Elliptical polarizing plate and image display device

Abstract

To provide an elliptical polarizing plate that has suppressed a change in visibility around an irregular shape processing part.SOLUTION: An elliptical polarizing plate (101) comprises: a polarizing plate (1) that includes transparent protective films (11, 12) on both sides of a polarizer (10) having a thickness of 15 μm or more; and a phase difference layer (3) that is laminated on the transparent protective film (11) of the polarizing plate. The elliptical polarizing plate has an irregular shape. An absorption axis direction of the polarizer (10) and a slow axis direction of the phase difference layer (3) form an angle of 10-80°. In the phase difference layer (3), a front face retardation Re(450) at a wavelength of 450 nm, a front face retardation Re(550) at a wavelength of 550 nm, and a front face retardation Re(650) at a wavelength of 650 nm satisfy Re(450)<Re(550)<Re(650). The phase difference layer includes at least one aligned liquid crystal layer in which liquid crystal molecules are homogeneously aligned.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an elliptically polarizing plate having a retardation layer on one main surface of the polarizing plate, and an image display device having an elliptically polarizing plate on the surface of an image display cell. [Background technology]

[0002] Mobile phones, smartphones, car navigation devices, PC monitors, televisions, and the like are display devices equipped with image display elements, and as image display elements, they are equipped with liquid crystal display devices and organic electroluminescence (EL) display devices. Due to their display principles, liquid crystal display devices have a polarizing plate disposed on the viewing side surface of the image display cell. In organic EL display devices, an elliptical polarizing plate (e.g., a circular polarizing plate formed by laminating a polarizing plate and a quarter-wave plate) is disposed on the viewing side surface of the image display cell to prevent external light from being reflected by a metal electrode (cathode) and being viewed as a mirror surface.

[0003] In recent years, organic EL display devices that can be made thin and curved have been increasingly adopted, and are now being used in instruments and the like arranged in the instrument panels and consoles of automobiles. Optical films such as polarizing plates used in these display devices may be processed into shapes (irregular shapes) that are not rectangular in plan view (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-47611 A Summary of the Invention [Problem to be solved by the invention]

[0005] In-vehicle image display devices are required to have small changes in display characteristics even in harsh environments such as high temperature and high humidity. However, an image display device equipped with a circular polarizing plate with a deformed shape on the surface of an organic EL cell has a problem that when exposed to a high temperature environment for a long time, coloration of reflected light is likely to be visually recognized around the deformed processed parts such as notches and cutouts.

[0006] In view of the above, an object of the present invention is to provide an elliptical polarizing plate in which changes in visibility around the deformed processed parts are suppressed.

Means for Solving the Problems

[0007] The present invention relates to a single-sheet elliptical polarizing plate having a deformed shape that is not rectangular in plan view. The elliptical polarizing plate includes a polarizing plate having transparent protective films on both sides of a polarizer with a thickness of 15 μm or more, and a retardation layer laminated on the transparent protective film on one surface of the polarizing plate. The angle formed by the absorption axis direction of the polarizer and the slow axis direction of the retardation layer is 10 to 80°. The retardation layer satisfies Re(450) < Re(550) < Re(650) for the front retardation Re(450) at a wavelength of 450 nm, the front retardation Re(550) at a wavelength of 550 nm, and the front retardation Re(650) at a wavelength of 650 nm.

[0008] The retardation layer includes at least one layer of an aligned liquid crystal layer in which liquid crystal molecules are homogeneously aligned. The retardation layer may include two or more layers of aligned liquid crystal layers, at least one of which is a homogeneously aligned liquid crystal layer. The retardation layer may include two or more layers of homogeneously aligned liquid crystal layers. The retardation layer may include an aligned liquid crystal layer in which liquid crystal molecules are homogeneously aligned and an aligned liquid crystal layer in which liquid crystal molecules are homeotropically aligned.

[0009] The elliptical polarizing plate of the present invention is suitably used for forming an in-vehicle image display device. In one embodiment, the elliptical polarizing plate is disposed and used on the viewing-side surface of the image display cell. The image display cell may be an organic EL cell.

Advantages of the Invention

[0010] In the elliptically polarizing plate of the present invention, even when exposed to a high-temperature environment for a long period of time, the change in the front retardation of the retardation layer is small, and the change in visibility around the irregularly shaped portion can be suppressed. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic plan view for explaining the planar shape of an irregular elliptically polarizing plate. FIG. [Diagram 2] 1 is a schematic plan view for explaining the planar shape of an irregular elliptically polarizing plate. FIG. [Diagram 3] 1 is a schematic plan view for explaining the planar shape of an irregular elliptically polarizing plate. FIG. [Figure 4] FIG. 2 is a cross-sectional view of an elliptically polarizing plate according to an embodiment. [Diagram 5] FIG. 2 is a cross-sectional view of an elliptically polarizing plate according to an embodiment. [Figure 6] FIG. 2 is a cross-sectional view of an elliptically polarizing plate according to an embodiment. [Figure 7] FIG. 2 is a cross-sectional view showing an example of a layered structure of an image display device. [Figure 8] FIG. 13 is a diagram for explaining a change in retardation in a contoured portion. [Figure 9] FIG. 2 is a diagram showing the planar shape and measurement points of the in-plane retardation of an irregular circular polarizing plate produced in an example. [Figure 10] 1 is a graph plotting the reflected hues of the circular polarizing plates of Examples and Comparative Examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention relates to a sheet of an elliptically polarizing plate having a shape (irregular shape) other than rectangular in a plan view. Figures 1 to 3 are plan views for explaining the planar shape of an irregular elliptically polarizing plate. Figures 4 to 6 are cross-sectional views of an elliptically polarizing plate according to an embodiment of the present invention.

[0013] The elliptical polarizing plate of the present invention includes a polarizing plate 1 having transparent protective films 11 and 12 laminated to both sides of a polarizer 10, and a retardation layer 3 on the transparent protective film 11. The angle between the absorption axis direction of the polarizer 10 and the slow axis direction of the retardation layer 3 is 10 to 80°.

[0014] [Shape of elliptical polarizing plate] In this specification, "irregular shape" refers to a shape other than a rectangle in plan view. An irregular elliptical polarizing plate typically has an irregularly processed portion that has been irregularly processed. Irregular elliptical polarizing plates include those that have an irregularly processed portion on the outer edge of an elliptical polarizing plate, so that the outer edge shape is not rectangular, those that have an irregularly processed portion at a portion spaced inward from the outer edge of a rectangular elliptical polarizing plate, and those that have an irregularly processed portion on both the outer edge and the portion spaced from the outer edge.

[0015] Examples of irregular shapes (irregularly processed parts) include those having a machined part that becomes a recess when viewed from above, and those having a through hole, as shown in Figures 1 and 2. Representative examples of recesses include a shape that resembles a boat shape, a rectangle, an R-shape that resembles a bathtub shape, a V-notch, and a U-notch. Another example of an irregular shape (irregularly processed part) is a shape that corresponds to an automobile meter panel, as shown in Figure 3. This shape includes a part in which the outer edge is formed in an arc shape that follows the rotation direction of the meter needle, and the outer edge forms a V-shape (including an R-shape) that is convex inward in the planar direction.

