Display device

Abstract

To provide a display device capable of maintaining good display performance even when tilting the device to view images.SOLUTION: A display device according to an embodiment includes a light-reflective image display layer, and an elliptically polarizing plate comprising a polarizer, λ / 2 portion, and λ / 4 portion, the λ / 2 portion being a laminate consisting of a first retardant element, second retardant element, second retardant element, and first retardant element stacked in the described order. An Nz coefficient and ρ coefficient of the λ / 4 portion satisfies a relationship represented by an expression (B) when the ρ coefficient of the image display layer is represented by an expression (A): ρ=ReM45 / ReoQ ...(A), 4.5ρ-0.160<Nz<4.5ρ+0.955 ...(B), where ReM45 represents an in-plane retardation for 550 nm wavelength in a projection plane having a tilt angle of 45° with respect to a thickness direction of the image display layer, and ReoQ represents an in-plane retardation of the λ / 4 portion at 550 nm wavelength.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a display device. [Background technology]

[0002] A prior art in this technical field is the technology described in Patent Document 1. Patent Document 1 discloses a laminate of a λ / 2 portion and a λ / 4 portion. 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] An object of the present invention is to provide a display device that can maintain display performance even when an image is viewed at an angle. [Means for solving the problem]

[0006] A display device according to one aspect of the present invention includes a light-reflective image display layer and an elliptical polarizing plate laminated on an image display surface of the light-reflective image display layer, the elliptical polarizing plate having a polarizer, a λ / 2 portion, and a λ / 4 portion, the polarizer, the λ / 2 portion, and the λ / 4 portion being arranged in this order from the light-reflective image display layer side, the λ / 4 portion, the λ / 2 portion, and the polarizer, The λ / 2 portion is a laminate in which a first retardation element, a second retardation element, a second retardation element and a first retardation element are stacked in the order of the first retardation element, the second retardation element, the second retardation element and the first retardation element, the first retardation element has reverse wavelength dispersion and is an element that provides an in-plane retardation of approximately λ / 4, and the second retardation element is an element that provides a thickness direction retardation, and when the in-plane retardation of the light-reflective image display layer at a wavelength of 550 nm on a projection plane inclined at an angle of 45° with respect to the thickness direction of the light-reflective image display layer is ReM45, the in-plane retardation of the λ / 4 portion at a wavelength of 550 nm is ReoQ, and the ρ coefficient of the light-reflective image display layer is expressed by formula (A), the Nz coefficient of the λ / 4 portion and the ρ coefficient satisfy the relationship shown in formula (B). Display device. ρ=ReM45 / ReoQ (A) 4.5ρ-0.160 <Nz<4.5ρ+0.955 ···(B)

[0007] In the display device, the Nz coefficient of the λ / 4 portion and the ρ coefficient satisfy the relationship shown in formula (B), and therefore the display performance can be maintained even when an image is viewed at an angle.

[0008] The first retarder element may be a positive A plate that provides an in-plane retardation of approximately λ / 4 at a wavelength of 550 nm.

[0009] The second retarder element may be a positive C-plate that imparts a thickness direction retardation.

[0010] The λ / 4 portion is a laminate in which a third retardation element and a first retardation element are stacked in this order from the light-reflective image display layer side, and the first retardation element of the λ / 4 portion has a reverse wavelength dispersion and provides an in-plane retardation of approximately λ / 4, and the third retardation element may be a positive C plate that provides a thickness direction retardation.

[0011] The first retarder element of the λ / 4 portion may be a positive A plate that provides a retardation of approximately λ / 4 as an in-plane retardation at a wavelength of 550 nm, and the third retarder element may be a positive C plate or a negative C plate that provides a thickness direction retardation. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a display device that can maintain display performance even when an image is viewed at an angle. [Brief explanation of the drawings]

[0013] [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, the slow axis of the λ / 4 portion, and the transmission axis of the polarizer. [Figure 3] FIG. 3 is a diagram for explaining the ρ coefficient of the image display layer. [Figure 4] FIG. 4 is a table showing the results of Examples 1 to 9 and Comparative Examples 1 to 6. [Figure 5] FIG. 5 is a graph plotting the Nz coefficient against the ρ coefficient in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] First, the terms used in this disclosure will be explained.

[0015] [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.

[0016] [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.

[0017] [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 λ(nm) is expressed by equation (1), where d represents the thickness (nm) of the retarder. Reo(λ)=(nx−ny)×d (1) The thickness direction retardation Reth(λ) at a wavelength 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) The in-plane retardation Reo and the thickness retardation Reth can be adjusted by changing the thickness d of the retarder.

[0018] [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)

[0019] 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)

[0020] The suitable 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 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)

[0021] 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)

[0022] 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.

[0023] [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 is parallel to nz, and nx≒ny indicates that the difference between nx and ny is less than 0.02. nx≒ny <nz ··· (7)

[0024] [Negative C Plate] A negative C plate is a retarder whose refractive index in each direction satisfies the relationship in equation (8). Unless otherwise specified, the slow axis is in the plane subtended by the nx and ny axes, and the fast axis is parallel to the nz axis. nx≒ny means that the difference between nx and ny is less than 0.02. nx≒ny>nz (8)

[0025] [Wavelength dispersion] The dispersion relationship between wavelength and retardation is also simply called wavelength dispersion. A retarder that satisfies equations (9) and (10) is said to have reverse wavelength dispersion, or simply called reverse dispersion. Re(450) / Re(550)≦1.00 (9) 1.00≦Re(650) / Re(550) (10)

[0026] 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.

