Optical laminate, optical laminate equipped with polarizing film, image display device, and adhesive sheet

Abstract

The present invention provides an optical laminate including a liquid crystal alignment solidified layer capable of suppressing occurrence of linear unevenness and reducing recesses caused by a localized load. The present invention also provides an optical laminate equipped with a polarizing film, said optical laminate comprising a polarizing film and an optical laminate such as that mentioned above. The present invention additionally provides an image display device including such an optical laminate. Moreover, the present invention provides an adhesive sheet which is preferably used for bonding a liquid crystal alignment solidified layer.　An optical laminate according to an embodiment of the present invention includes a first liquid crystal alignment solidified layer, an adhesive sheet, and a second liquid crystal alignment solidified layer in this order. When the thickness of the adhesive sheet is less than 20 μm, the average refractive index of the adhesive sheet is defined as n, the average refractive index of the first liquid crystal alignment solidified layer is defined as n1, and the average refractive index of the second liquid crystal alignment solidified layer is defined as n2, a maximum average refractive index difference selected from the group consisting of an average refractive index difference calculated by |n-n1| and an average refractive index difference calculated by |n-n2| is less than 0.11, and the indentation hardness of the adhesive sheet at 25°C exceeds 0.019 MPa.

Description

Optical laminate, optical laminate with polarizing film, image display device, and pressure-sensitive adhesive sheet

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

[0002] 2. Description of the Related Art In recent years, image display devices, such as liquid crystal display devices and electroluminescence (EL) display devices (for example, organic EL display devices and inorganic EL display devices), have rapidly become widespread.

[0003] An image display device generally includes an optical laminate including a retardation layer. In recent years, as a demand for thinner image display devices has increased, a demand for thinner optical laminates including such retardation layers has also increased. Therefore, there is a demand for thinner retardation layers, which contribute greatly to the thickness of the image display device.

[0004] As a thin retardation layer, an optical laminate in which two liquid crystal alignment solidified layers are bonded together by an interlayer adhesive is known. For example, a retardation layer-attached polarizing plate has been reported, which includes a polarizer, a first retardation layer (typically a liquid crystal alignment solidified layer), and a second retardation layer (typically a liquid crystal alignment solidified layer) in this order, and the first retardation layer (typically a liquid crystal alignment solidified layer) and the second retardation layer (typically a liquid crystal alignment solidified layer) are bonded together via an adhesive layer (Patent Document 1). The laminate of the first retardation layer (typically a liquid crystal alignment solidified layer), the adhesive layer, and the second retardation layer (typically a liquid crystal alignment solidified layer) included in this retardation layer-attached polarizing plate corresponds to an optical laminate in which two liquid crystal alignment solidified layers are bonded together by an interlayer adhesive.

[0005] However, conventional image display devices including an optical laminate including a liquid crystal alignment solidified layer have a problem in that they are prone to linear unevenness (typically, a phenomenon in which a thin line with a particularly noticeable pink color is observed in the absorption axis direction of a polarizer when viewed under a three-wavelength tube).Furthermore, conventionally, there is a problem in that dents are prone to occur due to local loads, such as dents in the OCA caused by bonding pressure applied during the manufacture of the image display device.

[0006] Japanese Patent Application Laid-Open No. 2019-204111

[0007] An object of the present invention is to provide an optical laminate including a liquid crystal alignment solidified layer that can suppress the occurrence of linear unevenness and reduce depressions due to local load. It is also an object of the present invention to provide an optical laminate with a polarizing film that includes such an optical laminate and a polarizing film. It is also an object of the present invention to provide an image display device that includes such an optical laminate. Furthermore, it is preferable to provide a pressure-sensitive adhesive sheet that can be used to bond the liquid crystal alignment solidified layer.

[0008] [1] An optical laminate according to an embodiment of the present invention is an optical laminate including a first liquid crystal alignment solidified layer, a pressure-sensitive adhesive sheet, and a second liquid crystal alignment solidified layer, in this order, wherein the pressure-sensitive adhesive sheet has a thickness of less than 20 μm, and the maximum average refractive index difference selected from the group consisting of the average refractive index difference calculated by |n - n1| and the average refractive index difference calculated by |n - n2|, where n is the average refractive index of the pressure-sensitive adhesive sheet, n1 is the average refractive index of the first liquid crystal alignment solidified layer, and n2 is the average refractive index of the second liquid crystal alignment solidified layer, is less than 0.11, and the pressure-sensitive adhesive sheet has an indentation hardness at 25°C of more than 0.019 MPa. [2] In the optical laminate described in [1] above, the pressure-sensitive adhesive sheet may be composed of an acrylic pressure-sensitive adhesive, and the acrylic pressure-sensitive adhesive may be formed from an acrylic pressure-sensitive adhesive composition containing an acrylic polymer obtained by polymerizing a monomer component. [3] In the optical laminate described in [2] above, the acrylic polymer may have a Tg of less than 13°C. [4] In the optical laminate according to any one of [1] to [3] above, the indentation hardness may be less than 0.157 MPa. [5] In the optical laminate according to any one of [1] to [4] above, the thickness of the pressure-sensitive adhesive sheet may be 4 μm or more. [6] In the optical laminate according to any one of [1] to [5] above, the average refractive index n of the pressure-sensitive adhesive sheet may be 1.52 or more. [7] In the optical laminate according to any one of [1] to [6] above, a polarizing film may be provided on at least one side selected from the group consisting of the first liquid crystal alignment solidified layer side and the second liquid crystal alignment solidified layer side, as viewed from the pressure-sensitive adhesive sheet. [8] The optical laminate with a polarizing film according to an embodiment of the present invention comprises a polarizing film on the first liquid crystal alignment solidified layer side, as viewed from the pressure-sensitive adhesive sheet, of the optical laminate according to any one of [1] to [6] above. [9] An optical laminate with a polarizing film according to an embodiment of the present invention includes a polarizing film on the second liquid crystal alignment solidified layer side of the optical laminate described in any one of [1] to [6] above, as viewed from the pressure-sensitive adhesive sheet.

[10] An image display device according to an embodiment of the present invention includes the optical laminate described in any one of [1] to [7] above.

[11] The pressure-sensitive adhesive sheet according to an embodiment of the present invention has a thickness of less than 20 μm, an average refractive index n of 1.50 or more, and an indentation hardness at 25° C. of more than 0.019 MPa.

[12] The pressure-sensitive adhesive sheet according to the above

[11] is composed of an acrylic pressure-sensitive adhesive, and the acrylic pressure-sensitive adhesive may be formed from an acrylic pressure-sensitive adhesive composition containing an acrylic polymer obtained by polymerizing a monomer component.

[13] In the pressure-sensitive adhesive sheet according to the above

[12] , the Tg of the acrylic polymer may be less than 13° C.

[14] In the pressure-sensitive adhesive sheet according to any one of the above

[11] to

[13] , the indentation hardness may be less than 0.157 MPa.

[15] In the pressure-sensitive adhesive sheet according to any one of the above

[11] to

[14] , the average refractive index n may be 1.54 or more.

[16] The pressure-sensitive adhesive sheet according to any one of the above

[11] to

[15] may be used for bonding a liquid crystal alignment solidified layer.

[0009] According to an embodiment of the present invention, an optical laminate including a liquid crystal alignment solidified layer can be provided, which can suppress the occurrence of linear unevenness and reduce depressions due to local load. It is also possible to provide an optical laminate with a polarizing film that includes such an optical laminate and a polarizing film. It is also possible to provide an image display device that includes such an optical laminate. It is also possible to provide a pressure-sensitive adhesive sheet that is preferably used for bonding the liquid crystal alignment solidified layer.

[0010] 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention, a schematic cross-sectional view of an optical laminate with a polarizing film according to one embodiment of the present invention, and a schematic cross-sectional view showing one embodiment of a laminate in which a pressure-sensitive adhesive layer is provided on the surface of the second liquid crystal alignment solidified layer of the optical laminate with a polarizing film according to one embodiment of the present invention, the surface being opposite to the pressure-sensitive adhesive sheet.

[0011] [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.

[0012] 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".

[0013] In this specification, when simply referring to a "liquid crystal alignment solidified layer", it is a concept that includes both the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer.

[0014] In this specification, with regard to the refractive indices (nx, ny, nz), "nx" is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), "ny" is the refractive index in the in-plane direction perpendicular to the slow axis (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction. In this specification, nx, ny, and nz are values ​​for light with a wavelength of 550 nm. In this specification, the average refractive index is calculated by (nx + ny + nz) / 3.

[0015] In this specification, with regard to the in-plane retardation (Re), "Re(λ)" is the in-plane retardation of a film measured with light having a wavelength of λ nm at 23° C. For example, "Re(550)" is the in-plane retardation of a film measured with light having a wavelength of 550 nm at 23° C. Re(λ) can be calculated by the formula: Re=(nx-ny)×d, where d (nm) is the thickness of the film.

[0016] In this specification, with regard to the thickness direction retardation (Rth), "Rth(λ)" is the retardation in the thickness direction of a film measured with light having a wavelength of λ nm at 23° C. For example, "Rth(550)" is the retardation in the thickness direction of a film measured with light having a wavelength of 550 nm at 23° C. Rth(λ) is calculated by the formula: Rth=(nx-nz)×d, where d (nm) is the thickness of the film.

[0017] In this specification, the "Nz coefficient" is calculated by Nz=Rth / Re.

[0018] <<1. Optical Laminate>> An optical laminate according to an embodiment of the present invention includes a first liquid crystal alignment solidified layer, a pressure-sensitive adhesive sheet, and a second liquid crystal alignment solidified layer, in this order. The optical laminate according to an embodiment of the present invention may include any appropriate other components as long as the effects of the present invention are not impaired, as long as the optical laminate includes the first liquid crystal alignment solidified layer, the pressure-sensitive adhesive sheet, and the second liquid crystal alignment solidified layer, in this order. Examples of such other components include a substrate and a release liner used when forming the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer. In an optical laminate according to one preferred embodiment of the present invention, the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer each constitute the outermost layer.

[0019] The optical laminate according to an embodiment of the present invention may further include a positive C plate in addition to the first liquid crystal alignment solidified layer, the pressure-sensitive adhesive sheet, and the second liquid crystal alignment solidified layer. The positive C plate has a refractive index characteristic of nz > nx = ny. The thickness direction retardation Rth(550) of the positive C plate is preferably -20 nm to -300 nm, more preferably -30 nm to -250 nm, even more preferably -40 nm to -200 nm, and particularly preferably -50 nm to -150 nm. Here, "nx = ny" includes not only the case where nx and ny are strictly equal, but also the case where nx and ny are substantially equal. That is, the in-plane retardation Re(550) of the positive C plate may be less than 10 nm.

[0020] The positive C plate can be formed, for example, using a liquid crystal composition containing a side-chain liquid crystal polymer described below. Examples of methods for forming the positive C plate include those described in paragraphs

[0020] to

[0028] of JP-A No. 2002-333642. In this case, the thickness of the positive C plate is preferably 0.5 μm to 10 μm, more preferably 0.5 μm to 8 μm, and even more preferably 0.5 μm to 5 μm.

[0021] Fig. 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. The optical laminate 100 shown in Fig. 1 has a first liquid crystal alignment solidified layer 11, an adhesive sheet 20, and a second liquid crystal alignment solidified layer 12, in this order, where the first liquid crystal alignment solidified layer 11 and the adhesive sheet 20 are directly laminated together, and the adhesive sheet 20 and the second liquid crystal alignment solidified layer 12 are directly laminated together.

[0022] The optical laminate according to an embodiment of the present invention may be used with a polarizing film provided on at least one side selected from the group consisting of the first liquid crystal alignment solidified layer side and the second liquid crystal alignment solidified layer side as viewed from the pressure-sensitive adhesive sheet. That is, the optical laminate according to an embodiment of the present invention is an optical laminate for laminating to a polarizing film, and may be used with a polarizing film provided on at least one side selected from the group consisting of the first liquid crystal alignment solidified layer side and the second liquid crystal alignment solidified layer side as viewed from the pressure-sensitive adhesive sheet. Such an embodiment is, for example, an embodiment in which a polarizing film 200 is laminated to the optical laminate 100 via an adhesive layer 30, as shown in FIG. 2 described later. Note that FIG. 2 shows an embodiment in which the polarizing film 200 is provided on the first liquid crystal alignment solidified layer 11 side as viewed from the pressure-sensitive adhesive sheet 20 in the optical laminate 100, but the polarizing film 200 may also be provided on the second liquid crystal alignment solidified layer 12 side as viewed from the pressure-sensitive adhesive sheet 20 in the optical laminate 100.

