A polarizing plate with a phase retardation layer and an image display device including the polarizing plate with the phase retardation layer.

Abstract

This invention provides a polarizing plate with a phase retardation layer that suppresses phase and color unevenness in harsh high-temperature and high-humidity environments. The polarizing plate with a phase retardation layer according to an embodiment of this invention comprises: a polarizing plate including polarizing elements; a first phase retardation layer composed of an extended film of a polycarbonate resin film; and a second phase retardation layer with a shear strength T of 15 MPa or higher.

Description

Technical Field

[0001] The present invention relates to a polarizing plate with a phase retardation layer and an image display device comprising the polarizing plate with the phase retardation layer. Prior Technology

[0002] Image display devices, represented by liquid crystal displays and electroluminescent (EL) displays (e.g., organic EL displays and inorganic EL displays), are rapidly becoming widespread. In these image display devices, polarizing plates with retardation layers are used to improve display characteristics and reduce reflections. Polarizing plates with retardation layers typically use polarizing elements and retardation films (typically λ / 4 plates). As the resin film constituting the retardation film, polycarbonate-based resin films that have undergone stretching treatment are known (e.g., Patent Document 1). It is known that in retardation films composed of polycarbonate-based resin films, phase difference and color difference inhomogeneity can occur under high temperature and high temperature and high humidity environments. Furthermore, with the increasing size of polarizing plates with retardation layers, phase difference and color difference inhomogeneity become more pronounced. [Previous Technical Documents] [Patent Literature]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-155187 Summary of the Invention

[0004] [The problem the invention aims to solve]

[0005] The present invention was made to solve the aforementioned problems. Its main objective is to provide a polarizing plate with a phase difference layer that suppresses phase difference and color unevenness under harsh high temperature and high humidity environments. [Technical means to solve the problem]

[0006] The polarizing plate with a phase retardation layer according to an embodiment of the present invention comprises: a polarizing plate including a polarizing element; a first phase retardation layer composed of an extended film of a polycarbonate resin film; and a second phase retardation layer having a shear breaking strength T of 15 MPa or more. In one embodiment, the puncture elastic modulus of the second phase difference layer is 50 g / mm or more. In one embodiment, the first phase difference layer functions as a λ / 4 plate with an in-plane phase difference Re(550) of 100 nm to 190 nm, and satisfies Re(450) / Re(550)<1. The angle between the slow axis of the first phase difference layer and the absorption axis of the polarizing element is 40º to 50º. In one embodiment, the second phase difference layer is composed of a resin film containing a polymer exhibiting negative birefringence. In one embodiment, the polymer system exhibiting negative birefringence is selected from at least one of the group consisting of acrylic resins, styrene resins, and maleimide resins. In one embodiment, the second phase difference layer satisfies nx=ny>nz or nz>nx=ny. In one embodiment, the polarizing plate with the phase retardation layer is elongated, and the first phase retardation layer is an obliquely extended film. In one embodiment, the first phase difference layer and the second phase difference layer are laminated via an adhesive layer. Another aspect of the present invention provides an image display device. This image display device includes the aforementioned polarizing plate with a phase retardation layer. [Effects of the Invention]

[0007] According to embodiments of the present invention, a polarizing plate with a phase retardation layer can be provided to suppress phase difference and color unevenness under harsh high-temperature and high-temperature and high-humidity environments. Furthermore, even when scaled up, the polarizing plate with the phase retardation layer of the present invention can still suppress phase difference and color unevenness under harsh high-temperature and high-temperature and high-humidity environments. Therefore, it can also be suitably used in larger image display devices used under harsh conditions, such as automotive image display devices. Simple Explanation of the Diagram

[0008] Figure 1 is a schematic cross-sectional view of a polarizing plate with a phase retardation layer according to one embodiment of the present invention. Figure 2 is a schematic diagram illustrating the specific order for determining the shear failure strength T. Implementation

[0009] The embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

[0010] (Definitions of terms and symbols) The definitions of terms and symbols used in this specification are as follows. (1) Refractive index (nx, ny, nz) "nx" is the refractive index in the direction where the in-plane refractive index is at its maximum (i.e., the slow axis direction), "ny" is the refractive index in the direction orthogonal to the slow axis (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction. (2) In-plane phase difference (Re) "Re(λ)" is the in-plane phase difference measured at 23°C using light with a wavelength of λ nm. For example, "Re(550)" is the in-plane phase difference measured at 23°C using light with a wavelength of 550 nm. Re(λ) is calculated using the formula: Re(λ) = (nx - ny) × d when the thickness of the layer (film) is set to d (nm). (3) Phase difference (Rth) in the thickness direction "Rth(λ)" is the phase difference in the thickness direction measured using light with a wavelength of λ nm at 23°C. For example, "Rth(50)" is the phase difference in the thickness direction measured using light with a wavelength of 550 nm at 23°C. Rth(λ) is calculated from the formula: Rth(λ) = (nx - nz) × d when the thickness of the layer (film) is set to d (nm). (4) Nz coefficient The Nz coefficient is obtained by Nz = Rth / Re. (5) Angle When an angle is mentioned in this specification, the angle includes both clockwise and counterclockwise angles relative to a reference direction. Therefore, for example, "45º" refers to ±45º.

[0011] A. Overall structure of a polarizing plate with a phase retardation layer Figure 1 is a schematic cross-sectional view of a polarizing plate with a phase retardation layer according to an embodiment of the present invention. The polarizing plate 100 with a phase retardation layer shown in the figure has, in sequence from the viewing side, a polarizing plate 10, a first phase retardation layer 20, and a second phase retardation layer 30. The second phase retardation layer 30 may also be disposed between the polarizing plate 10 and the first phase retardation layer 20. The second phase retardation layer 30 is preferably adjacent to the first phase retardation layer 20. The polarizing plate 10 typically includes a polarizing element 11 and protective layers 12 and 13 disposed on both sides of the polarizing element 11. The protective layer 13 may also be omitted. For example, when the first phase retardation layer 20 can also function as a protective layer, the protective layer 13 may also be omitted. The components constituting the polarizing plate with the phase retardation layer can be laminated via any suitable adhesive layer (not shown). Specific examples of adhesive layers include adhesive layers and bonding agents. The first phase retardation layer 20 and the second phase retardation layer 30 are preferably laminated via an adhesive layer (not shown). The first retardation layer 20 is composed of an extended film of a polycarbonate-based resin film. The second retardation layer 30 has a shear strength T of 15 MPa or higher. The extended film of the polycarbonate-based resin film can exhibit phase difference and color unevenness under harsh high-temperature and high-humidity environments. By using a retardation layer with a shear strength T of 15 MPa or higher as the second retardation layer, a polarizing plate with a retardation layer can be provided that maintains its excellent properties even when using an extended film of the polycarbonate-based resin film as the retardation layer, and suppresses phase difference and color unevenness under harsh high-temperature and high-humidity environments. Specifically, the extended film of the polycarbonate-based resin film expands due to heat and moisture absorption under harsh high-temperature and high-humidity environments, and may subsequently shrink. Near the center of the extended film of the polycarbonate-based resin film, shrinkage stress concentrates, and the phase difference may further increase. Furthermore, at the ends of the extended film of the polycarbonate resin film, such as the slow-axis end of the resin film, shrinkage stress can be mitigated by the adhesive layer or tack layer used for lamination. Therefore, at the ends of the extended film of the polycarbonate resin film, compared to the vicinity of the center, the phase difference change caused by the expansion and contraction of the film is reduced. As a result, phase difference inhomogeneity and color inhomogeneity may occur within the surface of the extended film of the polycarbonate resin film. In an embodiment of the present invention, a phase difference layer with a shear breaking strength T of 15 MPa or higher is used as the second phase difference layer. By using a phase difference layer with a shear breaking strength T of 15 MPa or higher, expansion of the extended film of the polycarbonate resin film due to heat and water absorption under harsh high-temperature and high-temperature and high-humidity environments can be suppressed. The result is a polarizing plate with a phase retardation layer that maintains its excellent properties even when using an extended film of polycarbonate resin film as a phase retardation layer, and suppresses phase retardation and color unevenness under harsh high-temperature and high-temperature and high-humidity environments. In this specification, "adjacent" includes not only direct adjacency but also adjacency separated by any bonding layer.

