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

Abstract

To provide an adhesive sheet for image display devices, which is an adhesive sheet for adhering two image display device constituent members, has a surface-adhering property capable of adhering a curved member having a curved portion without air bubbles, and has excellent durability after being adhered to a curved member, has an adhesive force of 2 N / cm or more to soda-lime glass at a temperature of 23°C and a peeling speed of 300 mm / min, has a displacement length of 10 mm or less in a holding force test of an adhesive surface based on JIS Z0237 at a temperature of 70°C, a load of 0.5 kg, a measurement time of 30 minutes, a width of 20 mm x a length of 20 mm, and has a peeling distance of 20 mm or less in a constant load peeling test.

Description

Technical Field

[0001] This invention relates to adhesive sheets for image display devices, adhesive sheets with release films, laminates for image display devices, and image display devices. Background Technology

[0002] To improve the visibility of an image display device, the following operation is performed: the gap between the image display panel, such as a liquid crystal display (LCD), plasma display panel (PDP), or electroluminescent display (ELD), and the protective panel and touch panel components disposed on its front side (visible side) are filled with resin such as adhesives or bonding agents to suppress the reflection of incident light and emitted light from the displayed image at the air layer interface.

[0003] For example, Patent Document 1 discloses a method for manufacturing a composite image display device having an image display device constituent member laminated on at least one side of a transparent double-sided adhesive sheet. The method involves attaching an adhesive sheet that has been cross-linked once using ultraviolet light to the image display device constituent member, and then irradiating the adhesive sheet with ultraviolet light through the image display device constituent member to cause it to undergo secondary curing.

[0004] In addition, Patent Document 2 discloses a pressure-sensitive adhesive sheet containing a (meth)acrylic copolymer having a UV crosslinking site, which is useful for display and touch panels.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent No. 4971529

[0008] Patent Document 2: Japanese Patent No. 6062740 Summary of the Invention

[0009] The problem the invention aims to solve

[0010] In recent years, there has been a growing demand for sophisticated design in image display devices. The shape of the protective panel on the front surface has gradually changed from a flat shape to a shape with curved ends or corners, and the display unit has been designed to be curved as a whole.

[0011] However, when using adhesive sheets to adhere image display device components made of resin films or the like to curved sections, the rebound of the resin films or the like can easily occur, making it difficult for the adhesive sheets to follow the curved sections. The adhesive sheets in the aforementioned Patent Documents 1 and 2 were studied for laminated structures obtained using flat image display device components in the past, but they did not take into account the adhesion reliability for curved surface components with curved sections.

[0012] Furthermore, when the curved portion of the aforementioned curved component has unevenness such as printing height differences, it is more prone to lifting and peeling at the interface between the adhesive sheet and the aforementioned unevenness compared to flat components. Therefore, for curved components with curved portions, a higher level of adhesive reliability and height difference tracking is required compared to the past.

[0013] Therefore, the problem to be solved by the present invention is to provide an adhesive sheet that can be bonded to curved surface components with curved portions without air bubbles and has excellent durability after being bonded to curved surface components.

[0014] Solution for solving the problem

[0015] In order to solve the above-mentioned problems, the inventors conducted in-depth research and found that by setting the adhesive force of the adhesive sheet, the offset length measured in the holding force test, and the peeling distance in the constant load peeling test to a specific range of values, the above-mentioned problems can be solved.

[0016] That is, the present invention takes the following [1] to

[15] as its main points.

[0017] [1] An adhesive sheet for an image display device, which is an adhesive sheet for bonding two components constituting an image display device, having an adhesive force of 2 N / cm or more against soda-lime glass at a temperature of 23°C and a peeling speed of 300 mm / min, having an offset length of 10 mm or less in a holding force test of an adhesive surface with a width of 20 mm and a length of 20 mm based on JISZ 0237 at a temperature of 70°C, a load of 0.5 kg, a test time of 30 minutes, and a constant load peeling test, and having a peeling distance of 20 mm or less.

[0018] (Measurement conditions)

[0019] 1) Adhere a 10mm wide and 100mm long area of ​​an adhesive sheet with a width of 10mm and a length of 150mm to the object to be adhered as the adhesive area, and use the area of ​​the adhesive sheet other than the adhesive area as the non-adhesive area. Fix the object to be adhered in the horizontal direction by hanging the non-adhesive area of ​​the adhesive sheet downwards.

[0020] 2) Apply a 0.45N load to the long end of the non-adhesive area of ​​the adhesive sheet for 30 minutes, and measure the distance at which the adhesive layer peels off from the substrate during this period as the constant load peel distance.

[0021] [2][1] The adhesive sheet for the image display device, wherein the balls in the inclined rolling ball adhesion test (inclination angle: 30°) are numbered 5 to 25.

[0022] [3] An adhesive sheet for an image display device according to [1] or [2], wherein the adhesive sheet is set to a thickness of 0.6 to 0.8 mm, and after applying a pressure of 1 kPa for 180 seconds at a temperature of 25°C, the residual creep strain after releasing the pressure and after 180 seconds is less than 20%.

[0023] [4] An 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.

[0024] [5] An adhesive sheet for an image display device according to any one of [1] to [4], wherein the loss tangent (Tanδ) measured by dynamic viscoelasticity determination in a stretching mode at a frequency of 1 Hz has two maximum values ​​(peak temperatures) with a difference of 5 to 50 °C.

[0025] [6] An adhesive sheet for an image display device according to any one of [1] to [5], wherein the outermost layer and the innermost layer are acrylic adhesive layers and there are at least 3 layers, and the total thickness of the outermost layer and the innermost layer is 5 to 70% of the overall thickness.

[0026] [7] An adhesive sheet for an image display device according to any one of [1] to [6], which is an adhesive sheet consisting of at least three layers: an outermost layer, an innermost layer, and an intermediate layer, wherein the outermost layer, the innermost layer, and the intermediate layer are formed of resin compositions comprising (meth)acrylic polymers with different compositions.

[0027] [8] The adhesive sheet for an image display device according to any one of claims [1] to [7] has active energy ray curing properties.

[0028] [9] The adhesive sheet for the image display device according to [8], wherein the cumulative light intensity when the adhesive sheet is irradiated is 3000 mJ / cm 2 After being cured by active energy rays with a wavelength of 365nm, the thickness is set to 0.6-0.8mm, and the strain (creep strain) when a pressure of 1kPa is applied for 10 seconds at a temperature of 25℃ is less than 3%.

[0029]

[10] An adhesive sheet for an image display device according to [8] or [9], wherein the cumulative light intensity when the adhesive sheet is irradiated is 3000 mJ / cm. 2 After being cured by active energy rays with a wavelength of 365nm, the thickness was set to 0.6-0.8mm, and the maximum value of the loss tangent (glass transition temperature) obtained by dynamic viscoelasticity measurement in shear mode at a frequency of 1Hz was below 0℃.

[0030]

[11] An adhesive sheet for an image display device according to any one of [1] to

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

[0031]

[12] The adhesive sheet for the image display device according to

[11] , wherein the aforementioned crosslinking agent (B) contains 0.5 to 50 parts by mass relative to 100 parts by mass of the (meth)acrylic polymer.

[0032]

[13] An adhesive sheet with a release film, comprising a structure in which an adhesive sheet for an image display device as described in any one of [1] to

[12] is laminated with a release film.

[0033]

[14] A laminate for an image display device, comprising a structure in which two image display device constituent components are sandwiched together with an adhesive sheet for the image display device described in any one of [1] to

[12] , wherein one of the two image display device constituent components is a cover glass having a curved shape, and the other is a component selected from the group consisting of a contact sensor, an image display panel, a surface protective film, an anti-reflective film, a color filter, a polarizing film and a phase difference film, or a component formed by a combination of two or more.

[0034]

[15] An image display device that uses the image display device laminate described in

[14] .

[0035] The effects of the invention

[0036] According to this adhesive sheet, since it can be bonded to curved components without air bubbles and has excellent durability after being bonded to curved components, it can be suitable as an adhesive sheet for image display devices with curved surfaces. Attached Figure Description

[0037] Figure 1 This is a diagram used to illustrate the evaluation method for constant load peeling tests.

[0038] Figure 2 This is a diagram used to illustrate the evaluation method for roller adhesion testing. Detailed Implementation

[0039] Hereinafter, a detailed description will be given regarding one embodiment of the present invention. However, the present invention is not limited to the following embodiment.

[0040] It should be noted that in this specification, "(meth)acrylic acid" refers to both "acrylic acid" and "methacrylic acid", and "(meth)acrylate" refers to both "acrylate" and "methacrylate".

[0041] The adhesive sheet for the image display device of the present invention (referred to as "this adhesive sheet") is generally a double-sided adhesive sheet having adhesive layers on both sides, used for bonding two image display device constituent components. In particular, this adhesive sheet can be suitably used when the image display device constituent components have curved shapes.

[0042] Furthermore, from the viewpoint of improving reliability, this adhesive sheet preferably has active energy ray curing property, which is cured by irradiation with active energy rays such as ultraviolet light.

[0043] <Adhesion>

[0044] This adhesive sheet exhibits an adhesion force of 2 N / cm or more to soda-lime glass at a temperature of 23°C and a peel speed of 300 mm / min. By maintaining an adhesion force of 2 N / cm or more, it prevents peeling when bonded to curved surfaces, thus demonstrating excellent adhesion to curved surfaces. From this perspective, an adhesion force of 3 N / cm or more is preferred, more preferably 4 N / cm or more, and even more preferably 5 N / cm or more. It should be noted that, from the viewpoint of suppressing the modulus of elasticity to balance height difference absorption and roller adhesion, the upper limit of the adhesion force is typically 50 N / cm, and preferably 30 N / cm.

[0045] Furthermore, when the adhesive sheet has the property of being cured by active energy rays, the cured adhesive sheet preferably exhibits an adhesion strength of 2 N / cm or more to soda-lime glass at a temperature of 23°C and a peel speed of 300 mm / min. By achieving an adhesion strength of 2 N / cm or more, excellent durability can be achieved when manufacturing laminates for image display devices. From this perspective, the cured adhesion strength is preferably 3 N / cm or more, more preferably 4 N / cm or more, and even more preferably 5 N / cm or more. It should be noted that, depending on the range of adhesion strength before curing, the upper limit of the adhesion strength is typically 50 N / cm, and preferably 30 N / cm.

[0046] [Methods for measuring adhesive strength]

[0047] The adhesive strength described above was measured using the following method.

[0048] A 100 μm thick polyethylene terephthalate (PET) film (manufactured by Toyobo Co., Ltd., COSMOSHINE A4300) was bonded to one side of the adhesive sheet, and the other side was rolled onto soda-lime glass to form an adhesive product. The adhesive product was then subjected to autoclaving (60°C, 0.2 MPa gauge pressure, 20 minutes) for final bonding, and the resulting sample was used for adhesive strength testing. Using this sample, the adhesive was peeled off at 23°C and 50% RH, with a peel angle of 180° and a peel speed of 300 mm / min. The peel force (N / cm) at this point was taken as the adhesive force.

[0049] In addition, regarding the adhesion after curing, a high-pressure mercury lamp was used to accumulate a light intensity of 3000 mJ / cm. 2 After irradiating the PET film surface of the sample used for adhesive strength testing with 365nm ultraviolet light, the sample is cured for 12 hours at a temperature of 23°C and a humidity of 50%RH. The resulting sample is used as the cured adhesive strength test sample, and the peel force is measured using the same method as described above.

[0050] <Persistence>

[0051] Furthermore, in a holding force test conducted according to JIS Z 0237 at a temperature of 70°C, a load of 0.5 kg, a testing time of 30 minutes, and on an adhesive surface with a width of 20 mm and a length of 20 mm, the offset length of this adhesive sheet is 10 mm or less. By keeping the offset length to 10 mm or less, the adhesive sheet will not undergo cohesive failure over time, even when bonded to curved surfaces, thus exhibiting excellent surface adhesion. From this perspective, an offset length of 8 mm or less is more preferable, and 5 mm or less is even more preferable.

[0052] Furthermore, when the adhesive sheet has the property of being cured by active energy radiation, the offset length measured in the holding force test of the cured adhesive sheet on an adhesive surface with a width of 20 mm and a length of 20 mm, based on JIS Z 0237 at a temperature of 70°C, a load of 0.5 kg, a measurement time of 30 minutes, is preferably 5 mm or less. By making the offset length 5 mm or less, excellent durability can be achieved when manufacturing laminates for image display devices. From this point of view, the offset length is more preferably 1 mm or less, and even more preferably 0.5 mm or less.

[0053] [Methods for measuring holding power]

[0054] The holding force described above was measured using the following method.