[0027] A retarder that satisfies the formulas (11) and (12) is said to have positive wavelength dispersion, or simply to have positive dispersion. Re(450) / Re(550)>1.00 (11) 1.00>Re(650) / Re(550) ··· (12)

[0028] [Layer laminate] An optical laminate in which a plurality of retarders are laminated may also be called a retarder laminate.

[0029] [Nz coefficient] The Nz coefficient of the retarder can be expressed by equation (13). 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 (13)

[0030] 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.

[0031] Fig. 1 is a schematic diagram showing the general configuration of a display device according to one embodiment. The display device 100 shown in Fig. 1 includes 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.

[0032] [Image display layer] The image display layer 10 forms an image internally 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 metal electrodes for wiring, the high-refractive index layer for the sub-pixel resonator structure, the black matrix, and other components included in the element structure function as reflective components that reflect 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-reflecting layer in the display device 100. In this embodiment, the combined reflected light, which is a combination of light reflected by the metal electrodes for wiring, the high-refractive index layer for the sub-pixel resonator structure, the black matrix, and other components included in the image display layer 10 as a light-reflecting layer, is sometimes referred to as "external reflected light." The image display layer 10 may be flexible, i.e., bendable, or rigid, i.e., unable to bend.

[0033] 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.

[0034] 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 an optical compensation member on the image display surface.

[0035] 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.

[0036] 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.

[0037] The elliptically polarizing plate 20 is laminated on the image display layer 10. 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.

[0038] 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.

[0039] 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.

[0040] In the present disclosure, "(meth)acrylic" means at least one selected from acrylic and methacrylic. The same applies to "(meth)acryloyl", "(meth)acrylate", etc.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] In the display device 100, the optical laminate 40 is disposed between the polarizer 31 (the 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. In this embodiment, unless otherwise specified, the slow axes of the λ / 2 portion 41 and the λ / 4 portion are parallel to nx.

[0058] 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°.

[0059] 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.

[0060] The λ / 2 section 41 has two delay phase elements (first delay phase elements) Q and two delay phase elements (second delay phase elements) ZA. The λ / 2 section 41 is a laminate in which the two delay phase elements Q and the two delay phase elements ZA are laminated in the order of delay phase element Q, delay phase element ZA, delay phase element ZA, and delay phase element Q, as shown in FIG.

[0061] [Lagging phase element Q] The retarder element Q is a retardation film having reverse dispersion and imparting an in-plane retardation 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 having an in-plane retardation of approximately λ / 4 at a wavelength of 550 nm. The retarder element Q may be obtained by curing a polymerizable liquid crystal compound, or by molding or further stretching a molten resin.

[0062] [Lagging phase element ZA] The retarder element ZA is a retardation film that imparts a thickness direction retardation to incident light. The retarder element ZA can be a positive C plate. The positive C plate refers to a positive C plate whose thickness direction retardation Reth(550) satisfies formula (14). -30nm≧Reth(550)≧-120nm ··· (14)

[0063] The suitable value range of Reth(550) of the retarder element ZA 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 ZA may be obtained by curing a polymerizable liquid crystal compound, or by molding or further stretching a molten resin. It is desirable that the in-plane retardation ReoZA(550) of the retarder element ZA is substantially 0. "Substantially 0" means a range of 0 nm ± 5.

[0064] When the retarder element Q and the retarder element ZA are layers obtained by curing a polymerizable liquid crystal, the retarder element Q and the retarder element ZA are formed on an alignment film provided on a substrate. The substrate may be a long substrate that has the function of supporting the alignment film. 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] The alignment film is not limited to a vertical alignment film, but may be an alignment film that aligns the molecular axes of the polymerizable liquid crystal compound horizontally, or an alignment film that aligns the molecular axes 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 ZA, a vertical alignment film can be used.

[0069] 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.

[0070] 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.

[0071] 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).

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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 in the λ / 2 section 41. "Almost aligned" means that the directions of the two slow axes may be misaligned by about ±5° (the same applies hereinafter).

[0083] The retarder element Q of the λ / 2 portion 41 may be a laminate of a plurality of retardation films that function as the retarder element Q as a whole. The directions of the slow axes of the plurality of retardation films that constitute the retarder element Q are approximately the same as the direction of the slow axis 41a. Similarly, the retarder element Z of the λ / 2 portion 41 may be a laminate of a plurality of retardation films that function as the retarder element Z as a whole.

[0084] The λ / 4 section 42 has a delay phase element Q. The delay phase element Q of the λ / 4 section 42 has the same characteristics as the delay phase element Q of the λ / 2 section 41, so a description thereof will be omitted. The λ / 4 section 42 may have a delay phase element (third delay phase element) ZB. In this case, the λ / 4 section 42 is a laminate in which the delay phase element Q and the delay phase element ZB are stacked in this order from the λ / 2 section 41 side. Unless otherwise specified, a configuration in which the λ / 4 section 42 has the delay phase element ZB will be described. The slow axis of the delay phase element Q of the λ / 4 section 42 corresponds to the slow axis of the λ / 4 section 42. Therefore, the retarder element Q of the λ / 4 section 42 is disposed relative to the λ / 2 section 41 so that the angle between its slow axis and the slow axis 41a of the λ / 2 section 41 is approximately 60°.

