Optical laminate and elliptically polarizing plate

Abstract

To provide an optical laminate and elliptically polarizing plate capable of ensuring good display performance when disposed on a light-reflection layer even when viewed at an angle in at least two orthogonal in-plane directions.SOLUTION: An optical laminate according to an embodiment comprises a λ / 2 portion with a first slow axis, and a λ / 4 portion with a second slow axis stacked on the λ / 2 portion in such a way that the second slow axis is within a range of approximately 60° with respect to the first slow axis, where λ / 2 portion has an NZ coefficient of approximately 0.5 and the λ / 4 portion has an NZ coefficient in a range of 0.3 to 0.7, inclusive.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical laminate and an elliptically polarizing plate. [Background technology]

[0002] Prior art in this technical field includes the technology described in Patent Document 1. Patent Document 1 discloses an optical laminate in which a λ / 2 portion and a λ / 4 portion are laminated. The optical laminate described in Patent Document 1 has a phase difference close to λ / 4 across the entire visible light range, and therefore when combined with a linear polarizer, functions as an elliptical polarizing plate with an ellipticity of 97% or more across the entire visible light range. If this is placed on a light-reflecting layer of an OLED display device or the like, it can suppress external light reflection across a wide range of the visible light range. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 003416 Summary of the Invention [Problem to be solved by the invention]

[0004] The optical laminate described in Patent Document 1 has insufficient viewing angle compensation. Therefore, the performance of the optical laminate described in Patent Document 1 is limited to when the display device is viewed from approximately the front, and when viewed at an angle, there is a problem that the reflectance of external light increases and the display performance deteriorates.

[0005] The present invention aims to provide an optical laminate and an elliptically polarizing plate that, when placed on a light-reflecting layer, can ensure good display performance even when viewed at an angle in at least two orthogonal in-plane directions. [Means for solving the problem]

[0006] An optical laminate according to one aspect of the present invention includes a λ / 2 portion having a first slow axis and a λ / 4 portion having a second slow axis and laminated on the λ / 2 portion such that the second slow axis is within a range of approximately 60° with respect to the first slow axis, and N of the λ / 2 portion Z The coefficient is approximately 0.5, and N Z The coefficient is between 0.3 and 0.7.

[0007] In the optical laminate, N in the λ / 2 portion Z The coefficient is approximately 0.5, and N Z By setting the coefficient to 0.3 or more and 0.7 or less, when the optical laminate is placed on a light-reflecting layer, good display performance can be ensured even when the optical laminate is viewed tilted in at least two orthogonal in-plane directions.

[0008] Each of the λ / 2 section and the λ / 4 section may have a first retardation element, and the first retardation element has reverse dispersion and provides a phase difference of approximately λ / 4. The direction of the slow axis of the first retardation element in the λ / 2 section may be approximately the same as the direction of the first slow axis, and the direction of the slow axis of the first retardation element in the λ / 4 section may be approximately the same as the direction of the second slow axis.

[0009] The λ / 2 section may have two first retardation elements and two second retardation elements, the λ / 4 section may have a first retardation element, the two first retardation elements in the λ / 2 section and the first retardation element in the λ / 4 section may have reverse dispersion and provide a phase difference of approximately λ / 4, the two second retardation elements in the λ / 2 section may be positive C plates, and the directions of the slow axes of the two first retardation elements and the two second retardation elements in the λ / 2 section may be approximately aligned with the direction of the first slow axis, and the direction of the slow axis of the first retardation element in the λ / 4 section may be approximately aligned with the direction of the second slow axis. In this case, when the optical laminate is placed on a light-reflecting layer, it is easy to ensure good display performance even when the optical laminate is viewed at an angle in two orthogonal in-plane directions and in oblique directions relative to the two orthogonal in-plane directions.

[0010] The two first retardation elements and the two second retardation elements may be laminated in the order of the first retardation element, the second retardation element, the second retardation element, and the first retardation element. In this case, when the optical laminate is disposed on the light-reflecting layer, good display performance can be more easily ensured even when the optical laminate is viewed at an angle in each of two orthogonal in-plane directions and in oblique directions relative to the two orthogonal in-plane directions.

[0011] The λ / 2 section has two first retardation elements and two second retardation elements, the λ / 4 section has a first retardation element and a second retardation element, the two first retardation elements in the λ / 2 section and the first retardation element in the λ / 4 section have reverse dispersion and provide a phase difference of approximately λ / 4, the two second retardation elements in the λ / 2 section and the second retardation element in the λ / 4 section are positive C plates, and the two first retardation elements in the λ / 2 section and the two first retardation elements have slow axes the direction of the first and second retardation elements of the λ / 4 section is approximately the same as the direction of the first slow axis, the directions of the slow axes of the first and second retardation elements of the λ / 4 section are approximately the same as the direction of the second slow axis, the two first and two second retardation elements of the λ / 2 section are stacked in the order of the first retardation element, the second retardation element, the second retardation element and the first retardation element, and the first and second retardation elements of the λ / 4 section may be stacked in the order of the first retardation element and the second retardation element from the λ / 2 section side.

[0012] In the above configuration, when the optical laminate is placed on the light-reflecting layer, good display performance can be ensured even when the optical laminate is viewed at an angle in two orthogonal in-plane directions and in diagonal directions relative to the two orthogonal in-plane directions.

[0013] An elliptical polarizing plate according to another aspect of the present invention comprises a polarizer and the optical laminate laminated on the polarizer, and the polarizer, the λ / 2 portion and the λ / 4 portion are arranged in the order of the polarizer, the λ / 2 portion and the λ / 4 portion.

[0014] The elliptically polarizing plate includes the optical laminate, and therefore, when the elliptically polarizing plate is disposed on a light-reflecting layer, good display performance can be ensured even when the elliptically polarizing plate is viewed at an angle in at least two orthogonal in-plane directions. [Effects of the Invention]

[0015] According to the present invention, an optical laminate and an elliptically polarizing plate can be provided that, when disposed on a light-reflecting layer, can ensure good display performance even when viewed at an angle in at least two orthogonal in-plane directions. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram showing a schematic configuration of a display device including an optical laminate according to one embodiment. [Figure 2] FIG. 2 is a schematic diagram showing the positional relationship between the slow axis of the λ / 2 portion (first slow axis), the slow axis of the λ / 4 portion (second slow axis), and the transmission axis of the polarizer. [Figure 3] FIG. 3 is a graph showing the wavelength dispersion characteristics of the in-plane retardation of the prototype elliptically polarizing plate. [Figure 4] FIG. 4 is a diagram for explaining the tilt angle when the elliptically polarizing plate is tilted in the experiment. [Figure 5] FIG. 5 is a diagram for explaining the in-plane angle and tilt direction in the experiment and calculation. [Figure 6] FIG. 6 is a diagram for explaining the in-plane angle region used in the experiments and calculations. [Figure 7] FIG. 7 is a table showing the results of the examples and comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0017] First, the terms used in this disclosure will be explained.

[0018] [Ochiaiko] In the present disclosure, a retarder refers to an optical medium having birefringence. Birefringence refers to an optical property in which the difference in refractive index between at least two of three orthogonal directions exceeds 0.02.

[0019] [Refractive index of retarder] The refractive indices of the retarder in the three orthogonal directions are referred to as nx, ny, and nz. nx represents the principal refractive index in a direction parallel to the retarder plane in the index ellipsoid formed by the retarder. ny represents the refractive index in a direction parallel to the retarder plane and perpendicular to the nx direction in the index ellipsoid formed by the retarder. nz represents the refractive index in a direction perpendicular to the retarder plane in the index ellipsoid formed by the retarder.

[0020] [In-plane retardation and thickness retardation of retarder] Retardation Re is a physical quantity that represents the anisotropy of retarders. Retardation Re includes in-plane retardation Reo and thickness retardation Reth. The in-plane retardation Reo(λ) at a wavelength of λ nm is expressed by equation (1), where d represents the thickness (nm) of the retarder. Reo(λ)=(nx−ny)×d (1) The retardation in the thickness direction Reth(λ) at a wavelength of λ nm is expressed by the formula (2): d in the formula (2) is the thickness (nm) of the retarder, similar to d in the formula (1). Reth(λ)= ―{nz―(nx+ny) / 2}×d ···(2)

[0021] [Positive A Plate] A positive A plate is a retarder whose refractive index in each direction satisfies the relationship in formula (3). Unless otherwise specified, the slow axis of a positive A plate is parallel to nx, and ny ≒ nz means that the difference between ny and nz is less than 0.02. nx>ny≒nz (3)

[0022] The positive A plate can function as a λ / 4 plate. The λ / 4 plate can have an in-plane retardation of approximately λ / 4 at a wavelength of 550 nm. The in-plane retardation Reo(550) at a wavelength of 550 nm of a λ / 4 plate having an in-plane retardation of approximately λ / 4 can be in the range of formula (4). 92 nm ≦ Reo(550) ≦ 183 nm (4)

[0023] The preferred range of Reo(550) of the λ / 4 plate is preferably 100 nm or more and 160 nm or less, and more preferably 110 nm or more and 150 nm or less. The in-plane retardation Reo(λ) and thickness direction retardation Reth(λ) of the positive A plate at a wavelength of λ nm satisfy the relationship shown in equation (5), which is derived from equations (1), (2), and (3). Reth(λ)=0.5×Reo(λ) ···(5)

[0024] The retardation in the thickness direction Reth(550) of the λ / 4 plate at a wavelength of 550 nm can be within the range of formula (6). 46 nm ≤ Reth(550) ≤ 92 nm (6)

[0025] The suitable range of the value of Reth(550) is preferably 50 nm or more and 80 nm or less, and more preferably 55 nm or more and 75 nm or less.

[0026] [Positive C Plate] A positive C plate is a retarder whose refractive index in each direction satisfies the relationship in formula (7). Unless otherwise specified, the slow axis of a positive C plate is parallel to nz, and nx≒ny means that the difference between nx and ny is less than 0.02. nx≒ny <nz ··· (7)

[0027] [Wavelength dispersion] The dispersion relationship between wavelength and retardation is also simply called wavelength dispersion. A retarder that satisfies formulas (8) and (9) is said to have reverse wavelength dispersion, or simply called reverse dispersion. Re(450) / Re(550)≦1.00 (8) 1.00≦Re(650) / Re(550) (9)

[0028] The retarder Re(450) / Re(550) in the present disclosure is preferably 0.90 or less, more preferably 0.85 or less, and usually 0.60 or more, preferably 0.70 or more. The retarder Re(650) / Re(550) in the present disclosure is preferably 1.02 or more, more preferably 1.10 or more, and usually 1.30 or less, preferably 1.20 or less.

[0029] A retarder that satisfies the formulas (10) and (11) is said to have positive wavelength dispersion, or simply to have positive dispersion. Re(450) / Re(550)>1.00 ··· (10) 1.00>Re(650) / Re(550) ··· (11)

[0030] [Lag phase laminate] An optical laminate in which a plurality of retarders are laminated may also be called a retarder laminate.

[0031] [Nz coefficient] The Nz coefficient of the retarder can be expressed by equation (12). Note that the in-plane retardation of the entire retarder laminate at a wavelength λ (nm) (for example, a wavelength of 550 nm) is ReoG, and the thickness direction retardation of the entire retarder laminate is RethG. Nz coefficient ≡(RethG / ReoG)+0.5 (12)

[0032] Next, an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and duplicate explanations will be omitted. The dimensional proportions of the drawings do not necessarily correspond to those in the description.