[0055] A 38 μm thick polyethylene terephthalate (PET) film (manufactured by Mitsubishi Chemical Corporation, DIAFOILS100) was adhered to one side of the adhesive sheet and cut into 20 mm wide pieces. The other side was adhered to a polished stainless steel plate (SUS304) with an adhesion area of ​​20 mm × 20 mm. This sample was used for holding force measurement. Using this sample, the adhesive sheet was held under a load of 0.5 kg and a temperature of 70 °C for 30 minutes, and the offset length (mm) was measured.

[0056] In addition, regarding the retention strength after curing, the cumulative light intensity using a high-pressure mercury lamp at a wavelength of 365 nm was 3000 mJ / cm. 2 The adhesive sheet is photocured by irradiating it with light to produce a cured adhesive sheet. The offset length can then be measured using the same method as described above.

[0057] <Constant Load Stripping>

[0058] Furthermore, the peel distance of this adhesive sheet in the constant load peel test is 20 mm or less. By making the peel distance 20 mm or less, even when bonded to curved surfaces, it is possible to suppress the occurrence of lift over time and achieve excellent adhesion to curved surfaces. From this point of view, 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.

[0059] [Method for determining peeling under constant load]

[0060] The above constant load peel test was performed using the following method.

[0061] A 100 μm thick polyethylene terephthalate (PET) film (manufactured by Toyobo Co., Ltd., COSMOSHINE A4300) was bonded to one side of an adhesive sheet. The film was cut to a width of 10 mm and a length of 150 mm, and a 10 mm wide and 100 mm long section was rolled onto soda-lime glass to create an adhesive sample. The area bonded to the soda-lime glass was designated as the adhesive area, and the area outside the adhesive area was designated as the non-adhesive area. The adhesive sample was then subjected to autoclaving (50°C, 0.2 MPa gauge pressure, 20 minutes), followed by curing at 40°C for 30 minutes for final attachment. The resulting sample was used for a constant load peel test. Using this sample, at 23°C and 50% RH, the soda-lime glass was fixed horizontally with the non-adhesive area of ​​the adhesive sheet hanging downwards. Subsequently, a 0.45N load was applied to the longitudinal end of the non-adhesive area of ​​the adhesive sheet for 30 minutes, and the distance at which the adhesive area of ​​the adhesive sheet peeled off from the soda-lime glass during this period was measured as the constant load peel distance.

[0062] By combining the adhesive strength, holding power, and constant load peeling properties described above, it is possible to produce adhesive sheets with excellent surface adhesion and durability.

[0063] <Rolling ball adhesion>

[0064] In the inclined rolling ball adhesion test, the ball number of this adhesive sheet is preferably 5 to 25, more preferably 8 to 20. By using the ball number within the above range in the inclined rolling ball adhesion test, positional shift will not occur when the adhesive sheet is roller-bonded to the component of the image display device, thus enabling the production of an adhesive sheet with excellent roller adhesion. The ball number is determined according to the inclined rolling ball adhesion test specified in JIS Z0237:2009, under conditions of a temperature of 23°C and an inclination angle of 30°.

[0065] <Residual creep strain>

[0066] The adhesive sheet is set to a thickness of 0.6 to 0.8 mm. After applying a pressure of 1 kPa for 180 seconds at a temperature of 25°C, the residual creep strain after releasing the pressure and waiting for 180 seconds is preferably 20% or less. By keeping the residual creep strain to 20% or less, adhesive breakdown does not occur during bonding, resulting in a laminate for an image display device without adhesive overflow. From this point of view, the residual creep strain is more preferably 10% or less, more preferably 7% or less, further preferably 5% or less, and particularly preferably 2% or less.

[0067] It should be noted that, when the adhesive sheet has the property of being cured by active energy rays, the residual creep strain of the cured adhesive sheet is preferably less than 5%.

[0068] Generally, after bonding two image display device components together using adhesive sheets to create a laminate for an image display device, the image display device is then used. When an image display device is manufactured using laminated materials, sometimes in the image display device When stress is applied locally to the laminate, the adhesive sheet may develop indentations, damaging the appearance and visibility of the image display device. By reducing the residual creep strain of the cured adhesive sheet to 5% or less, a laminate for an image display device with excellent indentation resistance can be obtained. From this point of view, the residual creep strain of the cured adhesive sheet is more preferably 3% or less, more preferably 1% or less, and even more preferably 0.5% or less.

[0069] It should be noted that the residual creep strain of the cured adhesive sheet was obtained using the following sample: a high-pressure mercury lamp with a cumulative light intensity of 3000 mJ / cm at a wavelength of 365 nm. 2 The sample is obtained by irradiating the adhesive sheet with light to cure it.

[0070] As mentioned above, the residual creep strain is the value when the thickness of the adhesive sheet is set to 0.6–0.8 mm. This is because, in order to accurately measure the residual creep strain of the adhesive sheet, it is necessary to avoid the influence of the measuring tool due to insufficient thickness of the adhesive sheet, which would lead to variations in the measurement results. Therefore, in order to measure the residual creep strain, the thickness of the adhesive sheet needs to be adjusted to a certain range.

[0071] By pre-adjusting the thickness of the adhesive sheet to the above-mentioned range and measuring the residual creep strain, the residual creep strain of the adhesive sheet can be accurately determined without being affected by the measuring tool.

[0072] <creep strain>

[0073] When the adhesive sheet is set to a thickness of 0.6 to 0.8 mm, the creep strain when subjected to a 1 kPa pressure for 10 seconds at a temperature of 25°C is preferably 10% or less. By setting the creep strain to 10% or less, an adhesive sheet with excellent resistance to adhesive degradation can be obtained. From this point of view, the creep strain is more preferably 7% or less, more preferably 5% or less, and even more preferably 3% or less.

[0074] It should be noted that, when the adhesive sheet has the property of being cured by active energy rays, the creep strain of the cured adhesive sheet is preferably 7% or less. By making the creep strain of the cured adhesive sheet 7% or less, a laminate for an image display device with excellent indentation resistance can be obtained. From this point of view, the creep strain of the cured adhesive sheet is preferably 7% or less, more preferably 5% or less, and even more preferably 3% or less.

[0075] It should be noted that the creep strain of the cured adhesive sheet was obtained using the following sample: a high-pressure mercury lamp with a cumulative light intensity of 3000 mJ / cm at a wavelength of 365 nm was used. 2 The sample is obtained by irradiating the adhesive sheet with light to cure it.

[0076] As mentioned above, the creep strain is the value when the thickness of this adhesive sheet is set to 0.6–0.8 mm. This is because, in order to accurately measure the creep strain of this adhesive sheet, it is necessary to avoid the influence of the measuring tool due to insufficient thickness of the adhesive sheet, which would lead to changes in the measurement results. Therefore, in order to measure the creep strain, the thickness of this adhesive sheet needs to be adjusted to a certain range.

[0077] By pre-adjusting the thickness of the adhesive sheet to the above-mentioned range and then measuring the creep strain, the creep strain of the adhesive sheet can be accurately determined without being affected by the measuring tool.

[0078] <Dynamic viscoelastic properties>

[0079] The ratio (E' / G') of the tensile storage modulus (E') to the shear storage modulus (G') obtained by dynamic viscoelasticity measurement of this adhesive sheet 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. Furthermore, it is preferably 100 or less, more preferably 50 or less, and even more preferably 30 or less.

[0080] In other words, if the E' / G' ratio of this adhesive sheet is 5.0 or higher, it can be determined that this adhesive sheet "has at least two layers with different glass transition temperatures" or "has a layer in which the glass transition temperature is inclined along the thickness direction." By having such a layer structure, this adhesive sheet achieves a high level of adhesion adaptability and durability, including good adhesion to curved surfaces, good roller adhesion, resistance to adhesive degradation, absorption of height differences, and resistance to indentation.

[0081] It should be noted that the tensile storage modulus (E') and the shear storage modulus (G') are obtained by the following method.

[0082] [Method for determining tensile storage modulus (E')]

[0083] The adhesive sheet was cut into pieces 4mm wide and 15mm long. Using a dynamic viscoelasticity measuring device (IT Measurement Control, "itkDVA-200"), under the conditions of tensile mode: vibration frequency 1Hz, heating rate: 3℃ / min, and temperature range: -120~80℃, the dynamic viscoelastic spectrum was measured. The tensile storage modulus (E') at 25℃ was read from the obtained data.

[0084] [Method for determining shear storage modulus (G')]

[0085] The adhesive sheets were stacked with a thickness of 0.6–0.8 mm, and the resulting sample was punched into a circle with a diameter of 8 mm as the test specimen. For this test specimen, the dynamic viscoelastic spectrum under shear mode was measured using a rheometer (TA Instruments, “DiscoveryHR2”) under the following test conditions, and the shear storage modulus (G') at 25°C was read from the obtained data.

[0086] [Measurement Conditions]

[0087] Adhesion tool: Φ8mm parallel plate

[0088] Strain: 0.1%

[0089] Frequency: 1Hz

[0090] Temperature: -120~200℃

[0091] Heating rate: 5℃ / min

[0092] As mentioned above, the shear storage modulus (G') is the value when the adhesive sheet is set to a thickness of 0.6–0.8 mm. This is because, in order to accurately measure the shear storage modulus (G') of the adhesive sheet, it is necessary to avoid the influence of the measuring tool due to insufficient thickness of the adhesive sheet, which would cause the measurement results to change. Therefore, in order to measure the shear storage modulus (G'), it is necessary to adjust the thickness of the adhesive sheet to a certain range before performing the measurement.

[0093] By pre-adjusting the thickness of the adhesive sheet to the above-mentioned 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 tool.

[0094] It should be noted that, given the active energy radiation curability of this adhesive sheet, the samples used in the aforementioned tensile storage modulus (E') and shear storage modulus (G') measurements can be either before or after curing. The cured adhesive sheet, when subjected to a high-pressure mercury lamp with a wavelength of 365 nm, achieves a cumulative light intensity of 3000 mJ / cm². 2 The adhesive sheet is obtained by irradiating it with light to cure it.

[0095] The loss tangent (Tanδ) of this adhesive sheet, obtained by dynamic viscoelasticity measurement in tensile mode, preferably has two maxima (peak temperatures: (T1) and (T2)). Furthermore, the difference between the two peak temperatures (T1) and (T2) is preferably 5–50°C, more preferably 10–40°C, and particularly preferably 15–30°C. By setting these ranges, a high level of adhesive adaptability and reliability can be achieved, including good adhesion to curved surfaces, good roller adhesion, resistance to adhesive breakdown, absorption of height differences, and resistance to indentation.

[0096] 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 viscoelastic spectrum data in the tensile mode obtained using the same method as the tensile storage modulus (E') above.

[0097] Furthermore, the shear storage modulus (G') of this adhesive sheet is not particularly limited. From the viewpoint of balancing height difference absorption and curved surface adhesion at a high level, it is preferably 50 to 400 kPa at 25°C, more preferably 60 to 300 kPa, and even more preferably 100 to 200 kPa.

[0098] In addition, 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.

[0099] Furthermore, the shear storage modulus (G') at 85°C is preferably 1–40 kPa, more preferably 5–35 kPa, and even more preferably 10–30 kPa.

[0100] By setting the shear storage modulus (G') of this adhesive sheet to this range, it is possible to produce an adhesive sheet with superior height difference absorption properties.

[0101] When the adhesive sheet has the property of being cured by active energy rays, the shear storage modulus (G') of the cured adhesive sheet is not particularly limited, but is preferably 50 to 500 kPa at 25°C, more preferably 60 to 400 kPa, and even more preferably 100 to 300 kPa.

[0102] In addition, 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.

[0103] Furthermore, the shear storage modulus (G') at 85°C is preferably 1–90 kPa, more preferably 5–80 kPa, and even more preferably 10–50 kPa.

[0104] By setting the shear storage modulus (G') of the cured adhesive sheet to this range, it is possible to produce an adhesive sheet with excellent indentation resistance and durability.

[0105] It should be noted that the shear storage modulus (G') at 65℃ and 85℃ was obtained by reading the shear storage modulus (G') at 65℃ and 85℃ from the dynamic viscoelastic spectrum data under the shear mode obtained using the same method as the shear storage modulus (G') determination described above.

[0106] The glass transition temperature (Tanδ), the maximum value of the loss tangent (Tanδ) obtained by dynamic viscoelasticity measurement in shear mode, is not particularly limited, but is preferably below 0°C, more preferably below -10°C, further preferably below -15°C, and particularly preferably below -20°C. The lower limit is typically -100°C. By setting it within the above range, it is possible to produce an adhesive sheet with excellent height difference absorption.

