Pressure-sensitive adhesive sheet, optical laminate, and image display device

Abstract

The present invention provides a pressure-sensitive adhesive sheet suitable for inhibiting delamination between members of an image display device in high-temperature environments. This pressure-sensitive adhesive sheet 1 has a first surface 1a and a second surface 1b, which are opposite to each other. The pressure-sensitive adhesive sheet 1 has a creep amount, as obtained by the following test, of 10 μm or greater, and the first surface 1a has an elastic modulus G1, as determined with an atomic force microscope, of 1.0 MPa or greater.　Test: A 500-gf load 54 is applied vertically downward to the pressure-sensitive adhesive sheet 1 adhered to a test plate 53 made of stainless steel so that the bonding area is 10 mm in length by 10 mm in width, while the test plate 53 is kept fixed. At 3,600 seconds after initiation of the application of the load 54, the amount of creep (dislocation amount) of the pressure-sensitive adhesive sheet 1 relative to the test plate 53 is measured.

Description

Pressure-sensitive adhesive sheet, optical laminate, and image display device

[0001] The present invention relates to a pressure-sensitive adhesive sheet, an optical laminate, and an image display device.

[0002] Various image display devices, such as liquid crystal display devices and electroluminescence (EL) display devices, generally include an optical laminate including an optical film such as a polarizing film and an adhesive sheet. An adhesive sheet is typically used to bond the optical films included in the optical laminate or to bond the optical laminate to an image display panel. A typical adhesive sheet is a sheet obtained by polymerizing and crosslinking a monomer group including an acrylic monomer, a silicone monomer, or the like to harden the monomer group. Patent Document 1 discloses an example of an adhesive sheet.

[0003] Patent No. 3052972

[0004] In conventional image display devices, peeling tends to occur between components, such as between an optical laminate and an image display panel, or between a pressure-sensitive adhesive sheet and an optical film, in a high-temperature environment. According to the inventors' studies, the problem of peeling between components tends to occur more significantly when a pressure-sensitive adhesive sheet produced by a method of curing a pressure-sensitive adhesive composition by irradiating it with light (a photocuring method) is used. This problem can also occur when the optical film includes a uniaxially stretched film such as a polarizer, or when the pressure-sensitive adhesive sheet has a thickness of 50 μm or less (particularly 30 μm or less).

[0005] Therefore, an object of the present invention is to provide a pressure-sensitive adhesive sheet that is suitable for suppressing peeling between components of an image display device in a high-temperature environment.

[0006] As a result of intensive research, the present inventors have found that the creep amount, which is an index of the susceptibility of a pressure-sensitive adhesive sheet to distortion due to stress, and the surface elastic modulus affect peeling between components in a high-temperature environment. Based on this finding, the present inventors have further researched and completed the present invention.

[0007] The present invention provides a pressure-sensitive adhesive sheet having a first surface and a second surface opposing each other, wherein the amount of creep determined by the following test is 10 μm or more, and the modulus of elasticity of the first surface measured using an atomic force microscope is 1.0 MPa or more. Test: The pressure-sensitive adhesive sheet is attached to a stainless steel test plate at a bonding surface measuring 10 mm long x 10 mm wide, and a load of 500 gf is applied vertically downward to the test plate while the test plate is fixed. The amount of creep (amount of displacement) of the pressure-sensitive adhesive sheet relative to the test plate is measured 3,600 seconds after the start of load application.

[0008] The present invention further provides an optical laminate comprising: the pressure-sensitive adhesive sheet; and an optical film containing at least one selected from the group consisting of a polarizing film and a retardation film.

[0009] The present invention further provides an image display device comprising the above optical laminate.

[0010] According to the present invention, it is possible to provide a pressure-sensitive adhesive sheet that is suitable for preventing peeling between components of an image display device in a high-temperature environment.

[0011] FIG. 1 is a cross-sectional view schematically illustrating an example of a pressure-sensitive adhesive sheet of the present invention. FIG. 2 is a schematic view illustrating a method for measuring the amount of creep for a pressure-sensitive adhesive sheet. FIG. 3 is a schematic view illustrating a method for measuring the amount of creep for a pressure-sensitive adhesive sheet. FIG. 4 is a view showing an example of an atomic force microscope image of a first surface of a pressure-sensitive adhesive sheet. FIG. 5 is a view showing an example of a histogram of elastic modulus measured with an atomic force microscope. FIG. 6 is a view showing an example of an atomic force microscope image of a cross section of a pressure-sensitive adhesive sheet. FIG. 7 is a schematic view illustrating an example of a method for manufacturing a pressure-sensitive adhesive sheet of the present invention. FIG. 8 is a schematic view illustrating an example of a method for manufacturing a pressure-sensitive adhesive sheet of the present invention. FIG. 9 is a schematic view illustrating an example of a method for manufacturing a pressure-sensitive adhesive sheet of the present invention. FIG. 10 is a cross-sectional view schematically illustrating an example of an optical laminate of the present invention. FIG. 11 is a cross-sectional view schematically illustrating an example of an optical laminate of the present invention.

[0012] A pressure-sensitive adhesive sheet according to a first aspect of the present invention is a pressure-sensitive adhesive sheet having a first surface and a second surface opposing each other, wherein the amount of creep determined by the following test is 10 μm or more, and the modulus of elasticity of the first surface measured using an atomic force microscope is 1.0 MPa or more. Test: The pressure-sensitive adhesive sheet is attached to a stainless steel test plate at a bonding surface measuring 10 mm long x 10 mm wide, and a load of 500 gf is applied vertically downward with the test plate fixed. The amount of creep (amount of displacement) of the pressure-sensitive adhesive sheet relative to the test plate is measured 3600 seconds after the start of load application.

[0013] In a second aspect of the present invention, for example, the pressure-sensitive adhesive sheet according to the first aspect has a first layer and a second layer located on the first layer, and the first surface coincides with the surface of the second layer.

[0014] In a third aspect of the present invention, for example, in the pressure-sensitive adhesive sheet according to the second aspect, the second layer has a thickness of 1.0 μm or less.

[0015] In a fourth aspect of the present invention, for example, in the pressure-sensitive adhesive sheet according to any one of the first to third aspects, the creep amount is 300 μm or less.

[0016] In a fifth aspect of the present invention, for example, in the pressure-sensitive adhesive sheet according to any one of the first to fourth aspects, the modulus of elasticity of the first surface is 10.0 MPa or less.

[0017] In a sixth aspect of the present invention, for example, in the pressure-sensitive adhesive sheet according to any one of the first to fifth aspects, the modulus of elasticity of the second surface measured using an atomic force microscope is less than 1.0 MPa.

[0018] In a seventh aspect of the present invention, for example, in the pressure-sensitive adhesive sheet according to any one of the first to sixth aspects, the first surface is a surface that has been subjected to a surface modification treatment.

[0019] In an eighth aspect of the present invention, for example, in the pressure-sensitive adhesive sheet according to the seventh aspect, the surface modification treatment is a corona treatment.

[0020] In a ninth aspect of the present invention, for example, the pressure-sensitive adhesive sheet according to any one of the first to eighth aspects is formed from a pressure-sensitive adhesive composition containing a group of monomers and / or a polymer of the group of monomers.

[0021] In a tenth aspect of the present invention, for example, in the pressure-sensitive adhesive sheet according to the ninth aspect, the group of monomers includes a (meth)acrylic monomer.

[0022] In an eleventh aspect of the present invention, for example, in the pressure-sensitive adhesive sheet according to the ninth or tenth aspect, the pressure-sensitive adhesive composition is photocurable.

[0023] In a twelfth aspect of the present invention, for example, in the pressure-sensitive adhesive sheet according to any one of the ninth to eleventh aspects, the content of solvent in the pressure-sensitive adhesive composition is 5 wt % or less.

[0024] In a thirteenth aspect of the present invention, for example, the pressure-sensitive adhesive sheet according to any one of the first to twelfth aspects has a thickness of 50 μm or less.

[0025] An optical laminate according to a fourteenth aspect of the present invention comprises: the pressure-sensitive adhesive sheet according to any one of the first to thirteenth aspects; and an optical film including at least one selected from the group consisting of a polarizing film and a retardation film.

[0026] In a fifteenth aspect of the present invention, for example, in the optical laminate according to the fourteenth aspect, the first surface of the pressure-sensitive adhesive sheet is in contact with the optical film.

[0027] In a sixteenth aspect of the present invention, for example, in the optical laminate according to the fourteenth or fifteenth aspect, the anchoring force between the pressure-sensitive adhesive sheet and the optical film is 10.0 N / 25 mm or more.

[0028] An image display device according to a seventeenth aspect of the present invention includes the optical laminate according to any one of the fourteenth to sixteenth aspects.

[0029] The present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be implemented in any modified form without departing from the gist of the present invention.

[0030] [Embodiment of Pressure-Sensitive Adhesive Sheet] An example of a pressure-sensitive adhesive sheet of this embodiment is shown in Fig. 1. The pressure-sensitive adhesive sheet 1 in Fig. 1 has a first surface 1a and a second surface 1b that face each other. As an example, the pressure-sensitive adhesive sheet 1 is attached to an optical film via the first surface 1a, and the pressure-sensitive adhesive sheet 1 is attached to an image display panel via the second surface 1b.

[0031] The adhesive sheet 1 has a creep amount of 10 μm or more as determined by the following test. Furthermore, the elastic modulus G1 of the first surface 1a measured using an atomic force microscope (AFM) is 1.0 MPa or more. Test: The adhesive sheet 1 is attached to a stainless steel test plate at a bonding surface measuring 10 mm long x 10 mm wide, and a load of 500 gf is applied vertically downward with the test plate fixed. The creep amount (displacement) of the adhesive sheet 1 relative to the test plate is measured 3,600 seconds after the load application begins.

[0032] According to the pressure-sensitive adhesive sheet 1 of this embodiment, peeling between components of an image display device in a high-temperature environment can be suppressed due to the creep amount and elastic modulus G1. Specifically, when the creep amount is 10 μm or more, peeling between the optical laminate and the image display panel tends to be suppressed. When the elastic modulus G1 of the first surface 1a is 1.0 MPa or more, peeling between the pressure-sensitive adhesive sheet 1 and the optical film tends to be suppressed. Since suppressing peeling between components of an image display device suppresses air intrusion and misalignment of the optical film, when the pressure-sensitive adhesive sheet 1 of this embodiment is used, problems with the image display function of the image display device tend to be less likely to occur.

[0033] Specifically, the creep amount of the pressure-sensitive adhesive sheet 1 can be evaluated by the following method (see FIGS. 2A and 2B ). First, the pressure-sensitive adhesive sheet 1 is bonded to a support film 51 so that the first surface 1a of the pressure-sensitive adhesive sheet 1 faces the support film 51, thereby producing a laminate. This laminate is cut into a 10 mm x 50 mm strip to prepare a test piece 52. The support film 51 is positioned to suppress deformation of the pressure-sensitive adhesive sheet 1 at the portion to which the load is applied during testing, thereby enabling more accurate measurement of the creep amount. The support film 51 can be, for example, a resin film such as a polyethylene terephthalate (PET) film. The support film 51 may be an optical film or a laminate including an optical film. The thickness of the support film 51 need only be such that it does not deform under the load, and is, for example, 20 to 200 μm. Next, as shown in FIGS. 2A and 2B , the test piece 52 is attached to the surface of a stainless steel test plate 53 with the pressure-sensitive adhesive sheet 1 at a joining surface measuring 10 mm long x 10 mm wide. Note that Figure 2B is the cross section B-B of Figure 2A. The test piece 52 is attached to the test plate 53 so as not to trap air bubbles between the test plate 53 and the PSA sheet 1. After attachment, the test plate 53 is placed in an autoclave at 50°C and 5 atmospheres (absolute pressure) for 15 minutes to homogenize the bond between the test plate 53 and the PSA sheet 1. Next, the test plate 53 and the test piece 52 are held vertically with the test plate 53 facing upward and left in a 25°C atmosphere for at least 5 minutes. Then, with the test plate 53 fixed, a 500g weight is fixed to the center of the lower end of the test piece 52, and a 500gf load 54 is applied vertically downward. The creep amount (displacement amount) of the PSA sheet 1 relative to the test plate 53 3600 seconds after the start of application of the load 54 is measured as the weight drop amount. A laser displacement meter can be used to measure the weight drop amount. The load 54 is applied in a 25°C atmosphere.