[0033] Fig. 1 is a schematic diagram showing the general configuration of a display device including an optical laminate according to one embodiment. The display device 100 shown in Fig. 1 has a light-reflective image display layer 10 (hereinafter simply referred to as "image display layer 10") and an elliptically polarizing plate 20. In the present disclosure, the term "elliptically polarizing plate" also includes the concept of a circularly polarizing plate.

[0034] [Image display layer] The image display layer 10 forms an image therein and displays the image on the image display surface 10a. The image display layer 10 includes an element structure for forming an image. Therefore, the electrodes included in the element structure, the wiring connecting the element structures, and the like function as a reflective portion that reflects light. Therefore, the image display layer 10 has light reflectivity that reflects light incident on the display device 100 from the elliptically polarizing plate 20 side, and functions as a light reflective layer in the display device 100. The image display layer 10 may be flexible so that it can bend, or rigid so that it cannot bend.

[0035] The image display layer 10 is not limited in terms of layer configuration and materials as long as it is configured to form an image on the image display surface 10a. The image display layer 10 may be a multi-layered structure including, for example, a portion (or layer) formed of electrodes and wiring using metals such as gold, silver, copper, iron, nickel, chromium, molybdenum, titanium, aluminum, or alloys thereof, a resin film, a bank material, a dielectric portion such as a light-emitting element, and other layers.

[0036] The image display layer 10 is, for example, a flat panel display device. An example of a flat panel display device is a thin (or panel-shaped) organic electroluminescence display device (hereinafter also referred to as an "OLED display device"). The display device exemplified as the image display layer 10 is a device that does not include a member for optical compensation on the image display surface.

[0037] When the image display layer 10 is an OLED display device, the reflector typically is an electrode (e.g., a metal electrode) included in the OLED display device. An OLED display device has a thin-film structure in which an organic light-emitting material layer is sandwiched between a pair of opposing electrodes. Electrons are injected into the organic light-emitting material layer from one electrode, and holes are injected from the other electrode, causing the electrons and holes to combine in the organic light-emitting material layer, resulting in self-luminescence. Of the two electrodes sandwiching the organic light-emitting material layer, the electrode on the image display surface 10a side has the function of transmitting light from the organic light-emitting material layer, while the other electrode has the function of reflecting light from the organic light-emitting material layer toward the image display surface 10a. Therefore, the other electrode typically functions as the reflector in the OLED display device.

[0038] OLED display devices have advantages over liquid crystal display devices that require a backlight, such as better visibility, the ability to be made thinner, and the ability to be driven by a low DC voltage.

[0039] The elliptically polarizing plate 20 is laminated on the image display layer 10. Therefore, in the display device 100, an image is viewed from the elliptically polarizing plate 20 side. Therefore, the side opposite the image display layer 10 with respect to the elliptically polarizing plate 20 is also referred to as the "viewing side." The elliptically polarizing plate 20 has a polarizer 31 and an optical laminate 40. As shown in FIG. 1 , in the elliptically polarizing plate 20, the polarizer 31 and the optical laminate 40 are arranged in this order from the viewing side.

[0040] The polarizer 31 is laminated on the optical laminate 40. The polarizer 31 can be an absorptive film that absorbs linearly polarized light having a vibration plane parallel to its absorption axis and transmits linearly polarized light having a vibration plane perpendicular to the absorption axis (parallel to its transmission axis). A suitable example of the polarizer 31 is a uniaxially stretched polyvinyl alcohol-based resin film to which a dichroic dye has been adsorbed and aligned. The polarizer 31 can be produced, for example, by a method including the steps of: uniaxially stretching a polyvinyl alcohol-based resin film; dyeing the polyvinyl alcohol-based resin film with the dichroic dye to adsorb it; treating the polyvinyl alcohol-based resin film with a crosslinking liquid such as a boric acid aqueous solution; and washing the film with water after the crosslinking liquid treatment.

[0041] The polyvinyl alcohol resin may be a saponified polyvinyl acetate resin. Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate with other monomers copolymerizable with vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth)acrylamides having an ammonium group.

[0042] In the present disclosure, "(meth)acrylic" means at least one selected from acrylic and methacrylic. The same applies to "(meth)acryloyl", "(meth)acrylate", etc.

[0043] The thickness of the polarizer 31 is usually 30 μm or less, preferably 15 μm or less, more preferably 13 μm or less, still more preferably 10 μm or less, and particularly preferably 8 μm or less. The thickness of the polarizer 31 is usually 2 μm or more, and preferably 3 μm or more.

[0044] The polarizer 31 may be a cured film formed by polymerizing a liquid crystal compound, in which a dichroic dye is oriented, as described in, for example, JP 2016-170368 A. The dichroic dye may have absorption in the wavelength range of 380 to 800 nm, and organic dyes are preferred. Examples of dichroic dyes include azo compounds. The liquid crystal compound is a liquid crystal compound that can be polymerized while remaining oriented, and may have a polymerizable group in the molecule. Alternatively, a polarizing film may be formed from a dichroic dye having liquid crystallinity, as described in WO 2011 / 024891.

[0045] The luminosity-corrected polarization degree of the polarizer 31 is preferably 90% or more, and more preferably 95% or more. There is no particular limitation on the upper limit, but it is 99.9999% or less. The luminosity-corrected single transmittance of the polarizing film is preferably 35% or more, and more preferably 40% or more. There is no particular limitation on the upper limit, but it is 49.9% or less. When the laminate includes a polarizer 31 with such performance, reflected light is less likely to leak, and coloring can be made less noticeable.

[0046] 1, a protective film 32 may be provided on one or both sides of a polarizer 31. A laminate in which a protective film 32 is laminated on a polarizer 31 may be referred to as a linear polarizing plate 30.

[0047] The protective film 32 can be a light-transmitting (preferably optically transparent) thermoplastic resin. For example, the protective film 32 can be a film made of a polyolefin resin such as a linear polyolefin resin (e.g., a polypropylene resin) or a cyclic polyolefin resin (e.g., a norbornene resin), a cellulose resin such as triacetyl cellulose or diacetyl cellulose, a polyester resin such as polyethylene terephthalate or polybutylene terephthalate, a polycarbonate resin, a (meth)acrylic resin such as a methyl methacrylate resin, a polystyrene resin, a polyvinyl chloride resin, an acrylonitrile-butadiene-styrene resin, an acrylonitrile-styrene resin, a polyvinyl acetate resin, a polyvinylidene chloride resin, a polyamide resin, a polyacetal resin, a modified polyphenylene ether resin, a polysulfone resin, a polyethersulfone resin, a polyarylate resin, a polyamideimide resin, or a polyimide resin.

[0048] The retardation value of the protective film 32 may be appropriately controlled to a suitable value. In order to improve the visibility of the screen when a user wears polarized sunglasses or the like, the in-plane retardation value at a wavelength of 550 nm may be set to 70 to 140 nm.

[0049] The thickness of the protective film 32 is usually 1 to 100 μm, but from the viewpoints of strength, handling, etc., it is preferably 5 to 60 μm, more preferably 10 to 55 μm, and even more preferably 15 to 40 μm.

[0050] When protective films 32 are attached to both sides of polarizer 31, the two protective films 32 may be made of the same type of thermoplastic resin or different types of thermoplastic resin. The two protective films 32 may have the same thickness or different thicknesses. Furthermore, the two protective films 32 may have the same retardation characteristics or different retardation characteristics.

[0051] As described above, at least one of the protective films 32 may have a surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, a light diffusion layer, an antireflection layer, a low refractive index layer, an antistatic layer, or an antifouling layer on its outer surface (the surface opposite to the polarizer 31). The thickness of the protective film 32 includes the thickness of the surface treatment layer.

[0052] The protective film 32 can be attached to the polarizer 31 via, for example, an adhesive layer or a pressure-sensitive adhesive layer. The adhesive for forming the adhesive layer can be a water-based adhesive, an active energy ray-curable adhesive, or a thermosetting adhesive, and is preferably a water-based adhesive or an active energy ray-curable adhesive. The pressure-sensitive adhesive layer can be one described below.

[0053] Examples of aqueous adhesives include adhesives made from aqueous polyvinyl alcohol resin solutions and aqueous two-component urethane emulsion adhesives. Among these, aqueous adhesives made from aqueous polyvinyl alcohol resin solutions are preferred. Examples of polyvinyl alcohol resins that can be used include vinyl alcohol homopolymers obtained by saponifying polyvinyl acetate, a homopolymer of vinyl acetate, polyvinyl alcohol copolymers obtained by saponifying copolymers of vinyl acetate with other copolymerizable monomers, and modified polyvinyl alcohol polymers in which the hydroxyl groups of these copolymers are partially modified. The aqueous adhesives may contain crosslinkers such as aldehyde compounds (e.g., glyoxal), epoxy compounds, melamine compounds, methylol compounds, isocyanate compounds, amine compounds, and polyvalent metal salts.

[0054] When a water-based adhesive is used, a drying step is preferably carried out to remove water contained in the water-based adhesive after bonding the polarizer 31 and the protective film 32. After the drying step, a curing step may be carried out, for example, at a temperature of 20 to 45°C.

[0055] The active energy ray-curable adhesive is an adhesive containing a curable compound that is cured by irradiation with active energy rays such as ultraviolet light, visible light, electron beams, and X-rays, and is preferably an ultraviolet ray-curable adhesive.

[0056] The curable compound may be a cationically polymerizable curable compound or a radically polymerizable curable compound. Examples of the cationically polymerizable curable compound include epoxy compounds (compounds having one or more epoxy groups in the molecule), oxetane compounds (compounds having one or more oxetane rings in the molecule), and combinations thereof. Examples of the radically polymerizable curable compound include (meth)acrylic compounds (compounds having one or more (meth)acryloyloxy groups in the molecule), other vinyl compounds having radically polymerizable double bonds, and combinations thereof. A cationically polymerizable curable compound and a radically polymerizable curable compound may be used in combination. An active energy ray-curable adhesive usually further contains a cationic polymerization initiator and / or a radical polymerization initiator for initiating the curing reaction of the curable compound.

[0057] When bonding the polarizer 31 and the protective film 32 together, at least one of the bonding surfaces may be subjected to a surface activation treatment to enhance adhesion. Examples of surface activation treatments include dry treatments such as corona treatment, plasma treatment, discharge treatment (e.g., glow discharge treatment), flame treatment, ozone treatment, UV ozone treatment, and ionizing actinic ray treatment (e.g., ultraviolet treatment, electron beam treatment), and wet treatments such as ultrasonic treatment using a solvent such as water or acetone, saponification treatment, and anchor coating treatment. These surface activation treatments may be performed alone or in combination of two or more.

[0058] When the protective films 32 are attached to both sides of the polarizer 31, the adhesive for attaching these protective films 32 may be the same type of adhesive or different types of adhesive.

[0059] In the display device 100, the optical laminate 40 is disposed between the polarizer 31 (linear polarizing plate 30 in the embodiment shown in FIG. 1) and the image display layer 10. The optical laminate 40 has a λ / 2 portion 41 and a λ / 4 portion 42. The λ / 2 portion 41 and the λ / 4 portion 42 are disposed in this order from the viewing side.

[0060] The λ / 2 portion 41 has a function of imparting a phase difference of λ / 2 to incident light of wavelength λ. The value of the Nz coefficient of the λ / 2 portion 41 is desirably approximately 0.5. The value of the Nz coefficient being approximately 0.5 means that the Nz coefficient is in the range of 0.5±0.1. The Nz coefficient of the λ / 2 portion 41 is preferably in the range of 0.45 to 0.55. Unless otherwise specified, the slow axis of the λ / 2 portion 41 is parallel to nx.