[0016] The shape of the irregular shape (irregularly processed portion) is not limited to the illustrated examples in Figs. 1 to 3. For example, the shape of the through hole may be an ellipse, a triangle, a rectangle, a pentagon, a hexagon, an octagon, or the like. The through hole is provided at any appropriate position depending on the purpose. The position of the through hole is not particularly limited. A single elliptical polarizing plate may have a plurality of through holes.

[0017] The shape of the elliptical polarizing plate may be a combination of a plurality of modified shapes. For example, a through hole may be formed at any position of the elliptical polarizing plate having the outer edge shape of Fig. 1, or a V-shaped or U-shaped notch may be formed at any position of the elliptical polarizing plate having the outer edge shape of Fig. 3.

[0018] When the irregularly shaped portion includes an R shape, the radius of curvature is, for example, 0.2 mm or more, and may be 0.5 mm or more, 1 mm or more, or 2 mm or more. The radius of curvature of the irregularly shaped portion may be, for example, 10 mm or less, and may be 7 mm or less, or 5 mm or less.

[0019] The irregularly shaped portion may be formed by any suitable method, examples of which include cutting with an end mill, punching with a Thomson blade or a pinnacle blade, and cutting by laser light irradiation.

[0020] Such an irregular shaped elliptically polarizing plate is suitable for use in an in-vehicle image display device such as an automobile meter panel, and in a mobile image display device such as a smartphone, a tablet PC, a smart watch, etc. As described in detail later, the elliptically polarizing plate of the present invention is particularly suitable for use in an in-vehicle image display device.

[0021] [Layer structure of elliptically polarizing plate] 4 is a cross-sectional view of an elliptical polarizing plate according to one embodiment of the present invention. An elliptical polarizing plate 101 comprises a polarizer 10 having transparent protective films 11 and 12 on both sides thereof and a retardation layer 3 on one side thereof.

[0022] <Polarizing plate> Examples of the polarizer 10 of the polarizing plate 1 include hydrophilic polymer films such as polyvinyl alcohol films and partially saponified ethylene-vinyl acetate copolymer films, which are uniaxially stretched after adsorbing a dichroic substance such as iodine or a dichroic dye, and polyene-based oriented films such as dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride.

[0023] A polyvinyl alcohol (PVA) film containing iodine is preferable as the polarizer 10 because it has a high degree of polarization and durability at high temperatures. As a material for the PVA film applied to the polarizer, polyvinyl alcohol or a derivative thereof is used. Examples of polyvinyl alcohol derivatives include polyvinyl formal, polyvinyl acetal, etc., as well as those modified with olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, their alkyl esters, acrylamide, etc. Polyvinyl alcohol with a degree of polymerization of about 1000 to 10000 and a degree of saponification of about 80 to 100 mol % is generally used.

[0024] A polarizer is obtained by subjecting a PVA-based film to iodine dyeing and stretching. In the manufacturing process of a polarizer, treatments such as washing with water, swelling, and crosslinking may be performed as necessary. Stretching may be performed either before or after iodine dyeing, or stretching may be performed while dyeing. Stretching may be performed in air (dry stretching), or in water or in an aqueous solution containing boric acid, potassium iodide, or the like (wet stretching), or these may be used in combination.

[0025] The thickness of the polarizer 10 is 15 μm or more. A polarizer with a large thickness tends to have high durability at high temperatures, making it suitable for in-vehicle use. From the viewpoint of thinning, the thickness of the polarizer 10 is preferably 100 μm or less, and may be 60 μm or less, 50 μm or less, or 40 μm or less.

[0026] <Transparent protective film> The polarizing plate 1 includes transparent protective films 11 and 12 on both main surfaces of a polarizer 10. By laminating the transparent protective films on both surfaces of the polarizer 10, changes in optical properties caused by dimensional changes of the polarizer at high temperatures tend to be suppressed.

[0027] Thermoplastic resins having excellent transparency, mechanical strength, and thermal stability are preferable as materials for forming the transparent films 11 and 12 as polarizer protective films. Specific examples of thermoplastic resins include cellulose-based resins such as triacetyl cellulose, polyester-based resins, polyethersulfone-based resins, polysulfone-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyolefin-based resins, (meth)acrylic-based resins, cyclic polyolefin-based resins (norbornene-based resins), polyarylate-based resins, polystyrene-based resins, polyvinyl alcohol-based resins, and mixtures thereof.

[0028] The transparent film 11 arranged on one surface of the polarizer 10 and the transparent film 12 arranged on the other surface thereof may be films made of the same resin material or may be films made of different resin materials.

[0029] The thickness of the transparent films 11 and 12 is not particularly limited, but from the standpoint of strength, workability such as handleability, thinness, and the like, it is preferably about 5 to 100 μm, and more preferably 10 to 80 μm.

[0030] <Adhesive> The polarizer 10 and the transparent protective films 11 and 12 are preferably bonded together via an appropriate adhesive layer (not shown). As the adhesive, various types of adhesives such as water-based adhesives, solvent-based adhesives, hot melt adhesives, and active energy ray curing adhesives are used. Among these, water-based adhesives and active energy ray curing adhesives are preferred because they can reduce the thickness of the adhesive layer. The adhesive material is not particularly limited as long as it is optically transparent, and examples of the adhesive material include epoxy resins, silicone resins, acrylic resins, polyurethane, polyamide, polyether, and polyvinyl alcohol. The thickness of the adhesive is preferably 5 μm or less, more preferably 0.01 to 3 μm, and even more preferably 0.05 to 2 μm.

[0031] <Retardation layer> The elliptical polarizing plate 101 includes a retardation layer 3 on the transparent protective film 11 of the polarizing plate 10. The retardation layer 3 may be composed of a single layer or may be a laminate of a plurality of retardation layers as shown in FIGS. 5 and 6.

[0032] The retardation layer 3 is arranged such that the angle formed by the absorption axis direction of the polarizer 10 and the slow axis direction of the retardation layer 3 is 10 to 80°. Since the absorption axis direction of the polarizer and the slow axis direction of the retardation layer are arranged at an angle that is neither parallel nor orthogonal, when the linearly polarized light emitted from the polarizer 10 passes through the retardation layer 3, it is converted into elliptical polarized light. Therefore, the laminate of the polarizing plate 1 and the retardation layer 3 functions as an elliptical polarizing plate.

[0033] The retardation layer 3 satisfies Re(450) < Re(550) < Re(650) for the front retardation Re(450) at a wavelength of 450 nm, the front retardation Re(550) at a wavelength of 550 nm, and the front retardation Re(650) at a wavelength of 650 nm. Since the retardation layer 3 has the characteristic of having a larger retardation as the wavelength becomes longer (so-called "reverse wavelength dispersion"), the elliptical polarizing plate can emit uniform elliptical polarized light over a wide wavelength range of visible light.

[0034] In the retardation layer 3, Re(450) / Re(550) is less than 1, preferably 0.65 to 0.99, more preferably 0.70 to 0.95, still more preferably 0.75 to 0.90, and may be 0.80 to 0.85. In the retardation layer 3, Re(650) / Re(550) is greater than 1, preferably 1.01 to 1.35, more preferably 1.03 to 1.30, still more preferably 1.05 to 1.25, and even more preferably 1.10 to 1.20.

