those described above. Another object of the present invention is to provide an adhesive sheet that is easy to design without causing physical property changes such as a decrease in productivity due to deterioration of curability, physical property differences between the front and back, and changes in the peel strength of the release sheet, even when an ultraviolet absorber is blended into a photocurable adhesive sheet.

Means for Solving the Problems

[0014] As a result of intensive studies to achieve the above object, the present inventors have found that by irradiating the adhesive layer with ultraviolet rays to cure it and then applying an ultraviolet absorber to the adhesive layer, the influence on the curability of the adhesive layer, the physical property difference between the front and back, and the peel strength of the release sheet are minimized. It has been found that an adhesive sheet having excellent physical properties, not causing the above problems associated with changes in the peel strength of the release sheet, and having excellent ultraviolet cut-off properties can be obtained. The present invention has been completed based on these findings.

[0015] That is, the first aspect of the present invention is forming an adhesive layer formed of a transparent photocurable adhesive base material on a support, irradiating the adhesive layer with ultraviolet rays to cure the adhesive layer, preparing a solution of an ultraviolet absorber, applying the solution to one surface of the cured adhesive layer to allow the ultraviolet absorber contained in the solution to penetrate in the thickness direction from the one surface of the adhesive layer, drying the adhesive layer and providing a method for manufacturing an adhesive sheet including the steps.

[0016] By irradiating the pressure-sensitive adhesive layer with ultraviolet rays before incorporating an ultraviolet absorber into the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer can be cured without being affected by the ultraviolet absorber. Therefore, it is possible to minimize physical property changes in the peel strength of the pressure-sensitive adhesive layer and the release sheet, such as a decrease in productivity due to deterioration of curability caused by the ultraviolet absorber and differences in physical properties between the front and back surfaces.

[0017] By applying a solution of an ultraviolet absorber to the cured pressure-sensitive adhesive layer, the ultraviolet absorber penetrates into the pressure-sensitive adhesive layer. Thereby, sufficient ultraviolet ray cut-off properties can be imparted to the pressure-sensitive adhesive layer. In addition, since the ultraviolet absorber penetrates in a solution state, the transparency of the pressure-sensitive adhesive layer is maintained.

[0018] Thereafter, the pressure-sensitive adhesive layer is dried by heating or the like. By this step, the pressure-sensitive adhesive layer returns to a state close to that before coating. That is, since the pressure-sensitive adhesive layer has been once cured, physical properties such as adhesiveness and viscoelasticity are restored to a state close to that before applying the solution.

[0019] Since the adhesive layer is cured before applying the ultraviolet absorber, once the composition, curing conditions, physical properties of the adhesive composition, the peel strength of the release sheet, etc. are determined, there is no need to redesign the composition and the peel strength of the release sheet by adding the ultraviolet absorber, and it is also easy to change the thickness of the pressure-sensitive adhesive layer. Then, by changing the coating conditions of the ultraviolet absorber solution thereafter, the ultraviolet absorption function imparted to the pressure-sensitive adhesive layer can be controlled. In this way, since the control of the physical properties of the pressure-sensitive adhesive layer and the release sheet and the control of the ultraviolet absorption function can be separated, it is not necessary to design the pressure-sensitive adhesive layer from 1 with respect to changes in the thickness of the pressure-sensitive adhesive layer, the ultraviolet absorption function, and the peel strength of the release sheet, which is efficient.

[0020] In the method for manufacturing a pressure-sensitive adhesive sheet according to the first aspect of the present invention, the solution of the ultraviolet absorber may be a solution in which the ultraviolet absorber is dissolved in a solvent, and may include a step of evaporating the solvent of the solution by drying the pressure-sensitive adhesive layer. By applying a solution in which an ultraviolet absorber is dissolved in a solvent to the cured adhesive layer, the solvent penetrates into the adhesive layer and the adhesive layer swells, and the ultraviolet absorber dissolved in the solvent penetrates into the adhesive layer swollen by the solvent. As a result, sufficient ultraviolet cut performance can be imparted to the adhesive layer, and the transparency of the adhesive layer is maintained because the ultraviolet absorber penetrates in the solution. The solvent that has penetrated into the adhesive layer evaporates by heating or the like, and the adhesive layer returns to a state close to that before swelling. That is, since the adhesive layer is once cured, physical properties such as adhesiveness and viscoelasticity are restored to a state close to that before applying the solution.

[0021] In the method for manufacturing an adhesive sheet according to the first aspect of the present invention, the solution of the ultraviolet absorber may further contain a dye compound whose maximum absorption wavelength in the absorption spectrum exists in the wavelength region of 380 to 430 nm. Further, the method for manufacturing an adhesive sheet according to the first aspect of the present invention may further include a step of preparing a solution of a dye compound whose maximum absorption wavelength in the absorption spectrum exists in the wavelength region of 380 to 430 nm and applying the solution to one surface of the cured adhesive layer. These configurations are preferable in that they impart an absorption function to light in a wavelength region (380 nm to 430 nm) on the longer wavelength side than the ultraviolet absorber to the adhesive layer, and can more efficiently suppress the deterioration of an organic EL element or the like. The solution of the dye compound may be a solution in which the dye compound is dissolved in a solvent.

[0022] The method for manufacturing an adhesive sheet according to the first aspect of the present invention may further include a step of bonding a release sheet to the surface of the adhesive layer opposite to the support. Bonding the release sheet is preferable in that it can protect the surface of the adhesive layer.

[0023] In the method for manufacturing an adhesive sheet according to the first aspect of the present invention, it is preferable that the absorption maximum wavelength of the absorption spectrum of the ultraviolet absorber exists in the wavelength region of 300 to 400 nm. With this configuration, deterioration of an image display device, particularly an organic EL display device, due to UVA can be efficiently suppressed.

[0024] Moreover, a second aspect of the present invention is an adhesive sheet having a support and a transparent adhesive layer on the support, wherein the adhesive layer is a single layer made of a transparent photocurable adhesive base material and has two opposing main surfaces, an ultraviolet absorber is dissolved in the adhesive layer, when the single-layer adhesive layer is equally divided into two in the thickness direction, an adhesive sheet is provided, characterized in that the concentration of the ultraviolet absorber in the region belonging to one of the two main surfaces, i.e., the first main surface, is different from the concentration of the ultraviolet absorber in the region belonging to the other main surface, i.e., the second main surface.

[0025] The adhesive sheet of the second aspect of the present invention can be obtained by the method for manufacturing the adhesive sheet of the first aspect of the present invention. By applying and infiltrating a solution of an ultraviolet absorber on one surface of the adhesive layer, a concentration difference of the ultraviolet absorber can occur on the front and back of the adhesive layer. The adhesive sheet that can have this configuration can minimize physical property changes such as a decrease in productivity due to deterioration of curability by the ultraviolet absorber, physical property differences between the front and back, and changes in the peeling force of the release sheet, as described above.

[0026] In the method for manufacturing the adhesive sheet of the first aspect of the present invention, depending on conditions such as the thickness of the adhesive layer and the penetration time of the ultraviolet absorber, the concentration of the ultraviolet absorber may be the same or substantially the same on the front and back of the adhesive layer. Therefore, the present invention also includes cases where an adhesive sheet having the same or substantially the same concentration of the ultraviolet absorber on the front and back of the adhesive layer is obtained by the method for manufacturing the adhesive sheet of the first aspect of the present invention.

[0027] The adhesive sheet of the second aspect of the present invention may further contain a dye compound whose maximum absorption wavelength in the absorption spectrum exists in the wavelength range of 380 to 430 nm dissolved therein. This configuration is preferable in that it imparts an absorption function to the adhesive layer for light in the wavelength region (380 nm to 430 nm) on the longer wavelength side than the ultraviolet absorber, and can more efficiently suppress the deterioration of organic EL elements and the like.

[0028] In the adhesive sheet according to the second aspect of the present invention, it is preferable that the difference between the adhesive force (N / 10 mm) of the first main surface and the adhesive force (N / 10 mm) of the second main surface is 1.0 N / 10 mm or less. This configuration is preferable in that two transparent optical members can be joined without a difference in adhesive force. The difference in the adhesive force (N / 10 mm) is preferably 0.5 N / 10 mm or less, and more preferably 0.3 N / 10 mm or less.

[0029] In the adhesive sheet according to the second aspect of the present invention, the adhesive layer is preferably an adhesive layer cured by ultraviolet irradiation. This configuration is preferable in that it can minimize a decrease in productivity due to deterioration of curability by an ultraviolet absorber, physical property changes such as physical property differences between the front and back, and changes in the peel force of the release sheet.

[0030] In the adhesive sheet according to the second aspect of the present invention, the second main surface faces the support, and the concentration of the ultraviolet absorber in the region where the first main surface belongs is preferably higher than the concentration of the ultraviolet absorber in the region where the second main surface belongs. This configuration can be obtained by applying a solution of an ultraviolet absorber to the first main surface.

[0031] In the adhesive sheet according to the second aspect of the present invention, it is preferable that the single-layer photocurable adhesive layer has a concentration gradient of the ultraviolet absorber in the thickness direction. This configuration can be obtained by applying a solution of an ultraviolet absorber to one main surface of the adhesive layer.

[0032] In the adhesive sheet according to the second aspect of the present invention, the support is preferably a release sheet. In this case, it is preferable that the support made of a release sheet is disposed on both sides of the adhesive layer. The fact that the support is a release sheet is preferable in that it can be joined to a transparent optical member after peeling.

