Optical laminate and image display device

Abstract

An optical laminate includes an optical substrate, a first adhesive sheet, a first optical film, and a second adhesive sheet in this order. The thickness of the first optical film is 15 [mu] m or less. The storage modulus G'of the second adhesive sheet at 25 DEG C is 0.15 MPa or more. When a first test in which the optical laminate is bonded to the surface of the glass sheet by means of the second adhesive sheet and the optical laminate is peeled from the glass sheet at a point in time when seven days have elapsed at 25 DEG C from the bonding, the degree of roughness of the peeled surface of the second adhesive sheet after peeling is represented by the arithmetic mean height Sa prescribed in ISO 25178 is 5.5 [mu] m or less. The optical laminate can improve the elastic modulus of the second adhesive sheet which can be used as a bonding surface with other members such as an image forming layer, and is suitable for handling with reoperation despite including the thin first optical film.

Description

Technical Field

[0001] The present invention relates to an optical laminate and an image display device. Background Art

[0002] Image display devices typified by liquid crystal display devices and electroluminescent (EL) display devices (for example, organic EL display devices and inorganic EL display devices) are rapidly spreading. The above-described various image display devices generally have a laminated structure including an image forming layer such as a liquid crystal layer and an EL light emitting layer and an optical laminate, and the optical laminate includes an optical film and an adhesive sheet. An optical laminate including a polarizing plate 1, an adhesive layer a, a retardation plate 2, and an adhesive layer a in this order is disclosed in Patent Document 1. The optical laminate of Patent Document 1 is an elliptical polarizing plate that can function as an antireflection layer in an organic EL display device.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2004-226842 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] For an image display device, narrowing of the bezel is required. However, in an image display device that has been bezel-narrowed, problems caused by dimensional changes of the optical laminate due to temperature are likely to occur. For example, when the dimensional change exceeds the width of the bezel, defects occur in the displayed image, and the allowable change range becomes smaller for the narrowed bezel. In order to suppress dimensional changes, it is conceivable to increase the elastic modulus of the adhesive sheet that can be a bonding surface with other members such as an image forming layer. In addition, if the elastic modulus becomes high, deformation of the adhesive sheet during peeling from other members is suppressed. In other words, an increase in the elastic modulus can also contribute to improving the adaptability (reworkability) of the optical laminate for the operation of peeling the optical laminate pasted on other members from the members, that is, rework.

[0008] For an image display device, there is also a requirement for thinning. In order to achieve thinning, it is conceivable to reduce the thickness of the optical film included in the optical laminate. However, the inventors have found through research that when the elastic modulus of the adhesive sheet that can be a bonding surface with other members is increased while the optical film is thinned, the reworkability tends to decrease.

[0009] An object of the present invention is to provide an optical laminate which sequentially includes an optical substrate, a first adhesive sheet, a first optical film, and a second adhesive sheet, and which can increase the elastic modulus of the second adhesive sheet that can be a bonding surface with other members such as an image forming layer, and is suitable for rework despite including a thin first optical film.

[0010] Means for Solving the Problem

[0011] The present invention provides an optical laminate which sequentially includes an optical substrate, a first adhesive sheet, a first optical film, and a second adhesive sheet,

[0012] The thickness of the above-mentioned first optical film is 15 μm or less,

[0013] The storage modulus G' of the above-mentioned second adhesive sheet at 25°C is 0.15 MPa or more,

[0014] When the optical laminate is bonded to the surface of a glass sheet through the above-mentioned second adhesive sheet, and a first test of peeling the optical laminate from the glass sheet is performed at the time when 7 days have passed at 25°C since the bonding, the roughness of the peeling surface of the above-mentioned second adhesive sheet after peeling is represented by the arithmetic mean height Sa defined in ISO 25178 as 5.5 μm or less.

[0015] Among them, the peeling of the optical laminate from the glass sheet is performed as a 90° peeling test defined in JIS Z0237:2009, the glass sheet is treated as a test plate, and the peeling speed is set to 300 mm / min.

[0016] According to another aspect, the present invention provides an image display device including the optical laminate of the present invention.

[0017] Effects of the Invention

[0018] The optical laminate of the present invention is suitable for rework. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a cross-sectional view schematically showing an example of the optical laminate of the present invention.

[0020] Figure 2 is a schematic view for explaining a case where a bending stress is applied to the optical laminate during rework.

[0021] Figure 3 is an observation image using a scanning electron microscope (SEM) showing the state of the cross section after peeling from a glass sheet in the second test for the optical laminate of Comparative Example 3.

[0022] Figure 4It is a cross-sectional view schematically showing an example of the optical laminate of the present invention.

[0023] Figure 5 It is a cross-sectional view schematically showing an example of the optical laminate of the present invention.

[0024] Figure 6 It is a cross-sectional view schematically showing an example of the optical laminate of the present invention.

[0025] Figure 7 It is a cross-sectional view schematically showing an example of the optical laminate of the present invention.

[0026] Figure 8 It is a cross-sectional view schematically showing an example of the image display device of the present invention.

[0027] Figure 9 It is an observation image using a surface property measuring machine showing the state of the peeled surface after peeling from a glass sheet in the second test for the optical laminate of Example 1.

[0028] Figure 10 It is an observation image using a surface property measuring machine showing the state of the peeled surface after peeling from a glass sheet in the second test for the optical laminate of Comparative Example 3. Detailed Description

[0029] The optical laminate of the first aspect of the present invention sequentially includes an optical substrate, a first adhesive sheet, a first optical film, and a second adhesive sheet.

[0030] The thickness of the above-mentioned first optical film is 15 μm or less.

[0031] The storage modulus G' of the above-mentioned second adhesive sheet at 25°C is 0.15 MPa or more.

[0032] When the above-mentioned optical laminate is adhered to the surface of a glass sheet through the above-mentioned second adhesive sheet, and a first test of peeling the above-mentioned optical laminate from the above-mentioned glass sheet is performed at the time when 7 days have passed at 25°C since the adhesion, the roughness of the peeled surface of the above-mentioned second adhesive sheet is represented by the arithmetic mean height Sa specified in ISO 25178 as 5.5 μm or less.

[0033] Among them, the peeling of the above-mentioned optical laminate from the above-mentioned glass sheet is carried out according to the 90° peeling test specified in JIS Z0237:2009, the above-mentioned glass sheet is treated as a test plate, and the peeling speed is set to 300 mm / min for implementation.

[0034] In the second embodiment of the present invention, for example, in the optical laminate of the first embodiment, when the optical laminate is bonded to the surface of a glass sheet by the above-described second adhesive sheet and a second test of peeling the optical laminate from the glass sheet is performed 14 days after the bonding at 25°C, the roughness of the peeled surface of the second adhesive sheet is represented by the arithmetic mean height Sa of 8.9 μm or less.

[0035] In the third embodiment of the present invention, for example, in the optical laminate of the first or second embodiment, the interfacial adhesion force based on the first adhesive sheet is 4.5 N / 25 mm or more.

[0036] In the fourth embodiment of the present invention, for example, in the optical laminate of the first or second embodiment, the interfacial adhesion force based on the first adhesive sheet is less than 4.5 N / 25 mm, and the adhesion force of the optical laminate evaluated in the first test with respect to the glass sheet is 4.5 N / 25 mm or less.

[0037] In the fifth embodiment of the present invention, for example, in the optical laminate of the first or second embodiment, the interfacial adhesion force based on the first adhesive sheet is less than 4.5 N / 25 mm, and the adhesion force of the optical laminate evaluated in the second test of peeling the optical laminate from the glass sheet 14 days after the bonding at 25°C by the second adhesive sheet with respect to the glass sheet is 6 N / 25 mm or less.

[0038] In the sixth embodiment of the present invention, for example, in the optical laminate of any one of the first to fifth embodiments, the storage modulus G' of the second adhesive sheet at 25°C is 2 MPa or less.

[0039] In the seventh embodiment of the present invention, for example, in the optical laminate of any one of the first to sixth embodiments, the first optical film is a retardation film.

[0040] In the eighth embodiment of the present invention, for example, in the optical laminate of any one of the first to seventh embodiments, a second optical film is further included between the optical substrate and the first adhesive sheet.

[0041] In the ninth embodiment of the present invention, for example, in the optical laminate of the eighth embodiment, the thickness of the second optical film is 15 μm or less.

[0042] In the tenth embodiment of the present invention, for example, in the optical laminate of the eighth or ninth embodiment, the second optical film is a retardation film.

[0043] In the eleventh embodiment of the present invention, for example, in the optical laminate of any one of the first to tenth embodiments, the optical substrate includes a polarizer.

[0044] In the twelfth aspect of the present invention, for example, in the optical laminate of any one of the first to eleventh aspects, at least one selected from the above-mentioned first adhesive sheet and the second adhesive sheet contains a (meth)acrylic polymer (A) as a main component.

[0045] The image display device according to the thirteenth aspect of the present invention includes the optical laminate of any one of the first to twelfth aspects.

[0046] Hereinafter, the present invention will be described in detail. However, the present invention is not limited to the following embodiments and can be arbitrarily modified and implemented without departing from the gist of the present invention.

[0047] [Optical laminate]

[0048] An example of the optical laminate of the present invention is shown in Figure 1 . Figure 1 The optical laminate 10 (10A) sequentially includes an optical substrate 1, a first adhesive sheet 2, a first optical film 3, and a second adhesive sheet 4. Each adjacent layer in the optical laminate 10A is in contact with each other. The first optical film 3 is sandwiched between the first adhesive sheet 2 and the second adhesive sheet 4. The thickness of the first optical film 3 is 15 μm or less. The second adhesive sheet 4 constitutes an exposed surface of the optical laminate 10A. When the optical laminate 10A is bonded to other members, the second adhesive sheet 4 can constitute a bonding surface with the other members. When the optical laminate 10A is bonded to the surface of a glass sheet by the second adhesive sheet 4 and a first test of peeling the optical laminate 10A from the glass sheet is performed at 25°C 7 days after the bonding, the roughness of the peeling surface of the second adhesive sheet 4 after peeling is represented by the arithmetic mean height Sa specified in ISO 25178 and is 5.5 μm or less.

[0049] During the re-operation, a bending stress is applied to the optical laminate 10 (see Figure 2 ; Figure 2The symbol 51 is an object to be laminated to the optical laminate 10). The inventors of the present invention have found through research that: when the elastic modulus of the second adhesive sheet 4 is increased and the optical laminate 10 includes a thin first optical film 3, (1) cohesive failure is likely to occur in the first adhesive sheet 2 due to stress concentration at the bent portion; (2) the second adhesive sheet 4 cannot be smoothly peeled off due to the intermittent progress of cohesive failure, and the peeling surface is rough; and (3) since the roughness of the peeling surface consumes the energy for peeling, the reworkability is reduced. In addition, through further research, it has been found that: regarding the degree of roughness generated on the peeling surface, it is highly likely that various factors are involved complexly. Therefore, in order to improve the response to rework, it is appropriate to determine the degree of roughness. It should be noted that when the first optical film 3 is thick, by dispersing the bending stress in the first optical film 3, the bending stress generated when the elastic modulus of the second adhesive sheet 4 is small becomes smaller, and thus the cohesive failure of the first adhesive sheet 2 and the roughness of the peeling surface of the second adhesive sheet 4 are less likely to occur. It should be noted that the roughness of the peeling surface is typically observed in the form of multiple ridge-like protrusions (refer to Figure 3 ). Figure 3 is an observation image using a scanning electron microscope (SEM) showing the state of the cross-section after peeling from the glass sheet in the second test for the optical laminate of Comparative Example 3.

[0050] The arithmetic mean height Sa is one of the three-dimensional surface property parameters related to the surface roughness specified in ISO 25178 established by the International Organization for Standardization. The evaluation of the arithmetic mean height Sa can be performed using a known surface property measuring machine capable of evaluating the surface property in accordance with the provisions of ISO 25187. The balance between the size of the measurable area and the measurement resolution is suitable for evaluating the above-mentioned roughness of the peeling surface. Therefore, it is preferable to use a non-contact measuring machine, particularly a laser microscope. An example of the measuring machine is the VK series manufactured by Keyence Corporation. The measuring area is preferably set to a square or rectangle with a side length of 4 μm or more. The side length of one side in the measuring area can be 4 to 6 μm. When evaluating the arithmetic mean height Sa, if necessary, filtering processes such as F-operation, S-filtering, and L-filtering can also be applied to the measurement data of the original surface. The evaluation of the arithmetic mean height Sa and the application of filtering processes can be performed using the analysis software attached to the surface property measuring machine.

[0051] Description of the first test: First, the optical laminate 10 is bonded to the surface of the glass sheet using the second adhesive sheet 4. The glass sheet used is a sheet of non-alkali glass. Non-alkali glass is glass that substantially does not contain alkali components (alkali metal oxides). Substantially not containing alkali components means that the weight ratio of the alkali components in the glass is, for example, 1000 ppm or less, and can be 500 ppm or less. An example of non-alkali glass is the Eagle series manufactured by Corning Incorporated. The glass sheet used has a sufficient thickness such that when the optical laminate 10 is peeled off, deformation, cracking, etc. do not occur, and has a sufficient size to bond the entire optical laminate 10 to be evaluated. The thickness of the glass sheet is preferably about 0.5 to 2 mm. The shape of the optical laminate 10 to be evaluated is set to a rectangle with a width of 25 mm and a length of 100 mm or more. The bonding is carried out at room temperature (25°C) using a pressing roller with a mass of 2 kg specified in Japanese Industrial Standards (hereinafter referred to as JIS) Z0237:2009. When bonding, no bubbles are included between the optical laminate 10 and the glass sheet. Preferably, by performing an autoclave treatment after bonding, the adhesion of the second adhesive sheet 4 to the glass sheet is homogenized. The conditions of the autoclave treatment are, for example, 50°C, 5 atmospheres (absolute pressure), and 15 minutes.