[0061] The λ / 4 portion 42 has a function of imparting a phase difference of approximately λ / 4 to incident light of wavelength λ. The Nz coefficient of the λ / 4 portion 42 preferably ranges from 0.3 to 0.7, more preferably from 0.4 to 0.6, and even more preferably from 0.45 to 0.55. Unless otherwise specified, the slow axis of the λ / 4 portion 42 is parallel to nx.

[0062] 2 is a schematic diagram showing the positional relationship between the slow axis 41a of the λ / 2 portion 41, the slow axis 42a of the λ / 4 portion 42, and the transmission axis 31a of the polarizer 31. As shown in FIG. 2, the λ / 2 portion 41 and the λ / 4 portion 42 are arranged such that the angle θ1 between the slow axis 41a of the λ / 2 portion 41 and the slow axis 42a of the λ / 4 portion 42 is approximately 60°. "Approximately 60°" refers to a range of 60°±5°. The λ / 2 portion 41 is preferably arranged with respect to the polarizer 31 such that the angle between the slow axis 41a of the λ / 2 portion 41 and the transmission axis 31a of the polarizer 31 is approximately 15°. "Approximately 15°" refers to a range of 15°±5°. In this case, the λ / 4 portion 42 is preferably disposed with respect to the polarizer 31 so that the angle θ3 formed between the slow axis 42a of the λ / 4 portion 42 and the transmission axis 31a of the polarizer 31 is approximately 75°. Approximately 75° means a range of 75°±5°.

[0063] Each of the λ / 2 section 41 and the λ / 4 section 42 has at least one retardation element (first retardation element) Q. The λ / 2 section 41 may have two retardation elements Q and two retardation elements (second retardation elements) Z. The λ / 4 section 42 may have one retardation element Z.

[0064] [Lagging phase element Q] The retarder element Q is a retardation film having reverse dispersion and imparting a phase difference of approximately λ / 4 to incident light of wavelength λ. Approximately λ / 4 means a range of one-sixth to one-third of the wavelength λ. The retarder element Q may be a λ / 4 plate. The retarder element Q may also be a positive A plate. The retarder element Q may be obtained by curing a polymerizable liquid crystal compound, or by molding or further stretching a molten resin.

[0065] [Lagging element Z] The retarder element Z can be a positive C-plate, whose thickness direction retardation Reth(550) satisfies the formula (13). -30nm≧Reth(550)≧-120nm ··· (13)

[0066] The suitable value range of Reth(550) of the retarder element Z is preferably −100 nm or more and −40 nm or less, more preferably −90 nm or more and −50 nm or less. The retarder element Z may be obtained by curing a polymerizable liquid crystal compound, or by molding or further stretching a molten resin.

[0067] When the retarder element Q and the retarder element Z are layers obtained by curing a polymerizable liquid crystal, the retarder element Q and the retarder element Z are formed on an alignment film provided on a substrate. The substrate has a function of supporting the alignment film and may be a substrate formed in a long length. This substrate functions as a releasable support and can support a retardation film for transfer. Furthermore, it is preferable that the surface of the substrate has sufficient adhesive strength to allow peeling. Examples of the substrate include the resin films exemplified as materials for the protective film 32.

[0068] The thickness of the substrate is not particularly limited, but is preferably in the range of 20 μm to 200 μm. When the thickness of the substrate is 20 μm or more, strength is imparted. On the other hand, when the thickness is 200 μm or less, an increase in processing waste and wear of the cutting blade can be suppressed when the substrate is cut into sheet substrates.

[0069] The substrate may be subjected to various anti-blocking treatments. Examples of anti-blocking treatments include an easy-adhesion treatment, a treatment for kneading a filler or the like, and an embossing (knurling) treatment. By subjecting the substrate to such anti-blocking treatments, it is possible to effectively prevent the substrates from sticking to each other when the substrates are wound up, i.e., so-called blocking, and it becomes possible to produce an optical film with high productivity.

[0070] The layer of the cured polymerizable liquid crystal compound is formed on the substrate via an alignment film. That is, the substrate and the alignment film are laminated in this order, and the layer of the cured polymerizable liquid crystal compound is laminated on the alignment film.

[0071] The alignment film is not limited to a vertical alignment film, but may be an alignment film that aligns the molecular axis of the polymerizable liquid crystal compound horizontally, or an alignment film that aligns the molecular axis of the polymerizable liquid crystal compound at an angle. When producing the retarder element Q, a horizontal alignment film can be used, and when producing the retarder element Z, a vertical alignment film can be used.

[0072] The alignment film preferably has solvent resistance so that it does not dissolve the composition containing the polymerizable liquid crystal compound described below when applied, and also has heat resistance during heat treatment to remove the solvent and orient the liquid crystal compound. Examples of alignment films include alignment films containing an alignment polymer, photo-alignment films, and groove alignment films that have a concavo-convex pattern or multiple grooves formed on the surface for alignment. The thickness of the alignment film is usually in the range of 10 nm to 10,000 nm, preferably in the range of 10 nm to 1,000 nm, more preferably 500 nm or less, and even more preferably in the range of 10 nm to 200 nm.

[0073] The resin used for the alignment film is not particularly limited as long as it is a resin used as a known material for alignment films, and examples thereof include a cured product obtained by curing a conventionally known monofunctional or polyfunctional (meth)acrylate monomer under a polymerization initiator. Specific examples of the (meth)acrylate monomer include 2-ethylhexyl acrylate, cyclohexyl acrylate, diethylene glycol mono-2-ethylhexyl ether acrylate, diethylene glycol monophenyl ether acrylate, tetraethylene glycol monophenyl ether acrylate, trimethylolpropane triacrylate, lauryl acrylate, lauryl methacrylate, isobornyl acrylate, isobornyl methacrylate, 2-phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, 2-hydroxypropyl acrylate, benzyl acrylate, tetrahydrofurfuryl methacrylate, 2-hydroxyethyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, methacrylic acid, and urethane acrylate. The resin may be one of these, or a mixture of two or more of them.

[0074] The type of polymerizable liquid crystal compound used in this embodiment is not particularly limited, but can be classified into rod-shaped types (rod-shaped liquid crystal compounds) and discotic types (discotic liquid crystal compounds) based on their shape. Each type can further be divided into low-molecular-weight types and high-molecular-weight types. The term "high-molecular-weight" generally refers to a compound with a degree of polymerization of 100 or more (see "Polymer Physics: Phase Transition Dynamics," by Masao Doi, p. 2, Iwanami Shoten, 1992).

[0075] In this embodiment, any polymerizable liquid crystal compound can be used. Furthermore, a mixture of two or more rod-shaped liquid crystal compounds, two or more discotic liquid crystal compounds, or a mixture of a rod-shaped liquid crystal compound and a discotic liquid crystal compound may also be used.

[0076] Suitable rod-shaped liquid crystal compounds include those described in claim 1 of JP-A-11-513019 or paragraphs

[0026] to

[0098] of JP-A-2005-289980. Suitable discotic liquid crystal compounds include those described in paragraphs

[0020] to

[0067] of JP-A-2007-108732 or paragraphs

[0013] to

[0108] of JP-A-2010-244038.

[0077] Two or more types of polymerizable liquid crystal compounds may be used in combination. In this case, at least one type has two or more polymerizable groups in the molecule. That is, the layer formed by curing the polymerizable liquid crystal compound is preferably a layer formed by fixing a liquid crystal compound having a polymerizable group by polymerization. In this case, after forming the layer, it is no longer necessary for the compound to exhibit liquid crystallinity.

[0078] The polymerizable liquid crystal compound has a polymerizable group capable of undergoing a polymerization reaction. Examples of the polymerizable group include functional groups capable of undergoing an addition polymerization reaction, such as a polymerizable ethylenically unsaturated group or a ring-polymerizable group. More specifically, examples of the polymerizable group include a (meth)acryloyl group, a vinyl group, a styryl group, and an allyl group. Among these, a (meth)acryloyl group is preferred. The term "(meth)acryloyl group" encompasses both a methacryloyl group and an acryloyl group.

[0079] A layer of a cured polymerizable liquid crystal compound can be formed, for example, by applying a composition containing the polymerizable liquid crystal compound onto an alignment film. The composition may contain components other than the polymerizable liquid crystal compound. For example, the composition preferably contains a polymerization initiator. The polymerization initiator used is selected from, for example, a thermal polymerization initiator or a photopolymerization initiator depending on the type of polymerization reaction. Examples of photopolymerization initiators include α-carbonyl compounds, acyloin ethers, α-hydrocarbon-substituted aromatic acyloin compounds, polynuclear quinone compounds, and combinations of triarylimidazole dimers and p-aminophenyl ketones. The amount of the polymerization initiator used is preferably 0.01% by mass to 20% by mass, more preferably 0.5% by mass to 5% by mass, based on the total solid content of the coating liquid.

[0080] The composition may contain a polymerizable monomer from the viewpoint of the uniformity and strength of the coating film. Examples of the polymerizable monomer include radically polymerizable or cationic polymerizable compounds. Among them, polyfunctional radically polymerizable monomers are preferred.

[0081] The polymerizable monomer is preferably one that can be copolymerized with the above-mentioned polymerizable liquid crystal compound. Specific examples of the polymerizable monomer include those described in paragraphs

[0018] to

[0020] of JP-A No. 2002-296423. The amount of the polymerizable monomer used is preferably 1 to 50% by mass, more preferably 2 to 30% by mass, based on the total mass of the polymerizable liquid crystal compound.

[0082] The composition may contain a surfactant from the viewpoint of the uniformity and strength of the coating film. Examples of surfactants include conventionally known compounds. Among these, fluorine-based compounds are particularly preferred. Specific examples of surfactants include the compounds described in paragraphs

[0028] to

[0056] of JP-A No. 2001-330725 and the compounds described in paragraphs

[0069] to

[0126] of JP-A No. 2003-295212.

[0083] The composition may contain a solvent, and an organic solvent is preferably used. Examples of organic solvents include amides (e.g., N,N-dimethylformamide), sulfoxides (e.g., dimethyl sulfoxide), heterocyclic compounds (e.g., pyridine), hydrocarbons (e.g., benzene, hexane), alkyl halides (e.g., chloroform, dichloromethane), esters (e.g., methyl acetate, ethyl acetate, butyl acetate), ketones (e.g., acetone, methyl ethyl ketone), and ethers (e.g., tetrahydrofuran, 1,2-dimethoxyethane). Among these, alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination.

[0084] The composition may contain various alignment agents, such as a vertical alignment promoter such as a polarizing film interface side vertical alignment agent or an air interface side vertical alignment agent, and a horizontal alignment promoter such as a polarizing film interface side horizontal alignment agent or an air interface side horizontal alignment agent. Furthermore, the composition may contain, in addition to the above components, an adhesion improver, a plasticizer, a polymer, etc.

[0085] When the λ / 2 section 41 has two retardation elements Q and two retardation elements Z and the λ / 4 section 42 has one retardation element Q and one retardation element Z, the retardation elements Q and Z may be arranged as shown in Table 1. [Table 1]

[0086] In Table 1, the arrangements in the columns for the λ / 2 portion 41 and the λ / 4 portion 42 indicate the arrangement of the λ / 2 portion 41 and the λ / 4 portion 42 in the optical laminate 40, with the λ / 2 portion 41 side being the viewing side. Therefore, the left side is the viewing side in each cell showing an example of the arrangement of the retarder element Q and the retarder element Z in the λ / 2 portion 41 and the λ / 4 portion 42. Q and Z in each cell represent the retarder element Q and the retarder element Z, respectively, and for example, the arrangement relationship of Q and Z corresponds to the arrangement relationship of the retarder element Q and the retarder element Z.

