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 in-plane non-uniformity of reflected hue. The polarizing plate with a phase retardation layer according to an embodiment of this invention comprises a polarizing plate including a polarizing element and a first phase retardation layer. The phase difference variation value RS of the polarizing plate with the phase retardation layer is 2.0 or less, and this phase difference variation value RS is the slope of an approximate straight line of the in-plane phase difference Re(550) of the polarizing plate with the phase retardation layer measured under tensions of 0 kg, 0.5 kg, 1 kg, 1.5 kg, and 2 kg.

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] In recent years, image display devices, represented by liquid crystal displays and electroluminescent (EL) displays (such as organic EL displays and inorganic EL displays), have become increasingly widespread. Typically, image display devices utilize polarizing plates and retardation plates. In practical terms, polarizing plates with an integral retardation layer, where the polarizing plate and retardation plate are integrated, are widely used (e.g., Patent Document 1). With the increasing demand for thinner image display devices, the demand for thinner polarizing plates with retardation layers has also intensified. To achieve thinner polarizing plates with retardation layers, the thinning of retardation plates is continuously being developed, using retardation plates made from liquid crystal materials. Regarding thin retardation plates, under high-temperature conditions, the dimensional shrinkage of the polarizing plate tends to increase, potentially altering the phase difference. Furthermore, the dimensional shrinkage effect is even greater in retardation layers formed using liquid crystal materials, resulting in further changes in the reflected hue. Previous technical documents Patent documents

[0003] Patent Document 1: Japanese Patent No. 3325560 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 retardation layer that suppresses in-plane non-uniformity of reflected hue and has excellent high-temperature durability. [Technical means to solve the problem]

[0006] The polarizing plate with a phase retardation layer in an embodiment of the present invention has a polarizing plate including a polarizing element and a first phase retardation layer. The phase difference change value RS of the polarizing plate with the phase retardation layer is 2.0 or less. The phase difference change value RS is the slope of an approximate straight line of the in-plane phase difference Re(550) of the polarizing plate with the phase retardation layer measured under tensions of 0 kg, 0.5 kg, 1 kg, 1.5 kg and 2 kg. In one embodiment, the polarizing plate with the aforementioned phase retardation layer further has a second phase retardation layer with a breakage elongation of 1% or more. In one embodiment, the above-described second retardation layer is a positive C-plate formed of a resin film containing a polymer exhibiting negative birefringence. In one embodiment, the polymer exhibiting negative birefringence is at least one selected from the group consisting of an acrylic resin having an aromatic ring introduced into a side chain, a styrene resin having an aromatic ring introduced into a side chain, and a maleimide resin having an aromatic ring introduced into a side chain. In one embodiment, the in-plane retardation Re(550) of the above-described first retardation is 100 nm < Re(550) < 160 nm, and Re(450) / Re(550) < 1 and Re(650) / Re(550) > 1 are satisfied. In one embodiment, the angle formed by the slow axis of the above-described first retardation layer and the absorption axis of the above-described polarizing element is 40° to 50°. In one embodiment, the above-described first retardation layer has a laminated structure of an alignment cured layer A of a liquid crystal compound and an alignment cured layer B of a liquid crystal compound, and the alignment cured layer A functions as a λ / 2 plate, and the alignment cured layer B functions as a λ / 4 plate. In one embodiment, the angle formed by the slow axis of the above-described alignment cured layer A of the liquid crystal compound and the absorption axis of the above-described polarizing element is 70° to 80°, and the angle formed by the slow axis of the above-described alignment cured layer B of the liquid crystal compound and the absorption axis of the above-described polarizing element is 10° to 20°. In another aspect of the present invention, there is provided an image display device. The image display device includes the above-described polarizing plate with a retardation layer. [Effects of the Invention]

[0007] According to an embodiment of the present invention, there can be provided a polarizing plate with a retardation layer in which in-plane unevenness of the reflected hue is suppressed and high-temperature durability is excellent. According to an embodiment of the present invention, even when including a retardation layer as an alignment cured layer of liquid crystal, a change in the retardation of the polarizing plate in a high-temperature environment is suppressed. Therefore, a change in the retardation of the polarizing plate with a retardation layer can be suppressed, and a change in the reflected hue can also be suppressed. As a result, there can be provided a polarizing plate with a retardation layer in which in-plane unevenness of the reflected hue is suppressed and excellent high-temperature durability is exhibited. Brief Explanation of Drawings

[0008] FIG. 1 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to another embodiment of the present invention. Embodiment

[0009] The following describes embodiments of the present invention, 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" refers to the refractive index in the direction of maximum refractive index within the plane (i.e., the slow axis direction), "ny" refers to the refractive index in the direction orthogonal to the slow axis within the plane (i.e., the fast axis direction), and "nz" refers to 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. When the thickness of the layer (film) is set as d (nm), Re(λ) is obtained by the formula: Re(λ) = (nx - ny) × d. (3) Phase difference (Rth) in the thickness direction "Rth(λ)" is the phase difference in the thickness direction measured at 23°C using light with a wavelength of λ nm. For example, "Rth(550)" is the phase difference in the thickness direction measured at 23°C using light with a wavelength of 550 nm. When the thickness of the layer (film) is set as d (nm), Rth(λ) is obtained by the formula: Rth(λ) = (nx - nz) × d. (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 directions relative to a reference direction. Therefore, for example, "45°" means ±45°.

[0011] A. Overall structure of the polarizing plate with phase retardation layer 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. 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 can be any phase retardation layer and may be omitted. Furthermore, the second phase retardation layer 30 may also be disposed on the viewing side of 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. The components constituting the polarizing plate with the phase retardation layer can be laminated using any suitable adhesive layer (not shown). Specific examples of adhesive layers include adhesive layers and bonding agents. The first phase retardation layer 20 is preferably an alignment and curing layer of a liquid crystal compound (hereinafter sometimes simply referred to as a liquid crystal alignment and curing layer). The second retardation layer 30 is preferably composed of a resin film containing a polymer exhibiting negative birefringence. In the example shown, the first retardation layer 20 is a single layer. In this specification, "liquid crystal alignment and curing layer" refers to a layer in which liquid crystal compounds are aligned in a specific direction within the layer, and the alignment state is fixed. Furthermore, "alignment and curing layer" includes the concept of an alignment-cured layer obtained by curing liquid crystal monomers as described below.

[0012] Figure 2 is a schematic cross-sectional view of a polarizing plate with a phase retardation layer according to another embodiment of the present invention. The polarizing plate 101 with a phase retardation layer in the figure example has, sequentially 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 can be any phase retardation layer and may be omitted. Furthermore, the second phase retardation layer 30 may also be disposed on the viewing side of the first phase retardation layer 20. The first phase retardation layer 20 is preferably a liquid crystal alignment and curing layer. The second phase retardation layer 30 is preferably composed of a resin film containing a polymer exhibiting negative birefringence. In the figure example, the first phase retardation layer 20 has a laminated structure of a liquid crystal alignment and curing layer A21 and a liquid crystal alignment and curing layer B22. When the first phase retardation layer has a laminated structure, either the liquid crystal alignment and curing layer A or the liquid crystal alignment and curing layer B can function as a λ / 4 plate, and the other can function as a λ / 2 plate. Even though a liquid crystal alignment curing layer with a multilayer structure is used as the first phase retardation layer 20, a polarizing plate with a phase retardation layer can still be provided, which suppresses in-plane non-uniformity of reflected hue and has excellent high-temperature durability.

[0013] The phase difference variation value RS of the polarizing plates 100 and 101 with the phase difference layer is 2.0 or less, preferably 1.9 or less, more preferably 1.8 or less, and even more preferably 1.7 or less. The phase difference variation value RS is, for example, -2.5 or more, preferably -2.4 or more, and more preferably -2.3 or more. By keeping the phase difference variation value RS within the above range, a polarizing plate with a phase difference layer whose in-plane non-uniformity of reflected hue is suppressed can be provided. The closer the phase difference variation value RS is to 0, the better. In this specification, the phase difference variation value RS refers to the slope of an approximate straight line of the in-plane phase difference Re(550) of the polarizing plate with the phase difference layer measured under tensions of 0 kg, 0.5 kg, 1 kg, 1.5 kg, and 2 kg.