[0023] The total thickness of the optical laminate according to the embodiment of the present invention may be any appropriate thickness as long as the effects of the present invention are not impaired. Such a total thickness is preferably 20 μm or less, more preferably 1 μm to 20 μm, even more preferably 2 μm to 15 μm, and particularly preferably 3 μm to 10 μm.

[0024] In the optical laminate according to an embodiment of the present invention, the thickness of the pressure-sensitive adhesive sheet is typically less than 20 μm, and may be 17 μm or less, 15 μm or less, 13 μm or less, or 10 μm or less. In the optical laminate according to an embodiment of the present invention, the lower limit of the thickness of the pressure-sensitive adhesive sheet is typically 1 μm or more, 2 μm or more, 3 μm or more, or 4 μm or more. In the optical laminate according to an embodiment of the present invention, one embodiment of the thickness of the pressure-sensitive adhesive sheet is preferably 1 μm to 20 μm, more preferably 2 μm to 17 μm, even more preferably 3 μm to 15 μm, and particularly preferably 4 μm to 13 μm. By adjusting the thickness of the pressure-sensitive adhesive sheet within the above range, the effects of the present invention can be more effectively exhibited. If the thickness of the pressure-sensitive adhesive sheet is too large, the effects of the present invention may not be exhibited, and in particular, there is a risk of depression due to localized load.

[0025] In the optical laminate according to an embodiment of the present invention, when the average refractive index of the pressure-sensitive adhesive sheet is n, the average refractive index of the first liquid crystal alignment solidified layer is n1, and the average refractive index of the second liquid crystal alignment solidified layer is n2, the maximum average refractive index difference selected from the group consisting of the average refractive index difference calculated by |n-n1| and the average refractive index difference calculated by |n-n2| (i.e., when |n-n1|>|n-n2|, the value of |n-n1|; when |n-n1|<|n-n2|, the value of |n-n2|; when |n-n1|=|n-n2|, the values ​​of |n-n1| and |n-n2|) is typically less than 0.11, preferably 0.10 or less, more preferably 0.09 or less, even more preferably 0.07 or less, particularly preferably 0.06 or less, and most preferably 0.05 or less. The lower limit of the maximum average refractive index difference is preferably as small as possible, and is preferably 0 or more. By adjusting the maximum average refractive index difference within the above range, the effects of the present invention can be more effectively exhibited, and in particular, the occurrence of linear unevenness can be effectively suppressed. If the maximum average refractive index difference is too large, the effects of the present invention may not be exhibited, and in particular, the occurrence of linear unevenness may occur. Note that |n-n1| above represents the absolute value of n-n1, and |n-n2| represents the absolute value of n-n2.

[0026] In the optical laminate according to an embodiment of the present invention, the pressure-sensitive adhesive sheet typically has an indentation hardness at 25°C of more than 0.019 MPa, preferably more than 0.019 MPa and less than 0.157 MPa, more preferably 0.020 MPa to 0.130 MPa, even more preferably 0.030 MPa to 0.100 MPa, particularly preferably 0.040 MPa to 0.090 MPa, and most preferably 0.045 MPa to 0.080 MPa. By adjusting the indentation hardness within the above range, the effects of the present invention can be more effectively exhibited, and in particular, depressions due to localized loads can be effectively reduced. If the indentation hardness is too low, the pressure-sensitive adhesive sheet may become too soft, which may result in depressions due to localized loads. On the other hand, if the indentation hardness is too high, the pressure-sensitive adhesive sheet may become too hard, which may reduce the adhesion between the pressure-sensitive adhesive sheet and the liquid crystal alignment solidified layer.

[0027] An optical laminate according to one embodiment of the present invention is an optical laminate comprising a first liquid crystal alignment solidified layer, a pressure-sensitive adhesive sheet, and a second liquid crystal alignment solidified layer in this order, (i) adjusting the thickness of the pressure-sensitive adhesive sheet to less than 20 μm, (ii) where the average refractive index of the pressure-sensitive adhesive sheet is n, the average refractive index of the first liquid crystal alignment solidified layer is n1, and the average refractive index of the second liquid crystal alignment solidified layer is n2, the maximum average refractive index difference selected from the group consisting of the average refractive index difference calculated by |n - n1 | and the average refractive index difference calculated by |n - n2 | is adjusted to less than 0.11, and (iii) the indentation hardness of the pressure-sensitive adhesive sheet at 25 ° C. is adjusted to exceed 0.019 MPa, thereby achieving the effects of the present invention. In the optical laminate according to the above embodiment, the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer can be any appropriate liquid crystal alignment solidified layer as long as the effects of the present invention are not impaired, but a representative embodiment will be described in the section below, <1-1. Liquid Crystal Alignment Solidified Layer>. In addition, in the optical laminate according to the above embodiment, any appropriate pressure-sensitive adhesive sheet can be adopted as the pressure-sensitive adhesive sheet as long as the effects of the present invention are not impaired. Representative embodiments will be described in the following section 1-2. Pressure-sensitive adhesive sheet.

[0028] 1-1. Liquid Crystal Alignment Solidified Layer The optical laminate according to the embodiment of the present invention includes a first liquid crystal alignment solidified layer and a second liquid crystal alignment solidified layer. By using the liquid crystal alignment solidified layer in this way, the optical laminate according to the embodiment of the present invention can be made thinner.

[0029] The liquid crystal alignment fixed layer may be a layer in which the liquid crystal compound is aligned in a predetermined direction within the layer, and the alignment state is fixed.

[0030] Examples of liquid crystal compounds used in the liquid crystal alignment solidified layer include liquid crystal polymers and liquid crystal monomers. The liquid crystal compound is preferably a polymerizable liquid crystal compound, i.e., a liquid crystal monomer. If the liquid crystal compound is polymerizable, the alignment state of the liquid crystal compound can be fixed by aligning the liquid crystal compound and then polymerizing it. The polymer formed by polymerization can be non-liquid crystal. Therefore, the formed liquid crystal alignment solidified layer does not undergo, for example, a transition to a liquid crystal phase, glass phase, or crystalline phase due to temperature changes that are specific to liquid crystal compounds. As a result, the liquid crystal alignment solidified layer is not affected by temperature changes and has excellent stability.

[0031] In one embodiment, the liquid crystal alignment solidified layer can be formed using a liquid crystal composition containing a liquid crystal monomer. In this specification, the liquid crystal monomer contained in the liquid crystal composition refers to a compound having a polymerizable group and liquid crystallinity. The polymerizable group refers to a group that participates in a polymerization reaction, preferably a photopolymerizable group. Here, the photopolymerizable group refers to a group that can participate in a polymerization reaction by an active radical or acid generated from a photopolymerization initiator. Examples of such liquid crystal monomers that can be used include polymerizable mesogen compounds described in JP-A-2002-533742 (WO 00 / 37585), EP 358208 (US Pat. No. 5,211,877), EP 66137 (US Pat. No. 4,388,453), WO 93 / 22397, EP 0,261,712, DE 19504224, DE 4408171, and GB 2,280,445. Examples of such polymerizable mesogenic compounds include LC242 (trade name) from BASF, E7 (trade name) from Merck, and LC-Silicon-CC3767 (trade name) from Wacker-Chem.

[0032] The mechanism by which the liquid crystal monomer exhibits liquid crystallinity may be thermotropic or lyotropic. The liquid crystal phase may be nematic or smectic. From the viewpoint of ease of production, the liquid crystallinity is preferably thermotropic nematic liquid crystal.

[0033] The temperature range in which the liquid crystal monomer exhibits liquid crystallinity varies depending on the type of the liquid crystal monomer, and specifically, such a temperature range is preferably 40°C to 120°C, more preferably 50°C to 100°C, and even more preferably 60°C to 90°C.

[0034] The birefringence Δn of the liquid crystal alignment solidified layer is preferably 0.06 or more, more preferably 0.08 or more, even more preferably 0.09 or more, and particularly preferably 0.10 or more. The upper limit of Δn may be, for example, 0.13, or may be, for example, 0.12. If Δn is within this range, the desired in-plane retardation can be achieved with a very thin thickness. As a result, the liquid crystal alignment solidified layer and the optical laminate can be made even thinner, which can ultimately contribute to significantly thinner image display devices, for example.

[0035] The liquid crystal alignment solidified layer may exhibit an inverse wavelength dispersion characteristic in which the retardation value increases according to the wavelength of the measurement light, a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light, or a flat wavelength dispersion characteristic in which the retardation value changes little depending on the wavelength of the measurement light.

[0036] The first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer can each typically function as a λ / 2 plate or a λ / 4 plate. The first liquid crystal alignment solidified layer can typically function as a λ / 2 plate, and the second liquid crystal alignment solidified layer can typically function as a λ / 4 plate.

[0037] Specifically, the Re(550) of the first liquid crystal alignment solidified layer is preferably 150 nm to 300 nm, more preferably 200 nm to 270 nm, and even more preferably 220 nm to 260 nm.

[0038] Specifically, the Re(550) of the second liquid crystal alignment solidified layer is preferably 100 nm to 200 nm, more preferably 110 nm to 160 nm, and even more preferably 120 nm to 140 nm.

[0039] The thickness of the first liquid crystal alignment solidified layer can typically be adjusted to obtain the desired in-plane retardation of the λ / 2 plate. In one embodiment, the thickness of the first liquid crystal alignment solidified layer is, for example, 0.5 μm to 5.0 μm, preferably 0.8 μm to 4.0 μm, more preferably 1.0 μm to 3.0 μm, even more preferably 1.2 μm to 2.5 μm, and most preferably 1.3 μm to 2.0 μm. In another embodiment, the thickness of the first liquid crystal alignment solidified layer is preferably 0.3 μm to 1.7 μm, more preferably 0.7 μm to 1.6 μm, even more preferably 1.0 μm to 1.5 μm, and particularly preferably 1.3 μm to 1.5 μm. Thus, according to an embodiment of the present invention, linear unevenness can be suppressed while the thickness of the first liquid crystal alignment solidified layer is thinner than conventional ones.

[0040] The thickness of the second liquid crystal alignment solidified layer can be typically adjusted to obtain a desired in-plane retardation of the λ / 4 plate. In one embodiment, the thickness of the second liquid crystal alignment solidified layer is, for example, 0.5 μm to 2.5 μm, preferably 0.6 μm to 2.0 μm, more preferably 0.7 μm to 1.5 μm, even more preferably 0.7 μm to 1.2 μm, and most preferably 0.7 μm to 1.1 μm.

[0041] The angle between the slow axis of the first liquid crystal alignment solidified layer and the transmission axis of the polarizer is preferably 10° to 20°, more preferably 12° to 18°, and even more preferably 14° to 16°. The angle between the slow axis of the second liquid crystal alignment solidified layer and the transmission axis of the polarizer is preferably 70° to 80°, more preferably 72° to 78°, and even more preferably 74° to 76°. The arrangement order of the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer may be reversed, and the angle between the slow axis of the first liquid crystal alignment solidified layer and the transmission axis of the polarizer and the angle between the slow axis of the second liquid crystal alignment solidified layer and the transmission axis of the polarizer may also be reversed.

[0042] The average refractive index of the liquid crystal alignment solidified layer can vary depending on the composition forming the liquid crystal alignment solidified layer (substantially, the type of liquid crystal compound, the type, number, combination, and amount of additives, etc.) The average refractive index n1 of the first liquid crystal alignment solidified layer and the average refractive index n2 of the second liquid crystal alignment solidified layer may be the same or different from each other (the average refractive index n1 of the first liquid crystal alignment solidified layer may be larger, and the average refractive index n2 of the second liquid crystal alignment solidified layer may be larger).

[0043] The average refractive index n1 of the first liquid crystal alignment fixed layer is preferably 1.55 to 1.75, and more preferably 1.60 to 1.70.

