Photocurable adhesive sheet, photocurable adhesive sheet with release film, laminate for constituting image display device, method for producing photocurable adhesive sheet, and method for producing laminate for image display device

Abstract

In one or several examples, this photocurable adhesive sheet is provided with one or more adhesive layers formed from an adhesive composition containing a (meth)acrylic polymer (A), a polyfunctional (meth)acrylate (B), and a cleavage-type photopolymerization initiator (C). At least one of the adhesive layers contains a polymer (B') of the polyfunctional (meth)acrylate (B) and a decomposition product (C') of the cleavage-type photopolymerization initiator (C). The total content of a polyfunctional (meth)acrylate (B1) having a mass average molecular weight of 300 or less in the total amount of the adhesive composition forming the one or more adhesive layers is less than 3 mass% of the total content of the (meth)acrylic polymer (A) in the total amount of the adhesive composition forming the one or more adhesive layers, and the gel fraction is 15% or less.

Description

Photocurable adhesive sheet, photocurable adhesive sheet with release film, laminate for image display device component, method for manufacturing a photocurable adhesive sheet, and method for manufacturing a laminate for an image display device.

[0001] The present invention relates to a photocurable adhesive sheet, a photocurable adhesive sheet with a release film, a laminate for an image display device, a method for manufacturing a photocurable adhesive sheet, and a method for manufacturing a laminate for an image display device. This application claims priority based on Japanese Patent Application No. 2024-158720 filed with the Japan Patent Office on September 13, 2024, and Japanese Patent Application No. 2025-051845 filed with the Japan Patent Office on March 26, 2025, the contents of which are incorporated herein by reference.

[0002] In recent years, to improve the visibility of image display devices, the gaps between image display panels such as liquid crystal displays (LCDs), plasma displays (PDPs), and electroluminescent displays (ELDs) and the protective panels or touch panel components placed on the front side (viewing side) are being filled with adhesive sheets or liquid adhesives. By filling the gaps between panels with adhesive sheets, reflection of incident light and light emitted from the displayed image at the air layer interface can be suppressed.

[0003] For example, Patent Document 1 discloses filling gaps between components of an image display device with an adhesive. Patent Document 1 also discloses filling the gaps with a liquid adhesive resin composition containing an ultraviolet-curable resin, and then curing it by irradiating it with ultraviolet light.

[0004] In some cases, gaps between components of an image display device are filled with an adhesive sheet. For example, Patent Document 2 discloses a method for manufacturing a laminate for an image display device in which components of an image display device are laminated via a transparent double-sided adhesive sheet. Patent Document 2 also discloses a method in which an adhesive sheet that has been primary crosslinked by ultraviolet light is bonded to the components of an image display device, and then the adhesive sheet is irradiated with ultraviolet light through the components of the image display device to perform secondary curing.

[0005] International Publication No. 2010 / 027041, Patent No. 4971529

[0006] In recent years, there has been a trend in the design of image display devices such as mobile phones to place the display across almost the entire image display surface. Along with this trend, cameras are now being positioned inside the display area of ​​the image display surface. The main methods for positioning a camera within the display area are to pass the camera lens through a hole in the image display panel to directly beneath the surface protection panel, and to position the camera in the layer beneath the image display panel. Of these, the latter method requires positioning the camera through the image display panel. Therefore, to ensure light transmission to the camera lens, holes are created in functional layers such as polarizing films and reflective films laminated on the surface of the image display panel, according to the camera's position and size.

[0007] Furthermore, adhesive sheets used to bond components of image display devices with such holes require the property (fluidity) that allows the adhesive to flow into the holes and fill every corner. Thus, while fluidity is required for adhesive sheets, this also means that the adhesive's resistance to oozing out is reduced, which is a challenge. In other words, the technical challenge is to achieve both fluidity and resistance to adhesive oozing, which are conflicting physical properties. Resistance to adhesive oozing can be explained as follows: When adhesive sheets are stored or transported in roll form, the adhesive may ooze out from the ends of the roll. The ability to suppress this oozing of the adhesive is referred to as "resistance to adhesive oozing."

[0008] Patent Document 2 uses an adhesive sheet that has been primary crosslinked by ultraviolet light. Since this adhesive sheet is primary crosslinked, it is assumed that the adhesive has resistance to oozing out, but 1000 mJ / cm ２ Because the material is crosslinked by high-intensity ultraviolet irradiation, there is room for improvement in its fluidity and ability to conform to pores.

[0009] In recent years, when laminating image display device components equipped with holes for positioning cameras within the display using adhesive sheets, there has been a demand to improve productivity by shortening the cycle time and lowering the hole-filling temperature. Therefore, the adhesive sheets require even greater fluidity than conventional products. Thus, while there is a need for adhesive sheets that excel in both fluidity (conformability) and resistance to adhesive leakage, satisfactory products have yet to be achieved because these are conflicting physical properties.

[0010] Furthermore, while it is important that the adhesive sheet used to bond the components of the image display device, which have the aforementioned holes, has fluidity, there has been insufficient evaluation from the perspective of practical properties regarding what degree of fluidity is sufficient. Since the adhesive is a viscoelastic material, it does not flow into the holes without interfering with the surrounding materials like a Newtonian fluid, but in reality flows into the holes while deforming the surrounding materials. As a result, slight deformation occurs in the materials (glass) above and below the holes, and this deformation may adversely affect the image captured by a camera placed behind the image display panel. On the other hand, increasing the fluidity of the adhesive to the point where it can flow into the holes without deforming the surrounding materials would require raising the bonding temperature too much. Therefore, this could adversely affect the surrounding materials or cause the adhesive to flow too much and leak out.

[0011] The present invention provides a photocurable adhesive sheet that can achieve both excellent fluidity and resistance to adhesive leakage, and which has the property of curing by active energy rays, an adhesive sheet with a release film using the same, a laminate for an image display device, and a method for manufacturing the same.

[0012] The present invention also provides a photocurable adhesive sheet that does not adversely affect captured images, is free from image distortion, and has the property of curing by active energy rays, an adhesive sheet with a release film using the same, a laminate for an image display device, and a method for manufacturing the same.

[0013] In view of these circumstances, the inventors have conducted extensive research and have found that, in a photocurable adhesive sheet comprising one or more adhesive layers formed from an adhesive composition containing a (meth)acrylic polymer (A), a polyfunctional (meth)acrylate (B), and a cleavage-type photopolymerization initiator (C), wherein at least one of the adhesive layers contains a polymer (B') of the polyfunctional (meth)acrylate (B) and a decomposition product (C') of the cleavage-type photopolymerization initiator (C), a photocurable adhesive sheet that satisfies both fluidity and adhesive extrusion resistance can be obtained by keeping the gel fraction of the photocurable adhesive sheet to 15% or less, and thus arrived at the present invention.

[0014] In addition, the inventors have discovered that a photocurable adhesive sheet satisfying the following formula (1) eliminates distortion in the captured image without adversely affecting the image, and thus conceived the present invention. P / (Y×Z / X ３ ) ≤ 0.0025 ... (1) In equation (1), X is the thickness (μm) of the photocurable adhesive sheet. Y is the depth (μm) of the hole in the glass plate (G) having a bottomed hole, and the depth (μm) of the hole is approximately 3 / 4 of the thickness (X) of the photocurable adhesive sheet. Z is the bottom area (μm) when the radius of the bottom surface of the bottomed hole is 2 mm. ２ ) is the PV value. The PV value is the Peak to Valley value (unit: wavelength: wave) measured from the displacement of interference fringes generated between a reference plane and the hole using a laser interferometer system under the conditions that a photocurable adhesive sheet, which has been bonded to a 0.2 mm thick glass plate (Gc) with a 4 mm diameter hole, and a 0.55 mm thick glass plate (Gh) is bonded together and the photocurable adhesive sheet follows the hole, and interference fringes are generated between the reference plane and the hole with the help of the laser interferometer system.

[0015] Preferred embodiments of the present invention include, but are not limited to, the following: [1] A photocurable adhesive sheet comprising one or more adhesive layers formed from an adhesive composition containing a (meth)acrylic polymer (A), a polyfunctional (meth)acrylate (B), and a cleavage-type photopolymerization initiator (C), wherein at least one of the adhesive layers contains a polymer (B') of the polyfunctional (meth)acrylate (B) and a decomposition product (C') of the cleavage-type photopolymerization initiator (C), the total content of polyfunctional (meth)acrylate (B1) having a mass average molecular weight of 300 or less in the total amount of the adhesive composition forming the one or more adhesive layers is less than 3% by mass of the total content of the (meth)acrylic polymer (A) in the total amount of the adhesive composition forming the one or more adhesive layers, and the gel fraction is 15% or less. [2] The photocurable adhesive sheet according to [1], wherein at least one of the adhesive layers contains a hydrogen abstraction-type photopolymerization initiator (D). [3] The photocurable adhesive sheet according to [2], wherein the total content of the hydrogen abstraction type photopolymerization initiator (D) in the one or more adhesive layers is 0.1 to 5% by mass of the total content of the (meth)acrylic polymer (A) in the one or more adhesive layers. [4] The photocurable adhesive sheet according to any one of [1] to [3], wherein the polymer (B') of the polyfunctional (meth)acrylate (B) is formed by a cleavage type photopolymerization initiator (C). [5] The photocurable adhesive sheet according to [4], wherein the total content of the cleavage type photopolymerization initiator (C) in the one or more adhesive layers is 1% by mass or less of the total content of the (meth)acrylic polymer (A) in the one or more adhesive layers. [6] The photocurable adhesive sheet according to any one of [1] to [5], wherein the thickness is 0.8 to 1.5 mm, and the shear creep strain after applying a pressure of 1000 Pa and a torque of 100 μN・m for 170 seconds at a temperature of 65°C is 320% or more. [7] A photocurable adhesive sheet according to any one of [1] to [6], having a thickness of 0.8 to 1.5 mm, and having a shear creep strain of 200% or less after applying a pressure of 1000 Pa and a torque of 100 μN·m at a temperature of 40°C for 170 seconds.[8] The photocurable adhesive sheet according to any one of [1] to [7], wherein the total content of the polymer (B') of the polyfunctional (meth)acrylate (B) in the one or more adhesive layers is 0.1 to 5% by mass of the total content of the (meth)acrylic polymer (A) in the one or more adhesive layers. [9] The photocurable adhesive sheet according to any one of [1] to [8], comprising a plurality of the adhesive layers.

[10] The cumulative light intensity is 50 to 500 mJ / cm. ２ A photocurable adhesive sheet according to any one of [1] to [9], which has been partially cured by irradiation with active energy rays within the range of [1] to [9].

[11] A method for manufacturing a photocurable adhesive sheet comprising one or more adhesive layers, wherein the cumulative light amount is 50 to 500 mJ / cm ２A method for producing an adhesive sheet, comprising irradiating it with active energy rays within a certain range to pre-cure an adhesive composition layer containing a (meth)acrylic polymer (A), a polyfunctional (meth)acrylate (B), and a cleavage-type photopolymerization initiator (C) to reduce the gel fraction of the photocurable adhesive sheet to 15% or less.

[12] The method for producing an adhesive sheet according to

[11] , wherein the adhesive composition layer further contains a hydrogen abstraction-type photopolymerization initiator (D).

[13] The method for producing an adhesive sheet according to

[11] or

[12] , wherein the total content of polyfunctional (meth)acrylate (B1) having a mass average molecular weight of 300 or less in the total amount of the adhesive composition forming the one or more adhesive layers is less than 3% by mass of the total content of (meth)acrylic polymer (A) in the total amount of the adhesive composition forming the one or more adhesive layers.

[14] The manufacturing method according to any one of

[11] to

[13] , wherein the total content of the polymer (B') of the polyfunctional (meth)acrylate (B) in the one or more adhesive layers is 0.1 to 5% by mass of the total content of the (meth)acrylic polymer (A) in the one or more adhesive layers.

[15] The manufacturing method according to

[12] , wherein the total content of the hydrogen abstraction type photopolymerization initiator (D) in the one or more adhesive layers is 0.1 to 5% by mass of the total content of the (meth)acrylic polymer (A) in the one or more adhesive layers.