[0087] Arrangement example a shown in Table 1 is the arrangement example shown in Fig. 1. That is, in the λ / 2 section 41, two retardation elements Q and two retardation elements Z are arranged in the order of retardation element Q, retardation element Z, retardation element Z, and retardation element Q from the viewer side. In the λ / 4 section 42, the retardation elements Q and Z are arranged in the order of retardation element Q and retardation element Z from the viewer side (λ / 2 section 41 side). In arrangement example a, the Rth (550 nm) of the retardation element Z in the λ / 4 section 42 is preferably -50 nm, -70 nm, or -90 nm, and of these, -70 nm is more preferable.

[0088] Arrangement example b is an arrangement example similar to arrangement example a, except that the arrangements of the retarder elements Q and Z in the λ / 4 section 42 are reversed.

[0089] Arrangement example c is an arrangement example similar to arrangement example a, except that in the λ / 2 section 41, two delay phase elements Q and two delay phase elements Z are arranged in the order of delay phase element Q, delay phase element Z, delay phase element Q, and delay phase element Z from the viewing side.

[0090] Arrangement example d is an arrangement example similar to arrangement example c, except that the arrangements of the retarder elements Q and Z in the λ / 4 section 42 are reversed.

[0091] Arrangement example e is an arrangement example similar to arrangement example b (or arrangement example d), except that in the λ / 2 section 41, two delay phase elements Q and two delay phase elements Z are arranged in the order of delay phase element Q, delay phase element Q, delay phase element Z, and delay phase element Z from the viewing side.

[0092] Arrangement example f is an arrangement example similar to arrangement example a, except that in the λ / 2 section 41, two delay phase elements Q and two delay phase elements Z are arranged in the order of delay phase element Z, delay phase element Q, delay phase element Z, and delay phase element Q from the viewing side.

[0093] The direction of the slow axis of the retarder element Q in the λ / 2 section 41 may be approximately aligned with the direction of the slow axis 41a of the λ / 2 section 41. Similarly, the direction of the slow axis of the retarder element Q in the λ / 4 section 42 may be approximately aligned with the direction of the slow axis 42a of the λ / 4 section 42. "Approximately aligned" means that the directions of the two slow axes may be misaligned by about ±5° (the same applies hereinafter).

[0094] The retarder elements Q in the λ / 2 section 41 and the λ / 4 section 42 may be a laminate of a plurality of retardation films that function as the retarder elements Q as a whole. The directions of the slow axes of the plurality of retardation films that constitute the retarder elements Q are approximately aligned with the direction of the slow axis 41a. Similarly, the retarder elements Z in the λ / 2 section 41 and the λ / 4 section 42 may be a laminate of a plurality of retardation films that function as the retarder elements Q as a whole. The directions of the slow axes of the plurality of retardation films that constitute the retarder elements Z are approximately aligned with the direction of the slow axis 42a.

[0095] The linear polarizer 30, the optical laminate 40, and the components (including the retarder elements Q and Z) that constitute the display device 100 can be laminated using, for example, an adhesive layer (not shown). When the image display layer 10 includes electrodes that the organic EL display element has, the organic EL display element and the optical laminate 40 may be laminated via an adhesive layer.

[0096] The pressure-sensitive adhesive layer can be composed of a pressure-sensitive adhesive composition whose main component is a resin such as a (meth)acrylic, rubber, urethane, ester, silicone, or polyvinyl ether resin. Among these, a pressure-sensitive adhesive composition whose base polymer is a (meth)acrylic resin, which is excellent in transparency, weather resistance, heat resistance, etc., is preferred. The pressure-sensitive adhesive composition may be an active energy ray-curable or thermosetting type. The thickness of the pressure-sensitive adhesive layer is usually 3 μm to 30 μm, and preferably 3 μm to 25 μm.

[0097] The (meth)acrylic resin (base polymer) used in the pressure-sensitive adhesive composition is preferably a polymer or copolymer containing one or more (meth)acrylic acid esters as monomers, such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. It is preferable to copolymerize a polar monomer into the base polymer. Examples of polar monomers include monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, or an epoxy group, such as (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, and glycidyl (meth)acrylate.

[0098] The pressure-sensitive adhesive composition may contain only the base polymer, but usually further contains a crosslinking agent. Examples of crosslinking agents include divalent or higher metal ions that form metal carboxylates with carboxyl groups; polyamine compounds that form amide bonds with carboxyl groups; polyepoxy compounds or polyols that form ester bonds with carboxyl groups; and polyisocyanate compounds that form amide bonds with carboxyl groups. Among these, polyisocyanate compounds are preferred.

[0099] [Method of manufacturing an elliptically polarizing plate and a display device] The elliptical polarizing plate 20 is manufactured by laminating a polarizer 31 and an optical laminate 40 including a λ / 2 portion 41 and a λ / 4 portion 42 via an adhesive layer. For example, as shown in FIG. 1 , when using a linear polarizing plate 30 in which protective films 32 are laminated on both sides of the polarizer 31, the polarizer 31 is manufactured and the protective films 32 are laminated on both sides of the polarizer 31 to obtain the linear polarizing plate 30. Then, an adhesive layer formed on a release film is laminated on the protective film 32 facing the optical laminate 40. The release film on the adhesive layer is peeled off, and the polarizer 31 and the separately manufactured λ / 2 portion 41 and λ / 4 portion 42 are bonded together via the exposed adhesive layer to obtain the elliptical polarizing plate 20. The display device 100 is obtained by laminating the elliptical polarizing plate 20 on an image display layer 10 via an adhesive layer, for example.

[0100] The optical laminate 40 includes a λ / 2 portion 41 and a λ / 4 portion 42. The Nz coefficient of the λ / 2 portion 41 is approximately 0.5, and the Nz coefficient of the λ / 4 portion 42 is 0.3 or more and 0.7 or less. When an elliptically polarizing plate 20 including such an optical laminate 40 is laminated on an image display layer 10 serving as a light-reflecting layer as shown in Fig. 1, good display performance can be ensured even when the elliptically polarizing plate 20 including the optical laminate 40 is viewed with the display device 100 tilted in at least two orthogonal in-plane directions.

[0101] For example, in the case of a mobile terminal (e.g., a smartphone) whose display surface is rectangular when viewed from the viewing side, the two orthogonal in-plane directions include the longitudinal and lateral directions of the rectangle. Mobile terminals such as smartphones tend to be used either vertically (equivalent to viewing the screen from the longitudinal direction) or horizontally (equivalent to viewing the screen from the lateral direction). Therefore, by ensuring good display performance even when viewed at an angle in at least the two orthogonal in-plane directions, the viewer can view a good image even when tilting the mobile terminal.

[0102] In a configuration in which the λ / 2 section 41 has two retarder elements Q and two retarder elements Z, and the λ / 4 section 42 has a retarder element Q and a retarder element Z, it is easy to achieve the above-mentioned Nz coefficient of the λ / 2 section 41 and the above-mentioned Nz coefficient of the λ / 4 section 42. In such a configuration, it is even easier to ensure good display performance even when the elliptical polarizer 20 is viewed with an inclination in at least two orthogonal in-plane directions. In particular, in the arrangement example a shown in Table 1, it is easy to ensure good display performance even when the elliptical polarizer 20 is viewed with an inclination in a direction other than the two orthogonal in-plane directions.

[0103] Figure 3 is a graph showing the measurement results of the wavelength dispersion of the in-plane retardation of the prototype elliptical polarizer 20. The black dots in the graph represent measurement points, and the solid line is a fitting based on theoretical calculations. The dotted line represents the wavelength dispersion for an ideal λ / 4 plate with an in-plane retardation of λ / 4 at each wavelength. The theoretical calculations used the transmittance and in-plane retardation of the polarizer 31, λ / 2 portion 41, and λ / 4 portion 42. The λ / 2 portion 41 and λ / 4 portion 42 of the elliptical polarizer 20 used in the measurements had the configuration shown in Example (a). The in-plane retardation of the λ / 2 portion 41 and λ / 4 portion 42 used in the measurements at a wavelength of 550 nm was 288 nm and 144 nm, respectively. The Nz coefficients of the λ / 2 portion 41 and λ / 4 portion 42 used in the measurements were both 0.5. Furthermore, in the elliptical polarizer used for the measurement, the angle formed between the slow axis 41a of the λ / 2 portion 41 and the transmission axis 31a of the polarizer 31 was 15.4°, and the angle formed between the slow axis 42a of the λ / 4 portion 42 and the transmission axis 31a of the polarizer 31 was 75.4°.

[0104] For the measurement, a retardation measuring device ("KOBRA-WPR", manufactured by Oji Scientific Instruments Co., Ltd.) was used.

[0105] The horizontal axis of Fig. 3 represents wavelength (nm), and the vertical axis represents in-plane retardation (nm). The solid line in Fig. 3 represents a fitting curve for the measurement results (plotted points in the figure). The dashed line in Fig. 3 is a straight line representing λ / 4. As shown in Fig. 3, the optical laminate 40 according to this embodiment and the elliptical polarizer 20 including it can achieve a phase difference close to λ / 4 over the entire visible light range, and therefore can achieve excellent viewing angle compensation function over the entire visible light range.

[0106] By applying the optical laminate 40 or the elliptical polarizer 20 including the same to LCD displays, head-mounted displays, etc., it is possible to provide a wide viewing angle and high contrast across the entire visible light range. Furthermore, by applying the optical laminate 40 or the elliptical polarizer 20 including the same to visible circularly polarized light communication, it is possible to provide a circularly polarized light source with little radiation angle dependency across the entire visible light range.

[0107] The present invention is not limited to the above-described embodiments, but is intended to include the scope indicated by the claims, and to include all modifications within the meaning and scope equivalent to the claims. [Example]

[0108] The present invention will be specifically described below with reference to examples. In the following description, "%" and "parts" mean "% by mass" and "parts by mass" unless otherwise specified. The present invention is not limited to the following examples.

[0109] ·Method of measuring film thickness The film thickness was measured using a contact film thickness meter ("MH-15M", "Counter TC101", "MS-5C", manufactured by Nikon Corporation).

[0110] ·Retardation measurement method The retardation in the thickness direction of the λ / 2 and λ / 4 parts and the in-plane retardation of the λ / 2, λ / 4 and elliptical polarizers were measured using a retardation measuring device (KOBRA-WPR, manufactured by Oji Scientific Instruments Co., Ltd.).

[0111] ·Method for measuring refractive index The refractive index of the film, layer, etc. was measured using a spectroscopic ellipsometer ("M-2000", manufactured by JA Woollam).

[0112] Visibility correction and hue calculation method The luminosity-corrected single transmittance Ty, single transmission hue a, single transmission hue b, and luminosity-corrected polarization degree Py, as well as the luminosity-corrected reflectance Ry10 and reflection hue a, which are described below. * 10, reflective hue b * 10. The luminosity-corrected reflectance Ry50 was calculated using the corresponding spectral spectra, namely, the single spectral transmittance T, the spectral polarization P, the spectral reflectance R, and the color matching function and standard illuminant.

[0113] The luminosity correction value is obtained by dividing the tristimulus value Y of the corresponding spectral spectrum by the tristimulus value Yo of the standard illuminant. * ,b * is the L of the corresponding spectroscopic spectrum * a * b * Hues a and b are the hues in the Lab color system of the corresponding spectral spectrum.

[0114] Of the stimulus values ​​of red, green, and blue light to the cone cells of the eye, the tristimulus value Y is the one that indicates the green stimulus. (See "Introduction to Color Engineering," co-authored by Shinoda Hiroyuki and Fujieda Ichiro, Morikita Publishing, pp. 106-107, 2007.) The color matching functions used were those recommended by the International Commission on Illumination (CIE) (1931). The standard illuminant used was D65 (ISO10526:1999 / CIES005 / E-1998). The standard white surface was considered a perfect reflecting surface.