[0085] [Lagging element ZB] The retarder element ZB is a retardation film that imparts a thickness direction retardation to incident light of wavelength λ. The retarder element ZB is a positive C plate or a negative C plate. The thickness direction retardation RethZB(550) at a wavelength of 550 nm typically ranges from −190 nm to less than 0, or from more than 0 to +40 nm, and preferably from −170 nm to less than 0 nm. The in-plane retardation ReoZB(550) is desirably substantially 0. "Substantially 0" refers to a range of 0 nm ±5. As with the retarder element ZA, the retarder element ZB may be obtained by curing a polymerizable liquid crystal or by molding or further stretching a molten resin. When the retarder element ZB is a layer obtained by curing a polymerizable liquid crystal, the retarder element ZB may be formed on an alignment film provided on a substrate, as with the retarder element Z.

[0086] The retarder element Q in the λ / 4 section 42 may be a laminate of a plurality of retardation films that function as a whole as the retarder element Q. The directions of the slow axes of the plurality of retardation films that constitute the retarder element Q are approximately the same as the direction of the slow axis 42a. Similarly, the retarder element ZB in the λ / 4 section 42 may be a laminate of a plurality of retardation films that function as a whole as the retarder element ZB.

[0087] The conditions that the display device 100 must satisfy will be further explained.

[0088] [ρ coefficient] As shown in FIG. 3 , a plane perpendicular to the direction D2 of the tilt angle α with respect to the thickness direction D1 of the image display layer 10 is referred to as the projection plane VP. The in-plane retardation of the image display layer 10 at a wavelength of 550 nm on the projection plane VP when the tilt angle α is 45° is defined as ReM45. The in-plane retardation of the λ / 4 section 42 is defined as ReoQ. In this embodiment, ReoQ corresponds to the in-plane retardation of the retarder element Q. In this case, the ρ coefficient is defined by equation (A). ρ=ReM45 / ReoQ (A)

[0089] When the ρ coefficient is defined by formula (A), the Nz coefficient of the λ / 4 unit 42 and the ρ coefficient satisfy the relationship shown in formula (B) in the display device 100. In other words, the λ / 4 unit 42 is designed so that the Nz coefficient satisfies formula (B). 4.5ρ-0.160 <Nz<4.5ρ+0.955 ···(B)

[0090] The Nz coefficient of the λ / 4 portion 42 in the formula (B) is defined by the following formula (C). Nz={(RethQ+RethZB) / (ReoQ+ReoZB)}+0.5···(C) In the formula (C), ReoQ is the in-plane retardation of the retarder element Q in the λ / 4 section 42, as described above, and ReoZB is the in-plane retardation of the retarder element ZB in the λ / 4 section 42. In the formula (C), RethQ is the thickness direction retardation of the retarder element Q of the λ / 4 portion 42, and RethZB is the thickness direction retardation of the retarder element ZB of the λ / 4 portion 42.

[0091] In formula (B), when the value of the ρ coefficient is in the range of −0.06 or more and −0.02 or less, the value of the Nz coefficient of the λ / 4 portion 42 is in the range of more than −0.43 and less than 0.87. In formula (B), when the value of the ρ coefficient is in the range of −0.02 or more and less than 0, the value of the Nz coefficient of the λ / 4 portion 42 is in the range of more than −0.25 and less than 0.96. In formula (B), when the value of the ρ coefficient is in the range of more than 0 and not more than 0.04, the value of the Nz coefficient of the λ / 4 portion 42 is in the range of more than −0.16 and less than 1.14. In formula (B), when the value of the ρ coefficient is in the range of more than 0.04 and less than 0.08, the value of the Nz coefficient of the λ / 4 portion 42 is in the range of more than 0.02 and less than 1.32.

[0092] It is more preferable that the relationship between the Nz coefficient and the ρ coefficient of the λ / 4 portion 42 has the relationship shown in formula (D). 4.5ρ-0.035≦Nz≦4.5ρ+0.690 (D)

[0093] In formula (D), when the value of the ρ coefficient is in the range of −0.06 to −0.02, the value of the Nz coefficient of the λ / 4 portion 42 is in the range of −0.31 to 0.60. In formula (D), when the value of the ρ coefficient is in the range of −0.02 or more and less than 0, the value of the Nz coefficient of the λ / 4 portion 42 is in the range of −0.13 or more and less than 0.69. In formula (D), when the value of the ρ coefficient is in the range of more than 0 and not more than 0.04, the value of the Nz coefficient of the λ / 4 portion 42 is in the range of more than -0.04 and not more than 0.87. In formula (D), when the value of the ρ coefficient is in the range of 0.04 to 0.08, the value of the Nz coefficient of the λ / 4 portion 42 is in the range of 0.15 to 1.05.

[0094] The linear polarizer 30, the optical laminate 40, and the components constituting the display device 100 (including the retarder elements Q, ZA, and ZB) can be laminated using, for example, an adhesive layer (not shown). When the image display layer 10 includes electrodes of the organic EL display element, the organic EL display element and the optical laminate 40 may be laminated via an adhesive layer.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] [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.

[0099] The display device 100 satisfies formulas (A) and (B). In this case, the λ / 4 portion 42 of the elliptically polarizing plate 20 is designed taking into consideration the light reflectivity of the image display layer 10 in the direction of the tilt angle of 45°. Therefore, even when the display device 100 is tilted, external light reflection is prevented, and good display performance can be achieved. The configuration of the display device 100 makes it possible to achieve the above-mentioned good display performance across the entire visible range.