[0012] As described above, the shear strength T of the second retardation layer is 15 MPa or higher. A resin film with a shear strength T of 15 MPa or higher is typically used as the second retardation layer. By using a resin film with a shear strength T of 15 MPa or higher as the second retardation layer, a polarizing plate with a retardation layer can be provided that maintains its excellent properties even when using an extended film of a polycarbonate-based resin film as the retardation layer, and suppresses phase difference and color difference in harsh high-temperature and high-temperature and high-humidity environments. The shear strength T of the second retardation layer is preferably 20 MPa or higher, more preferably 25 MPa or higher, further preferably 30 MPa or higher, and particularly preferably 35 MPa or higher. Furthermore, the shear strength T of the second retardation layer is, for example, 100 MPa or lower. The shear strength T is the force required to cut (break) the layers of a single film or a laminate, and can be obtained, for example, using SAICAS (Surface and Interface Cutting Analysis System). Refer to Figure 2 to illustrate the specific sequence for determining the shear failure strength. Figure 2 shows a laminate containing a polarizing plate, a first retardation layer, and a second retardation layer, arranged from top to bottom. The shear strength obtained by oblique cutting this laminate using a precision oblique cutting device (e.g., the SAICAS DN-20 model manufactured by Daipla Wintes) is the shear failure strength. Oblique cutting can be performed by making the cutting edge move in a biaxial direction (horizontal and vertical directions). The shear failure strength T (MPa) is obtained by the following formula. T(MPa)=FH(kN) / (2×Wd(m 2)×cot ) Here, FH is the horizontal load generated by the blade, W is the width of the blade (m), and d is the vertical displacement of the blade (m). This refers to the shearing angle. Furthermore, the shearing angle can vary depending on the cutting conditions and the material of the object being cut, but it is approximately 45º.

[0013] In one embodiment, an adhesive layer is disposed as the outermost layer of the polarizing plate 100 with the retardation layer (for example, disposed on the surface of the second retardation layer 30 of the example without the first retardation layer 20), which can be attached to an image display device (essentially an image display unit). Practically, it is preferable to temporarily attach a release liner to the surface of the adhesive layer before supplying the polarizing plate with the retardation layer to use. By temporarily attaching the release liner, the adhesive layer can be protected during the period before actual use, and the polarizing plate with the retardation layer can be rolled up.

[0014] The polarizing plate with the retardation layer can be a single sheet or a strip. In this specification, "strip" refers to a long, thin shape with a length sufficient to match its width, such as a long shape with a length greater than 10 times its width, preferably greater than 20 times. When the polarizing plate is a strip, it can be laminated with a retardation layer fabricated by oblique extension in a roll-to-roll manner, simplifying the manufacturing process. The strip-shaped polarizing plate with the retardation layer can be wound into a roll.

[0015] The thickness of the polarizing plate with the retardation layer can be set to any suitable value. In one embodiment, the total thickness of the polarizing plate with the retardation layer is preferably 250 μm or less, more preferably 140 μm or less, further preferably 120 μm or less, further preferably 100 μm or less, further preferably 90 μm or less, and particularly preferably 85 μm or less. The total thickness of the polarizing plate with the retardation layer can, for example, be 30 μm or more. Furthermore, the total thickness of the polarizing plate with the retardation layer refers to the sum of the thickness of the polarizing plate, the retardation layers (the first retardation layer and the second retardation layer), and the adhesive layer used to bond these layers (i.e., the total thickness of the polarizing plate with the retardation layer does not include the thickness of the adhesive layer disposed as the outermost layer and the release liner that can be temporarily adhered to its surface).

[0016] The following section will explain in more detail the constituent elements of a polarizing plate with a phase retardation layer.

[0017] B. Polarizing plate B-1. Polarizing element A polarizing element is typically composed of a resin film containing a dichroic substance (represented by iodine). Any suitable resin film suitable for use as a polarizing element can be used as the resin film. A polyvinyl alcohol-based resin (hereinafter referred to as "PVA-based resin") film is representative of the resin film. The resin film can be a single layer or a laminate of two or more layers.

[0018] As a specific example of a polarizing element composed of a single-layer resin film, a polarizing element in which a PVA-based resin film has undergone dyeing and stretching treatment using iodine (typically uniaxial stretching) can be cited. The aforementioned dyeing using iodine is performed, for example, by immersing the PVA-based resin film in an aqueous iodine solution. The stretching ratio of the aforementioned uniaxial stretching is preferably 3 to 7 times. Stretching can be performed after dyeing, or simultaneously with dyeing. Alternatively, dyeing can be performed after stretching. Depending on the needs, the PVA-based resin film may undergo swelling treatment, crosslinking treatment, washing treatment, drying treatment, etc. For example, by immersing the PVA-based resin film in water for washing before dyeing, not only can stains or anti-blocking agents on the surface of the PVA-based resin film be washed away, but the PVA-based resin film can also swell to prevent uneven dyeing.

[0019] As a specific example of a polarizing element obtained using a laminate, examples include a laminate consisting of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a laminate consisting of a resin substrate and a PVA-based resin layer coated on the resin substrate. A polarizing element obtained using a laminate consisting of a resin substrate and a PVA-based resin layer coated on the resin substrate can be manufactured, for example, by coating a PVA-based resin solution onto a resin substrate, drying it 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; and stretching and dyeing the laminate to form a polarizing element from the PVA-based resin layer. In this embodiment, it is preferable to form a polyvinyl alcohol-based resin layer comprising a halide and a polyvinyl alcohol-based resin on one side of the resin substrate. Stretching typically includes immersing the laminate in an aqueous boric acid solution for stretching. Furthermore, the stretching can be further included, as needed, in the form of aerial stretching of the laminate at a high temperature (e.g., above 95°C) before stretching in a boric acid aqueous solution. In addition, in this embodiment, it is preferable to feed the laminate to a drying shrinkage treatment in which it is heated while being conveyed in the length direction, causing it to shrink by more than 2% in the width direction. Typically, the manufacturing method of this embodiment includes sequentially performing aerial assisted stretching, dyeing, underwater stretching, and drying shrinkage treatments on the laminate. By introducing assisted stretching, even when PVA is coated on a thermoplastic resin, the crystallinity of PVA can be improved, achieving higher optical properties. Furthermore, by simultaneously improving the alignment of PVA beforehand, problems such as decreased alignment or dissolution of PVA during immersion in water in subsequent dyeing or stretching steps can be prevented, achieving higher optical properties. Furthermore, when the PVA-based resin layer is immersed in a liquid, compared to the case where the PVA-based resin layer does not contain halides, the disorder of polyvinyl alcohol molecule alignment and the decrease in alignment can be suppressed. This improves the optical properties of polarizing elements obtained by immersing the laminate in a liquid through dyeing and water-stretching processes. Furthermore, by shrinking the laminate in the width direction using a drying shrinkage process, optical properties are further enhanced. The resulting resin substrate / polarizing element laminate can be used directly (i.e., the resin substrate can be used as a protective layer for the polarizing element), or the resin substrate can be peeled off from the resin substrate / polarizing element laminate, and an appropriate protective layer can be applied to the peeled surface according to the desired laminate before use. Details of this method for manufacturing polarizing elements are described, for example, in Japanese Patent Application Publication No. 2012-73580 (Japanese Patent No. 5414738) and Japanese Patent No. 6470455. The entire contents of these publications are incorporated herein by reference.

[0020] The thickness of the polarizing element is preferably 1 μm to 25 μm, more preferably 1 μm to 15 μm, even more preferably 1 μm to 10 μm, even more preferably 1 μm to 8 μm, and particularly preferably 2 μm to 5 μm. In embodiments of the present invention, even when using polarizing elements of the above thickness, phase difference unevenness and color unevenness of the polarizing plate with the phase difference layer can be suppressed under harsh high-temperature and high-temperature and high-humidity environments.