[0044] The average refractive index n2 of the second liquid crystal alignment fixed layer is preferably 1.45 to 1.65, and more preferably 1.50 to 1.60.

[0045] The average refractive index n1 of the first liquid crystal alignment solidified layer and the average refractive index n2 of the second liquid crystal alignment solidified layer may be reversed. The absolute value of the difference between the average refractive index n1 of the first liquid crystal alignment solidified layer and the average refractive index n2 of the second liquid crystal alignment solidified layer may be, for example, 0.00 to 0.20. The average refractive index of the liquid crystal alignment solidified layer will typically be determined based on the composition of the liquid crystal alignment solidified layer to obtain the desired optical characteristics. As a result, linear unevenness may occur, but according to embodiments of the present invention, such linear unevenness can be suppressed.

[0046] A side-chain thermotropic liquid crystal polymer may be introduced into the first liquid crystal alignment solidified layer and / or the second liquid crystal alignment solidified layer (essentially, the liquid crystal composition forming these layers). The introduction of a side-chain thermotropic liquid crystal polymer can induce homeotropic alignment (vertical alignment) of the liquid crystal monomer. As a result, the nz of the first liquid crystal alignment solidified layer and / or the second liquid crystal alignment solidified layer can be increased, and as a result, the Nz coefficient of the first liquid crystal alignment solidified layer and / or the second liquid crystal alignment solidified layer can be appropriately adjusted. Ultimately, the Nz coefficient of the retardation layer can be set to, for example, a range of 0.30 to 0.70 without providing a positive C plate.

[0047] A typical example of a side-chain thermotropic liquid crystal polymer is a copolymer having a monomer unit containing a thermotropic liquid crystal fragment side chain and a monomer unit containing a non-liquid crystal fragment side chain. When the polymer has a thermotropic liquid crystal fragment in its side chain, the side-chain liquid crystal polymer can be oriented when a liquid crystal composition containing the liquid crystal monomer is heated to a predetermined temperature. Furthermore, when the side-chain polymer has a non-liquid crystal fragment in its side chain, the non-liquid crystal fragment can interact with the photopolymerizable liquid crystal monomer, causing the photopolymerizable liquid crystal monomer to be homeotropically oriented.

[0048] As the side chain type thermotropic liquid crystal polymer, a copolymer having a liquid crystalline monomer unit represented by general formula (I) and a non-liquid crystalline monomer unit represented by general formula (II) is preferably used.

[0049] In formula (I), R 1 is a hydrogen atom or a methyl group, and R 2 is a cyano group, a fluoro group, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms; X 1 is —CO— or —OCO—, a is an integer of 1 to 6, and b and c are each independently 1 or 2.

[0050] In formula (II), R 3 is a hydrogen atom or a methyl group, and R 4 is an alkyl group having 7 to 22 carbon atoms, a fluoroalkyl group having 1 to 22 carbon atoms, or a group represented by the following general formula (III):

[0051] In formula (III), R 5 is an alkyl group having 1 to 5 carbon atoms, and d is an integer of 1 to 6.

[0052] The ratio of the liquid crystalline monomer unit to the non-liquid crystalline monomer unit in the side chain liquid crystal monomer can be appropriately set depending on the purpose. The ratio (molar ratio) of the non-liquid crystalline monomer to the total of the liquid crystalline monomer unit and the non-liquid crystalline monomer unit is preferably 0.05 to 0.80, more preferably 0.10 to 0.60, and even more preferably 0.15 to 0.50.

[0053] The ratio of the liquid crystal monomer to the side-chain liquid crystal polymer in the liquid crystal composition can be appropriately set depending on the purpose. The content of the liquid crystal monomer relative to the content of the side-chain liquid crystal polymer is preferably 1.2 to 20 times, more preferably 1.3 to 10 times, even more preferably 1.4 to 9 times, and particularly preferably 1.5 to 8 times.

[0054] The side-chain liquid crystal polymer and the method for forming the liquid crystal alignment solidified layer are described, for example, in Japanese Patent No. 6769921, the description of which is incorporated herein by reference.

[0055] <1-2. Pressure-sensitive adhesive sheet> The optical laminate according to the embodiment of the present invention has a pressure-sensitive adhesive sheet between the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer.

[0056] The thickness of the adhesive sheet is as described above.

[0057] The average refractive index n of the pressure-sensitive adhesive sheet is, for example, 1.45 or more, preferably 1.50 or more, more preferably 1.52 or more, even more preferably 1.54 or more, particularly preferably 1.56 or more, and most preferably 1.57 or more. The upper limit of the average refractive index n of the pressure-sensitive adhesive sheet is preferably 1.70 or less.

[0058] The indentation hardness of the pressure-sensitive adhesive sheet at 25° C. is as described above.

[0059] Any appropriate pressure-sensitive adhesive sheet can be used as the pressure-sensitive adhesive sheet as long as it does not impair the effects of the present invention. Pressure-sensitive adhesive sheets are typically composed of a pressure-sensitive adhesive. Examples of such pressure-sensitive adhesives include acrylic pressure-sensitive adhesives, rubber pressure-sensitive adhesives, silicone pressure-sensitive adhesives, polyester pressure-sensitive adhesives, urethane pressure-sensitive adhesives, epoxy pressure-sensitive adhesives, and polyether pressure-sensitive adhesives. To further enhance the effects of the present invention, the pressure-sensitive adhesive sheet is preferably composed of an acrylic pressure-sensitive adhesive, which is formed from an acrylic pressure-sensitive adhesive composition containing an acrylic polymer obtained by polymerizing a monomer component. The main polymer component contained in a pressure-sensitive adhesive composition, such as this acrylic polymer, is sometimes referred to as a base polymer. The content of the base polymer in the pressure-sensitive adhesive composition is, for example, 50 wt% or more, or may be 60 wt% or more, 70 wt% or more, 80 wt% or more, or even 90 wt% or more. The upper limit of the content of the base polymer in the pressure-sensitive adhesive composition may be, for example, 99.9 wt% or less, 99 wt% or less, or 95 wt% or less.

[0060] The pressure-sensitive adhesive sheet can be formed by any appropriate method as long as the effects of the present invention are not impaired. The pressure-sensitive adhesive sheet can be formed, for example, by drying a coating film of a pressure-sensitive adhesive composition provided on a substrate. Heating, for example, can be used as a drying means. A release film, for example, can be used as the substrate. A known film that can be used when forming a solvent-based pressure-sensitive adhesive sheet can be used as the release film. The pressure-sensitive adhesive sheet formed on the substrate can be transferred to another layer included in the optical laminate according to an embodiment of the present invention, for example, a first liquid crystal alignment solidified layer or a second liquid crystal alignment solidified layer. The substrate may be another layer that can be included in the optical laminate according to an embodiment of the present invention.

[0061] The drying temperature of the coating film may be any appropriate temperature within a range that does not impair the effects of the present invention. Such a drying temperature may be, for example, 130°C or lower, 125°C or lower, 120°C or lower, 110°C or lower, or 100°C or lower. The drying temperature may be, for example, 60°C or higher, or 80°C or higher. The drying time of the coating film may be any appropriate time within a range that does not impair the effects of the present invention. Such a drying time may be, for example, 30 to 300 seconds, 40 to 240 seconds, or 60 to 180 seconds.

[0062] In the optical laminate according to an embodiment of the present invention, examples of the adhesive that constitutes the adhesive sheet include, as described above, acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. Below, as a representative embodiment among these, an adhesive sheet composed of an acrylic adhesive formed from an acrylic adhesive composition containing an acrylic polymer will be described in detail.

[0063] <1-2-a. Acrylic Polymer> The content of the acrylic polymer in the acrylic pressure-sensitive adhesive composition is preferably 50% by weight or more, more preferably 70% by weight or more, and even more preferably 90% by weight or more, calculated as solid content.

[0064] The acrylic pressure-sensitive adhesive composition may contain only one type of acrylic polymer, or two or more types of acrylic polymers.

[0065] The Tg of the acrylic polymer is, for example, less than 20°C, preferably less than 15°C, more preferably less than 13°C, even more preferably greater than -15°C and less than 13°C, even more preferably greater than -10°C and less than 13°C, particularly preferably greater than -5°C and less than 13°C, and most preferably greater than -3°C and less than 13°C. By adjusting the Tg of the acrylic polymer within the above range, the effects of the present invention can be more effectively exhibited. If the Tg of the acrylic polymer is too high, the pressure-sensitive adhesive sheet may become too hard, which may reduce the adhesion between the pressure-sensitive adhesive sheet and the liquid crystal alignment solidified layer.

[0066] The acrylic polymer is obtained by polymerizing a monomer component, which preferably includes an aromatic ring-containing monomer (m1).

[0067] The content of the aromatic ring-containing monomer (m1) in the monomer component is, for example, 30% by weight or more, or may be 50% by weight or more, 60% by weight or more, 70% by weight or more, 75% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more. The upper limit of the content of the aromatic ring-containing monomer (m1) in the monomer component is, for example, 100% by weight, or may be 98% by weight or less, 96% by weight or less, 94% by weight or less, 92% by weight or less, 90% by weight or less, 85% by weight or less, 80% by weight or less, or 75% by weight or less. From the viewpoint of being able to further exert the effects of the present invention, the content of the aromatic ring-containing monomer (m1) in the monomer components is preferably 50% by weight to 100% by weight, more preferably 60% by weight to 95% by weight, even more preferably 65% ​​by weight to 90% by weight, and particularly preferably 67% by weight to 88% by weight.

[0068] The aromatic ring-containing monomer (m1) may be a compound containing at least one aromatic ring and at least one ethylenically unsaturated group in one molecule. The aromatic ring-containing monomer (m1) may be a single type or two or more types.

[0069] Examples of the ethylenically unsaturated group include a (meth)acryloyl group, a vinyl group, and a (meth)allyl group.From the viewpoint of further exhibiting the effects of the present invention, the ethylenically unsaturated group is preferably a (meth)acryloyl group or a vinyl group, more preferably a (meth)acryloyl group, and more preferably an acryloyl group.Therefore, preferred embodiments of the aromatic ring-containing monomer (m1) include an aromatic ring-containing (meth)acrylate and an aromatic ring-containing vinyl compound.

[0070] From the viewpoint of being able to suppress a decrease in flexibility of the PSA, the aromatic ring-containing monomer (m1) is preferably a compound having one ethylenically unsaturated group per molecule (i.e., a monofunctional monomer).

[0071] The number of aromatic rings contained in one molecule of the aromatic ring-containing monomer (m1) may be 1 or may be 2 or more. The upper limit of the number of aromatic rings contained in the aromatic ring-containing monomer (m1) is not particularly limited, and may be, for example, 16 or less, 12 or less, 8 or less, 6 or less, 4 or less, 3 or less, or 2 or less.

[0072] The aromatic ring contained in the aromatic ring-containing monomer (m1) may be, for example, a hydrocarbon ring such as a benzene ring (which may be a benzene ring constituting a part of a biphenyl structure or a fluorene structure); a condensed ring of a naphthalene ring, an indene ring, an azulene ring, an anthracene ring, or a phenanthrene ring; or a heterocycle such as a pyridine ring, a pyrimidine ring, a pyridazine ring, a pyrazine ring, a triazine ring, a pyrrole ring, a pyrazole ring, an imidazole ring, a triazole ring, an oxazole ring, an isoxazole ring, a thiazole ring, or a thiophene ring. Examples of heteroatoms contained in such heterocycles include nitrogen, sulfur, and oxygen, and preferably nitrogen and sulfur. The aromatic ring-containing monomer (m1) may have a structure in which one or more carbon rings and one or more heterocycles are condensed, such as a dinaphthothiophene structure.

[0073] The aromatic ring contained in the aromatic ring-containing monomer (m1) may have a substituent on a ring-constituting atom. The substituent may be of one type or of two or more types. Examples of the substituent include an alkyl group, an alkoxy group, an aryloxy group, a hydroxyl group, a halogen atom, a hydroxyalkyl group, a hydroxyalkyloxy group, and a glycidyloxy group.

