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

Abstract

To provide an optical laminate with a liquid crystal alignment solidifying layer, capable of suppressing generation of linear unevenness and recess due to local load, an optical laminate with a polarization film comprising the optical laminate and a polarization film, an image display device including the optical laminate, and a pressure-sensitive adhesive sheet preferably used for bonding the liquid crystal alignment solidifying layer.SOLUTION: An optical laminate according to an embodiment of the present invention includes a first liquid crystal alignment solidifying layer, a pressure-sensitive adhesive sheet, and a second liquid crystal alignment solidifying layer in this order, where a thickness of the pressure-sensitive adhesive sheet is less than 20 μm, when an average refractive index of the pressure-sensitive adhesive sheet is n, an average refractive index of the first liquid crystal alignment solidifying layer is n1, and an average refractive index of the second liquid crystal alignment solidifying layer is n2, a maximum average refractive index difference selected from a 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 an indentation hardness of the pressure-sensitive adhesive sheet at 25°C exceeds 0.019 MPa.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] In recent years, image display devices typified by liquid crystal display devices and electroluminescence (EL) display devices (for example, organic EL display devices, inorganic EL display devices) have been rapidly spreading.

[0003] An image display device generally includes an optical laminate including a retardation layer. In recent years, as the demand for thinning of image display devices has increased, there has also been an increasing demand for thinning of such optical laminates including a retardation layer. For this reason, thinning of the retardation layer that makes a large contribution to the thickness is required.

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

[0005] However, conventionally, an image display device including an optical laminate including a liquid crystal alignment cured layer has a problem that line irregularities (typically, a phenomenon in which a thin pink line is particularly noticeable in the absorption axis direction of the polarizer when viewed under a three-wavelength tube) are likely to occur. Further, conventionally, there is a problem that a dent is likely to occur due to a local load such as a dent occurring in the OCA due to the bonding pressure applied during the manufacture of the image display device.

Prior Art Documents

Patent Document

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] The problems of the present invention are to provide an optical laminate including a liquid crystal alignment cured layer that can suppress the occurrence of linear unevenness and reduce dents due to local loads. Another problem is to provide an optical laminate with a polarizing film including such an optical laminate and a polarizing film. Still another problem is to provide an image display device including such an optical laminate. Further preferably, it is to provide an adhesive sheet used for bonding the liquid crystal alignment cured layer.

Means for Solving the Problems

[0008] [1] An optical laminate according to an embodiment of the present invention is an optical laminate including a first liquid crystal alignment cured layer, an adhesive sheet, and a second liquid crystal alignment cured layer in this order, wherein the thickness of the adhesive sheet is less than 20 μm, and when the average refractive index of the adhesive sheet is n, the average refractive index of the first liquid crystal alignment cured layer is n1, and the average refractive index of the second liquid crystal alignment cured 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] In the optical laminate according to [1] above, the adhesive sheet may be composed of an acrylic adhesive, and the acrylic adhesive may be formed from an acrylic adhesive composition containing an acrylic polymer obtained by polymerizing a monomer component. [3] In the optical laminate according to [2] above, the Tg of the acrylic polymer may be 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 and used on at least one side selected from the group consisting of the first liquid crystal alignment cured layer side and the second liquid crystal alignment cured 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 includes a polarizing film on the first liquid crystal alignment cured layer side as viewed from the pressure-sensitive adhesive sheet of the optical laminate according to any one of [1] to [6] above. [9] The optical laminate with a polarizing film according to an embodiment of the present invention includes a polarizing film on the second liquid crystal alignment cured layer side as viewed from the pressure-sensitive adhesive sheet of the optical laminate according to any one of [1] to [6] above.

[10] The image display device according to an embodiment of the present invention includes the optical laminate according to 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 exceeding 0.019 MPa.

[12] The pressure-sensitive adhesive sheet according to

[11] above 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.

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

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

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

[11] to

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

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

[11] to

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

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

[11] to

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

Advantages of the Invention

[0009] According to an embodiment of the present invention, it is possible to provide an optical laminate including a liquid crystal alignment solidification layer that can suppress the occurrence of linear unevenness and reduce dents due to local loads. Further, it is possible to provide an optical laminate with a polarizing film including such an optical laminate and a polarizing film. Furthermore, it is possible to provide an image display device including such an optical laminate. Furthermore, it is possible to provide a pressure-sensitive adhesive sheet preferably used for bonding a liquid crystal alignment solidification layer.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0011] [Regarding Terms] In this specification, when there is an expression of "weight", it may be read as "mass", which is a SI unit customarily used to indicate weight. Vice versa.

[0012] In this specification, when there is an expression of "(meth)acryl", it means "acryl and / or methacryl"; when there is an expression of "(meth)acrylate", it means "acrylate and / or methacrylate"; when there is an expression of "(meth)allyl", it means "allyl and / or methallyl"; when there is an expression of "(meth)acrolein", it means "acrolein and / or methacrolein".

[0013] In this specification, when simply referred to as "liquid crystal alignment solidification layer", it is a concept including both the first liquid crystal alignment solidification layer and the second liquid crystal alignment solidification layer.

[0014] In this specification, regarding the refractive indices (nx, ny, nz), "nx" is the refractive index in the direction where the in-plane refractive index is maximum (i.e., the slow axis direction), "ny" is the refractive index in the direction orthogonal to the slow axis in the plane (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, regarding the in-plane retardation (Re), "Re(λ)" is the in-plane retardation of the film measured with light of wavelength λ nm at 23°C. For example, "Re(550)" is the in-plane retardation of the film measured with light of wavelength 550 nm at 23°C. Re(λ) is obtained by the formula: Re = (nx - ny) × d, where d (nm) is the thickness of the film.

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

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

[0018] ≪≪1. Optical laminate≫≫ The optical laminate according to an embodiment of the present invention includes a first liquid crystal alignment cured layer, an adhesive sheet, and a second liquid crystal alignment cured layer in this order. The optical laminate according to an embodiment of the present invention may include any other appropriate member as long as the effects of the present invention are not impaired, if it includes a first liquid crystal alignment cured layer, an adhesive sheet, and a second liquid crystal alignment cured layer in this order. Examples of such other members include a base material used when forming the first liquid crystal alignment cured layer and the second liquid crystal alignment cured layer, and a release liner. In the optical laminate according to one preferred embodiment of the present invention, the first liquid crystal alignment cured layer and the second liquid crystal alignment cured 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 cured layer, the adhesive sheet, and the second liquid crystal alignment cured layer. The positive C plate exhibits a refractive index characteristic of nz > nx = ny. The retardation Rth(550) in the thickness direction of the positive C plate is preferably -20 nm to -300 nm, more preferably -30 nm to -250 nm, still 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 exactly 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 can be less than 10 nm.

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

[0020] to

[0028] of JP-A-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 still 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 cured layer 11, an adhesive sheet 20, and a second liquid crystal alignment cured layer 12 in this order. The first liquid crystal alignment cured layer 11 and the adhesive sheet 20 are directly laminated, and the adhesive sheet 20 and the second liquid crystal alignment cured layer 12 are directly laminated.

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

[0023] The total thickness of the optical laminate according to the embodiment of the present invention can adopt any appropriate total 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, still 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 adhesive sheet is typically less than 20 μm, may be 17 μm or less, may be 15 μm or less, may be 13 μm or less, or may be 10 μm or less. In the optical laminate according to an embodiment of the present invention, the lower limit value of the thickness of the adhesive sheet is typically 1 μm or more, may be 2 μm or more, may be 3 μm or more, or may be 4 μm or more. In the optical laminate according to an embodiment of the present invention, one embodiment of the thickness of the adhesive sheet is preferably 1 μm to 20 μm, more preferably 2 μm to 17 μm, still more preferably 3 μm to 15 μm, and particularly preferably 4 μm to 13 μm. By adjusting the thickness of the adhesive sheet within the above range, the effects of the present invention can be more effectively exhibited. If the thickness of the adhesive sheet is too large, the effects of the present invention may not be exhibited, and in particular, there is a risk of indentation due to local load.

[0025] In the optical laminate according to an embodiment of the present invention, when the average refractive index of the adhesive sheet is n, the average refractive index of the first liquid crystal alignment cured layer is n1, and the average refractive index of the second liquid crystal alignment cured 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| (that is, 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, still more preferably 0.07 or less, particularly preferably 0.06 or less, and most preferably 0.05 or less. The lower the lower limit of the above maximum average refractive index difference, the more preferable it is, and preferably it is 0 or more. By adjusting the above 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 above 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| 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 indentation hardness of the adhesive sheet at 25°C is typically more than 0.019 MPa, preferably more than 0.019 MPa and less than 0.157 MPa, more preferably from 0.020 MPa to 0.130 MPa, still more preferably from 0.030 MPa to 0.100 MPa, particularly preferably from 0.040 MPa to 0.090 MPa, and most preferably from 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. In particular, dents caused by local loads can be effectively reduced. If the indentation hardness is too small, the adhesive sheet becomes too soft, and there is a risk of dents due to local loads. On the other hand, if the indentation hardness is too large, the adhesive sheet becomes too hard, and there is a risk of a decrease in the adhesion between the adhesive sheet and the liquid crystal alignment curing layer.