[0100] 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]

[0101] The present invention will be described in more detail below with reference to examples. In the following description, "%" and "parts" mean mass % and mass parts unless otherwise specified. The present invention is not limited to the following examples. In the following description, a positive C plate that can be used for both the retarder element ZA and the retarder element ZB may also be referred to as the retarder element Z.

[0102] [Measurement method] ·How to measure film thickness The film thickness was measured using a contact film thickness meter ("MH-15M", "Counter TC101", "MS-5C", manufactured by Nikon Corporation).

[0103] ·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.).

[0104] Refractive index measurement method The refractive index of the film, layer, etc. was measured using a spectroscopic ellipsometer ("M-2000", manufactured by JA Woollam).

[0105] 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 luminosity-corrected reflectance Ry45, which will be described later, were calculated using the corresponding spectral spectra, i.e., the single spectral transmittance T, the spectral polarization degree P, the spectral reflectance R, the color matching functions, and the standard illuminant.

[0106] 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. Hues a and b are the hues in the Lab color system of the corresponding spectral spectrum (see "Introduction to Color Engineering," co-authored by Hiroyuki Shinoda and Ichiro Fujieda, 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).

[0107] 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.

[0108] 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.

[0109] The absorption axis of the polarizer coincided with the stretching direction of the polyvinyl alcohol.

[0110] ·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 was calculated.

[0111] The spectral reflectance R was measured at tilt angles θ = 10° and θ = 45° (tilt angles are described later), 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.

[0112] The direction perpendicular to the plane (hereinafter, for ease of explanation, referred to as "plane p") formed by an axis parallel to the refractive index nx and an axis parallel to the refractive index ny (corresponding to direction D1 shown in Figure 3) is defined as a tilt angle θ = 0°. With the in-plane angle φ in plane p as the central tilt axis, the spectral reflectance R was measured for tilt angles θ of 10° and 45° in 5° increments within the range of equation (15). Plane p corresponds to the surfaces of retarder elements Q, ZA, and ZB, the surface of an elliptical polarizer, etc., and is also a plane parallel to image display surface 10a. 0°≦φ<360° (15)

[0113] The average value of the visibility-corrected reflectance over the in-plane angle range (the angle range shown in formula (15), the same applies below) at a tilt angle θ of 10° was defined as Ry10. The average value of the visibility-corrected reflectance over the in-plane angle range at a tilt angle θ of 45° was defined as Ry45.

[0114] [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]

[0115] [Preparation of composition for forming vertical alignment film] Sunever SE610 manufactured by Nissan Chemical Industries, Ltd. was used.

[0116] [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.

[0117] [Polymerizable liquid crystal compound A] [ka]

[0118] [Polymerizable liquid crystal compound B] [ka]

[0119] 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.

[0120] [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.

[0121] [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.

[0122] 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.

[0123] 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.

[0124] [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.

[0125] Next, a composition for forming retarder element Q (reverse dispersion positive A plate) was applied to the horizontal alignment film using a bar coater and dried for 1 minute at 120°C. The applied film was irradiated with ultraviolet light (under a nitrogen atmosphere, cumulative light intensity at a wavelength of 365 nm: 500 mJ / cm) using a high-pressure mercury lamp (Uniqure VB-15201BY-A, manufactured by Ushio Inc.). 2 ) to form the retarder element Q. The retarder element Q had a film thickness of 2.3 μm.

[0126] A film formed by a COP film, an alignment film, and a horizontally aligned liquid crystal cured film was attached to glass via an adhesive layer on the retarder element Q. The COP film was peeled off to obtain a sample for measuring retardation. The in-plane retardation ReoQ(λ) of the retarder element Q at each wavelength was measured, and the results were as follows: 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.

[0127] The retarder element Q was a positive A plate that satisfied the relationship nx>ny≒nz. The thickness direction retardation RethQ(λ) was measured at each wavelength, and the results were as follows: RethQ(450)=61nm, RethQ(550)=72nm, RethQ(650)=73nm, It was.

[0128] [Fabrication of retarder element Z (positive C plate)] The COP film was subjected to a corona treatment under the same conditions as above. The composition for forming a vertical alignment film was applied to the COP film using a bar coater and dried at 80°C for 1 minute to obtain a vertical alignment film. The thickness of the obtained vertical alignment film was 50 nm.

[0129] A composition for forming a retarder element Z was applied to the vertical alignment film using a bar coater and dried at 90 °C for 120 seconds. The coated film was irradiated with ultraviolet light (in a nitrogen atmosphere, integrated light quantity at a wavelength of 365 nm: 500 mJ / cm 2 ) using a high-pressure mercury lamp (“Unicure VB-15201BY-A”, manufactured by Ushio Electric Co., Ltd.) to form a retarder element Z. Thus, a film formed by a COP film, a vertical alignment film, and a retarder element Z was obtained. The film thickness of the retarder element Z was 0.6 μm.

[0130] An adhesive layer was laminated on the retarder element Z. Through the adhesive layer, the film formed by the COP film, the alignment film, and the retarder 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 the retarder element Z at a wavelength of 550 nm, RethZ(550)= -70 nm, and it was such. As a result of measuring the in-plane retardation ReoZ(550) of the retarder element Z at a wavelength of 550 nm, ReoZ(550)= 0.1 nm, and the in-plane retardation of the retarder element Z was substantially 0. The retarder element Z was a positive C-plate satisfying the relationship nx≒ny < nz.

