TWI870554B - Double-sided adhesive sheet, laminate for image display device, and image display device - Google Patents

Abstract

The present invention provides a double-sided adhesive sheet for bonding two components for image display devices, which has excellent adhesive properties such as step absorption, adhesive force, and bonding reliability, and can peel off the components for image display devices by cooling operation. The present invention provides a double-sided adhesive sheet: the ratio (E'/G') of the tensile storage modulus (E') to the shear storage modulus (G') is 5.0 or more, the peak temperature (T1) of the loss tangent (Tanδ) obtained by dynamic viscoelasticity measurement in a shear mode with a frequency of 1 Hz is below -10°C, and the peak temperature (T2) of the loss tangent (Tanδ) obtained by dynamic viscoelasticity measurement in a shear mode with a frequency of 1 Hz is below -10°C. The peak temperature (T2) of the loss tangent (Tanδ) obtained by dynamic viscoelasticity measurement in the tensile mode of 10 Hz is above -10°C (wherein, when two or more peak temperatures are observed, the higher temperature is set as the peak temperature (T2)), and the 180° peeling adhesion force at 23°C with the adhered surfaces of the two image display device components is above 5 N/20 mm.

Description

Double-sided adhesive sheet, laminate for image display device, and image display device

The present invention relates to a double-sided adhesive sheet for bonding two components for an image display device, a laminate for an image display device, and an image display device.

In recent years, in order to improve the visibility of image display devices, resins such as adhesives or bonding agents are used to fill the gap between the image display panel of a liquid crystal display (LCD), plasma display (PDP) or electroluminescent display (ELD) and the protective panel or touch panel component arranged on its front side (visual side) to suppress the reflection of incident light or outgoing light from the displayed image at the air layer interface.

For example, Patent Document 1 discloses a method for manufacturing a multilayer structure for an image display device having a structure for an image display device laminated on at least one side of a transparent double-sided adhesive sheet. The method includes laminating an adhesive sheet that has been cross-linked once by ultraviolet rays to the structure for an image display device, and then irradiating the adhesive sheet with ultraviolet rays through the structure for an image display device to cure it secondary.

When the components of the image display device are bonded and integrated using an adhesive in this manner, work errors such as positional deviation or inclusion of air bubbles or foreign matter may occur during the bonding operation. Therefore, in order to correct this error, it is necessary to peel off the structural members for the image display device, and therefore the adhesive used for this purpose is required to have re-peelability (reworkability). In particular, laminates of non-flexible plate-like members are difficult to separate once they are bonded. When bonding large-scale picture components that are difficult to bond, components with curved surfaces, or expensive components, an adhesive is required. Reworkability.

Furthermore, even when the components for an image display device are completely bonded with an adhesive, if problems such as poor bonding or poor hardening occur after bonding, it is desirable to reuse part of the components such as expensive components instead of discarding them. From the perspective of this reuse, the requirements for re-peelability (reworkability) are also increasing.

Previously, as an adhesive that has re-peelability (reworkability) and is suitable for image display devices, for example, Patent Document 2 proposes an adhesive for optical films that uses a specific acrylic triblock copolymer, does not require chemical cross-linking, has excellent adhesive properties and durability, and can be peeled off with moderate peel strength without leaving any paste residue.

Furthermore, Patent Document 3 discloses a double-sided adhesive sheet that is characterized by being configured to be re-peelable on at least one of the touch panel and the display surface of the display device, and having optical isotropy, and discloses a re-peelable configuration that is achieved by making the adhesive force of the adhesive layer on the display device side to the display surface of the display device smaller than the adhesive force of the adhesive layer on the touch panel side to the bonding surface of the touch panel.

Furthermore, Patent Document 4 discloses an adhesive sheet having an internal interface (internal peeling interface) that can be peeled off on a surface different from the bonding surface between the adhesive and the adherend as a re-peelable adhesive material.

Prior art literature Patent Literature

Patent document 1: Japanese Patent No. 4971529

Patent document 2: Japanese Patent No. 5203964

Patent document 3: Japanese Patent Publication No. 2004-231723

Patent document 4: International Publication No. 2010/137523

In the actual manufacturing process, there is a situation where the components of the image display device are peeled (separated) by cooling operation, but the evaluation of re-peelability disclosed in the above patent documents 2 to 4 is performed at room temperature, and the evaluation of re-peelability based on cooling operation is not performed. Therefore, the above patent documents 2 to 4 do not perform the design of the adhesive sheet from the perspective of re-peelability based on cooling operation.

Therefore, the problem to be solved by the present invention is to provide a double-sided adhesive sheet with excellent adhesive properties such as gradient absorbency, adhesive force, and bonding reliability, and can be peeled off (separated) from components used in image display devices by cooling operations.

The inventors of the present invention have conducted intensive research to solve the above problems and found that the above problems can be solved by setting the ratio of the tensile storage modulus (E') to the shear storage modulus (G'), the peak temperature of the loss tangent obtained by the dynamic viscoelasticity measurement in the shear mode, the peak temperature of the loss tangent obtained by the dynamic viscoelasticity measurement in the tensile mode, and the 180° peeling adhesion force to specified values in the double-sided adhesive sheet.

That is, the present invention takes the following [1] to [13] as its main purpose.

[1] A double-sided adhesive sheet for bonding two components of an image display device, wherein the ratio (E'/G') of the tensile storage modulus (E') to the shear storage modulus (G') is 5.0 or more, the peak temperature (T1) of the loss tangent (Tanδ) obtained by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz is below -10°C, and the peak temperature (T2) of the loss tangent (Tanδ) obtained by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz is below -10°C. The peak temperature (T2) of the loss tangent (Tanδ) obtained by dynamic viscoelasticity measurement in the tensile mode is above -10°C (wherein, when two or more peak temperatures are observed, the highest temperature is set as the peak temperature (T2)), and the 180° peeling adhesion force at 23°C to each adhered surface of the above two image display device components is above 5N/20mm.

[2] For the double-sided adhesive sheet described in [1], the difference between the peak temperature (T2) of the loss tangent (Tanδ) obtained by dynamic viscoelasticity measurement in the tensile mode at a frequency of 1 Hz and the peak temperature (T1) of the loss tangent (Tanδ) obtained by dynamic viscoelasticity measurement in the shear mode at a frequency of 1 Hz is 5~50℃.

[3] A double-sided adhesive sheet as described in [1] or [2], wherein the two components for the image display device are formed of different materials.

[4] A double-sided adhesive sheet as described in any one of [1] to [3], wherein one of the two components for the image display device is glass, and the other comprises any one or a combination of two or more of the group consisting of a touch sensor, an image display panel, a surface protection panel, a polarizing film and a phase difference film.

[5] A double-sided adhesive sheet as described in [4], wherein the glass is a cover glass having a curved shape.

[6] A double-sided adhesive sheet as described in any one of [1] to [5], which is configured so that the two components for forming the image display device can be separated by a cooling operation.

[7] A double-sided adhesive sheet as described in [6], wherein the cooling operation is performed at a temperature below -50°C.

[8] A double-sided adhesive sheet as described in any one of [1] to [7], having a thickness of 50 to 1000 μm.

[9] A double-sided adhesive sheet as described in any one of [1] to [8], wherein the double-sided adhesive sheet has at least three layers, the outermost layer and the innermost layer being (meth) acrylic adhesive layers, and the combined ratio of the thickness of the outermost layer and the innermost layer to the overall thickness is 5 to 70%.

[10] A double-sided adhesive sheet as described in any one of [1] to [9], which is photocurable.

[11] A multilayer body for an image display device, which is formed by bonding two image display device components together via a double-sided adhesive sheet as described in any one of [1] to [10].

[12] A laminate for an image display device, which is formed by bonding two image display device components together via an adhesive layer formed by hardening a double-sided adhesive sheet as described in any one of [1] to [10].

[13] An image display device, which is constructed using the image display device laminate as described in [12].

The double-sided adhesive sheet of the present invention has excellent adhesive properties such as step absorption, adhesive force, and bonding reliability, and has excellent reworkability, and can easily peel off the components for image display devices through cooling operations. Therefore, it can be suitably used for laminating components of an image display device, and it can especially suitably be used for laminating large-screen components that are difficult to bond, components with curved surfaces, or expensive components.

1: Adhesive sheet

2: Glass

3:ITO

4:PET

5: Copper

FIG. 1 is a diagram for explaining the evaluation test method of ITO (Indium Tin Oxides) corrosion resistance reliability and Cu corrosion resistance reliability in the embodiment. (A) is a top view of the ITO pattern of the ITO glass substrate or a top view of the copper pattern of the copper glass substrate for corrosion resistance reliability evaluation. (B) is a top view showing the state of the adhesive sheet coated on the ITO glass substrate for ITO corrosion resistance reliability evaluation or a top view showing the state of the adhesive sheet coated on the copper glass substrate for Cu corrosion resistance reliability evaluation. (C) is a cross-sectional view of the sample for ITO corrosion resistance reliability evaluation. (D) is a cross-sectional view of the sample for Cu corrosion resistance reliability evaluation.

Below, an example of an implementation method of the present invention is described in detail. However, the present invention is not limited to the following implementation method.

Furthermore, in this specification, the meaning of "(meth)acrylic acid" includes "acrylic acid" and "methacrylic acid", and the meaning of "(meth)acrylate" includes "acrylate" and "methacrylate".

The double-sided adhesive sheet of the present invention usually contains a plurality of (meth) acrylic adhesive layers and is used to bond two components of an image display device. In addition, from the perspective of improving bonding reliability, the double-sided adhesive sheet of the present invention is preferably photocurable by curing by irradiation with active energy rays such as ultraviolet rays.

In addition, the peak temperature (T1) of the loss tangent (Tanδ) of the double-sided adhesive sheet of the present invention obtained by the dynamic viscoelasticity measurement in the shear mode with a frequency of 1 Hz is below -10°C, preferably -100~-15°C, and particularly preferably -50~-20°C. By making the peak temperature (T1) of the loss tangent (Tanδ) within the above range, the step absorption and bonding reliability can be excellent. Furthermore, the peak temperature (T1) of the loss tangent obtained by the dynamic viscoelasticity measurement in the shear mode is obtained by the following method.

[Dynamic viscoelasticity measurement in shear mode]

The sample to be measured is layered in a manner to a thickness of 0.6~0.8mm, and the obtained sample is punched into a circular shape with a diameter of 8mm to make a measurement sample. The dynamic viscoelastic spectrum of the measurement sample in the shear mode is measured under the following measurement conditions using a rheometer (manufactured by TA Instruments, "DiscoveryHR2"). The temperature at which the loss tangent (Tanδ) reaches a maximum value, i.e., the peak temperature (T1), is read from the dynamic viscoelastic spectrum data obtained by the measurement.

Furthermore, as mentioned above, the dynamic viscoelasticity measurement under shear mode is the value when the thickness of the sample to be measured is set to 0.6~0.8mm. The reason is that in order to accurately measure the dynamic viscoelasticity under shear mode, it is necessary to avoid the situation where the measurement result changes due to the influence of insufficient sample thickness on the measurement fixture. Therefore, in order to measure the dynamic viscoelasticity under shear mode, it is necessary to adjust the sample to a certain thickness range before measuring. By adjusting the thickness of the sample to the above range in advance and then measuring the dynamic viscoelasticity under shear mode, the dynamic viscoelasticity spectrum of the sample can be accurately grasped without being affected by the measurement fixture.

In addition, when the sample is light-curable, the sample used can be before or after curing.