[0027] An optical laminate according to one embodiment of the present invention is an optical laminate including a first liquid crystal alignment curing layer, an adhesive sheet, and a second liquid crystal alignment curing layer in this order, (i) the thickness of the adhesive sheet is adjusted to less than 20 μm, (ii) when the average refractive index of the adhesive sheet is n, the average refractive index of the first liquid crystal alignment curing layer is n1, and the average refractive index of the second liquid crystal alignment curing 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 adhesive sheet at 25°C is adjusted to exceed 0.019 MPa, whereby the effects of the present invention can be exhibited. In the optical laminate according to the above embodiment, the first liquid crystal alignment curing layer and the second liquid crystal alignment curing layer can adopt any appropriate liquid crystal alignment curing layer as long as the effects of the present invention are not impaired. Representative embodiments will be described in the section of <<1-1. Liquid crystal alignment curing layer>> below. Also, in the optical laminate according to the above embodiment, any appropriate adhesive sheet can be adopted for the adhesive sheet as long as the effects of the present invention are not impaired. Representative embodiments will be described in the section of <<1-2. Adhesive sheet>> below.

[0028] <<1-1. Liquid crystal alignment and curing layer>> The optical laminate according to an embodiment of the present invention includes a first liquid crystal alignment and curing layer and a second liquid crystal alignment and curing layer. The optical laminate according to an embodiment of the present invention can be made thinner by using such a liquid crystal alignment and curing layer.

[0029] Note that the liquid crystal alignment and curing layer can be a layer in which a liquid crystal compound is aligned in a predetermined direction within the layer and the alignment state is fixed.

[0030] Examples of the liquid crystal compound used for the liquid crystal alignment and curing layer include liquid crystal polymers and liquid crystal monomers. The liquid crystal compound is preferably a polymerizable liquid crystal compound, that is, a liquid crystal monomer. When the liquid crystal compound is polymerizable, the alignment state of the liquid crystal compound can be fixed by polymerizing the liquid crystal compound after aligning it. The polymer formed by polymerization can be non-liquid crystalline. Therefore, in the formed liquid crystal alignment and curing layer, for example, transitions to a liquid crystal phase, a glass phase, and a crystal phase due to a temperature change peculiar to the liquid crystal compound do not occur. As a result, the liquid crystal alignment and curing layer is not affected by temperature changes and is extremely stable.

[0031] In one embodiment of the liquid crystal alignment curing layer, it can be formed using a liquid crystal composition containing a liquid crystal monomer. As used herein, the liquid crystal monomer contained in the liquid crystal composition refers to a compound having a polymerizable group and having liquid crystallinity. The polymerizable group means a group involved in a polymerization reaction, preferably a photopolymerizable group. Here, the photopolymerizable group refers to a group that can participate in a polymerization reaction by active radicals, acids, etc. generated from a photopolymerization initiator. As such a liquid crystal monomer, for example, polymerizable mesogenic compounds described in JP-T-2002-533742 (WO00 / 37585), EP358208 (US5211877), EP66137 (US4388453), WO93 / 22397, EP0261712, DE19504224, DE4408171, and GB2280445 can be used. Examples of such polymerizable mesogenic compounds include LC242 under the trade name of BASF, E7 under the trade name of Merck, and LC-Sillicon-CC3767 under the trade name of Wacker-Chem.

[0032] The mechanism for the manifestation of liquid crystallinity of the liquid crystal monomer may be thermotropic or lyotropic. Also, the configuration of the liquid crystal phase may be nematic liquid crystal or smectic liquid crystal. From the viewpoint of ease of manufacture, thermotropic nematic liquid crystal is preferred for the liquid crystallinity.

[0033] The temperature range in which the liquid crystal monomer exhibits liquid crystallinity varies depending on its type. 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 cured layer is preferably 0.06 or more, more preferably 0.08 or more, still more preferably 0.09 or more, and particularly preferably 0.10 or more. The upper limit of Δn can be, for example, 0.13, or can be, for example, 0.12. If Δn is in such a range, a desired in-plane retardation can be realized with a very thin thickness. As a result, it becomes possible to further thin the liquid crystal alignment cured layer and the optical laminate, and for example, it can ultimately contribute to a remarkable thinning of the image display device.

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

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

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

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

[0039] The thickness of the first liquid crystal alignment and curing layer can typically be adjusted so as to obtain a desired in-plane retardation of the λ / 2 plate. In one embodiment, the thickness of the first liquid crystal alignment and curing 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, still 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 and curing layer is preferably 0.3 μm to 1.7 μm, more preferably 0.7 μm to 1.6 μm, still more preferably 1.0 μm to 1.5 μm, and particularly preferably 1.3 μm to 1.5 μm. Thus, according to the embodiment of the present invention, linear unevenness can be suppressed while reducing the thickness of the first liquid crystal alignment and curing layer as compared with the prior art.

[0040] The thickness of the second liquid crystal alignment and curing layer can typically be adjusted so as to obtain a desired in-plane retardation of the λ / 4 plate. In one embodiment, the thickness of the second liquid crystal alignment and curing 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, still more preferably 0.7 μm to 1.2 μm, and most preferably 0.7 μm to 1.1 μm.

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

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

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

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

[0045] The average refractive index n1 of the first liquid crystal alignment cured layer and the average refractive index n2 of the second liquid crystal alignment cured layer may be opposite. The absolute value of the difference between the average refractive index n1 of the first liquid crystal alignment cured layer and the average refractive index n2 of the second liquid crystal alignment cured layer can be, for example, 0.00 to 0.20. The average refractive index of the liquid crystal alignment cured layer will typically conform to the composition for forming the liquid crystal alignment cured layer in order to obtain desired optical properties. As a result, linear unevenness may occur, but according to the embodiments of the present invention, such linear unevenness can be suppressed.

[0046] A side-chain type thermotropic liquid crystal polymer may be introduced into the first liquid crystal alignment cured layer and / or the second liquid crystal alignment cured layer (substantially, the liquid crystal composition for forming them). By introducing the side-chain type thermotropic liquid crystal polymer, an action of homeotropically aligning (vertically aligning) the liquid crystal monomer can occur. As a result, the nz of the first liquid crystal alignment cured layer and / or the second liquid crystal alignment cured layer can be increased, and as a result, the Nz coefficient of the first liquid crystal alignment cured layer and / or the second liquid crystal alignment cured layer can be appropriately adjusted. Finally, for example, the Nz coefficient of the retardation layer can be made to be in the range of 0.30 to 0.70 without providing a positive C plate.

[0047] As the side-chain type thermotropic liquid crystal polymer, typically, 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 can be mentioned. When the liquid crystal composition containing the liquid crystal monomer is heated to a predetermined temperature due to the polymer having a thermotropic liquid crystal fragment in the side chain, the side-chain type liquid crystal polymer can be oriented. Further, when the side-chain type polymer has a non-liquid crystal fragment in the side chain, the non-liquid crystal fragment can interact with the photopolymerizable liquid crystal monomer to cause an action of homeotropically orienting the photopolymerizable liquid crystal monomer.

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

Chemical formula

Chemical formula

[0049] In formula (I), R 1 is a hydrogen atom or a methyl group, 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 -CO2- 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, 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).

Chemical formula

[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 crystal monomer unit to the non-liquid crystal monomer unit in the side-chain liquid crystal monomer can be appropriately set according to the purpose. The ratio (molar ratio) of the non-liquid crystal monomer to the total of the liquid crystal monomer unit and the non-liquid crystal monomer unit is preferably 0.05 to 0.80, more preferably 0.10 to 0.60, and still 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 according to the purpose. The content of the liquid crystal monomer is preferably 1.2 to 20 times, more preferably 1.3 to 10 times, still more preferably 1.4 to 9 times, and particularly preferably 1.5 to 8 times the content of the side-chain liquid crystal polymer.

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

[0055] ≪1-2. Adhesive Sheet≫ The optical laminate according to the embodiment of the present invention has an adhesive sheet between the first liquid crystal alignment curing layer and the second liquid crystal alignment curing layer.

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

[0057] The average refractive index n of the adhesive sheet is, for example, 1.45 or more, preferably 1.50 or more, more preferably 1.52 or more, still 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 adhesive sheet is preferably 1.70 or less.

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

[0059] As the pressure-sensitive adhesive sheet, any appropriate pressure-sensitive adhesive sheet can be employed as long as the effects of the present invention are not impaired. The pressure-sensitive adhesive sheet typically consists of a pressure-sensitive adhesive. Examples of such pressure-sensitive adhesives include acrylic pressure-sensitive adhesives, rubber-based pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, polyester-based pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, epoxy-based pressure-sensitive adhesives, and polyether-based pressure-sensitive adhesives. In terms of being able to more effectively exhibit the effects of the present invention, the pressure-sensitive adhesive sheet is preferably 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 monomer components. The main polymer component contained in the pressure-sensitive adhesive composition, such as this acrylic polymer, may be referred to as a base polymer. The content ratio of the base polymer contained in the pressure-sensitive adhesive composition is, for example, 50% by weight or more, and may be 60% by weight or more, 70% by weight or more, 80% by weight or more, or 90% by weight or more. The upper limit of the content ratio of the base polymer contained in the pressure-sensitive adhesive composition may be, for example, 99.9% by weight or less, 99% by weight or less, or 95% by weight 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. As the means of drying, for example, heating can be employed. As the substrate, for example, a release film may be employed. As the release film, a known film that can be used when forming a solvent-type pressure-sensitive adhesive sheet can be employed. The pressure-sensitive adhesive sheet formed on the substrate can be transferred to other layers included in the optical laminate according to an embodiment of the present invention, such as the first liquid crystal alignment curing layer or the second liquid crystal alignment curing layer. The substrate may be another layer that the optical laminate according to an embodiment of the present invention may include.

[0061] The drying temperature of the coating film can adopt any appropriate drying temperature as long as the effects of the present invention are not impaired. Such drying temperatures include, for example, 130°C or lower, and may be 125°C or lower, 120°C or lower, 110°C or lower, or 100°C or lower. The drying temperature is, for example, 60°C or higher, and may be 80°C or higher. The drying time of the coating film can adopt any appropriate drying time as long as the effects of the present invention are not impaired. Such drying times include, for example, 30 seconds to 300 seconds, and may be 40 seconds to 240 seconds, or 60 seconds to 180 seconds.