[0021] In one embodiment, the boric acid content of the polarizing element is preferably 20% by weight or less, more preferably 5% to 20% by weight, and even more preferably 10% to 18% by weight. When the boric acid content of the polarizing element is within this range, a polarizing plate with a phase retardation layer exhibits excellent high-temperature durability can be provided. When the boric acid content is less than 5% by weight, there is a risk of polyolefin formation and decreased durability in the polarizing element. According to embodiments of the present invention, even when placed in harsh high-temperature environments and high-temperature and high-humidity environments, phase difference changes caused by dimensional shrinkage of the polarizing plate can be suppressed, and phase difference unevenness and color unevenness can be suppressed. The boric acid content of the polarizing element can be adjusted, for example, by adjusting the boric acid content in the aqueous solution used in the following steps. The boric acid content can be determined, for example, by neutralization using the following formula as the amount of boric acid contained in each unit weight of the polarizing element.

[0022] The iodine content of the polarizing element is preferably 2% by weight or more, and more preferably 2% to 10% by weight. When the iodine content of the polarizing element is within this range, the synergistic effect with the aforementioned boric acid content can maintain the ease of curl adjustment during bonding, effectively suppress curling during heating, and improve the appearance durability during heating. In this specification, "iodine content" refers to the total amount of iodine contained in the polarizing element (PVA-based resin film). More specifically, when iodine exists in the polarizing element in the form of iodide ions (I-), iodine molecules (I2), polyiodide ions (I3-, I5-), etc., the iodine content in this specification refers to the amount of iodine containing all of these forms. The iodine content can be determined, for example, using the calibration curve method of fluorescence X-ray analysis. Furthermore, polyiodide ions exist in the polarizing element in the form of PVA-iodine complexes. By forming such complexes, dichroism can be exhibited in the wavelength range of visible light. Specifically, the PVA-triiodide complex (PVA·I₃⁻) exhibits an absorption peak near 470 nm, while the PVA-pentaiodide complex (PVA·I₅⁻) shows an absorption peak near 600 nm. This indicates that polyiodide ions can absorb light across a broad visible spectrum, depending on their morphology. On the other hand, iodide ions (I⁻) exhibit an absorption peak near 230 nm, which is essentially unrelated to visible light absorption. Therefore, polyiodide ions existing in their PVA complex state may primarily be related to the absorption performance of polarizing elements.

[0023] The polarizing element preferably exhibits absorption dichroism at any wavelength from 380 nm to 780 nm. The elemental transmittance Ts of the polarizing element is preferably 40% to 48%, more preferably 41% to 46%. The polarization P of the polarizing element is preferably 97.0% or higher, more preferably 99.0% or higher, and even more preferably 99.9% or higher. The aforementioned elemental transmittance is typically the Y value obtained after visual sensitivity correction using a UV-Vis spectrophotometer. The aforementioned polarization is typically based on the parallel transmittance Tp and orthogonal transmittance Tc obtained after visual sensitivity correction using a UV-Vis spectrophotometer, and is calculated using the following formula. Polarization (%) = {(Tp-Tc) / (Tp+Tc)} 1 / 2×100

[0024] B-2. Protective layer Protective layers 12 and 13 are formed of any suitable film that can be used as a protective layer for polarizing elements. Specific examples of materials that form the main component of the aforementioned film include cellulose resins such as triacetyl cellulose (TAC); or transparent resins such as polyester, polyvinyl alcohol, polycarbonate, polyamide, polyimide, polyether ether, polyether ether, polystyrene, polynorbornene, polyolefin, (meth)acrylate, and acetate. Also, thermosetting or UV-curing resins such as (meth)acrylate, urethane, (meth)acrylate urethane, epoxy, and silicone resins can be used. In addition, glassy polymers such as silicate polymers can also be used. Furthermore, polymer films described in Japanese Patent Application Publication No. 2001-343529 (WO01 / 37007) can also be used. As the material for this membrane, for example, a resin composition containing a thermoplastic resin having substituted or unsubstituted amide groups on the side chains and a thermoplastic resin having substituted or unsubstituted phenyl and nitrile groups on the side chains can be used. Examples include resin compositions having an alternating copolymer formed from isobutylene and N-methylmaleimide and an acrylonitrile-styrene copolymer. The polymer membrane can, for example, be an extruded product of the above resin composition.

[0025] A polarizing plate with a phase retardation layer is typically disposed on the viewing side of the image display device, and a protective layer 12 is typically disposed on its viewing side. Therefore, the protective layer 12 may also be subjected to surface treatments such as hard coating, anti-reflection treatment, anti-adhesion treatment, and anti-glare treatment as needed.

[0026] The thickness of the protective layer is preferably 10 μm to 50 μm, more preferably 10 μm to 30 μm. Furthermore, when surface treatment is performed, the thickness of the outer protective layer (protective layer 12) includes the thickness of the surface treatment layer.

[0027] C. First phase difference layer The first retardation layer is an extended film of a 20-series polycarbonate resin film. The extended film of the polycarbonate resin film may exhibit phase retardation and color unevenness under harsh high-temperature and high-humidity environments. According to embodiments of the present invention, a polarizing plate with a retardation layer can be provided that maintains its excellent properties even when using an extended film of a polycarbonate resin film as the retardation layer, and suppresses phase retardation and color unevenness under harsh high-temperature and high-humidity environments.

[0028] The first retardation layer 20 may have any appropriate optical and / or mechanical properties according to the purpose. The first retardation layer 20 typically has a slow axis. In one embodiment, the angle θ formed between the slow axis of the first retardation layer 20 and the absorption axis of the polarizing element 11 is preferably 40° to 50°, more preferably 42° to 48°, and still more preferably about 45°. When the angle θ is within this range, by making the first retardation layer a λ / 4 plate as described later, a polarizing plate with a phase difference layer having very excellent circular polarization characteristics (and as a result, very excellent antireflection characteristics) can be obtained.

[0029] The first retardation layer preferably has a refractive index characteristic satisfying nx > ny, and more preferably shows a relationship of nx > ny ≥ nz. Typically, the first retardation layer is provided to impart antireflection characteristics to the polarizing plate and can function as a λ / 4 plate in one embodiment. At this time, the in-plane retardation Re(550) of the first retardation layer is preferably 100 nm to 190 nm, more preferably 110 nm to 170 nm, and still more preferably 130 nm to 160 nm. Furthermore, "ny = nz" here not only includes the case where ny and nz are exactly equal, but also includes the case where they are substantially equal. Therefore, within the range that does not impair the effects of the present invention, there may be a case where ny < nz.

[0030] The Nz coefficient of the first retardation layer is preferably 0.9 to 3, more preferably 0.9 to 2.5, still more preferably 0.9 to 1.5, and particularly preferably 0.9 to 1.3. By satisfying this relationship, when the obtained polarizing plate with a phase difference layer is used in an image display device, a very excellent reflected hue can be achieved.

[0031] The first retardation layer may show an inverse dispersion wavelength characteristic in which the phase difference value increases corresponding to the wavelength of the measurement light, may show a positive wavelength dispersion characteristic in which the phase difference value decreases corresponding to the wavelength of the measurement light, or may show a flat wavelength dispersion characteristic in which the phase difference value hardly changes due to the wavelength of the measurement light. In one embodiment, the first retardation layer shows an inverse dispersion wavelength characteristic. At this time, Re(450) / Re(550) of the retardation layer is preferably less than 1, more preferably 0.8 or more and less than 1, and still more preferably 0.8 or more and 0.95 or less. With such a configuration, very excellent antireflection characteristics can be achieved.

[0032] The first phase retardation layer comprises a resin with an absolute value of photoelasticity preferably below 2 × 10⁻¹¹ m² / N, more preferably 2.0 × 10⁻¹³ m² / N to 1.5 × 10⁻¹¹ m² / N, and even more preferably 1.0 × 10⁻¹² m² / N to 1.2 × 10⁻¹¹ m² / N. When the absolute value of the photoelasticity is within this range, phase difference changes are less likely to occur when shrinkage stress occurs during heating. As a result, thermal unevenness in the obtained image display device can be effectively prevented.

[0033] As described above, the first retardation layer is composed of an extended film of a polycarbonate resin film. In one embodiment, the thickness of the first retardation layer is preferably 50 μm or less, more preferably 10 μm to 40 μm, and even more preferably 20 μm to 30 μm. By utilizing a polycarbonate resin film of this thickness, the first retardation layer can suppress curling and also contribute to improved bending durability and reflective hue.