[Measurement conditions]

Adhesion fixture: Φ8mm parallel plate

Strain: 0.1%

Frequency: 1Hz

Temperature: -120~200℃

Heating rate: 5℃/min

In addition, the peak temperature (T2) of the loss tangent (Tan δ) obtained by dynamic viscoelasticity measurement in the tensile mode at a frequency of 1 Hz for the double-sided adhesive sheet of the present invention is -10°C or above, preferably -5~20°C, and particularly preferably 0~15°C. By setting the peak temperature (T2) of the loss tangent (Tan δ) within the above range, it is possible to produce one with excellent re-peelability (reworkability) and cutting processability.

Furthermore, the peak temperature (T2) of the loss tangent (Tanδ) obtained by dynamic viscoelastic measurement in the tensile mode is obtained by the following method.

[Dynamic viscoelastic measurement in tensile mode]

The dynamic viscoelasticity spectrum of the sample to be measured in the tensile mode is measured using a dynamic viscoelasticity measuring device (IT Meter and Control, itkDVA- 200) in the tensile mode: vibration frequency 1 Hz, measuring temperature: -120~80℃, heating rate: 3℃/min. The temperature at which the loss tangent (Tanδ) reaches a maximum value, i.e., the peak temperature (T2), is read from the dynamic viscoelasticity spectrum data obtained by the measurement. In the case of observing two or more peak temperatures, the highest temperature is set as the peak temperature (T2).

In addition, when the sample is light-curable, the sample used can be before or after curing, but it is preferably after curing.

Furthermore, in the present invention, the difference between the peak temperature (T2) of the loss tangent (Tan δ) obtained by measuring the dynamic viscoelasticity in the tensile mode with a frequency of 1 Hz and the peak temperature (T1) of the loss tangent (Tan δ) obtained by measuring the dynamic viscoelasticity in the shear mode with a frequency of 1 Hz is preferably 5 to 50°C, more preferably 10 to 40°C, and particularly preferably 15 to 30°C. By setting it within the above range, it is possible to achieve an excellent balance of performance such as step absorption, bonding reliability, impact resistance, re-peelability (reworkability), and cutting processability.

The double-sided adhesive sheet of the present invention has a 180° peeling adhesion of 5N/20mm or more, preferably 6N/20mm or more, and particularly preferably 7N/20mm or more, at 23°C between the adhered surfaces of the two image display device components to be bonded. The upper limit of the 180° peeling adhesion is usually 50N/20mm. The above 180° peeling adhesion is measured by the following method.

[180° peel adhesion test method]

A 100μm thick polyethylene terephthalate (PET) film (DIAFOIL T100 manufactured by Mitsubishi Chemical Co., Ltd.) was bonded to one side of a double-sided adhesive sheet, and the other side was rolled and pressed onto a sodium calcium glass plate to produce a bonded product. Afterwards, the bonded product was autoclaved (60°C, gauge pressure 0.2MPa, 20 minutes) and finally bonded. Then, a high-pressure mercury lamp was used to irradiate the PET film surface with 365nm ultraviolet light in a manner such that the accumulated light amount became 3000mJ/ ^cm2 , and then cured for 12 hours in an environment of 23°C and 50%RH, and the resulting product was used as a sample for 180° peel adhesion measurement. The sample was used and the peeling force (N/cm) at a peeling angle of 180° and a peeling speed of 300 mm/min in an environment of 23°C and 50% RH was defined as 180° peeling adhesion.

As the layer structure of the double-sided adhesive sheet of the present invention, it is preferable that the surface layer and the back layer be two layers of (meth)acrylic adhesive layer, and it is more preferable that the surface layer and the backmost layer be made of (meth)acrylic. It should be at least three layers of adhesive layers, preferably the outermost layer and the innermost layer should be three layers of (meth)acrylic adhesive layers [surface layer (adhesive layer)/middle layer/innermost layer (adhesive layer)]. By having a multi-layered layer structure, it is possible to achieve excellent reworkability, step absorption, and bonding reliability.

Furthermore, in the present invention, in terms of reworkability, step absorption, adhesion, and bonding reliability, it is preferable to have at least two layers with different glass transition temperatures, and it is particularly preferable to have a (meth)acrylic layer with a glass transition temperature of -10°C or lower. The outermost layer and the innermost layer formed by the adhesive layer (hereinafter referred to as the "low Tg layer"), and the middle layer (hereinafter referred to as the "high Tg layer") formed of a resin composition containing a (meth)acrylic resin with a glass transition temperature higher than -10°C. In this specification, unless otherwise specified, the glass transition temperature is defined as the peak temperature of the loss tangent (Tan δ) obtained by dynamic viscoelasticity measurement in the shear mode at a frequency of 1 Hz, and is measured by the above method.

The glass transition temperature of the above-mentioned low Tg layer is usually below -10°C, preferably -100~-15°C, and particularly preferably -50~-20°C.

The glass transition temperature of the above-mentioned high Tg layer is usually higher than -10°C, preferably -5~20°C, and most preferably 0~15°C.

In addition, the difference in glass transition temperature between the high Tg layer and the low Tg layer (high Tg layer - low Tg layer) is usually 5°C or higher, preferably 10°C or higher, and particularly preferably 20°C or higher. The upper limit is usually 50 ℃. By setting the difference in glass transition temperature within the above range, there is a tendency to have excellent reworkability, step absorption, adhesion, and bonding reliability. Furthermore, when the double-sided adhesive sheet has multiple high Tg layers and low Tg layers, the difference in glass transition temperature between the high Tg layer and the low Tg layer is the difference in glass transition temperature between the high Tg layer with the highest glass transition temperature and the low Tg layer with the lowest glass transition temperature.

As a preferred layer structure of the double-sided adhesive sheet of the present invention, as described above, the outermost layer and the innermost layer are at least three layers of (meth) acrylic adhesive layers, and it is particularly preferred that the outermost layer and the innermost layer are three layers of (meth) acrylic adhesive layers [outermost layer (adhesive layer)/intermediate layer/innermost layer (adhesive layer)]. In this case, the outermost and innermost surfaces (surfaces to be bonded to the image display device component) of the double-sided adhesive sheet are preferably low Tg layers. In addition, the intermediate layer sandwiched between the outermost and innermost surfaces is preferably a high Tg layer. Furthermore, the low Tg layers used for the outermost layer and the innermost layer may have different glass transition temperatures, but it is preferred that the glass transition temperatures of the outermost layer and the innermost layer are the same, and it is particularly preferred that the outermost layer and the innermost layer are (meth) acrylic adhesive layers formed of the same resin composition.

That is, one of the best layer structures of the double-sided adhesive sheet of the present invention is a three-layer structure of low Tg layer/high Tg layer/low Tg layer formed of two types of resin compositions. By adopting this layer structure, it is possible to achieve excellent reworkability, step absorption, adhesion, and bonding reliability.

The shear storage modulus (G') of the double-sided adhesive sheet is preferably 5×10 ³ ~5×10 ⁸ Pa, more preferably 1×10 ⁴ ~1×10 ⁷ Pa, and particularly preferably 2×10 ⁴ ~1×10 ⁶ Pa. By making the double-sided adhesive sheet have a shear storage modulus (G') within this range, the step absorption can be maintained and appropriate processability can be given. The shear storage modulus (G') is the shear storage modulus at 25°C, which can be obtained by reading the shear storage modulus (G') at 25°C from the dynamic viscoelastic spectrum data obtained by the dynamic viscoelasticity measurement in the shear mode.

Furthermore, when the double-sided adhesive sheet has at least three layers in which the outermost layer and the innermost layer are (meth)acrylic adhesive layers, in terms of reworkability, it is preferable that the shear storage modulus (G') of the middle layer is greater than the shear storage modulus (G') of the outermost layer and the innermost layer.

The tensile storage modulus (E') of the double-sided adhesive sheet is preferably 2.5×10 ⁴ ~5×10 ⁸ Pa, more preferably 5×10 ⁴ ~5×10 ⁷ Pa, and particularly preferably 1×10 ⁵ ~5×10 ⁶ Pa. By having a tensile storage modulus (E') in such a range, the handling and cutting processability can be excellent. The tensile storage modulus (E') is the tensile storage modulus at 25°C, which can be obtained by reading the tensile storage modulus (E') at 25°C from the dynamic viscoelastic spectrum data obtained by the dynamic viscoelasticity measurement in the tensile mode.

As described above, the double-sided adhesive sheet of the present invention preferably has at least two layers with different glass transition temperatures. The double-sided adhesive sheet having at least two layers with different glass transition temperatures can be distinguished based on the ratio of the tensile storage modulus (E') obtained by tensile viscoelasticity measurement to the shear storage modulus (G') obtained by shear viscoelasticity measurement. Generally, when the adhesive sheet is an isotropic elastic body, the relationship between the tensile storage modulus (E') and the shear storage modulus (G') is E'=3G'.

However, when there are at least two layers with different glass transition temperatures, that is, when it is an anisotropic elastic body, this relationship does not hold (E'≠3G').

The ratio (E'/G') of the tensile storage modulus (E') to the shear storage modulus (G') of the double-sided adhesive sheet of the present invention is 5.0 or more, preferably 6.0 or more, more preferably 7.0 or more, and more preferably 8.0 or more. Also, it is preferably 100 or less, more preferably 50 or less, and more preferably 30 or less.

That is, by making the E'/G' ratio of the double-sided adhesive sheet 5.0 or more, it can be determined that it has "at least two layers with different glass transition temperatures" or "layers with glass transition temperatures that are inclined in the thickness direction", has excellent reworkability, and can be easily used with at least any component of the image display device by the cooling operation. The interface part of the adhesive surface is peeled off.

The thickness of the double-sided adhesive sheet of the present invention is preferably 50 to 1000 μm, more preferably 60 to 500 μm, and even more preferably 75 to 300 μm. If the thickness of the sheet is too thin, the step absorption will tend to decrease. If it is too thick, the reworkability will tend to be difficult to obtain.

Furthermore, when the double-sided adhesive sheet has at least three layers in which the outermost layer and the innermost layer are (meth)acrylic adhesive layers, the total ratio of the thickness of the outermost layer and the innermost layer to the overall thickness is preferably 5 to 70%, more preferably 10 to 60%, and even more preferably 20 to 45%. By setting the thickness of the outermost layer and the innermost layer within the above range, it is possible to produce a product with excellent reworkability, step absorption, and bonding reliability.

The double-sided adhesive sheet of the present invention is used to bond two components of image display devices. Specifically, it is used to bond components of LCD, PDP or EL image display devices such as computers, mobile terminals (PDAs), game consoles, televisions (TVs), car navigation, touch panels, handwriting tablets, etc.

Furthermore, from the viewpoint of reworkability, it is preferable that the two image display device components are formed of different materials.

As the above-mentioned component for the image display device, more specifically, it is preferred that one of the two components for the image display device is glass and the other is a film, and it is particularly preferred that the glass is a tempered glass and the film is any one of the group consisting of a touch sensor, an image display panel, a surface protection panel, a polarizing film and a phase difference film, or a laminate comprising a combination of two or more of these.

In recent years, for image display panels such as liquid crystal displays (LCDs), plasma displays (PDP), and electroluminescent displays (ELD), cover glass with a curved shape has been mostly used from a design perspective. However, the cover glass is expensive and is a component that needs to be reused. By using the double-sided adhesive sheet of the present invention, reworkability is excellent, and therefore it can be effectively used for products with Curved cover glass.