[0062] In the optical laminate according to the embodiment of the present invention, as the adhesive constituting the adhesive sheet, as described above, for example, acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, polyether adhesives can be mentioned. Hereinafter, as representative embodiments 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 ratio of the acrylic polymer in the acrylic adhesive composition is preferably 50% by weight or more, more preferably 70% by weight or more, and still more preferably 90% by weight or more in terms of solid content.

[0064] The acrylic polymer in the acrylic adhesive composition may be only one kind or two or more kinds.

[0065] The acrylic polymer has a Tg of, for example, less than 20°C, preferably less than 15°C, more preferably less than 13°C, still more preferably more than -15°C and less than 13°C, still more preferably more than -10°C and less than 13°C, particularly preferably more than -5°C and less than 13°C, and most preferably more 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 expressed. If the Tg of the acrylic polymer is too large, the adhesive sheet may become too hard, and the adhesion between the adhesive sheet and the liquid crystal alignment curing layer may decrease.

[0066] The acrylic polymer is obtained by polymerizing monomer components. The monomer components preferably include an aromatic ring-containing monomer (m1).

[0067] The content ratio of the aromatic ring-containing monomer (m1) in the monomer components is, for example, 30% by weight or more, and 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 ratio of the aromatic ring-containing monomer (m1) in the monomer components is 100% by weight, and 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 more effectively expressing the effects of the present invention, the content ratio of the aromatic ring-containing monomer (m1) in the monomer components is preferably 50% to 100% by weight, more preferably 60% to 95% by weight, still more preferably 65% to 90% by weight, and particularly preferably 67% to 88% by weight.

[0068] As the aromatic ring-containing monomer (m1), a compound containing at least one aromatic ring and at least one ethylenically unsaturated group in one molecule can be used. The aromatic ring-containing monomer (m1) may be only one kind or two or more kinds.

[0069] Examples of the ethylenically unsaturated group include a (meth)acryloyl group, a vinyl group, and a (meth)allyl group. From the viewpoint of being able to more effectively exhibit the effects of the present invention, as the ethylenically unsaturated group, a (meth)acryloyl group and a vinyl group are preferable, a (meth)acryloyl group is more preferable, and an acryloyl group is even more preferable. Therefore, preferable embodiments of the aromatic ring-containing monomer (m1) include aromatic ring-containing (meth)acrylates and aromatic ring-containing vinyl compounds.

[0070] From the viewpoint of being able to suppress a decrease in the flexibility of the adhesive, etc., as the aromatic ring-containing monomer (m1), a compound in which the number of ethylenically unsaturated groups contained in one molecule is 1 (that is, a monofunctional monomer) is preferable.

[0071] The number of aromatic rings contained in one molecule of the aromatic ring-containing monomer (m1) may be 1 or 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, may be 12 or less, may be 8 or less, may be 6 or less, may be 4 or less, may be 3 or less, or may be 2 or less.

[0072] Examples of the aromatic ring contained in the aromatic ring-containing monomer (m1) include a benzene ring (which may be a benzene ring constituting a part of a biphenyl structure or a fluorene structure); a condensed ring such as a naphthalene ring, an indene ring, an azulene ring, an anthracene ring, or a phenanthrene ring; and hydrocarbon rings such as these may be used. Examples of the heteroatom contained in such a heterocyclic ring 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 carbocyclic rings and one or more heterocyclic rings are condensed, such as a dinaphthothiophene structure.

[0073] The aromatic ring contained in the aromatic ring-containing monomer (m1) may have a substituent on the ring-constituting atom. The substituent may be only one type or 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 directly bonded or may be bonded via a linking group. Such a linking group may be, for example, a group containing at least one structure selected from the group consisting of an alkylene group, an oxyalkylene group, a poly(oxyalkylene) group, a phenyl group, an alkylphenyl group, an alkoxyphenyl group, a group having a structure in which one or more hydrogen atoms in these groups are substituted with a hydroxyl group (e.g., a hydroxyalkylene group), an oxy group (-O- group), and a thiooxy group (-S- group). From the viewpoint of more effectively expressing the effects of the present invention, such a linking group preferably includes a group containing at least one structure selected from the group consisting of an alkylene group, an oxyalkylene group, and a poly(oxyalkylene) group. The number of carbon atoms in the alkylene group and the oxyalkylene group is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 to 2. The number of repeating units of the oxyalkylene unit in the poly(oxyalkylene) group is preferably 2 to 3.

[0075] From the viewpoint of more effectively expressing 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 "aromatic ring-containing plural monomer (m2)"). Examples of the aromatic ring-containing plural 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] As one embodiment of the aromatic ring-containing monomer (m1), the content ratio of the multi-aromatic-ring-containing monomer (m2) in the aromatic ring-containing monomer (m1) may be, for example, 50% by weight or more, may be 70% by weight or more, may be 80% by weight or more, may be 85% by weight or more, may be 90% by weight or more, may be 95% by weight or more, or may be 98% by weight or more. The upper limit of the content ratio of the multi-aromatic-ring-containing monomer (m2) in the aromatic ring-containing monomer (m1) is 100% by weight. From the viewpoint of more effectively expressing the effects of the present invention, the content ratio of the multi-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, still 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] As another embodiment of the aromatic ring-containing monomer (m1), the content ratio of the multi-aromatic-ring-containing monomer (m2) in the aromatic ring-containing monomer (m1) may be, for example, less than 50% by weight, may be less than 40% by weight, may be less than 30% by weight, may be less than 20% by weight, may be less than 10% by weight, or may be less than 5% by weight. In this embodiment, the aromatic ring-containing monomer (m1) preferably contains a monomer (m3) having one aromatic ring in one molecule, which will be described later.

[0078] Examples of the linking group that the multi-aromatic-ring-containing monomer (m2) may have include, for example, 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-(CH2) n - group, where n is 1 to 3, preferably 1), a linear alkylene group (-(CH2) n - group, where n is 1 to 6, preferably 1 to 3), and groups in which the alkylene groups in the oxyalkylene group, thiooxyalkylene group, and linear alkylene group are partially halogenated or completely halogenated.

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

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

[0081] Examples of monomers having a condensed aromatic ring structure include, for example, (meth)acrylate containing a naphthalene ring, (meth)acrylate containing an anthracene ring, vinyl group-containing naphthalene, and vinyl group-containing anthracene. 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, for example, 9,9-bis(4-hydroxyphenyl)fluorene (meth)acrylate and 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene (meth)acrylate. Since monomers having a fluorene structure contain a structural portion 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-condensed aromatic rings are directly chemically bonded.

[0083] Examples of the monomer having a dinaphthothiophene structure include (meth)acryloyl group-containing dinaphthothiophene, vinyl group-containing dinaphthothiophene, and (meth)allyl group-containing dinaphthothiophene. Specific examples include (meth)acryloyloxymethyldinaphthothiophene (for example, a compound having a structure in which CH2CH(R 1 )C(O)OCH2- is bonded to the 5-position or 6-position of the dinaphthothiophene ring, R 1 being a hydrogen atom or a methyl group.), (meth)acryloyloxyethyldinaphthothiophene (for example, a compound having a structure in which CH2CH(R 1 )C(O)OCH(CH3)- or CH2CH(R 1 )C(O)OCH2CH2- is bonded to the 5-position or 6-position of the dinaphthothiophene ring, R 1 being a hydrogen atom or a methyl group.), vinyldinaphthothiophene (for example, a compound having a structure in which a vinyl group is bonded to the 5-position or 6-position of the naphthothiophene ring), and (meth)allyloxydinaphthothiophene. The monomer having a dinaphthothiophene structure can be included in the concept of a monomer having a condensed aromatic ring structure by including a naphthalene structure and by having a structure in which a thiophene ring and two naphthalene structures are condensed.

[0084] Examples of the monomer having a dibenzothiophene structure include (meth)acryloyl group-containing dibenzothiophene and vinyl group-containing dibenzothiophene. The monomer having a dibenzothiophene structure can be included in the concept of a monomer having a condensed aromatic ring structure because it has a structure in which a thiophene ring and two benzene rings are condensed. Note that neither the dinaphthothiophene structure nor the dibenzothiophene structure corresponds to a structure in which two or more non-condensed aromatic rings are directly chemically bonded.

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

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

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

[0088] As another embodiment of the aromatic ring-containing monomer (m1), the content ratio of the monomer (m3) having one aromatic ring in one 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 monomer (m2) containing a plurality of aromatic rings.

[0089] As the aromatic ring-containing monomer (m1), from the viewpoint of being able to more effectively exhibit the effects of the present invention, among those described above, specifically, m-phenoxybenzyl acrylate, 1-naphthylmethyl acrylate, ethoxylated o-phenylphenol acrylate, benzyl acrylate, phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, 6-acryloyloxymethyldinaphthothiophene, 6-methacryloyloxymethyldinaphthothiophene, 5-acryloyloxyethyldinaphthothiophene, 6-acryloyloxyethyldinaphthothiophene, 6-vinyldinaphthothiophene, 5-vinyldinaphthothiophene are preferably mentioned.

