CN118159886A

CN118159886A - Polarizing plate with retardation layer and image display device

Info

Publication number: CN118159886A
Application number: CN202280072258.5A
Authority: CN
Inventors: 有贺草平; 柳沼宽教; 笹川泰介
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2021-10-26
Filing date: 2022-10-13
Publication date: 2024-06-07
Also published as: TW202323876A; WO2023074388A1; JP2023064220A; KR20240095215A

Abstract

The present invention provides a polarizing plate with a retardation layer having excellent durability even under severe high-temperature and high-humidity environments. The polarizing plate with a retardation layer according to an embodiment of the present invention includes: a first phase difference layer having a first main surface and a second main surface facing each other; a polarizer disposed on the first principal surface side of the first retardation layer; and a first layer disposed on the second principal surface side of the first retardation layer; the first retardation layer is formed of a stretched film of a resin film and satisfies the relationship of Re (450) < Re (550), and the first retardation layer is a resin layer having a shear fracture strength of 85MPa or more. Wherein Re (450) and Re (550) are in-plane retardation measured at 23℃with light of wavelength 450nm and light of wavelength 550nm, respectively.

Description

Polarizing plate with retardation layer and image display device

Technical Field

The present invention relates to a polarizing plate with a retardation layer and an image display device.

Background

In recent years, image display devices typified by liquid crystal display devices and Electroluminescence (EL) display devices (for example, organic EL display devices and inorganic EL display devices) have been rapidly spreading. The image display device typically uses a polarizing plate and a phase difference plate. In practical use, a polarizing plate with a retardation layer in which a polarizing plate and a retardation plate are integrated is widely used (for example, patent document 1). In recent years, as the use of image display devices has been expanding, various performances of polarizing plates with retardation layers have been demanded to be improved. For example, a polarizing plate with a retardation layer may be required to have durability under severe high-temperature and high-humidity environments, which has not been required in the past.

Prior art literature

Patent literature

Patent document 1: japanese patent No. 3325560

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made to solve the above-described conventional problems, and a main object thereof is to provide a polarizing plate with a retardation layer having excellent durability even in a severe high-temperature and high-humidity environment.

Means for solving the problems

The polarizing plate with a retardation layer according to an embodiment of the present invention includes: a first phase difference layer having a first main surface and a second main surface facing each other; a polarizer disposed on the first principal surface side of the first retardation layer; and a first layer disposed on the second principal surface side of the first retardation layer; the first retardation layer is formed of a stretched film of a resin film and satisfies the relationship of Re (450) < Re (550), and the first retardation layer is a resin layer having a shear fracture strength of 85MPa or more.

Another embodiment of the present invention provides a polarizing plate with a retardation layer, comprising: a first phase difference layer having a first main surface and a second main surface facing each other; a polarizer disposed on the first principal surface side of the first retardation layer; a first layer disposed on the second principal surface side of the first phase difference layer; and a second layer disposed on the first principal surface side of the first retardation layer; the first retardation layer is formed of a stretched film of a resin film and satisfies the relationship of Re (450) < Re (550), the first layer is a resin layer having a shear fracture strength of 60MPa or more, and the second layer is a resin layer having a shear fracture strength of 60MPa or more.

Wherein Re (450) and Re (550) are in-plane retardation measured at 23℃with light of wavelength 450nm and light of wavelength 550nm, respectively.

In one embodiment, re (550) of the first phase difference layer is 100nm to 200nm, and an angle formed between a slow axis of the first phase difference layer and an absorption axis of the polarizer is 40 DEG to 50 DEG or 130 DEG to 140 deg.

In one embodiment, the polarizing plate with a retardation layer has a second retardation layer disposed on the second main surface side of the first retardation layer, the refractive index characteristics of the second retardation layer show a relationship of nz > nx=ny, and the first layer is disposed between the first retardation layer and the second retardation layer.

In one embodiment, the first layer functions as an adhesive layer.

In one embodiment, the first retardation layer contains a resin having positive refractive index anisotropy, the resin containing at least one bonding group selected from the group consisting of a carbonate bond and an ester bond, and at least one structural unit selected from the group consisting of a structural unit represented by the following general formula (1) and a structural unit represented by the following general formula (2);

In the general formulae (1) and (2), R ¹～R³ is independently a direct bond, a substituted or unsubstituted alkylene group having 1 to 4 carbon atoms, R ⁴～R⁹ is independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted aryl group having 4 to 10 carbon atoms, a substituted or unsubstituted acyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 10 carbon atoms, a substituted or unsubstituted aryloxy group having 1 to 10 carbon atoms, a substituted or unsubstituted amino group, a substituted or unsubstituted vinyl group having 1 to 10 carbon atoms, a substituted or unsubstituted ethynyl group having 1 to 10 carbon atoms, a sulfur atom having a substituent, a silicon atom having a halogen atom, a nitro group, or a cyano group; wherein R ⁴～R⁹ may be the same or different from each other, and at least two adjacent groups in R ⁴～R⁹ may be bonded to each other to form a ring.

In one embodiment, the polarizing plate with a retardation layer has a protective layer disposed on the opposite side of the polarizer from the first retardation layer, and the shrinkage rate of the protective layer after being left for 240 hours at 85 ℃ is less than 0.05%.

In one embodiment, the protective layer is composed of a triacetyl cellulose film or a cycloolefin resin film.

According to another aspect of the present invention, there is provided an image display apparatus. The image display device includes the polarizing plate with a retardation layer.

Effects of the invention

According to the embodiment of the present invention, a polarizing plate with a retardation layer having excellent durability even in a severe high-temperature and high-humidity environment can be realized.

Drawings

Fig. 1 is a schematic cross-sectional view showing a schematic configuration of a polarizing plate with a retardation layer according to a first embodiment of the present invention.

Fig. 2 is a schematic cross-sectional view showing a schematic configuration of a polarizing plate with a retardation layer according to a second embodiment of the present invention.

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. For the sake of clarity of the description, the drawings may schematically show the width, thickness, shape, etc. of each part in comparison with the embodiments, but are always examples and do not limit the explanation of the present invention. In the drawings, the same or equivalent elements are denoted by the same reference numerals, and overlapping description thereof may be omitted.

(Definition of terms and symbols)

The definitions of terms and symbols in the present specification are as follows.

(1) Refractive index (nx, ny, nz)

"Nx" is a refractive index in a direction in which the in-plane refractive index becomes maximum (i.e., a slow axis direction), "ny" is a refractive index in a direction orthogonal to the slow axis (i.e., a fast axis direction), and "nz" is a refractive index in a thickness direction.

(2) In-plane phase difference (Re)

"Re (λ)" is the in-plane retardation of the film measured at 23℃with light of wavelength λnm. For example, "Re (450)" is the in-plane retardation of the film measured at 23℃with light having a wavelength of 450 nm. Re (λ) is represented by the formula: re (λ) = (nx-ny) ×d.

(3) Retardation in thickness direction (Rth)

"Rth (λ)" is the retardation in the thickness direction of the film measured at 23℃with light having a wavelength of λnm. For example, "Rth (450)" is the retardation in the thickness direction of the film measured at 23℃with light having a wavelength of 450 nm. Rth (λ) is represented by the formula: rth (λ) = (nx-nz) ×d.

(4) Nz coefficient

The Nz coefficient is obtained by nz=rth/Re.

(5) Angle of

In the case of referring to an angle in the present specification, the angle includes angles in both the clockwise and counterclockwise directions unless otherwise specified.

A. Polarizing plate with phase difference layer

Fig. 1 is a schematic cross-sectional view showing a schematic configuration of a polarizing plate with a retardation layer according to a first embodiment of the present invention. The polarizing plate 100 with a retardation layer includes: a first retardation layer 21 having a first main surface 21a and a second main surface 21b facing each other; a polarizing plate 10 disposed on the first main surface 21a side of the first retardation layer 21; a first layer 31 disposed on the second main surface 21b side of the first retardation layer 21; the second phase difference layer 22 and the adhesive layer 40. The polarizing plate 10 includes a polarizer 11 and a protective layer 12 in this order from the first retardation layer 21 side. The protective layer is not disposed between the polarizer 11 and the first retardation layer 21, and the first retardation layer 21 is disposed adjacent to the polarizer 11 and can function as a protective material for the polarizer 11. The polarizing plate 100 with a retardation layer is typically disposed in the image display device such that the polarizer 11 is on the visible side of the first retardation layer 21. The polarizing plate 100 with a retardation layer can be obtained by laminating the polarizing plate 10 obtained by laminating the polarizer 11 and the protective layer 12 with other layers, for example.

Fig. 2 is a schematic cross-sectional view showing a schematic configuration of a polarizing plate with a retardation layer according to a second embodiment of the present invention. The second embodiment differs from the first embodiment in that a second layer 32 is provided on the first principal surface 21a side of the first retardation layer 21. Specifically, the polarizing plate 100 with a retardation layer further has a second layer 32 disposed between the polarizing plate 10 (polarizer 11) and the first retardation layer 21.

In the illustrated example, the polarizing plate 10 includes the polarizer 11 and the protective layer 12 disposed on one side of the polarizer 11, but may further include a second protective layer disposed on the other side of the polarizer 11. In addition, although the polarizer 10 includes the polarizer 11 and the protective layer 12, the protective layer 12 may be omitted.

The first retardation layer 21 is formed of a stretched film of a resin film, and satisfies the relationship of Re (450) < Re (550). Re (550) of the first retardation layer 21 is typically 100nm to 200nm. The angle between the slow axis of the first retardation layer 21 and the absorption axis of the polarizer 11 is preferably 40 ° to 50 °, more preferably 42 ° to 48 °, still more preferably 44 ° to 46 °, and particularly preferably about 45 °; or preferably 130 ° to 140 °, more preferably 132 ° to 138 °, still more preferably 134 ° to 136 °, and particularly preferably about 135 °.

The members constituting the polarizing plate with the retardation layer may be laminated via any suitable adhesive layer (not shown). Specific examples of the adhesive layer include an adhesive layer and an adhesive layer. For example, the protective layer 12 is bonded to the polarizer 11 via an adhesive layer (preferably, an active energy ray-curable adhesive is used). The thickness of the adhesive layer is preferably 0.4 μm or more, more preferably 0.4 μm to 3.0 μm, and still more preferably 0.6 μm to 2.2 μm. For example, the first retardation layer 20 is bonded to the polarizing plate 10 (polarizer 11) via an adhesive layer (for example, an acrylic adhesive). The thickness of the adhesive layer is preferably 1 μm to 10 μm.