[16] The manufacturing method according to

[12] , wherein the content ratio (mass ratio) of the hydrogen abstraction type photopolymerization initiator (D) to the cleavage type photopolymerization initiator (C) in the adhesive composition forming the one or more adhesive layers is 2 / 8 to 8 / 2.

[17] An adhesive sheet obtained by curing a photocurable adhesive sheet according to any one of [1] to

[10] . A photocurable adhesive sheet with a release film, comprising: a photocurable adhesive sheet according to any one of [1] to

[10] , and a release film, wherein the photocurable adhesive sheet and the release film are laminated together. A laminate for an image display device, comprising: a photocurable adhesive sheet according to any one of [1] to

[10] , and at least two or more image display device components laminated via the photocurable adhesive sheet, wherein the photocurable adhesive sheet is laminated between at least two image display device components.

[20] The laminated body for an image display device component according to

[19] , wherein the image display device component member is at least one or more selected from the group consisting of a touch panel, an image display panel, a surface protection panel, a polarizing film, and a retardation film.

[21] A method for manufacturing a laminated body for an image display device, wherein the laminated body for an image display device is an adhesive sheet which is a cured product of the photocurable adhesive sheet according to any one of [1] to

[10] , and at least two or more image display device component members laminated via the adhesive sheet, and the manufacturing method includes forming a laminate by bonding the photocurable adhesive sheet to one side of a first image display device component member, bringing the bonding surface of a second image display device component member having a bottomed hole into face-to-face contact with the photocurable adhesive sheet of the laminate, and closely adhering the bonding surface of the second image display device component member and the photocurable adhesive sheet under reduced pressure to form a laminate, performing a heat and pressure treatment on the laminate to hot melt the photocurable adhesive sheet so that the adhesive sheet follows into the bottomed hole of the second image display device component member, and irradiating the photocurable adhesive sheet between the first image display device component member and the second image display device component member with active energy rays to cure the adhesive sheet.

[22] The ratio of the depth (mm) to the bottom area (mm ２ ) of the bottomed hole of the second image display device component member is 1.0×10 －５ to 3.0×10 －１ (mm －１ ), and the manufacturing method according to

[21] .

[23] The manufacturing method according to

[21] or

[22] , wherein either one or both of the first image display device component member and the second image display device component member are at least one or more selected from the group consisting of a touch panel, an image display panel, a surface protection panel, a polarizing film, and a retardation film.

[0016]

[24] A photocurable adhesive sheet including one or more adhesive layers formed from an adhesive composition containing a (meth)acrylic polymer (A) and satisfying the following formula (1). P / (Y × Z / X ３) ≤ 0.0025 ... (1) In equation (1), X is the thickness (μm) of the photocurable adhesive sheet. Y is the depth (μm) of the hole in the glass plate (G) having a bottomed hole, and the depth (μm) of the hole is approximately 3 / 4 of the thickness (X) of the photocurable adhesive sheet. Z is the bottom area (μm) when the radius of the bottom surface of the bottomed hole is 2 mm. ２ ) P is the PV value. The PV value is the Peak to Valley value (unit is wavelength: wave) measured from the displacement of interference fringes generated between a reference plane and the hole using a laser interferometer system under conditions where a photocurable adhesive sheet, which has been bonded to a 0.2 mm thick glass plate (Gc) having a 4 mm diameter hole, and a 0.55 mm thick glass plate (Gh) is bonded together and the photocurable adhesive sheet follows the hole, and interference fringes are generated between the reference plane and the hole with respect to the hole.

[25] The photocurable adhesive sheet according to

[24] , having a thickness of 0.8 to 1.5 mm, and having a shear creep strain of 320% or more after applying a pressure of 1000 Pa and a torque of 100 μN·m for 170 seconds at a temperature of 65°C.

[26] A photocurable adhesive sheet according to

[24] or

[25] , having a thickness of 0.8 to 1.5 mm, and having a shear creep strain of 200% or less after applying a pressure of 1000 Pa and a torque of 100 μN·m at a temperature of 40°C for 170 seconds.

[27] A photocurable adhesive sheet according to any one of

[24] to

[26] , comprising a plurality of adhesive layers.

[28] An integrated light amount of 50 to 500 mJ / cm ２ A photocurable adhesive sheet according to any one of

[24] to

[27] , which has been partially cured by irradiation with active energy rays within the range.

[29] A photocurable adhesive sheet according to any one of [1] to

[10] that satisfies the following formula (1): P / (Y×Z / X ３ ) ≤ 0.0025 ... (1) In equation (1), X is the thickness (μm) of the photocurable adhesive sheet. Y is the depth (μm) of the hole in the glass plate (G) having a bottomed hole, and the depth (μm) of the hole is approximately 3 / 4 of the thickness (X) of the photocurable adhesive sheet. Z is the bottom area (μm) when the radius of the bottom surface of the bottomed hole is 2 mm. ２). P is the PV value. The PV value is the Peak to Valley value (unit: wavelength: wave) measured from the displacement of interference fringes by generating interference fringes between the reference plane and the bottomed hole using a laser interferometer system under the condition that a photocurable adhesive sheet, which is bonded to a glass plate (Gc) with a bottomed hole having a diameter of 4 mm and a thickness of 0.2 mm and a glass plate (Gh) with a thickness of 0.55 mm, is bonded to follow the bottomed hole.

[0017] According to the present invention, there are provided a photocurable adhesive sheet capable of achieving both excellent fluidity and resistance to adhesive protrusion, and having a property of being cured by active energy rays, an adhesive sheet with a release film using the same, a laminate for an image display device configuration, and a laminate for an image display device, and a method for manufacturing the same.

[0018] According to the present invention, there are also provided a photocurable adhesive sheet that does not adversely affect a captured image, has no distortion in the image, and has a property of being cured by active energy rays, an adhesive sheet with a release film using the same, a laminate for an image display device configuration, and a laminate for an image display device, and a method for manufacturing the same.

[0019] [Explanation of Terms] In this specification, "X to Y" (X and Y are arbitrary numbers) includes, in addition to the meaning of "X or more and Y or less", the meaning of "preferably larger than X" and the meaning of "preferably smaller than Y". Also, "X or more" includes the meaning of "preferably larger than X", and "less than X" includes the meaning of "preferably smaller than Y". "(Meth)acryl" is a general term for "acryl" and "methacryl". "(Meth)acrylate" is a general term for "acrylate" and "methacrylate". "(Meth)acryloyl group" is a general term for "acryloyl group" and "methacryloyl group", and is a group represented by CH ２ = C(R)-C(=O)- (R is a hydrogen atom or a methyl group). "Sheet" conceptually includes sheet, film, and tape.

[0020] [Photocurable Adhesive Sheet] In one or more examples, the photocurable adhesive sheet may comprise one or more adhesive layers formed from an adhesive composition containing a (meth)acrylic polymer (A), a polyfunctional (meth)acrylate (B), and a cleavage-type photopolymerization initiator (C). The adhesive layer of the photocurable adhesive sheet is a partially cured adhesive composition layer formed from the adhesive composition, and is in a partially cured state. Therefore, at least one of the adhesive layers contains a polymer (B') of the polyfunctional (meth)acrylate (B) and a decomposition product (C') of the cleavage-type photopolymerization initiator (C). The total content of polyfunctional (meth)acrylate (B1) with a mass-average molecular weight of 300 or less in the total amount of the adhesive composition forming one or more adhesive layers is less than 3% by mass of the total content of the (meth)acrylic polymer (A) in the total amount of the adhesive composition forming one or more adhesive layers. The gel fraction of the photocurable adhesive sheet is 15% or less.

[0021] Preferably, one or more adhesive layers contain a hydrogen abstraction type photopolymerization initiator (D). The adhesive layer of the photocurable adhesive sheet is, for example, an adhesive composition containing a (meth)acrylic polymer (A), a polyfunctional (meth)acrylate (B), a cleavage type photopolymerization initiator (C), and a hydrogen abstraction type photopolymerization initiator (D), with an integrated light intensity of 50 to 500 mJ / cm². ２ The material can be formed by pre-curing by irradiation with active energy rays within a specified range. In the pre-curing reaction, the polyfunctional (meth)acrylate (B) polymerizes in the presence of the (meth)acrylic polymer (A) by the action of the cleavage-type photopolymerization initiator (C), while most of the (meth)acrylic polymer (A) and the hydrogen abstraction-type photopolymerization initiator (D) remain unreacted. The adhesive layer of the photocurable adhesive sheet of the present invention is in a pre-cured state. The photocurable adhesive sheet of the present invention can be further cured by further irradiation with active energy rays.

[0022] In one or more examples, the photocurable adhesive sheet may comprise one or more adhesive layers formed from an adhesive composition containing a (meth)acrylic polymer (A). In this case, the photocurable adhesive sheet satisfies the following formula (1): P / (Y×Z / X３ ) ≤ 0.0025 ... (1) In equation (1), X is the thickness (μm) of the photocurable adhesive sheet. Y is the depth (μm) of the hole in the glass plate (G) having a bottomed hole, and the depth (μm) of the hole is approximately 3 / 4 of the thickness (X) of the photocurable adhesive sheet. Z is the bottom area (μm) when the radius of the bottom surface of the bottomed hole is 2 mm. ２ ) is the PV value. The PV value is the Peak to Valley value (unit: wavelength: wave) measured from the displacement of interference fringes generated between a reference plane and the hole using a laser interferometer system under the conditions that a photocurable adhesive sheet, which has been bonded to a 0.2 mm thick glass plate (Gc) with a 4 mm diameter hole, and a 0.55 mm thick glass plate (Gh) is bonded together and the photocurable adhesive sheet follows the hole, and interference fringes are generated between the reference plane and the hole with the help of the laser interferometer system.

[0023] The following describes the details and preferred embodiments of the photocurable adhesive sheet.

[0024] ((meth)acrylic polymer (A)) In the adhesive composition, (meth)acrylic polymer (A) is preferably the main component. That is, it is preferably the component with the highest mass percentage among the components constituting the adhesive composition. In this case, the mass percentage of (meth)acrylic polymer (A) among the components constituting the adhesive composition may be 50% by mass or more, of which 70% by mass or more, of which 80% by mass or more, and of which 90% by mass or more. The (meth)acrylic polymer (A) may contain two or more copolymers with different polymerization components. The (meth)acrylic polymer (A) is preferably one that contains 50% by mass or more of the monomer component shown in the following formula 1 as the polymerization component.

[0025]

[0026] In formula 1, R １ represents a hydrogen atom or a methyl group, R ２ This represents a linear or branched alkyl group having 4 to 18 carbon atoms.

[0027] Examples of monomers represented by formula 1 include n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, and isononyl (meth)acrylate. Examples include t-butylcyclohexyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, isobornyl (meth)acrylate, 3,5,5-trimethylcyclohexane (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, etc. These may be used individually or in combination of two or more. These can be used individually or in combination of two or more.

[0028] In particular, it is especially preferable to include one or more alkyl (meth)acrylates having 4 to 18, preferably 4 to 15, alkyl groups such as n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, and lauryl (meth)acrylate.

[0029] The (meth)acrylic polymer (A) may be a copolymer having other copolymerizable monomers as copolymer components other than the monomer components described above. The other copolymerizable monomer units may be present in 1 to 50% by mass, 2 to 40% by mass, 3 to 35% by mass, or 5 to 30% by mass in the (meth)acrylic polymer (A). The lower and upper limits of the content can be combined arbitrarily.

[0030] Other copolymerizable monomers include, for example, (a) carboxyl group-containing monomers (hereinafter also referred to as "copolymerizable monomer a1"), (b) hydroxyl group-containing monomers (hereinafter also referred to as "copolymerizable monomer a2"), (c) amino group-containing monomers (hereinafter also referred to as "copolymerizable monomer a3"), (d) epoxy group-containing monomers (hereinafter also referred to as "copolymerizable monomer a4"), (e) amide group-containing monomers (hereinafter also referred to as "copolymerizable monomer a5"), (f) vinyl monomers (hereinafter also referred to as "copolymerizable monomer a6"), (g) (meth)acrylate monomers with 1 to 3 carbon atoms in the alkyl group (hereinafter also referred to as "copolymerizable monomer a7"), (h) macromonomers (hereinafter also referred to as "copolymerizable monomer a8"), (i) aromatic group-containing monomers (hereinafter also referred to as "copolymerizable monomer a9"), and (j) other functional group-containing monomers (hereinafter also referred to as "copolymerizable monomer a10"). These can be used individually or in combination of two or more types.