[0090] The monomer component may contain a monomer copolymerizable with the aromatic ring-containing monomer (m1) (hereinafter sometimes referred to as "copolymerizable monomer (m4)"). The copolymerizable monomer (m4) may be only one kind or two or more kinds. 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 of 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 methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, amyl group, hexyl group, cyclohexyl group, heptyl group, 2-ethylhexyl group, isooctyl group, nonyl group, decyl group, isodecyl group, dodecyl group, isomyristyl group, lauryl group, tridecyl group, pentadecyl group, hexadecyl group, heptadecyl group, and octadecyl group. The alkyl (meth) acrylate may be only one kind or two or more kinds. From the viewpoint of more effectively expressing the effects of the present invention, butyl acrylate is preferably mentioned as the alkyl (meth) acrylate.

[0092] The content ratio of the 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, 13% by weight or less. The lower limit value of the content ratio of the 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. Also, the monomer component may not contain the alkyl (meth) acrylate.

[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 ratio 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 value of the content ratio 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, 2.5% by weight or less. Further, the monomer component may not contain a hydroxyl group-containing monomer.

[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 ratio 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 value of the content ratio 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. Further, 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 also contains 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; N-vinyl group-containing lactam-based monomers such as N-vinylpyrrolidone and N-vinyl-ε-caprolactam.

[0098] The content ratio 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 value of the content ratio 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. Further, the monomer component may not contain an amide group-containing monomer.

[0099] As the copolymerizable monomer (m4), in addition to the above, as other copolymerizable monomers, for example, 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; phosphoric acid group-containing monomers such as 2-hydroxyethylacryloyl phosphate; alkylaminoalkyl (meth)acrylates such as aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and t-butylaminoethyl (meth)acrylate; alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; succinimide-based monomers such as N-(meth)acryloyloxymethylene succinimide, N-(meth)acryloyl-6-oxyhexamethylene succinimide, and N-(meth)acryloyl-8-oxyoctamethylene succinimide; maleimide-based monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; itaconimide-based monomers such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, and N-laurylitaconimide; vinyl-based monomers such as vinyl acetate and vinyl propionate; cyanoacrylate-based monomers such as acrylonitrile and methacrylonitrile; epoxy group-containing (meth)acrylates such as glycidyl (meth)acrylate; glycol-based (meth)acrylates such as carbitol (meth)acrylate, ethyl carbitol (meth)acrylate, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, and methoxypolypropylene glycol (meth)acrylate; (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, fluorine (meth)acrylate, and silicone (meth)acrylate;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, 10-acryloyloxydecyltriethoxysilane, etc.; may be mentioned.

[0100] The content ratio of other copolymer monomers in the monomer component may be, for example, 5% by weight or less, 3% by weight or less, or 1% by weight or less. Also, other copolymer monomers may not be contained in the monomer component.

[0101] The acrylic polymer can be the base polymer in the acrylic adhesive composition. The acrylic polymer can be formed by various known polymerization methods such as solution polymerization, radiation polymerization using electron beams or ultraviolet rays (UV), 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, etc.

[0102] As the polymerization solvent for solution polymerization, for example, known polymerization solvents such as ethyl acetate and toluene can be used. Solution polymerization can be carried out, for example, by using a polymerization initiator and under an inert gas stream such as nitrogen. The polymerization conditions can adopt any appropriate conditions as long as the effects of the present invention are not impaired. Such polymerization conditions are, for example, a polymerization temperature of 50°C to 70°C and a polymerization time of 5 hours to 30 hours.

[0103] As the polymerization initiator, chain transfer agent, and emulsifier that can be used for radical polymerization, any appropriate compound can be adopted as long as the effects of the present invention are not impaired.

[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'-dimethylenebisobutylamidine), 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate (e.g., VA-057 manufactured by Wako Pure Chemical Industries, Ltd.); persulfates such as potassium persulfate and ammonium persulfate; peroxide initiators such as di(2-ethylhexyl) peroxydicarbonate, di(4-t-butylcyclohexyl) peroxydicarbonate, di-sec-butyl peroxydicarbonate, t-butyl peroxyneodecanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, di(4-methylbenzoyl) peroxide, dibenzoyl peroxide, t-butyl peroxyisobutyrate, 1,1-di(t-hexylperoxy) cyclohexane, t-butyl hydroperoxide, and hydrogen peroxide; redox initiators obtained by combining a peroxide and a reducing agent such as a combination of a persulfate and sodium bisulfite and a combination of a peroxide and sodium ascorbate. The polymerization initiator may be only one kind or two or more kinds. The amount of the polymerization initiator used can be any appropriate amount as long as the effects of the present invention are not impaired. Such an amount is, for example, 0.005 parts by weight to 1 part by weight, or may be 0.02 parts by weight to 0.5 parts by weight, in total, based on 100 parts by weight of the monomer component.

[0105] Examples of the chain transfer agent include lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimercapto-1-propanol. The chain transfer agent may be only one kind or two or more kinds. The amount of the chain transfer agent used can be any appropriate amount as long as the effects of the present invention are not impaired. Such an amount is, for example, 0.1 part by weight or less in total with respect to 100 parts by weight of the monomer component.

[0106] In radiation polymerization, polymerization is advanced by irradiating radiation such as an electron beam or ultraviolet rays (UV) to a monomer to form a base polymer. When radiation polymerization is carried out with an electron beam, the use of a photoinitiator is not particularly necessary. When radiation polymerization is carried out with UV, a photoinitiator may be used because of advantages such as shortening the polymerization time. The photoinitiator may be only one kind or two or more kinds.

[0107] Examples of the photoinitiator include benzoin ether-based photoinitiators, acetophenone-based photoinitiators, α-ketol-based photoinitiators, photoactive oxime-based photoinitiators, benzoin-based photoinitiators, benzyl-based photoinitiators, benzophenone-based photoinitiators, ketal-based photoinitiators, and thioxanthone-based photoinitiators. The amount of the photoinitiator used can be any appropriate amount as long as the effects of the present invention are not impaired. Such an amount is, for example, 0.05 to 1.5 parts by weight, and may be 0.1 to 1 part by weight, with respect to 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 ratio 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 still more preferably 90% by weight or more in terms of solid content.

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

[0111] Examples of the crosslinking agent that the acrylic pressure-sensitive adhesive composition may contain include isocyanate-based crosslinking agents, peroxide-based crosslinking agents, epoxy-based crosslinking agents, imine-based crosslinking agents, and polyfunctional metal chelates. As the crosslinking agent that the acrylic pressure-sensitive adhesive composition may contain, at least one selected from the group consisting of isocyanate-based crosslinking agents, epoxy-based crosslinking agents, and peroxide-based crosslinking agents is preferable, at least one selected from the group consisting of isocyanate-based crosslinking agents and peroxide-based crosslinking agents is more preferable, and an isocyanate-based crosslinking agent is still more preferable.

[0112] As for the individual types of crosslinking agents that can be selected as the crosslinking agent (for example, isocyanate crosslinking agents), there may be only one kind or two or more kinds.

[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 the aromatic isocyanate compound include phenylenediisocyanate, 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 the alicyclic isocyanate compound 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 multimers (dimers, trimers, pentamers, etc.) of the above isocyanate compounds, adducts obtained by adding to polyhydric alcohols such as trimethylolpropane, urea-modified products, biuret-modified products, allophanate-modified products, isocyanurate-modified products, carbodiimide-modified products, urethane prepolymers obtained by adding 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 perspective of reactivity, the TDI-based crosslinking agent is more suitable than xylylene diisocyanate and its derivatives, in other words, the xylylene diisocyanate-based (XDI-based) crosslinking agent. The isocyanate-based crosslinking agent may contain, as a TDI-based crosslinking agent, an adduct of a polyhydric alcohol and tolylene diisocyanate. A specific example of the adduct is a trimethylolpropane / tolylene diisocyanate trimer adduct.

[0119] Commercially available products may be adopted as the isocyanate-based crosslinking agent. Such commercially available products include, for example, Millionate MT, Millionate MTL, Millionate MR-200, Millionate MR-400, Coronate L, Coronate HL, 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, Takenate 600 (all manufactured by Mitsui Chemicals, Inc.). Among these, Takenate D-101E and Takenate D110N are preferred.

[0120] The blending amount of the isocyanate - based cross - linking agent in the acrylic - based pressure - sensitive adhesive composition is, for example, 0.01 to 20 parts by weight with respect to 100 parts by weight of the acrylic - based polymer. The lower limit of the blending 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 blending 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. Representative blending amounts may be 0.03 to 1 part by weight or 0.05 to 0.5 part by weight.

[0121] The blending amount of cross - linking agents other than the isocyanate - based cross - linking agent (for example, peroxide - based cross - linking agents) in the acrylic - based pressure - sensitive adhesive composition is, for example, 2 parts by weight or less with respect to 100 parts by weight of the base polymer, and may be 1 part by weight or less or 0.5 part by weight or less. The lower limit of the blending amount is, for example, 0.1 parts by weight or more, and may be 0.2 parts by weight or more or 0.3 parts by weight or more. Representative blending amounts may be 0.1 to 1 part by weight or 0.3 to 0.5 part by weight. The acrylic - based pressure - sensitive adhesive composition may not contain cross - linking agents other than the isocyanate - based cross - linking agent.

[0122] The acrylic pressure-sensitive adhesive composition may further contain known additives. As the additives, any appropriate additives can be employed as long as the effects of the present invention are not impaired. Examples of such additives include silane coupling agents, solvents, colorants, pigments, powders, dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners, antioxidants, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, inorganic fillers, organic fillers, metal powders, particles, and foils. Also, within a controllable range, a redox system with a reducing agent added may be used. The blending amount of the additives can be any appropriate blending amount as long as the effects of the present invention are not impaired. Such blending amounts are, for example, a total of, for example, 10 parts by weight or less, 5 parts by weight or less, or even 1 part by weight or less with respect to 100 parts by weight of the acrylic polymer.

