Optical laminate and image display device

Abstract

The present invention provides an optical laminate that, even while having a layer formed through the solidification of liquid crystals, is capable of preventing early display failures in an image display device. This optical laminate includes a first liquid crystal alignment solidified layer, a first adhesive sheet, and a second liquid crystal alignment solidified layer in the order stated. The ratio A / B of the thickness A of a first laminated portion of the optical laminate, which includes all of the layers from the first adhesive sheet on that are positioned on the first liquid crystal alignment solidified layer side, including the first adhesive sheet, and the thickness B of a second laminated portion of the optical laminate, which includes all of the layers that are positioned before the first adhesive sheet on the second liquid crystal alignment solidified layer side, is 0.5-2. The total thickness of the optical laminate is at least 80 μm.

Description

Optical laminate and image display device

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

[0002] In recent years, image display devices, such as liquid crystal display devices and electroluminescence (EL) display devices (e.g., organic EL display devices and inorganic EL display devices), have rapidly become popular. Image display devices generally include an optical laminate including optical substrates such as a polarizing film and a retardation film. In an optical laminate including multiple optical substrates, a bonding layer that bonds the adjacent optical substrates together is usually disposed between the optical substrates. One example of the bonding layer is a pressure-sensitive adhesive sheet formed from a pressure-sensitive adhesive composition. Patent Document 1 discloses an example of an optical laminate including a pressure-sensitive adhesive sheet and optical substrates. The optical laminate of Patent Document 1 may include a polarizing film and a retardation film formed by solidifying liquid crystal.

[0003] Japanese Patent Application Laid-Open No. 2020-140212

[0004] According to the investigations of the present inventors, image display devices that use an optical laminate having a layer formed by solidifying liquid crystal tend to be prone to initial display defects.

[0005] An object of the present invention is to provide an optical laminate that can suppress initial display defects in an image display device, even though it has a layer formed by solidifying a liquid crystal.

[0006] [1] An optical laminate according to an embodiment of the present invention is an optical laminate comprising, in this order, a first liquid crystal alignment solidified layer, a first pressure-sensitive adhesive sheet, and a second liquid crystal alignment solidified layer, wherein a ratio A / B of a thickness A of a first laminate portion of the optical laminate including all layers located on the first liquid crystal alignment solidified layer side from the first pressure-sensitive adhesive sheet, including the first pressure-sensitive adhesive sheet, to a thickness B of a second laminate portion of the optical laminate including all layers located on the second liquid crystal alignment solidified layer side from the first pressure-sensitive adhesive sheet is 0.5 or more and 2 or less, and a total thickness of the optical laminate is 80 μm or more. [2] In the optical laminate described in [1] above, the second laminate portion may include a second pressure-sensitive adhesive sheet located on the opposite side of the second liquid crystal alignment solidified layer from the first pressure-sensitive adhesive sheet. [3] In the optical laminate described in [1] or [2] above, the second laminate portion may include, in this order, a second pressure-sensitive adhesive sheet and a release liner located on the opposite side of the second liquid crystal alignment solidified layer from the first pressure-sensitive adhesive sheet. [4] In the optical laminate described in any of [1] to [3] above, the total thickness of the optical laminate may be 100 μm or more and 200 μm or less. [5] In the optical laminate described in any of [1] to [4] above, the absolute value of the difference between the refractive index n1 of the second liquid crystal alignment solidified layer at a wavelength of 589 nm and the refractive index n2 of the first pressure-sensitive adhesive sheet at a wavelength of 589 nm may be 0.08 or less. [6] In the optical laminate described in any of [1] to [5] above, the storage modulus G' of the first pressure-sensitive adhesive sheet at 25°C may be 0.15 MPa or more. [7] In the optical laminate described in any of [1] to [6] above, the first pressure-sensitive adhesive sheet may include a crosslinked product of a base polymer. [8] In the optical laminate described in [7] above, the base polymer may be a (meth)acrylate polymer. [9] In the optical laminate described in [7] or [8] above, the monomer component M constituting the base polymer may include an aromatic ring-containing monomer a1.

[10] In the optical laminate described in [9] above, the aromatic ring-containing monomer a1 may be a high-boiling point monomer.

[11] In the optical laminate described in [9] or

[10] above, the aromatic ring-containing monomer a1 may be phenoxybenzyl acrylate.

[12] In the optical laminate described in any of [9] to

[11] above, the content of the aromatic ring-containing monomer a1 in the monomer component M may be 50% by weight or more.

[13] In the optical laminate described in any of [7] to

[12] above, the first pressure-sensitive adhesive sheet may be a layer formed by curing a pressure-sensitive adhesive composition containing the base polymer, a polyfunctional monomer, a thermal crosslinking agent, and a photopolymerization initiator.

[14] The optical laminate described in any of [1] to

[13] above may include a polarizing film.

[15] The optical laminate described in

[14] above may include the polarizing film, the first liquid crystal alignment solidified layer, the first pressure-sensitive adhesive sheet, and the second liquid crystal alignment solidified layer, in this order.

[16] In the optical laminate according to any one of [1] to

[15] above, at least one layer selected from the group consisting of the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer may be a retardation layer.

[17] An image display device according to an embodiment of the present invention includes the optical laminate according to any one of [1] to

[16] above.

[0007] According to an embodiment of the present invention, an optical laminate that can suppress initial display defects in an image display device, even though it has a layer formed by solidifying a liquid crystal, can be provided.

[0008] Fig. 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. Fig. 2 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. Fig. 3 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. Fig. 4 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. Fig. 5 is a schematic cross-sectional view of an image display device according to one embodiment of the present invention.

[0009] [Terminology] In this specification, when the expression "weight" appears, it may be read as "mass," which is commonly used as an SI unit indicating weight, and vice versa.

[0010] In this specification, the expression "(meth)acrylic" means "acrylic and / or methacrylic", the expression "(meth)acrylate" means "acrylate and / or methacrylate", the expression "(meth)allyl" means "allyl and / or methallyl", and the expression "(meth)acrolein" means "acrolein and / or methacrolein".

[0011] The present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be implemented in any modified form without departing from the gist of the present invention.

[0012] 1. Optical Laminate An example of an optical laminate according to an embodiment of the present invention is shown in FIG. 1. The optical laminate 1 (1A) in FIG. 1 includes a first liquid crystal alignment solidified layer 2, a first adhesive sheet 3, and a second liquid crystal alignment solidified layer 4, in this order. The first adhesive sheet 3 is sandwiched between the first liquid crystal alignment solidified layer 2 and the second liquid crystal alignment solidified layer 4. The first liquid crystal alignment solidified layer 2 and the second liquid crystal alignment solidified layer 4 are bonded via the first adhesive sheet 3. In the optical laminate 1A in FIG. 1, adjacent layers are in contact with each other. However, layers other than those described above may be included between adjacent layers. In the optical laminate 1A, a first laminate portion 11 including all layers located on the side of the first liquid crystal alignment solidified layer 2 from the first adhesive sheet 3 (the first liquid crystal alignment solidified layer 2 and the first adhesive sheet 3 in FIG. 1) has a thickness A. The first laminate portion 11 is configured to include the first adhesive sheet 3. The first laminated portion 11 constitutes one exposed surface 13 of the optical laminate 1A. In the optical laminate 1A, the second laminated portion 12, which includes all layers located on the second liquid crystal alignment solidified layer 4 side of the first adhesive sheet 3 (the second liquid crystal alignment solidified layer 4 in FIG. 1 ), has a thickness B. The second laminated portion 12 does not include the first adhesive sheet 3. The second laminated portion 12 constitutes the other exposed surface 14 of the optical laminate 1A. The ratio A / B of the thickness A of the first laminated portion 11 to the thickness B of the second laminated portion 12 is 0.5 or more and 2 or less. The total thickness of the optical laminate is 80 μm or more. The total thickness corresponds to the sum of the thickness A and the thickness B.

[0013] According to the studies of the present inventors, it is presumed that the initial display defects of image display devices using the optical laminate 1 are caused by the occurrence of fine cracks in the liquid crystal alignment solidified layer when the optical laminate 1 is handled, such as when attached to an image forming layer. Furthermore, according to the studies, the liquid crystal alignment layer is generally a harder layer than the first pressure-sensitive adhesive sheet 3 also included in the optical laminate 1, and therefore, stress generated during handling is likely to concentrate thereon, which may be a cause of the occurrence of cracks. In the optical laminate 1 according to an embodiment of the present invention, setting the ratio A / B to be 0.5 or more and 2 or less and setting the total thickness to be 80 μm or more makes the liquid crystal alignment solidified layer less likely to bend when the optical laminate 1 is handled, which is thought to contribute to suppressing the occurrence of cracks.

[0014] Another example of an optical laminate according to an embodiment of the present invention is shown in FIG. 2 . The optical laminate 1 (1B) in FIG. 2 includes a first liquid crystal alignment solidified layer 2, a first adhesive sheet 3, a second liquid crystal alignment solidified layer 4, and a second adhesive sheet 5, in this order. The second adhesive sheet 5 is included in a second laminate portion 12. In other words, the second laminate portion 12 of the optical laminate 1B includes a second adhesive sheet 5 located on the opposite side of the second liquid crystal alignment solidified layer 4 from the first adhesive sheet 3. The second liquid crystal alignment solidified layer 4 is sandwiched between the first adhesive sheet 3 and the second adhesive sheet 5. Stress due to bending or the like tends to concentrate on the second liquid crystal alignment solidified layer 4 sandwiched between a pair of relatively soft adhesive sheets. Therefore, the crack suppression effect of the present invention is more advantageous in the optical laminate 1B including the second adhesive sheet 5. In the optical laminate 1B, adjacent layers are in contact with each other. However, layers other than those described above may be included between adjacent layers.

[0015] Another example of an optical laminate according to an embodiment of the present invention is shown in Figure 3. The optical laminate 1 (1C) in Figure 3 includes a first liquid crystal alignment solidified layer 2, a first pressure-sensitive adhesive sheet 3, a second liquid crystal alignment solidified layer 4, a second pressure-sensitive adhesive sheet 5, and a release liner 6, in this order. The second pressure-sensitive adhesive sheet 5 and the release liner 6 are included in a second laminate portion 12. In other words, the second laminate portion 12 of the optical laminate 1C includes a second pressure-sensitive adhesive sheet 5 and a release liner 6 located on the opposite side of the second liquid crystal alignment solidified layer 4 from the first pressure-sensitive adhesive sheet 3. The release liner 6 can protect the second pressure-sensitive adhesive sheet 5. The release liner 6 may be peeled off when attaching the optical laminate 1C to an object using the second pressure-sensitive adhesive sheet 5. In the optical laminate 1C, adjacent layers are in contact with each other. However, layers other than those described above may be included between adjacent layers.

[0016] The lower limit of the ratio A / B may be 0.51 or more, 0.53 or more, 0.54 or more, 0.55 or more, 0.56 or more, 0.57 or more, 0.58 or more, 0.59 or more, or even 0.6 or more. The upper limit of the ratio A / B may be 1.95 or less, 1.9 or less, 1.85 or less, 1.82 or less, 1.8 or less, 1.77 or less, 1.75 or less, 1.72 or less, 1.7 or less, or even 1.67 or less.

[0017] The lower limit of the total thickness may be 90 μm or more, 95 μm or more, 100 μm or more, or even 105 μm or more. The upper limit of the total thickness may be, for example, 300 μm or less, 275 μm or less, 250 μm or less, 240 μm or less, 230 μm or less, 220 μm or less, 210 μm or less, 200 μm or less, 190 μm or less, 180 μm or less, or even 170 μm or less. The total thickness of the optical laminate 1 may be 100 μm or more and 200 μm or less.

[0018] <1-1. Liquid crystal alignment solidified layer> A liquid crystal alignment solidified layer is a layer in which liquid crystal compounds are aligned in a predetermined direction within the layer, and the alignment state is fixed. The liquid crystal alignment solidified layer includes a cured alignment layer obtained by curing a liquid crystal monomer.

[0019] In the liquid crystal alignment solidified layer, rod-shaped liquid crystal compounds are typically aligned in a predetermined direction (homogeneous alignment). Examples of liquid crystal compounds include nematic liquid crystals and discotic liquid crystals. The liquid crystal compound can be a liquid crystal polymer or a liquid crystal monomer. The liquid crystal monomer may be polymerizable and / or crosslinkable.

[0020] Specific examples of the liquid crystal monomer are the polymerizable mesogenic compounds described in JP-A-2002-533742, EP 358208, EP 66137, WO 93 / 22397, EP 0261712, DE 19504224, DE 4408171, and GB 2280445. Examples of the polymerizable mesogenic compound include LC242 manufactured by BASF, E7 manufactured by Merck, and LC-Silicon-CC3767 manufactured by Wacker-Chem. The liquid crystal monomer is preferably a nematic monomer.