[0131] <Fabrication of a negative C-plate> Two TAC films with a thickness of 60 μm (“Fujitac TG60UL”, manufactured by Fujifilm) were adhered through an adhesive layer to obtain a TAC film laminate formed by the TAC film, the adhesive, and the TAC film. Next, the TAC film laminate was bonded to glass through an adhesive layer to obtain a sample for measuring retardation. As a result of measuring the thickness-direction retardation Reth(550) at a wavelength of 550 nm, Reth(550)= +40 nm, It was. The TAC film laminate was a negative C-plate that satisfied the relationship nx≒ny>nz, so the in-plane retardation of the TAC film laminate was essentially zero.

[0132] [Lag phase laminate 1] The vertical alignment film and the retarder element Z in the retarder element Z formed on the COP film, and the retarder element Q in the retarder element Q in the horizontal alignment film and the retarder element Q formed on the COP film were bonded together using an adhesive, and then the COP film on the retarder element Z side was peeled off to obtain a film in which the COP film and the retarder laminate 1 were laminated in this order. The arrangement of the retarder element Q and the retarder element Z in the retarder laminate 1 was as follows. The retarder element Z in the retarder laminate 1 was a positive C plate. To indicate the arrangement of the retarder element Q and the retarder element Z relative to the COP film, the COP film is shown in parentheses in the following arrangement. Therefore, the following notation indicates that the retarder element Z and the retarder element Q are arranged in the order of the retarder element Q and the retarder element Z from the COP film side. Similar notation may be used for the arrangement between elements (or between layers). (COP film) / Q / Z

[0133] [Lag phase laminate 2] The vertical alignment film and the retarder element Z in the retarder element Z formed on the COP film and the retarder element Q in the retarder element Q in the horizontal alignment film and the retarder element Q formed on the COP film were bonded together via an adhesive, and then the COP film on the retarder element Q side was peeled off to obtain a film in which the COP film and the retarder laminate 2 were laminated in this order. The positional relationship between the retarder element Q and the retarder element Z in the retarder laminate 2 was as follows. The retarder element Z of the retarder laminate 2 was a positive C plate. (COP film) / Z / Q

[0134] [Lag phase laminate 3] The above TAC film laminate was bonded to the horizontal alignment film formed on the COP film and the retarder element Q of the retarder element Q via an adhesive, and then the COP film on the retarder element Q side was peeled off to obtain a retarder laminate 3. The TAC film laminate was a negative C plate. Therefore, the retarder laminate 3 was a laminate of the retarder element ZB, which was a negative C plate, and the retarder element Q.

[0135] <Elliptical polarizing plate EP1> ·λ / 2 part Two films 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 were in the same direction when the lagging retarder elements Z sides were in close contact with each other. The lagging retarder element Z sides of each film were bonded together using 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, 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. Note that 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 Z ... The retarder element Z in the λ / 2 portion is a positive C plate because it is the retarder element Z in the retarder laminate 1. Therefore, since the retarder element Z in the λ / 2 portion is the retarder element ZA, the retarder element Z of the elliptical polarizer EP1 will hereinafter be referred to as the retarder element ZA.

[0136] ·λ / 4 part The retardation layer 2 having the retardation element Z manufactured by adjusting the thickness direction retardation to be RethZ(550)=-70 nm was defined as the λ / 4 part. Hereinafter, when the retardation layer 2 is used in the λ / 4 part, the retardation element Z of the retardation layer 2 will be referred to as the retardation element ZB, and the thickness direction retardation at a wavelength of 550 nm will be referred to as RethZB(550).

[0137] Elliptical polarizer EP1 The surface of the polarizer laminated with a TAC film opposite the TAC film was bonded to the retarder element Q side of a film formed from a COP film and a 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 retarder element Q side of the λ / 2 portion was 15°. Next, the retarder element Q side of the laminate was bonded to the retarder element Q side of a film formed from a COP film and a λ / 4 portion 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 retarder axis of the λ / 4 portion was 75°. The Nz coefficient of the λ / 2 portion was 0.51, and the Nz coefficient of the λ / 4 portion was 0.51.

[0138] The elliptical polarizing plate EP1 had a layer structure of a TAC film, a polarizer, an adhesive layer, a λ / 2 part (retardant element Q, adhesive layer, retardant element ZA, adhesive layer, retardant element ZA, adhesive layer, retardant element Q), an adhesive layer, a λ / 4 part (retardant element Q, adhesive layer, retardant element ZB).

[0139] <Elliptical polarizing plate EP2> An elliptical polarizer EP2 was obtained in the same manner as the elliptical polarizer EP1, except that the retardation element ZB (retardation element Z) obtained by adjusting the thickness direction retardation to RethZB(550) = -30 nm was used as the λ / 4 portion. Z The coefficient was 0.79.

[0140] <Elliptical polarizing plate EP3> An elliptical polarizer EP3 was obtained in the same manner as the elliptical polarizer EP1, except that the λ / 4 portion was made of a retarder laminate 2 having a retarder element ZB (retarder element Z) adjusted so that the thickness direction retardation was RethZB(550) = -100 nm. The Nz coefficient of the λ / 4 portion was 0.30.

[0141] <Elliptical polarizing plate EP4> Elliptical polarizer EP4 was obtained in the same manner as elliptical polarizer EP1, except that the λ / 4 portion was made of a retarder laminate 2 having a retarder element ZB (retarder element Z) adjusted so that the thickness direction retardation was RethZB(550) = -170 nm. The Nz coefficient of the λ / 4 portion was -0.20.