[0123] <<2. Polarization Film - Attached Optical Laminate>> The polarization film - attached optical laminate according to an embodiment of the present invention includes a polarization film on the side of the first liquid crystal alignment and solidification layer when viewed from the pressure - sensitive adhesive sheet included in the optical laminate of the embodiment of the present invention.

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

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

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

[0127] <2-1-a. Polarizer> The polarizer is typically composed of a film made of a polyvinyl alcohol (PVA)-based resin containing a dichroic substance (e.g., iodine). Examples of the PVA-based resin include polyvinyl alcohol, partially formalized polyvinyl alcohol, ethylene-vinyl alcohol copolymer, and ethylene-vinyl acetate copolymer-based partial saponified product.

[0128] The PVA-based resin preferably includes an acetacetyl-modified PVA-based resin. When the total amount of the PVA-based resin is 100% by weight, the blending amount of the acetacetyl-modified PVA-based resin is preferably 5% to 20% by weight, more preferably 8% to 12% by weight.

[0129] The polarizer preferably contains an iodide or sodium chloride (sometimes collectively referred to as a halide). Examples of the iodide 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, based on 100 parts by weight of the PVA-based resin. The halide can be incorporated into the coating solution for forming the PVA-based resin layer, which is a precursor of the polarizer, in the manufacturing method described below, and can ultimately be introduced into the polarizer. By introducing the halide into the polarizer, the orientation of PVA molecules in the polarizer can be enhanced, so that a polarizer having excellent optical properties (typically, the coexistence of a high degree of polarization and a high single transmittance) can be realized.

[0130] The polarizer preferably exhibits absorption dichroism at any wavelength in the range of 380 nm to 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 the liquid crystal alignment curing layer, significant thinning of the optical laminate becomes possible.

[0132] The polarizer can be produced by any suitable 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 the polarizer composed of a single-layer resin film include hydrophilic polymer films such as PVA-based films, partially formalized PVA-based films, and ethylene-vinyl acetate copolymer-based partially saponified films, which are subjected to dyeing treatment with dichroic substances such as iodine and dichroic dyes and stretching treatment, and polyene-based alignment films such as dehydrated products of PVA and dehydrochlorinated products of polyvinyl chloride. Preferably, a polarizer obtained by dyeing a PVA-based film with iodine and uniaxially stretching it is used because of its excellent optical properties.

[0134] The above-mentioned iodine staining is performed, for example, by immersing a PVA-based film in an aqueous iodine solution. The draw ratio of the above-mentioned uniaxial drawing is preferably 3 to 7 times. The drawing may be performed after the dyeing treatment, or may be performed while dyeing. Also, dyeing may be performed after drawing. If necessary, the PVA-based film is subjected to a swelling treatment, a crosslinking treatment, a washing treatment, a drying treatment, etc. For example, by immersing the PVA-based film in water and washing it before dyeing, not only can the dirt on the surface of the PVA-based film and the blocking inhibitor be washed, but also the PVA-based film can be swollen to prevent uneven dyeing and the like.

[0135] Specific examples of the polarizer of the laminate 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 formed by coating on the resin substrate. The polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer formed by coating on the resin substrate can be produced, for example, by coating a PVA-based resin solution on 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 stretching and dyeing the laminate to make the PVA-based resin layer a polarizer. Preferably, a PVA-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 includes immersing the polarizer of the laminate in an aqueous boric acid solution and stretching it. Further, the stretching may further include, if necessary, air stretching the laminate at a high temperature (for example, 95°C or higher) before stretching in the aqueous boric acid solution. Preferably, the laminate is subjected to a drying shrinkage treatment in which it is heated while being conveyed in the longitudinal direction to shrink by 2% or more in the width direction. Typically, it includes subjecting the laminate to an air-assisted stretching treatment, a dyeing treatment, a stretching treatment in water, and a drying shrinkage treatment in this order. By introducing the assisted stretching, even when PVA is applied onto the thermoplastic resin, it becomes possible to enhance the crystallinity of PVA and achieve high optical properties. Also, by enhancing the orientation of PVA in advance at the same time, problems such as a decrease in the orientation of PVA or dissolution when immersed in water in the subsequent dyeing process or stretching process can be prevented, and high optical properties can be achieved. Further, when the PVA-based resin layer is immersed in a liquid, compared with the case where the PVA-based resin layer does not contain a halide, the disorder of the orientation of polyvinyl alcohol molecules and the decrease in the orientation can be suppressed. Thereby, the optical properties of the polarizer obtained through a treatment process such as a dyeing treatment and a stretching treatment in water, which are performed by immersing the laminate in a liquid, can be improved. Further, by shrinking the laminate in the width direction by the drying shrinkage treatment, the optical properties can be improved. The obtained laminate of the resin substrate / polarizer may be used as it is (that is, the resin substrate may be used as a protective layer for the polarizer), or an arbitrary appropriate protective layer according to the purpose may be laminated on the peeling surface obtained by peeling the resin substrate from the laminate of the resin substrate / polarizer, or on the surface opposite to the peeling surface and used. Details of such a method for manufacturing a polarizer are described, for example, in JP-A-2012-73580 and Japanese Patent No. 6470455. The entire descriptions 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 suitable resin film. Representative materials for such resin films include cellulose resins such as triacetyl cellulose (TAC), cycloolefin resins such as polynorbornene, (meth)acrylic resins, polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyolefin resins such as polyethylene, and polycarbonate resins. Representative examples of (meth)acrylic resins include (meth)acrylic resins having a lactone ring structure. (Meth)acrylic resins having a lactone ring structure are described, for example, in JP-A-2000-230016, JP-A-2001-151814, JP-A-2002-120326, JP-A-2002-254544, and JP-A-2005-146084. These publications are incorporated herein by reference. From the viewpoint of ease of profiling and the like, cellulose resins are preferred, and TAC is more preferred. From the viewpoint of obtaining a polarizing plate with low moisture permeability and excellent durability, cycloolefin resins and (meth)acrylic resins are preferred.

[0138] The protective layer may be surface-treated as necessary. Examples of surface treatment include hard coat treatment, antireflection treatment, anti-sticking treatment, and antiglare treatment. The protective layer may be treated as necessary to improve visibility when viewed through polarized sunglasses (typically, by imparting an (elliptical) polarization function or a very high retardation). By performing such treatment, excellent visibility can be achieved even when viewing a display screen through a polarizing lens 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 retardation in the thickness direction Rth(550) may be -10 nm to +10 nm.

[0140] The thickness of the protective layer is preferably 10 μm to 80 μm, more preferably 12 μm to 40 μm, and still more preferably 15 μm to 35 μm, respectively. When the protective layer is surface-treated, the thickness of the protective layer is the thickness including the thickness of the surface treatment layer.

[0141] <2-2. Adhesive layer> In the optical laminate with a polarizing film according to one embodiment of the present invention, as the adhesive layer that can be provided between the polarizing film and the optical laminate, any appropriate adhesive layer can be adopted as long as the effects of the present invention are not impaired. Such an adhesive layer is usually adhered through an ultraviolet curable adhesive or an aqueous adhesive, etc. Examples of the aqueous adhesive include isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl-based latexes, aqueous polyurethanes, and aqueous polyesters. In addition to the above, electron beam curable adhesives and the like can also be mentioned as the adhesive layer. The adhesive layer may contain a metal compound filler.

[0142] ≪≪3. Other embodiments including the optical laminate≫≫ In the optical laminate according to the embodiment of the present invention or the optical laminate with a polarizing film according to the embodiment of the present invention, an adhesive layer can be provided on the surface of the second liquid crystal alignment and curing layer on the side opposite to the adhesive sheet.

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

[0144] As the adhesive layer, any appropriate adhesive layer can be adopted as long as the effects of the present invention are not impaired. As such an adhesive layer, for example, an adhesive layer made of a known adhesive that can be used for bonding optical members can be adopted. As such an adhesive layer, preferably, an adhesive layer composed of a known acrylic adhesive can be mentioned.

[0145] A release liner may be provided on the surface of the adhesive layer. Examples of the release liner include films, papers, woven fabrics, non-woven fabrics, porous materials, nets, foams, foils, or laminates thereof made of resins, papers, fibers, metals, or composite materials thereof. Examples of the resin include, for example, polyethylene, polypropylene, polybutene, polybutadiene, polymethylpentene, polyvinyl chloride, vinyl chloride copolymer, polyethylene terephthalate, polybutylene terephthalate, polyurethane, and ethylene-vinyl acetate copolymer.

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

[0147] ≪≪4. Image display device≫≫ The image display device according to an embodiment of the present invention includes the optical laminate according to an embodiment of the present invention.

[0148] Typical examples of the image display device include a liquid crystal display device and an organic EL display device. The image display device according to an embodiment of the present invention typically includes the optical laminate according to an embodiment of the present invention on its viewing side.

[0149] ≪≪5. Adhesive sheet≫≫ Among the pressure-sensitive adhesive sheets described in the previous section of "<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 exceeding 0.010 MPa, when used in an optical laminate, has a very high effect of suppressing the occurrence of linear unevenness and a very high effect of reducing dents due to local loads, 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 exceeding 0.010 MPa.

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

[0151] Regarding the thickness of the pressure-sensitive adhesive sheet according to an embodiment of the present invention, the description in the previous section of "<1. Optical laminate>" can be incorporated by reference.