[0021] The liquid crystal alignment solidified layer can be formed by applying a coating liquid containing a liquid crystal compound to the surface of a substrate that has been subjected to an alignment treatment, orienting the liquid crystal compound in a direction corresponding to the alignment treatment, and fixing the alignment state. A release film may be used as the substrate. The liquid crystal alignment solidified layer formed on the release film can be transferred to another layer that may be included in the optical laminate 1, such as a pressure-sensitive adhesive sheet. However, the method for forming the liquid crystal alignment solidified layer is not limited to the above example.

[0022] For further specific examples of liquid crystal compounds and details of the method for forming a liquid crystal alignment solidified layer, reference can be made to JP 2006-163343 A. However, the liquid crystal alignment solidified layer and the method for forming it are not limited to the contents described in that publication.

[0023] The liquid crystal alignment solidified layer may be included in the optical laminate 1 as an optical substrate such as a retardation layer. Compared to ordinary optical substrates made of resin films, the liquid crystal alignment solidified layer is suitable for achieving desired optical properties, such as retardation, while reducing the thickness. In the optical laminate 1 according to an embodiment of the present invention, at least one layer selected from the group consisting of the first liquid crystal alignment solidified layer 2 and the second liquid crystal alignment solidified layer 4 may be a retardation layer. Furthermore, at least one layer selected from the group consisting of the first liquid crystal alignment solidified layer 2 and the second liquid crystal alignment solidified layer 4 may be an anti-reflection retardation layer, a viewing angle compensation retardation layer, or a tilted alignment retardation layer for viewing angle compensation. The retardation layer has a refractive index characteristic represented by, for example, the formula nx > ny. However, the refractive index characteristic of the retardation layer is not limited to the above example. The retardation layer can have various refractive index characteristics known as retardation layers, such as a refractive index characteristic represented by the formula nz > nx = ny.

[0024] The retardation layer may have an Re(550) of 10 nm or more, 30 nm or more, 50 nm or more, 80 nm or more, or even 100 nm or more. Re(550) is the in-plane retardation of the retardation layer for light with a wavelength of 550 nm.

[0025] The Re(550) of the retardation layer may be 100 nm to 180 nm, 110 nm to 170 nm, 120 nm to 160 nm, or even 135 nm to 155 nm, in which case the retardation layer can function as a so-called λ / 4 plate. The Re(550) of the retardation layer may be 180 nm to 320 nm, 200 nm to 290 nm, or even 230 nm to 280 nm, in which case the retardation layer can function as a so-called λ / 2 plate. At least one layer selected from the group consisting of the first liquid crystal alignment solidified layer 2 and the second liquid crystal alignment solidified layer 4 may be a layer that can function as a λ / 4 plate or a λ / 2 plate. The first liquid crystal alignment solidified layer 2 may be a layer that can function as a λ / 4 plate (or a λ / 2 plate), and the second liquid crystal alignment solidified layer 4 may be a layer that can function as a λ / 2 plate (or a λ / 4 plate). The optical laminate 1, in which at least one layer selected from the group consisting of the first liquid crystal alignment solidified layer 2 and the second liquid crystal alignment solidified layer 4 is a layer that can function as a λ / 4 plate or a λ / 2 plate and further includes a polarizing film, may be an elliptically polarizing film or a circularly polarizing film.

[0026] The optical laminate 1A including the first liquid crystal alignment solidified layer 2, the first pressure-sensitive adhesive sheet 3, and the second liquid crystal alignment solidified layer 4 may function as a retardation layer as a whole.

[0027] The optical laminate 1 according to the embodiment of the present invention may include a retardation layer other than the liquid crystal alignment solidified layer which is a retardation layer.

[0028] The thickness of the first liquid crystal alignment solidified layer 2 and the second liquid crystal alignment solidified layer 4 is, for example, 5 μm or less, and may be 4 μm or less, or even 3 μm or less. The lower limit of the thickness is, for example, 0.5 μm or more, and may be 1 μm or more. The thickness may be 0.5 μm or more and 5 μm or less, or 1 μm or more and 4 μm or less. The thicknesses of the first liquid crystal alignment solidified layer 2 and the second liquid crystal alignment solidified layer 4 may be the same or different from each other.

[0029] The first liquid crystal alignment solidified layer 2 and the second liquid crystal alignment solidified layer 4 may have the same structure or different structures.

[0030] The liquid crystal alignment solidified layer has a higher electron density than ordinary optical substrates, and therefore tends to have a high refractive index. The refractive index n1 of at least one layer selected from the group consisting of the first liquid crystal alignment solidified layer 2 and the second liquid crystal alignment solidified layer 4 with respect to light having a wavelength of 589 nm may be 1.50 or more, such as 1.51 or more, 1.52 or more, 1.53 or more, 1.54 or more, 1.55 or more, 1.56 or more, 1.57 or more, 1.58 or more, or even 1.59 or more. The upper limit of the refractive index n1 is, for example, 1.70 or less. When incorporated into an image display device, the liquid crystal alignment solidified layer located on the viewing side, for example, the first liquid crystal alignment solidified layer 2, and the liquid crystal alignment solidified layer located on the opposite side from the viewing side, for example, the second liquid crystal alignment solidified layer 4, may have the same refractive index n1 or different refractive indices n1. The refractive index of the liquid crystal alignment solidified layer is given by the formula: refractive index = (nx + ny + nz) / 3, where nx is the refractive index in the direction (slow axis) in the plane of the layer where the refractive index is maximum, ny is the refractive index in the direction (fast axis) perpendicular to the slow axis in the plane, and nz is the refractive index in the thickness direction.

[0031] The absolute value of the difference between the refractive index n1 of at least one layer selected from the group consisting of the first liquid crystal alignment solidified layer 2 and the second liquid crystal alignment solidified layer 4 with respect to light having a wavelength of 589 nm and the refractive index n2 of the first pressure-sensitive adhesive sheet 3 with respect to light having a wavelength of 589 nm may be 0.08 or less, or may be 0.075 or less, 0.07 or less, 0.06 or less, 0.05 or less, 0.045 or less, 0.04 or less, 0.035 or less, or even 0.03 or less. Furthermore, the absolute value of the difference between the refractive index n1 of the second liquid crystal alignment solidified layer 4 with respect to light having a wavelength of 589 nm and the refractive index n2 of the first pressure-sensitive adhesive sheet 3 with respect to light having a wavelength of 589 nm may be within the above-mentioned range. In addition to cracks that penetrate the liquid crystal alignment solidified layer in the thickness direction (hereinafter referred to as "penetrating cracks"), which can be a cause of the above-mentioned initial display defects, there is a possibility that even finer cracks that do not penetrate the layer (hereinafter referred to as "microcracks"). According to the studies of the present inventors, microcracks can be observed as interference unevenness between the liquid crystal alignment layer and other layers. A small absolute value of the refractive index difference can contribute to suppressing interference unevenness caused by microcracks and making the microcracks less visible.

[0032] <1-2. First Pressure-Sensitive Adhesive Sheet> The storage modulus G' at 25°C (hereinafter referred to as "G'(25°C)") of the first pressure-sensitive adhesive sheet 3 is, for example, 0.05 MPa or more, and may be 0.07 MPa or more, 0.09 MPa or more, 0.1 MPa or more, 0.12 MPa or more, 0.14 MPa or more, 0.15 MPa or more, 0.17 MPa or more, 0.18 MPa or more, 0.2 MPa or more, 0.25 MPa or more, 0.3 MPa or more, 0.35 MPa or more, 0.4 MPa or more, 0.45 MPa or more, 0.5 MPa or more, 0.7 MPa or more, 1 MPa or more, 5 MPa or more, 10 MPa or more, 20 MPa or more, or even 25 MPa or more. The upper limit of G'(25°C) is not particularly limited, but may be, for example, 200 MPa or less, 180 MPa or less, 150 MPa or less, 130 MPa or less, 100 MPa or less, 80 MPa or less, or even 50 MPa or less. Having G'(25°C) of the first pressure-sensitive adhesive sheet 3 in the above-mentioned range, particularly in the range of 0.15 MPa or more, can contribute to suppressing the occurrence of through cracks in the liquid crystal alignment solidified layer, particularly in the second liquid crystal alignment solidified layer 4 that can be sandwiched between the first pressure-sensitive adhesive sheet 3 and the second pressure-sensitive adhesive sheet 5.

[0033] The G' (25°C) of the first pressure-sensitive adhesive sheet 3 can be determined as follows. First, a measurement sample made of the same adhesive as that constituting the first pressure-sensitive adhesive sheet 3 is prepared. The measurement sample is in the form of a strip having a width of 10 mm, a length of 40 mm, and a thickness of 150 μm. The measurement sample may be obtained by cutting a laminate having a plurality of first pressure-sensitive adhesive sheets 3 into the above-mentioned strip shape. Next, dynamic viscoelasticity measurement is performed on the measurement sample. G' (25°C) can be determined from the results of the dynamic viscoelasticity measurement. For the dynamic viscoelasticity measurement, an apparatus capable of performing dynamic tensile viscoelasticity testing, such as the RSA-G2 manufactured by TA Instruments, can be used. The conditions for the dynamic viscoelasticity measurement are as follows. Furthermore, the tensile storage modulus E' (25°C) determined by the dynamic tensile viscoelasticity test can be converted to the storage modulus G' (25°C) in the shear direction based on the relational expression E' = 3 × G'. (Measurement conditions) Distance between chucks: 15 mm Frequency: 1 Hz Deformation mode: Tensile Measurement temperature: -70°C to 150°C Heating rate: 5°C / min

[0034] When the first adhesive sheet 3 contains a crosslinked base polymer, the G' (25°C) of the first adhesive sheet 3 can vary depending on, for example, the degree and state of crosslinking in the crosslinked base polymer, the weight average molecular weight and molecular weight distribution of the base polymer, and the composition and polymerization rate of the monomer component M described below.

[0035] The thickness of the first pressure-sensitive adhesive sheet 3 is not particularly limited and may be, for example, 500 μm or less, 250 μm or less, 150 μm or less, 100 μm or less, 50 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, 15 μm or less, or even 10 μm or less. The lower limit of the thickness of the first pressure-sensitive adhesive sheet 3 is, for example, 2 μm or more, 3 μm or more, 4 μm or more, 4.5 μm or more, or even 5 μm or more. The thickness of the first pressure-sensitive adhesive sheet 3 may be 4 μm or more and 8 μm or less, or 4 μm or more and 7 μm or less.

[0036] The refractive index n2 of the first pressure-sensitive adhesive sheet 3 with respect to light having a wavelength of 589 nm is, for example, 1.45 or more, and may be 1.46 or more, 1.47 or more, 1.48 or more, 1.49 or more, 1.50 or more, 1.51 or more, 1.52 or more, 1.53 or more, 1.54 or more, 1.55 or more, 1.56 or more, 1.57 or more, or even 1.58 or more. The upper limit of the refractive index n2 is, for example, 1.70 or less, and may be 1.69 or less, 1.68 or less, 1.67 or less, 1.66 or less, 1.65 or less, 1.64 or less, 1.63 or less, 1.62 or less, 1.61 or less, 1.60 or less, 1.59 or less, or even 1.58 or less. In this specification, the refractive index of the pressure-sensitive adhesive sheet refers to the refractive index of the surface of the pressure-sensitive adhesive sheet. The refractive index of the pressure-sensitive adhesive sheet can be measured using an Abbe refractometer at a measurement temperature of 25°C and a measurement wavelength of 589 nm. The Abbe refractometer may be, for example, a "DR-4M" model manufactured by ATAGO or an equivalent. The refractive index n2 of the first pressure-sensitive adhesive sheet 3 may vary depending on the degree and state of crosslinking in the crosslinked body of the base polymer, as well as the composition of the monomer component M and the pressure-sensitive adhesive composition A.

[0037] The glass transition temperature (Tg) of the first pressure-sensitive adhesive sheet 3 is, for example, -20°C or higher, and may be -15°C, -10°C or higher, -5°C or higher, 0°C or higher, above 0°C, 1°C or higher, 2°C or higher, 4°C or higher, or even 6°C or higher. There are no particular limitations on the upper limit of the Tg of the first pressure-sensitive adhesive sheet 3, and it may be, for example, 100°C or lower, 80°C or lower, or even 50°C or lower. The Tg of the first pressure-sensitive adhesive sheet 3 can be measured by a method described later in the examples.

[0038] The first pressure-sensitive adhesive sheet 3 is usually composed of a pressure-sensitive adhesive. The first pressure-sensitive adhesive sheet 3 may contain a crosslinked product of a base polymer. The first pressure-sensitive adhesive sheet 3 may be a layer formed by curing a pressure-sensitive adhesive composition A containing a base polymer.

[0039] <1-2-1. Pressure-sensitive adhesive composition A> The pressure-sensitive adhesive composition A contains a base polymer.