[0034] The first retardation layer 20 is composed of a polycarbonate resin film, such as a polycarbonate-based resin or a polyester-carbonate-based resin (hereinafter sometimes simply referred to as polycarbonate-based resin). When the first retardation layer is composed of a resin film exhibiting inverse wavelength dispersion characteristics, a polycarbonate-based resin or a polyester-carbonate-based resin is preferable. Furthermore, the polycarbonate-based resin can also be combined (e.g., blended, copolymerized) with polyester-based resins, polyvinyl acetal-based resins, polyaryl ester-based resins, cyclic olefin-based resins, cellulose-based resins, polyvinyl alcohol-based resins, polyamide-based resins, polyimide-based resins, polyether-based resins, polystyrene-based resins, acrylic-based resins, etc.

[0035] As the aforementioned polycarbonate resin, any suitable polycarbonate resin can be used as long as the effects of the present invention are achieved. For example, the polycarbonate resin may comprise: structural units derived from genus dihydroxy compounds; structural units derived from isosorbide dihydroxy compounds; and structural units derived from at least one dihydroxy compound selected from the group consisting of alicyclic diols, alicyclic diethanols, di-, tri-, or polyethylene glycols, and alkyl diols or spirodiols. Preferably, the polycarbonate resin comprises: structural units derived from genus dihydroxy compounds; structural units derived from isosorbide dihydroxy compounds; and structural units derived from alicyclic diethanols and / or structural units derived from di-, tri-, or polyethylene glycols; more preferably, it comprises: structural units derived from genus dihydroxy compounds; structural units derived from isosorbide dihydroxy compounds; and structural units derived from di-, tri-, or polyethylene glycols. The polycarbonate resin may also, as needed, comprise structural units derived from other dihydroxy compound sources. Furthermore, details of the polycarbonate resins that can be preferably used in the embodiments of the present invention are described, for example, in Japanese Patent Application Publication Nos. 2014-10291, 2014-26266, 2015-212816, 2015-212817, and 2015-212818, which are incorporated herein by reference.

[0036] The glass transition temperature of the aforementioned polycarbonate resin is preferably above 110°C and below 150°C, and more preferably above 120°C and below 140°C. If the glass transition temperature is too low, the heat resistance tends to deteriorate, which may cause dimensional changes after film formation, and may also reduce the image quality of the obtained organic EL panel and other image display devices. If the glass transition temperature is too high, the forming stability during film formation may deteriorate, or the transparency of the film may be damaged. Furthermore, the glass transition temperature can be determined according to JIS K 7121 (1987).

[0037] The molecular weight of the aforementioned polycarbonate resin can be expressed as reduced viscosity. Reduced viscosity is determined as follows: using dichloromethane as a solvent, the polycarbonate concentration is precisely adjusted to 0.6 g / dL, and the measurement is performed using an Ubbelohde viscometer at a temperature of 20.0℃ ± 0.1℃. The lower limit of reduced viscosity is generally preferably 0.30 dL / g, more preferably 0.35 dL / g or higher. The upper limit of reduced viscosity is generally preferably 1.20 dL / g, more preferably 1.00 dL / g, and even more preferably 0.80 dL / g. When the reduced viscosity is less than the above lower limit, a decrease in the mechanical strength of the molded article may occur. On the other hand, when the reduced viscosity is greater than the above upper limit, a decrease in flowability during molding may occur, leading to a decrease in productivity or formability.

[0038] Commercially available films can also be used as polycarbonate-based resin films. Specific examples of commercially available products include "Pure Ace WR-S", "Pure Ace WR-W", and "Pure Ace WR-M" manufactured by Teijin Corporation, and "NRF" manufactured by Nitto Denko Corporation.

[0039] The first retardation layer 20 is obtained, for example, by stretching a film formed from the aforementioned polycarbonate resin. Any suitable forming process can be used as a method for forming the film from the polycarbonate resin. Specific examples include compression molding, transfer molding, injection molding, extrusion molding, blow molding, powder molding, FRP molding, casting coating (e.g., casting), calendering, and hot pressing. Extrusion molding or casting coating is preferred because it improves the smoothness of the obtained film and achieves good optical uniformity. The forming conditions can be appropriately set according to the composition or type of resin used and the desired characteristics of the retardation layer. Furthermore, as mentioned above, since there are many commercially available film products made from polycarbonate resins, these commercially available films can also be directly used for stretching.

[0040] The thickness of the resin film (unstretched film) can be set to any appropriate value according to the required thickness of the first retardation layer, the required optical properties, the stretching conditions described later, etc. Preferably, it is 50 μm to 300 μm.

[0041] The aforementioned stretching can be performed using any suitable stretching method and conditions (e.g., stretching temperature, stretching ratio, stretching direction). Specifically, various stretching methods such as free-end stretching, fixed-end stretching, free-end shrinkage, and fixed-end shrinkage can be used individually, or simultaneously or sequentially. Regarding the stretching direction, it can be performed in various directions or dimensions such as the length direction, width direction, thickness direction, and oblique direction. The stretching temperature relative to the glass transition temperature (Tg) of the resin film is preferably Tg-30℃ to Tg+60℃, more preferably Tg-10℃ to Tg+50℃.

[0042] By appropriately selecting the above-mentioned stretching methods and stretching conditions, a phase retardation film with the desired optical properties (e.g., refractive index characteristics, in-plane phase difference, Nz coefficient) can be obtained.

[0043] In one embodiment, the retardation film is fabricated by uniaxial stretching or fixed-end uniaxial stretching of a resin film. A specific example of fixed-end uniaxial stretching is a method in which the resin film is shifted in the length direction while being stretched in the width direction (lateral direction). The stretching ratio is preferably 1.1 to 3.5 times.

[0044] In another embodiment, the extended film constituting the first retardation layer is preferably an elongated, obliquely extended film. In this embodiment, the extended film constituting the first retardation layer can be fabricated by continuously obliquely extending an elongated resin film in a direction with an angle θ relative to its length direction. By employing oblique extension, an elongated extended film having an alignment angle (with a slow axis in the direction of angle θ) with respect to the length direction of the film can be obtained. For example, when laminating with a polarizing element, this can be done in a roll-to-roll manner, simplifying the manufacturing process. Furthermore, angle θ can be the angle formed between the absorption axis of the polarizing element and the slow axis of the retardation layer in the polarizing plate with the retardation layer attached. As described above, angle θ is preferably 40º~50º, more preferably 42º~48º, and even more preferably about 45º.

[0045] As an example of a stretching machine used for oblique stretching, a tenter stretching machine can be described as one that can apply conveying force, stretching force, or traction force at different speeds in the transverse and / or longitudinal directions. Tensioning machines include transverse single-axis stretching machines, simultaneous bi-axis stretching machines, etc., but any suitable stretching machine can be used as long as it can continuously stretch a long strip of resin film obliquely.

[0046] In the aforementioned stretching machine, by appropriately controlling the speeds of the left and right sides respectively, a phase difference layer (essentially a strip-shaped phase difference film) with the desired in-plane phase difference and a slow axis in the desired direction can be obtained.

[0047] The stretching temperature of the aforementioned film can vary depending on the desired in-plane phase difference value and thickness of the retardation layer, the type of resin used, the thickness of the film used, and the stretching ratio. Specifically, the stretching temperature is preferably Tg-30℃ to Tg+30℃, more preferably Tg-15℃ to Tg+15℃, and even more preferably Tg-10℃ to Tg+10℃. By stretching at this temperature, a first retardation layer with appropriate characteristics in the embodiments of the present invention can be obtained. Furthermore, Tg is the glass transition temperature of the constituent materials of the film.

[0048] D. Second phase difference layer As described above, the shear strength T of the second retardation layer is 15 MPa or higher. By ensuring that the shear strength T of the second retardation layer is 15 MPa or higher, the expansion of the polycarbonate resin film due to heat and water absorption can be suppressed. As a result, a polarizing plate with a retardation layer can be provided that maintains its excellent properties even when using a polycarbonate resin film as a retardation layer, and suppresses phase difference and color difference in harsh high-temperature and high-temperature and high-humidity environments. The second retardation layer is typically a resin film with a shear strength T of 15 MPa or higher.

