Display device

Abstract

A display device is provided that can maintain display performance even when viewing an image at an angle. One embodiment of the display device includes a light-reflective image display layer; and an elliptical polarizer having a polarizer, a λ / 2 portion, and a λ / 4 portion. The λ / 2 portion is a stack of a first retardation element, a second retardation element, and a first retardation element. When the in-plane retardation at a wavelength of 550 nm in a projection plane at an angle of 45° relative to the thickness direction of the image display layer is defined as ReM45, the in-plane retardation at a wavelength of 550 nm in the λ / 4 portion is defined as ReoQ, and the ρ coefficient (ρ) of the image display layer is expressed by equation (A), the Nz coefficient (Nz) of the λ / 4 portion and the ρ coefficient (ρ) satisfy the relationship shown in equation (B). ρ=ReM45 / ReoQ (A) 4.5ρ-0.160<Nz<4.5ρ+0.955 (B).

Description

Technical Field

[0001] This invention relates to display devices. Background Technology

[0002] As prior art in this technical field, there is the technology described in Patent Document 1. Patent Document 1 discloses a method of stacking λ / 2 and λ / 4 portions. The optical laminate described in Patent Document 1 has a phase difference close to λ / 4 across the entire visible light region; therefore, when combined with a linear polarizer, it functions as an ellipsoidal plate with an ellipticity of 97% or more across the entire visible light region. If it is disposed on a light-reflecting layer in an OLED display device or similar device, external light reflection can be suppressed over a wide range of the visible light region.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: International Publication No. 2018 / 003416 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] The viewing angle compensation of the optical laminate described in Patent Document 1 is insufficient. Therefore, the performance of the optical laminate described in Patent Document 1 is limited to the case where the display device is viewed from a generally frontal perspective, and there is a problem that the external light reflectivity increases and the display performance decreases when viewed at an angle.

[0008] The purpose of this invention is to provide a display device that can maintain display performance even when viewing an image at an angle.

[0009] Methods for solving problems

[0010] One aspect of the display device of the present invention includes a light-reflective image display layer and an elliptic polarizing plate stacked on the image display surface of the light-reflective image display layer.

[0011] The aforementioned elliptic polarizer has a polarizer, a λ / 2 section, and a λ / 4 section.

[0012] The aforementioned polarizer, the aforementioned λ / 2 portion, and the aforementioned λ / 4 portion are arranged in the following order from the light-reflective image display layer side: the aforementioned λ / 4 portion, the aforementioned λ / 2 portion, and the aforementioned polarizer.

[0013] The aforementioned λ / 2 section is a stack formed by layering the first retardation element, the second retardation element, the third retardation element, and the fourth retardation element in the order described above.

[0014] The first delay element is an element with inverse wavelength dispersion and imparts an in-plane phase difference of approximately λ / 4. The second delay element is an element that imparts a phase difference in the thickness direction. When the in-plane delay of the light-reflective image display layer at a wavelength of 550 nm in the projection plane at an inclination angle of 45° relative to the thickness direction of the light-reflective image display layer is set to ReM45, the in-plane delay at a wavelength of 550 nm in the λ / 4 portion is set to ReoQ, and the ρ coefficient (ρ) of the light-reflective image display layer is expressed by Equation (A), the Nz coefficient (Nz) of the λ / 4 portion and the ρ coefficient (ρ) satisfy the relationship shown in Equation (B).

[0015] ρ=ReM45 / ReoQ···(A)

[0016] 4.5ρ-0.160<Nz<4.5ρ+0.955···(B)

[0017] In the above-mentioned display device, since the Nz coefficient of the above-mentioned λ / 4 part and the above-mentioned ρ coefficient satisfy the relationship shown in Equation (B), the display performance can be maintained even when the image is viewed at an angle.

[0018] The aforementioned first delay element can be a positive A-plate that imparts an in-plane phase difference of approximately λ / 4 as a wavelength of 550 nm.

[0019] The second delay element mentioned above can be a positive C-plate that imparts a phase difference in the thickness direction.

[0020] The aforementioned λ / 4 section may be a stack of a third delay film element and a first delay film element stacked from the light-reflective image display layer side in the order of the third delay film element and the first delay film element. The first delay film element in the aforementioned λ / 4 section is an element with inverse wavelength dispersion and imparts an in-plane phase difference of approximately λ / 4, and the aforementioned third delay film element is a positive C-plate that imparts a phase difference in the thickness direction.

[0021] The first delay element in the λ / 4 section described above may be a positive A plate that imparts an in-plane phase difference of approximately λ / 4 as a wavelength of 550 nm, and the third delay element may be a positive C plate or a negative C plate that imparts a phase difference in the thickness direction.

[0022] Invention Effects

[0023] According to the present invention, a display device is provided that can maintain display performance even when viewing an image at an angle. Attached Figure Description

[0024] Figure 1This is a schematic diagram illustrating the general configuration of a display device having an optical laminate in one embodiment.