As the substrate of the above-mentioned film, a transparent resin is preferred, for example, polyester resin, polyolefin resin, (meth) acrylic resin, polyurethane resin, polyether sulfone resin, polycarbonate resin, polysulfone resin, polyether resin, polyether ketone resin, (meth) acrylonitrile resin, cycloolefin resin, etc. Among them, polyester resin is preferred, and polyethylene terephthalate (PET) is particularly preferred. These resins can be used alone or in combination of two or more.

By bonding the image display device components to the two adhesive surfaces of the double-sided adhesive sheet of the present invention, a multilayer image display device is obtained in which the two image display device components are bonded together via the double-sided adhesive sheet. In addition, the multilayer image display device is usually irradiated with active energy rays and the adhesive sheet is photocured to obtain a multilayer image display device in which the two image display device components are bonded together via the adhesive layer cured by the double-sided adhesive sheet.

The double-sided adhesive sheet of the present invention is preferably constructed in a manner that two image display device components can be peeled (separated) by a cooling operation. It is particularly preferably constructed in a manner that the image display device components can be peeled (separated) by a cooling operation at the interface portion with the adhered surface of at least one of the image display device components. Furthermore, "peelable (separable)" refers to a state in which the image display device components bonded via the double-sided adhesive sheet can be easily peeled (separated) without destroying the above components, and in particular, can be peeled (separated) at the interface between the double-sided adhesive sheet and the image display device components. In addition, the above cooling operation is performed by the following method.

[Cooling operation]

By cooling the above-mentioned image display device laminate, the image display device components can be separated, especially by peeling off the interface portion with the adhered surface of at least one image display device component.

Furthermore, depending on the situation, the image display device laminate may be cooled and peeled off before being irradiated with the active energy rays without irradiating the active energy rays. Even in this case, the image display device component can be separated, especially the interface portion with the adhered surface of at least one image display device component can be separated.

The above method can easily recycle components used in image display devices.

The cooling temperature of the multilayer body for the above-mentioned image display device is preferably below -50°C, more preferably below -80°C, and further preferably below -100°C. The lower limit of the cooling temperature is not particularly limited, but is usually around -300°C, preferably around -200°C.

Furthermore, when cooling the above-mentioned image display device laminate, it is preferred to place one of the image display components of the image display device laminate in contact with a SUS (Steel Use Stainless, Japanese Stainless Steel Standard) cooling plate that has reached the above-mentioned cooling temperature, and it is particularly preferred to place the component side of the image display device component with a lower linear expansion coefficient in contact with the SUS cooling plate.

The above-mentioned strippable time is usually within 600 seconds, preferably within 300 seconds, more preferably within 180 seconds, even more preferably within 120 seconds, further preferably within 60 seconds, and particularly preferably within 30 seconds.

The principle that the double-sided adhesive sheet of the present invention can be used to peel off the component (adherend) of the image display device by cooling operation is considered as follows. When the double-sided adhesive sheet attached to two adherends is cooled, the adherends shrink as the temperature decreases, generating a stress of elastic modulus of the adherends × shrinkage strain. The strain or stress becomes a peeling force for separating the double-sided adhesive sheet and the adherend at the interface. Therefore, the two adherends connected to the double-sided adhesive sheet are preferably made of materials with different linear expansion coefficients, and further, the two adherends are preferably made of different types of materials.

The double-sided adhesive sheet of the present invention is not easy to relax the strain or stress (difference) received from the adherend, or is not easy to relax due to cooling. This is a key point that makes the double-sided adhesive sheet reworkable. Specifically, it is possible to increase the glass transition temperature (Tg) of the double-sided adhesive sheet. However, if the glass transition temperature (Tg) is simply raised, the adhesive properties such as step absorption, adhesive force, and bonding reliability will decrease. Therefore, in the present invention, the ratio (E'/G') of the tensile storage modulus (E') to the shear storage modulus (G') of the double-sided adhesive sheet is set to 5.0 or more, and further, the peak temperature (T1) of the loss tangent (Tanδ) obtained by the dynamic viscoelasticity measurement of the double-sided adhesive sheet in the shear mode with a frequency of 1 Hz is set to below -10°C, and further, the peak temperature (T2) of the loss tangent (Tanδ) obtained by the dynamic viscoelasticity measurement of the tensile mode with a frequency of 1 Hz is set to above -10°C (wherein, when two or more peak temperatures are observed, the highest temperature is set as the peak temperature (T2)).

The double-sided adhesive sheet of the present invention having the above-mentioned characteristics preferably has at least two layers of (meth)acrylic adhesive, and the above-mentioned (meth)acrylic adhesive layer is formed by a resin composition containing a (meth)acrylic copolymer.

Furthermore, when there are at least three layers with the outermost layer and the innermost layer being (meth)acrylic adhesive layers, the middle layer is also formed of a resin composition containing a (meth)acrylic copolymer.

The following describes the resin composition that forms the (meth)acrylic adhesive layer and the intermediate layer.

The resin composition comprises a (meth)acrylic acid copolymer as a main component, and may further contain a crosslinking agent (B), a photoinitiator (C), a silane coupling agent (D), an anticorrosive agent (E), and other additives.

The above-mentioned "main component" refers to a (meth)acrylic acid-based copolymer containing 50% by mass or more, preferably 70% by mass or more, and more preferably 80% by mass or more, based on the entire resin composition.

[(Meth)acrylic acid copolymer]

As the above-mentioned (meth)acrylic acid-based copolymer, for example, there can be cited those obtained by copolymerizing a (meth)acrylic acid alkyl ester monomer having an alkyl group with 4 to 18 carbon atoms and a monomer component copolymerizable with the (meth)acrylic acid alkyl ester monomer.

酯等脂環式(甲基)丙烯酸酯單體等。該等亦可使用1種或組合使用2種以上。 Examples of the alkyl (meth)acrylate monomers in which the alkyl group has 4 to 18 carbon atoms include straight-chain alkyl (meth)acrylate monomers such as n-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, n-octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, cetyl (meth)acrylate, and stearyl (meth)acrylate; and isobutyl (meth)acrylate, butyl (meth)acrylate, and butyl (meth)acrylate. Branched chain alkyl (meth)acrylate monomers such as 2-butyl (meth)acrylate, 3-butyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, isostearyl (meth)acrylate, etc.; cyclohexyl (meth)acrylate, 3-butyl cyclohexyl (meth)acrylate, 3,5,5-trimethylcyclohexane (meth)acrylate, dicyclopentyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, isostearyl (meth)acrylate, etc.; cyclohexyl (meth)acrylate, 3-butyl cyclohexyl (meth)acrylate, 3,5,5-trimethylcyclohexane (meth)acrylate, dicyclopentyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, isooctyl (meth)acrylate, isooctyl (meth)acrylate, isodecyl (meth)acrylate, isostearyl (meth)acrylate, etc.

Alicyclic (meth)acrylate monomers such as esters, etc. These may be used alone or in combination of two or more.

Examples of monomer components that can copolymerize with the above-mentioned (meth)acrylate monomers having an alkyl group with 4 to 18 carbon atoms include: (meth)acrylate monomers containing hydroxyl groups, (meth)acrylate monomers containing nitrogen atoms, (meth)acrylate monomers containing carboxyl groups, (meth)acrylate monomers containing epoxy groups, vinyl monomers, (meth)acrylate monomers having an alkyl group with 1 to 3 carbon atoms, and other copolymerizable monomers.

Examples of the hydroxyl-containing (meth)acrylate monomers 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, glycerol (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, hydroxyphenyl (meth)acrylate, etc. These monomers may be used alone or in combination of two or more.

Examples of the nitrogen-containing (meth)acrylate monomers include aminoalkyl (meth)acrylates such as aminomethyl (meth)acrylate, aminoethyl (meth)acrylate, aminopropyl (meth)acrylate, and aminoisopropyl (meth)acrylate; aminoalkyl (meth)acrylates such as N-alkylaminoalkyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and N,N-dimethylaminopropyl (meth)acrylate; (meth)acrylate monomers; (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N-butyl (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, N-hydroxymethylpropane (meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, diacetone (meth)acrylamide, maleic acid amide, maleimide and other amide-containing (meth)acrylate monomers. These may be used alone or in combination of two or more.

In addition, as the above-mentioned carboxyl group-containing (meth)acrylate monomer, for example, (meth)acrylic acid, (meth)acrylic acid dimer, etc. can be listed. These can also be used alone or in combination of two or more.

Examples of the above-mentioned epoxy-containing (meth)acrylate monomers include: (meth)acrylate glycidyl, (meth)acrylate methyl glycidyl, (meth)acrylate 3,4-epoxyhexylmethyl, (meth)acrylate 4-hydroxybutyl glycidyl ether, etc. These monomers may be used alone or in combination of two or more.

Examples of the above-mentioned vinyl monomers include: (meth) alkyl acrylates having an alkyl group with 1 to 12 carbon atoms, functional monomers having functional groups such as hydroxyl, amide and alkoxyalkyl groups in the molecule, polyalkylene glycol di(meth) acrylates, vinyl ester monomers such as vinyl acetate, vinyl propionate and vinyl laurate, and aromatic vinyl monomers such as styrene, chlorostyrene, chloromethylstyrene, α-methylstyrene and other substituted styrenes. These monomers may be used alone or in combination of two or more.

As the (meth)acrylic acid alkyl ester monomers in which the carbon number of the alkyl group is 1 to 3, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, etc. These monomers may be used alone or in combination of two or more.

As the above-mentioned other copolymerizable monomers, for example, monomers containing anhydride groups such as maleic anhydride and itaconic anhydride, heterocyclic alkaline monomers such as vinyl pyrrolidone, vinyl pyridine, and vinyl carbazole, and macromonomers can be listed. These monomers can be used alone or in combination of two or more.

In the present invention, when making a double-sided adhesive sheet, a (meth) acrylic copolymer obtained by copolymerizing the above-mentioned various monomer components can be used in a manner having a specified loss tangent peak temperature and specific physical properties. The copolymerization method can also be carried out according to previously known methods such as solution free radical polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, etc.

Among them, when the double-sided adhesive sheet of the present invention has at least three layers with the outermost layer and the innermost layer being a (meth)acrylic adhesive layer, it is preferred that the (meth)acrylic adhesive layer as the outermost layer and the innermost layer is formed by a resin composition containing a (meth)acrylic copolymer (A) having a glass transition temperature of -10°C or less, and it is more preferred that the (meth)acrylic copolymer contained in the resin composition only contains the (meth)acrylic copolymer (A).

[(Meth)acrylic acid copolymer (A)]

The (meth)acrylic copolymer (A) having a glass transition temperature of -10°C or less is preferably substantially free of structural units derived from carboxyl-containing (meth)acrylate monomers, and comprises polar-group-containing (meth)acrylate monomers (a2) and (meth)acrylate monomers (a1) as monomer components constituting the (meth)acrylic copolymer (A), wherein (a2) is at least one selected from the group consisting of hydroxyl-containing (meth)acrylate monomers and nitrogen-containing (meth)acrylate monomers, and (a1) is a monomer other than (a2), and the glass transition temperature (Tg) of the homopolymer formed by the monomer components is less than -30°C.

Furthermore, the above-mentioned "substantially free of structural units derived from carboxyl-containing (meth)acrylate monomers" includes not only the case where the structural units are completely free of structural units, but also the case where the (meth)acrylic copolymer (A) contains less than 0.5% by mass, preferably less than 0.1% by mass of structural units derived from carboxyl-containing (meth)acrylate monomers.

