Adhesive sheet for image display device, adhesive sheet with release film, laminate for image display device, and image display device

Abstract

As an adhesive sheet having excellent rounded surface bondability for bonding to a rounded member having a curved portion without forming air bubbles and also having excellent durability after the bonding to a rounded member, an adhesive sheet for image display devices which is used for the bonding between two image display device components is provided, in which the bonding force to a soda-lime glass is 2 N / cm or more at a peeling rate of 300 mm / min at a temperature of 23°C, the transposition length measured by a retention force test on an adhered surface having a size of 20 mm in width × 20 mm in length at a temperature of 70°C, a load of 0.5 kg and a measurement time period of 30 minutes in accordance with JIS Z 0237 is 10 mm or less, and a peel distance in a stable weight peeling test is 20 mm or less.

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive sheet for an image display device, a pressure-sensitive adhesive sheet with a release film, a laminate for an image display device, and an image display device. [Background technology]

[0002] In order to improve the visibility of image display devices, the gap between an image display panel such as a liquid crystal display (LCD), plasma display (PDP) or electroluminescence display (ELD) and a protective panel or touch panel member placed on the front side (viewing side) of the image display panel is filled with a resin such as an adhesive or glue to suppress reflection of incident light and outgoing light from the displayed image at the air layer interface.

[0003] For example, Patent Document 1 discloses a method for manufacturing a component laminate for an image display device, which has a configuration in which an image display device component is laminated on at least one side of a transparent double-sided adhesive sheet, in which an adhesive sheet that has been primarily crosslinked by ultraviolet light is attached to the image display device component, and then the adhesive sheet is irradiated with ultraviolet light through the image display device component to cause secondary curing.

[0004] Furthermore, Patent Document 2 discloses a pressure-sensitive adhesive sheet containing a (meth)acrylic copolymer having an ultraviolet-crosslinkable site, as an adhesive sheet useful for displays and touch panels. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4971529 [Patent Document 2] Patent No. 6062740 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, there has been a demand for high design quality in image display devices, and the shape of the front protection panel is changing from flat to designs with curved edges and corners, or even designs in which the entire display unit is curved.

[0007] However, when a pressure-sensitive adhesive sheet is used to attach an image display device component made of a resin film or the like to a curved portion, the repulsion of the resin film or the like is likely to have an effect, making it difficult to make the pressure-sensitive adhesive sheet follow the curved portion. The pressure-sensitive adhesive sheets in Patent Documents 1 and 2 were developed for laminated structures using conventional flat image display device components, and did not take into consideration the reliability of attachment to curved members having curved portions.

[0008] Furthermore, when the curved surface member has unevenness such as printing steps in the curved portion, lifting or peeling is more likely to occur at the interface between the adhesive sheet and the uneven portion than in a flat member. For this reason, curved surface members with curved portions require even higher levels of adhesive reliability and step-following ability than before.

[0009] Therefore, the problem that the present invention aims to solve is to provide an adhesive sheet that has excellent curved surface adhesion properties that allow it to be attached to curved components with curved portions without air bubbles, and that has excellent durability after being attached to the curved component. [Means for solving the problem]

[0010] As a result of extensive research into solving the above-mentioned problems, the inventors have discovered that the above-mentioned problems can be solved by setting the adhesive strength of the adhesive sheet, the slippage length measured in a holding power test, and the peel distance in a constant load peel test to specific numerical ranges.

[0011] That is, the gist of the present invention is the following [1] to

[15] . [1] An adhesive sheet for use in bonding two components of an image display device, which has an adhesive strength of 2 N / cm or more to soda lime glass at a temperature of 23°C and a peeling speed of 300 mm / min, and in a holding strength test conforming to JIS Z 0237 at a temperature of 70°C, a load of 0.5 kg, a measurement time of 30 minutes, and a slippage length of 10 mm or less measured on an adhesive surface of 20 mm wide x 20 mm long, and in the following constant load peeling test, the peeling distance is 20 mm or less. (Measurement conditions) 1) A 10 mm wide, 150 mm long adhesive sheet is attached to an adherend in a region of 10 mm wide and 100 mm long to form an attached region, and the area of ​​the adhesive sheet other than the attached region is formed as a non-attached region, and the adherend is fixed horizontally so that the non-attached region of the adhesive sheet hangs down. 2) A load of 0.45 N is applied to the longitudinal end of the non-adhered area of ​​the pressure-sensitive adhesive sheet for 30 minutes, and the distance that the adhered area of ​​the pressure-sensitive adhesive layer peels from the adherend during this time is measured as the constant-load peel distance. [2] The pressure-sensitive adhesive sheet for an image display device according to [1], which has a ball number of 5 to 25 in an inclined ball tack test (inclination angle: 30°). [3] The pressure-sensitive adhesive sheet for image display devices according to [1] or [2], wherein the pressure-sensitive adhesive sheet has a thickness of 0.6 to 0.8 mm, and after applying a pressure of 1 kPa at a temperature of 25°C for 180 seconds, the pressure is released and the residual creep strain is 20% or less 180 seconds later. [4] The pressure-sensitive adhesive sheet for an image display device according to any one of [1] to [3], wherein the ratio (E' / G') of the tensile storage modulus (E') to the shear storage modulus (G') is 5.0 or more. [5] The pressure-sensitive adhesive sheet for an image display device according to any one of [1] to [4], wherein the loss tangent (Tan δ) obtained by dynamic viscoelasticity measurement in a tensile mode at a frequency of 1 Hz has two maximum values ​​(peak temperatures), the difference between which is 5 to 50°C. [6] An adhesive sheet for an image display device according to any one of [1] to [5], which has at least three layers, the outermost layer and the innermost layer of which are acrylic adhesive layers, and the ratio of the total thickness of the outermost layer and the innermost layer to the total thickness is 5 to 70%. [7] A pressure-sensitive adhesive sheet for an image display device according to any one of [1] to [6], which comprises at least three layers: a surface layer, a back layer, and an intermediate layer, and the surface layer, the back layer, and the intermediate layer are formed from resin compositions containing (meth)acrylic polymers having different compositions. [8] The pressure-sensitive adhesive sheet for an image display device according to any one of claims [1] to [7], which has active energy ray curability. [9] The pressure-sensitive adhesive sheet is irradiated with active energy rays having a wavelength of 365 nm at an integrated light dose of 3000 mJ / cm 2 The pressure-sensitive adhesive sheet for an image display device according to [8], which, after being irradiated and cured, has a thickness of 0.6 to 0.8 mm and exhibits a distortion (creep distortion) of 3% or less when a pressure of 1 kPa is applied at a temperature of 25°C for 10 seconds.

[10] The pressure-sensitive adhesive sheet is irradiated with active energy rays having a wavelength of 365 nm at an integrated light dose of 3000 mJ / cm 2 The pressure-sensitive adhesive sheet for an image display device according to [8] or [9], which, after being irradiated and cured, has a thickness of 0.6 to 0.8 mm and a maximum value of the loss tangent (glass transition temperature) obtained by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz of 0°C or less.

[11] The pressure-sensitive adhesive sheet for an image display device according to any one of [1] to

[10] , wherein the pressure-sensitive adhesive sheet is formed from a resin composition containing a (meth)acrylic resin, a crosslinking agent (B), and a photopolymerization initiator (C).

[12] The pressure-sensitive adhesive sheet for an image display device according to

[11] , wherein the content by mass of the crosslinking agent (B) is 0.5 to 50 parts by mass per 100 parts by mass of the (meth)acrylic polymer.

[13] A pressure-sensitive adhesive sheet with a release film, comprising the pressure-sensitive adhesive sheet for an image display device according to any one of [1] to

[12] and a release film laminated together.

[14] A laminate for an image display device, comprising two components of an image display device laminated together via the adhesive sheet for an image display device according to any one of [1] to

[12] , wherein one of the two components of the image display device is a cover glass having a curved surface, and the other is a member consisting of one or a combination of two or more of the group consisting of a touch sensor, an image display panel, a surface protection film, an anti-reflection film, a color filter, a polarizing film, and a retardation film.

[15] An image display device using the laminate for an image display device according to

[14] . [Effects of the Invention]

[0012] This adhesive sheet has excellent curved surface adhesion properties, allowing it to be attached to curved surfaces without any air bubbles, and has excellent durability after being attached to curved surfaces, making it suitable for use as an adhesive sheet for image display devices with curved surfaces. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram for explaining an evaluation method of a constant load peel test. [Figure 2] FIG. 1 is a diagram for explaining an evaluation method for a roll lamination test. DETAILED DESCRIPTION OF THE INVENTION

[0014] An example of an embodiment of the present invention will be described in detail below, but the present invention is not limited to the following embodiment. In this specification, "(meth)acrylic" encompasses "acrylic" and "methacrylic", and "(meth)acrylate" encompasses "acrylate" and "methacrylate".

[0015] The pressure-sensitive adhesive sheet for an image display device of the present invention (referred to as "the pressure-sensitive adhesive sheet") is usually a double-sided pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers on both sides, and is used to bond two components of an image display device. In particular, the pressure-sensitive adhesive sheet can be suitably used when the components of the image display device have a curved surface. In addition, from the viewpoint of improving reliability, the present pressure-sensitive adhesive sheet preferably has active energy ray curability, that is, it is cured by irradiation with active energy rays such as ultraviolet rays.

[0016] <Adhesive strength> This pressure-sensitive adhesive sheet has an adhesive strength of 2 N / cm or more to soda lime glass at a temperature of 23°C and a peeling speed of 300 mm / min. Having an adhesive strength of 2 N / cm or more prevents peeling even when attached to a curved surface, enabling excellent curved surface attachment. From this perspective, the adhesive strength is preferably 3 N / cm or more, more preferably 4 N / cm or more, and even more preferably 5 N / cm or more. The upper limit of adhesive strength is usually 50 N / cm, preferably 30 N / cm, in order to reduce the modulus of elasticity in order to achieve a balance between level difference absorbency and roll attachment.

[0017] Furthermore, when the pressure-sensitive adhesive sheet is active energy ray-curable, the pressure-sensitive adhesive sheet after curing preferably has an adhesive strength to soda-lime glass of 2 N / cm or more at a temperature of 23°C and a peeling speed of 300 mm / min. An adhesive strength of 2 N / cm or more allows the sheet to exhibit excellent durability when used as a laminate for an image display device. From this perspective, the adhesive strength after curing is preferably 3 N / cm or more, more preferably 4 N / cm or more, and even more preferably 5 N / cm or more. Taking into account the range of adhesive strength before curing, the upper limit of adhesive strength is usually 50 N / cm, preferably 30 N / cm.

[0018] [Method for measuring adhesive strength] The adhesive strength is measured by the following method. A 100 μm thick polyethylene terephthalate (PET) film (Cosmoshine A4300, manufactured by Toyobo Co., Ltd.) was laminated to one side of this adhesive sheet, and the other side was roll-pressed onto soda lime glass to form a laminate. The laminate was then autoclaved (temperature 60°C, gauge pressure 0.2 MPa, 20 minutes) to form a finished laminate, which served as a sample for measuring adhesive strength. This sample was peeled at a peel angle of 180° and a peel speed of 300 mm / min under conditions of 23°C and 50% RH, and the peel strength (N / cm) was determined as the adhesive strength. The adhesive strength after curing was measured by irradiating the PET film surface of the adhesive strength measurement sample with 365 nm ultraviolet light using a high-pressure mercury lamp with an integrated light intensity of 3000 mJ / cm. 2 After irradiating the sample so as to obtain the above value, the sample is left to cure for 12 hours in an environment of a temperature of 23°C and a humidity of 50% RH to serve as a sample for measuring adhesive strength after curing, and the peel strength is measured in the same manner as above.

[0019] <Holding power> Furthermore, this pressure-sensitive adhesive sheet exhibits a slippage length of 10 mm or less when measured in a holding strength test conforming to JIS Z 0237 at a temperature of 70°C, a load of 0.5 kg, a measurement time of 30 minutes, and on an adhesive surface measuring 20 mm wide x 20 mm long. A slippage length of 10 mm or less prevents the pressure-sensitive adhesive sheet from undergoing cohesive failure over time, even when applied to a curved surface member, and allows the sheet to exhibit excellent curved surface adhesion. From this perspective, a slippage length of 8 mm or less is more preferable, and a slippage length of 5 mm or less is even more preferable.

[0020] Furthermore, when the pressure-sensitive adhesive sheet is active energy ray-curable, the pressure-sensitive adhesive sheet after curing preferably has a slippage length of 5 mm or less, as measured in a holding strength test on an adhesive surface of 20 mm wide x 20 mm long, at a temperature of 70°C, a load of 0.5 kg, and a measurement time of 30 minutes, in accordance with JIS Z 0237. A slippage length of 5 mm or less allows the sheet to exhibit excellent durability when used as a laminate for an image display device. From this perspective, the slippage length is more preferably 1 mm or less, and even more preferably 0.5 mm or less.