[0031] Examples of copolymerizable monomers a1 include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypropyl (meth)acrylate, carboxybutyl (meth)acrylate, ω-carboxypolycaprolactone mono(meth)acrylate, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxypropyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxypropyl phthalic acid, 2-(meth)acryloyloxyethyl maleic acid, 2-(meth)acryloyloxypropyl maleic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxypropyl succinic acid, crotonic acid, fumaric acid, maleic acid, and itaconic acid. These may be used individually or in combination of two or more.

[0032] Examples of copolymerizable monomer a2 include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. These may be used individually or in combination of two or more.

[0033] Examples of copolymerizable monomer a3 include aminoalkyl (meth)acrylates such as aminomethyl (meth)acrylate, aminoethyl (meth)acrylate, aminopropyl (meth)acrylate, and aminoisopropyl (meth)acrylate; N-alkylaminoalkyl (meth)acrylates such as N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate. These may be used individually or in combination of two or more types.

[0034] Examples of copolymerizable monomer a4 include glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate glycidyl ether. These may be used individually or in combination of two or more.

[0035] Examples of copolymerizable monomer a5 include (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methylolpropane(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide, diacetone(meth)acrylamide, maleic acid amide, and maleimide. These may be used individually or in combination of two or more.

[0036] Examples of copolymerizable monomer a6 include compounds having a vinyl group in the molecule. Examples of such compounds include alkyl (meth)acrylates having 1 to 12 carbon atoms in the alkyl group, functional monomers having functional groups such as hydroxyl groups, amide groups, and alkoxyalkyl groups in the molecule, polyalkylene glycol di(meth)acrylates, vinyl ester monomers such as vinyl acetate, N-vinyl-2-pyrrolidone, vinyl propionate, and vinyl laurate, and aromatic vinyl monomers such as styrene, chlorostyrene, chloromethylstyrene, α-methylstyrene, and other substituted styrenes. These may be used individually or in combination of two or more.

[0037] Examples of copolymerizable monomer a7 include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, etc. These may be used individually or in combination of two or more.

[0038] The (meth)acrylic polymer (A) may have units based on macromonomers, but units based on macromonomers are not essential. Copolymerizable monomer a8 is a macromonomer, a high molecular weight monomer having terminal functional groups and high molecular weight backbone components. The number average molecular weight of the macromonomer may be 1000 or more, 1500 or more, or 2000 or more. The upper limit of the number average molecular weight is usually 10000. Examples of copolymerizable monomer a8 include polymethyl methacrylate macromonomer. By using copolymerizable monomer a8, a graft copolymer can be made in which structural units derived from macromonomers are introduced as branch components of the graft copolymer. The backbone components of the macromonomer are preferably composed of (meth)acrylic acid ester polymers and vinyl polymers. Examples include linear or branched alkyl (meth)acrylates with 4 to 18 carbon atoms in the alkyl group, alicyclic alkyl (meth)acrylates, and the same as copolymerizable monomer a1, copolymerizable monomer a2, and copolymerizable monomer a7. These can be used individually or in combination of two or more types.

[0039] Examples of copolymerizable monomer a9 include benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and nonylphenol EO-modified (meth)acrylate. These may be used individually or in combination of two or more.

[0040] Examples of copolymerizable monomer a10 include (meth)acrylic-modified silicones, fluorine-containing monomers such as 2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3-tetrafluoropropyl (meth)acrylate, 2,2,3,3-tetrafluoropropyl (meth)acrylate, 1H,1H,5H-octafluoropentyl (meth)acrylate, and 1H,1H,2H,2H-tridecafluoro-n-octyl (meth)acrylate. These may be used individually or in combination of two or more.

[0041] From the viewpoint of preventing metal corrosion and resistance to humid heat whitening, the (meth)acrylic polymer (A) is preferably free of copolymerizable monomer a1 or substantially free of it. Free of copolymerizable monomer a1 or substantially free of it means not only that it is completely free, but also that the (meth)acrylic acid ester (co)polymer may contain copolymerizable monomer a1 in an amount of less than 0.5% by mass, preferably less than 0.1% by mass. From the viewpoint of imparting adhesiveness and cohesiveness to the adhesive, the (meth)acrylic polymer (A) is preferably free of copolymerizable monomers and / or nitrogen atom-containing monomers. Therefore, it is particularly preferable that the (meth)acrylic polymer (A) has copolymerizable monomer a2, copolymerizable monomer a3, copolymerizable monomer a5, or other nitrogen atom-containing monomers, especially copolymerizable monomer a5, as copolymerizable components.

[0042] The (meth)acrylic polymer (A) may include block copolymers and / or graft copolymers. A block copolymer is a copolymer having multiple polymer chains having repeating units derived from (meth)acrylic acid esters, in which multiple polymer chains with different chemical structures are linked linearly. A graft copolymer is a copolymer containing repeating units derived from (meth)acrylic acid esters as a trunk component, and having repeating units derived from macromonomers as branch components of the graft copolymer.

[0043] The glass transition temperature of the (meth)acrylic polymer (A) is preferably -40 to 20°C, more preferably -30 to 10°C, and even more preferably -20 to 0°C, from the viewpoint of fluidity and adhesive extrusion resistance. If the glass transition temperature of the (meth)acrylic polymer (A) is above the lower limit of the above numerical range, adhesive extrusion resistance is improved. If the glass transition temperature of the (meth)acrylic polymer (A) is below the upper limit of the above numerical range, fluidity is improved.

[0044] Here, the glass transition temperature refers to the peak temperature of tanδ measured by the shear method at a frequency of 1 Hz using a rheometer (TA Instruments "DHR-2") on a sample made by forming a sheet of (meth)acrylic polymer (A) to a thickness of 0.8 to 1.5 mm and punching it out in a circular shape with a diameter of 8 mm.

[0045] The mass-average molecular weight (Mw) of the (meth)acrylic polymer (A) is preferably 200,000 or more, more preferably 300,000 or more, and even more preferably 400,000 or more, from the viewpoint of obtaining high cohesive force. Furthermore, the upper limit of the mass-average molecular weight (Mw) of the (meth)acrylic polymer (A) is preferably 1,500,000 or less, more preferably 1,200,000 or less, even more preferably 1,100,000 or less, and especially preferably 1,000,000 or less, from the viewpoint of handling and uniform stirring. The lower and upper limits of the mass-average molecular weight of the (meth)acrylic polymer (A) can be arbitrarily combined. The mass-average molecular weight of the (meth)acrylic polymer (A) is a value on a standard polystyrene basis measured by gel permeation chromatography (GPC).

[0046] (Polyfunctional (meth)acrylate (B) and polymer (B')) The adhesive layer of the photocurable adhesive sheet contains a polymer (B') of polyfunctional (meth)acrylate (B). Preferably, the polymer (B') is formed by the action of a cleavage-type photopolymerization initiator (C). The polymer (B') may be either (1) or (2) below. (1) A polymer of polyfunctional (meth)acrylate (B) that has been polymerized in advance. (2) A polymer of polyfunctional (meth)acrylate (B) that has been incorporated into a sheet-like adhesive composition and then polymerized when producing a photocurable adhesive sheet. In particular, from the viewpoint of uniform dispersion, the polymer (B') of (2) above is preferred.

[0047] The presence of polymer (B') moderately restricts the (meth)acrylic polymer (A) through mechanical interactions such as entanglement and intermolecular forces with polymer (B'), moderately reducing its fluidity, thereby improving the adhesive's ability to bleed out of the photocurable adhesive sheet. Furthermore, it is preferable that the (meth)acrylic polymer (A) is not crosslinked by chemical bonds, as it flows sufficiently under high temperatures from autoclave treatment and fills pores such as camera holes.

[0048] By using weak light such that polymer (B') is formed by a cleavage-type photopolymerization initiator (C) and hydrogen abstraction-type photopolymerization initiator (D) does not react, the (meth)acrylic polymer (A) can be kept in a state where it is not crosslinked by chemical bonds.

[0049] The polyfunctional (meth)acrylate (B) only needs to be able to form a polymer (B'), and may be a polyfunctional (meth)acrylate monomer or an oligomer. The polyfunctional (meth)acrylate (B) only needs to be a (meth)acrylate with two or more functions, and is not particularly limited. Examples of polyfunctional (meth)acrylate (B) include 1,4-butanediol di(meth)acrylate, glycerin di(meth)acrylate, neopentyl glycol di(meth)acrylate, glycerin glycidyl ether di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, tricyclodecane dimethacrylate, tricyclodecane dimethanol di(meth)acrylate, bisphenol A polyethoxy di(meth)acrylate, bisphenol A polypropoxy di( Difunctional (meth)acrylates such as meth)acrylate, bisphenol F polyethoxy di(meth)acrylate, ethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, hydroxybivalate di(meth)acrylate, and di(meth)acrylate of the ε-caprolactone adduct of neopentyl glycol hydroxybivalate;Trimethylolpropanetrioxyethyl (meth)acrylate, ε-caprolactone-modified tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propoxylated pentaerythritol tri(meth)acrylate, ethoxylated pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, propoxylated pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate Examples of UV-curable polyfunctional (meth)acrylic monomers include trifunctional or more (meth)acrylates such as phosphate, tris(acryloxyethyl) isocyanurate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, tripentaerythritol hexa(meth)acrylate, tripentaerythritol penta(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane polyethoxytri(meth)acrylate, and ditrimethylolpropane tetra(meth)acrylate. Also, examples of polyfunctional (meth)acrylic oligomers such as polyester (meth)acrylate, epoxy (meth)acrylate, urethane (meth)acrylate, and polyether (meth)acrylate can be given.

[0050] The polyfunctional (meth)acrylate (B) may be one type or two or more types. If there are two or more polyfunctional (meth)acrylates (B), the polymer (B') may include copolymers of two or more polyfunctional (meth)acrylates (B).

[0051] The content of the polymer (B') of the polyfunctional (meth)acrylate (B) in one or more adhesive layers is preferably 0.1 to 5% by mass, more preferably 0.2 to 3% by mass, and more preferably 0.5 to 2% by mass, of the total content of the (meth)acrylic polymer (A) in one or more adhesive layers, from the viewpoint of fluidity and adhesive extrusion resistance. When the content of polymer (B') is above the lower limit of the above numerical range, adhesive extrusion resistance tends to improve. When the content of polymer (B') is below the upper limit of the above numerical range, fluidity tends to improve.

[0052] The less polyfunctional (meth)acrylate (B1) with a mass-average molecular weight of 300 or less is used among the polyfunctional (meth)acrylate (B), the better the fluidity. In one or more examples, the total content of polyfunctional (meth)acrylate (B1) with a mass-average molecular weight of 300 or less in the total amount of the adhesive composition forming one or more adhesive layers is less than 3% by mass of the total content of (meth)acrylic polymer (A) in the total amount of the adhesive composition forming one or more adhesive layers, and may be less than 2% by mass, less than 1% by mass, or less than 0% by mass.

[0053] (Fracture-type photopolymerization initiator (C) and decomposition product (C')) The filure-type photopolymerization initiator (C) is a component for the polymerization reaction of the polyfunctional (meth)acrylate (B). The reactivity of the filure-type photopolymerization initiator (C) is generally higher than that of the hydrogen abstraction-type photopolymerization initiator (D). The filure-type photopolymerization initiator (C) is excited by irradiation with active energy rays during the pre-curing reaction of the adhesive composition, causing the polyfunctional (meth)acrylate (B) to polymerize and form a polymer (B'), which contributes to ensuring the adhesive's resistance to oozing out of the adhesive sheet. In the adhesive layer after the formation of the polymer (B'), the decomposition product (C') of the filure-type photopolymerization initiator (C) remains. The total content of the filure-type photopolymerization initiator (C) in one or more adhesive layers may be 1% by mass or less of the total content of the (meth)acrylic polymer (A) in one or more adhesive layers.