As the (meth)acrylate monomer (a1) whose glass transition temperature (Tg) when forming a homopolymer from the monomer components is less than -30°C (preferably less than -40°C, and more preferably less than -50°C), there can be mentioned those (meth)acrylate alkyl ester monomers whose carbon number of the alkyl group is 4 to 18 and whose glass transition temperature is less than -30°C. Specifically, for example, there can be mentioned: straight chain (meth)acrylate alkyl ester monomers such as n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-heptyl acrylate, n-hexyl acrylate, n-octyl acrylate, nonyl acrylate, lauryl methacrylate, stearyl methacrylate; branched chain (meth)acrylate alkyl ester monomers such as 2-ethylhexyl acrylate, isononyl acrylate, isodecyl acrylate, etc. These monomers can be used alone or in combination of two or more. Among them, branched chain alkyl (meth)acrylate is preferred, and 2-ethylhexyl acrylate is particularly preferred.

As the above-mentioned polar group-containing (meth)acrylate monomer (a2), the above-mentioned hydroxyl group-containing (meth)acrylate monomer and nitrogen atom-containing (meth)acrylate monomer can be listed, among which the hydroxyl group-containing (meth)acrylate monomer is preferred, and 2-hydroxyethyl acrylate is particularly preferred.

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

In terms of step absorption and bonding reliability, the glass transition temperature of the (meth)acrylic copolymer (A) obtained by copolymerization is preferably below -10°C, more preferably -100~-15°C, and particularly preferably -50~-20°C.

The mass average molecular weight of the above-mentioned (meth)acrylic copolymer (A) is preferably 50,000 to 1.5 million, more preferably 100,000 to 700,000, and even more preferably 150,000 to 600,000.

In this specification, the mass average molecular weight is measured by the following method.

A sample obtained by dissolving 4 mg of a (meth)acrylic acid copolymer in 12 mL of THF was used as a test sample. The molecular weight distribution curve was measured under the following conditions using a gel permeation chromatography (GPC) analyzer (manufactured by Tosoh Corporation, HLC-8320GPC) to determine the mass average molecular weight (Mm).

‧Guard column: TSKguardcolumnHXL

‧Separation column: TSKgelGMHXL (4 pieces)

‧Temperature: 40℃

‧Injection volume: 100μL

‧Polystyrene conversion

‧Solvent: THF

‧Flow rate: 1.0mL/min

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

Furthermore, when the double-sided adhesive sheet of the present invention has at least three layers in which the outermost layer and the innermost layer are (meth)acrylic adhesive layers, it is preferred that the middle layer (the layer sandwiched between the outermost layer and the innermost layer) is formed by a resin composition containing a (meth)acrylic copolymer (A') having a glass transition temperature higher than -10°C, and it is more preferred that the (meth)acrylic copolymer contained in the resin composition only contains the (meth)acrylic copolymer (A').

[(Meth)acrylic acid copolymer (A')]

The (meth)acrylic copolymer (A') having a glass transition temperature higher than -10°C preferably comprises at least one (meth)acrylic monomer (a2) containing a polar group selected from the group consisting of (meth)acrylic monomers containing hydroxyl groups and (meth)acrylic monomers containing nitrogen atoms, and (meth)acrylic alkyl monomers (a3) having an alkyl group with a carbon number of 1 to 18 as monomer components constituting the (meth)acrylic copolymer (A').

As the above-mentioned polar group-containing (meth)acrylate monomer (a2), the above-mentioned hydroxyl group-containing (meth)acrylate monomer and nitrogen atom-containing (meth)acrylate monomer can be listed, among which nitrogen atom-containing (meth)acrylate is preferred, amide group-containing (meth)acrylate is more preferred, and (meth)acrylamide is particularly preferred.

酯。 Examples of the alkyl (meth)acrylate monomer (a3) having an alkyl group with 1 to 18 carbon atoms include the alkyl (meth)acrylate monomer having 4 to 18 carbon atoms and the alkyl (meth)acrylate monomer having 1 to 3 carbon atoms. Among them, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate and isoborneol (meth)acrylate are particularly preferred. Furthermore, from the viewpoint of the versatility of the monomers and the Tg of the (meth)acrylic copolymer (A') being above -10°C, methyl (meth)acrylate, ethyl methacrylate, tert-butyl (meth)acrylate, isobutyl methacrylate, isobutyl (meth)acrylate,

ester.

Furthermore, as the copolymerization component of the (meth)acrylate copolymer (A'), monomers other than the above-mentioned monomers (a2) and (a3) can be used. As the above-mentioned monomers other than the above-mentioned monomers (a2) and (a3), the above-mentioned various monomers can be used.

In terms of reworkability, the glass transition temperature of the (meth)acrylic copolymer (A') obtained by copolymerizing these copolymers is preferably higher than -10°C, more preferably -5 to 20°C, and particularly preferably 0 to 15°C.

The mass average molecular weight of the (meth)acrylic copolymer (A') is 50,000 to 1,000,000, preferably 70,000 to 700,000, and particularly preferably 100,000 to 500,000.

[Crosslinking agent (B)]

The resin composition forming each layer may contain a crosslinking agent (B) in addition to the above-mentioned (meth) acrylic copolymer. It is particularly preferred to mix the crosslinking agent (B) in the resin composition forming the middle layer of the double-sided adhesive sheet.

唑啉基、氮丙啶基、乙烯基、胺基、亞胺基、醯胺基中之至少1種交聯性官能基之交聯劑，亦可使用1種或組合使用2種以上。又，作為交聯劑(B)，亦包含交聯劑(B)與上述(甲基)丙烯酸系共聚物化學鍵結之態樣。 As the crosslinking agent (B), a crosslinking agent having at least double bond crosslinking is preferred. For example, a crosslinking agent having a group selected from (meth)acryloyl, epoxy, isocyanate, carboxyl, hydroxyl, carbodiimide,

A crosslinking agent having at least one crosslinking functional group selected from the group consisting of oxazoline, aziridine, vinyl, amino, imine, and amide may be used alone or in combination of two or more. In addition, the crosslinking agent (B) also includes a state where the crosslinking agent (B) is chemically bonded to the above-mentioned (meth)acrylic copolymer.

Among them, the crosslinking agent having a (meth)acrylic group is preferred, and in terms of cutting processability and bonding reliability, the multifunctional (meth)acrylate is particularly preferred. Here, multifunctional refers to a crosslinking agent having two or more crosslinking functional groups. Furthermore, it may have three or more, or four or more crosslinking functional groups as needed. In addition, the crosslinking functional groups may also be protected by a protective group that can be deprotected.

Examples of the multifunctional (meth)acrylate include 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, tricyclodecane dimethanol di(meth)acrylate, bisphenol A polyethoxy di(meth)acrylate, bisphenol A polypropoxy di(meth)acrylate, and the like. acrylate, bisphenol F polyethoxy di(meth)acrylate, ethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trihydroxymethylpropane trioxyethyl (meth)acrylate, ε-caprolactone modified tri(2-hydroxyethyl) isocyanuric acid 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 meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, tri(acryloxyethyl) isocyanurate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, tripentaerythritol hexa(meth)acrylate, tripentaerythritol penta(meth)acrylate, hydroxypivalate neopentyl glycol di(meth)acrylate UV-curable multifunctional (meth)acrylic monomers such as acrylate, ε-caprolactone adduct of neopentyl glycol hydroxypivalate, trihydroxymethylpropane tri(meth)acrylate, trihydroxymethylpropane polyethoxy tri(meth)acrylate, di-trihydroxymethylpropane tetra(meth)acrylate, and multifunctional (meth)acrylic oligomers such as polyester (meth)acrylate, epoxy (meth)acrylate, (meth)acrylic urethane, and polyether (meth)acrylate. These can also be used alone or in combination of two or more. Among them, propoxypentaerythritol tri(meth)acrylate is preferred.

The content of the crosslinking agent (B) is usually 0.5 to 50 parts by mass, preferably 1 to 40 parts by mass, and particularly preferably 5 to 30 parts by mass relative to 100 parts by mass of the (meth)acrylic copolymer. If the content is within the above range, it is easier to obtain cutting processability and bonding reliability.

[Photopolymerization initiator (C)]

The resin composition preferably contains a photopolymerization initiator (C). As the above-mentioned photopolymerization initiator (C), currently known ones can be appropriately used. Among them, from the perspective of the ease of controlling the crosslinking reaction, a photopolymerization initiator that is sensitive to ultraviolet light with a wavelength of less than 380nm is preferred.

Photopolymerization initiators (C) are roughly classified into two types according to the mechanism of free radical generation, which are cleavage-type photopolymerization initiators that can generate free radicals by cleaving the single bond of the photopolymerization initiator itself, and hydrogen-abstracting-type photopolymerization initiators that can form an excited complex with the hydrogen donor in the system after photoexcitation to transfer hydrogen from the hydrogen donor.

The above-mentioned cleavage-type photopolymerization initiator decomposes into another compound when generating free radicals by light irradiation, and once excited, it loses its function as a reaction initiator. Therefore, it will not remain as an active species in the adhesive and other hardened materials after the crosslinking reaction is completed, and it is impossible to cause unexpected light degradation to the hardened materials, so it is better.

On the other hand, when hydrogen-absorptive photopolymerization initiators undergo a free radical generation reaction by irradiating active energy rays such as ultraviolet rays, they do not produce decomposition products like cleavage-type photopolymerization initiators. Therefore, they are less likely to become volatile components after the reaction is completed, which can reduce damage to the adherend and is more useful.

啉基苯基)丁烷-1-酮、2-甲基-1-[4-(甲硫基)苯基]-2-

啉基丙烷-1-酮、2-(二甲胺基)-2-[(4-甲基苯基)甲基]-1-[4-(4-

啉基)苯基]-1-丁酮、雙(2,4,6-三甲基苯甲醯基)-苯基氧化膦、2,4,6-三甲基苯甲醯基二苯基氧化膦、及其等之衍生物等。其中，較佳為低聚(2-羥基-2-甲基-1-(4-(1-甲基乙烯基)苯基)丙酮)。 Examples of the above-mentioned cleavage-type photopolymerization initiator include 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propane-1-one, 1-(4-(2-hydroxyethoxy)phenyl)-2-hydroxy-2-methyl-1-propane-1-one, 2-hydroxy-1-[4-[4-(2-hydroxy-2-methyl-propionyl)benzyl]phenyl]-2-methyl-propane-1-one, oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone), methyl benzoate, 2-benzyl-2-dimethylamino-1-(4-[4-(2-hydroxy-2-methyl-propionyl)benzyl]phenyl]-2-methyl-propane-1-one, and oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone).

1-[(4-(methylthio)phenyl)butane-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-

Linopropan-1-one, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-

[0043] The present invention relates to oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)acetone, bis(2,4,6-trimethylbenzyl)phenylphosphine oxide, 2,4,6-trimethylbenzyldiphenylphosphine oxide, and their derivatives. Among them, oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)acetone) is preferred.

、2-氯9-氧硫

、3-甲基9-氧硫

、2,4-二甲基9-氧硫

、2-甲基蒽醌、2-乙基蒽醌、2-第三丁基蒽醌、2-胺基蒽醌及其衍生物等。其中，較佳為4-甲基二苯甲酮、2,4,6-三甲基二苯甲酮。 Examples of the hydrogen-absorptive photopolymerization initiator include benzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, 3,3'-dimethyl-4-methoxybenzophenone, methyl 2-benzoylbenzoate, methyl benzoylcarboxylate, bis(2-phenyl-2-glyoxylate)oxyethylene, 4-(1,3-acryloyl-1,4,7,10,13-pentaoxotridecyl)benzophenone, 9-oxythiophene,

, 2-chloro-9-oxysulfur

, 3-methyl 9-oxosulfur

, 2,4-dimethyl 9-oxysulfide

, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone and their derivatives, etc. Among them, 4-methylbenzophenone and 2,4,6-trimethylbenzophenone are preferred.