[0049] The second phase retardation layer preferably has a puncture elastic modulus of 50 g / mm or more, more preferably 52 g / mm or more, and even more preferably 55 g / mm or more. For example, the puncture elastic modulus of the second phase retardation layer is 200 g / mm or less. By ensuring the puncture elastic modulus of the second phase retardation layer is within the above range, the expansion of the first phase retardation layer, which is an extension film of the polycarbonate resin film, due to heat and water absorption can be further suppressed. In this specification, the puncture elastic modulus refers to the value obtained by dividing the force (g) before the phase retardation film breaks (or cracks) when the needle (puncture fixture) punctures perpendicularly to the main surface of the phase retardation film (the aforementioned second phase retardation layer) is perpendicular to the film's surface, by the deformation (mm) at that moment. A needle with a tip diameter of 1 mm can be used. A 0.5R needle is used. The needle speed can be set to 0.33 cm / s. The puncture modulus is measured by sandwiching a phase difference membrane between two plates with a circular hole of 15 mm or less in diameter that allows the needle to pass through. The puncture modulus can be measured at a temperature of 23°C. For example, the puncture modulus of five phase difference membranes can be measured, and their average value can be taken as the puncture modulus of the phase difference membrane. The puncture modulus can be measured using commercially available equipment. Examples of commercially available equipment include the portable compression testing machine "KES-G5 Needle Penetration Force Measurement Specification" manufactured by Kato Tech Co., Ltd., and the small benchtop testing machine "EZ Test" manufactured by Shimadzu Corporation.

[0050] The second retardation layer preferably has an elongation at break of 1% or more, more preferably 2% or more, and even more preferably 3% or more. For example, the elongation at break of the second retardation layer is 5% or less. By using a retardation layer with an elongation at break of 1% or more as the second retardation layer, a polarizing plate with a retardation layer can be provided that maintains its excellent properties even when using an extended film of a polycarbonate-based resin film as the retardation layer, and suppresses phase difference and color difference in harsh high-temperature and high-temperature and high-humidity environments. In this specification, the elongation at break of the retardation layer can be measured using a thermomechanical analysis (TMA) apparatus.

[0051] The second retardation layer 30 is preferably composed of a resin film containing a polymer exhibiting negative birefringence. Here, "exhibiting negative birefringence" means that when the polymer is aligned by extension or the like, the refractive index in the extension direction decreases relatively. In other words, it means that the refractive index in the direction orthogonal to the extension direction increases. By using a resin film containing a polymer exhibiting negative birefringence, the second retardation layer can suppress phase difference changes caused by the expansion and contraction of the first retardation layer, which is an extension film of a polycarbonate-based resin film, due to heat and water absorption.

[0052] The second retardation layer is preferably a positive C-plate whose refractive index characteristics show a relationship of nx=ny>nz or nz>nx=ny, and more preferably a relationship of nz>nx=ny. By using a positive C-plate as the second retardation layer, oblique reflections can be effectively prevented, and a wide field of view for anti-reflection is possible. The phase difference Rth(550) in the thickness direction of the second retardation layer is preferably -20 nm to -300 nm, more preferably -30 nm to -250 nm, further preferably -40 nm to -200 nm, and particularly preferably -50 nm to -150 nm. Here, "nx=ny" not only refers to the case where nx and ny are strictly equal, but also includes the case where nx and ny are substantially equal. That is, the in-plane phase difference Re(550) of the second retardation layer may not reach 10 nm.

[0053] The thickness of the second phase difference layer 30 can be set to any appropriate thickness in accordance with the above-mentioned shear failure strength T and puncture elastic modulus. The thickness of the second phase difference layer is preferably 1 μm to 30 μm, more preferably 2 μm to 25 μm, and even more preferably 3 μm to 20 μm.

[0054] Polymers exhibiting negative birefringence can be exemplified by those with side chains incorporating aromatic rings and / or carbonyl groups, or other chemical bonds or functional groups with high polarization anisotropy. Specifically, examples include acrylic resins, styrene resins, and maleimide resins. A single polymer exhibiting negative birefringence can be used, or two or more can be used in combination.

[0055] Acrylic resins can be obtained, for example, by addition polymerization of acrylate monomers. Examples of acrylic resins include polymethyl methacrylate (PMMA), polybutyl methacrylate, and polycyclohexyl methacrylate.

[0056] Styrene-based resins can be obtained, for example, by addition polymerization of styrene monomers. Examples of styrene monomers include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, p-chlorostyrene, p-nitrostyrene, p-aminostyrene, p-carboxystyrene, p-phenylstyrene, 2,5-dichlorostyrene, and p-tert-butylstyrene.

[0057] Maleimide-based resins can be obtained, for example, by addition polymerization of maleimide monomers. Examples of maleimide monomers include: N-ethylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-(2-methylphenyl)maleimide, N-(2-ethylphenyl)maleimide, N-(2-propylphenyl)maleimide, N-(2-isopropylphenyl)maleimide, N-(2,6-dimethylphenyl)maleimide, and N-(2,6-dipropylphenyl)maleimide. Maleimide, N-(2,6-diisopropylphenyl)maleimide, N-(2-methyl-6-ethylphenyl)maleimide, N-(2-chlorophenyl)maleimide, N-(2,6-dichlorophenyl)maleimide, N-(2-bromophenyl)maleimide, N-(2,6-dibromophenyl)maleimide, N-(2-biphenyl)maleimide, N-(2-cyanophenyl)maleimide, etc. Maleimide monomers can be obtained, for example, from companies such as Tokyo Chemical Industry Co., Ltd.

[0058] In addition polymerization, the birefringence properties of the obtained resin can also be controlled by substituting the side chains after polymerization, or by carrying out maleicimization or grafting reactions.

[0059] Polymers exhibiting negative birefringence can also be copolymerized with other monomers. By copolymerizing other monomers, brittleness, processability, and heat resistance can be improved. Examples of such other monomers include olefins such as ethylene, propylene, 1-butene, 1,3-butadiene, 2-methyl-1-butene, 2-methyl-1-pentene, and 1-hexene; acrylonitrile; (meth)acrylates such as methyl acrylate and methyl methacrylate; maleic anhydride; and vinyl esters such as vinyl acetate.

[0060] When the polymer exhibiting negative birefringence is a copolymer of the aforementioned styrene monomers and other monomers, the preferred blending ratio of the styrene monomer is 50 mol% to 80 mol%. When the polymer exhibiting negative birefringence is a copolymer of the aforementioned maleimide monomers and other monomers, the preferred blending ratio of the maleimide monomer is 2 mol% to 50 mol%. By blending within this range, a polymer film with excellent toughness and processability can be obtained.

[0061] As polymers exhibiting negative birefringence as described above, styrene-maleic anhydride copolymers, styrene-acrylonitrile copolymers, styrene-(meth)acrylate copolymers, styrene-maleimide copolymers, ethylene ester-maleimide copolymers, and olefin-maleimide copolymers are preferred. These polymers can be used alone or in combination of two or more. These polymers exhibit high negative birefringence and excellent heat resistance. These polymers are available, for example, from NOVA Chemicals Japan and Arakawa Chemical Industry Co., Ltd.

[0062] As for the polymer exhibiting negative birefringence, it is preferable to use a polymer having repeating units represented by the following general formula (II). Such a polymer can exhibit even higher negative birefringence and has excellent heat resistance and mechanical strength. Such a polymer can be obtained by using an N-phenyl-substituted maleimide, for example, a maleimide monomer with an N-substituent introduced as a starting material having a phenyl group having a substituent at least at the ortho position. [Chemistry 1]

[0063] In the above general formula (II), R1 to R5 each independently represent a hydrogen atom, a halogen atom, a carboxylic acid, a carboxylic acid ester, a hydroxyl group, a nitro group, or a straight-chain or branched alkyl or alkoxy group with 1 to 8 carbon atoms (but R1 and R5 are not hydrogen atoms at the same time), R6 and R7 represent hydrogen atoms or straight-chain or branched alkyl or alkoxy groups with 1 to 8 carbon atoms, and n represents an integer of 2 or more.