[0054] The cleavage-type photopolymerization initiator (C) is not particularly limited, but examples include 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-(4-(2-hydroxyethoxy)phenyl)-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-[4-{4-(2-hydroxy-2-methyl-propionyl)benzyl}phenyl]-2-methyl-propan-1-one, oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone), methyl phenylglyoxylate, 2-benzyl-2-di Examples include methylamino-1-(4-morpholinophenyl)butan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)2,4,4-trimethylpentylphosphine oxide, and their derivatives.

[0055] The total content of the cleavage-type photopolymerization initiator (C) in one or more adhesive layers is preferably 1% by mass or less, more preferably 0.9% by mass or less, and even more preferably 0.8% by mass or less, of the total content of the (meth)acrylic polymer (A) in one or more adhesive layers, from the viewpoint of resistance to yellowing. The lower limit of the content of the cleavage-type photopolymerization initiator (C) is usually 0.1% by mass, but is not particularly limited. When the content of the cleavage-type photopolymerization initiator (C) is below the upper limit, resistance to yellowing tends to improve.

[0056] (Hydrogen abstraction type photopolymerization initiator (D)) The hydrogen abstraction type photopolymerization initiator (D) is primarily a component for the crosslinking reaction of the (meth)acrylic polymer (A). The hydrogen abstraction type photopolymerization initiator (D) is not excited by the irradiation of active energy rays during the pre-curing reaction of the adhesive composition and remains in the photocurable adhesive sheet, thereby maintaining the fluidity of the photocurable adhesive sheet and contributing to pore-filling properties. The hydrogen abstraction type photopolymerization initiator (D) remaining in the photocurable adhesive sheet is excited by the irradiation of active energy rays during post-curing, contributing to the crosslinking reaction of the (meth)acrylic polymer (A) and enabling adhesion of image display device components.

[0057] The hydrogen abstraction type photopolymerization initiator (D) is not particularly limited, but examples include benzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, 3,3'-dimethyl-4-methoxybenzophenone, 4-(meth)acryloyloxybenzophenone, 2-methyl benzoylbenzoate, methyl benzoyl formate, bis(2-phenyl-2-oxoacetic acid)oxybisethylene, 4-(1,3-acryloyl-1,4,7,10,13-pentaoxotridecyl)benzophenone, thioxanthone, 2-chlorothioxanthone, 3-methylthioxanthone, 2,4-dimethylthioxanthone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, and their derivatives.

[0058] The total content of hydrogen abstraction type photopolymerization initiator (D) in one or more adhesive layers is preferably 0.1 to 5% by mass, more preferably 0.2 to 3% by mass, and even more preferably 0.3 to 2% by mass, of the total content of (meth)acrylic polymer (A) in one or more adhesive layers, from the viewpoint of fluidity and heat resistance reliability. When the content of hydrogen abstraction type photopolymerization initiator (D) is above the lower limit of the above numerical range, curing tends to proceed sufficiently during main curing after pre-curing, improving heat resistance reliability. When the content of hydrogen abstraction type photopolymerization initiator (D) is below the upper limit of the above numerical range, it does not contribute to the reaction during pre-curing and does not chemically crosslink the (meth)acrylic polymer (A), thus tending to improve fluidity.

[0059] (Other Components) The photocurable adhesive sheet and the adhesive composition before pre-curing may further contain other components besides the (meth)acrylic polymer (A), polyfunctional (meth)acrylate (B), cleavage-type photopolymerization initiator (C), and hydrogen abstraction-type photopolymerization initiator (D). Examples of other components include various additives such as tackifying resins, antioxidants, light stabilizers, metal deactivators, anti-aging agents, hygroscopic agents, polymerization inhibitors, ultraviolet absorbers, rust inhibitors, inorganic particles, and silane coupling agents. In addition to additives, reaction catalysts such as tertiary amine compounds, quaternary ammonium compounds, and tin laurate compounds may also be used.

[0060] (Properties of the photocurable adhesive sheet) The gel fraction of the photocurable adhesive sheet is 15% or less. The gel fraction is preferably 14% or less, more preferably 13% or less, and even more preferably 12% or less. If the gel fraction is below the above upper limit, both excellent fluidity and resistance to adhesive leakage can be achieved. The lower limit of the gel fraction of the photocurable adhesive sheet is not particularly limited and may be, for example, 0%.

[0061] The preferred range of gel fraction for achieving both fluidity and adhesive oozing resistance tends to vary depending on the thickness of the photocurable adhesive sheet. As the thickness decreases, the volume of fluid flow under the same fluidity conditions is smaller, and higher fluidity is required to fill the pores. Therefore, the preferred range of gel fraction decreases. Also, as the amount of change from the standard dimensions under storage conditions decreases, the range of the preferred gel fraction for satisfying sufficient adhesive oozing resistance also decreases. For example, when the thickness of the photocurable adhesive sheet is 130 μm or less, and particularly 100 μm or less, the gel fraction is preferably 8% or less, more preferably 6% or less, and even more preferably 4% or less.

[0062] The shear creep strain of a photocurable adhesive sheet with a thickness of 0.8 to 1.5 mm, after applying a pressure of 1000 Pa and a torque of 100 μN·m at 65°C for 170 seconds, is preferably 320% or more, more preferably 350% or more, even more preferably 400% or more, particularly preferably 450% or more, and most preferably 500% or more. The higher the shear creep strain of a photocurable adhesive sheet with a thickness of 0.8 to 1.5 mm, after applying a pressure of 1000 Pa and a torque of 100 μN·m at 65°C for 170 seconds, the better the fluidity and the better the hole-filling ability. The upper limit of the shear creep strain of a photocurable adhesive sheet with a thickness of 0.8 to 1.5 mm, after applying a pressure of 1000 Pa and a torque of 100 μN·m at 65°C for 170 seconds, is not particularly limited and may be, for example, 1000%.

[0063] The preferred range of creep strain at 65°C tends to vary depending on the thickness of the photocurable adhesive sheet. Thinner sheets have a smaller flow volume under the same fluidity conditions, requiring higher fluidity at 65°C to fill pores. Therefore, the preferred range of creep strain at 65°C tends to be larger.

[0064] For a thickness of 0.8 to 1.5 mm, the shear creep strain after applying a pressure of 1000 Pa and a torque of 100 μN·m for 170 seconds at a temperature of 40°C is preferably 200% or less, more preferably 190% or less, even more preferably 180% or less, particularly preferably 160% or less, and most preferably 140% or less. The lower the shear creep strain after applying a pressure of 1000 Pa and a torque of 100 μN·m for 170 seconds at a temperature of 40°C for a thickness of 0.8 to 1.5 mm, the better the adhesive's resistance to oozing out and the easier it is to maintain the sheet shape. The lower limit of the shear creep strain after applying a pressure of 1000 Pa and a torque of 100 μN·m for 170 seconds at a temperature of 40°C for a thickness of 0.8 to 1.5 mm is not particularly limited and may be, for example, 10%.

[0065] The preferred creep strain range at 40°C tends to vary depending on the thickness of the photocurable adhesive sheet. The thinner the sheet, the smaller the change from the reference dimensions under storage conditions. Therefore, the preferred creep strain range at 40°C, assuming a harsh storage environment to satisfy sufficient adhesive extrusion resistance, tends to be larger.

[0066] For sheets cured under the curing conditions described below, the shear creep strain after applying a pressure of 1000 Pa and a torque of 100 μN·m at 80°C for 180 seconds with a thickness of 0.8 to 1.5 mm is preferably 10% or more, more preferably 13% or more, even more preferably 16% or more, particularly preferably 18% or more, especially preferably 20% or more, and most preferably 23% or more. For sheets after UV irradiation, the higher the shear creep strain after applying a pressure of 1000 Pa and a torque of 100 μN·m at 80°C for 180 seconds with a thickness of 0.8 to 1.5 mm, the less foaming and peeling occurs at the interface with the adherend, and the better the sheet can follow the thermal dimensional changes of the adherend. On the other hand, there is no particular upper limit to the shear creep strain after 180 seconds at 80°C following the curing conditions described above. However, a preferred upper limit is around 1000%, and a more preferred upper limit for the creep strain is 500% or less, even more preferably 300% or less, and particularly preferably 100% or less. If the creep strain is too high, the adhesive sheet may protrude from the end face of the bonded member in a high-temperature environment, causing the end face to become sticky, or the bonded member may shift position.

[0067] The photocurable adhesive sheet may have one adhesive layer or multiple adhesive layers, and is not particularly limited. In the case of a photocurable adhesive sheet having multiple adhesive layers, it is preferable to have an intermediate layer as a layer other than the adhesive layer, and the composition of the intermediate layer is arbitrary. However, from the viewpoint of further improving interlayer adhesion, it is preferable that the resin composition forming the layer other than the adhesive layer also contains (meth)acrylic polymer (A) as the main component. In particular, it is preferable that it contains the same (meth)acrylic polymer (A) as the adhesive layer as the main component. Furthermore, it is preferable that the layer other than the adhesive layer also contains (meth)acrylic polymer (A), polyfunctional (meth)acrylate (B), cleavage-type photopolymerization initiator (C), and hydrogen abstraction-type photopolymerization initiator (D).

[0068] In the case of a two-layer structure consisting of an outermost layer and an innermost layer, if the outermost and innermost layers have different hardnesses, it is possible to achieve both fluidity and resistance to adhesive leakage, which are conflicting challenges, by functionally separating each layer. The high-hardness layer provides rigidity to the adhesive sheet, ensuring handling and resistance to adhesive leakage, while the flexible layer can conform to the irregularities of the adherend surface, such as bottomed holes.

[0069] In the case of a three-layer structure consisting of an outermost layer, an innermost layer, and an intermediate layer, if the intermediate layer and the outer and inner layers have different hardnesses, the conflicting challenges of fluidity and adhesive overflow resistance can be reconciled by functionally separating each layer. The high-hardness layer provides rigidity to the adhesive sheet, ensuring handling and adhesive overflow resistance, while the flexible layer allows it to flow-follow the irregularities of the adherend surface, such as bottomed holes. If the intermediate layer is harder than the outer and inner layers, the flexible outer and inner layers can easily flow-follow the irregularities of the adherend. In the case of a three-layer structure, the thickness ratio of each layer (outermost layer:intermediate layer:innermost layer) is preferably 1:0.5:1 to 1:10:1, more preferably 1:0.7:1 to 1:6:1, and particularly preferably 1:1:1 to 1:4:1.

[0070] When forming an adhesive layer from an adhesive composition containing a (meth)acrylic polymer (A), a polyfunctional (meth)acrylate (B), a cleavage-type photopolymerization initiator (C), and a hydrogen abstraction-type photopolymerization initiator (D), the photocurable adhesive sheet is suitable for use when the cumulative light intensity is 50 to 500 mJ / cm². ２ It is preferable that the sheet of the adhesive composition containing a (meth)acrylic polymer (A), a polyfunctional (meth)acrylate (B), a cleavage-type photopolymerization initiator (C), and a hydrogen abstraction-type photopolymerization initiator (D) is pre-cured by irradiation with active energy rays within the specified range.

[0071] (Method for manufacturing photocurable adhesive sheets) The method for manufacturing photocurable adhesive sheets involves using an integrated light intensity of 50 to 500 mJ / cm². ２ This method includes pre-curing an adhesive composition layer containing a (meth)acrylic polymer (A), a polyfunctional (meth)acrylate (B), and a cleavage-type photopolymerization initiator (C) by irradiating it with active energy rays within a certain range, thereby reducing the gel fraction of the photocurable adhesive sheet to 15% or less.

[0072] In the preliminary curing stage, it is preferable to polymerize the polyfunctional (meth)acrylate (B) in the presence of a (meth)acrylic polymer (A) by the action of a cleavage-type photopolymerization initiator (C).

[0073] The adhesive composition can be prepared by mixing a (meth)acrylic polymer (A), a polyfunctional (meth)acrylate (B), and a cleavage-type photopolymerization initiator (C). A hydrogen abstraction-type photopolymerization initiator (D) or other components may be used as needed.