[0142] <Elliptical Polarizing Plate EP5> Elliptical polarizer EP5 was obtained in the same manner as elliptical polarizer EP1, except that the λ / 4 portion was made of a retarder laminate 2 having a retarder element ZB (retarder element Z) adjusted so that the thickness direction retardation was RethZB(550) = -190 nm. The Nz coefficient of the λ / 4 portion was -0.34.

[0143] <Elliptical polarizing plate EP6> An elliptical polarizer EP6 was obtained in the same manner as the elliptical polarizer EP1, except that it did not contain the retarder element ZB. The Nz coefficient at the λ / 4 portion was 1.00.

[0144] <Elliptical Polarizing Plate EP7> Elliptical polarizer EP7 was obtained in the same manner as elliptical polarizer EP1, except that the λ / 4 portion was made of a retarder laminate 2 having a retarder element ZB (retarder element Z) adjusted so that the thickness direction retardation was RethZB(550) = -40 nm. The Nz coefficient of the λ / 4 portion was 0.72.

[0145] <Elliptical Polarizing Plate EP8> Elliptical polarizer EP8 was obtained in the same manner as elliptical polarizer EP1, except that the λ / 4 portion was made of a retarder laminate 2 having a retarder element ZB (retarder element Z) adjusted so that the thickness direction retardation was RethZB(550) = -140 nm. The Nz coefficient of the λ / 4 portion was 0.01.

[0146] <Elliptical Polarizing Plate EP9> An elliptical polarizer EP9 was obtained in the same manner as the elliptical polarizer EP1, except that the λ / 4 portion was made of a retarder laminate 2 having a retarder element ZB (retarder element Z) adjusted so that the thickness direction retardation was RethZB(550) = -160 nm. The Nz coefficient of the λ / 4 portion was -0.13.

[0147] <Elliptical Polarizing Plate EP10> The surface of the polarizer laminated with a TAC film opposite the TAC film was bonded to the retarder element Q side of a film formed of a COP film and a 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 side of the above laminate was bonded to the retarder element Q side of the retarder laminate 3 via an adhesive layer to obtain an elliptical polarizing plate EP10. At this time, the angle between the transmission axis of the polarizer and the slow axis of the λ / 4 portion was 75°. At this time, the Nz coefficient of the λ / 2 portion was 0.51, and the Nz coefficient of the λ / 4 portion was 1.28.

[0148] <Elliptical Polarizing Plate EP11> An elliptical polarizer EP11 was obtained in the same manner as the elliptical polarizer EP1, except that the λ / 4 portion was made of a retarder laminate 2 having a retarder element ZB (retarder element Z) adjusted so that the thickness direction retardation was RethZB(550) = -120 nm. The Nz coefficient of the λ / 4 portion was 0.15.

[0149] [Preparation of light-reflecting layer] The following three types of light-reflecting layers were used. Light-reflecting layer A: A commercially available smartphone equipped with an OLED display manufactured by Samsung Electronics, the GALAXY Tab S 8.4 SC-03G, was disassembled, and the cover glass and elliptical polarizer were removed. Light-reflective layer B: A commercially available smartphone equipped with an OLED display manufactured by Huawei Technologies, the Mate 30 Pro, was disassembled, and the cover glass and elliptical polarizer were removed before use. Light-reflecting layer C: A commercially available smartphone equipped with an OLED display device manufactured by Apple Inc., iPhone® X, was disassembled, and the cover glass and elliptical polarizer were removed.

[0150] Table 1 shows the in-plane retardation ReM45 of each light-reflecting layer at a wavelength of 550 nm on the projection plane with an inclination angle of 45° (projection plane VP described with reference to FIG. 3). [Table 1]

[0151] <Retardation of elliptical polarizers EP1 to EP5, EP7 to EP11> An adhesive layer was laminated on the retarder element ZB of each of the elliptical polarizers EP1 to EP5 and EP7 to EP11. The elliptical polarizers EP1 to EP5 and EP7 to EP11 were attached to glass via the adhesive layer to obtain samples for measuring retardation. The in-plane retardation Reo(λ) of the elliptical polarizers EP1 to EP5 and EP7 to EP11 at each wavelength was measured, and the results were as follows: Reo(450)=112nm, Reo(550)=138nm, Reo(650)=162nm, Reo(450) / Reo(550)=0.81, Reo(650) / Reo(550)=1.17, It was.

[0152] <Retardation of elliptical polarizer EP6> An adhesive layer was laminated on the retarder element Q of the elliptical polarizer EP6, and the elliptical polarizer EP6 was attached to glass via the adhesive layer to obtain a sample for measuring retardation. 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.

[0153] <Visual confirmation of display performance> For the combinations of the prepared elliptically polarizing plates EP1 to EP11 and the light reflecting layers A, B, and C, the display performance of the elliptically polarizing plates EP1 to EP11 was visually confirmed as follows. (Visual inspection method) The test was conducted outdoors on a clear day by five observers. Observations were made over the entire in-plane angle range defined by equation (15) for both tilt angles of 10° and 45°. 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.

[0154] <Reflectance at an inclination angle of 10° when using light-reflecting layer A> The elliptically polarizing plates EP1 to EP5 were each attached to the light-reflecting layer A with an adhesive, and the luminosity-corrected reflectance at an inclination angle of θ = 10° was measured and calculated, resulting in Ry10 = 4.7% for all samples. Furthermore, when the reflected external light was observed at an inclination angle of θ = 10°, it was confirmed that reflected light was well prevented in all cases, providing good display performance.