[0040] [1-2-1a. Base Polymer] The base polymer may be a (meth)acrylic polymer. In this case, the first pressure-sensitive adhesive sheet 3 is an acrylic pressure-sensitive adhesive sheet. A (meth)acrylic polymer refers to a polymer in which the main structural unit of the base polymer is a (meth)acrylate unit. A main structural unit refers to the structural unit that accounts for the largest weight proportion of all structural units of the base polymer. The weight proportion of the main structural unit is, for example, 50% or more, and may be 60% or more, 65% or more, 70% or more, 75% or more, 80% or more, 85% or more, 90% or more, or even 92% or more. The upper limit of this proportion is, for example, 100% or less, and may be 99% or less.

[0041] The base polymer is obtained from a monomer composition containing a monomer component M. The monomer component M contains one or more monomers.

[0042] (Monomer Composition) Monomer Component M The monomer component M, which is contained in the monomer composition and which constitutes the base polymer upon polymerization of the composition, may contain an aromatic ring-containing monomer a1. The content of the aromatic ring-containing monomer a1 in the monomer component M is, for example, 15 to 99 wt %. The aromatic ring-containing monomer a1 may be the main monomer contained in the monomer component M. In other words, the content of the aromatic ring-containing monomer a1 in the monomer component M may be 50 wt % or more, 60 wt % or more, 65 wt % or more, 70 wt % or more, 75 wt % or more, 80 wt % or more, or even 85 wt % or more. The content may be 60 to 99 wt %, 70 to 95 wt %, or 80 to 90 wt %. The aromatic ring-containing monomer a1 may contribute to increasing the refractive index n2 of the first pressure-sensitive adhesive sheet 3. The aromatic ring-containing monomer a1 is a compound containing an aromatic ring in its structure and a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. Examples of aromatic rings are a benzene ring, a naphthalene ring, and a biphenyl ring. The aromatic ring-containing monomer a1 may be an aromatic ring-containing (meth)acrylate. The aromatic ring-containing monomer a1 can be used alone or in combination of two or more.

[0043] Examples of aromatic ring-containing (meth)acrylates include benzyl (meth)acrylate, phenyl (meth)acrylate, o-phenylphenol (meth)acrylate, phenoxy (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxypropyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxybenzyl (meth)acrylate, ethylene oxide-modified nonylphenol (meth)acrylate, ethylene oxide-modified cresol (meth)acrylate, and phenol ethylene oxide-modified (meth)acrylate. Examples of suitable aromatic ring-containing monomers include those having a benzene ring, such as hydroxybenzyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, methoxybenzyl (meth)acrylate, chlorobenzyl (meth)acrylate, cresyl (meth)acrylate, and polystyryl (meth)acrylate; those having a naphthalene ring, such as hydroxyethylated β-naphthol acrylate, 2-naphthoethyl (meth)acrylate, 2-naphthoxyethyl acrylate, and 2-(4-methoxy-1-naphthoxy)ethyl (meth)acrylate; and those having a biphenyl ring, such as biphenyl (meth)acrylate. From the viewpoint of increasing the refractive index n2 of the first pressure-sensitive adhesive sheet 3, benzyl (meth)acrylate and phenoxybenzyl (meth)acrylate are preferred, with phenoxybenzyl acrylate (POB-A) being more preferred. The aromatic ring-containing monomer a1 may be phenoxybenzyl acrylate.

[0044] The boiling point of aromatic ring-containing monomer a1 typically tends to be higher than that of monomers that do not contain aromatic rings. This tendency, although dependent on the molecular structure, may be stronger as the number of aromatic rings contained increases. Commercially available monomers and other monomers commonly used in forming PSA sheets are purified to remove impurities such as by-products. However, according to the inventors' studies, for monomers with high boiling points, the increased temperature required for distillation, a common purification method, tends to promote polymerization of impurities during purification. To avoid this, milder purification conditions are required, which tends to result in a higher amount of residual impurities. Impurities, particularly polyfunctional ones, can cause gelation during polymerization of the base polymer. For example, for high-boiling point monomers, monomers with even lower residual impurity levels than monomers commonly used in forming PSA sheets may be used. Using monomers with even lower residual impurities is suitable, for example, for increasing the Mw of the base polymer. Further purification may be performed to achieve this reduction. If purification by distillation is difficult, other purification methods, such as adsorption, may be used.

[0045] In view of the above, the aromatic ring-containing monomer a1 may be a high-boiling point monomer. In this specification, a high-boiling point monomer can be specified as a monomer that satisfies at least one condition selected from the group consisting of the following A to C. The high-boiling point monomer may also be a monomer that satisfies condition C. Phenoxybenzyl acrylate satisfies conditions A to C. A: A boiling point of 240°C or higher under a pressure of 760 mmHg B: A boiling point of 90°C or higher under a pressure of 0.2 mmHg C: A boiling point of 65°C or higher under a pressure of 0.1 mmHg

[0046] An example of an impurity that may be contained in the aromatic ring-containing (meth)acrylate is a polyfunctional acrylate such as a diacrylate. An example of a diacrylate is a compound represented by the following formula:

[0047] From another perspective of the above viewpoint, the monomer component M may include a monomer containing two or more aromatic rings. The monomer may be a (meth)acrylate having two or more aromatic rings in a side chain. The upper limit of the number of aromatic rings is, for example, 5 or less, and may be 4 or less, or even 3 or less. The number of aromatic rings may be 2.

[0048] From another aspect of the above viewpoint, the monomer component M may contain a high-boiling point monomer. The high-boiling point monomer may be a (meth)acrylate.

[0049] Other monomers that may be contained in the monomer component M will be described.

[0050] An example of such a monomer is alkyl(meth)acrylate a2. The number of carbon atoms in the alkyl group in alkyl(meth)acrylate a2 is not particularly limited and may be, for example, 1 to 30. The alkyl group may be linear, branched, or cyclic. Examples of the alkyl group include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, amyl, hexyl, cyclohexyl, heptyl, 2-ethylhexyl, isooctyl, nonyl, decyl, isodecyl, dodecyl, isomyristyl, lauryl, tridecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl. The alkyl(meth)acrylate a2 may be used alone or in combination of two or more. When two or more types are combined, the average carbon number of the alkyl group is preferably 3 to 9. The alkyl(meth)acrylate a2 is preferably butyl acrylate.

[0051] The content of alkyl (meth)acrylate a2 in the monomer component M may be 97% by weight or less, 95% by weight or less, 90% by weight or less, 85% by weight or less, 80% by weight or less, 75% by weight or less, 70% by weight or less, 65% by weight or less, 60% by weight or less, 55% by weight or less, 50% by weight or less, 45% by weight or less, 40% by weight or less, 35% by weight or less, 30% by weight or less, 25% by weight or less, 22% by weight or less, 20% by weight or less, 17% by weight or less, 15% by weight or less, or even 13% by weight or less. The lower limit of the content is, for example, 1% by weight or more, 3% by weight or more, or even 5% by weight or more. The monomer component M may not contain alkyl (meth)acrylate a2.

[0052] Another example of the other monomer is at least one monomer selected from the group consisting of hydroxyl group-containing monomer a3, amide group-containing monomer a4, and carboxyl group-containing monomer a5. In other words, the monomer component M may contain at least one monomer selected from the group consisting of hydroxyl group-containing monomer a3, amide group-containing monomer a4, and carboxyl group-containing monomer a5. These monomers can be used alone or in combination of two or more.

[0053] The hydroxyl group-containing monomer a3 is a compound that contains a hydroxyl group in its structure and a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. The hydroxyl group-containing monomer a3 may be a hydroxyl group-containing (meth)acrylate. Examples of hydroxyl group-containing (meth)acrylates include hydroxyl group-containing alkyl (meth)acrylates 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, and 12-hydroxylauryl (meth)acrylate; and hydroxyl group-containing cycloalkyl (meth)acrylates such as (4-hydroxymethylcyclohexyl)-methyl acrylate. Among these, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred.

[0054] The content of the hydroxyl group-containing monomer a3 in the monomer component M may be 0.1% by weight or more, 0.2% by weight or more, 0.3% by weight or more, 0.5% by weight or more, 1% by weight or more, 1.5% by weight or more, or even 2% by weight or more. The upper limit of the content is, for example, 9% by weight or less, and may be 7% by weight or less, 5% by weight or less, 4.5% by weight or less, 4% by weight or less, 3.5% by weight or less, 3% by weight or less, 2.5% by weight or less, or even 2% by weight or less. The monomer component M may not contain a hydroxyl group-containing monomer.

[0055] The amide group-containing monomer a4 is a compound that contains an amide group in its structure and a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group, etc. The amide group-containing monomer a4 may be an amide group-containing (meth)acrylate. Examples of the amide group-containing (meth)acrylate include acrylamide-based 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-methylol(meth)acrylamide, N-methylol-N-propane(meth)acrylamide, aminomethyl(meth)acrylamide, aminoethyl(meth)acrylamide, mercaptomethyl(meth)acrylamide, and mercaptoethyl(meth)acrylamide; N-acryloyl heterocyclic monomers such as N-(meth)acryloylmorpholine, N-(meth)acryloylpiperidine, and N-(meth)acryloylpyrrolidine; and N-vinyl group-containing lactam monomers such as N-vinylpyrrolidone and N-vinyl-ε-caprolactam.

[0056] The carboxyl group-containing monomer a5 is a compound containing a carboxyl group and a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group in its structure. The carboxyl group-containing monomer a5 may be a carboxyl group-containing (meth)acrylate. Examples of the carboxyl group-containing (meth)acrylate include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid.

[0057] The total content of the amide-containing monomer a4 and the carboxyl group-containing monomer a5 in the monomer component M is, for example, 10% by weight or less, and may be 7% by weight or less, 5% by weight or less, or even 3% by weight or less. The lower limit of the content is, for example, 0.5% by weight or more, and may be 1% by weight or more. The monomer component M may not contain the amide group-containing monomer a4. The monomer component M may not contain the carboxyl group-containing monomer a5.

[0058] Another example of the other monomer is a monomer (copolymerizable monomer a6) that can be copolymerized with each of the above-mentioned monomers. The copolymerizable monomer a6 usually has a polymerizable functional group containing an unsaturated double bond, such as a (meth)acryloyl group or a vinyl group. Examples of the copolymerizable monomer a6 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 allylsulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, and sulfopropyl (meth)acrylate; phosphoric acid group-containing monomers such as 2-hydroxyethyl acryloyl phosphate; alkylaminoalkyl (meth)acrylates such as aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and t-butylaminoethyl (meth)acrylate; alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; and succinimide-based monomers such as N-(meth)acryloyloxymethylene succinimide, N-(meth)acryloyl-6-oxyhexamethylene succinimide, and N-(meth)acryloyl-8-oxyoctamethylene succinimide. monomers; maleimide-based monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; itaconimide-based monomers such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, and N-laurylitaconimide; vinyl-based monomers such as vinyl acetate and vinyl propionate; cyanoacrylate-based monomers such as acrylonitrile and methacrylonitrile; epoxy group-containing (meth)acrylates such as glycidyl (meth)acrylate; glycol-based (meth)acrylates such as carbitol (meth)acrylate, ethyl carbitol (meth)acrylate, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, and methoxypolypropylene glycol (meth)acrylate;(Meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, fluorine (meth)acrylate, and silicone (meth)acrylate; and 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;

[0059] The content of copolymerizable monomer a6 in monomer component M is, for example, 5% by weight or less, and may be 3% by weight or less, or even 1% by weight or less. Monomer component M may not contain copolymerizable monomer a6.

[0060] Formation of Base Polymer and Other Components Various known polymerization methods can be applied to form the base polymer from the monomer composition, such as solution polymerization, radiation polymerization using electron beams or ultraviolet (UV) rays, bulk polymerization, and emulsion polymerization. Polymerization is typically radical polymerization. The base polymer may be any of a random copolymer, block copolymer, graft copolymer, etc. of the monomer component M. However, the method for forming the base polymer is not limited to the above examples.

[0061] As the polymerization solvent for solution polymerization, known polymerization solvents such as ethyl acetate and toluene can be used. Solution polymerization can be carried out, for example, using a polymerization initiator and under a stream of an inert gas such as nitrogen. The polymerization conditions are, for example, 50 to 70°C and 5 to 30 hours.

[0062] The polymerization initiator, chain transfer agent, emulsifier, etc. used in the radical polymerization are not particularly limited and can be selected appropriately.

[0063] Examples of the polymerization initiator include 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'-dimethyleneisobutylamidine), and 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; di(2-ethylhexyl)peroxydicarbonate, di(4-t-butylcyclohexyl)peroxydicarbonate, di-s Examples of the polymerization initiator include peroxide initiators such as ec-butyl peroxydicarbonate, t-butyl peroxyneodecanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, di(4-methylbenzoyl)peroxide, dibenzoyl peroxide, t-butyl peroxyisobutyrate, 1,1-di(t-hexylperoxy)cyclohexane, t-butyl hydroperoxide, and hydrogen peroxide; and redox initiators that combine a peroxide and a reducing agent, such as a combination of a persulfate and sodium hydrogen sulfite, or a combination of a peroxide and sodium ascorbate. However, the polymerization initiator is not limited to the above examples.