[0034] As described above, in this embodiment, the creep amount of the pressure-sensitive adhesive sheet 1 is 10 μm or more. The creep amount of the pressure-sensitive adhesive sheet 1 is preferably 15 μm or more, and may be 20 μm or more, 30 μm or more, 40 μm or more, 50 μm or more, 60 μm or more, 70 μm or more, 80 μm or more, 90 μm or more, 100 μm or more, 110 μm or more, 120 μm or more, or even 130 μm or more. The greater the creep amount of the pressure-sensitive adhesive sheet 1, the more likely peeling between components of the image display device, particularly between the optical laminate and the image display panel, tends to be suppressed in a high-temperature environment. However, if the creep amount of the pressure-sensitive adhesive sheet 1 is excessively large, tearing (glue tearing) tends to occur inside the pressure-sensitive adhesive sheet 1 in a high-temperature environment. According to the inventors' studies, tearing of the pressure-sensitive adhesive sheet 1 in a high-temperature environment is particularly likely to occur in a pressure-sensitive adhesive sheet 1 produced by a method of curing a pressure-sensitive adhesive composition by irradiating it with light (photocuring method). In order to prevent the adhesive sheet 1 from tearing in a high-temperature environment, the upper limit of the creep amount of the adhesive sheet 1 may be, for example, 500 μm or less, 400 μm or less, 300 μm or less, 250 μm or less, 200 μm or less, 180 μm or less, 160 μm or less, or even 150 μm or less.

[0035] Specifically, the elastic modulus G1 of the first surface 1a can be evaluated by the following method. First, the pressure-sensitive adhesive sheet 1 is cut into a size of approximately 0.8 cm length x 0.5 cm width to prepare a test piece. Next, the test piece is fixed to a sample stage using conductive double-sided tape. At this time, the test piece is positioned so that the second surface 1b of the test piece faces the sample stage and the first surface 1a is exposed to the outside. The test piece is left to stand for at least one hour to stabilize.

[0036] Next, using an AFM, the number of measurement points was 2 in an area of ​​20 μm length × 20 μm width on the first surface 1 a of the test piece. 8The elastic modulus is measured so that the modulus becomes (256). At this time, the interval between adjacent measurement points is adjusted to about 1 μm. The elastic modulus is measured, for example, over the entire area of ​​20 μm length x 20 μm width on the first surface 1a of the test piece. The elastic modulus can be determined by the JKR two-point method using the load-displacement curve obtained by force curve measurement. As the AFM, a commercially available scanning probe microscope (for example, MFP-3D Standalone manufactured by ASYLUM RESEARCH) can be used. Details of the elastic modulus measurement conditions are as follows. Measurement conditions Measurement mode: Force mode Cantilever: Olympus OMCL-AC240TS (resonance frequency: 75 kHz, spring constant: 1.7 N / m, tip shape: Sphere (hemisphere) (radius 10 nm), Poisson's ratio: 0.5) Scanning range: 20 μm vertical x 20 μm horizontal Number of data points: 16 x 16 (256) Push-in speed: 1.98 μm / s Trigger point: 0.05 V Measurement temperature: 25°C

[0037] The above measurement allows for obtaining data on the elastic modulus at multiple positions on the first surface 1a of the test piece. By mapping this data, an AFM image such as that shown in FIG. 3A can be obtained. In this AFM image, visual information in the form of a color tone is assigned to each pixel based on the numerical value of the elastic modulus. The size of one pixel in the AFM image corresponds to the size of the tip of the cantilever. The number of pixels constituting the AFM image corresponds to the number of measurement points.

[0038] Next, a histogram of the elastic modulus is created with a class width of 0.02 MPa (FIG. 3B). In this histogram, the horizontal axis represents the elastic modulus, and the vertical axis represents the frequency (number of measurement points). The elastic modulus (mode) corresponding to the maximum frequency M in the histogram is identified as the elastic modulus G1 of the first surface 1a.

[0039] In this embodiment, the number of peaks present in the histogram created by the above method is preferably one. As an example, one peak P is shown in FIG. 3B. Peak P is typically unimodal. However, the histogram may have multiple peaks or multimodal peaks.

[0040] As described above, in this embodiment, the elastic modulus G1 of the first surface 1a is 1.0 MPa or more. For example, when the first surface 1a of the pressure-sensitive adhesive sheet 1 is in contact with an optical film, a modulus G1 of 1.0 MPa or more tends to adjust the anchoring force between the pressure-sensitive adhesive sheet 1 and the optical film to a sufficiently large value. The elastic modulus G1 is preferably 1.1 MPa or more, and may be 1.2 MPa or more, 1.3 MPa or more, 1.4 MPa or more, 1.5 MPa or more, 1.6 MPa or more, 1.7 MPa or more, 1.8 MPa or more, or even 1.9 MPa or more. The upper limit of the elastic modulus G1 is not particularly limited, and may be, for example, 10.0 MPa or less, 5.0 MPa or less, 3.0 MPa or less, or even 2.0 MPa or less.

[0041] The elastic modulus G2 of the second surface 1b measured using an AFM is not particularly limited, but is preferably smaller than the elastic modulus G1. The elastic modulus G2 may be, for example, less than 1.0 MPa, 0.9 MPa or less, 0.8 MPa or less, or even 0.7 MPa or less. The lower limit of the elastic modulus G2 of the second surface 1b may be, for example, 0.1 MPa or more, 0.3 MPa or more, or even 0.5 MPa or more. However, in some cases, the elastic modulus G2 of the second surface 1b may be 1.0 MPa or more, or may be within the range described above for the elastic modulus G1. The elastic modulus G2 of the second surface 1b can be measured using the same method as the elastic modulus G1 of the first surface 1a.

[0042] The first surface 1a of the pressure-sensitive adhesive sheet 1 is, for example, a surface that has been subjected to a surface modification treatment. The first surface 1a that has been subjected to a surface modification treatment tends to have a high elastic modulus G1. On the other hand, it is preferable that the second surface 1b of the pressure-sensitive adhesive sheet 1 has not been subjected to a surface modification treatment. Examples of surface modification treatments include corona treatment, plasma treatment, excimer treatment, and flame treatment. It is preferable that the first surface 1a has been subjected to corona treatment as the surface modification treatment.

[0043] The surface modification treatment may be carried out in an inert gas atmosphere. By carrying out the surface modification treatment in a state where the oxygen concentration is reduced by an inert gas, the risk of ignition of residual monomers can be reduced. Specifically, the surface modification treatment is preferably carried out at an oxygen concentration of 8% by volume or less, more preferably 6% by volume or less, and even more preferably 3% by volume or less. If the oxygen concentration is too low, the introduction of functional groups into the surface of the pressure-sensitive adhesive sheet 1 by the surface modification treatment may be insufficient. Therefore, the oxygen concentration is preferably 0.01% by volume or more, more preferably 0.1% by volume or more, and particularly preferably 0.5% by volume or more. Specific examples of inert gases include nitrogen and argon. The surface modification treatment may be carried out under normal pressure (1 atmosphere).

[0044] The conditions for the surface modification treatment, which is a corona treatment, are expressed in terms of the discharge amount, for example, 1 W / m 2 min or more, 10 W / m 2 ・Min or more, 20W / m 2 ・Min or more, 30W / m 2 ・Min or more, 40W / m 2 ・Min or more, 50W / m 2 min or more, and even 60 W / m 2 However, when corona treatment is performed on the first surface 1a of the pressure-sensitive adhesive sheet 1, if the discharge amount is excessively large, unevenness in the elastic modulus occurs within the first surface 1a, and the elastic modulus G1 determined by the above method may not increase sufficiently. From the viewpoint of adjusting the elastic modulus G1 of the first surface 1a to an appropriate value, the discharge amount is preferably 400 W / m 2 min or less, 350 W / m 2 ・Min or less, 300W / m 2 ・Min or less, 250W / m 2 ・Min or less, 200W / m 2 ・Min or less, 150W / m 2 ・Min or less, 100W / m 2 min or less, and even 80 W / m 2 ・It may be less than min.

[0045] As shown in FIG. 1 , the pressure-sensitive adhesive sheet 1 preferably has a first layer 5 and a second layer 6 located on the first layer 5. The second layer 6 is typically in direct contact with the first layer 5. The second layer 6 may entirely or partially cover the surface of the first layer 5. As an example, the first surface 1a of the pressure-sensitive adhesive sheet 1 coincides with the surface 6a of the second layer 6, and the second surface 1b of the pressure-sensitive adhesive sheet 1 coincides with the surface 5a of the first layer 5. The second layer 6 is typically a layer that has a higher elastic modulus and a smaller thickness than the first layer 5. Note that the pressure-sensitive adhesive sheet 1 does not need to have a laminated structure of the first layer 5 and the second layer 6, and may be a single-layer film, as long as the creep amount and the elastic modulus G1 of the first surface 1a are adjusted to be within the above-mentioned ranges.

[0046] As described below, the first layer 5 and the second layer 6 can be produced, for example, by subjecting a cured sheet formed from a pressure-sensitive adhesive composition to a surface modification treatment. Specifically, the second layer 6, which has a high elastic modulus, is formed in the surface-modified portion, and the first layer 5 is formed in the remaining portion. The first layer 5 and the second layer 6 produced in this manner have the same composition, and can be said to be formed from the same pressure-sensitive adhesive composition.

[0047] The thickness of the first layer 5 is, for example, 500 μm or less, and may be 250 μm or less, 150 μm or less, 100 μm or less, 50 μm or less, 30 μm or less, 25 μm or less, or even 20 μm or less. The lower limit of the thickness of the first layer 5 is, for example, 2 μm or more, and may be 5 μm or more. The thickness of the first layer 5 can be calculated based on, for example, the thickness of the pressure-sensitive adhesive sheet 1 and the thickness of the second layer 6.

[0048] The thickness of the second layer 6 is, for example, 1.0 μm or less, and may be 0.8 μm or less, 0.5 μm or less, 0.4 μm or less, 0.3 μm or less, 0.2 μm or less, or even 0.1 μm or less. The lower limit of the thickness of the second layer 6 is not particularly limited, and is, for example, 0.001 μm or more. The thickness of the second layer 6 tends to be sufficiently smaller than that of the first layer 5.

[0049] The thickness of the second layer 6 can be measured, for example, by the following method. First, the pressure-sensitive adhesive sheet 1 is attached to a support film so that the first surface 1a of the pressure-sensitive adhesive sheet 1 faces the support film, thereby producing a laminate. An optical film or the like can be used as the support film. The produced laminate is frozen, and then cut in the thickness direction using an ultramicrotome to obtain a test piece. This test piece is a slice with a thickness of approximately 200 nm, and its main surface (the surface with the largest area) coincides with the cross section of the laminate. Next, this test piece is fixed on a silicon wafer and left to stand overnight to stabilize.

[0050] Next, using an AFM, two measurement points were measured in an area of ​​1 μm length x 1 μm width near the interface between the pressure-sensitive adhesive sheet 1 and the support film on the main surface of the test piece. 14 The modulus of elasticity is measured so that the value of the modulus of elasticity becomes (16384). At this time, the distance between adjacent measurement points is adjusted to about 8 nm. The measurement of the modulus of elasticity is performed, for example, over the entire area of ​​1 μm vertically and 1 μm horizontally on the main surface of the test piece. The modulus of elasticity can be determined by the JKR two-point method using the load-displacement curve obtained by force curve measurement. As the AFM, a commercially available scanning probe microscope (for example, MFP-3D Standalone manufactured by ASYLUM RESEARCH) can be used. Details of the conditions for measuring the modulus of elasticity are as follows. Measurement conditions Measurement mode: Force mode Cantilever: Olympus OMCL-AC240TS (resonance frequency: 75 kHz, spring constant: 1.7 N / m, tip shape: Sphere (hemisphere) (radius 10 nm), Poisson's ratio: 0.5) Scanning range: 1 μm vertical x 1 μm horizontal Number of data points: 128 x 128 (16384) Push-in speed: 1.98 μm / s Trigger point: 0.05 V Measurement temperature: 25°C

[0051] The above measurements allow for the acquisition of data on the modulus of elasticity at multiple positions on the main surface of the test piece. By mapping this data, an AFM image such as that shown in Figure 4 can be obtained. In this AFM image, visual information is assigned to each pixel in a color tone based on the numerical value of the modulus of elasticity. The size of one pixel in the AFM image corresponds to the size of the tip of the cantilever. The number of pixels constituting the AFM image corresponds to the number of measurement points.

[0052] As shown in Figure 4, the AFM image shows a region where the pressure-sensitive adhesive sheet 1 is present, in which a region with a relatively low elastic modulus (first layer 5) and a region with a relatively high elastic modulus (second layer 6) can be confirmed. The region with a relatively high elastic modulus is located near the interface between the pressure-sensitive adhesive sheet 1 and the support film. The thickness of the second layer 6 can be determined based on the obtained AFM image. Specifically, the distance between the first layer 5 and the support film in the AFM image can be measured at any number of points (e.g., five or more points), and the average of the obtained values ​​can be considered to be the thickness of the second layer 6.

[0053] The thickness of the pressure-sensitive adhesive sheet 1 is, for example, 500 μm or less, and may be 250 μm or less, 150 μm or less, 100 μm or less, 50 μm or less, 30 μm or less, 25 μm or less, or even 20 μm or less. The lower limit of the thickness of the pressure-sensitive adhesive sheet 1 is, for example, 2 μm or more, and may be 5 μm or more.