[0014] As described above, in one embodiment, the first retardation layer is a single layer. In this embodiment, the polarizing plate with the retardation layer is cut into a rectangle, (i) the angle between the absorption axis of the polarizing element and the long side direction of the polarizing plate with the retardation layer is set to approximately 45° (approximately -45°) counterclockwise, and (ii) when the plate is arranged such that the slow axis corresponds to the long side direction of the polarizing plate with the retardation layer, the phase difference change value RS under the state of applying the above-mentioned tension to the long side direction of the polarizing plate with the retardation layer (the direction parallel to the slow axis of the first retardation layer) is preferably 1.9 or less, more preferably 1.8 or less, and even more preferably 1.7 or less. The closer the phase difference change value RS is to 0, the better. Furthermore, when the polarizing plate with the retardation layer is cut into a rectangle, (iii) the angle between the absorption axis of the polarizing element and the long side of the polarizing plate with the retardation layer is set to approximately 45° clockwise, and (iv) when the plate is configured such that the slow axis corresponds to the short side of the polarizing plate with the retardation layer, the phase difference change value RS under the state of applying the above-mentioned tension to the long side of the polarizing plate with the retardation layer (the direction orthogonal to the slow axis of the first retardation layer) is preferably -2.5 or more, more preferably -2.4 or more, and even more preferably -2.3 or more. The closer the phase difference change value RS is to 0, the better.

[0015] As described above, in one embodiment, the first phase difference layer has a stacked structure of a liquid crystal alignment and curing layer A and a liquid crystal alignment and curing layer B. Either liquid crystal alignment and curing layer A or liquid crystal alignment and curing layer B can function as a λ / 4 plate, and the other can function as a λ / 2 plate. In one embodiment, liquid crystal alignment and curing layer A functions as a λ / 2 plate, and liquid crystal alignment and curing layer B functions as a λ / 4 plate. In this embodiment, the polarizing plate with the retardation layer is cut into a rectangle; (v) the angle between the absorption axis of the polarizing element and the long side of the polarizing plate with the retardation layer is set to approximately 45° (approximately -45°) counterclockwise; (vi) the angle between the slow axis of the liquid crystal alignment and curing layer A and the absorption axis of the polarizing element is set to approximately 75° (approximately -75°) counterclockwise; and the angle between the slow axis of the liquid crystal alignment and curing layer B and the absorption axis of the polarizing element is set to approximately 15° (approximately -15°) counterclockwise; (vii) the phase difference change value RS under the state of applying the above tension to the long side of the polarizing plate with the retardation layer (a direction approximately 30° relative to the slow axis of the liquid crystal alignment and curing layer A) is preferably 1.8 or less, more preferably 1.6 or less, further preferably 1.2 or less, and particularly preferably 1.0 or less. The closer the phase difference change value RS is to 0, the better. Furthermore, the polarizing plate with the retardation layer is cut into a rectangle. (viii) The angle between the absorption axis of the polarizing element and the long side of the polarizing plate with the retardation layer is set to approximately 45° clockwise. (ix) The angle between the slow axis of the liquid crystal alignment and curing layer A and the absorption axis of the polarizing element is set to approximately 75° clockwise, and the angle between the slow axis of the liquid crystal alignment and curing layer B and the absorption axis of the polarizing element is set to approximately 15° clockwise. (x) Under the aforementioned tension applied to the long side of the polarizing plate with the retardation layer (at approximately 120° to the slow axis of the liquid crystal alignment and curing layer A), the phase difference change value RS is preferably -1.5 or more, more preferably -1.2 or more, further preferably -1.0 or more, and particularly preferably -0.8 or more. The closer the phase difference change value RS is to 0, the better.

[0016] In one embodiment, the polarizing plates 100 and 101 with the retardation layer have an adhesive layer disposed on the outermost layer (for example, the surface of the second retardation layer 30 in the example figure where the first retardation layer 20 is not deposited), and can be attached to an image display device (essentially an image display unit). In practical terms, it is preferable that a release liner is temporarily adhered to the surface of the adhesive layer before using the polarizing plate. By temporarily adhering the release liner, the adhesive layer can be appropriately protected.

[0017] The thickness of the polarizing plate can be set to any suitable value. In one embodiment, the thickness of the polarizing plate is, for example, 30 μm to 150 μm, preferably 40 μm to 100 μm, and even more preferably 50 μm to 80 μm. Furthermore, in another embodiment, the total thickness of the polarizing plate with the retardation layer is preferably 40 μm to 120 μm, more preferably 40 μm to 110 μm, and even more preferably 40 μm to 100 μm. A polarizing plate with a retardation layer comprising a polarizing plate of a certain thickness can have this thickness. With such a polarizing plate with a retardation layer, the effect of dimensional shrinkage of the polarizing plate under high-temperature conditions tends to increase. According to embodiments of the present invention, even with a polarizing plate with a retardation layer having the above-mentioned thickness, a polarizing plate with a retardation layer that suppresses in-plane non-uniformity of reflected hue and has excellent high-temperature durability can be provided. 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 layer (or the first and second retardation layers when a second retardation layer is present), and the bonding layer used to make them equally stacked (i.e., the total thickness of the polarizing plate with the retardation layer does not include the thickness of the adhesive layer that is set as the outermost layer and the release liner that can temporarily adhere to its surface).

[0018] The following is a more detailed explanation of the constituent elements of a polarizing plate with a phase retardation layer.

[0019] B.Polarizing plate B-1. Polarizing element A polarizing element is typically composed of a resin film containing a dichroic substance (typically iodine). Any suitable resin film suitable for use as a polarizing element can be used. A typical resin film is a polyvinyl alcohol (PVA) based resin film. The resin film can be a single layer or a laminate of two or more layers.

[0020] As a specific example of a polarizing element composed of a single-layer resin film, one can exemplify this by applying iodine-based dyeing and stretching treatments (typically uniaxial stretching) to a PVA-based resin film. The aforementioned iodine-based dyeing is performed, for example, by immersing the PVA-based 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. The PVA-based resin film can be subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, etc., as needed. For example, by immersing the PVA-based resin film in water for washing before dyeing, not only can dirt or anti-blocking agents on the surface of the PVA-based film be washed away, but the PVA-based resin film can also swell to prevent uneven dyeing.

[0021] As a specific example of a polarizing element obtained using a laminate, a polarizing element obtained using the following laminates can be cited: a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate; or a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate. A polarizing element obtained using a laminate 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 and drying it to form a PVA-based resin layer on the resin substrate, thus obtaining a laminate of the resin substrate and the PVA-based resin layer; 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 to stretch it. Furthermore, the stretching process may further include, as needed, air-stretching the laminate at a high temperature (e.g., above 95°C) before stretching in the boric acid aqueous solution. In addition, in this embodiment, it is preferable to subject the laminate to a drying shrinkage treatment, which involves heating while conveying along its long side, causing it to shrink by more than 2% in its width direction. Typically, the manufacturing method of this embodiment includes sequentially applying an air-assisted stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment to the laminate. By introducing assisted stretching, even when PVA is coated onto 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 a decrease in the alignment or dissolution of PVA during subsequent dyeing or stretching steps when immersed in water can be prevented, achieving higher optical properties. Furthermore, when the PVA-based resin layer is immersed in a liquid, compared to when the PVA-based resin layer does not contain halides, the orientation disorder of polyvinyl alcohol molecules and the decrease in orientation can be suppressed. This improves the optical properties of the polarizing element obtained by immersing the laminate in a liquid through dyeing and water-stretching processes. Furthermore, by shrinking the laminate in the width direction through a drying shrinkage process, optical properties can be improved. The obtained 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 any suitable protective layer can be deposited on the peeled surface for use. Details of this method for manufacturing a polarizing element are described, for example, in Japanese Patent Application Publication No. 2012-73580 (Japanese Patent No. 5414738) and Japanese Patent No. 6470455. All information contained in these gazettes is incorporated herein by reference for informational purposes only.