[0033] In the pressure-sensitive adhesive sheet according to the second aspect of the present invention, it is preferable that the absorption maximum wavelength of the absorption spectrum of the ultraviolet absorber exists in the wavelength range of 300 to 400 nm. With this configuration, deterioration of an image display device, particularly an organic EL display device, due to UVA can be efficiently suppressed.

[0034] In the pressure-sensitive adhesive sheet according to the second aspect of the present invention, the thickness of the pressure-sensitive adhesive layer is preferably 5 μm to 500 μm. If the thickness of the pressure-sensitive adhesive layer is within this range, it is suitable for forming a concentration gradient of the ultraviolet absorber in the thickness direction of the pressure-sensitive adhesive layer. The thickness of the pressure-sensitive adhesive layer is more preferably 5 μm to 400 μm, and even more preferably 50 μm to 400 μm.

Advantages of the Invention

[0035] According to the method for manufacturing a pressure-sensitive adhesive sheet and the pressure-sensitive adhesive sheet of the present invention, even when an ultraviolet absorber is blended in a photocurable pressure-sensitive adhesive sheet, a decrease in productivity due to deterioration of the curability of the pressure-sensitive adhesive layer, physical property changes such as physical property differences between the front and back, and changes in the peeling force of the release sheet are less likely to occur. In addition, it is not necessary to design the pressure-sensitive adhesive layer from 1 regarding changes in the thickness of the pressure-sensitive adhesive layer, the ultraviolet absorption function, and the peeling of the release sheet, and the efficiency is good.

Brief Description of the Drawings

[0036]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0037] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited thereto and is merely illustrative. FIGS. 1(a) to (e) are diagrams schematically showing the steps for carrying out an embodiment of a method for manufacturing an adhesive sheet according to the first aspect of the present invention. First, as shown in FIG. 1(a), an adhesive layer 10 formed of a transparent photocurable adhesive base material is formed on a support S1 (adhesive layer forming step).

[0038] The support is not particularly limited, but a plastic film is preferred. Examples of materials such as the plastic film include plastic materials such as polyester resins such as polyethylene terephthalate (PET), acrylic resins such as polymethyl methacrylate (PMMA), polycarbonate, triacetyl cellulose (TAC), polysulfone, polyarylate, polyimide, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, ethylene-propylene copolymer, trade name "Arton" (cyclic olefin polymer, manufactured by JSR Corporation), trade name "Zeonoa" (cyclic olefin polymer, manufactured by Nippon Zeon Co., Ltd.) and other cyclic olefin polymers. Note that only one kind of these plastic materials may be used, or two or more kinds may be used. The support may be a release sheet. The release sheet is not particularly limited, and examples thereof include plastic films surface-treated with a release treatment agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide-based agent.

[0039] The photocurable adhesive base material is not particularly limited as long as it is a transparent material having adhesiveness usable for optical applications. For example, it can be appropriately selected and used from acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. From the viewpoints of transparency, processability, and durability, it is preferable to use an acrylic adhesive. The photocurable adhesive base material can be used alone or in combination of two or more of the above adhesives. The acrylic polymer used as the base polymer of the acrylic adhesive is not particularly limited in a restrictive sense, but is preferably a homopolymer or copolymer of a monomer mainly composed of an alkyl (meth)acrylate. Here, the expression "(meth)acrylic" is used to mean either one or both of "acrylic" and "methacrylic", and the same applies in other cases. In the present invention, the term "acrylic polymer" is used to mean that, in addition to the above-mentioned alkyl (meth)acrylates, other monomers copolymerizable therewith are also included.

[0040] When the photocurable adhesive base material contains an acrylic polymer which is an acrylic adhesive, preferably, the acrylic polymer contains, as the main monomer unit having the largest weight ratio, monomer units derived from an alkyl acrylate having a linear or branched alkyl group and / or an alkyl methacrylate having a linear or branched alkyl group.

[0041] The (meth)acrylic acid alkyl esters having a linear or branched alkyl group for forming the monomer unit of the acrylic polymer, that is, the (meth)acrylic acid alkyl esters having a linear or branched alkyl group contained in the monomer component for forming the acrylic polymer include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate, etc., and (meth)acrylic acid alkyl esters having a linear or branched alkyl group with 1 to 20 carbon atoms can be mentioned. As the (meth)acrylic acid alkyl ester for the acrylic polymer, one kind of (meth)acrylic acid alkyl ester may be used, or two or more kinds of (meth)acrylic acid alkyl esters may be used. In the present embodiment, as the (meth)acrylic acid alkyl ester for the acrylic polymer, at least one selected from the group consisting of n-butyl acrylate, 2-ethylhexyl acrylate, and isostearyl acrylate is preferably used.

[0042] The proportion of monomer units derived from (meth)acrylic acid alkyl esters having linear or branched alkyl groups in the acrylic polymer is preferably 50% by weight or more, more preferably 60% by weight or more, still more preferably 70% by weight or more, still more preferably 80% by weight or more, and still more preferably 90% by weight or more. That is, the proportion of (meth)acrylic acid alkyl esters in the monomer component composition of the raw materials for forming the acrylic polymer is preferably 50% by weight or more, more preferably 60% by weight or more, still more preferably 70% by weight or more, still more preferably 80% by weight or more, and still more preferably 90% by weight or more.

[0043] The acrylic polymer contained in the photocurable adhesive base material may contain monomer units derived from an alicyclic monomer. Examples of the alicyclic monomer that forms the monomer units of the acrylic polymer, that is, the alicyclic monomer contained in the monomer components for forming the acrylic polymer, include, for example, cycloalkyl (meth)acrylate, (meth)acrylate having a bicyclic hydrocarbon ring, and (meth)acrylate having a tricyclic or higher hydrocarbon ring. Examples of the cycloalkyl (meth)acrylate include cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, and cyclooctyl (meth)acrylate. Examples of the (meth)acrylate having a bicyclic hydrocarbon ring include bornyl (meth)acrylate and isobornyl (meth)acrylate. Examples of the (meth)acrylate having a tricyclic or higher hydrocarbon ring include dicyclopentanyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, tricyclopentanyl (meth)acrylate, 1-adamantyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, and 2-ethyl-2-adamantyl (meth)acrylate. As the alicyclic monomer for the acrylic polymer, one kind of alicyclic monomer may be used, or two or more kinds of alicyclic monomers may be used. In the present embodiment, as the alicyclic monomer for the acrylic polymer, at least one selected from the group consisting of cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate, and isobornyl methacrylate is preferably used.

[0044] From the viewpoint of achieving appropriate flexibility in the photocurable adhesive base material formed including the acrylic polymer, the proportion of the monomer units derived from the alicyclic monomer in the acrylic polymer is preferably 5 to 60% by weight, more preferably 10 to 50% by weight, and still more preferably 12 to 40% by weight.

[0045] The acrylic polymer contained in the photocurable adhesive base material may contain monomer units derived from a hydroxyl group-containing monomer. The hydroxyl group-containing monomer is a monomer having at least one hydroxyl group in the monomer unit. When the acrylic polymer in the photocurable adhesive base material contains hydroxyl group-containing monomer units, it is easy to obtain adhesiveness and appropriate cohesive force in the photocurable adhesive base material.

[0046] Examples of the hydroxyl group-containing monomer for forming the monomer units of the acrylic polymer, that is, the hydroxyl group-containing monomer contained in the monomer component for forming the acrylic polymer, include hydroxyl group-containing (meth)acrylic acid esters, vinyl alcohol, and allyl alcohol. Examples of the hydroxyl group-containing (meth)acrylic acid esters include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, hydroxyoctyl (meth)acrylate, hydroxydecyl (meth)acrylate, hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate. As the hydroxyl group-containing monomer for the acrylic polymer, one kind of hydroxyl group-containing monomer may be used, or two or more kinds of hydroxyl group-containing monomers may be used. In the present embodiment, as the hydroxyl group-containing monomer for the acrylic polymer, at least one selected from the group consisting of 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, and 4-hydroxybutyl methacrylate is preferably used.

[0047] In the acrylic polymer, the proportion of monomer units derived from the hydroxyl group-containing monomer is preferably 1% by weight or more, more preferably 2% by weight or more, more preferably 3% by weight or more, more preferably 7% by weight or more, more preferably 10% by weight or more, and more preferably 15% by weight or more. In the acrylic polymer, the proportion of monomer units derived from the hydroxyl group-containing monomer is preferably 35% by weight or less, more preferably 30% by weight or less. These configurations regarding the proportion of the hydroxyl group-containing monomer are suitable for realizing adhesiveness and appropriate cohesive force in the photocurable pressure-sensitive adhesive base material formed including the acrylic polymer.

[0048] The acrylic polymer contained in the photocurable pressure-sensitive adhesive base material may contain monomer units derived from a nitrogen atom-containing monomer. The nitrogen atom-containing monomer is a monomer having at least one nitrogen atom in the monomer unit. When the acrylic polymer in the photocurable pressure-sensitive adhesive base material contains nitrogen atom-containing monomer units, it is easy to obtain hardness and good adhesive reliability in the photocurable pressure-sensitive adhesive base material.