[0115] Measurement method for polarizer spectral polarization degree P, single unit spectral transmittance T, and single unit transmittance hue a, b The spectral transmittance in the transmission axis direction and the spectral transmittance in the absorption axis direction of the polarizer were measured using an ultraviolet-visible spectrophotometer ("V7100", manufactured by JASCO Corporation), and the spectral polarization degree P, the single spectral transmittance T, the single transmission hue a, and the single transmission hue b were calculated.

[0116] The single-piece spectral transmittance T is the average value of the spectral transmittance in the transmission axis direction and the spectral transmittance in the absorption axis direction. The degree of spectral polarization P is obtained by dividing the difference between the spectral transmittance in the transmission axis direction and the spectral transmittance in the absorption axis direction by the sum of the spectral transmittance in the transmission axis direction and the spectral transmittance in the absorption axis direction. The spectral transmittance in the transmission axis direction is the transmittance at each wavelength for linearly polarized light vibrating parallel to the polarizer transmission axis. The spectral transmittance in the absorption axis direction is the transmittance at each wavelength for linearly polarized light that vibrates parallel to the absorption axis of the polarizer.

[0117] The absorption axis of the polarizer coincides with the stretching direction of the polyvinyl alcohol.

[0118] ·Measurement of reflectance and reflected hue The spectral reflectance R was measured using the SCI mode of a display measurement system (DMS803, manufactured by Instrument Systems) when an elliptically polarizing plate was placed on the light-reflecting layer, and the luminosity-corrected reflectance Ry and reflective hue a * , reflection hue b * was calculated.

[0119] The luminosity-corrected reflectance and reflection hue at an inclination angle θ = 10° (the inclination angle will be described later) are Ry10 and a * 10, b * The luminosity corrected reflectance at an inclination angle θ=50° is called Ry50.

[0120] The spectral reflectance R was measured at tilt angles θ = 10° and θ = 50°, with the reflection intensity of the light-reflecting layer alone (without an elliptically polarizing plate) set at 100%. The measurement wavelength ranged from 380 nm to 780 nm in 1 nm increments.

[0121] The light-reflecting layer was prepared by removing the cover glass and elliptically polarizing plate from an organic EL display device taken out of a commercially available smartphone (Samsung Galaxy S9 SC-02K smartphone).

[0122] As shown in Figure 4, the direction perpendicular to the plane p, which is defined by an axis parallel to the refractive index nx and an axis parallel to the refractive index ny (the direction of the dashed line n in Figure 4), is defined as the tilt angle θ = 0°. The plane p corresponds to the viewing-side surface of the elliptically polarizing plate. As shown in Figure 5, the direction of the in-plane angle φ is defined as the tilt central axis. In Figure 5, the white arrows schematically show the tilt angles of the plane p at φ = 0°, 45°, 90°, 135°, 180°, 225°, 270°, 315°, and 315°. In each experimental example described below, the spectral reflectance R was measured in 5° increments within the range of Equation (14). φ = 90° was defined as the angle at which Ry50 was minimized. In Figure 5, the position of the in-plane angle φ = 0° (or 90°) on the plane p is for convenience of illustration. 0°≦φ<360° (14) From now on, Ry10, a * 10, b * Let 10 be the average value of the in-plane angle range in equation (14).

[0123] Definition of normalized reflected luminance L The normalized reflected luminance L50 at an inclination angle θ=50° was calculated using an LCD analysis simulator (LCD Master ver.6, manufactured by Shintech Co., Ltd.).

[0124] The above simulator calculations can obtain a luminosity-corrected reflected luminance, which is normalized to 1 as the luminosity-corrected reflectance calculated using the spectral reflectance when a standard illuminant is incident on a standard white surface.

[0125] Hereinafter, the normalized reflected luminance L expressed as a percentage of the above-mentioned luminance is used, and in particular, the normalized reflected luminance at an inclination angle θ=50° is referred to as L50. For the calculations by the simulator, the spectral transmittance in the transmission axis direction and the spectral transmittance in the absorption axis direction of the polarizer described in this specification, measured with the above-mentioned UV-visible spectrophotometer, and the refractive indexes of the retarder elements Q and Z described in this specification, measured with the above-mentioned ellipsometer, were used.

[0126] In the calculation, the light-reflecting layer was assumed to be a perfect mirror surface with a reflectance of 100%.

[0127] The in-plane angle φ shown in Equation (14) was calculated in 1° increments with the tilt central axis as the center. In each calculation example, the angle φ at which the normalized reflected luminance L was minimized was set to φ=90°.

[0128] Due to the simulator's specifications, the luminance calculated by the simulator does not include the effects of interfacial reflection between the atmosphere and the top surface of the ellipsoidal polarizer. Therefore, there is a discrepancy between the measured luminosity-corrected reflectance Ry and the calculated normalized reflected luminance L, corresponding to the interfacial reflection between the atmosphere and the top surface of the ellipsoidal polarizer. This discrepancy can be estimated using Fresnel's equation. Assuming the refractive index of a commonly used front panel is approximately 1.5, the difference between the normalized reflected luminance L50 and the luminosity-corrected reflectance Ry50 at an inclination angle of 50° is roughly estimated to be approximately 5.9 to 6.2%. Despite this discrepancy, a correlation between the normalized reflected luminance L50 and the luminosity-corrected reflectance Ry50 has been confirmed, and we determined that the correlation between the measured values ​​can be adequately estimated using simulator calculations.

[0129] (Experimental value: Ry50) Within the range of the in-plane angle φ in equation (14), in-plane angular areas PA1, PA2, PA3, and PA4 are set as shown in Fig. 6. The in-plane angular areas PA1, PA2, PA3, and PA4 are within the ranges shown in equations (15) to (18). In-plane angular area PA1: 85°≦φ≦95° and 265°≦φ≦275° (15) In-plane angular area PA2: 355°≦φ≦5° and 175°≦φ≦185 (16) In-plane angular area PA3: 40°≦φ≦50° and 220°≦φ≦230 (17) In-plane angular area PA4: 130°≦φ≦140° and 310°≦φ≦320° (18)

[0130] In each experimental example described below, the average luminosity-corrected reflectance Ry50 was calculated for each in-plane angular region shown in Figure 6 and equations (15) to (18). In the following description, "Ry50 (regions PA1 to PA4)" refers to the average value of Ry50 in the in-plane angular regions PA1 to PA4. (Calculated value: L50) For each experimental example, the average normalized reflected luminance L50 was calculated for each in-plane angle φ region as shown in equations (15) to (18). In the following description, "L50 (regions PA1 to PA4)" indicates the average L50 value for the in-plane angle regions PA1 to PA4.

[0131] The following preparations were made for the experiment.

[0132] [Preparation of light-reflecting layer] An organic EL display device was taken out of a commercially available smartphone (Samsung smartphone Galaxy S9 SC-02K), from which the cover glass and elliptically polarizing plate had been peeled off, and the resulting display device was used as a light-reflecting layer.

[0133] [Preparation of composition for forming horizontal alignment film] Five parts of a photo-alignment material (weight average molecular weight: 30,000) having the following structure was mixed with 95 parts of cyclopentanone (solvent). The resulting mixture was stirred at 80°C for 1 hour to obtain a composition for forming a horizontal alignment film. [ka]

[0134] [Preparation of composition for forming vertical alignment film] Sunever SE610 manufactured by Nissan Chemical Industries, Ltd. was used.

[0135] [Preparation of Composition for Forming Retardation Element Q] To form retarder element Q (reverse dispersion positive A plate), the following polymerizable liquid crystal compound A and polymerizable liquid crystal compound B were used. Polymerizable liquid crystal compound A was produced by the method described in JP-A No. 2010-31223. Polymerizable liquid crystal compound B was produced according to the method described in JP-A No. 2009-173893. The molecular structures of each are shown below.

[0136] [Polymerizable liquid crystal compound A] [ka]

[0137] [Polymerizable liquid crystal compound B] [ka]

[0138] Polymerizable liquid crystal compound A and polymerizable liquid crystal compound B were mixed in a mass ratio of 90:10. To 100 parts of the resulting mixture, 1.0 part of a leveling agent ("Megafac F-556" manufactured by DIC Corporation) and 6 parts of a polymerization initiator, 2-dimethylamino-2-benzyl-1-(4-morpholinophenyl)butan-1-one ("Omnirad369" manufactured by IGM Resins BV), were added. Furthermore, N-methyl-2-pyrrolidone (NMP) was added so that the solids concentration became 13%, and the mixture was stirred at 80°C for 1 hour to obtain a composition for forming retarder element Q.

[0139] [Preparation of Composition for Forming Retardation Element Z] To form a retarder element Z (positive C plate), a composition was prepared as follows: 0.1 parts of F-556 as a leveling agent and 3 parts of Omnirad369 as a polymerization initiator were added to 100 parts of a polymerizable liquid crystal compound ("Paliocolor LC242" manufactured by BASF). Cyclopentanone was added to the mixture so that the solids concentration became 13%, to obtain a composition for forming retarder element Z.

[0140] [Preparation of Polarizer] A polyvinyl alcohol (PVA) film with an average degree of polymerization of approximately 2,400, a degree of saponification of 99.9 mol% or more, and a thickness of 75 μm was prepared. The PVA film was immersed in pure water at 30°C and then immersed in an aqueous solution containing iodine, potassium iodide, and water in a mass ratio of 0.02 / 2 / 100 at 30°C for iodine dyeing (iodine dyeing step). The PVA film after the iodine dyeing step was then immersed in an aqueous solution containing potassium iodide, boric acid, and water in a mass ratio of 12 / 5 / 100 at 56.5°C for boric acid treatment (boric acid treatment step). The PVA film after the boric acid treatment step was washed with pure water at 8°C and then dried at 65°C to obtain a polarized film in which iodine was adsorbed and aligned in the polyvinyl alcohol. The PVA film was stretched in both the iodine dyeing step and the boric acid treatment step. The total stretch ratio of the PVA film was 5.3 times. The resulting polarizing film had a thickness of 10 μm.

[0141] A polarizing film and a saponified triacetyl cellulose (TAC) film (KC4UYTAC, 40 μm thick, manufactured by Konica Minolta, Inc.) were bonded together using a nip roll with a water-based adhesive. The resulting laminate was dried at 60°C for 2 minutes while maintaining a tension of 430 N / m, yielding a polarizer with a TAC film as a protective film on one side. The water-based adhesive was prepared by adding 3 parts of carboxyl-modified polyvinyl alcohol (Kuraray Co., Ltd., "Kuraray Poval KL318") and 1.5 parts of a water-soluble polyamide epoxy resin (Taoka Chemical Co., Ltd., "Sumirez Resin 650," a 30% solids aqueous solution) to 100 parts of water.

[0142] The optical properties of the obtained polarizer were measured: the luminous efficiency-corrected single transmittance Ty was 41.9%, the luminous efficiency-corrected polarization degree Py was 99.962%, the single transmission hue a was -1.5, and the single transmission hue b was 3.6.