[0107] Furthermore, when the adhesive sheet has the property of being cured by active energy radiation, the maximum value (peak temperature) of the loss tangent (Tanδ) of the cured adhesive sheet, obtained by dynamic viscoelasticity measurement in shear mode, i.e., the glass transition temperature, is preferably below 0°C, more preferably below -10°C, even more preferably below -15°C, and particularly preferably below -20°C. The lower limit is typically -100°C. By setting it within the above range, it is possible to produce an adhesive sheet with improved peel resistance at low temperatures, excellent low-temperature characteristics, and superior impact resistance.

[0108] The glass transition temperature (Tg) mentioned above is obtained by reading the temperature at which the loss tangent (Tanδ) reaches its maximum value, i.e., the peak temperature, from the dynamic viscoelastic spectrum data in the shear mode obtained using the same method as the storage modulus (G') in the shear mode mentioned above.

[0109] <Gel fraction>

[0110] The adhesive sheet is preferably in a state where the gel content is above 10% and below 90%.

[0111] By ensuring a gel fraction of 10% or more, the adhesive sheet will not experience cohesive failure over time, even when bonded to curved surfaces, thus exhibiting excellent surface adhesion. From this perspective, a gel fraction of 20% or more is preferred, more preferably 40% or more, and even more preferably 60% or more.

[0112] On the other hand, from the viewpoint of height difference tracking during curved surface bonding, the gel fraction is preferably 90% or less, more preferably 80% or less, and even more preferably 75% or less.

[0113] In addition, this adhesive sheet has active energy radiation curing properties, at 3000 mJ / cm 2 When the cumulative light intensity is irradiated with active energy rays with a wavelength of 365 nm to solidify it, the gel fraction increases compared with that before solidification. 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.

[0114] By ensuring that the gel fraction after curing with active energy rays is within the aforementioned range, the adhesive sheet can be given shape stability and durability when manufactured into a laminate for an image display device.

[0115] Furthermore, the gel fraction after curing is preferably increased by 2% or more, more preferably by 3% or more, and even more preferably by 5% or more, in terms of the difference in gel fraction compared to before curing. By making the difference in gel fraction before and after curing within the above range, there is a tendency to impart height difference tracking and durability when manufacturing an image display device.

[0116] To adjust the gel fraction of the adhesive sheet to the aforementioned range, it is preferable to adjust the composition and molecular weight of the (meth)acrylic polymer described later, or to adjust the type and amount of crosslinking agent (B) and photopolymerization initiator (C), or to adjust the intensity and cumulative light intensity of the irradiated active energy rays. However, this method is not limited to these methods.

[0117] This adhesive sheet can be a single layer or multiple layers, preferably at least three layers, more preferably at least three layers including an outermost layer, an innermost layer, and an intermediate layer, and particularly preferably with the outermost and innermost layers being acrylic adhesive layers and having at least three layers. By making this layer configuration, it is possible to produce an adhesive sheet with excellent adhesion adaptability, such as curved surface adhesion and height difference tracking.

[0118] When the adhesive sheet comprises at least three layers—an outermost layer, an innermost layer, and an intermediate layer—the outermost and innermost layers, along with the intermediate layer (the layer sandwiched between the outermost and innermost layers), are preferably formed from resin compositions containing (meth)acrylic polymers with different compositions, particularly resin compositions containing (meth)acrylic polymers as the main component. By forming this layer configuration, the wet-heat whitening of the adhesive sheet can be effectively suppressed. Furthermore, the aforementioned outermost and innermost layers can be formed from resin compositions containing (meth)acrylic polymers with different compositions, particularly resin compositions containing (meth)acrylic polymers as the main component, but are preferably formed from resin compositions containing (meth)acrylic polymers with the same composition.

[0119] When this adhesive sheet has at least three layers (outermost layer / middle layer / innermost layer) with the outermost and innermost layers being acrylic adhesive layers, the outermost and innermost layers (the surfaces to which they are bonded to the components constituting the image display device) are preferably low-Tg layers. Furthermore, the middle layer sandwiched between the outermost and innermost layers is preferably a high-Tg layer. Moreover, the low-Tg layers used in the outermost and innermost layers can have different glass transition temperatures (Tg), but the glass transition temperatures of the outermost and innermost layers are preferably the same, and the outermost and innermost layers are particularly preferably the same acrylic adhesive layer.

[0120] The aforementioned low Tg layer refers to a layer whose maximum value of the loss tangent (Tanδ) (glass transition temperature) obtained by dynamic viscoelasticity measurement under the aforementioned shear mode is typically below -10°C, preferably -100 to -15°C, and particularly preferably -50 to -20°C.

[0121] In addition, the aforementioned high Tg layer refers to a layer whose maximum value of the loss tangent (Tanδ) (glass transition temperature) obtained by dynamic viscoelasticity measurement under the aforementioned shear mode is typically higher than -10°C, preferably -5 to 20°C, and particularly preferably 0 to 15°C.

[0122] Furthermore, when this adhesive sheet has at least three layers, with the outermost and innermost layers being acrylic adhesive layers, the ratio of the total thickness of the outermost and innermost layers to the overall thickness is preferably 5 to 70%, more preferably 10 to 60%, and particularly preferably 20 to 45%. By setting the thickness of the outermost and innermost layers within the above range, it is possible to produce an adhesive sheet with excellent adhesion adaptability and durability, such as surface adhesion and height difference absorption.

[0123] It should be noted that the thickness of this adhesive sheet is preferably 50-1000 μm, more preferably 60-500 μm, and particularly preferably 75-300 μm.

[0124] This adhesive sheet is used to attach components of two image display devices. Specifically, it can be used to attach components of image display devices such as liquid crystal displays (LCDs), plasma displays (PDPs), or electroluminescent displays (ELDs) for personal computers, mobile terminals (PDAs), game consoles, televisions (TVs), car navigation systems, touch panels, stylus tablets, etc.

[0125] More specifically, among the two components of the image display device, one is glass and the other is a thin film. More preferably, the glass is tempered glass and the thin film is a laminate formed by any one or more of the following: a contact sensor, an image display panel, a surface protection panel, a polarizing film, and a phase difference film.

[0126] In recent years, from an aesthetic point of view, curved cover glass has become increasingly used in image display panels such as liquid crystal displays (LCDs), plasma display panels (PDPs), or electroluminescent displays (ELDs). However, such cover glass is expensive. To suppress the reduction in yield caused by bonding errors, this adhesive sheet is used, which has excellent adhesion to curved surfaces. Therefore, it can also be effectively used for cover glass with curved shapes.

[0127] Examples of such films include resin films in which one or more of the following resins are used as the main component: 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, and cellulose resins. In this case, the main component resin refers to the resin with the highest mass percentage among the resins constituting the resin film, specifically resins that account for 50% or more by mass, 60% or more by mass, 70% or more by mass, 80% or more by mass, 90% or more by mass, or 95% or more by mass (including 100% by mass) of the resins constituting the resin film.

[0128] When an image display device component made of the aforementioned resin film is bonded to a cover glass with a curved shape using an adhesive sheet, a bending stress conforming to the curved shape is continuously applied to the resin film in order to cause the resin film to bend along the curved shape of the cover glass. Therefore, the adhesive sheet is continuously subjected to a force—a rebound force—to restore the resin film to its flatness, making it difficult for the adhesive sheet to follow the curved portion. Therefore, improving the peel strength under constant load—that is, the peel strength under high adhesive force, holding force, and specified load—becomes crucial for achieving both curved surface adhesion and post-bonding durability.

[0129] As described above, the adhesive sheet having the aforementioned characteristics preferably has an acrylic adhesive layer, which is preferably formed from a resin composition comprising an acrylic polymer. Furthermore, when the adhesive sheet has three layers, with the outermost and innermost layers being acrylic adhesive layers, the intermediate layer is also preferably formed from a resin composition comprising an acrylic polymer.

[0130] The following describes the resin composition for forming the acrylic adhesive layer and the intermediate layer.

[0131] The above-mentioned resin composition contains a (meth)acrylic polymer, preferably a (meth)acrylic polymer as the 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.

[0132] The aforementioned "main component" refers to a component containing, based on the total amount of the resin composition, 50% or more by mass of (meth)acrylic polymer, preferably 70% or more by mass, and more preferably 80% or more by mass.

[0133] [(Meth)acrylic polymers]

[0134] Examples of the aforementioned (meth)acrylic polymers include polymers obtained by copolymerizing alkyl (meth)acrylic acid ester monomers with 4 to 18 carbon atoms in the alkyl group with monomer components that can copolymerize with them.

[0135] Examples of (meth)acrylate alkyl ester monomers having 4 to 18 carbon atoms in the aforementioned alkyl group include, for example, (meth)acrylate n-butyl ester, (meth)acrylate pentyl ester, (meth)acrylate hexyl ester, (meth)acrylate heptyl ester, (meth)acrylate n-octyl ester, (meth)acrylate nonyl ester, (meth)acrylate decyl ester, (meth)acrylate undecyl ester, (meth)acrylate lauryl ester, (meth)acrylate tridecyl ester, (meth)acrylate tetradecyl ester, (meth)acrylate cetyl ester, (meth)acrylate stearyl ester, etc., which are straight-chain alkyl esters of (meth)acrylate; (meth)acrylate isobutyl ester, (meth)acrylate sec-butyl ester, ( Branched alkyl methacrylates, such as tert-butyl methacrylate, isoamyl methacrylate, neopentyl methacrylate, 2-ethylhexyl methacrylate, isooctyl methacrylate, isononyl methacrylate, isodecanyl methacrylate, isostearyl methacrylate, etc.; alicyclic methacrylates, such as cyclohexyl methacrylate, tert-butylcyclohexyl methacrylate, 3,5,5-trimethylcyclohexane(meth)acrylate, dicyclopentyl methacrylate, dicyclopentenyl methacrylate, dicyclopentenoxyethyl methacrylate, isobornyl methacrylate, etc. These can be used alone or in combination of two or more.

[0136] Examples of monomer components capable of copolymerizing with alkyl (meth)acrylate monomers having 4 to 18 carbon atoms in the aforementioned alkyl groups include, for example, hydroxyl-containing monomers, nitrogen-containing monomers, carboxyl-containing monomers, epoxy-containing monomers, vinyl monomers, alkyl (meth)acrylate monomers having 1 to 3 carbon atoms in the alkyl group, and other copolymerizable monomers.

[0137] Examples of hydroxyl-containing monomers mentioned above 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, glyceryl 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, polypropylene glycol polybutylene glycol mono(meth)acrylate, and hydroxyphenyl (meth)acrylate. These can be one type or a combination of two or more.

[0138] Examples of nitrogen-containing monomers include, for instance, aminoalkyl methacrylates such as (meth)acrylate, aminoethyl methacrylate, aminopropyl methacrylate, and aminoisopropyl methacrylate; amino alkylaminoalkyl methacrylates, N,N-dimethylaminoethyl methacrylate, and N,N-dimethylaminopropyl methacrylate; and amide-containing monomers such as (meth)acrylate, N,N-dimethyl(meth)acrylate, N-butyl(meth)acrylate, N-hydroxymethyl(meth)acrylate, N-hydroxymethylpropane(meth)acrylate, N-methoxymethyl(meth)acrylate, N-butoxymethyl(meth)acrylate, diacetone(meth)acrylate, maleamide, and maleimide. These can be one type or a combination of two or more.

[0139] In addition, examples of the aforementioned carboxyl-containing monomers include (meth)acrylic acid and (meth)acrylic acid dimers. These can be one type or a combination of two or more.

[0140] Examples of epoxy-containing monomers mentioned above include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, 3,4-epoxycyclohexyl methyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate glycidyl ether. These can be one type or a combination of two or more.

[0141] Examples of the aforementioned vinyl monomers include, for instance, alkyl (meth)acrylates with alkyl groups having 1 to 12 carbon atoms; functional monomers having functional groups such as hydroxyl, amide, and alkoxyalkyl groups within 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 styrene. They may be one type or a combination of two or more.

[0142] Examples of alkyl methacrylate monomers having 1 to 3 carbon atoms in the aforementioned alkyl group include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, and isopropyl methacrylate. These may be one type or a combination of two or more types.

[0143] Other copolymerizable monomers mentioned above include, for example, maleic anhydride, itaconic anhydride, and other monomers containing anhydride groups; heterocyclic basic monomers such as vinylpyrrolidone, vinylpyridine, and vinylcarbazole; and macromolecular monomers. These can be one type or a combination of two or more.

[0144] In this invention, in order to produce adhesive sheets with specific physical properties, it is sufficient to use (meth)acrylic polymers obtained by copolymerizing the above-mentioned monomer components. The copolymerization method can be carried out according to existing known methods, such as solution free radical polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, etc.

[0145] When the adhesive sheet has at least three layers, with the outermost and innermost layers being acrylic adhesive layers, the outermost and innermost acrylic adhesive layers are preferably formed from a resin composition comprising a (meth)acrylic polymer (A) with a glass transition temperature of -10°C or less, and more preferably, the (meth)acrylic polymer contained in the resin composition consists only of (meth)acrylic polymer (A).