[0064] The polymerization initiators may be used alone or in combination of two or more. The total amount of the polymerization initiators used is, for example, 0.005 to 1 part by weight, or may be 0.02 to 0.5 parts by weight, relative to 100 parts by weight of the monomer component M.

[0065] Examples of the chain transfer agent include lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimercapto-1-propanol. The chain transfer agents may be used alone or in combination of two or more. The total amount of the chain transfer agents used is, for example, 0.1 parts by weight or less per 100 parts by weight of the monomer component M.

[0066] In radiation polymerization, a monomer component M is irradiated with radiation such as an electron beam or ultraviolet (UV) light to cause polymerization to proceed and form a base polymer. When radiation polymerization is carried out using an electron beam, the use of a photopolymerization initiator is not particularly necessary. When radiation polymerization is carried out using UV light, a photopolymerization initiator may be used because it has the advantage of being able to shorten the polymerization time. The photopolymerization initiators can be used alone or in combination of two or more.

[0067] Examples of the photopolymerization initiator include various photopolymerization initiators such as benzoin ether-based, acetophenone-based, α-ketol-based, photoactive oxime-based, benzoin-based, benzil-based, benzophenone-based, ketal-based, and thioxanthone-based photopolymerization initiators. However, the photopolymerization initiator is not limited to the above examples. The amount of the photopolymerization initiator used is, for example, 0.05 to 1.5 parts by weight, or may be 0.1 to 1 part by weight, relative to 100 parts by weight of the monomer component M.

[0068] The weight average molecular weight (Mw) of the base polymer is, for example, 700,000 or more, and may be 750,000 or more, 800,000 or more, 850,000 or more, 900,000 or more, 950,000 or more, or even 1,000,000 or more. The upper limit of Mw is, for example, 2,000,000 or less, 1,900,000 or less, 1,800,000 or less, 1,700,000 or less, 1,600,000 or less, or even 1,500,000 or less.

[0069] The PSA composition A may contain components other than the above-mentioned components.

[0070] [1-2-1b. Other Components] Crosslinking Agent The pressure-sensitive adhesive composition A may contain a crosslinking agent. Examples of crosslinking agents that the pressure-sensitive adhesive composition A may contain include isocyanate-based crosslinking agents, peroxide-based crosslinking agents, epoxy-based crosslinking agents, imine-based crosslinking agents, and polyfunctional metal chelates. The pressure-sensitive adhesive composition A preferably contains an isocyanate-based crosslinking agent and / or a peroxide-based crosslinking agent, and more preferably contains an isocyanate-based crosslinking agent. In other words, the crosslinked product of the base polymer contained in the first pressure-sensitive adhesive sheet 3 may have a crosslinked structure due to a peroxide-based crosslinking agent, or may have a crosslinked structure due to an isocyanate-based crosslinking agent, or may have both crosslinked structures.

[0071] As the isocyanate-based crosslinking agent, a compound having at least two isocyanate groups (isocyanate compound) can be used. The number of isocyanate groups contained in the isocyanate compound is preferably 3 or more. The upper limit of the number of isocyanate groups is not particularly limited, and is, for example, 5. Examples of the isocyanate compound include aromatic isocyanate compounds, alicyclic isocyanate compounds, and aliphatic isocyanate compounds.

[0072] Examples of aromatic isocyanate compounds are phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, and xylylene diisocyanate.

[0073] Examples of the alicyclic isocyanate compound are 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated tetramethylxylylene diisocyanate.

[0074] Examples of 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.

[0075] The isocyanate-based crosslinking agent may be a polymer (dimer, trimer, pentamer, etc.) of the above-mentioned isocyanate compound, an adduct obtained by adding the compound to a polyhydric alcohol such as trimethylolpropane, a urea-modified compound, a biuret-modified compound, an allophanate-modified compound, an isocyanurate-modified compound, a carbodiimide-modified compound, or a urethane prepolymer obtained by adding the compound to a polyether polyol, a polyester polyol, an acrylic polyol, a polybutadiene polyol, a polyisoprene polyol, or the like.

[0076] The isocyanate-based crosslinking agent is preferably an aromatic isocyanate compound and its derivatives, more preferably tolylene diisocyanate and its derivatives, in other words, a tolylene diisocyanate-based (TDI-based) crosslinking agent. From the viewpoint of reactivity, a TDI-based crosslinking agent is more suitable than xylylene diisocyanate and its derivatives, in other words, a xylylene diisocyanate-based (XDI-based) crosslinking agent. The isocyanate-based crosslinking agent may contain an adduct of a polyhydric alcohol and tolylene diisocyanate as the TDI-based crosslinking agent. A specific example of the adduct is a trimethylolpropane / tolylene diisocyanate trimer adduct.

[0077] Commercially available isocyanate crosslinking agents can be used. Examples of commercially available products include Millionate MT, Millionate MTL, Millionate MR-200, Millionate MR-400, Coronate L, Coronate HL, and Coronate HX (all 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, and Takenate 600 (all manufactured by Mitsui Chemicals, Inc.). Of these, Takenate D-101E and Takenate D110N are preferred.

[0078] The isocyanate-based crosslinking agents may be used alone or in combination of two or more kinds.

[0079] The amount of the isocyanate crosslinking agent in the PSA composition A is, for example, 0.01 to 20 parts by weight relative to 100 parts by weight of the base polymer. The lower limit of the amount may be 0.05 parts by weight or more, 0.1 parts by weight or more, 0.15 parts by weight or more, 0.2 parts by weight or more, or even 0.3 parts by weight or more. The upper limit of the amount may 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, or even 0.5 parts by weight or less.

[0080] The amount of the non-isocyanate crosslinking agent, for example, a peroxide crosslinking agent, blended in the PSA composition A may be, for example, 2 parts by weight or less, 1 part by weight or less, or even 0.5 parts by weight or less, relative to 100 parts by weight of the base polymer. The lower limit of the blending amount may be, for example, 0.01 parts by weight or more, 0.05 parts by weight or more, 0.1 parts by weight or more, 0.15 parts by weight or more, or even 0.2 parts by weight or more. The blending amount may be 0.05 to 1 part by weight, or 0.1 to 0.5 parts by weight. The PSA composition A may not contain a non-isocyanate crosslinking agent.

[0081] Additives The pressure-sensitive adhesive composition A may contain additives. Examples of additives include refractive index improvers, silane coupling agents, solvents, colorants, pigments, powders, dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners, antioxidants, antiaging agents, light stabilizers, UV absorbers, polymerization inhibitors, inorganic or organic fillers, metal powders, particles, and foil-like materials. Redox systems containing reducing agents may also be used within controllable limits. However, the additives are not limited to the above examples. The total amount of additives may be, for example, 10 parts by weight or less, 5 parts by weight or less, or even 1 part by weight or less, per 100 parts by weight of the base polymer.

[0082] The pressure-sensitive adhesive composition A may contain a refractive index enhancer as an additive. The refractive index enhancer can contribute to improving the refractive index of the first pressure-sensitive adhesive sheet 3. An example of the refractive index enhancer is a high refractive index monomer. Examples of the high refractive index monomer include phenoxybenzyl acrylate (refractive index 1.566), 1-naphthylmethyl acrylate (refractive index 1.595), ethoxylated o-phenylphenol acrylate (number of repeating oxyethylene units: 1, refractive index 1.578), benzyl acrylate (refractive index 1.519), phenoxyethyl acrylate (refractive index 1.517), phenoxydiethylene glycol acrylate (refractive index 1.510), 6-acryloyloxymethyldinaphthothioate, Examples of suitable high refractive index monomers include 6-vinyldinaphthothiophene (6VDNT, refractive index 1.802), 5-vinyldinaphthothiophene (5VDNT, refractive index 1.793), 6-vinyldinaphthothiophene (6MDNTA, refractive index 1.75), 6-methacryloyloxymethyldinaphthothiophene (6MDNTMA, refractive index 1.726), 5-acryloyloxyethyldinaphthothiophene (5EDNTA, refractive index 1.786), 6-acryloyloxyethyldinaphthothiophene (6EDNTA, refractive index 1.722), 6-vinyldinaphthothiophene (6VDNT, refractive index 1.802), and 5-vinyldinaphthothiophene (5VDNT, refractive index 1.793). The high refractive index monomer serving as the refractive index improver is preferably a monomer having a higher refractive index than the aromatic ring-containing monomer a1 that may be contained in the monomer component M. The refractive index of the high refractive index monomer serving as the refractive index improver may be 1.6 or more, 1.65 or more, or even 1.7 or more. The upper limit of the refractive index of the high refractive index monomer is, for example, 3.0 or less, and may be 2.5 or less, 2.0 or less, or even 1.9 or less. The refractive index of the monomer can be measured using an Abbe refractometer under conditions of a measurement wavelength of 550 nm and a measurement temperature of 25°C. For example, the Abbe refractometer that can be used is the "DR-4M" model manufactured by ATAGO or an equivalent. When the nominal value of the refractive index at 25°C is provided by the manufacturer of the monomer, etc., that nominal value can be used as the refractive index.

[0083] When the pressure-sensitive adhesive composition A contains a refractive index enhancer, the blending amount thereof may be, for example, 15 parts by weight or less, 12 parts by weight or less, or even 10 parts by weight or less, relative to 100 parts by weight of the base polymer. The lower limit of the blending amount is not particularly limited, and is, for example, 0.5 parts by weight or more. The pressure-sensitive adhesive composition A does not need to contain a refractive index enhancer.

[0084] The PSA composition A may contain a silane coupling agent as an additive. Examples of the silane coupling agent include epoxy group-containing silane coupling agents such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 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-dimethylbutylidene)propylamine, and N-phenyl-γ-aminopropyltrimethoxysilane; (meth)acrylic group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane; and isocyanate group-containing silane coupling agents such as 3-isocyanatepropyltriethoxysilane.

[0085] When the pressure-sensitive adhesive composition A contains a silane coupling agent, the amount thereof may be, for example, 5 parts by weight or less, 3 parts by weight or less, 1 part by weight or less, 0.5 parts by weight or less, 0.4 parts by weight or less, 0.2 parts by weight or less, or even 0.1 parts by weight or less, relative to 100 parts by weight of the base polymer. The lower limit of the amount is not particularly limited, and is, for example, 0.02 parts by weight or more. The pressure-sensitive adhesive composition A does not need to contain a silane coupling agent.

[0086] The pressure-sensitive adhesive composition A may be substantially free of a photocuring agent such as a photopolymerization initiator.

[0087] The PSA composition A is typically a solvent-based composition that can be dried to form the first PSA sheet 3. In this case, the first PSA sheet 3 formed from the PSA composition A is usually a solvent-based composition. Solvent-based compositions are also called thermosetting compositions.

[0088] <1-2-2. Formation of Pressure-Sensitive Adhesive Sheet> The first pressure-sensitive adhesive sheet 3 can be formed, for example, by drying a coating film of the pressure-sensitive adhesive composition A provided on a substrate. Heat can be used for drying. A release film may be used as the substrate. The first pressure-sensitive adhesive sheet 3 formed on the release film can be transferred to, for example, another layer that may be included in the optical laminate. The substrate may be another layer that may be included in the optical laminate.

[0089] As the release film, a known film that can be used when forming a solvent-based pressure-sensitive adhesive sheet can be used.

[0090] The drying temperature of the coating film is, for example, 100° C. or higher, and may be 110° C. or higher, 120° C. or higher, 130° C. or higher, or even 140° C. or higher. The upper limit of the drying temperature may be, for example, 170° C. or lower, 160° C. or lower, or even 150° C. or lower. The drying time of the coating film can be appropriately adjusted depending on the composition of the pressure-sensitive adhesive composition A, and may be, for example, 30 to 300 seconds, 40 to 240 seconds, or even 60 to 180 seconds.

[0091] The method for forming the first pressure-sensitive adhesive sheet 3 from the pressure-sensitive adhesive composition A is not limited to the above example. For example, the first pressure-sensitive adhesive sheet 3 may be formed by the following method.