The above-mentioned photopolymerization initiator (C) is not limited to the substances listed above. In addition, the photopolymerization initiator (C) can use any one of the cleavage type photopolymerization initiator and the hydrogenation type photopolymerization initiator, and can also use a combination of the two.

The content of the photopolymerization initiator (C) is not particularly limited. It is usually 0.1 to 10 parts by mass, preferably 0.2 to 5 parts by mass, and particularly preferably 0.3 to 3 parts by mass, relative to 100 parts by mass of the (meth)acrylic copolymer.

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

[Silane coupling agent (D)]

In order to improve the adhesion with the components of the image display device, especially glass, it is preferred to mix a silane coupling agent (D) in the resin composition. Among them, the silane coupling agent (D) is preferably contained in the resin composition that forms the (meth) acrylic adhesive layer of the double-sided adhesive sheet that is connected to the components of the image display device.

Examples of the above-mentioned silane coupling agent (D) include compounds having unsaturated groups such as vinyl, acryloxy, and methacryloxy, amino, epoxy, and hydrolyzable functional groups such as alkoxy.

As the above-mentioned silane coupling agent (D), for example, N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane, N-(β-aminoethyl)-γ-aminopropyl methyldimethoxysilane, γ-aminopropyl triethoxysilane, γ-glycidyloxypropyl trimethoxysilane, γ-methacryloxypropyl trimethoxysilane, etc. These can be used alone or in combination of two or more. Among them, γ-glycidyloxypropyl trimethoxysilane is preferred in terms of good adhesion to components of image display devices and less discoloration such as yellowing.

The content of the silane coupling agent (D) is preferably 0.01 to 5 parts by mass, and particularly preferably 0.2 to 3 parts by mass, relative to 100 parts by mass of the (meth)acrylic copolymer.

Furthermore, coupling agents such as organic titanium ester compounds can also be effectively used in the same manner as the silane coupling agent (D).

[Metal anticorrosive agent (E)]

The resin composition also preferably contains a metal anti-corrosion agent (E). The metal anti-corrosion agent (E) is preferably contained in the resin composition that forms the (meth) acrylic adhesive layer that is connected to the component for the image display device of the double-sided adhesive sheet.

Examples of the above-mentioned metal corrosion inhibitor (E) include benzotriazole compounds, benzimidazole compounds, benzothiazole compounds, and other triazole derivatives.

As a metal corrosion inhibitor, it is preferred to select at least one of benzotriazole compounds, 1,2,3-triazole and 1,2,4-triazole. Among them, in addition to metal corrosion protection, based on the excellent reliability as a double-sided adhesive sheet, triazole derivatives such as 1,2,3-triazole and 1,2,4-triazole are preferred, and 1,2,3-triazole is particularly preferred.

From the viewpoint of metal anticorrosion agent seepage and metal anticorrosion effect, the content of the above metal anticorrosion agent (E) is preferably 0.01 to 5 parts by mass, more preferably 0.03 to 1 part by mass, and particularly preferably 0.05 to 0.5 parts by mass relative to 100 parts by mass of the (meth)acrylic acid copolymer.

[Other additives]

In addition to the above-mentioned components, the resin composition may also contain other additives. Examples of the above-mentioned other additives include: light stabilizers, ultraviolet absorbers, metal deactivators, anti-aging agents, antistatic agents, moisture absorbents, foaming agents, defoaming agents, inorganic particles, viscosity adjusters, adhesive resins, photosensitizers, fluorescent agents and other additives, reaction catalysts (tertiary amine compounds, quaternary ammonium compounds, tin laurate compounds, etc.). These can be used alone or in combination of two or more.

Furthermore, the resin composition for forming the adhesive may also contain known ingredients appropriately.

The above resin composition is obtained by mixing a predetermined amount of a (meth)acrylic copolymer, a crosslinking agent (B) as required, a photopolymerization initiator (C), a silane coupling agent (D), a metal anticorrosive agent (E) and other additives. There is no particular limitation on the mixing method thereof, and there is no particular limitation on the mixing order of the components. In addition, a heat treatment step may be added when manufacturing the resin composition. In this case, it is more desirable to mix the components of the resin composition in advance and then perform the heat treatment. In the above mixing, the various mixed components may be concentrated and master batched.

Furthermore, as mentioned above, the mixing method is not particularly limited, and for example, a universal mixer, planetary mixer, Banbury mixer, kneader, frame mixer, pressure kneader, three-roll grinder, double-roll grinder, etc. can be used. When mixing the components of the resin composition, a solvent can also be used for mixing as needed. Furthermore, the resin composition can also be used as a solvent-free system that does not contain a solvent. By using it as a solvent-free system, it can have the advantages of no solvent residue, improved heat resistance and light resistance.

[Manufacturing method of double-sided adhesive sheet]

The following describes the method for manufacturing the double-sided adhesive sheet of the present invention, but is not limited to the method. The double-sided adhesive sheet of the present invention preferably has at least 2 layers of (meth) acrylic adhesive, and more preferably has at least 3 layers with the outermost layer and the innermost layer being (meth) acrylic adhesive. The double-sided adhesive sheet of the present invention is typically preferably a double-sided adhesive sheet with a release film formed by laminating a double-sided adhesive sheet and a release film by the following steps. Furthermore, the pre-curing in the following step can also be omitted.

First, prepare the (meth) acrylic adhesive layer (or middle layer) of the release film. The (meth) acrylic adhesive layer (or middle layer) of the release film can be obtained by heating and melting the resin composition (hot melting), applying the obtained composition on the release film, and then sandwiching it with another release film and heating it. Prepare the (meth) acrylic adhesive layer (or middle layer) of the release film according to the number of layers required for the double-sided adhesive sheet.

As the above-mentioned release film, for example, films including polyester resin, polyolefin resin, polycarbonate resin, polystyrene resin, acrylic resin, triacetyl cellulose resin, fluororesin, etc. can be listed. In addition, films obtained by coating silicone resin on these films and performing release treatment, and release paper, etc. can also be appropriately selected and used. Among them, polyester resin and polyolefin resin are preferred, and polyester resin and polyolefin resin subjected to release treatment are particularly preferred. Furthermore, it is also preferred to use release films with different peeling forces and release films with different thicknesses on both sides of the (meth)acrylic adhesive layer.

Then, the release film is peeled off from the (meth) acrylic adhesive layer (or intermediate layer) of the obtained release film and the (meth) acrylic adhesive layer (or intermediate layer) is laminated, thereby obtaining the double-sided adhesive sheet of the present invention laminated with the release film.

In addition, when the double-sided adhesive sheet has at least three layers, the outermost layer and the innermost layer are (meth) acrylic adhesive layers, for example, the outermost layer (adhesive layer)/middle layer/innermost layer (adhesive layer), the adhesive sheet can be prepared by the following method: the resin composition is applied on a release film to form the outermost layer, the middle layer is applied on the outermost layer to form the adhesive layer, and the adhesive layer is applied on the innermost layer to form the adhesive layer. A method of forming a middle layer by using a resin composition, and then forming an innermost layer on the formed middle layer; a method of applying a resin composition on a release film in the same manner as above, forming a top layer and a middle layer in advance, and then laminating the coated surfaces to each other; and a method of simultaneously forming a top layer, a middle layer, and an innermost layer by applying a plurality of layers of the resin composition and co-extruding and forming.

In addition to the above method, multiple layers of double-sided adhesive sheets can also be prepared by, for example, applying a resin composition on a release film to form a (meth)acrylic adhesive layer, and then applying another resin composition on the formed (meth)acrylic adhesive layer to form a resin layer, and repeating this operation.

The obtained double-sided adhesive sheet is preferably pre-cured in a manner that has potential active energy ray reactivity, in other words, in a manner that retains active energy ray reactivity and crosslinks the active energy ray. When pre-curing, it is sufficient to irradiate the active energy ray through the above-mentioned release film to allow each layer to crosslink the active energy ray. At this time, by controlling the irradiation amount of the active energy ray, the degree of crosslinking of the active energy ray can also be adjusted. As mentioned above, by irradiating ultraviolet rays through the release film, a part of the active energy ray can also be blocked, thereby adjusting the degree of crosslinking of the active energy ray.

The double-sided adhesive sheet obtained in this way is an optically transparent adhesive sheet. Here, "optically transparent" means that the total light transmittance is above 80%, preferably above 85%, and more preferably above 90%.

The double-sided adhesive sheet of the present invention is usually circulated in a state where the (meth) acrylic adhesive layer on both sides is sandwiched by a release film. Then, when using the double-sided adhesive sheet, the release film is peeled off from the (meth) acrylic adhesive layer, and the (meth) acrylic adhesive layer is attached to the image display component.

(Explanation of words and sentences, etc.)

Furthermore, generally, "sheet" refers to a product that is thinner in the JIS definition, whose thickness is smaller than its length and width, and is flat. Generally, "film" refers to a product that is extremely thin compared to its length and width, and whose maximum thickness is arbitrarily limited, and is thin and flat, and is usually supplied in the form of a roll (Japanese Industrial Standard JISK6900). However, the boundary between sheet and film is not clear, and there is no need to distinguish between the two in the wording in the present invention. Therefore, in the present invention, "film" also includes "sheet", and "sheet" also includes "film".

In addition, when it is expressed as a "panel" such as an image display panel, a protective panel, etc., it includes a plate body, a sheet, and a film.

In this manual, when "x~y" (x and y are arbitrary numbers) is recorded, unless otherwise specified, it includes the meaning of "above x and below y", as well as the meaning of "preferably greater than x" and "preferably less than y".

Furthermore, when "x or more" (x is an arbitrary number) is recorded, unless otherwise specified, it includes the meaning of "x or more" and "preferably greater than x". When "y or less" (y is an arbitrary number) is recorded, unless otherwise specified, it also includes the meaning of "y or less" and "preferably less than y".

Implementation example

The following is further described in detail through embodiments and comparative examples. However, the present invention is not limited to these embodiments.

In the embodiment, the hydroxyl value, mass average molecular weight and glass transition temperature of the (meth)acrylic copolymer are measured by the following method.

<Hydroxyl value>

The hydroxyl value of (meth)acrylic acid copolymers is determined by neutralization titration.

Take 2g of sample into an Erlenmeyer flask, add 10mL of acetic anhydride: pyridine = 1:13 mixed solution using a full pipette, and then add 10mL of toluene. Install an air condenser on the top of the Erlenmeyer flask and heat at 95℃ for 90 minutes. After heating, add 10mL of toluene and 10mL of pure water, stir and cool to room temperature (23℃). Then, add a few drops of phenolphthalein solution and titrate with 0.1mol/L potassium hydroxide solution. In addition, as a blank test, do not take a sample into the Erlenmeyer flask and perform the same operation as above. Calculate the hydroxyl value based on the following calculation formula (1).

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

‧f: coefficient of 0.1mol/L potassium hydroxide solution

[Acid value]

The above acid value is measured by the following method. Take Y g of (meth) acrylic acid copolymer into a beaker and dissolve it in a mixed solvent of toluene: methanol = 7:3. Then, add an appropriate amount of phenolphthalein after dissolution, stir with a stirrer, and titrate with 0.1 mol/L potassium hydroxide solution. Read the potassium hydroxide solution volume X mL when the solution turns light pink as the end point, and calculate the acid value based on the following calculation formula (2).