[0054] (Adhesive Composition) The adhesive sheet 1 is formed from an adhesive composition containing, for example, a group of monomers and / or a polymer of the monomers. Specifically, the adhesive sheet 1 can be produced by subjecting a cured sheet formed from the above-mentioned adhesive composition to a surface modification treatment. The adhesive composition is preferably a photocurable adhesive composition (photocurable composition) that cures when irradiated with light. However, the adhesive composition may also be a thermosetting adhesive composition that cures when heated.

[0055] Generally, PSA sheets are manufactured by, for example, the following thermosetting method. First, a PSA composition is prepared by blending a crosslinking agent or the like with a polymer produced by polymerizing a polymerizable monomer in an organic solvent. This PSA composition is applied to a substrate such as a release liner, and the organic solvent is removed by heating to form a sheet. If necessary, heat aging is performed to complete the crosslinking, thereby manufacturing a PSA sheet. This manufacturing process requires the combustion of a large amount of fuel, such as LNG, to generate the thermal energy required for the thermal removal of the solvent and for heat aging. Furthermore, releasing the thermally removed organic solvent directly into the atmosphere can have a significant adverse effect on the surrounding environment. Therefore, the organic solvent is often burned in a deodorizing furnace or the like before being released. In this case, not only is additional fuel required for combustion in the deodorizing furnace, but the organic solvent itself is also converted into CO2 by combustion and released into the atmosphere, resulting in a manufacturing process with extremely large CO2 emissions.

[0056] In recent years, climate change caused by greenhouse gases has become an urgent issue, and governments around the world have set numerical targets to reduce CO2 emissions. Therefore, it is preferable to select a manufacturing process that does not use organic solvents and has low CO2 emissions when manufacturing adhesive sheets. Methods that use light to produce adhesive sheets (photocuring methods) tend to reduce the amount of energy required to form adhesive sheets and CO2 emissions compared to thermal curing methods.

[0057] According to the studies of the present inventors, in the past, when a pressure-sensitive adhesive sheet formed from a photocurable pressure-sensitive adhesive composition was used, peeling tended to occur more easily between components of an image display device, particularly between the pressure-sensitive adhesive sheet and an optical film, compared to when a pressure-sensitive adhesive sheet formed from a thermosetting pressure-sensitive adhesive composition was used. This tendency is presumably due to the fact that when a pressure-sensitive adhesive sheet formed from a thermosetting pressure-sensitive adhesive composition is bonded to an optical film, curing of the pressure-sensitive adhesive sheet proceeds further on the surface of the optical film, whereas when a pressure-sensitive adhesive sheet formed from a photocurable pressure-sensitive adhesive composition is bonded to the optical film, curing hardly proceeds at all after bonding. In the present embodiment, by adjusting the creep amount and the elastic modulus G1 of the first surface 1a within the above ranges, peeling between components of an image display device tends to be sufficiently suppressed, even when the pressure-sensitive adhesive sheet 1 is formed from a photocurable pressure-sensitive adhesive composition.

[0058] As described above, the pressure-sensitive adhesive composition contains a group of monomers and / or a polymer of the monomers. The group of monomers includes, for example, a (meth)acrylic monomer. The content of the (meth)acrylic component, i.e., the (meth)acrylic monomer and its polymer, in the pressure-sensitive adhesive composition may be 50% by weight or more, 60% by weight or more, 70% by weight or more, or even 80% by weight or more. In this case, an acrylic pressure-sensitive adhesive sheet 1 can be formed whose main components are a (meth)acrylic polymer and its crosslinked product. However, the pressure-sensitive adhesive composition is not limited to the above examples. In this specification, (meth)acrylic means acrylic and methacrylic. (Meth)acrylate means acrylate and methacrylate.

[0059] An example of the (meth)acrylic monomer is a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms on the side chain. The number of carbon atoms in the alkyl group may be 7 or less, 6 or less, 5 or less, or even 4 or less. The alkyl group may be linear or branched. Examples of the (meth)acrylic acid alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. acrylate, n-octyl(meth)acrylate, isooctyl(meth)acrylate, n-nonyl(meth)acrylate, isononyl(meth)acrylate, n-decyl(meth)acrylate, isodecyl(meth)acrylate, n-dodecyl(meth)acrylate (lauryl(meth)acrylate), n-tridecyl(meth)acrylate, n-tetradecyl(meth)acrylate, pentadecyl(meth)acrylate, hexadecyl(meth)acrylate, heptadecyl(meth)acrylate, and octadecyl(meth)acrylate. The (meth)acrylic acid alkyl ester may be n-butyl(meth)acrylate.

[0060] The amount of the (meth)acrylic acid alkyl ester blended per 100 parts by weight of the monomer group may be, for example, 40 parts by weight or more, 50 parts by weight or more, 60 parts by weight or more, 70 parts by weight or more, 80 parts by weight or more, 85 parts by weight or more, 90 parts by weight or more, or even 95 parts by weight or more. In calculating the blending amount of a specific monomer, the weight of the polymer is converted into the weight of each monomer before polymerization.

[0061] The monomer group may include a carboxyl group-containing monomer. The carboxyl group-containing monomer may be a (meth)acrylic monomer; in other words, the (meth)acrylic monomer may include a carboxyl group-containing monomer. Examples of carboxyl group-containing monomers include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. The amount of the carboxyl group-containing monomer per 100 parts by weight of the monomer group may be, for example, 10 parts by weight or less, 9 parts by weight or less, 8 parts by weight or less, 7 parts by weight or less, 6 parts by weight or less, 5 parts by weight or less, 4.8 parts by weight or less, 4 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, or even 0.5 parts by weight or less. The lower limit of the amount may be, for example, 0.1 parts by weight or more, and in some cases, 0.5 parts by weight or more. The monomer group may not contain a carboxyl group-containing monomer.

[0062] The monomer group may contain a hydroxy group-containing monomer. The hydroxy group-containing monomer may be a (meth)acrylic monomer, in other words, the (meth)acrylic monomer may contain a hydroxy group-containing monomer. The hydroxy group-containing monomer may contribute to improving the cohesive strength of the PSA sheet. Examples of hydroxy group-containing monomers are 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)-methyl acrylate. The hydroxy group-containing monomer is preferably 2-hydroxyethyl (meth)acrylate or 4-hydroxybutyl (meth)acrylate. The amount of the hydroxy group-containing monomer blended per 100 parts by weight of the monomer group may be, for example, 20 parts by weight or less, 15 parts by weight or less, 10 parts by weight or less, 7.5 parts by weight or less, 5 parts by weight or less, 4 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, or even 0.5 parts by weight or less. The lower limit of the blended amount may be, for example, 0.01 parts by weight or more, 0.03 parts by weight or more, or even 0.05 parts by weight or more. The monomer group may not contain a hydroxy group-containing monomer.

[0063] The monomer group may include an ether group-containing monomer. The ether group-containing monomer may be a (meth)acrylic monomer, in other words, the (meth)acrylic monomer may include an ether group-containing monomer. The ether group-containing monomer can contribute to improving the anchoring strength between the pressure-sensitive adhesive sheet 1 and the optical film.

[0064] The ether group-containing monomer is preferably an alkoxy group-containing monomer. Examples of the alkoxy group-containing monomer include alkylene oxide adducts represented by the following chemical formula (A): 1 is a hydrogen atom or a methyl group. 2 is an alkyl group. The alkyl group may be linear or branched. 2is preferably a linear alkyl group. 2 Examples of n are methyl and ethyl groups. In formula (A), n is an integer of 1 to 30, preferably an integer of 1 to 12, and may be an integer of 1 to 5.

[0065] Examples of the alkylene oxide adduct represented by formula (A) are 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-(2-ethoxyethoxy)ethyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, and methoxypolyethylene glycol (meth)acrylate, and preferably 2-methoxyethyl acrylate (MEA).

[0066] The ether group-containing monomer is not limited to the alkylene oxide adduct. The ether group-containing monomer may have a ring structure, and the ring structure may have an ether group. Examples of the ring structure having an ether group include a tetrahydrofuran ring and a dioxane ring. Examples of the ether group-containing monomer having a ring structure include cyclic trimethylolpropane formal (meth)acrylate and tetrahydrofurfuryl (meth)acrylate.

[0067] The amount of the ether group-containing monomer blended per 100 parts by weight of the monomer group is, for example, 1 part by weight or more, and may be 5 parts by weight or more, 10 parts by weight or more, 20 parts by weight or more, 25 parts by weight or more, 30 parts by weight or more, 40 parts by weight or more, 50 parts by weight or more, 60 parts by weight or more, 70 parts by weight or more, 80 parts by weight or more, or even 90 parts by weight or more. The upper limit of the blended amount is, for example, 99 parts by weight or less, and in some cases may be 50 parts by weight or less. The monomer group may not contain an ether group-containing monomer.

[0068] The monomer group may include a nitrogen atom-containing monomer. A nitrogen atom-containing monomer refers to a monomer having at least one nitrogen atom in the molecule (per molecule). In this specification, a monomer having a hydroxy group and a nitrogen atom in the molecule is classified as a nitrogen atom-containing monomer. A monomer having a carboxyl group and a nitrogen atom in the molecule is classified as a carboxyl group-containing monomer.

[0069] Preferred nitrogen atom-containing monomers are N-vinyl cyclic amides, (meth)acrylamides, etc. The nitrogen atom-containing monomers may be used alone or in combination of two or more.

[0070] The N-vinyl cyclic amide is preferably one represented by the following formula (B):

[0071] In formula (B), R 1 is a divalent organic group, preferably a divalent saturated or unsaturated hydrocarbon group, and more preferably a divalent saturated hydrocarbon group (e.g., an alkylene group having 3 to 5 carbon atoms). 1 are directly bonded via a single bond to form a ring structure.

[0072] The N-vinyl cyclic amide represented by formula (B) is preferably N-vinyl-2-pyrrolidone (NVP), N-vinyl-2-piperidone, N-vinyl-2-caprolactam, N-vinyl-3-morpholinone, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, or the like, more preferably N-vinyl-2-pyrrolidone or N-vinyl-2-caprolactam, and even more preferably N-vinyl-2-pyrrolidone.

[0073] Examples of (meth)acrylamides include (meth)acrylamide, N-alkyl(meth)acrylamide, N,N-dialkyl(meth)acrylamide, etc. Examples of N-alkyl(meth)acrylamides include N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-n-butyl(meth)acrylamide, N-octylacrylamide, etc. N-alkyl(meth)acrylamides also include (meth)acrylamides having an amino group, such as dimethylaminoethyl(meth)acrylamide, diethylaminoethyl(meth)acrylamide, and dimethylaminopropyl(meth)acrylamide.

[0074] Examples of N,N-dialkyl(meth)acrylamides include N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, N,N-di(n-butyl)(meth)acrylamide, and N,N-di(t-butyl)(meth)acrylamide.

[0075] (Meth)acrylamides also include, for example, various N-hydroxyalkyl(meth)acrylamides, such as N-methylol(meth)acrylamide, N-(2-hydroxyethyl)(meth)acrylamide, N-(2-hydroxypropyl)(meth)acrylamide, N-(1-hydroxypropyl)(meth)acrylamide, N-(3-hydroxypropyl)(meth)acrylamide, N-(2-hydroxybutyl)(meth)acrylamide, N-(3-hydroxybutyl)(meth)acrylamide, N-(4-hydroxybutyl)(meth)acrylamide, and N-methyl-N-2-hydroxyethyl(meth)acrylamide.

[0076] (Meth)acrylamides also include, for example, various N-alkoxyalkyl(meth)acrylamides, such as N-methoxymethyl(meth)acrylamide and N-butoxymethyl(meth)acrylamide.

[0077] Examples of nitrogen atom-containing monomers other than N-vinyl cyclic amides and (meth)acrylamides include amino group-containing monomers such as aminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, and t-butylaminoethyl (meth)acrylate; cyano group-containing monomers such as acrylonitrile and methacrylonitrile; (meth)acryloylmorpholine, N-vinylpiperazine, N-vinylpyrrole, N-vinylimidazole, N-vinylpyrazine, N-vinylmorpholine, N-vinylpyrazole, vinylpyridine, vinylpyrimidine, vinyloxazole, vinylisoxazole, vinylthiazole, vinylisothiazole, vinylpyridazine, (meth)acryloylpyrrolidone, (meth)acryloylpyrrolidine, (meth)acryloylpiperidine, N-methyl Examples of the monomer include heterocycle-containing monomers such as vinylpyrrolidone; maleimide-based monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; itaconimide-based monomers such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-laurylitaconimide, and N-cyclohexylitaconimide; and imide group-containing monomers such as succinimide-based monomers such as N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, and N-(meth)acryloyl-8-oxyoctamethylenesuccinimide; and isocyanate group-containing monomers such as 2-(meth)acryloyloxyethylisocyanate.