[0035] In one embodiment, the elliptical polarizing plate 101 is a circular polarizing plate in which the retardation layer 3 is a quarter-wave plate, and the angle between the absorption axis direction of the polarizer 10 and the slow axis direction of the retardation layer 3 is approximately 45°. A circular polarizing plate having a retardation layer 3 with reverse wavelength dispersion has a small difference between the front retardation of the retardation layer and the quarter-wave over a wide wavelength range of visible light, so that the circularly polarized light is broadbanded. By arranging a broadband circular polarizing plate on the surface of an organic EL display device, the reflected light is less colored, and excellent anti-reflection properties can be achieved.

[0036] In order to convert the elliptically polarizing plate into a circular polarizing plate for the purpose of preventing reflection in an organic EL display device, the front retardation R(550) of the retardation layer 3 at a wavelength of 550 nm is preferably 100 to 180 nm, more preferably 110 to 170 nm, further preferably 120 to 150 nm, and may be 125 to 145 nm. The angle ψ between the absorption axis direction of the polarizer 10 and the slow axis direction of the retardation layer 3 is preferably 40 to 50°, and may be 43 to 47° or 44 to 46°.

[0037] When the retardation layer 3 is a laminate of multiple retardation layers and the in-plane slow axis directions of the multiple retardation layers are not parallel, it is preferable that the angle ψ and the front retardation R(550) calculated from the relation between the analyzer angle θ obtained by elliptically measuring the elliptically polarizing plate by the rotating analyzer method and the transmitted light intensity I(θ) are within the above range. Hereinafter, the angle ψ and the front retardation obtained by elliptically measuring the polarizing plate may be referred to as the "apparent arrangement angle" and the "apparent front retardation".

[0038] The retardation layer 3 includes at least one aligned liquid crystal layer in which liquid crystal molecules are aligned homogeneously. When the retardation layer 3 is composed of one retardation layer 31 as in the circular polarizer 101 shown in Fig. 4, the retardation layer 31 is an aligned liquid crystal layer in which liquid crystal molecules are aligned homogeneously.

[0039] The homogeneously aligned liquid crystal layer is a positive A plate in which the alignment direction of the liquid crystal molecules is the slow axis direction, and the refractive index anisotropy is such that nx>ny≒nz, where nx is the in-plane refractive index in the slow axis direction (liquid crystal alignment direction), ny is the in-plane refractive index in the fast axis direction, and nz is the thickness direction. The homogeneously aligned liquid crystal layer is formed, for example, by applying a liquid crystal composition containing a liquid crystal compound onto a supporting substrate, aligning the liquid crystal compound homogeneously, and then fixing the aligned state.

[0040] Examples of the liquid crystal compound include rod-shaped liquid crystal compounds and discotic liquid crystal compounds. As the liquid crystal compound, a rod-shaped liquid crystal compound is preferred because it is easily homogeneously oriented due to the orientation control force of the supporting substrate. The rod-shaped liquid crystal compound may be a main chain type liquid crystal or a side chain type liquid crystal. The rod-shaped liquid crystal compound may be a liquid crystal polymer or a polymerized product of a polymerizable liquid crystal compound. As long as the liquid crystal compound (monomer) before polymerization exhibits liquid crystallinity, it may not exhibit liquid crystallinity after polymerization.

[0041] The liquid crystal compound is preferably a thermotropic liquid crystal that exhibits liquid crystallinity by heating. Thermotropic liquid crystals undergo phase transitions between a crystal phase, a liquid crystal phase, and an isotropic phase with temperature changes. Examples of rod-shaped liquid crystal compounds that exhibit thermotropic properties include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoates, cyclohexane carboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes, and alkenylcyclohexylbenzonitriles.

[0042] Examples of the polymerizable liquid crystal compound include a polymerizable liquid crystal compound in which the alignment state of a rod-shaped liquid crystal compound can be fixed by using a polymer binder, a polymerizable liquid crystal compound having a polymerizable functional group in which the alignment state of a liquid crystal compound can be fixed by polymerization, etc. Among these, a photopolymerizable liquid crystal compound having a photopolymerizable functional group is preferred.

[0043] The photopolymerizable liquid crystal compound (liquid crystal monomer) has a mesogen group and at least one photopolymerizable functional group in one molecule. The temperature at which the liquid crystal monomer exhibits liquid crystallinity (liquid crystal phase transition temperature) is preferably 40 to 200°C, more preferably 50 to 150°C, and even more preferably 55 to 100°C.

[0044] Examples of the mesogenic group of the liquid crystal monomer include cyclic structures such as a biphenyl group, a phenylbenzoate group, a phenylcyclohexane group, an azoxybenzene group, an azomethine group, an azobenzene group, a phenylpyrimidine group, a diphenylacetylene group, a diphenylbenzoate group, a bicyclohexane group, a cyclohexylbenzene group, and a terphenyl group. The terminals of these cyclic units may have a substituent such as a cyano group, an alkyl group, an alkoxy group, or a halogen group.

[0045] Examples of the photopolymerizable functional group include a (meth)acryloyl group, an epoxy group, and a vinyl ether group. Among them, a (meth)acryloyl group is preferable. The photopolymerizable liquid crystal monomer preferably has two or more photopolymerizable functional groups in one molecule. By using a liquid crystal monomer containing two or more photopolymerizable functional groups, a crosslinked structure is introduced into the liquid crystal layer after photocuring, which tends to improve the durability of the aligned liquid crystal layer.

[0046] As the photopolymerizable liquid crystal monomer, any suitable liquid crystal monomer can be adopted. For example, the compounds described in International Publication No. 00 / 37585, U.S. Patent No. 5211877, U.S. Patent No. 4388453, International Publication No. 93 / 22397, European Patent No. 0261712, German Patent No. 19504224, German Patent No. 4408171, British Patent No. 2280445, Japanese Unexamined Patent Application Publication No. 2017-206460, International Publication No. 2014 / 126113, International Publication No. 2016 / 114348, International Publication No. 2014 / 010325, Japanese Unexamined Patent Application Publication No. 2015-200877, Japanese Unexamined Patent Application Publication No. 2010-31223, International Publication No. 2011 / 050896, Japanese Unexamined Patent Application Publication No. 2011-207765, Japanese Unexamined Patent Application Publication No. 2010-31223, Japanese Unexamined Patent Application Publication No. 2010-270108, International Publication No. 2008 / 119427, Japanese Unexamined Patent Application Publication No. 2008-107767, Japanese Unexamined Patent Application Publication No. 2008-273925, International Publication No. 2016 / 125839, Japanese Unexamined Patent Application Publication No. 2008-273925, etc. can be mentioned. By selecting the liquid crystal monomer, it is possible to adjust the birefringence expressibility and the wavelength dispersion of the retardation, and it is also possible to form a retardation layer 31 having a wavelength dispersion of Re(450) < Re(550) < Re(650) with a single-layer homogeneous alignment liquid crystal layer.

[0047] The liquid crystal monomer, various alignment control agents, polymerization initiators, leveling agents, etc. are mixed with a solvent to prepare a liquid crystal composition, which is applied onto a support substrate to align the liquid crystal compound, thereby forming an aligned liquid crystal layer. By using a flexible film as the support substrate, a series of processes from the application of the liquid crystal composition onto the support substrate to the photocuring of the liquid crystal monomer and the subsequent heat treatment can be carried out by roll-to-roll, so that the productivity can be improved.