[0074] The aromatic ring and the ethylenically unsaturated group contained in the aromatic ring-containing monomer (m1) may be bonded directly or via a linking group. Examples of such linking groups include alkylene groups, oxyalkylene groups, poly(oxyalkylene) groups, phenyl groups, alkylphenyl groups, alkoxyphenyl groups, and groups in which one or more hydrogen atoms in these groups have been substituted with hydroxyl groups (e.g., hydroxyalkylene groups), oxy groups (-O- groups), and thiooxy groups (-S- groups). In terms of further enhancing the effects of the present invention, such linking groups are preferably groups containing at least one structure selected from the group consisting of alkylene groups, oxyalkylene groups, and poly(oxyalkylene) groups. The number of carbon atoms in the alkylene group and oxyalkylene group is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 to 2. The number of repeating oxyalkylene units in the poly(oxyalkylene) group is preferably 2 to 3.

[0075] From the viewpoint of further exhibiting the effects of the present invention, the aromatic ring-containing monomer (m1) may contain a monomer having two or more aromatic rings in one molecule (hereinafter, sometimes referred to as a "multiple aromatic ring-containing monomer (m2)"). Examples of the multiple aromatic ring-containing monomer (m2) include a monomer having a structure in which two or more non-condensed aromatic rings are bonded via a linking group, a monomer having a structure in which two or more non-condensed aromatic rings are directly chemically bonded, a monomer having a condensed aromatic ring structure, a monomer having a fluorene structure, a monomer having a dinaphthothiophene structure, and a monomer having a dibenzothiophene structure.

[0076] In one embodiment of the aromatic ring-containing monomer (m1), the content of the multiple aromatic ring-containing monomer (m2) in the aromatic ring-containing monomer (m1) may be, for example, 50% by weight or more, 70% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more, 95% by weight or more, or 98% by weight or more. The upper limit of the content of the multiple aromatic ring-containing monomer (m2) in the aromatic ring-containing monomer (m1) is 100% by weight. From the viewpoint of further exhibiting the effects of the present invention, the content of the multiple aromatic ring-containing monomer (m2) in the aromatic ring-containing monomer (m1) is preferably 80% by weight to 100% by weight, more preferably 85% by weight to 100% by weight, even more preferably 90% by weight to 100% by weight, particularly preferably 95% by weight to 100% by weight, and most preferably 98% by weight to 100% by weight.

[0077] In another embodiment of the aromatic ring-containing monomer (m1), the content of the multiple aromatic ring-containing monomer (m2) in the aromatic ring-containing monomer (m1) may be, for example, less than 50% by weight, less than 40% by weight, less than 30% by weight, less than 20% by weight, less than 10% by weight, or less than 5% by weight. In this embodiment, the aromatic ring-containing monomer (m1) preferably contains a monomer (m3) having one aromatic ring per molecule, as described below.

[0078] Examples of the linking group that the aromatic ring-containing monomer (m2) may have include an oxy group (—O—), a thiooxy group (—S—), an oxyalkylene group (—O—(CH2) n - group, where n is 1 to 3, preferably 1), a thiooxyalkylene group (-S-(CH) n - group, where n is 1 to 3, preferably 1), a straight chain alkylene group (-(CH) n - group, where n is 1 to 6, preferably 1 to 3), an oxyalkylene group, a thiooxyalkylene group, and a linear alkylene group in which the alkylene group is partially or completely halogenated.

[0079] Examples of monomers having a structure in which two or more non-fused aromatic rings are bonded via a linking group include phenoxybenzyl (meth)acrylate (e.g., m-phenoxybenzyl (meth)acrylate), thiophenoxybenzyl (meth)acrylate, and benzyl benzyl (meth)acrylate.

[0080] Examples of monomers having a structure in which two or more non-fused aromatic rings are directly chemically bonded include biphenyl structure-containing (meth)acrylates, triphenyl structure-containing (meth)acrylates, and vinyl group-containing biphenyls, and specific examples include o-phenylphenol (meth)acrylate and biphenylmethyl (meth)acrylate.

[0081] Examples of monomers having a condensed aromatic ring structure include naphthalene ring-containing (meth)acrylates, anthracene ring-containing (meth)acrylates, vinyl group-containing naphthalenes, and vinyl group-containing anthracenes. Specific examples include 1-naphthylmethyl (meth)acrylate (also known as 1-naphthalenemethyl (meth)acrylate), hydroxyethylated β-naphthol acrylate, 2-naphthoethyl (meth)acrylate, 2-naphthoxyethyl acrylate, and 2-(4-methoxy-1-naphthoxy)ethyl (meth)acrylate.

[0082] Examples of monomers having a fluorene structure include 9,9-bis(4-hydroxyphenyl)fluorene(meth)acrylate and 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene(meth)acrylate. Note that, since monomers having a fluorene structure contain a structural moiety in which two benzene rings are directly chemically bonded, they can be included in the concept of monomers having a structure in which two or more non-fused aromatic rings are directly chemically bonded.

[0083] Examples of monomers having a dinaphthothiophene structure include (meth)acryloyl group-containing dinaphthothiophenes, vinyl group-containing dinaphthothiophenes, and (meth)allyl group-containing dinaphthothiophenes. Specific examples include (meth)acryloyloxymethyl dinaphthothiophenes (e.g., dinaphthothiophenes having CHCH(R) at the 5th or 6th position of the dinaphthothiophene ring).1 ) C(O)OCH2- bonded compound, R 1 is a hydrogen atom or a methyl group), (meth)acryloyloxyethyl dinaphthothiophene (for example, CHCH(R 1 )C(O)OCH(CH3)- or CH2CH(R 1 ) C(O)OCH2CH2- bonded compound, R 1 is a hydrogen atom or a methyl group.), vinyl dinaphthothiophene (for example, a compound having a structure in which a vinyl group is bonded to the 5th or 6th position of a naphthothiophene ring), and (meth)allyloxydinaphthothiophene. Note that a monomer having a dinaphthothiophene structure can be included in the concept of a monomer having a fused aromatic ring structure by including a naphthalene structure or by having a structure in which a thiophene ring and two naphthalene structures are fused together.

[0084] Examples of monomers having a dibenzothiophene structure include (meth)acryloyl group-containing dibenzothiophenes and vinyl group-containing dibenzothiophenes. Note that, since monomers having a dibenzothiophene structure have a structure in which a thiophene ring and two benzene rings are fused, they can be included in the concept of monomers having a fused aromatic ring structure. Note that neither the dinaphthothiophene structure nor the dibenzothiophene structure corresponds to a structure in which two or more non-fused aromatic rings are directly chemically bonded.

[0085] The aromatic ring-containing monomer (m1) may be a monomer (m3) having one aromatic ring per molecule. The monomer (m3) having one aromatic ring per molecule may be useful, for example, for adjusting the flexibility and adhesive properties of the PSA, improving transparency, etc.

[0086] Examples of the monomer (m3) having one aromatic ring in one molecule include carbon-containing aromatic ring (meth)acrylates such as benzyl (meth)acrylate, methoxybenzyl (meth)acrylate, phenyl (meth)acrylate, ethoxylated phenol (meth)acrylate, phenoxypropyl (meth)acrylate, phenoxybutyl (meth)acrylate, cresyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and chlorobenzyl (meth)acrylate; 2-(4,6-dibromo-2-s-butylphenoxy)ethyl (meth)acrylate, and 2-(4,6-dibromo-2-isopropylphenoxy)ethyl (meth)acrylate. bromine-substituted aromatic ring-containing (meth)acrylates such as 6-(4,6-dibromo-2-s-butylphenoxy)hexyl (meth)acrylate, 6-(4,6-dibromo-2-isopropylphenoxy)hexyl (meth)acrylate, 2,6-dibromo-4-nonylphenyl acrylate, and 2,6-dibromo-4-dodecylphenyl acrylate; carbon-containing aromatic ring-containing vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, and tert-butylstyrene; and compounds having a vinyl substituent on a heteroaromatic ring such as N-vinylpyridine, N-vinylpyrimidine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, and N-vinyloxazole.

[0087] In one embodiment of the aromatic ring-containing monomer (m1), the content of the monomer (m3) having one aromatic ring per molecule in the aromatic ring-containing monomer (m1) may be, for example, less than 50% by weight, less than 30% by weight, less than 20% by weight, less than 15% by weight, less than 10% by weight, less than 5% by weight, or less than 2% by weight. The lower limit of the content of the monomer (m3) having one aromatic ring per molecule in the aromatic ring-containing monomer (m1) is 0% by weight.

[0088] In another embodiment of the aromatic ring-containing monomer (m1), the content of the monomer (m3) having one aromatic ring per molecule in the aromatic ring-containing monomer (m1) may be, for example, 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, 90% by weight or more, or 95% by weight or more. In this embodiment, the aromatic ring-containing monomer (m1) may not contain the multiple aromatic ring-containing monomer (m2).

[0089] From the viewpoint of further exhibiting the effects of the present invention, among the above-mentioned examples, specific preferred examples of the aromatic ring-containing monomer (m1) include m-phenoxybenzyl acrylate, 1-naphthylmethyl acrylate, ethoxylated o-phenylphenol acrylate, benzyl acrylate, phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, 6-acryloyloxymethyl dinaphthothiophene, 6-methacryloyloxymethyl dinaphthothiophene, 5-acryloyloxyethyl dinaphthothiophene, 6-acryloyloxyethyl dinaphthothiophene, 6-vinyl dinaphthothiophene, and 5-vinyl dinaphthothiophene.

[0090] The monomer component may contain a monomer copolymerizable with the aromatic ring-containing monomer (m1) (hereinafter, this may be referred to as "copolymerizable monomer (m4)"). The copolymerizable monomer (m4) may be one type or two or more types. Examples of the copolymerizable monomer (m4) include alkyl (meth)acrylate, hydroxyl group-containing monomer, carboxyl group-containing monomer, and amide group-containing monomer.

[0091] The number of carbon atoms in the alkyl group in the alkyl (meth)acrylate is, for example, 1 to 30. The alkyl group may be linear, branched, or cyclic. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, an amyl group, a hexyl group, a cyclohexyl group, a heptyl group, a 2-ethylhexyl group, an isooctyl group, a nonyl group, a decyl group, an isodecyl group, a dodecyl group, an isomyristyl group, a lauryl group, a tridecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, and an octadecyl group. The alkyl (meth)acrylate may be of one type, or two or more types. From the viewpoint of further exhibiting the effects of the present invention, butyl acrylate is preferred as the alkyl (meth)acrylate.

[0092] The content of alkyl (meth)acrylate in the monomer component may be, for example, 50% 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 13% by weight or less. The lower limit of the content of alkyl (meth)acrylate in the monomer component is, for example, 1% by weight or more, 3% by weight or more, or 5% by weight or more. In addition, alkyl (meth)acrylate may not be contained in the monomer component.

[0093] The hydroxyl group-containing monomer 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 may be a hydroxyl group-containing (meth)acrylate. Examples of the hydroxyl group-containing (meth)acrylate 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.

[0094] The content of the hydroxyl group-containing monomer in the monomer component may be, for example, 0.5% by weight or more, 1% by weight or more, or 1.5% by weight or more. The upper limit of the content of the hydroxyl group-containing monomer in the monomer component may be, for example, 10% by weight or less, 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, or 2.5% by weight or less. In addition, the hydroxyl group-containing monomer may not be contained in the monomer component.

[0095] The carboxyl group-containing monomer is a compound that contains a carboxyl group in its structure and a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. The carboxyl group-containing monomer 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.

[0096] The content of the carboxyl group-containing monomer in the monomer component may be, for example, 10% by weight or less, 7% by weight or less, 5% by weight or less, or 3% by weight or less. The lower limit of the content of the carboxyl group-containing monomer in the monomer component may be, for example, 0.5% by weight or more, or 1% by weight or more. In addition, the monomer component may not contain a carboxyl group-containing monomer.

[0097] The amide group-containing monomer 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. The amide group-containing monomer 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.

[0098] The content of the amide group-containing monomer in the monomer component may be, for example, 10% by weight or less, 7% by weight or less, 5% by weight or less, or 3% by weight or less. The lower limit of the content of the amide group-containing monomer in the monomer component may be, for example, 0.5% by weight or more, or 1% by weight or more. In addition, the amide group-containing monomer may not be contained in the monomer component.