[0146] [(Meth)acrylate polymer (A)]

[0147] The aforementioned (meth)acrylic polymer (A) with a glass transition temperature of -10°C or less preferably does not substantially contain structural units derived from carboxyl-containing monomers, and as a monomer component constituting the aforementioned (meth)acrylic polymer (A), it includes a monomer (a2) containing a polar group and a (meth)acrylate monomer (a1), wherein the monomer (a2) containing a polar group is at least one selected from the group consisting of hydroxyl-containing monomers and nitrogen-containing monomers, and the (meth)acrylate monomer (a1) is a monomer other than (a2) mentioned above, and the glass transition temperature (Tg) of the homopolymer formed from the monomer components is -30°C or less.

[0148] It should be noted that the above-mentioned "substantially free of structural units derived from carboxyl-containing monomers" means not only that it is completely free, but also that the (meth)acrylic polymer contains less than 0.5% by mass, preferably less than 0.1% by mass, of carboxyl-containing monomers.

[0149] As for (meth)acrylate monomers (a1) with a glass transition temperature (Tg) of -30°C or below (preferably -40°C or below, particularly -50°C or below) when forming homopolymers from the aforementioned monomer components, examples include: alkyl (meth)acrylate monomers with 4 to 18 carbon atoms in the aforementioned alkyl group, and monomers with a glass transition temperature of -30°C or below. Specifically, examples include linear alkyl (meth)acrylate monomers such as n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-heptyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, nonyl (meth)acrylate, lauryl methacrylate, and stearyl methacrylate; and branched alkyl (meth)acrylate monomers such as 2-ethylhexyl acrylate, isononyl acrylate, and isodecanyl acrylate. These can be one type or a combination of two or more. Among them, branched alkyl (meth)acrylate monomers are preferred, and 2-ethylhexyl acrylate is particularly preferred.

[0150] As monomers containing polar groups (a2), examples include hydroxyl-containing monomers and nitrogen-containing monomers, among which hydroxyl-containing monomers are preferred, and 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are particularly preferred.

[0151] Furthermore, monomers other than those described above (a1) and (a2) can be used as copolymer components of the (meth)acrylic polymer (A). Various monomers mentioned above can be used as monomers other than those described above (a1) and (a2), among which alkyl (meth)acrylic esters with 1 to 3 carbon atoms in the alkyl group are preferred, and methyl (meth)acrylic esters are particularly preferred.

[0152] From the viewpoint of high difference absorption and adhesive reliability, the glass transition temperature of the (meth)acrylic polymer (A) obtained by copolymerizing these materials is preferably below -10°C, more preferably -100 to -15°C, and particularly preferably -50 to -20°C.

[0153] In this invention, the glass transition temperature (Tg) of the acrylic polymer (A) is determined by reading the temperature at which the loss tangent (loss modulus G" / storage modulus G' = tanδ) reaches its maximum when the dynamic viscoelasticity is measured in shear mode at a frequency of 1 Hz using a dynamic viscoelasticity measuring device.

[0154] The weight-average molecular weight of the above-mentioned (meth)acrylic polymer (A) is preferably 50,000 or more and 1,500,000 or less, more preferably 100,000 or more and 700,000 or less, and particularly preferably 150,000 or more and 600,000 or less.

[0155] In this specification, the weight-average molecular weight is determined by the following method.

[0156] The sample obtained by dissolving 4 mg of (meth)acrylic acid polymer in 12 mL of THF was used as the test sample. The molecular weight distribution curve was determined using a gel permeation chromatography (GPC) analyzer (Tosoh Corporation, HLC-8320GPC) under the following conditions, and the weight-average molecular weight (Mw) was calculated.

[0157] • Protective column: TSKguardcolumnHXL

[0158] • Separation column: TSKgelGMHXL (4 columns)

[0159] Temperature: 40℃

[0160] Injection volume: 100μL

[0161] Polystyrene conversion

[0162] Solvent: THF

[0163] • Flow rate: 1.0 mL / min

[0164] The hydroxyl value of the above-mentioned (meth)acrylic polymer (A) is usually 20-150 mgKOH / g, preferably 30-100 mgKOH / g, and more preferably 40-80 mgKOH / g.

[0165] Furthermore, as described above, when this adhesive sheet has at least three layers, with the outermost and innermost layers being acrylic adhesive layers, the outermost and innermost layers and the intermediate layer (the layer sandwiched between the outermost and innermost layers) are preferably formed from resin compositions containing (meth)acrylic polymers with different compositions, and more preferably from resin compositions containing (meth)acrylic polymers as the main component. By forming such a layer configuration, it is possible to effectively suppress the wet-heat whitening of the adhesive sheet.

[0166] The intermediate layer is preferably formed of a resin composition containing an acrylic polymer (A') with a glass transition temperature higher than -10°C, and more preferably the (meth)acrylic polymer contained in the resin composition consists only of the (meth)acrylic polymer (A').

[0167] [(Meth)acrylate polymer (A')]

[0168] In the above-mentioned (meth)acrylic polymer (A') with a glass transition temperature higher than -10°C, the monomer components constituting the above-mentioned (meth)acrylic polymer (A') preferably include at least one monomer containing a polar group selected from the group consisting of hydroxyl-containing monomers and nitrogen-containing monomers (a2), and an alkyl (meth)acrylic ester monomer (a3) ​​having 1 to 18 carbon atoms in the alkyl group.

[0169] As the monomer (a2) containing the polar group mentioned above, examples include the aforementioned hydroxyl-containing monomers and nitrogen-containing monomers, among which nitrogen-containing monomers are preferred, amide-containing monomers are more preferred, and (meth)acrylamide is particularly preferred.

[0170] As the alkyl (meth)acrylate monomer (a3) ​​having 1 to 18 carbon atoms in the aforementioned alkyl group, examples include alkyl (meth)acrylate monomers having 4 to 18 carbon atoms in the aforementioned alkyl group and alkyl (meth)acrylate monomers having 1 to 3 carbon atoms in the alkyl group. Among these, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, and isobornyl (meth)acrylate are particularly preferred. Furthermore, from the viewpoint of the versatility of the monomer and ensuring that the Tg of the (meth)acrylate polymer (A') is -10°C or higher, methyl (meth)acrylate, ethyl (meth)acrylate, tert-butyl (meth)acrylate, isobutyl (meth)acrylate, and isobornyl (meth)acrylate are even more preferred.

[0171] Furthermore, monomers other than those described above (a2) and (a3) ​​can be used as copolymer components of the (meth)acrylate polymer (A'). The various monomers mentioned above can also be used as monomers other than those described above (a2) and (a3).

[0172] From the viewpoint of reprocessability, the glass transition temperature of the (meth)acrylic polymer (A') obtained by copolymerizing these polymers is preferably higher than -10°C, more preferably -5 to 20°C, and particularly preferably 0 to 15°C.

[0173] The weight average molecular weight of the (meth)acrylic polymer (A') is 50,000 or more and 1,000,000 or less, preferably 70,000 or more and 700,000 or less, and particularly preferably 100,000 or more and 500,000 or less.

[0174] [Crosslinking agent (B)]

[0175] In addition to the aforementioned (meth)acrylic acid polymer, the resin composition forming each layer may also contain a crosslinking agent (B). It is particularly preferred to incorporate the crosslinking agent (B) into the resin composition forming the intermediate layer of the adhesive sheet.

[0176] As the aforementioned crosslinking agent (B), a crosslinking agent having at least two crosslinking bonds is preferred. Examples include crosslinking agents having at least one crosslinking functional group selected from (meth)acryloyl, epoxy, isocyanate, carboxyl, hydroxyl, carbodiimide, oxazoline, aziridinyl, vinyl, amino, imino, and amide groups. One or more such crosslinking agents may be used. Furthermore, the method of chemically bonding the crosslinking agent (B) to the aforementioned (meth)acrylic polymer is also included.

[0177] Among these, crosslinking agents having (meth)acryloyl groups are preferred, and from the viewpoint of obtaining adhesive adaptability and reliability, multifunctional (meth)acrylates are particularly preferred. Here, multifunctional means having two or more crosslinking functional groups. It should be noted that, depending on the need, three or more or four or more crosslinking functional groups may be present. In addition, the aforementioned crosslinking functional groups can be protected with a deprotecting group.

[0178] Other examples of the aforementioned polyfunctional (meth)acrylates include, for example, 1,4-butanediol di(meth)acrylate, glycerol di(meth)acrylate, neopentyl glycol di(meth)acrylate, glycerol glycidyl ether di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, tricyclodecane dimethacrylate, tricyclodecanediethanol di(meth)acrylate, bisphenol A polyethoxydi(meth)acrylate, and bisphenol A polypropoxydi(meth)acrylate. Ester, Bisphenol F polyethoxydi(meth)acrylate, Ethylene glycol di(meth)acrylate, Neopentyl glycol di(meth)acrylate, Trimethylolpropane trioxyethyl(meth)acrylate, ε-caprolactone modified tri(2-hydroxyethyl)isocyanurate tri(meth)acrylate, Pentaerythritol tri(meth)acrylate, Propoxylated pentaerythritol tri(meth)acrylate, Ethoxylated pentaerythritol tri(meth)acrylate, Pentaerythritol tetra(meth)acrylate, Propoxylated pentaerythritol tetra(meth)acrylate Acrylic esters, ethoxylated pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, tri(acryloyloxyethyl)isocyanurate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, tripentaerythritol hexa(meth)acrylate, tripentaerythritol penta(meth)acrylate, neopentyl glycol di(meth)acrylate with hydroxypentanoic acid In addition to UV-curable multifunctional (meth)acrylate monomers such as di(meth)acrylates of esters and ε-caprolactone adducts of neopentyl glycol hydroxypentanoate, trimethylolpropane tri(meth)acrylate, trimethylolpropane polyethoxytri(meth)acrylate, and bis(trimethylolpropane)tetra(meth)acrylate, other multifunctional (meth)acrylate oligomers include polyester (meth)acrylates, epoxy (meth)acrylates, urethane (meth)acrylates, and polyether (meth)acrylates. These can be one type or a combination of two or more. Among them, propoxylated pentaerythritol tri(meth)acrylate and polypropylene glycol di(meth)acrylate are preferred.

[0179] The content of crosslinking agent (B) relative to 100 parts by weight of the above-mentioned (meth)acrylic polymer is typically 0.5 to 50 parts by weight, preferably 1 to 40 parts by weight, and particularly preferably 5 to 30 parts by weight. If the content is within the above range, adhesive adaptability and reliability are easily obtained, and therefore it is preferred.

[0180] [Photopolymerization Initiator (C)]

[0181] The resin composition preferably contains a photopolymerization initiator (C). As the photopolymerization initiator (C), existing known substances can be used appropriately, wherein, from the viewpoint of ease of controlling the crosslinking reaction, a photopolymerization initiator that is responsive to ultraviolet light with a wavelength of 380 nm or less is preferred.

[0182] Photopolymerization initiators (C) are broadly classified into two categories based on their free radical generation mechanisms: cracking photopolymerization initiators, which can generate free radicals by breaking and decomposing the single bonds of the photopolymerization initiator itself; and hydrogen abstraction photopolymerization initiators, which, after being photoexcited, form excited complexes with hydrogen donors in the system, enabling the transfer of hydrogen from the hydrogen donors.

[0183] When the aforementioned crack-initiating photopolymerization initiator generates free radicals through light irradiation, it decomposes to form other compounds. Once activated, it no longer functions as a reaction initiator. Therefore, it does not remain as an active species in the cured adhesive or other products after the crosslinking reaction is completed, and it is unlikely to cause unexpected photodegradation of the cured product, thus making it preferred.

[0184] On the other hand, hydrogen-abstracting photopolymerization initiators do not produce decomposition products like crack-breaking photopolymerization initiators when they generate free radicals by irradiating active energy rays such as ultraviolet rays. Therefore, they are less likely to become volatile components after the reaction is completed, which can reduce the damage to the adhered material, and this is useful.

[0185] Examples of crack-opening photopolymerization initiators include 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxycyclohexylphenyl one, 2-hydroxy-2-methyl-1-phenyl-propane-1-one, 1-(4-(2-hydroxyethoxy)phenyl)-2-hydroxy-2-methyl-1-propane-1-one, 2- -1-[4-{4-(2-hydroxy-2-methyl-propanoyl)benzyl}phenyl]-2-methyl-propane-1-one, oligomeric (2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)acetone), methyl phenylglyoxylate, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butane-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane-1-one, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholino)phenyl]-1-butanone, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, and their derivatives, etc. Among these, oligomeric (2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)acetone) is preferred.