[0152] The average refractive index n of the pressure-sensitive adhesive sheet according to an embodiment of the present invention is typically 1.50 or more, preferably 1.52 or more, more preferably 1.54 or more, still 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 of the pressure-sensitive adhesive sheet at 25°C according to the embodiment of the present invention is typically more than 0.010 MPa, preferably more than 0.010 MPa and less than 0.157 MPa, more preferably 0.020 MPa to 0.130 MPa, still 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. In particular, dents caused by local loads can be effectively reduced. If the indentation hardness is too small, the pressure-sensitive adhesive sheet becomes too soft, and there is a risk of dents due to local loads. On the other hand, if the indentation hardness is too large, the pressure-sensitive adhesive sheet becomes too hard, and the adhesion between the pressure-sensitive adhesive sheet and an optical member (e.g., a liquid crystal alignment cured layer) adjacent thereto may decrease.

[0154] Note that, as a method for measuring the indentation hardness, a method that can appropriately measure the indentation hardness for the pressure-sensitive adhesive sheet according to the embodiment of the present invention may be adopted. Such a measurement method may be, for example, the measurement method in the examples, that is, a method using a laminate having a structure of a polarizing film / adhesive / first liquid crystal alignment cured layer / pressure-sensitive adhesive sheet / second liquid crystal alignment cured layer / pressure-sensitive adhesive sheet / release liner as an evaluation sample, or alternatively, a method using a laminate having a structure of a pressure-sensitive adhesive sheet / release liner as an evaluation sample.

[0155] The measurement method in the above-described example of indentation hardness is, as will be described later, using a laminate having a structure of a polarizing film / adhesive / first liquid crystal alignment cured layer / adhesive sheet / second liquid crystal alignment cured layer / adhesive sheet / release liner obtained in the examples and comparative examples as an evaluation sample, cutting it into 3 mm × 5 mm, and fixing a cross-section prepared with an ultramicrotome (manufactured by Leica, device name: Leica EM UC7) under freezing conditions of -60°C to a predetermined support (a brass block of about 10 mm × 8 mm × 6 mm), and then using a nanoindentation (Triboindenter manufactured by Hysitron Inc.) under an atmosphere of 25°C, using a Berkovich (triangular pyramid) indenter to measure the indentation hardness when the adhesive sheet surface is indented up to 1000 nm.

[0156] The adhesive sheet according to an embodiment of the present invention typically consists of an adhesive. Examples of such adhesives include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. In terms of more effectively expressing the effects of the present invention, the adhesive sheet is preferably composed of an acrylic adhesive, and the acrylic adhesive is formed from an acrylic adhesive composition containing an acrylic polymer obtained by polymerizing monomer components. Such a main polymer component contained in the adhesive composition as the acrylic polymer may be referred to as a base polymer. The content ratio of the base polymer contained in the adhesive composition is, for example, 50% by weight or more, and may be 60% by weight or more, 70% by weight or more, 80% by weight or more, or 90% by weight or more. The upper limit of the content ratio of the base polymer contained in the adhesive composition may be, for example, 99.9% by weight or less, 99% by weight or less, or 95% by weight or less.

[0157] The adhesive sheet according to an embodiment of the present invention can be formed by any suitable method as long as the effects of the present invention are not impaired. As such a forming method, the description in the previous section of <<1-2. Adhesive sheet>> can be cited.

[0158] A typical embodiment of the pressure-sensitive adhesive sheet according to an embodiment of the present invention is a pressure-sensitive adhesive sheet composed of a pressure-sensitive adhesive formed from a pressure-sensitive adhesive composition containing an acrylic polymer. For such an acrylic polymer and acrylic pressure-sensitive adhesive composition, reference can be made to the descriptions in the previous section <1-2-a. Acrylic polymer> and the previous section <1-2-b. Acrylic pressure-sensitive adhesive composition>.

[0159] A release liner may be provided on the surface of the pressure-sensitive adhesive sheet. Examples of the release liner include films, papers, woven fabrics, non-woven fabrics, porous materials, nets, foams, foils, or laminates thereof composed of resins, papers, fibers, metals, or composite materials thereof. Examples of resins include, for example, polyethylene, polypropylene, polybutene, polybutadiene, polymethylpentene, polyvinyl chloride, vinyl chloride copolymer, polyethylene terephthalate, polybutylene terephthalate, polyurethane, and ethylene-vinyl acetate copolymer.

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

Examples

[0161] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. The test and evaluation methods in the examples and the like are as follows. In addition, when "parts" are described, it means "parts by weight" unless otherwise specified, and when "%" is described, it means "% by weight" unless otherwise specified.

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

[0163] <Measurement of Refractive Index> 〔Refractive Index of Pressure-Sensitive Adhesive Sheet〕 The refractive index of the adhesive sheet was measured using an Abbe refractometer (manufactured by ATAGO, product name "DR-M2 / 1550") at a wavelength of 589 nm and a temperature of 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 Axoscan (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 equation of the ellipse (x2 / a2)+(y2 / b2)=1, a is nx, b is ny, and x and y are the refractive indices in the x and y directions at the angle θ on the ellipse. The refractive index in the transmission axis direction was calculated by solving the simultaneous equations using y=tan θ and the above nx and ny.

[0164] <Measurement of indentation hardness> The laminate obtained in the examples and comparative examples, having a structure of polarizing film / adhesive / first liquid crystal alignment solidified layer / adhesive sheet / release liner, was peeled off from the release liner to prepare an evaluation sample. It was 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. The cross-section was then fixed to a specified support (a block with a brass base measuring approximately 10 mm x 8 mm x 6 mm). In an atmosphere of 25° C., a microindentation hardness tester (Triboindenter manufactured by Hysitron Inc.) was used to measure the indentation hardness when the adhesive sheet surface was indented to a depth of 1000 nm using a Berkovich (triangular pyramid) indenter.

[0165] <Tgの測定> An adhesive sheet was laminated to a thickness of about 1 mm and used as a measurement sample. Using ARES-G2 (manufactured by TA Instruments), dynamic viscoelasticity measurement was performed under the following conditions, and the temperature at which the loss tangent (tanδ) reaches its maximum (peak top temperature) was defined as the glass transition temperature (Tg) of the adhesive sheet. (Measurement conditions) Deformation mode: torsion Measurement frequency: 1 Hz Temperature rising rate: 5°C / min Shape: parallel plate, 8 mmφ

[0166] <Evaluation of linear unevenness> On the second liquid crystal alignment curing layer side of the optical laminate obtained in the examples and comparative examples, the acrylic adhesive manufactured in Production Example 12 was placed, and it was bonded to a V3 reflector (manufactured by NEODIS) through the acrylic adhesive to obtain 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 unevenness was observed. ○: Slight linear unevenness was observed. △: Linear unevenness was observed, but it was acceptable for practical use. ×: Linear unevenness was significant.

[0167] <Measurement of pressing load> A laminate having the configuration of a polarizing film / adhesive / first liquid crystal alignment curing layer / adhesive sheet / second liquid crystal alignment curing layer / adhesive sheet / release liner obtained in the examples and comparative examples was used as an evaluation sample, cut into a 1 cm square, and a sample with the outermost adhesive layer fixed to a predetermined support (slide glass manufactured by Matsunami Glass Industry Co., Ltd.) was used as a measurement sample. In a 25°C atmosphere, using a micro-indentation hardness tester (nano-indentation) (ENT-NEXUS manufactured by ELIONIX) and using a Berkovich (triangular pyramid) indenter, the pressing load when pressing from the outermost surface side on the polarizing film side to 40 μm was measured.

[0168] <Evaluation of dent due to local load> The laminate having the structure of polarizing film / adhesive / first liquid crystal alignment cured layer / adhesive sheet / second liquid crystal alignment cured layer / adhesive sheet / release liner obtained in the examples and comparative examples was cut into pieces of 1 cm in length and 1 cm in width to prepare samples. The release liner was peeled off, and the exposed adhesive sheet was bonded to an aluminum reflector (manufactured by Toray Film Processing Co., Ltd., product name: Serapiel DMS-X42, total light reflectance: 86%). Next, a glass plate (manufactured by Matsunami Glass Industry Co., Ltd., thickness = 0.7 mm) was placed so that the surface of the sample on the polarizing film side was in contact with the glass plate. Then, a weight was placed on a conical indenter (diameter 1.5 mm, height 0.8 mm) through a PET sheet (manufactured by Toray Industries, Inc., thickness = 80 μm) from the aluminum reflector side, and it was pushed in for 30 seconds. The measurement was carried out with the weight of the weight (load) being 400 g (2.2 MPa). After that, except for the weight and the indenter, the surface of the sample that had been in contact with the glass plate was visually observed for reflection at a polar angle of 30° to 60° and one full azimuth angle rotation to check for the presence or absence of indentations. When the surface of the sample was defined as the X-axis and the Y-axis, and the axis perpendicular to the XY plane was defined as the Z-axis, the angle inclined from the Z-axis in the XY plane direction was defined as the polar angle (θ), the MD direction of the polarizing film was set to 0°, and the measurement angle defined in the counterclockwise direction from the MD direction of this polarizing film was defined as the azimuth angle (φ) for evaluation. Note that the visibility of the dent does not depend only on the actual amount of the dent, and the larger the refractive index difference between the liquid crystal alignment cured layer and the adhesive layer, the easier it can be visually recognized. The dent evaluation was performed according to the following criteria. ◎: No visible dent was present. 〇: A slight dent was visible, but it was at a level that did not cause problems in actual use. △: A dent was visible, but it was at a level that did not cause problems in actual use. ×: A significant dent (scratch) was visible, and it was at a level that caused problems in actual use.