[0099] In addition to the above, examples of the copolymerizable monomer (m4) include other copolymerizable monomers, such as acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; caprolactone adducts of acrylic acid; sulfonic acid group-containing monomers such as allyl sulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, and sulfopropyl (meth)acrylate; phosphate group-containing monomers such as 2-hydroxyethyl acryloyl phosphate; aminoethyl (meth)acrylate, N,N-dimethyl Alkylaminoalkyl (meth)acrylates such as aminoethyl (meth)acrylate and t-butylaminoethyl (meth)acrylate; alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; succinimide-based monomers such as N-(meth)acryloyloxymethylene succinimide, N-(meth)acryloyl-6-oxyhexamethylene succinimide, and N-(meth)acryloyl-8-oxyoctamethylene succinimide; N-cyclohexylmaleimide maleimide-based monomers such as 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; glycidyl (meth)acrylate acrylate and other epoxy group-containing (meth)acrylates; 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;Examples of such silane monomers include 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.

[0100] The content of the other copolymerizable monomer in the monomer component may be, for example, 5% by weight or less, 3% by weight or less, or 1% by weight or less. In addition, the monomer component may not contain any other copolymerizable monomer.

[0101] The acrylic polymer can be a base polymer in the acrylic pressure-sensitive adhesive composition. The acrylic polymer can be formed by various known polymerization methods such as solution polymerization, radiation polymerization using electron beams or ultraviolet (UV) rays, bulk polymerization, and emulsion polymerization. The polymerization is typically radical polymerization. The acrylic polymer may be any of a random copolymer, a block copolymer, a graft copolymer, and the like.

[0102] 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. Any appropriate polymerization conditions can be adopted as long as they do not impair the effects of the present invention. Examples of such polymerization conditions include a polymerization temperature of 50°C to 70°C and a polymerization time of 5 to 30 hours.

[0103] As the polymerization initiator, chain transfer agent, and emulsifier that can be used in radical polymerization, any appropriate compounds can be used within the range that does not impair the effects of the present invention.

[0104] 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 combining peroxides and reducing agents, such as combinations of persulfates and sodium bisulfite, and combinations of peroxides and sodium ascorbate. The polymerization initiator may be a single type or two or more types. The polymerization initiator may be used in any appropriate amount as long as it does not impair the effects of the present invention. The total amount used is, for example, 0.005 to 1 part by weight, and may be 0.02 to 0.5 parts by weight, relative to 100 parts by weight of the monomer components.

[0105] Examples of chain transfer agents include lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimercapto-1-propanol. Only one type of chain transfer agent may be used, or two or more types may be used. The amount of chain transfer agent used may be any appropriate amount as long as it does not impair the effects of the present invention. Such an amount used is, for example, 0.1 parts by weight or less in total, relative to 100 parts by weight of the monomer components.

[0106] In radiation polymerization, a monomer 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 of advantages such as the ability to shorten the polymerization time. The photopolymerization initiator may be of only one type or of two or more types.

[0107] Examples of photopolymerization initiators include benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, and thioxanthone-based photopolymerization initiators. The amount of the photopolymerization initiator used may be any appropriate amount as long as it does not impair the effects of the present invention. Such an amount is, for example, 0.05 to 1.5 parts by weight, or may be 0.1 to 1 part by weight, per 100 parts by weight of the monomer component.

[0108] <1-2-b. Acrylic Pressure-Sensitive Adhesive Composition> In one embodiment of the present invention, the pressure-sensitive adhesive sheet is composed of an acrylic pressure-sensitive adhesive, and the acrylic pressure-sensitive adhesive is formed from an acrylic pressure-sensitive adhesive composition containing an acrylic polymer obtained by polymerizing a monomer component.

[0109] As described above, the content of the acrylic polymer in the acrylic pressure-sensitive adhesive composition is preferably 50% by weight or more, more preferably 70% by weight or more, and even more preferably 90% by weight or more, calculated as solid content.

[0110] The acrylic pressure-sensitive adhesive composition may contain a crosslinking agent. The crosslinking agent may be one kind or two or more kinds.

[0111] Examples of crosslinking agents that can be contained in the acrylic pressure-sensitive adhesive composition include isocyanate-based crosslinking agents, peroxide-based crosslinking agents, epoxy-based crosslinking agents, imine-based crosslinking agents, and polyfunctional metal chelates. The crosslinking agent that can be contained in the acrylic pressure-sensitive adhesive composition is preferably at least one selected from the group consisting of isocyanate-based crosslinking agents, epoxy-based crosslinking agents, and peroxide-based crosslinking agents, more preferably at least one selected from the group consisting of isocyanate-based crosslinking agents and peroxide-based crosslinking agents, and even more preferably an isocyanate-based crosslinking agent.

[0112] The crosslinking agent may be selected from one type of crosslinking agent (for example, an isocyanate crosslinking agent), or may be selected from two or more types of crosslinking agents.

[0113] 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.

[0114] Examples of aromatic isocyanate compounds include phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, and xylylene diisocyanate.

[0115] Examples of alicyclic isocyanate compounds include 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated tetramethylxylylene diisocyanate.

[0116] Examples of the aliphatic isocyanate compound include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.

[0117] Examples of the isocyanate-based crosslinking agent include polymers (dimers, trimers, pentamers, etc.) of the above-mentioned isocyanate compounds, adducts obtained by addition to polyhydric alcohols such as trimethylolpropane, urea-modified products, biuret-modified products, allophanate-modified products, isocyanurate-modified products, carbodiimide-modified products, and urethane prepolymers obtained by addition to polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, polyisoprene polyols, etc.

[0118] 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.

[0119] Commercially available isocyanate crosslinking agents may be used. Examples of such 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.

[0120] The amount of the isocyanate crosslinking agent in the acrylic pressure-sensitive adhesive composition is, for example, 0.01 to 20 parts by weight per 100 parts by weight of the acrylic polymer. The lower limit of the amount may be 0.02 parts by weight or more, 0.03 parts by weight or more, 0.04 parts by weight or more, or 0.05 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, 0.5 parts by weight or less, 0.3 parts by weight or less, 0.1 parts by weight or less, or 0.08 parts by weight or less. A typical amount may be 0.03 to 1 part by weight, or 0.05 to 0.5 parts by weight.

[0121] The amount of a crosslinking agent other than an isocyanate-based crosslinking agent (e.g., a peroxide-based crosslinking agent) blended in the acrylic pressure-sensitive adhesive composition is, for example, 2 parts by weight or less, or may be 1 part by weight or less, or may be 0.5 parts by weight or less, relative to 100 parts by weight of the base polymer. The lower limit of the blending amount is, for example, 0.1 parts by weight or more, or may be 0.2 parts by weight or more, or may be 0.3 parts by weight or more. A typical blending amount may be 0.1 to 1 part by weight, or may be 0.3 to 0.5 parts by weight. The acrylic pressure-sensitive adhesive composition may not contain a crosslinking agent other than an isocyanate-based crosslinking agent.

[0122] The acrylic pressure-sensitive adhesive composition may further contain known additives. Any appropriate additive may be used as long as it does not impair the effects of the present invention. Examples of such additives include 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 fillers, organic fillers, metal powders, particles, and foil-like materials. Furthermore, redox systems containing reducing agents may be used within controllable limits. Any appropriate amount of additive may be used as long as it does not impair the effects of the present invention. Such an amount may be, for example, 10 parts by weight or less, 5 parts by weight or less, or even 1 part by weight or less, in total, per 100 parts by weight of the acrylic polymer.

[0123] <<2. Optical Laminate with Polarizing Film>> An optical laminate with a polarizing film according to an embodiment of the present invention includes a polarizing film on the first liquid crystal alignment solidified layer side of the optical laminate according to an embodiment of the present invention, as viewed from the pressure-sensitive adhesive sheet included in the optical laminate.

[0124] The polarizing film may be laminated directly to the first liquid crystal alignment solidified layer included in the optical laminate according to an embodiment of the present invention, or may be laminated via an interlayer adhesive (typically, an adhesive).

[0125] Fig. 2 is a schematic cross-sectional view of an optical laminate with a polarizing film according to one embodiment of the present invention. The optical laminate 500 with a polarizing film shown in Fig. 2 includes a polarizing film 200, an adhesive layer 30, and an optical laminate 100, in this order. The polarizing film 200 and the adhesive layer 30 are directly laminated together, the adhesive layer 30 and the first liquid crystal alignment solidified layer 11 are directly laminated together, the first liquid crystal alignment solidified layer 11 and the pressure-sensitive adhesive sheet 20 are directly laminated together, and the pressure-sensitive adhesive sheet 20 and the second liquid crystal alignment solidified layer 12 are directly laminated together.

[0126] <2-1. Polarizing Film> The polarizing film 200 typically includes a polarizer 40 and protective layers 51, 52 arranged on both sides of the polarizer 40. Depending on the purpose, at least one of the protective layers 51, 52 may be omitted. Therefore, the polarizing film may be a so-called double-protected polarizing film, a so-called single-protected polarizing film, or may be composed of a polarizer alone.

[0127] <2-1-a. Polarizer> 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.

[0128] The PVA-based resin preferably contains an acetoacetyl-modified PVA-based resin, and 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.

[0129] 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).

[0130] 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.

[0131] 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. By combining such a thin polarizer with a liquid crystal alignment solidified layer, it is possible to significantly reduce the thickness of the optical laminate.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] 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 can enhance the crystallinity of the PVA, even when the PVA is coated on a thermoplastic resin, thereby enabling the achievement of high optical properties. Furthermore, by simultaneously enhancing 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 enabling the achievement of 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 processes 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.

[0137] <2-1-b. Protective Layer> 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. A typical example of a (meth)acrylic resin is a (meth)acrylic resin 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.

[0138] 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.

[0139] 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.

[0140] 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.

[0141] <2-2. Adhesive Layer> In an optical laminate with a polarizing film according to one embodiment of the present invention, any suitable adhesive layer may be used as the adhesive layer that can be provided between the polarizing film and the optical laminate, as long as the effects of the present invention are not impaired. Such an adhesive layer is typically adhered via an ultraviolet-curable adhesive or a water-based adhesive. Examples of water-based adhesives include isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl-based latex adhesives, water-based polyurethanes, and water-based polyesters. In addition to the above, examples of the adhesive layer include electron beam-curable adhesives. The adhesive layer may contain a metal compound filler.

[0142] <<3. Other embodiments including optical laminate>> In the optical laminate according to an embodiment of the present invention or the optical laminate with a polarizing film according to an embodiment of the present invention, a pressure-sensitive adhesive layer can be provided on the surface of the second liquid crystal alignment solidified layer opposite to the pressure-sensitive adhesive sheet.

[0143] 3 is a schematic cross-sectional view showing one embodiment of a laminate having a polarizing film and a pressure-sensitive adhesive layer provided on the surface of the second liquid crystal alignment solidified layer opposite to the pressure-sensitive adhesive sheet in an optical laminate with a polarizing film according to an embodiment of the present invention. The laminate 600 shown in FIG. 3 includes a polarizing film 200, an adhesive layer 30, an optical laminate 100, and a pressure-sensitive adhesive layer 60, in this order. The polarizing film 200 and the adhesive layer 30 are directly laminated together, the adhesive layer 30 and the first liquid crystal alignment solidified layer 11 are directly laminated together, the first liquid crystal alignment solidified layer 11 and the pressure-sensitive adhesive sheet 20 are directly laminated together, the pressure-sensitive adhesive sheet 20 and the second liquid crystal alignment solidified layer 12 are directly laminated together, and the second liquid crystal alignment solidified layer 12 and the pressure-sensitive adhesive layer 60 are directly laminated together.

[0144] As the pressure-sensitive adhesive layer, any appropriate pressure-sensitive adhesive layer can be used as long as the effects of the present invention are not impaired. For example, a pressure-sensitive adhesive layer made of a known pressure-sensitive adhesive that can be used for bonding optical components can be used. A preferred example of such a pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer made of a known acrylic pressure-sensitive adhesive.