[0078] The content of the nitrogen atom-containing monomer in the monomer group is, for example, 40% by weight or less, and may be 35% by weight or less, 30% by weight or less, 25% by weight or less, 20% by weight or less, 15% by weight or less, 10% by weight or less, or even 8% by weight or less. The lower limit of the content may be, for example, 1% by weight or more, 3% by weight or more, or even 5% by weight or more. The monomer group may not contain a nitrogen atom-containing monomer.

[0079] The monomer group preferably includes a carboxyl group-containing monomer and / or a nitrogen atom-containing monomer, and more preferably includes both a carboxyl group-containing monomer and a nitrogen atom-containing monomer. In particular, when a nitrogen atom-containing monomer, especially both a nitrogen atom-containing monomer and a carboxyl group-containing monomer, is present in the photopolymerization system, the molecular weight of the polymer tends to increase. This tendency may be due to the fact that the increased viscosity of the polymerization system caused by the formation of hydrogen bonds inhibits the termination reaction between the growing ends of the polymer, making it easier for the monomer to remain at the end of the growing chain. The molecular weight of the polymer may affect the creep amount of the pressure-sensitive adhesive sheet 1.

[0080] In the pressure-sensitive adhesive composition, each of the above-mentioned monomers may be contained as a polymer. When the pressure-sensitive adhesive composition is photocurable, the polymer is preferably a partial polymer. The partial polymer may be either a homopolymer or a copolymer. The partial polymer can contribute to the stable formation of a coating layer, which will be described later, by appropriately increasing the viscosity of the pressure-sensitive adhesive composition.

[0081] The pressure-sensitive adhesive composition may contain a photopolymerization initiator. An example of the photopolymerization initiator is a photoradical generator that generates radicals upon irradiation with light. The photopolymerization initiator may have an absorption coefficient with respect to light having a wavelength of 340 nm of, for example, 0.1 L / (g cm) or more, 0.5 L / (g cm) or more, 1.0 L / (g cm) or more, 3.0 L / (g cm) or more, or even 5.0 L / (g cm) or more. The upper limit of this absorption coefficient is not particularly limited, and may be, for example, 50 L / (g cm) or less. The absorption coefficient of the photopolymerization initiator is a value calculated from the absorbance of a 0.01 mg / mL methanol solution measured with a visible-ultraviolet spectrophotometer using a quartz cell with an optical path length of 1 cm.

[0082] Examples of the photopolymerization initiator include benzoin ethers such as benzoin methyl ether, benzoin isopropyl ether, and benzil dimethyl ketal; substituted benzoin ethers such as anisole methyl ether; substituted acetophenones such as 2,2-diethoxyacetophenone and 2,2-dimethoxy-2-phenylacetophenone; α-hydroxyalkylphenones such as 1-hydroxycyclohexyl-phenyl ketone, 2-hydroxy-2-methylpropiophenone, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, and 2,2'-dihydroxy-2,2'-dimethyl-1,1'-[methylenebis(4,1-phenylene)]bis(propan-1-one); and substituted alpha alkyl phenones such as 2-methyl-2-hydroxypropiophenone. aromatic sulfonyl chlorides such as 2-naphthalenesulfonyl chloride; photoactive oximes such as 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime; benzophenone-based compounds such as benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, acrylated benzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, and 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone; thioxanthone-based compounds such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and 2,4-diethylthioxanthone;2,4,6-trichloro-s-triazine, 2-phenyl-4,6-bis(trichloromethyl)-s-triazine, 2-(p-methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine, 2-(p-tolyl)-4,6-bis(trichloromethyl)-s-triazine, 2-piperonyl-4,6-bis(trichloromethyl)-s-triazine, 2,4-bis(trichloromethyl)-6-styryl-s-triazine, 2-(naphth-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2-(4-methoxy-naphth-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2,4-trichloromethyl-(piperonyl)-6-triazine, 2,4-trichloromethyl- Examples of suitable adhesive compositions include triazine-based compounds such as (4'-methoxystyryl)-6-triazine; oxime ester-based compounds such as 1,2-octanedione, 1-[4-(phenylthio)-, 2-(O-benzoyloxime)], and O-(acetyl)-N-(1-phenyl-2-oxo-2-(4'-methoxy-naphthyl)ethylidene)hydroxylamine; phosphine-based compounds such as bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 2,4,6-trimethylbenzoyldiphenylphosphine oxide; quinone-based compounds such as 9,10-phenanthrenequinone, camphorquinone, and ethylanthraquinone; borate-based compounds; carbazole-based compounds; imidazole-based compounds; and titanocene-based compounds. The adhesive composition may contain one or more photopolymerization initiators. Alpha-hydroxyalkylphenones tend to have high absorption of light with a wavelength of 340±10 nm.

[0083] Another example of the photopolymerization initiator is a compound having a chemical structure shown in the following formula (1) (hereinafter referred to as chemical structure X) in the molecule.

[0084] R in the formula (1) 1 and R 2 are each independently a C1 to C8 alkyl group; —OH, a C1 to C4 alkoxy group, —CN, —COOR 51 , -OOCR 52 , or -NR 53 R 54a C1-C4 alkyl group in which a hydrogen atom is substituted by -; a C3-C6 alkenyl group; or -CH2-C6H4-R 55 It is. 1 and R 2 may be bonded to each other to form a C2 to C9 alkylene group, a C3 to C6 oxyalkylene group, or an azaalkylene group. 51 is a C1 to C8 alkyl group. 52 is a C1 to C4 alkyl group. 53 and R 54 are each independently a hydrogen atom, a C1 to C12 alkyl group; —OH, a C1 to C4 alkoxy group, —CN, or —COOR 59 a C2-C4 alkyl group in which a hydrogen atom is substituted with at least one group selected from the group consisting of: a C3-C5 alkenyl group; or a cyclohexyl group. 53 and R 54 are bonded to each other to form —O— or —N(R 60 )-Optionally, it may be a C3 to C9 alkylene group. 55 is a C1 to C4 alkyl group. 59 is a C1 to C4 alkyl group. 60 represents a hydrogen atom, a C1-C4 alkyl group, an allyl group, a C1-C4 hydroxyalkyl group, -CH2CH2-COOR 61 Or -CH2CH2CN. 61 is a C1 to C4 alkyl group.

[0085] X is -OR 56 , or -NR 57 R 58 It is. 56 is a hydrogen atom, -SiR 62 3. A C1 to C8 alkyl group or a C3 to C6 alkenyl group. 57 and R 58 represents a C1 to C12 alkyl group; —OH, a C1 to C4 alkoxy group, —CN, and —COOR 63a C2-C4 alkyl group in which a hydrogen atom is substituted with at least one group selected from the group consisting of: a C3-C5 alkenyl group; or a cyclohexyl group. 57 and R 58 are bonded to each other to form —O— or —N(R 64 )-Optionally, it may be a C3 to C9 alkylene group. 62 is a C1 to C6 alkyl group. 63 is a C1 to C4 alkyl group. 64 represents a hydrogen atom, a C1-C4 alkyl group, an allyl group, a C1-C4 hydroxyalkyl group, -CH2CH2-COOR 65 Or -CH2CH2CN. 65 is a C1 to C4 alkyl group.

[0086] The chemical structure X can be bonded to a hydrogen atom or a structure substituted with a hydrogen atom through the carbon atom indicated by * in formula (1).

[0087] The alkyl group, alkoxy group, alkenyl group, alkylene group, oxyalkylene group, azaalkylene group, and hydroxyalkyl group described in the explanation of formula (1) may be unbranched or branched. Furthermore, the expression "Cn1 to Cn2" (n1 and n2 are natural numbers) in this specification, including the explanation of formula (1), means that the number of carbon atoms is in the range of n1 to n2.

[0088] R 1 and R 2 may be, independently of each other, a C1 to C8 alkyl group, a C3 to C6 alkenyl group, or a C1 to C8 alkyl group. 1 and R 2 may be, independently of each other, a C1 to C4 alkyl group, a C1 to C3 alkyl group, or a C1 to C2 alkyl group. 1 and R 2 may be a methyl group.

[0089] R 1 and R 2 may be the same.

[0090] X is -OR 56 It may be R 56 may be a hydrogen atom or a C1 to C8 alkyl group, or may be a hydrogen atom. In other words, X may be —OH.

[0091] R 1 , R 2 and X may take any combination of the above preferred examples.

[0092] The chemical structure X may be a structure shown in the following formula (2): In the chemical structure X of formula (2), when a substitution structure of a hydrogen atom is bonded to the carbon atom indicated by *, the substitution structure and —COCR in formula (2) 1 XR 2 The group is in a para-position relationship with respect to the benzene ring of the chemical structure X.

[0093] The photopolymerization initiator may be a compound having two or more chemical structures X in one molecule.

[0094] The photopolymerization initiator may be a compound represented by the following formula (3). The compound of formula (3) has two chemical structures X in one molecule. The two chemical structures X are located at both ends of the photopolymerization initiator molecule. More specifically, the two chemical structures X are bonded to each other via -A- at the carbon atom of the phenylene group represented by * above.

[0095] R in formula (3) 1 ' and R 2 ' are mutually exclusive and R 1 and R 2 Independently of 1 and R 2 R 1 ' and / or R 2 ' is R 1 and / or R 2 may be the same as R 1 , R 2 , R 1 ' and R 2 ' may all be the same.

[0096] X' in formula (3) is a group that can be taken as X, independently of X in formula (1). X' and X may be the same.

[0097] A is -O-, -CYR 3 - or -C(CH3)R 4 is.

[0098] Y is a hydrogen atom, —Cl, —Br, or —O—R 71 , -NR 72 R 73 , or -S-R 74 It is. 3 represents a hydrogen atom, a C1-C8 alkyl group, a C3-C6 alkenyl group, a benzyl group, -CH2-C6H4-R 75 or a phenyl group. 4 is a C1-C6 alkyl or alkylene group, and this alkylene group is bonded to a carbon atom of the phenylene group of the compound of formula (3).

[0099] R 71 is a hydrogen atom, -Si(R 76 ) 3, C1 to C12 alkyl group, C2 to C18 acyl group, —CO—NH—R 77 , a C2 to C20 hydroxyalkyl group, a C2 to C20 methoxyalkyl group, 3-R 78 -2-hydroxypropyl group, 3-[1,3,3,3-tetramethyl-1-[(trimethylsilyl)oxy]disiloxanyl]propyl group, 2,3-dihydroxypropyl group, or a C2 to C21 hydroxyalkyl group or a C3 to C25 alkyl group in which the carbon chain is interrupted by 1 to 9 oxygen atoms. 72 and R 73 are each independently a C1 to C12 alkyl group; —OH, a C1 to C4 alkoxy group, —CN, and —COOR 79 a C2-C4 alkyl group in which a hydrogen atom is substituted with at least one group selected from the group consisting of: a C3-C5 alkenyl group; a cyclohexyl group; or a C7-C9 phenylalkyl group. 72 and R 73 are bonded to each other to form —O— or —N(R 80)-Optionally, it may be a C3 to C9 alkylene group. 74 represents a C1 to C18 alkyl group, a hydroxyethyl group, a 2,3-dihydroxypropyl group, a cyclohexyl group, a benzyl group, a phenyl group, a C1 to C12 alkylphenyl group, -CH2-COOR 81 -CH2CH2-COOR 82 , or —CH(CH3)—COOR 83 It is. 75 is a C1 to C4 alkyl group. 76 is a C1 to C6 alkyl group. 77 is a C1 to C12 alkyl group. 78 is a C1 to C18 alkoxy group. 79 is a C1 to C4 alkyl group. 80 represents a hydrogen atom, a C1-C4 alkyl group, an allyl group, a benzyl group, a C1-C4 hydroxyalkyl group, -CH2CH2-COOR 84 , or —CH2CH2CN. 81 , R 82 and R 83 are each independently a C1 to C18 alkyl group. 84 is a C1 to C4 alkyl group.

[0100] The alkyl group, alkenyl group, acyl group, hydroxyalkyl group, methoxyalkyl group, alkoxy group, alkyl moiety in a phenylalkyl group, and alkylene group described in the explanation of formula (3) may all be unbranched or branched.

[0101] R in formula (3) 1 , R 2 , R 1 ' and R 2 Preferred examples of R ′ are those described above in the explanation of formula (1). 1 and R 2 The preferred examples of X′ in formula (3) are the same as the preferred examples of X described above in the explanation of formula (1). A is —CYR 3 -. Y may be a hydrogen atom. R 3may be a hydrogen atom. 3 - and Y and R 3 and may both be hydrogen atoms. In other words, A may be —CH—.

[0102] R in formula (3) 1 , R 2 , R 1 ', R 2 ', X, X', and A may take any combination of the preferred examples above.

[0103] The photopolymerization initiator may be a compound represented by the following formula (4): The compound of formula (4) is a type of compound of formula (3).