[0052] Next, the optical laminate 10 in the state of being bonded to the above surface is placed at 25°C, and the optical laminate 10 is peeled off from the glass sheet at the time 7 days after bonding. The peeling is carried out according to the 90° peeling test specified in JIS Z0237:2009, treating the glass sheet as the test plate, and setting the peeling speed to 300 mm / min. The peeling direction is the long side direction of the optical laminate 10. The peeling can be carried out using a tensile testing machine. The peeling surface (exposed surface) of the second adhesive sheet 4 in the peeled optical laminate 10 becomes the evaluation surface for the arithmetic mean height Sa. It should be noted that the above peeling in the first test can be carried out within 12 hours, preferably within 6 hours, from the above time.

[0053] When performing the first test, the arithmetic mean height Sa of the peeling surface of the peeled second adhesive sheet 4 can be 5.2 μm or less, 5 μm or less, 4.7 μm or less, 4.5 μm or less, 4.2 μm or less, 4 μm or less, 3.7 μm or less, 3.5 μm or less, 3.2 μm or less, 3 μm or less, 2.9 μm or less, 2.8 μm or less, 2.7 μm or less, 2.6 μm or less, 2.5 μm or less, and further can be 2.4 μm or less. The lower limit of this Sa is, for example, 0 μm or more, and can be 1 μm or more.

[0054] When the optical laminate 10 is bonded to the surface of the glass sheet through the second adhesive sheet 4, and the second test of peeling the optical laminate 10 from the glass sheet is carried out at the time 14 days after bonding at 25°C, the roughness of the peeled surface of the second adhesive sheet 4 can be represented by the above arithmetic mean height Sa of 8.9 μm or less, or can be 8.5 μm or less, 8 μm or less, 7.7 μm or less, 7.5 μm or less, 7 μm or less, 6.5 μm or less, 6 μm or less, 5.5 μm or less, 5 μm or less, 4.7 μm or less, 4.5 μm or less, 4.2 μm or less, 4 μm or less, 3.7 μm or less, 3.5 μm or less, 3.2 μm or less, 3.1 μm or less, 3 μm or less, 2.9 μm or less, 2.8 μm or less, and further can be 2.7 μm or less. The lower limit of this Sa is, for example, 0 μm or more, and can be 1 μm or more. The second test can be carried out in the same manner as the first test except for the different peeling timing. The peeling in the second test can be carried out within 24 hours, preferably within 12 hours, from the time after 14 days have passed. The adhesive force of the optical laminate 10 to the glass sheet generally increases with the passage of time after bonding. However, compared with the period when the first 7 days have passed, the degree of increase in the next 7-day period is generally smaller. It should be noted that the re-operation of the optical laminate 10 is generally carried out within the period of 1 to 2 weeks after bonding.

[0055] The arithmetic mean height Sa of the peeled surface may vary in various ways depending on, for example, the types and quantities of the layers included in the optical laminate 10, the composition and properties of each layer, and the relationships between the layers. As examples of the factors that may affect the arithmetic mean height Sa, for the optical substrate 1, the types and quantities of the included layers, thickness, and elastic modulus can be considered; for the first adhesive sheet 2 and the second adhesive sheet 4, the composition, thickness, and elastic modulus can be considered; for the first optical film 3, the types of layers, thickness, and elastic modulus can be considered; for the relationships between the layers, the interfacial adhesion force based on the first adhesive sheet, the presence or absence of the second optical film 5 described later and its type, thickness, and elastic modulus, etc. can be considered. It is speculated that these factors interact with each other and change the above arithmetic mean height Sa of the optical laminate 10.

[0056] The interfacial adhesion force based on the first adhesive sheet 2 can be 4.5 N / 25 mm or more, and can also be 5 N / 25 mm or more, 5.5 N / 25 mm or more, 5.7 N / 25 mm or more, 6 N / 25 mm or more, 6.2 N / 25 mm or more, 6.5 N / 25 mm or more, 6.7 N / 25 mm or more, and further can be 6.9 N / 25 mm or more. The upper limit of the interfacial adhesion force is, for example, 50 N / 25 mm or less. The interfacial adhesion force within the above range can help to make the arithmetic mean height Sa evaluated by the first test and / or the arithmetic mean height Sa evaluated by the second test fall within the above range. The interfacial adhesion force can be evaluated by the third test. In the third test, for a test piece of a rectangular optical laminate 10 (without the second adhesive sheet 4) with a width of 25 mm and a length of 100 mm or more, the part containing the optical substrate 1 and the part containing the first optical film 3 are separated at the first adhesive sheet 2. The third test can be implemented as follows. First, the optical laminate 10 in a state without the second adhesive sheet 4 is adhered to a polyethylene terephthalate (PET) film. The adhesion is carried out in such a way that the side surface of the part containing the first optical film 3 faces the PET film. The adhesion can use an adhesive. The adhesive used is an adhesive having an adhesive strength sufficient to prevent the part containing the first optical film 3 from peeling off from the PET film in the third test. The PET film is a film for preventing the part containing the first optical film 3 from breaking in the third test. The thickness of the PET film can be set to about 50 - 200 μm. The adhesion is carried out at 25°C using a pressing roller with a mass of 2 kg specified in JIS Z0237:2009. During adhesion, no bubbles are included between the optical laminate 10 and the PET sheet. After standing for 2 days since adhesion, the whole is cut into the shape of a test piece and adhered to the surface of a stainless steel (SUS) plate as a test plate using an adhesive sheet. The adhesive sheet used is an adhesive sheet having an adhesive strength sufficient to prevent the SUS plate from peeling off from the test piece in the third test. The SUS plate used is a SUS plate having a sufficient thickness such that it will not be deformed, etc. in the third test and having a sufficient size to allow the whole test piece to be adhered. The adhesion is carried out at 25°C using a pressing roller with a mass of 2 kg specified in JIS Z0237:2009. Next, using a tensile testing machine, the part containing the optical substrate 1 and the part containing the first optical film 3 and the second adhesive sheet 4 are separated at the first adhesive sheet 2. The peeling angle when separating is set to 90°, and the peeling speed is set to 300 mm / min. The peeling direction is the direction of the long side of the test piece. The average value of the peeling force measured at the time of separation can be used as the interfacial adhesion force based on the first adhesive layer 2.

[0057] The adhesion force of the optical laminate 10 evaluated in the first test (adhesion force after 7 days) to the glass sheet can be 3.5 N / 25 mm or more, and can also be 3.7 N / 25 mm or more, 4 N / 25 mm or more, 4.2 N / 25 mm or more, 4.5 N / 25 mm or more, 4.7 N / 25 mm or more, 5 N / 25 mm or more, 5.2 N / 25 mm or more, 5.5 N / 25 mm or more, 5.7 N / 25 mm or more, 6 N / 25 mm or more, 6.2 N / 25 mm or more, and further can be 6.5 N / 25 mm or more. The upper limit of the above adhesion force is, for example, 10 N / 25 mm or less, can be 9 N / 25 mm or less, 8 N / 25 mm or less, and further can be 7.5 N / 25 mm or less.

[0058] The adhesion force of the optical laminate 10 evaluated in the second test (adhesion force after 14 days) to the glass sheet can be 4.5 N / 25 mm or more, and can also be 4.7 N / 25 mm or more, 5 N / 25 mm or more, 5.2 N / 25 mm or more, 5.5 N / 25 mm or more, 5.7 N / 25 mm or more, 6 N / 25 mm or more, 6.2 N / 25 mm or more, 6.5 N / 25 mm or more, 6.7 N / 25 mm or more, 7 N / 25 mm or more, 7.2 N / 25 mm or more, and further can be 7.5 N / 25 mm or more. The upper limit of the above adhesion force is, for example, 11 N / 25 mm or less, can be 10 N / 25 mm or less, 9 N / 25 mm or less, and further can be 8 N / 25 mm or less.

[0059] The initial adhesion force of the optical laminate 10 to the glass sheet can be 1 N / 25 mm or more, and can also be 1.2 N / 25 mm or more, 1.5 N / 25 mm or more, 1.7 N / 25 mm or more, 2 N / 25 mm or more, 2.2 N / 25 mm or more, 2.5 N / 25 mm or more, 2.7 N / 25 mm or more, 3 N / 25 mm or more, 3.2 N / 25 mm or more, and further can be 3.5 N / 25 mm or more. The upper limit of the above adhesion force is, for example, 7 N / 25 mm or less, can be 6 N / 25 mm or less, 5 N / 25 mm or less, and further can be 4 N / 25 mm or less. The initial adhesion force can be evaluated by performing the same peeling as in the first test on the optical laminate 10 before being left for 7 days, which is in a state of being attached to the surface of the glass sheet in the first test.

[0060] When the interlayer adhesion force of the first adhesive sheet 2 is less than 4.5 N / 25 mm, the adhesion force of the optical laminate 10 after 7 days can be 4.5 N / 25 mm or less. The interlayer adhesion force can also be 4.3 N / 25 mm or less, 4 N / 25 mm or less, and further can be 3.8 N / 25 mm or less. The lower limit of the interlayer adhesion force is, for example, 2.5 N / 25 mm or more, and can be 2.8 N / 25 mm or more, 3 N / 25 mm or more, 3.3 N / 25 mm or more, and further can be 3.5 N / 25 mm or more. The adhesion force of the optical laminate 10 after 7 days can be 4.2 N / 25 mm or less, 4 N / 25 mm or less, and further can be 3.9 N / 25 mm or less. The lower limit of the adhesion force after 7 days is, for example, 3 N / 25 mm or more. The interlayer adhesion force and the adhesion force after 7 days within the above ranges can help the arithmetic mean height Sa evaluated by the first test to reach the above ranges. The adhesion force after 7 days can be evaluated by performing the first test on the optical laminate 10.

[0061] When the interlayer adhesion force of the first adhesive sheet 2 is less than 4.5 N / 25 mm, the adhesion force of the optical laminate 10 after 14 days can be 6 N / 25 mm or less. The interlayer adhesion force can also be 4.3 N / 25 mm or less, 4 N / 25 mm or less, and further can be 3.8 N / 25 mm or less. The lower limit of the interlayer adhesion force is, for example, 2.5 N / 25 mm or more, and can be 2.8 N / 25 mm or more, 3 N / 25 mm or more, 3.3 N / 25 mm or more, and further can be 3.5 N / 25 mm or more. The adhesion force of the optical laminate 10 after 14 days can be 5.8 N / 25 mm or less, 5.5 N / 25 mm or less, 5.3 N / 25 mm or less, 5 N / 25 mm or less, 4.8 N / 25 mm or less, and further can be 4.6 N / 25 mm or less. The lower limit of the adhesion force after 14 days is, for example, 3.5 N / 25 mm or more. The interlayer adhesion force and the adhesion force after 14 days within the above ranges can help the arithmetic mean height Sa evaluated by the second test to reach the above ranges. The adhesion force after 14 days can be evaluated by performing the second test on the optical laminate 10.

[0062] The storage modulus G’ of the second adhesive sheet 4 at 25°C is 0.15 MPa or more. The storage modulus G’ can be 0.18 MPa or more, 0.2 MPa or more, 0.23 MPa or more, 0.25 MPa or more, 0.28 MPa or more, 0.3 MPa or more, 0.33 MPa or more, 0.35 MPa or more, 0.38 MPa or more, and further can be 0.4 MPa or more. The upper limit of the storage modulus G’ is, for example, 4 MPa or less, and can be 3.5 MPa or less, 3 MPa or less, 2.5 MPa or less, 2 MPa or less, 1.5 MPa or less, 1 MPa or less, 0.8 MPa or less, 0.6 MPa or less, 0.5 MPa or less, 0.4 MPa or less, and further can be 0.35 MPa or less. The storage modulus G’ can be measured by the following method. First, prepare a measurement adhesive sheet corresponding to the second adhesive sheet 4, and make a measurement sample from the prepared adhesive sheet. The shape of the measurement sample is disc-shaped, and the diameter of the bottom surface of the measurement sample is 8 mm and the thickness is 2 mm. The measurement sample can be formed by punching a laminate of multiple adhesive sheets into a disc shape. Next, perform dynamic viscoelasticity measurement on the measurement sample. Based on the results of the dynamic viscoelasticity measurement, the storage modulus G’ at 25°C can be determined. The dynamic viscoelasticity measurement can use, for example, ARES-G2 manufactured by TA Instruments. The conditions for the dynamic viscoelasticity measurement are as follows.

[0063] · Measurement conditions

[0064] Frequency: 1 Hz

[0065] Deformation mode: Torsion

[0066] Measurement temperature: -70°C to 150°C

[0067] Heating rate: 5°C / min

[0068] (Optical substrate 1)

[0069] The optical substrate 1 can optionally include one or two or more layers that can form an optical laminate. Examples of the layers that can be included in the optical substrate 1 are a polarizer, a transparent protective film, an adhesive sheet, an adhesive layer, and a surface protective film. However, the layers that can be included in the optical substrate 1 are not limited to the above examples. The optical substrate 1 can also include a glass film.

[0070] The optical substrate 1 can include a polarizer. The optical laminate 10 including a polarizer can be a polarizing film with an adhesive sheet. The optical laminate 10 including a polarizer and a retardation film can be a circularly polarized film with an adhesive sheet or an elliptically polarized film with an adhesive sheet.

[0071] Examples of the polarizer include films obtained by adsorbing dichroic substances such as iodine and dichroic dyes onto hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and partially saponified ethylene-vinyl acetate copolymer films, followed by unidirectional stretching; and polyene-oriented films such as dehydrated products of polyvinyl alcohol and dehydrochlorinated products of polyvinyl chloride. Among these, a polarizer formed from a polyvinyl alcohol film and a dichroic substance such as iodine is preferred, and an iodine-based polarizer containing iodine and / or iodide ions is more preferred. The thickness of the polarizer is not particularly limited and is usually about 5 to 80 μm. The polarizer is not limited to the above examples, and various polarizers can be used.