[0049] Examples of the nitrogen atom-containing monomer that forms the monomer unit of the acrylic polymer, i.e., the nitrogen atom-containing monomer included in the monomer components for forming the acrylic polymer, include N-vinyl cyclic amides and (meth)acrylamides. Examples of the N-vinyl cyclic amide as the nitrogen atom-containing monomer include N-vinyl-2-pyrrolidone, N-vinyl-2-piperidone, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, and N-vinyl-3,5-morpholinedione. Examples of the (meth)acrylamides as the nitrogen atom-containing monomer include (meth)acrylamide, N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-n-butyl(meth)acrylamide, N-octyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, and N,N-diisopropyl(meth)acrylamide. As the nitrogen atom-containing monomer for the acrylic polymer, one type of nitrogen atom-containing monomer may be used, or two or more types of nitrogen atom-containing monomers may be used. In the present embodiment, N-vinyl-2-pyrrolidone is preferably used as the nitrogen atom-containing monomer for the acrylic polymer.

[0050] From the viewpoint of achieving appropriate hardness, adhesiveness, and transparency in the photocurable pressure-sensitive adhesive base material formed including the acrylic polymer, the proportion of the monomer unit derived from the nitrogen atom-containing monomer in the acrylic polymer is preferably 1% by weight or more, more preferably 3% by weight or more, still more preferably 5% by weight or more. Further, from the viewpoints of achieving sufficient transparency and suppressing excessive hardening to realize good adhesive reliability in the photocurable pressure-sensitive adhesive base material formed including the acrylic polymer, the proportion of the monomer unit derived from the nitrogen atom-containing monomer in the acrylic polymer is preferably 30% by weight or less, more preferably 25% by weight or less.

[0051] The acrylic polymer contained in the photocurable pressure-sensitive adhesive base material may contain monomer units derived from a carboxy group-containing monomer. The carboxy group-containing monomer is a monomer that has at least one carboxy group in the monomer unit. When the acrylic polymer in the photocurable pressure-sensitive adhesive base material contains carboxy group-containing monomer units, good adhesion reliability may be obtained in the photocurable pressure-sensitive adhesive base material.

[0052] Examples of the carboxy group-containing monomer for forming the monomer units of the acrylic polymer, that is, the carboxy group-containing monomer contained in the monomer components for forming the acrylic polymer, include (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid. As the carboxy group-containing monomer for the acrylic polymer, one type of carboxy group-containing monomer may be used, or two or more types of carboxy group-containing monomers may be used. In the present embodiment, acrylic acid is preferably used as the carboxy group-containing monomer for the acrylic polymer.

[0053] From the viewpoint of ensuring good adhesion reliability by obtaining the contribution of the interaction between the polar group and the carboxy group when a polar group is present on the surface of the adherend in the photocurable pressure-sensitive adhesive base material formed including the acrylic polymer, the proportion of the monomer units derived from the carboxy group-containing monomer in the acrylic polymer is preferably 0.1% by weight or more, more preferably 0.5% by weight or more. Further, from the viewpoint of suppressing excessive hardening and realizing good adhesion reliability in the photocurable pressure-sensitive adhesive base material formed including the acrylic polymer, the proportion of the monomer units derived from the carboxy group-containing monomer in the acrylic polymer is preferably 20% by weight or less, more preferably 15% by weight or less.

[0054] The acrylic polymer contained in the photocurable pressure-sensitive adhesive base material may have a crosslinked structure derived from a polyfunctional (meth)acrylate as a copolymerizable crosslinking agent. Examples of the polyfunctional (meth)acrylate include 1,6-hexanediol di(meth)acrylate, butanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl (meth)acrylate, and vinyl (meth)acrylate. As the polyfunctional (meth)acrylate for the acrylic polymer, one type of polyfunctional (meth)acrylate may be used, or two or more types of polyfunctional (meth)acrylate may be used. In the present embodiment, as the polyfunctional (meth)acrylate for the acrylic polymer, at least one selected from the group consisting of 1,6-hexanediol diacrylate, dipentaerythritol hexaacrylate, and trimethylolpropane triacrylate is preferably used.

[0055] The proportion of the monomer unit derived from the polyfunctional (meth)acrylate in the acrylic polymer is preferably 0.01% by weight or more, more preferably 0.03% by weight or more, more preferably 0.05% by weight or more, and more preferably 0.1% by weight or more. The proportion of the monomer unit derived from the polyfunctional (meth)acrylate in the acrylic polymer is preferably 1% by weight or less, more preferably 0.5% by weight or less. These configurations regarding the proportion of the polyfunctional (meth)acrylate are suitable for achieving appropriate hardness and adhesiveness in the photocurable pressure-sensitive adhesive base material formed including the acrylic polymer.

[0056] When the photocurable adhesive base material contains the above acrylic polymer as an adhesive, the content of the acrylic polymer in the photocurable adhesive base material is, for example, 85 to 100% by weight.

[0057] The above-mentioned photocurable adhesive base material contains a photoinitiator in addition to the monomers for forming an acrylic polymer. Examples of the photoinitiator include benzoin ether-based photoinitiators, acetophenone-based photoinitiators, α-ketol-based photoinitiators, aromatic sulfonyl chloride-based photoinitiators, photoactive oxime-based photoinitiators, benzoin-based photoinitiators, benzyl-based photoinitiators, benzophenone-based photoinitiators, ketal-based photoinitiators, and thioxanthone-based photoinitiators. Examples of the benzoin ether-based photoinitiators include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, and 2,2-dimethoxy-1,2-diphenylethane-1-one. Examples of the acetophenone-based photoinitiators include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl phenyl ketone, 4-phenoxydichloroacetophenone, and 4-(t-butyl)dichloroacetophenone. Examples of the α-ketol-based photoinitiators include 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one. Examples of the aromatic sulfonyl chloride-based photoinitiators include 2-naphthalenesulfonyl chloride. Examples of the photoactive oxime-based photoinitiators include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime. Examples of the benzoin-based photoinitiators include benzoin. Examples of the benzyl-based photoinitiators include benzyl. Examples of the benzophenone-based photoinitiators include benzophenone, benzoyl benzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, and polyvinylbenzophenone. Examples of the ketal-based photoinitiators include benzyldimethyl ketal.Examples of the thioxanthone-based photoinitiators include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone. The photocurable pressure-sensitive adhesive base material may contain one type of such photoinitiator or two or more types of such photoinitiators. The content of the photoinitiator in the photocurable pressure-sensitive adhesive base material is, for example, 0.01 to 3% by weight.

[0058] The photocurable pressure-sensitive adhesive base material may further contain additives such as a crosslinking agent, a crosslinking accelerator, a silane coupling agent, a tackifier resin, an antioxidant, a filler, a colorant such as a pigment or a dye, an antioxidant, a chain transfer agent, a plasticizer, a softening agent, a surfactant, a rust inhibitor, and an antistatic agent, as necessary. Examples of the tackifier resin include rosin derivatives, polyterpene resins, petroleum resins, and oil-soluble phenols.

[0059] Note that the photocurable pressure-sensitive adhesive base material preferably does not contain or substantially does not contain an ultraviolet absorber. Such a configuration is preferable in that when the pressure-sensitive adhesive sheet of the present invention is subjected to the adhesive layer curing step described later, the curability can be minimized, such as deterioration of curability, physical property differences between the front and back, and changes in the peeling force of the release sheet. When the ratio of the ultraviolet absorber in the total amount (100% by mass) of the photocurable pressure-sensitive adhesive base material is 0.05% by weight or less (preferably 0.01% by mass or less), it can be said that the photocurable pressure-sensitive adhesive base material substantially does not contain an ultraviolet absorber.

[0060] The method for forming the adhesive layer is not particularly limited. For example, the photocurable pressure-sensitive adhesive base material is applied (coated) on a support, and the obtained adhesive composition layer is dried and cured, or the photocurable pressure-sensitive adhesive base material is applied (coated) on a support, and the obtained adhesive composition layer is irradiated with active energy rays for curing. If necessary, it may be further dried by heating.

[0061] For the application (coating) of the above photocurable adhesive base material, known coating methods can be used. For example, coaters such as gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, spray coater, comma coater, and direct coater can be mentioned.

[0062] The drying and curing temperature is preferably 40 to 200 °C, more preferably 50 to 180 °C, and even more preferably 70 to 170 °C. The drying and curing time can be appropriately selected as an appropriate time, for example, 5 seconds to 20 minutes, preferably 5 seconds to 10 minutes, and more preferably 10 seconds to 5 minutes.

[0063] Examples of the above active energy rays include ionizing radiations such as α-rays, β-rays, γ-rays, neutron rays, electron rays, and ultraviolet rays. In particular, ultraviolet rays are preferred. Also, the irradiation energy, irradiation time, irradiation method, etc. of the active energy rays are not particularly limited, and can be appropriately set according to the thickness of the adhesive layer 10, etc., so as to obtain the desired viscosity and viscoelasticity.

[0064] The main surface of the adhesive layer formed above that does not face the support is preferably laminated with another support (including a release sheet) in order to block oxygen that inhibits curing by the above active energy rays and / or ultraviolet irradiation described later.

[0065] Next, as shown in FIG. 1(b), the adhesive layer 10 is irradiated with ultraviolet rays U to cure the adhesive layer 10 (adhesive layer curing step). In FIG. 1(b), 10a is the cured adhesive layer of the adhesive layer 10. At this stage, the adhesive layer does not contain or substantially does not contain an ultraviolet absorber, so physical property changes such as a decrease in productivity due to deterioration of curability by the ultraviolet absorber, physical property differences between the front and back, and changes in the peeling force of the release sheet are less likely to occur, and a highly reliable adhesive layer 10a can be obtained.