[0025] Figure 2 This is a schematic diagram showing the configuration relationship between the slow axis of the λ / 2 section, the slow axis of the λ / 4 section, and the transmission axis of the polarizer.

[0026] Figure 3 This is a diagram used to illustrate the ρ coefficients of the image display layer.

[0027] Figure 4 Table 2 shows the results of Examples 1-9 and Comparative Examples 1-6.

[0028] Figure 5 It is relative to Figure 4 The ρ coefficients in Table 2 are used to plot the Nz coefficients. Detailed Implementation

[0029] The embodiments of the present invention will be described below. First, the terminology used in this application will be explained.

[0030] [Delayed playback]

[0031] In this application, a retardation plate refers to an optical medium with birefringence. Birefringence means that the difference in refractive index in at least two of the three orthogonal directions exceeds 0.02, resulting in different optical properties.

[0032] [Refractive index of the delay film]

[0033] The refractive indices in the three orthogonal directions mentioned above in the retardation film are called nx, ny, and nz. nx represents the principal refractive index in the direction parallel to the plane of the retardation film within the refractive index ellipsoid formed by the retardation film. ny represents the refractive index in the direction parallel to the plane of the retardation film and orthogonal to the nx direction within the refractive index ellipsoid formed by the retardation film. nz represents the refractive index in the direction perpendicular to the plane of the retardation film within the refractive index ellipsoid formed by the retardation film.

[0034] [In-plane retardation and thickness-direction retardation of retardation sheets]

[0035] Retardation Re is a physical quantity that represents the anisotropy of a retardation sheet. There are in-plane retardation Reo and thickness-direction retardation Reth.

[0036] The in-plane retardation Reo(λ) at wavelength λ (nm) is represented by equation (1). In equation (1), d represents the thickness of the retardation plate (nm).

[0037] Reo(λ)=(nx―ny)×d···(1)

[0038] The thickness retardation Reth(λ) at wavelength λ (nm) is represented by equation (2). In equation (2), d is the same as d in equation (1) as the thickness (nm) of the retardation plate.

[0039] Reth(λ)=―{nz―(nx+ny) / 2}×d···(2)

[0040] The in-plane delay Reo and the thickness direction delay Reth can be adjusted by changing the thickness d of the delay sheet.

[0041] [Form A]

[0042] The positive A plate is a retardation plate whose refractive index in all directions satisfies the relationship of equation (3). Unless otherwise specified, the slow axis of the positive A plate is parallel to nx, and ny≈nz indicates that the difference between ny and nz is less than 0.02.

[0043] nx>ny≈nz····(3)

[0044] The positive A plate can function as a λ / 4 plate. The in-plane phase difference of the λ / 4 plate at a wavelength of 550 nm can be approximately λ / 4. The in-plane delay Reo(550) at a wavelength of 550 nm of the λ / 4 plate with an in-plane phase difference of approximately λ / 4 can be within the range of equation (4).

[0045] 92nm≤Reo(550)≤183nm···(4)

[0046] The suitable range of Reo(550) for 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 the thickness direction retardation Reth(λ) of the positive A plate at wavelength λ(nm) have the relationship of Equation (5) derived from Equations (1), (2), and (3).

[0047] Reth(λ)=0.5×Reo(λ)···(5)

[0048] The thickness retardation Reth(550) at a wavelength of 550 nm for the λ / 4 plate can be within the range of Equation (6).

[0049] 46nm≤Reth(550)≤92nm···(6)

[0050] The suitable range 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.

[0051] [Positive C board]

[0052] The positive C-plate is a retardation plate whose refractive index in all directions satisfies the relationship of equation (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.

[0053] nx≈ny<nz···(7)

[0054] [Negative C plate]

[0055] The negative C plate is a retardation plate whose refractive index in all directions satisfies the relationship of equation (8). Unless otherwise specified, the slow axis lies in the plane stretched by the nx and ny axes, and the fast axis is parallel to the nz axis. nx≈ny indicates that the difference between nx and ny is less than 0.02.

[0056] nx≈ny>nz···(8)

[0057] [Wavelength Dispersion]

[0058] The dispersion relationship between wavelength and delay is also referred to as wavelength dispersion. A delay plate that satisfies equations (9) and (10) is called inverse wavelength dispersion, or simply inverse dispersion.

[0059] Re(450) / Re(550)≤1.00···(9)

[0060] 1.00≤Re(650) / Re(550)···(10)

[0061] The Re(450) / Re(550) ratio of the delay chip in this application is preferably 0.90 or less, more preferably 0.85 or less, typically 0.60 or more, and preferably 0.70 or more. The Re(650) / Re(550) ratio of the delay chip in this application is preferably 1.02 or more, more preferably 1.10 or more, typically 1.30 or less, and preferably 1.20 or less.