[0022] The thickness of the polarizing element is preferably 1 μm to 15 μm, more preferably 1 μm to 10 μm, further preferably 1 μm to 8 μm, and particularly preferably 2 μm to 5 μm. In one embodiment, the thickness of the polarizing element is, for example, 7 μm or more, or for example, 8 μm or more, or for example, 10 μm or more, or for example, 12 μm or more, or for example, 15 μm or more. When the thickness of the polarizing element is large, the size shrinkage of the polarizing plate with the retardation layer tends to increase. In embodiments of the present invention, even when using polarizing elements of the above-mentioned thickness, in-plane reflection hue unevenness of the polarizing plate with the retardation layer can be suppressed. The thickness of the polarizing element is, for example, 30 μm or less.

[0023] 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. If the boric acid content of the polarizing element is within this range, a polarizing plate with an attached retardation layer exhibiting excellent high-temperature durability can be provided. When the boric acid content is less than 5% by weight, polyolefin formation occurs in the polarizing element, potentially leading to a decrease in durability. According to embodiments of the present invention, even when placed in a high-temperature environment, the phase difference caused by dimensional shrinkage of the polarizing plate is suppressed, and changes in reflected hue are also suppressed. As a result, a polarizing plate with an attached retardation layer that suppresses in-plane non-uniformity of reflected hue and possesses excellent high-temperature durability can be provided. 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 calculated, for example, using the following formula based on a neutralization method, in the form of the boric acid content per unit weight of the polarizing element. [Number 1]

[0024] The iodine content of the polarizing element is preferably 2% by weight or more, and more preferably 2% to 10% by weight. If the iodine content of the polarizing element is within this range, the ease of adjustment during bonding can be well maintained through the synergistic effect with the aforementioned boric acid content, and shrinkage during heating can be well suppressed, while appearance durability during heating can be improved. In this specification, "iodine content" refers to the total iodine content contained in the polarizing element (PVA-based resin film). More specifically, iodine in the polarizing element exists in the form of iodide ions (I-), iodine molecules (I2), and polyiodide ions (I3-, I5-), etc. Therefore, the iodine content in this specification means the content of iodine including all such forms. The iodine content can be calculated, for example, by the calibration curve method of fluorescence X-ray analysis. Furthermore, in the polarizing element, polyiodide ions exist 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, depending on their morphology, can absorb light across a wide range of visible light. On the other hand, iodide ions (I⁻) have an absorption peak near 230 nm and do not actually participate in visible light absorption. Therefore, polyiodide ions existing in their PVA complex state can primarily participate in the absorption performance of polarizing elements.

[0025] The polarizing element preferably exhibits dichroic absorption at any wavelength from 380 nm to 780 nm. The single-unit 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 single-unit transmittance is representative of the Y value obtained after measurement using a UV-Vis spectrophotometer and after visual sensitivity correction. The aforementioned polarization is representative of the parallel transmittance Tp and orthogonal transmittance Tc obtained after measurement using a UV-Vis spectrophotometer and after visual sensitivity correction, and can be calculated according to the following formula. Polarization (%) = {(Tp-Tc) / (Tp+Tc)} 1 / 2×100

[0026] B-2. Protective layer Protective layers 12 and 13 are formed from 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 film include: cellulose resins such as triacetin cellulose (TAC), or transparent resins such as polyester, polyvinyl alcohol, polycarbonate, polyamide, polyimide, polyether ether, polyurethane, polystyrene, polyvinyl chloride, polyolefin, (meth)acrylic acid, and acetate. Also examples include: thermosetting resins or UV-curing resins such as (meth)acrylic acid, urethane, (meth)acrylate urethane, epoxy, and silicone. In addition, examples include: glassy polymers such as silicate polymers. 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 of resin compositions include alternating copolymers comprising isobutylene and N-methylmaleimide, and acrylonitrile-styrene copolymers. The polymer membrane can be, for example, an extruded product of the above resin composition.

[0027] The polarizing plate with the phase retardation layer is typically disposed on the viewing side of the image display device, and the protective layer 12 is typically disposed on the viewing side. Therefore, the protective layer 12 can also be subjected to surface treatments such as hard coating, anti-reflection treatment, anti-sticking treatment, and anti-glare treatment as needed.

[0028] The thickness of the protective layer is preferably 10 μm to 50 μm, more preferably 10 μm to 30 μm. Furthermore, when a surface treatment is applied, the thickness of the outer protective layer (protective layer 12) includes the thickness of the surface treatment layer.

[0029] C. First phase difference layer The first retardation layer 20 is preferably an alignment and curing layer of a liquid crystal compound. By using a liquid crystal compound, an in-plane retardation equivalent to that of a resin film can be achieved with a thickness much thinner than that of a resin film. Furthermore, if it is a liquid crystal alignment and curing layer, the phase difference caused by dimensional shrinkage of the polarizer with the retardation layer under high-temperature conditions may become more significant. In embodiments of the present invention, even if a retardation layer is used as an alignment and curing layer of a liquid crystal compound, a polarizer with a retardation layer in which in-plane non-uniformity of reflected hue is suppressed can be provided. The first retardation layer can be a single layer or a stack of two or more layers. The first retardation layer is typically provided to impart anti-reflective properties to the polarizer.

[0030] C-1. The first phase difference layer as a single layer When the first phase difference layer 20 is a single layer, the first phase difference layer, as a single layer, can function as a λ / 4 plate. The in-plane phase difference Re(550) of the first phase difference layer is preferably greater than 100 nm and less than 160 nm, more preferably 110 nm to 155 nm, and even more preferably 130 nm to less than 150 nm.

[0031] The Nz coefficient of the first retardation layer, which is a single layer, is preferably 0.9 to 1.5, and more preferably 0.9 to 1.3. By satisfying this relationship, when the obtained polarizing plate with the retardation layer is used in an image display device, very good reflective hue can be achieved.

[0032] The thickness of the first phase difference layer is preferably 0.5 μm to 10 μm, more preferably 0.5 μm to 7 μm, and even more preferably 1 μm to 5 μm.

[0033] The first phase retardation layer preferably exhibits inverse wavelength dispersion characteristics. In this case, Re(550) / Re(650) is preferably greater than 1, more preferably greater than 1 and less than 1.2, and even more preferably 1.01 to 1.15. Furthermore, the Re(450) / Re(550) of the first phase retardation layer is preferably less than 1, more preferably less than 0.95, and even more preferably less than 0.90. For example, Re(450) / Re(550) is 0.8 or more. With this configuration, very excellent anti-reflection characteristics can be achieved.

[0034] The angle 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 even more preferably about 45°. If the angle is within this range, by using the first retardation layer as a λ / 4 plate as described above, a polarizing plate with a retardation layer that has very excellent circular polarization characteristics (resulting in very excellent anti-reflection characteristics) can be obtained.

[0035] As described above, the first retardation layer 20 is preferably an alignment and curing layer of a liquid crystal compound. By using a liquid crystal compound, the difference between nx and ny in the obtained retardation layer can be made much larger than that in non-liquid crystal materials, thus making the thickness of the retardation layer used to obtain the desired in-plane retardation exceptionally small. As a result, further thinning of the polarizing plate with the retardation layer can be achieved.

[0036] The phase retardation layer, serving as the alignment and curing layer of a liquid crystal compound, can be formed using a composition containing a polymerizable liquid crystal compound. In this specification, the polymerizable liquid crystal compound contained in the composition refers to a compound having polymerizable groups and liquid crystal properties. A polymerizable group refers to a group that participates in a polymerization reaction, preferably a photopolymerizable group. Here, a photopolymerizable group refers to a group that can participate in a polymerization reaction due to active free radicals or acids generated by a photopolymerization initiator.