[0066] The ultraviolet rays may be directly irradiated onto the adhesive layer 10, but in order to block oxygen that inhibits curing by ultraviolet irradiation, it is preferable to irradiate through a support. Fig. 1(b) shows an embodiment in which ultraviolet rays are irradiated onto the adhesive layer 10 through the support S2. When irradiating ultraviolet rays through a support, another support S2 (including a release sheet) is bonded to the main surface of the adhesive layer 10 opposite to the main surface facing the support S1, and ultraviolet rays are irradiated through the support. The illuminance and time of ultraviolet irradiation are appropriately set according to the composition of the photocurable adhesive base material, the thickness of the adhesive layer, and the like. For ultraviolet irradiation, a high-pressure mercury lamp, a low-pressure mercury lamp, a metal halide lamp, or the like can be used.

[0067] Next, as shown in Fig. 1(c), after the support S2 is peeled off and removed, a solution 12 of the ultraviolet absorber 11 is applied to one surface of the adhesive layer 10a (solution application step). The solution of the ultraviolet absorber is not particularly limited as long as it is liquid, can be applied to the adhesive layer, and penetrates. For example, when the ultraviolet absorber is liquid, the ultraviolet absorber itself may be applied as a solution as it is. Also, it may be a solution in which the ultraviolet absorber is dissolved in a solvent. Alternatively, it may be a solution in which the ultraviolet absorber is mixed with the dye compound described below. Fig. 1(c) shows an embodiment in which a solution 12 in which the ultraviolet absorber 11 is dissolved in a solvent 13 is applied to one surface of the adhesive layer 10a.

[0068] On the surface of the adhesive layer 10a, the ultraviolet absorber 11 in the solution 12 penetrates into the adhesive layer 10a in the thickness direction (solution penetration step). This state is shown in Fig. 1(d). When the solution 12 is a solution in which the ultraviolet absorber 11 is dissolved in the solvent 13, the solvent 13 penetrates and swells on the surface of the adhesive layer 10a, and the ultraviolet absorber 11 penetrates into the adhesive layer 10a in a state of being dissolved in the solvent. The ultraviolet absorber 11 becomes in a "dissolved" state in the adhesive layer 10a.

[0069] Also, in the process of the ultraviolet absorber 11 penetrating into the adhesive layer 10a, a concentration gradient can be formed in the thickness direction. Therefore, the concentration of the ultraviolet absorber 11 on the side where the solution 12 is applied may be higher than that on the opposite side surface. This state is shown in Fig. 1(d).

[0070] Thereafter, by drying the pressure-sensitive adhesive layer 10a, the pressure-sensitive adhesive sheet 1 shown in FIG. 1(e) can be obtained (drying step). When the solution 12 is a solution in which the ultraviolet absorber 11 is dissolved in a solvent, the penetrated solvent 13 evaporates by the drying step. By drying the pressure-sensitive adhesive layer 10a, the pressure-sensitive adhesive layer 10a returns to a state close to that before coating. Therefore, the difference in physical properties between the front and back and the change in the peeling force of the release sheet can be minimized. When the pressure-sensitive adhesive layer 10a is dried, the penetration of the ultraviolet absorber 11 into the pressure-sensitive adhesive layer 10a stops, and the concentration gradient of the ultraviolet absorber is fixed.

[0071] The ultraviolet absorber is not particularly limited. For example, triazine-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, oxybenzophenone-based ultraviolet absorbers, salicylic acid ester-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, etc. can be mentioned, and these can be used alone or in combination of two or more. Among these, triazine-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, and benzophenone-based ultraviolet absorbers are preferable, and a triazine-based ultraviolet absorber having 2 or less hydroxyl groups in one molecule, and a benzotriazole-based ultraviolet absorber having 1 benzotriazole skeleton in one molecule, at least one ultraviolet absorber selected from the group consisting of benzophenone-based ultraviolet absorbers is preferable because of its good solubility and high ultraviolet absorption ability near a wavelength of 380 nm.

[0072] Examples of triazine-based ultraviolet absorbers having two or less hydroxyl groups in one molecule include, specifically, 2,4-bis -[{4-(4-ethylhexyloxy)-4-hydroxy}-phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine (Tinosorb S, manufactured by BASF), 2,4-bis[2-hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-triazine (TINUVIN460, manufactured by BASF), the reaction product of 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl)-5-hydroxyphenyl and [(C 10 -C 16 (mainly C 12 -C 13 ) alkyloxy)methyl]oxirane (TINUVIN400, manufactured by BASF), 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl]-5-[3-(dodecyloxy)-2-hydroxypropoxy]phenol), the reaction product of 2-(2,4-dihydroxyphenyl)-4,6-bis-(2,4-dimethylphenyl)-1,3,5-triazine and (2-ethylhexyl)-glycidic acid ester (TINUVIN405, manufactured by BASF), 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]-phenol (TINUVIN1577, manufactured by BASF), 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]-phenol (ADK STAB LA46, manufactured by ADEKA), 2-(2-hydroxy-4-[1-octyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-triazine (TINUVIN479, manufactured by BASF), and the like.

[0073] In addition, as benzotriazole-based ultraviolet absorbers having one benzotriazole skeleton in one molecule, 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol (TINUVIN 928, manufactured by BASF), 2-(2-hydroxy-5-tert-butylphenyl)-2H-benzotriazole (TINUVIN PS, manufactured by BASF), benzenepropanoic acid and 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxy (C 7-9Ester compounds of (side-chain and linear alkyl) (TINUVIN 384-2, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (TINUVIN 900, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol (TINUVIN 928, manufactured by BASF), reaction product of methyl-3-(3-(2H-benzotriazol-2-yl)-5-t-butyl-4-hydroxyphenyl)propionate / polyethylene glycol 300 (TINUVIN 1130, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-p-cresol (TINUVIN P, manufactured by BASF), 2(2H-benzotriazol-2-yl)-4-6-bis(1-methyl-1-phenylethyl)phenol (TINUVIN 234, manufactured by BASF), 2-[5-chloro(2H)-benzotriazol-2-yl]-4-methyl-6-(tert-butyl)phenol (TINUVIN 326, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (TINUVIN 328, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol (TINUVIN 329, manufactured by BASF), reaction product of methyl 3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl)propionate and polyethylene glycol 300 (TINUVIN 213, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol (TINUVIN 571, manufactured by BASF), 2-[2-hydroxy-3-(3,4,5,6-tetrahydrophthalimidomethyl)-5-methylphenyl]benzotriazole (Sumisorb 250, manufactured by Sumitomo Chemical Co., Ltd.), etc. can be mentioned.

[0074] In addition, examples of the benzophenone-based ultraviolet absorber (benzophenone-based compound) and oxybenzophenone-based ultraviolet absorber (oxybenzophenone-based compound) include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid (anhydrous and trihydrate salts), 2-hydroxy-4-octyloxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone, 4-benzyloxy-2-hydroxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone (Seesorb106, manufactured by Cipro Kasei Co., Ltd.), 2,2'-dihydroxy-4,4-dimethoxybenzophenone, and the like.

[0075] Examples of the salicylic acid ester-based ultraviolet absorber (salicylic acid ester-based compound) include phenyl-2-acryloyloxybenzoate, phenyl-2-acryloyloxy-3-methylbenzoate, phenyl-2-acryloyloxy-4-methylbenzoate, phenyl-2-acryloyloxy-5-methylbenzoate, phenyl-2-acryloyloxy-3-methoxybenzoate, phenyl-2-hydroxybenzoate, phenyl-2-hydroxy-3-methylbenzoate, phenyl-2-hydroxy-4-methylbenzoate, phenyl-2-hydroxy-5-methylbenzoate, phenyl 2-hydroxy-3-methoxybenzoate, 2,4-di-tert-butylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate (TINUVIN120, manufactured by BASF), and the like.

[0076] Examples of the cyanoacrylate-based ultraviolet absorber (cyanoacrylate-based compound) include alkyl-2-cyanoacrylate, cycloalkyl-2-cyanoacrylate, alkoxyalkyl-2-cyanoacrylate, alkenyl-2-cyanoacrylate, alkynyl-2-cyanoacrylate, and the like.

[0077] The maximum absorption wavelength of the ultraviolet absorber preferably exists in the wavelength range of 300 to 400 nm, and more preferably exists in the wavelength range of 320 to 380 nm. The maximum absorption wavelength means, in the spectral absorption spectrum in the wavelength range of 300 to 460 nm, when there are multiple absorption maxima, the absorption maximum wavelength showing the maximum absorbance among them.

[0078] The solution of the ultraviolet absorber may further contain a dye compound whose maximum absorption wavelength of the absorption spectrum exists in the wavelength range of 380 to 430 nm. Alternatively, a solution of the dye compound may be applied to the adhesive layer 10a separately from the solution of the ultraviolet absorber. The maximum absorption wavelength of the absorption spectrum of the dye compound more preferably exists in the wavelength range of 380 to 420 nm. The solution of the dye compound may be a solution in which the dye compound is dissolved in a solvent.

[0079] By applying a solution containing a dye compound whose maximum absorption wavelength of the absorption spectrum exists in the wavelength range of 380 to 430 nm to the adhesive layer 10a in addition to the ultraviolet absorber, light in the wavelength range on the longer wavelength side (380 nm to 430 nm) than the ultraviolet absorber can also be sufficiently absorbed, and deterioration of an organic EL element or the like can be suppressed more efficiently.

[0080] Examples of the dye compound include organic dye compounds and inorganic dye compounds. Among these, organic dye compounds are preferred from the viewpoints of dispersibility in resin components such as base polymers and maintenance of transparency.

[0081] Examples of the organic dye compounds include azomethine compounds, indole compounds, cinnamic acid compounds, pyrimidine compounds, porphyrin compounds, cyanine compounds, and the like.