[0143] [Fabrication of retarder element Q (reverse dispersion positive A plate)] Corona treatment was carried out on a cyclic olefin resin (COP) film (ZF-14-50) manufactured by Zeon Corporation. The corona treatment was carried out using a TEC-4AX manufactured by Ushio Inc. The corona treatment was carried out once under the conditions of an output of 0.78 kW and a treatment speed of 10 m / min. The composition for forming a horizontal alignment film was applied to the COP film using a bar coater and dried at 80°C for 1 minute. A polarized UV irradiation device ("SPOT CURE SP-9", manufactured by Ushio Inc.) was used to irradiate the coated film with an integrated light dose of 100 mJ / cm at a wavelength of 313 nm. 2 Polarized UV exposure was carried out at an axial angle of 45° so that the resulting horizontal alignment film had a thickness of 100 nm.

[0144] Next, a composition for forming a retarder element Q (reverse dispersion positive A plate) was applied to the horizontal alignment film using a bar coater and dried at 120°C for 1 minute. The coating film was irradiated with ultraviolet light (under a nitrogen atmosphere, cumulative light intensity at a wavelength of 365 nm: 500 mJ / cm2) using a high-pressure mercury lamp (Uniqure VB-15201BY-A, manufactured by Ushio Inc.), thereby forming a retarder element Q. The retarder element Q had a film thickness of 2.3 μm.

[0145] An adhesive layer was laminated on retarder element Q. A film consisting of a COP film, an alignment film, and a horizontally aligned liquid crystal cured film was attached to glass via the adhesive layer. The COP film was peeled off to obtain a sample for measuring retardation. As a result of measuring the in-plane retardation ReoQ(λ) of the retarder element Q at each wavelength, ReoQ(450)=121nm, ReoQ(550)=142nm, ReoQ(650)=146nm, ReoQ(450) / ReoQ(550)=0.85, ReoQ(650) / ReoQ(550)=1.03, and the retarder element Q exhibited reverse wavelength dispersion.

[0146] The retardation sub-element Q was a positive A plate that satisfied the relationship nx > ny ≒ nz. As a result of measuring the thickness-direction retardation RethQ(λ) at each wavelength, RethQ(450) = 61 nm, RethQ(550) = 72 nm, RethQ(650) = 73 nm, and it was like this.

[0147] [Production of retardation sub-element Z (positive C plate)] Corona treatment was performed on the COP film. The conditions of the corona treatment were the same as above. On the COP film, a composition for forming a vertical alignment film was applied with a bar coater and dried at 80°C for 1 minute to obtain a vertical alignment film. The film thickness of the obtained vertical alignment film was 50 nm.

[0148] A composition for forming retardation sub-element Z was applied to the vertical alignment film using a bar coater and dried at 90°C for 120 seconds. Ultraviolet rays were irradiated (in a nitrogen atmosphere, integrated light quantity at a wavelength of 365 nm: 500 mJ / cm 2 ) to form retardation sub-element Z. In this way, a film formed by the COP film, the vertical alignment film, and retardation sub-element Z was obtained. The film thickness of retardation sub-element Z was 0.6 μm.

[0149] An adhesive layer was laminated on retardation sub-element Z. Through the adhesive layer, the film formed by the COP film, the alignment film, and retardation sub-element Z was bonded to glass. The COP film was peeled off to obtain a sample for measuring retardation. As a result of measuring the thickness-direction retardation RethZ(550) of retardation sub-element Z at a wavelength of 550 nm, RethZ(550) = -70 nm, and it was like this. Retardation sub-element Z was a positive C plate that satisfied the relationship nx ≒ ny < nz.

[0150] [Retardation laminate 1] The vertical alignment film and the retarder element Z (C plate) formed on the COP film were bonded to the retarder element Q (A plate) formed on the COP film via an adhesive. The COP film on the retarder element Q side was then peeled off to obtain a film in which the COP film and the retarder laminate 1 were laminated in this order. The positional relationship between the retarder elements Q and Z in the retarder laminate 1 was as follows: To indicate the positional relationship between the retarder elements Q and Z relative to the COP film, the COP film is shown in parentheses in the following positional relationship. Therefore, the following notation indicates that the retarder elements Z and Q are arranged in the order of the retarder element Z and the retarder element Q from the COP film side. Similar notation may be used for the positional relationship between elements (or layers). (COP film) / Z / Q

[0151] [Lag phase laminate 2] The vertical alignment film and the lagging retarder element Z surface of the lagging retarder element Z formed on the COP film were bonded to the horizontal alignment film and the lagging retarder element Q surface of the lagging retarder element Q formed on the COP film via an adhesive, and then the COP film on the lagging retarder element Z side was peeled off to obtain a film in which the COP film and the lagging retarder laminate 2 were laminated in this order. The positional relationship between the lagging retarder element Q and the lagging retarder element Z in the lagging retarder laminate 2 was as follows: (COP film) / Q / Z

[0152] [Lag phase laminate 3] The horizontal alignment film formed on the COP film and the lagging retarder element Q (A plate) of the horizontal alignment film and the lagging retarder element Q (A plate) of the COP film were bonded together via an adhesive, and then the COP film on one of the lagging retarder elements Q was peeled off to obtain a film in which the COP film and the lagging retarder laminate 3 were laminated in this order. The positional relationship between the lagging retarder element Q and the lagging retarder element Z in the lagging retarder laminate 3 was as follows: (COP film) / Q / Q

[0153] [Lag phase laminate 4] The vertical alignment film formed on the COP film and the lagging retarder element Z surface of the lagging retarder element Z (C plate) were bonded to the vertical alignment film formed on the COP film and the lagging retarder element Z of the lagging retarder element Z (C plate) via an adhesive, and then the COP film on one of the lagging retarder element Z sides was peeled off to obtain a film in which the COP film and the lagging retarder laminate 4 were laminated in this order. The positional relationship between the lagging retarder element Q and the lagging retarder element Z in the lagging retarder laminate 4 was as follows: (COP film) / Z / Z

[0154] [Lag phase laminate 5] The side of the delay phase element Z of the film formed from the COP film and the delay phase laminate 2 was bonded to the side of the delay phase element Z of the film formed from the COP film and the delay phase laminate 4 via an adhesive layer, and then the COP film on the side of the delay phase element Q was peeled off to obtain a film in which the delay phase laminate 5 and the COP film were laminated in this order. The positional relationship between the delay phase element Q and the delay phase element Z in the delay phase laminate 5 was as follows: Q / Z / Z / Z / (COP film)

[0155] [Example 1] <λ / 2 part> A film formed of two COP films and a lagging retarder laminate 2 was prepared, cut so that the slow axes of the two layers of lagging retarder elements Q would coincide when the lagging retarder elements Z sides were in close contact with each other, and the lagging retarder element Z sides of each film were bonded together via an adhesive. The COP film on one of the lagging retarder element Q sides was then peeled off to obtain a film in which the COP film and a λ / 2 part (lagging retarder element Q, adhesive layer, lagging retarder element Z, adhesive layer, lagging retarder element Z, adhesive layer, lagging retarder element Q) were laminated in this order. The λ / 2 part (lagging retarder element Q, adhesive layer, lagging retarder element Z, adhesive layer, lagging retarder element Z, adhesive layer, lagging retarder element Q) means that in the λ / 2 part, the lagging retarder element Q, adhesive layer, lagging retarder element Z, adhesive layer, lagging retarder element Z, adhesive layer, lagging retarder element Q, adhesive layer, lagging retarder element Q, adhesive layer, lagging retarder element Q, adhesive layer, lagging retarder element Q, adhesive layer, lagging retarder element Q, adhesive layer, lagging retarder element Q, adhesive layer, lagging retarder element Q, adhesive layer, lagging retarder element Q, adhesive layer, lagging retarder element Q, adhesive layer, lagging retarder element Q, adhesive layer, lagging retarder element Q, adhesive layer, lagging retarder element Z ... Z, adhesive layer, lagging retarder element Q

[0156] <λ / 4 part> The retarder laminate 1 was used as the λ / 4 portion.

[0157] <Elliptical polarizing plate> In a polarizer laminated with a TAC film, the surface of the polarizer opposite to the TAC film was bonded to the retarder element Q side of a film formed from the above-mentioned COP film and the λ / 2 portion via an adhesive layer, and the COP film was peeled off to obtain a laminate. At this time, the angle between the transmission axis of the polarizer and the slow axis of the λ / 2 portion was 15°. Next, the retarder element Q of the above-mentioned laminate and the retarder element Q of a film formed from the COP film and the λ / 4 portion were bonded via an adhesive layer, and the COP film was peeled off to obtain an elliptical polarizing plate EP1. At this time, the angle between the transmission axis of the polarizer and the slow axis of the λ / 4 portion was 75°. N of the λ / 2 portion Z The coefficient is 0.51, and the N Z The coefficient was 0.51.

[0158] In the elliptical polarizing plate EP1, a polarizer, an adhesive layer, a λ / 2 portion (retarder element Q, adhesive layer, retarder element Z, adhesive layer, retarder element Z, adhesive layer, retarder element Q), an adhesive layer, and a λ / 4 portion (retarder element Q, adhesive layer, retarder element Z) were laminated in this order on a TAC film. The arrangement of the retarder element Q and the retarder element Z in the optical laminate formed by laminating the λ / 2 portion and the λ / 4 portion in the elliptical polarizing plate EP1 was the arrangement of arrangement example a in Table 1.

[0159] Retardation An adhesive layer was laminated on the retarder element Z located on the opposite side of the TAC film in the elliptically polarizing plate EP1. The elliptically polarizing plate EP1 was attached to glass via the adhesive layer to obtain a sample for measuring retardation.

[0160] As a result of measuring the in-plane retardation Reo(λ) at each wavelength, Reo(450)=112nm Reo(550)=138nm Reo(650)=162nm Reo(450) / Reo(550)=0.81 Reo(650) / Reo(550)=1.17, It was.

[0161] Reflectance and reflection hue at an inclination angle of 10° The elliptically polarizing plate EP1 was adhered to the light-reflecting layer via an adhesive to obtain sample S1. The luminosity-corrected reflectance and the in-plane angle average value of the reflected hue at an inclination angle θ of 10° for sample S1 were measured, and the results were Ry10=4.6%, a * 10=0.00, b * 10=-0.25.

[0162] Reflectance at an inclination angle of 50° (experimental value) The average value of the luminosity-corrected reflectance Ry50 for each in-plane angle region of sample S1 at an inclination angle θ = 50° was measured and calculated. Ry50 (area PA1)=6.0% Ry50 (area PA2)=6.2% Ry50 (area PA3)=6.3% Ry50 (area PA4) = 6.3%, It was.

[0163] Reflectance at an inclination angle of 50° (calculated value) As a calculation model for the elliptical polarizer EP1, a laminate (hereinafter referred to as "elliptical polarizer EP1s") was designed that had the same laminate structure as the elliptical polarizer EP1, except that the TAC film and adhesive layer in the elliptical polarizer EP1 were omitted. The elliptical polarizer EP1s was a laminate in which a polarizer, a λ / 2 portion, and a λ / 4 portion were laminated in this order. The λ / 2 portion and the λ / 4 portion each had the following configuration. λ / 2 part: Q / Z / Z / Q λ / 4: Q / Z The angle between the transmission axis of the polarizer and the slow axis of the λ / 2 portion was set to 15°. The angle between the transmission axis of the polarizer and the slow axis of the λ / 4 portion was set to 75°. The average value of the normalized reflection luminance L50 at an inclination angle θ=50° was calculated for each in-plane angle region, and the results were as follows: L50(area PA1)=0.03% L50(area PA2)=0.12% L50(area PA3)=0.07% L50(area PA4)=0.05%, It was.

[0164] Visual confirmation of display performance Visual confirmation of display performance was carried out outdoors on a sunny day by five observers. Observations were made at each in-plane angle corresponding to areas PA1 to PA4 for both a tilt angle of 10° and a tilt angle of 50°. If four or more of the five observers did not notice rainbow-colored reflected light from the light-reflecting layer, the display was evaluated as having good display performance with reflected light well prevented. Otherwise, the display performance was evaluated as being impaired. The method for visual confirmation of display performance was the same when carried out in other examples and comparative examples described below.