The polarizing plate 100 with a retardation layer can be attached to, for example, an image display panel included in an image display device by the pressure-sensitive adhesive layer 40 disposed on the second main surface 21b side of the first retardation layer 21. The thickness of the adhesive layer 40 is preferably 10 μm to 20 μm. The adhesive layer 40 is formed of, for example, an acrylic adhesive. Although not shown, in actual use, a release liner is bonded to the surface of the pressure-sensitive adhesive layer 40. The release liner may be temporarily attached until the polarizing plate with the retardation layer is provided for use. By using a release liner, for example, the adhesive layer 40 can be protected, and a roll of the polarizing plate with a retardation layer can be formed.

The first layer 31 and the second layer 32 are resin layers. Specifically, the first layer 31 and the second layer 32 may be cured layers of resins, or layers including combinations thereof. The first layer 31 and the second layer 32 are preferably disposed in direct contact with the first retardation layer 21 (formed directly on the first retardation layer 21), respectively. In one embodiment, the first layer 31 may function as an adhesive layer for fixing the first retardation layer 21 and a layer (for example, the second retardation layer 22) disposed adjacent to the first retardation layer 21. Further, the adjacent includes not only the direct adjacent but also the adjacent through the adhesive layer.

The shear fracture strength of the second layer 32 is preferably 60MPa to 200MPa, more preferably 80MPa to 120 MPa.

As shown in fig. 1, in the state where the polarizing plate 100 with a retardation layer does not have the second layer 32 (the state where the polarizing plate 10 is disposed adjacent to the first retardation layer 21), the shear fracture strength of the first layer 31 exceeds 80MPa, preferably 85MPa or more, and more preferably 90MPa or more. On the other hand, the shear fracture strength of the first layer 31 is preferably 200MPa or less.

As shown in fig. 2, in the case where the polarizing plate 100 with a retardation layer has the second layer 32, the shear fracture strength of the first layer 31 is 40MPa or more, preferably 50MPa or more, and more preferably 60MPa or more. On the other hand, the shear fracture strength of the first layer 31 is preferably 200MPa or less, and may be less than 85MPa or 80 MPa.

By providing the first layer or providing the first layer and the second layer, a polarizing plate with a retardation layer having excellent durability even in a severe high-temperature and high-humidity environment can be realized. Specifically, a polarizing plate with a retardation layer in which cracking and peeling are suppressed even in a severe high-temperature and high-humidity environment can be realized. Details are as follows. Since the first retardation layer used in the embodiment of the present invention exhibits very excellent circularly polarized light characteristics, a polarizing plate (circularly polarizing plate) with a retardation layer having a very excellent antireflection function can be realized. Further, by using such a first retardation layer in combination with a second retardation layer having refractive index characteristics of nz > nx=ny, which will be described later, it is possible to realize a wide viewing angle of the antireflection function. On the other hand, since the stretched film of the resin film constituting the first retardation layer has a large heat shrinkage and a high water absorption rate, the reliability in a high-temperature and high-humidity environment may be insufficient, and further, cracks and/or peeling may occur in a severe high-temperature and high-humidity environment which has recently become a new standard for characteristics. According to the embodiment of the present invention, by providing the first layer or providing the first layer and the second layer, durability and reliability of the entire polarizing plate with the retardation layer under a severe high-temperature and high-humidity environment can be significantly improved while maintaining excellent characteristics of the first retardation layer. As a result, a polarizing plate with a retardation layer in which cracking and peeling are suppressed even in a severe high-temperature and high-humidity environment can be realized. The above mechanism is presumed, and is not limited to or restricting the embodiment of the present invention.

The refractive index characteristics of the second phase difference layer 22, which may be included in the polarizing plate with a phase difference layer, typically exhibit a relationship of nz > nx=ny. By providing such a retardation layer, reflection in an oblique direction can be prevented well, and a wide viewing angle of an antireflection function can be achieved.

The polarizing plate with the retardation layer may have another retardation layer (not shown). The optical characteristics (for example, refractive index characteristics, in-plane retardation, nz coefficient, photoelastic coefficient), thickness, arrangement position, and the like of the other retardation layer can be appropriately set according to the purpose.

The polarizing plate with the retardation layer may be monolithic or elongated. In the present specification, "elongated" means an elongated shape sufficiently long with respect to the width and length, and includes, for example, an elongated shape having a length of 10 times or more, preferably 20 times or more, with respect to the width and length. The elongated polarizing plate with the retardation layer may be wound into a roll.

B. Polarizer

As the polarizer 11, any suitable polarizer may be used. For example, the resin film forming the polarizer may be a single-layer resin film or a laminate of two or more layers.

Specific examples of the polarizer formed of a single-layer resin film include: hydrophilic polymer films such as polyvinyl alcohol (PVA) films, partially formalized PVA films, and ethylene-vinyl acetate copolymer partially saponified films are subjected to dyeing treatment with a dichroic substance such as iodine or a dichroic dye, stretching treatment, and multi-functional alignment films such as dehydrated PVA or dehydrochlorinated polyvinyl chloride. From the viewpoint of excellent optical characteristics, a polarizer obtained by dyeing a PVA-based film with iodine and uniaxially stretching the film is preferably used.

The dyeing with iodine can be performed, for example, by immersing the PVA-based film in an aqueous iodine solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. Stretching may be performed after dyeing treatment or may be performed while dyeing. In addition, dyeing may be performed after stretching. If necessary, the PVA-based film is subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, and the like. For example, by immersing the PVA-based resin film in water and washing the same with water before dyeing, not only dirt and an anti-blocking agent on the surface of the PVA-based film can be washed, but also the PVA-based film can be swelled to prevent uneven dyeing.

Specific examples of the polarizer obtained by using the laminate of two or more layers include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, and a polarizer obtained by using a laminate of a resin substrate and a PVA-based resin layer formed on the resin substrate by coating. A polarizer obtained by using a laminate of a resin base material and a PVA-based resin layer formed on the resin base material can be produced, for example, by the following method: coating a PVA-based resin solution on a resin substrate and drying the same to form a PVA-based resin layer on the resin substrate, thereby obtaining a laminate of the resin substrate and the PVA-based resin layer; the laminate was stretched and dyed to prepare a polarizer from the PVA-based resin layer. In the present embodiment, it is preferable to form a polyvinyl alcohol resin layer containing a halide and a polyvinyl alcohol resin on one side of the resin base material. Stretching typically involves immersing the laminate in an aqueous boric acid solution to perform stretching. Further, the stretching may further include, if necessary, subjecting the laminate to air stretching at a high temperature (for example, 95 ℃ or higher) before stretching in the aqueous boric acid solution. In the present embodiment, it is preferable that the laminate is subjected to a drying shrinkage treatment in which the laminate is heated while being conveyed along the longitudinal direction so as to shrink by 2% or more in the width direction. Typically, the manufacturing method of the present embodiment includes: the laminate was sequentially subjected to an air-assisted stretching treatment, a dyeing treatment, an in-water stretching treatment, and a drying shrinkage treatment. By introducing the auxiliary stretching, even when PVA is coated on the thermoplastic resin, crystallinity of PVA can be improved, and high optical characteristics can be achieved. In addition, by simultaneously improving the orientation of PVA in advance, problems such as degradation and dissolution of the orientation of PVA can be prevented when immersed in water in the subsequent dyeing step and stretching step, and high optical characteristics can be achieved. In addition, in the case of immersing the PVA-based resin layer in a liquid, disturbance of orientation and decrease of orientation of polyvinyl alcohol molecules are suppressed as compared with the case where the PVA-based resin layer does not contain a halide. Thus, the optical characteristics of the polarizer obtained by the treatment step of immersing the laminate in a liquid, such as dyeing treatment or stretching treatment in water, can be improved. Further, the laminate is shrunk in the width direction by the drying shrinkage treatment, whereby the optical characteristics can be improved. The resulting laminate of the resin substrate and the polarizer may be used as it is (that is, the resin substrate may be used as the protective layer of the polarizer), or the resin substrate may be peeled off from the laminate of the resin substrate and the polarizer, and any appropriate protective layer according to the purpose may be laminated on the peeled surface or on the surface opposite to the peeled surface. Details of such a method for producing a polarizer are described in, for example, japanese patent application laid-open No. 2012-73580 and japanese patent No. 6470455. The entire disclosures of these publications may be incorporated into this specification by reference.

The thickness of the polarizer is preferably 15 μm or less, more preferably 12 μm or less, further preferably 10 μm or less, particularly preferably 8 μm or less, and particularly preferably 5 μm or less. The lower limit of the thickness of the polarizer may be, for example, 1 μm. When the thickness of the polarizer is within such a range, curling at the time of heating can be favorably suppressed, and excellent durability of appearance at the time of heating can be obtained.

The polarizer preferably exhibits absorption dichroism at any one of wavelengths 380nm to 780 nm. The polarizer has a monomer transmittance of, for example, 41.5% to 46.0%, preferably 43.0% to 46.0%, and more preferably 44.5% to 46.0%. The degree of polarization of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and still more preferably 99.9% or more.

C. Protective layer

The protective layer 12 and the second protective layer, not shown, are each formed of any suitable film that can be used as a protective layer of a polarizer. Specific examples of the material that becomes the main component of the film include cellulose resins such as Triacetylcellulose (TAC), transparent resins such as polyester resins, polyvinyl alcohol resins, polycarbonate resins, polyamide resins, polyimide resins, polyethersulfone resins, polysulfone resins, polystyrene resins, cyclic olefin resins (for example, polynorbornene resins), polyolefin resins, (meth) acrylic resins, and acetate resins. Further, a thermosetting resin such as a (meth) acrylic resin, a urethane resin, a (meth) acrylic urethane resin, an epoxy resin, or a silicone resin, an ultraviolet curable resin, or the like can be mentioned. In addition, for example, a vitreous polymer such as a siloxane polymer can be used. In addition, a polymer film described in Japanese patent application laid-open No. 2001-343529 (WO 01/37007) can also be used. As a material of the film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in a side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in a side chain, and for example, a resin composition having an alternating copolymer of isobutylene and N-methylmaleimide and an acrylonitrile-styrene copolymer can be used. The polymer film may be, for example, an extrusion molded product of the above resin composition.