[0072] A polarizer formed by dyeing a polyvinyl alcohol film with iodine and performing unidirectional stretching can be produced, for example, by immersing the polyvinyl alcohol in an aqueous solution of iodine for dyeing and stretching it to 3 to 7 times its original length. If necessary, the polyvinyl alcohol can be immersed in an aqueous solution of potassium iodide containing boric acid, zinc sulfate, zinc chloride, etc. Further, if necessary, the polyvinyl alcohol film can be immersed in water for washing before dyeing. By washing the polyvinyl alcohol film, in addition to removing dirt and anti-sticking agents on the surface of the polyvinyl alcohol film, it is also possible to expect the effect of swelling the polyvinyl alcohol film to suppress the occurrence of uneven dyeing. The stretching of the polyvinyl alcohol film can be performed after dyeing with iodine, while dyeing, or before dyeing. The stretching can be performed in an aqueous solution of boric acid, potassium iodide, etc., or in a water bath.

[0073] As the polarizer, a thin polarizer with a thickness of 10 μm or less can be used. From the viewpoint of thinning, the thickness of the polarizer is preferably 1 to 7 μm. The thin polarizer tends to have less thickness unevenness and excellent visual recognition. In addition, it tends to be able to suppress dimensional changes and has excellent durability.

[0074] Representative examples of the thin polarizer are the polarizers described in each of Japanese Patent Application Laid-Open No. 51-069644, Japanese Patent Application Laid-Open No. 2000-338329, International Publication No. 2010 / 100917, Japanese Patent No. 4751481, and Japanese Patent Application Laid-Open No. 2012-073563. The polarizers in each publication can be obtained by a production method including a step of stretching a laminate of a polyvinyl alcohol resin (hereinafter also referred to as a PVA resin) layer and a stretching resin substrate, and a step of dyeing. According to this production method, since the PVA resin layer is supported by the stretching resin substrate, even when the PVA resin layer is thin, it is possible to suppress defects such as breakage caused by stretching.

[0075] In a production method including a step of stretching in a stacked state and a step of dyeing, from the aspect of being able to stretch at a high magnification and thereby improve the polarization performance, a production method including a step of stretching in an aqueous boric acid solution described in each of International Publication No. 2010 / 100917, Japanese Patent No. 4751481, and Japanese Unexamined Patent Application Publication No. 2012-073563 is preferred. Further, a production method including a step of stretching assistively in a gas atmosphere before stretching in an aqueous boric acid solution described in Japanese Patent No. 4751481 and Japanese Unexamined Patent Application Publication No. 2012-073563 is particularly preferred.

[0076] The optical substrate 1 may include a transparent protective film. The transparent protective film may function as a protective film for a polarizer. The transparent protective film is disposed, for example, in contact with the main surface (the surface having the largest area) of the layered polarizer. The polarizer may be disposed between two transparent protective films.

[0077] As the material of the transparent protective film, a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, etc. can be used, for example. Examples of the thermoplastic resin that can be used for the transparent protective film are cellulose resins such as cellulose triacetate, polyesters such as PET, polyethersulfone, polysulfone, polycarbonate, polyamide, polyimide, polyolefin, (meth)acrylic resin, cyclic polyolefin (norbornene resin), polyarylate, polystyrene, polyvinyl alcohol, and mixtures thereof. The material of the transparent protective film may be a thermosetting resin or an ultraviolet curable resin such as (meth)acrylic, urethane, acrylic urethane, epoxy, or silicone. When the polarizer is sandwiched between two transparent protective films, the materials of the respective transparent protective films may be the same or different. For example, a transparent protective film formed of a thermoplastic resin may be adhered to one main surface of the polarizer, and a transparent protective film formed of a thermosetting resin or an ultraviolet curable resin may be adhered to the other main surface.

[0078] When formed of a thermoplastic resin, the content of the thermoplastic resin in the transparent protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. When the content of the thermoplastic resin in the transparent protective film is 50% by weight or more, there is a tendency that the high transparency and the like originally possessed by the thermoplastic resin can be sufficiently exhibited.

[0079] The transparent protective film may also contain one or more additives. Examples of the additives are ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, and colorants. However, the additives are not limited to the above examples.

[0080] The thickness of the transparent protective film can be appropriately determined and can be about 10 to 200 μm from the viewpoints of workability such as strength and processability and film properties.

[0081] The polarizer and the transparent protective film can be adhered using an adhesive. The adhesive can be an aqueous adhesive. Examples of the aqueous adhesive are isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl-based latexes, aqueous polyurethanes, and aqueous polyesters. As other adhesives, ultraviolet curable adhesives, electron beam curable adhesives, etc. can be cited. The electron beam curable adhesive can exhibit suitable adhesiveness to various transparent protective films. The adhesive can also contain a metal compound filler.

[0082] A hard coat can be provided on the surface of the transparent protective film opposite to the surface in contact with the polarizer. In addition, various treatments for the purpose of antireflection, anti-adhesion, diffusion, antiglare, etc. can be applied to the opposite surface.

[0083] An example of the optical laminate 10 including the optical substrate 1 is shown in Figure 4 , where the optical substrate 1 includes a polarizer and a transparent protective film. Figure 4 The optical laminate 10B in

[0084] sequentially includes a first transparent protective film 12A, a polarizer 11, a second transparent protective film 12B, a first adhesive sheet 2, a second optical film 3, and a second adhesive sheet 4. The polarizer 11 is sandwiched between the first transparent protective film 12A and the second transparent protective film 12B. Each adjacent layer included in the optical substrate 1 is in contact with each other. Figure 5 Figure 5 Another example of the optical laminate 10 including the optical substrate 1 is shown in Figure 4 The optical laminate 10C in Figure 4is the same as the optical laminate 10B. The surface protective film 13 is in contact with the first transparent protective film 12A. The surface protective film 13 can have the function of protecting the outermost layer during the circulation and storage of the optical laminate 10C, and also in the state where the optical laminate 10C is introduced into the image display device. Additionally, the surface protective film 13 can be a surface protective film that functions as a window to the external space in the state of being introduced into the image display device. Typically, the surface protective film 13 is a resin film. Resins that can form the surface protective film 13 are, for example, polyesters such as PET, polyolefins such as polyethylene and polypropylene, acrylic acid, cycloolefins, polyimides, and polyamides, and polyesters are preferred. However, the surface protective film 13 is not limited to the above examples. The surface protective film 13 can also be a glass film or a laminated film containing a glass film. The surface protective film 13 can be subjected to surface treatments such as antiglare, antireflection, and antistatic. The surface protective film 13 can be joined to the transparent protective film 12A by an adhesive or an adhesive sheet. The adhesive sheet for joining the surface protective film 13 can be a layer exemplified as the first adhesive sheet 2 or the second adhesive sheet 4 in this specification. The thickness of the surface protective film 13 is, for example, 10 to 80 μm.

[0085] The thickness of the optical substrate 1 is, for example, 20 to 150 μm, and can be 50 to 100 μm.

[0086] The optical substrate 1 is not limited to the above examples.

[0087] (The first adhesive sheet 2)

[0088] The first adhesive sheet 2 is, for example, an acrylic adhesive sheet containing (meth)acrylic polymer (A) as the base polymer. The first adhesive sheet 2 can contain (meth)acrylic polymer (A) as the main component. However, the first adhesive sheet 2 is not limited to the above examples. The first adhesive sheet 2 containing (meth)acrylic polymer (A) as the main component can be a layer formed from an adhesive composition (B) containing (meth)acrylic polymer (A) as the main component. Additionally, the first adhesive sheet 2 containing (meth)acrylic polymer (A) as the main component can be a layer formed from a photocurable composition (C) containing a monomer group containing (meth)acrylic monomers and / or a partial polymer of the monomer group. In this specification, (meth)acrylate refers to acrylate and / or methacrylate. The main component refers to the component with the largest content rate. The content rate of the main component is, for example, 50% by weight or more, can be 60% by weight or more, 70% by weight or more, and further can be 80% by weight or more.

[0089] <(Meth)acrylic polymer (A)>

[0090] (Meth)acrylic polymer (A) may have a structural unit derived from an alkyl (meth)acrylate. The structural unit derived from an alkyl (meth)acrylate may be the main structural unit in (meth)acrylic polymer (A). In the present specification, the main structural unit means the structural unit having the largest content rate in the polymer. The content rate of the main structural unit is, for example, 50% by weight or more, may be 60% by weight or more, 70% by weight or more, and further may be 80% by weight or more.

[0091] The number of carbon atoms of the alkyl group in the alkyl (meth)acrylate is not particularly limited, and is, for example, 1 to 30. The alkyl group may be linear, branched, or cyclic. Examples of the alkyl group are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, hexyl, cyclohexyl, heptyl, 2-ethylhexyl, isooctyl, nonyl, decyl, isodecyl, dodecyl, isotetradecyl, lauryl, tridecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl. The alkyl (meth)acrylate may be used alone, or two or more thereof may be used in combination. In the case of using two or more in combination, the average number of carbon atoms of the alkyl group is preferably 3 to 9. The alkyl (meth)acrylate is preferably butyl acrylate.

[0092] In (meth)acrylic polymer (A), the content rate of the structural unit derived from an alkyl (meth)acrylate may be 50% by weight or more, 60% by weight or more, 70% by weight or more, and further may be 80% by weight or more.

[0093] Other examples of the monomer capable of forming (meth)acrylic polymer (A) are at least one monomer selected from an aromatic ring-containing monomer, an amide group-containing monomer, a carboxyl group-containing monomer, and a hydroxyl group-containing monomer. In other words, (meth)acrylic polymer (A) may have a structural unit derived from at least one monomer selected from an aromatic ring-containing monomer, an amide group-containing monomer, a carboxyl group-containing monomer, and a hydroxyl group-containing monomer. These monomers may be used alone, or two or more thereof may be used in combination.

[0094] (Meth)acrylic polymer (A) may have a structural unit derived from an alkyl (meth)acrylate and a structural unit derived from at least one monomer selected from an aromatic ring-containing monomer, an amide group-containing monomer, a carboxyl group-containing monomer, and a hydroxyl group-containing monomer.

[0095] (Meth)acrylic polymer (A) may have a structural unit derived from a carboxyl group-containing monomer. The carboxyl group-containing monomer is a compound that contains a carboxyl group in its structure and contains a polymerizable unsaturated double bond such as (meth)acryloyl group or vinyl group. Examples of the carboxyl group-containing monomer are (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Among these, acrylic acid is preferred from the viewpoints of copolymerizability, price, and improvement of the adhesive properties of the adhesive sheet.

[0096] When having a structural unit derived from a carboxyl group-containing monomer, particularly acrylic acid, it is suitable for improving the self-polymerization property of the isocyanate crosslinking agent that can be contained in the adhesive composition (B). Specifically, the structural unit derived from the carboxyl group-containing monomer has a tendency to promote the reaction between isocyanate crosslinking agents by introducing water molecules in the atmosphere. The improvement of the self-polymerization property of the isocyanate crosslinking agent is particularly helpful for, for example, suppressing the peeling of the adhesive sheet in a humid environment and stabilizing the physical properties of the adhesive sheet in a system with a high content of the isocyanate crosslinking agent. When having a structural unit derived from a carboxyl group-containing monomer, it is also suitable for suppressing the excessive increase in the adhesive strength of the adhesive sheet that occurs over time.

[0097] (Meth)acrylic polymer (A) may have a structural unit derived from an aromatic ring-containing monomer. The aromatic ring-containing monomer is a compound that contains an aromatic ring structure in its structure and contains a polymerizable unsaturated double bond such as (meth)acryloyl group or vinyl group. Examples of the aromatic ring are benzene ring, naphthalene ring, and biphenyl ring. The aromatic ring-containing monomer is preferably an aromatic ring-containing (meth)acrylate.

[0098] Examples of the aromatic ring-containing (meth)acrylate are (meth)acrylates having a benzene ring such as benzyl (meth)acrylate, phenyl (meth)acrylate, o-phenylphenol (meth)acrylate, phenoxymethyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxypropyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, ethylene oxide-modified nonylphenol (meth)acrylate, ethylene oxide-modified cresol (meth)acrylate, phenol ethylene oxide-modified (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, methoxybenzyl (meth)acrylate, chlorobenzyl (meth)acrylate, tolyl (meth)acrylate, styryl (meth)acrylate; (meth)acrylates having a naphthalene ring such as hydroxyethylated β-naphthol acrylate, 2-naphthyl ethyl (meth)acrylate, 2-naphthoxyethyl acrylate, 2-(4-methoxy-1-naphthyloxy)ethyl (meth)acrylate; aromatic ring-containing (meth)acrylates having a biphenyl ring such as biphenyl (meth)acrylate. Among these, from the viewpoints of improving the adhesive properties and durability of the adhesive sheet, benzyl (meth)acrylate and phenoxyethyl (meth)acrylate are preferred, and benzyl acrylate is more preferred.

[0099] The structural unit derived from the aromatic ring-containing monomer can improve the compatibility of the (meth)acrylic polymer (A) with the polymer (D) mainly composed of the structural unit derived from the isocyanate crosslinking agent described later, and thus is suitable for maintaining the transparency of the adhesive sheet. In addition, the structural unit derived from the aromatic ring-containing monomer is also suitable for adjusting the adhesiveness of the adhesive sheet.