[0145] A release liner may be provided on the surface of the pressure-sensitive adhesive layer. Examples of the release liner include films, paper, woven fabrics, nonwoven fabrics, porous materials, nets, foams, foils, and laminates thereof, made of resin, paper, fiber, metal, or composite materials thereof. Examples of resins include polyethylene, polypropylene, polybutene, polybutadiene, polymethylpentene, polyvinyl chloride, vinyl chloride copolymers, polyethylene terephthalate, polybutylene terephthalate, polyurethane, and ethylene-vinyl acetate copolymers.

[0146] The thickness of the release liner is, for example, 5 μm to 200 μm, and may be 5 to 100 μm. The surface of the release liner may be subjected to various surface treatments such as release treatment, antifouling treatment, and antistatic treatment, as necessary.

[0147] <<4. Image Display Device>> An image display device according to an embodiment of the present invention includes an optical laminate according to an embodiment of the present invention.

[0148] Representative examples of image display devices include liquid crystal display devices and organic EL display devices. An image display device according to an embodiment of the present invention typically includes an optical laminate according to an embodiment of the present invention on the viewing side thereof.

[0149] <<5. Pressure-Sensitive Adhesive Sheet>> Among the pressure-sensitive adhesive sheets described above in the section <<1-2. Pressure-Sensitive Adhesive Sheet>>, a pressure-sensitive adhesive sheet having a thickness of less than 20 μm, an average refractive index n of 1.50 or more, and an indentation hardness at 25° C. of more than 0.010 MPa is highly effective in suppressing the occurrence of linear unevenness when used in an optical laminate, and is highly effective in reducing depressions due to local load, and can be a pressure-sensitive adhesive sheet according to an embodiment of the present invention. That is, the pressure-sensitive adhesive sheet according to an embodiment of the present invention has a thickness of less than 20 μm, an average refractive index n of 1.50 or more, and an indentation hardness at 25° C. of more than 0.010 MPa.

[0150] The pressure-sensitive adhesive sheet according to the embodiment of the present invention can be useful not only in the use form of the optical laminate of the present invention, i.e., in the use form provided between the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer, but also in other use forms. The pressure-sensitive adhesive sheet according to the embodiment of the present invention can be preferably used for bonding the liquid crystal alignment solidified layer.

[0151] The thickness of the pressure-sensitive adhesive sheet according to the embodiment of the present invention can be determined from the explanation in the previous section <<1. Optical laminate>>.

[0152] The average refractive index n of the pressure-sensitive adhesive sheet according to the embodiment of the present invention is typically 1.50 or more, preferably 1.52 or more, more preferably 1.54 or more, even more preferably 1.56 or more, and particularly preferably 1.57 or more. The upper limit of the average refractive index n of the pressure-sensitive adhesive sheet is preferably 1.70 or less.

[0153] The indentation hardness at 25°C of the pressure-sensitive adhesive sheet according to an embodiment of the present invention typically exceeds 0.010 MPa, preferably exceeds 0.010 MPa and is less than 0.157 MPa, more preferably 0.020 MPa to 0.130 MPa, even more preferably 0.030 MPa to 0.100 MPa, particularly preferably 0.040 MPa to 0.090 MPa, and most preferably 0.045 MPa to 0.080 MPa. By adjusting the indentation hardness within the above range, the effects of the present invention can be more effectively exhibited, and in particular, depressions due to localized loads can be effectively reduced. If the indentation hardness is too low, the pressure-sensitive adhesive sheet may become too soft, which may result in depressions due to localized loads. On the other hand, if the indentation hardness is too high, the pressure-sensitive adhesive sheet may become too hard, which may reduce the adhesion between the pressure-sensitive adhesive sheet and an adjacent optical component (e.g., a liquid crystal alignment solidified layer).

[0154] The indentation hardness may be measured by any method that can appropriately measure the indentation hardness of the pressure-sensitive adhesive sheet according to an embodiment of the present invention. Such a measurement method may be, for example, the measurement method in the examples, i.e., a method in which a laminate having a configuration of polarizing film / adhesive / first liquid crystal alignment solidified layer / pressure-sensitive adhesive sheet / second liquid crystal alignment solidified layer / pressure-sensitive adhesive sheet / release liner is used as the evaluation sample, or a method in which a laminate having a configuration of pressure-sensitive adhesive sheet / release liner is used as the evaluation sample.

[0155] The measurement method for the above indentation hardness in the examples, as described below, is a method in which a laminate having a configuration of polarizing film / adhesive / first liquid crystal alignment solidified layer / adhesive sheet / second liquid crystal alignment solidified layer / adhesive sheet / release liner obtained in the examples and comparative examples is used as an evaluation sample, cut into a piece of 3 mm x 5 mm, and cross-sectioned using an ultramicrotome (manufactured by Leica, device name: Leica EM UC7) under freezing conditions of -60°C, which is then fixed to a predetermined support (a brass block of approximately 10 mm x 8 mm x 6 mm), and in an atmosphere of 25°C, a Berkovich (triangular pyramid) indenter is used to measure the indentation hardness when the adhesive sheet surface is indented to a depth of 1000 nm using a microindentation hardness tester (Triboindenter manufactured by Hysitron Inc.).

[0156] The pressure-sensitive adhesive sheet according to an embodiment of the present invention is typically composed of a pressure-sensitive adhesive. Examples of such pressure-sensitive adhesives include acrylic pressure-sensitive adhesives, rubber pressure-sensitive adhesives, silicone pressure-sensitive adhesives, polyester pressure-sensitive adhesives, urethane pressure-sensitive adhesives, epoxy pressure-sensitive adhesives, and polyether pressure-sensitive adhesives. To further enhance the effects of the present invention, the pressure-sensitive adhesive sheet is preferably composed of an acrylic pressure-sensitive adhesive, which is formed from an acrylic pressure-sensitive adhesive composition containing an acrylic polymer obtained by polymerizing a monomer component. The main polymer component contained in a pressure-sensitive adhesive composition, such as this acrylic polymer, is sometimes referred to as a base polymer. The content of the base polymer in the pressure-sensitive adhesive composition is, for example, 50 wt % or more, or may be 60 wt % or more, 70 wt % or more, 80 wt % or more, or even 90 wt % or more. The upper limit of the content of the base polymer in the pressure-sensitive adhesive composition may be, for example, 99.9 wt % or less, 99 wt % or less, or 95 wt % or less.

[0157] The pressure-sensitive adhesive sheet according to the embodiment of the present invention can be formed by any appropriate method as long as the effects of the present invention are not impaired. As for such a formation method, the explanation in the above section <1-2. Pressure-sensitive adhesive sheet> can be cited.

[0158] A typical embodiment of the PSA sheet according to the present invention is a PSA sheet composed of an acrylic PSA formed from an acrylic PSA composition containing an acrylic polymer. For such acrylic polymers and acrylic PSA compositions, the explanations in the previous sections <1-2-a. Acrylic polymer> and <1-2-b. Acrylic PSA composition> can be cited.

[0159] A release liner may be provided on the surface of the PSA sheet. Examples of release liners include films, paper, woven fabrics, nonwoven fabrics, porous materials, nets, foams, foils, and laminates thereof, made of resin, paper, fiber, metal, or composite materials thereof. Examples of resins include polyethylene, polypropylene, polybutene, polybutadiene, polymethylpentene, polyvinyl chloride, vinyl chloride copolymers, polyethylene terephthalate, polybutylene terephthalate, polyurethane, and ethylene-vinyl acetate copolymers.

[0160] The thickness of the release liner is, for example, 5 μm to 200 μm, and may be 5 to 100 μm. The surface of the release liner may be subjected to various surface treatments such as release treatment, antifouling treatment, and antistatic treatment, as necessary.

[0161] The present invention will be specifically described below using examples, but the present invention is not limited to these examples. The test and evaluation methods used in the examples are as follows. The term "parts" means "parts by weight" unless otherwise specified, and the term "%" means "% by weight" unless otherwise specified.

[0162] <Measurement of Thickness> Measurement was carried out using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., "MCPD9800").

[0163] <Measurement of refractive index> [Refractive index of adhesive sheet] The refractive index of the adhesive sheet was measured using an Abbe refractometer (manufactured by ATAGO, product name "DR-M2 / 1550"). The measurement wavelength was 589 nm, and the measurement temperature was 25°C. [Refractive index of liquid crystal alignment solidified layer] The refractive index of the liquid crystal alignment solidified layer was determined in the transmission axis direction as follows. The in-plane retardation Re(550) and thickness direction retardation Rth(550) were measured using an Axoscan (manufactured by Axometrics). nx, ny, and nz were calculated from the following simultaneous equations. Re(550) = (nx - ny) × d Nz = Rth(550) / Re(550) = (nx - nz) / (nx - ny) Furthermore, in the ellipse formula (x2 / a2) + (y2 / b2) = 1, a is set to nx, b is set to ny, and x and y are set to the refractive index in the x and y directions at an angle θ on the ellipse, and the simultaneous equations were solved from y = tan θ and the above nx and ny to calculate the refractive index in the transmission axis direction.

[0164] <Measurement of indentation hardness> The laminate obtained in the examples and comparative examples, having a polarizing film / adhesive / first liquid crystal alignment solidified layer / adhesive sheet / release liner configuration, was used as an evaluation sample, cut into 3 mm x 5 mm pieces, and cross-sections were prepared using an ultramicrotome (manufactured by Leica, device name: Leica EM UC7) under frozen conditions at -60 ° C. The cross-sections were fixed to a predetermined support (a brass block of approximately 10 mm x 8 mm x 6 mm). In an atmosphere of 25 ° C., a Berkovich (triangular pyramid) indenter was used to measure the indentation hardness when the adhesive sheet surface was indented to 1000 nm using a microindentation hardness tester (nanoindenter) (manufactured by Hysitron Inc., Triboindenter).

[0165] <Measurement of Tg> A measurement sample was prepared by laminating pressure-sensitive adhesive sheets to a thickness of approximately 1 mm. Dynamic viscoelasticity measurement was carried out under the following conditions using an ARES-G2 (manufactured by TA Instruments), and the temperature at which the loss tangent (tan δ) was maximized (peak top temperature) was taken as the glass transition temperature (Tg) of the pressure-sensitive adhesive sheet. (Measurement conditions) Deformation mode: torsion Measurement frequency: 1 Hz Heating rate: 5°C / min Shape: parallel plate, 8 mmφ

[0166] <Evaluation of Linear Irregularities> The acrylic adhesive produced in Production Example 12 was placed on the second liquid crystal alignment solidified layer side of the optical laminates obtained in the Examples and Comparative Examples, and the laminate was attached to a V3 reflector (manufactured by NEODIS) via the acrylic adhesive to prepare a test sample. The obtained test sample was visually observed under a three-wavelength fluorescent lamp and evaluated according to the following criteria: ◎: No linear irregularities were observed ○: Slight linear irregularities were observed △: Linear irregularities were observed, but to a level acceptable for practical use ×: Significant linear irregularities were observed

[0167] <Measurement of Indentation Load> The laminates obtained in the Examples and Comparative Examples, each having a configuration of polarizing film / adhesive / first liquid crystal alignment solidified layer / adhesive sheet / second liquid crystal alignment solidified layer / adhesive sheet / release liner, were used as evaluation samples, which were cut into 1 cm squares and used as measurement samples with the outermost adhesive layer fixed to a predetermined support (a slide glass, manufactured by Matsunami Glass Industrial Co., Ltd.). In an atmosphere of 25°C, a Berkovich (triangular pyramid) indenter was used with a microindentation hardness tester (ENT-NEXUS, manufactured by ELIONIX) to measure the indentation load when indented 40 μm from the outermost layer on the polarizing film side.