The shrinkage of the protective layer 12 after being left at 85 ℃ for 240 hours is preferably less than 0.05%, more preferably 0.04% or less, and still more preferably 0.03% or less. The lower limit of the shrinkage ratio may be, for example, 0.01%, as the shrinkage ratio is smaller. If the shrinkage is in this range, cracks in the polarizer and peeling of the polarizer and the retardation layer in a severe high-temperature and high-humidity environment can be more favorably suppressed. The protective layer 12 is preferably formed of a triacetyl cellulose (TAC) film or a cycloolefin resin film. The TAC film and the cycloolefin resin film are preferably formed by extrusion or casting, and stretching is not included in the film formation. As a result, the residual stress is small, and thus the above-described desired shrinkage rate can be achieved.

The polarizing plate with a retardation layer according to the embodiment of the present invention is typically disposed on the visible side of an image display device, and the protective layer 12 is disposed on the visible side. Therefore, the protective layer 12 may be subjected to surface treatments such as Hard Coat (HC) treatment, antireflection treatment, anti-blocking treatment, and antiglare treatment, as necessary. Further, the protective layer 12 may be subjected to a treatment (typically, an (elliptical) circularly polarized light function is given and an ultra-high phase difference is given) to improve visibility when viewing through polarized sunglasses, if necessary. By performing such a treatment, excellent visibility can be achieved even when the display screen is visually recognized through a polarized lens such as polarized sunglasses. Therefore, the polarizing plate with the retardation layer can be suitably applied to an image display device that can be used outdoors.

The thickness of the protective layer is typically 300 μm or less, preferably 100 μm or less, more preferably 5 μm to 80 μm, and still more preferably 10 μm to 60 μm. When the surface treatment is performed, the thickness of the protective layer includes the thickness of the surface treatment layer.

In one embodiment, the second protective layer is preferably optically isotropic. In the present specification, "optically isotropic" means that the in-plane retardation Re (550) is 0nm to 10nm, and the retardation Rth (550) in the thickness direction is-10 nm to +10nm.

D. first phase difference layer

D-1 characteristics of the first phase-difference layer

The in-plane retardation Re (550) of the first retardation layer 21 is as described above 100nm to 200nm, preferably 110nm to 180nm, more preferably 120nm to 160nm, and still more preferably 130nm to 150nm. That is, the first retardation layer can function as a so-called λ/4 plate.

The first retardation layer satisfies the relationship of Re (450) < Re (550), preferably satisfies the relationship of Re (550) < Re (650). That is, the first phase difference layer exhibits an inverse dispersion wavelength dependence in which the phase difference value increases as the wavelength of the measurement light increases. Re (450)/Re (550) of the first retardation layer exceeds 0.5 and is lower than 1.0, for example, preferably 0.7 to 0.95, more preferably 0.75 to 0.92, and still more preferably 0.8 to 0.9.Re (650)/Re (550) is preferably 1.0 or more and less than 1.15, more preferably 1.03 to 1.1.

The first retardation layer has a relationship of nx > ny because of the in-plane retardation as described above. The first retardation layer exhibits any suitable refractive index characteristics as long as it has a relationship of nx > ny. The refractive index characteristics of the first retardation layer representatively show a relationship of nx > ny.gtoreq.nz. Further, "ny=nz" herein includes not only the case where ny and nz are completely equal but also the case where ny and nz are substantially equal. Therefore, ny < nz may sometimes be in a range that does not impair the effects of the present invention. The Nz coefficient of the first retardation layer is preferably 0.9 to 2.0, more preferably 0.9 to 1.5, and still more preferably 0.9 to 1.2. By satisfying such a relationship, when the polarizing plate with a retardation layer is used in an image display device, a very excellent reflection hue can be achieved.

The thickness of the first retardation layer may be set so as to function most appropriately as a λ/4 plate. In other words, the thickness may be set in such a manner that a desired in-plane retardation can be obtained. Specifically, the thickness is preferably 15 μm to 70. Mu.m, more preferably 20 μm to 60. Mu.m, and most preferably 20 μm to 50. Mu.m.

The shrinkage of the first retardation layer in the slow axis direction when heated to 180 minutes at 80 to 125 ℃ is, for example, 4% or less, preferably 3.5% or less, and more preferably 3% or less. The lower limit of the shrinkage ratio may be, for example, 0.5%, as the shrinkage ratio is smaller. If the shrinkage ratio of the first retardation layer is within such a range, cracking in a severe high-temperature and high-humidity environment can be more favorably suppressed.

The elongation at break of the stretched film constituting the first retardation layer is preferably 200% or more, more preferably 210% or more, still more preferably 220% or more, and particularly preferably 245% or more. The upper limit of the elongation at break may be 500%, for example. When the elongation at break of the stretched film constituting the first retardation layer is within such a range, cracking in a severe high-temperature and high-humidity environment can be more favorably suppressed by a synergistic effect with the effect caused by the above shrinkage. In the present specification, "elongation at break" refers to the elongation at break of a film during uniaxial stretching at a fixed end at a specific stretching temperature (for example, tg-2 ℃).

The absolute value of the photoelastic coefficient of the first retardation layer is preferably 20×10 ^-12(m²/N or less, more preferably 1.0×10 ^-12(m²/N)～15×10^-12(m²/N, and still more preferably 2.0×10 ^-12(m²/N)～12×10^-12(m²/N). When the absolute value of the photoelastic coefficient is within such a range, display unevenness can be suppressed when the polarizing plate with a retardation layer is applied to an image display device.

D-2 constituent Material of the first phase-difference layer

The first retardation layer typically contains a resin containing at least one bonding group selected from the group consisting of carbonate bonds and ester bonds. In other words, the first retardation layer contains a polycarbonate-based resin, a polyester-based resin, or a polyester-carbonate-based resin (hereinafter, these may be simply referred to as a polycarbonate-based resin).

In one embodiment, the polycarbonate resin comprises a structural unit derived from a fluorene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, and a structural unit derived from at least one dihydroxy compound selected from the group consisting of an alicyclic diol, an alicyclic dimethanol, a di-, tri-, or polyethylene glycol, and an alkylene glycol or a spiro glycol. The polycarbonate resin preferably contains a structural unit derived from a fluorene dihydroxy compound, a structural unit derived from an isosorbide dihydroxy compound, a structural unit derived from alicyclic dimethanol, and/or a structural unit derived from di-, tri-, or polyethylene glycol; further, it is preferable to include a structural unit derived from a fluorene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, and a structural unit derived from di-, tri-, or polyethylene glycol. The polycarbonate resin may contain a structural unit derived from another dihydroxy compound, if necessary. Further, details of the polycarbonate-based resin which can be suitably used in the present invention are described in, for example, japanese patent application laid-open publication No. 2014-10291, japanese patent application laid-open publication No. 2014-26266, japanese patent application laid-open publication No. 2015-212816, japanese patent application laid-open publication No. 2015-212817, and Japanese patent application laid-open publication No. 2015-212818, which are incorporated herein by reference.

In one embodiment, the polycarbonate resin comprises at least one structural unit selected from the group consisting of the structural unit represented by the general formula (1) and/or the structural unit represented by the general formula (2). These structural units are structural units derived from divalent oligofluorene, and may be referred to as oligofluorene structural units hereinafter. Such polycarbonate-based resins have positive refractive index anisotropy.

In one embodiment, the first retardation layer may further contain an acrylic resin. The content of the acrylic resin is typically 0.5 to 1.5 mass%. In the present specification, the percentage or part of the "mass" unit and the percentage or part of the "weight" unit have the same meaning.

In one embodiment, the first retardation layer may further contain an antioxidant. As the antioxidant, any suitable compound may be used. Specific examples thereof include pentaerythritol-tetrakis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ]: trade name "Irganox 1010" (manufactured by BASF corporation), 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-t-butyl-4-hydroxybenzyl) benzene: trade name "Irganox 1330" (manufactured by BASF corporation), tris (3, 5-di-tert-butyl-4-hydroxybenzyl) isocyanurate: trade name "Irganox 3114" (manufactured by BASF corporation), stearyl 3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate: trade name "Irganox 1076" (manufactured by BASF corporation), 2' -thiodiethyl bis [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate ]: trade name "Irganox 1035" (manufactured by BASF corporation), N' -hexamethylenebis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionamide ]: trade name "Irganox1098" (manufactured by BASF corporation), bis [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionic acid ] [ ethylenebis (oxyethylene) ]: trade names "Irganox 245" (manufactured by BASF corporation), 1, 6-hexanediol bis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ] trade names "Irganox 259" (manufactured by BASF corporation), 4- [ [4, 6-bis (octylthio) -1,3, 5-triazin-2-yl ] amino ] -2, 6-di-tert-butylphenol: trade name "Irganox 565" (manufactured by BASF corporation), 2' -methylenebis [6- (2H-benzotriazol-2-yl) -4- (1, 3-tetramethylbutyl) phenol: trade name "Adekastab LA-31" (manufactured by ADEKA corporation), and the like. The content of the antioxidant is typically 1.5 to 3.5 mass%.

D-2-1 polycarbonate resin

< Oligofluorene structural unit >)

The oligofluorene structural unit is represented by the above general formula (1) or (2). In the general formulae (1) and (2), R ¹～R³ is each independently a direct bond, a substituted or unsubstituted alkylene group having 1 to 4 carbon atoms, and R ⁴～R⁹ is each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted aryl group having 4 to 10 carbon atoms, a substituted or unsubstituted acyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 10 carbon atoms, a substituted or unsubstituted aryloxy group having 1 to 10 carbon atoms, a substituted or unsubstituted amino group, a substituted or unsubstituted vinyl group having 1 to 10 carbon atoms, a substituted or unsubstituted ethynyl group having 1 to 10 carbon atoms, a sulfur atom having a substituent, a silicon atom having a substituent, a halogen atom, a nitro group, or a cyano group. Wherein R ⁴～R⁹ may be the same as or different from each other, and at least two adjacent groups in R ⁴～R⁹ may be bonded to each other to form a ring.