[0037] Liquidity can be thermotropic or lyotropic. Furthermore, the liquid crystal phase can be either nematic or smectic. From a manufacturing ease perspective, thermotropic nematic liquid crystals exhibit better liquidity.

[0038] In one embodiment, the phase retardation layer system as a single layer is formed using a composition comprising a liquid crystal compound represented by the following formula (1). L 1-SP 1-A 1-D 3-G 1-D 1-Ar-D 2-G 2-D 4-A 2-SP 2-L 2(1)

[0039] L1 and L2 independently represent monovalent organic groups, and at least one of L1 and L2 represents a polymerizable group. A monovalent organic group includes any suitable group. As a polymerizable group represented by at least one of L1 and L2, a free radical polymerizable group (a group capable of free radical polymerization) can be cited. Any suitable free radical polymerizable group can be used. Acrylonitrile or methacrylonitrile is preferred. From the viewpoint of faster polymerization and improved productivity, acrylonitrile is preferred. Methacrylonitrile can also be used similarly as a polymerizable group for highly birefringent liquid crystals.

[0040] SP 1 and SP 2 each independently represent a single-bonded, straight-chain, or branched alkyl group, or one or more divalent linkages of -CH 2- that constitute a straight-chain or branched alkyl group having 1 to 14 carbon atoms, substituted with -O-. Examples of straight-chain or branched alkyl groups having 1 to 14 carbon atoms are preferably: methylene, ethyl, propyl, butyl, pentyl, and hexyl.

[0041] A1 and A2 respectively represent alicyclic hydrocarbon groups or aromatic ring substituents. A1 and A2 are preferably aromatic ring substituents with 6 or more carbon atoms or extended alkyl rings with 6 or more carbon atoms.

[0042] D1, D2, D3, and D4 independently represent single-bond or divalent linkage groups. Specifically, D1, D2, D3, and D4 represent single bonds, -O-CO-, -C(=S)O-, -CR1R2-, -CR1R2-CR3R4-, -O-CR1R2-, -CR1R2-O-CR3R4-, -CO-O-CR1R2-, -O-CO-CR1R2-, -CR1R2-O-CO-CR3R4-, -CR1R2-CO-O-CR3R4-, -NR1-CR2R3-, or -CO-NR1-. However, at least one of D1, D2, D3, and D4 represents -O-CO-. Preferably, D3 is -O-CO-, and more preferably, D3 and D4 are -O-CO-. D1 and D2 are preferably single bonds. R1, R2, R3 and R4 independently represent a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 4 carbon atoms.

[0043] G1 and G2 independently represent single bonds or alicyclic hydrocarbon groups. Specifically, G1 and G2 can represent unsubstituted or substituted divalent alicyclic hydrocarbon groups with 5 to 8 carbon atoms. Furthermore, one or more of the -CH2- atoms constituting the alicyclic hydrocarbon group can be substituted with -O-, -S-, or -NH-. G1 and G2 preferably represent single bonds.

[0044] Ar represents an aromatic hydrocarbon ring or an aromatic heterocycle. For example, Ar represents an aromatic ring selected from the group composed of the bases represented by the following formulas (Ar-1) to (Ar-6). Furthermore, in the following formulas (Ar-1) to (Ar-6), *1 represents the bond position with D1, and *2 represents the bond position with D2. [Chemistry 1]

[0045] In formula (Ar-1), Q1 represents N or CH, Q2 represents -S-, -O-, or -N(R5)-. R5 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

[0046] In formulas (Ar-1) to (Ar-6), Z1, Z2, and Z3 independently represent a hydrogen atom, a monovalent aliphatic hydrocarbon group with 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group with 3 to 20 carbon atoms, a monovalent aromatic hydrocarbon group with 6 to 20 carbon atoms, a halogen atom, a cyano group, a nitro group, -NR6R7, or -SR8. R6 to R8 independently represent a hydrogen atom or an alkyl group with 1 to 6 carbon atoms. Z1 and Z2 can be bonded together to form a ring. The ring can be any of alicyclic, heterocyclic, or aromatic rings, preferably aromatic rings. The formed ring can be substituted with substituents.

[0047] In formulas (Ar-2) and (Ar-3), A3 and A4 independently represent groups selected from the groups consisting of -O-, -N(R9)-, -S-, and -CO-, respectively, and R9 represents a hydrogen atom or a substituent. Examples of substituents represented by R9 that are identical to those that Y1 in formula (Ar-1) can possess can be cited.

[0048] In formula (Ar-2), X represents a hydrogen atom, or a nonmetallic atom of group 14-16, either unsubstituted or with a substituent. Examples of nonmetallic atoms of group 14-16 represented by X include: oxygen, sulfur, nitrogen (unsubstituted or with a substituent), and carbon (unsubstituted or with a substituent). Examples of substituents include those identical to those that Y1 in formula (Ar-1) may have.

[0049] In equation (Ar-3), D5 and D6 independently represent single bonds, -O-CO-, -C(=S)O-, -CR1R2-, -CR1R2-CR3R4-, -O-CR1R2-, -CR1R2-O-CR3R4-, -CO-O-CR1R2-, -O-CO-CR1R2-, -CR1R2-O-CO-CR3R4-, -CR1R2-CO-O-CR3R4-, -NR1-CR2R3-, or -CO-NR1-. R1, R2, R3, and R4 are as described above.

[0050] In formula (Ar-3), SP3 and SP4 independently represent single bonds, linear or branched alkyl groups having 1 to 12 carbon atoms, or one or more divalent linkages of -CH2- that constitute linear or branched alkyl groups having 1 to 12 carbon atoms, substituted with -O-, -S-, -NH-, -N(Q)-, or -CO-, where Q represents a polymerizable group.

[0051] In formula (Ar-3), L3 and L4 independently represent monovalent organic groups, and at least one of L3 and L4, as well as L1 and L2 in formula (1) above, represents a polymerizable group.

[0052] In formulas (Ar-4) to (Ar-6), Ax represents an organogroup having 2 to 30 carbon atoms and at least one aromatic ring selected from the group consisting of aromatic hydrocarbon rings and aromatic heterocycles. In formulas (Ar-4) to (Ar-6), Ax preferably has an aromatic heterocycle, and more preferably has a benzothiazole ring. In formulas (Ar-4) to (Ar-6), Ay represents a hydrogen atom, an unsubstituted or substituent alkyl group having 1 to 6 carbon atoms, or an organogroup having 2 to 30 carbon atoms and at least one aromatic ring selected from the group consisting of aromatic hydrocarbon rings and aromatic heterocycles. In formulas (Ar-4) to (Ar-6), Ay preferably represents a hydrogen atom.

[0053] In formulas (Ar-4) to (Ar-6), Q3 represents a hydrogen atom, or an alkyl group with 1 to 6 carbon atoms that is unsubstituted or may have substituents. In formulas (Ar-4) to (Ar-6), Q3 preferably represents a hydrogen atom.

[0054] In this case of Ar, it is preferable to exemplify the base (atomic group) represented by the above formula (Ar-4) or the above formula (Ar-6).

[0055] Specific examples of liquid crystal compounds represented by formula (1) are disclosed in International Publication No. 2018 / 123551. The contents of that publication are incorporated herein by reference. Such compounds may be used alone or in combination of two or more.

[0056] The composition containing the liquid crystal compound preferably contains a polymerization initiator. Any suitable polymerization initiator is used. Preferably, it is a photopolymerization initiator capable of initiating the polymerization reaction by irradiation with ultraviolet light. Examples of photopolymerization initiators include: α-carbonyl compounds (described in U.S. Patent Nos. 2,367,661 and 2,367,670), alcohol-ketone ethers (described in U.S. Patent No. 2,448,828), α-hydrocarbon-substituted aromatic alcohol-ketone compounds (described in U.S. Patent No. 2,722,512), and polynuclear quinone compounds (described in U.S. Patent Nos. 3,046,127 and 2,951,758). The polymerization initiator can be a combination of triarylimidazolium dimers and p-aminophenyl ketones (described in U.S. Patent No. 3,549,367), acediazole compounds (described in U.S. Patent No. 4,212,970), and acetylsphosphine oxide compounds (described in Japanese Patent Publications Nos. 63-40799, 5-29234, 10-95788, and 10-29997). The descriptions in these publications are incorporated herein by reference. A single polymerization initiator may be used, or a combination of two or more may be used.