[0092] First, a coating film of pressure-sensitive adhesive composition A is formed on a substrate. However, in addition to a base polymer, pressure-sensitive adhesive composition A also contains a thermal crosslinking agent, a photopolymerization initiator, and a multifunctional monomer. An example of a thermal crosslinking agent is the crosslinking agent described above. Next, the coating film is dried to form a pressure-sensitive adhesive sheet precursor. Heating can be used in combination with drying. Examples of drying temperatures and drying times are as described above, but conditions are set so that the coating film does not completely harden. The pressure-sensitive adhesive sheet precursor may be formed by adjusting the amount of crosslinking agent added to pressure-sensitive adhesive composition A. Next, the pressure-sensitive adhesive sheet precursor is irradiated with light to promote a photocuring reaction in which the multifunctional monomer acts as a photocrosslinking agent, thereby forming a first pressure-sensitive adhesive sheet 3. The light is, for example, visible light or ultraviolet light with a wavelength shorter than 450 nm. The formed first pressure-sensitive adhesive sheet 3 is a layer formed by curing pressure-sensitive adhesive composition A, which contains a base polymer, a multifunctional monomer, a thermal crosslinking agent, and a photopolymerization initiator. Depending on the photocuring conditions and the types and conditions of processes performed after curing, the photopolymerization initiator may remain on the formed first pressure-sensitive adhesive sheet 3. The hardness of the pressure-sensitive adhesive sheet precursor is usually lower than that of the first pressure-sensitive adhesive sheet 3. However, a certain level of adhesiveness can be obtained even in the state of the pressure-sensitive adhesive sheet precursor. For example, it is also possible to form the first pressure-sensitive adhesive sheet 3 by adhering the pressure-sensitive adhesive sheet precursor to an object and then allowing a photocuring reaction to proceed, and this method can contribute to improving the anchoring force of the first pressure-sensitive adhesive sheet 3 to the object.

[0093] A polyfunctional monomer is a compound containing two or more polymerizable functional groups. The polyfunctional monomer may be a (meth)acrylic monomer. Examples of polyfunctional monomers 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 polymerizable functional groups such as epoxy groups, aziridine groups, oxazoline groups, hydrazine groups, and methylol groups in one molecule. The polyfunctional monomer is preferably a monomer having two or more C=C bonds in one molecule.

[0094] Examples of polyfunctional monomers include (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol diacrylate (N Polyfunctional acrylates (such as ester compounds of polyhydric alcohols and (meth)acrylic acid) such as 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and tetramethylolmethane tri(meth)acrylate; allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyl di(meth)acrylate, and hexyl di(meth)acrylate. The polyfunctional monomer is preferably a polyfunctional acrylate, and more preferably trimethylolpropane tri(meth)acrylate, hexanediol di(meth)acrylate, or dipentaerythritol hexa(meth)acrylate.

[0095] When a polyfunctional monomer is blended, the blending amount of the polyfunctional monomer in the PSA composition A may be, for example, 50 parts by weight or less, 45 parts by weight or less, 40 parts by weight or less, or 35 parts by weight or less, relative to 100 parts by weight of the base polymer. The lower limit of the blending amount may be, for example, 1 part by weight or more, 3 parts by weight or more, 5 parts by weight or more, 7 parts by weight or more, 10 parts by weight or more, or even 15 parts by weight or more, relative to 100 parts by weight of the base polymer.

[0096] The photopolymerization initiator may be a photoradical generator that generates radicals when exposed to visible light and / or ultraviolet light having a wavelength shorter than 450 nm.

[0097] Examples of the photopolymerization initiator include benzoin ethers such as benzoin methyl ether, benzoin isopropyl ether, and benzil dimethyl ketal; substituted benzoin ethers such as anisole methyl ether; substituted acetophenones such as 2,2-diethoxyacetophenone and 2,2-dimethoxy-2-phenylacetophenone; α-hydroxyalkylphenones such as 1-hydroxycyclohexyl-phenyl ketone; substituted alpha-ketol such as 2-methyl-2-hydroxypropiophenone; aromatic sulfonyl chlorides such as 2-naphthalenesulfonyl chloride; photoactive oximes such as 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime; and benzophenone compounds such as benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, acrylated benzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, and 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone. Thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and 2,4-diethylthioxanthone; 2,4,6-trichloro-s-triazine, 2-phenyl-4,6-bis(trichloromethyl)-s-triazine, 2-(p-methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine, and 2-(p-tolyl)-4,6-bis(trichloromethyl)-s-triazine , 2-piperonyl-4,6-bis(trichloromethyl)-s-triazine, 2,4-bis(trichloromethyl)-6-styryl-s-triazine, 2-(naphth-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2-(4-methoxy-naphth-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2,4-trichloromethyl-(piperonyl)-6-triazine, 2,4-trichloromethyl-(4'-methoxystyryl)-6-triazine and other triazine-based compounds;Oxime ester compounds such as 1,2-octanedione, 1-[4-(phenylthio)phenyl]-, 2-(o-benzoyloxime), O-(acetyl)-N-(1-phenyl-2-oxo-2-(4'-methoxy-naphthyl)ethylidene)hydroxylamine; phosphine compounds such as bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 2,4,6-trimethylbenzoyldiphenylphosphine oxide; quinone compounds such as 9,10-phenanthrenequinone, camphorquinone, and ethylanthraquinone; borate compounds; carbazole compounds; imidazole compounds; and titanocene compounds. The pressure-sensitive adhesive composition A may contain one or more photopolymerization initiators.

[0098] Specific examples of the photopolymerization initiator include 2,2-dimethoxy-1,2-diphenylethan-1-one (Omnirad 651, manufactured by IGM Resins B.V.), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 819, manufactured by IGM Resins B.V.), and 1-hydroxycyclohexyl phenyl ketone (Omnirad 184, manufactured by IGM Resins B.V.). However, the photopolymerization initiator is not limited to the above examples.

[0099] When a photopolymerization initiator is blended, the content of the photopolymerization initiator in the pressure-sensitive adhesive composition A is, for example, 0.02 to 10 parts by weight, or may be 0.05 to 5 parts by weight, 0.1 to 3 parts by weight, or even 0.2 to 2 parts by weight, relative to 100 parts by weight of the base polymer.

[0100] In the optical laminate 1 according to the embodiment of the present invention, the anchoring force of the first pressure-sensitive adhesive sheet 3 to the first liquid crystal alignment solidified layer 2 may be 4 N / 25 mm or more, 4.5 N / 25 mm or more, 5 N / 25 mm or more, 5.5 N / 25 mm or more, 6 N / 25 mm or more, 6.5 N / 25 mm or more, 7 N / 25 mm or more, 7.5 N / 25 mm or more, 8 N / 25 mm or more, 8.5 N / 25 mm or more, or 9 N / 25 mm or more. There is no upper limit to the anchoring force.

[0101] <1-3. Second Pressure-Sensitive Adhesive Sheet> The optical laminates 1B and 1C include a second pressure-sensitive adhesive sheet 5. The second pressure-sensitive adhesive sheet 5 constitutes one exposed surface of the optical laminate 1B. Furthermore, the second pressure-sensitive adhesive sheet 5 can constitute one exposed surface of the optical laminate 1C by peeling off the release liner 6. When the optical laminates 1B and 1C are bonded to another member, the second pressure-sensitive adhesive sheet 5 can constitute the bonding surface with the other member.

[0102] The second pressure-sensitive adhesive sheet 5 may be a known pressure-sensitive adhesive sheet that can be used in optical laminates and image display devices. The second pressure-sensitive adhesive sheet 5 may be a (meth)acrylic pressure-sensitive adhesive sheet. The second pressure-sensitive adhesive sheet 5 may be formed by a known method. The pressure-sensitive adhesive sheet described above in the description of the first pressure-sensitive adhesive sheet 3, in other words, a pressure-sensitive adhesive sheet corresponding to the first pressure-sensitive adhesive sheet 3, may be used as the second pressure-sensitive adhesive sheet 5. However, in this case, the configuration of the first pressure-sensitive adhesive sheet 3 and the configuration of the second pressure-sensitive adhesive sheet 5 may be the same or different.

[0103] <<1-4. Release Liner>> The optical laminate 1C includes a release liner 6. The optical laminate 1C may be used after the release liner 6 is peeled off.

[0104] The release liner 6 is, for example, a film, paper, woven fabric, nonwoven fabric, porous material, net, foam, foil, or laminate thereof made of resin, paper, fiber, metal, or a composite material thereof. Examples of resins include 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. Furthermore, the materials and resins that can be used to make the release liner 6 are not limited to the above examples.

[0105] The thickness of the release liner 6 is, for example, 5 to 200 μm, and may be 5 to 100 μm. The surface of the release liner 6 may be subjected to various surface treatments such as release treatment, antifouling treatment, and antistatic treatment as needed. For the release treatment, various release agents such as silicone-based, fluorine-based, long-chain alkyl-based, and fatty acid amide-based release agents, or particles such as silica powder can be used.

[0106] The base material used in forming the second pressure-sensitive adhesive sheet 5 , such as a release film, may be used as the release liner 6 .

[0107] <1-5. Polarizing Film> The optical laminate 1 according to the embodiment of the present invention may include layers other than those described above. An example of the other layer is an optical substrate. The optical laminate 1 may include one or more optical substrates. In other words, the optical substrate that may be included in the optical laminate 1 may be a single layer or a laminate. An example of an optical substrate is a polarizing film. The optical laminate 1 may include a polarizing film.

[0108] An example of an optical laminate 1 including a polarizing film is shown in Figure 4. The optical laminate 1 (1D) in Figure 4 includes a polarizing film 7, a first liquid crystal alignment solidified layer 2, a first adhesive sheet 3, and a second liquid crystal alignment solidified layer 4, in this order. The optical laminate 1D also includes a polarizing film 7, a first liquid crystal alignment solidified layer 2, a first adhesive sheet 3, a second liquid crystal alignment solidified layer 4, and a second adhesive sheet 5, in this order. In the optical laminate 1D, adjacent layers are in contact with each other. However, layers other than those described above may be included between adjacent layers.

[0109] Another example of an optical laminate 1 including a polarizing film is shown in Figure 5. The optical laminate 1 (1E) in Figure 5 includes, in this order, a polarizing film 7, a first liquid crystal alignment solidified layer 2, a first pressure-sensitive adhesive sheet 3, a second liquid crystal alignment solidified layer 4, a second pressure-sensitive adhesive sheet 5, and a release liner 6. In the optical laminate 1E, adjacent layers are in contact with each other. However, layers other than those described above may be included between adjacent layers.

[0110] The polarizing film 7 typically includes a polarizer and protective layers disposed on both sides of the polarizer. Depending on the purpose, at least one of the protective layers may be omitted. Therefore, the polarizing film 7 may be a so-called double-protected polarizing film, a so-called single-protected polarizing film, or may be composed of a polarizer alone.

[0111] A polarizer is typically made of a film made of a polyvinyl alcohol (PVA)-based resin containing a dichroic substance (e.g., iodine). Examples of PVA-based resins include polyvinyl alcohol, partially formalized polyvinyl alcohol, ethylene-vinyl alcohol copolymer, and partially saponified ethylene-vinyl acetate copolymer.

[0112] The PVA-based resin preferably contains an acetoacetyl-modified PVA-based resin. The amount of the acetoacetyl-modified PVA-based resin is preferably 5 to 20% by weight, and more preferably 8 to 12% by weight, based on 100% by weight of the total PVA-based resin.

[0113] The polarizer preferably contains iodide or sodium chloride (sometimes collectively referred to as a halide). Examples of iodides include potassium iodide, sodium iodide, and lithium iodide. The content of the halide in the polarizer is preferably 5 to 20 parts by weight, more preferably 10 to 15 parts by weight, relative to 100 parts by weight of the PVA-based resin. In the manufacturing method described below, the halide is blended into a coating liquid that forms a PVA-based resin layer, which is a precursor of the polarizer, and can be finally introduced into the polarizer. Introducing a halide into the polarizer can improve the orientation of PVA molecules in the polarizer, thereby realizing a polarizer with excellent optical properties (typically, both a high degree of polarization and a high single-unit transmittance).

[0114] The polarizer preferably exhibits absorptive dichroism at any wavelength between 380 nm and 780 nm. The single transmittance of the polarizer is preferably 41.0% to 46.0%, more preferably 42.0% to 45.0%. The degree of polarization of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and even more preferably 99.9% or more.

[0115] The thickness of the polarizer is, for example, 12 μm or less, preferably 10 μm or less, more preferably 1 μm to 8 μm, and even more preferably 3 μm to 7 μm. For example, combining such a thin polarizer with a liquid crystal alignment solidified layer is suitable for reducing the thickness of the optical laminate.

[0116] The polarizer can be produced by any appropriate method. For example, the resin film forming the polarizer may be a single-layer resin film or a laminate of two or more layers.

[0117] Specific examples of polarizers composed of a single-layer resin film include hydrophilic polymer films such as PVA films, partially formalized PVA films, and partially saponified ethylene-vinyl acetate copolymer films that have been dyed with iodine or a dichroic substance such as a dichroic dye and stretched, and polyene-based oriented films such as dehydrated PVA films and dehydrochlorinated polyvinyl chloride films. Preferably, a polarizer obtained by dyeing a PVA film with iodine and uniaxially stretching it is used because of its excellent optical properties.

[0118] The dyeing with iodine is carried out, for example, by immersing the PVA-based film in an aqueous iodine solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching may be carried out after the dyeing treatment or while dyeing. Alternatively, the PVA-based film may be stretched and then dyed. If necessary, the PVA-based film may be subjected to a swelling treatment, a crosslinking treatment, a washing treatment, a drying treatment, or the like. For example, by immersing the PVA-based film in water and washing it before dyeing, it is possible to wash away dirt and antiblocking agents from the surface of the PVA-based film and also to swell the PVA-based film, thereby preventing uneven dyeing and the like.