[0064] The polymer exhibiting negative birefringence is not limited to the aforementioned substances; cyclic olefin copolymers disclosed in Japanese Patent Application Publication No. 2005-350544, for example, can also be used. Furthermore, compositions comprising polymers and inorganic microparticles disclosed in Japanese Patent Application Publication Nos. 2005-156862 and 2005-227427 are also preferred. Moreover, these substances can be modified and reused through copolymerization, branching, crosslinking, molecular end modification (or capping), and stereoregular modification.

[0065] The resin composition forming the second phase difference layer may further contain any suitable additives as needed. Specific examples of additives include plasticizers, heat stabilizers, light stabilizers, lubricants, antioxidants, UV absorbers, flame retardants, colorants, antistatic agents, compatibilizers, crosslinking agents, and tackifiers. The type and amount of additives can be appropriately set according to the purpose. The additive content is typically about 3 to 10 parts by weight relative to 100 parts by weight of the total solids in the resin composition. If the additive content becomes excessive, it may impair the transparency of the polymer film, or the additive may seep out from the surface of the polymer film.

[0066] As a method for forming the second retardation layer, any suitable forming method can be used. Examples include compression molding, transfer molding, injection molding, extrusion molding, blow molding, powder molding, FRP molding, and solvent casting. Among these, extrusion molding and solvent casting are preferred. This is because they can produce a retardation film with high smoothness and good optical uniformity. Specifically, extrusion molding involves heating and melting a resin composition containing the aforementioned thermoplastic resin, plasticizer, and additives, and then extruding it in thin film form onto the surface of a casting roller using a T-die or similar device, followed by cooling to form the film. Solvent casting involves degassing a concentrated solution (concentrate) containing the aforementioned resin composition in a solvent, uniformly casting it in thin film form onto the surface of a metallic annular belt, rotating drum, or plastic substrate, and then evaporating the solvent to form the film. Furthermore, the forming conditions can be appropriately set according to the composition or type of resin used and the forming process.

[0067] E. Attached layer As described above, the first retardation layer and the second retardation layer are laminated via an adhesive layer. Preferably, the first retardation layer and the second retardation layer are laminated via an adhesive layer. By using an adhesive layer, the expansion of the first retardation layer, which is an extension film of the polycarbonate-based resin film, due to heat and water absorption can be further suppressed. As the adhesive for forming the adhesive layer, any suitable adhesive can be used, for example, a UV-curing adhesive. By using a UV-curing adhesive, an adhesive layer with high hardness and thin thickness can be formed.

[0068] F. Adhesive layer As the adhesive layer constituting the outermost adhesive layer (the adhesive layer between the polarizing plate with the phase retardation layer and the image display device), any suitable adhesive can be used. Examples of adhesives include rubber-based adhesives, acrylic adhesives, silicone adhesives, carbamate adhesives, vinyl alkyl ether adhesives, polyvinyl alcohol adhesives, polyvinylpyrrolidone adhesives, polyacrylamide adhesives, and cellulose adhesives. Among these adhesives, those with excellent optical transparency, suitable wettability, coagulation, and adhesion, as well as excellent weather resistance or heat resistance, are preferred. Acrylic adhesives are preferred as exhibiting these characteristics.

[0069] G. Image display device The polarizing plate with a phase retardation layer described in items A through F above is applicable to image display devices. Therefore, embodiments of the present invention include image display devices using such polarizing plates with phase retardation layers. Representative examples of image display devices include liquid crystal display devices and electroluminescent (EL) display devices (e.g., organic EL display devices and inorganic EL display devices). The image display device of the embodiments of the present invention has a polarizing plate with a phase retardation layer described in items A through F above on its viewing side. The polarizing plate with the phase retardation layer is laminated such that the phase retardation layer is on the image display unit (e.g., liquid crystal unit, organic EL unit, inorganic EL unit) side (with the polarizing element on the viewing side).

[0070] As described above, the polarizing plate with a phase retardation layer according to the embodiments of the present invention can suppress phase difference unevenness and color unevenness under harsh high-temperature and high-temperature and high-humidity environments. Furthermore, a polarizing plate with a phase retardation layer can be provided that suppresses phase difference unevenness and color unevenness even when the polarizing plate with the phase retardation layer is enlarged (e.g., a 300 mm × 410 mm polarizing plate with a phase retardation layer). Therefore, it can be preferably used as a polarizing plate with a phase retardation layer for use in large automotive image display devices that may be placed under more severe conditions. [Example]

[0071] The present invention will now be described in detail with reference to the embodiments, but the present invention is not limited to these embodiments. The methods for measuring each characteristic are described below. Furthermore, unless otherwise specified, "parts" and "%" in the embodiments and comparative examples refer to weight.

[0072] (1) Thickness Thicknesses below 10 μm were measured using an interferometric film thickness gauge (manufactured by Otsuka Electronics Co., Ltd., product name "MCPD-3000"). Thicknesses exceeding 10 μm were measured using a digital micrometer (manufactured by Anritsu Co., Ltd., product name "KC-351C").

[0073] (2) Shear failure strength T The polarizing plates with phase retardation layers obtained in Examples 1 and 2 and Comparative Example 1 were obliquely cut using a precision oblique cutting device (Daipla Wintes, "SAICAS DN-20 type"). The shear failure strength T of the second phase retardation layer (positive C plate) was determined based on the shear strength at this time. The cutting conditions are shown below. Blade: Made of single-crystal diamond Blade width: 1 mm Rake angle: 10º Horizontal speed of the blade: 1 μm / second Vertical velocity of the blade: 0.05 μm / s The shear failure strength T (MPa) of the second phase difference layer is calculated using the following formula and converted into the amount per 1 μm thickness. T(MPa)=FH(kN) / (2×Wd(m 2)×cot ) Here, FH is the horizontal load generated by the blade, W is the width of the blade (m), and d is the vertical displacement of the blade (m). It is 45º.

[0074] (3) Puncture elastic modulus For the phase difference layers obtained in Examples 3-5, the puncture modulus of elasticity was measured. A needle was installed in a portable compression testing machine (product name: KES-G5 needle penetration force test specification) manufactured by Kato Tech Co., Ltd. The needle was vertically punctured into the main surface of the phase difference layer, which was fixed between two plates with a circular hole of 11 mm diameter. The force (g) before breakage was calculated divided by the deformation (mm) at that moment. This operation was performed on five phase difference layers (samples for puncture testing), and the average value was taken as the puncture modulus of elasticity of the phase difference layer. A needle with a tip diameter of 1 mm was used. A 0.5R needle was used. The needle speed was 0.33 cm / second.

[0075] (4) Uneven color The polarizing plate with the retardation layer obtained in the examples and comparative examples was cut into sections 50 mm long and 150 mm wide, and used as a sample. The section 25 mm long and 75 mm wide of the sample was defined as the center, and the section 25 mm long and 10 mm wide was defined as the end. Furthermore, the plates were arranged such that the slow axis direction of the retardation film, which serves as the first retardation layer, corresponds to the transverse direction of the sample. Next, the adhesive layer of the polarizing plate with the phase retardation layer was laminated onto a 0.5 mm thick glass plate (80 mm × 150 mm). Then, the polarizing plate with the phase retardation layer laminated to the glass plate was placed at 85°C for 120 hours. Afterward, the sample was placed on a reflective plate, and the hue values ​​a and b at the center and ends were measured using a spectrophotometer (reflection) (KONICA MINOLTA, product name: CM-26d, light source D65). From the obtained values, the color unevenness Δa * b * (center - ends) was calculated using the following formula. Furthermore, the same evaluation was also conducted for samples that were placed at 60°C and 95%RH for 120 hours. Δa * b * (center - end) = √(a * center - a * end)² + (b * center - b * end)²