[0074] The mixing method is not particularly limited, nor is the mixing order of each component particularly limited. A heat treatment step may be added when preparing the adhesive composition. In this case, it is desirable to mix each component of the adhesive composition beforehand before heat treatment. Various mixed components may be concentrated and made into a masterbatch and used. The equipment used for mixing is also not particularly limited. For example, a universal kneader, planetary mixer, Banbury mixer, kneader, gate mixer, pressure kneader, three-roll, or two-roll kneader can be used. A solvent may be used for mixing as needed. The adhesive composition may also be used as a solvent-free system that does not contain a solvent. Using it as a solvent-free system improves heat resistance and light resistance.

[0075] The total content of polyfunctional (meth)acrylate (B) in the total amount of the adhesive composition used to form one or more adhesive layers is preferably 0.1 to 5% by mass, more preferably 0.2 to 3% by mass, and even more preferably 0.5 to 2% by mass, of the total content of (meth)acrylic polymer (A) in the total amount of the adhesive composition used to form one or more adhesive layers, from the viewpoint of fluidity and adhesive extrusion resistance. When the content of polyfunctional (meth)acrylate (B) is above the lower limit of the above numerical range, adhesive extrusion resistance tends to improve. When the content of polyfunctional (meth)acrylate (B) is below the upper limit of the above numerical range, fluidity tends to improve.

[0076] Among the polyfunctional (meth)acrylates (B), the less polyfunctional (meth)acrylate (B1) with a mass-average molecular weight of 300 or less is used, the better the fluidity. In one or more preferred examples, the total content of polyfunctional (meth)acrylate (B1) in the total amount of the adhesive composition forming one or more adhesive layers is less than 3% by mass, preferably less than 2% by mass, more preferably less than 1% by mass, and even more preferably less than 0.5% by mass, of the total content of (meth)acrylic polymer (A) in the total amount of the adhesive composition forming one or more adhesive layers.

[0077] The content of the hydrogen abstraction type photopolymerization initiator (D) in the total amount of the adhesive composition used to form one or more adhesive layers is preferably 0.1 to 5% by mass, more preferably 0.2 to 3% by mass, and even more preferably 0.3 to 2% by mass, of the total content of the (meth)acrylic polymer (A) in the total amount of the adhesive composition used to form one or more adhesive layers, from the viewpoint of fluidity and heat resistance reliability. If the content of the hydrogen abstraction type photopolymerization initiator (D) is above the lower limit of the above numerical range, curing tends to proceed sufficiently during main curing after pre-curing, improving heat resistance reliability. If it is below the upper limit of the above numerical range, it does not contribute to the reaction during pre-curing and does not chemically crosslink the (meth)acrylic polymer (A), thus tending to improve fluidity.

[0078] From the viewpoint of resistance to yellowing, the content of the cleavage-type photopolymerization initiator (C) in the total amount of the adhesive composition used to form one or more adhesive layers is preferably 1% by mass or less, more preferably 0.9% by mass or less, and even more preferably 0.8% by mass or less, of the total content of the (meth)acrylic polymer (A) in the total amount of the adhesive composition forming one or more adhesive layers. The lower limit of the content of the cleavage-type photopolymerization initiator (C) may normally be 0.1% by mass. When the content of the cleavage-type photopolymerization initiator (C) is below the upper limit of the above numerical range, resistance to yellowing tends to improve.

[0079] In an adhesive composition forming one or more adhesive layers, the ratio of hydrogen abstraction type photopolymerization initiator (D) to cleavage type photopolymerization initiator (C) (mass ratio) (D / C) (D / C) is preferably 8 / 2 to 2 / 8, particularly preferably 7 / 3 to 5 / 5, and even more preferably 7 / 3 to 6 / 4. The cleavage type photopolymerization initiator (C) reacts before the hydrogen abstraction type photopolymerization initiator (D) in the pre-curing reaction. In the adhesive composition, it is preferable that the content ratio of hydrogen abstraction type photopolymerization initiator (D) is higher than that of cleavage type photopolymerization initiator (C).

[0080] The photocurable adhesive sheet described above comprises one or more adhesive layers formed from an adhesive composition containing a (meth)acrylic polymer (A), a polyfunctional (meth)acrylate (B), and a cleavage-type photopolymerization initiator (C). At least one adhesive layer contains a polymer (B') of the polyfunctional (meth)acrylate (B) and a decomposition product (C') of the cleavage-type photopolymerization initiator (C). The gel fraction of the photocurable adhesive sheet is 15% or less, and it is preferably in a pre-cured state. In addition, the total content of polyfunctional (meth)acrylate (B1) in the total amount of the adhesive composition forming one or more adhesive layers is less than 3% by mass of the total content of (meth)acrylic polymer (A) in the total amount of the adhesive composition forming one or more adhesive layers. Therefore, it is possible to achieve both excellent fluidity and resistance to adhesive leakage. Thus, the hot-melted photocurable adhesive sheet can be made to conform to the pores of the adherend and fill every corner. Furthermore, by laminating a photocurable adhesive sheet between two adherends and irradiating it with active energy rays for post-curing, two adherends, particularly components of an image display device, can be joined together. In addition, even if the adherends change size, the adhesive filling the pores will not foam, demonstrating excellent foam resistance reliability.

[0081] In one or more examples, the photocurable adhesive sheet comprises one or more adhesive layers formed from an adhesive composition containing a (meth)acrylic polymer (A), satisfying the following formula (1): P / (Y×Z / X ３ ) ≤ 0.0025 ... (1) In equation (1), X is the thickness (μm) of the photocurable adhesive sheet. Y is the depth (μm) of the hole in the glass plate (G) having a bottomed hole, and the depth (μm) of the hole is approximately 3 / 4 of the thickness (X) of the photocurable adhesive sheet. Z is the bottom area (μm) when the radius of the bottom surface of the bottomed hole is 2 mm. ２) is the PV value. The PV value is the Peak to Valley value (unit: wavelength: wave) measured from the displacement of interference fringes generated between a reference plane and the hole using a laser interferometer system under the condition that a photocurable adhesive sheet, which has been bonded to a 0.2 mm thick glass plate (Gc) with a 4 mm diameter hole, and a 0.55 mm thick glass plate (Gh) are bonded together and the photocurable adhesive sheet follows the hole, and interference fringes are generated between the reference plane and the hole with the hole. Z is the bottom area of ​​the hole, but in this invention, Z is calculated assuming the radius of the hole is 2 mm.

[0082] In order to ensure that the adhesive sheet conforms to the holes of the optical component without air bubbles, the thickness of the adhesive sheet is related to the depth and volume of the holes. Equation (1) uses (Y × Z / X) to consider the relationship between the volume of the holes and the fluidity in three dimensions. ３ ) was used.

[0083] In the above equation (1), since the distortion of the image captured by the camera through the hole is suppressed, P / (Y×Z / X ３ It is important that P / (Y×Z / X) is 0.0025 or less. ３ P / (Y×Z / X) is preferably 0.0023 or less, more preferably 0.0020 or less, even more preferably 0.0015 or less, particularly preferably 0.0013 or less, especially preferably 0.0011 or less, while 0.0001 or more is preferred, more preferably 0.0003 or more, even more preferably 0.0005 or more, particularly preferably 0.0010 or more. ３ If the value of P / (Y×Z / X) is below the upper limit mentioned above, it is preferable because it can suppress distortion of the image captured by the camera through the hole. ３ If the value is above the aforementioned lower limit, the adhesive sheet will flow excessively, which is preferable because it can suppress the leakage of adhesive in the pre-bonding process.

[0084] In formula (1), P (PV value) is preferably 0.01 to 5.0, more preferably 0.05 to 4.5, even more preferably 0.1 to 4.0, particularly preferably 0.15 to 3.5, especially preferably 0.2 to 3.0, and most preferably 0.25 to 2.0, from the viewpoint of suppressing distortion of the image captured by the camera through the hole. A value below the upper limit is preferable because it can suppress distortion of the image captured by the camera through the hole, and a value above the lower limit is preferable because it can suppress excessive flow of the adhesive sheet and the leakage of adhesive in the pre-bonding process.

[0085] An adhesive sheet satisfying formula (1) can be formed from an adhesive composition containing a (meth)acrylic polymer (A). For example, it can be obtained in the same manner as the photocurable adhesive sheet described above. In particular, an adhesive sheet satisfying formula (1) can be produced by appropriately adding crosslinking agents and photopolymerization initiators and adjusting the UV irradiation amount.

[0086] [Applications] The photocurable adhesive sheet can be used as an adhesive sheet after post-curing. For example, in post-curing, the integrated light dose is 500 to 10000 mJ / cm². ２ An adhesive sheet may be obtained by irradiating the photocurable adhesive sheet with active energy rays within the specified range. In post-curing (main curing), the (meth)acrylic polymer (A) of the photocurable adhesive sheet is crosslinked by the action of a hydrogen abstraction type photopolymerization initiator (D).

[0087] A photocurable adhesive sheet with a release film, in which a photocurable adhesive sheet and a release film are laminated together, is also useful. For example, a photocurable adhesive sheet with a release film may be obtained by laminating a single or multilayer adhesive composition onto a release film and then pre-curing it.

[0088] Examples of release films include polyester film, polyolefin film, polycarbonate film, polystyrene film, acrylic film, triacetylcellulose film, and fluororesin film. Among these, polyester film and polyolefin film are particularly preferred.

[0089] The thickness of the release film is not particularly limited. In particular, from the viewpoint of processability and handling, for example, 25 to 500 μm is preferred, 38 to 250 μm is more preferred, and 50 to 200 μm is even more preferred.

[0090] Photocurable adhesive sheets are also useful as laminates for image display device components for manufacturing image display devices. Image display devices are not particularly limited and include, for example, liquid crystal displays, organic EL displays, inorganic EL displays, electronic paper, plasma displays, and microelectromechanical system (MEMS) displays.

[0091] The laminate for the image display device comprises a photocurable adhesive sheet and at least two or more image display device components laminated via the photocurable adhesive sheet. In the laminate for the image display device, the photocurable adhesive sheet is laminated between at least two image display device components.

[0092] The components of the image display device are not particularly limited and include, for example, a touch panel, an image display panel, a surface protection panel, a polarizing film, and a phase difference film. These may be used individually or in combination of two or more types.

[0093] Examples of layer configurations for laminates used in image display devices include: release film / photocurable adhesive sheet / touch panel, image display panel / photocurable adhesive sheet / touch panel, image display panel / photocurable adhesive sheet / touch panel / photocurable adhesive sheet / protective panel, polarizing film / photocurable adhesive sheet / touch panel, and polarizing film / photocurable adhesive sheet / touch panel / photocurable adhesive sheet / protective panel.

[0094] In a laminate for an image display device, the touch panel may be a protective panel with touch panel functionality added, or an image display panel with touch panel functionality added. Therefore, the laminate for an image display device may have a layer configuration such as, for example, release film / photocurable adhesive sheet / protective panel, release film / photocurable adhesive sheet / image display panel, or image display panel / photocurable adhesive sheet / protective panel.

[0095] The touch panel may be resistive, capacitive, or electromagnetic induction type, and is not particularly limited.

[0096] The material of the protective panel is not particularly limited and may be glass, acrylic resin, polycarbonate resin, alicyclic polyolefin resin such as cycloolefin polymer, styrene resin, polyvinyl chloride resin, phenolic resin, melamine resin, epoxy resin, or other plastics.

[0097] The image display panel may include other optical films such as polarizing films or other phase difference films, liquid crystal materials, and a backlight system. Typically, the surface of the photocurable adhesive sheet or adhesive sheet that adheres to the image display panel is an optical film. The control method for the liquid crystal material is not particularly limited and may be STN, VA, or IPS.

[0098] The laminate for image display device components comprises a photocurable adhesive sheet before post-curing. The laminate for image display device components can be obtained by further post-curing the photocurable adhesive sheet of the laminate for image display device components. The laminate for image display device components comprises an adhesive sheet, which is a cured product of the photocurable adhesive sheet, and at least two or more image display device components laminated via the adhesive sheet. The laminate for image display device components can be used, for example, as a component for manufacturing an image display device.