The content of the oligofluorene structural unit in the polycarbonate resin is preferably 1 to 40% by mass, more preferably 10 to 35% by mass, still more preferably 15 to 30% by mass, and particularly preferably 18 to 25% by mass, relative to the entire resin. If the content of the oligofluorene structural unit is too large, there is a possibility that problems such as an excessively large photoelastic coefficient, insufficient reliability, and insufficient phase difference manifestation may occur. Further, since the ratio of the oligofluorene structural unit to the resin increases, the range of molecular design becomes narrow, and improvement becomes difficult when modification of the resin is required. On the other hand, even if the desired inverse dispersion wavelength dependence is obtained by a very small amount of oligofluorene structural units, in this case, the optical characteristics are sensitively changed with a small variation in the content of oligofluorene structural units, and therefore, it is sometimes difficult to concentrate each characteristic in a certain range for production.

Details of the oligofluorene structural unit are described in, for example, pamphlet of International publication No. 2015/159928. This publication is incorporated by reference into this specification.

< Other structural units >)

The polycarbonate resin may typically contain other structural units in addition to the oligofluorene structural unit. In one embodiment, the other structural units may preferably be derived from a dihydroxy compound or a diester compound. In order to exhibit the target inverse dispersion wavelength property, it is necessary to incorporate an oligofluorene structural unit having negative intrinsic birefringence into the polymer structure together with a structural unit having positive intrinsic birefringence, and therefore, a dihydroxy compound or a diester compound as a raw material for the structural unit having positive birefringence is more preferable as another monomer to be copolymerized.

As comonomers there may be mentioned: the compound having a structural unit containing an aromatic ring may be introduced, or the compound having an aliphatic structure may be not introduced.

Specific examples of the above-mentioned compound having an aliphatic structure will be given below. Dihydroxy compounds of linear aliphatic hydrocarbons such as ethylene glycol, 1, 3-propanediol, 1, 2-propanediol, 1, 4-butanediol, 1, 3-butanediol, 1, 2-butanediol, 1, 5-heptanediol, 1, 6-hexanediol, 1, 9-nonanediol, 1, 10-decanediol, and 1, 12-dodecanediol; dihydroxy compounds of branched aliphatic hydrocarbons such as neopentyl glycol and hexanediol; for example, a dihydroxy compound of a secondary alcohol or a tertiary alcohol as an alicyclic hydrocarbon such as 1, 2-cyclohexanediol, 1, 4-cyclohexanediol, 1, 3-adamantanediol, hydrogenated bisphenol A, 2, 4-tetramethyl-1, 3-cyclobutanediol, etc.; dihydroxy compounds such as 1, 2-cyclohexanedimethanol, 1, 3-cyclohexanedimethanol, 1, 4-cyclohexanedimethanol, tricyclodecanedimethanol, pentacyclopentadecanedimethanol, 2, 6-decalin dimethanol, 1, 5-decalin dimethanol, 2, 3-norbornane dimethanol, 2, 5-norbornane dimethanol, 1, 3-adamantane dimethanol, and limonene, which are dihydroxy compounds derived from terpene compounds, etc., as primary alcohols of alicyclic hydrocarbons; alkylene oxide glycols such as diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, and polypropylene glycol; dihydroxy compounds having a cyclic ether structure such as isosorbide; dihydroxy compounds having a cyclic acetal structure such as spiroglycol and dioxane glycol; alicyclic dicarboxylic acids such as 1, 2-cyclohexanedicarboxylic acid, 1, 3-cyclohexanedicarboxylic acid and 1, 4-cyclohexanedicarboxylic acid; aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and the like.

Specific examples of the above-mentioned compound into which the structural unit containing an aromatic ring can be introduced will be given below. 2, 2-bis (4-hydroxyphenyl) propane, 2-bis (3-methyl-4-hydroxyphenyl) propane, 2-bis (4-hydroxy-3, 5-dimethylphenyl) propane, 2-bis (4-hydroxy-3, 5-diethylphenyl) propane 2, 2-bis (4-hydroxy- (3-phenyl) propane, 2-bis (4-hydroxy- (3, 5-diphenyl) phenyl) propane, 2-bis (4-hydroxy-3, 5-dibromophenyl) propane, bis (4-hydroxyphenyl) methane 1, 1-bis (4-hydroxyphenyl) ethane, 2-bis (4-hydroxyphenyl) butane, 2-bis (4-hydroxyphenyl) pentane, 1-bis (4-hydroxyphenyl) -1-phenylethane, bis (4-hydroxyphenyl) diphenylmethane 1, 1-bis (4-hydroxyphenyl) -2-ethyl hexane, 1-bis (4-hydroxyphenyl) decane, bis (4-hydroxy-3-nitrophenyl) methane, 3-bis (4-hydroxyphenyl) pentane, 1, 3-bis (2- (4-hydroxyphenyl) -2-propyl) benzene, aromatic bisphenol compounds such as 1, 3-bis (2- (4-hydroxyphenyl) -2-propyl) benzene, 2-bis (4-hydroxyphenyl) hexafluoropropane, 1-bis (4-hydroxyphenyl) cyclohexane, bis (4-hydroxyphenyl) sulfone, 2,4 '-dihydroxydiphenyl sulfone, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxy-3-methylphenyl) sulfide, bis (4-hydroxyphenyl) disulfide, 4' -dihydroxydiphenyl ether, 4 '-dihydroxy-3, 3' -dichlorodiphenyl ether; dihydroxy compounds having an ether group bonded to an aromatic group, such as 2, 2-bis (4- (2-hydroxyethoxy) phenyl) propane, 2-bis (4- (2-hydroxypropoxy) phenyl) propane, 1, 3-bis (2-hydroxyethoxy) benzene, 4' -bis (2-hydroxyethoxy) biphenyl, and bis (4- (2-hydroxyethoxy) phenyl) sulfone; aromatic dicarboxylic acids such as terephthalic acid, phthalic acid, isophthalic acid, 4' -biphenyl dicarboxylic acid, 4' -diphenylether dicarboxylic acid, 4' -diphenylketone dicarboxylic acid, 4' -diphenoxyethane dicarboxylic acid, 4' -diphenylsulfone dicarboxylic acid, and 2, 6-naphthalene dicarboxylic acid.

The aliphatic dicarboxylic acid and the aromatic dicarboxylic acid component listed above may be dicarboxylic acids themselves as the raw materials of the polyester carbonate, but depending on the production method, dicarboxylic acid esters such as methyl esters and phenyl esters, or dicarboxylic acid derivatives such as dicarboxylic acid halides may be used as the raw materials.

As the comonomer, a dihydroxy compound having a fluorene ring such as 9, 9-bis (4- (2-hydroxyethoxy) phenyl) fluorene, 9-bis (4-hydroxyphenyl) fluorene, 9-bis (4-hydroxy-3-methylphenyl) fluorene, or a dicarboxylic acid compound having a fluorene ring, which are previously known as compounds containing a structural unit having negative birefringence, may be used in combination with the oligofluorene compound.

The resin used in the embodiment of the present invention preferably contains a structural unit represented by the following formula (3) as a copolymerization component in the structural unit that can be introduced by the compound having an alicyclic structure.

As the dihydroxy compound into which the structural unit of the above formula (3) can be introduced, spiroglycol can be used.

The resin used in the embodiment of the present invention preferably contains 5 to 90 mass% of the structural unit represented by the above formula (3). The upper limit is further preferably 70 mass% or less, and particularly preferably 50 mass% or less. The lower limit is further preferably 10 mass% or more, more preferably 20 mass% or more, and particularly preferably 25 mass% or more. When the content of the structural unit represented by the above formula (3) is not less than the above lower limit, sufficient mechanical properties, heat resistance, and a low photoelastic coefficient can be obtained. Further, the compatibility with the acrylic resin is improved, and the transparency of the obtained resin composition can be further improved. Further, since the polymerization rate of the spiroglycol is relatively low, the polymerization reaction can be easily controlled by controlling the content thereof to be less than the upper limit.

The resin used in the embodiment of the present invention preferably further contains a structural unit represented by the following formula (4) as a copolymerization component.

Examples of the dihydroxy compound into which the structural unit represented by formula (4) can be introduced include Isosorbide (ISB), anhydromannitol, isoidide, and the like having a stereoisomeric relationship. One kind of them may be used alone, or two or more kinds may be used in combination.

The resin used in the embodiment of the present invention preferably contains 5 to 90 mass% of the structural unit represented by the formula (4). The upper limit is further preferably 70 mass% or less, and particularly preferably 50 mass% or less. The lower limit is further preferably 10 mass% or more, and particularly preferably 15 mass% or more. When the content of the structural unit represented by the above formula (4) is not less than the above lower limit, sufficient mechanical properties, heat resistance, and a low photoelastic coefficient can be obtained. Further, since the structural unit represented by the above formula (4) has a characteristic of high water absorption, if the content of the structural unit represented by the above formula (4) is not more than the above upper limit, the dimensional change of the molded article due to water absorption can be suppressed within an allowable range.

The resin used in the embodiment of the present invention may further contain another structural unit. Further, the structural unit is sometimes referred to as "other structural unit". As the monomer having another structural unit, 1, 4-cyclohexanedimethanol, tricyclodecanedimethanol, 1, 4-cyclohexanedicarboxylic acid (and derivatives thereof) are more preferably used, and 1, 4-cyclohexanedimethanol and tricyclodecanedimethanol are particularly preferred. Resins containing structural units derived from these monomers are excellent in balance among optical properties, heat resistance, mechanical properties, and the like. Further, since the polymerization reactivity of the diester compound is relatively low, it is preferable not to use a diester compound other than the diester compound containing an oligofluorene structural unit from the viewpoint of improving the reaction efficiency.

The glass transition temperature (Tg) of the resin used in the embodiment of the present invention is preferably 110 ℃ or more and 160 ℃ or less. The upper limit is further preferably 155℃or lower, more preferably 150℃or lower, and particularly preferably 145℃or lower. The lower limit is further preferably 120℃or higher, particularly preferably 130℃or higher. If the glass transition temperature is outside the above range, there is a tendency that the heat resistance is deteriorated, dimensional change may occur after film formation, or the quality reliability of the first retardation layer may be deteriorated under the use condition. On the other hand, when the glass transition temperature is too high, film thickness unevenness may occur during film formation, or the film becomes brittle and the stretchability may be deteriorated, and the transparency of the film may be impaired.