[Calculation formula] Acid value (mgKOH/g) = X×(f×M×56.1)/Y‧‧‧(2)

‧f: coefficient of potassium hydroxide solution

‧M: Molar concentration (mol/L)

‧X: Potassium hydroxide solution volume (mL)

‧Y: Sample volume (g)

Furthermore, when the acid value is low, use 0.01mol/L KOH solution to improve accuracy.

<Mass average molecular weight>

The mass average molecular weight of the (meth)acrylic acid copolymer is measured using a gel permeation chromatography (GPC) analyzer (manufactured by Tosoh Corporation, HLC-8320GPC). Specifically, 4 mg of the (meth)acrylic acid copolymer is dissolved in 12 mL of THF as a test sample, and the molecular weight distribution curve is measured under the following conditions to obtain the mass average molecular weight (Mw).

‧Guard column: TSKguardcolumnHXL

‧Separation column: TSKgelGMHXL (4 pieces)

‧Temperature: 40℃

‧Injection volume: 100μL

‧Polystyrene conversion

‧Solvent: THF

‧Flow rate: 1.0mL/min

<Glass transition temperature (Tg)>

The glass transition temperature (Tg) of (meth)acrylic copolymers is measured using a rheometer (manufactured by TA Instruments, "DiscoveryHR2"). Specifically, for (meth)acrylic copolymers with a thickness of 0.6~0.8mm, the dynamic viscoelastic spectrum is measured in the temperature range of -120~200℃ under the conditions of a jig: Φ8mm parallel plate, strain: 0.1%, frequency: 1Hz, temperature: -120~200℃, and heating rate: 5℃/min. The temperature at which the loss tangent (Tanδ) reaches a maximum value is read from the obtained data to obtain the glass transition temperature (Tg).

<Implementation Example 1>

酯/丙烯醯胺之共聚物(A'-1)[質量平均分子量29萬、Tg4℃]1kg、作為交聯劑(B)之丙氧化季戊四醇三丙烯酸酯(B-1)100g、及作為光聚合起始劑(C)之2,4,6-三甲基二苯甲酮與4-甲基二苯甲酮之混合物(C-1)5g均勻地進行熔融混練，製作樹脂組合物1。 The (meth)acrylic copolymer includes 2-ethylhexyl acrylate/methyl acrylate/methyl methacrylate/isopropyl methacrylate.

1 kg of a copolymer of ester/acrylamide (A'-1) [mass average molecular weight 290,000, Tg 4°C], 100 g of propoxylated pentaerythritol triacrylate (B-1) as a crosslinking agent (B), and 5 g of a mixture of 2,4,6-trimethylbenzophenone and 4-methylbenzophenone (C-1) as a photopolymerization initiator (C) were uniformly melt-kneaded to prepare a resin composition 1.

1 kg of a copolymer (A-1) containing 2-ethylhexyl acrylate/2-hydroxyethyl acrylate/methyl acrylate [mass average molecular weight 440,000, Tg-25°C, hydroxyl value 67 mgKOH/g] as a (meth)acrylic copolymer, 10 g of (C-1) as a photopolymerization initiator (C), and 1 g of 3-glycidyloxypropyltrimethoxysilane (D-1) as a silane coupling agent (D) were uniformly melt-kneaded to prepare a resin composition 2.

The resin composition 1 is sandwiched between two release-treated polyethylene terephthalate films ("DIAFOIL MRF (thickness 75μm)" manufactured by Mitsubishi Chemical Corporation/"DIAFOIL MRT (thickness 38μm)" manufactured by Mitsubishi Chemical Corporation), i.e., two release films, and formed into a sheet at a temperature of 80°C in a manner such that the thickness becomes 50μm, thereby preparing a sheet for the intermediate layer (1).

The resin composition 2 is sandwiched between two release-treated polyethylene terephthalate films ("DIAFOIL MRF (thickness 75μm)" manufactured by Mitsubishi Chemical Corporation/"DIAFOIL MRT (thickness 38μm)" manufactured by Mitsubishi Chemical Corporation), i.e., two release films, and formed into a sheet at a temperature of 80°C in a manner such that the thickness becomes 25μm, thereby preparing two adhesive sheets (2) for the front and back layers.

The middle layer sheet (1) with the release films on both sides peeled off is attached to the adhesive surface of the front and back layer adhesive sheet (2) with the release films on one side peeled off to produce a laminate having a layer structure of (2)/(1)/(2).

The release film left on the surface of the above-mentioned adhesive sheet (2) for the front and back layers is irradiated with light by a high-pressure mercury lamp in such a way that the cumulative light intensity at a wavelength of 365nm becomes 2000mJ/ ^cm2 for pre-curing, thereby producing the double-sided adhesive sheet (pre-cured product) of Example 1.

Furthermore, in the double-sided adhesive sheet of Example 1, the shear storage modulus (G') of the surface and inner layers at a temperature of 25°C is lower than the shear storage modulus (G') of the middle layer, and either layer has room for photohardening by light irradiation.

<Implementation Example 2>

1 kg of (A-1) as a (meth)acrylic copolymer, 10 g of (C-1) as a photopolymerization initiator (C), and 1 g of 1,2,3-triazole (E-1) as a metal anticorrosive agent (E) were uniformly melt-kneaded to prepare resin composition 3.

Furthermore, as a metal corrosion inhibitor, the absorbance of (E-1) at 365nm is 0.3mL/(g‧cm), and its water solubility at 25°C is higher than 1000g/L.

The resin composition 1 prepared in the above-mentioned Example 1 is sandwiched between two release-treated polyethylene terephthalate films ("DIAFOIL MRF (thickness 75μm)" manufactured by Mitsubishi Chemical Corporation/"DIAFOIL MRT (thickness 38μm)" manufactured by Mitsubishi Chemical Corporation), i.e., two release films, and is formed into a sheet at a temperature of 80°C in a manner such that the thickness becomes 67μm, thereby preparing a sheet (1) for the intermediate layer.

The resin composition 3 is sandwiched between two release-treated polyethylene terephthalate films ("DIAFOIL MRF (thickness 75μm)" manufactured by Mitsubishi Chemical Corporation/"DIAFOIL MRT (thickness 38μm)" manufactured by Mitsubishi Chemical Corporation), i.e., two release films, and formed into a sheet at a temperature of 80°C in a manner such that the thickness becomes 17μm, thereby preparing two adhesive sheets (3) for the front and back layers.

The middle layer sheet (1) with the release films on both sides peeled off is attached to the adhesive surface of the front and back layer adhesive sheet (3) with the release films on one side peeled off to produce a laminate having a layer structure of (3)/(1)/(3).

The release film left on the surface of the above-mentioned adhesive sheet (3) for the front and back layers is irradiated with light by a high-pressure mercury lamp at a wavelength of 365nm in such a way that the cumulative light intensity becomes 1000mJ/ ^cm2 for pre-curing, thereby producing the double-sided adhesive sheet (pre-cured product) of Example 2.

Furthermore, in the double-sided adhesive sheet of Example 2, the shear storage modulus (G') of the surface and inner layers at a temperature of 25°C is lower than the shear storage modulus (G') of the middle layer, and either layer has room for photohardening by light irradiation.

<Implementation Example 3>

1 kg of (A'-1) as a (meth)acrylic copolymer, 100 g of (B-1) as a crosslinking agent (B), 4 g of (C-1) as a photopolymerization initiator (C), and 4 g of oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)acetone) (C-2) were uniformly melt-kneaded to prepare a resin composition 4.

The resin composition 4 is sandwiched between two release-treated polyethylene terephthalate films ("DIAFOIL MRF (thickness 75μm)" manufactured by Mitsubishi Chemical Corporation/"DIAFOIL MRT (thickness 38μm)" manufactured by Mitsubishi Chemical Corporation), i.e., two release films, and formed into a sheet at a temperature of 80°C in a manner such that the thickness becomes 75μm, thereby preparing a sheet for the intermediate layer (4).

The resin composition 2 prepared in the above-mentioned Example 1 is sandwiched between two release-treated polyethylene terephthalate films ("DIAFOIL MRF (thickness 75μm)" manufactured by Mitsubishi Chemical Corporation/"DIAFOIL MRT (thickness 38μm)" manufactured by Mitsubishi Chemical Corporation), i.e., two release films, and is formed into a sheet at a temperature of 80°C in such a way that the thickness becomes 13μm, thereby preparing two adhesive sheets (2) for the surface and back layers.

The middle layer sheet (4) with the release films on both sides peeled off is attached to the adhesive surface of the front and back layer adhesive sheet (2) with the release films on one side peeled off to produce a laminate having a layer structure of (2)/(4)/(2).

The release film left on the surface of the above-mentioned adhesive sheet (2) for the front and back layers is irradiated with light by a high-pressure mercury lamp at a wavelength of 365nm in such a way that the cumulative light intensity becomes 1000mJ/ ^cm2 for pre-curing, thereby producing the double-sided adhesive sheet (pre-cured product) of Example 3.

Furthermore, in the double-sided adhesive sheet of Example 3, the shear storage modulus (G') of the surface and inner layers at a temperature of 25°C is lower than the shear storage modulus (G') of the middle layer, and either layer has room for photohardening by light irradiation.

<Comparison Example 1>

1 kg of (A-1) as a (meth)acrylic copolymer, 200 g of (B-1) as a crosslinking agent (B), and 8 g of (C-1) as a photopolymerization initiator (C) were uniformly melt-kneaded to prepare resin composition 5.

1 kg of (A-1) as a (meth)acrylic copolymer and 10 g of (C-1) as a photopolymerization initiator (C) were uniformly melt-kneaded to prepare resin composition 6.

The resin composition 5 is sandwiched between two release-treated polyethylene terephthalate films ("DIAFOIL MRF (thickness 75μm)" manufactured by Mitsubishi Chemical Corporation/"DIAFOIL MRT (thickness 38μm)" manufactured by Mitsubishi Chemical Corporation), i.e., two release films, and formed into a sheet at a temperature of 80°C in a manner such that the thickness becomes 67μm, thereby preparing a sheet for the intermediate layer (5).

The resin composition 6 is sandwiched between two release-treated polyethylene terephthalate films ("DIAFOIL MRF (thickness 75μm)" manufactured by Mitsubishi Chemical Corporation/"DIAFOIL MRT (thickness 38μm)" manufactured by Mitsubishi Chemical Corporation), i.e., two release films, and formed into a sheet at a temperature of 80°C in a manner such that the thickness becomes 17μm, thereby preparing two adhesive sheets (6) for the front and back layers.

The intermediate layer sheet (5) with the release film on both sides peeled off is attached to the adhesive surface of the surface layer adhesive sheet (6) with the release film on one side peeled off to produce a laminate having a layer structure of (6)/(5)/(6).

The release film left on the surface of the above-mentioned adhesive sheet (6) for the front and back layers is irradiated with light by a high-pressure mercury lamp at a wavelength of 365nm in such a way that the cumulative light intensity becomes 2000mJ/ ^cm2 for pre-curing, thereby producing a double-sided adhesive sheet (pre-cured product) of Comparative Example 1.

Furthermore, in the double-sided adhesive sheet of Comparative Example 1, the shear storage modulus (G') of the surface and inner layers at a temperature of 25°C is lower than the shear storage modulus (G') of the middle layer, and there is room for light curing of either layer by light irradiation.

<Comparison Example 2>

1 kg of (A'-1) as a (meth)acrylic copolymer, 100 g of (B-1) as a crosslinking agent (B), 5 g of (C-1) as a photopolymerization initiator (C), and 1 g of (D-1) as an additive (D) were uniformly melt-kneaded to prepare a resin composition 7.