[0119] Specific examples of laminate polarizers include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate. A polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate can be produced, for example, by applying a PVA-based resin solution to the resin substrate and drying it to form a PVA-based resin layer on the resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer, and then stretching and dyeing the laminate to convert the PVA-based resin layer into a polarizer. Preferably, a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin is formed on one side of the resin substrate.

[0120] The stretching typically involves immersing the laminate polarizer in a boric acid aqueous solution and stretching it. Furthermore, the stretching may further include, if necessary, in-air stretching of the laminate at a high temperature (e.g., 95°C or higher) before stretching in the boric acid aqueous solution. Preferably, the laminate is subjected to a drying shrinkage treatment in which the laminate is heated while being transported in the longitudinal direction, thereby shrinking the laminate by 2% or more in the width direction. Typically, the method involves subjecting the laminate to an in-air auxiliary stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment, in this order. The introduction of auxiliary stretching makes it possible to increase the crystallinity of the PVA, even when the PVA is coated on a thermoplastic resin, thereby achieving high optical properties. Furthermore, by simultaneously increasing the orientation of the PVA in advance, problems such as a decrease in orientation or dissolution of the PVA can be prevented when the PVA is immersed in water in the subsequent dyeing or stretching steps, thereby achieving high optical properties. Furthermore, when the PVA-based resin layer is immersed in a liquid, the disordering of the polyvinyl alcohol molecules and the decrease in the orientation can be suppressed compared to when the PVA-based resin layer does not contain a halide. This can improve the optical properties of a polarizer obtained through treatment steps in which the laminate is immersed in a liquid, such as a dyeing treatment and an underwater stretching treatment. Furthermore, the optical properties can be improved by shrinking the laminate in the width direction through a drying shrinkage treatment. The obtained resin substrate / polarizer laminate may be used as is (i.e., the resin substrate may serve as a protective layer for the polarizer). Alternatively, any suitable protective layer may be laminated on the peeled surface of the resin substrate / polarizer laminate after peeling the resin substrate from the resin substrate / polarizer laminate, or on the surface opposite to the peeled surface. Details of such a polarizer manufacturing method are described, for example, in JP-A-2012-73580 and JP-A-6470455. The entire disclosures of these publications are incorporated herein by reference.

[0121] The protective layers that can be disposed on both sides of the polarizer are typically composed of any appropriate resin film. Typical materials for such resin films include cellulose-based resins such as triacetyl cellulose (TAC), cycloolefin-based resins such as polynorbornene, (meth)acrylic resins, polyester-based resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyolefin-based resins such as polyethylene, and polycarbonate-based resins. Representative examples of (meth)acrylic resins include (meth)acrylic resins having a lactone ring structure. Examples of (meth)acrylic resins having a lactone ring structure are described in, for example, JP 2000-230016 A, JP 2001-151814 A, JP 2002-120326 A, JP 2002-254544 A, and JP 2005-146084 A. These publications are incorporated herein by reference. From the viewpoint of ease of processing into modified shapes, etc., cellulose-based resins are preferred, and TAC is more preferred. From the viewpoint of obtaining a polarizing plate with low moisture permeability and excellent durability, cycloolefin-based resins and (meth)acrylic resins are preferred.

[0122] The protective layer may be subjected to a surface treatment as needed. Examples of surface treatments include hard coating, anti-reflection, anti-sticking, and anti-glare treatments. The protective layer may be subjected to a treatment to improve visibility when viewed through polarized sunglasses (typically, by imparting an (elliptically) circular polarization function or an ultra-high phase difference) as needed. By performing such treatments, excellent visibility can be achieved even when the display screen is viewed through polarized lenses such as polarized sunglasses.

[0123] The protective layer may be optically isotropic, for example, the in-plane retardation Re(550) may be 0 nm to 10 nm, and the thickness direction retardation Rth(550) may be −10 nm to +10 nm.

[0124] The thickness of each protective layer is preferably 10 μm to 80 μm, more preferably 12 μm to 40 μm, and even more preferably 15 μm to 35 μm. When the protective layer is surface-treated, the thickness of the protective layer includes the thickness of the surface-treated layer.

[0125] The optical laminate 1 according to the embodiment of the present invention may include a surface protective film. The surface protective film is disposed, for example, on the outermost layer on the viewing side of the optical laminate 1. The surface protective film may be a known surface protective film included in an optical laminate that can be used in an image display device. The surface protective film may be a glass film.

[0126] The optical laminate 1 according to an embodiment of the present invention may include any layer other than those described above. The optical laminate 1 may include at least one layer selected from the group consisting of a pressure-sensitive adhesive sheet, an adhesive layer, and a release liner on the side opposite the first pressure-sensitive adhesive sheet 3 relative to the second liquid crystal alignment solidified layer 4. The outermost layer on the side opposite the first pressure-sensitive adhesive sheet 3 relative to the second liquid crystal alignment solidified layer 4 may be a release liner. The optical laminate 1 may include at least one layer selected from the group consisting of a pressure-sensitive adhesive sheet, an adhesive layer, an optical substrate, a surface protective film, a hard coat layer, and a release liner on the side opposite the first pressure-sensitive adhesive sheet 3 relative to the first liquid crystal alignment solidified layer 2. The outermost layer on the side opposite the first pressure-sensitive adhesive sheet 3 relative to the first liquid crystal alignment solidified layer 2 may be a surface protective film. The optical substrate may include at least one layer selected from the group consisting of a retardation layer and a polarizing film, or may include a polarizing film.

[0127] The optical laminate 1 according to the embodiment of the present invention can be distributed and stored, for example, as a rolled body obtained by rolling up a strip-shaped optical laminate 1 or as a sheet-shaped optical laminate 1 .

[0128] The optical laminate 1 according to the embodiment of the present invention is typically used in an image display device. In other words, the optical laminate 1 may be used for an image display device. The image display device is, for example, an EL display such as a liquid crystal display, an organic EL display, or an inorganic EL display. The uses of the optical laminate 1 are not limited to the above examples. Furthermore, the image display device in which the optical laminate 1 can be used is not limited to the above examples.

[0129] The optical laminate 1 according to the embodiment of the present invention can be formed by laminating each of the layers included therein. Layers that have been subjected to a surface modification treatment may be laminated. The surface modification treatment is, for example, at least one selected from the group consisting of corona treatment, plasma treatment, excimer UV light treatment, and flame treatment, and may be corona treatment and / or plasma treatment, or may be corona treatment. Each surface modification treatment can be performed using a corresponding known treatment device.

[0130] 2. Image Display Device An example of an image display device according to an embodiment of the present invention is shown in Fig. 6. The image display device 15 of Fig. 6 has a layered structure in which a polarizing film 7, a first liquid crystal alignment solidified layer 2, a first adhesive sheet 3, a second liquid crystal alignment solidified layer 4, a second adhesive sheet 5, an image forming layer (e.g., an organic EL layer or a liquid crystal layer) 8, and a substrate 9 are layered in this order. The image display device 15 has the optical laminate 1D of Fig. 4. The image forming layer 8 and the substrate 9 may have the same configurations as the substrate and the image forming layer, respectively, provided in known image display devices.

[0131] The image display device 15 in Fig. 6 may be an organic EL display or a liquid crystal display. However, the image display device 15 is not limited to the above examples. The image display device 15 may be an electroluminescence (EL) display, a plasma display (PD), a field emission display (FED), or the like. The image display device 15 can be used for home appliances, in-vehicle applications, public information displays (PID), and the like.

[0132] The image display device of the present invention may have any configuration as long as it includes the optical layered body of the present invention.

[0133] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the examples shown below.

[0134] In this example, a first pressure-sensitive adhesive sheet was prepared, and its refractive index, G' (25°C), and glass transition temperature (Tg) were evaluated. Furthermore, an optical laminate (see Figure 5) was prepared in which a polarizing film, a first liquid crystal alignment solidified layer, a first pressure-sensitive adhesive sheet, a second liquid crystal alignment solidified layer, a second pressure-sensitive adhesive sheet, and a release liner were laminated in this order. The refractive index difference between the first pressure-sensitive adhesive sheet and the second liquid crystal alignment solidified layer, the resistance to through-cracks, the observed state of microcracks, the anchoring strength of the first pressure-sensitive adhesive sheet to the first liquid crystal alignment solidified layer, and durability at a temperature of 80°C were evaluated for the prepared optical laminate.

[0135] <<Preparation of First Pressure-Sensitive Adhesive Sheet>> <Preparation of Base Polymer> (Preparation of (Meth)Acrylic Polymer P1) A four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser was charged with 81.9 parts by weight of n-butyl acrylate (BA), 0.1 parts by weight of 4-hydroxybutyl acrylate (4HBA), 13.2 parts by weight of benzyl acrylate (BzA), and 4.8 parts by weight of acrylic acid (AA). Furthermore, 0.1 parts by weight of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator was charged together with ethyl acetate relative to 100 parts by weight of the monomer mixture. After introducing nitrogen gas while gently stirring to replace the atmosphere with nitrogen, the liquid temperature in the flask was maintained at around 55°C and a polymerization reaction was carried out for 7 hours. The monomer concentration during polymerization was 35% by weight. Thereafter, ethyl acetate was added to the resulting reaction solution to adjust the solids concentration to 30% by weight, yielding a solution of (meth)acrylic polymer P1.

[0136] (Preparation of (meth)acrylic polymers P2 to P4) Solutions of (meth)acrylic polymers P2 to P4 were obtained in the same manner as for (meth)acrylic polymer P1, except that the types and amounts of monomers were changed as shown in Table 1 below.

[0137]

[0138] The abbreviations of the monomers shown in Table 1 are as follows. For POB-A, a commercially available monomer (manufactured by Kyoeisha Chemical Co., Ltd., purity 94%) was further purified by adsorption. BA: n-butyl acrylate 4HBA: 4-hydroxybutyl acrylate POB-A: phenoxybenzyl acrylate BzA: benzyl acrylate AA: acrylic acid

[0139] <Preparation of Pressure-Sensitive Adhesive Compositions> Solvent-based Pressure-Sensitive Adhesive Compositions A1 to A8 were obtained by mixing the (meth)acrylic polymer prepared above as a base polymer with a crosslinking agent and additives so as to obtain the compositions shown in Table 2. The blending amounts of the crosslinking agent and additives shown in Table 2 are values ​​(unit: parts by weight) when the weight of the base polymer is taken as 100 parts by weight.

[0140]

[0141] The abbreviations in Table 2 are as follows: D-110N: Trimethylolpropane / xylylene diisocyanate trimer adduct (Takenate D-110N, manufactured by Mitsui Chemicals, Inc.) BPO: Benzoyl peroxide M315: Isocyanuric acid ethylene oxide modified di- and triacrylate (manufactured by Toagosei Co., Ltd.) TMPTA: Trimethylolpropane triacrylate (Viscoat #295, manufactured by Osaka Organic Chemical Industry Co., Ltd.) Omnirad 184: 1-hydroxycyclohexyl phenyl ketone (Omnirad 184, manufactured by IGM Resins B.V.)

[0142] <Preparation of first pressure-sensitive adhesive sheet and pressure-sensitive adhesive sheet precursor> (Preparation of first pressure-sensitive adhesive sheet S1) Pressure-sensitive adhesive composition A1 was applied to the surface of a release liner PET film (Mitsubishi Chemical Corporation, MRF38-NS2) so that the pressure-sensitive adhesive sheet would have a predetermined thickness after drying. A fountain coater was used to apply the pressure-sensitive adhesive composition A1. The coating film formed by application was dried in an air-circulating constant-temperature oven at 120°C for 1 minute to produce a first pressure-sensitive adhesive sheet S1 (thickness 5 μm).

[0143] (Preparation of First Pressure-Sensitive Adhesive Sheet S2) A first pressure-sensitive adhesive sheet S2 (thickness: 5 μm) was prepared in the same manner as for the preparation of the first pressure-sensitive adhesive sheet S1, except that the pressure-sensitive adhesive composition A2 was used instead of the pressure-sensitive adhesive composition A1.

[0144] (Preparation of First Pressure-Sensitive Adhesive Sheet S3) A first pressure-sensitive adhesive sheet S3 (thickness: 5 μm) was prepared in the same manner as for the preparation of the first pressure-sensitive adhesive sheet S1, except that the pressure-sensitive adhesive composition A3 was used instead of the pressure-sensitive adhesive composition A1.

[0145] (Preparation of First Pressure-Sensitive Adhesive Sheet S4) A first pressure-sensitive adhesive sheet S4 (thickness: 5 μm) was prepared in the same manner as for the preparation of the first pressure-sensitive adhesive sheet S1, except that the pressure-sensitive adhesive composition A4 was used instead of the pressure-sensitive adhesive composition A1.