D-2-2 acrylic resin

As the acrylic resin, an acrylic resin is used as the thermoplastic resin. Examples of the monomer that becomes a structural unit of the acrylic resin include the following compounds: methyl methacrylate, methacrylic acid, methyl acrylate, acrylic acid, benzyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, stearyl (meth) acrylate, glycidyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, norbornyl (meth) acrylate; dicyclopentenyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, acryloyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2- (meth) acryloyloxyethyl succinate, 2- (meth) acryloyloxyethyl maleate, 2- (meth) acryloyloxyethyl phthalate, 2- (meth) acryloyloxyethyl hexahydrophthalate, 2- (meth) acryloyloxyethyl, pentamethylpiperidinyl (meth) acrylate, tetramethylpiperidine (meth) acrylate, dimethylaminoethyl (meth) acrylate, and, diethylaminoethyl (meth) acrylate, cyclopentyl methacrylate, cyclopentyl acrylate, cyclohexyl methacrylate, cyclohexyl acrylate, cycloheptyl methacrylate, cycloheptyl acrylate, cyclooctyl methacrylate, cyclooctyl acrylate, cyclododecyl methacrylate, cyclododecyl acrylate. These may be used alone or in combination of two or more. The mode of combining two or more monomers may be: copolymerization of two or more monomers, blending of two or more homopolymers of one monomer, and combinations of these. Further, other monomers copolymerizable with these acrylic monomers (for example, olefin monomers and vinyl monomers) may be used in combination.

The acrylic resin contains structural units derived from methyl methacrylate. The content of the structural unit derived from methyl methacrylate in the acrylic resin is preferably 70% by mass or more and 100% by mass or less. The lower limit is more preferably 80 mass% or more, still more preferably 90 mass% or more, and particularly preferably 95 mass% or more. Within this range, excellent compatibility with the polycarbonate-based resin of the present invention can be obtained. As the structural unit other than methyl methacrylate, methyl acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, and styrene are preferably used. By copolymerizing methyl acrylate, thermal stability can be improved. The refractive index of the acrylic resin can be adjusted by using phenyl (meth) acrylate, benzyl (meth) acrylate, and styrene, and therefore, by matching the refractive index of the combined resins, the transparency of the obtained resin composition can be improved. By using such an acrylic resin, an inverse dispersion retardation film having excellent expansibility and retardation expression and having a small haze can be obtained.

The weight average molecular weight Mw of the acrylic resin is 10,000 to 200,000. The lower limit is preferably 30,000 or more, particularly preferably 50,000 or more. The upper limit is preferably 180,000 or less, particularly preferably 150,000 or less. If the molecular weight is in such a range, compatibility with the polycarbonate resin can be obtained, and therefore, the transparency of the final retardation film (retardation layer) can be improved, and the effect of sufficiently improving the expansibility at the time of stretching can be obtained. The weight average molecular weight is a molecular weight in terms of polystyrene as measured by GPC. In addition, from the viewpoint of compatibility, the acrylic resin preferably contains substantially no branched structure. The absence of the branched structure can be confirmed by unimodal GPC curve of the acrylic resin.

D-2-3. Blending of polycarbonate-based resin and acrylic-based resin

When a polycarbonate resin and an acrylic resin are used in combination, the polycarbonate resin and the acrylic resin are blended to prepare a resin composition, which is used in a method for producing a retardation film (first retardation layer) (the production method is described in the following item D-3). The polycarbonate resin and the acrylic resin are preferably capable of being blended in a molten state. As a method of blending in a molten state, melt kneading using an extruder is typically exemplified. The kneading temperature (melt resin temperature) is preferably 200 to 280 ℃, more preferably 220 to 270 ℃, and still more preferably 230 to 260 ℃. When the kneading temperature is within this range, pellets of a resin composition in which two resins are uniformly blended can be obtained while suppressing thermal decomposition. If the temperature of the molten resin in the extruder exceeds 280 ℃, coloration and/or thermal decomposition of the resin may occur. On the other hand, if the temperature of the molten resin in the extruder is lower than 200 ℃, the viscosity of the resin may become too high, which may cause an excessive load to be applied to the extruder or insufficient melting of the resin. Any suitable structure may be used as the structure of the extruder, the structure of the screw, and the like. In order to obtain transparency of the resin which can withstand the use of the optical film, a twin screw extruder is preferably used. Further, since the cooling roll or the conveying roll may be contaminated by the remaining low molecular components in the resin or the low molecular weight thermally decomposed components in the extrusion kneading in the film forming step or the stretching step, an extruder having a vacuum vent is preferably used to remove them.

The content of the acrylic resin in the resin composition (as a result of the first retardation layer) is 0.5 mass% or more and 2.0 mass% or less as described above. The lower limit is more preferably 0.6 mass% or more. The upper limit is preferably 1.5% by mass or less, more preferably 1.0% by mass or less, still more preferably 0.9% by mass or less, and particularly preferably 0.8% by mass or less. Thus, by blending the acrylic resin into the polycarbonate resin at a very limited ratio, the expandability and the phase difference manifestation can be remarkably improved. Further, haze can be suppressed. This effect is not theoretically clear, and is an unexpectedly excellent effect obtained by trial and error. Further, if the content of the acrylic resin is too small, the above-mentioned effects may not be obtained. On the other hand, if the content of the acrylic resin is too large, haze may be high. In addition, in many cases, the expansibility and the phase difference expressivity are insufficient or are rather reduced as compared with the case in the above-described range.

In order to modify the mechanical properties and/or the solvent resistance, the resin composition may further be blended with a synthetic resin such AS an aromatic polycarbonate, an aliphatic polycarbonate, an aromatic polyester, an aliphatic polyester, a polyamide, a polystyrene, a polyolefin, an acrylic acid, an amorphous polyolefin, ABS, AS, polylactic acid, polybutylene succinate, a rubber, or a combination thereof.

The resin composition may further comprise an additive. Specific examples of the additives include: heat stabilizers, antioxidants, catalyst deactivators, ultraviolet absorbers, light stabilizers, mold release agents, dye pigments, impact modifiers, antistatic agents, slip agents, lubricants, plasticizers, compatibilizers, nucleating agents, flame retardants, inorganic fillers, foaming agents. The kind, amount, combination, content, and the like of the additives contained in the resin composition can be appropriately set according to the purpose.

D-3 method for forming first phase difference layer

The first phase difference layer may be obtained by: a film is formed from the polycarbonate resin (resin composition in the case of using an acrylic resin in combination) described in the above item D-2, and the film is stretched. As a method for forming the film, any suitable molding method may be used. Specific examples include: compression molding, transfer molding, injection molding, extrusion molding, blow molding, powder molding, FRP molding, cast coating (e.g., casting), calendaring, hot pressing, and the like. Among them, an extrusion molding method or a casting coating method is preferable, which can improve the smoothness of the obtained film and obtain good optical uniformity. The casting method is particularly preferably an extrusion molding method because of the possibility of occurrence of problems caused by residual solvents, and among them, a melt extrusion molding method using a T-die is preferable from the viewpoint of film productivity or easiness of subsequent stretching treatment. The molding conditions may be appropriately set according to the composition or type of the resin used, the desired characteristics of the first retardation layer, and the like. Thus, a resin film containing a polycarbonate resin and, if necessary, an acrylic resin can be obtained.

The thickness of the resin film (unstretched film) may be set to any appropriate value according to the desired thickness of the obtained first retardation layer, the desired optical characteristics, stretching conditions described later, and the like. Preferably 50 μm to 300. Mu.m.

The stretching may be performed by any suitable stretching method or stretching conditions (e.g., stretching temperature, stretching ratio, stretching direction). Specifically, various stretching methods such as free end stretching, fixed end stretching, free end shrinkage, fixed end shrinkage, and the like may be used alone, or may be used simultaneously or sequentially. The stretching direction may be performed in various directions or dimensions such as a longitudinal direction, a width direction, a thickness direction, and an oblique direction.

By appropriately selecting the stretching method and the stretching conditions, a retardation layer having the desired optical characteristics (for example, refractive index characteristics, in-plane retardation, nz coefficient) can be obtained.

In one embodiment, the stretching temperature of the film is preferably from the glass transition temperature (Tg) to tg+30 ℃, more preferably from Tg to tg+15 ℃, and most preferably from Tg to tg+10 ℃. When an acrylic resin is used in combination, the stretching temperature is at a temperature of Tg or less. In general, when a film of a polycarbonate resin is stretched, the film is in a glass state at a temperature of Tg or less, and thus stretching is substantially impossible. On the other hand, by blending a small amount of an acrylic resin (typically polymethyl methacrylate), stretching can be performed at a temperature of Tg or less without substantially changing Tg of the polycarbonate resin. Further, although not clearly understood in theory, by stretching at a temperature of Tg or lower, an inverse dispersion retardation film (first retardation layer) excellent in expansibility and retardation expression and having a small haze can be obtained. Specifically, the stretching temperature is preferably from Tg to Tg-10deg.C, more preferably from Tg to Tg-8deg.C, and even more preferably from Tg to Tg-5deg.C. The film may be stretched appropriately even at a temperature higher than Tg, for example, at most about tg+5 ℃, or at most about tg+2 ℃.

The stretched film obtained in the manner described above may be subjected to a heating treatment of heating at a temperature of 105 ℃ or higher for 2 minutes or more, as required. By performing the heat treatment, the first retardation layer having the above-described desired shrinkage ratio can be formed. The heating temperature is preferably 105℃to 140℃and more preferably 110℃to 130℃and still more preferably 115℃to 125 ℃. The heating time is preferably 2 minutes to 150 minutes, more preferably 3 minutes to 120 minutes, and still more preferably 5 minutes to 60 minutes.

The stretched film may be subjected to a relaxation treatment as needed. This can alleviate stress caused by stretching, and a retardation layer having the above-described desired shrinkage ratio can be formed. As the mild treatment conditions, any suitable conditions may be employed. For example, the stretched film is contracted in the stretching direction at a specific relaxation temperature and a specific relaxation rate (shrinkage rate). The temperature for moderation is preferably 60℃to 150 ℃. The relaxation rate is preferably 3% to 6%. In the case of performing the relaxation treatment, the relaxation treatment may be typically performed before the heating treatment.

In the manner described above, a phase difference film constituting the first phase difference layer can be obtained.