[0021] [Method for measuring holding power] The holding power is measured by the following method. A 38 μm thick polyethylene terephthalate (PET) film (Mitsubishi Chemical Corporation, Diafoil S100) was laminated to one side of this adhesive sheet and cut to a 20 mm width, and the other side was attached to a polished stainless steel plate (SUS304) so ​​that the adhesive area was 20 mm x 20 mm to form a sample for holding power measurement. This sample was held under conditions of a load of 0.5 kg and a temperature of 70°C for 30 minutes, and the slippage length (mm) of the adhesive sheet was measured. In addition, the post-curing holding power is 3000mJ / cm when the integrated light intensity of 365nm wavelength is applied to this adhesive sheet. 2 The adhesive sheet is irradiated with light from a high-pressure mercury lamp to photocure the adhesive so that the thickness satisfies the above formula (1), and a cured adhesive sheet is produced. The misalignment length can be measured using this sheet in the same manner as above.

[0022] <Constant load peeling> Furthermore, this pressure-sensitive adhesive sheet has a peel distance of 20 mm or less in the constant-load peel test described below. A peel distance of 20 mm or less can prevent lifting over time even when attached to a curved surface component, and can exhibit excellent curved surface attachment properties. From this perspective, the peel distance in the constant-load peel test is preferably 15 mm or less, more preferably 12 mm or less, and even more preferably 8 mm or less.

[0023] [Constant load peel measurement method] The constant load peel test is measured by the following method. A 100 μm-thick polyethylene terephthalate (PET) film (Cosmoshine A4300, manufactured by Toyobo Co., Ltd.) was bonded to one side of the adhesive sheet. This was cut to a width of 10 mm and a length of 150 mm, and a 10 mm wide and 100 mm long region was roll-pressed onto soda lime glass to form a bonded product. The region bonded to the soda lime glass was designated the bonded region, and the region other than the bonded region was designated the non-bonded region. The bonded product was then autoclaved (temperature 50°C, gauge pressure 0.2 MPa, 20 minutes), and then cured at a temperature of 40°C for 30 minutes, resulting in a final bonded product. This was used as a sample for a constant-load peel test. Using this sample, the soda lime glass was fixed horizontally so that the non-bonded region of the adhesive sheet drooped downward in an environment of 23°C and 50% RH. A load of 0.45 N is then applied to the longitudinal end of the non-bonded area of ​​the adhesive sheet for 30 minutes, and the distance over which the bonded area of ​​the adhesive sheet peels from the soda-lime glass during this time is measured as the constant load peel distance.

[0024] When the pressure-sensitive adhesive sheet has adhesive strength, holding power, and constant-load peeling properties within the above ranges, it can be made to have excellent curved surface lamination properties and durability.

[0025] <Ball tuck> The present PSA sheet preferably has a ball number in an inclined ball tack test of 5 to 25, more preferably 8 to 20. By having a ball number in the above range in an inclined ball tack test, the PSA sheet does not misalign when roll-laid to a component of an image display device, and excellent roll-lamination properties can be achieved. The ball number is determined based on the inclined ball tack test specified in JIS Z 0237:2009, at a temperature of 23°C and a tilt angle of 30°.

[0026] <Residual creep strain> This pressure-sensitive adhesive sheet preferably has a thickness of 0.6 to 0.8 mm, and after a pressure of 1 kPa is applied for 180 seconds at 25°C and the pressure is released, the residual creep strain is preferably 20% or less 180 seconds later. A residual creep strain of 20% or less makes it possible to obtain a laminate for an image display device that does not experience adhesive crushing or adhesive overflow during lamination. From this perspective, the residual creep strain is more preferably 10% or less, with 7% or less being preferred, 5% or less being even more preferred, and 2% or less being particularly preferred.

[0027] When the pressure-sensitive adhesive sheet is active energy ray-curable, the residual creep strain in the pressure-sensitive adhesive sheet after curing is preferably 5% or less. Generally, when two components of an image display device are bonded together via an adhesive sheet to form a laminate for an image display device, and then the laminate for constituting an image display device is used to form an image display device, localized stress is applied to the laminate for constituting an image display device, which can cause indentations on the adhesive sheet and impair the appearance and visibility of the image display device. By ensuring that the residual creep strain of the adhesive sheet after curing is 5% or less, a laminate for an image display device with excellent resistance to indentations can be obtained. From this perspective, the residual creep strain of the adhesive sheet after curing is preferably 3% or less, more preferably 1% or less, and even more preferably 0.5% or less. The residual creep strain in the adhesive sheet after curing was measured when the adhesive sheet was exposed to an integrated light intensity of 3000 mJ / cm at a wavelength of 365 nm. 2 The adhesive is obtained by irradiating the adhesive with light from a high-pressure mercury lamp and photocuring it.

[0028] As mentioned above, the residual creep strain is the value when the thickness of this PSA sheet is 0.6 to 0.8 mm. This is because, in order to accurately measure the residual creep strain of this PSA sheet, it is necessary to avoid fluctuations in the measurement results due to the influence of the measuring jig caused by insufficient thickness of the PSA sheet. Therefore, in order to measure the residual creep strain, it is necessary to adjust the PSA sheet to a certain thickness range. By preliminarily adjusting the thickness of the pressure-sensitive adhesive sheet to fall within the above range and then measuring the residual creep strain, the residual creep strain of the pressure-sensitive adhesive sheet can be accurately determined without being affected by the measuring jig.

[0029] <Creep strain> The pressure-sensitive adhesive sheet preferably has a thickness of 0.6 to 0.8 mm and a creep strain of 10% or less when a pressure of 1 kPa is applied for 10 seconds at a temperature of 25°C. A creep strain of 10% or less makes it possible to obtain a pressure-sensitive adhesive sheet with excellent resistance to adhesive crushing. From this perspective, the creep strain is more preferably 7% or less, more preferably 5% or less, and even more preferably 3% or less.

[0030] When the pressure-sensitive adhesive sheet is active energy ray-curable, the creep strain of the cured pressure-sensitive adhesive sheet is preferably 7% or less. Having a creep strain of 7% or less in the cured pressure-sensitive adhesive sheet allows for the production of a laminate for an image display device with excellent resistance to indentations. From this perspective, the residual creep strain of the cured pressure-sensitive adhesive sheet is preferably 7% or less, more preferably 5% or less, and even more preferably 3% or less. The creep strain in the adhesive sheet after curing was measured when the adhesive sheet was exposed to an integrated light intensity of 3000 mJ / cm at a wavelength of 365 nm. 2 The adhesive is obtained by irradiating the adhesive with light from a high-pressure mercury lamp and photocuring it.

[0031] As mentioned above, the creep strain is a value when the thickness of the pressure-sensitive adhesive sheet is 0.6 to 0.8 mm. This is because, in order to accurately measure the creep strain of the pressure-sensitive adhesive sheet, it is necessary to avoid fluctuations in the measurement results due to the influence of the measuring jig caused by insufficient thickness of the pressure-sensitive adhesive sheet. Therefore, in order to measure the creep strain, it is necessary to adjust the thickness of the pressure-sensitive adhesive sheet to a certain range. By measuring the creep strain after adjusting the thickness of the pressure-sensitive adhesive sheet to fall within the above range in advance, the creep strain of the pressure-sensitive adhesive sheet can be accurately determined without being affected by the measuring jig.

[0032] <Dynamic viscoelastic properties> The ratio (E' / G') of the tensile storage modulus (E') to the shear storage modulus (G') of the pressure-sensitive adhesive sheet obtained by dynamic viscoelasticity measurement is preferably 5.0 or more, more preferably 6.0 or more, even more preferably 7.0 or more, and particularly preferably 8.0 or more. Also, it is preferably 100 or less, more preferably 50 or less, and even more preferably 30 or less. That is, when the E' / G' ratio of the present pressure-sensitive adhesive sheet is 5.0 or more, it can be determined that the present pressure-sensitive adhesive sheet "has at least two layers with different glass transition temperatures" or "has layers whose glass transition temperatures are gradient in the thickness direction." By having such a layer structure, the present pressure-sensitive adhesive sheet can combine high levels of lamination suitability and durability, such as curved surface lamination ability, roll lamination ability, adhesive crush resistance, step absorption ability, and indentation resistance. The tensile storage modulus (E') and shear storage modulus (G') can be obtained by the following method.

[0033] [Method for measuring tensile storage modulus (E')] This adhesive sheet is cut to a width of 4 mm and a length of 15 mm, and the dynamic viscoelasticity spectrum in the tensile mode is measured using a dynamic viscoelasticity measuring device (IT Measurement and Control Co., Ltd., "itkDVA-200") at a vibration frequency of 1 Hz, a heating rate of 3°C / min, and a temperature range of -120 to 80°C. The tensile storage modulus (E') at 25°C is read from the obtained data.

[0034] [Method for measuring shear storage modulus (G')] This pressure-sensitive adhesive sheet is laminated to a thickness of 0.6 to 0.8 mm and punched out into a circle with a diameter of 8 mm to serve as a measurement sample. The dynamic viscoelasticity spectrum of this measurement sample is measured in shear mode using a rheometer (TA Instruments, "Discovery HR2") under the measurement conditions below, and the shear storage modulus (G') at 25°C is read from the obtained data. [Measurement conditions] Adhesive jig: Φ8mm parallel plate Distortion: 0.1% Frequency: 1Hz Temperature: -120~200℃ Heating rate: 5℃ / min

[0035] As mentioned above, the shear storage modulus (G') is the value when the pressure-sensitive adhesive sheet has a thickness of 0.6 to 0.8 mm. This is because, in order to accurately measure the shear storage modulus (G') of the pressure-sensitive adhesive sheet, it is necessary to avoid fluctuations in the measurement results due to the influence of the measuring jig caused by an insufficient thickness of the pressure-sensitive adhesive sheet. Therefore, to measure the shear storage modulus (G'), it is necessary to adjust the pressure-sensitive adhesive sheet to a certain thickness range before measurement. By preliminarily adjusting the thickness of the adhesive sheet to within the above range and then measuring the shear storage modulus (G'), the shear storage modulus (G') of the adhesive sheet can be accurately determined without being affected by the measuring jig.

[0036] When the pressure-sensitive adhesive sheet is active energy ray-curable, the sample used in the tensile storage modulus (E') measurement and the shear storage modulus (G') measurement may be either before or after curing. The cured pressure-sensitive adhesive sheet is prepared by irradiating the pressure-sensitive adhesive sheet with an integrated light intensity of 3000 mJ / cm at a wavelength of 365 nm. 2 The resin is obtained by irradiating the resin with light from a high-pressure mercury lamp and photo-curing the resin.

[0037] The loss tangent (Tan δ) obtained by dynamic viscoelasticity measurement in a tensile mode of this pressure-sensitive adhesive sheet preferably has two maximum values ​​(peak temperatures: (T1) and (T2)). The difference between the two peak temperatures (T1) and (T2) is preferably 5 to 50°C, more preferably 10 to 40°C, and particularly preferably 15 to 30°C. By keeping the difference within the above range, it is possible to achieve a high level of lamination suitability and reliability, such as curved surface lamination, roll lamination, adhesive crush resistance, step absorbency, and indentation resistance. The peak temperatures (T1) and (T2) of the loss tangent can be obtained by reading the temperature at which the loss tangent (Tanδ) reaches its maximum value, i.e., the peak temperature, from the dynamic viscoelasticity spectrum data in the tensile mode obtained in the same manner as in the measurement of the tensile storage modulus (E') described above.

[0038] Furthermore, the shear storage modulus (G') of the present pressure-sensitive adhesive sheet is not particularly limited, but from the viewpoint of achieving high levels of both level difference absorbency and curved surface lamination, it is preferably 50 to 400 kPa at 25°C, more preferably 60 to 300 kPa, and even more preferably 100 to 200 kPa. The shear storage modulus (G') at 65°C is preferably 5 to 60 kPa, more preferably 10 to 50 kPa, and even more preferably 20 to 45 kPa. Furthermore, the shear storage modulus (G') at 85°C is preferably 1 to 40 kPa, more preferably 5 to 35 kPa, and even more preferably 10 to 30 kPa. By setting the shear storage modulus (G') of the present pressure-sensitive adhesive sheet within this range, it is possible to obtain a pressure-sensitive adhesive sheet with better level difference absorbency.