[0186] Examples of hydrogen-abstracting photopolymerization initiators 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 their derivatives. Among these, 4-methylbenzophenone and 2,4,6-trimethylbenzophenone are preferred.

[0187] The photopolymerization initiator (C) described above is not limited to the substances listed above. In addition, the photopolymerization initiator (C) can be any one of crack-opening photopolymerization initiators and hydrogen-abstracting photopolymerization initiators, or a combination of both.

[0188] The content of photopolymerization initiator (C) is not particularly limited, but is usually 0.1 to 10 parts by weight relative to 100 parts by weight of (meth)acrylic polymer, preferably 0.2 to 5 parts by weight, and particularly preferably 0.3 to 3 parts by weight.

[0189] By setting the content of the photopolymerization initiator (C) within the above range, a suitable reaction sensitivity to active energy rays can be obtained.

[0190] [Silane Coupling Agent (D)]

[0191] Furthermore, to improve adhesion to components of the image display device, especially to glass, it is preferable to incorporate a silane coupling agent (D) into the resin composition. Preferably, the silane coupling agent (D) is included in the resin composition forming the acrylic adhesive layer that contacts the components of the image display device in the double-sided adhesive sheet.

[0192] Examples of silane coupling agents (D) include compounds having unsaturated groups such as vinyl, acryloyloxy, and methacryloyloxy, as well as amino, epoxy, and hydrolyzable functional groups such as alkoxy.

[0193] Examples of the aforementioned silane coupling agent (D) include N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-aminopropyltriethoxysilane, 3-epoxypropoxypropyltrimethoxysilane, and 3-methacryloyloxypropyltrimethoxysilane. These can be used alone or in combination of two or more. From the viewpoint of good adhesion to components of the image display device and minimal discoloration such as yellowing, 3-epoxypropoxypropyltrimethoxysilane is preferred.

[0194] The content of the silane coupling agent (D) is preferably 0.01 to 5 parts by weight, and particularly preferably 0.2 to 3 parts by weight, relative to 100 parts by weight of the (meth)acrylic polymer.

[0195] It should be noted that, similar to silane coupling agents (D), coupling agents such as organotitanate compounds can also be effectively utilized.

[0196] [Metal Corrosion Inhibitor (E)]

[0197] The resin composition preferably also contains an anti-metal corrosion agent (E). The anti-metal corrosion agent (E) is preferably contained in the resin composition forming the acrylic adhesive layer that contacts the components of the image display device in the double-sided adhesive sheet.

[0198] Examples of metal corrosion inhibitors (E) include, for example, benzotriazole compounds, benzimidazole compounds, benzothiazole compounds, and other triazole derivatives.

[0199] As the aforementioned metal corrosion inhibitor (E), it is preferable to select one or more of benzotriazole compounds, 1,2,3-triazole, and 1,2,4-triazole. Among these, from the perspective of excellent reliability as a double-sided adhesive sheet in addition to metal corrosion resistance, triazole derivatives such as 1,2,3-triazole and 1,2,4-triazole are preferred, and 1,2,3-triazole is particularly preferred.

[0200] From the viewpoint of preventing the leaching of metal corrosion inhibitors and the effect of preventing metal corrosion, the content of the aforementioned metal corrosion inhibitor (E) is preferably 0.01 to 5 parts by mass relative to 100 parts by mass of the (meth)acrylic polymer, more preferably 0.03 to 1 part by mass, and particularly preferably 0.05 to 0.5 parts by mass.

[0201] [Other Additives]

[0202] In addition to the components mentioned above, the resin composition may contain other additives. Examples of such additives include light stabilizers, UV absorbers, metal inertizers, antioxidants, antistatic agents, hygroscopic agents, foaming agents, defoamers, inorganic particles, viscosity modifiers, tackifying resins, photosensitizers, fluorescent agents, and various other additives; reaction catalysts (tertiary amine compounds, quaternary ammonium compounds, tin lauryl compounds, etc.). These can be used alone or in combination of two or more.

[0203] In addition, it may contain other known components that are typically compounded into resin compositions that form adhesives.

[0204] The above-described resin composition is obtained by separately mixing a specified amount of a (meth)acrylic acid polymer, a crosslinking agent (B) as needed, a photopolymerization initiator (C), a silane coupling agent (D), a metal corrosion inhibitor (E), and other additives. There are no particular limitations on the mixing method or the order in which the components are mixed. Furthermore, a heat treatment step can be added during the manufacture of the resin composition; in this case, it is preferable to perform heat treatment after pre-mixing the components of the resin composition. In the above mixing process, a substance that concentrates the various mixed components to form a masterbatch can be used.

[0205] Furthermore, there are no particular limitations on the mixing method described above; for example, a universal mixer, planetary mixer, Banbury mixer, kneader, valve mixer, pressure kneader, three-roll mill, two-roll mill, etc., can be used. When mixing the components of the resin composition, a solvent can be used as needed. Alternatively, the resin composition can also be used in a solvent-free system. Using it in a solvent-free system provides advantages such as no solvent residue, improved heat resistance, and improved lightfastness.

[0206] [Manufacturing method of adhesive sheet]

[0207] The following describes a method for manufacturing this adhesive sheet, but is not limited to this method. This adhesive sheet can be a single layer or multiple layers, preferably having a multi-layer structure, and more preferably having at least three layers, with the outermost and innermost layers being acrylic adhesive layers. Typically, this adhesive sheet is preferably manufactured in the form of an adhesive sheet with a release film, having a structure formed by laminating this adhesive sheet with a release film, through the following steps. It should be noted that the pre-curing step in the following steps can be omitted.

[0208] In addition, the aforementioned release film can be laminated on only one side of the adhesive sheet or on both sides.

[0209] As the material for the release film, a known release film may be used appropriately.

[0210] As a material for release film, appropriate selections and uses can be made of materials such as release paper, which are made by coating silicone resin onto films such as polyester film, polyolefin film, polycarbonate film, polystyrene film, acrylic film, cellulose triacetate film, and fluoropolymer film.

[0211] The aforementioned release film may have other layers as needed, such as an antistatic layer, a hard coating layer, and an anchoring layer.

[0212] When release films are stacked on both sides of this adhesive sheet, one release film and the other release film can have the same stacking configuration and / or material, or they can have different stacking configurations and / or materials. Furthermore, they can have the same thickness or different thicknesses.

[0213] In addition, release films with different peel strengths and different thicknesses can be laminated on both sides of this adhesive sheet.

[0214] The thickness of the release film is not particularly limited. However, from the viewpoint of processability and operability, it is preferably 10 to 250 μm, more preferably 25 to 200 μm, and even more preferably 35 to 190 μm.

[0215] As a method for manufacturing this adhesive sheet, when the adhesive sheet is a single layer, for example, by applying a substance obtained by heating and melting the aforementioned resin composition (thermal melting) onto a release film, and further holding and heating it with another release film, an adhesive sheet with a release film can be obtained. Alternatively, when the adhesive sheet is multilayered, by preparing an adhesive sheet with a release film in a number corresponding to the required number of layers of the adhesive sheet using the above method, peeling off the release film and stacking the adhesive sheets, a multilayered adhesive sheet can be obtained.

[0216] When the adhesive sheet is multilayered, it is possible to manufacture a multilayered adhesive sheet by repeatedly applying the aforementioned resin composition onto a release sheet to form an adhesive layer, and then further applying other resin compositions onto the formed adhesive layer to form a resin layer. Alternatively, instead of the aforementioned release sheet, the adhesive sheet can be made by applying a resin composition to the substrate. Furthermore, this adhesive sheet can also be manufactured by using a method of simultaneously forming multiple layers of resin composition through multilayer coating and co-extrusion molding.

[0217] It should be noted that this adhesive sheet can also be formed by, for example, injecting a resin composition into a mold, instead of using a release film or an adhesive as described above.

[0218] Furthermore, this adhesive sheet can also be manufactured by directly filling the components of the image display device, which are the adhered objects, with a resin composition.

[0219] The resulting adhesive sheet is preferably pre-cured by reactive energy radiation crosslinking in a manner that exhibits latent reactive energy radiation reactivity, in other words, in a manner that exhibits residual reactive energy radiation reactivity. In the case of pre-curing, reactive energy radiation is applied through the release film to induce reactive energy radiation crosslinking in each layer. At this time, the degree of reactive energy radiation crosslinking (gel fraction) can be adjusted by controlling the amount of reactive energy radiation applied. However, as mentioned above, by applying ultraviolet light through the release film, a portion of the reactive energy radiation can be blocked, thus adjusting the degree of reactive energy radiation crosslinking (gel fraction).

[0220] The adhesive sheet obtained by this operation is an optically transparent 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.

[0221] In addition, the haze value of the adhesive sheet is preferably 10% or less, more preferably 5% or less, and particularly preferably 3% or less.

[0222] This adhesive sheet is typically distributed as an adhesive sheet with a release film sandwiched between two acrylic adhesive layers on both sides. When using a double-sided adhesive sheet, the release film is peeled off from the acrylic adhesive layers, and the acrylic adhesive layers are then adhered to the image display component.

[0223] [Laminator for Image Display Devices]

[0224] An image display device as an example of an embodiment of the present invention The laminate (referred to as "the laminate for this image display device") is a structure in which two image display device components are laminated together with this adhesive sheet sandwiched between them.

[0225] Of the aforementioned two components constituting the image display device, preferably, one is a cover glass with a curved shape, and the other is any one of the following components, or a combination of two or more: a contact sensor, an image display panel, a surface protective film, an anti-reflective film, a color filter, a polarizing film, and a phase difference film. With the above-described configuration, the effects of the present invention can be particularly enjoyed.

[0226] [Image display device]

[0227] An example of an embodiment of the present invention describes an image display device obtained using a laminate of the present image display device.

[0228] As an example of this image display device, an image display device having a structure in which this image display device is combined with other image display device components by means of a laminate.

[0229] At this point, “other components of an image display device” can include, for example, FPC cables, reflective sheets, light guide plates and light sources, diffusion films, prism sheets, liquid crystal panels, organic EL panels, anti-reflective films, color filters, polarizing plates, phase retardation plates, glass substrates, surface protective films, and components obtained by combining these components into one.

[0230] Specific examples of this image display device include liquid crystal displays, organic EL displays, inorganic EL displays, electronic paper, plasma displays, and microelectromechanical systems (MEMS) displays used in personal computers, mobile terminals (PDAs), game consoles, televisions (TVs), car navigation systems, touch panels, stylus tablets, etc.

[0231] (Explanation of statements, etc.)

[0232] It should be noted that, generally speaking, "sheet" refers to a thin, flat product whose thickness is small relative to its length and width, as defined by JIS; and generally, "film" refers to a thin, flat product with extremely small thickness relative to its length and width, and whose maximum thickness is arbitrarily defined, usually supplied in roll form (Japanese Industrial Standard JIS K6900). However, the boundary between sheet and film is not defined, and there is no need to distinguish between the two in this invention. Therefore, in this invention, when referred to as "film," it is also considered to include "sheet," and when referred to as "sheet," it is also considered to include "film."

[0233] Additionally, when referred to as "panel" as in image display panel, protective panel, etc., it includes sheet, sheet, and film.

[0234] In this specification, when denoted as "x~y" (x and y are arbitrary numbers), unless otherwise specified, it includes the meaning of "above x and below y" as well as "preferably greater than x" and "preferably less than y".

[0235] Furthermore, when it is written as "x or above" (where x is any number), unless otherwise specified, it includes the meaning of "x or above" and "preferably greater than x". When it is written as "y or below" (where y is any number), unless otherwise specified, it includes the meaning of "y or below" and "preferably less than y".

[0236] Example

[0237] The present invention will now be described in more detail through examples and comparative examples. However, the present invention is not limited to these examples.

[0238] First, details of the raw materials for the resin compositions prepared in the examples will be explained.

[0239] <(meth)acrylic polymers>

[0240] • (Meth)acrylic polymer (A-1): An acrylic polymer formed from 2-ethylhexyl acrylate / methyl acrylate / 2-hydroxyethyl acrylate (weight average molecular weight: 430,000, Tg: -25℃, hydroxyl value: 67 mgKOH / g)

[0241] • (Meth)acrylic polymer (A'-1): A (meth)acrylic polymer formed from 2-ethylhexyl acrylate / methyl acrylate / acrylamide / methyl methacrylate / isobornyl methacrylate (weight average molecular weight: 250,000, Tg: 4℃)

[0242] • (Meth)acrylic polymer (A'-2): An acrylic polymer formed from methyl acrylate / ethyl acrylate / 2-ethylhexyl acrylate / 2-hydroxyethyl acrylate (weight average molecular weight: 540,000, Tg: 1℃, hydroxyl value: 62mgKOH / g)

[0243] It should be noted that the weight-average molecular weight, glass transition temperature (Tg), and hydroxyl value of the above-mentioned (meth)acrylic polymers were determined by the following methods.