E. Second phase difference layer

The second phase difference layer may be a so-called positive C plate whose refractive index characteristics exhibit a relationship of nz > nx=ny, as described above. By using the positive C plate as the second phase difference layer, reflection in the oblique direction can be well prevented, and a wide viewing angle of the antireflection function can be achieved. In this case, the retardation Rth (550) in the thickness direction of the second phase difference layer is preferably-50 nm to-300 nm, more preferably-70 nm to-250 nm, still more preferably-90 nm to-200 nm, particularly preferably-100 nm to-180 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 phase difference Re (550) of the second phase difference layer may be below 10nm.

The second phase difference layer having refractive index characteristics of nz > nx=ny may be formed of any suitable material. The second phase difference layer is preferably formed of a film containing a liquid crystal material fixed in a vertical alignment. The liquid crystal material (liquid crystal compound) capable of vertical alignment may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of the method for forming the liquid crystal compound and the retardation layer include those described in [0020] to [0028] of JP-A-2002-333642 and a method for forming the retardation layer. In this case, the thickness of the second phase difference layer 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.

F. First and second layers (heat and moisture resistant layer)

The first layer 31 and the second layer 32 may each have any suitable structure as long as the shear fracture strength is satisfied. The first layer 31 and the second layer 32 may have the same structure or may have different structures. As described above, by providing the first layer or providing the first layer and the second layer, a polarizing plate with a retardation layer having excellent durability even in a severe high-temperature and high-humidity environment can be realized. Hereinafter, the first layer 31 and the second layer 32 are collectively referred to as a heat-resistant and moisture-resistant layer.

The heat and moisture resistant layer preferably has substantially optical isotropy. The in-plane retardation Re (550) of the heat and moisture resistant layer is preferably 0nm to 10nm, more preferably 0nm to 5nm, still more preferably 0nm to 3nm, particularly preferably 0nm to 2nm. The retardation Rth (550) in the thickness direction of the heat and moisture resistant layer is preferably-10 nm to +10nm, more preferably-5 nm to +5nm, still more preferably-3 nm to +3nm, particularly preferably-2 nm to +2nm. When Re (550) and Rth (550) of the heat and moisture resistant layer are in such a range, adverse effects on display characteristics can be prevented when applied to an image display device.

The higher the light transmittance at 380nm at a thickness of 3 μm, the more preferable the heat and moisture resistant layer. Specifically, the light transmittance is preferably 85% or more, more preferably 88% or more, and still more preferably 90% or more. If the light transmittance is in such a range, the desired transparency can be ensured. The light transmittance can be measured, for example, by a method according to ASTM-D-1003.

The lower the haze of the heat and moisture resistant layer, the more preferable. Specifically, the haze is preferably 5% or less, more preferably 3% or less, further preferably 1.5% or less, and particularly preferably 1% or less. When the haze is 5% or less, a good transparent feeling can be imparted to the polarizing plate with the retardation layer. As a result, the display content of the image display device can be visually recognized well.

In one embodiment, the higher the adhesion between the heat and moisture resistant layer and the first retardation layer, the more preferable. Specifically, in the checkerboard peel test described in JIS K5600-5-6, the adhesion is preferably in a state of 2 minutes or less, more preferably in a state of 1 minute or less, and particularly preferably in a state of 0 minutes. When the adhesion is 2 minutes or less as measured by the checkered peeling test, peeling of the polarizing plate with the retardation layer under severe high-temperature and high-humidity environment can be favorably suppressed, and problems relating to appearance such as peeling at the time of secondary processing can be suppressed.

As described above, the heat and moisture resistant layer is typically a cured layer or a cured layer of resin. The cured layer may be, for example, a cured layer of a thermosetting resin, an active energy ray curable resin, or an active energy ray curable resin. Specific examples of the cured layer include a hard coat layer, an adhesive layer formed of an active energy ray-curable adhesive, and a crosslinked layer formed of a crosslinking agent, in addition to a simple cured layer. The cured layer may be, for example, a cured layer of a coating film of an organic solvent solution of a thermoplastic resin. These may constitute the heat and moisture resistant layer alone or may constitute the heat and moisture resistant layer by combining two or more kinds.

(Hard coat)

The hard coat layer (essentially, the composition forming the hard coat layer) contains a curing component and a representative photopolymerization initiator. Typical examples of the curing component include active energy ray-curable (meth) acrylates. Examples of the active energy ray-curable (meth) acrylate include ultraviolet-curable (meth) acrylate and electron beam-curable (meth) acrylate. Preferably ultraviolet curable (meth) acrylate. The reason for this is that the hard coat layer can be formed efficiently by a simple processing operation. The ultraviolet curable (meth) acrylate includes ultraviolet curable monomers, oligomers, polymers, and the like. The ultraviolet curable (meth) acrylate contains a monomer component and an oligomer component having preferably 2 or more ultraviolet polymerizable functional groups, more preferably 3 to 6. Specific examples of the ultraviolet curable (meth) acrylate include: urethane acrylates, pentaerythritol triacrylate, ethoxylated glycerol triacrylate, polyether urethane diacrylates. In addition to these, a curing component of an active energy ray-curable adhesive to be described later may be used. The curing component may be used alone or in combination of two or more. The curing method may be a radical polymerization method or a cationic polymerization method. In one embodiment, an organic-inorganic hybrid material obtained by mixing silica particles, polysilsesquioxane compounds, or the like with (meth) acrylic acid esters can be used. The constituent materials and the forming method of the hard coat layer are described in, for example, japanese patent application laid-open publication No. 2011-237789, japanese patent application laid-open publication No. 2020-064236, and Japanese patent application laid-open publication No. 2010-152331. The descriptions of these publications are incorporated by reference into this specification. In the present specification, "(meth) acrylic" means acrylic acid and/or methacrylic acid. In addition, (meth) acrylic acid may be abbreviated as acrylic acid.

(Active energy ray-curable adhesive)

Examples of the active energy ray-curable adhesive include ultraviolet ray-curable adhesives and electron beam-curable adhesives. In addition, from the viewpoint of the curing mechanism, examples of the active energy ray-curable adhesive include: radical curable, cationic curable, anionic curable, a mixture of radical curable and cationic curable.

The adhesive contains a curing component and a typical photopolymerization initiator, as in the case of the composition for forming the hard coat layer. As the curing component, monomers and/or oligomers having a functional group such as a (meth) acrylate group or a (meth) acrylamide group are typically exemplified. Specific examples of the curing component include: tripropylene glycol diacrylate, 1, 6-hexanediol diacrylate, 1, 9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, phenoxydiethylene glycol acrylate, cyclic trimethylolpropane formal acrylate, dioxane diol diacrylate, trimethylolpropane triacrylate, glycerol triacrylate, EO-modified diglycerol tetraacrylate, gamma-butyrolactone acrylate, polyethylene glycol diacrylate, hydroxypivalic acid neopentyl glycol acrylic acid adduct, acryloylmorpholine, unsaturated fatty acid hydroxyalkyl ester modified epsilon-caprolactone, N-methylpyrrolidone, diethylacrylamide, hydroxyethylacrylamide, N-methylolacrylamide, N-methoxymethylacrylamide, N-ethoxymethylacrylamide, 3, 4-epoxycyclohexenylmethyl-3 ',4' -epoxycyclohexene carboxylate, neopentyl glycol glycidyl ether, dicyclopentadiene type epoxy resin. As the curing component, 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, 4-hydroxybutyl acrylate, neopentyl glycol diacrylate, isocyanatoEO-modified triacrylate, and the like can also be used. In addition to these, the curing component of the hard coat layer described above may also be used. The curing component may be used alone or in combination of two or more. The adhesive may further contain an oligomer component in addition to the above-mentioned curing component. By using the oligomer component, the viscosity of the adhesive before curing can be reduced, and the workability can be improved. Typical examples of the oligomer component include: (meth) acrylic oligomers, and urethane-based (meth) acrylic oligomers.

(Crosslinked layer formed of crosslinking agent)

The crosslinked layer (essentially the composition forming the crosslinked layer) contains a curing component and a crosslinking agent. The curing component includes those described above for the hard coat layer and the active energy ray-curable adhesive. The crosslinking agent may be a thermal crosslinking agent or a photocrosslinking agent. That is, the crosslinked layer may be a thermally crosslinked layer or a photocrosslinked layer. Examples of the thermal crosslinking agent include an organic crosslinking agent and a polyfunctional metal chelate. Examples of the organic crosslinking agent include: isocyanate-based crosslinking agent, peroxide-based crosslinking agent, epoxy-based crosslinking agent, and imine-based crosslinking agent. The polyfunctional metal chelate is obtained by covalent bonding or coordinate bonding of a polyvalent metal and an organic compound. Examples of the photocrosslinking agent include photoacid generators. Examples of the photoacid generator include organic peroxides. The thermal crosslinking agent or the photo crosslinking agent may be used alone or in combination of two or more.

(Cured layer of thermosetting resin)

As the thermosetting resin, any suitable thermosetting resin may be used as long as the cured layer has the above-described desired storage modulus. Typical examples of the thermosetting resin include: epoxy resin, (meth) acrylic resin, unsaturated polyester resin, polyurethane resin, alkyd resin, melamine resin, urea resin, phenolic resin. For example, oxetane compounds (monomers, oligomers, polymers) may be blended into the thermosetting resin.

(Cured layer)

The cured layer may be, for example, a cured layer of a coating film of an organic solvent solution of a thermoplastic resin, as described above. Regarding the thermoplastic, any suitable thermoplastic resin may be used as long as the cured layer has the above-described desired storage modulus. Typical examples of the thermoplastic resin include (meth) acrylic resins and epoxy resins.

The glass transition temperature (Tg) of the (meth) acrylic resin is preferably 100℃to 220℃and more preferably 110℃to 200℃and still more preferably 120℃to 160 ℃. The (meth) acrylic resin may have a repeating unit including a ring structure. Examples of the repeating unit including a ring structure include: lactone ring units, glutaric anhydride units, glutarimide units, maleic anhydride units, maleimide (N-substituted maleimide) units. The repeating unit of the (meth) acrylic resin may include only one kind of repeating unit including a ring structure, or may include two or more kinds. The (meth) acrylic resin may be a copolymer of a (meth) acrylic monomer and a boron-containing monomer (boron-containing (meth) acrylic resin). The boron-containing (meth) acrylic resin may also have a repeating unit including a ring structure as described above.