[0100] (Meth)acrylic polymer (A) may have a structural unit derived from an amide group-containing monomer. The amide group-containing monomer is a compound that contains an amide group in its structure and contains a polymerizable unsaturated double bond such as (meth)acryloyl group and vinyl group. Examples of the amide group-containing monomer are acrylamide monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropylacrylamide, N-methyl(meth)acrylamide, N-butyl(meth)acrylamide, N-hexyl(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-hydroxymethyl-N-propyl(meth)acrylamide, aminomethyl(meth)acrylamide, aminoethyl(meth)acrylamide, mercaptomethyl(meth)acrylamide, mercaptoethyl(meth)acrylamide; N-acryloyl heterocyclic monomers such as N-(meth)acryloylmorpholine, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine; N-vinyl lactam monomers containing N-vinyl such as N-vinylpyrrolidone, N-vinyl-ε-caprolactam. Among these, from the viewpoint of improving the durability of the adhesive sheet, N-vinyl lactam monomers are preferred.

[0101] (Meth)acrylic polymer (A) may have a structural unit derived from a hydroxyl group-containing monomer. The hydroxyl group-containing monomer is a compound that contains a hydroxyl group in its structure and contains a polymerizable unsaturated double bond such as (meth)acryloyl group and vinyl group. Examples of the hydroxyl group-containing monomer are hydroxyl group-containing (meth)acrylic acid alkyl esters such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxydodecyl (meth)acrylate; hydroxyl group-containing (meth)acrylic acid cycloalkyl esters such as methyl (4-hydroxymethylcyclohexyl) acrylate. Among these, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred.

[0102] In the (meth)acrylic polymer (A), the total content ratio of structural units derived from at least one monomer selected from aromatic ring-containing monomers, amide group-containing monomers, carboxyl group-containing monomers, and hydroxyl group-containing monomers is, for example, 0 to 40% by weight, may be 0.1 to 30% by weight, and further may be 0.1 to 20% by weight. However, the content ratio is not limited to the above examples.

[0103] When the (meth)acrylic polymer (A) has a structural unit derived from a carboxyl group-containing monomer, the content ratio of this structural unit is not particularly limited. For example, it is 0.1% by weight or more, may be 1% by weight or more, 2% by weight or more, 3% by weight or more, and further may be 4% by weight or more. The upper limit of the content ratio is, for example, 25% by weight or less, may be 20% by weight or less, and further may be 10% by weight or less. The (meth)acrylic polymer (A) may also not have a structural unit derived from a carboxyl group-containing monomer.

[0104] When the (meth)acrylic polymer (A) has a structural unit derived from an aromatic ring-containing monomer, the content ratio of this structural unit is not particularly limited. For example, it is 3 to 25% by weight, may be 22% by weight or less, and further may be 20% by weight or less. The lower limit of the content ratio may be 8% by weight or more, and further may be 12% by weight or more. The (meth)acrylic polymer (A) may also not have a structural unit derived from an aromatic ring-containing monomer.

[0105] When the (meth)acrylic polymer (A) has a structural unit derived from an amide group-containing monomer, the content ratio of this structural unit is not particularly limited. For example, it is 0.1 to 10% by weight, may be 0.2 to 8% by weight, and further may be 0.6 to 6% by weight. The (meth)acrylic polymer (A) may also not have a structural unit derived from an amide group-containing monomer.

[0106] When the (meth)acrylic polymer (A) has a structural unit derived from a hydroxyl group-containing monomer, the content ratio of this structural unit is not particularly limited. For example, it is 1% by weight or less, may be 0.5% by weight or less, and further may be 0.1% by weight or less. The (meth)acrylic polymer (A) may also not have a structural unit derived from a hydroxyl group-containing monomer.

[0107] The (meth)acrylic polymer (A) may further have a structural unit derived from a comonomer other than the above monomers. The comonomer can be used, for example, for the purpose of improving the adhesiveness and heat resistance of the adhesive sheet. The comonomer can be used alone or two or more thereof can be used in combination.

[0108] The comonomer usually has a polymerizable functional group containing an unsaturated double bond such as (meth)acryloyl or vinyl. Examples of the comonomer include acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; caprolactone adducts of acrylic acid; sulfonic acid group-containing monomers such as allyl sulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, and (meth)acrylic acid sulfopropyl ester; phosphoric acid group-containing monomers such as 2-hydroxyethyl acryloyl phosphate; (meth)acrylic acid alkylaminoalkyl esters such as (meth)acrylic acid aminoethyl ester, (meth)acrylic acid N,N-dimethylaminoethyl ester, and (meth)acrylic acid tert-butylaminoethyl ester; (meth)acrylic acid alkoxyalkyl esters such as (meth)acrylic acid methoxyethyl ester and (meth)acrylic acid ethoxyethyl ester; succinimide monomers such as N-(meth)acryloxymethylene succinimide, N-(meth)acryloyl-6-oxohexamethylene succinimide, and N-(meth)acryloyl-8-oxooctamethylene succinimide; maleimide monomers such as N-cyclohexyl maleimide, N-isopropyl maleimide, N-dodecyl maleimide, and N-phenyl maleimide; itaconimide monomers such as N-methyl itaconimide, N-ethyl itaconimide, N-butyl itaconimide, N-octyl itaconimide, N-2-ethylhexyl itaconimide, N-cyclohexyl itaconimide, and N-dodecyl itaconimide; vinyl monomers such as vinyl acetate and vinyl propionate; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; epoxy group-containing (meth)acrylates such as (meth)acrylic acid glycidyl ester; diol (meth)acrylates such as polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, and methoxypolypropylene glycol (meth)acrylate; (meth)acrylate monomers such as (meth)acrylic acid tetrahydrofurfuryl ester, fluorine-containing (meth)acrylate, polysiloxane (meth)acrylate, and 2-methoxyethyl acrylate; silane monomers containing silicon atoms such as 3-acryloxypropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 4-vinylbutyltrimethoxysilane, 4-vinylbutyltriethoxysilane, 8-vinyloctyltrimethoxysilane, 8-vinyloctyltriethoxysilane, 10-methacryloyloxydecyltrimethoxysilane, 10-acryloyloxydecyltrimethoxysilane, 10-methacryloyloxydecyltriethoxysilane, and 10-acryloyloxydecyltriethoxysilane.

[0109] Other examples of comonomers are polyfunctional monomers having two or more unsaturated double bonds such as tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, bisphenol A diglycidyl ether di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and caprolactone-modified dipentaerythritol hexa(meth)acrylate.

[0110] When the (meth)acrylic polymer (A) has a structural unit derived from a comonomer, the content rate of this structural unit is, for example, 10% by weight or less, can be 7% by weight or less, and further can be 5% by weight or less. The (meth)acrylic polymer (A) may not have a structural unit derived from a comonomer.

[0111] The weight-average molecular weight of the (meth)acrylic polymer (A) is generally 300,000 to 4,000,000. From the viewpoint of durability, the weight-average molecular weight of the (meth)acrylic polymer (A) is preferably 1,000,000 or more, and can also be 1,500,000 or more. The weight-average molecular weight of the (meth)acrylic polymer (A) can be 3,000,000 or less, and can also be 2,000,000 or less. From the aspect of heat resistance, a weight-average molecular weight of 300,000 or more is preferred. When the weight-average molecular weight is 4,000,000 or less, the adhesive sheet tends not to harden easily and not to peel off easily. The weight-average molecular weight (Mw) / number-average molecular weight (Mn) representing the molecular weight distribution is preferably 1.8 to 10, more preferably 1.8 to 7, and further preferably 1.8 to 5. From the aspect of durability, a molecular weight distribution (Mw / Mn) of 10 or less is preferred. The weight-average molecular weight and the molecular weight distribution (Mw / Mn) can be determined by measurement by GPC (gel permeation chromatography) and calculated by conversion to polystyrene.

[0112] The (meth)acrylic polymer (A) can be formed by various known polymerization methods such as solution polymerization, radiation polymerization using electron beams, ultraviolet rays (UV), etc., bulk polymerization, and emulsion polymerization. The polymerization is typically radical polymerization. The (meth)acrylic polymer (A) can be any copolymer such as a random copolymer, a block copolymer, a graft copolymer, etc. However, the formation method of the (meth)acrylic polymer (A) is not limited to the above examples. It should be noted that when the adhesive sheet is a layer formed from the photocurable composition (C), the (meth)acrylic polymer (A) is mainly formed by radiation polymerization using electron beams, UV, etc.

[0113] As the polymerization solvent for solution polymerization, known polymerization solvents such as ethyl acetate and toluene can be used, for example. Solution polymerization can be carried out, for example, under an inert gas stream such as nitrogen while using a polymerization initiator. The polymerization conditions are, for example, 50 to 70 °C and 5 to 30 hours.

[0114] The polymerization initiator, chain transfer agent, emulsifier, etc. for radical polymerization are not particularly limited and can be appropriately selected. The weight-average molecular weight of the (meth)acrylic polymer (A) can be controlled according to the types and amounts of the polymerization initiator and chain transfer agent, as well as the polymerization conditions, etc.

[0115] Examples of the polymerization initiator are azo initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(2-methylpropionamidine) disulfate, 2,2'-azobis(N,N'-dimethylisobutyramidine), 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate (for example, VA-057 manufactured by Wako Pure Chemical Industries, Ltd.); persulfates such as potassium persulfate and ammonium persulfate; peroxide initiators such as di(2-ethylhexyl) peroxydicarbonate, di(4-tert-butylcyclohexyl) peroxydicarbonate, di-sec-butyl peroxydicarbonate, tert-butyl peroxyneodecanoate, tert-hexyl peroxypivalate, tert-butyl peroxypivalate, dilauroyl peroxide, dioctanoyl peroxide, 1,1,3,3-tetramethylbutyl 2-ethylhexanoate peroxide, bis(4-methylbenzoyl) peroxide, benzoyl peroxide, tert-butyl peroxyisobutyrate, 1,1-bis(tert-hexylperoxy)cyclohexane, tert-butyl hydroperoxide, hydrogen peroxide; redox initiators combining peroxides and reducing agents such as a combination of persulfate and sodium bisulfite, and a combination of peroxide and sodium ascorbate. However, the polymerization initiator is not limited to the above examples.

[0116] The polymerization initiator can be used alone or two or more thereof can be used in combination. The total amount of the polymerization initiator used is, for example, 0.005 to 1 part by weight, and can also be 0.02 to 0.5 part by weight, based on 100 parts by weight of the monomer component.

[0117] Examples of the chain transfer agent are dodecyl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimercapto-1-propanol. The chain transfer agent can be used alone or two or more thereof can be used in combination. The total amount of the chain transfer agent used is, for example, 0.1 part by weight or less, based on 100 parts by weight of the monomer component.

[0118] In radiation polymerization, polymerization is carried out by irradiating a monomer group with radiation such as an electron beam or UV, thereby forming a (meth)acrylic polymer (A). In the case of forming an adhesive sheet from a photocurable composition (C), polymerization is carried out by irradiating the photocurable composition (C) with light, thereby forming a (meth)acrylic polymer (A). In the case of radiation polymerization using an electron beam, it is not particularly necessary to use a photoinitiator. In the case of radiation polymerization using UV, a photoinitiator can be used because of advantages such as the ability to shorten the polymerization time. The photoinitiator can be used alone or two or more thereof can be used in combination.

[0119] Examples of the photoinitiator are various photoinitiators such as benzoin ethers, acetophenones, α-hydroxy ketones, photoactive oximes, benzoins, benzils, benzophenones, ketals, thioxanthones, etc. However, the photoinitiator is not limited to the above examples. The amount of the photoinitiator is, for example, 0.05 to 1.5 parts by weight, and can also be 0.1 to 1 part by weight with respect to 100 parts by weight of the monomer component.

[0120] <Adhesive composition (B)>

[0121] The adhesive composition (B) is typically a composition capable of forming an adhesive sheet by drying. In this case, the adhesive sheet formed from the adhesive composition (B) usually becomes a solvent type (also called a thermosetting type).

[0122] The adhesive composition (B) may contain a crosslinking agent. Examples of the crosslinking agent that can be contained in the adhesive composition (B) are isocyanate crosslinking agents, peroxide crosslinking agents, epoxy crosslinking agents, imine crosslinking agents, and polyfunctional metal chelates. The adhesive composition (B) preferably contains an isocyanate crosslinking agent and a peroxide crosslinking agent, and more preferably contains an isocyanate crosslinking agent.

[0123] As the isocyanate 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 are aromatic isocyanate compounds, alicyclic isocyanate compounds, and aliphatic isocyanate compounds. The isocyanate crosslinking agent is preferably a compound capable of self-polymerization by reaction with water.

[0124] Examples of the aromatic isocyanate compounds are phthalic diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene 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.

[0125] Examples of the alicyclic isocyanate compounds are 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated toluene diisocyanate, and hydrogenated tetramethylxylylene diisocyanate.

[0126] Examples of the aliphatic isocyanate compounds are trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.

[0127] The isocyanate crosslinking agent may be a polymer (dimer, trimer, pentamer, etc.) of the above isocyanate compounds, an adduct obtained by adding a polyol such as trimethylolpropane, a urea-modified product, a biuret-modified product, a urethane-modified product, an isocyanurate-modified product, a carbodiimide-modified product, or a urethane prepolymer obtained by adding a polyether polyol, a polyester polyol, an acrylic polyol, a polybutadiene polyol, a polyisoprene polyol, or the like.

[0128] The isocyanate crosslinking agent is preferably an aromatic isocyanate compound and its derivative, more preferably toluene diisocyanate and its derivative, that is, a toluene diisocyanate-based (TDI-based) crosslinking agent. From the viewpoint of reactivity, the TDI-based crosslinking agent is more suitable than xylylene diisocyanate and its derivative, that is, a xylylene diisocyanate-based (XDI-based) crosslinking agent. The isocyanate crosslinking agent may contain an adduct of a polyol and toluene diisocyanate as the TDI-based crosslinking agent. Specific examples of the adduct are trimethylolpropane / toluene diisocyanate trimer adduct.