[0099] Examples of layer configurations for laminates used in image display devices include: release film / adhesive sheet / touch panel, image display panel / adhesive sheet / touch panel, image display panel / adhesive sheet / touch panel / adhesive sheet / protective panel, polarizing film / adhesive sheet / touch panel, and polarizing film / adhesive sheet / touch panel / adhesive sheet / protective panel.

[0100] The following describes an example of a method for manufacturing a laminate for an image display device. The method for manufacturing a laminate for an image display device is not limited to the method described below. The method for manufacturing a laminate for an image display device includes: forming a laminate by bonding a photocurable adhesive sheet to one side of a first image display device component; forming a laminate by bringing the bonding surface of the second image display device component and the photocurable adhesive sheet of the laminate into close contact under reduced pressure, with the bonding surface of the second image display device component having a bottomed hole facing the photocurable adhesive sheet of the laminate; hot-melting the photocurable adhesive sheet by applying heat and pressure treatment to the laminate, thereby causing the adhesive sheet to follow into the bottomed hole of the second image display device component; and curing the adhesive sheet by irradiating the photocurable adhesive sheet between the first image display device component and the second image display device component with active energy rays.

[0101] The heating and pressurizing treatment is preferably carried out at a temperature of 40°C to 80°C, applying a pressure of 0.2 MPa to 0.8 MPa. The temperature is preferably 45 to 78°C, more preferably 50 to 75°C. The pressure is preferably 0.25 to 0.75 MPa, more preferably 0.30 to 0.70 MPa. The time for applying the pressure is preferably 5 minutes or more, more preferably 5 to 60 minutes, and even more preferably 10 to 45 minutes.

[0102] Suitable active energy rays include ultraviolet light and visible light. Examples of light sources for irradiating with active energy rays include high-pressure mercury lamps, low-pressure mercury lamps, metal halide lamps, xenon lamps, halogen lamps, LED lamps, fluorescent lamps, and electron beam irradiation devices. The light source can be selected according to the wavelength and intensity of the light being irradiated.

[0103] There are no particular limitations regarding the irradiation time or irradiation method of the active energy rays. When obtaining a laminate for an image display device by ultraviolet irradiation, the integrated light intensity of ultraviolet irradiation at a wavelength of 365 nm is 500 to 10,000 mJ / cm². ２ Preferably, 1000 to 8000 mJ / cm² ２ More preferably, 2000 to 5000 mJ / cm ２ This is even more preferable. When ultraviolet light is irradiated from both the front and back surfaces of the laminate, the integrated light quantity is the sum of the integrated ultraviolet light quantity irradiated from the front surface and the integrated ultraviolet light quantity irradiated from the back surface.

[0104] Bottom area (mm²) of the bottomed hole of the second image display device component ２ The ratio of depth (mm) to () is 1.0 × 10 －６ ~3.0 x 10 －１ (mm －１ ) may also be 5.0 × 10 －６ ~1.0 x 10 －３ (mm －１ ) may also be 1.0 × 10 －５ ~1.0 x 10 －４ (mm －１ ) is also acceptable.

[0105] The embodiments will be described in more detail below, but the present invention is not limited to the following description.

[0106] [Materials] ((meth)acrylic polymer (A)) ・(meth)acrylic polymer (A-1): Copolymer consisting of 77% by mass of 2-ethylhexyl acrylate, 19% by mass of vinyl acetate, and 4% by mass of acrylic acid (weight-average molecular weight 400,000, glass transition temperature -16°C)

[0107] • (Meth)acrylic polymer (A-2): An acrylic copolymer (weight average molecular weight: 160,000, glass transition temperature: -36°C) obtained by random copolymerization of 15 parts by mass of polymethyl methacrylate macromonomer with a number average molecular weight of 2400 (glass transition temperature 105°C), 81 parts by mass of butyl acrylate (glass transition temperature -55°C), and 4 parts by mass of acrylic acid (glass transition temperature 106°C).

[0108] • (Meth)acrylic polymer (A-3): An acrylic copolymer (weight average molecular weight: 220,000, glass transition temperature: -45°C) obtained by random copolymerization of 6 parts by mass of polymethyl methacrylate macromonomer with a number average molecular weight of 2400 (glass transition temperature 105°C), 90 parts by mass of butyl acrylate (glass transition temperature -55°C), and 4 parts by mass of acrylic acid (glass transition temperature 106°C).

[0109] The glass transition temperatures of each copolymer component in (meth)acrylic polymers are the literature values ​​of the glass transition temperatures obtained from homopolymers of those components. For macromonomers, the literature values ​​of the glass transition temperatures obtained from homopolymers of the components forming the high molecular weight skeleton in the macromonomers are listed. The glass transition temperature of (meth)acrylic copolymers is the value calculated using Fox's formula from the glass transition temperatures and composition ratios of each copolymer component.

[0110] (Polyfunctional (meth)acrylate (B)) ・Polyfunctional (meth)acrylate (B-1): 1,9-nonanediol diacrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., "Viscoat #260") ・Polyfunctional (meth)acrylate (B-2): Polypropylene glycol #400 diacrylate (manufactured by Shin Nakamura Chemical Industry Co., Ltd., "NK Ester APG400") ・Polyfunctional (meth)acrylate (B-3): Polytetramethylene glycol diacrylate (manufactured by Shin Nakamura Chemical Industry Co., Ltd., "NK Ester A-PTMG65")

[0111] (Fracture-type photopolymerization initiator (C)) • Fracture-type photopolymerization initiator (C-1): Ethylphenyl (2,4,6-trimethylbenzoyl) phosphinate ("Omnirad TPO-L" manufactured by IGM RESINS B.V.)

[0112] (Hydrogen abstraction type photopolymerization initiator (D)) ・Hydrogen abstraction type photopolymerization initiator (D-1): A mixture of methyl phenylglyoxylate (Omnirad MBF, manufactured by IGM RESINS B.V.) and 4-methacryloyloxybenzophenone (MBP, manufactured by Shinryo Co., Ltd.) uniformly mixed in a ratio of 7:3. ・Hydrogen abstraction type photopolymerization initiator (D-2): A mixture of 2,4,6-trimethylbenzophenone and 4-methylbenzophenone (Esacure TZT, manufactured by IGM).

[0113] [Example A1] 100 parts by mass of (meth)acrylic polymer (A-1), 0.8 parts by mass of polyfunctional (meth)acrylate (B-1), 0.5 parts by mass of cleavage-type photopolymerization initiator (C-1), and 1.0 part by mass of hydrogen abstraction-type photopolymerization initiator (D-1) were uniformly mixed to obtain an adhesive composition. The obtained adhesive composition was sandwiched between two mold-release treated polyethylene terephthalate films (Mitsubishi Chemical Corporation, Diafoil MRV, 100 μm thick / Mitsubishi Chemical Corporation, Diafoil MRQ, 75 μm thick) and formed into a sheet with a thickness of 100 μm. The integrated light intensity at a wavelength of 365 nm was 150 mJ / cm² on both the front and back surfaces. ２ Each side (300 mJ / cm² total for both the front and back surfaces) ２ A photocurable adhesive sheet was fabricated by slightly hardening it with light from a high-pressure mercury lamp so that it would become partially cured. This photocurable adhesive sheet was in a partially cured state and was a photocurable sheet that would harden further with additional light irradiation.

[0114] [Examples A2 and A3, Comparative Examples A1-A4] As shown in Table 1, adhesive sheets were prepared under the same conditions as in Example A1, except that the composition of the adhesive composition and the amount of ultraviolet irradiation were changed.

[0115] [Example A4] 100 parts by mass of (meth)acrylic polymer (A-1), 1.4 parts by mass of polyfunctional (meth)acrylate (B-1), 0.35 parts by mass of cleavage-type photopolymerization initiator (C-1), and 1 part by mass of hydrogen abstraction-type photopolymerization initiator (D-1) were uniformly mixed to prepare an intermediate layer resin composition. The intermediate layer resin composition was sandwiched between two mold-release treated polyethylene terephthalate films (Mitsubishi Chemical Corporation, Diafoil MRV, 100 μm thick / Mitsubishi Chemical Corporation, Diafoil MRQ, 75 μm thick), and shaped into a sheet with a thickness of 50 μm to produce an intermediate layer sheet (α).

[0116] Next, 100 parts by mass of (meth)acrylic polymer (A-1), 0.9 parts by mass of polyfunctional (meth)acrylate (B-1), 0.35 parts by mass of cleavage-type photopolymerization initiator (C-1), and 1 part by mass of hydrogen abstraction-type photopolymerization initiator (D-1) were uniformly mixed to prepare an outer layer resin composition. The outer layer resin composition was sandwiched between two mold-release treated polyethylene terephthalate films (Mitsubishi Chemical Corporation, Diafoil MRV, 100 μm thick / Mitsubishi Chemical Corporation, Diafoil MRQ, 75 μm thick). Subsequently, it was shaped into a sheet with a thickness of 25 μm to produce an outer layer sheet (β). Separately, the outer layer resin composition was sandwiched between two peeled polyethylene terephthalate films (Mitsubishi Chemical Corporation, Diafoil MRF, 75 μm thick / Toyobo Industries Ltd., E7006, 38 μm thick), and shaped into a sheet with a thickness of 35 μm to produce the outer layer sheet (β').

[0117] The PET film on both sides of the intermediate layer sheet (α) was peeled off. The PET film on one side of the outer layer sheet (β) and outer layer sheet (β') was peeled off. The exposed adhesive surfaces of the outer layer sheet (β) and outer layer sheet (β') were sequentially laminated to both surfaces of the intermediate layer sheet (α). A sheet having three layers, outer layer sheet (β) / intermediate layer sheet (α) / outer layer sheet (β'), was prepared. The integrated light intensity of 150 mJ / cm² at a wavelength of 365 nm was applied to the front and back surfaces, respectively, via the PET film remaining on each surface of the outer layer sheet (β) and outer layer sheet (β'). ２ Each side (300 mJ / cm² total for both the front and back surfaces) ２The material was irradiated with light from a high-pressure mercury lamp. A photocurable adhesive sheet was then fabricated by slightly curing it.

[0118] [Example A5] 100 parts by mass of (meth)acrylic polymer (A-1), 3 parts by mass of polyfunctional (meth)acrylate (B-1), 0.5 parts by mass of cleavage-type photopolymerization initiator (C-1), and 1 part by mass of hydrogen abstraction-type photopolymerization initiator (D-1) were uniformly mixed to prepare an intermediate layer resin composition. The intermediate layer resin composition was sandwiched between two mold-release treated polyethylene terephthalate films (Mitsubishi Chemical Corporation, Diafoil MRV, 100 μm thick / Mitsubishi Chemical Corporation, Diafoil MRQ, 75 μm thick), and formed into a sheet with a thickness of 50 μm to produce an intermediate layer sheet (α).

[0119] Next, 100 parts by mass of (meth)acrylic polymer (A-1), 1.1 parts by mass of polyfunctional (meth)acrylate (B-1), 0.5 parts by mass of cleavage-type photopolymerization initiator (C-1), and 1 part by mass of hydrogen abstraction-type photopolymerization initiator (D-1) were uniformly mixed to prepare an outer layer resin composition. The outer layer resin composition was sandwiched between two mold-release treated polyethylene terephthalate films (Mitsubishi Chemical Corporation, Diafoil MRV, 100 μm thick / Mitsubishi Chemical Corporation, Diafoil MRQ, 75 μm thick). Subsequently, it was shaped into a sheet with a thickness of 50 μm to produce an outer layer sheet (β). Separately, the outer layer resin composition was sandwiched between two peeled polyethylene terephthalate films (Mitsubishi Chemical Corporation, Diafoil MRF, 75 μm thick / Toyobo Industries Ltd., E7006, 38 μm thick), and shaped into a sheet with a thickness of 50 μm to produce the outer layer sheet (β').