As the epoxy resin, an epoxy resin having an aromatic ring is preferably used. By using an epoxy resin having an aromatic ring, adhesion between the cured layer and the first retardation layer can be improved. Examples of the epoxy resin having an aromatic ring include: bisphenol-type epoxy resins such as bisphenol-a-type epoxy resins, bisphenol-F-type epoxy resins, and bisphenol-S-type epoxy resins; novolac epoxy resins such as phenol novolac epoxy resin, cresol novolac epoxy resin, hydroxybenzaldehyde phenol novolac epoxy resin, and the like; and multifunctional epoxy resins such as glycidyl ether of tetrahydroxyphenyl methane, glycidyl ether of tetrahydroxybenzophenone, and epoxidized polyvinyl phenol, naphthol-type epoxy resins, naphthalene-type epoxy resins, biphenyl-type epoxy resins, and the like. Bisphenol A type epoxy resin, biphenyl type epoxy resin, bisphenol F type epoxy resin are preferably used. The epoxy resin may be used alone or in combination of two or more.

As the organic solvent, any suitable organic solvent capable of dissolving or uniformly dispersing the thermoplastic resin may be used. Specific examples of the organic solvent include: ethyl acetate, toluene, methyl Ethyl Ketone (MEK), methyl isobutyl ketone (MIBK), cyclopentanone, cyclohexanone.

The resin concentration of the organic solvent solution is preferably 3 to 20 parts by weight based on 100 parts by weight of the solvent. With such a resin concentration, a uniform coating film can be formed in close contact with the first retardation layer.

The thickness of the heat and moisture resistant layer is preferably 500nm to 5. Mu.m, more preferably 800nm to 4. Mu.m, and still more preferably 1 μm to 3. Mu.m. Even if the heat-resistant and moisture-resistant layer has such a very small thickness, a polarizing plate with a retardation layer having excellent durability even under severe high-temperature and high-humidity environments can be realized. If the thickness of the heat and moisture resistant layer is too small, the heat and moisture resistant layer itself may be difficult to form, and the effect may be insufficient even if the heat and moisture resistant layer is formed. Even if the thickness of the heat and moisture resistant layer is too thick, there is a possibility that curling occurs due to curing shrinkage, making the heat and moisture resistant layer itself difficult to form, or the heat and moisture resistant layer is not sufficiently cured, and functions as a fragile layer instead.

The heat and moisture resistant layer is typically formed by applying a composition for forming a heat and moisture resistant layer to the first phase difference layer, and hardening or curing the applied film. Specifically, the first layer is formed by applying a composition forming a layer to the second main surface of the first phase difference layer, and hardening or curing the applied film; the second layer (where present) is formed by applying a composition forming a layer to the first main surface of the first retardation layer, and hardening or curing the applied film. When the heat and moisture resistant layer is an active energy ray-curable layer, the coating film can be cured by irradiation of active energy rays (e.g., visible rays, ultraviolet rays, electron beams) to the coating film. When the heat-resistant moisture-resistant layer is a thermosetting layer, the coating film can be cured by heating the coating film. When the heat and moisture resistant layer is a cured layer, the coated film can be cured by heating the coated film.

The surface of the surface on which the heat and moisture resistant layer is formed (for example, the surface of the first retardation layer) may be modified in advance. Specifically, the surface energy of the formation face may be raised by surface modification in advance. The shear fracture strength of the obtained heat and moisture resistant layer can be adjusted by surface modification, for example. In addition, the adhesion between the heat and moisture resistant layer and the first retardation layer can be improved. The surface modification is performed by, for example, corona treatment or plasma treatment. They may be used alone or in combination.

G. Image display device

The polarizing plate with a retardation layer described above can be applied to an image display device. Accordingly, the embodiment of the present invention also includes an image display device using such a polarizing plate with a retardation layer. As typical examples of the image display device, a liquid crystal display device and an organic EL display device are given. The image display device according to the embodiment of the present invention typically includes the polarizing plate with the retardation layer described in the above items a to F on the visible side thereof.

Examples

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. The thickness is measured by the following measurement method. In addition, "parts" and "%" in examples and comparative examples are based on weight unless otherwise specified.

< Thickness >

The thickness of 10 μm or less was measured by a scanning electron microscope (manufactured by Japanese electric Co., ltd., product name "JSM-7100F"). The thickness exceeding 10 μm was measured using a digital micrometer (manufactured by ANRITSU Co., ltd., product name "KC-351C").

Example 1

(Production of polarizing plate)

An amorphous isophthalic acid-copolymerized polyethylene terephthalate film (thickness: 100 μm) having a long shape and a Tg of about 75 ℃ was used as a thermoplastic resin substrate, and one side of the resin substrate was subjected to corona treatment.

To 9:1 to 100 parts by weight of a PVA based resin obtained by mixing polyvinyl alcohol (polymerization degree: 4200, saponification degree: 99.2 mol%) and acetoacetyl-modified PVA (trade name: GOHSEFIMER, manufactured by Nippon chemical industry Co., ltd.), 13 parts by weight of potassium iodide was added, and the resultant was dissolved in water to prepare a PVA aqueous solution (coating liquid).

The PVA aqueous solution was applied to the corona treated surface of the resin substrate and dried at 60 ℃ to form a PVA-based resin layer having a thickness of 13 μm, thereby producing a laminate.

The obtained laminate was uniaxially stretched to 2.4 times in the machine direction (longitudinal direction) in an oven at 130 ℃.

Subsequently, the laminate was immersed in an insolubilization bath (an aqueous boric acid solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40 ℃ for 30 seconds (insolubilization treatment).

Then, the laminate was immersed in a dyeing bath having a liquid temperature of 30 ℃ (an aqueous iodine solution obtained by mixing iodine and potassium iodide in 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 monomer transmittance (Ts) of the finally obtained polarizer became a desired value (dyeing treatment).

Subsequently, the laminate was immersed in a crosslinking bath (an aqueous boric acid solution obtained by mixing 3 parts by weight of potassium iodide with 100 parts by weight of water and 5 parts by weight of boric acid) at a liquid temperature of 40 ℃ for 30 seconds (crosslinking treatment).

Thereafter, the laminate was immersed in an aqueous boric acid solution (boric acid concentration: 4 wt% and potassium iodide concentration: 5 wt%) at a liquid temperature of 70 ℃ and uniaxially stretched (in-water stretching treatment) between rolls having different peripheral speeds so that the total stretching ratio became 5.5 times.

Thereafter, the laminate was immersed in a washing bath (aqueous solution obtained by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 20 ℃.

Thereafter, the laminate was dried in an oven maintained at about 90 ℃ while being brought into contact with a SUS heated roller maintained at a surface temperature of about 75 ℃ (drying shrinkage treatment).

In this way, a polarizer having a thickness of about 5 μm was formed on the resin substrate.

An HC-TAC film was attached as a visible side protective layer to the surface (surface opposite to the resin base) of the obtained polarizer via an ultraviolet curable adhesive. Further, the HC-TAC film is a film in which a hard coat layer (thickness: 7 μm) is formed on a triacetyl cellulose (TAC) film (thickness: 25 μm), and is bonded so that the TAC film becomes the polarizer side. Then, the resin substrate was peeled off to obtain a polarizing plate having a constitution of an HC-TAC film/polarizer. The shrinkage of the HC-TAC film after 240 hours at 85℃was 0.03%.

(Production of retardation film constituting first retardation layer)

The polymerization was carried out using a batch polymerization apparatus comprising two vertical reactors equipped with stirring blades and a reflux cooler controlled at 100 ℃. 29.60 parts by mass (0.046 mol) of bis [9- (2-phenoxycarbonylethyl) fluoren-9-yl ] methane, 29.21 parts by mass (0.200 mol) of Isosorbide (ISB), 42.28 parts by mass (0.139 mol) of Spiroglycol (SPG), 63.77 parts by mass (0.298 mol) of diphenyl carbonate (DPC), and 1.19X10 ^-2 parts by mass (6.78X10 ^-5 mol) of calcium acetate monohydrate as a catalyst were added. The inside of the reactor was subjected to nitrogen substitution under reduced pressure, and then heated by a heat medium, and stirring was started at a point in time when the internal temperature reached 100 ℃. The internal temperature was brought to 220℃40 minutes after the start of the temperature increase, and the pressure was reduced while the temperature was kept at that temperature, and 13.3kPa was reached after the temperature was 220℃for 90 minutes. The phenol vapor by-produced together with the polymerization reaction was introduced into a reflux condenser at 100℃to return a plurality of monomer components contained in the phenol vapor to the reactor, and the uncondensed phenol vapor was introduced into a condenser at 45℃to be recovered. Nitrogen gas was introduced into the 1 st reactor, and once the pressure was restored to the atmospheric pressure, the oligomerization reaction liquid in the 1 st reactor was transferred to the 2 nd reactor. Then, the temperature rise and pressure reduction in the 2 nd reactor were started, and the internal temperature was 240℃and the pressure was 0.2kPa over 50 minutes. Thereafter, polymerization is carried out until a specific stirring power is reached. Nitrogen is introduced into the reactor at a point of time when a specific power is reached to restore the pressure, and the produced polyester carbonate-based resin is extruded into water, and the pellet is obtained by cutting the strands.

The obtained polyester-carbonate resin (pellet) was dried under vacuum at 80℃for 5 hours, and then a film-forming apparatus comprising a single screw extruder (manufactured by Toshiba machinery Co., ltd., barrel set temperature: 250 ℃), a T-die (width: 200mm, set temperature: 250 ℃), a cooling roll (set temperature: 120 ℃ C. To 130 ℃ C.), and a winder was used to prepare a long resin film having a thickness of 135. Mu.m. The obtained long resin film was stretched in the width direction at a stretching temperature of 133℃and a stretching ratio of 2.8 times to obtain a retardation film having a thickness of 48. Mu.m. The Re (550) of the obtained retardation film was 141nm, re (450)/Re (550) was 0.82, and the nz coefficient was 1.12.