[0039] When the present pressure-sensitive adhesive sheet is active energy ray-curable, the shear storage modulus (G') of the cured pressure-sensitive adhesive sheet is not particularly limited, but is preferably 50 to 500 kPa, more preferably 60 to 400 kPa, and even more preferably 100 to 300 kPa at 25°C. The shear storage modulus (G') at 65°C is preferably 10 to 100 kPa, more preferably 15 to 90 kPa, and even more preferably 20 to 55 kPa. Furthermore, the shear storage modulus (G') at 85°C is preferably 1 to 90 kPa, more preferably 5 to 80 kPa, and even more preferably 10 to 50 kPa. By setting the shear storage modulus (G') of the cured pressure-sensitive adhesive sheet within this range, a pressure-sensitive adhesive sheet with excellent resistance to indentations and durability can be obtained.

[0040] The shear storage modulus (G') at 65°C and 85°C can be obtained by reading the shear storage modulus (G') at 65°C and 85°C from the dynamic viscoelasticity spectrum data in shear mode obtained in the same manner as in the measurement of the shear storage modulus (G') described above.

[0041] The maximum value (peak temperature) of the loss tangent (Tanδ) obtained by dynamic viscoelasticity measurement in shear mode of the pressure-sensitive adhesive sheet, i.e., the glass transition temperature, is not particularly limited, but is preferably 0°C or lower, more preferably -10°C or lower, even more preferably -15°C or lower, and particularly preferably -20°C or lower. The lower limit is usually -100°C. By ensuring that the temperature falls within this range, a pressure-sensitive adhesive sheet with excellent level difference absorbency can be obtained.

[0042] Furthermore, when the pressure-sensitive adhesive sheet is active energy ray-curable, the maximum value (peak temperature) of the loss tangent (Tan δ) obtained by dynamic viscoelasticity measurement in shear mode of the cured pressure-sensitive adhesive sheet, i.e., the glass transition temperature, is preferably 0°C or lower, more preferably -10°C or lower, even more preferably -15°C or lower, and particularly preferably -20°C or lower. The lower limit is usually -100°C. By setting the temperature within this range, a pressure-sensitive adhesive sheet with improved peel resistance at low temperatures and excellent low-temperature properties and impact resistance can be obtained.

[0043] The glass transition temperature (Tg) can be obtained by reading the temperature at which the loss tangent (Tanδ) reaches its maximum value, i.e., the peak temperature, from the dynamic viscoelasticity spectrum data in shear mode obtained in the same manner as in the measurement of the storage modulus (G') in shear mode described above.

[0044] <Gel fraction> The present pressure-sensitive adhesive sheet preferably has a gel fraction of 10% or more and 90% or less. A gel fraction of 10% or more prevents the PSA sheet from undergoing cohesive failure over time even when applied to a curved surface member, and allows the sheet to exhibit excellent curved surface application properties. From this perspective, the gel fraction is preferably 20% or more, more preferably 40% or more, and even more preferably 60% or more. On the other hand, from the viewpoint of conformability to unevenness when attached to a curved surface, the gel fraction is preferably 90% or less, more preferably 80% or less, and even more preferably 75% or less.

[0045] The adhesive sheet is also curable with active energy rays, and can be irradiated with active energy rays having a wavelength of 365 nm at an integrated light dose of 3000 mJ / cm. 2 When the composition is irradiated and cured, the gel fraction increases compared to before curing, and the gel fraction is preferably 70% or more and 95% or less, more preferably 73% or more and 90% or less, and even more preferably 78% or more and 85% or less. When the gel fraction after curing with active energy rays is within the above range, the pressure-sensitive adhesive sheet can be provided with shape stability and durability when used as a laminate for an image display device. Furthermore, the gel fraction after curing is preferably increased by 2% or more, more preferably 3% or more, and even more preferably 5% or more, as a difference in gel fraction, compared to before curing. When the difference in gel fraction before and after curing is within the above range, it tends to be possible to impart step-following ability and durability when used in an image display device.

[0046] In the present pressure-sensitive adhesive sheet, the gel fraction can be adjusted to the above range preferably by adjusting the composition or molecular weight of the (meth)acrylic polymer described below, by adjusting the type or amount of the crosslinking agent (B) or the photopolymerization initiator (C), or by adjusting the intensity or integrated amount of the active energy ray irradiated, although this is not limitative.

[0047] The pressure-sensitive adhesive sheet may have a single layer or multiple layers, but preferably has at least three layers, more preferably at least three layers consisting of an outermost layer, an innermost layer, and an intermediate layer, and particularly preferably has at least three layers in which the outermost layer and the innermost layer are acrylic pressure-sensitive adhesive layers. By using such a layer structure, a pressure-sensitive adhesive sheet with excellent lamination suitability, such as curved surface lamination ability and step-following ability, can be obtained.

[0048] When the pressure-sensitive adhesive sheet comprises at least three layers, namely, a surface layer, a back layer, and an intermediate layer, the surface layer, the back layer, and the intermediate layer (the layer sandwiched between the surface layer and the back layer) are preferably formed from a resin composition containing, particularly as a main component, a (meth)acrylic polymer of different composition. Such a layer configuration can effectively suppress wet heat whitening of the pressure-sensitive adhesive sheet. Furthermore, the surface layer and the back layer may be formed from a resin composition containing, particularly as a main component, a (meth)acrylic polymer of different composition, but are preferably formed from a resin composition containing a (meth)acrylic polymer of the same composition.

[0049] When the pressure-sensitive adhesive sheet has at least three layers (top layer / intermediate layer / rearmost layer) with the top layer and the rearmost layer being acrylic pressure-sensitive adhesive layers, the top layer and the rearmost layer (the surfaces to be attached to the components of the image display device) are preferably low Tg layers. The intermediate layer sandwiched between the top layer and the rearmost layer is preferably a high Tg layer. Furthermore, the low Tg layers used as the top layer and the rearmost layer may have different glass transition temperatures (Tg), but it is preferable that the top layer and the rearmost layer have the same glass transition temperature, and it is particularly preferable that the top layer and the rearmost layer be the same acrylic pressure-sensitive adhesive layer.

[0050] The low Tg layer refers to a layer in which the maximum value (glass transition temperature) of loss tangent (Tanδ) obtained by dynamic viscoelasticity measurement in the shear mode is usually −10°C or lower, preferably −100 to −15°C, and particularly preferably −50 to −20°C. The high Tg layer refers to a layer in which the maximum value (glass transition temperature) of the loss tangent (Tan δ) obtained by dynamic viscoelasticity measurement in the shear mode is usually higher than -10°C, preferably -5 to 20°C, and particularly preferably 0 to 15°C.

[0051] Furthermore, when the pressure-sensitive adhesive sheet has at least three layers, the outermost and innermost layers of which are acrylic pressure-sensitive adhesive layers, the ratio of the total thickness of the outermost and innermost layers to the total thickness is preferably 5 to 70%, more preferably 10 to 60%, and particularly preferably 20 to 45%. By setting the thicknesses of the outermost and innermost layers within the above ranges, a pressure-sensitive adhesive sheet can be obtained that has excellent durability and suitability for lamination, such as curved surface lamination and step absorbency. The thickness of the present pressure-sensitive adhesive sheet is preferably 50 to 1000 μm, more preferably 60 to 500 μm, and particularly preferably 75 to 300 μm.

[0052] This adhesive sheet is used to bond two components of image display devices, specifically, to bond components of image display devices such as liquid crystal displays (LCDs), plasma displays (PDPs) or electroluminescent displays (ELDs) found in personal computers, mobile terminals (PDAs), game consoles, televisions (TVs), car navigation systems, touch panels, pen tablets, etc.

[0053] More specifically, as for the above-mentioned image display device components, it is preferable that one of the two image display device components is glass and the other is film, and it is particularly preferable that the glass is tempered glass and the film is any one selected from the group consisting of a touch sensor, an image display panel, a surface protection panel, a polarizing film, and a retardation film, or a laminate consisting of a combination of two or more types. In recent years, image display panels such as liquid crystal displays (LCDs), plasma displays (PDPs) and electroluminescent displays (ELDs) have increasingly been using curved cover glass for design reasons. However, such cover glass is expensive, and it is important to minimize yield losses due to bonding errors. However, by using this adhesive sheet, which has excellent curved surface bonding properties, it can also be effectively used on curved cover glass.

[0054] Examples of the film include resin films containing one or more resins as the main component resin selected from polyester resins, polyolefin resins, (meth)acrylic resins, polyurethane resins, polyethersulfone resins, polycarbonate resins, polysulfone resins, polyether resins, polyetherketone resins, (meth)acrylonitrile resins, cycloolefin resins, epoxy resins, polyimide resins, cellulose resins, etc. In this case, the main component resin refers to the resin with the highest mass proportion among the resins constituting the resin film, and is a resin that accounts for 50 mass% or more, particularly 60 mass% or more, particularly 70 mass% or more, particularly 80 mass% or more, particularly 90 mass% or more, and particularly 95 mass% or more (including 100 mass%) of the resins constituting the resin film.

[0055] When an image display device component made of the above-mentioned resin film or the like is attached to a curved cover glass via an adhesive sheet, the resin film or the like is curved to fit the curved shape of the cover glass, and therefore the resin film is continuously subjected to a bending stress corresponding to the curved shape. As a result, the adhesive sheet is continuously subjected to a force that causes the resin film to return to a flat shape, i.e., a repulsive force, making it difficult to make the adhesive sheet follow the curved portion. Therefore, the key to providing curved surface attachment and durability after attachment is to improve the adhesive sheet's high adhesive strength, holding power, and peel resistance when a constant load is continuously applied, i.e., constant-load peel strength.

[0056] As described above, the present pressure-sensitive adhesive sheet having the above-mentioned properties preferably has an acrylic pressure-sensitive adhesive layer, and the acrylic pressure-sensitive adhesive layer is preferably formed from a resin composition containing an acrylic polymer. Furthermore, when the present pressure-sensitive adhesive sheet has three layers in which the outermost layer and the innermost layer are acrylic pressure-sensitive adhesive layers, the intermediate layer is also preferably formed from a resin composition containing an acrylic polymer. The resin compositions that form the acrylic pressure-sensitive adhesive layer and the intermediate layer will be described below.

[0057] The resin composition contains a (meth)acrylic polymer, preferably as a main component, and may further contain a crosslinking agent (B), a photopolymerization initiator (C), a silane coupling agent (D), a corrosion inhibitor (E), and other additives.

[0058] The term "main component" means that the resin composition contains 50% by mass or more, preferably 70% by mass or more, and more preferably 80% by mass or more of a (meth)acrylic polymer based on the entire resin composition.

[0059] [(Meth)acrylic polymer] The (meth)acrylic polymer may be, for example, a copolymer of an alkyl(meth)acrylate monomer having an alkyl group with 4 to 18 carbon atoms and a monomer component copolymerizable therewith.

[0060] Examples of the alkyl (meth)acrylate monomer having 4 to 18 carbon atoms in the alkyl group include linear alkyl (meth)acrylates such as n-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, n-octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, cetyl (meth)acrylate, and stearyl (meth)acrylate; isobutyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate; and isobutyl (meth)acrylate. Examples of suitable alicyclic (meth)acrylates include branched alkyl (meth)acrylates such as pentyl (meth)acrylate, neopentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, and isostearyl (meth)acrylate, as well as alicyclic (meth)acrylates such as cyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, 3,5,5-trimethylcyclohexane (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, and isobornyl (meth)acrylate. These may be used alone or in combination of two or more.

[0061] Examples of the monomer component copolymerizable with the alkyl(meth)acrylate monomer having 4 to 18 carbon atoms in the alkyl group include hydroxyl group-containing monomers, nitrogen atom-containing monomers, carboxy group-containing monomers, epoxy group-containing monomers, vinyl monomers, alkyl(meth)acrylate monomers having 1 to 3 carbon atoms in the alkyl group, and other copolymerizable monomers.

[0062] Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-1-methylethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, glycerin mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polyethylene glycol polypropylene glycol mono(meth)acrylate, polyethylene glycol polybutylene glycol mono(meth)acrylate, hydroxyphenyl (meth)acrylate, etc. These may be used alone or in combination of two or more.

[0063] Examples of the nitrogen atom-containing monomer include aminoalkyl (meth)acrylates such as aminomethyl (meth)acrylate, aminoethyl (meth)acrylate, aminopropyl (meth)acrylate, and aminoisopropyl (meth)acrylate, amino group-containing (meth)acrylate monomers such as N-alkylaminoalkyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and N,N-dimethylaminopropyl (meth)acrylate, and amide group-containing (meth)acrylate monomers such as (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 alone or in combination of two or more.

[0064] Examples of the carboxyl group-containing monomer include (meth)acrylic acid, (meth)acrylic acid dimer, etc. These may be used alone or in combination of two or more.

[0065] Examples of the epoxy group-containing monomer include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, etc. These may be used alone or in combination of two or more.

[0066] Examples of the vinyl monomer include (meth)acrylic acid alkyl esters in which the alkyl group has 1 to 12 carbon atoms, 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, vinyl propionate, and vinyl laurate, and aromatic vinyl monomers such as styrene, chlorostyrene, chloromethylstyrene, α-methylstyrene, and other substituted styrenes. These may be used alone or in combination of two or more.