[0169] <Evaluation of Adhesion> The side of the optical laminate with a polarizing film obtained in the examples and comparative examples was bonded to a polyethylene terephthalate (PET) film (manufactured by Toray Industries, Inc., trade name: Lumirror, thickness = 125 μm). An adhesive (manufactured by Monotaro, trade name: Mottokutsuketarou) was used for the bonding. The bonding was carried out using a pressure roller with a mass of 2 kg defined in JIS Z0237:2009 under a temperature atmosphere of 25°C, and bubbles were prevented from being included between the second liquid crystal alignment cured layer and the PET film during the bonding. After leaving it to stand for 2 days from the bonding, it was cut into a shape of 25 mm × 150 mm and bonded to the surface of a stainless steel (SUS) plate, which is a test plate, using an adhesive sheet (manufactured by Nitto Denko Corporation, trade name: No. 500). The bonding was carried out using a pressure roller with a mass of 2 kg defined in JIS Z0237:2009 under a temperature atmosphere of 25°C. Next, under a temperature atmosphere of 25 ± 5°C, using a tensile tester (manufactured by Shimadzu Corporation, trade name: Autograph AG-X), the laminated portion of the polarizing film / adhesive / first liquid crystal alignment cured layer / adhesive sheet (laminated portion P) was attempted to be peeled off from the laminated portion of the second liquid crystal alignment cured layer / adhesive / PET film / adhesive sheet / SUS plate (laminated portion Q) in the long side direction at a peeling angle of 90° and a peeling speed of 300 mm / min. Evaluation was carried out according to the following criteria. 〇: When peeling, the first liquid crystal alignment cured layer and the second liquid crystal alignment cured layer are sufficiently adhered. △: When peeling, although the peeling is slightly easy, it is at a level where there is no problem in actual use. ×: When peeling, it easily peels off, and the adhesive strength is insufficient.

[0170] [Production Example 1] Preparation of the first liquid crystal alignment cured layer A photopolymerizable liquid crystal compound showing a nematic liquid crystal phase (BASF's "Paliocolor LC242", the following chemical formula) was dissolved in cyclopentanone to prepare a solution with a solid content concentration of 30% by weight. To this solution, a surfactant (BYK-360 manufactured by BYK Chemie) and a photopolymerization initiator (Omnirad907 manufactured by IGM Resins) were added to prepare a liquid crystal composition solution. The addition amounts of the surfactant and the polymerization initiator were 0.01 part by weight and 3 parts by weight, respectively, based on 100 parts by weight of the photopolymerizable liquid crystal compound. As the substrate, a biaxially stretched norbornene-based film (Zeonoa Film manufactured by Nippon Zeon, thickness 33 μm, Re(550) = 135 nm) was prepared. The above liquid crystal composition was coated on this substrate with a bar coater so that Re(550) became 240 nm, and heated at 100 °C for 3 minutes to align the liquid crystal. After cooling to room temperature, ultraviolet rays with an integrated light amount of 400 mJ / cm2 were irradiated in a nitrogen atmosphere to perform photocuring, and a laminate having a structure of substrate / First liquid crystal alignment cured layer was obtained. The first liquid crystal alignment cured layer was homogeneously aligned, its thickness was 1.7 μm, and its average refractive index was 1.590.

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

[0172] [Production Example 3]: Preparation of a polarizer As the thermoplastic resin substrate, an amorphous isophthal copolymer polyethylene terephthalate film (thickness: 100 μm), which is long and has a Tg of about 75°C, was used, and one side of the resin substrate was subjected to corona treatment. 13 parts by weight of potassium iodide was added to 100 parts by weight of a PVA-based resin obtained by mixing polyvinyl alcohol (degree of polymerization 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosefimer") at a ratio of 9:1, and the mixture was dissolved in water to prepare a PVA aqueous solution (coating solution). The PVA aqueous solution was applied to the corona-treated surface of the resin substrate and dried at 60°C to form a PVA-based resin layer with a thickness of 13 μm, thereby producing a laminate. The obtained laminate was uniaxially stretched 2.4 times in the longitudinal direction (length direction) in an oven at 130°C (air-assisted stretching treatment). Next, the laminate was immersed in an insolubilization bath with a liquid temperature of 40°C (an aqueous boric acid solution obtained by mixing 4 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds (insolubilization treatment). Next, the laminate was immersed in a dyeing bath with a liquid temperature of 30°C (an aqueous iodine solution obtained by mixing iodine and potassium iodide at a weight ratio of 1:7 with respect to 100 parts by weight of water) for 60 seconds while adjusting the concentration so that the single transmittance (Ts) of the finally obtained polarizer becomes a desired value (dyeing treatment). Next, the laminate was immersed in a crosslinking bath with a liquid temperature of 40°C (an aqueous boric acid solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds (crosslinking treatment). Thereafter, while the laminate was immersed in an aqueous boric acid solution with a liquid temperature of 70°C (boric acid concentration 4 wt%, potassium iodide concentration 5 wt%), uniaxial stretching was performed in the longitudinal direction (length direction) between rolls with different peripheral speeds so that the total stretching ratio became 5.5 times (stretching treatment in water). Thereafter, the laminate was immersed in a washing bath with a liquid temperature of 20°C (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) (washing treatment). Thereafter, while drying in an oven maintained at about 90°C, it was brought into contact with a SUS heating roll whose surface temperature was maintained at about 75°C (dry shrinkage treatment). In this way, a polarizer with a thickness of about 5 μm was formed on the resin substrate, and a laminate having a resin substrate / polarizer structure was obtained. The single transmittance Ts of the polarizer was 43.3%.

[0173] [Production Example 4]: Production of Polarizing Film An HC-COP film was laminated on the surface of the polarizer obtained in Production Example 3 (the surface opposite to the resin base material) via an ultraviolet-curable adhesive. The HC-COP film is a film in which an HC layer (thickness 4 μm) is formed on a cycloolefin-based resin (COP) film (thickness 25 μm), and it was laminated such that the COP film was on the polarizer side. The Re(550) of the COP film was 135 nm. Next, the resin base material was peeled off, and a triacetyl cellulose (TAC) film (thickness 25 μm) was laminated on the peeled surface via an ultraviolet-curable adhesive. In this way, a polarizing 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 a polarizing film and a first liquid crystal alignment cured layer 10 parts by weight of hydroxyethyl acrylamide (trade name "HEAA", manufactured by KJ Chemicals), 4 parts by weight of 2-acetoacetoxyethyl methacrylate (trade name "AAEM", manufactured by Mitsubishi Chemicals), 60 parts by weight of acryloylmorpholine (trade name "ACMO", manufactured by KJ Chemicals), 11 parts by weight of tripropylene glycol diacrylate (trade name "Aronix M-220", manufactured by Toagosei Co., Ltd.), 1 part of 4-vinylphenylboronic acid (manufactured by Fujifilm Wako Pure Chemical Corporation), 10 parts by weight of an acrylic oligomer (trade name "ARUFON UP-1190", manufactured by Toagosei Co., Ltd.), 1 part by weight of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (trade name "Omnirad819", manufactured by IGM Resins B.V.), 2 parts by weight of 1-hydroxycyclohexyl phenyl ketone (trade name "Omnirad184", manufactured by IGM Resins B.V.), and 1 part by weight of diethylthioxanthone (trade name "KAYACURE DETX-S", manufactured by Nippon Kayaku Co., Ltd.) were stirred at 50 °C for 1 hour to prepare an adhesive.

[0175] [Production Example 6]: Acrylic polymer (1) and acrylic pressure-sensitive adhesive composition (1) Into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler, 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. To 100 parts by weight of this monomer mixture, 0.1 part by weight of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator was charged together with ethyl acetate, and nitrogen gas was introduced with gentle stirring for nitrogen substitution. Then, the polymerization reaction was carried out for 7 hours while maintaining the liquid temperature in the flask at around 55°C. The monomer concentration during polymerization was set to 40% by weight. Thereafter, ethyl acetate was added to the obtained reaction solution to adjust the solid content concentration to 30%, and a solution of acrylic polymer (1) was prepared. To 100 parts by weight of the solid content of acrylic polymer (1), 0.2 part by weight of an isocyanate-based crosslinking agent (trimethylolpropane / xylene diisocyanate trimer adduct, manufactured by Mitsui Chemicals, Inc., Takenate D-110N) was added, and ethyl acetate was added as a diluting solvent so that the solid content became 15%, followed by mixing and stirring 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) Instead of charging 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), 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, and the solution of acrylic polymer (3) and acrylic pressure-sensitive adhesive composition (3) were prepared in the same manner as in Production Example 6.

[0178] [Production Example 9]: Acrylic Polymer (4) and Acrylic Pressure-Sensitive Adhesive Composition (4) Instead of charging 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), 95 parts by weight of phenoxybenzyl acrylate (POB-A) and 5 parts by weight of 4-hydroxybutyl acrylate (4HBA) were charged, and the solution of acrylic polymer (4) and acrylic pressure-sensitive adhesive composition (4) were prepared in the same manner as in Production Example 6.