[0129] Isocyanate crosslinking agents can be commercially available products. Examples of commercially available products are Millionate MT, Millionate MTL, Millionate MR-200, Millionate MR-400, Coronate L, Coronate HL, Coronate HX (the above are manufactured by Tosoh Corporation), Takenate D-101E, Takenate D-110N, Takenate D-120N, Takenate D-140N, Takenate D-160N, Takenate D-165N, Takenate D-170HN, Takenate D-178N, Takenate 500, Takenate 600 (the above are manufactured by Mitsui Chemicals, Inc.). Among these, Takenate D-101E is preferred.

[0130] Isocyanate crosslinking agents can be used alone or two or more of them can be used in combination.

[0131] With respect to 100 parts by weight of the (meth)acrylic polymer (A), the compounding amount of the isocyanate crosslinking agent in the adhesive composition (B) is, for example, 0.01 to 20 parts by weight. The lower limit of the compounding amount can be 0.05 parts by weight or more, 0.1 parts by weight or more, and further can be 0.15 parts by weight or more. The upper limit of the compounding amount can be 15 parts by weight or less, 13 parts by weight or less, 10 parts by weight or less, 8 parts by weight or less, 5 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, and further can be 0.5 parts by weight or less.

[0132] In the adhesive composition (B), when the compounding amount of the isocyanate crosslinking agent is about 2 parts by weight or more with respect to 100 parts by weight of the (meth)acrylic polymer (A), sometimes a polymer (D) mainly composed of structural units derived from the isocyanate crosslinking agent is formed by the reaction between the isocyanate crosslinking agents when forming the adhesive sheet. The formation of the polymer (D) can contribute to the improvement of the cohesion of the adhesive sheet and the suppression of the dimensional change of the adhesive sheet caused thereby. In addition, the combination of the (meth)acrylic polymer (A) and the polymer (D) is suitable for improving the durability of the adhesive sheet in a high-temperature and high-humidity environment.

[0133] With respect to 100 parts by weight of the (meth)acrylic polymer (A), the compounding amount of the crosslinking agent other than isocyanates in the adhesive composition (B) is preferably 2 parts by weight or less, more preferably 1 part by weight or less. From the viewpoint of the durability of the adhesive sheet, the adhesive composition (B) can substantially contain no crosslinking agent other than isocyanates, especially epoxy crosslinking agents.

[0134] The adhesive composition (B) may also contain an oligomer. Examples of the oligomer that may be contained in the adhesive composition (B) are (meth)acrylic oligomers. However, the oligomer is not limited to the above examples. The oligomer may also be a tackifier.

[0135] The weight-average molecular weight (Mw) of the oligomer is, for example, 1000 or more, may be 2000 or more, 3000 or more, and further may be 4000 or more. The upper limit of Mw is, for example, 30000 or less, may be 15000 or less, 10000 or less, and further may be 7000 or less.

[0136] (The (meth)acrylic oligomer may have the same composition as the above-mentioned (meth)acrylic polymer (A) except for the difference in Mw.

[0137] (The (meth)acrylic oligomer has, for example, one or two or more structural units derived from the following monomers: (meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, and dodecyl (meth)acrylate; esters of (meth)acrylic acid and alicyclic alcohols such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentyl (meth)acrylate; aromatic ring-containing (meth)acrylic esters such as phenyl (meth)acrylate and benzyl (meth)acrylate; and (meth)acrylic esters obtained from terpene compound-derived alcohols.

[0138] Preferably, the (meth)acrylic oligomer has a structural unit derived from a (meth)acrylic monomer having a relatively large structure. In this case, the adhesiveness of the adhesive sheet can be further improved. Examples of the acrylic monomer include (meth)acrylic alkyl esters containing an alkyl group having a branched structure such as isobutyl (meth)acrylate and tert-butyl (meth)acrylate; esters formed from (meth)acrylic acid and an alicyclic alcohol such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentyl (meth)acrylate; and (meth)acrylic esters containing an aromatic ring such as phenyl (meth)acrylate and benzyl (meth)acrylate. It is preferred that the monomer has a cyclic structure, and more preferably has two or more cyclic structures. Further, from the viewpoint of not easily hindering the polymerization and / or formation when ultraviolet irradiation is carried out during the polymerization of the (meth)acrylic oligomer and / or the formation of the adhesive sheet, it is preferred that the above monomer does not have an unsaturated bond. For example, (meth)acrylic alkyl esters containing an alkyl group having a branched structure and esters formed from (meth)acrylic acid and an alicyclic alcohol can be used.

[0139] Specific examples of the (meth)acrylic oligomer are copolymers of butyl acrylate, methyl acrylate and acrylic acid, copolymers of cyclohexyl methacrylate and isobutyl methacrylate, copolymers of cyclohexyl methacrylate and isobornyl methacrylate, copolymers of cyclohexyl methacrylate and acryloylmorpholine, copolymers of cyclohexyl methacrylate and diethylacrylamide, copolymers of 1-adamantyl acrylate and methyl methacrylate, copolymers of dicyclopentyl methacrylate and isobornyl methacrylate, copolymers of at least one selected from dicyclopentyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, isobornyl acrylate and cyclopentyl methacrylate and methyl methacrylate, homopolymers of dicyclopentyl acrylate, homopolymers of 1-adamantyl methacrylate and homopolymers of 1-adamantyl acrylate.

[0140] Examples of the polymerization method of the (meth)acrylic oligomer are the same as those of the polymerization method of the above (meth)acrylic polymer (A).

[0141] When the adhesive composition (B) contains an oligomer, its blending amount is, for example, 70 parts by weight or less, and may be 50 parts by weight or less, and further may be 40 parts by weight or less, relative to 100 parts by weight of the (meth)acrylic polymer (A). The lower limit of the blending amount is, for example, 1 part by weight or more, and may be 2 parts by weight or more, and further may be 3 parts by weight or more, relative to 100 parts by weight of the (meth)acrylic polymer (A). The adhesive composition (B) may also not contain an oligomer.

[0142] The adhesive composition (B) may further contain known additives. Examples of the additives are silane coupling agents, solvents, colorants, pigments, powders, dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners, antioxidants, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, inorganic or organic fillers, metal powders, particles, and foils. In the range that can be controlled, redox types added with reducing agents can also be used. However, the additives are not limited to the above examples. With respect to 100 parts by weight of the (meth)acrylic polymer (A), the total blending amount of the additives is, for example, 10 parts by weight or less, may be 5 parts by weight or less, and further may be 1 part by weight or less.

[0143] The adhesive composition (B) may contain a silane coupling agent as an additive. Examples of the silane coupling agent are epoxy group-containing silane coupling agents such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; amino group-containing silane coupling agents such as 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutyl)propylamine, N-phenyl-γ-aminopropyltrimethoxysilane; (meth)acryloyl group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane; and isocyanate group-containing silane coupling agents such as 3-isocyanatopropyltriethoxysilane.

[0144] When the adhesive composition (B) contains a silane coupling agent, with respect to 100 parts by weight of the (meth)acrylic polymer (A), the blending amount is, for example, 5 parts by weight or less, may be 3 parts by weight or less, 1 part by weight or less, 0.5 part by weight or less, 0.4 part by weight or less, 0.2 part by weight or less, and further may be 0.1 part by weight or less. The lower limit of the blending amount is not particularly limited and is, for example, 0.02 part by weight or more. The adhesive composition (B) may also not contain a silane coupling agent.

[0145] The adhesive composition (B) may also be substantially free of photocuring agents such as photoinitiators.

[0146] The first adhesive sheet 2 can be formed, for example, by drying a coating film of the adhesive composition (B) provided on a substrate. Drying can be carried out by heating. As the substrate, a release film can be used. The first adhesive sheet 2 formed on the release film can be transferred, for example, to the optical substrate 1 and other layers that the optical laminate 10 such as the first optical film 3 may include. The substrate can be the optical substrate 1 and other layers that the optical laminate 10 such as the first optical film 3 may include. However, the method for forming the first adhesive sheet 2 from the adhesive composition (B) is not limited to the above examples.

[0147] As the release film, a known film that can be used when forming a solvent-based adhesive sheet can be used.

[0148] The drying temperature of the coating film is, for example, 130°C or lower, and can be 125°C or lower, 120°C or lower, 110°C or lower, and further can be 100°C or lower. The drying temperature is, for example, 60°C or higher, and can also be 80°C or higher. The drying time of the coating film can be appropriately adjusted according to the composition of the adhesive composition (B), and is, for example, 30 seconds to 300 seconds, 40 seconds to 240 seconds, and further can be 60 seconds to 180 seconds.

[0149] <Photocurable composition (C)>

[0150] The photocurable composition (C) is a composition that can form an adhesive sheet by irradiation with light. The adhesive sheet formed from the photocurable composition (C) generally becomes a photocurable type. The photocurable composition (C) contains, for example, a monomer group containing (meth)acrylic monomers and / or a partial polymer of the monomer group. The content of the (meth)acrylic components in the photocurable composition, that is, the (meth)acrylic monomers and their partial polymers, can be 50% by weight or more, 60% by weight or more, 70% by weight or more, and further can be 80% by weight or more. In this case, an acrylic adhesive sheet mainly composed of (meth)acrylic polymers and their crosslinked products can be formed.

[0151] Examples of the monomers that the monomer group can contain are the same as those described above in the description of the (meth)acrylic polymer (A).

[0152] The photocurable composition (C) generally contains a photoinitiator. Examples of the photoinitiator are photo radical generators that generate radicals by visible light and / or ultraviolet light having a wavelength shorter than 450 nm. Examples of the photoinitiator are the same as those described above in the description of the (meth)acrylic polymer (A). The blending amount of the photoinitiator in the photocurable composition (C) is, for example, 0.02 to 10 parts by weight, and can also be 0.05 to 5 parts by weight, based on 100 parts by weight in total of the monomer group and its partial polymer.

[0153] The photocurable composition (C) may contain a crosslinking agent. Examples of the crosslinking agent are polyfunctional monomers 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 monomers having two or more C═C bonds in one molecule, and monomers having one or more C═C bonds, and one or more epoxy groups, aziridinyl groups, oxazolinyl groups, hydrazino groups, hydroxymethyl groups and other polymerizable functional groups in one molecule. The polyfunctional monomer is preferably a monomer having two or more C═C bonds in one molecule.

[0154] Examples of the crosslinking agent that the photocurable composition (C) may contain are (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 (NDDA), 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate and other polyfunctional acrylates (ester compounds formed from polyhydric alcohols and (meth)acrylic acid, etc.); allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyl di(meth)acrylate, hexyl di(meth)acrylate. The polyfunctional monomer is preferably a polyfunctional acrylate, more preferably trimethylolpropane tri(meth)acrylate, hexanediol di(meth)acrylate, dipentaerythritol hexa(meth)acrylate.

[0155] The blending amount of the crosslinking agent varies depending on the molecular weight, the number of functional groups, etc., but is, for example, 5 parts by weight or less, may also be 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, and further may be 0.5 part by weight or less, per 100 parts by weight in total of the monomer group and its partial polymers. The lower limit of the blending amount is, for example, 0.01 part by weight or more, and further may be 0.05 part by weight % or more.

[0156] The photocurable composition (C) may also contain additives other than those described above. Examples of the additives are chain transfer agents, silane coupling agents, viscosity modifiers, tackifiers, plasticizers, softeners, anti-aging agents, fillers, colorants, antioxidants, surfactants, antistatic agents and ultraviolet absorbers. However, the additives are not limited to the above examples. Examples of the silane coupling agent are the same as those described above in the description of the adhesive composition (B).

[0157] The content rate of the solvent in the photocurable composition (C) is, for example, 5% by weight or less, and may be 4% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, and further may be 0.5% by weight or less. The photocurable composition (C) may substantially not contain a solvent. Substantially not containing a solvent means that it is allowed to contain solvents, etc. from additives, etc. at a content rate of, for example, 0.1% by weight or less, preferably 0.05% by weight or less, and more preferably 0.01% by weight or less.

[0158] The viscosity of the photocurable composition (C) is preferably 5 to 100 poise.

[0159] The first adhesive sheet 2 can be formed, for example, by irradiating light on a coating film of the photocurable composition (C) provided on a substrate. A release film can be used as the substrate. The first adhesive sheet 2 formed on the release film can be transferred, for example, to the optical substrate 1 and other layers that the optical laminate 10 such as the first optical film 3 may include. However, the method of forming the first adhesive sheet 2 from the photocurable composition (C) is not limited to the above examples.

[0160] The irradiated light is, for example, visible light or ultraviolet light having a wavelength shorter than 450 nm. The light may include light having a wavelength in the same region as the absorption wavelength of the photoinitiator contained in the photocurable composition. Light obtained by blocking short-wavelength light of 300 nm or less through a filter, etc. can be irradiated. The light source of the light is, for example, a light irradiation device equipped with an ultraviolet irradiation lamp. Examples of the ultraviolet irradiation lamp are ultraviolet 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 lights, chemical lamps, germicidal lamps, low-pressure discharge mercury lamps, and excimer lasers. Two or more ultraviolet irradiation lamps can also be combined.

[0161] The irradiation intensity of the light is, for example, 1 to 20 mW / cm 2 . The cumulative light amount of the light is, for example, 100 to 5000 mJ / cm 2 .

[0162] The thickness of the first adhesive sheet 2 is, for example, 1 to 50 μm, and may be 2 to 30 μm, 2 to 25 μm, and further may be 5 to 20 μm.

[0163] The storage modulus G' of the first adhesive sheet 2 at 25°C may be smaller than the storage modulus G' of the second adhesive sheet 4 at 25°C. The storage modulus G' of the first adhesive sheet 2 at 25°C may be less than 0.15 MPa, may be 0.14 MPa or less, 0.12 MPa or less, and further may be 0.1 MPa or less. The lower limit of the storage modulus G' is, for example, 0.01 MPa or more, and may also be 0.03 MPa or more, and further may be 0.05 MPa or more.