[0067] Examples of the alkyl(meth)acrylate monomer in which the alkyl group has 1 to 3 carbon atoms include methyl(meth)acrylate, ethyl(meth)acrylate, n-propyl(meth)acrylate, i-propyl(meth)acrylate, etc. These may be used alone or in combination of two or more.

[0068] Examples of the other copolymerizable monomers include acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride, heterocyclic basic monomers such as vinylpyrrolidone, vinylpyridine and vinylcarbazole, macromonomers, etc. These may be used alone or in combination of two or more.

[0069] In the present invention, a (meth)acrylic polymer obtained by copolymerizing the above-mentioned various monomer components may be used so that the pressure-sensitive adhesive sheet has specific physical properties when made into a pressure-sensitive adhesive sheet, and the copolymerization method may be a conventionally known method, such as solution radical polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, etc.

[0070] In particular, when the present pressure-sensitive adhesive sheet has at least three layers, the outermost and innermost acrylic pressure-sensitive adhesive layers being the outermost and innermost acrylic pressure-sensitive adhesive layers, it is preferred that the outermost and innermost acrylic pressure-sensitive adhesive layers be formed from a resin composition containing a (meth)acrylic polymer (A) having a glass transition temperature of −10° C. or lower, and more preferably that the (meth)acrylic polymer contained in the resin composition consists solely of the (meth)acrylic polymer (A).

[0071] [(Meth)acrylic polymer (A)] The (meth)acrylic polymer (A) having a glass transition temperature of -10°C or less preferably contains substantially no structural units derived from carboxy group-containing monomers, and contains, as monomer components constituting the (meth)acrylic polymer (A), at least one polar group-containing monomer (a2) selected from the group consisting of hydroxy group-containing monomers and nitrogen atom-containing monomers, and a (meth)acrylate monomer (a1) other than (a2), which has a glass transition temperature (Tg) of -30°C or less when formed into a homopolymer from the monomer components.

[0072] The above phrase "substantially free of structural units derived from carboxyl group-containing monomers" not only refers to a case where the structural units are completely free of the monomers, but also includes a case where the (meth)acrylic polymer contains 0.5% by mass or less, preferably 0.1% by mass or less, of the carboxyl group-containing monomers.

[0073] Examples of the (meth)acrylate monomer (a1) having a glass transition temperature (Tg) of −30° C. or lower (preferably −40° C. or lower, particularly preferably −50° C. or lower) when a homopolymer is formed from the above monomer components include the aforementioned alkyl (meth)acrylate monomers having an alkyl group of 4 to 18 carbon atoms, which have a glass transition temperature of −30° C. or lower. Specific examples include linear alkyl (meth)acrylate monomers such as n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-heptyl acrylate, n-hexyl acrylate, n-octyl acrylate, nonyl acrylate, lauryl methacrylate, and stearyl methacrylate; and branched alkyl (meth)acrylate monomers such as 2-ethylhexyl acrylate, isononyl acrylate, and isodecyl acrylate. These may be used alone or in combination of two or more. Among these, branched alkyl (meth)acrylates are preferred, with 2-ethylhexyl acrylate being particularly preferred.

[0074] Examples of the polar group-containing monomer (a2) include the above-mentioned hydroxyl group-containing monomers and nitrogen atom-containing monomers, of which hydroxyl group-containing monomers are preferred, with 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate being particularly preferred.

[0075] Furthermore, as the copolymerization component of the (meth)acrylic polymer (A), a monomer other than the above-mentioned monomers (a1) and (a2) can be used. As the monomer other than the above-mentioned monomers (a1) and (a2), the various monomers mentioned above can be used, and among them, it is preferable to use an alkyl(meth)acrylate having an alkyl group with 1 to 3 carbon atoms, and it is particularly preferable to use methyl(meth)acrylate.

[0076] The glass transition temperature of the (meth)acrylic polymer (A) obtained by copolymerizing these is preferably -10°C or lower, more preferably -100 to -15°C, particularly preferably -50 to -20°C, from the viewpoint of level difference absorbability and lamination reliability.

[0077] In the present invention, the glass transition temperature (Tg) of the acrylic polymer (A) can be determined by reading the temperature at which the loss tangent (loss modulus G" / storage modulus G'=tanδ) becomes maximum when the dynamic viscoelasticity is measured in a shear mode at a frequency of 1 Hz using a dynamic viscoelasticity measuring device.

[0078] The weight average molecular weight of the (meth)acrylic polymer (A) is preferably from 50,000 to 1,500,000, more preferably from 100,000 to 700,000, and particularly preferably from 150,000 to 600,000.

[0079] In this specification, the weight average molecular weight is measured by the following method. A measurement sample is prepared by dissolving 4 mg of a (meth)acrylic polymer in 12 mL of THF, and a molecular weight distribution curve is measured under the following conditions using a gel permeation chromatography (GPC) analyzer (Tosoh Corporation, HLC-8320GPC) to determine the weight average molecular weight (Mw). Guard column: TSKguardcolumnHXL Separation column: TSKgel GMHXL (4 columns) ·Temperature: 40℃ ·Injection volume: 100μL Polystyrene equivalent Solvent: THF ·Flow rate: 1.0mL / min

[0080] The hydroxyl value of the (meth)acrylic polymer (A) is usually from 20 to 150 mgKOH / g, preferably from 30 to 100 mgKOH / g, and more preferably from 40 to 80 mgKOH / g.

[0081] Furthermore, as described above, when the pressure-sensitive adhesive sheet has at least three layers, the outermost and innermost layers of which are acrylic pressure-sensitive adhesive layers, it is preferable that the outermost and innermost layers and the intermediate layer (the layer sandwiched between the outermost and innermost layers) are formed from a resin composition containing, preferably as a main component, a (meth)acrylic polymer having a different composition. By using such a layer configuration, it is possible to effectively suppress wet heat whitening of the pressure-sensitive adhesive sheet. Among these, the intermediate layer is preferably formed from a resin composition containing an acrylic polymer (A') having a glass transition temperature higher than -10°C, and more preferably, the (meth)acrylic polymer contained in the resin composition consists solely of the (meth)acrylic polymer (A').

[0082] [(Meth)acrylic polymer (A')] The (meth)acrylic polymer (A') having a glass transition temperature higher than -10°C preferably contains, as monomer components constituting the (meth)acrylic polymer (A'), at least one polar group-containing monomer (a2) selected from the group consisting of hydroxyl group-containing monomers and nitrogen atom-containing monomers, and an alkyl (meth)acrylate monomer (a3) ​​in which the alkyl group has 1 to 18 carbon atoms.

[0083] Examples of the polar group-containing monomer (a2) include the aforementioned hydroxyl group-containing monomers and nitrogen atom-containing monomers, of which nitrogen atom-containing monomers are preferred, amide group-containing monomers are more preferred, and (meth)acrylamide is particularly preferred.

[0084] Examples of the alkyl(meth)acrylate monomer (a3) ​​having an alkyl group of 1 to 18 carbon atoms include the alkyl(meth)acrylate monomer having an alkyl group of 4 to 18 carbon atoms and the alkyl(meth)acrylate monomer having an alkyl group of 1 to 3 carbon atoms, of which methyl(meth)acrylate, ethyl(meth)acrylate, n-propyl(meth)acrylate, isopropyl(meth)acrylate, n-butyl(meth)acrylate, isobutyl(meth)acrylate, t-butyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, lauryl(meth)acrylate, tridecyl(meth)acrylate, and isobornyl(meth)acrylate are particularly preferred. Furthermore, from the viewpoints of versatility of the monomer and achieving a Tg of −10° C. or higher for the (meth)acrylic polymer (A′), methyl(meth)acrylate, ethyl methacrylate, t-butyl(meth)acrylate, isobutyl methacrylate, and isobornyl(meth)acrylate are even more preferred.

[0085] Furthermore, as a copolymerization component of the (meth)acrylate polymer (A'), a monomer other than the above-mentioned monomers (a2) and (a3) ​​can be used. As the monomer other than the above-mentioned monomers (a2) and (a3), the various monomers described above can be used.

[0086] The glass transition temperature of the (meth)acrylic polymer (A') obtained by copolymerizing these is preferably higher than -10°C, more preferably from -5 to 20°C, particularly preferably from 0 to 15°C, from the viewpoint of reworkability.

[0087] The weight average molecular weight of the (meth)acrylic polymer (A') is preferably 50,000 or more and 1,000,000 or less, more preferably 70,000 or more and 700,000 or less, and even more preferably 100,000 or more and 500,000 or less.

[0088] [Crosslinking agent (B)] The resin composition forming each layer may contain a crosslinking agent (B) in addition to the (meth)acrylic polymer. In particular, it is preferable to blend the crosslinking agent (B) into the resin composition forming the intermediate layer of the pressure-sensitive adhesive sheet.

[0089] The crosslinking agent (B) is preferably a crosslinking agent having at least a double bond crosslink. For example, a crosslinking agent having at least one crosslinkable functional group selected from (meth)acryloyl group, epoxy group, isocyanate group, carboxy group, hydroxy group, carbodiimide group, oxazoline group, aziridine group, vinyl group, amino group, imino group, and amide group can be used. One or more crosslinking agents may be used in combination. Also included is an embodiment in which the crosslinking agent (B) is chemically bonded to the (meth)acrylic polymer.

[0090] Among these, crosslinking agents having a (meth)acryloyl group are preferred, and polyfunctional (meth)acrylates are particularly preferred in terms of achieving lamination suitability and reliability. Here, "polyfunctional" refers to those having two or more crosslinkable functional groups. It is also possible to have three or more, or four or more crosslinkable functional groups as necessary. Furthermore, the crosslinkable functional groups may be protected with deprotectable protecting groups.

[0091] Examples of the polyfunctional (meth)acrylate 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 polyprop ... Tris(meth)acrylate, bisphenol F polyethoxydi(meth)acrylate, ethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane trioxyethyl(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 tetra(meth)acrylate, propoxylated pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, tris(acryloxyethyl) isocyanurate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, tripentaerythritol UV-curable polyfunctional (meth)acrylic monomers such as erythritol hexa(meth)acrylate, tripentaerythritol penta(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, di(meth)acrylate of hydroxypivalic acid neopentyl glycol adduct ε-caprolactone, trimethylolpropane tri(meth)acrylate, trimethylolpropane polyethoxy tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, as well as polyester(meth)acrylate,Examples of suitable polyfunctional (meth)acrylic oligomers include epoxy (meth)acrylate, urethane (meth)acrylate, and polyether (meth)acrylate. These may be used alone or in combination of two or more. Among these, propoxylated pentaerythritol tri(meth)acrylate and polypropylene glycol di(meth)acrylate are preferred.

[0092] The content of the crosslinking agent (B) is usually 0.5 to 50 parts by mass, preferably 1 to 40 parts by mass, and particularly preferably 5 to 30 parts by mass, relative to 100 parts by mass of the (meth)acrylic polymer. If the content is within the above range, it is preferable because proper lamination and reliability are easily obtained.

[0093] [Photopolymerization initiator (C)] The resin composition preferably contains a photopolymerization initiator (C). As the photopolymerization initiator (C), any currently known initiator can be used as appropriate, and among them, a photopolymerization initiator that is sensitive to ultraviolet light having a wavelength of 380 nm or less is preferred from the viewpoint of ease of control of the crosslinking reaction.

[0094] Photopolymerization initiators (C) are broadly classified into two types based on the radical generation mechanism: cleavage-type photopolymerization initiators that can generate radicals by cleaving and decomposing the single bond of the photopolymerization initiator itself, and hydrogen abstraction-type photopolymerization initiators that form an exciplex between the photoexcited photopolymerization initiator and the hydrogen donor in the system and can transfer hydrogen from the hydrogen donor.

[0095] The cleavage-type photopolymerization initiator is preferably used because it decomposes into a different compound when it generates radicals upon irradiation with light, and once excited, it no longer functions as a reaction initiator. Therefore, it does not remain as an active species in the cured product such as an adhesive after the crosslinking reaction is completed, and there is no possibility of causing unexpected photodegradation of the cured product. On the other hand, hydrogen abstraction photopolymerization initiators do not produce decomposition products, unlike cleavage photopolymerization initiators, during a radical-generating reaction upon irradiation with active energy rays such as ultraviolet rays. Therefore, they are less likely to become volatile components after the reaction is completed, and are therefore useful in that they can reduce damage to the adherend.

[0096] Examples of the cleavage-type photopolymerization initiator include 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxycyclohexyl phenyl 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)propan-1-one, Examples of suitable methyl phenylglyoxylates include 2-benzyl-2-dimethylamino-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, and derivatives thereof. Among these, oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone) is preferred.