[0104] Specific examples of photopolymerization initiators are shown in the following formulas (5) to (9). The photopolymerization initiator may be a compound represented by at least one formula selected from the group consisting of formulas (5) to (9), a compound represented by at least one formula selected from the group consisting of formulas (5) to (8), a compound represented by at least one formula selected from the group consisting of formulas (5) to (7), or a compound represented by formula (5). The compound of formula (8) is derived from a vinyl compound having chemical structure X in its side chain. More specifically, it is an oligomer of the vinyl compound.

[0105]

[0106]

[0107]

[0108]

[0109]

[0110] The photopolymerization initiators represented by formulas (5) to (9) are commercially available as Omnirad 127, Esacure KIP 160, Esacure one, Esacure KIP 150, and Omnirad 1173 (all manufactured by IGM Resins). The photopolymerization initiator may be at least one selected from these groups.

[0111] Specific examples of the photopolymerization initiator include 1-hydroxycyclohexyl-phenyl ketone, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)2-methylpropan-1-one, and 2,2-dimethoxy-2-phenylacetophenone. Each of the above photopolymerization initiators is commercially available as Omnirad 184, Omnirad 819, Omnirad 127, and Omnirad 651, respectively (all manufactured by IGM Resin).

[0112] The amount of the photopolymerization initiator in the pressure-sensitive adhesive composition is, for example, 20 parts by weight or less, and may be 10 parts by weight or less, 5.0 parts by weight or less, 3.0 parts by weight or less, 1.0 parts by weight or less, 0.5 parts by weight or less, 0.3 parts by weight or less, 0.25 parts by weight or less, 0.2 parts by weight or less, 0.15 parts by weight or less, 0.1 parts by weight or less, or even 0.05 parts by weight or less, relative to 100 parts by weight of the total of the monomer group and polymers thereof. The lower limit of the amount is, for example, 0.01 parts by weight or more, and may be 0.03 parts by weight or more, relative to 100 parts by weight of the total of the monomer group and polymers thereof.

[0113] The pressure-sensitive adhesive composition may contain a crosslinking agent. An example of the crosslinking agent is a polyfunctional monomer having two or more polymerizable functional groups in one molecule. The polyfunctional monomer may be a (meth)acrylic monomer. Examples of the polyfunctional monomer are a monomer having two or more C=C bonds in one molecule, and a monomer having one or more C=C bonds and one or more polymerizable functional groups such as epoxy groups, aziridine groups, oxazoline groups, hydrazine groups, methylol groups, etc. in one molecule. The polyfunctional monomer is preferably a monomer having two or more C=C bonds in one molecule.

[0114] Examples of the polyfunctional monomer include (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol diacrylate (N Polyfunctional acrylates (e.g., ester compounds of polyhydric alcohols and (meth)acrylic acid) such as 1,12-dodecanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and tetramethylolmethane tri(meth)acrylate; allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyl di(meth)acrylate, and hexyl di(meth)acrylate. The polyfunctional monomer is preferably a polyfunctional acrylate, and more preferably 1,9-nonanediol diacrylate, trimethylolpropane tri(meth)acrylate, hexanediol di(meth)acrylate, or dipentaerythritol hexa(meth)acrylate.

[0115] The crosslinking agent may contain a crosslinking agent other than the above-mentioned polyfunctional monomer. Examples of the other crosslinking agent include an isocyanate-based crosslinking agent. The pressure-sensitive adhesive composition may contain an isocyanate-based crosslinking agent as the crosslinking agent, or may contain both the above-mentioned polyfunctional monomer and an isocyanate-based crosslinking agent. The isocyanate-based crosslinking agent can contribute to improving the anchoring strength between the pressure-sensitive adhesive sheet 1 and the optical film.

[0116] As the isocyanate-based crosslinking agent, a compound having at least two isocyanate groups (isocyanate compound) can be used. The number of isocyanate groups contained in the isocyanate compound is preferably 3 or more. The upper limit of the number of isocyanate groups is not particularly limited, and is, for example, 5. Examples of the isocyanate compound include aromatic isocyanate compounds, alicyclic isocyanate compounds, and aliphatic isocyanate compounds.

[0117] Examples of aromatic isocyanate compounds include phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, and xylylene diisocyanate.

[0118] Examples of alicyclic isocyanate compounds include 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated tetramethylxylylene diisocyanate.

[0119] Examples of the aliphatic isocyanate compound include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), pentamethylene diisocyanate (PDI), 1,2-propylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.

[0120] Examples of the isocyanate-based crosslinking agent include polymers (dimers, trimers, pentamers, etc.) of the above-mentioned isocyanate compounds, adducts obtained by adding them to polyhydric alcohols such as trimethylolpropane, urea-modified products, biuret-modified products, allophanate-modified products, isocyanurate-modified products, carbodiimide-modified products, and urethane prepolymers obtained by adding them to polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, polyisoprene polyols, etc.

[0121] The isocyanate-based crosslinking agent preferably includes an aliphatic isocyanate compound and / or a derivative of an aliphatic isocyanate compound. It is particularly preferable that the isocyanate-based crosslinking agent is at least one selected from the group consisting of pentamethylene diisocyanate (PDI)-based crosslinking agents (PDI and its derivatives) and hexamethylene diisocyanate (HDI)-based crosslinking agents (HDI and its derivatives). Specific examples of PDI-based crosslinking agents include isocyanurate-modified PDI. Specific examples of HDI-based crosslinking agents include isocyanurate-modified HDI and biuret-modified HDI.

[0122] The amount of crosslinking agent in the pressure-sensitive adhesive composition varies depending on the molecular weight, number of functional groups, etc., but may be, for example, 5 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, or even 0.5 parts by weight or less, relative to 100 parts by weight of the total of the monomer group and its polymer. The lower the amount of crosslinking agent in the pressure-sensitive adhesive composition, the greater the amount of creep of the pressure-sensitive adhesive sheet 1 tends to be. The lower limit of the amount may be, for example, 0.01 parts by weight or more, 0.05 parts by weight or more, or even 0.1 parts by weight or more.

[0123] When the pressure-sensitive adhesive composition contains an isocyanate-based crosslinking agent, the amount of the isocyanate-based crosslinking agent may be, for example, 0.02 parts by weight or more, 0.05 parts by weight or more, 0.1 parts by weight or more, 0.5 parts by weight or more, or even 1 part by weight or more, relative to 100 parts by weight of the total of the monomer group and its polymer. When the pressure-sensitive adhesive composition contains an isocyanate-based crosslinking agent, adjusting the amount of the hydroxy group-containing monomer in the pressure-sensitive adhesive composition to a small value tends to further improve the anchoring strength between the pressure-sensitive adhesive sheet 1 and the optical film.

[0124] When an isocyanate-based crosslinking agent is added, the pressure-sensitive adhesive sheet may harden, especially in a high-temperature environment. In such cases, the stress relaxation property of the pressure-sensitive adhesive sheet is impaired, so that the expansion and contraction stress of the optical film is easily transmitted to the interface between the pressure-sensitive adhesive sheet and the adherend, which tends to cause peeling. When the anchoring force between the pressure-sensitive adhesive sheet and the optical film can be ensured by means other than the addition of an isocyanate-based crosslinking agent, it is desirable that the pressure-sensitive adhesive composition does not contain an isocyanate-based crosslinking agent.

[0125] The pressure-sensitive adhesive composition may further contain a rework improver, which is a component that segregates on the surface of an adherend when the pressure-sensitive adhesive sheet 1 is attached to an adherend such as alkali-free glass or a transparent conductive layer, thereby reducing the adhesive strength (e.g., adhesive strength P0 described below) between the pressure-sensitive adhesive sheet 1 and the adherend.

[0126] The rework improver may be, for example, a silane coupling agent having an alkoxysilyl group, and preferably further has a polar group in addition to the alkoxysilyl group. Specific examples of the alkoxy group contained in the alkoxysilyl group in the rework improver include a methoxy group and an ethoxy group. Examples of the polar group include a carboxyl group, an acid anhydride group, and an epoxy group. The carboxyl group may be a group generated by hydrolysis of an acid anhydride group. Examples of the acid anhydride group include carboxylic anhydride groups such as succinic anhydride, phthalic anhydride, and maleic anhydride. The rework improver may have an ether group other than an epoxy group, or may have a polyether skeleton.

[0127] The rework improver preferably has at least one selected from the group consisting of an acid anhydride group and an epoxy group. When a rework improver having an acid anhydride group or an epoxy group is used, the adhesive strength between the adhesive sheet 1 and the glass (adhesive strength P1, described below) tends to be improved by applying a heat treatment after the adhesive sheet 1 is attached to alkali-free glass.

[0128] Examples of the rework improver include an alkoxysilane compound having a polar group, an organopolysiloxane compound having a polar group and an alkoxysilyl group, and a polyether compound having an alkoxysilyl group.

[0129] Examples of alkoxysilane compounds having a polar group include 2-trimethoxysilylethylsuccinic anhydride, 3-trimethoxysilylpropylsuccinic anhydride (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "X-12-967C"), 3-triethoxysilylpropylsuccinic anhydride, 3-methyldiethoxysilylpropylsuccinic anhydride, and 1-carboxy-3-triethoxysilylpropylsuccinic anhydride.

[0130] Examples of organopolysiloxane compounds having a polar group and an alkoxysilyl group include an acid anhydride group-containing oligomeric silane coupling agent (trade name "X-24-9591F") and an epoxy group-containing oligomeric silane coupling agent (trade names "X-41-1053", "X-41-1059A", "X-41-1056", "X-40-2651", etc.), all of which are manufactured by Shin-Etsu Chemical Co., Ltd.

[0131] Examples of polyether compounds having an alkoxysilyl group include MS Polymer S203, S303, S810, SILYL EST250, EST280, SAT10, SAT200, SAT220, SAT350, and SAT400 manufactured by Kaneka Corporation, and EXCESTAR S2410, S2420, and S3430 manufactured by Asahi Glass Co., Ltd.

[0132] The amount of the rework improver in the pressure-sensitive adhesive composition is, for example, 0.01 parts by weight or more, 0.05 parts by weight or more, 0.1 parts by weight or more, 0.2 parts by weight or more, 0.5 parts by weight or more, or even 0.6 parts by weight or more, relative to 100 parts by weight of the total of the monomer group and its polymer. The upper limit of the amount is, for example, 10 parts by weight or less, 5 parts by weight or less, or even 1 part by weight or less. The pressure-sensitive adhesive composition does not need to contain a rework improver.

[0133] The PSA composition may contain additives other than those described above. Examples of the additives include chain transfer agents, silane coupling agents other than rework improvers, viscosity modifiers, tackifiers, plasticizers, softeners, antioxidants, fillers, colorants, antioxidants, surfactants, antistatic agents, and UV absorbers.

[0134] The solvent content in the PSA composition is, for example, 5 wt% or less, and may be 4 wt% or less, 3 wt% or less, 2 wt% or less, 1 wt% or less, or even 0.5 wt% or less. The PSA composition may be substantially free of solvent. "Substantially free of solvent" means that solvents derived from additives and the like are allowed at a content of, for example, 0.1 wt% or less, preferably 0.05 wt% or less, and more preferably 0.01 wt% or less.

[0135] The viscosity of the pressure-sensitive adhesive composition is preferably 5 to 150 poise. A pressure-sensitive adhesive composition having a viscosity in the above range is particularly suitable for forming a coating layer, which will be described later.

[0136] (Physical Properties of Pressure-Sensitive Adhesive Sheet) The polymerization rate of the monomer group in the pressure-sensitive adhesive sheet 1 is preferably 90% or more, and may be 95% or more, 98% or more, or even 99% or more.

[0137] The gel fraction of the pressure-sensitive adhesive sheet 1 is, for example, 50% or more, and may be 75% or more, 80% or more, or even 85% or more.

[0138] (Method for Producing Pressure-Sensitive Adhesive Sheet) The method for producing the pressure-sensitive adhesive sheet 1 is not particularly limited. As an example, when the pressure-sensitive adhesive composition is photocurable, the pressure-sensitive adhesive sheet 1 can be produced by the following method. First, as shown in FIGS. 5A and 5B , a first laminate 15 is produced, which includes, in this order, a base sheet 21, a coating layer 22 containing a pressure-sensitive adhesive composition, and a release liner 23. A cured sheet 20 is formed from the coating layer 22 by irradiating the first laminate 15 with light 14 ( FIG. 5C ). The release liner 23 is peeled from the cured sheet 20, and a surface modification treatment is performed on the exposed surface of the cured sheet 20. The surface modification treatment is performed, for example, by irradiating the exposed surface of the cured sheet 20 with active energy rays 13 ( FIG. 5D ). A pressure-sensitive adhesive sheet 1 is formed from the cured sheet 20 by the surface modification treatment ( FIG. 5E ). In particular, a second layer 6 with a high elastic modulus is formed in the surface-modified portion, and a first layer 5 is formed in the remaining portion.