[0164] The first adhesive sheet 2 is not limited to the above examples.

[0165] (The first optical film 3)

[0166] The thickness of the first optical film 3 is 15 μm or less. The thickness of the first optical film 3 can be 13 μm or less, 11 μm or less, 10 μm or less, 8 μm or less, 6 μm or less, 5 μm or less, 4 μm or less, 3 μm or less, 2.5 μm or less, 2 μm or less, 1.5 μm or less, and further can be 1 μm or less. The lower limit of the thickness is, for example, 0.5 μm or more, can be 0.7 μm or more, and further can be 1 μm or more.

[0167] The first optical film 3 is, for example, a retardation film. However, the first optical film 3 is not limited to a retardation film. The retardation film, for example, has a refractive index characteristic represented by the formula nx > ny and has a slow axis. However, the retardation film is not limited to the above examples. The retardation film can, for example, have a refractive index characteristic represented by the formula nz > nx = ny and has various refractive index characteristics known as a retardation film. In the present specification, nx, ny, and nz are the refractive index in the direction (slow axis) where the refractive index in the plane of the film reaches the maximum, the refractive index in the direction (fast axis) orthogonal to the slow axis in the plane, and the refractive index in the thickness direction, respectively.

[0168] Hereinafter, the retardation film that can be the first optical film 3 will be described. The retardation film can have a Re(550) of 10 nm or more, 30 nm or more, 50 nm or more, 80 nm or more, and further can have 100 nm or more. Re(550) is the in-plane phase difference of the retardation film with respect to light having a wavelength of 550 nm. The in-plane phase difference can be obtained by setting the thickness of the retardation film to d (nm) and using the formula Re = (nx - ny) × d.

[0169] The Re(550) of the retardation film can be 100 nm to 180 nm, 110 to 170 nm, 120 to 160 nm, and further can be 135 nm to 155 nm. In this case, the retardation film can function as a so-called λ / 4 wave plate. The Re(550) of the retardation film can be 180 nm to 320 nm, 200 to 290 nm, and further can be 230 to 280 nm. In this case, the retardation film can function as a so-called λ / 2 wave plate. The first optical film 3 can be a layer that can function as a λ / 4 wave plate or a λ / 2 wave plate. When the first optical film 3 is a layer that can function as a λ / 4 wave plate and the optical substrate 1 includes a polarizer, the optical laminate 10 can be an elliptically polarized film or a circularly polarized film.

[0170] The retardation film may be an alignment fixing layer for a liquid crystal compound (hereinafter referred to as a liquid crystal alignment fixing layer). In other words, the first optical film 3 may be a liquid crystal alignment fixing layer. In this specification, the liquid crystal alignment fixing layer refers to a layer in which a liquid crystal compound is aligned in a given direction within the layer and its alignment state is fixed. It should be noted that the liquid crystal alignment fixing layer includes an alignment curing layer obtained by curing a liquid crystal monomer. The liquid crystal alignment fixing layer is suitable for obtaining a desired retardation while reducing the thickness.

[0171] In the liquid crystal alignment fixing layer, typically, rod-shaped liquid crystal compounds are aligned in a state of being arranged along a given direction (homogeneous alignment). Examples of the liquid crystal compound are nematic liquid crystals and discotic liquid crystals. The liquid crystal compound may be a liquid crystal polymer or a liquid crystal monomer. The liquid crystal monomer may have polymerizability and / or crosslinkability.

[0172] Specific examples of the liquid crystal monomer are polymerizable mesogenic compounds described in each of Japanese Patent Application Laid-Open No. 2002-533742, EP358208, EP66137, WO93 / 22397, EP0261712, DE19504224, DE4408171, and GB2280445. Examples of the polymerizable mesogenic compound are LC242 manufactured by BASF Corporation, E7 manufactured by Merck KGaA, and LC-Sillicon-CC3767 manufactured by Wacker-Chemie GmbH. The liquid crystal monomer is preferably a nematic monomer.

[0173] The retardation film as the liquid crystal alignment fixing layer can be formed by coating a coating liquid containing a liquid crystal compound on the surface of a substrate film that has been subjected to an alignment treatment, aligning the liquid crystal compound along the direction corresponding to the alignment treatment, and fixing the alignment state. A release film can be used as the substrate. The retardation film formed on the release film can be transferred to other layers that the optical laminate 10 such as the first adhesive sheet 2 and the second adhesive sheet 4 may include. However, the method of forming the retardation film as the liquid crystal alignment fixing layer is not limited to the above examples.

[0174] Regarding further specific examples of the liquid crystal compound and details of the method for forming the liquid crystal alignment fixing layer, reference can be made to Japanese Patent Application Laid-Open No. 2006-163343. However, the retardation film as the liquid crystal alignment fixing layer and its forming method are not limited to the content described in this publication.

[0175] The first optical film 3 may be a liquid crystal alignment fixing layer having a thickness of 15 μm or less.

[0176] The retardation film may be a stretched resin film. Examples of resins capable of forming the retardation film are polycarbonate, polyvinyl acetal, norbornene resins, acrylic resins, and cellulose esters. The retardation film may be a stretched resin film containing polycarbonate.

[0177] The retardation film may be an antireflection retardation film, a viewing angle compensation retardation film, or an inclined alignment retardation film for viewing angle compensation.

[0178] The first optical film 3 is not limited to the above examples.

[0179] (The second adhesive sheet 4)

[0180] As long as the storage modulus G' of the second adhesive sheet 4 at 25°C is 0.15 MPa or more, it may have the same composition and properties as the first adhesive sheet 2. Hereinafter, matters that may be the differences from the first adhesive sheet 2 in the second adhesive sheet 4 will be described.

[0181] The (meth)acrylic polymer (A) that the second adhesive sheet 4 may contain preferably has a structural unit derived from an aromatic ring-containing monomer. In a system in which a large amount of isocyanate crosslinking agent is incorporated to increase the storage modulus G', the above structural unit can contribute to improving the compatibility between the (meth)acrylic polymer (A) and the polymer (D) containing a structural unit derived from the isocyanate crosslinking agent as a main component.

[0182] When the adhesive composition (B) capable of forming the second adhesive sheet 4 contains an isocyanate crosslinking agent, the blending amount of the isocyanate crosslinking agent relative to 100 parts by weight of the (meth)acrylic polymer (A) may be 3 parts by weight or more, may be 4 parts by weight or more, 5 parts by weight or more, 6 parts by weight or more, 7 parts by weight or more, and further may be 8 parts by weight or more. The upper limit of the blending amount may be 15 parts by weight or less, 14 parts by weight or less, 13 parts by weight or less, and further may be 12 parts by weight or less.

[0183] The thickness of the second adhesive sheet 4 is, for example, 1 to 100 μm, may be 2 to 50 μm, 2 to 40 μm, and further may be 5 to 35 μm.

[0184] The adhesive composition (B) and the photocurable composition (C) capable of forming the second adhesive sheet 4 may contain polyhydroxyalkylamine compounds (hereinafter referred to as amine compounds (E)). The amine compounds (E) can change the properties of the second adhesive sheet 4. The number of hydroxyl groups contained in the amine compounds (E) is, for example, 2 or more, and may be 3 or more. The upper limit of the number of hydroxyl groups is, for example, 5 or less.

[0185] The number of nitrogen atoms (typically amino groups) contained in the amine compound (E) is, for example, 1 or more, and can be 2 or more. The upper limit of the number of nitrogen atoms is, for example, 5 or less.

[0186] Examples of the amine compound (E) having 1 nitrogen atom are diol amines such as diethanolamine, dipropanolamine, diisopropanolamine, N-methyldiethanolamine, N-methyldiisopropanolamine, N-ethyldiethanolamine, N-ethyldiisopropanolamine, N-butyldiethanolamine, N-butyldiisopropanolamine; and triol amines such as triethanolamine, tripropanolamine, and triisopropanolamine.

[0187] Examples of the amine compound (E) having 2 nitrogen atoms are the compounds represented by the following formula (1).

[0188] [Chemical formula 1]

[0189]

[0190] In formula (1), R 1 , R 2 , R 3 and R 4 independently represent a hydrogen atom, or a general formula -(R 5 O) m (R 6 O) n -H. In the above general formula, R 5 and R 6 independently represent an alkylene group. Among them, the alkylene group of R 5 is different from the alkylene group of R 6 . m and n are independently integers of 0 or more. Among them, at least one of m and n is an integer of 1 or more. At least two of R 1 , R 2 , R 3 and R 4 represent the general formula -(R 5 O) m (R 6 O) n -H, and R 1 , R 2 , R 3 and R 4 can each be the general formula -(R 5 O) m (R 6 O) n -H. X represents a divalent hydrocarbon group. p is an integer of 1 or more.

[0191] R 5 and R 6Among them, examples of the alkylene group include alkylene groups having about 2 to 6 carbon atoms such as ethylene, propylene, trimethylene, tetramethylene, ethyl ethylene, pentamethylene, hexamethylene, etc. (preferably alkylene groups having 2 to 4 carbon atoms, more preferably alkylene groups having 2 or 3 carbon atoms). The alkylene group can have any of a linear or branched form. As the alkylene group, ethylene and propylene can be suitably used. m and n are, for example, 0 to 20, preferably 1 to 10. It can be that one of m and n is 0 and the other is an integer of 1 or more (especially 1).

[0192] In X, the divalent hydrocarbon group can be in any form of saturated or unsaturated. Examples of the divalent hydrocarbon group include alkylene, cycloalkylene, and arylene. The alkylene group can have any of a linear or branched form. Examples of the alkylene group include alkylene groups having about 1 to 6 carbon atoms such as methylene, ethylene, propylene, trimethylene, tetramethylene, etc. (preferably alkylene groups having 1 to 4 carbon atoms, more preferably alkylene groups having 2 or 3 carbon atoms). Examples of the cycloalkylene group include cycloalkylene groups having about 5 to 12 members such as 1,2-cyclohexylene, 1,3-cyclohexylene, 1,4-cyclohexylene. Examples of the arylene group include 1,2-phenylene, 1,3-phenylene, 1,4-phenylene.

[0193] In formula (1), p is not particularly limited as long as it is an integer of 1 or more, for example, it is an integer of 1 to 10, preferably an integer of 1 to 6, and more preferably an integer of 1 to 4.

[0194] Examples of the amine compound (E) represented by formula (1) include N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine, N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine, N,N,N',N'-tetrakis(2-hydroxyethyl)trimethylenediamine, N,N,N',N'-tetrakis(2-hydroxypropyl)trimethylenediamine. Other examples of the amine compound (E) represented by formula (1) include polyoxyethylene condensates of ethylenediamine, polyoxypropylene condensates of ethylenediamine, polyoxyethylene-polyoxypropylene condensates of ethylenediamine, etc., which are polyoxyalkylene condensates of alkylene diamines. As the amine compound (E) represented by formula (1), commercially available products such as EDP-300, EDP-450, EDP-1100, Pluronic (above, manufactured by ADEKA Corporation) can be used.

[0195] As the amine compound (E), the above-mentioned amine compounds can be used alone, or two or more of them can be used in combination.

[0196] The molecular weight of the amine compound (E) is, for example, 1500 or less, and can be 1000 or less, 800 or less, 500 or less, 400 or less, and further can be 300 or less. The lower limit of the molecular weight is not particularly limited and can be 100 or more, 200 or more, 400 or more, and further can be 1000 or more.

[0197] With respect to 100 parts by weight of the (meth)acrylic polymer (A), the compounding amount of the amine compound (E) is, for example, 0.01 to 5 parts by weight, and may be 0.1 part by weight or more. The upper limit of the compounding amount may be 3.5 parts by weight or less, and may also be 3 parts by weight or less, 2 parts by weight or less, 1.5 parts by weight or less, 1 part by weight or less, and further may be 0.5 part by weight or less.

[0198] The adhesive composition (B) and the photocurable composition (C) that can form the second adhesive sheet 4 may contain a polyether compound having a polyether skeleton (hereinafter referred to as polyether compound (F)). The polyether compound (F) can change the properties of the second adhesive sheet 4. The polyether compound (F) may contain a silicon atom, and may further contain a hydroxyl group and / or a hydrolyzable group bonded to the silicon atom.

[0199] The polyether compound (F) preferably has a reactive silyl group represented by the general formula -SiR a M 3-a at at least one terminal. In the above general formula, R is independently a monovalent organic group having 1 to 20 carbon atoms which may optionally have a substituent. M is independently a hydroxyl group or a hydrolyzable group. a is an integer from 0 to 3, may be an integer from 0 to 2, or may also be an integer from 1 to 3.

[0200] The polyether compound (F) has, for example, at least one reactive silyl group per molecule on average at its terminal. When the polyether compound is linear, the polyether compound may have one or two reactive silyl groups at its terminal, and preferably has two reactive silyl groups. When the polyether compound is branched, the polyether compound has at least one reactive silyl group at the terminal of the main chain or the side chain. The number of reactive silyl groups can be appropriately adjusted according to the number of terminals of the polyether compound, and is preferably two or more, and may also be three or more.

[0201] Preferably, the polyether compound (F) has a reactive silyl group at at least a part of its molecular terminal and has at least one, preferably 1.1 to 5, more preferably 1.1 to 3 reactive silyl groups in its molecule.

[0202] Specific examples of the polyether compound (F) are MS polymers S203, S303, S810 manufactured by Kaneka Corporation; SILYL EST250, EST280; SAT10, SAT200, SAT220, SAT350, SAT400; and EXCESTARS2410, S2420, S3430 manufactured by AGC Inc.

[0203] With respect to 100 parts by weight of the (meth)acrylic polymer (A), the compounding amount of the polyether compound (F) is, for example, 0.1 to 5 parts by weight, it can be 0.3 parts by weight or more, and further can be 0.5 parts by weight or more. The upper limit of the compounding amount can be 4 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, and further can be 1 part by weight or less.