[0120] The PET film on both sides of the intermediate layer sheet (α) was peeled off. The PET film on one side of the outer layer sheet (β) and outer layer sheet (β') was peeled off. The exposed adhesive surfaces of the outer layer sheet (β) and outer layer sheet (β') were sequentially laminated to both surfaces of the intermediate layer sheet (α). A sheet with three layers, consisting of outer layer sheet (β), intermediate layer sheet (α), and outer layer sheet (β'), was fabricated. Through the PET film remaining on each surface of the outer layer sheet (β) and outer layer sheet (β'), the integrated light intensity at a wavelength of 365 nm was 175 mJ / cm² to the front and back surfaces, respectively. ２ Each side (350 mJ / cm² total for both the front and back surfaces) ２ The material was irradiated with light from a high-pressure mercury lamp. A photocurable adhesive sheet was then fabricated by slightly curing it.

[0121] The photocurable adhesive sheets prepared in Examples A1-A5 and Comparative Examples A1-A4 were subjected to the following various measurements and evaluations. The evaluation results are shown in Table 1.

[0122] (Gel fraction) The release film was removed from the prepared photocurable adhesive sheet and used as a sample. The sample was wrapped in a 150-mesh stainless steel wire mesh and immersed in ethyl acetate for 24 hours. After drying at 75°C for 4.5 hours, the mass of the adhesive was measured before and after immersion in ethyl acetate, and the difference between the two weights was taken as the weight of the insoluble adhesive remaining in the wire mesh. The gel fraction (%) was calculated as the mass percentage of the insoluble adhesive remaining in the wire mesh relative to the mass of the adhesive before immersion in ethyl acetate.

[0123] (Creep Test) Multiple sheets of the prepared adhesive were used to create stacks with a thickness of 0.8 to 1.5 mm, and then punched out in a circular shape with a diameter of 8 mm. Using a rheometer (TA Instruments "DHR-2"), the shear creep strain (%) was measured under the conditions of a measuring jig: 8 mm diameter parallel plate, temperature: 40°C or 65°C, after applying a pressure of 1000 Pa and a torque of 100 μN·m for 170 seconds. The shear creep strain (%) at 40°C is an indicator of adhesive extrusion resistance. The smaller the shear creep strain (%) at 40°C, the smaller the deformation and the better the adhesive extrusion resistance, even in constant temperature environments such as in summer. The shear creep strain (%) at 65°C is an indicator of hole-filling ability. The larger the shear creep strain (%) at 65°C, the higher the fluidity during autoclave treatment after bonding and the better the hole-filling ability.

[0124] (Creep test after curing) The prepared adhesive sheet was subjected to a high-pressure mercury lamp test, with an integrated light intensity of 3000 mJ / cm² at 365 nm. ２ To achieve this, the adhesive sheet was cured by irradiating it with ultraviolet light through a release-treated polyethylene terephthalate film. Multiple sheets of the cured adhesive sheet were used to create layers with a thickness of 0.8 to 1.5 mm, and then punched out in the shape of a circle with a diameter of 8 mm. Using a rheometer (TA Instruments "DHR-2"), the strain (%) after 180 seconds was measured with a measuring jig: 8 mm diameter parallel plate, temperature: 80°C, pressure: 1000 Pa, torque: 100 μN·m.

[0125] (Hole-filling properties (fluidity)) A polyethylene terephthalate film with an adhesive layer (total thickness 75 μm) was prepared by laminating a 25 μm thick double-sided adhesive sheet onto one side of a 50 μm thick polyethylene terephthalate film (Toyobo Co., Ltd. "Cosmoshine A4300") using a hand roll. The polyethylene terephthalate film with the adhesive layer was cut to 54 mm x 82 mm. At the four corners of the cut film, cylindrical bottomed holes with a diameter of 4 mm were made so that the distance from the edge to the center of the hole was 6 mm. Depth (mm) / bottom area (mm) of this bottomed hole ２) is 9.95 x 10 －３ A substrate for evaluating hole-filling properties was prepared by roll-laminating a film with bottomed holes to a 54 mm x 82 mm, 0.55 mm thick soda-lime glass, resulting in four bottomed holes with a diameter of 4 mm and a depth of 75 μm.

[0126] One side of the release film was peeled off the prepared adhesive sheet, and the exposed adhesive surface was roll-pressed onto soda-lime glass (82 mm x 54 mm x 0.55 mm thick). Next, the remaining release film was peeled off, and the exposed adhesive surface was placed opposite the side of the substrate with a bottomed hole for hole-filling performance evaluation, and pressed together under reduced pressure (absolute pressure 2 kPa) using a vacuum laminating machine. The laminate was heated and pressurized using an autoclave (65°C, gauge pressure 0.45 MPa, 20 minutes) to produce a laminate for hole-filling performance evaluation. This laminate was visually inspected. Hole-filling performance (flowability) was evaluated according to the following criteria.

[0127] Good: No bubbles with a diameter of 1 mm or more were found inside any of the bottomed holes. Poor: At least one or more bottomed holes contained bubbles with a diameter of 1 mm or more. The diameter of the bubbles was determined by the longest diameter if the bubbles were not spherical.

[0128] (Adhesive Extrusion Resistance) The prepared adhesive sheet was half-cut into a 30 mm x 30 mm square, starting from one release film (Mitsubishi Plastics, Diafoil MRQ, 75 μm thick) and not penetrating the other release film (Mitsubishi Plastics, Diafoil MRV, 100 μm thick). The cut release film (Mitsubishi Plastics, Diafoil MRQ, 75 μm thick) was peeled off. The exposed adhesive surface was covered with a release-treated polyethylene terephthalate film (Mitsubishi Plastics, Diafoil MRT, 50 μm thick). Both release films were cut to 50 mm x 50 mm to prepare samples for adhesive extrusion resistance evaluation. The samples for adhesive extrusion resistance evaluation were cured for 300 hours in an environment of 40°C and 90% humidity. The amount of adhesive extrusion on the edge of the adhesive sheet after curing was observed. For the cut and cured adhesive sheets, the distance of adhesive overflow at the center of each side was measured. The average distance of the four sides was calculated as the amount of adhesive overflow (mm). Adhesive overflow resistance was evaluated according to the following criteria: Good: Adhesive overflow was observed, but the size of the overflowed portion was less than 2 mm. Poor: The adhesive sheet was crushed after curing, and the amount of adhesive overflow was 2 mm or more.

[0129]

[0130] The active energy ray irradiation doses in Table 1 represent the total irradiation dose for both the front and back surfaces.

[0131] In Examples A1-A5, the gel fraction of the photocurable adhesive sheets was sufficiently small. The shear creep strain at 65°C was sufficiently large, indicating excellent hole-filling properties. Furthermore, the shear creep strain at 40°C was sufficiently small, indicating excellent resistance to adhesive leakage.

[0132] In contrast, Comparative Example A1 exhibited high shear creep strain at 40°C and insufficient adhesive extrusion resistance. As shown in the results for Comparative Examples A2-A4, when the (meth)acrylic polymer (A) was directly crosslinked using a hydrogen abstraction type photopolymerization initiator, the crosslinking was dense, resulting in low shear creep strain at 65°C and insufficient pore-filling properties. It was not possible to achieve both pore-filling properties and adhesive extrusion resistance simultaneously.

[0133] [Example B1] 100 parts by mass of (meth)acrylic polymer (A-1), 1.4 parts by mass of polyfunctional (meth)acrylate (B-1), 0.5 parts by mass of cleavage-type photopolymerization initiator (C-1), and 1.2 parts by mass of hydrogen abstraction-type photopolymerization initiator (D-1) were uniformly mixed to prepare an intermediate layer resin composition. The intermediate layer resin composition was sandwiched between two mold-release treated polyethylene terephthalate films (Mitsubishi Chemical Corporation, Diafoil MRV, 100 μm thick / Mitsubishi Chemical Corporation, Diafoil MRQ, 75 μm thick), and formed into a sheet with a thickness of 25 μm to produce an intermediate layer sheet (α).

[0134] Next, 100 parts by mass of (meth)acrylic polymer (A-1), 0.9 parts by mass of polyfunctional (meth)acrylate (B-1), 0.5 parts by mass of cleavage-type photopolymerization initiator (C-1), and 1.2 parts by mass of hydrogen abstraction-type photopolymerization initiator (D-1) were uniformly mixed to prepare an outer layer resin composition. The outer layer resin composition was sandwiched between two mold-release treated polyethylene terephthalate films (Mitsubishi Chemical Corporation, Diafoil MRV, 100 μm thick / Mitsubishi Chemical Corporation, Diafoil MRQ, 75 μm thick). Subsequently, it was shaped into a sheet with a thickness of 25 μm to produce an outer layer sheet (β). Separately, the outer layer resin composition was sandwiched between two peeled polyethylene terephthalate films (Mitsubishi Chemical Corporation, Diafoil MRF, 75 μm thick / Toyobo Industries Ltd., E7006, 38 μm thick), and shaped into a sheet with a thickness of 25 μm to produce the outer layer sheet (β').

[0135] The PET film on both sides of the intermediate layer sheet (α) was peeled off. The PET film on one side of the outer layer sheet (β) and outer layer sheet (β') was peeled off. The exposed adhesive surfaces of the outer layer sheet (β) and outer layer sheet (β') were sequentially laminated to both surfaces of the intermediate layer sheet (α). A sheet with three layers, consisting of outer layer sheet (β), intermediate layer sheet (α), and outer layer sheet (β'), was prepared. The integrated light intensity at a wavelength of 365 nm was 87.5 mJ / cm² through the PET film remaining on each surface of the outer layer sheet (β) and outer layer sheet (β'). ２ Each side (175 mJ / cm² total for both the front and back surfaces)２ The material was irradiated with light from a high-pressure mercury lamp. A photocurable adhesive sheet was then fabricated by slightly curing it.

[0136] [Examples B2-B5, Comparative Example B1] As shown in Table 2, adhesive sheets were prepared under the same conditions as in Example B1, except that the composition of the adhesive composition, the amount of ultraviolet irradiation, the thickness, and the layer structure were changed.

[0137] The photocurable adhesive sheets prepared in Examples B1-B5 and Comparative Example B1 were subjected to the following various measurements and evaluations. The evaluation results are shown in Table 2.

[0138] (Substrate for evaluating hole-filling properties (H-1) with four bottomed holes with a depth of 75 μm) A polyethylene terephthalate film with an adhesive layer (total thickness 75 μm) was prepared by laminating a 25 μm thick double-sided adhesive sheet onto one side of a 50 μm thick polyethylene terephthalate film (Toyobo Co., Ltd. "Cosmoshine A4300") using a hand roll. The polyethylene terephthalate film with the adhesive layer was cut to 50 mm x 70 mm. At the four corners of the cut film, cylindrical bottomed holes with a diameter of 4 mm (radius 2 mm) were made so that the distance from the edge to the center of the hole was 6 mm. Depth (mm) / bottom area (mm) of this bottomed hole ２ ) is 9.95 x 10 －３ The following was done. A substrate (H-1) for evaluating hole-filling properties was prepared by roll-laminating a film with bottomed holes to a 50 mm x 70 mm cover glass (product name: Cover Glass #1 50 x 70, manufactured by Matsunami Glass Co., Ltd.), resulting in four bottomed holes with a diameter of 4 mm (radius 2 mm) and a depth of 75 μm.

[0139] (A substrate for evaluating hole-filling properties (H-2) with four bottomed holes with a depth of 53 μm) A polyethylene terephthalate film with an adhesive layer (total thickness 53 μm) was prepared by laminating a 25 μm thick double-sided adhesive sheet onto one side of a 38 μm thick polyethylene terephthalate film (Mitsubishi Chemical's "Diafoil T100") using a hand roll. The polyethylene terephthalate film with the adhesive layer was cut to 50 mm x 70 mm. At the four corners of the cut film, cylindrical bottomed holes with a diameter of 4 mm (radius 2 mm) were made so that the distance from the edge to the center of the hole was 6 mm. Depth (mm) / bottom area (mm) of these bottomed holes２ ) is 6.66 x 10 －３ The following was done. A substrate (H-2) for evaluating hole-filling properties was prepared by roll-laminating a film with bottomed holes to a 50 mm x 70 mm cover glass (product name: Cover Glass #1 50 x 70, manufactured by Matsunami Glass Co., Ltd.), resulting in four bottomed holes with a diameter of 4 mm (radius 2 mm) and a depth of 53 μm.