[0244] [Weight-average molecular weight]

[0245] The weight-average molecular weight of (meth)acrylic acid polymers was determined using a gel permeation chromatography (GPC) analyzer (Tosoh Corporation, HLC-8320GPC). Specifically, 4 mg of (meth)acrylic acid polymer was dissolved in 12 mL of THF and used as the test sample. The molecular weight distribution curve was determined under the following conditions to calculate the weight-average molecular weight (Mw).

[0246] • Protective column: TSKguardcolumnHXL

[0247] • Separation column: TSKgelGMHXL (4 columns)

[0248] Temperature: 40℃

[0249] Injection volume: 100μL

[0250] Polystyrene conversion

[0251] Solvent: THF

[0252] • Flow rate: 1.0 mL / min

[0253] [Glass transition temperature (Tg)]

[0254] The glass transition temperature (Tg) of (meth)acrylic polymers was determined using a rheometer (TA Instruments, Discovery HR2). Specifically, for (meth)acrylic polymers with a thickness of 0.6–0.8 mm, dynamic viscoelastic spectra were measured over a temperature range of -120–200 °C under the following conditions: tool: Φ8 mm parallel plate; strain: 0.1%; frequency: 1 Hz; temperature: -120–200 °C; heating rate: 5 °C / min. The temperature at which the loss tangent (Tanδ) reaches its maximum value was read from the obtained data, and the glass transition temperature (Tg) was then determined.

[0255] [Hydroxy value]

[0256] The hydroxyl value of (meth)acrylic acid polymers was determined by neutralization titration.

[0257] Take 2g of sample into an Erlenmeyer flask, add 10mL of a mixture of acetic anhydride and pyridine (1:13) using a quantitative pipette, and then add 10mL of toluene. Install an air cooler in the upper part of the Erlenmeyer flask and heat at 95°C for 90 minutes. After heating, add 10mL of toluene and 10mL of pure water, and cool to room temperature (23°C) while stirring. Then, add a few drops of phenolphthalein solution and titrate with 0.1mol / L potassium hydroxide (KOH) solution. Alternatively, as a blank test, do not take a sample into the Erlenmeyer flask and perform the same operation as above. Calculate the hydroxyl value according to the following formula (1).

[0258] (Calculation formula)

[0259] Hydroxyl value = 5.611 × (volume of potassium hydroxide solution used in blank test (mL) - volume of potassium hydroxide solution used in titration (mL)) × f / sample volume collected (g) + acid value…(1)

[0260] •f: Factor of 0.1 mol / L potassium hydroxide solution

[0261] [Acid Value]

[0262] The acid value was determined by the following method. Yg of the acrylic copolymer was collected in a beaker and dissolved in a toluene:methanol mixture of 7:3. After dissolution, an appropriate amount of phenolphthalein was added, and the solution was titrated with 0.1 mol / L KOH solution while stirring. The endpoint was reached when the KOH solution turned a pale pink color, measured in mL. The acid value was calculated using the following formula (2).

[0263] (Calculation formula)

[0264] Acid value (mgKOH / g) = X × (f × M × 56.1) / Y…(2)

[0265] ·f: Factor of KOH solution

[0266] • M: Molar concentration (mol / L)

[0267] • X: Volume of KOH solution (mL)

[0268] • Y: Sample amount (g)

[0269] It should be noted that, in order to improve accuracy, a 0.01 mol / L KOH solution is used when the acid value is low.

[0270] <Crosslinking agent (B)>

[0271] • Crosslinking agent (B-1): Propoxylated pentaerythritol triacrylate

[0272] • Crosslinking agent (B-2): Polypropylene glycol #400 diacrylate

[0273] <Photopolymerization Initiator (C)>

[0274] • Photopolymerization initiator (C-1): A mixture of 2,4,6-trimethylbenzophenone and 4-methylbenzophenone (IGM's "Esacure TZT")

[0275] <Silane Coupling Agent (D)>

[0276] • Silane coupling agent (D-1): 3-epoxypropoxypropyltrimethoxysilane

[0277] <Example 1>

[0278] Resin composition 1 is prepared by uniformly melting and mixing 1 kg of (meth)acrylic polymer (A'-1), 100 g of crosslinking agent (B-1), and 5 g of photopolymerization initiator (C-1).

[0279] The resin composition 1 described above is sandwiched between two release films (DIAFOIL MRF (thickness 75 μm) manufactured by Mitsubishi Chemical Corporation) or "DIAFOIL MRT (thickness 38 μm) manufactured by Mitsubishi Chemical Corporation), i.e. two release films, and formed into a sheet at a temperature of 80°C with a thickness of 67 μm to produce an intermediate layer sheet (1-1).

[0280] Resin composition 2 is prepared by uniformly melting and mixing 1 kg of (meth)acrylic polymer (A-1), 15 g of photopolymerization initiator (C-1), and 2 g of silane coupling agent (D-1).

[0281] The resin composition 2 described above is sandwiched between two release films of polyethylene terephthalate (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 formed into a sheet at a temperature of 80°C with a thickness of 16.5 μm, to produce two outermost and innermost (outermost and innermost) adhesive sheets (2-1).

[0282] After peeling off the release film on both sides, the middle layer is glued to the adhesive surface of the innermost layer after peeling off the release film on one side, using the adhesive sheet (2-1), to create a laminate composed of layers (2-1) / (1-1) / (2-1).

[0283] Through the release film remaining on the surface of the outermost adhesive sheet (2-1), the cumulative light intensity at a wavelength of 365 nm is 1000 mJ / cm. 2The adhesive sheet (pre-cured product) with a release film was prepared by pre-curing it by irradiating it with a high-pressure mercury lamp.

[0284] It should be noted that the adhesive sheet of Example 1 has the potential to be photocured by light irradiation, and is a sheet with active energy ray curing properties.

[0285] <Examples 2 and 3>

[0286] Except for the proportions, thickness composition, and pre-curing conditions shown in Table 1, the adhesive sheets (pre-cured products) with release films of Examples 2 and 3 were prepared in the same manner as in Example 1.

[0287] It should be noted that the adhesive sheets of Examples 2 and 3 have the potential to be photocured by light irradiation, and are sheets with active energy ray curing properties.

[0288] <Example 4>

[0289] A resin composition 5 is prepared by uniformly melting and mixing 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).

[0290] The resin composition 5 described above is sandwiched between two release films (DIAFOIL MRF (thickness 75 μm) manufactured by Mitsubishi Chemical Corporation) and two release films, i.e., two release films, and formed into a sheet at a temperature of 80°C with a thickness of 100 μm.

[0291] Through the release film on the surface, the cumulative light intensity at a wavelength of 365nm is 1000mJ / cm. 2 In this manner, the adhesive sheet (pre-cured product) with a release film is produced by irradiating it with a high-pressure mercury lamp.

[0292] It should be noted that the adhesive sheet of Example 4 has the potential to be photocured by light irradiation, and is a sheet with active energy ray curing properties.

[0293] <Comparative Examples 1-3>

[0294] Except for the proportions shown in Table 1, the adhesive sheets with release films of Comparative Examples 1 to 3 were prepared in the same manner as in Example 1.

[0295] It should be noted that the adhesive sheets of Comparative Examples 1 to 3 have the potential to be photocured by light irradiation, and are sheets with active energy ray curing properties.

[0296] <Evaluation of Physical Properties of Adhesive Sheets>

[0297] The physical properties of the adhesive sheets of Examples 1-4 and Comparative Examples 1-3 obtained by the aforementioned operation were measured as follows.

[0298] [Adhesion]

[0299] Peel off one of the release films from the adhesive sheets with release films of Examples 1-4 and Comparative Examples 1-3, and attach a 100 μm thick polyethylene terephthalate film (manufactured by Toyobo Co., Ltd., COSMOSHINEA4300) as an inner lining film to prepare a laminate.

[0300] After cutting the above-mentioned laminated product into lengths of 150mm and widths of 10mm, the adhesive surface exposed by peeling off the remaining release film is pressed onto the soda-lime glass by making a manual roller move back and forth once. The adhesive sheet is then subjected to autoclave treatment (temperature of 60°C, gauge pressure of 0.2MPa, 20 minutes) for final attachment.

[0301] The peel force (N / cm) of the adhesive test sample was measured when it was peeled from the glass at a peel angle of 180° and a peel speed of 300 mm / min under the conditions of a temperature of 23°C and a humidity of 50%RH.

[0302] [Adhesion strength after curing]

[0303] Peel off one of the release films from the adhesive sheets with release films of Examples 1-4 and Comparative Examples 1-3, and attach a 100 μm thick polyethylene terephthalate film (manufactured by Toyobo Co., Ltd., COSMOSHINEA4300) as an inner lining film to prepare a laminate.

[0304] After cutting the aforementioned laminated product into 150mm long and 10mm wide pieces, the adhesive surface exposed by peeling off the remaining release film is pressed onto the soda-lime glass by manually rolling the roller back and forth once. Finally, an autoclave treatment (60°C, 0.2MPa gauge pressure, 20 minutes) is performed for final attachment, using a high-pressure mercury lamp with a cumulative light intensity of 3000mJ / cm². 2 The sample for testing adhesive strength was prepared by irradiating the inner lining film with 365nm ultraviolet light and then curing it at 23°C and 50%RH for 12 hours.

[0305] The peel force (N / cm) of the cured adhesive sample was measured when it was peeled from the glass at a peel angle of 180° and a peel speed of 300 mm / min under the conditions of a temperature of 23°C and a humidity of 50%RH.

[0306] [Persistence]

[0307] Peel off one of the release films from the adhesive sheets with release films of Examples 1-4 and Comparative Examples 1-3, and attach a 38 μm thick polyethylene terephthalate (PET) film (manufactured by Mitsubishi Chemical Corporation, DIAFOILS100) as an inner liner film to prepare a laminate.

[0308] After cutting the above-mentioned laminated product into lengths of 150 mm and widths of 20 mm, the adhesive surface exposed by peeling off the remaining release film is pasted onto a polished stainless steel plate (SUS304) with an attachment area of ​​20 mm × 20 mm, as a sample for holding force measurement.

[0309] After preheating the holding force test sample at 70°C for 15 minutes, a load of 0.5 kg was applied, and the sample was kept at 70°C for 30 minutes. The offset length (mm) of the adhesive sheet was then measured.

[0310] [Retention strength after curing]

[0311] For the adhesive sheets with release films of Examples 1-4 and Comparative Examples 1-3, a high-pressure mercury lamp was used to obtain a cumulative light intensity of 3000 mJ / cm at a wavelength of 365 nm. 2 The adhesive sheet is photocured by irradiating it with light through a release film, thus preparing the cured adhesive sheet.

[0312] Peel off one of the release films from the cured adhesive sheet and attach a 38μm thick polyethylene terephthalate (PET) film (manufactured by Mitsubishi Chemical Corporation, DIAFOIL S100) as the inner lining film to prepare the laminate.

[0313] After cutting the above-mentioned laminated product into lengths of 150 mm and widths of 20 mm, the adhesive surface exposed by peeling off the remaining release film is pasted onto a polished stainless steel plate (SUS304) with an attachment area of ​​20 mm × 20 mm, and used as a sample for measuring the holding power after curing.

[0314] After preheating the cured holding force test sample at 70°C for 15 minutes, a load of 0.5 kg was applied, and the sample was kept at 70°C for 30 minutes. The offset length (mm) of the adhesive sheet was then measured.

[0315] [Constant Load Stripping]

[0316] Peel off one of the release films from the adhesive sheets with release films of Examples 1-4 and Comparative Examples 1-3, and attach a 100 μm thick polyethylene terephthalate film (manufactured by Toyobo Co., Ltd., COSMOSHINEA4300) as an inner lining film to prepare a laminate.

[0317] After cutting the above-mentioned laminated product into 150mm long and 10mm wide sections, a manual roller is used to roll back and forth once. A 10mm wide and 100mm long area of ​​the adhesive surface exposed after peeling off the remaining release film is then pressed onto the soda-lime glass as the bonding area. The area of ​​the adhesive sheet other than the bonding area is designated as the non-bonded area. Subsequently, the product is subjected to autoclaving (50℃, 0.2MPa gauge pressure, 20 minutes) and cured at 40℃ for 30 minutes for final bonding. The resulting sample is used for the constant load peel test.

[0318] Using this sample, at a temperature of 23°C and a humidity of 50% RH, the soda-lime glass was fixed horizontally with the non-adhesive area of ​​the adhesive sheet hanging downwards. A load of 0.45 N was applied to the longitudinal end of the non-adhesive area of ​​the adhesive sheet for 30 minutes. The distance at which the adhesive area of ​​the adhesive sheet peeled off from the soda-lime glass during this period was measured as the constant load peel distance (refer to...). Figure 1 ).