[0048] The support substrate may have an alignment ability for aligning the liquid crystal compound in a predetermined direction. For example, by using a stretched film as the support substrate, it is possible to align the liquid crystal compound homogeneously along the stretching direction. The stretch ratio of the stretched film may be such that it can exhibit the alignment ability, for example, about 1.1 to 5 times. The stretched film may be a biaxially stretched film. Even if a biaxially stretched film is used, if a film having different stretch ratios in the longitudinal direction and the transverse direction is used, the liquid crystal compound can be aligned along the direction with the larger stretch ratio. The stretched film may be an obliquely stretched film. By using an obliquely stretched film as the support substrate, the liquid crystal compound can be aligned in a direction that is not parallel to either the longitudinal direction or the transverse direction of the support substrate.

[0049] The support substrate may have an alignment film on the surface on which the oriented liquid crystal layer is formed. The alignment film may be appropriately selected depending on the type of liquid crystal compound, the material of the support substrate, and the like. As the alignment film for homogeneously aligning the liquid crystal compound in a predetermined direction, a polyimide-based or polyvinyl alcohol-based alignment film that has been subjected to a rubbing treatment is preferably used. A photo-alignment film may also be used. A resin film serving as the support substrate may be subjected to a rubbing treatment without providing an alignment film.

[0050] When the liquid crystal compound is a thermotropic liquid crystal, the liquid crystal composition is applied onto a support substrate, and the liquid crystal compound is aligned in a liquid crystal state by heating. The liquid crystal composition layer formed on the support substrate is heated to a liquid crystal phase, and the liquid crystal compound is aligned. Specifically, after the liquid crystal composition is applied onto the support substrate, the liquid crystal composition is heated to a temperature equal to or higher than the N (nematic phase)-I (isotropic liquid phase) transition temperature of the liquid crystal composition to make the liquid crystal composition into an isotropic liquid state. From there, the liquid crystal composition is gradually cooled as necessary to express the nematic phase. At this time, it is desirable to keep the temperature at which the liquid crystal phase is exhibited once, and grow the liquid crystal phase domain to form a monodomain. Alternatively, after the liquid crystal composition is applied onto the support substrate, the temperature may be maintained within a temperature range at which the nematic phase is expressed for a certain period of time to align the liquid crystal compound in a predetermined direction.

[0051] The heating temperature for aligning the liquid crystal compound in a predetermined direction may be appropriately selected depending on the type of liquid crystal composition, and is usually about 40 to 200°C. If the heating temperature is too low, the transition to the liquid crystal phase tends to be insufficient, and if the heating temperature is too high, alignment defects may increase. The heating time may be adjusted so that the liquid crystal phase domain grows sufficiently, and is usually about 30 seconds to 30 minutes.

[0052] After the liquid crystal compound is oriented by heating, it is preferable to cool the liquid crystal compound to a temperature equal to or lower than the glass transition temperature. The cooling method is not particularly limited, and may be, for example, by removing the liquid crystal compound from the heated atmosphere to room temperature. Forced cooling such as air cooling or water cooling may also be performed.

[0053] By irradiating the liquid crystal layer with light, the photopolymerizable liquid crystal compound (liquid crystal monomer) is photocured while maintaining liquid crystal regularity. Any light capable of polymerizing the photopolymerizable liquid crystal compound may be used as the irradiated light, and ultraviolet or visible light having a wavelength of 250 to 450 nm is usually used. When photocuring the liquid crystal composition, the liquid crystal compound can be aligned in a predetermined direction by using polarized light in a predetermined direction. When the liquid crystal compound is aligned by the alignment regulating force of the supporting substrate as described above, the irradiated light may be non-polarized (natural light).

[0054] The polymerized product after the liquid crystal monomer is photocured by irradiation with light is non-liquid crystal, and transition between liquid crystal phase, glass phase, and crystalline phase does not occur due to temperature changes. Therefore, the liquid crystal layer photocured with the liquid crystal monomer oriented in a specific direction is unlikely to undergo change in molecular orientation due to temperature changes. Since all positive A plates are homogeneously oriented liquid crystal layers, changes in front retardation and in-plane variations due to heating are suppressed, and coloring of reflected light in irregularly shaped areas tends to be reduced.

[0055] When the phase difference layer 3 consists of a single layer of homogeneous alignment liquid crystal layer 31, the alignment liquid crystal layer 31 satisfies Re(450) < Re(550) < Re(650), and the angle ψ formed between the absorption axis direction of the polarizer 10 and the slow axis direction (liquid crystal alignment direction) of the homogeneous alignment liquid crystal layer 31 is 10 to 80°. When the elliptical polarizing plate 101 is used as a circular polarizing plate, Re(550) of the alignment liquid crystal layer 31 is preferably 100 to 180 nm, more preferably 110 to 170 nm, even more preferably 120 to 150 nm, and may be 125 to 145 nm. The angle ψ is preferably 40 to 50°, and may be 43 to 47° or 44 to 46°.

[0056] As described above, the phase difference layer 3 may be a laminate of two or more phase difference layers. Examples of the elliptical polarizing plate in which the phase difference layer 3 is a laminate of two or more layers include, as shown in FIG. 5, a form including two (or more) positive A plates 32 and 33 as the phase difference layer, and as shown in FIG. 6, a form including a positive A plate 31 in which the phase difference layer 3 is a homogeneous alignment liquid crystal layer and a positive C plate 36.

[0057] The elliptical polarizing plate 102 shown in FIG. 5 has a laminated structure in which the phase difference layer 3 is a laminate of two positive A plates 32 and 33. As an example of the phase difference layer 3 composed of two positive A plates, a configuration in which the phase difference layer 32 disposed closer to the polarizing plate 1 is a half-wave plate and the phase difference layer 33 disposed farther from the polarizing plate 1 is a quarter-wave plate can be mentioned.

[0058] In this laminated structure, it is preferable to arrange such that the angle formed between the slow axis direction of the half-wave plate and the absorption axis direction of the polarizer is 75° ± 5°, and the angle formed between the slow axis direction of the quarter-wave plate and the absorption axis direction of the polarizer is 15° ± 5°. In this way, by laminating the plurality of phase difference layers 32 and 33 and the polarizer 10 at an angle such that their optical axes are neither parallel nor orthogonal, even when the phase difference layers 32 and 33 do not have inverse wavelength dispersion, it is possible to function as a circular polarizing plate over a wide wavelength range of visible light.

[0059] The principle of realizing wideband circularly polarized light by stacking a polarizer and multiple retardation layers is as explained, for example, in JP-A-10-63816 using a Poincaré sphere. The multiple retardation layers are not limited to a combination of a half-wave plate and a quarter-wave plate, and may be a laminated structure of three or more retardation layers. The arrangement angle of each retardation layer is not limited to the above, and it is sufficient that the angle between the slow axis direction of each retardation layer and the absorption axis direction of the polarizer is in the range of 10° to 80°.

[0060] When the retardation layer 3 includes a plurality of positive A plates, as described above, the apparent arrangement angle ψ is preferably 40 to 50°, and may be 43 to 47° or 44 to 46°. The apparent front retardation Re(550) of the retardation layer 3 is preferably 100 to 180 nm, more preferably 110 to 170 nm, and further preferably 120 to 150 nm, and may be 125 to 145 nm.