[0057] From the viewpoint of workability in forming a phase retardation layer, the composition containing the liquid crystal compound preferably contains a solvent. Any suitable solvent can be used, but an organic solvent is preferred.

[0058] Compositions containing liquid crystal compounds may further contain any other suitable components. Examples include: antioxidants such as phenolic antioxidants, liquid crystal compounds other than those mentioned above, leveling agents, surfactants, tilt angle control agents, alignment aids, plasticizers, and crosslinking agents.

[0059] The liquid crystal alignment and curing layer can be formed by applying an alignment treatment to the surface of a specific substrate, coating the surface with a composition (coating liquid) containing a liquid crystal compound, aligning the liquid crystal compound in a direction corresponding to the alignment treatment, and fixing the alignment state. In one embodiment, the substrate is any suitable resin film, and the liquid crystal alignment and curing layer formed on the substrate can be transferred to the surface of a polarizing plate.

[0060] As for the aforementioned alignment treatment, any suitable alignment treatment can be adopted. Specifically, examples include: mechanical alignment treatment, physical alignment treatment, and chemical alignment treatment. Specific examples of mechanical alignment treatment include: triboelectric treatment and stretching treatment. Specific examples of physical alignment treatment include: magnetic field alignment treatment and electric field alignment treatment. Specific examples of chemical alignment treatment include: oblique vapor deposition and photo-alignment treatment. The processing conditions for each alignment treatment can be any suitable condition depending on the purpose.

[0061] The alignment of the liquid crystal compound is performed at a temperature suitable for displaying the liquid crystal phase, depending on the type of liquid crystal compound. This temperature treatment causes the liquid crystal compound to be in a liquid crystal state, and the liquid crystal compound is aligned accordingly with the alignment treatment direction of the substrate surface.

[0062] In one embodiment, the alignment state is fixed by cooling the liquid crystal compound aligned in the manner described above. When the liquid crystal compound is a polymerizable monomer or a crosslinking monomer, the alignment state is fixed by subjecting the liquid crystal compound aligned in the manner described above to polymerization or crosslinking treatment.

[0063] Details of the method for forming the alignment-cured layer are described in Japanese Patent Application Publication No. 2006-163343. The description in that publication is incorporated herein by reference.

[0064] C-2. First phase difference layer with layered structure In one embodiment, the first retardation layer has a stacked structure of an alignment and curing layer A (hereinafter also referred to as layer A) of a liquid crystal compound and an alignment and curing layer B (hereinafter also referred to as layer B) of a liquid crystal compound. When the first retardation layer has a stacked structure, either the liquid crystal alignment and curing layer A or the liquid crystal alignment and curing layer B can function as a λ / 4 plate, and the other can function as a λ / 2 plate. For example, when the liquid crystal alignment and curing layer A functions as a λ / 2 plate and the liquid crystal alignment and curing layer B functions as a λ / 4 plate, the Re(550) of the liquid crystal alignment and curing layer A is preferably 200 nm to 300 nm, more preferably 200 nm to 270 nm, further preferably 210 nm to 260 nm, and particularly preferably 230 nm to 260 nm. The Re(550) of the liquid crystal alignment curing layer B is preferably 100 nm to 200 nm, more preferably 100 nm to 170 nm, further preferably 110 nm to 150 nm, and especially preferably 110 nm to 130 nm.

[0065] The thickness of the A layer can be adjusted, for example, in such a way as to obtain an in-plane phase difference required for a λ / 2 plate. The thickness of the A layer is, for example, 2.0 μm to 4.0 μm. The thickness of the B layer can be adjusted, for example, in such a way as to obtain an in-plane phase difference required for a λ / 4 plate. The thickness of the B layer is, for example, 0.5 μm to 2.5 μm. In the present embodiment, the angle formed by the slow axis of the A layer and the absorption axis of the polarizing element is preferably 10° to 20°, more preferably 12° to 18°, and even more preferably 12° to 16°. Also, the angle formed by the slow axis of the B layer and the absorption axis of the polarizing element is preferably 70° to 80°, more preferably 72° to 78°, and even more preferably 72° to 76°. When the first retardation layer has a laminated structure, each layer (for example, the A layer and the B layer) may exhibit an inverse wavelength dispersion characteristic in which the phase difference value increases with the wavelength of the measurement light, may exhibit a positive wavelength dispersion characteristic in which the phase difference value decreases with the wavelength of the measurement light, or may exhibit a flat wavelength dispersion characteristic in which the phase difference value hardly changes regardless of the wavelength of the measurement light.

[0066] The retardation layer (when having a laminated structure, at least one layer) typically exhibits a refractive index characteristic showing a relationship of nx > ny = nz. Furthermore, "ny = nz" includes not only the case where ny and nz are exactly equal, but also the case where they are substantially equal. Therefore, within the scope of not impairing the effects of the present invention, there may be cases where ny > nz or ny < nz. The Nz coefficient of the retardation layer is preferably 0.9 to 1.5, more preferably 0.9 to 1.3.

[0067] In this embodiment, as the above-described liquid crystal compound for the first retardation layer, for example, a liquid crystal compound (nematic liquid crystal) having a nematic phase as the liquid crystal phase can be cited. As such a liquid crystal compound, for example, a liquid crystal polymer or a liquid crystal monomer can be used. The mechanism of manifestation of the liquid crystallinity of the liquid crystal compound can be either a lyotropic type or a thermotropic type. The liquid crystal polymer and the liquid crystal monomer can be used separately or in combination.

[0068] When the liquid crystal compound is a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer or a crosslinking monomer. This is because the alignment state of the liquid crystal monomer can be fixed by polymerizing or crosslinking (i.e., hardening). After aligning the liquid crystal monomers, for example, if the liquid crystal monomers are polymerized or crosslinked with each other, the alignment state can be fixed. Here, although a polymer is formed by polymerization and a three-dimensional network structure is formed by crosslinking, these are not liquid crystals. Therefore, the resulting retardation layer will not undergo transformations to a liquid crystal phase, glassy phase, or crystalline phase due to temperature changes characteristic of liquid crystal compounds. As a result, the retardation layer becomes a retardation layer with extremely excellent stability, unaffected by temperature changes.

[0069] The temperature range for liquid crystal display varies depending on the type of liquid crystal. Specifically, the preferred temperature range is 40°C to 120°C, more preferably 50°C to 100°C, and even more preferably 60°C to 90°C.

[0070] As the aforementioned liquid crystal monomer, any suitable liquid crystal monomer can be used. For example, polymerizable liquid crystal precursor compounds described in Japanese Patent Publication No. 2002-533742 (WO00 / 37585), EP358208 (US5211877), EP66137 (US4388453), WO93 / 22397, EP0261712, DE19504224, DE4408171, and GB2280445 can be used. Specific examples of such polymerizable liquid crystal precursor compounds include BASF's LC242, Merck's E7, and Wacker-Chem's LC-Sillicon-CC3767. Nematic liquid crystal monomers are preferred. Details of the specific examples of the liquid crystal compound and the method for forming the alignment and curing layer are as described above.

[0071] Although the scenario where liquid crystal alignment and curing layer A functions as a λ / 2 plate and liquid crystal alignment and curing layer B functions as a λ / 4 plate has been described, it is also possible to use liquid crystal alignment and curing layer A as a λ / 4 plate and liquid crystal alignment and curing layer B as a λ / 2 plate. Furthermore, the angle between the slow axis of liquid crystal alignment and curing layer A and the absorption axis of the polarizing element can be set to approximately 75°, and the angle between the slow axis of liquid crystal alignment and curing layer B and the absorption axis of the polarizing element can be set to approximately 15°.