[0146] (Preparation of Precursor of First Pressure-Sensitive Adhesive Sheet S5) Pressure-Sensitive Adhesive Composition A5 was applied to the surface of a release liner PET film (Mitsubishi Chemical Corporation, MRF38-NS2) so that the thickness of the pressure-sensitive adhesive sheet after drying would be a predetermined thickness. A fountain coater was used to apply Pressure-Sensitive Adhesive Composition A5. The coating film formed by application was subjected to a drying treatment at 120°C for 1 minute in an air-circulating constant-temperature oven, thereby forming a pressure-sensitive adhesive sheet precursor.

[0147] (Preparation of Precursor of First Pressure-Sensitive Adhesive Sheet S6) Pressure-Sensitive Adhesive Composition A6 was applied to the surface of a release liner PET film (Mitsubishi Chemical Corporation, MRF38-NS2) so that the thickness of the pressure-sensitive adhesive sheet after drying would be a predetermined thickness. A fountain coater was used to apply Pressure-Sensitive Adhesive Composition A6. The coating film formed by application was subjected to a drying treatment at 110°C for 1 minute in an air-circulating constant-temperature oven, thereby forming a pressure-sensitive adhesive sheet precursor.

[0148] (Preparation of Precursor of First Pressure-Sensitive Adhesive Sheet S7) Pressure-Sensitive Adhesive Composition A7 was applied to the surface of a release liner PET film (Mitsubishi Chemical Corporation, MRF38-NS2) so that the thickness of the pressure-sensitive adhesive sheet after drying would be a predetermined thickness. A fountain coater was used to apply Pressure-Sensitive Adhesive Composition A7. The coating film formed by application was subjected to a drying treatment at 110°C for 1 minute in an air-circulating constant-temperature oven, thereby forming a pressure-sensitive adhesive sheet precursor.

[0149] (Preparation of Precursor of First Pressure-Sensitive Adhesive Sheet S8) Pressure-Sensitive Adhesive Composition A8 was applied to the surface of a release liner PET film (Mitsubishi Chemical Corporation, MRF38-NS2) so that the thickness of the pressure-sensitive adhesive sheet after drying would be a predetermined thickness. A fountain coater was used to apply Pressure-Sensitive Adhesive Composition A8. The coating film formed by application was subjected to a drying treatment at 110°C for 1 minute in an air-circulating constant-temperature oven, thereby forming a pressure-sensitive adhesive sheet precursor.

[0150] <<Preparation of Liquid Crystal Alignment Solidified Layer>> <Preparation of First Liquid Crystal Alignment Solidified Layer> A photopolymerizable liquid crystal compound exhibiting a nematic liquid crystal phase (BASF, Paliocolor LC242) was dissolved in cyclopentanone to prepare a solution with a solids concentration of 30 wt %. A surfactant (BYK-360, BYK-Chemie) and a photopolymerization initiator (Omnirad 907, IGM Resins B.V.) were added to this solution to prepare a liquid crystal composition solution. The amounts of the surfactant and polymerization initiator added were 0.01 parts by weight and 3 parts by weight, respectively, per 100 parts by weight of the photopolymerizable liquid crystal compound. A biaxially stretched norbornene-based film (ZEON Corporation, Zeonor Film, thickness 33 μm, Re(550) = 135 nm) was prepared as a substrate film. The liquid crystal composition solution was applied to a substrate film using a bar coater so that Re(550) was 240 nm, and the liquid crystal was aligned by heating at 100°C for 3 minutes. After cooling to room temperature, the liquid crystal was aligned by irradiating the substrate with an integrated light intensity of 400 mJ / cm under a nitrogen atmosphere. 2 The film was photocured by irradiating it with ultraviolet light of 1.75 .ANG. to obtain a laminate having a structure of a substrate film / a first liquid crystal alignment solidified layer. The first liquid crystal alignment solidified layer was homogeneously oriented, had a thickness of 1.7 μm, and a refractive index of 1.590.

[0151] <Preparation of second liquid crystal alignment solidified layer> A laminate of substrate film / second liquid crystal alignment solidified layer (homogeneous alignment, thickness 0.92 μm, Re(550)=130 nm) was obtained in the same manner as in the preparation of the first liquid crystal alignment solidified layer, except for changing the coating thickness. The refractive index of the second liquid crystal alignment solidified layer was 1.590.

[0152] <<Preparation of Optical Laminate>> <Preparation of Adhesive for Laminating Polarizing Film and First Liquid Crystal Alignment Solidified Layer> 10 parts by weight of hydroxyethyl acrylamide (trade name "HEAA", manufactured by KJ Chemicals), 4 parts by weight of 2-acetoacetoxyethyl methacrylate (trade name "AAEM", manufactured by Mitsubishi Chemicals), 60 parts by weight of acryloylmorpholine (trade name "ACMO", manufactured by KJ Chemicals), 11 parts by weight of tripropylene glycol diacrylate (trade name "Aronix M-220", manufactured by Toagosei Co., Ltd.), 1 part by weight of 4-vinylphenylboronic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 10 parts by weight of acrylic oligomer (trade name "ARUFON UP-1190", manufactured by Toagosei Co., Ltd.), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (trade name "Omnirad 819", manufactured by IGM) An adhesive was prepared by stirring 1 part by weight of 1-hydroxycyclohexyl phenyl ketone (trade name "Omnirad 184", manufactured by IGM Resins B.V.) 2 parts by weight of 1-hydroxycyclohexyl phenyl ketone (trade name "Omnirad 184", manufactured by IGM Resins B.V.) and 1 part by weight of diethyl thioxanthone (trade name "KAYACUREDETX-S", manufactured by Nippon Kayaku Co., Ltd.) at 50°C for 1 hour.

[0153] <Preparation of Second Pressure-Sensitive Adhesive Sheet> A commercially available (meth)acrylic pressure-sensitive adhesive sheet formed on a release liner was prepared as the second pressure-sensitive adhesive sheet. A plurality of second pressure-sensitive adhesive sheets with release liner thicknesses different from each other were prepared.

[0154] <Preparation of Optical Laminate L1> A commercially available polarizing film was prepared, and the first liquid crystal alignment solidified layer side of a laminate having a substrate film / first liquid crystal alignment solidified layer structure was bonded to its protective film via the adhesive (thickness 1 μm) prepared above. The substrate film was then peeled off to obtain a laminate having a polarizing film / adhesive / first liquid crystal alignment solidified layer structure. Next, the exposed surface of the first liquid crystal alignment solidified layer was plasma-treated, and the exposed surface was bonded to the exposed surface of a first pressure-sensitive adhesive sheet S1 formed on a release liner to obtain a laminate having a polarizing film / adhesive / first liquid crystal alignment solidified layer / first pressure-sensitive adhesive sheet S1 / release liner structure. Next, the release liner was peeled off from the first pressure-sensitive adhesive sheet S1, and the second liquid crystal alignment solidified layer side of a laminate having a substrate film / second liquid crystal alignment solidified layer structure was bonded to the exposed surface of the first pressure-sensitive adhesive sheet S1 exposed by peeling. Prior to lamination, the exposed surface of the second liquid crystal alignment solidified layer in the laminate was corona-treated. Next, the substrate film was peeled off to obtain a laminate having a configuration of polarizing film / adhesive / first liquid crystal alignment solidified layer / first pressure-sensitive adhesive sheet S1 / second liquid crystal alignment solidified layer. Next, the exposed surface of the second liquid crystal alignment solidified layer was plasma-treated, and then the exposed surface was bonded to the exposed surface of the second pressure-sensitive adhesive sheet formed on the release liner to obtain an optical laminate L1 having a configuration of polarizing film / adhesive / first liquid crystal alignment solidified layer / first pressure-sensitive adhesive sheet S1 / second liquid crystal alignment solidified layer / second pressure-sensitive adhesive sheet / release liner. The total thickness of the optical laminate L1 was 140 μm, and the ratio A / B in the optical laminate L1 was 0.93.

[0155] <Preparation of optical laminate L2> Optical laminate L2 was prepared in the same manner as optical laminate L1, except that the thickness of the polarizing film and the thickness of the release liner on which the second pressure-sensitive adhesive sheet was formed were changed. The total thickness of optical laminate L2 was 168 μm, and the ratio A / B in optical laminate L2 was 1.81.

[0156] <Preparation of optical laminate L3> Optical laminate L3 was prepared in the same manner as optical laminate L1, except that the first pressure-sensitive adhesive sheet S2 was used instead of the first pressure-sensitive adhesive sheet S1. The total thickness of optical laminate L3 was 140 μm, and the ratio A / B of optical laminate L3 was 0.93.

[0157] <Preparation of optical laminate L4> Optical laminate L4 was prepared in the same manner as optical laminate L3, except that the thickness of the polarizing film and the thickness of the release liner on which the second pressure-sensitive adhesive sheet was formed were changed. The total thickness of optical laminate L4 was 168 μm, and the ratio A / B in optical laminate L4 was 1.81.

[0158] <Preparation of optical laminate L5> Optical laminate L5 was prepared in the same manner as optical laminate L3, except that the thickness of the polarizing film and the thickness of the release liner on which the second pressure-sensitive adhesive sheet was formed were changed. The total thickness of optical laminate L5 was 108 μm, and the ratio A / B in optical laminate L5 was 0.63.

[0159] <Preparation of optical laminate L6> Optical laminate L6 was prepared in the same manner as optical laminate L1, except that the first pressure-sensitive adhesive sheet S3 was used instead of the first pressure-sensitive adhesive sheet S1. The total thickness of optical laminate L6 was 140 μm, and the ratio A / B of optical laminate L6 was 0.93.

[0160] <Preparation of optical laminate L7> Optical laminate L7 was prepared in the same manner as optical laminate L6, except that the thickness of the polarizing film and the thickness of the release liner on which the second pressure-sensitive adhesive sheet was formed were changed. The total thickness of optical laminate L7 was 168 μm, and the ratio A / B in optical laminate L7 was 1.81.

[0161] <Preparation of optical laminate L8> Optical laminate L8 was prepared in the same manner as optical laminate L6, except that the thickness of the polarizing film and the thickness of the release liner on which the second pressure-sensitive adhesive sheet was formed were changed. The total thickness of optical laminate L8 was 108 μm, and the ratio A / B in optical laminate L8 was 0.63.

[0162] <Preparation of optical laminate L9> Optical laminate L9 was prepared in the same manner as optical laminate L1, except that the first pressure-sensitive adhesive sheet S4 was used instead of the first pressure-sensitive adhesive sheet S1. The total thickness of optical laminate L9 was 140 μm, and the ratio A / B of optical laminate L9 was 0.93.

[0163] <Preparation of optical laminate L10> Optical laminate L10 was prepared in the same manner as optical laminate L9, except that the thickness of the polarizing film and the thickness of the release liner on which the second pressure-sensitive adhesive sheet was formed were changed. The total thickness of optical laminate L10 was 168 μm, and the ratio A / B in optical laminate L10 was 1.81.

[0164] <Preparation of optical laminate L11> Optical laminate L11 was prepared in the same manner as optical laminate L9, except that the thickness of the polarizing film and the thickness of the release liner on which the second pressure-sensitive adhesive sheet was formed were changed. The total thickness of optical laminate L11 was 108 μm, and the ratio A / B in optical laminate L11 was 0.63.

[0165] <Preparation of Optical Laminate L12> A commercially available polarizing film was prepared, and the first liquid crystal alignment solidified layer side of a laminate having a substrate film / first liquid crystal alignment solidified layer structure was bonded to its protective film via the adhesive (thickness 1 μm) prepared above. The substrate film was then peeled off to obtain a laminate having a polarizing film / adhesive / first liquid crystal alignment solidified layer structure. Next, the exposed surface of the first liquid crystal alignment solidified layer was plasma treated, and then this exposed surface was bonded to the exposed surface of the precursor of the first pressure-sensitive adhesive sheet S5 formed on a release liner to obtain a laminate having a polarizing film / adhesive / first liquid crystal alignment solidified layer / pressure-sensitive adhesive sheet precursor / release liner structure. Next, the release liner was peeled off from the pressure-sensitive adhesive sheet, and the second liquid crystal alignment solidified layer side of the laminate having a substrate film / second liquid crystal alignment solidified layer structure was bonded to the exposed surface of the pressure-sensitive adhesive sheet precursor exposed by peeling. Prior to bonding, the exposed surface of the second liquid crystal alignment solidified layer in the laminate was corona-treated. Next, ultraviolet light (accumulated light amount 1000 mJ / cm ) was applied from a high-pressure mercury lamp to the substrate film side of the obtained laminate. 2) to photocure the pressure-sensitive adhesive sheet precursor, producing a first pressure-sensitive adhesive sheet S5. The substrate film was then peeled off to obtain a laminate having a configuration of polarizing film / adhesive / first liquid crystal alignment solidified layer / first pressure-sensitive adhesive sheet S5 / second liquid crystal alignment solidified layer. The exposed surface of the second liquid crystal alignment solidified layer was then plasma-treated, and the exposed surface was then bonded to the exposed surface of a second pressure-sensitive adhesive sheet formed on a release liner to obtain an optical laminate L12 having a configuration of polarizing film / adhesive / first liquid crystal alignment solidified layer / first pressure-sensitive adhesive sheet S5 / second liquid crystal alignment solidified layer / second pressure-sensitive adhesive sheet / release liner. The total thickness of the optical laminate L12 was 168 μm, and the ratio A / B in the optical laminate L12 was 1.81.