[0062] A delay plate that satisfies equations (11) and (12) is called a positive wavelength dispersion, or simply positive dispersion.

[0063] Re(450) / Re(550)>1.00···(11)

[0064] 1.00>Re(650) / Re(550)···(12)

[0065] [Delay-lapse film stack]

[0066] Optical stacks containing multiple retardation plates are sometimes referred to as retardation plate stacks.

[0067] [Nz coefficient]

[0068] The Nz coefficient (Nz) of the delay film can be expressed by equation (13). It should be noted that the in-plane delay of the entire delay film stack at wavelength λ (nm) (e.g., wavelength 550nm) is set as ReoG, and the thickness direction delay of the entire delay film stack is set as RethG.

[0069] Nz≡(RethG / ReoG)+0.5···(13)

[0070] Next, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same or equivalent parts are labeled with the same symbols, and repeated descriptions are omitted. The scale of the drawings may not be consistent with the scale of the description.

[0071] Figure 1 This is a schematic diagram illustrating the general configuration of a display device according to one embodiment. Figure 1 The display device 100 shown includes a light-reflective image display layer 10 (hereinafter simply referred to as "image display layer 10") and an ellipsoidal polarizer 20. In this application, the ellipsoidal polarizer also includes the concept of a circular polarizer.

[0072] [Image Display Layer]

[0073] 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 element structures for forming the image. Therefore, the metal electrodes for wiring portions, the high-refractive-index layer for the resonator structure of the sub-pixels, and the black matrix included in the aforementioned element structures function as reflective elements for reflected light. Therefore, the image display layer 10 has light reflectivity, reflecting light incident on the display device 100 from the elliptical polarizer 20 side, and functions as a light reflective layer in the display device 100. In this embodiment, the reflected light, which is a unified reflection of the light from the metal electrodes for wiring portions, the high-refractive-index layer for the resonator structure of the sub-pixels, and the black matrix included in the image display layer 10 as a light reflective layer, is sometimes referred to as "external light reflection light." The image display layer 10 can be flexible or rigid.

[0074] The image display layer 10 is not limited in terms of layer composition and materials, as long as it is configured to form an image on the image display surface 10a. For example, the image display layer 10 may be a multilayer stack consisting of electrodes and wiring formed using metals such as gold, silver, copper, iron, nickel, chromium, molybdenum, titanium, aluminum, and their alloys, as well as a resin film, a barrier element, a light-emitting element, and other dielectric parts, and other layers.

[0075] The image display layer 10 may be, for example, a flat panel display device. An example of a flat panel display device is a thin (or panel-shaped) organic electroluminescent display device (hereinafter also referred to as "OLED display device"). The display device exemplified as the image display layer 10 is a device in which no component for optical compensation is included on the image display surface.

[0076] In the case of an OLED display device where the image display layer 10 is an OLED display device, typically, the electrodes (e.g., metal electrodes) provided by the OLED display device are the aforementioned reflective portions. The OLED display device has a thin film structure in which an organic light-emitting material layer is sandwiched between a pair of opposing electrodes. By injecting electrons into the organic light-emitting material layer from one electrode and holes into the organic light-emitting material layer from the other electrode, electrons and holes combine within the organic light-emitting material layer to achieve 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 aforementioned other electrode typically functions as a reflective portion in the OLED display device.

[0077] Compared to LCD displays that require a backlight, OLED displays offer advantages such as better visibility, the ability to be further thinned, and the ability to be driven by low DC voltage.

[0078] An elliptic polarizer 20 is stacked on the image display layer 10. In the display device 100, the image is viewed from the side of the elliptic polarizer 20. Therefore, the side opposite to the image display layer 10 with reference to the elliptic polarizer 20 is also called the "viewing side". The elliptic polarizer 20 has a polarizer 31 and an optical laminate 40. Figure 1 As shown, in the elliptical polarizer 20, a polarizer 31 and an optical laminate 40 are arranged sequentially from the observation side.

[0079] Polarizer 31 is laminated on optical laminate 40. Polarizer 31 can be an absorption-type film with the following properties: absorbing linearly polarized light having a vibration plane parallel to its absorption axis and transmitting linearly polarized light having a vibration plane orthogonal to the absorption axis (parallel to the transmission axis). As polarizer 31, a film formed by adsorbing and oriented dichroic dyes onto a uniaxially stretched polyvinyl alcohol-based resin film can be suitable. Polarizer 31 can be manufactured, for example, by a method including: a step of uniaxially stretching a polyvinyl alcohol-based resin film; a step of adsorbing dichroic dyes by dyeing the polyvinyl alcohol-based resin film with dichroic dyes; a step of treating the polyvinyl alcohol-based resin film adsorbed with dichroic dyes using a crosslinking solution such as boric acid aqueous solution; and a step of washing with water after treatment with the crosslinking solution.