[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-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas introduction tube, and a cooler. To 100 parts by weight of this monomer mixture, 0.1 part by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with 100 parts by weight of ethyl acetate, and nitrogen gas was introduced while gently stirring for nitrogen substitution. Then, the liquid temperature in the flask was maintained at around 55 °C and a polymerization reaction was carried out for 8 hours to prepare a solution of acrylic polymer (5). To 100 parts by weight of the solid content of the acrylic polymer (5), 0.1 part by weight of an isocyanate crosslinking agent (trimethylolpropane / tolylene diisocyanate adduct, manufactured by Tosoh Corporation, trade name "Coronate L"), 0.3 part by weight of a peroxide crosslinking agent (benzoyl peroxide, manufactured by NOF Corporation, trade name "Niper BMT"), and 0.2 part by weight of an epoxy group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403") were blended to prepare an acrylic pressure-sensitive adhesive composition (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) Instead of charging 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), 19 parts by weight of benzyl acrylate (BzA), 0.1 part 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, and the procedure was the same as in Production Example 6 to prepare a solution of the acrylic polymer (6). To 100 parts by weight of the solid content of the acrylic polymer (6), 0.45 part by weight of an isocyanate crosslinking agent (trimethylolpropane / tolylene diisocyanate adduct, manufactured by Tosoh Corporation, trade name "Coronate L"), 0.1 part by weight of a peroxide crosslinking agent (benzoyl peroxide, manufactured by NOF Corporation, trade name "Niper BMT"), and 0.2 part by weight of an epoxy group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403") were blended to prepare an acrylic pressure-sensitive adhesive composition (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) Into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler, a monomer mixture containing 94.9 parts by weight of butyl acrylate (BA), 5 parts by weight of acrylic acid, and 0.1 part by weight of 2-hydroxyethyl acrylate (HEA) was charged. Further, 0.1 part by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with 100 parts by weight of ethyl acetate with respect to 100 parts by weight of this monomer mixture, and nitrogen gas was introduced while gently stirring for nitrogen substitution. After that, the polymerization reaction was carried out for 8 hours while maintaining the liquid temperature in the flask at around 55 °C to prepare a solution of an acrylic polymer (A) having a weight average molecular weight (Mw) of 2.2 million. With respect to 100 parts by weight of the solid content of the solution of the acrylic polymer (A), 0.6 part by weight of an isocyanate-based crosslinking agent (trimethylolpropane / toluene diisocyanate adduct: manufactured by Tosoh Corporation, trade name "Coronate L"), 0.2 part by weight of a peroxide crosslinking agent (benzoyl peroxide, manufactured by NOF Corporation, trade name "Niper BMT"), and 0.2 part by weight of an epoxy group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403") were blended to prepare an acrylic pressure-sensitive adhesive composition (A).

[0182] [Example 1] On the TAC film side of the polarizing film, after laminating the first liquid crystal alignment cured layer side of the laminate having the structure of the base material / first liquid crystal alignment cured layer obtained in Production Example 1 through the adhesive (thickness: 1 μm) obtained in Production Example 5, the base material was peeled off to obtain a laminate having a structure of polarizing film / adhesive / first liquid crystal alignment cured layer. Next, the acrylic pressure-sensitive adhesive composition (1) obtained in Production Example 6 was applied to a release liner (manufactured by Mitsubishi Chemical Corporation, MRF38-NS2) so that the thickness after drying would be 5 μm, cured and dried under the conditions of a drying temperature of 120 °C and a drying time of 90 seconds, and then laminated on the plasma-irradiated first liquid crystal alignment cured layer side of the above laminate to obtain a laminate having a structure of polarizing film / adhesive / first liquid crystal alignment cured layer / adhesive sheet (1) / release liner. After peeling off the release liner, the side of the second liquid crystal alignment cured layer of the laminate having the structure of the base material / second liquid crystal alignment cured layer obtained in Production Example 2 was corona-irradiated and bonded to the adhesive sheet (1) side of the above laminate, and then the base material was peeled off to obtain an optical laminate with a polarizing film having a structure of polarizing film / adhesive / first liquid crystal alignment cured layer / adhesive sheet (1) / second liquid crystal alignment cured layer. Separately, the acrylic pressure-sensitive adhesive composition (A) obtained in Production Example 12 was applied to a release liner (manufactured by Mitsubishi Chemical Corporation, MRF38-NS2) so that the thickness after drying would be 25 μm, and then cured and dried under the conditions of a drying temperature of 155°C and a drying time of 90 seconds to obtain a laminate of pressure-sensitive adhesive sheet (A) / release liner. Corona irradiation was performed on the surface of the second liquid crystal alignment cured layer of the optical laminate with a polarizing film having a structure of polarizing film / adhesive / first liquid crystal alignment cured layer / adhesive sheet (1) / second liquid crystal alignment cured layer, and the pressure-sensitive adhesive sheet (A) side of the laminate of pressure-sensitive adhesive sheet (A) / release liner was bonded to the corona-treated surface. Thus, an optical laminate (1) with a polarizing film having a structure of polarizing film / adhesive / first liquid crystal alignment cured layer / adhesive sheet (1) / second liquid crystal alignment cured layer / pressure-sensitive adhesive sheet (A) / release liner was obtained. In the optical laminate (1) with a polarizing film, the angle formed by the transmission axis of the polarizer of the polarizing film and the slow axis of the first liquid crystal alignment cured layer was 15°, and the angle formed by the transmission axis of the polarizer of the polarizing film and the slow axis of the second liquid crystal alignment cured layer was 75°. The average refractive index of each of the first liquid crystal alignment cured layer and the second liquid crystal alignment cured layer was 1.59, the refractive index nLC1 of the first liquid crystal alignment cured layer in the transmission axis direction of the polarizer was 1.66, and the refractive index nLC2 of the second liquid crystal alignment cured layer in the transmission axis direction of the polarizer was 1.56. The results are shown in Table 1.

[0183] [Example 2] The acrylic pressure-sensitive adhesive composition (1) obtained in Production Example 6 was applied so that the thickness after drying was 10 μm, and the procedure was the same as in Example 1, to obtain a polarizing film / adhesive / 1st liquid crystal alignment cured layer / pressure-sensitive adhesive sheet (2) / 2nd liquid crystal alignment cured layer / pressure-sensitive adhesive sheet (A) / release liner-structured optical laminate with a polarizing film (2). The results are shown in Table 1.

[0184] [Example 3] The procedure was the same 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, to obtain a polarizing film / adhesive / 1st liquid crystal alignment cured layer / pressure-sensitive adhesive sheet (3) / 2nd liquid crystal alignment cured layer / pressure-sensitive adhesive sheet (A) / release liner-structured optical laminate with a polarizing film (3). The results are shown in Table 1.

[0185] [Example 4] The procedure was the same 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, to obtain a polarizing film / adhesive / 1st liquid crystal alignment cured layer / pressure-sensitive adhesive sheet (4) / 2nd liquid crystal alignment cured layer / pressure-sensitive adhesive sheet (A) / release liner-structured optical laminate with a polarizing film (4). The results are shown in Table 1.

[0186] [Example 5] The procedure was the same 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, to obtain a polarizing film / adhesive / 1st liquid crystal alignment cured layer / pressure-sensitive adhesive sheet (5) / 2nd liquid crystal alignment cured layer / pressure-sensitive adhesive sheet (A) / release liner-structured optical laminate with a polarizing film (5). The results are shown in Table 1.

[0187] [Comparative Example 1] Instead of using the acrylic pressure-sensitive adhesive composition (1) obtained in Production Example 6, the same procedure as in Example 1 was carried out except that the acrylic pressure-sensitive adhesive composition (5) obtained in Production Example 10 was used, and a polarizing film / adhesive / first liquid crystal alignment cured layer / adhesive sheet (C1) / second liquid crystal alignment cured layer / adhesive sheet (A) / release liner-structured optical laminate with a polarizing film (C1) was obtained. The results are shown in Table 1.

[0188] [Comparative Example 2] Instead of using the acrylic pressure-sensitive adhesive composition (1) obtained in Production Example 6, the same procedure as in Example 1 was carried out except that the acrylic pressure-sensitive adhesive composition (6) obtained in Production Example 11 was used, and a polarizing film / adhesive / first liquid crystal alignment cured layer / adhesive sheet (C2) / second liquid crystal alignment cured layer / adhesive sheet (A) / release liner-structured optical laminate with a polarizing film (C2) was obtained. 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 was 20 μm, and a polarizing film / adhesive / first liquid crystal alignment cured layer / adhesive sheet (C3) / second liquid crystal alignment cured layer / adhesive sheet (A) / release liner-structured optical laminate with a polarizing film (C3) was obtained. The results are shown in Table 1.

[0190]

Table 1

Industrial Applicability

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

Explanation of Signs

[0192] 11 First liquid crystal alignment cured layer 12 Second liquid crystal alignment cured layer 20 Adhesive sheet 30 Adhesive layer 40 Polarizer 51 Protective layer 52 Protective layer 60 Adhesive layer 100 Optical laminate 200 Polarizing film 600 Laminate

Claims

1. An optical laminate including a first liquid crystal alignment cured layer, an adhesive sheet, and a second liquid crystal alignment cured layer in this order, wherein the thickness of the adhesive sheet is less than 20 μm, when the average refractive index of the adhesive sheet is n, the average refractive index of the first liquid crystal alignment cured layer is n1, and the average refractive index of the second liquid crystal alignment cured 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, an optical laminate.

2. The optical laminate according to claim 1, wherein the adhesive sheet is composed of an acrylic adhesive, and the acrylic adhesive is formed from an acrylic 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 thickness of the adhesive sheet is 4 μm or more.

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

7. The optical laminate according to claim 1, which is used with a polarizing film provided on at least one side selected from the group consisting of the first liquid crystal alignment cured layer side and the second liquid crystal alignment cured layer side when viewed from the adhesive sheet.

8. A polarizing film - attached optical laminate including a polarizing film on the first liquid crystal alignment cured layer side when viewed from the adhesive sheet of the optical laminate according to any one of claims 1 to 6.

9. A polarizing film - attached optical laminate including a polarizing film on the second liquid crystal alignment cured layer side when viewed from the adhesive sheet of the optical laminate according to any one of claims 1 to 6.

10. An image display device including 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 exceeding 0.019 MPa.

12. The adhesive sheet according to claim 11, which is composed of an acrylic adhesive, and the acrylic adhesive is formed from an acrylic 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 curing layer.

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