[0082] As the organic dye compound, commercially available products can be preferably used. Specifically, as the indole-based compound, BONASORB UA3911 (trade name, maximum absorption wavelength of absorption spectrum: 398 nm, half-value width: 48 nm, manufactured by Orient Chemical Industries Co., Ltd.) can be used. As the cinnamic acid-based compound, SOM-5-0106 (trade name, maximum absorption wavelength of absorption spectrum: 416 nm, half-value width: 50 nm, manufactured by Orient Chemical Industries Co., Ltd.) can be used. As the porphyrin-based compound, FDB-001 (trade name, maximum absorption wavelength of absorption spectrum: 420 nm, half-value width: 14 nm, manufactured by Yamada Chemical Industry Co., Ltd.) can be used. As the cyanine-based compound, a merocyanine compound (trade name: FDB-009, maximum absorption wavelength of absorption spectrum: 394 nm, half-value width: 43 nm, manufactured by Yamada Chemical Industry Co., Ltd.) etc. can be mentioned.

[0083] The solvent is not particularly limited as long as it can dissolve the ultraviolet absorber and / or the dye compound and can swell the pressure-sensitive adhesive layer 10a. However, since an aqueous solvent has poor wettability to the pressure-sensitive adhesive layer and additives are difficult to penetrate, a non-aqueous solvent is preferred. The non-aqueous solvent is not particularly limited. For example, esters such as methyl acetate, ethyl acetate, isopropyl acetate, and butyl acetate; alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, and tert-butanol; aromatic hydrocarbons such as toluene, xylene, and ethylbenzene; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; alicyclic ketones such as cyclopentanone and cyclohexanone; aliphatic hydrocarbons such as hexane, heptane, and octane; alicyclic hydrocarbons such as cyclohexane; halogenated hydrocarbons such as chloroform, dichloromethane, and 1,2-dichloroethane; ethers such as diethyl ether, dimethoxyethane, tetrahydrofuran, and dioxane; amides such as N,N-dimethylformamide and N,N-dimethylacetamide; nitriles such as acetonitrile, propionitrile, and benzonitrile can be mentioned, and esters, alcohols, aromatic hydrocarbons, and ketones are preferred. The solvent can be used alone or in combination of two or more.

[0084] The concentration of the ultraviolet absorber in the solution can be appropriately set according to the desired ultraviolet absorption function to be imparted to the pressure-sensitive adhesive layer 10a. For example, the upper limit is 50% by weight or less (e.g., 1 to 50% by weight, 1 to 45% by weight, 1 to 40% by weight, 1 to 35% by weight, 1 to 30% by weight, 1 to 25% by weight, 1 to 20% by weight, 1 to 15% by weight, etc.) or the lower limit is 1% by weight or more (e.g., 1 to 50% by weight, 2 to 50% by weight, 3 to 50% by weight, 4 to 50% by weight, 5 to 50% by weight) and can be selected from this range. If the concentration of the ultraviolet absorber in the solution is within this range, while dissolving the ultraviolet absorber, the pressure-sensitive adhesive layer 10a can be sufficiently swollen, and an appropriate ultraviolet absorption function can be imparted to the pressure-sensitive adhesive layer 10a.

[0085] When the dye compound is contained in the solution of the ultraviolet absorber, or when the solution of the dye compound is separately applied, the concentration of the dye compound can be appropriately set. For example, it can be selected from the range of 1 to 50% by weight, preferably 2 to 40% by weight, more preferably 3 to 30% by weight, and still more preferably 5 to 20% by weight. If the concentration of the dye compound in the solution is within this range, while dissolving the dye compound, an absorption function in a wavelength region longer than that of appropriate ultraviolet rays can be imparted to the pressure-sensitive adhesive layer 10a.

[0086] For the application (coating) of the solution 12 to the pressure-sensitive adhesive layer 10a, known coating methods can be used. For example, coaters such as a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, a spray coater, a comma coater, and a direct coater can be mentioned.

[0087] The coating amount of the solution of the ultraviolet absorber and / or the dye compound on the pressure-sensitive adhesive layer 10a can be appropriately set according to the desired ultraviolet absorption function to be imparted to the pressure-sensitive adhesive layer 10a. For example, 1 to 1000 μg / cm 2 , preferably 1 to 500 μg / cm 2 , more preferably 1 to 100 μg / cm 2 , still more preferably 1 to 50 μg / cm 2It can be selected from the range. If the coating amount of the ultraviolet absorber and / or the solution of the dye compound is within this range, while dissolving the ultraviolet absorber and / or the dye compound, a sufficient ultraviolet absorption function and / or absorption function in a longer wavelength region can be imparted to the pressure-sensitive adhesive layer 10a.

[0088] After applying the solution of the ultraviolet absorber and / or the dye compound to the pressure-sensitive adhesive layer 10a, if necessary, it may be left standing to allow the ultraviolet absorber and / or the dye compound to penetrate. There is no particular limitation on the standing time, and for example, it can be appropriately selected from within 15 minutes, and for example, it can be selected from the range of 1 second to 10 minutes, preferably 5 seconds to 5 minutes. The standing temperature can be carried out at room temperature (about 10 to 30 °C). When standing under the above conditions, the ultraviolet absorber and / or the dye compound can penetrate sufficiently into the pressure-sensitive adhesive layer 10a.

[0089] The heating and drying temperature in the drying step is preferably 40 to 200 °C, more preferably 50 to 180 °C, and even more preferably 70 to 170 °C. The drying time can be appropriately selected as an appropriate time, but for example, it is 5 seconds to 20 minutes, preferably 5 seconds to 10 minutes, and more preferably 10 seconds to 5 minutes. By drying under the above conditions, the pressure-sensitive adhesive layer 10a can be returned to a state close to that before coating.

[0090] FIG. 2(a) is a cross-sectional view showing an embodiment of the pressure-sensitive adhesive sheet of the second aspect of the present invention, and FIG. 2(b) is a cross-sectional view showing another embodiment of the pressure-sensitive adhesive sheet of the second aspect of the present invention.

[0091] Referring to FIG. 2(a), a pressure-sensitive adhesive sheet 2A according to an embodiment of the present invention includes an optically transparent pressure-sensitive adhesive layer 21, and a support is not bonded to one first main surface 21a of the pressure-sensitive adhesive layer 21, and a support S1 composed of a release sheet bonded to the other second main surface 21b of the pressure-sensitive adhesive layer 21.

[0092] Referring to Fig. 2(b), an adhesive sheet 2B according to an embodiment of the present invention comprises an optically transparent adhesive layer 21, a first support S2 made of a release sheet bonded to one first main surface 21a of the adhesive layer 21, and a second support S1 made of a release sheet bonded to the other second main surface 21b of the adhesive layer 21. The adhesive sheet 2B can be obtained by bonding the support S2 to the first main surface 21a of the adhesive sheet 2A.

[0093] In Figs. 2(a) and (b), the dotted line X-X' is a line that bisects the adhesive layer 21 into two equal parts in the thickness direction. When the thickness of the adhesive layer 21 is not uniform, the dotted line X-X' is a line that bisects the thickness at each point.

[0094] In Fig. 2, the adhesive layer 21 is a single layer made of a transparent photocurable adhesive base material and having two opposing main surfaces (a first main surface and a second main surface). The adhesive layer 21 can be formed by the above-described adhesive layer forming step and adhesive layer curing step, and corresponds to the adhesive layer 10a in Fig. 1. Therefore, the adhesive layer 21 is preferably an adhesive layer cured by ultraviolet irradiation.

[0095] The fact that the adhesive layer is a "single layer" means that it does not have a laminated structure. For example, an adhesive layer formed of a transparent photocurable adhesive base material and then another adhesive layer formed of the same transparent photocurable adhesive base material on top of it has a laminated structure and is not a single layer. Similarly, an adhesive layer formed of a transparent photocurable adhesive base material in which an ultraviolet absorber is dissolved and then another adhesive layer formed of a transparent photocurable adhesive base material in which the ultraviolet absorber is dissolved at a different concentration on top of it has a laminated structure and is not a single layer.

[0096] The thickness of the adhesive layer 21 is not particularly limited, but is usually 5 μm to 500 μm, preferably 5 μm to 400 μm, and more preferably 50 μm to 400 μm. If the thickness of the adhesive layer 21 is within this range, it is suitable for forming a concentration gradient of the ultraviolet absorber in the thickness direction of the adhesive layer 21.

[0097] Although the total light transmittance of the entire pressure-sensitive adhesive layer 21 is not particularly limited, it is preferably 80% or more, preferably 90% or more, as measured in accordance with JIS K7361. The higher the total light transmittance of the pressure-sensitive adhesive layer 21, the more preferable it is. Furthermore, the haze value is preferably 1.5% or less, more preferably 1% or less.

[0098] The ultraviolet absorber 11 is dissolved in the pressure-sensitive adhesive layer 21. By allowing the ultraviolet absorber to penetrate into the pressure-sensitive adhesive layer in the solution penetration step, the ultraviolet absorber can be dissolved in the pressure-sensitive adhesive layer. Here, "dissolved" means, for example, that the ultraviolet absorber is dissolved to such an extent that the transparency of the pressure-sensitive adhesive layer can be maintained, that is, to such an extent that cloudiness due to light scattering of the ultraviolet absorber does not occur. Specifically, it is preferable that the ultraviolet absorber is contained in the pressure-sensitive adhesive layer such that the haze value of the pressure-sensitive adhesive layer is 1.5% or less, preferably 1% or less. When the dye compound is contained in the pressure-sensitive adhesive layer 21, the dye compound is also dissolved in the pressure-sensitive adhesive layer.