[0097] Examples of the hydrogen abstraction photopolymerization initiator include benzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, 3,3'-dimethyl-4-methoxybenzophenone, methyl 2-benzoylbenzoate, methyl benzoylformate, 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 derivatives thereof. Among these, 4-methylbenzophenone and 2,4,6-trimethylbenzophenone are preferred.

[0098] The photopolymerization initiator (C) is not limited to the substances listed above. The photopolymerization initiator (C) may be either a cleavage-type photopolymerization initiator or a hydrogen-abstraction-type photopolymerization initiator, or a combination of both.

[0099] The content of the photopolymerization initiator (C) is not particularly limited, but is usually 0.1 to 10 parts by mass, preferably 0.2 to 5 parts by mass, and particularly preferably 0.3 to 3 parts by mass, per 100 parts by mass of the (meth)acrylic polymer. By setting the content of the photopolymerization initiator (C) within the above range, it is possible to obtain an appropriate reaction sensitivity to active energy rays.

[0100] [Silane coupling agent (D)] The resin composition preferably contains a silane coupling agent (D) to enhance adhesion to components of an image display device, particularly glass. In particular, the silane coupling agent (D) is preferably contained in a resin composition that forms an acrylic pressure-sensitive adhesive layer that contacts the double-sided pressure-sensitive adhesive sheet with the components of an image display device.

[0101] Examples of the silane coupling agent (D) include compounds having unsaturated groups such as vinyl groups, acryloxy groups, and methacryloxy groups, amino groups, epoxy groups, and the like, as well as hydrolyzable functional groups such as alkoxy groups.

[0102] Examples of the silane coupling agent (D) include N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-methacryloxypropyltrimethoxysilane. These may be used alone or in combination of two or more. Among these, 3-glycidoxypropyltrimethoxysilane is preferred because of its good adhesion to components of the image display device and its reduced discoloration, such as yellowing.

[0103] The content of the silane coupling agent (D) is preferably 0.01 to 5 parts by mass, particularly preferably 0.2 to 3 parts by mass, per 100 parts by mass of the (meth)acrylic polymer.

[0104] Similar to the silane coupling agent (D), a coupling agent such as an organic titanate compound can also be effectively used.

[0105] [Metal corrosion inhibitor (E)] The resin composition also preferably contains a metal corrosion inhibitor (E). In particular, the metal corrosion inhibitor (E) is preferably contained in a resin composition that forms an acrylic pressure-sensitive adhesive layer that contacts the image display device component of the double-sided pressure-sensitive adhesive sheet.

[0106] Examples of the metal corrosion inhibitor (E) include benzotriazole compounds, benzimidazole compounds, benzothiazole compounds, and other triazole derivatives.

[0107] The metal corrosion inhibitor (E) is preferably at least one selected from benzotriazole compounds, 1,2,3-triazole, and 1,2,4-triazole. Among these, triazole derivatives such as 1,2,3-triazole and 1,2,4-triazole are preferred, with 1,2,3-triazole being particularly preferred, as they are excellent in reliability as double-sided PSA sheets in addition to metal corrosion prevention properties.

[0108] From the viewpoints of preventing bleed-out of the metal corrosion inhibitor and the metal corrosion inhibitory effect, the content of the metal corrosion inhibitor (E) is preferably 0.01 to 5 parts by mass, more preferably 0.03 to 1 part by mass, and particularly preferably 0.05 to 0.5 parts by mass, relative to 100 parts by mass of the (meth)acrylic polymer.

[0109] [Other additives] The resin composition may contain other additives in addition to the above components. Examples of the other additives include various additives such as light stabilizers, ultraviolet absorbers, metal deactivators, antioxidants, antistatic agents, moisture absorbers, foaming agents, antifoaming agents, inorganic particles, viscosity modifiers, tackifier resins, photosensitizers, and fluorescent agents, as well as reaction catalysts (such as tertiary amine compounds, quaternary ammonium compounds, and tin laurate compounds). These may be used alone or in combination of two or more. In addition, other known components that are usually blended in resin compositions that form pressure-sensitive adhesives may also be appropriately contained.

[0110] The resin composition can be obtained by mixing a (meth)acrylic polymer, optionally a crosslinking agent (B), a photopolymerization initiator (C), a silane coupling agent (D), a metal corrosion inhibitor (E), and other additives in predetermined amounts. The mixing method is not particularly limited, and the order in which the components are mixed is also not particularly limited. A heat treatment step may be included in the production of the resin composition. In this case, it is desirable to mix the components of the resin composition in advance and then perform the heat treatment. In the above-mentioned mixing, a masterbatch made by concentrating the various mixed components may be used.

[0111] As mentioned above, the mixing method is not particularly limited, and for example, a universal kneader, a planetary mixer, a Banbury mixer, a kneader, a gate mixer, a pressure kneader, a three-roll mill, a two-roll mill, etc. can be used. When mixing the components of the resin composition, a solvent may be used as needed. The resin composition can also be used as a solvent-free system that does not contain a solvent. Using a solvent-free system has the advantage that no solvent remains, thereby improving heat resistance and light resistance.

[0112] [Manufacturing method of adhesive sheet] The following describes a method for producing the present pressure-sensitive adhesive sheet, but is not limited to this method. The present pressure-sensitive adhesive sheet may be a single layer or multiple layers, but preferably has a multiple-layer structure, and more preferably has at least three layers, with the outermost and innermost layers being acrylic pressure-sensitive adhesive layers. The present pressure-sensitive adhesive sheet is preferably produced as a pressure-sensitive adhesive sheet with a release film, typically by the following steps, having a structure in which the present pressure-sensitive adhesive sheet and a release film are laminated together. Note that the pre-curing step described below may be omitted. The release film may be laminated on only one side of the pressure-sensitive adhesive sheet, or on both sides.

[0113] As the material for such a release film, any known release film can be used appropriately. As the material for the release film, for example, a film such as a polyester film, a polyolefin film, a polycarbonate film, a polystyrene film, an acrylic film, a triacetyl cellulose film, or a fluororesin film that has been coated with a silicone resin to provide a release treatment, or release paper, etc. can be appropriately selected and used. The release film may have other layers, such as an antistatic layer, a hard coat layer, or an anchor layer, as needed.

[0114] When release films are laminated on both sides of the present pressure-sensitive adhesive sheet, one release film may have the same layer structure or material as the other release film, or a different layer structure or material, and may have the same or different thicknesses. Furthermore, release films with different peel strengths or thicknesses can be laminated on both sides of the pressure-sensitive adhesive sheet.

[0115] The thickness of the release film is not particularly limited, but from the viewpoint of processability and handleability, it is preferably 10 to 250 μm, more preferably 25 to 200 μm, and even more preferably 35 to 190 μm.

[0116] As a method for producing the present pressure-sensitive adhesive sheet, when the present pressure-sensitive adhesive sheet is a single layer, for example, the resin composition is heated and melted (hot melt), and then coated on a release film, and then sandwiched between other release films and heated, thereby obtaining a pressure-sensitive adhesive sheet with a release film. When the present pressure-sensitive adhesive sheet is a multi-layered sheet, a pressure-sensitive adhesive sheet with a release film in the number corresponding to the layers required for the pressure-sensitive adhesive sheet is prepared by the above method, and the release films are peeled off and the pressure-sensitive adhesive sheets are laminated, thereby obtaining a pressure-sensitive adhesive sheet with a multi-layered configuration.

[0117] When the pressure-sensitive adhesive sheet has a multilayer structure, the above-mentioned resin composition is applied to a release sheet to form a pressure-sensitive adhesive layer, and then another resin composition is applied to the formed pressure-sensitive adhesive layer to form a resin layer, and so on. A pressure-sensitive adhesive sheet with a multilayer structure can also be produced by repeating this process. Instead of using the release sheet, the resin composition may be applied to an adherend to form a pressure-sensitive adhesive sheet. Furthermore, the pressure-sensitive adhesive sheet can also be produced by a method in which multiple layers are simultaneously formed by multilayer coating or co-extrusion molding of the resin composition.

[0118] The pressure-sensitive adhesive sheet can also be formed by, for example, pouring the resin composition into a mold, without using a release film or adherend as described above. Furthermore, the present pressure-sensitive adhesive sheet can also be realized by directly filling the resin composition between the adherend, that is, the constituent members of an image display device.

[0119] The obtained pressure-sensitive adhesive sheet is preferably pre-cured by crosslinking with active energy rays so as to have latent active energy ray reactivity, in other words, so as to retain active energy ray reactivity. When pre-curing, each layer may be crosslinked with active energy rays by irradiating with active energy rays through the release film. In this case, it is possible to adjust the degree of active energy ray crosslinking (gel fraction) by controlling the amount of active energy ray irradiation, but as mentioned above, it is also possible to adjust the degree of active energy ray crosslinking (gel fraction) by irradiating with ultraviolet rays through the release film so as to partially block the active energy rays.

[0120] The pressure-sensitive adhesive sheet thus obtained is an optically transparent pressure-sensitive adhesive sheet. Here, "optically transparent" means that the total light transmittance is 80% or more, preferably 85% or more, and more preferably 90% or more. The haze value of the pressure-sensitive adhesive sheet is preferably 10% or less, more preferably 5% or less, and particularly preferably 3% or less.

[0121] This pressure-sensitive adhesive sheet is usually distributed in the form of a pressure-sensitive adhesive sheet with release films, in which the acrylic pressure-sensitive adhesive layers on both sides are sandwiched between release films. When using the double-sided pressure-sensitive adhesive sheet, the release films are peeled off from the acrylic pressure-sensitive adhesive layer, and the acrylic pressure-sensitive adhesive layer is attached to a component for image display.

[0122] [Laminate for image display device] A laminate for constituting an image display device (referred to as "the present laminate for the image display device") as an example of an embodiment of the present invention has a configuration in which two components of the image display device are laminated together via the present adhesive sheet. It is preferable that one of the two image display device components is a cover glass having a curved surface, and the other is a component consisting of one or a combination of two or more of the following: a touch sensor, an image display panel, a surface protection film, an anti-reflection film, a color filter, a polarizing film, and a retardation film. With the above configuration, the effects of the present invention can be particularly enjoyed.

[0123] [Image display device] An image display device according to an embodiment of the present invention is an image display device that uses the present laminate for an image display device. An example of the present image display device is an image display device having a structure in which the present laminate for an image display device is combined with other components of the image display device. In this case, examples of "other components of the image display device" include FPC cables, reflective sheets, light guide plates and light sources, diffusion films, prism sheets, liquid crystal panels, organic EL panels, anti-reflection films, color filters, polarizing plates, retardation plates, glass substrates, surface protection films, and integrated composites of these components.

[0124] Specific examples of the image display device include liquid crystal displays, organic EL displays, inorganic EL displays, electronic paper, plasma displays, and microelectromechanical system (MEMS) displays used in personal computers, mobile terminals (PDAs), game consoles, televisions (TVs), car navigation systems, touch panels, pen tablets, etc.

[0125] (Explanation of terms, etc.) In general, a "sheet" is defined in JIS as a thin, flat product whose thickness is small relative to its length and width, and a "film" is generally a thin, flat product whose thickness is extremely small compared to its length and width and whose maximum thickness is arbitrarily limited, and is usually supplied in the form of a roll (Japanese Industrial Standard JISK6900). However, the boundary between sheet and film is unclear, and there is no need to distinguish between the two in the present invention. Therefore, in the present invention, when the term "film" is used, it is intended to include "sheet," and when the term "sheet" is used, it is intended to include "film." Furthermore, when the term "panel" is used, such as an image display panel or a protective panel, it encompasses a plate, a sheet, and a film.

[0126] In this specification, when it is written "x to y" (x and y are any numbers), unless otherwise specified, it means "greater than x and less than y", as well as "preferably greater than x" and "preferably smaller than y". Furthermore, when it is stated that the amount is "x or more" (x is any number), unless otherwise specified, it includes the meaning of "x or more" as well as "preferably greater than x", and when it is stated that the amount is "y or less" (y is any number), it includes the meaning of "y or less" as well as "preferably less than y" unless otherwise specified. [Example]

[0127] The present invention will be explained in more detail below with reference to examples and comparative examples, but it should be understood that the present invention is not limited to these examples.

[0128] First, the raw materials of the resin compositions prepared in the examples will be described in detail.

[0129] <(Meth)acrylic polymer> (Meth)acrylic polymer (A-1): an acrylic polymer consisting of 2-ethylhexyl acrylate, methyl acrylate, and 2-hydroxyethyl acrylate (weight average molecular weight: 430,000, Tg: -25°C, hydroxyl value: 67 mgKOH / g) (Meth)acrylic polymer (A'-1): a (meth)acrylic polymer consisting of 2-ethylhexyl acrylate / methyl acrylate / acrylamide / methyl methacrylate / isobornyl methacrylate (weight average molecular weight: 250,000, Tg: 4°C) (Meth)acrylic polymer (A'-2): an acrylic polymer consisting of methyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, and 2-hydroxyethyl acrylate (weight average molecular weight: 540,000, Tg: 1°C, hydroxyl value: 62 mgKOH / g)

[0130] The weight average molecular weight, glass transition temperature (Tg) and hydroxyl value of the (meth)acrylic polymer were measured by the following methods.