[0072] D. Second phase difference layer In one embodiment, the polarizing plate with a phase retardation layer according to the present invention preferably further has a second phase retardation layer. By further having a second phase retardation layer, a polarizing plate with a phase retardation layer can be provided that suppresses in-plane non-uniformity of reflected hue and has excellent high-temperature durability.

[0073] The elongation at break of the second retardation layer is preferably 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 suppresses in-plane non-uniformity of reflected hue and exhibits excellent high-temperature durability. In this specification, the elongation at break of the retardation layer can be measured using a thermomechanical analysis apparatus (TMA).

[0074] 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 becomes relatively smaller. In other words, it means that the refractive index in the direction orthogonal to the extension direction becomes larger. Since it is composed of a resin film containing a polymer exhibiting negative birefringence, the phase difference change of the second retardation layer caused by the dimensional shrinkage of the polarizer can be reduced. Therefore, a polarizer with a retardation layer can be provided where the in-plane non-uniformity of the reflected hue is further suppressed and it has excellent high-temperature durability.

[0075] The second retardation layer is preferably a positive C-plate, exhibiting a refractive index characteristic of nz > nx = ny. By using a positive C-plate as the second retardation layer, oblique reflection can be effectively prevented, achieving a wide viewing angle for anti-reflection functionality. The phase difference Rth(550) in the thickness direction of the second retardation layer is preferably -10 nm to -200 nm, more preferably -20 nm to -180 nm, further preferably -30 nm to -160 nm, and particularly preferably -40 nm to -140 nm. Here, "nx = ny" includes not only the case where nx and ny are strictly equal, but also the case where nx and ny are substantially equal. That is, the in-plane phase difference Re(550) of the second retardation layer may not reach 10 nm.

[0076] The thickness of the second retardation layer 30 can be set to any appropriate thickness. The thickness of the second retardation layer is preferably 1 μm to 30 μm, more preferably 2 μm to 20 μm, and even more preferably 3 μm to 8 μm.

[0077] Polymers exhibiting negative birefringence include, for example, polymers with aromatic rings and / or carbonyl groups or other chemical bonds or functional groups with high polarization anisotropy introduced into their side chains. Specifically, examples include acrylic resins, styrene resins, and maleimide resins. Preferably, at least one polymer selected from the group consisting of acrylic resins with aromatic rings introduced into their side chains, styrene resins with aromatic rings introduced into their side chains, and maleimide resins with aromatic rings introduced into their side chains can be used; more preferably, styrene resins with aromatic rings introduced into their side chains can be used. Only one polymer exhibiting negative birefringence can be used, or two or more can be combined.

[0078] 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.

[0079] 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, p-tert-butylstyrene, etc.

[0080] Maleimide 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.

[0081] In addition polymerization, the birefringence properties of the obtained resin can also be controlled by substituting the side chains or carrying out maleicimization or grafting reactions after polymerization.

[0082] 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.

[0083] 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.

[0084] 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 Chemical Japan and Arakawa Chemical Industry Co., Ltd.

[0085] 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 higher negative birefringence and has excellent heat resistance and mechanical strength. Such a polymer can be obtained, for example, by using an N-phenyl-substituted maleimide, wherein the N-phenyl-substituted maleimide is a maleimide monomer with an N-substituent having a phenyl group having a substituent at least at the ortho position as a starting material. [Chemistry 2]

[0086] In the above general formula (II), R1 to R5 independently represent hydrogen atoms, halogen atoms, carboxylic acids, carboxylic acid esters, hydroxyl groups, nitro groups, or straight-chain or branched alkyl or alkoxy groups with 1 to 8 carbon atoms (wherein 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.

[0087] The polymer exhibiting negative birefringence is not limited to those described above; for example, cyclic olefin copolymers disclosed in Japanese Patent Application Publication No. 2005-350544 may also be used. Furthermore, compositions comprising polymers and inorganic microparticles disclosed in Japanese Patent Application Publication Nos. 2005-156862 and 2005-227427 are also suitable. Moreover, they can be modified by copolymerization, branching, crosslinking, molecular end modification (or sealing), and stereoregular modification before use.

[0088] The resin composition forming the second phase difference layer may 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. Typically, the additive content is approximately 3 to 10 parts by weight relative to 100 parts by weight of the total solids content of the resin composition. If the additive content is too high, the transparency of the polymer film may be impaired, or the additives may seep out from the surface of the polymer film.

[0089] 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 (fiber reinforced plastics) molding, and solvent casting. Among these, extrusion molding and solvent casting are preferred because they can produce retardation films with higher smoothness and better optical uniformity. Specifically, extrusion molding is a method as follows: a resin composition containing the aforementioned thermoplastic resin, plasticizer, additives, etc., is heated to melt it, and then extruded in thin film form onto the surface of a casting roller using a T-die or the like, and then cooled to form a film. Solvent casting is a method as follows: a thick solution (film-forming solution) obtained by dissolving the aforementioned resin composition in a solvent is defoamed, and then uniformly cast in thin film form onto the surface of a metallic belt or drum, or a plastic substrate, etc., so that the solvent evaporates and a film is formed. Furthermore, the molding conditions can be appropriately set according to the composition or type of resin used, the molding process, etc.

[0090] E. Adhesive layer As the adhesive constituting the outermost adhesive layer (the adhesive layer between the image display device 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, appropriate wetting, cohesiveness, and adhesion properties, as well as excellent weather resistance or heat resistance, are preferred. Acrylic adhesives are preferred as adhesives exhibiting these characteristics.

[0091] F. Image display device The polarizing plate with a phase retardation layer described in items A to E above can be applied 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, 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 to E above on its viewing side. The polarizing plate with a 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 (the polarizing element is on the viewing side). Example

[0092] The present invention will now be specifically described with reference to 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 are based on weight.

[0093] (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 Hikari Tsuji, product name "KC-351C").

[0094] (2) Uneven reflection hue The polarizing plate with a phase retardation layer obtained in the examples and comparative examples was cut into 60 mm long and 130 mm wide sections to prepare a sample. The portion of the sample with a length of 30 mm and a width of 25 mm was designated as measurement position A, the portion with a length of 30 mm and a width of 65 mm was designated as measurement position B, and the portion with a length of 30 mm and a width of 105 mm was designated as measurement position C. 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 80°C for 500 hours. Using a spectrophotometer (manufactured by Konica Minolta, product name: CM-26d, light source D65), the hue a* and hue b* values ​​at measurement positions A, B, and C were measured. The hue a* and hue b* values ​​at each measurement position were plotted, and the results from measurement positions A and B, and B and C were compared. The value with the largest hue difference (larger distance between plots) was considered the hue inhomogeneity of each sample.

[0095] (3) Phase difference change value RS The polarizing plates with phase retardation layers obtained in the examples and comparative examples were cut into samples with a width of 15 mm and a length of 200 mm. Tension was applied along the length of the obtained samples using a tension meter (manufactured by MYCARBON, product name: Digital Luggage Scale). At tensions of 0 kg, 0.5 kg, 1 kg, 1.5 kg, and 2 kg, the in-plane phase difference (Re(550)) was measured using a phase difference measuring device (manufactured by Oji Measurement Instrument Co., Ltd., product name: KOBRA-WPR). An approximate straight line was obtained based on the Re(550) values ​​measured at each tension, and the slope of the approximate straight line was taken as the phase difference change value RS.

[0096] (4) Elongation at break The second phase difference layer obtained in Manufacturing Examples 3 and 5 was cut into short strips with a width of 4 mm and a length of 2 cm and used as test samples. Tensile tests were performed using a thermomechanical analysis apparatus (TMA) (trade name "TMA Q400", manufactured by TA Instruments) to determine the elongation at break (%). The measurement was performed under the conditions of a clamping distance of 8 mm and a tensile speed of 0.1% strain / min.