[0099] The ultraviolet absorber 11 is formed by the ultraviolet absorber 11 penetrating into the pressure-sensitive adhesive layer 21 through the solution coating step, the solution penetration step, and the drying step, and a concentration gradient of the ultraviolet absorber 11 can occur in the thickness direction of the pressure-sensitive adhesive layer 21 as shown in FIG. 2. Therefore, when the single-layer pressure-sensitive adhesive layer 21 is equally divided into two in the thickness direction, the concentration of the ultraviolet absorber in the region to which one of the two main surfaces, the first main surface 21a, belongs is different from the concentration of the ultraviolet absorber in the region to which the other second main surface 21b belongs. Even when there is no ultraviolet absorber in the region where the concentration of the ultraviolet absorber is low (the concentration of the ultraviolet absorber is 0), it is included in the scope of the present invention. Similarly, when the dye compound is dissolved in the pressure-sensitive adhesive layer 21, a concentration difference or a concentration gradient between the front and back of the pressure-sensitive adhesive layer can occur.

[0100] When there is a concentration gradient within each region, the concentration of the ultraviolet absorber and / or the dye compound in the region belonging to the first major surface and the concentration of the ultraviolet absorber and / or the dye compound in the region belonging to the second major surface shall each mean the average concentration of the ultraviolet absorber and / or the dye compound within each region.

[0101] FIG. 2(a) shows an embodiment in which the second major surface 21b faces the support S1 and the concentration of the ultraviolet absorber in the region belonging to the first major surface 21a is higher than the concentration of the ultraviolet absorber in the region belonging to the second major surface 21b. This can be obtained by applying a solution of the ultraviolet absorber to the first major surface 21a and allowing the ultraviolet absorber to penetrate and dissolve in the adhesive layer 21 over the depth in the thickness direction from the first major surface 21a.

[0102] The adhesive sheet of the second side of the present invention can minimize physical property changes such as differences in physical properties such as the adhesiveness and viscoelasticity of the front and back surfaces. For example, the difference between the adhesive force (N / 10 mm) of the first major surface and the adhesive force (N / 10 mm) of the second major surface is, for example, 1.0 N / 10 mm or less, preferably 0.5 N / 10 mm or less, more preferably 0.3 N / 10 mm or less.

[0103] The adhesive sheet of the second side of the present invention can be used to bond a transparent optical member to another optical member in an image display device such as a liquid crystal image display device or an organic EL image display device. Examples of the optical member include a polarizing film, a retardation film, a transparent cover member such as a cover glass, and various other transparent optical members. Also, a glass substrate on which a transparent conductive layer such as a patterned ITO film is formed can be included in the optical member of the present invention. Further, the adhesive sheet of the second side of the present invention can also be suitably used as a surface protection film for preventing the adhesion of scratches and dirt to the optical member.

[0104] FIG. 3 is a cross-sectional view of an optical member laminate showing an example of the simplest embodiment using the adhesive sheet according to the present invention. Referring to FIG. 3, the optical member laminate 3 is composed of an optically transparent first optical member 31 and a second optical member 32 joined to the first optical member 31 via an optically transparent adhesive layer 21. The optical member laminate 3 is formed by peeling the supports S1 and S2 from the adhesive sheet 2B shown in FIG. 2(b) and bonding them to the first and second optical members. The transparent first optical member 31 and the second optical member 32 can be composed of a polarizing film, a retardation film, an optical film used in other optical display devices, or a transparent cover member such as a visual recognition side cover glass of an optical display device. The first optical member 31 is joined to the first main surface 21a of the adhesive layer 21, and the second optical member 32 is joined to the second main surface 21b of the adhesive layer 21, respectively.

[0105] FIG. 4 is a cross-sectional view showing an embodiment in which the adhesive layer 21 is applied to a configuration in which a transparent conductive layer 42, such as a patterned ITO film, is formed on the adhesive layer side surface of the optical member 41 to form a touch panel sensor. Examples of the optical member 41 in this case include, for example, a glass substrate of a display panel in a liquid crystal display device or an organic EL display device.

[0106] As shown in FIG. 4, the main surface 21b of the adhesive layer 21 is joined to both the adhesive layer side surface of the second optical member 41 and the transparent conductive layer 42 so as to fill the step between the optical member 41 and the transparent conductive layer 42. This configuration can be obtained by peeling the support S2 of the adhesive sheet 2B shown in FIG. 2(b) and then bonding the optical member 41 having the transparent conductive layer 42 formed on the main surface 21b, and peeling the support S1 as necessary.

Example

[0107] Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

[0108] (Production of Adhesive Sheet A) A monomer mixture composed of 66 parts by weight of 2-ethylhexyl acrylate (2EHA), 19 parts by weight of 2-hydroxyethyl acrylate (HEA), and 15 parts by weight of N-vinyl-2-pyrrolidone (NVP) was blended with 0.035 parts by weight of a photoinitiator (trade name "Irgacure 184", manufactured by BASF) and 0.035 parts by weight of a photoinitiator (trade name "Irgacure 651", manufactured by BASF). Then, ultraviolet rays were irradiated until the viscosity (measurement conditions: BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30 °C) reached about 20 Pa·s to obtain a prepolymer composition in which a part of the above monomer components was polymerized.

[0109] Next, 0.15 parts by weight of hexanediol diacrylate (HDDA) was added to the prepolymer composition and mixed to obtain an acrylic pressure-sensitive adhesive composition. The above acrylic pressure-sensitive adhesive composition was applied onto the peeled surface of a release film (trade name "MRF#38", manufactured by Mitsubishi Rayon Co., Ltd.) so that the thickness after forming the pressure-sensitive adhesive layer was 100 μm to form a pressure-sensitive adhesive composition layer. Then, a release film (trade name "MRN#38", manufactured by Mitsubishi Rayon Co., Ltd.) was laminated onto the surface of the pressure-sensitive adhesive composition layer. Thereafter, ultraviolet irradiation was performed under the conditions of illuminance: 5 mW / cm 2 and light quantity: 1500 mJ / cm 2 to photocure the pressure-sensitive adhesive composition layer and form a pressure-sensitive adhesive sheet A.

[0110] (Preparation of pressure-sensitive adhesive sheet B) A pressure-sensitive adhesive sheet B was formed in the same manner as the pressure-sensitive adhesive sheet A, except that the addition amount of hexanediol diacrylate (HDDA) was 0.1 part by weight.

[0111] (Preparation of pressure-sensitive adhesive sheet C) As a monomer mixture, 96 parts by weight of butyl acrylate (BA) and 4 parts by weight of acrylic acid (AA) were used. A pressure-sensitive adhesive sheet C was formed in the same manner as the pressure-sensitive adhesive sheet A, except that 0.1 part by weight of 2-hydroxyethyl acrylate (HEA) was used instead of hexanediol diacrylate (HDDA) and the thickness after forming the pressure-sensitive adhesive layer was 23 μm.

[0112] (Production of Adhesive Sheet D) As the monomer mixture, 57 parts by weight of butyl acrylate (BA), 23 parts by weight of 4-hydroxybutyl acrylate (4HBA), 8 parts by weight of 2-hydroxyethyl acrylate (HEA), and 12 parts by weight of cyclohexyl acrylate (CHA) were used. Instead of hexanediol diacrylate (HDDA), 0.02 parts by weight of dipentaerythritol hexaacrylate (DPHA) was used. An adhesive sheet D was formed in the same manner as adhesive sheet A, except that the thickness after forming the adhesive layer was 150 μm.

[0113] (Production of Adhesive Sheet E) An adhesive sheet E was formed in the same manner as adhesive sheet A, except that as the monomer mixture, 29 parts by weight of 2-ethylhexyl acrylate (2EHA), 21 parts by weight of 4-hydroxybutyl acrylate (4HBA), 29 parts by weight of isostearyl acrylate (ISTA), and 21 parts by weight of isobornyl acrylate (IBXA) were used.

[0114] (Production of Adhesive Sheet F) As the monomer mixture, 41 parts by weight of 2-ethylhexyl acrylate (2EHA), 1 part by weight of 4-hydroxybutyl acrylate (4HBA), 17 parts by weight of N-vinyl-2-pyrrolidone (NVP), and 41 parts by weight of isostearyl acrylate (ISTA) were used. Instead of hexanediol diacrylate (HDDA), 0.02 parts by weight of trimethylolpropane triacrylate (TMPTA) was used. An adhesive sheet F was formed in the same manner as adhesive sheet A.

[0115] (Example 1) The release film on one main surface (referred to as the "first surface") of the adhesive sheet A was peeled off, and an ethyl acetate solution with a concentration of 10% by weight of an ultraviolet absorber (Tinosorb S, manufactured by BASF) was applied to the exposed first surface using a Wire Wound Rod type No. 7 bar coater manufactured by RD Specialties. After application, the adhesive sheet A was heated and dried in an oven at 110 °C for 2 minutes to volatilize and remove the solvent, thereby obtaining an adhesive sheet A containing an adhesive layer in which the ultraviolet absorber was dissolved.

[0116] (Example 2) An adhesive sheet A containing an adhesive layer in which the ultraviolet absorber and the dye compound were dissolved was obtained in the same manner as in Example 1, except that a solution in which 10% by weight each of Tinosorb S (manufactured by BASF) as the ultraviolet absorber and FDB-009 (manufactured by Yamada Chemical Industry Co., Ltd., maximum absorption wavelength of the absorption spectrum: 394 nm) as the dye compound were dissolved in ethyl acetate was applied.