[0155] <Reflectance at an inclination angle of 10° when using light-reflecting layer B> The elliptically polarizing plates EP1, EP6 to EP9 were each attached to the light-reflecting layer B with an adhesive, and the luminosity-corrected reflectance at an inclination angle of θ = 10° was measured and calculated, resulting in Ry10 = 4.6% for all samples. Furthermore, visual observation of reflected ambient light at an inclination angle of θ = 10° confirmed that reflected light was well prevented in all cases, providing good display performance.

[0156] <Reflectance at an inclination angle of 10° when using light-reflecting layer C> The samples were each made by adhering elliptical polarizers EP2, EP3, EP6, EP10, and EP11 onto light-reflecting layer C with adhesive, and the luminosity-corrected reflectance at an inclination angle of θ = 10° was measured and calculated, resulting in Ry10 = 4.5% in all cases. Furthermore, visual observation of reflected ambient light at an inclination angle of θ = 10° confirmed that reflected light was well prevented in all cases, resulting in good display performance.

[0157] (1) Examples 1 to 3 The elliptically polarizing plates EP1, EP3, and EP4 were each attached to the light-reflecting layer A via an adhesive, and the luminous efficiency-corrected reflectance Ry45 at an inclination angle θ of 45° was measured and calculated for the samples. The calculation results are shown in Figure 4. Furthermore, when the external light reflection of the light-reflecting layer at an inclination angle θ of 45° was observed under sunlight, it was confirmed that reflected light was well prevented in all cases, resulting in good display performance.

[0158] (2) Examples 4 to 6 The elliptically polarizing plates EP7, EP1, and EP8 were each attached to the light-reflecting layer B via an adhesive, and the luminous efficiency-corrected reflectance Ry45 at an inclination angle θ of 45° was measured and calculated for the samples. The calculation results are shown in Figure 4. Furthermore, when the external light reflection of the light-reflecting layer at an inclination angle θ of 45° was observed under sunlight, it was confirmed that reflected light was well prevented in all cases, resulting in good display performance.

[0159] (3) Examples 7 to 9 The elliptically polarizing plates EP6, EP2, and EP3 were each attached to the light-reflecting layer C via an adhesive, and the luminous efficiency-corrected reflectance Ry45 at an inclination angle θ of 45° was measured and calculated for the samples. The calculation results are shown in Figure 4. Furthermore, when the external light reflection of the light-reflecting layer at an inclination angle θ of 45° was observed under sunlight, it was confirmed that reflected light was well prevented in all cases, resulting in good display performance.

[0160] (4) Comparative Examples 1 and 2 The elliptically polarizing plates EP2 and EP5 were each attached to the light-reflecting layer A via an adhesive, and the luminosity-corrected reflectance Ry45 at an inclination angle θ of 45° was measured and calculated for the samples. The calculation results are shown in Figure 4. Furthermore, when the external light reflection of the light-reflecting layer at an inclination angle θ of 45° was observed under sunlight, it was confirmed that in both cases, strong rainbow-colored reflected light was visible, impairing display performance.

[0161] (5) Comparative Examples 3 and 4 The elliptically polarizing plates EP6 and EP9 were each attached to the light-reflecting layer B via an adhesive, and the luminosity-corrected reflectance Ry45 at an inclination angle θ of 45° was measured and calculated for the samples. The calculation results are shown in Figure 4. Furthermore, when the external light reflection of the light-reflecting layer at an inclination angle θ of 45° was observed under sunlight, it was confirmed that in both cases, strong rainbow-colored reflected light was visible, impairing display performance.

[0162] (6) Comparative Examples 5 and 6 The elliptically polarizing plates EP10 and EP11 were each attached to the light-reflecting layer C via an adhesive, and the luminosity-corrected reflectance Ry45 at an inclination angle θ of 45° was measured and calculated for the samples. The calculation results are shown in Figure 4. Furthermore, when the external light reflection of the light-reflecting layer at an inclination angle θ of 45° was observed under sunlight, it was confirmed that in both cases, strong rainbow-colored reflected light was visible, impairing display performance.

[0163] FIG. 4 is a table showing the results of Examples 1 to 9 and Comparative Examples 1 to 6. In the chart of FIG. 4, A, B, and C in the "Type" column in the "Light Reflecting Layer" column correspond to light reflecting layer A, light reflecting layer B, and light reflecting layer C. The ρ coefficient in the "Light Reflecting Layer" column is a value calculated by substituting the ReM45 of the light reflecting layers A, B, and C shown in Table 1 and the in-plane retardation ReoQ of the λ / 4 portion retarder element Q of the elliptical polarizers EP1 to EP11 combined with the light reflecting layers A, B, and C into formula (A). The "Nz coefficient" is a value calculated by substituting the in-plane retardation and the thickness direction retardation of the retarder element Q and the retarder element ZB in the λ / 4 portion into formula (C). In the "Visual inspection at an inclination angle of 45°" column, "◯" indicates "good display performance with reflected light well prevented," and "×" indicates "rainbow-colored reflected light is visible, impairing display performance," as described below.