[0097] [Manufacturing Example 1: Production of Polarizing Plate] 1. Fabrication of polarizing elements For a long roll of a 30 μm thick polyvinyl alcohol (PVA) resin film (manufactured by Kuraray, product name "PE3000"), a uniaxial stretching process is carried out in the long side direction by a roller stretching machine, which stretches the film 5.9 times in the long side direction. At the same time, swelling, dyeing, crosslinking, and washing processes are applied, and finally drying is applied to produce a 12 μm thick polarizing element. Specifically, the swelling treatment is carried out in pure water at 20°C, extending the fiber by 2.2 times. Next, the dyeing treatment, to achieve a monomer transmittance of 45.0% for the obtained polarizing element, is carried out in an aqueous solution at 30°C with an iodine concentration adjusted to a potassium iodide weight ratio of 1:7, extending the fiber by 1.4 times. Then, the crosslinking treatment employs a two-stage process. The first stage is carried out in an aqueous solution at 40°C containing dissolved boric acid and potassium iodide, extending the fiber by 1.2 times. The boric acid content in the first stage crosslinking treatment aqueous solution is 5.0% by weight, and the potassium iodide content is 3.0% by weight. The second stage crosslinking treatment is carried out in an aqueous solution at 65°C containing dissolved boric acid and potassium iodide, extending the fiber by 1.6 times. The boric acid content in the second stage crosslinking treatment aqueous solution is 3.7% by weight, and the potassium iodide content is 5.0% by weight. Finally, the washing treatment is carried out in an aqueous solution of potassium iodide at 20°C. The aqueous solution used for washing contained 3.1% potassium iodide by weight. Finally, the drying process was carried out at 70°C for 5 minutes to obtain the polarizing element.

[0098] 2. Production of polarizing plates On the surface of the polarizing element obtained above (the side opposite to the resin substrate), an HC-COP film is laminated as a protective layer using a UV-curable adhesive. Specifically, the adhesive is coated to a total thickness of 1.0 μm and laminated using a roller press. Then, UV (Ultraviolet) light is irradiated from the protective layer side to cure the adhesive. Furthermore, the HC-COP film is a film with a 2 μm thick hard coating (HC) layer formed on a cycloolefin (COP) film (manufactured by Zeon Corporation, Japan, product name "ZF12", thickness 25 μm), laminated with the COP film facing the polarizing element side. Subsequently, the resin substrate is peeled off to obtain a polarizing plate consisting of a protective layer (HC layer / COP film) / adhesive layer / polarizing element.

[0099] [Manufacturing Example 2: Fabrication of the First Phase Difference Layer A (Single First Phase Difference Layer)] 55 parts by weight of the compound represented by formula (I), 25 parts by weight of the compound represented by formula (II), and 20 parts by weight of the compound represented by formula (III) were added to 400 parts by weight of cyclopentanone (CPN), and the mixture was heated to 60°C and stirred to dissolve. The solution was then allowed to return to room temperature, and 3 parts by weight of Irgacure 907 (manufactured by BASF Japan), 0.2 parts by weight of MEGAFAC F-554 (manufactured by DIC), and 0.1 parts by weight of p-methoxyphenol (MEHQ) were added to the solution, followed by stirring. The resulting solution was clear and homogeneous. The solution was filtered using a 0.20 μm membrane filter to obtain a polymerizable composition. Furthermore, using spin coating, the alignment film was coated onto a 0.7 mm thick glass substrate with polyimide solvent. After drying at 100°C for 10 minutes, it was calcined at 200°C for 60 minutes to obtain the coating film. The obtained coating film was then rubbed using a commercially available friction device to form an alignment film. Next, the polymeric composition obtained above was coated onto a substrate (essentially an alignment film) using a spin coating method and dried at 100°C for 2 minutes. After the coated film was cooled to room temperature, it was irradiated with ultraviolet light at an intensity of 30 mW / cm² for 30 seconds using a high-pressure mercury lamp to obtain a first retardation layer (3 μm thick) serving as the alignment curing layer of the liquid crystal compound. The in-plane phase difference Re(550) of the first retardation layer is 130 nm. Furthermore, the Re(450) / Re(550) of the first retardation layer is 0.851, exhibiting reverse wavelength dispersion characteristics. The first retardation layer can function as a λ / 4 plate. [Chemistry 3] [Chemistry 4]

[0100] [Manufacturing Example 3: Fabrication of the Second Phase Difference Layer] In a high-pressure reactor equipped with a stirrer, condenser, nitrogen inlet pipe, and thermometer, 48 parts by weight of hydroxypropyl methylcellulose (manufactured by 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 added. After nitrogen was introduced for 1 hour, the mixture was stirred and maintained at 49°C for 24 hours to carry out free radical suspension polymerization. Subsequently, the mixture was cooled to room temperature, and the resulting suspension containing 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 resin was dissolved in a toluene-methyl ethyl ketone mixed solution (toluene / methyl ethyl ketone 50% / 50% by weight) to prepare a 20% solution. Furthermore, 5 parts by weight of tributyl trimellitate were added as a plasticizer to 100 parts by weight of the trans-butened ester resin to prepare the film-forming solution. The support membrane system used was a biaxially stretched polyester (polyethylene terephthalate-polyethylene isophthalate copolymer) membrane (75 μm thick). The prepared film-forming solution was coated onto the support membrane to a dried film thickness of 5 μm and dried at 140°C. The dried coating (positive C plate) had Re(550) ≒ 0 nm and Rth(550) = -75 nm.

[0101] [Manufacturing Example 4: Fabrication of the First Phase Difference Layer B (the first phase difference layer with a stacked structure)] A liquid crystal composition (coating solution) was prepared by dissolving 10 g of a polymerizable liquid crystal (manufactured by BASF: trade name "Paliocolor LC242", represented by the following formula) of a display nematic liquid crystal phase and 3 g of a photopolymerization initiator for the polymerizable liquid crystal compound (manufactured by BASF: trade name "Irgacure 907") in 40 g of toluene. [Chemistry 5]

[0102] An alignment treatment was performed by rubbing the surface of a polyethylene terephthalate (PET) film (38 μm thick) with a rubbing cloth. The alignment treatment direction was set such that, when attached to a polarizing plate, the direction relative to the absorption axis of the polarizing element was 15° from the viewing side. The liquid crystal coating solution was applied to the alignment-treated surface using a rod coater and dried at 90°C for 2 minutes to align the liquid crystal compound. The liquid crystal layer thus formed was then irradiated with light of 1 mJ / cm² using a metal halide lamp to harden it, thereby forming a liquid crystal alignment cured layer A on the PET film. The thickness of the liquid crystal alignment cured layer A was 2.5 μm, and the in-plane phase difference Re(550) was 270 nm. Furthermore, the liquid crystal alignment cured layer A exhibited a refractive index characteristic of nx > ny = nz.

[0103] By changing the coating thickness and setting the alignment treatment direction to 75° relative to the absorption axis of the polarizing element when viewed from the viewing side, a liquid crystal alignment and curing layer B is formed on the PET film in the same manner as described above. The thickness of the liquid crystal alignment and curing layer B is 1.5 μm, and the in-plane phase difference Re(550) is 140 nm. Furthermore, the liquid crystal alignment and curing layer B exhibits a refractive index characteristic of nx > ny = nz.