[0131] [Weight average molecular weight] The weight-average molecular weight of the (meth)acrylic polymer was measured using a gel permeation chromatography (GPC) analyzer (HLC-8320GPC, manufactured by Tosoh Corporation). Specifically, 4 mg of the (meth)acrylic polymer was dissolved in 12 mL of THF to prepare a measurement sample, and the molecular weight distribution curve was measured under the following conditions to determine the weight-average molecular weight (Mw). Guard column: TSKguardcolumnHXL Separation column: TSKgel GMHXL (4 columns) ·Temperature: 40℃ ·Injection volume: 100μL Polystyrene equivalent Solvent: THF ·Flow rate: 1.0mL / min

[0132] [Glass transition temperature (Tg)] The glass transition temperature (Tg) of the (meth)acrylic polymer was measured using a rheometer (Discovery HR2, manufactured by TA Instruments). Specifically, for a (meth)acrylic polymer with a thickness of 0.6 to 0.8 mm, the dynamic viscoelasticity spectrum was measured over a temperature range of −120 to 200°C under the following conditions: jig: Φ8 mm parallel plates, strain: 0.1%, frequency: 1 Hz, temperature: −120 to 200°C, and heating rate: 5°C / min. From the obtained data, the temperature at which the loss tangent (Tan δ) reached its maximum value was read, thereby determining the glass transition temperature (Tg).

[0133] [Hydroxyl value] The hydroxyl value of the (meth)acrylic polymer was measured by neutralization titration. A 2g sample was placed in an Erlenmeyer flask, and 10mL of a 1:13 mixture of acetic anhydride and pyridine was added using a volumetric pipette. Then, 10mL of toluene was added. An air cooling tube was attached to the top of the Erlenmeyer flask, and the mixture was heated at 95°C for 90 minutes. After heating, 10mL of toluene and 10mL of pure water were added, and the mixture was allowed to cool with stirring until it reached room temperature (23°C). A few drops of phenolphthalein solution were then added, and titration was performed with 0.1mol / L potassium hydroxide (KOH) solution. A blank test was also performed in the same manner as above, but without placing a sample in the Erlenmeyer flask. The hydroxyl value was calculated using the following formula (1): (calculation formula) Hydroxyl value = 5.611 × (amount of potassium hydroxide solution used in the blank test (mL) – amount of potassium hydroxide solution used in the titration (mL)) × f / amount of sample taken (g) + acid value (1) f: Factor of 0.1 mol / L potassium hydroxide solution

[0134] [Acid value] The acid value was measured by the following method. Y g of acrylic copolymer was placed in a beaker and dissolved in a mixed solvent of toluene:methanol = 7:3. After dissolution, an appropriate amount of phenolphthalein was added, and while stirring with a stirrer, titration was performed with a 0.1 mol / L KOH solution. The amount of KOH solution at the point when the solution turned light pink (X mL) was read as the endpoint, and the acid value was calculated based on the following formula (2). (calculation formula) Acid value (mgKOH / g)=X×(f×M×56.1) / Y (2) f: Factor of KOH solution M: Molar concentration (mol / L) ·X:KOH solution volume (mL) Y: Sample amount (g) When the acid value was low, a 0.01 mol / L KOH solution was used to improve accuracy.

[0135] <Crosslinking agent (B)> Crosslinking agent (B-1): Propoxylated pentaerythritol triacrylate Crosslinking agent (B-2): Polypropylene glycol #400 diacrylate

[0136] <Photopolymerization initiator (C)> Photopolymerization initiator (C-1): A mixture of 2,4,6-trimethylbenzophenone and 4-methylbenzophenone (IGM "Esacure TZT")

[0137] <Silane coupling agent (D)> Silane coupling agent (D-1): 3-glycidoxypropyltrimethoxysilane

[0138] Example 1 Resin composition 1 was prepared by uniformly melt-kneading 1 kg of the (meth)acrylic polymer (A'-1), 100 g of the crosslinking agent (B-1), and 5 g of the photopolymerization initiator (C-1). The above resin composition 1 was sandwiched between two release-treated polyethylene terephthalate films (Diafoil MRF (thickness 75 μm) manufactured by Mitsubishi Chemical Corporation / Diafoil MRT (thickness 38 μm) manufactured by Mitsubishi Chemical Corporation), i.e., two release films, and shaped into a sheet at a temperature of 80°C to a thickness of 67 μm, to produce an intermediate layer sheet (1-1).

[0139] Resin composition 2 was prepared by uniformly melt-kneading 1 kg of the (meth)acrylic polymer (A-1), 15 g of the photopolymerization initiator (C-1), and 2 g of the silane coupling agent (D-1). The above resin composition 2 was sandwiched between two release-treated polyethylene terephthalate films (Diafoil MRF (thickness 75 μm) manufactured by Mitsubishi Chemical Corporation / Diafoil MRT (thickness 38 μm) manufactured by Mitsubishi Chemical Corporation), i.e., two release films, and shaped into a sheet at a temperature of 80°C to a thickness of 16.5 μm, to produce two adhesive sheets (2-1) for the outermost layer and the innermost layer (outermost and innermost layers).

[0140] The intermediate layer sheet (1-1), from which the release films on both sides had been peeled off, was attached to the adhesive surface of the outermost / backside layer adhesive sheet (2-1), from which the release film on one side had been peeled off, to produce a laminate having a layer structure of (2-1) / (1-1) / (2-1). Through the release film remaining on the surface of the outermost backing layer adhesive sheet (2-1), an integrated light intensity of 1000 mJ / cm at a wavelength of 365 nm is applied. 2 The adhesive sheet with release film of Example 1 (preliminarily cured product) was prepared by irradiating the adhesive sheet with release film with light from a high-pressure mercury lamp so that the adhesive sheet had a viscosity of 1000 ppm or less. The pressure-sensitive adhesive sheet of Example 1 was a sheet that had potential for photocuring by light irradiation and was active energy ray-curable.

[0141] <Examples 2 and 3> Pressure-sensitive adhesive sheets with release films (pre-cured products) of Examples 2 and 3 were produced in the same manner as in Example 1, except that the formulation, thickness configuration, and pre-curing conditions shown in Table 1 were used. The pressure-sensitive adhesive sheets of Examples 2 and 3 were sheets that had the ability to be photocured by light irradiation and were active energy ray-curable.

[0142] Example 4 Resin composition 5 was prepared by uniformly melt-kneading 1 kg of (meth)acrylic polymer (A'-2), 80 g of crosslinking agent (B-2), 10 g of photopolymerization initiator (C-1) and 1 g of silane coupling agent (D-1). The above resin composition 5 was sandwiched between two release-treated polyethylene terephthalate films (Diafoil MRF (thickness 75 μm) manufactured by Mitsubishi Chemical Corporation / Diafoil MRT (thickness 38 μm) manufactured by Mitsubishi Chemical Corporation), i.e., two release films, and shaped into a sheet at a temperature of 80°C to a thickness of 100 μm. Through the release film on the surface, the cumulative light intensity of 365 nm is 1000 mJ / cm 2 The adhesive sheet with release film of Example 4 (preliminarily cured product) was prepared by irradiating the adhesive sheet with release film with light from a high-pressure mercury lamp so that the adhesive sheet had a viscosity of 1000 ppm or less. The pressure-sensitive adhesive sheet of Example 4 was a sheet that had potential for photocuring by light irradiation and was active energy ray-curable.

[0143] <Comparative Examples 1 to 3> Pressure-sensitive adhesive sheets with release films of Comparative Examples 1 to 3 were produced in the same manner as in Example 1, except that the formulations shown in Table 1 were used. The pressure-sensitive adhesive sheets of Comparative Examples 1 to 3 were sheets that had potential for photocuring by light irradiation and had active energy ray curability.

[0144] <Adhesive sheet physical property evaluation> The physical properties of the pressure-sensitive adhesive sheets of Examples 1 to 4 and Comparative Examples 1 to 3 obtained above were measured as follows.

[0145] [Adhesive strength] One release film was peeled off from each of the release film-attached pressure-sensitive adhesive sheets of Examples 1 to 4 and Comparative Examples 1 to 3, and a 100 μm thick polyethylene terephthalate film (Cosmoshine A4300, manufactured by Toyobo Co., Ltd.) was attached as a backing film to prepare a laminate. The laminate was cut to a length of 150 mm and a width of 10 mm, and the remaining release film was then peeled off to expose the adhesive surface, which was then roll-pressed onto a soda lime glass with a hand roller, and the adhesive sheet was then autoclaved (temperature 60°C, gauge pressure 0.2 MPa, 20 minutes) to finish adhesion. The adhesive strength measurement sample was peeled off from glass at a peel angle of 180° and a peel speed of 300 mm / min in an environment of 23° C. and 50% RH, and the peel strength (N / cm) was measured.

[0146] [Adhesive strength after curing] One release film was peeled off from each of the release film-attached pressure-sensitive adhesive sheets of Examples 1 to 4 and Comparative Examples 1 to 3, and a 100 μm thick polyethylene terephthalate film (Cosmoshine A4300, manufactured by Toyobo Co., Ltd.) was attached as a backing film to prepare a laminate. The laminate was cut to a length of 150 mm and a width of 10 mm, after which the remaining release film was peeled off and the exposed adhesive surface was roll-pressed onto a soda lime glass by rolling a hand roller back and forth once to adhere the adhesive sheet to the glass. The glass was then autoclaved (temperature 60°C, gauge pressure 0.2 MPa, 20 minutes) to finish adhesion, and ultraviolet light of 365 nm was irradiated from the backing film surface using a high-pressure mercury lamp at an integrated light intensity of 3000 mJ / cm. 2 After irradiation so as to obtain the above, the sample was cured at a temperature of 23°C and a humidity of 50% RH for 12 hours to prepare a sample for measuring adhesive strength after curing. The adhesive strength measurement sample after curing was peeled off at a peel angle of 180° and a peel speed of 300 mm / min in an environment of 23° C. and 50% RH, and the peel strength (N / cm) from glass was measured.

[0147] [Holding force] One of the release films was peeled off from the adhesive sheets with release films of Examples 1 to 4 and Comparative Examples 1 to 3, and a 38 μm thick polyethylene terephthalate (PET) film (Diafoil S100, manufactured by Mitsubishi Chemical Corporation) was attached as a backing film to prepare a laminate. The above laminate was cut to a length of 150 mm and a width of 20 mm, and then the remaining release film was peeled off to expose the adhesive surface, which was then attached to a polished stainless steel plate (SUS304) with an adhesive area of ​​20 mm x 20 mm to prepare a sample for measuring holding power. This holding power measurement sample was preheated at 70°C for 15 minutes, then a 0.5 kg weight was placed on it and it was held at 70°C for 30 minutes, and the slippage length (mm) of the adhesive sheet was measured.

[0148] [Retention power after curing] The adhesive sheets with release films of Examples 1 to 4 and Comparative Examples 1 to 3 were irradiated with an integrated light intensity of 3000 mJ / cm at a wavelength of 365 nm. 2 The adhesive sheet was irradiated with light from a high-pressure mercury lamp through a release film to photo-cure the adhesive sheet, thereby preparing a cured adhesive sheet. After the adhesive sheet was cured, one of the release films was peeled off, and a 38 μm thick polyethylene terephthalate (PET) film (Diafoil S100, manufactured by Mitsubishi Chemical Corporation) was attached as a backing film to prepare a laminate. The laminate was cut to a length of 150 mm and a width of 20 mm, and the remaining release film was then peeled off to expose the adhesive surface, which was then attached to a polished stainless steel plate (SUS304) with an adhesive area of ​​20 mm x 20 mm to prepare a sample for measuring holding power after curing. This post-curing holding power measurement sample was preheated at 70°C for 15 minutes, then a 0.5 kg weight was placed on it and it was held at 70°C for 30 minutes, and the slippage length (mm) of the adhesive sheet was measured.