[0168] <Evaluation of Indentation Due to Local Load> The laminates obtained in the Examples and Comparative Examples, each having a polarizing film / adhesive / first liquid crystal alignment solidified layer / adhesive sheet / second liquid crystal alignment solidified layer / adhesive sheet / release liner configuration, were cut into 1 cm long and 1 cm wide pieces to serve as samples. The release liner was peeled off, and the exposed adhesive sheet was attached to an aluminum reflector (manufactured by Toray Advanced Film Co., Ltd., product name: Cerapeel DMS-X42, total light reflectance: 86%). The sample was then placed on a glass plate (manufactured by Matsunami Glass Industry Co., Ltd., thickness = 0.7 mm) so that the polarizing film side of the sample was in contact with the glass plate. Next, a weight was placed on a conical indenter (diameter 1.5 mm, height 0.8 mm) from the aluminum reflector side through a PET sheet (manufactured by Toray Industries, Inc., thickness = 80 μm) and pressed for 30 seconds. Measurements were performed with a weight (load) of 400 g (2.2 MPa) of the weight. The weight and indenter were then removed, and the surface of the sample that had been in contact with the glass plate was visually observed by reflection at polar angles of 30° to 60° and around one azimuth angle to check for the presence or absence of dents. The surface of the sample was defined as the X-axis and Y-axis, and the axis perpendicular to the XY plane was defined as the Z-axis. The polar angle (θ) was the angle tilted from the Z-axis toward the XY plane, and the MD direction of the polarizing film was defined as 0°. The measurement angle defined counterclockwise from the MD direction of the polarizing film was defined as the azimuth angle (φ). Note that the visibility of dents does not depend solely on the actual amount of dents; the greater the refractive index difference between the liquid crystal alignment solidified layer and the pressure-sensitive adhesive layer, the easier they may be to see. The dents were evaluated according to the following criteria: ◎: No visible dents. 〇: Slight dents were visible, but at a level that was not problematic for practical use. △: dents were visible, but at a level that was not problematic for practical use. ×: Significant dents (dents) were visible, at a level that was problematic for practical use.

[0169] <Evaluation of Adhesion> The second liquid crystal alignment solidified layer side of the polarized film-attached optical laminate obtained in the Examples and Comparative Examples was bonded to a polyethylene terephthalate (PET) film (manufactured by Toray Industries, Inc., product name: Lumirror, thickness = 125 μm). An adhesive (manufactured by Monotaro, product name: Motto Kutsuke Taro) was used for bonding. Bonding was performed in a temperature atmosphere of 25°C using a pressure roller with a mass of 2 kg as specified in JIS Z0237:2009, ensuring that no air bubbles were trapped between the second liquid crystal alignment solidified layer and the PET film during bonding. After leaving the laminate for 2 days, a 25 mm x 150 mm shape was cut out and bonded to the surface of a stainless steel (SUS) plate as a test plate using an adhesive sheet (manufactured by Nitto Denko Corporation, product name: No. 500). Bonding was performed in a temperature atmosphere of 25°C using a pressure roller with a mass of 2 kg as specified in JIS Z0237:2009. Next, in an atmosphere having a temperature of 25±5°C, a tensile tester (Shimadzu Corporation, product name: Autograph AG-X) was used to attempt to peel the polarizing film / adhesive / first liquid crystal alignment solidified layer / adhesive sheet laminate (laminate portion P) from the second liquid crystal alignment solidified layer / adhesive / PET film / adhesive sheet / SUS plate laminate (laminate portion Q) in the long side direction at a peel angle of 90° and a peel rate of 300 mm / min. Evaluation was performed according to the following criteria. ◯: The first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer were sufficiently adhered to each other upon peeling. Δ: The peeling was somewhat light upon peeling, but at a level that is not problematic for practical use. ×: The layers peeled easily upon peeling, and the adhesion was insufficient.

[0170] [Production Example 1] Preparation of First Liquid Crystal Alignment Solidified Layer A photopolymerizable liquid crystal compound exhibiting a nematic liquid crystal phase (BASF's "Paliocolor LC242," chemical formula shown below) was dissolved in cyclopentanone to prepare a solution with a solids concentration of 30 wt %. A surfactant (BYK-Chemie's "BYK-360") and a photopolymerization initiator (IGM Resins' "Omnirad 907") were added to this solution to prepare a liquid crystal composition solution. The surfactant and polymerization initiator were added in amounts of 0.01 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's "ZEONORFILM," thickness 33 μm, Re(550) = 135 nm) was prepared as a substrate. The liquid crystal composition was applied to the substrate with a bar coater so that Re(550) was 240 nm, and the substrate was heated at 100° C. for 3 minutes to align the liquid crystal. After cooling to room temperature, the substrate was irradiated with an integrated light dose of 400 mJ / cm 2 in a nitrogen atmosphere. 2 The first liquid crystal alignment solidified layer was homogeneously aligned, had a thickness of 1.7 μm, and had an average refractive index of 1.590.

[0171] [Production Example 2]: Preparation of second liquid crystal alignment solidified layer A laminate having a structure of substrate / second liquid crystal alignment solidified layer (Re(550)=130 nm) was obtained in the same manner as in the production of the first liquid crystal alignment solidified layer in Production Example 1, except for changing the coating thickness. The second liquid crystal alignment solidified layer was homogeneously aligned, had a thickness of 0.92 μm, and had an average refractive index of 1.590.

[0172] [Manufacturing Example 3]: Preparation of Polarizer A long, amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) with a Tg of approximately 75°C was used as the thermoplastic resin substrate. One side of the resin substrate was subjected to a corona treatment. A PVA-based resin (a 9:1 mixture of polyvinyl alcohol (degree of polymerization: 4200, degree of saponification: 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIRM") was mixed with 100 parts by weight of the PVA-based resin, and 13 parts by weight of potassium iodide was added and dissolved in water to prepare an aqueous PVA solution (coating solution). The PVA-based resin was applied to the corona-treated surface of the resin substrate and dried at 60°C to form a 13 μm-thick PVA-based resin layer, producing a laminate. The resulting laminate was uniaxially stretched 2.4 times in the longitudinal direction (longitudinal direction) in an oven at 130°C (in-air auxiliary stretching treatment). Next, the laminate was immersed for 30 seconds in an insolubilizing bath (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) having a liquid temperature of 40°C (insolubilization treatment), then immersed for 60 seconds in a dyeing bath (an iodine aqueous solution obtained by blending iodine and potassium iodide with 100 parts by weight of water in a weight ratio of 1:7) having a liquid temperature of 30°C while adjusting the concentration so that the single transmittance (Ts) of the finally obtained polarizer would be a desired value (dyeing treatment), then immersed for 30 seconds in a crosslinking bath (a boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with 100 parts by weight of water) having a liquid temperature of 40°C (crosslinking treatment). The laminate was then immersed in a boric acid aqueous solution (boric acid concentration 4 wt %, potassium iodide concentration 5 wt %) at a liquid temperature of 70°C and uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls operating at different peripheral speeds to a total stretch ratio of 5.5 times (underwater stretching treatment). The laminate was then immersed in a cleaning bath (aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 20°C (washing treatment). The laminate was then dried in an oven maintained at approximately 90°C and brought into contact with a SUS heated roll maintained at a surface temperature of approximately 75°C (drying shrinkage treatment). In this way, a polarizer approximately 5 μm thick was formed on the resin substrate, yielding a laminate having a resin substrate / polarizer configuration. The polarizer's single transmittance Ts was 43.3%.

[0173] [Production Example 4]: Preparation of Polarized Film An HC-COP film was bonded to the surface of the polarizer obtained in Production Example 3 (the surface opposite to the resin substrate) via a UV-curable adhesive. The HC-COP film was a cycloolefin resin (COP) film (thickness 25 μm) with an HC layer (thickness 4 μm) formed thereon, and the COP film was bonded to the polarizer side. The COP film had an Re(550) of 135 nm. Next, the resin substrate was peeled off, and a triacetyl cellulose (TAC) film (thickness 25 μm) was bonded to the peeled surface via a UV-curable adhesive. In this way, a polarized film having a configuration of HC layer / COP film (protective layer) / polarizer / TAC film (protective layer) was obtained.

[0174] [Production Example 5]: Adhesive for laminating polarizing film and first liquid crystal alignment solidified layer Hydroxyethyl acrylamide (trade name "HEAA", manufactured by KJ Chemicals) 10 parts by weight, 2-acetoacetoxyethyl methacrylate (trade name "AAEM", manufactured by Mitsubishi Chemicals) 4 parts by weight, acryloylmorpholine (trade name "ACMO", manufactured by KJ Chemicals) 60 parts by weight, tripropylene glycol diacrylate (trade name "Aronix M-220", 1 part by weight of 4-vinylphenylboronic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) manufactured by Toagosei Co., Ltd.) 11 parts by weight, acrylic oligomer (trade name "ARUFON UP-1190", manufactured by Toagosei Co., Ltd.) 10 parts by weight, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (trade name "Omnirad 819", manufactured by IGM Resins) 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.

[0175] [Production Example 6]: Acrylic Polymer (1) and Acrylic Pressure-Sensitive Adhesive Composition (1) 85 parts by weight of phenoxybenzyl acrylate (POB-A), 2 parts by weight of 4-hydroxybutyl acrylate (4HBA), and 13 parts by weight of butyl acrylate (BA) were charged into a four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser. 0.1 parts by weight of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator was charged to 100 parts by weight of this monomer mixture together with ethyl acetate. Nitrogen gas was introduced with gentle stirring to replace the atmosphere, and the liquid temperature in the flask was maintained at around 55°C, allowing the polymerization reaction to proceed for 7 hours. The monomer concentration during polymerization was 40% by weight. Thereafter, ethyl acetate was added to the obtained reaction solution to adjust the solid content concentration to 30%, thereby preparing a solution of acrylic polymer (1). 0.2 parts by weight of an isocyanate crosslinking agent (trimethylolpropane / xylylene diisocyanate trimer adduct, manufactured by Mitsui Chemicals, Inc., Takenate D-110N) and ethyl acetate as a dilution solvent were added to 100 parts by weight of the solid content of acrylic polymer (1), and the mixture was mixed and stirred to prepare an acrylic pressure-sensitive adhesive composition (1).

[0176] [Production Example 7]: Acrylic polymer (2) and acrylic pressure-sensitive adhesive composition (2) A solution of acrylic polymer (2) and an acrylic pressure-sensitive adhesive composition (2) were prepared in the same manner as in Production Example 6, except that 70 parts by weight of phenoxybenzyl acrylate (POB-A), 1 part by weight of 4-hydroxybutyl acrylate (4HBA), and 29 parts by weight of butyl acrylate (BA) were charged instead of 85 parts by weight of phenoxybenzyl acrylate (POB-A), 2 parts by weight of 4-hydroxybutyl acrylate (4HBA), and 13 parts by weight of butyl acrylate (BA).

[0177] [Production Example 8]: Acrylic polymer (3) and acrylic pressure-sensitive adhesive composition (3) A solution of acrylic polymer (3) and an acrylic pressure-sensitive adhesive composition (3) were prepared in the same manner as in Production Example 6, except that 80 parts by weight of benzyl acrylate (BzA), 1 part by weight of 4-hydroxybutyl acrylate (4HBA), and 19 parts by weight of butyl acrylate (BA) were charged instead of 85 parts by weight of phenoxybenzyl acrylate (POB-A), 2 parts by weight of 4-hydroxybutyl acrylate (4HBA), and 13 parts by weight of butyl acrylate (BA).

[0178] [Production Example 9]: Acrylic polymer (4) and acrylic pressure-sensitive adhesive composition (4) A solution of acrylic polymer (4) and an acrylic pressure-sensitive adhesive composition (4) were prepared in the same manner as in Production Example 6, except that 95 parts by weight of phenoxybenzyl acrylate (POB-A) and 5 parts by weight of 4-hydroxybutyl acrylate (4HBA) were charged instead of 85 parts by weight of phenoxybenzyl acrylate (POB-A), 2 parts by weight of 4-hydroxybutyl acrylate (4HBA), and 13 parts by weight of butyl acrylate (BA).