[0104] [Example 1] A protective layer (triacetin cellulose (TAC) film, thickness: 20 μm) is bonded to the polarizing element of the polarizing plate obtained in Manufacturing Example 1 via an adhesive layer, thereby obtaining a polarizing plate consisting of a protective layer (HC layer / COP film) / adhesive layer / polarizing element / adhesive layer / protective layer (TAC). Furthermore, for the liquid crystal alignment and curing layer A and liquid crystal alignment and curing layer B obtained in Manufacturing Example 4, they were sequentially transferred (bonded) with the angle between the absorption axis of the polarizing element and the slow axis of alignment and curing layer A being 15° and the angle between the absorption axis of the polarizing element and the slow axis of alignment and curing layer B being 75°. Alignment and curing layer A and alignment and curing layer B were respectively laminated using a UV-curable adhesive (1 μm thickness after curing). Subsequently, an ultraviolet-curable adhesive (1 μm thick after curing) is coated on the liquid crystal alignment curing layer B, and the second phase difference layer obtained in the stacking manufacturing example 3 is stacked to obtain a stack of liquid crystal alignment curing layer A / adhesive layer / liquid crystal alignment curing layer B / adhesive layer / second phase difference layer. Subsequently, the TAC side surface of the obtained polarizing plate was laminated with the liquid crystal alignment and curing layer A of the aforementioned laminate via an acrylic adhesive layer (5 μm thick). Then, the substrate of the second retardation layer was peeled off. Afterward, an acrylic adhesive (26 μm thick) was coated on the peeled surface of the substrate of the second retardation layer, resulting in a polarizing plate with a retardation layer consisting of a protective layer (HC layer / COP film) / adhesive layer / polarizing element / adhesive layer / protective layer (TAC) / adhesive layer / first retardation layer (liquid crystal alignment and curing layer A / adhesive layer / liquid crystal alignment and curing layer B) / adhesive layer / second retardation layer / adhesive layer. The obtained polarizing plate was evaluated as described above. The results are shown in Table 1.

[0105] [Example 2] Except for the un-deposited second retardation layer, the operation was performed in the same manner as in Example 1 to obtain a polarizing plate with a retardation layer. The obtained polarizing plate was evaluated as described above. The results are shown in Table 1.

[0106] [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, it is represented as a block polymer with a weight average molecular weight of 5000), 80 parts by weight of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (manufactured by BASF, trade name Paliocolor LC242), and 5 parts by weight of a photopolymerization initiator (manufactured by Ciba Specialty Chemicals, trade name Irgacure 907) in 200 parts by weight of cyclopentanone. The solution was then coated onto a PET substrate that had undergone vertical alignment treatment using a rod coater and dried at 80°C for 4 minutes to orient the liquid crystals. The liquid crystal layer was then irradiated with ultraviolet light to harden it, thereby forming a retardation layer (3 μm thick) exhibiting refractive index characteristics of nz > nx = ny on the substrate. The elongation at break of the obtained retardation layer was 3%. [Chemistry 6]

[0107] (Comparative Example 1) Except that the phase retardation layer obtained in Manufacturing Example 5 was used instead of the second phase retardation layer obtained in Manufacturing Example 3, the operation was performed in the same manner as in Example 1 to obtain a polarizing plate with a phase retardation layer. The obtained polarizing plate was evaluated as described above. The results are shown in Table 1.

[0108] [Example 3] A protective layer (triacetin cellulose (TAC) film, thickness: 20 μm) is bonded to the polarizing element of the polarizing plate obtained in Manufacturing Example 1 via an adhesive layer, thereby obtaining a polarizing plate consisting of a protective layer (HC layer / COP film) / adhesive layer / polarizing element / adhesive layer / protective layer (TAC). Furthermore, the first retardation layer A obtained in Manufacturing Example 2 is bonded to the protective layer (TAC) of the polarizing plate at an angle of 45° between the absorption axis of the polarizing element and the slow axis of the first retardation layer A. The first retardation layer and the protective layer (TAC) are laminated using an ultraviolet-curing adhesive (1 μm thick after curing). Next, the TAC side surface of the obtained polarizing plate was laminated with the first retardation layer via an acrylic adhesive layer (5 μm thick). Then, the substrate of the second retardation layer was peeled off. Subsequently, an acrylic adhesive (26 μm thick) was applied to the peeled surface of the second retardation layer substrate to obtain a polarizing plate with a retardation layer consisting of a protective layer (HC layer / COP film) / adhesive layer / polarizing element / adhesive layer / protective layer (TAC) / adhesive layer / first retardation layer / adhesive layer / second retardation layer / adhesive layer. The obtained polarizing plate was evaluated as described above. The results are shown in Table 1.

[0109] (Comparative Example 2) Except for the un-deposited second retardation layer, the operation was performed in the same manner as in Example 2 to obtain a polarizing plate with a retardation layer. The obtained polarizing plate was evaluated as described above. The results are shown in Table 1.

[0110] (Comparative Example 3) Except that the phase retardation layer obtained in Manufacturing Example 5 was used instead of the second phase retardation layer obtained in Manufacturing Example 3, the operation was performed in the same manner as in Example 1 to obtain a polarizing plate with a phase retardation layer. The obtained polarizing plate was evaluated as described above. The results are shown in Table 1.

[0111] [Table 1] Composition of the first phase difference layer Composition of the second phase difference layer Phase difference change (slope) Uneven reflection hue Example 1 Two-layer stacked structure resin 0.8 0.3 Example 2 none 1.6 0.62 Comparative Example 1 liquid crystal 2.1 0.81 Example 3 Single layer resin 1.7 0.7 Comparative Example 2 none 2.7 0.91 Comparative Example 3 liquid crystal 3.2 1.11

[0112] [evaluate] As can be seen from Table 1, the in-plane non-uniformity of the reflected hue of the polarizing plate with the phase retardation layer in the embodiment of the present invention is suppressed. [Industrial Applicability]

[0113] The polarizing plate with phase retardation layer of the present invention is suitable for use in image display devices such as liquid crystal display devices, organic EL display devices and inorganic EL display devices.

[0114] 10:Polarizing plate 11: Polarizing element 12: Protective layer 13: Protective layer 20: First phase difference layer 21: Liquid crystal alignment solidified layer A 22: Liquid crystal alignment and curing layer B 30: Second phase difference layer 100: Polarizing plate with phase retardation layer 101: Polarizing plate with phase retardation layer

Claims

1. A polarizing plate with a phase retardation layer, comprising a polarizing plate including a polarizing element and a first phase retardation layer, wherein the phase difference variation value RS of the polarizing plate with the phase retardation layer is 2.0 or less, and the phase difference variation value RS is the slope of an approximate straight line of the in-plane phase difference Re(550) of the polarizing plate with the phase retardation layer measured under tensions of 0 kg, 0.5 kg, 1 kg, 1.5 kg and 2 kg.

2. The polarizing plate with a phase retardation layer as claimed in claim 1, further having a second phase retardation layer with an elongation at break of 1% or more.

3. The polarizing plate with a phase retardation layer as claimed in claim 2, wherein the second phase retardation layer is a positive C-plate composed of a resin film containing a polymer exhibiting negative birefringence.

4. The polarizing plate with a phase retardation layer as claimed in claim 3, wherein the polymer exhibiting negative birefringence is selected from at least one of the group consisting of acrylic resins with aromatic rings introduced into their side chains, styrene resins with aromatic rings introduced into their side chains, and maleimide resins with aromatic rings introduced into their side chains.

5. A polarizing plate with a phase retardation layer as claimed in any of claims 1 to 4, wherein the first phase retardation layer is an alignment and curing layer of a liquid crystal compound, and the in-plane phase difference Re(550) of the first phase retardation layer is 100 nm < Re(550) < 160 nm, and satisfies Re(450) / Re(550) < 1 and Re(650) / Re(550) > 1.

6. The polarizing plate with a phase retardation layer as claimed in claim 5, wherein the angle between the slow axis of the first phase retardation layer and the absorption axis of the polarizing element is 40° to 50°.

7. A polarizing plate with a phase retardation layer as claimed in any of claims 1 to 4, wherein the first phase retardation layer has a stacked structure of an alignment and curing layer A of a liquid crystal compound and an alignment and curing layer B of a liquid crystal compound, and the alignment and curing layer A functions as a λ / 2 plate and the alignment and curing layer B functions as a λ / 4 plate.

8. The polarizing plate with a phase retardation layer as claimed in claim 7, wherein the angle between the slow axis of the alignment and curing layer A of the liquid crystal compound and the absorption axis of the polarizing element is 70° to 80°, and the angle between the slow axis of the alignment and curing layer B of the liquid crystal compound and the absorption axis of the polarizing element is 10° to 20°.

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

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