[0139] Irradiation of light 14 onto first laminate 15 is typically carried out from the side of base sheet 21 ( FIG. 5A ). At this time, light 14 passes through base sheet 21 to reach coating layer 22 and cure the coating layer 22. However, irradiation with light 14 may also be carried out from the side of release liner 23, or from both the sides of release liner 23 and base sheet 21 ( FIG. 5B ). Cured sheet 20 formed from coating layer 22 is sandwiched between base sheet 21 and release liner 23 until release liner 23 is peeled off, and constitutes part of second laminate 16.

[0140] The light 14 is, for example, visible light or ultraviolet light having a wavelength shorter than 450 nm. The light 14 may include light having a wavelength in the same region as the absorption wavelength of the photopolymerization initiator contained in the pressure-sensitive adhesive composition. Light having a wavelength of 300 nm or less may be irradiated by filtering out short-wavelength light using a filter or the like. Filtering out short-wavelength light is suitable for suppressing deterioration of the base sheet 21 and / or the release liner 23 due to the light 14. The light source of the light 14 is, for example, a light irradiation device equipped with an ultraviolet irradiation lamp. Examples of ultraviolet irradiation lamps include light-emitting diodes (LEDs), low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, microwave-excited mercury lamps, black light lamps, chemical lamps, germicidal lamps, low-pressure discharge mercury lamps, and excimer lasers. Two or more ultraviolet irradiation lamps may be combined. LEDs can narrow the wavelength band of the irradiated ultraviolet light compared to other light sources.

[0141] The light source of the light 14 may be an LED that emits light with a peak wavelength of 300 to 450 nm, or an LED that emits light with a peak wavelength of 340±10 nm (hereinafter referred to as LED 340). According to the inventors' studies, the use of LED 340 may contribute to at least one of improving the polymerization rate of the monomer group in the pressure-sensitive adhesive sheet 1 (specifically, the curable sheet 20), improving the molecular weight of the polymer, and reducing the amount of residual photopolymerization initiator, compared to using a black light source, for example. Furthermore, LED 340 tends to suppress heat generation compared to using an LED that emits light with a peak wavelength of approximately 365 nm. The suppression of heat generation can contribute to temperature control of the coating layer 22. The peak wavelength refers to the wavelength at which the intensity reaches a maximum value in a spectrum showing the relationship between light wavelength and intensity.

[0142] The illuminance of the light 14 irradiated onto the first laminate 15 (specifically, the coating layer 22) is, for example, 2.0 to 30 mW / cm 2 The illuminance is 2.5 mW / cm 2 Above, 3.0mW / cm 2 Above, 3.5mW / cm 2 Above, 4.0mW / cm 2Above, 5.0mW / cm 2 Above, 6.0mW / cm 2 Above, 7.0mW / cm 2 Above, 8.0mW / cm 2 Above, 9.0mW / cm 2 or more, and even 10 mW / cm 2 The upper limit of the illuminance may be, for example, 25 mW / cm 2 less than 20 mW / cm 2 Below 15mW / cm 2 It may be the following:

[0143] The time for which the first laminate 15 (specifically, the coating layer 22) is irradiated with the light 14 is, for example, 10 to 1,000 seconds, and may be 60 seconds or more, 100 seconds or more, 150 seconds or more, 200 seconds or more, 250 seconds or more, or even 300 seconds or more. The upper limit of the time is, for example, 800 seconds or less, and may be 600 seconds or less, 500 seconds or less, 400 seconds or less, 350 seconds or less, 300 seconds or less, or even 250 seconds or less. The irradiation with the light 14 may be continuous or intermittent.

[0144] The integrated amount of light 14 on the first laminate 15 (specifically, the coating layer 22) is, for example, 25 mJ / cm 2 or more, and 100 mJ / cm 2 Above, 250mJ / cm 2 Above, 500mJ / cm 2 Above, 750mJ / cm 2 Above, 850mJ / cm 2 Above, 1000mJ / cm 2 Above, 1250mJ / cm 2 or more, and even 1500 mJ / cm 2 The upper limit of the integrated light amount is not particularly limited, and may be, for example, 5000 mJ / cm 2 or less, and 2 Below, 3000mJ / cm 2 Below, 2500mJ / cm 2 Below, 2000mJ / cm 2 Below, 1750 mJ / cm 2 It may be the following:

[0145] An example of the substrate of the release liner 23 (hereinafter referred to as "liner substrate") is a resin film. Examples of resins that can be contained in the liner substrate include polyesters such as polyethylene terephthalate and polyethylene naphthalate, acetate resins, polyethersulfone, polycarbonate, polyamide, polyimide, polyolefin, (meth)acrylic resins, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl alcohol, polyarylate, and polyphenylene sulfide. The resin is preferably a polyester such as polyethylene terephthalate.

[0146] The release liner 23 may have light 14 transparency, or may have light 14 transparency of the same order as that of the base sheet 21 .

[0147] The thickness of the release liner 23 is, for example, 10 to 200 μm, and may be 25 to 150 μm.

[0148] The release liner 23 may include a layer other than the liner substrate. The release liner 23 may include a release layer. The release liner 23 may include, for example, a liner substrate and a release layer formed on one surface of the liner substrate. This release liner 23 can be used such that the release layer is on the coating layer 22 side.

[0149] The release layer is typically a cured layer of a release agent composition containing a release agent. A variety of release agents can be used as the release agent, including silicone-based release agents, fluorine-based release agents, long-chain alkyl-based release agents, fatty acid amide-based release agents, and silica powder. The release liner 23 may be provided with a cured layer of a release agent composition containing a silicone-based release agent as the main component (hereinafter referred to as the "silicone release layer"). A silicone release layer is particularly suitable for achieving both good adhesion to the pressure-sensitive adhesive sheet 1 and good releasability. In this specification, the term "main component" refers to the component with the highest content.

[0150] Silicone-based release agents are various curable silicone materials such as addition reaction type, condensation reaction type, ultraviolet curable type, electron beam curable type, and solventless type, with addition reaction curable silicone materials being preferred. Addition reaction curable silicone materials are particularly suitable for forming a release layer that has both good adhesion and releasability to the pressure-sensitive adhesive sheet 1. The curable silicone material may be a silicone-modified resin in which reactive silicone is introduced into an organic resin such as a urethane, epoxy, or alkyd resin by graft polymerization or the like.

[0151] An example of an addition reaction curable silicone material is a polyorganosiloxane having a vinyl group or an alkenyl group in the molecule. The addition reaction curable silicone material may not have a hydrosilyl group. Examples of alkenyl groups include 3-butenyl, 4-pentenyl, 5-hexenyl, 6-heptenyl, 7-octenyl, 8-nonenyl, 9-decenyl, 10-undecenyl, and 11-dodecenyl groups. Examples of polyorganosiloxanes include polyalkylalkylsiloxanes such as polydimethylsiloxane, polydiethylsiloxane, and polymethylethylsiloxane, polyalkylarylsiloxanes, and copolymers of multiple Si atom-containing monomers such as poly(dimethylsiloxane-diethylsiloxane). The polyorganosiloxane is preferably polydimethylsiloxane.

[0152] A release agent composition containing a silicone-based release agent as a main component (hereinafter referred to as "silicone release agent composition") usually contains a crosslinking agent. An example of the crosslinking agent is a polyorganosiloxane having a hydrosilyl group. The crosslinking agent may have two or more hydrosilyl groups in one molecule.

[0153] The silicone release agent composition may contain a curing catalyst. An example of the curing catalyst is a platinum-based catalyst. Examples of the platinum-based catalyst are chloroplatinic acid, platinum olefin complexes, and chloroplatinic acid olefin complexes. The amount of the platinum-based catalyst used is, for example, 10 to 1,000 ppm (by weight, platinum equivalent) based on the total solids content of the composition.

[0154] The silicone release agent composition may contain additives. Examples of additives are release control agents and adhesion promoters. Examples of release control agents are unreactive silicone resins, and more specific examples are organosiloxanes such as octamethylcyclotetrasiloxane, and MQ resins. The amount of the release control agent and adhesion promoter used is, for example, 1 to 30% by weight in total, based on the total solids content of the composition. Further examples of additives are fillers, antistatic agents, antioxidants, UV absorbers, plasticizers, and colorants. The amount of the additional additives used is, for example, 10% by weight or less in total, based on the total solids content of the composition.

[0155] The silicone release agent composition may contain an organic solvent. Examples of organic solvents include hydrocarbon solvents such as cyclohexane, n-hexane, and n-heptane; aromatic solvents such as toluene and xylene; ester solvents such as ethyl acetate and methyl acetate; ketone solvents such as acetone and methyl ethyl ketone; and alcohol solvents such as methanol, ethanol, and butanol. Two or more organic solvents may be contained. The amount of organic solvent used is preferably 80 to 99.9% by weight of the silicone release agent composition.

[0156] The release layer can be formed, for example, by heating and drying a coating film containing the release agent composition formed on a liner substrate. Various coating methods can be used to apply the release agent composition, such as roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and die coating. For heating and drying, for example, hot air drying can be used. The heating temperature and time vary depending on the heat resistance of the liner substrate, but are typically 80 to 150°C and about 10 seconds to 10 minutes. If necessary, irradiation with active energy rays such as ultraviolet rays may be used in combination.

[0157] The thickness of the release layer is, for example, 10 to 300 nm. The upper limit of the thickness may be 200 nm or less, 150 nm or less, 120 nm or less, 110 nm or less, 100 nm or less, less than 100 nm, 90 nm or less, 80 nm or less, 70 nm or less, less than 70 nm, or even 65 nm or less. The lower limit of the thickness may be 15 nm or more, 20 nm or more, 25 nm or more, 30 nm or more, 35 nm or more, 40 nm or more, 45 nm or more, or even 50 nm or more.

[0158] The release liner 23 may be in the form of a sheet or a continuous piece.

[0159] An example of the base sheet 21 is a resin film. Examples of the resin contained in the base sheet 21 are the same as the examples of the resin that can be contained in the liner base material.

[0160] The base sheet 21 preferably has excellent light 14 transmittance.

[0161] The thickness of the base sheet 21 is, for example, 10 to 200 μm, and may be 25 to 150 μm.

[0162] The base sheet 21 may have a release layer on the surface facing the coating layer 22. Examples of the release layer that the base sheet 21 may have and the manufacturing method thereof are the same as the examples of the release layer that the release liner 23 may have and the manufacturing method thereof. Both the release liner 23 and the base sheet 21 may have a release layer. In this case, both release layers may be formed from a release agent composition containing the same release agent as a main component. Furthermore, the thicknesses of both release layers may be different; for example, the release layer provided on the base sheet 21 may be thicker.

[0163] For the base sheet 21 , a sheet having a greater peel strength from the cured sheet 20 than the release liner 23 can usually be selected.

[0164] The base sheet 21 may be in the form of a sheet or a continuous sheet.

[0165] The first laminate 15 can be formed, for example, by forming a coating layer 22 on a base sheet 21 (or a release liner 23), and then placing the release liner 23 (or base sheet 21) on the formed coating layer 22. Alternatively, the first laminate 15 may be formed by applying the PSA composition in a pouring manner into the space between the base sheet 21 and the release liner 23, which are held at a predetermined distance so that their main surfaces face each other.

[0166] The coating layer 22 can be formed by various coating methods such as roll coating, kiss roll coating, gravure coating, reverse coating, roll brush, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and die coating.

[0167] The thickness of the coating layer 22 can be adjusted according to the desired thickness of the adhesive sheet 1, and may be, for example, 5 to 500 μm, 5 to 250 μm, 5 to 150 μm, 5 to 100 μm, 5 to 50 μm, 5 to 30 μm, 5 to 25 μm, or even 5 to 20 μm.

[0168] Examples of surface modification treatments that can be performed on the cured sheet 20 include corona treatment, plasma treatment, excimer treatment, and flame treatment, with corona treatment being preferred. In other words, the active energy rays 13 may be at least one selected from the group consisting of electron beams, ion beams, plasma beams, and ultraviolet rays. Each surface modification treatment can be performed using a corresponding known treatment device. Conditions for the surface modification treatment include those described above.

[0169] [Embodiment of Optical Laminate] An example of the optical laminate of this embodiment is shown in Figure 6. The optical laminate 10 of Figure 6 includes the above-mentioned pressure-sensitive adhesive sheet 1 and at least one optical film 2 selected from the group consisting of a polarizing film and a retardation film. The pressure-sensitive adhesive sheet 1 is preferably in direct contact with the optical film 2. In the example of Figure 6, the first surface 1a of the pressure-sensitive adhesive sheet 1 is in contact with the optical film 2. The optical laminate 10 may have a structure in which the base sheet used in producing the pressure-sensitive adhesive sheet 1 is laminated on the pressure-sensitive adhesive sheet 1. The optical laminate 10 can be used as an optical film with a pressure-sensitive adhesive sheet.

[0170] (Optical Film) The optical film 2 has a surface 2a facing the pressure-sensitive adhesive sheet 1. For example, the surface 2a is in contact with the first surface 1a of the pressure-sensitive adhesive sheet 1. The surface 2a of the optical film 2 may have been subjected to a surface modification treatment. The surface 2a that has been subjected to the surface modification treatment tends to improve the anchoring force between the pressure-sensitive adhesive sheet 1 and the optical film 2. Examples of surface modification treatments include those described above for the pressure-sensitive adhesive sheet 1.