[0179] [Production Example 10]: Acrylic Polymer (5) and Acrylic Pressure-Sensitive Adhesive Composition (5) A monomer mixture containing 91 parts by weight of butyl acrylate (BA), 6 parts by weight of acryloylmorpholine (trade name "ACMO", manufactured by KJ Chemicals), 2.7 parts by weight of acrylic acid (AA), and 0.3 parts by weight of 4-hydroxybutyl acrylate (4HBA) was charged into a four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser. 0.1 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with 100 parts by weight of ethyl acetate per 100 parts by weight of this monomer mixture. Nitrogen gas was introduced with gentle stirring to replace the atmosphere, and the temperature in the flask was maintained at around 55°C while the polymerization reaction was carried out for 8 hours to prepare a solution of acrylic polymer (5). An acrylic pressure-sensitive adhesive composition (5) was prepared by blending 0.1 parts by weight of an isocyanate crosslinking agent (trimethylolpropane / tolylene diisocyanate adduct, manufactured by Tosoh Corporation, trade name "Coronate L"), 0.3 parts by weight of a peroxide crosslinking agent (benzoyl peroxide, manufactured by Nippon Oil & Fats Corporation, trade name "Niper BMT"), and 0.2 parts by weight of an epoxy group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403") per 100 parts by weight of the solids content of the acrylic polymer (5). The polymer concentration of the acrylic pressure-sensitive adhesive composition (5) was adjusted to 5% by weight.

[0180] [Production Example 11]: Acrylic polymer (6) and acrylic pressure-sensitive adhesive composition (6) A solution of acrylic polymer (6) was prepared in the same manner as in Production Example 6, except that 19 parts by weight of benzyl acrylate (BzA), 0.1 parts by weight of 4-hydroxybutyl acrylate (4HBA), 5 parts by weight of acrylic acid (AA), and 75.9 parts by weight of butyl acrylate (BA) were charged instead of 85 parts by weight of phenoxybenzyl acrylate (POB-A), 2 parts by weight of 4-hydroxybutyl acrylate (4HBA), and 13 parts by weight of butyl acrylate (BA). An acrylic pressure-sensitive adhesive composition (6) was prepared by blending 0.45 parts by weight of an isocyanate crosslinking agent (trimethylolpropane / tolylene diisocyanate adduct, manufactured by Tosoh Corporation, trade name "Coronate L"), 0.1 parts by weight of a peroxide crosslinking agent (benzoyl peroxide, manufactured by Nippon Oil & Fats Corporation, trade name "Niper BMT"), and 0.2 parts by weight of an epoxy group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403") per 100 parts by weight of the solids content of the acrylic polymer (6). The polymer concentration of the acrylic pressure-sensitive adhesive composition (6) was adjusted to 5% by weight.

[0181] [Production Example 12]: Acrylic polymer (A) and acrylic pressure-sensitive adhesive composition (A) A monomer mixture containing 94.9 parts by weight of butyl acrylate (BA), 5 parts by weight of acrylic acid, and 0.1 parts by weight of 2-hydroxyethyl acrylate (HEA) was charged into a four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser. Furthermore, 0.1 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator and 100 parts by weight of ethyl acetate were charged to 100 parts by weight of this monomer mixture. Nitrogen gas was introduced with gentle stirring to replace the atmosphere, and the temperature in the flask was maintained at around 55°C, allowing the polymerization reaction to proceed for 8 hours to prepare a solution of acrylic polymer (A) having a weight average molecular weight (Mw) of 2,200,000. An acrylic pressure-sensitive adhesive composition (A) was prepared by blending 0.6 parts by weight of an isocyanate crosslinking agent (trimethylolpropane / tolylene diisocyanate adduct: manufactured by Tosoh Corporation, trade name "Coronate L"), 0.2 parts by weight of a peroxide crosslinking agent (benzoyl peroxide, manufactured by NOF Corporation, trade name "Niper BMT"), and 0.2 parts by weight of an epoxy group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403") relative to 100 parts by weight of the solids content of the solution of acrylic polymer (A).

[0182] [Example 1] The first liquid crystal alignment solidified layer side of the laminate having a substrate / first liquid crystal alignment solidified layer configuration obtained in Production Example 1 was bonded to the TAC film side of a polarizing film via the adhesive (thickness 1 μm) obtained in Production Example 5, and then the substrate was peeled off to obtain a laminate having a polarizing film / adhesive / first liquid crystal alignment solidified layer configuration. Next, the acrylic pressure-sensitive adhesive composition (1) obtained in Production Example 6 was applied to a release liner (Mitsubishi Chemical Corporation, MRF38-NS2) so as to have a thickness after drying of 5 μm, and the coating was cured and dried under conditions of a drying temperature of 120°C and a drying time of 90 seconds, and then bonded to the plasma-irradiated first liquid crystal alignment solidified layer side of the laminate to obtain a laminate having a configuration of polarizing film / adhesive / first liquid crystal alignment solidified layer / pressure-sensitive adhesive sheet (1) / release liner. After peeling off the release liner, the second liquid crystal alignment solidified layer side of the laminate having the substrate / second liquid crystal alignment solidified layer configuration obtained in Production Example 2, the second liquid crystal alignment solidified layer side of which had been corona-irradiated, was bonded to the pressure-sensitive adhesive sheet (1) side of the above laminate, and the substrate was peeled off to obtain an optical laminate with a polarizing film having the configuration of polarizing film / adhesive / first liquid crystal alignment solidified layer / pressure-sensitive adhesive sheet (1) / second liquid crystal alignment solidified layer. Separately, the acrylic pressure-sensitive adhesive composition (A) obtained in Production Example 12 was applied to a release liner (Mitsubishi Chemical Corporation, MRF38-NS2) so as to have a thickness after drying of 25 μm, and the coating was cured and dried under conditions of a drying temperature of 155° C. and a drying time of 90 seconds to obtain a pressure-sensitive adhesive sheet (A) / release liner laminate. The surface of the second liquid crystal alignment solidified layer of a polarizing film-attached optical laminate having a polarizing film / adhesive / first liquid crystal alignment solidified layer / adhesive sheet (1) / second liquid crystal alignment solidified layer configuration was subjected to corona irradiation, and the adhesive sheet (A) side of an adhesive sheet (A) / release liner laminate was attached to the corona-treated surface. This resulted in a polarizing film-attached optical laminate (1) having a polarizing film / adhesive / first liquid crystal alignment solidified layer / adhesive sheet (1) / second liquid crystal alignment solidified layer / adhesive sheet (A) / release liner configuration. In the polarizing film-attached optical laminate (1), the angle between the transmission axis of the polarizer of the polarizing film and the slow axis of the first liquid crystal alignment solidified layer was 15°, and the angle between the transmission axis of the polarizer of the polarizing film and the slow axis of the second liquid crystal alignment solidified layer was 75°.The average refractive index of each of the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer was 1.59, the refractive index nLC1 of the first liquid crystal alignment solidified layer in the transmission axis direction of the polarizer was 1.66, and the refractive index nLC2 of the second liquid crystal alignment solidified layer in the transmission axis direction of the polarizer was 1.56. The results are shown in Table 1.

[0183] [Example 2] The same procedure as in Example 1 was carried out, except that the acrylic pressure-sensitive adhesive composition (1) obtained in Production Example 6 was applied so that the thickness after drying would be 10 μm, to obtain an optical laminate (2) with a polarizing film having a configuration of polarizing film / adhesive / first liquid crystal alignment solidified layer / pressure-sensitive adhesive sheet (2) / second liquid crystal alignment solidified layer / pressure-sensitive adhesive sheet (A) / release liner. The results are shown in Table 1.

[0184] Example 3 An optical laminate (3) with a polarizing film was obtained in the same manner as in Example 1, except that the acrylic pressure-sensitive adhesive composition (2) obtained in Production Example 7 was used instead of the acrylic pressure-sensitive adhesive composition (1) obtained in Production Example 6. The results are shown in Table 1.

[0185] Example 4 An optical laminate (4) with a polarizing film was obtained in the same manner as in Example 1, except that the acrylic pressure-sensitive adhesive composition (3) obtained in Production Example 8 was used instead of the acrylic pressure-sensitive adhesive composition (1) obtained in Production Example 6. The results are shown in Table 1.

[0186] Example 5 An optical laminate (5) with a polarizing film was obtained in the same manner as in Example 1, except that the acrylic pressure-sensitive adhesive composition (4) obtained in Production Example 9 was used instead of the acrylic pressure-sensitive adhesive composition (1) obtained in Production Example 6. The results are shown in Table 1.

[0187] Comparative Example 1 An optical laminate (C1) with a polarizing film was obtained in the same manner as in Example 1, except that the acrylic pressure-sensitive adhesive composition (5) obtained in Production Example 10 was used instead of the acrylic pressure-sensitive adhesive composition (1) obtained in Production Example 6. The results are shown in Table 1.

[0188] Comparative Example 2 An optical laminate (C2) with a polarizing film was obtained in the same manner as in Example 1, except that the acrylic pressure-sensitive adhesive composition (6) obtained in Production Example 11 was used instead of the acrylic pressure-sensitive adhesive composition (1) obtained in Production Example 6. The results are shown in Table 1.

[0189] [Comparative Example 3] The same procedure as in Example 1 was carried out, except that the acrylic pressure-sensitive adhesive composition (1) obtained in Production Example 6 was applied so that the thickness after drying would be 20 μm, to obtain an optical laminate (C3) with a polarizing film having a configuration of polarizing film / adhesive / first liquid crystal alignment solidified layer / pressure-sensitive adhesive sheet (C3) / second liquid crystal alignment solidified layer / pressure-sensitive adhesive sheet (A) / release liner. The results are shown in Table 1.

[0190]

[0191] The optical laminate according to the embodiment of the present invention can be suitably used in image display devices (typically, liquid crystal display devices and organic EL display devices).

Claims

1. An optical laminate comprising a first liquid crystal alignment solidified layer, an adhesive sheet, and a second liquid crystal alignment solidified layer in this order, wherein the thickness of the adhesive sheet is less than 20 μm, and wherein, when the average refractive index of the adhesive sheet is n, the average refractive index of the first liquid crystal alignment solidified layer is n1, and the average refractive index of the second liquid crystal alignment solidified layer is n2, the maximum average refractive index difference selected from the group consisting of the average refractive index difference calculated by |n-n1| and the average refractive index difference calculated by |n-n2| is less than 0.11, and the indentation hardness of the adhesive sheet at 25°C exceeds 0.019 MPa.

2. The optical laminate according to claim 1, wherein the pressure-sensitive adhesive sheet is made of an acrylic pressure-sensitive adhesive, and the acrylic pressure-sensitive adhesive is formed from an acrylic pressure-sensitive adhesive composition containing an acrylic polymer obtained by polymerizing a monomer component.

3. The optical laminate according to claim 2, wherein the Tg of the acrylic polymer is less than 13°C.

4. The optical laminate according to claim 1, wherein the indentation hardness is less than 0.157 MPa.

5. The optical laminate according to claim 1, wherein the adhesive sheet has a thickness of 4 μm or more.

6. The optical laminate according to claim 1, wherein the average refractive index n of the pressure-sensitive adhesive sheet is 1.52 or more.

7. The optical laminate described in claim 1, which is used by providing a polarizing film on at least one side selected from the group consisting of the first liquid crystal alignment solidified layer side and the second liquid crystal alignment solidified layer side as viewed from the pressure-sensitive adhesive sheet.

8. An optical laminate with a polarizing film, comprising a polarizing film on the first liquid crystal alignment solidified layer side of the optical laminate described in any one of claims 1 to 6, as viewed from the adhesive sheet.

9. An optical laminate with a polarizing film, comprising a polarizing film on the second liquid crystal alignment solidified layer side of the optical laminate described in any one of claims 1 to 6, as viewed from the adhesive sheet.

10. An image display device comprising the optical laminate according to any one of claims 1 to 7.

11. An adhesive sheet having a thickness of less than 20 μm, an average refractive index n of 1.50 or more, and an indentation hardness at 25° C. of more than 0.019 MPa.

12. The pressure-sensitive adhesive sheet according to claim 11, which is composed of an acrylic pressure-sensitive adhesive, and the acrylic pressure-sensitive adhesive is formed from an acrylic pressure-sensitive adhesive composition containing an acrylic polymer obtained by polymerizing a monomer component.

13. The pressure-sensitive adhesive sheet according to claim 12, wherein the Tg of the acrylic polymer is less than 13°C.

14. The pressure-sensitive adhesive sheet according to claim 11, wherein the indentation hardness is less than 0.157 MPa.

15. The pressure-sensitive adhesive sheet according to claim 11, wherein the average refractive index n is 1.54 or more.

16. The pressure-sensitive adhesive sheet according to any one of claims 11 to 15, which is used for bonding a liquid crystal alignment solidified layer.

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