[0117] (Comparative Example 1) The release film on the first surface of the adhesive sheet A was peeled off, and the adhesive sheet A without applying the solution of the ultraviolet absorber was used as Comparative Example 1.

[0118] (Example 3) An adhesive sheet B containing an adhesive layer in which the ultraviolet absorber was dissolved was obtained in the same manner as in Example 1, except that an ethyl acetate solution with a concentration of 12% by weight of an ultraviolet absorber (Tinuvin 928, manufactured by BASF) was applied using the adhesive sheet B.

[0119] (Example 4) An adhesive layer B in which the ultraviolet absorber was dissolved was obtained in the same manner as in Example 1, except that a methyl ethyl ketone solution with a concentration of 12% by weight of an ultraviolet absorber (Tinuvin 928, manufactured by BASF) was applied using the adhesive sheet B.

[0120] (Example 5) An adhesive sheet B was obtained in the same manner as in Example 1, except that an ethyl acetate solution having a concentration of 15% by weight of an ultraviolet absorber (Seesorb 106, manufactured by Cypro Kasei Co., Ltd.) was applied using the adhesive sheet B. The obtained adhesive sheet B contained an adhesive layer in which the ultraviolet absorber was dissolved.

[0121] (Comparative Example 2) The release film on the first surface of the adhesive sheet B was peeled off, and the adhesive sheet B without applying the solution of the ultraviolet absorber was used as Comparative Example 2.

[0122] (Example 6) An adhesive sheet C was obtained in the same manner as in Example 1, except that an adhesive sheet C was used. The obtained adhesive sheet C contained an adhesive layer in which an ultraviolet absorber (Tinosorb S, manufactured by BASF) was dissolved.

[0123] (Example 7) An adhesive sheet C was obtained in the same manner as in Example 1, except that an ethyl acetate solution having a concentration of 12% by weight of an ultraviolet absorber (Tinuvin 928, manufactured by BASF) was applied using the adhesive sheet C. The obtained adhesive sheet C contained an adhesive layer in which the ultraviolet absorber was dissolved.

[0124] (Example 8) An adhesive sheet C was obtained in the same manner as in Example 1, except that a methyl ethyl ketone solution having a concentration of 12% by weight of an ultraviolet absorber (Tinuvin 928, manufactured by BASF) was applied using the adhesive sheet C. The obtained adhesive sheet C contained an adhesive layer in which the ultraviolet absorber was dissolved.

[0125] (Example 9) An adhesive sheet C was obtained in the same manner as in Example 1, except that an ethyl acetate solution having a concentration of 15% by weight of an ultraviolet absorber (Seesorb 106, manufactured by Cypro Kasei Co., Ltd.) was applied using the adhesive sheet C. The obtained adhesive sheet C contained an adhesive layer in which the ultraviolet absorber was dissolved.

[0126] (Comparative Example 3) The release film on the first surface of the adhesive sheet C was peeled off, and the adhesive sheet C without applying the solution of the ultraviolet absorber was used as Comparative Example 3.

[0127] (Comparative Example 4) An adhesive sheet C was used, and an adhesive sheet C not containing an ultraviolet absorber was obtained in the same manner as in Example 1, except that ethyl acetate not containing an ultraviolet absorber was applied.

[0128] (Example 10) An adhesive sheet D containing an adhesive layer in which an ultraviolet absorber (Tinosorb S, manufactured by BASF) was dissolved was obtained in the same manner as in Example 1, except that the adhesive sheet D was used.

[0129] (Comparative Example 5) The release film on the first surface of the adhesive sheet D was peeled off, and the adhesive sheet D without applying a solution of the ultraviolet absorber was used as Comparative Example 5.

[0130] (Example 11) An adhesive sheet E containing an adhesive layer in which an ultraviolet absorber (Tinosorb S, manufactured by BASF) was dissolved was obtained in the same manner as in Example 1, except that the adhesive sheet E was used.

[0131] (Comparative Example 6) The release film on the first surface of the adhesive sheet F was peeled off, and the adhesive sheet E without applying a solution of the ultraviolet absorber was used as Comparative Example 6.

[0132] (Example 12) An adhesive sheet F containing an adhesive layer in which an ultraviolet absorber (Tinosorb S, manufactured by BASF) was dissolved was obtained in the same manner as in Example 1, except that the adhesive sheet F was used.

[0133] (Comparative Example 7) The release film on the first surface of the adhesive sheet F was peeled off, and the adhesive sheet F without applying a solution of the ultraviolet absorber was used as Comparative Example 7.

[0134] (Comparative Example 8) An adhesive sheet F not containing an ultraviolet absorber was obtained in the same manner as in Example 1, except that the adhesive sheet F was used and ethyl acetate not containing an ultraviolet absorber was applied.

[0135] (Comparative Example 9) As a monomer mixture, 70 parts by weight of butyl acrylate (BA), 14 parts by weight of 4-hydroxybutyl acrylate (4HBA), and 16 parts by weight of N-vinyl-2-pyrrolidone (NVP) were used. Further, an adhesive sheet having an adhesive layer in which an ultraviolet absorber (Tinosorb S, manufactured by BASF) was uniformly dissolved was obtained in the same manner as in Adhesive Sheet D, except that 0.0009 parts by weight of the ultraviolet absorber was blended in the acrylic adhesive composition.

[0136] The following evaluations were performed using the adhesive sheets obtained in Examples 1 to 12 and Comparative Examples 1 to 8 above. <Transmittance Evaluation> The release films of the adhesive sheets obtained in the examples and comparative examples were peeled off, and the transmittance by wavelength of light (wavelength range: 300 to 800 nm) was evaluated using a spectrophotometer (U4100, manufactured by Hitachi High-Tech Science Corporation). The transmittance (%) at 380 nm and 420 nm is shown in Table 1.

[0137] <Adhesion Evaluation> The release films of the adhesive sheets obtained in the examples and comparative examples were peeled off. The surface coated with the ultraviolet absorber solution was defined as the first surface, and the opposite main surface was defined as the second surface. The obtained adhesive sheet was cut into a width of 100 mm and a length of 100 mm, and the first surface or the second surface was bonded to alkali glass, and a PET film (thickness: 25 μm) was bonded to the opposite surface. Then, it was bonded with a hand roller and heated and pressurized (5 atm, 50 °C) in an autoclave for 15 minutes. The adhesion (N / 10 mm) of the sample thus obtained was measured using an autograph (tensile speed: 60 mm / min, peel angle: 180°). For each condition, three samples were prepared and their number average value was taken. The adhesion (N / 10 mm) to alkali glass of the first surface and the second surface and the difference therebetween are shown in Table 1.

[0138]

Table 1

[0139] As shown in Table 1, it was revealed that by applying a solution of an ultraviolet absorber to the adhesive layer of an adhesive sheet cured by ultraviolet rays, an excellent ultraviolet absorption function can be imparted to the adhesive layer. It was also revealed that by using different types of ultraviolet absorbers or by using them in combination with dye compounds, the wavelength absorption in the ultraviolet region can be selectively controlled. Further, the difference in adhesive force between the first surface and the second surface of the adhesive layer was 1.0 N / mm, and it was found that by applying a solution of an ultraviolet absorber to the adhesive layer of the cured adhesive sheet, the physical property differences such as the adhesive force on the front and back of the adhesive layer can be minimized.

[0140] <Evaluation of the Distribution of Ultraviolet Absorber in the Thickness Direction of the Adhesive> In order to examine the distribution state of the ultraviolet absorber (Tinosorb S) in the thickness direction of Example 10 and Comparative Example 9, TOF-SIMS analysis (Ar gas cluster ion etching method) was performed. Samples stored for 1 month after production were used. The release films of the adhesive sheets obtained in Example 10 and Comparative Example 9 were peeled off, and TOF-SIMS analysis was performed from the first surface side under the following measurement conditions. The results are shown in Fig. 5. Fig. 5(a) shows the results of Example 10, and Fig. 5(b) shows the results of Comparative Example 9. In Fig. 5, the scale of the left vertical axis represents the intensity of butyl acrylate (BA, C3+H3+O2) and N-vinylpyrrolidone (NVP, C4+H6+N+O), and the scale of the right vertical axis represents the intensity of the ultraviolet absorber (Tinosorb S, C 30 +H 32 +N3+O5).

[0141] Analytical instrument: TOF-SIMS (manufactured by ULVAC-PHI, TRIFT V) Etching ion: Ar gas cluster ion Irradiated primary ion: Bi3 2+ Acceleration voltage: 30 kV Measurement polarity: negative ion

[0142] As can be seen from Fig. 5(a), the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of Example 10 has a concentration gradient of an ultraviolet absorber (Tinosorb S) from the first surface to the second surface. On the other hand, as can be seen from Fig. 5(b), the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of Comparative Example 9 has the ultraviolet absorber (Tinosorb S) distributed at a constant concentration from the first surface to the second surface.