[0171] The surface 2 a is preferably subjected to a corona treatment as a surface modification treatment. When the surface 2 a is subjected to a corona treatment, the conditions such as the discharge amount can be appropriately adjusted within the ranges described above for the PSA sheet 1, for example.

[0172] As described above, the optical film 2 includes at least one selected from the group consisting of a polarizing film and a retardation film. The optical film 2 may be a laminated film including a polarizing film and / or a retardation film. The optical film 2 may include a glass film. However, the optical film 2 is not limited to the above examples.

[0173] The polarizing film includes a polarizer. The polarizing film typically includes a polarizer and a protective film (transparent protective film). The protective film is disposed, for example, in contact with a main surface (the surface having the largest area) of the polarizer. The polarizer may be disposed between two protective films. The protective film may be disposed on at least one surface of the polarizer.

[0174] The polarizer is not particularly limited, and examples thereof include a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, or an ethylene-vinyl acetate copolymer partially saponified film, which has been uniaxially stretched after adsorbing a dichroic substance such as iodine or a dichroic dye; a polyene-based oriented film such as a dehydrated polyvinyl alcohol or a dehydrochlorinated polyvinyl chloride; etc. A polarizer typically comprises a polyvinyl alcohol film (polyvinyl alcohol films include an ethylene-vinyl acetate copolymer partially saponified film) and a dichroic substance such as iodine.

[0175] The thickness of the polarizer is not particularly limited and may be, for example, 80 μm or less, 50 μm or less, 30 μm or less, 25 μm or less, or even 20 μm or less. The lower limit of the polarizer thickness is not particularly limited and may be, for example, 1 μm or more, 5 μm or more, 10 μm or more, or even 15 μm or more. A thin polarizer (for example, a thickness of 20 μm or less) is suppressed in dimensional change and can contribute to improving the durability of the optical laminate, particularly durability at high temperatures.

[0176] The material for the protective film may be, for example, a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, moisture-blocking properties, isotropy, etc. Specific examples of such thermoplastic resins include cellulose resins such as triacetyl cellulose, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth)acrylic resins, cyclic polyolefin resins (norbornene-based resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. The material for the protective film may be a thermosetting resin or an ultraviolet-curable resin such as a (meth)acrylic, urethane, acrylic urethane, epoxy, or silicone-based resin. When the polarizing film has two protective films, the materials of the two protective films may be the same or different. For example, a protective film made of a thermoplastic resin may be bonded to one main surface of the polarizer via an adhesive, and a protective film made of a thermosetting resin or an ultraviolet-curable resin may be bonded to the other main surface of the polarizer. The protective film may contain one or more optional additives, such as ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, color inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, and colorants.

[0177] Films containing (meth)acrylic resins tend to have low adhesive strength with pressure-sensitive adhesive sheets. However, in this embodiment, by appropriately adjusting the creep amount and elastic modulus G1 of the pressure-sensitive adhesive sheet 1, even when the surface of the protective film containing (meth)acrylic resin corresponds to the surface 2a of the optical film 2, the anchoring force between the pressure-sensitive adhesive sheet 1 and the optical film 2 can be adjusted to a sufficiently high value.

[0178] The thickness of the protective film can be determined as appropriate, but is generally about 10 to 200 μm in view of strength, workability such as handling, thinness, and the like.

[0179] The polarizer and the protective film are usually adhered to each other via an aqueous adhesive or the like. Examples of aqueous adhesives include isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl latex, aqueous polyurethane, and aqueous polyester. Examples of adhesives other than the above-mentioned adhesives include ultraviolet-curable adhesives and electron beam-curable adhesives. Electron beam-curable polarizing plate adhesives exhibit suitable adhesive properties for various protective films. The adhesive may contain a metal compound filler.

[0180] In the polarizing film, a retardation film or the like can be formed on the polarizer instead of the protective film. Another protective film or a retardation film or the like can be further provided on the protective film.

[0181] The protective film may have a hard coat layer on the surface opposite to the surface bonded to the polarizer, and may also be subjected to treatments for purposes such as anti-reflection, anti-sticking, diffusion, and anti-glare.

[0182] The polarizing film may be a circular polarizing film.

[0183] The retardation film may be a film obtained by stretching a polymer film or a film obtained by aligning and fixing a liquid crystal material. The retardation film has birefringence, for example, in the in-plane and / or thickness direction.

[0184] The retardation film includes an anti-reflection retardation film (see JP 2012-133303 A,

[0221] ,

[0222] ,

[0228] ), a viewing angle compensation retardation film (see JP 2012-133303 A,

[0225] ,

[0226] ), an inclined orientation retardation film for viewing angle compensation (see JP 2012-133303 A,

[0227] ), and the like.

[0185] The specific structure of the retardation film, such as the retardation value, arrangement angle, three-dimensional birefringence, whether it is a single layer or a multilayer, is not particularly limited, and any known retardation film can be used.

[0186] The thickness of the retardation film is preferably 20 μm or less, more preferably 10 μm or less, still more preferably 1 to 9 μm, and particularly preferably 3 to 8 μm.

[0187] The retardation film may include, for example, a quarter-wave plate and / or a half-wave plate in which a liquid crystal material is aligned and fixed.

[0188] (Characteristics of Optical Laminate) In this embodiment, the anchoring force F between the pressure-sensitive adhesive sheet 1 and the optical film 2 tends to be large. The anchoring force F is, for example, 10.0 N / 25 mm or more, and may be 11.0 N / 25 mm or more, 12.0 N / 25 mm or more, 13.0 N / 25 mm or more, 14.0 N / 25 mm or more, 15.0 N / 25 mm or more, 16.0 N / 25 mm or more, 17.0 N / 25 mm or more, or even 18.0 N / 25 mm or more. The upper limit of the anchoring force F is not particularly limited, and may be, for example, 50 N / 25 mm or less, or 30 N / 25 mm or less.

[0189] The anchoring force F between the pressure-sensitive adhesive sheet 1 and the optical film 2 can be measured by the following method. First, the optical laminate 10 to be evaluated is cut into a size of 25 mm wide x 150 mm long to prepare a test piece. Next, the entire surface of the optical film 2 provided on the test piece is placed on a stainless steel test plate via double-sided tape, and a 2 kg roller is moved back and forth once to press them together. Next, the pressure-sensitive adhesive sheet 1 provided on the test piece is placed on the evaluation sheet, and a 2 kg roller is moved back and forth once to press them together. The evaluation sheet is not particularly limited as long as it has a size of 30 mm wide x 150 mm long and does not peel off from the pressure-sensitive adhesive sheet 1 during the test. For example, an ITO film (such as 125 Tetolite OES (manufactured by Oike Kogyo Co., Ltd.)) can be used as the evaluation sheet. Next, using a commercially available tensile tester, while gripping the evaluation sheet, the pressure-sensitive adhesive sheet 1 is peeled from the optical film 2 at a peel angle of 180° and a pulling rate of 300 mm / min, and the average value of the peel force is specified as the anchoring force F between the pressure-sensitive adhesive sheet 1 and the optical film 2. The above test is performed in an atmosphere of 23°C.

[0190] From the viewpoint of reworkability, the optical laminate 10 preferably has an adhesive strength P0 of 8.0 N / 25 mm or less as determined by the following Test 1. Test 1: The adhesive sheet 1 is attached to alkali-free glass, and then peeled off from the alkali-free glass at a peeling speed of 300 mm / min and a peeling angle of 90°. The force required for this (adhesive strength P0) is measured.

[0191] Test 1 is performed by the following method. First, the optical laminate 10 is cut into a strip measuring 150 mm long x 25 mm wide to prepare a test piece. Next, the test piece is attached to alkali-free glass via an adhesive sheet 1. The alkali-free glass is glass that is substantially free of alkali components (alkali metal oxides), and more specifically, the weight ratio of alkali components in the glass is, for example, 1000 ppm or less, or even 500 ppm or less. The alkali-free glass is, for example, in the form of a plate, and has a thickness of 0.5 mm or more.

[0192] The test piece is attached to the alkali-free glass using, for example, a laminator, taking care not to trap air bubbles between the alkali-free glass and the adhesive sheet 1. After attaching the test piece, the test piece is placed in an autoclave at 50°C and 5 atmospheres (absolute pressure) for 15 minutes to homogenize the bond between the alkali-free glass and the adhesive sheet 1, and to adhere the adhesive sheet 1 to the alkali-free glass. Next, the test piece is peeled from the alkali-free glass at a peel speed of 300 mm / min and a peel angle of 90° (measurement length: 80 mm). At this time, the force required to peel the test piece from the alkali-free glass is measured once every 0.5 s. The average of the obtained measurements is determined as the adhesive strength P0.

[0193] The adhesive strength P0 is preferably 7.0 N / 25 mm or less, and may be 6.0 N / 25 mm or less, 5.0 N / 25 mm or less, 4.5 N / 25 mm or less, 4.0 N / 25 mm or less, or even 3.5 N / 25 mm or less. The lower limit of the adhesive strength P0 may be, for example, 0.5 N / 25 mm or more, 1.0 N / 25 mm or more, or even 1.5 N / 25 mm or more. The adhesive strength P0 is preferably 0.5 to 7.0 N / 25 mm.

[0194] The difference (F-P) between the anchoring force F and the adhesive force P is preferably 5.0 N / 25 mm or more, and may be 6.0 N / 25 mm or more, 7.0 N / 25 mm or more, 8.0 N / 25 mm or more, 9.0 N / 25 mm or more, 10.0 N / 25 mm or more, 11.0 N / 25 mm or more, 12.0 N / 25 mm or more, or even 13.0 N / 25 mm or more. The upper limit of the difference (F-P) is, for example, 20 N / 25 mm or less.

[0195] Furthermore, from the viewpoint of durability, it is preferable that the adhesiveness of the pressure-sensitive adhesive sheet 1 of the optical laminate 10 improves when it is heat-treated while in contact with alkali-free glass. As an example, it is preferable that the adhesive strength P1 of the optical laminate 10 is 8.0 N / 25 mm or more as determined by the following Test 2. Test 2: The pressure-sensitive adhesive sheet 1 is attached to alkali-free glass and heat-treated at 60°C for 100 hours. The pressure-sensitive adhesive sheet 1 is peeled from the alkali-free glass at a peel speed of 300 mm / min and a peel angle of 90°. The force required for this (adhesive strength P1) is measured.

[0196] Test 2 can be performed in the same manner as Test 1, except that the bond between the alkali-free glass and the adhesive sheet 1 is homogenized in an autoclave, followed by heat treatment at 60°C under atmospheric pressure for 100 hours, and then the temperature of the test piece is lowered to room temperature (e.g., 23°C) before the test piece is peeled off from the alkali-free glass.

[0197] The adhesive strength P1 is preferably 9.0 N / 25 mm or more, and may be 9.5 N / 25 mm or more, 10.0 N / 25 mm or more, or even 10.5 N / 25 mm or more. The upper limit of the adhesive strength P1 is, for example, 20 N / 25 mm or less.

[0198] Another example of the optical laminate of the present embodiment is shown in Fig. 7. The optical laminate 11 in Fig. 7 has a laminated structure in which a pressure-sensitive adhesive sheet 1, an optical film 2A, a pressure-sensitive adhesive sheet 7, and an optical film 2B are laminated in this order. The optical laminate 11 may have a structure in which the base sheet used in producing the pressure-sensitive adhesive sheet 1 is laminated on the pressure-sensitive adhesive sheet 1.

[0199] In the optical laminate 11, typically, the optical film 2A is a retardation film, and the optical film 2B is a polarizing film. The pressure-sensitive adhesive sheet 7 functions as an interlayer pressure-sensitive adhesive between the optical films 2A and 2B. The pressure-sensitive adhesive sheet 7 may be one using a known pressure-sensitive adhesive, or may be one described above for the pressure-sensitive adhesive sheet 1.

[0200] The optical laminates 10 and 11 of the present embodiment can be distributed and stored, for example, as a rolled body obtained by rolling up a strip-shaped optical laminate, or as a sheet-shaped optical laminate.

[0201] The optical laminate of this embodiment is typically used in an image display device. The image display device includes, for example, the optical laminate 10 or 11, and can be formed by bonding the optical laminate 10 or 11 to an image display panel. The bonding is performed, for example, using a pressure-sensitive adhesive sheet 1. The image display device may be an organic EL display or a liquid crystal display. However, the image display device is not limited to the above examples. The image display device may be an electroluminescence (EL) display, a plasma display (PD), a field emission display (FED), or the like. The image display device can be used for home appliance applications, in-vehicle applications, public information displays (PID), and the like.

[0202] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the examples shown below.