[0076] (5) Uneven phase difference The polarizing plate with the retardation layer obtained in the examples and comparative examples was cut into sections 50 mm long and 150 mm wide, and used as a sample. The section 25 mm long and 75 mm wide of the sample was defined as the center, and the section 25 mm long and 10 mm wide was defined as the end. Furthermore, the plates were arranged such that the slow axis direction of the retardation film, which serves as the first retardation layer, corresponds to the transverse direction of the sample. Next, the adhesive layer of the polarizing plate with the phase retardation layer was laminated onto a 0.5 mm thick glass plate (80 mm × 150 mm). Then, the polarizing plate with the phase retardation layer laminated onto the glass plate was placed at 85°C for 120 hours. Afterwards, the in-plane phase difference (Re(587.4)) at the center and ends was measured using a phase difference measuring device (manufactured by Oji Measurement Instrument Co., Ltd., product name: KOBRA-WPR). From the measured in-plane phase difference, ΔRe(center - ends) was calculated using the following formula. Furthermore, the same evaluation was also conducted for samples that were placed at 60°C and 95%RH for 120 hours. ΔRe(center - end) = Re(587.4) center - Re(587.4) end

[0077] (6)Judgment The following criteria are used to evaluate the obtained polarizer with phase retardation layer. A polarizer that fully meets the following criteria is rated as 0 (Good): ΔRe (center-to-end) below 3.0 under high temperature conditions (85℃, 120 hours); ΔRe (center-to-end) below 2.5 under high temperature and high humidity conditions (60℃, 95%RH, 120 hours); Δa*b* (center-to-end) below 1.2 under high temperature conditions (85℃, 120 hours); and Δa*b* (center-to-end) below 0.85 under high temperature and high humidity conditions (60℃, 95%RH, 120 hours). A polarizer that does not meet any of these criteria is rated as × (Poor).

[0078] [Manufacturing Example 1: Production of Polarizing Plate] 1. Fabrication of polarizing elements Prepare a polyvinyl alcohol (PVA) film with an average degree of polymerization of 2,400, a saponification degree of 99.9 mol%, and a thickness of 45 μm. The PVA film is swelled by immersing it in a swelling bath (water bath) at 20°C for 30 seconds between rollers with different peripheral speed ratios, simultaneously extending it 2.2 times in the conveying direction (swelling step). Then, it is dyed by immersing it in a dyeing bath (an aqueous solution of 0.1 wt% iodine and 0.9 wt% potassium iodide) at 30°C for 30 seconds, simultaneously extending it 3.3 times in the conveying direction compared to the original PVA film (a PVA film that is completely unstretched in the conveying direction) (dyeing step). Next, the dyed PVA film is immersed in a crosslinking bath (an aqueous solution of 3.0 wt% boric acid and 3.0 wt% potassium iodide) at 40°C for 28 seconds, extending it 3.6 times in the conveying direction compared to the original PVA film (crosslinking step). Next, the obtained polyvinyl alcohol film was immersed in a stretching bath (an aqueous solution of boric acid at 4.0 wt% and potassium iodide at 5.0 wt%) at 61°C for 60 seconds, stretching it in the transport direction to 6.0 times its original size (stretching step). Then, it was immersed in a washing bath (an aqueous solution of potassium iodide at 2.0 wt%) at 20°C for 10 seconds (washing step). The washed polyvinyl alcohol film was dried at 40°C for 30 seconds to fabricate a polarizing element. The polarizing element had a thickness of 18 μm.

[0079] 2. Fabrication of polarizing plates As an adhesive, an aqueous solution containing acetylated polyvinyl alcohol resin (average degree of polymerization of 1,200, degree of saponification of 98.5 mol%, degree of acetylation of 5 mol%) and hydroxymethyl melamine in a weight ratio of 3:1 was used. Using this adhesive, a 30 μm thick transparent protective film (manufactured by Nippon Shokubai) containing a (meth)acrylic resin (a modified acrylic polymer with a lactone ring structure) was laminated as a protective layer onto one side (display element side) of the polarizing element obtained above using a roller laminator, and a 49 μm thick transparent protective film with HC formed on a triacetyl cellulose film (manufactured by Fujifilm, trade name "TJ40UL") was laminated as a protective layer onto the other side (viewing side). The film was then heated and dried in an oven (temperature 90°C, time 10 minutes) to produce a polarizing plate with transparent protective films laminated on both sides of the polarizing element. The obtained polarizing element has a single-element transmittance of 41.7% and a polarization degree of 99.9%.

[0080] [Manufacturing Example 2: Fabrication of the First Phase Difference Layer] 1. Polymerization of polyester carbonate resins Polymerization was carried out using a batch polymerization apparatus consisting of two vertical reactors equipped with agitators and reflux condensers controlled at 100°C. 29.60 parts by mass (0.046 mol) of bis[9-(2-phenoxycarbonylethyl)en-9-yl]methane, 29.21 parts by mass (0.200 mol) of isosorbide (ISB), 42.28 parts by mass (0.139 mol) of spirodiol (SPG), 63.77 parts by mass (0.298 mol) of diphenyl carbonate (DPC), and 1.19 × 10⁻² parts by mass (6.78 × 10⁻⁵ mol) of calcium acetate monohydrate as a catalyst were added. After purging the reactor with nitrogen under reduced pressure, it was heated using a heat transfer medium, and stirring was initiated when the internal temperature reached 100°C. Forty minutes after the start of heating, the internal temperature reaches 220°C and is maintained at this temperature. Simultaneously, depressurization begins, and after 90 minutes of reaching 220°C, the pressure is reduced to 13.3 kPa. Phenol vapor produced as a byproduct of the polymerization reaction is introduced into a 100°C reflux condenser, returning a certain amount of monomer components contained in the phenol vapor to the reactor. Uncondensed phenol vapor is then introduced into a 45°C condenser for recovery. Nitrogen is introduced into the first reactor to temporarily restore atmospheric pressure, after which the oligomerized reaction liquid in the first reactor is transferred to the second reactor. Subsequently, heating and depressurization are initiated in the second reactor, raising the internal temperature to 240°C and the pressure to 0.2 kPa over 50 minutes. Polymerization then proceeds until the specified stirring power is reached. Upon reaching the specified power, nitrogen is introduced into the reactor for repressurization, and the resulting polyester carbonate resin is extruded into water for wire cutting to obtain granules.

[0081] 2. Fabrication of the phase retardation film After vacuum drying the obtained polyester carbonate resin (particles) at 80°C for 5 hours, a strip resin film with a thickness of 130 μm was produced using a film forming apparatus equipped with a single-shaft extruder (manufactured by Toshiba Machine Co., Ltd., cylinder set temperature: 250°C), a T-die (width 200 mm, set temperature: 250°C), a cooling roller (set temperature: 120°C~130°C), and a winding machine. The obtained polycarbonate resin film was obliquely stretched using the method of Example 2 of Japanese Patent Application Publication No. 2014-194483 to obtain a phase retardation film with a thickness of 47 μm. The obtained phase retardation film had a Re(550) of 144 nm, a Re(450) / Re(550) of 0.86, an Nz coefficient of 1.21, and an alignment angle (direction of the slow axis) of 45º relative to the length direction.

[0082] [Manufacturing Example 3: Fabrication of the Second Phase Difference Layer 1] In an autoclave equipped with a stirrer, condenser, nitrogen inlet pipe, and thermometer, 48 parts by weight of hydroxypropyl methylcellulose (Shin-Etsu Chemical, trade name: Metolose 60SH-50), 1560 parts by weight of distilled water, 8161 parts by weight of diisopropyl fumarate, 240 parts by weight of 3-ethyl-3-oxetanebutyl methyl acrylate, and 45 parts by weight of tributyl peroxypentanoate as a polymerization initiator were placed. After purging with nitrogen for 1 hour, the mixture was stirred and kept at 49°C for 24 hours to carry out free radical suspension polymerization. Subsequently, the mixture was cooled to room temperature, and the suspension containing the generated polymer particles was centrifuged. The obtained polymer was washed twice with distilled water and twice with methanol, and then dried under reduced pressure. The obtained fumarate-based resin was dissolved in a toluene-methyl ethyl ketone mixed solution (toluene / methyl ethyl ketone, 50% by weight / 50% by weight) to prepare a 20% solution. Furthermore, 5 parts by weight of tributyl trimellitate as a plasticizer were added to 100 parts by weight of fumarate resin to prepare a concentrated solution. A biaxially stretched polyester (polyethylene terephthalate / isophthalate copolymer) film (75 μm thick) was used as the support film. The prepared concentrated solution was coated onto the support film to achieve a film thickness of 5 μm after drying, and dried at 140°C. The dried coating (positive C plate) had an in-plane phase difference Re(550) ≒0 nm and Rth(550) = -75 nm. Furthermore, the resulting phase difference film had a puncture modulus T of 57.2 g / mm and a shear breaking strength of 58.7 MPa.