(Production of liquid Crystal alignment cured layer constituting second phase Difference layer)

A liquid crystal coating liquid was prepared by dissolving 20 parts by weight of a side chain type liquid crystal polymer represented by the following chemical formula (I) (wherein numerals 65 and 35 in the formula represent mol% of monomer units, and the polymer is represented by a block polymer for convenience: weight average molecular weight 5000), 80 parts by weight of a polymerizable liquid crystal (manufactured by BASF corporation: trade name PaliocolorLC 242) exhibiting a nematic liquid crystal phase, and 5 parts by weight of a photopolymerization initiator (manufactured by Ciba SPECIALITY CHEMICALS corporation: trade name Irgacure 907) in 200 parts by weight of cyclopentanone. Then, the coating liquid was coated on the PET substrate subjected to the vertical alignment treatment by a bar coater, and then dried by heating at 80 ℃ for 4 minutes, thereby aligning the liquid crystal. The liquid crystal layer was irradiated with ultraviolet light to cure the liquid crystal layer, whereby a liquid crystal alignment cured layer (thickness: 3 μm) exhibiting refractive index characteristics of nz > nx=ny was formed on the substrate.

(Preparation of ultraviolet-curable adhesive 1)

An ultraviolet curable adhesive 1 was prepared by mixing 5 parts of 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane (product name "KBM-303" manufactured by Xinyue chemical Co., ltd.), 35 parts of 4-hydroxybutyl acrylate (product name "manufactured by Osaka organic chemical Co., ltd.), 24 parts of neopentyl glycol diacrylate (product name" LIGHT ACRYLATE NP-A "manufactured by Kyowa chemical Co., ltd.), 10 parts of isocyanuric acid EO-modified triacrylate (product name" ARONIX M-315 "manufactured by east Asian Synthesis Co., ltd.), 5 parts of pentaerythritol triacrylate (product name" A-TMM-3LM-N "manufactured by Xinzhongcun chemical Co., ltd.), 15 parts of urethane-based acrylic oligomer (product name" UV3000B "manufactured by Mitsubishi chemical Co., ltd.), 3 parts of photopolymerization initiator (product name" Omnirad 184 "manufactured by IGM RESINS Co., ltd.), 2 parts of photopolymerization initiator (product name" CPI-100P ") and 1 part of boric acid (Fuji and photo-pure chemical Co.).

(Production of polarizing plate with retardation layer)

The liquid crystal alignment cured layer was bonded to one side of the retardation film using the ultraviolet curable adhesive 1. Specifically, an ultraviolet-curable adhesive was applied to a retardation film so that the thickness after curing became 1 μm, and the ultraviolet-curable adhesive was cured by irradiation with ultraviolet light in a nitrogen atmosphere so that the cumulative light amount became 900mJ/cm ², and a liquid crystal alignment cured layer was bonded to one side of the retardation film via an adhesive layer.

Then, the above-mentioned polarizing plate was bonded to the other side of the retardation film via an acrylic pressure-sensitive adhesive layer having a thickness of 5 μm, to obtain a polarizing plate with a retardation layer.

Example 2

A polarizing plate with a retardation layer was obtained in the same manner as in example 1, except that the coated surface of the retardation film was subjected to corona treatment in advance when the uv curable adhesive was applied to the retardation film.

Example 3

A polarizing plate with a retardation layer was obtained in the same manner as in example 1, except that a hard coat layer shown below was provided on the retardation film before the polarizing plate was bonded to the retardation film.

(Preparation of hard coating)

A composition for forming a hard coat layer was prepared by diluting 13 parts of urethane acrylate (product name "NK oligo UA-53H" manufactured by Xinzhou chemical Co., ltd.), 17 parts of pentaerythritol triacrylate (product name "Viscoat #300" manufactured by Osaka organic chemical Co., ltd.), 70 parts of ethoxylated glycerol triacrylate (product name "A-GLY-9E" manufactured by Xinzhou chemical Co., ltd.), and 3 parts of photopolymerization initiator (product name "Omnirad 907" manufactured by IGM RESINS Co., ltd.) with a mixed solvent of cyclopentanone/toluene. The composition for forming a hard coat layer was applied to a retardation film using a bar coater so that the thickness after curing became 2. Mu.m, heated at 60℃for 1 minute, and then irradiated with ultraviolet rays under a nitrogen atmosphere so that the cumulative light amount became 250mJ/cm ², thereby forming a hard coat layer (HC layer) having a thickness of 2. Mu.m.

Example 4

A polarizing plate with a retardation layer was obtained in the same manner as in example 2, except that the HC layer was provided on the retardation film before the polarizing plate was bonded to the retardation film.

Example 5

A polarizing plate with a retardation layer was obtained in the same manner as in example 1, except that the above HC layer was provided on the retardation film before the liquid crystal alignment cured layer was laminated on the retardation film, the liquid crystal alignment cured layer was laminated using an ultraviolet-curable adhesive 2 shown below instead of the ultraviolet-curable adhesive 1, and the above HC layer was provided on the retardation film before the polarizing plate was laminated on the retardation film.

(Preparation of ultraviolet-curable adhesive 2)

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Comparative example 1

A polarizing plate with a retardation layer was obtained in the same manner as in example 1, except that the ultraviolet-curable adhesive 2 was used instead of the ultraviolet-curable adhesive 1 to bond a liquid crystal alignment cured layer.

Comparative example 2

A polarizing plate with a retardation layer was obtained in the same manner as in example 1, except that the above HC layer was provided on the retardation film before the liquid crystal alignment cured layer was laminated on the retardation film, and the liquid crystal alignment cured layer was laminated using an ultraviolet curable adhesive 2 shown below instead of the ultraviolet curable adhesive 1.

Comparative example 3

A polarizing plate with a retardation layer was obtained in the same manner as in example 1, except that the ultraviolet-curable adhesive 2 was used instead of the ultraviolet-curable adhesive 1 to bond a liquid crystal alignment cured layer, and the HC layer was provided on the retardation film before bonding the polarizing plate to the retardation film.

The following evaluation was performed for each example and comparative example. The evaluation results are summarized in table 1.

< Evaluation >

1. Shear fracture Strength

For each of examples and comparative examples, the shear fracture strength of the layers (first layer, second layer) formed on the surface of the retardation film was measured using a diagonal cutting device "saics EN" manufactured by DAIPLA WINTES corporation. The cutting width of the cutting blade for oblique cutting used for measurement was set to 1mm, the rake angle was set to 20 °, and the relief angle was set to 10 °. The measurement was performed in a constant speed mode (horizontal speed of the cutter 10 μm/sec, vertical speed of 0.1 μm/sec) at 23 ℃.

The shear fracture strength FS (MPa) can be calculated from the horizontal force FH acting on the cutting blade when the layer to be measured is obliquely cut, the area D of the shearing surface, and the shearing angle θ by the following formula. In the oblique cutting of the layer to be measured, the maximum value of FS expressed in a region having a depth of 30% to 70% from the surface on the side where the blade is inserted (the surface on the opposite side to the retardation film) is used as the shear fracture strength of each layer.

FS＝(FH/2D)cotθ

Hast assay

The obtained polarizing plate with a retardation layer was subjected to an accelerated test concerning durability under a high-temperature and high-humidity environment, i.e., HAST test. HAST test was performed in accordance with JIS C60068. Specifically, the polarizing plate with the retardation layer was heated and humidified by placing it in an oven controlled at 110 ℃ and 85% rh for 36 hours, and the state of the polarizing plate with the retardation layer after the heating and humidification was visually observed, and evaluated according to the following criteria. The results are shown in Table 1.

Good: no cracks and peeling were confirmed

The following are permissible: confirming slight cracking or peeling

Poor: obvious crack and/or confirmed peeling

TABLE 1

As is clear from table 1, the polarizing plate with the retardation layer of the example was inhibited from cracking and peeling even under severe high-temperature and high-humidity environments. In each of the examples and comparative examples, HAST test was performed without the liquid crystal alignment cured layer, but the results were the same as described above regardless of the presence or absence of the liquid crystal alignment cured layer.

Industrial applicability

The polarizing plate with a retardation layer of the present invention can be suitably used for an image display device (typically, a liquid crystal display device, an organic EL display device).

Symbol description

10. Polarizing plate

11. Polarizer

12. Protective layer

21. First phase difference layer

22. Second phase difference layer

31. First layer

32. Second layer

100. A polarizing plate with a retardation layer.

Claims

1. A polarizing plate with a retardation layer, comprising:

A first phase difference layer having a first main surface and a second main surface facing each other;

a polarizer disposed on the first principal surface side of the first retardation layer; and

A first layer disposed on the second principal surface side of the first phase difference layer;

The first retardation layer is formed of a stretched film of a resin film and satisfies the relationship Re (450) < Re (550),

The first layer is a resin layer, the shear fracture strength is more than 85MPa,

2. A polarizing plate with a retardation layer, comprising:

a polarizer disposed on the first principal surface side of the first retardation layer;

a first layer disposed on the second principal surface side of the first phase difference layer; and

A second layer disposed on the first principal surface side of the first phase difference layer;

The first layer is a resin layer, the shear fracture strength is more than 60MPa,

The second layer is a resin layer, the shear fracture strength is more than 60MPa,

3. The polarizing plate with a retardation layer as claimed in claim 1 or 2, wherein Re (550) of the first retardation layer is 100nm to 200nm, and an angle formed between a slow axis of the first retardation layer and an absorption axis of the polarizer is 40 ° to 50 ° or 130 ° to 140 °.

4. The polarizing plate with a retardation layer as claimed in any one of claims 1 to 3,

Having a second phase difference layer disposed on the second main surface side of the first phase difference layer, wherein refractive index characteristics show a relationship of nz > nx=ny,

The first layer is disposed between the first phase difference layer and the second phase difference layer.

5. The polarizing plate with a retardation layer as claimed in claim 4, wherein the first layer functions as an adhesive layer.

6. The polarizing plate with a retardation layer as claimed in any one of claims 1 to 5, wherein the first retardation layer contains a resin having positive refractive index anisotropy, the resin comprising at least one bonding group selected from the group consisting of a carbonate bond and an ester bond, and at least one structural unit selected from the group consisting of a structural unit represented by the following general formula (1) and a structural unit represented by the following general formula (2);

7. The polarizing plate with a retardation layer as claimed in any one of claims 1 to 6,

Which has a protective layer disposed on the opposite side of the polarizer from the first phase difference layer,

The shrinkage of the protective layer after being placed at 85 ℃ for 240 hours is lower than 0.05%.

8. The polarizing plate with a retardation layer as claimed in claim 7, wherein the protective layer is composed of a triacetyl cellulose film or a cycloolefin resin film.

9. An image display device provided with the polarizing plate with a retardation layer as claimed in any one of claims 1 to 8.