[0143] The variations of the present invention are appended below. 〔Appended Note 1〕A pressure-sensitive adhesive layer formed of a transparent photocurable pressure-sensitive adhesive base material is formed on a support, the pressure-sensitive adhesive layer is irradiated with ultraviolet rays to cure the pressure-sensitive adhesive layer, a solution of an ultraviolet absorber is prepared, the solution is applied to one surface of the cured pressure-sensitive adhesive layer, and the ultraviolet absorber contained in the solution is allowed to penetrate in the thickness direction from the one surface of the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer is dried A method for manufacturing a pressure-sensitive adhesive sheet, characterized by including the steps. 〔Appended Note 2〕The solution of the ultraviolet absorber is a solution in which the ultraviolet absorber is dissolved in a solvent, The method for manufacturing a pressure-sensitive adhesive sheet according to Appended Note 1, including the step of evaporating the solvent of the solution by drying the pressure-sensitive adhesive layer. 〔Appended Note 3〕The solution of the ultraviolet absorber further contains a dye compound whose maximum absorption wavelength in the absorption spectrum exists in the wavelength region of 380 to 430 nm. The method for manufacturing a pressure-sensitive adhesive sheet according to Appended Note 1 or 2. 〔Appended Note 4〕Furthermore, a solution of a dye compound whose maximum absorption wavelength in the absorption spectrum exists in the wavelength region of 380 to 430 nm is prepared, and the method for manufacturing a pressure-sensitive adhesive sheet according to Appended Note 1 or 2, including the step of applying the solution to one surface of the cured pressure-sensitive adhesive layer. 〔Appended Note 5〕The solution of the dye compound is a solution in which the dye compound is dissolved in a solvent. The method for manufacturing a pressure-sensitive adhesive sheet according to Appended Note 4. 〔Appended Note 6〕Furthermore, the method for manufacturing a pressure-sensitive adhesive sheet according to any one of Appended Notes 1 to 5, including the step of laminating a release sheet on the surface of the pressure-sensitive adhesive layer opposite to the support. 〔Supplementary Note 7〕The method for manufacturing the pressure-sensitive adhesive sheet according to any one of Supplementary Notes 1 to 6, characterized in that the absorption maximum wavelength of the absorption spectrum of the ultraviolet absorber is present in the wavelength range of 300 to 400 nm. 〔Supplementary Note 8〕A pressure-sensitive adhesive sheet having a support and a transparent pressure-sensitive adhesive layer on the support, wherein the pressure-sensitive adhesive layer is a single layer made of a transparent photocurable pressure-sensitive adhesive base material and having two opposing main surfaces, an ultraviolet absorber is dissolved in the pressure-sensitive adhesive layer, when the single-layer pressure-sensitive adhesive layer is equally divided into two in the thickness direction, a pressure-sensitive adhesive sheet, characterized in that the concentration of the ultraviolet absorber in the region belonging to one of the two main surfaces, i.e., the first main surface, is different from the concentration of the ultraviolet absorber in the region belonging to the other main surface, i.e., the second main surface. 〔Supplementary Note 9〕The pressure-sensitive adhesive sheet according to Supplementary Note 8, wherein a dye compound having a maximum absorption wavelength of the absorption spectrum in the wavelength range of 380 to 430 nm is further dissolved in the pressure-sensitive adhesive layer. 〔Supplementary Note 10〕The pressure-sensitive adhesive sheet according to Supplementary Note 8 or 9, characterized in that the difference between the adhesive force (N / 10 mm) of the first main surface and the adhesive force (N / 10 mm) of the second main surface is 1.0 N / 10 mm or less. 〔Supplementary Note 11〕The pressure-sensitive adhesive sheet according to any one of Supplementary Notes 8 to 11, wherein the pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer cured by ultraviolet irradiation. 〔Supplementary Note 12〕The pressure-sensitive adhesive sheet according to any one of Supplementary Notes 8 to 11, characterized in that the second main surface faces the support, and the concentration of the ultraviolet absorber in the region belonging to the first main surface is higher than the concentration of the ultraviolet absorber in the region belonging to the second main surface. 〔Supplementary Note 13〕The pressure-sensitive adhesive sheet according to any one of Supplementary Notes 8 to 12, characterized in that the single-layer photocurable pressure-sensitive adhesive layer has a concentration gradient of the ultraviolet absorber in the thickness direction. 〔Supplementary Note 14〕The pressure-sensitive adhesive sheet according to any one of Supplementary Notes 8 to 13, characterized in that the support is made of a release sheet. 〔Supplementary Note 15〕The pressure-sensitive adhesive sheet according to Supplementary Note 14, characterized in that the support made of a release sheet is disposed on both sides of the pressure-sensitive adhesive layer. 〔Appended Note 16〕The pressure-sensitive adhesive sheet according to any one of Appended Notes 8 to 15, characterized in that the absorption maximum wavelength of the absorption spectrum of the ultraviolet absorber exists in the wavelength range of 300 to 400 nm. 〔Appended Note 17〕The pressure-sensitive adhesive sheet according to any one of Appended Notes 8 to 16, characterized in that the thickness of the pressure-sensitive adhesive layer is 5 to 500 μm.

Industrial Applicability

[0144] The present invention is useful for a method for manufacturing a pressure-sensitive adhesive sheet having a transparent pressure-sensitive adhesive layer that can be used for bonding a transparent optical member to another optical member, and a pressure-sensitive adhesive sheet obtainable by the manufacturing method.

Explanation of Symbols

[0145] 10 Pressure-sensitive adhesive layer (before curing by ultraviolet rays) 10a Pressure-sensitive adhesive layer (after curing by ultraviolet rays) S1, S2 Support (release sheet) U: Ultraviolet ray 11 Ultraviolet absorber 12 Solution of ultraviolet absorber 13 Solvent 21 Pressure-sensitive adhesive layer (after curing by ultraviolet rays) 21a Main surface (first surface) 21b Main surface (second surface) 31, 32, 41 Optical member 42 Transparent conductive layer

Claims

1. Form an adhesive layer on a support, which is formed of a transparent photocurable adhesive base material, Irradiate the adhesive layer with ultraviolet rays to cure the adhesive layer, Prepare a solution of an ultraviolet absorber, Apply the solution to one surface of the cured adhesive layer, and allow the ultraviolet absorber contained in the solution to penetrate in the thickness direction from the one surface of the adhesive layer, Dry the adhesive layer A method for manufacturing an adhesive sheet, characterized by including the steps.

2. The solution of the ultraviolet absorber is a solution in which the ultraviolet absorber is dissolved in a solvent, The method for manufacturing an adhesive sheet according to claim 1, including the step of evaporating the solvent of the solution by drying the adhesive layer.

3. The method for manufacturing an adhesive sheet according to claim 1 or 2, wherein the solution of the ultraviolet absorber further contains a dye compound whose maximum absorption wavelength in the absorption spectrum exists in the wavelength range of 380 to 430 nm.

4. Furthermore, the method for manufacturing an adhesive sheet according to claim 1 or 2, including the step of preparing a solution of a dye compound whose maximum absorption wavelength in the absorption spectrum exists in the wavelength range of 380 to 430 nm, and applying the solution to one surface of the cured adhesive layer.

5. The method for manufacturing an adhesive sheet according to claim 4, wherein the solution of the dye compound is a solution in which the dye compound is dissolved in a solvent.

6. Furthermore, the method for manufacturing an adhesive sheet according to any one of claims 1 to 5, including the step of laminating a release sheet on the surface of the adhesive layer opposite to the support.

7. The method for manufacturing an adhesive sheet according to any one of claims 1 to 6, characterized in that the absorption maximum wavelength of the absorption spectrum of the ultraviolet absorber exists in the wavelength range of 300 to 400 nm.

8. An adhesive sheet having a support and a transparent adhesive layer on the support, The adhesive layer is a single layer made of a transparent photocurable adhesive base material and having two opposing main surfaces, An ultraviolet absorber is dissolved in the adhesive layer, When the single-layer adhesive layer is equally divided into two in the thickness direction An adhesive sheet, characterized in that the concentration of the ultraviolet absorber in the region belonging to one first main surface of the two main surfaces is different from the concentration of the ultraviolet absorber in the region belonging to the other second main surface.

9. The pressure-sensitive adhesive sheet according to claim 8, wherein a dye compound having a maximum absorption wavelength of the absorption spectrum in a wavelength region of 380 to 430 nm is further dissolved in the pressure-sensitive adhesive layer.

10. The pressure-sensitive adhesive sheet according to claim 8 or 9, wherein a difference between the adhesive force (N / 10 mm) of the first main surface and the adhesive force (N / 10 mm) of the second main surface is 1.0 N / 10 mm or less.

11. The pressure-sensitive adhesive sheet according to any one of claims 8 to 10, wherein the pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer cured by ultraviolet irradiation.

12. The pressure-sensitive adhesive sheet according to any one of claims 8 to 11, wherein the second main surface faces the support, and a concentration of the ultraviolet absorber in a region to which the first main surface belongs is higher than a concentration of the ultraviolet absorber in a region to which the second main surface belongs.

13. The pressure-sensitive adhesive sheet according to any one of claims 8 to 12, wherein the single-layer photocurable pressure-sensitive adhesive layer has a concentration gradient of the ultraviolet absorber in a thickness direction.

14. The pressure-sensitive adhesive sheet according to any one of claims 8 to 13, wherein the support is made of a release sheet.

15. The pressure-sensitive adhesive sheet according to claim 14, wherein the support made of a release sheet is disposed on both surfaces of the pressure-sensitive adhesive layer.

16. The pressure-sensitive adhesive sheet according to any one of claims 8 to 15, wherein a maximum absorption wavelength of an absorption spectrum of the ultraviolet absorber exists in a wavelength region of 300 to 400 nm.

17. The pressure-sensitive adhesive sheet according to any one of claims 8 to 16, wherein a thickness of the pressure-sensitive adhesive layer is 5 to 500 μm.

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