[0083] [Manufacturing Example 4: Fabrication of the Second Phase Difference Layer 2] Except for changing the thickness to 18 μm, the phase retardation film (positive C plate) was fabricated in the same manner as in Manufacturing Example 3. The resulting phase retardation film had Re(550) = 0 nm and Rth(550) = 200 nm. Furthermore, the resulting phase retardation film had a puncture elastic modulus T of 133.3 g / mm and a shear breaking strength of 39.8 MPa.

[0084] [Example 1] The first retardation layer obtained in Manufacturing Example 2 was bonded to the polarizing element of the polarizing plate obtained in Manufacturing Example 1 using an acrylic adhesive (20 μm thick). The bonding was performed with the absorption axis of the polarizing element at a 45° angle to the slow axis of the first retardation film. Next, the first retardation layer was laminated with the second retardation layer obtained in Manufacturing Example 3 using an ultraviolet-curable adhesive (1 μm thick after curing), resulting in a polarizing plate (thickness: 192 μm) with a phase retardation layer consisting of a protective layer (HC layer / TAC film), an adhesive layer, a polarizing element, an adhesive layer, a (meth)acrylic resin layer, an adhesive layer, a first retardation layer, an adhesive layer, and a second retardation layer. Then, an acrylic adhesive (26 μm thick) was applied to the surface of the second retardation layer that was not in contact with the first retardation layer, thus forming a polarizing plate with an adhesive layer and a phase retardation layer. The resulting polarizing plate with a phase retardation layer was then evaluated as described above. The results are shown in Table 1.

[0085] [Example 2] Except for using the second retardation layer obtained in Manufacturing Example 4, a polarizing plate with a retardation layer (thickness: 204 μm) was obtained in the same manner as in Example 1. The obtained polarizing plate with the retardation layer was subjected to the above evaluation. The results are shown in Table 1.

[0086] [Manufacturing Example 5: Fabrication of the positive C-plate as a liquid crystal alignment and curing layer] A liquid crystal coating solution was prepared by dissolving 20 parts by weight of a side-chain liquid crystal polymer represented by the following chemical formula (where the numbers 65 and 35 represent moles of monomer units; for convenience, block polymers are used, with a weight average molecular weight of 5000), 80 parts by weight of a polymerizable liquid crystal (BASF: Paliocolor LC242) displaying a nematic liquid crystal phase, and 5 parts by weight of a photopolymerization initiator (Ciba Specialty Chemicals: Irgacure 907) in 200 parts by weight of cyclopentanone. The coating solution was then applied to a PET substrate that had undergone vertical alignment treatment using a rod coater, and subsequently heated and dried at 80°C for 4 minutes to orient the liquid crystal. The liquid crystal layer was then irradiated with ultraviolet light to harden it, thereby forming a retardation layer (4 μm thick) on the substrate displaying refractive index characteristics of nz>nx=ny. The obtained phase difference layer has a puncture elastic modulus T of 43.1 g / mm and a shear failure strength of 0.6 MPa. [Chemistry 2]

[0087] (Comparative Example 1) Except that the positive C-plate obtained in Manufacturing Example 5, which serves as the liquid crystal alignment and curing layer, was used as the second retardation layer, a polarizing plate with a retardation layer (thickness: 191 μm) was obtained in the same manner as in Example 1. The obtained polarizing plate with the retardation layer was subjected to the above evaluation. The results are shown in Table 1.

[0088] (Comparative Example 2) Except for the absence of a second retardation layer, a polarizing plate with a retardation layer (thickness: 185 μm) was obtained in the same manner as in Example 1. The obtained polarizing plate with the retardation layer was used for the above evaluation. The results are shown in Table 1.

[0089] [Table 1] Second phase difference layer thickness Puncture elastic modulus (g / mm) Shear strength (MPa) Phase difference unevenness Uneven color determination ∆Re(Center-End) ∆a*b* (Center-End) μm 85℃ 60℃ / 95%RH 85℃ 60℃ / 95%RH Example 1 Resin film 1 5 57.2 58.7 2.7 2.3 1 0.8 〇 Example 2 Resin film 2 18 133.3 39.8 2.5 2.2 1.1 0.7 〇 Comparative Example 1 Liquid crystal alignment solidified layer 4 43.1 0.6 3.8 2.7 1.5 1 × Comparative Example 2 - - - - 3.3 2.7 1.3 0.9 ×

[0090] [evaluate] As shown in Table 1, the phase difference unevenness and color unevenness of the polarizing plate with phase difference layer in the embodiment of the present invention are suppressed when placed in a harsh high temperature environment and a high temperature and high humidity environment. [Industrial Applicability]

[0091] The polarizing plate with a phase retardation layer according to the embodiments of the present invention can be preferably used in image display devices such as liquid crystal display devices, organic EL display devices and inorganic EL display devices, and can also be preferably used in automotive image display devices.

[0092] 10:Polarizing plate 11: Polarizing element 12: Protective layer 13: Protective layer 20: First phase difference layer 30: Second phase difference layer 100: Polarizing plate with phase retardation layer d: Displacement of the blade in the vertical direction FH: Horizontal load generated by the blade W: Blade width

Claims

1. A polarizing plate with a phase retardation layer, comprising: a polarizing plate including a polarizing element; a first phase retardation layer formed of an extended film of a polycarbonate-based resin film; and a second phase retardation layer having a shear breaking strength T of 15 MPa or more, wherein the polarizing plate, the first phase retardation layer, and the second phase retardation layer are laminated in the order of polarizing plate / first phase retardation layer / second phase retardation layer or polarizing plate / second phase retardation layer / first phase retardation layer, wherein the second phase retardation layer is formed of a resin film comprising a polymer exhibiting negative birefringence, wherein the polymer exhibiting negative birefringence is selected from at least one of the group consisting of acrylic resins, styrene resins, and maleimide resins, wherein the shear breaking strength T is calculated and converted into a value per 1 μm thickness from the shear strength obtained by oblique cutting using a precision oblique cutting device under the following conditions: cutting edge: single crystal diamond; cutting edge width: 1 mm; cutting edge rake angle: 10º; horizontal speed of cutting edge: 1 Vertical velocity of the blade in μm / s: 0.05 μm / s T(MPa)=FH(kN) / (2×Wd(m2)×cotφ) Here, FH is the horizontal load generated by the blade, W is the width of the blade (m), d is the vertical displacement of the blade (m), and φ is 45º.

2. The polarizing plate with a phase retardation layer as claimed in claim 1, wherein the puncture elastic modulus of the second phase retardation layer is 50 g / mm or more. The puncture elastic modulus is the value of the force (g) before the second phase retardation layer breaks when the second phase retardation layer is fixed between two plates with circular holes of diameter 15 mm or less, and a needle with a front end diameter of 1 mmφ and 0.5R is punctured perpendicularly to the main surface of the second phase retardation layer at a speed of 0.33 cm / s.

3. A polarizing plate with a phase retardation layer as claimed in claim 1, wherein the first phase retardation layer functions as a λ / 4 plate, the in-plane phase difference Re(550) is 100 nm to 190 nm, and Re(450) / Re(550) < 1, and the angle between the slow axis of the first phase retardation layer and the absorption axis of the polarizing element is 40º to 50º.

4. A polarizing plate with a phase retardation layer as requested in claim 1, wherein the second phase retardation layer satisfies nx = ny > nz or nz > nx = ny.

5. A polarizing plate with a phase retardation layer as claimed in claim 1, wherein the polarizing plate with the phase retardation layer is elongated and the first phase retardation layer is an obliquely extended film.

6. A polarizing plate with a phase retardation layer as claimed in claim 1, wherein the first phase retardation layer and the second phase retardation layer are laminated via an adhesive layer.

7. An image display device comprising a polarizing plate with a phase retardation layer as claimed in claim 1.

Images