[0165] The results of visual inspection in Example 1 when the inclination angle was 10° and when the inclination angle was 50° were as follows. (Visual confirmation at an inclination angle of 10°) When the external light reflection of the light-reflecting layer of sample S1 at an inclination angle θ=10° was observed from the elliptically polarizing plate EP1 side under sunlight, it was confirmed that reflected light was well prevented and good display performance was achieved. (Visual confirmation at an inclination angle of 50°) When the external light reflection of the light-reflecting layer of sample S1 was observed under sunlight at an inclination angle θ=50°, it was confirmed that the display performance was excellent, with reflected light well prevented at all in-plane angles corresponding to areas PA1 to PA4.

[0166] FIG. 7 is a diagram showing the results of Example 1, and also shows the results of Examples 2 and beyond. In FIG. 7, "1," "2," "3," and "4" in the "Retarder Element" column indicate that retarder elements corresponding to "1," "2," "3," and "4" are arranged from the viewing side. In the "50° Inclined Visual Observation" column in the diagram shown in FIG. 7, "◯" indicates that reflected light is well prevented and good display performance is achieved, while "×" indicates that rainbow-colored reflected light was observed, impairing display performance. In other words, "◯" corresponds to the case where rainbow-colored reflected light was not observed, as indicated by the evaluation of "×."

[0167] <Example 2> An elliptical polarizing plate EP2 was obtained in the same manner as in Example 1, except that the thickness direction retardation RethZ(550) at a wavelength of 550 nm of the λ / 4 portion of the retarder element Z was set to -50 nm and the Nz coefficient at the λ / 4 portion was set to 0.65. The elliptical polarizing plate EP2 had a layer structure of a TAC film, a polarizer, an adhesive layer, a λ / 2 portion (lagging element Q, adhesive layer, lagging element Z, adhesive layer, lagging element Z, adhesive layer, lagging element Q), an adhesive layer, and a λ / 4 portion (lagging element Q, adhesive layer, lagging element Z).

[0168] The elliptically polarizing plate EP2 was attached to the light-reflecting layer via an adhesive to obtain sample S2. The average luminosity-corrected reflectance Ry50 of sample S2 at an inclination angle θ of 50° was measured for each in-plane angle region, and the results are shown in the table in Figure 7.

[0169] As a calculation model for the elliptically polarizing plate EP2, a laminate (hereinafter referred to as "elliptically polarizing plate EP2s") was designed that had the same laminate structure as the elliptically polarizing plate EP2, except that the TAC film and adhesive layer in the elliptically polarizing plate EP2 were omitted, as in Example 1. The average values ​​of the normalized reflected luminance L50 of the elliptically polarizing plate EP2s at an inclination angle θ = 50° for each in-plane angle region were calculated, and the results are shown in the table of FIG.

[0170] When the external light reflection of the light-reflecting layer of sample S2 at an inclination angle θ=50° was visually observed under sunlight, it was confirmed that the display performance was excellent, with reflected light well prevented at all in-plane angles corresponding to areas PA1 to PA4.

[0171] Example 3 An elliptical polarizing plate EP3 was obtained in the same manner as in Example 1, except that the thickness direction retardation RethZ(550) at a wavelength of 550 nm of the λ / 4 portion of the retarder element Z was set to -90 nm and the Nz coefficient at the λ / 4 portion was set to 0.37. The elliptical polarizing plate EP3 had a layer structure of a TAC film, a polarizer, an adhesive layer, a λ / 2 portion (lagging element Q, adhesive layer, lagging element Z, adhesive layer, lagging element Z, adhesive layer, lagging element Q), an adhesive layer, and a λ / 4 portion (lagging element Q, adhesive layer, lagging element Z).

[0172] The elliptically polarizing plate EP3 was attached to the light-reflecting layer with an adhesive to obtain sample S3. The average luminosity-corrected reflectance Ry50 of sample S3 at an inclination angle θ of 50° was measured for each in-plane angle region, and the results are shown in the table in Figure 7.

[0173] As a calculation model for the elliptically polarizing plate EP3, a laminate (hereinafter referred to as "elliptically polarizing plate EP3s") was designed that had the same laminate structure as the elliptically polarizing plate EP3, except that the TAC film and adhesive layer in the elliptically polarizing plate EP3 were omitted, as in Example 1. The average values ​​of the normalized reflected luminance L50 of the elliptically polarizing plate EP3s at an inclination angle θ = 50° for each in-plane angle region were calculated, and the results are shown in the table of FIG.

[0174] When the external light reflection of the light-reflecting layer of sample S3 at an inclination angle θ=50° was observed under sunlight, it was confirmed that the display performance was excellent, with reflected light well prevented at all in-plane angles corresponding to areas PA1 to PA4.

[0175] Example 4 The elliptical polarizing plate for calculation was named EP4s, which had a laminate structure of a polarizer, a λ / 2 portion (a retarder element Q, a retarder element Z, a retarder element Z, a retarder element Q), and a λ / 4 portion (a retarder element Z, a retarder element Q). The angle between the transmission axis of the polarizer and the retarder axis of the λ / 2 portion was set to 15°. The angle between the transmission axis of the polarizer and the slow axis of the λ / 4 portion was set to 75°.

[0176] The average value of the normalized reflected luminance L50 of the elliptically polarizing plate EP4s at an inclination angle θ of 50° was calculated for each in-plane angle region, and the results are shown in the table of FIG.

[0177] <Example 5> A film formed of a COP film and a lagging retarder laminate 2 and a film formed of a COP film and a lagging retarder laminate 1 were prepared, cut so that the slow axes of the two layers of lagging retarder elements Q would be in the same direction when the lagging retarder element Z and the lagging retarder element Q were in close contact, and the lagging retarder element Z side of the lagging retarder laminate 2 was bonded to the lagging retarder element Q side of the lagging retarder laminate 1 via an adhesive. Then, the COP film on the lagging retarder element Z side was peeled off to obtain a film in which the COP film and the λ / 2 parts (lagging retarder elements Q, Z, Q, Z) were laminated in this order.

[0178] An elliptically polarizing plate EP5 was obtained in the same manner as in Example 1 except for the λ / 2 portion.

[0179] The above elliptical polarizing plate EP5 had a layer structure of a TAC film, a polarizer, an adhesive layer, a λ / 2 part (lag element Q, adhesive layer, lag element Z, adhesive layer, lag element Q, adhesive layer, lag element Z), an adhesive layer, a λ / 4 part (lag element Q, adhesive layer, lag element Z).

[0180] The elliptically polarizing plate EP5 was attached to the light-reflecting layer with an adhesive to obtain sample S5. The average luminosity-corrected reflectance Ry50 of sample S5 at an inclination angle θ of 50° was measured for each in-plane angle region, and the results are shown in the table in Figure 7.

[0181] When the external light reflection of the light-reflecting layer of sample S5 at an inclination angle θ=50° was observed under sunlight, it was confirmed that the in-plane angles corresponding to areas PA1 and PA2 were good at preventing reflected light and provided good display performance, but that the in-plane angles corresponding to areas PA3 and PA4 were bad at preventing reflected light with strong rainbow colors, impairing display performance.

[0182] As a calculation model for the elliptically polarizing plate EP5, a laminate (hereinafter referred to as "elliptically polarizing plate EP5s") was designed that had the same layer structure as the elliptically polarizing plate EP5, except that the TAC film and adhesive layer in the elliptically polarizing plate EP5 were omitted, as in Example 1. The average values ​​of the normalized reflected luminance L50 of the elliptically polarizing plate EP5s at an inclination angle θ=50° for each in-plane angle region were calculated, and the results are shown in the table of FIG.

[0183] Example 6 The elliptical polarizing plate for calculation was named EP6s, with a laminate structure of a polarizer, a λ / 2 portion (a retarder element Q, a retarder element Z, a retarder element Q, a retarder element Z), and a λ / 4 portion (a retarder element Z, a retarder element Q). The angle between the transmission axis of the polarizer and the slow axis of the λ / 2 portion was set to 15°. The angle between the transmission axis of the polarizer and the slow axis of the λ / 4 portion was set to 75°.

[0184] The average value of the normalized reflected luminance L50 of the elliptical polarizer EP6s at an inclination angle θ of 50° was calculated for each in-plane angle region, and the results are shown in the table of FIG.

[0185] Example 7 The elliptical polarizing plate for calculation was named EP7s, with a laminate structure of a polarizer, a λ / 2 portion (a retarder element Z, a retarder element Q, a retarder element Z, a retarder element Q), and a λ / 4 portion (a retarder element Z, a retarder element Q). The angle between the transmission axis of the polarizer and the slow axis of the λ / 2 portion was set to 15°. The angle between the transmission axis of the polarizer and the slow axis of the λ / 4 portion was set to 75°.

[0186] The average value of the normalized reflected luminance L50 of the elliptically polarizing plate EP7s at an inclination angle θ of 50° was calculated for each in-plane angle region, and the results are shown in the chart of FIG.

[0187] Example 8 The lamination structure of the elliptical polarizer was a polarizer, a λ / 2 portion (a retarder element Q, a retarder element Q, a retarder element Z, a retarder element Z), and a λ / 4 portion (a retarder element Q, a retarder element Z), and the elliptical polarizer EP8s was used for calculation. The angle between the transmission axis of the polarizer and the retarder axis of the λ / 2 portion was 15°. The angle between the transmission axis of the polarizer and the slow axis of the λ / 4 portion was set to 75°.

[0188] The average value of the normalized reflected luminance L50 of the elliptically polarizing plate EP8s at an inclination angle θ of 50° was calculated for each in-plane angle region, and the results are shown in the chart of FIG.

[0189] <Comparative Example 1> An elliptical polarizing plate EP9 was obtained in the same manner as in Example 1, except that the retarder laminate 3 was set to a λ / 2 portion and the retarder element Q was set to a λ / 4 portion, and the retarder element Q side of the film formed from the COP film and the retarder laminate 3 was bonded to the retarder element Q side of the film formed from the COP film, a horizontal alignment film, and the retarder element Q via an adhesive layer.

[0190] The elliptical polarizing plate EP9 had a layer structure of a TAC film, a polarizer, an adhesive layer, a λ / 2 portion (retarder element Q, adhesive layer, retarder element Q), an adhesive layer, and a λ / 4 portion (retarder element Q).

[0191] Sample S9 was obtained by adhering the elliptically polarizing plate EP9 onto the light-reflecting layer using an adhesive. The average luminosity-corrected reflectance Ry50 of Sample S9 at an inclination angle θ of 50° was measured for each in-plane angle region, and the results are shown in the table in Figure 7.

[0192] When the external light reflection of the light-reflective layer of sample S9 at a tilt angle θ=50° was observed under sunlight, it was confirmed that the in-plane angle corresponding to area PA1 prevented reflected light to a certain extent, providing good display performance, but at the in-plane angle corresponding to area PA2, strong rainbow-colored reflected light was observed.At the in-plane angles corresponding to areas PA3 and PA4, strong rainbow-colored reflected light was observed, confirming that display performance was impaired, and that tilts in three orthogonal directions impaired display performance.

[0193] As a calculation model for the elliptically polarizing plate EP9, a laminate (hereinafter referred to as "elliptically polarizing plate EP9s") was designed that had the same layer structure as the elliptically polarizing plate EP9, except that the TAC film and adhesive layer in the elliptically polarizing plate EP9 were omitted, as in Example 1. The average values ​​of the normalized reflected luminance L50 of the elliptically polarizing plate EP9s at an inclination angle θ of 50° were calculated for each in-plane angle region, and the results are shown in the table of FIG.