[0319] [Ball Stickiness]

[0320] The viscosity of the inclined rolling ball was measured according to the specifications in JIS Z 0237:2009 at a temperature of 23°C and an inclination angle of 30°.

[0321] Specifically, the adhesive sheets with release films from Examples 1-4 and Comparative Examples 1-3 were cut to a length of 10 cm and a width of 2.5 cm. One release film was peeled off, and a 25 μm thick polyethylene terephthalate film (manufactured by Mitsubishi Chemical Corporation, DIAFOIL S100) was pasted on as an inner liner to prepare a laminate. The rolling ball viscosity test sample was placed 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. After peeling off the other release film of the adhesive sheet, the ball was rolled towards the adhesive surface (10 cm in length) while changing the size of the ball (ball number). The ball number of the ball that stopped on the adhesive surface was taken as the value of the rolling ball viscosity.

[0322] [Extensional storage modulus (E') and peak temperatures (T1), (T2)]

[0323] The adhesive sheets with release films from Examples 1-4 and Comparative Examples 1-3 were cut into pieces with a width of 4 mm and a length of 15 mm. The dynamic viscoelastic spectra were measured in the tensile mode using a dynamic viscoelasticity measuring device (IT Measurement Control, itkDVA-200) under the following conditions: vibration frequency of 1 Hz, heating rate of 3 °C / min, and temperature range of -120 to 80 °C. The tensile storage modulus (E') at 25 °C was read from the obtained data.

[0324] In addition, the maximum values ​​of the loss tangent (Tanδ), i.e., the peak temperatures (T1) and (T2), were read from the above dynamic viscoelastic spectrum data.

[0325] [Tensile storage modulus (E') and peak temperatures (T1) and (T2) after curing]

[0326] For the adhesive sheets with release films prepared in the examples and comparative examples, the cumulative light intensity at a wavelength of 365 nm is 3000 mJ / cm. 2 The adhesive sheet is cured by irradiating it with a high-pressure mercury lamp through a release film.

[0327] For the cured adhesive sheet, the dynamic viscoelastic spectrum under tensile mode was measured using the same test conditions as the uncured adhesive sheet (pre-cured product). The tensile storage modulus (E') of the cured adhesive sheet at 25°C was then calculated based on the obtained data.

[0328] In addition, the maximum values ​​of the loss tangent (Tanδ), i.e., the peak temperatures (T1) and (T2), were read from the above dynamic viscoelastic spectrum data.

[0329] [Shear storage modulus (G') and glass transition temperature (Tg)]

[0330] The adhesive sheets from Examples 1-4 and Comparative Examples 1-3 were stacked with a thickness of 0.6-0.8 mm, and the resulting samples were punched into circular shapes with a diameter of 8 mm as test specimens. Dynamic viscoelastic spectra were measured for these test specimens using a rheometer (TA Instruments, Discovery HR2) under the following measurement conditions. Shear storage modulus (G') at 25°C, 65°C, and 85°C was read from the measured data.

[0331] In addition, the maximum value of the loss tangent (Tanδ) was read from the above dynamic viscoelastic spectrum data, which is the glass transition temperature (Tg).

[0332] (Measurement conditions)

[0333] Adhesion tool: Φ8mm parallel plate

[0334] Strain: 0.1%

[0335] Frequency: 1Hz

[0336] Temperature: -120~200℃

[0337] Heating rate: 5℃ / min

[0338] [Shear storage modulus (G') and glass transition temperature (Tg) after curing]

[0339] For the adhesive sheets with release films in Examples 1-4 and Comparative Examples 1-3, the cumulative light intensity at a wavelength of 365 nm is 3000 mJ / cm. 2 The adhesive sheet is cured by irradiating it with a high-pressure mercury lamp through a release film.

[0340] For the cured adhesive sheet, it is stacked with a thickness of 0.6 to 0.8 mm. The resulting sample is punched into a circle with a diameter of 8 mm and used as a test sample. The dynamic viscoelastic spectrum is measured by shearing method under the same test conditions as the uncured adhesive sheet (pre-cured product). The storage modulus (G') of the cured adhesive sheet at temperatures of 25℃, 65℃ and 85℃ is calculated based on the obtained data.

[0341] In addition, the maximum value of the loss tangent (Tanδ) was read from the above dynamic viscoelastic spectrum data, which is the glass transition temperature (Tg).

[0342] [Residual creep strain]

[0343] The adhesive sheets from Examples 1-4 and Comparative Examples 1-3 were stacked with a thickness of 0.6-0.8 mm, and the resulting samples were punched into circles with a diameter of 8 mm as test specimens. Using a rheometer (TA Instruments, Discovery HR2), a pressure of 1 kPa was applied to the test specimen for 180 seconds at a temperature of 25°C, and after releasing the pressure and waiting for 180 seconds, the strain (%) was read, which is the residual creep strain (%).

[0344] Furthermore, for the adhesive sheets with release films in Examples 1-4 and Comparative Examples 1-3, the cumulative light intensity at a wavelength of 365 nm was 3000 mJ / cm. 2 The adhesive sheet was photocured by irradiating it through a release film using a high-pressure mercury lamp. The cured adhesive sheet was then stacked in layers with a thickness of 0.6–0.8 mm. The resulting sample was punched into a circle with a diameter of 8 mm as the test specimen. Using a rheometer (TA Instruments Discovery HR2), a pressure of 1 kPa was applied to the test specimen for 180 seconds at 25°C. After releasing the pressure and waiting another 180 seconds, the strain, i.e., the residual creep strain (%), was recorded.

[0345] [creep strain]

[0346] The adhesive sheets from Examples 1-4 and Comparative Examples 1-3 were stacked with a thickness of 0.6-0.8 mm, and the resulting samples were punched into circles with a diameter of 8 mm to serve as test specimens. Using a rheometer (TA Instruments, Discovery HR2), a pressure of 1 kPa was applied to the test specimen for 10 seconds at a temperature of 25°C, and the creep strain (%) was read.

[0347] Furthermore, for the adhesive sheets with release films in Examples 1-4 and Comparative Examples 1-3, the cumulative light intensity at a wavelength of 365 nm was 3000 mJ / cm. 2 The adhesive sheet is cured by irradiating it with a high-pressure mercury lamp through a release film.

[0348] The cured adhesive sheets were stacked in layers with a thickness of 0.6–0.8 mm, and the resulting sample was punched into a circle with a diameter of 8 mm as the test specimen. Using a rheometer (TA Instruments Discovery HR2), a pressure of 1 kPa was applied to the test specimen for 10 seconds at a temperature of 25°C, and the creep strain (%) was read.

[0349] [Gel score]

[0350] The release film was peeled off from the adhesive sheets with release film in Examples 1-4 and Comparative Examples 1-3, and a small piece of adhesive sheet of about 0.1g was collected.

[0351] The collected adhesive fragments were wrapped in a pre-made bag-shaped SUS sieve (#150) of mass (X), and the bag was sealed to prepare a sample. The mass (Y) of this sample was then measured. The sample was then immersed in ethyl acetate and stored in the dark at 23°C for 24 hours. Afterward, the sample was removed and heated at 70°C for 4.5 hours to evaporate the ethyl acetate. The mass (Z) of the dried sample was then measured. Based on the measured masses, the gel fraction was calculated using the following formula.

[0352] Gel fraction (%) = [(ZX) / (YX)] × 100

[0353] Furthermore, for the adhesive sheets of Examples 1-4 and Comparative Examples 1-3, a high-pressure mercury lamp was used to achieve a cumulative light intensity of 3000 mJ / cm at 365 nm. 2 The adhesive sheet is cured by irradiating it with light through a release film, thus preparing a cured adhesive sheet. The cured adhesive sheet is then subjected to the same gel fraction evaluation steps as described above to determine its gel fraction.

[0354] <Paste Adaptability>

[0355] For the adhesive sheets of Examples 1-4 and Comparative Examples 1-3, the following procedures were performed to evaluate their adhesive adaptability.

[0356] [Surface Adhesion]

[0357] As a component of the image display device, a glass plate (covering glass with a curved shape) measuring 156mm × 73mm × 0.5mm and bent at the long side end with a radius of curvature of 3mm is prepared. A 2mm wide and 10μm thick print is applied around the inner curved surface of this component.

[0358] Peel off one of the release films from the adhesive sheets with release films of Examples 1-4 and Comparative Examples 1-3, and attach a 125 μm thick polyethylene terephthalate film (manufactured by Toyobo Co., Ltd., COSMOSHINEA4100) to the exposed adhesive surface to prepare a laminate.

[0359] After the adhesive surface exposed by peeling off the residual release film in the laminate is aligned with the inner curved surface of the aforementioned cover glass, a diaphragm vacuum bonding device is used to bond the laminate under the conditions of 30°C, 0.1MPa, and 60 seconds to produce a laminate for an image display device.

[0360] After storing the aforementioned image display device laminate at 23°C and 50% humidity for 200 hours, visual observation was performed. When peeling or cohesive failure of the adhesive sheet was observed on the curved surface of the covering glass, it was judged as "× (bad)". When the adhesive sheet did not peel or cohesive failure and maintained a good appearance, it was judged as "○ (good)". The defect patterns that presented "× (bad)" are recorded in (Table 1).

[0361] [Height Difference Absorption]

[0362] For the adhesive sheets with release films in Examples 1-4 and Comparative Examples 1-3, they were cut into 52mm × 80mm pieces using a Thomson punching machine while the release films were stacked.

[0363] Using a vacuum press, the adhesive surface exposed by peeling off the release film on one side is pressed onto the printing surface of a soda-lime glass (82mm×54mm×thickness 0.5mm, printing thickness: 8~40μm) with different printing thicknesses applied to the edge 5mm using a vacuum press (temperature 25℃, pressure 0.1MPa).

[0364] Next, the remaining release film is peeled off and pressed onto the soda-lime glass (82mm×54mm×0.5mm thick) without printing height difference. Then, it is subjected to autoclave treatment (temperature 60℃, gauge pressure 0.2MPa, 20 minutes) for final attachment to create a glass / double-sided adhesive sheet / glass laminate with height difference.

[0365] Visually inspect the produced laminate to confirm the printing thickness is such that there are no air bubbles near the printing height difference and the laminate adheres well. A print thickness of 20% or more (for good adhesion) is categorized as "◎ (Perfect)", 10% or more as "○ (Good)", and less than 10% as "× (Bad)".

[0366] [Resistance to adhesive colloid disintegration]

[0367] For the adhesive sheets with release films of Examples 1-4 and Comparative Examples 1-3, one release film was peeled off and cut in half to 10mm × 10mm. The exposed adhesive surface was placed opposite a 0.6mm thick soda-lime glass sheet, and the adhesive sheet was pressed to the glass using a vacuum bonding machine at a temperature of 23°C, a gauge pressure of 0.4MPa, and a pressing time of 60 seconds.

[0368] For the center of each side of the adhesive sheet, the distance from which the adhesive overflows from the half-cut mark is measured, and the average value of the four sides is taken as the adhesive overflow distance (μm). Cases with an adhesive overflow distance of less than 300μm are judged as "◎ (perfect)", cases with an overflow distance of less than 500μm are judged as "○ (good)", and cases with an overflow distance of more than 500μm are judged as "× (bad)".

[0369] [Roller adhesion]

[0370] For the adhesive sheets with release films in Examples 1-4 and Comparative Examples 1-3, a roller bonding device using two plate-shaped adsorption bases was used to perform the bonding operation, and the positional deviation during the roller bonding operation was evaluated.

[0371] Specifically, the adhesive sheet with release film prepared in the examples and comparative examples is cut into 70mm × 100mm pieces and fixed to the first adsorption base of the roller bonding device. The adhesive surface exposed after peeling off one release film is positioned opposite the substrate film (100μm thick polyethylene terephthalate film (Toyobo Co., Ltd., COSMOSHINE A4300) fixed to the second adsorption base) (see reference). Figure 2 ).

[0372] Using an adsorption platform, an adhesive sheet and a substrate film are rolled together under the following conditions to create a laminate for evaluating roll adhesion.

[0373] (Conditions for the roller bonding device)

[0374] Roller diameter: 12mm

[0375] • Delivery speed: 25mm / second

[0376] Roller pressure: 0.2MPa

[0377] • Roller rubber hardness: 70 (ASKER A)

[0378] • Abutment adsorption pressure: 0.05 MPa

[0379] Temperature: 23℃

[0380] Prepare 30 of the aforementioned laminates and visually inspect their appearance. If all 30 laminates are successfully bonded without any positional offset at the end of the roller bonding starting point, they are judged as "◎ (perfect)". If 1 to 3 laminates out of 30 have a positional offset of more than 1 mm (yield of more than 90%), they are judged as "○ (good)". If 4 or more have a positional offset, they are judged as "× (bad)".