[0149] [Constant load peeling] One release film was peeled off from each of the release film-attached pressure-sensitive adhesive sheets of Examples 1 to 4 and Comparative Examples 1 to 3, and a 100 μm thick polyethylene terephthalate film (Cosmoshine A4300, manufactured by Toyobo Co., Ltd.) was attached as a backing film to prepare a laminate. The laminate was cut to a length of 150 mm and a width of 10 mm, and the remaining release film was peeled off to expose a 10 mm wide and 100 mm long region of the adhesive surface, which was then pressed against soda lime glass with a hand roller, forming a bonded region, while the area of ​​the adhesive sheet other than the bonded region was formed into a non-bonded region. The laminate was then autoclaved (temperature 50°C, gauge pressure 0.2 MPa, 20 minutes), and then cured at 40°C for 30 minutes to form a finished bonded sample, which was used for the constant-load peel test. Using this sample, soda-lime glass was fixed horizontally so that the non-bonded area of ​​the adhesive sheet hung down in an environment of 23°C and 50% RH, and a load of 0.45 N was applied to the longitudinal end of the non-bonded area of ​​the adhesive sheet for 30 minutes. The distance by which the bonded area of ​​the adhesive sheet peeled off from the soda-lime glass during this time was measured as the constant-load peel distance (see Figure 1).

[0150] [Ball Tuck] Measurement was carried out at a temperature of 23°C and an inclination angle of 30° based on the inclined ball tack test specified in JIS Z 0237:2009. Specifically, the pressure-sensitive adhesive sheets with release films of Examples 1 to 4 and Comparative Examples 1 to 3 were cut to a length of 10 cm and a width of 2.5 cm, and then one of the release films was peeled off and a 25 μm thick polyethylene terephthalate film (Diafoil S100, manufactured by Mitsubishi Chemical Corporation) was attached as a backing film to prepare a laminate. This ball tack measurement sample was set in a testing machine with an inclination angle of 30°, at a position 10 cm from the starting point of the ball rolling to the sample, and after peeling off the other release film of the pressure-sensitive adhesive sheet, balls were rolled on the adhesive surface (10 cm long) while changing the size of the ball (ball number), and the ball number of the ball that stopped on the adhesive surface was recorded as the ball tack value.

[0151] [Tensile storage modulus (E') and peak temperatures (T1, T2)] The adhesive sheets with release films of Examples 1 to 4 and Comparative Examples 1 to 3 were cut to a width of 4 mm and a length of 15 mm, and the dynamic viscoelasticity spectrum in the tensile mode was measured using a dynamic viscoelasticity measuring device (IT Measurement Control Co., Ltd., itkDVA-200) at a vibration frequency of 1 Hz, a heating rate of 3°C / min, and a temperature range of -120 to 80°C. The tensile storage modulus (E') at 25°C was read from the obtained data. Furthermore, the maximum values ​​of the loss tangent (Tan δ), that is, the peak temperatures (T1) and (T2), were read from the dynamic viscoelasticity spectrum data.

[0152] [Tensile storage modulus (E') and peak temperatures (T1, T2) after curing] The adhesive sheets with release film prepared in the examples and comparative examples were exposed to an integrated light intensity of 3000 mJ / cm at a wavelength of 365 nm. 2 The adhesive sheet was irradiated with light from a high-pressure mercury lamp through a release film to photo-cure the adhesive sheet, thereby preparing a cured adhesive sheet. The dynamic viscoelasticity spectrum in tensile mode was measured for the cured adhesive sheet under the same measurement conditions as for the uncured adhesive sheet (pre-cured product), and the tensile storage modulus (E') of the cured adhesive sheet at a temperature of 25°C was calculated from the obtained data. Furthermore, the maximum values ​​of the loss tangent (Tan δ), that is, the peak temperatures (T1) and (T2), were read from the dynamic viscoelasticity spectrum data.

[0153] [Shear storage modulus (G') and glass transition temperature (Tg)] The pressure-sensitive adhesive sheets of Examples 1 to 4 and Comparative Examples 1 to 3 were laminated to a thickness of 0.6 to 0.8 mm and punched out into a circle with a diameter of 8 mm to serve as a measurement sample. The dynamic viscoelasticity spectrum of this measurement sample was measured using a rheometer (TA Instruments, Discovery HR2) under the following measurement conditions. The shear storage modulus (G') at 25°C, 65°C, and 85°C was read from the data obtained by the measurement. Furthermore, the maximum value of the loss tangent (Tan δ), that is, the glass transition temperature (Tg), was read from the dynamic viscoelasticity spectrum data. (Measurement conditions) Adhesive jig: Φ8mm parallel plate Distortion: 0.1% Frequency: 1Hz Temperature: -120~200℃ Heating rate: 5℃ / min

[0154] [Shear storage modulus (G') and glass transition temperature (Tg) after curing] The adhesive sheets with release films of Examples 1 to 4 and Comparative Examples 1 to 3 were irradiated with an integrated light intensity of 3000 mJ / cm at a wavelength of 365 nm. 2 The adhesive sheet was irradiated with light from a high-pressure mercury lamp through a release film to photo-cure the adhesive sheet, thereby preparing a cured adhesive sheet. The cured adhesive sheets were laminated to a thickness of 0.6 to 0.8 mm and punched into circles with a diameter of 8 mm to serve as measurement samples.The dynamic viscoelasticity spectrum was measured using the shear method under the same measurement conditions as for the adhesive sheets before curing (pre-cured products), and the storage modulus (G') of the cured adhesive sheets at temperatures of 25°C, 65°C, and 85°C was calculated from the obtained data. Furthermore, the maximum value of the loss tangent (Tan δ), that is, the glass transition temperature (Tg), was read from the dynamic viscoelasticity spectrum data.

[0155] [Residual creep strain] The pressure-sensitive adhesive sheets of Examples 1 to 4 and Comparative Examples 1 to 3 were laminated to a thickness of 0.6 to 0.8 mm and punched out into a circle with a diameter of 8 mm to prepare a measurement sample. A pressure of 1 kPa was applied to this measurement sample at 25°C for 180 seconds using a rheometer (TA Instruments, Discovery HR2), and the strain (%), i.e., residual creep strain (%), was read 180 seconds after the pressure was released. In addition, the pressure-sensitive adhesive sheets with release films of Examples 1 to 4 and Comparative Examples 1 to 3 were irradiated with an integrated light intensity of 3000 mJ / cm 2 at a wavelength of 365 nm. 2A cured adhesive sheet was prepared by irradiating the adhesive sheet with light from a high-pressure mercury lamp through a release film and photocuring it so that the cured adhesive sheets reached a thickness of 0.6 to 0.8 mm, and then punching out a circle with a diameter of 8 mm to prepare a measurement sample. A pressure of 1 kPa was applied to this measurement sample at a temperature of 25°C for 180 seconds, and the strain, i.e., the residual creep strain (%), was then read 180 seconds after the pressure was released using a rheometer (TA Instruments, Discovery HR2).

[0156] [Creep strain] The pressure-sensitive adhesive sheets of Examples 1 to 4 and Comparative Examples 1 to 3 were laminated to a thickness of 0.6 to 0.8 mm and punched into a circle with a diameter of 8 mm to prepare a measurement sample. The creep strain (%) of this measurement sample was measured using a rheometer (TA Instruments, Discovery HR2) when a pressure of 1 kPa was applied for 10 seconds at a temperature of 25°C. In addition, the pressure-sensitive adhesive sheets with release films of Examples 1 to 4 and Comparative Examples 1 to 3 were irradiated with an integrated light intensity of 3000 mJ / cm 2 at a wavelength of 365 nm. 2 The adhesive sheet was irradiated with light from a high-pressure mercury lamp through a release film to photo-cure the adhesive sheet, thereby preparing a cured adhesive sheet. The cured pressure-sensitive adhesive sheets were laminated to a thickness of 0.6 to 0.8 mm and punched out into a circle with a diameter of 8 mm to prepare a measurement sample. A pressure of 1 kPa was applied to this measurement sample at 25°C for 10 seconds using a rheometer (TA Instruments, Discovery HR2), and the creep strain (%) was measured.

[0157] [Gel fraction] The release films were peeled off from the pressure-sensitive adhesive sheets with release films of Examples 1 to 4 and Comparative Examples 1 to 3, and approximately 0.1 g of pressure-sensitive adhesive sheet pieces were collected. The collected adhesive sheet pieces were wrapped in a bag-shaped SUS mesh (#150) with a mass (X), and the bag was closed to create a sample, and the mass (Y) of the sample was measured. The sample was immersed in ethyl acetate and stored in a dark place at 23°C for 24 hours, then removed and heated at 70°C for 4.5 hours to evaporate the ethyl acetate, and the mass (Z) of the dried sample was measured. The gel fraction was calculated from each measured mass using the following formula: Gel fraction (%) = [(ZX) / (YX)] × 100

[0158] The pressure-sensitive adhesive sheets of Examples 1 to 4 and Comparative Examples 1 to 3 were also exposed to a high-pressure mercury lamp with an integrated light intensity of 3000 mJ / cm 2 at 365 nm. 2 The adhesive sheet was irradiated with light through the release film to cure the adhesive sheet so that the gel fraction of the cured adhesive sheet was determined using the same procedure as in the gel fraction evaluation procedure described above.

[0159] <Lamination suitability> The adhesive sheets of Examples 1 to 4 and Comparative Examples 1 to 3 were evaluated for lamination suitability as follows.

[0160] [Curved surface lamination properties] A glass plate (curved cover glass) measuring 156 mm x 73 mm x 0.5 mm thick, with the long side edge curved to a radius of curvature of 3 mm, was prepared as a component of the image display device. This component had a 2 mm wide, 10 μm thick print applied along the periphery of the inner curved surface. One release film was peeled off from the adhesive sheets with release films of Examples 1 to 4 and Comparative Examples 1 to 3, and a 125 μm thick polyethylene terephthalate film (Cosmoshine A4100, manufactured by Toyobo Co., Ltd.) was attached to the exposed adhesive surface to prepare a laminate. The release film remaining on the laminate was peeled off, and the exposed adhesive surface was placed facing the inner curved surface of the cover glass.Then, using a diaphragm-type vacuum laminating device, the laminate was bonded under conditions of a temperature of 30°C, a pressure of 0.1 MPa, and a pressure application time of 60 seconds, to produce a laminate for an image display device.

[0161] The laminate for image display devices was stored for 200 hours at a temperature of 23°C and a humidity of 50%, and then visually observed. Those in which peeling or cohesive failure of the adhesive sheet was observed on the curved surface of the cover glass were rated as "× (poor)", and those in which the adhesive sheet did not peel or cohesive failure and maintained a good appearance were rated as "○ (good)". The failure modes of those rated as "× (poor)" are listed in Table 1.

[0162] [Bump absorption] The pressure-sensitive adhesive sheets with release films of Examples 1 to 4 and Comparative Examples 1 to 3 were cut into 52 mm x 80 mm pieces using a Thomson punch with the release films still laminated. The release film on one side was peeled off, and the exposed adhesive surface was pressed using a vacuum press (temperature 25°C, press pressure 0.1 MPa) onto the printed surface of soda lime glass (82 mm x 54 mm x thickness 0.5 mm, printing thickness: 8 to 40 μm) with printing of varying thicknesses applied to the 5 mm peripheral edge, so that the four sides of the adhesive sheet overlapped the printing steps. The remaining release film was then peeled off, and soda lime glass (82 mm x 54 mm x 0.5 mm thick) without any printed steps was press-laminated, and then autoclaved (temperature 60°C, gauge pressure 0.2 MPa, 20 minutes) to finish lamination, producing a stepped glass / double-sided pressure-sensitive adhesive sheet / glass laminate. The produced laminate was visually inspected to confirm the print thickness that would allow for good appearance lamination without bubbles near the print step. A ratio of step thickness (μm) / adhesive sheet thickness (μm) that allowed for good appearance lamination was rated as "Excellent" (◎), "Good" (○) if it was 10% or more, and "Poor" if it was less than 10%.

[0163] [Glue crush resistance] One release film was peeled off from the pressure-sensitive adhesive sheets with release films of Examples 1 to 4 and Comparative Examples 1 to 3, and the sheets were half-cut to 10 mm x 10 mm. The exposed adhesive surface was placed facing a piece of soda-lime glass with a thickness of 0.6 mm, and the pressure-sensitive adhesive sheet and the glass were pressure-bonded using a vacuum laminator at a temperature of 23°C, a gauge pressure of 0.4 MPa, and a pressure application time of 60 seconds. The adhesive overflow distance (μm) was measured from the half-cut mark at the center of each side of the adhesive sheet, and the average value of the four sides was taken as the adhesive overflow distance. Adhesive overflow distances of 300 μm or less were rated as "Excellent", those of 500 μm or less were rated as "Good", and those of more than 500 μm were rated as "Poor".