The resin composition 7 was sandwiched between two release-treated polyethylene terephthalate films ("DIAFOIL MRF (thickness 75 μm)" manufactured by Mitsubishi Chemical Corporation/"DIAFOIL MRT (thickness 38 μm)" manufactured by Mitsubishi Chemical Corporation), i.e., two release films, and formed into a sheet at a temperature of 80°C in such a manner that the thickness became 100 μm. The sheet was irradiated with light from one side of the release film by a high-pressure mercury lamp in such a manner that the accumulated light amount at a wavelength of 365 nm became 1000 mJ/ ^cm2 , and pre-cured to produce a double-sided adhesive sheet (pre-cured product) of Comparative Example 2.

Furthermore, the (meth) acrylic adhesive layer in the double-sided adhesive sheet of Comparative Example 2 has room for photocuring by light irradiation.

<Comparison Example 3>

1 kg of copolymer 1 (mass average molecular weight 540,000, Tg 1°C, hydroxyl value 62 mgKOH/g) containing methyl acrylate/ethyl acrylate/2-ethylhexyl acrylate/2-hydroxyethyl acrylate as a (meth) acrylic copolymer, 100 g of polypropylene glycol diacrylate (B-2, molecular weight 536) as a crosslinking agent (B), 10 g of (C-1) as a photopolymerization initiator (C), and 1 g of (D-1) as an additive (D) were uniformly melt-kneaded to prepare a resin composition 8.

The resin composition 8 was sandwiched between two release-treated polyethylene terephthalate films ("DIAFOIL MRF (thickness 75 μm)" manufactured by Mitsubishi Chemical Corporation/"DIAFOIL MRT (thickness 38 μm)" manufactured by Mitsubishi Chemical Corporation), i.e., two release films, and formed into a sheet at a temperature of 80°C in such a manner that the thickness became 100 μm. The sheet was irradiated with light from one side of the release film by a high-pressure mercury lamp in such a manner that the accumulated light amount at a wavelength of 365 nm became 1000 mJ/ ^cm2 , and pre-cured to produce a double-sided adhesive sheet (pre-cured product) of Comparative Example 3.

Furthermore, the (meth) acrylic adhesive layer in the double-sided adhesive sheet of Comparative Example 3 has room for photocuring by light irradiation.

<Comparison Example 4>

1 kg of (A-1) as a (meth)acrylic copolymer, 180 g of (B-3) as a crosslinking agent (B), and 10 g of (C-1) as a photopolymerization initiator (C) were uniformly melt-kneaded to prepare resin composition 9.

1 kg of (A-1) as a (meth)acrylic copolymer and 12 g of (C-1) as a photopolymerization initiator (C) were uniformly melt-kneaded to prepare a resin composition 10.

The resin composition 9 is sandwiched between two release-treated polyethylene terephthalate films ("DIAFOIL MRF (thickness 75μm)" manufactured by Mitsubishi Chemical Corporation/"DIAFOIL MRT (thickness 38μm)" manufactured by Mitsubishi Chemical Corporation), i.e., two release films, and formed into a sheet at a temperature of 80°C in a manner such that the thickness becomes 67μm, thereby preparing a sheet for the intermediate layer (9).

The resin composition 10 is sandwiched between two release-treated polyethylene terephthalate films ("DIAFOIL MRF (thickness 75μm)" manufactured by Mitsubishi Chemical Corporation/"DIAFOIL MRT (thickness 38μm)" manufactured by Mitsubishi Chemical Corporation), i.e., two release films, and formed into a sheet at a temperature of 80°C in a manner such that the thickness becomes 17μm, thereby preparing two adhesive sheets (10) for the front and back layers.

The middle layer sheet (9) with the release films on both sides peeled off is attached to the adhesive surface of the front and back layer adhesive sheet (10) with the release films on one side peeled off to produce a laminate having a layer structure of (10)/(9)/(10).

The release film left on the surface of the above-mentioned adhesive sheet (10) for the front and back layers is irradiated with light by a high-pressure mercury lamp in such a way that the cumulative light intensity at a wavelength of 365nm becomes 2000mJ/ ^cm2 for pre-curing, thereby producing a double-sided adhesive sheet (pre-cured product) of Comparative Example 4.

Furthermore, in the double-sided adhesive sheet of Comparative Example 4, the shear storage modulus (G') of the surface and inner layers at a temperature of 25°C is lower than the shear storage modulus (G') of the middle layer, and either layer has room for photohardening by light irradiation.

[Physical property evaluation]

The physical properties of the double-sided adhesive sheets of Examples 1 to 3 and Comparative Examples 1 to 4 obtained above were measured in the following manner. In addition, for the physical properties of each layer alone, the sheets for each layer were prepared and pre-cured under the same conditions, and the obtained ones were used for measurement. The double-sided adhesive sheets of Examples 1 to 3 and Comparative Examples 1 to 4, and the physical properties of each layer alone are shown in the following Table 1.

<Peak temperature (T1) of shear storage modulus (G') and loss tangent (Tanδ)>

For each of the double-sided adhesive sheets (pre-cured products) of Examples 1 to 3 and Comparative Examples 1 to 4, i.e., double-sided adhesive sheets before curing (hereinafter collectively referred to as "double-sided adhesive sheets before curing"), two release films were peeled off, and the adhesive sheets were stacked in a manner to a thickness of 0.6 to 0.8 mm, and then punched into a circular shape with a diameter of 8 mm, and the obtained ones were used as test samples.

Using a rheometer (manufactured by TA Instruments, "DiscoveryHR2"), the dynamic viscoelastic spectrum in the shear mode was measured in the temperature range of -120~200℃ under the conditions of adhesive fixture: Φ8mm parallel plate, strain: 0.1%, frequency: 1Hz, temperature: -120~200℃, and heating rate: 5℃/min. Based on the obtained data, the shear storage modulus (G') of the double-sided adhesive sheet before curing at 25℃ was calculated.

In addition, the temperature at which the loss tangent (Tanδ) of the obtained dynamic viscoelastic spectrum data reaches a maximum value is the peak temperature (T1).

Next, the double-sided adhesive sheet before curing was photocured by irradiating the double-sided adhesive sheet with light at a wavelength of 365 nm so that the accumulated light amount became 3000 mJ/cm ² using a high-pressure mercury lamp, thereby preparing a double-sided adhesive sheet after curing.

For each of the above-mentioned double-sided adhesive sheets after curing (hereinafter collectively referred to as "double-sided adhesive sheets after curing"), the two release films were peeled off in the same manner as above, and the adhesive sheets were stacked in a manner to a thickness of 0.6~0.8mm, and punched into a circular shape with a diameter of 8mm. The obtained ones were used as test specimens. Under the same test conditions as the above-mentioned double-sided adhesive sheets before curing, the dynamic viscoelastic spectrum of the test specimen under the shear mode was measured, and the storage modulus (G') of the double-sided adhesive sheets after curing at a temperature of 25°C was calculated based on the obtained data.

In addition, the temperature at which the loss tangent (Tanδ) of the obtained dynamic viscoelastic spectrum data reaches a maximum value is the peak temperature (T1).

<Peak temperature (T2) of tensile storage modulus (E') and loss tangent (Tanδ)>

The double-sided adhesive sheets (pre-cured products) of Examples 1 to 3 and Comparative Examples 1 to 4, i.e., the double-sided adhesive sheets before curing, were irradiated with light by a high-pressure mercury lamp at a wavelength of 365 nm to a cumulative light intensity of 3000 mJ/ ^cm2 , and then cut into sample sizes of 4 mm wide by 15 mm long. The dynamic viscoelasticity measuring device (IT Meter and The dynamic viscoelastic spectrum in the tensile mode was measured by using an itkDVA-200 (manufactured by Control Co., Ltd.) with a vibration frequency of 1 Hz, a measuring temperature of -120 to 80°C, and a heating rate of 3°C/min. The tensile storage modulus (E') of the double-sided adhesive sheet after curing at 25°C was calculated based on the data obtained.

In addition, the temperature at which the loss tangent (Tanδ) of the obtained dynamic viscoelastic spectrum data reaches a maximum value is the peak temperature (T2).

The double-sided adhesive sheets of Examples 1 to 3 and Comparative Examples 1 to 4 obtained above were used to perform the following evaluations. The evaluation results are shown in Table 1 below.

<180° peeling adhesion>

For each of the double-sided adhesive sheets (pre-cured products) of Examples 1 to 3 and Comparative Examples 1 to 4, one of the release films was peeled off and a 100 μm PET film (manufactured by Mitsubishi Chemical Corporation, "DIAFOIL T100") was laminated as a backing film. After cutting it into pieces of 150 mm in length and 20 mm in width, the adhesive surface exposed by peeling off the remaining release film was rolled and pressed onto a sodium calcium glass plate to produce a laminated product. The laminated products were subjected to autoclave treatment (60°C, gauge pressure 0.2 MPa, 20 minutes) and final lamination. A high-pressure mercury lamp was used to irradiate the PET film surface with light at 365 nm in a manner such that the accumulated light intensity was 3000 mJ/cm2 ^. The products were then cured at 23°C and 50% RH for 12 hours to prepare samples for 180° peel adhesion measurement.

For the above samples, the peeling force (N/20mm) was measured at a peeling angle of 180° and a peeling speed of 300mm/min at a temperature of 23°C and 50%RH. Then, those that did not reach 5N/20 mm and were easy to peel were judged as "× (bad)", and those that were 5N/20mm or more were judged as "○ (good)".

<Reworkability>

Using a Thomson punching machine, the double-sided adhesive sheets (pre-cured products) of the above-mentioned Examples 1 to 3 and Comparative Examples 1 to 4 were cut into a size of 52mm×80mm with a release film laminated thereon. The release film on one side was peeled off, and the exposed adhesive surface was bonded to a sodium calcium glass plate (54mm×82mm, thickness 0.6mm) by a hand roller.

Next, peel off the release film on the adhesive side of the attached polarizing plate (Sanritz, "VLC2"), and use a hand roller to stick a polyethylene terephthalate film (Mitsubishi Chemical, "DIAFOIL T100", 54mm×82mm, thickness 38μm) to the exposed adhesive surface. Then, peel off the other release film of the double-sided adhesive sheet stuck to the sodium calcium glass plate, and stick it to the polarizing plate with the protective film on the polarizing plate side peeled off using a hand roller.

Then, after final lamination by autoclave treatment (60°C, gauge pressure 0.2MPa, 20 minutes), a high-pressure mercury lamp was used to irradiate light from the side of the soda-lime glass plate so that the cumulative light intensity at 365nm became 3000mJ/cm ² to photoharden the adhesive sheet (post-hardened product). Thereafter, by curing at room temperature (23°C) for 12 hours, a sample for reworkability evaluation (soda-lime glass plate/double-sided adhesive sheet/adhered polarizing plate/PET film) was produced.

These were placed on a SUS cooling plate (surface temperature -120° C.) with the soda-lime glass plate in contact with the cooling plate (with the soda-lime glass plate on the lower side), and the time until the soda-lime glass plate and the polarizing plate were separated was measured. Five samples for each double-sided adhesive sheet were produced for the above-mentioned reworkability evaluation, and each piece was measured five times, and the evaluation was performed as follows based on the average value of the time until separation.

Those that can be separated within 30 seconds will be judged as "◎ (very good)", those that cannot be separated within 30 seconds but can be separated within 120 seconds will be judged as "○ (good)", and those that cannot be separated after more than 120 seconds and are not suitable for actual users will be judged as "× (poor)".