[0061] When the retardation layer 3 includes two or more positive A plates, at least one of the positive A plates is a homogeneously aligned liquid crystal layer, and preferably, all of the positive A plates are aligned liquid crystal layers. When all of the positive A plates are homogeneously aligned liquid crystal layers, the thickness of the retardation layer 3 can be reduced. In addition, as described above, when all of the positive A plates are homogeneously aligned liquid crystal layers, the change in front retardation and in-plane variation due to heating are suppressed, and the coloring of reflected light at the irregularly processed portion tends to be reduced.

[0062] The positive A plate other than the oriented liquid crystal layer may be a film of a non-liquid crystal resin material (polymer). Examples of the polymer include polycarbonate resins, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyarylate resins, sulfone resins such as polysulfone and polyethersulfone, sulfide resins such as polyphenylene sulfide, polyimide resins, cyclic polyolefin (polynorbornene) resins, polyamide resins, polyolefin resins such as polyethylene and polypropylene, and cellulose esters.

[0063] 6, the retardation layer 3 has a laminated structure of one positive A plate 31 and one positive C plate 36. The positive A plate 31 is a homogeneously aligned liquid crystal layer.

[0064] The elliptical polarizer 103 in FIG. 6 corresponds to a configuration in which a positive C plate having a refractive index anisotropy of nz>nx≒ny is laminated on the homogeneously aligned liquid crystal layer 31 of the elliptical polarizer 101 in FIG. 4. By laminating the positive C plate on the positive A plate 31, the phase difference in the diagonal direction of the positive A plate is cancelled by the positive C plate, so that the phase difference layer 3, which is a laminate of the positive A plate 31 and the positive C plate 36, has a refractive index anisotropy of nx>nz>ny, and the change in retardation due to the viewing angle is small. A circular polarizer having a phase difference layer in which the positive A plate and the positive C plate are laminated can reduce reflected light not only from the front of the display device but also from diagonal directions.

[0065] The positive C plate may be a homeotropically aligned liquid crystal layer in which a liquid crystal compound is homeotropically aligned, or a film of a non-liquid crystal resin material (polymer) having negative intrinsic birefringence.

[0066] A polymer having negative intrinsic birefringence refers to a polymer whose refractive index in the oriented direction becomes relatively small when the polymer is oriented by stretching, etc. Examples of polymers having negative intrinsic birefringence include those in which a chemical bond or functional group with large polarization anisotropy, such as an aromatic or carbonyl group, is introduced into the side chain of the polymer, and specific examples thereof include acrylic resins, styrene resins, maleimide resins, and fumaric acid ester resins.

[0067] The method for producing the resin film is not particularly limited, and either the solution method or the melting method may be adopted. When the resin film is formed by the solution method, the molecular chains of the polymer tend to be oriented in the in-plane direction. When the molecular chains of the polymer having negative intrinsic birefringence are oriented in the plane, the thickness direction refractive index nz of the coating film becomes relatively small compared to the in-plane refractive index, and a positive C plate characteristic having a refractive index anisotropy of nz>nx≒ny (thickness direction retardation Rth is a negative value) is expressed. In addition, a positive C plate having a front retardation of approximately 0 is obtained by biaxially stretching a film of a polymer having negative intrinsic birefringence so that the front retardation is approximately 0. Note that nx≒ny is not limited to the case where nx and ny are completely equal, and it is sufficient that the front retardation Re(550) at a wavelength of 550 nm is 10 nm or less. The front retardation Re(550) of the positive C plate is preferably 5 nm or less, and may be 3 nm or less or 1 nm or less.

[0068] From the viewpoint of reducing the thickness of the retardation layer, the positive C plate 36 is preferably a homeotropically aligned liquid crystal layer. The homeotropically aligned liquid crystal layer is formed, for example, by applying a liquid crystal composition containing a liquid crystal compound onto a supporting substrate, aligning the liquid crystal compound homeotropically, and then fixing the aligned state. For details of the homeotropically aligned liquid crystal layer, see, for example, JP2008-216782A.

[0069] The positive C plate 36 has a thickness direction retardation Rth represented by Rth=(nx-nz)×d that is smaller than 0. Here, nz and nz are as described above, and d is the thickness. The thickness direction retardation Rth of the positive C plate 36 is, for example, −30 to −200 nm, and preferably −50 to −150 nm. The sum of the thickness direction retardation of the positive A plate 31 and the thickness direction retardation of the positive C plate 36 is preferably 30 to 110 nm, more preferably 40 to 100 nm, and further preferably 50 to 90 nm.

[0070] 6 shows a configuration in which the retardation layer 31 arranged closer to the polarizer 10 is a positive A plate of a homogeneously aligned liquid crystal layer, and the retardation layer 36 arranged farther from the polarizer 10 is a positive C plate, but the positive C plate may be arranged closer to the polarizer 10, and the positive A plate may be arranged farther from the polarizer 10. Also, instead of the positive A plate 31 made of one homogeneously aligned liquid crystal layer, a retardation layer in which a plurality of positive A plates 32 and 33 are laminated may be used.

[0071] [Elliptical polarizing plate] An elliptical polarizing plate is formed by laminating a retardation layer 3 on the transparent protective film 11 on one surface of the polarizing plate 1. The arrangement angle between the polarizer 10 and the retardation layer 3 of the polarizing plate 1 is as described above.

[0072] The polarizing plate 1 and the retardation layer 3 are preferably bonded together via an appropriate adhesive or pressure-sensitive adhesive. As shown in Fig. 5 and Fig. 6, when the retardation layer 3 is a laminate of a plurality of retardation layers, a laminate of a plurality of retardation layers may be bonded to the polarizing plate, or a plurality of retardation layers may be sequentially laminated on the polarizing plate. An appropriate adhesive or pressure-sensitive adhesive is used to bond the plurality of retardation layers. The retardation layer 3 may include a film or an alignment film used as a support substrate when forming an aligned liquid crystal layer.

[0073] The elliptically polarizing plate may have various additional layers in addition to the polarizing plate and the retardation layer, such as an antireflection layer, a pressure-sensitive adhesive for bonding the elliptically polarizing plate to an image display cell, a surface protection film for protecting the surface of the elliptically polarizing plate, and the like.

[0074] As described above, the elliptically polarizing plate of the present invention is processed into a modified shape. From the viewpoint of productivity, it is preferable to carry out the processing into the modified shape after laminating each layer constituting the elliptically polarizing plate.

[0075] [Image display device] 7 is a cross-sectional view showing an example of a laminated structure of an image display device, in which the surface of the retardation layer 3 of the elliptical polarizing plate 105 is attached to the surface of the image display cell 50 via an adhesive layer (not shown). The oriented liquid crystal film may have two or more oriented liquid crystal layers. Examples of the image display cell 50 include a liquid crystal cell and an organic EL cell. The elliptical polarizing plate of the present invention can be suitably used as a circular polarizing plate for blocking reflected light of external light in an in-vehicle organic EL display device.

[0076] In-vehicle image display devices are required to have little change in display characteristics even when exposed to high-temperature environments for long periods of time. When a circularly polarizing plate with a special shape is applied to an organic EL display device, coloring of reflected light is easily visible around the specially processed parts such as notches in a high-temperature environment. When the cause of this was investigated, it was found that one of the factors that makes coloring of reflected light easily visible around the specially processed parts is the large variation in the amount of change in front retardation when a high-temperature durability test is performed.