[0204] The second adhesive sheet 4 is not limited to the above examples.

[0205] In the optical laminate 10, at least one selected from the first adhesive sheet 2 and the second adhesive sheet 4 may contain the (meth)acrylic polymer (A) as a main component. In addition, in the optical laminate 10, at least one selected from the first adhesive sheet 2 and the second adhesive sheet 4 may be a layer formed of the adhesive composition (B) containing the (meth)acrylic polymer (A) as a main component.

[0206] The thickness of the first adhesive sheet 2 may be smaller than the thickness of the second adhesive sheet 4. For example, the thickness of the first adhesive sheet 2 is 10 μm or less, preferably 8 μm or less, more preferably 5 μm or less, and the thickness of the second adhesive sheet 4 can be 15 μm or more, preferably 17 μm or more, more preferably 20 μm or more.

[0207] (Another layer)

[0208] The optical laminate 10 of the present invention may also include another layer other than the above. An example of the other layer is the second optical film 5. An example of the optical laminate 10 further including the second optical film 5 is shown in Figure 6 . Figure 6 The optical laminate 10D is the same as the Figure 1 optical laminate 10A except that the second optical film 5 is further included between the optical substrate 1 and the first adhesive sheet 2. The second optical film 5 of the optical laminate 10D is in contact with each of the optical substrate 1 and the first adhesive sheet 2. An adhesive layer or another adhesive sheet may be provided between the optical substrate 1 and the second optical film 5. The other adhesive sheet may have the same constitution as the first adhesive sheet 2 or the second adhesive sheet 4.

[0209] Examples of the constitution and characteristics of the second optical film 5 are the same as those of the first optical film 3. The second optical film 5 may be a retardation film. The retardation film may be a liquid crystal alignment fixing layer. The thickness of the second optical film 5 may be 15 μm or less. The second optical film 5 may be a liquid crystal alignment fixing layer with a thickness of 15 μm or less.

[0210] One of the first optical film 3 and the second optical film 5 may be a retardation film capable of functioning as a λ / 2 wave plate, and the other may be a retardation film functioning as a λ / 4 wave plate. In addition, when the optical substrate 1 includes a polarizer, the optical laminate 10D may be a broadband elliptical polarization film or a circular polarization film.

[0211] Another example of the additional layer is a release liner. An example of the optical laminate 10 further including a release liner is shown in Figure 7 . Figure 7 The optical laminate 10E of Figure 6 is the same as the optical laminate 10D of Figure 7 , except that a release liner 6 is provided on the side of the second adhesive sheet 4 opposite to the first optical film 3 side.

[0212] The release liner 6 is in contact with the second adhesive sheet 4. By peeling off the release liner 6, the optical laminate 10E can be used, for example, as an optical film with an adhesive sheet.

[0213] The release liner 6 is, for example, a film, paper, woven fabric, non-woven fabric, porous material, net, foam, foil, or a laminate thereof formed of resin, paper, fiber, metal, or a composite material thereof. Examples of the resin are polyethylene, polypropylene, polybutene, polybutadiene, polymethylpentene, polyvinyl chloride, vinyl chloride copolymer, polyethylene terephthalate, polybutylene terephthalate, polyurethane, ethylene-vinyl acetate copolymer, and polyester. However, the release liner 6 is not limited to the above examples. In addition, the material constituting the release liner 6 and the resins that can be constituted are not limited to the above examples.

[0213] The thickness of the release liner 6 is, for example, 5 to 200 μm, and may be 5 to 100 μm. As needed, various surface treatments such as a release treatment, an antifouling treatment, and an antistatic treatment can be performed on the surface of the release liner 6. The release treatment can use various release agents such as silicone-based, fluorine-based, long-chain alkyl-based, fatty acid amide-based, or particles such as silica powder.

[0214] The release film used in the formation of the second adhesive sheet 4 can be used as the release liner 6.

[0215] The optical laminate of the present invention can be circulated and stored, for example, in the form of a wound body formed by winding a strip-shaped optical laminate or in the form of a single-sheet optical laminate.

[0216] Typically, the optical laminate of the present invention can be used in an image display device. The image display device is, for example, an EL display such as a liquid crystal display, an organic EL display, and an inorganic EL display. The use of the optical laminate of the present invention is not limited to the above examples. In addition, the image display devices that can use the optical laminate of the present invention are not limited to the above examples.

[0217] The optical laminate of the present invention can be formed by laminating the respective layers contained therein. The layers that have undergone surface modification treatment can be laminated. The surface modification treatment can be performed, for example, on the surface of the first adhesive sheet 2 on the side of the first optical film 3 and / or on the surface of the first optical film 3 on the side of the first adhesive sheet 2.

[0218] The surface modification treatment is, for example, at least one selected from corona treatment, plasma treatment, excimer UV light treatment, and flame treatment, can be corona treatment and / or plasma treatment, and can be corona treatment. Various surface modification treatments can be implemented by corresponding known treatment apparatuses.

[0219] As an example, the discharge amount in corona treatment is, for example, 0.6 to 25 kJ / m 2 . The lower limit of the discharge amount can be 1 kJ / m 2 or more, 2 kJ / m 2 or more, 5 kJ / m 2 or more, 7 kJ / m 2 or more, 9 kJ / m 2 or more, more than 9 kJ / m 2 , and further can be 10 kJ / m 2 or more. The upper limit of the discharge amount can be 22 kJ / m 2 or less, 20 kJ / m 2 or less, 17 kJ / m 2 or less, 15 kJ / m 2 or less, and further can be 12 kJ / m 2 or less.

[0220] [Image display device]

[0221] An example of the image display device of the present invention is shown in Figure 8 . Figure 8 The image display device 21 shown in has a laminated structure in which an optical substrate 1, a second optical film 5, a first adhesive sheet 2, a first optical film 3, a second adhesive sheet 4, an image forming layer (such as an organic EL layer or a liquid crystal layer) 8, and a substrate 9 are laminated in sequence. The image display device 21 has an Figure 6 optical laminate 10E. The substrate 9 and the image forming layer 8 only need to have the same configurations as the substrate and the image forming layer respectively provided in known image display devices.

[0222] Figure 8The image display device 21 can be an organic EL display or a liquid crystal display. However, the image display device 21 is not limited to this example. The image display device 21 can be an electroluminescent (EL) display, a plasma display (PD), a field emission display (FED: Field Emission Display), etc. The image display device 21 can be used for home appliance applications, in-vehicle applications, public information display (PID) applications, etc.

[0223] The image display device of the present invention can have any configuration as long as it includes the optical laminate of the present invention.

[0224] Embodiment

[0225] Hereinafter, the present invention will be described in more detail by way of examples. The present invention is not limited to the examples shown below.

[0226] In this embodiment, an optical laminate including, in order, an optical substrate as a polarizing film, a retardation film as a second optical film, a first adhesive sheet, a retardation film as a first optical film, and a second adhesive sheet was produced. The polarizing film has a laminated structure of a first transparent protective film, a polarizer, and a second transparent protective film.

[0227] [Production of optical substrate]

[0228] (Production of polarizer)

[0229] A long strip of polyvinyl alcohol (PVA) resin film (manufactured by Kuraray Co., Ltd., PE3000, thickness 30 μm) was unidirectionally stretched along the length direction using a roller stretching machine (total stretching ratio 5.9 times), and at the same time, the above resin film was successively subjected to swelling, dyeing, crosslinking, cleaning, and drying treatments to produce a polarizer with a thickness of 12 μm. In the swelling treatment, the resin film was treated in pure water at 20°C while being stretched 2.2 times. In the dyeing treatment, the resin film was treated in an aqueous solution at 30°C containing iodine and potassium iodide in a weight ratio of 1:7 while being stretched 1.4 times. The iodine concentration in the aqueous solution was adjusted so that the monomer transmittance of the produced polarizer reached 45.0%. The crosslinking treatment was carried out in two stages. In the first-stage crosslinking treatment, the resin film was treated in an aqueous solution at 40°C in which boric acid and potassium iodide were dissolved while being stretched 1.2 times. The content rate of boric acid in the aqueous solution used in the first-stage crosslinking treatment was 5.0% by weight, and the content rate of potassium iodide was set to 3.0% by weight. In the second-stage crosslinking treatment, the resin film was stretched 1.6 times while being treated in an aqueous solution at 65°C in which boric acid and potassium iodide were dissolved. The content rate of boric acid in the aqueous solution used in the second-stage crosslinking treatment was 4.3% by weight, and the content rate of potassium iodide was set to 5.0% by weight. In the cleaning treatment, an aqueous solution of potassium iodide at 20°C was used, and the content rate of potassium iodide in the aqueous solution used in the cleaning treatment was set to 2.6% by weight. The drying treatment was carried out under drying conditions of 70°C and 5 minutes.

[0230] (Production of polarizing film)

[0231] Using a polyvinyl alcohol-based adhesive, triacetyl cellulose (TAC) films (manufactured by Konica Minolta, KC2UA, thickness 25 μm) were respectively adhered to each main surface of the above-produced polarizer. Among them, a hard coat (thickness 7 μm) was formed on the main surface of the TAC film adhered to one main surface, which was opposite to the polarizer side. In this way, a polarizing film having a structure of protective layer / hard coat-free polarizer / protective layer was obtained.

[0232] [Production of the first optical film]

[0233] As a liquid crystal compound, a polymerizable liquid crystal material (manufactured by BASF, Paliocolor LC242) showing a nematic liquid crystal phase was prepared. 10 g of the above polymerizable liquid crystal material and 3 g of a corresponding photoinitiator (manufactured by BASF, IRGACURE 907) were dissolved in 40 g of toluene to prepare a liquid crystal composition as a coating solution. Next, the coating solution was applied to the surface of a PET film which was a substrate film obtained by subjecting the surface to an alignment treatment, and dried by heating at 90 °C for 2 minutes, thereby forming a liquid crystal layer. Next, the formed liquid crystal layer was irradiated with light of 1 mJ / cm 2 to cure the liquid crystal layer, thereby forming a retardation film as a liquid crystal alignment fixing layer. The thickness of the retardation film was 1 μm, and the in-plane retardation Re(550) was 140 nm, that is, the formed retardation film was a λ / 4 wave plate.

[0234] [Fabrication of the Second Optical Film]

[0235] A retardation film was formed in the same manner as in the fabrication of the first optical film except that a liquid crystal alignment fixing layer with a thickness of 2 μm was formed by adjusting the coating amount of the coating solution. The in-plane retardation Re(550) of the retardation film was 280 nm, that is, the formed retardation film was a λ / 2 wave plate.

[0236] [Fabrication of the First Adhesive Sheet and the Second Adhesive Sheet]

[0237] [Fabrication of (Meth)acrylic Polymer A1]

[0238] A monomer mixture containing 91.5 parts by weight of butyl acrylate (BA), 3 parts by weight of acrylic acid (AA), 0.5 part by weight of 4-hydroxybutyl acrylate (HBA), and 5 parts by weight of acryloylmorpholine (ACMO) was added to a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet tube, and a condenser. Further, 0.1 part by weight of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator was added together with ethyl acetate relative to 100 parts by weight of the monomer mixture. After nitrogen replacement was carried out by introducing nitrogen while slowly stirring, the liquid temperature in the flask was maintained at around 55 °C and a polymerization reaction was carried out for 7 hours. Then, ethyl acetate was added to the obtained reaction solution to adjust the solid content concentration to 30%, and a solution of (meth)acrylic polymer A1 was obtained.

[0239] [Fabrication of (Meth)acrylic Polymer A2]

[0240] The types and amounts of the monomers and the polymerization initiator were changed as shown in Table 1, and a solution of (meth)acrylic polymer A2 was obtained in the same manner as (meth)acrylic polymer A1 except for this.

[0241] [Table 1]

[0242]

[0243] The abbreviations in Table 1 are as described below.

[0244] BA: n-Butyl acrylate

[0245] AA: Acrylic acid

[0246] HBA: 4-Hydroxybutyl acrylate

[0247] BzA: Benzyl acrylate

[0248] ACMO: Acryloylmorpholine

[0249] AIBN: Azobisisobutyronitrile, 2,2’-Azobis(2-methylpropionitrile) (manufactured by Kishida Chemical Co., Ltd.)

[0250] (Production of Adhesive Composition)

[0251] A solvent-based adhesive composition was obtained by mixing a (meth)acrylic polymer, a crosslinking agent, and an additive so as to have the composition shown in Table 2 below.

[0252] (Production of Adhesive Sheets B1 to B10)

[0253] The adhesive composition was coated on the surface of a PET film as a base film (release liner) so that the thickness of the dried adhesive sheet reached a given thickness. A jet coater was used for coating the adhesive composition. The coated film formed by coating was dried in an air-circulation type constant-temperature oven at 150 °C (B1) or 90 °C (B2 to B10) for 1 minute, whereby adhesive sheets B1 to B10 were produced.

[0254] [Table 2]

[0255]

[0256] The abbreviations in Table 2 are as described below.