<Step-by-step absorption>

For each of the double-sided adhesive sheets (pre-cured products) of the above-mentioned Examples 1 to 3 and Comparative Examples 1 to 4, a Thomson punching machine was used to cut them into a size of 52mm×80mm while being laminated with a release film.

Peel off the release film on one side, and apply printing steps to the exposed adhesive surface on the four sides of the double-sided adhesive sheet. Use a vacuum press (temperature 25℃, pressure 0.1MPa) to press and bond the printed surface of a sodium calcium glass plate (82mm×54mm×thickness 0.5mm) with a printing thickness of 15μm or 25μm at 5mm around the periphery.

Next, the remaining release film is peeled off, and a sodium calcium glass plate (82mm×54mm×thickness 0.5mm) without printing steps is laminated under pressure, and then an autoclave treatment (60℃, gauge pressure 0.2MPa, 20 minutes) is performed for final lamination to produce a laminate (sodium calcium glass plate with printing steps/double-sided adhesive sheet/sodium calcium glass plate).

The produced laminate was visually inspected and evaluated as described below.

The double-sided adhesive sheet did not follow the printing step and retained air bubbles near the printing step, which was not suitable for lamination with printing steps as "× (normal)", the sheet had no air bubbles and could be laminatable with good appearance at a printing step of 15μm, but retained air bubbles at a printing step of 25μm as "○ (good)", and the sheet had no air bubbles and could be laminatable with good appearance at both printing steps of 15μm and 25μm as "◎ (very good)".

<Fitting reliability>

The double-sided adhesive sheets (pre-cured products) of the above-mentioned Examples 1 to 3 and Comparative Examples 1 to 4 were cut into a size of 52 mm × 80 mm with a release film laminated thereon using a Thomson punch. The release film on one side was peeled off, and the exposed adhesive surface was bonded to a sodium calcium glass plate 1 (54 mm × 82 mm, thickness 0.6 mm) by a hand roller. Then, the release film on the adhesive side of the attached polarizing plate (manufactured by Sanritz, "VLC2") was peeled off, and the exposed adhesive surface was bonded to a sodium calcium glass plate 2 (54 mm × 82 mm, thickness 0.6 mm) by a hand roller. Then, the other release film of each double-sided adhesive sheet attached to the sodium calcium glass plate 1 is peeled off and attached to the polarizing plate with the protective film on the side of the polarizing plate peeled off by a hand roller.

Then, after the final bonding was performed by autoclave treatment (60°C, gauge pressure 0.2MPa, 20 minutes), light was irradiated from the sodium calcium glass plate 1 side using a high-pressure mercury lamp in such a way that the accumulated light amount at 365nm became 3000mJ/ ^cm2 to photocure the adhesive sheet (post-cured product). After that, by curing at room temperature (23°C) for 12 hours, a sample for evaluating heat blister resistance was prepared (sodium calcium glass plate 1/double-sided adhesive sheet/attached polarizing plate/sodium calcium glass plate 2).

Place the mixture in an environment of 85°C for 300 hours and visually observe for any foaming.

Those with bubbles at the interface of the attached polarizing plate/double-sided adhesive sheet will be judged as "× (bad)", and those without bubbles and good appearance will be judged as "○ (good)".

<ITO corrosion resistance>

As shown in Figure 1(A), a substrate for evaluating ITO corrosion resistance was prepared by forming an ITO 200Å film on a 60mm×45mm, 0.7mm thick glass under patterning conditions of 70μm line width/30μm line spacing (patterning accuracy ±8μm), 46cm line length, 5mm×5mm electrode size, and 50mm electrode spacing.

For each of the double-sided adhesive sheets (pre-cured products) of Examples 1 to 3 and Comparative Examples 1 to 4, the single-sided release film was peeled off, and the sheet was laminated to a PET film ("DIAFOIL T100", manufactured by Mitsubishi Chemical Corporation, thickness 50μm) with a roller, and then cut into 52mm width.

Afterwards, the release film on the other side is peeled off, and the adhesive sheet is placed between the electrodes, and then bonded to the substrate by rollers, and then subjected to autoclave treatment (temperature 60°C, gauge pressure 0.2MPa, 20 minutes) for final bonding.

Afterwards, light was irradiated from the PET film side with a high-pressure mercury lamp at a wavelength of 365 nm to a cumulative light intensity of 2000 mJ/ ^cm2 for light curing (formally cured product). Afterwards, the film was cured at room temperature for 12 hours to prepare a sample for evaluating ITO corrosion resistance (see Figure 1(C)).

For this sample, an environmental test was conducted in a hot and humid environment of 65°C and 90%RH×500h to confirm that the resistance value between the electrodes increased (see Figure 1(B)). In the above environmental test, the resistance value increased by more than 4% and was judged as "× (bad)", the resistance value increased by more than 3% and was suppressed to less than 4% and was judged as "○ (good)", and the resistance value increased and further suppressed to less than 3% and was judged as "◎ (very good)".

<Cu corrosion resistance>

As shown in Figure 1(A), a substrate for evaluating Cu corrosion resistance was prepared by sequentially depositing ITO 1300Å and copper (Cu) 3000Å on a 60mm×45mm, 0.7mm thick glass under patterning conditions of 70μm line width/30μm line spacing (patterning accuracy ±8μm), 46cm line length, 5mm×5mm electrode size, and 50mm electrode spacing.

For each of the double-sided adhesive sheets (pre-cured products) of Examples 1 to 3 and Comparative Examples 1 to 4, the single-sided release film was peeled off, and the sheet was laminated to a PET film ("DIAFOIL T100", manufactured by Mitsubishi Chemical Corporation, thickness 50μm) with a roller, and then cut into 52mm width.

Afterwards, the release film on the other side is peeled off, and the adhesive sheet is placed between the electrodes, and then bonded to the substrate by rollers, and then subjected to autoclave treatment (temperature 60°C, gauge pressure 0.2MPa, 20 minutes) for final bonding.

Thereafter, light was irradiated from the PET film side using a high-pressure mercury lamp so that the accumulated light amount at a wavelength of 365 nm became 3000 mJ/ ^cm2 to perform light curing (final cured product).

After that, the samples were cured at room temperature (23°C) for 12 hours to prepare samples for evaluation of Cu corrosion resistance (see Figure 1 (D)).

For this sample, an environmental test was conducted in a hot and humid environment of 65°C and 90%RH×500h to confirm that the resistance value between the electrodes increased (see Figure 1(B)). In the above environmental test, the resistance value increased by more than 3% and was judged as "× (bad)", the resistance value increased by more than 1% and was suppressed to less than 3% and was judged as "○ (good)", and the resistance value increased and was further suppressed to less than 1% and was judged as "◎ (very good)".

Regarding the double-sided adhesive sheets of Examples 1 to 3, the ratio of the tensile storage modulus (E') to the shear storage modulus (G') is 5.0 or more, and the peak temperature (T1) of the loss tangent (Tan δ) obtained by the dynamic viscoelasticity measurement in the shear mode at a frequency of 1 Hz is -10°C or less. , the peak temperature (T2) of the loss tangent (Tan δ) obtained by the dynamic viscoelasticity measurement in the tensile mode at a frequency of 1 Hz is above -10°C, and the adhesion force is above 5N/20mm. Therefore, it has step absorption, reliability, metal corrosion resistance, and excellent reworkability. Among them, the transparent double-sided adhesive sheet laminates of Examples 2 to 3 are particularly excellent in reworkability and metal corrosion resistance through the selection of the blending of the surface layer and the middle layer, the selection of the layer thickness ratio, etc.

On the other hand, in the double-sided adhesive sheet of Comparative Example 1, the ratio of the tensile storage modulus (E') to the shear storage modulus (G') was 4.9, so the reworkability was poor.

In addition, in the double-sided adhesive sheet of Comparative Example 2 or Comparative Example 3, the (meth) acrylic adhesive layer is a single layer, and the peak temperature (T1) of the loss tangent (Tanδ) obtained by dynamic viscoelasticity measurement in the shear mode at a frequency of 1 Hz is higher than -10°C, or the adhesive force is less than 5.0N/20mm. Therefore, the double-sided adhesive sheet is harder and the step absorption is poor, or bubbles are generated at the end of the bonding surface during the reliability test, resulting in poor bonding reliability.

Regarding the double-sided adhesive sheet of Comparative Example 4, the peak temperature (T2) of the loss tangent (Tan δ) obtained by the dynamic viscoelasticity measurement in the tensile mode at a frequency of 1 Hz was lower than -10°C, so the reworkability was poor.

In the above embodiments, the specific form of the present invention is shown, but the above embodiments are only illustrative and are not to be interpreted restrictively. It is intended that various changes that are obvious to the industry are included in the scope of the present invention.

[Industrial availability]

The double-sided adhesive sheet of the present invention has excellent adhesive properties such as step absorption, adhesive force, and bonding reliability, and can be easily peeled off (separated) from the components of the image display device by cooling operation. Therefore, it can be suitably used for bonding components of the image display device.

Furthermore, the laminated body for an image display device and the image display device of the present invention can be easily peeled (separated) from the constituent members for an image display device, and are excellent in reworkability.

Claims (13)

A double-sided adhesive sheet for bonding two components of an image display device, wherein the ratio (E'/G') of the tensile storage modulus (E') to the shear storage modulus (G') is 5.0 or more, the peak temperature (T1) of the loss tangent (Tanδ) obtained by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz is below -10°C, The peak temperature (T2) of the loss tangent (Tanδ) obtained by dynamic viscoelasticity measurement in the tensile mode of Hz is above -10℃ (wherein, when more than two peak temperatures are observed, the highest temperature is set as the peak temperature (T2)), and the 180° peeling adhesion force at 23℃ to each adhered surface of the above two image display device components is above 5 N/20 mm. A double-sided adhesive sheet as claimed in claim 1, wherein the difference between the peak temperature (T2) of the loss tangent (Tanδ) obtained by dynamic viscoelasticity measurement in a tensile mode at a frequency of 1 Hz and the peak temperature (T1) of the loss tangent (Tanδ) obtained by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz is 5 to 50°C. A double-sided adhesive sheet as claimed in claim 1 or 2, wherein the two components for constituting the image display device are formed of different materials. A double-sided adhesive sheet as claimed in claim 1 or 2, wherein one of the two components for the image display device is glass, and the other comprises any one or a combination of two or more of the group consisting of a touch sensor, an image display panel, a surface protection panel, a polarizing film and a phase difference film. A double-sided adhesive sheet as claimed in claim 4, wherein the glass is a cover glass having a curved shape. The double-sided adhesive sheet of claim 1 or 2 is constructed in such a way that the two image display device components can be separated by a cooling operation. The double-sided adhesive sheet of claim 6, wherein the cooling operation is performed at a temperature below -50°C. The double-sided adhesive sheet of claim 1 or 2 has a thickness of 50 to 1000 μm. A double-sided adhesive sheet as claimed in claim 1 or 2, wherein the double-sided adhesive sheet has at least three layers, the outermost layer and the innermost layer being (meth) acrylic adhesive layers, and the combined ratio of the thickness of the outermost layer and the innermost layer to the overall thickness is 5 to 70%. The double-sided adhesive sheet of claim 1 or 2 is photocurable. A multilayer body for an image display device is formed by bonding two image display device components via a double-sided adhesive sheet as described in any one of claims 1 to 10. A laminate for an image display device is formed by bonding two image display device components together via an adhesive layer formed by hardening a double-sided adhesive sheet as described in any one of claims 1 to 10. An image display device is constructed using a multilayer body such as the image display device of claim 12.