[0077] Figure 8 is an enlarged view of the periphery of the irregularly processed part of the irregularly processed circular polarizer, and the diagonal lines in the figure represent the slow axis direction of the retardation layer. In a conventional irregularly processed circular polarizer, after a heat durability test, the in-plane retardation of region A in the figure is 10 nm or more larger than that of region B, and the reflected light is visually colored blue in region A, where the in-plane retardation is relatively large, and red in region B, where the in-plane retardation is relatively small. When the irregularly processed part is a notch, the difference in color is easily recognized because region A and region B are close to each other.

[0078] When an elliptical polarizing plate is exposed to a high-temperature environment, stress is generated at the interface between the layers due to differences in the thermal dimensional change rates of the polarizer, transparent protective film, and retardation layer, causing a change in the retardation of the retardation layer. Stretched films tend to have large thermal shrinkage in the stretching direction, and in an elliptical polarizing plate in which the absorption axis direction of the polarizer and the slow axis direction of the retardation layer are arranged at an angle that is neither parallel nor perpendicular, the behavior of the thermal shrinkage of the polarizer (polarizing plate) and the thermal shrinkage of the retardation layer differs, so that the change in the retardation of the retardation layer due to stress is likely to be large.

[0079] In a single-sheet elliptical polarizing plate, stress is easily relaxed near the outer edge, but in region A, where the slow axis direction of the retardation layer and the processing direction of the irregularly processed part (the tangent direction of the outer edge) are approximately parallel, and region B, where the slow axis direction of the retardation layer and the processing direction of the irregularly processed part are approximately perpendicular, the behavior of stress relaxation is different, and it is considered that the difference in the change in retardation due to heating becomes large.

[0080] In the elliptical polarizing plate of the present invention, the polarizer 10 has a large thickness of 15 μm or more, and transparent protective films 11 and 12 are attached to both sides of the polarizer 10, so that dimensional change of the polarizing plate 1 is suppressed. Furthermore, the positive A plate of the retardation layer 3 is a homogeneously aligned liquid crystal layer, and the dimensional change due to heating is smaller than that of a stretched film, so that the change in the front retardation of the retardation layer 3 due to heating is suppressed. In addition, the aligned liquid crystal layer cured in a state in which the liquid crystal compound is aligned does not undergo phase transition due to temperature change, and the aligned state is fixed, which is also considered to be a factor in suppressing the retardation change due to heating.

[0081] In the elliptical polarizing plate of the present invention, the retardation layer 3 contains a homogeneously aligned liquid crystal layer, so that the variation in the front retardation of the retardation layer after the heat durability test is small even in a region where the processing angle changes greatly over a small area, such as an R-shaped or V-shaped notch. Therefore, the color difference around the irregularly processed part is difficult to recognize, and the display characteristics are excellent. Such an irregularly shaped elliptical polarizing plate can be suitably used for an in-vehicle image display device that requires small changes in characteristics under high temperature environments. EXAMPLES

[0082] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0083] [Comparative Example 1] <Preparation of polarizing plate> A town name protection film was attached to both sides of a stretched polyvinyl alcohol polarizer with a thickness of 18 μm using an ultraviolet-curing adhesive. A triacetyl cellulose film (total thickness 49 μm) with a 3 μm-thick hard coat layer on one side was used as the transparent protective film on one side, and the side without the hard coat layer was attached to the polarizer. A stretched film (thickness 30 μm) of a modified acrylic resin with an introduced lactone ring structure was used as the transparent protective film on the other side.

[0084] <Preparation of Retardation Layer> (Preparation of polycarbonate film) According to the method described in Example 1 of Japanese Patent No. 5204200, a polycarbonate resin containing isosorbide-derived structural units (37.1 mol%), 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene-derived structural units (47.4 mol%), and 1,4-cyclohexanedimethanol-derived structural units (15.5 mol%) was prepared, and filmed and stretched. This stretched polycarbonate film was a positive A plate with a refractive index anisotropy of nx>ny=nz, and had a thickness of 37 μm, Re(450)=123 nm, Re(550)=144 nm, and Re(650)=152 nm.

[0085] (Preparation of homeotropically aligned liquid crystal layer) A liquid crystal composition was prepared by dissolving 20 parts by weight of a side-chain liquid crystal polymer having a weight average molecular weight of 5000 and represented by the following chemical formula (n=0.35, and shown as a block polymer for convenience), 80 parts by weight of a polymerizable liquid crystal compound exhibiting a nematic liquid crystal phase (BASF's "Paliocolor LC242"), and 5 parts by weight of a photopolymerization initiator (IGM Resins' "Omnirad907") in 400 parts by weight of cyclopentanone.

[0086] [ka]

[0087] The liquid crystalline composition was applied to the surface of a biaxially stretched norbornene film (ZEON Corporation's "ZEONORFILM", thickness: 52 μm, front retardation: 50 nm) using a bar coater so that the thickness after drying would be 1 μm. The film was then heated at 80° C. for 2 minutes to align the liquid crystals. After cooling to room temperature, the film was then irradiated with 700 mJ / cm 2 in a nitrogen atmosphere. 2The liquid crystal monomer was photocured by irradiating it with ultraviolet light of 1000 nm, thereby obtaining a laminate A in which a homeotropically aligned liquid crystal layer (thickness 3 μm) was formed on the film substrate. This homeotropically aligned liquid crystal layer was a positive C plate having a refractive index anisotropy of nz>nx=ny, and the homeotropically aligned liquid crystal layer was transferred onto a glass plate and measured for a thickness direction retardation Rth(550) of 100 nm at a wavelength of 550 nm.

[0088] (Preparation of adhesive) An ultraviolet-curable adhesive composition A was prepared by mixing 50 parts by weight of unsaturated fatty acid hydroxyalkyl ester-modified ε-caprolactone (Daicel's "Placcel FA1DDM"), 25 parts by weight of acryloylmorpholine (Kojin's "ACMO"), 10 parts by weight of polypropylene glycol (n=3) diacrylate (Toagosei's "Aronix M-220"), 15 parts by weight of an epoxy group-containing acrylic oligomer having a weight average molecular weight of 2900 (Toagosei's "ARFON UG-4100"), and 2 parts by weight of "Omnirad 907" and 2 parts by weight of "KAYACURE DETX-S" (Nippon Kayaku) as photopolymerization initiators.

[0089] (Lamination of polycarbonate film and homeotropic alignment liquid crystal layer) After corona treatment was performed on the surface of the homeotropic aligned liquid crystal layer side of the polycarbonate film and the laminate A, the adhesive composition A was applied, and the laminate was laminated with a roll laminator. The laminate was then cured with 700 mJ / cm 2 UV curing equipment (V bulb) manufactured by Fusion UV Systems. 2 The adhesive was cured by irradiation with ultraviolet light of 1000 nm, to obtain a laminated retardation layer in which the polycarbonate film and the homeotropic alignment liquid crystal layer were laminated together via the adhesive layer.

[0090] <Preparation of circular polarizing plate> The acrylic film side of the polarizing plate was attached to the polycarbonate film side of the laminated retardation layer through an acrylic adhesive sheet having a thickness of 20 μm. At this time, the angle between the absorption axis direction of the polarizer and the stretching direction (slow axis direction) of the polycarbonate film was set to 45°. Then, the film substrate was peeled off from the surface of the homeotropic alignment liquid crystal layer, and an acrylic adhesive sheet having a thickness of 23 μm was attached to the exposed surface of the homeotropic alignment liquid crystal layer. In this way, a circular polarizing plate with adhesive was obtained in which an adhesive sheet was laminated on a laminate (circular polarizing plate) in which a stretched polycarbonate film was attached to the polarizing plate through an adhesive layer, and a homeotropic alignment liquid crystal layer was attached thereon through an adhesive layer.