[0164] [Roll lamination] The release film-attached pressure-sensitive adhesive sheets of Examples 1 to 4 and Comparative Examples 1 to 3 were subjected to lamination using a roll laminating device with two plate-like suction stages between them, and positional deviation during the roll laminating operation was evaluated. Specifically, the pressure-sensitive adhesive sheets with release films prepared in the Examples and Comparative Examples were cut to 70 mm x 100 mm and fixed to the first suction stage of a roll laminating device. One of the release films was peeled off, and the exposed adhesive surface was placed opposite a substrate film (a 100 μm-thick polyethylene terephthalate film (Cosmoshine A4300, manufactured by Toyobo Co., Ltd.) fixed to the second suction stage (see Figure 2). The pressure-sensitive adhesive sheet and the substrate film were roll-laminated via an adsorption stage under the following conditions to prepare a laminate for evaluating roll-laminability. (Roll laminating equipment conditions) Roll diameter: 12mm Feed rate: 25mm / sec Roll pressure: 0.2MPa Roller hardness: 70 (Asker A) Stage suction pressure: 0.05 MPa ·Temperature: 23℃ Thirty sheets of the laminate were produced and visually inspected for appearance. All 30 sheets were evaluated as excellent if they could be bonded without misalignment at the end of the roll lamination starting point, good if 1 to 3 sheets out of 30 (90% or more yield) had misalignment of 1 mm or more, and poor if 4 or more sheets had misalignment.

[0165] [Indentation resistance] For the pressure-sensitive adhesive sheets with release film of Examples 1 to 4 and Comparative Examples 1 to 3, the release film was peeled off from one side and a 50 μm thick copper foil was laminated. The remaining release film was peeled off and the exposed adhesive surface was rolled back and forth with a hand roller over the entire surface of a soda lime glass (82 mm × 54 mm × 0.5 mm thick) to roll-press the pressure-sensitive adhesive sheet, which was then autoclaved (temperature 60°C, gauge pressure 0.2 MPa, 20 minutes) to achieve a finish adhesion. 365 nm ultraviolet light was irradiated from the soda lime glass surface using a high-pressure mercury lamp at an integrated light intensity of 3000 mJ / cm. 2 After irradiation so as to obtain the above value, the sample was cured at a temperature of 23°C and a humidity of 50% RH for 12 hours to prepare a sample for evaluating the resistance to indentation. A polyimide film (Upilex-S, manufactured by Ube Industries, Ltd.) measuring 20 mm in width, 30 mm in length, and 125 μm in thickness was placed on the copper foil surface of the sample, and pressed using a press at a temperature of 25°C, a pressure of 0.3 MPa, and a processing time of 10 seconds. The pressed sample was allowed to stand at room temperature (23°C) for 12 hours. The samples after pressing were visually observed, and those for which no impression was visible were rated as "Excellent (◎)", those for which only a slight uneven shape due to the transfer of the edge portion of the polyimide film was partially visible were rated as "Good (○)", and those for which the uneven shape was clearly visible were rated as "Poor (×)".

[0166] <Reliability> The pressure-sensitive adhesive sheets of Examples 1 to 4 and Comparative Examples 1 to 3 were evaluated for reliability after application as follows.

[0167] [Low temperature characteristics] One release film was peeled off from each of the release film-attached pressure-sensitive adhesive sheets of Examples 1 to 4 and Comparative Examples 1 to 3, and a 100 μm thick polyethylene terephthalate film (Cosmoshine A4300, manufactured by Toyobo Co., Ltd.) was attached as a backing film to prepare a laminate. The laminate was cut to a length of 150 mm and a width of 10 mm, after which the remaining release film was peeled off and the exposed adhesive surface was roll-pressed onto a soda lime glass by rolling a hand roller back and forth once to adhere the adhesive sheet to the glass. The glass was then autoclaved (temperature 60°C, gauge pressure 0.2 MPa, 20 minutes) to finish adhesion, and ultraviolet light of 365 nm was irradiated from the backing film surface using a high-pressure mercury lamp at an integrated light intensity of 3000 mJ / cm. 2 After irradiation so as to obtain the above, the sample was cured at a temperature of 23°C and a humidity of 50% RH for 12 hours to prepare a sample for measuring adhesive strength after curing. The adhesive strength measurement sample after curing was peeled off at a temperature of 0°C at a peel angle of 180° and a peel speed of 300 mm / min, and the peel strength (N / cm) from glass was measured.

[0168] [Humidity and heat haze] For the pressure-sensitive adhesive sheets with release films of Examples 1 to 4 and Comparative Examples 1 to 3, one release film was peeled off, and soda lime glass (82 mm x 54 mm x 0.5 mm thick) was roll-laminated using a hand roller with one stroke. The remaining release film was peeled off, and the exposed adhesive surface was roll-laminated using a hand roller with one stroke to another piece of soda lime glass (82 mm x 54 mm x 0.5 mm thick), and the sheet was autoclaved (temperature 60°C, gauge pressure 0.2 MPa, 20 minutes) to achieve finish lamination. A high-pressure mercury lamp was used to irradiate one of the glass surfaces with 365 nm ultraviolet light at an integrated dose of 3000 mJ / cm. 2 After irradiation so as to obtain the above value, the sample was cured at a temperature of 23°C and 50% RH for 12 hours to prepare a sample for evaluating wet heat haze. The above sample was stored in an environmental tester at a temperature of 85°C and a humidity of 85% RH for 500 hours, and the haze value of the sample after storage was measured in accordance with JIS K7136 using a haze meter (NDH5000, manufactured by Nippon Denshoku Industries Co., Ltd.).

[0169] [Durability] Laminates for image display devices were produced by the above-described method using the pressure-sensitive adhesive sheets of Examples 1 to 4 and Comparative Examples 1 to 3. A high-pressure mercury lamp was used to irradiate the curved cover glass surface of the laminate with an integrated light intensity of 3000 mJ / cm at 365 nm. 2 After irradiating the sample with light so as to achieve the above, the sample was cured for 12 hours at a temperature of 23°C and a humidity of 50% RH to prepare a sample for durability evaluation. The above samples were stored for 1000 hours under an environmental test at a temperature of 85°C and a humidity of 85% RH, after which the samples were visually observed, and samples in which foaming or peeling was observed in the adhesive sheet were rated as "× (poor)", and samples in which no foaming or peeling was observed were rated as "○ (good)".

[0170] [Table 1]

[0171] The adhesive sheets of Examples 1 to 4 had an adhesive strength to soda lime glass of 2 N / cm or more, a slippage length measured in a holding strength test of 10 mm or less, and a peel distance of 20 mm in a constant load peel test, and therefore had excellent curved surface adhesion properties and foaming resistance and peelability in durability tests. Among them, the pressure-sensitive adhesive sheets of Examples 1 to 3 had a ratio of tensile storage modulus (E') to shear storage modulus (G') of 5.0 or more, and were highly suitable for lamination. Furthermore, the pressure-sensitive adhesive sheets of Examples 1 to 3 had a glass transition temperature of 0°C or less after curing, and were excellent in low-temperature properties. Furthermore, among these, the adhesive sheets of Examples 1 and 2 were adhesive sheets consisting of three layers: a surface layer, a back layer, and an intermediate layer, and the surface layer, back layer, and intermediate layer were formed from resin compositions containing (meth)acrylic polymers of different compositions as the main component resin, and therefore had particularly excellent resistance to moist heat whitening in reliability evaluations.

[0172] In contrast, the adhesive sheet of Comparative Example 1 had a slippage length of 10 mm or more in the holding power test, and therefore underwent cohesive failure when used to bond curved members, demonstrating poor curved surface bonding properties. The adhesive sheets of Comparative Examples 2 and 3 had peel lengths of 20 mm or more or adhesive strengths of 2 N / cm or less in the constant load peel test, and therefore underwent peeling when bonded to curved members, demonstrating poor curved surface bonding properties.

[0173] Although the above examples show specific embodiments of the present invention, the examples are merely illustrative and should not be construed as limiting. Various modifications that are obvious to those skilled in the art are intended to fall within the scope of the present invention. [Industrial Applicability]

[0174] The adhesive sheet for an image display device of the present invention has excellent curved surface adhesion properties, allowing it to be attached to curved members having curved portions without air bubbles, and has excellent durability after being attached to the curved member, so it can be used to attach components of an image display device, and is particularly suitable for attaching components of an image display device having a curved shape.

Claims

1. An adhesive sheet for use in bonding two image display device components, the pressure-sensitive adhesive sheet is active energy ray-curable, the pressure-sensitive adhesive sheet is formed from a resin composition containing a (meth)acrylic polymer, a crosslinking agent (B), a photopolymerization initiator (C), and a silane coupling agent (D); the (meth)acrylic copolymer contains a structural unit derived from at least one selected from the group consisting of a hydroxyl group-containing monomer and a nitrogen atom-containing monomer, the crosslinking agent (B) is a polyfunctional (meth)acrylate, The adhesive strength to soda lime glass at a temperature of 23°C and a peeling speed of 300 mm / min is 2 N / cm or more, The slippage length measured in a holding strength test in accordance with JIS Z 0237 at a temperature of 70°C, a load of 0.5 kg, a measurement time of 30 minutes, on an adhesive surface of 20 mm width x 20 mm length is 10 mm or less, The pressure-sensitive adhesive sheet was irradiated with active energy rays having a wavelength of 365 nm at an integrated light dose of 3000 mJ / cm 2 After being irradiated and cured, the thickness is 0.6 to 0.8 mm, and the distortion (creep strain) when a pressure of 1 kPa is applied for 10 seconds at a temperature of 25°C is 3% or less; and A pressure-sensitive adhesive sheet for an image display device, which exhibits a peel distance of 20 mm or less in the following constant load peel test. (Measurement conditions) 1) A 10 mm wide, 150 mm long adhesive sheet is attached to an adherend in a region of 10 mm wide and 100 mm long to form an attached region, and the area of ​​the adhesive sheet other than the attached region is formed as a non-attached region, and the adherend is fixed horizontally so that the non-attached region of the adhesive sheet hangs downward. 2) A load of 0.45 N is applied to the longitudinal end of the non-bonded region of the pressure-sensitive adhesive sheet for 30 minutes, and the distance that the bonded region of the pressure-sensitive adhesive layer peels from the adherend during this time is measured as the constant-load peel distance.

2. 2. The pressure-sensitive adhesive sheet for an image display device according to claim 1, wherein the ball number in an inclined ball tack test (inclination angle: 30°) is 5 to 25.

3. 3. The pressure-sensitive adhesive sheet for an image display device according to claim 1 or 2, wherein the pressure-sensitive adhesive sheet has a thickness of 0.6 to 0.8 mm, and after applying a pressure of 1 kPa at a temperature of 25°C for 180 seconds, the pressure is released and the residual creep strain is 20% or less 180 seconds after the pressure is released.

4. 4. The pressure-sensitive adhesive sheet for an image display device according to claim 1, wherein the ratio (E' / G') of the tensile storage modulus (E') to the shear storage modulus (G') is 5.0 or more.

5. The pressure-sensitive adhesive sheet for an image display device according to any one of claims 1 to 4, wherein the loss tangent (Tan δ) obtained by dynamic viscoelasticity measurement in a tensile mode at a frequency of 1 Hz has two maximum values ​​(peak temperatures), and the difference between the maximum values ​​is 5 to 50°C.

6. 6. The pressure-sensitive adhesive sheet for an image display device according to claim 1, wherein the pressure-sensitive adhesive sheet has at least three layers, the outermost layer and the innermost layer being acrylic pressure-sensitive adhesive layers, and the ratio of the total thickness of the outermost layer and the innermost layer to the total thickness is 5 to 70%.

7. The pressure-sensitive adhesive sheet for an image display device according to any one of claims 1 to 6, which is composed of at least three layers: a surface layer, a back layer, and an intermediate layer, and the surface layer, the back layer, and the intermediate layer are formed from resin compositions containing (meth)acrylic polymers having different compositions.

8. The pressure-sensitive adhesive sheet was irradiated with active energy rays having a wavelength of 365 nm at an integrated light dose of 3000 mJ / cm 2 The pressure-sensitive adhesive sheet for an image display device according to any one of claims 1 to 7, wherein after being irradiated and cured, the pressure-sensitive adhesive sheet has a thickness of 0.6 to 0.8 mm and a maximum value of loss tangent (glass transition temperature) obtained by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz is 0°C or less.

9. The pressure-sensitive adhesive sheet for an image display device according to any one of claims 1 to 8, wherein the content by mass of the crosslinking agent (B) is 0.5 to 50 parts by mass per 100 parts by mass of the (meth)acrylic polymer.

10. 10. A pressure-sensitive adhesive sheet with a release film, comprising the pressure-sensitive adhesive sheet for an image display device according to claim 1 and a release film laminated together.

11. A configuration in which two image display device components are laminated via the pressure-sensitive adhesive sheet for an image display device according to any one of claims 1 to 9, and of the two image display device components, One is a cover glass having a curved surface, and the other is a laminate for an image display device, which is a component consisting of one or a combination of two or more of the group consisting of a touch sensor, an image display panel, a surface protective film, an anti-reflection film, a color filter, a polarizing film, and a retardation film.

12. An image display device using the laminate for an image display device according to claim 11.

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