[0381] [Indentation resistance]

[0382] For the adhesive sheets with release films in Examples 1-4 and Comparative Examples 1-3, the release film on one side was peeled off, and a copper foil with a thickness of 50 μm was adhered. For the adhesive surface exposed after peeling off the remaining release film, a manual roller was moved back and forth once to press the adhesive sheet onto the entire surface of soda-lime glass (82 mm × 54 mm × 0.5 mm thickness), and final attachment was achieved by autoclaving (temperature 60°C, gauge pressure 0.2 MPa, 20 minutes). A high-pressure mercury lamp was used, with a cumulative light intensity of 3000 mJ / cm². 2 Samples for evaluating indentation resistance were prepared by irradiating a soda-lime glass surface with 365nm ultraviolet light and then curing it at 23°C and 50%RH for 12 hours.

[0383] A polyimide film (UPILEX-S, manufactured by Ube Industries, Inc.) measuring 20 mm in width, 30 mm in length, and 125 μm in thickness was placed on the copper foil surface of the aforementioned sample. The sample was then pressed using a press at a temperature of 25°C, a pressure of 0.3 MPa, and a processing time of 10 seconds. The pressurized sample was then allowed to stand at room temperature (23°C) for 12 hours.

[0384] Visually inspect the pressed sample. If no indentation is visible to the naked eye, it is judged as "◎ (perfect)". If a slight uneven shape caused by the transfer of the polyimide film at the edge is observed in a local area, it is judged as "○ (good)". If an uneven shape is clearly visible, it is judged as "× (bad)".

[0385] <Reliability>

[0386] The reliability of the adhesive sheets after bonding was evaluated as follows for the adhesive sheets of Examples 1-4 and Comparative Examples 1-3.

[0387] [Low temperature characteristics]

[0388] Peel off one of the release films from the adhesive sheets with release films of Examples 1-4 and Comparative Examples 1-3, and attach a 100 μm thick polyethylene terephthalate film (manufactured by Toyobo Co., Ltd., COSMOSHINEA4300) as an inner lining film to prepare a laminate.

[0389] After cutting the aforementioned laminated product into 150mm long and 10mm wide pieces, the adhesive surface exposed by peeling off the remaining release film is pressed onto the soda-lime glass by manually rolling the roller back and forth once. Finally, an autoclave treatment (60°C, 0.2MPa gauge pressure, 20 minutes) is performed for final attachment, using a high-pressure mercury lamp with a cumulative light intensity of 3000mJ / cm². 2 The sample for testing adhesive strength was prepared by irradiating the inner lining film with 365nm ultraviolet light and then curing it at 23°C and 50%RH for 12 hours.

[0390] The peel force (N / cm) of the cured adhesive sample was measured when it was peeled from the glass at a temperature of 0°C, a peel angle of 180°, and a peel speed of 300 mm / min.

[0391] [Humidity and Haze]

[0392] For the adhesive sheets with release films in Examples 1-4 and Comparative Examples 1-3, one release film was peeled off, and a manual roller was moved back and forth once to adhere a piece of soda-lime glass (82mm × 54mm × 0.5mm thickness). The manual roller was then moved back and forth once more, and the adhesive surface exposed by peeling off the remaining release film was rolled onto another piece of soda-lime glass (82mm × 54mm × 0.5mm thickness). Finally, an autoclave treatment (temperature 60°C, gauge pressure 0.2MPa, 20 minutes) was performed for final attachment. A high-pressure mercury lamp was used, with a cumulative light intensity of 3000 mJ / cm². 2 The sample for evaluating damp heat haze was prepared by irradiating a glass surface with 365nm ultraviolet light and then curing it at 23°C and 50%RH for 12 hours.

[0393] The above samples were stored in an environmental testing machine at 85°C and 85%RH for 500 hours. The haze value of the stored samples was calculated using a haze meter (NDH5000, manufactured by Nippon Denshoku Kogyo Co., Ltd.) according to JIS K7136.

[0394] [Durability]

[0395] Using the adhesive sheets from Examples 1-4 and Comparative Examples 1-3, a laminate for an image display device was fabricated using the aforementioned method. A high-pressure mercury lamp was used to achieve a flux of 3000 mJ / cm². 2 The sample for durability evaluation was prepared by irradiating the curved glass surface of the laminate with a cumulative light intensity of 365 nm, and then curing it at a temperature of 23°C and a humidity of 50%RH for 12 hours.

[0396] After storing the above samples in an environment of 85°C and 85%RH for 1000 hours, visually inspect the samples. If foaming or peeling is observed in the adhesive sheet, it is judged as "× (bad)" and if no foaming or peeling is observed, it is judged as "○ (good)".

[0397] [Table 1]

[0398]

[0399] The adhesive sheets of Examples 1 to 4 have an adhesive force of 2 N / cm or more for soda-lime glass, an offset length of less than 10 mm measured in the holding force test, and a peel distance of less than 20 mm in the constant load peel test. Therefore, they have excellent foaming resistance and peeling properties in curved surface adhesion and durability tests.

[0400] In Examples 1 and 2, the ratio of tensile storage modulus (E') to shear storage modulus (G') of the adhesive sheets is 5.0 or higher, ensuring high-quality adhesion compatibility. Furthermore, the adhesive sheets of Examples 1 to 3 exhibit excellent low-temperature characteristics with a glass transition temperature below 0°C after curing.

[0401] Furthermore, the adhesive sheets in Examples 1 and 2 are adhesive sheets formed by three layers: an outermost layer, an innermost layer, and a middle layer. The outermost and innermost layers and the middle layer are formed by resin compositions with different compositions, including (meth)acrylic polymers as the main component resins. Therefore, the resistance to damp heat whitening in the reliability evaluation is particularly excellent.

[0402] In contrast, the adhesive sheet of Comparative Example 1 exhibited an offset length of 10 mm or more in the holding force test. Therefore, if used to bond curved components, the adhesive sheet would experience cohesive failure, resulting in poor adhesion to curved surfaces. For the adhesive sheets of Comparative Example 2 and Comparative Example 3, the peel length in the constant load peel test was 20 mm or more, or the adhesive force was 2 N / cm or less. Therefore, peeling occurred when bonded to curved components, resulting in poor adhesion to curved surfaces.

[0403] The above embodiments illustrate specific aspects of the present invention, but these embodiments are merely illustrative and not intended to be limiting. Various modifications that are obvious to those skilled in the art are within the scope of the present invention.

[0404] Industrial availability

[0405] The adhesive sheet for the image display device of the present invention has excellent surface adhesion and durability after being bonded to curved surface components with curved portions, enabling bubble-free bonding. Therefore, it can be used to bond components of the image display device, and is particularly suitable for bonding components of the image display device with curved shapes.

Claims

1. An adhesive sheet for an image display device, which is used to adhere two components constituting an image display device. The adhesive sheet is formed from a resin composition comprising a (meth)acrylic polymer, a crosslinking agent (B), a photopolymerization initiator (C), and a silane coupling agent (D). The (meth)acrylate polymer is a polymer obtained by copolymerizing an alkyl (meth)acrylate monomer having 4 to 18 carbon atoms with a monomer component capable of copolymerizing therewith. The monomer component capable of copolymerizing with the alkyl (meth)acrylate monomer having 4 to 18 carbon atoms is at least one selected from the group consisting of hydroxyl-containing monomers and nitrogen-containing monomers. The crosslinking agent (B) is a polyfunctional (meth)acrylate. The crosslinking agent (B) is present in a mass ratio of 0.5 to 50 parts by mass relative to 100 parts by mass of the (meth)acrylic polymer. At an environment of 23°C and 50%RH, with a peel angle of 180° and a peel speed of 300mm / min, the adhesion force to soda-lime glass is above 2N / cm. In a holding force test of an adhesive surface measuring 20mm width × 20mm length based on JIS Z 0237 at a temperature of 70℃, a load of 0.5kg, a testing time of 30 minutes, the offset length relative to the SUS304 stainless steel plate measured was less than 10mm. In the following constant load peel test, the peel distance is less than 20 mm. Measurement conditions: 1) A 10mm wide and 100mm long section of an adhesive sheet measuring 10mm wide and 150mm long is adhered to the soda-lime glass as the adhesive area. The area of ​​the adhesive sheet excluding the adhesive area is designated as the non-adhesive area. The soda-lime glass is then fixed horizontally by extending the non-adhesive area of ​​the adhesive sheet downwards. 2) In an environment of 23°C and 50%RH, a 0.45N load is applied to the non-adhesive area of ​​the adhesive sheet along its length for 30 minutes. The distance at which the adhesive layer peels off from the soda-lime glass during this period is taken as the constant load peel distance.

2. The adhesive sheet for an image display device according to claim 1, wherein, According to the tilted rolling ball viscosity test specified in JIS Z 0237:2009, the ball numbers in the tilted rolling ball viscosity test are 5~25 under the conditions of temperature 23℃ and tilt angle of 30°.

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

4. The adhesive sheet for an image display device according to claim 1 or 2, wherein, The ratio of tensile storage modulus E' to shear storage modulus G', E' / G', is 5.0 or higher. The tensile storage modulus E' and shear storage modulus G' are determined using the following method. Method for determining tensile storage modulus E': Using a dynamic viscoelasticity measuring device, under the conditions of tensile mode: vibration frequency 1 Hz, heating rate 3℃ / min, and temperature range -120~80℃, the dynamic viscoelastic spectrum was measured. Based on the obtained data, the tensile storage modulus E' at 25℃ was read. Method for determining shear storage modulus G': Using a rheometer, the dynamic viscoelastic spectrum under shear mode was measured according to the following measurement conditions. Based on the obtained data, the shear storage modulus G' at 25°C was read. Measurement conditions Adhesion tool: Φ8mm parallel plate Strain: 0.1% Frequency: 1Hz Temperature: -120~200℃ Heating rate: 5℃ / min.

5. The adhesive sheet for an image display device according to claim 1 or 2, wherein, Using a dynamic viscoelasticity measuring device, under the conditions of tensile mode: vibration frequency 1Hz, heating rate: 3℃ / min, and temperature range: -120~80℃, the dynamic viscoelastic spectrum under tensile mode was measured. The loss tangent Tanδ obtained from the data has two maximum values, i.e., peak temperatures, with a difference of 5~50℃.

6. The adhesive sheet for an image display device according to claim 1 or 2, wherein the outermost layer and the innermost layer are acrylic adhesive layers and the adhesive sheet has at least 3 layers, and the ratio of the total thickness of the outermost layer and the innermost layer to the overall thickness is 5 to 70%.

7. The adhesive sheet for an image display device according to claim 1 or 2, wherein the adhesive sheet comprises at least three layers: an outermost layer, an innermost layer, and an intermediate layer, wherein the outermost layer, the innermost layer, and the intermediate layer are formed from resin compositions comprising (meth)acrylic polymers of different compositions.

8. The adhesive sheet for an image display device according to claim 1 or 2, wherein it has active energy radiation curing properties.

9. The adhesive sheet for an image display device according to claim 8, wherein, The cumulative light intensity when the adhesive sheet is irradiated is 3000 mJ / cm. 2 After being cured by active energy rays with a wavelength of 365nm, and with a thickness of 0.6~0.8mm, the creep strain when a pressure of 1kPa is applied for 10 seconds at a temperature of 25℃ is less than 3%.

10. The adhesive sheet for an image display device according to claim 8, wherein, The cumulative light intensity when the adhesive sheet is irradiated is 3000 mJ / cm. 2 After being cured by active energy rays with a wavelength of 365 nm, and with a thickness of 0.6~0.8 mm, the dynamic viscoelastic spectrum under shear mode was measured using a rheometer under the following conditions. The maximum value of the loss tangent, i.e., the glass transition temperature, was found to be below 0 °C. Measurement conditions Adhesion tool: Φ8mm parallel plate Strain: 0.1% Frequency: 1Hz Temperature: -120~200℃ Heating rate: 5℃ / min.

11. An adhesive sheet with a release film, comprising a configuration in which the image display device according to any one of claims 1 to 10 is laminated with the adhesive sheet and the release film.

12. A laminate for an image display device, comprising a structure in which two image display device constituent components are laminated together with an adhesive sheet for the image display device according to any one of claims 1 to 10, wherein one of the two image display device constituent components is a cover glass having a curved shape, and the other is a component selected from the group consisting of a contact sensor, an image display panel, a surface protective film, an anti-reflective film, a color filter, a polarizing film, and a phase difference film, or a component formed by a combination of two or more of these components.

13. An image display device using the image display device laminate of claim 12.

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