[0091] <Processing of circular polarizing plates> Using a Thomson blade, the above-mentioned circular polarizing plate with adhesive was punched out into a rectangle of 300 mm x 100 mm with the absorption axis direction of the polarizer as the long side. Then, using an end mill, a bathtub-shaped notch was formed in one long side and an R-shaped (semicircular) notch was formed in the other long side, processing into the irregular shape shown in Figure 9. The radius of curvature of the curved part of the notch was 10 mm.

[0092] [Comparative Example 2] <Preparation of Retardation Layer> (Fabrication of a quarter-wave plate) A film was prepared using polycarbonate resin ("DURABIO" manufactured by Mitsubishi Chemical) and stretched uniaxially at the free end. This stretched film (quarter-wave plate) was a positive A plate with a refractive index anisotropy of nx>ny=nz, with a thickness of 20 μm, Re(450)=143 nm, Re(550)=140 nm, and Re(650)=137 nm.

[0093] (Making a half-wave plate) By changing the thickness and stretching ratio of the above film, stretched films (½ wavelength plates) with a thickness of 40 μm, Re(450)=277 nm, Re(550)=270 nm, and Re(650)=265 nm were obtained.

[0094] (Preparation of adhesive sheet) In a reaction vessel, 92 parts by weight of butyl acrylate, 5 parts by weight of N-acryloylmorpholine, 2.9 parts by weight of acrylic acid, and 0.1 parts by weight of 2-hydroxyethyl acrylate as monomers, and 0.1 parts by weight of azobisisobutyronitrile as a polymerization initiator were added together with ethyl acetate, and the mixture was reacted at 55°C for 8 hours under a nitrogen gas stream. Ethyl acetate was then added to the reaction solution to obtain a solution of an acrylic polymer having a weight average molecular weight of 1.78 million. This solution was mixed with 0.15 parts by weight of dibenzoyl peroxide ("Niper BMT" manufactured by Nippon Oil & Fats Co., Ltd.) and 0.6 parts by weight of trimethylolpropane / tolylene diisocyanate adduct ("Coronate L" manufactured by Tosoh Co., Ltd.) as crosslinking agents per 100 parts by weight of the polymer to obtain a pressure-sensitive adhesive composition. This adhesive composition was applied to the release-treated surface of a 38 μm-thick release-treated polyethylene terephthalate film ("MRF38" manufactured by Mitsubishi Chemical), and then dried and crosslinked at 150°C to produce adhesive sheet A with a thickness of 5 μm.

[0095] <Preparation of circular polarizing plate> The above-mentioned 1 / 2 wavelength plate was attached to the surface of the polarizing plate on the acrylic film side. At that time, the angle between the absorption axis direction of the polarizer and the stretching direction (slow axis direction) of the 1 / 2 wavelength plate was set to 75°. Then, the 1 / 4 wavelength plate was attached to the surface of the 1 / 1 wavelength plate via the adhesive sheet A. At that time, the angle between the absorption axis direction of the polarizer and the stretching direction (slow axis direction) of the 1 / 4 wavelength plate was set to 15°. Then, an acrylic adhesive sheet having a thickness of 23 μm was attached to the 1 / 4 wavelength plate. In this way, a circular polarizing plate with adhesive was obtained in which an adhesive sheet was laminated on a laminate (circular polarizing plate) in which a 1 / 2 wavelength plate made of a stretched film was attached to the polarizing plate via an adhesive layer, and a 1 / 4 wavelength plate made of a stretched film was attached to the laminate via an adhesive layer. This circular polarizing plate with adhesive was processed into an irregular shape in the same manner as in Example 1.

[0096] [Example 1] <Preparation of retardation plate> (Preparation of homogeneously aligned liquid crystal 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, heated to 60° C. and stirred for dissolution, and then cooled to room temperature to prepare a solution with a solid content concentration of 20% by weight.

[0097] [ka]

[0098] To this solution, 0.2 parts by weight of a surfactant (DIC's "Megafac F-554"), 3 parts by weight of a photopolymerization initiator (Omnirad 907), and 0.1 parts by weight of p-methoxyphenol were added to prepare a liquid crystal composition solution.

[0099] A film having an alignment layer that was rubbed on a triacetyl cellulose film was used as the film substrate. The above liquid crystal composition was applied by spin coating onto the alignment layer of the film substrate, and the liquid crystal was aligned by heating at 100°C for 2 minutes. After cooling to room temperature, the film was irradiated with an integrated light amount of 900 mJ / cm2 in a nitrogen atmosphere. 2 The film was then exposed to ultraviolet light for photocuring to obtain a laminate B in which a homogeneously aligned liquid crystal layer (thickness 3 μm) was formed on the film substrate. This homogeneously aligned liquid crystal layer was a positive A plate with a refractive index anisotropy of nx>ny=nz, and the front retardation measured by transferring the homogeneously aligned liquid crystal layer onto a glass plate was Re(450)=118nm, Re(550)=145nm, and Re(650)=152nm.

[0100] (Lamination of homogeneously aligned liquid crystal layer and homeotropically aligned liquid crystal layer) After corona treatment was performed on the surfaces of the aligned liquid crystal layer side of the laminate A and the laminate B, the adhesive composition A was applied, the laminates were laminated together using a roll laminator, and the laminates were cured with 700 mJ / cm 2 using a UV curing device (V bulb) manufactured by Fusion UV Systems. 2The adhesive was cured by irradiation with ultraviolet light of 1000 nm, thereby obtaining a laminated retardation layer in which the homeotropic alignment liquid crystal layer and the homogeneous alignment liquid crystal layer were laminated together via the adhesive layer.

[0101] <Preparation and processing of circular polarizing plates> The film substrate was peeled off from the surface of the homogeneously aligned liquid crystal layer of the laminated retardation layer, and the acrylic film side surface of the polarizing plate was attached to the surface of the homogeneously aligned liquid crystal layer exposed through an acrylic adhesive sheet having a thickness of 20 μm. At that time, the angle between the absorption axis direction of the polarizer and the alignment direction (slow axis direction) of the homogeneously aligned liquid crystal layer was set to 45°. Then, the film substrate was peeled off from the surface of the homeotropically aligned liquid crystal layer, and an acrylic adhesive sheet having a thickness of 23 μm was attached to the surface of the exposed homeotropically aligned liquid crystal layer. In this way, a circular polarizing plate with an adhesive was obtained in which an adhesive sheet was laminated on a laminate (circular polarizing plate) in which a homogeneously aligned liquid crystal layer was attached to the polarizing plate through an adhesive layer, and a homeotropically aligned liquid crystal layer was attached thereon through an adhesive layer. This circular polarizing plate with an adhesive was processed into an irregular shape in the same manner as in Example 1.

[0102] [Example 2] <Preparation of Retardation Layer> (Preparation of homogeneously aligned liquid crystal layer (quarter wave plate)) A photopolymerizable liquid crystal compound exhibiting a nematic liquid crystal phase (BASF's "Paliocolor LC242") was dissolved in cyclopentanone to prepare a solution with a solid content of 30% by weight. A surfactant (BYK-360, BYK-Chemie) and a photopolymerization initiator (Omnirad 907) were added to this solution to prepare a liquid crystal composition solution. The amounts of the leveling agent and the polymerization initiator added were 0.01 parts by weight and 3 parts by weight, respectively, relative to 100 parts by weight of the photopolymerizable liquid crystal compound.