[0194] <Comparative Example 2> An elliptical polarizing plate EP10 was obtained in the same manner as in Example 1, except that the lagging phase laminate 3 was set to the λ / 2 portion and the lagging phase laminate 1 was set to the λ / 4 portion, and the lagging phase element Q side of the film formed from the COP film and the lagging phase laminate 3 was bonded to the lagging phase element Q side of the film formed from the COP film and the lagging phase laminate 1 via an adhesive layer.

[0195] The elliptical polarizing plate EP10 had a layer structure of a TAC film, a polarizer, an adhesive layer, a λ / 2 part (retardant element Q, adhesive layer, retardant element Q), an adhesive layer, a λ / 4 part (retardant element Q, adhesive layer, retardant element Z).

[0196] The elliptically polarizing plate EP10 was attached to the light-reflecting layer via an adhesive to obtain sample S10. The average luminosity-corrected reflectance Ry50 of sample S10 at an inclination angle θ of 50° was measured for each in-plane angle region, and the results are shown in the table in Figure 7.

[0197] When the external light reflection of the light-reflective layer of sample S10 at a tilt angle θ=50° was observed under sunlight, it was confirmed that the in-plane angle corresponding to area PA1 effectively prevented reflected light and provided good display performance, but strong rainbow-colored reflected light was observed at the in-plane angle corresponding to area PA2. Strong rainbow-colored reflected light was observed at the in-plane angles corresponding to areas PA3 and PA4, confirming that the display performance was impaired, and that tilts in three orthogonal directions impaired the display performance.

[0198] As a calculation model for the elliptically polarizing plate EP10, a laminate (hereinafter referred to as "elliptically polarizing plate EP10s") was designed that had the same layer structure as the elliptically polarizing plate EP10, except that the TAC film and adhesive layer in the elliptically polarizing plate EP10 were omitted, as in Example 1. The average values ​​of the normalized reflected luminance L50 of the elliptically polarizing plate EP10s at an inclination angle θ=50° for each in-plane angle region were calculated, and the results are shown in the table of FIG.

[0199] <Comparative Example 3> An elliptical polarizing plate EP11 was obtained in the same manner as in Example 1, except that the lagging phase laminate 3 was set to the λ / 2 portion, the lagging phase laminate 5 was set to the λ / 4 portion, and the lagging phase element Q side of the film formed from the COP film and the lagging phase laminate 3 was bonded to the lagging phase element Q side of the film formed from the COP film and the lagging phase laminate 5 via an adhesive layer.

[0200] The elliptical polarizing plate EP11 had a layer structure of a TAC film, a polarizer, an adhesive layer, a λ / 2 part (retardant element Q, adhesive layer, retardant element Q), an adhesive layer, a λ / 4 part (retardant element Q, adhesive layer, retardant element Z, adhesive layer, retardant element Z, adhesive layer, retardant element Z).

[0201] The elliptically polarizing plate EP11 was attached to the light-reflecting layer via an adhesive to obtain sample S11. The average luminosity-corrected reflectance Ry50 of sample S11 at an inclination angle θ of 50° was measured for each in-plane angle region, and the results are shown in the table in Figure 7.

[0202] When the external light reflection of the light-reflecting layer of sample S11 at an inclination angle θ=50° was observed under sunlight, strong rainbow-colored reflected light was observed at all in-plane angles corresponding to areas PA1 to PA4, confirming that this impairs display performance.

[0203] As a calculation model for the elliptically polarizing plate EP11, a laminate (hereinafter referred to as "elliptically polarizing plate EP11s") was designed that had the same layer structure as the elliptically polarizing plate EP11, except that the TAC film and adhesive layer in the elliptically polarizing plate EP11 were omitted, as in Example 1. The average values ​​of the normalized reflected luminance L50 of the elliptically polarizing plate EP11s at an inclination angle θ=50° were calculated for each in-plane angle region, and the results are shown in the table of FIG.

[0204] <Results common to Examples 2 and 3, Example 5, and Comparative Examples 1 to 3> The in-plane retardation Reo(λ) at each wavelength was measured for the elliptically polarizing plates EP2 and EP3 (Examples 2 and 3), the elliptically polarizing plate EP5 (Example 5), and the elliptically polarizing plates EP9 to EP11 (Comparative Examples 1 to 3). The results are as follows, and are the same as those for the elliptically polarizing plate EP1 (Example 1). Reo(450)=112nm, Reo(550)=138nm, Reo(650)=162nm, Reo(450) / Reo(550)=0.81, Reo(650) / Reo(550)=1.17,

[0205] The luminosity-corrected reflectance and reflected hue at an inclination angle θ of 10° were measured for each of samples S2 and S3 (Examples 2 and 3), sample S5 (Example 5), and samples S9 to S11 (Comparative Examples 1 to 3). As a result, all of them had Ry10=4.6%, a * 10=0.00, b * 10=-0.25.

[0206] When the external light reflection of the light-reflecting layer of samples S2 and S3 (Examples 2 and 3), sample S5 (Example 5), and samples S9 to S11 (Comparative Examples 1 to 3) was observed under sunlight at an inclination angle θ of 10°, it was confirmed that, similar to sample S1 (Example 1), the display performance was good with reflected light well prevented.

[0207] [Consideration of results] λ / 2 N of 41 Z The coefficient is approximately 0.5 and the N Z The coefficient satisfies the condition that the coefficient is 0.3 or more and 0.7 or less. On the other hand, Comparative Examples 1 to 3 do not satisfy the above condition. As shown in FIG. 7, in Examples 1 to 8, the visual observation results for an inclination angle of 50° (hereinafter referred to as "50° inclined visual observation results") confirmed that good display performance was achieved with reflected light well prevented at least at in-plane angles corresponding to areas PA1 and PA2. In contrast, in Comparative Examples 1 to 3, the visual observation results for an inclination angle of 50° confirmed that good display performance was not achieved in both areas PA1 and PA2, or in area PA2.

[0208] In the experiment, the in-plane angle φ was set to φ=90°, which is the angle at which Ry50 is smallest (darkest), and was used as the reference for the in-plane angle φ. Therefore, the areas PA1 and PA2 correspond to two directions that are perpendicular to the reference φ=90°, and correspond to the case where the direction in which an elliptical polarizer applied to a display device is tilted and observed is the vertical direction or the horizontal direction. On the other hand, the areas PA3 and PA4 correspond to the oblique direction in which an elliptical polarizer applied to a display device is tilted and observed. Therefore, N of the λ / 2 section 41 Z The coefficient is approximately 0.5 and the N Z It can be seen that in Examples 1 to 8, which satisfy the condition that the coefficient is 0.3 or more and 0.7 or less, good display performance can be ensured even when the elliptically polarizing plate is viewed tilted in at least two orthogonal in-plane directions.

[0209] In Examples 1 to 3, the results of visual observation at a 50° angle confirmed that good display performance was achieved, with reflected light being well prevented even at in-plane angles corresponding to regions PA1 to PA4. That is, it can be seen that in Examples 1 to 3, good display performance can be ensured even when the elliptical polarizer is tilted vertically, horizontally, or obliquely in the display device. Therefore, it can be seen that the arrangement order of the two retarder elements Q and two retarder elements Z in the λ / 2 portion and the arrangement order of the retarder elements Q and Z in the λ / 4 portion, as adopted in Examples 1 to 3, are preferable.

[0210] In experimental examples where any of the Ry50 (regions PA1 to PA4) was 8.1% or higher, it was confirmed that in the regions where the result was 8.1% or higher, rainbow-colored reflected light was strongly visible, impairing the display performance in those regions. Therefore, a preferable value for Ry50 (regions PA1 to PA4) is less than 8.1%, more preferably 6.8% or less, and even more preferably 6.3% or less. From the correspondence relationship between the Ry50 value and L50, it is expected that in experimental examples where any of the L50 (regions PA1 to PA4) was 1.13% or higher, rainbow-colored reflected light was strongly visible, impairing the display performance. A preferable value for L50 (regions PA1 to PA4) is less than 1.13%, more preferably 0.78% or less, and even more preferably 0.12% or less.

[0211] From the above viewpoint, it can be understood that the arrangement order of the two retardation elements Q and two retardation elements Z in the λ / 2 section and the arrangement order of the retardation elements Q and Z in the λ / 4 section are preferably the arrangement orders adopted in Examples 1 to 3.

[0212] As mentioned above, in the experiment, the in-plane angle φ at which Ry50 is smallest (darkest) is set to φ=90°. Therefore, the Ry50 of area PA1 is used as the reference and the Ry50 of areas PA1 to PA4 are compared. In this case, in Example 1, the Ry50 of area PA1 is 6.0, and areas PA2 to PA4 are also 6.2 or 6.3. That is, in Example 1, the Ry50 of areas PA1 to PA4 is less than 6.3, and the Ry50 of areas PA2 to PA4 is approximately the same value as the Ry50 of area PA1, which should be used as the reference. Therefore, in Example 1, approximately constant display performance is ensured in areas PA1 to PA4. Therefore, it can be understood that the configuration of Example 1 is more preferable. [Explanation of symbols]

[0213] 20... elliptical polarizing plate, 31... polarizer, 40... optical laminate, 41... λ / 2 portion, 41a... slow axis (first slow axis), 42... λ / 4 portion, 42a... slow axis (second slow axis), Q... slow phase element (first slow phase element), Z... slow phase element (second slow phase element).

Claims

1. a λ / 2 section having a first slow axis; a λ / 4 section having a second slow axis and laminated on the λ / 2 section such that the second slow axis is within a range of approximately 60° with respect to the first slow axis; Equipped with the λ / 2 section has two first retardation elements and two second retardation elements, the two first delay phase elements and the two second delay phase elements are stacked in the order of the first delay phase element, the second delay phase element, the second delay phase element, and the first delay phase element, the λ / 4 section has a first retardation element, the two first retardation elements included in the λ / 2 section and the first retardation element included in the λ / 4 section are elements that provide a phase difference of approximately λ / 4, the two second retardation elements included in the λ / 2 section are positive C plates, the directions of the slow axes of the two first retarder elements included in the λ / 2 portion are substantially aligned with the direction of the first slow axis, the direction of the slow axis of the first retarder element of the λ / 4 portion substantially coincides with the direction of the second slow axis, N of the λ / 2 part Ｚ The coefficient is approximately 0.5, N of the λ / 4 section Ｚ The coefficient is equal to or greater than 0.3 and equal to or less than 0.7, The two first retardation elements included in the λ / 2 portion and the first retardation element included in the λ / 4 portion satisfy the following formulas (A) and (B), where Re(450) is a retardation for light having a wavelength of 450 nm, Re(550) is a retardation for light having a wavelength of 550 nm, and Re(650) is a retardation for light having a wavelength of 650 nm: Optical laminate. Re(450) / Re(550)≦1.00... (A) 1.00≦Re(650) / Re(550)... (B)

2. the λ / 4 section has a second retardation element, the second retardation element included in the λ / 4 section is a positive C-plate, the first delay phase element and the second delay phase element included in the λ / 4 portion are laminated in this order from the λ / 2 portion side; The optical laminate according to claim 1 .

3. A polarizer; The optical laminate according to claim 1 or 2 laminated on the polarizer; Equipped with The polarizer, the λ / 2 portion, and the λ / 4 portion are arranged in this order: the polarizer, the λ / 2 portion, and the λ / 4 portion. Elliptical polarizer.

Images