[0140] The prepared adhesive sheet with release film was cut to 50 mm x 70 mm, and one side of the release film was peeled off to expose the adhesive surface, which was then roll-pressed onto soda-lime glass (82 mm x 54 mm x 0.55 mm thick). Next, the remaining release film was peeled off, and the exposed adhesive surface was placed opposite the side of the substrate with a bottomed hole for pore-filling evaluation, and pressed together under reduced pressure (absolute pressure 2 kPa) using a vacuum laminating machine. The laminate was then heated and pressurized using an autoclave (65°C, gauge pressure 0.5 MPa, 20 minutes) to produce a laminate for PV value evaluation.

[0141] The combinations of adhesive sheets and substrates for evaluating hole-filling properties are shown in the table. Y is the depth (μm) of the holes in the glass plate (G) with bottomed holes, and the depth (μm) of these holes was selected to be approximately three-quarters of the thickness (X) of the photocurable adhesive sheet.

[0142] (Measurement of PV values) The PV values ​​of the PV value evaluation laminate were measured using a Zygo GPI-XP interferometer (manufactured by Zygo Corporation) and a MetroPro analysis system. The perforated portion of the PV value evaluation laminate was placed between the interferometer and a mirror, and the laser light was reflected by the mirror. The interference fringes generated by passing through the sample were read by the interferometer. GPI Application was selected from the MetroPro menu, the Surface / Wavefront Map was displayed, and the calculated PV value (unit: WAVE, wavelength) was read.

[0143] (Glass Distortion) For the PV value evaluation laminate, the shape of the fluorescent lamp was illuminated so that its shape could be seen, and the shape of the fluorescent lamp reflected on the surface of the laminate was confirmed. The following criteria were used for evaluation: Good: The outer edge of the fluorescent lamp is clearly visible on the bottomed hole as a reflected image. Poor: The outer edge of the fluorescent lamp appears distorted and curved on the bottomed hole as a reflected image.

[0144]

[0145] The active energy ray irradiation doses in Table 2 represent the total irradiation dose for both the front and back surfaces.

[0146] As shown in Table 2, adhesive sheets that satisfy equation (1) do not deform the surrounding glass when filling the bottomed hole and exhibit good camera hole characteristics, whereas adhesive sheets that do not satisfy equation (1) deform the surrounding glass to a large extent when filling the bottomed hole and therefore exhibit unsuitable properties as camera holes.

[0147] The present invention provides a photocurable adhesive sheet that can achieve both excellent fluidity and resistance to adhesive leakage, and which has the property of curing by active energy rays, an adhesive sheet with a release film using the same, a laminate for an image display device, and a method for manufacturing the same.

[0148] The present invention also provides a photocurable adhesive sheet that does not adversely affect captured images, is free from image distortion, and has the property of being cured by active energy rays, an adhesive sheet with a release film using the same, a laminate for an image display device, and a method for manufacturing the same.

Claims

1. A photocurable adhesive sheet comprising one or more adhesive layers formed from an adhesive composition containing a (meth)acrylic polymer (A), a polyfunctional (meth)acrylate (B), and a cleavage-type photopolymerization initiator (C), wherein at least one of the adhesive layers contains a polymer (B') of the polyfunctional (meth)acrylate (B) and a decomposition product (C') of the cleavage-type photopolymerization initiator (C), the total content of polyfunctional (meth)acrylate (B1) with a mass-average molecular weight of 300 or less in the total amount of the adhesive composition forming the one or more adhesive layers is less than 3% by mass of the total content of the (meth)acrylic polymer (A) in the total amount of the adhesive composition forming the one or more adhesive layers, and the gel fraction is 15% or less.

2. The photocurable adhesive sheet according to claim 1, wherein at least one layer of the adhesive layer contains a hydrogen abstraction type photopolymerization initiator (D).

3. The photocurable adhesive sheet according to claim 2, wherein the total content of the hydrogen abstraction type photopolymerization initiator (D) in the one or more adhesive layers is 0.1 to 5% by mass of the total content of the (meth)acrylic polymer (A) in the one or more adhesive layers.

4. The photocurable adhesive sheet according to claim 1, wherein the polymer (B') of the polyfunctional (meth)acrylate (B) is formed by a cleavage-type photopolymerization initiator (C).

5. The photocurable adhesive sheet according to claim 4, wherein the total content of the cleavage-type photopolymerization initiator (C) in the one or more adhesive layers is 1% by mass or less of the total content of the (meth)acrylic polymer (A) in the one or more adhesive layers.

6. The photocurable adhesive sheet according to claim 1, wherein the thickness is 0.8 to 1.5 mm, and the shear creep strain after applying a pressure of 1000 Pa and a torque of 100 μN·m for 170 seconds at a temperature of 65°C is 320% or more.

7. The photocurable adhesive sheet according to claim 1, wherein the thickness is 0.8 to 1.5 mm, and the shear creep strain after applying a pressure of 1000 Pa and a torque of 100 μN·m for 170 seconds at a temperature of 40°C is 200% or less.

8. The photocurable adhesive sheet according to claim 1, wherein the total content of the polymer (B') of the polyfunctional (meth)acrylate (B) in the one or more adhesive layers is 0.1 to 5% by mass of the total content of the (meth)acrylic polymer (A) in the one or more adhesive layers.

9. The photocurable adhesive sheet according to claim 1, comprising a plurality of adhesive layers.

10. Cumulative light intensity is 50-500 mJ / cm ２ A photocurable adhesive sheet according to claim 1, which is partially cured by irradiation with active energy rays within a certain range.

11. A method for manufacturing a photocurable adhesive sheet comprising one or more adhesive layers, wherein the cumulative light intensity is 50 to 500 mJ / cm². ２ A manufacturing method comprising irradiating an adhesive composition layer containing a (meth)acrylic polymer (A), a polyfunctional (meth)acrylate (B), and a cleavage-type photopolymerization initiator (C) with active energy rays within a certain range to pre-cure the gel fraction of the photocurable adhesive sheet to 15% or less.

12. The manufacturing method according to claim 11, wherein the adhesive composition layer further contains a hydrogen abstraction type photopolymerization initiator (D).

13. The manufacturing method according to claim 11, wherein the total content of polyfunctional (meth)acrylate (B1) having a mass-average molecular weight of 300 or less in the total amount of the adhesive composition forming the one or more adhesive layers is less than 3% by mass of the total content of (meth)acrylic polymer (A) in the total amount of the adhesive composition forming the one or more adhesive layers.

14. The manufacturing method according to claim 11, wherein the total content of the polymer (B') of the polyfunctional (meth)acrylate (B) in the one or more adhesive layers is 0.1 to 5% by mass of the total content of the (meth)acrylic polymer (A) in the one or more adhesive layers.

15. The manufacturing method according to claim 12, wherein the total content of the hydrogen abstraction type photopolymerization initiator (D) in the one or more adhesive layers is 0.1 to 5% by mass of the total content of the (meth)acrylic polymer (A) in the one or more adhesive layers.

16. The manufacturing method according to claim 12, wherein the content ratio (mass ratio) of the hydrogen abstraction type photopolymerization initiator (D) to the cleavage type photopolymerization initiator (C) in the adhesive composition for forming the one or more adhesive layers is 2 / 8 to 8 / 2.

17. An adhesive sheet obtained by curing a photocurable adhesive sheet according to any one of claims 1 to 10.

18. A photocurable adhesive sheet with a release film, comprising: a photocurable adhesive sheet according to any one of claims 1 to 10; and a release film, wherein the photocurable adhesive sheet and the release film are laminated together.

19. A laminate for an image display device comprising: a photocurable adhesive sheet according to any one of claims 1 to 10; and at least two or more image display device components laminated via the photocurable adhesive sheet, wherein the photocurable adhesive sheet is laminated between at least two image display device components.

20. The laminate for an image display device according to claim 19, wherein the image display device component is at least one selected from the group consisting of a touch panel, an image display panel, a surface protection panel, a polarizing film, and a phase difference film.

21. A method for manufacturing a laminate for an image display device, wherein the laminate for an image display device comprises: an adhesive sheet which is a cured product of a photocurable adhesive sheet described in any one of claims 1 to 10; and at least two or more image display device components laminated via the adhesive sheet, the manufacturing method comprising: forming a laminate by bonding the photocurable adhesive sheet to one side of a first image display device component; forming a laminate by bringing the bonding surface of the second image display device component and the photocurable adhesive sheet into close contact under reduced pressure with the bonding surface of the second image display device component and the photocurable adhesive sheet facing each other; causing the adhesive sheet to conform to the bottomed hole of the second image display device component by applying a heat and pressure treatment to the laminate to hot-melt the photocurable adhesive sheet; and curing the adhesive sheet by irradiating the photocurable adhesive sheet between the first image display device component and the second image display device component with active energy rays.

22. Bottom area (mm²) of the bottomed hole of the second image display device component. ２ The ratio of depth (mm) to ) is 1.0 × 10 －５ ~3.0 x 10 －１ (mm －１ The manufacturing method according to claim 21, which is as follows:

23. The manufacturing method according to claim 21, wherein either or both of the first image display device component and the second image display device component are at least one selected from the group consisting of a touch panel, an image display panel, a surface protection panel, a polarizing film, and a phase difference film.

24. A photocurable adhesive sheet comprising one or more adhesive layers formed from an adhesive composition containing a (meth)acrylic polymer (A), and satisfying the following formula (1): P / (Y×Z / X ３ ) ≤ 0.0025 ... (1) In equation (1), X is the thickness (μm) of the photocurable adhesive sheet. Y is the depth (μm) of the hole in the glass plate (G) having a bottomed hole, and the depth (μm) of the hole is approximately 3 / 4 of the thickness (X) of the photocurable adhesive sheet. Z is the bottom area (μm) when the radius of the bottom surface of the bottomed hole is 2 mm. ２ ) is the PV value. The PV value is the Peak to Valley value (unit: wavelength: wave) measured from the displacement of interference fringes generated between a reference plane and the hole using a laser interferometer system under the conditions that a photocurable adhesive sheet, which has been bonded to a 0.2 mm thick glass plate (Gc) with a 4 mm diameter hole, and a 0.55 mm thick glass plate (Gh) is bonded together and the photocurable adhesive sheet follows the hole, and interference fringes are generated between the reference plane and the hole with the help of the laser interferometer system.

25. The photocurable adhesive sheet according to claim 24, wherein the thickness is 0.8 to 1.5 mm, and the shear creep strain after applying a pressure of 1000 Pa and a torque of 100 μN·m for 170 seconds at a temperature of 65°C is 320% or more.

26. The photocurable adhesive sheet according to claim 24, wherein the thickness is 0.8 to 1.5 mm, and the shear creep strain after applying a pressure of 1000 Pa and a torque of 100 μN·m for 170 seconds at a temperature of 40°C is 200% or less.

27. The photocurable adhesive sheet according to claim 24, comprising a plurality of adhesive layers.

28. The photocurable adhesive sheet according to claim 24, which is temporarily cured by irradiation with active energy rays within the range of an integrated light quantity of 50 to 500 mJ / cm ２ .

29. A photocurable adhesive sheet according to claim 1, satisfying the following formula (1): P / (Y×Z / X ３ ) ≤ 0.0025 ... (1) X: Thickness of the photocurable adhesive sheet (μm). Y: Depth of the hole in the glass plate (G) having a bottomed hole (μm), where the depth of the hole (μm) is approximately 3 / 4 of the thickness of the photocurable adhesive sheet (X). Z: Bottom area (μm) when the radius of the bottom surface of the bottomed hole is 2 mm. ２ ) is the result. P (PV value): A 0.2 mm thick glass plate (Gc) with a 4 mm diameter bottomed hole is bonded to a 0.55 mm thick glass plate (Gh), and when the photocurable adhesive sheet is made to follow the bottomed hole, interference fringes are generated between the reference plane and the bottomed hole using a laser interferometer system, and the Peak to Valley value (unit is wavelength: wave) measured from the displacement of the interference fringes is defined as the PV value.

Images