[0257] D101E: Trimethylolpropane / Toluene diisocyanate trimer adduct (manufactured by Mitsui Chemicals, Inc., Takenate D-101E); Isocyanate-based crosslinking agent

[0258] Peroxide: Benzoyl peroxide; Peroxide-based crosslinking agent

[0259] EDP-300: N,N,N’,N’-Tetrakis(2-hydroxypropyl)ethylenediamine (manufactured by ADEKA Corporation, EDP-300); Amine compound (E)

[0260] KBM403: 3-Glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM-403); silane coupling agent

[0261] SAT10: Polyether compound having an alkoxysilyl group (manufactured by KANEKA CORPORATION, SILYL SAT10); polyether compound (F)

[0262] (Preparation of photocurable composition C1)

[0263] 95.1 parts by weight of BA, 4.8 parts by weight of AA, 0.1 part by weight of HBA, 0.05 part by weight of 1-hydroxycyclohexyl-phenyl ketone (Omnirad184, manufactured by IGM Resins B.V.) as a photoinitiator, and 0.05 part by weight of 2,2-dimethoxy-1,2-diphenylethane-1-one (Omnirad651, manufactured by IGM Resins B.V.) were put into a four-necked flask, and ultraviolet rays were irradiated in a nitrogen atmosphere to obtain a monomer slurry in which photopolymerization partially occurred. The irradiation of ultraviolet rays was carried out until the viscosity of the liquid in the flask (measurement conditions: BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30 °C) reached about 20 Pa·s. Next, 0.09 part by weight of 1,9-nonanediol diacrylate (NDDA) as a crosslinking agent was added to 100 parts by weight of the monomer slurry and mixed uniformly to obtain photocurable composition C1.

[0264] (Preparation of release liner)

[0265] 30 parts by weight of an addition reaction curable silicone (LTC761 containing hexenyl polyorganosiloxane, 30 wt% toluene solution, manufactured by Toray Dow Corning), 0.9 part by weight of a release control agent (BY24-850 containing unreacted organosilicon resin, manufactured by Toray Dow Corning), 2 parts by weight of a curing catalyst (SRX212 containing a platinum catalyst, manufactured by Toray Dow Corning), and a toluene / hexane mixed solvent (volume ratio 1:1) as a diluting solvent were mixed to obtain an organosilicon-based release agent composition. The concentration of the organosilicon solid component in the release agent composition was 1.0 wt%. Next, the release agent composition was coated on one side of a liner substrate (Lumirror XD500P as a polyester film, thickness 75 μm) using a wire bar and heated at 130 °C for 1 minute to produce a first release liner having a release layer (thickness 60 nm) on one side. In addition, a second release liner having a release layer (thickness 120 nm) on one side was produced by the same method as the first release liner except that the thickness of the release agent composition coated on the liner substrate was changed.

[0266] (Production of Adhesive Sheet B11)

[0267] The photocurable composition C1 was coated on the surface of the release layer of the first release liner using a coater to form a coating layer (thickness: 20 μm). Next, the second release liner was disposed on the formed coating layer to obtain a laminate of the first release liner / coating layer / second release liner. The second release liner was disposed such that the release layer was in contact with the coating layer. Next, ultraviolet rays (Black light source) were irradiated from the side of the first release liner under the conditions of an illuminance of 2.5 mW / cm 2 and an irradiation time of 640 seconds to photocure the coating layer, thereby producing the adhesive sheet B11.

[0268] [Production of Ultraviolet-Curable Adhesive Composition α]

[0269] 29.2 parts by weight of 2-hydroxyethyl acrylamide (HEAA), 16.7 parts by weight of 2-acetoacetoxyethyl methacrylate (AAEM), 33.3 parts by weight of ACMO, 20.8 parts by weight of tripropylene glycol diacrylate (manufactured by Toagosei Co., Ltd., ARONIX M-220) as a crosslinking agent, 3 parts by weight of 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one (manufactured by BASF, IRGACURE 907) as a photopolymerization initiator, and 3 parts by weight of diethylthioxanthone (manufactured by Nippon Kayaku Co., Ltd., KAYACURE DETX-S) as a radical polymerization initiator were mixed and stirred for 1 hour, thereby producing the ultraviolet-curable adhesive composition α.

[0270] [Production of Optical Laminate]

[0271] (Example 1)

[0272] The second optical film (λ / 2 wave plate) was bonded to the exposed surface of the protective layer (without hard coat) in the polarizing film using the ultraviolet-curable adhesive composition α. The bonding was carried out as follows. First, the adhesive composition α was coated on the above-mentioned exposed surface of the polarizing film with a coating thickness of 0.5 μm using an MCD coater (manufactured by Fuji Machine Co., Ltd.). Next, after the second optical film was disposed on the coated film, ultraviolet rays were irradiated from both sides to cure the adhesive composition α. The second optical film was disposed such that the λ / 2 wave plate was in contact with the coated film. Using a metal halide lamp, the peak illuminance was 1600 mW / cm 2 and the cumulative irradiation dose was 1000 / mJ / cm 2Ultraviolet rays were irradiated under the condition of (wavelength 380 - 440 nm). After the irradiation of ultraviolet rays, hot air drying was carried out at 70 °C for 3 minutes. Next, the base film used in the production of this film was peeled off from the second optical film, and the adhesive sheet B1 was attached to the peeled surface. Next, the base film used in the production of this sheet was peeled off from the adhesive sheet B1, and the stripping surface was subjected to corona treatment at a discharge amount of 10 kJ / m 2 The stripping surface was subjected to corona treatment. Next, the first optical film (λ / 4 wave plate) was attached to the corona-treated stripping surface. Among them, the bonding surface of the first optical film to the adhesive sheet B1 was previously subjected to corona treatment at a discharge amount of 10 kJ / m 2 Next, the base film used in the production of this film was peeled off from the first optical film, and the adhesive sheet B2 was attached to the peeled surface, obtaining the optical laminate of Example 1 in which the polarizing film / second optical film / first adhesive sheet / first optical film / second adhesive sheet / base film (peeling liner) were laminated in sequence. The attachment of the second optical film to the polarizing film and the attachment of the first optical film to the first adhesive sheet were carried out by adjusting the polarization axis of the polarizing film and the slow axis directions of the respective optical films so as to obtain an optical laminate that functions as a circular polarizing film.

[0273] (Examples 2 - 10, Comparative Examples 1 - 6)

[0274] The types of the first adhesive sheet and the second adhesive sheet, and the presence or absence and discharge amount of corona treatment for the first adhesive sheet and the first optical film were set as shown in Table 3 below. Except for this, the optical laminates of Examples 2 - 10 and Comparative Examples 1 - 6 were obtained in the same manner as in Example 1. It should be noted that for the adhesive sheet B11 of Example 10, the peeled surface after peeling off the second peeling liner was attached to the second optical film.

[0275] [Table 3]

[0276]

[0277] [Evaluation]

[0278] (Weight average molecular weight (Mw) of (meth)acrylic polymer)

[0279] The weight average molecular weight (Mw) of the (meth)acrylic polymer was measured by GPC (gel permeation chromatography).

[0280] · Analytical device: HLC - 8120GPC manufactured by Tosoh Corporation

[0281] · Chromatographic column: G7000H manufactured by Tosoh Corporation XL +GMH XL +GMH XL

[0282] · Column size: Each is φ7.8 mm × 30 cm, totaling 90 cm

[0283] · Column temperature: 40 °C

[0284] · Flow rate: 0.8 mL / min

[0285] · Injection volume: 100 μL

[0286] · Eluent: Tetrahydrofuran

[0287] · Detector: Differential refractometer (RI)

[0288] · Standard sample: Polystyrene

[0289] (Roughness of the peeling surface of the second adhesive sheet after peeling; arithmetic mean height Sa)

[0290] For each of the optical laminates of the examples and comparative examples, the arithmetic mean height Sa of the peeling surface of the second adhesive sheet after peeling was evaluated by the above-described first test, second test, and measurement of the surface properties of the peeling surface using a surface property measuring machine. As the glass sheet, Eagle XG (thickness: 0.7 mm) manufactured by Corning was used. The bonding of the optical laminate to the surface of the glass sheet was carried out by peeling the substrate film bonded to the second adhesive sheet. In addition, at the time of bonding, an autoclave treatment was carried out at 50 °C, 5 atm (absolute pressure), and for 15 minutes. The peeling in the first test and the second test was carried out within 1 hour after 7 days and 14 days, respectively, from the time of bonding. The first test, the second test, and the surface property measurement were carried out in an atmosphere of 25 ± 5 °C. As the surface property measuring machine, a shape measuring laser microscope VK9510 manufactured by Keyence was used. The measurement area of the surface properties was set to a rectangle with a side length of 4.2 μm × 5.6 μm. When calculating Sa from the original surface data, a Gaussian filter was applied.

[0291] (Interlayer adhesion force based on the first adhesive sheet)

[0292] For each of the optical laminates of the examples and comparative examples, the interlayer adhesion force based on the first adhesive sheet was evaluated by the above-described third test. In the third test, the portion including the polarizing film and the second optical film was separated from the portion including the first optical film and the second adhesive sheet. As the PET film, Lumirror (thickness: 125 μm) manufactured by Toray Industries, Inc. was used. As the adhesive sheet for bonding the test piece to the SUS plate, No. 500 manufactured by Nitto Denko Corporation was used. As the tensile testing machine, Autograph AG-X manufactured by Shimadzu Corporation was used. The third test was carried out in an atmosphere of 25 ± 5 °C.

[0293] (Storage modulus G' of the second adhesive sheet at 25 °C)

[0294] The storage modulus G'(25°C) of the second adhesive sheet included in each of the optical laminates of the examples and comparative examples was evaluated by the above method. Among them, the measurement sample was prepared by laminating the produced adhesive sheets and punching the obtained laminate into a disc shape. For the dynamic viscoelasticity measurement of the measurement sample, ARES-G2 manufactured by TA Instruments was used.

[0295] (Adhesion force of the optical laminate to the glass sheet)

[0296] For each of the optical laminates of the examples and comparative examples, the initial adhesion force, the adhesion force after 7 days, and the adhesion force after 14 days were evaluated by the above method. The conditions for peeling the optical laminate from the glass sheet for evaluating the adhesion force were set to be the same as those in the first test and the second test.

[0297] (Reoperability)

[0298] For each of the optical laminates of the examples and comparative examples, the first test and the second test for evaluating the arithmetic mean height Sa were carried out, and the reoperability was evaluated based on the following evaluation criteria according to the peeling state in each test. The reoperability evaluated by the first test and the second test is shown in Table 4 below as the reoperability after 7 days and the reoperability after 14 days, respectively.

[0299] <Evaluation criteria>

[0300] A: The optical laminate can be peeled from the glass sheet, and no paste residue or interlayer peeling caused by peeling is observed.

[0301] B: The optical laminate can be peeled from the glass sheet, but a small amount of paste residue caused by peeling is observed on the attachment surface of the glass sheet.

[0302] C: The optical laminate can be peeled from the glass sheet, but interlayer peeling is observed inside the optical laminate after peeling.

[0303] D: It is difficult to peel the optical laminate from the glass sheet due to interlayer peeling.

[0304] The evaluation results are shown in Table 4 below. In addition, for the optical laminates of Example 1 and Comparative Example 3, the states of the peeling surfaces after peeling from the glass sheet in the second test are shown in Figure 9 and Figure 10 . It should be noted that Figure 9 and Figure 10 The images shown are observation images obtained by a laser microscope VK9510.

[0305] [Table 4]

[0306]

[0307] As shown in Table 4, the optical laminate of the embodiment is suitable for coping with re-operation.

[0308] Industrial Applicability

[0309] The optical laminate of the present invention can be used in image display devices such as EL displays and liquid crystal displays.

Claims

1. An optical laminate which successively includes an optical substrate, a first adhesive sheet, a first optical film, and a second adhesive sheet, wherein the thickness of the first optical film is 15 μm or less, the storage modulus G' of the second adhesive sheet at 25°C is 0.15 MPa or more, when the optical laminate is bonded to the surface of a glass sheet through the second adhesive sheet, and a first test of peeling the optical laminate from the glass sheet is carried out at the time when 7 days have passed at 25°C since bonding, the roughness of the peeling surface of the second adhesive sheet after peeling is represented by the arithmetic mean height Sa specified in ISO 25178 as 5.5 μm or less, Among them, the peeling of the optical laminate from the glass sheet is carried out as a 90° peeling test specified in JIS Z0237:2009, the glass sheet is treated as a test plate, and the peeling speed is set to 300 mm / min.

2. The optical laminate according to claim 1, wherein when the optical laminate is bonded to the surface of a glass sheet through the second adhesive sheet, and a second test of peeling the optical laminate from the glass sheet is carried out at the time when 14 days have passed at 25°C since bonding, the roughness of the peeling surface of the second adhesive sheet after peeling is represented by the arithmetic mean height Sa as 8.9 μm or less.

3. The optical laminate according to claim 1, wherein the interfacial adhesion force based on the first adhesive sheet is 4.5 N / 25 mm or more.

4. The optical laminate according to claim 1, wherein the interfacial adhesion force based on the first adhesive sheet is less than 4.5 N / 25 mm, and the adhesion force of the optical laminate to the glass sheet evaluated in the first test is 4.5 N / 25 mm or less.

5. The optical laminate according to claim 1, wherein the interfacial adhesion force based on the first adhesive sheet is less than 4.5 N / 25 mm, and the adhesion force of the optical laminate to the glass sheet evaluated in the second test of peeling the optical laminate from the glass sheet at the time when 14 days have passed at 25°C since bonding the optical laminate to the surface of the glass sheet through the second adhesive sheet is 6 N / 25 mm or less.

6. The optical laminate according to claim 1, wherein the storage modulus G' of the second adhesive sheet at 25°C is 2 MPa or less.

7. The optical laminate according to claim 1, wherein the first optical film is a retardation film.

8. The optical laminate according to claim 1, wherein a second optical film is further included between the optical substrate and the first adhesive sheet.

9. The optical laminate according to claim 8, wherein the thickness of the second optical film is 15 μm or less.

10. The optical laminate according to claim 8, wherein the second optical film is a retardation film.

11. The optical laminate according to claim 1, wherein the optical substrate includes a polarizer.

12. The optical laminate according to claim 1, wherein At least one selected from the first adhesive sheet and the second adhesive sheet contains a (meth)acrylic polymer (A) as a main component.

13. An image display device including the optical laminate according to any one of claims 1 to 12.

Images