[0203] Monomer Syrup A1: 95.5 parts by weight of n-butyl acrylate (BA), 4.4 parts by weight of acrylic acid (AA), 0.1 parts by weight of 4-hydroxybutyl acrylate (HBA), 0.05 parts by weight of 1-hydroxycyclohexyl-phenyl ketone (Omnirad 184, manufactured by IGM Resins BV) as photopolymerization initiators, and 0.05 parts by weight of 2,2-dimethoxy-2-phenylacetophenone (Omnirad 651, manufactured by IGM Resins BV) were placed in a four-neck flask and irradiated with ultraviolet light under a nitrogen atmosphere to obtain a partially photopolymerized monomer syrup A1. UV irradiation was continued until the viscosity of the liquid in the flask reached approximately 20 Pa s (measurement conditions: BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30°C).

[0204] [Monomer Syrup A2] Monomer Syrup A2 was prepared in the same manner as Monomer Syrup A1, except that the monomers and photopolymerization initiator were changed as shown in Table 1.

[0205]

[0206] The abbreviations in Table 1 are as follows: BA: n-butyl acrylate AA: acrylic acid HBA: 4-hydroxybutyl acrylate Omnirad 184: 1-hydroxycyclohexyl-phenyl ketone (Omnirad 184, manufactured by IGM Resins BV) Omnirad 651: 2,2-dimethoxy-2-phenylacetophenone (Omnirad 651, manufactured by IGM Resins BV) Omnirad 819: bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 819, manufactured by IGM Resins BV)

[0207] [Adhesive Compositions C1 to C8] Next, the monomer syrup, the monomer, the crosslinking agent, and the silane coupling agent were mixed so as to have the compositions shown in Table 2 below, thereby obtaining adhesive compositions C1 to C8.

[0208]

[0209] The abbreviations in Table 2 are as follows: NVP: N-vinyl-2-pyrrolidone NDDA: 1,9-nonanediol diacrylate KBM403: 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403")

[0210] The final composition of the monomers contained in each PSA composition is shown in Table 3 below.

[0211]

[0212] Example 1 Preparation of Release Liner A silicone-based release agent composition was obtained by mixing 30 parts by weight of an addition reaction curable silicone (LTC761 containing a hexenyl group-containing polyorganosiloxane, a 30 wt % toluene solution, manufactured by Dow Corning Toray), 0.9 parts by weight of a release control agent (BY24-850 containing an unreactive silicone resin, manufactured by Dow Corning Toray), and 2 parts by weight of a curing catalyst (SRX212 containing a platinum catalyst, manufactured by Dow Corning Toray), and a toluene / hexane mixed solvent (volume ratio 1:1) as a dilution solvent. The silicone solids concentration in the release agent composition was 1.0 wt %. Next, the release agent composition was applied with a wire bar to one side of a liner substrate (Lumirror XD500P, a polyester film, 75 μm thick), and heated at 130° C. for 1 minute to prepare a release liner having a release layer (60 nm thick) on one side.

[0213] [Preparation of Pressure-Sensitive Adhesive Sheet] The pressure-sensitive adhesive composition C1 was applied to one side of a substrate sheet (PET separator, MRF38, manufactured by Mitsubishi Plastics) using an applicator to form a coating layer (thickness: 20 μm). Next, a release liner was placed on the formed coating layer to obtain a first laminate. The release liner was placed so that the release layer was in contact with the coating layer. Next, light was irradiated from the substrate sheet side of the first laminate. As the light source, a combination of a black light source (BL) and an LED emitting light with a peak wavelength of 340 nm was used. The irradiation conditions for each light source were as follows. The illuminance of the light was measured using an illuminance meter (UD-T3040T2, manufactured by Topcon Technohouse Co., Ltd.) at a position near the ultraviolet light incident surface of the substrate sheet. BL: Illuminance 6.2 mW / cm 2 and irradiation time 95 seconds (integrated light amount 589 mJ / cm 2 ) LED: Illuminance 3.1mW / cm 2 and irradiation time 90 seconds (cumulative light amount 279 mJ / cm 2 )

[0214] The coating layer was photocured by the irradiation of light, and a second laminate composed of the release liner, the cured sheet (thickness: 20 μm), and the substrate sheet was obtained. Next, the release liner was peeled off from the second laminate, and a discharge amount of 61 W / m was applied to the exposed surface of the cured sheet. 2 As a result, a layer with a high elastic modulus (second layer) was formed in the area that had been subjected to the corona treatment, and the pressure-sensitive adhesive sheet of Example 1 was obtained.

[0215] (Examples 2 to 10 and Comparative Examples 1 to 3) Pressure-sensitive adhesive sheets of Examples 2 to 10 and Comparative Examples 1 to 3 were obtained in the same manner as in Example 1, except that the pressure-sensitive adhesive composition used and the discharge amount in the corona treatment were changed as shown in Table 4. In Comparative Example 1, no corona treatment was performed, and the cured sheet was regarded as the pressure-sensitive adhesive sheet.

[0216] [AFM Measurement] Elastic Modulus G1 of First Surface and Elastic Modulus G2 of Second Surface For the PSA sheets of the Examples and Comparative Examples, the elastic modulus G1 of the first surface and the elastic modulus G2 of the second surface were measured using an AFM by the method described above. Note that for Examples 1 to 10 and Comparative Examples 2 and 3, the surface that had been subjected to the corona treatment was considered to be the first surface, and for Comparative Example 1, the surface of the PSA sheet exposed by peeling the release liner from the second laminate was considered to be the first surface. An MFP-3D Standalone manufactured by ASYLUM RESEARCH was used as the scanning probe microscope.

[0217] Thickness of the Second Layer In all of the pressure-sensitive adhesive sheets of the Examples, a layer with a high elastic modulus (second layer) was formed in the area that had been subjected to corona treatment. The thickness of this second layer was measured using an AFM according to the method described above. As a result, the thickness of the second layer in all of the pressure-sensitive adhesive sheets of the Examples was approximately 100 nm to 150 nm. Note that test pieces for measuring the thickness of the second layer were prepared by cutting the laminate obtained by laminating the pressure-sensitive adhesive sheet to a support film with an ultramicrotome. The support film used was polarizing film D1, which will be described later.

[0218] [Creep Amount] The creep amount was measured for the pressure-sensitive adhesive sheets of the Examples and Comparative Examples by the method described above. A 50 μm thick PET film was used as the support film 51. A SUS304 plate (30 mm × 75 mm, 2.5 mm thick) was used as the test plate 53. A Keyence LK-H057 laser displacement meter was used.

[0219] [Preparation of Optical Laminate] Next, polarizing film D1 was prepared and combined with the pressure-sensitive adhesive sheets of the Examples and Comparative Examples to prepare optical laminates. Polarizing film D1 was prepared by the following method. First, an 80 μm-thick polyvinyl alcohol film was stretched to 3 times its original size between rolls with different speed ratios while dyeing for 1 minute in a 0.3% iodine solution at 30°C. Next, the film was stretched to a total stretch ratio of 6 times while immersed for 0.5 minutes in an aqueous solution containing 4% boric acid and 10% potassium iodide at 60°C. Next, the film was immersed for 10 seconds in an aqueous solution containing 1.5% potassium iodide at 30°C for cleaning, and then dried at 50°C for 4 minutes to obtain a 20 μm-thick polarizer. A saponified triacetyl cellulose (TAC)-based transparent protective film (25 μm thick, manufactured by Fujifilm Corporation) was bonded to one side of the polarizer using a polyvinyl alcohol-based adhesive. Furthermore, a cycloolefin polymer (COP) transparent protective film (thickness: 13 μm, manufactured by Zeon Corporation) that had been subjected to corona treatment was attached to the other surface of the polarizer using a polyvinyl alcohol adhesive, thereby obtaining polarizing film D1 having a configuration of TAC transparent protective film / polarizer / COP transparent protective film.

[0220] In Examples 1 to 10 and Comparative Examples 1 to 3, the optical laminate was prepared by placing the polarizing film D1 on the first surface of the pressure-sensitive adhesive sheet. At this time, the polarizing film D1 was placed so that the surface on the COP-based transparent protective film side was in contact with the pressure-sensitive adhesive sheet.

[0221] [Anchor Force] The anchor force F between the pressure-sensitive adhesive sheet and the polarizing film was measured using the method described above for the optical laminate produced by the method described above. The double-sided tape used was "No. 531" manufactured by Nitto Denko Corporation. The stainless steel test plate used was a SUS304 plate (width 40 mm x length 120 mm). The evaluation sheet used was an ITO film (125 Tetolite OES, manufactured by Oike Kogyo). The tensile tester used was an autograph SHIMAZU AG-I 10KN (manufactured by Shimadzu Corporation).

[0222] [Durability] The durability (85°C durability) of the optical laminate prepared by the above method was evaluated by the following method. First, the optical laminate was cut into a strip measuring 300 mm long x 220 mm wide to prepare a test specimen. Next, the test specimen was attached to the surface of 0.7 mm thick alkali-free glass (manufactured by Corning Incorporated, product name "EG-XG") using an adhesive sheet. At this time, the second surface of the adhesive sheet was brought into contact with the alkali-free glass. The test specimen was attached to the alkali-free glass using a laminator. After attaching the test specimen, it was placed in an autoclave at 50°C and 0.5 MPa for 15 minutes to homogenize the bond between the alkali-free glass and the adhesive sheet, and the adhesive sheet was adhered to the alkali-free glass. Next, the test specimen was subjected to a heat treatment at 85°C under atmospheric pressure for 500 hours. The appearance of the adhesive sheet between the polarizing film and the alkali-free glass was visually observed, and peeling and internal tearing (glue tearing) were evaluated according to the following criteria. Peeling (Evaluation criteria) A: No peeling is observed. B: There is slight peeling at the edge, but it does not affect the image display function. C: There is significant peeling that may affect the image display function. Glue cracking (Evaluation criteria) A: No glue cracking is observed. B: There is slight glue cracking at the edge. C: There is glue cracking at the edge.

[0223]

[0224] As can be seen from Table 4, the pressure-sensitive adhesive sheets of the examples, in which the creep amount was 10 μm or more and the elastic modulus G1 of the first surface was 1.0 MPa or more, showed better peeling evaluation results in the durability test than the comparative examples. From these results, it can be inferred that the pressure-sensitive adhesive sheets of the examples are suitable for suppressing peeling between components of an image display device in a high-temperature environment.

[0225] The pressure-sensitive adhesive sheet of the present invention can be used, for example, in optical laminates and image display devices.

Claims

1. An adhesive sheet having a first surface and a second surface opposed to each other, the creep amount determined by the following test is 10 μm or more, and the elastic modulus of the first surface measured using an atomic force microscope is 1.0 MPa or more. Test: A load of 500 gf is applied vertically downward to the adhesive sheet attached to a stainless steel test plate at a joint surface of 10 mm length x 10 mm width with the test plate fixed. The creep amount (displacement amount) of the adhesive sheet relative to the test plate is measured 3600 seconds after the load is applied.

2. The pressure-sensitive adhesive sheet according to claim 1, comprising a first layer and a second layer positioned on the first layer, the first surface coinciding with the surface of the second layer.

3. The pressure-sensitive adhesive sheet according to claim 2, wherein the second layer has a thickness of 1.0 μm or less.

4. The pressure-sensitive adhesive sheet according to claim 1, wherein the creep amount is 300 μm or less.

5. The pressure-sensitive adhesive sheet according to claim 1, wherein the elastic modulus of the first surface is 10.0 MPa or less.

6. The pressure-sensitive adhesive sheet according to claim 1, wherein the elastic modulus of the second surface measured using an atomic force microscope is less than 1.0 MPa.

7. The adhesive sheet according to claim 1, wherein the first surface is a surface that has been subjected to a surface modification treatment.

8. The pressure-sensitive adhesive sheet according to claim 7, wherein the surface modification treatment is a corona treatment.

9. The pressure-sensitive adhesive sheet according to claim 1, which is formed from a pressure-sensitive adhesive composition containing a monomer group and / or a polymer of said monomer group.

10. The pressure-sensitive adhesive sheet according to claim 9, wherein the monomer group includes a (meth)acrylic monomer.

11. The pressure-sensitive adhesive sheet according to claim 9, wherein the pressure-sensitive adhesive composition is photocurable.

12. The pressure-sensitive adhesive sheet according to claim 9, wherein the pressure-sensitive adhesive composition contains a solvent in an amount of 5% by weight or less.

13. The pressure-sensitive adhesive sheet according to claim 1, having a thickness of 50 μm or less.

14. An optical laminate comprising: the pressure-sensitive adhesive sheet according to any one of claims 1 to 13; and an optical film comprising at least one selected from the group consisting of a polarizing film and a retardation film.

15. The optical laminate according to claim 14, wherein the first surface of the pressure-sensitive adhesive sheet is in contact with the optical film.

16. The optical laminate according to claim 14, wherein the anchoring strength between the pressure-sensitive adhesive sheet and the optical film is 10.0 N / 25 mm or more.

17. An image display device comprising the optical laminate according to claim 14.

Images