[0103] A biaxially stretched norbornene-based film (ZEONORFILM manufactured by ZEON CORPORATION, thickness: 33 μm) was used as the film substrate. The above liquid crystal composition was applied to the surface of the film substrate using a bar coater so that the thickness after drying would be 1 μm, and the liquid crystal was aligned by heating at 100° C. for 3 minutes. After cooling to room temperature, the film was irradiated with an integrated light dose of 400 mJ / cm under a nitrogen atmosphere. 2 The film was then exposed to ultraviolet light for photocuring to obtain a laminate C in which a homogeneously aligned liquid crystal layer (thickness 1 μm) was formed on the film substrate. This homogeneously aligned liquid crystal layer was a positive A plate with a refractive index anisotropy of nx>ny=nz, and the front retardation measured by transferring the homogeneously aligned liquid crystal layer onto a glass plate was Re(450)=156nm, Re(550)=144nm, and Re(650)=138nm.

[0104] (Preparation of homogeneously aligned liquid crystal layer (1 / 2 wavelength plate)) Laminate D was obtained in the same manner as above, except for changing the coating thickness of the liquid crystal composition, in which a homogeneously aligned liquid crystal layer with a thickness of 2 μm, Re(450)=300 nm, Re(550)=280 nm, and Re(650)=268 nm was formed on a film substrate.

[0105] <Preparation of circular polarizing plate> The acrylic film side of the polarizing plate was attached to the surface of the aligned liquid crystal layer of the laminate D via an acrylic adhesive sheet having a thickness of 20 μm. At that time, the angle between the absorption axis direction of the polarizer and the alignment direction (slow axis direction) of the homogeneously aligned liquid crystal layer (1 / 2 wavelength plate) was set to 75°. Then, the film substrate was peeled off from the surface of the homogeneously aligned liquid crystal layer, and the surface of the homogeneously aligned liquid crystal layer of the laminate C was attached to the surface of the exposed homogeneously aligned liquid crystal layer via an adhesive sheet A. At that time, the angle between the absorption axis direction of the polarizer and the alignment direction (slow axis direction) of the homogeneously aligned liquid crystal layer (1 / 4 wavelength plate) was set to 15°. Then, the film substrate was peeled off from the surface of the homogeneously aligned liquid crystal layer, and an acrylic adhesive sheet having a thickness of 23 μm was attached. In this way, a homogeneously aligned liquid crystal layer (1 / 2 wavelength plate) was attached to a polarizing plate via an adhesive layer, and a homogeneously aligned liquid crystal layer (1 / 4 wavelength plate) was attached to the homogeneously aligned liquid crystal layer (1 / 2 wavelength plate) via an adhesive layer to obtain a laminate (circular polarizing plate) on which an adhesive sheet was laminated. This circular polarizing plate with adhesive was processed into a modified shape in the same manner as in Example 1.

[0106] [evaluation] <Phase difference change> The adhesive sheet attached to the surface of the retardation layer of the polarizing plate with adhesive of the examples and comparative examples was attached to a glass plate to prepare an evaluation sample. The front retardation (initial value) at a wavelength of 550 nm was measured in an ellipsoidal polarization measurement mode using a retardation meter (Oji Scientific Instruments' "KOBRA 21-ADH") at seven points (1) to (7) shown in Figure 9. The evaluation sample was then placed in an air-circulating thermostatic oven at 95°C, and the front retardation was measured after 240 hours.

[0107] Table 1 shows the difference ΔRe between the maximum and minimum front retardation values ​​at seven points of the sample after a 95°, 240-hour heat durability test, and the standard deviation σ. [Table 1]

[0108] <Changes in reflected light hue> For the circular polarizing plates of Comparative Example 1 and Example 2, an evaluation sample was prepared by attaching an adhesive sheet attached to the surface of the retardation layer to a glass plate, and the evaluation sample was placed on an aluminum deposition film (manufactured by Toray) so that the glass plate side was facing downward. Using a spectrophotometer (Konica Minolta "CM-26"), the reflected light hue was measured when white light was incident from the polarizing plate side. The measurement was performed at seven points (1) to (7) shown in FIG. 9. The reflected light hue was measured again at seven points for the evaluation sample after a heat durability test at 95°C for 240 hours.

[0109] a * b * Figure 10 shows the reflected light hue before the heat test (▲) and the reflected light hue after the heat durability test (◯) plotted on a hue plane. * , the vertical axis is b * It is.

[0110] Compared to Comparative Examples 1 and 2, in which a stretched film was used as the positive A plate, Examples 1 and 2, in which a homogeneously oriented liquid crystal layer was used as the positive A plate, showed smaller in-plane variation in the front retardation of the circular polarizing plate after the heat durability test, and therefore showed less variation in the reflected light hue and more uniform characteristics. [Explanation of symbols]

[0111] 1 Polarizing plate 10 Polarizer 11,12 Transparent protective film 3 Retardation layer 31 Retardation layer (homogeneous alignment liquid crystal layer) 32 Retardation layer (homogeneous alignment liquid crystal layer) 33 Retardation layer (homogeneous alignment liquid crystal layer) 36 Retardation layer (homeotropic alignment liquid crystal layer) 101, 102, 103, 105 Elliptical polarizing plate 50 Image display cells 201 Image display device

Claims

1. a polarizing plate including a polarizer, a first transparent protective film bonded to a first main surface of the polarizer, and a second transparent protective film bonded to a second main surface of the polarizer; and a retardation layer bonded to the first transparent protective film of the polarizing plate, An elliptical polarizing plate having an irregular shape other than a rectangle in a plan view, an angle between an absorption axis direction of the polarizer and a slow axis direction of the retardation layer is 10 to 80°; The polarizer has a thickness of 15 μm or more, The retardation layer is a front retardation Re(450) at a wavelength of 450 nm, a front retardation Re(550) at a wavelength of 550 nm, and a front retardation Re(650) at a wavelength of 650 nm satisfy Re(450)<Re(550)<Re(650); At least one aligned liquid crystal layer in which liquid crystal molecules are aligned homogeneously; Elliptical polarizer.

2. The retardation layer includes two or more aligned liquid crystal layers, 2. The elliptically polarizing plate according to claim 1, wherein at least one of the layers is an aligned liquid crystal layer in which liquid crystal molecules are homogeneously aligned.

3. 2. The circular polarizer according to claim 1, wherein the retardation layer includes an aligned liquid crystal layer in which liquid crystal molecules are homogeneously aligned, and an aligned liquid crystal layer in which liquid crystal molecules are homeotropically aligned.

4. 2. The circular polarizer according to claim 1, wherein the retardation layer includes two or more aligned liquid crystal layers in which liquid crystal molecules are aligned homogeneously, and the angle between the slow axis directions of the aligned liquid crystal layers is 10 to 80 degrees.

5. 5. An in-vehicle image display device comprising the elliptically polarizing plate according to claim 1 on a viewing side surface of an image display cell.

6. The in-vehicle image display device according to claim 5 , wherein the image display cell is an organic EL cell.

Images