[0166] <Preparation of optical laminate L13> Optical laminate L13 was prepared in the same manner as optical laminate L12, except that the thickness of the polarizing film and the thickness of the release liner on which the second pressure-sensitive adhesive sheet was formed were changed. The total thickness of optical laminate L13 was 108 μm, and the ratio A / B in optical laminate L13 was 0.63.

[0167] <Preparation of optical laminate L14> Optical laminate L14 was prepared in the same manner as optical laminate L1, except that the first pressure-sensitive adhesive sheet S4 was used instead of the first pressure-sensitive adhesive sheet S1, and the thickness of the polarizing film and the thickness of the release liner on which the second pressure-sensitive adhesive sheet was formed were changed. The total thickness of optical laminate L14 was 77 μm, and the ratio A / B in optical laminate L14 was 1.40.

[0168] <Preparation of optical laminate L15> Optical laminate L15 was prepared in the same manner as optical laminate L14, except that the thickness of the polarizing film and the thickness of the release liner on which the second pressure-sensitive adhesive sheet was formed were changed. The total thickness of optical laminate L15 was 142 μm, and the ratio A / B in optical laminate L15 was 0.44.

[0169] <Preparation of optical laminate L16> Optical laminate L16 was prepared in the same manner as optical laminate L12, except that the precursor of first pressure-sensitive adhesive sheet S6 was used instead of the precursor of first pressure-sensitive adhesive sheet S5, and the thickness of the polarizing film and the thickness of the release liner on which the second pressure-sensitive adhesive sheet was formed were changed. The total thickness of optical laminate L16 was 108 μm, and the ratio A / B in optical laminate L16 was 0.63.

[0170] <Preparation of optical laminate L17> Optical laminate L17 was prepared in the same manner as optical laminate L12, except that the precursor of first pressure-sensitive adhesive sheet S7 was used instead of the precursor of first pressure-sensitive adhesive sheet S5, and the thickness of the polarizing film and the thickness of the release liner on which the second pressure-sensitive adhesive sheet was formed were changed. The total thickness of optical laminate L17 was 108 μm, and the ratio A / B in optical laminate L17 was 0.63.

[0171] <Preparation of optical laminate L18> Optical laminate L18 was prepared in the same manner as optical laminate L12, except that the precursor of first pressure-sensitive adhesive sheet S8 was used instead of the precursor of first pressure-sensitive adhesive sheet S5, and the thickness of the polarizing film and the thickness of the release liner on which the second pressure-sensitive adhesive sheet was formed were changed. The total thickness of optical laminate L18 was 108 μm, and the ratio A / B in optical laminate L18 was 0.63.

[0172] <<Evaluation>> <Evaluation of First Pressure-Sensitive Adhesive Sheets> The following evaluations were performed on the first pressure-sensitive adhesive sheets S1 to S8. The evaluations were performed on the first pressure-sensitive adhesive sheets formed on release liners using the procedure described above. However, for the first pressure-sensitive adhesive sheets S5 to S8, the evaluations were performed on pressure-sensitive adhesive sheets obtained by photocuring precursors of the first pressure-sensitive adhesive sheets S5 to S8 formed on release liners with ultraviolet light. The ultraviolet irradiation conditions were the same as those used when producing the optical laminate L12.

[0173] [Refractive Index] The refractive index of the first pressure-sensitive adhesive sheet was measured using an Abbe refractometer at a measurement temperature of 25°C and a measurement wavelength of 589 nm. The Abbe refractometer used was a "DR-4M" model manufactured by ATAGO. When measuring the refractive index, only the first pressure-sensitive adhesive sheet was set against a prism with an Abbe refractive index diameter (the release liner was removed).

[0174] [G' (25°C) of Pressure-Sensitive Adhesive Sheet] The G' (25°C) of the first pressure-sensitive adhesive sheet was measured using the method described above. A measurement sample was prepared by peeling the first pressure-sensitive adhesive sheet to be evaluated from the release liner and cutting a laminate (150 μm thick) into a 10 mm wide, 40 mm long strip. A TA Instruments RSA-G2 was used for the dynamic viscoelasticity measurement. The dynamic viscoelasticity measurement conditions were as follows. The tensile storage modulus E' (25°C) obtained by measurement was converted to the storage modulus G' (25°C) in the shear direction based on the relational expression E' = 3 × G'. (Measurement conditions) Distance between chucks: 15 mm Frequency: 1 Hz Deformation mode: Tensile Measurement temperature: -70°C to 150°C Heating rate: 5°C / min

[0175] [Glass Transition Temperature (Tg) of Pressure-Sensitive Adhesive Sheet] The Tg of the first pressure-sensitive adhesive sheet was measured by the following method. The release liner was peeled from the first pressure-sensitive adhesive sheet to be evaluated, and a laminate (150 μm thick) formed by laminating multiple sheets was cut into a strip of 10 mm width and 40 mm length to prepare a measurement sample. Next, dynamic viscoelasticity measurement was carried out under the following measurement conditions using a dynamic viscoelasticity measuring device (TA Instruments, RSA-G2). The peak top temperature of the measured tan δ (= tensile storage modulus E' / tensile loss modulus E") was identified as the Tg. (Measurement Conditions) Distance between chucks: 15 mm Frequency: 1 Hz Deformation mode: Tensile Measurement temperature: -70°C to 150°C Heating rate: 5°C / min

[0176] The evaluation results are shown in Table 3 below.

[0177]

[0178] <<Evaluation of Optical Laminates>> The optical laminates L1 to L18 were evaluated as follows.

[0179] <Through cracks> Each optical laminate was evaluated for resistance to through cracks using the following method. First, each optical laminate was fixed to the surface of a glass plate (manufactured by Corning, Eagle XG) using an acrylic adhesive sheet (thickness: 25 μm) with the polarizing film as the bonding surface. The fixing was performed in an atmosphere of 23° C. and 50% RH. The optical laminate to be fixed was a rectangle measuring 50 mm × 150 mm. Ten evaluation samples were prepared for each optical laminate to be evaluated. Next, a load of 500 g was applied for 3 seconds using a pen tip to the vicinity of the center of the release liner exposed as the outermost layer. After the load application, the optical laminate was observed as a transmitted image using an optical microscope (magnification: 10x), and the number of samples among the 10 evaluation samples in which cracks were visible was evaluated according to the following criteria. A: The number of samples in which cracks were visible was 0. B: The number of samples in which cracks were visible was 1 or 2. C: The number of samples in which cracks were visible was 3 or 4. D: The number of samples in which cracks were visible was 5 or more.

[0180] <Microcracks> Each optical laminate was evaluated for the state in which microcracks were observed by the following method. First, a load was applied to the optical laminate fixed to the surface of a glass plate in the same manner as in the evaluation of through cracks. The optical laminate after the load application was observed as a reflected image under an optical microscope (10x magnification), and the number of samples in which bright spots were visible out of 10 evaluation samples was evaluated according to the following criteria: A: The number of samples in which bright spots were visible was 0 B: The number of samples in which bright spots were visible was 1 or 2 C: The number of samples in which bright spots were visible was 3 or 4 D: The number of samples in which bright spots were visible was 5 or more

[0181] <Anchor Strength> For each optical laminate, the anchoring strength of the first pressure-sensitive adhesive sheet to the first liquid crystal alignment solidified layer was evaluated by the following method. First, the optical laminate was cut into a size of 25 mm wide x 150 mm long to prepare a test specimen. Next, the entire surface of the polarized film provided on the test specimen was placed on a stainless steel test plate (SUS304, width 40 mm x length 120 mm) via double-sided tape (Nitto Denko Corporation, No. 531), and they were pressed together by rolling a 2 kg roller once. Next, the release liner was peeled off from the test specimen to expose the second pressure-sensitive adhesive sheet, and an evaluation sheet (Oike Kogyo Co., Ltd., 125 Tetolite OES, width 30 mm x length 150 mm) was placed on top of the exposed second pressure-sensitive adhesive sheet, and they were pressed together by rolling a 2 kg roller once. Next, using a tensile tester (Shimadzu Corporation, Autograph SHIMAZU AG-I 10KN), while holding the evaluation sheet, interlayer peeling was performed between the first pressure-sensitive adhesive sheet and the first liquid crystal alignment solidified layer at a peel angle of 180° and a peel speed of 300 mm / min. The average value of the peel force measured during peeling was determined as the anchoring force. The test was carried out at 23°C.

[0182] <80°C Durability> Each optical laminate was subjected to an 80°C durability test using the following method. First, the release liner was peeled off, and the exposed second pressure-sensitive adhesive sheet was attached to the surface of a glass plate (Corning, Eagle XG) using a hand roller. The attachment was performed in an atmosphere of 23°C and 50% RH. Next, the laminate was treated for 15 minutes in an autoclave at 50°C and 5 atmospheres (absolute pressure), and then left to cool to 23°C to stabilize the bonding of the laminate to the glass plate. Next, the entire laminate was left in a heated atmosphere at 80°C for 500 hours. After leaving the laminate, the sample was returned to an atmosphere of 23°C and 50% RH. Peeling of the first pressure-sensitive adhesive sheet was visually confirmed, and the durability at high temperatures was evaluated according to the following criteria: A: No peeling was observed. B: Minute bubbles were observed at the corners of the sample, but at a level that does not pose a practical problem. C: Minute bubbles were observed at the corners and sides of the sample, but at a level that does not pose a practical problem.

[0183] The evaluation results are shown in Table 4 below.

[0184]

[0185] The optical laminates of the Examples were less susceptible to through cracks than the Comparative Examples.

[0186] 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 comprising, in this order, a first liquid crystal alignment solidified layer, a first adhesive sheet, and a second liquid crystal alignment solidified layer, wherein the ratio A / B of the thickness A of a first laminated portion of the optical laminate, including all layers located on the first liquid crystal alignment solidified layer side of the first adhesive sheet, to the thickness B of a second laminated portion of the optical laminate, including all layers located on the second liquid crystal alignment solidified layer side of the first adhesive sheet, is 0.5 or more and 2 or less, and the total thickness of the optical laminate is 80 μm or more.

2. The optical laminate according to claim 1, wherein the second laminate portion includes a second adhesive sheet located on the opposite side of the second liquid crystal alignment solidified layer from the first adhesive sheet.

3. The optical laminate described in claim 1, wherein the second laminated portion includes, in this order, a second adhesive sheet and a release liner located on the opposite side of the second liquid crystal alignment solidified layer from the first adhesive sheet.

4. The optical laminate according to claim 1, wherein the total thickness of the optical laminate is 100 μm or more and 200 μm or less.

5. The optical laminate described in claim 1, wherein the absolute value of the difference between the refractive index n1 of the second liquid crystal alignment solidified layer for light with a wavelength of 589 nm and the refractive index n2 of the first adhesive sheet for light with a wavelength of 589 nm is 0.08 or less.

6. The optical laminate according to claim 1, wherein the storage modulus G' of the first pressure-sensitive adhesive sheet at 25°C is 0.15 MPa or more.

7. The optical laminate according to claim 1, wherein the first pressure-sensitive adhesive sheet comprises a crosslinked base polymer.

8. The optical laminate according to claim 7, wherein the base polymer is a (meth)acrylate polymer.

9. The optical laminate according to claim 7, wherein the monomer component M constituting the base polymer includes an aromatic ring-containing monomer a1.

10. The optical laminate according to claim 9, wherein the aromatic ring-containing monomer a1 is a high-boiling point monomer.

11. The optical laminate according to claim 9, wherein the aromatic ring-containing monomer a1 is phenoxybenzyl acrylate.

12. The optical laminate according to claim 9, wherein the content of the aromatic ring-containing monomer a1 in the monomer component M is 50% by weight or more.

13. The optical laminate according to claim 7, wherein the first adhesive sheet is a layer formed by curing an adhesive composition containing the base polymer, a polyfunctional monomer, a thermal crosslinking agent, and a photopolymerization initiator.

14. The optical laminate according to claim 1, wherein the optical laminate includes a polarizing film.

15. The optical laminate according to claim 14, comprising the polarizing film, the first liquid crystal alignment solidified layer, the first adhesive sheet, and the second liquid crystal alignment solidified layer in this order.

16. The optical laminate according to claim 1, wherein at least one layer selected from the group consisting of the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer is a retardation layer.

17. An image display device comprising the optical laminate according to any one of claims 1 to 16.

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