[0164] As shown in FIG. 4, Examples 1 to 9 were evaluated as "good" in the "visual observation at a tilt angle of 45°." That is, in Examples 1 to 9, even when the display devices obtained by laminating an elliptically polarizing plate on a light-reflecting layer were tilted under sunlight to observe the external light reflection of the light-reflecting layer, reflected light was well prevented, and good display performance was achieved. On the other hand, Comparative Examples 1 to 6 were evaluated as "poor." That is, in Comparative Examples 1 to 6, when the display devices obtained by laminating an elliptically polarizing plate on a light-reflecting layer were tilted under sunlight to observe the external light reflection of the light-reflecting layer, iridescent reflected light was visible, impairing the display performance. Note that sunlight covers the entire visible range, so the above-mentioned display performance evaluation corresponds to an evaluation of the entire visible range. While FIG. 4 shows the results at a tilt angle of 45°, as mentioned above, the results at a tilt angle of 10° were similar to those at a tilt angle of 45°.

[0165] Figure 5 is a graph plotting the Nz coefficient against the ρ coefficient in Figure 4. The horizontal axis in Figure 5 represents the ρ coefficient, and the vertical axis represents the Nz coefficient. Lines L1, L2, L3, L4, and L5 in Figure 5 are lines expressed by the following equations. L1:Nz=4.5ρ+0.955 L2:Nz=4.5ρ-0.160 L3:Nz=4.5ρ+0.690 L4: Nz=4.5ρ-0.035 L5: Nz=4.5ρ+0.5

[0166] From the relationship between lines L1 to L4 in FIG. 5 and the plot points of the examples and comparative examples, it can be seen that in Examples 1 to 9, the relationship between the Nz coefficient and the ρ coefficient at the λ / 4 portion satisfies formula (B), whereas in Comparative Examples 1 to 6, the relationship between the Nz coefficient and the ρ coefficient at the λ / 4 portion does not satisfy formula (B). Therefore, it can be seen that, when the relationship between the Nz coefficient and the ρ coefficient at the λ / 4 portion satisfies formula (B), good display performance can be obtained, with reflected light well prevented across the entire visible range, even when the external light reflection of the light-reflecting layer is observed with the display device tilted. Furthermore, from the relationship between lines L1 to L4 in FIG. 5 and the plot points of the examples and comparative examples, it can be seen that it is preferable that the relationship between the Nz coefficient and the ρ coefficient at the λ / 4 portion satisfies formula (D).

[0167] From the results of Ry45 shown in FIG. 4, it can be seen that Ry is preferably 8.1% or less. [Explanation of symbols]

[0168] 20... elliptical polarizing plate, 31... polarizer, 41... λ / 2 portion, 42... λ / 4 portion, 100... display device, Q... retarder element (first retarder element), ZA... (second retarder element), ZB... retarder element (third retarder element).

Claims

1. a light-reflective image display layer; an elliptically polarizing plate laminated on the image display surface of the light-reflective image display layer; Equipped with the elliptically polarizing plate has a polarizer, a λ / 2 portion and a λ / 4 portion; the polarizer, the λ / 2 portion, and the λ / 4 portion are arranged in this order from the light-reflective image display layer side, the λ / 4 portion, the λ / 2 portion, and the polarizer; the λ / 2 portion is a laminate in which a first delay phase element, a second delay phase element, a second delay phase element, and a first delay phase element are laminated 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 first retarder element is a positive A plate having reverse wavelength dispersion and imparting an in-plane retardation of approximately λ / 4 at a wavelength of 550 nm; the second retarder element is a positive C plate that imparts a thickness direction retardation, When the in-plane retardation of the light-reflective image display layer at a wavelength of 550 nm on a projection plane having an inclination angle of 45° with respect to the thickness direction of the light-reflective image display layer is ReM45, the in-plane retardation of the λ / 4 part at a wavelength of 550 nm is ReoQ, and the ρ coefficient of the light-reflective image display layer is expressed by formula (A), the Nz coefficient of the λ / 4 part and the ρ coefficient satisfy the relationship shown in formula (B). Display device. ρ=ReM45 / ReoQ...(A) 4.5ρ-0.160<Nz<4.5ρ+0.955...(B)

2. The first retarder element satisfies formula (i), The second retarder element satisfies formula (ii): The display device according to claim 1 . nx>ny≒nz...(i) nx≒ny<nz... (ii) [In formula (i), nx represents a principal refractive index in a direction parallel to a first retarder plane in a first index ellipsoid formed by the first retarder element, ny represents a refractive index in a direction parallel to the first retarder plane in the first index ellipsoid and perpendicular to the direction of nx, and nz represents a refractive index in a direction perpendicular to the first retarder plane in the first index ellipsoid, In formula (ii), nx represents the principal refractive index in a direction parallel to the second retarder plane in a second index ellipsoid formed by the second retarder element, ny represents the refractive index in a direction parallel to the second retarder plane in the second index ellipsoid and perpendicular to the direction of nx, and nz represents the refractive index in a direction perpendicular to the second retarder plane in the second index ellipsoid.

3. the λ / 4 portion is a laminate in which a third retardation element and a first retardation element are laminated in this order from the light-reflective image display layer side, and the first retardation element of the λ / 4 portion has a reverse wavelength dispersion and provides an in-plane retardation of approximately λ / 4; The third retarder element is an element that imparts a thickness direction retardation. The display device according to claim 1 or 2.

4. the first retardation element included in the λ / 4 section is a positive A plate that provides a phase difference of approximately λ / 4 as an in-plane phase difference at a wavelength of 550 nm, the third retarder element is a positive C-plate or a negative C-plate that imparts a thickness direction retardation; The display device according to claim 3 .

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