[0080] As a polyvinyl alcohol-based resin, a resin obtained by saponifying a polyvinyl acetate-based resin can be used. Besides polyvinyl acetate as a homopolymer of vinyl acetate, copolymers of vinyl acetate with other monomers that can be copolymerized can also be cited as polyvinyl acetate-based resins. Examples of other monomers that can be copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth)acrylamides containing ammonium groups.

[0081] In this application, "(meth)acrylic acid" refers to at least one selected from acrylic acid and methacrylic acid. The same applies to "(meth)acryloyl", "(meth)acrylate", etc.

[0082] The thickness of the polarizer 31 is typically 30 μm or less, preferably 15 μm or less, more preferably 13 μm or less, even more preferably 10 μm or less, and particularly preferably 8 μm or less. The thickness of the polarizer 31 is typically 2 μm or more, preferably 3 μm or more.

[0083] As polarizer 31, for example as described in Japanese Patent Application Publication No. 2016-170368, a polarizer formed by aligning dichroic pigments in a cured film polymerized from a liquid crystal compound can be used. As the dichroic pigment, a dichroic pigment having absorption in the wavelength range of 380 to 800 nm can be used, preferably an organic dye. Examples of dichroic pigments include azo compounds. The liquid crystal compound is a liquid crystal compound capable of polymerization in an oriented state and may have polymerizable groups within its molecules. Alternatively, as described in WO2011 / 024891, a polarizing film can be formed from a dichroic pigment possessing liquid crystal properties.

[0084] The visibility correction polarization degree of polarizer 31 is preferably 90% or more, more preferably 95% or more. There is no particular upper limit, but it is 99.9999% or less.

[0085] Furthermore, the transmittance of the visibility correction monomer of the polarizing film is preferably 35% or more, more preferably 40% or more. There is no particular upper limit, but it is 49.9% or less. By giving the laminate such properties a polarizer 31, reflected light is less likely to leak, and coloration is less noticeable.

[0086] like Figure 1 As shown, a protective film 32 can be provided on one or both sides of the polarizer 31. Sometimes, the laminate with the protective film 32 on the polarizer 31 is also called a linear polarizer 30.

[0087] The protective film 32 can be a light-transmitting (preferably optically transparent) thermoplastic resin. For example, the protective film 32 can be a film comprising polyolefin resins such as chain-like polyolefin resins (polypropylene resin, etc.), cyclic polyolefin resins such as norbornene resins, cellulose resins such as triacetyl cellulose and diacetyl cellulose, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polycarbonate resins, (meth)acrylic resins such as methyl methacrylate resins, polystyrene resins, polyvinyl chloride resins, acrylonitrile-butadiene-styrene resins, acrylonitrile-styrene resins, polyvinyl acetate resins, polyvinylidene chloride resins, polyamide resins, polyacetal resins, modified polyphenylene ether resins, polysulfone resins, polyethersulfone resins, polyarylate resins, polyamide-imide resins, and polyimide resins.

[0088] The phase difference value of the protective film 32 can also be appropriately controlled to a suitable value. In order to improve the visibility of the image when the user wears polarized sunglasses, the in-plane phase difference value at a wavelength of 550nm can be set to 70-140nm.

[0089] The thickness of the protective film 32 is typically 1 to 100 μm, and from the viewpoint of strength and operability, it is preferably 5 to 60 μm, more preferably 10 to 55 μm, and even more preferably 15 to 40 μm.

[0090] When protective films 32 are bonded to both sides of the polarizer 31, the two protective films 32 can be made of the same thermoplastic resin or different thermoplastic resins. Furthermore, the thicknesses of the two protective films 32 can be the same or different. Additionally, the two protective films 32 can have the same phase difference characteristics or different phase difference characteristics.

[0091] As described above, at least one of the protective films 32 may have a surface treatment layer (coating) such as a hard coating, an anti-glare layer, a light diffusion layer, an anti-reflection layer, a low refractive index layer, an antistatic layer, or an anti-fouling layer on its outer surface (the side opposite to the polarizer 31). It should be noted that the thickness of the protective film 32 includes the thickness of the surface treatment layer.

[0092] The protective film 32 can be attached to the polarizer 31, for example, by means of an adhesive layer or a bonding agent layer. As the adhesive forming the adhesive layer, a water-based adhesive, an active energy radiation-curing adhesive, or a thermosetting adhesive can be used, preferably a water-based adhesive or an active energy radiation-curing adhesive. As the bonding agent layer, a bonding agent layer described later can be used.

[0093] Examples of water-based adhesives include adhesives containing aqueous solutions of polyvinyl alcohol (PVA) resins and water-based two-component urethane emulsion adhesives. Among these, water-based adhesives containing aqueous solutions of PVA resins are particularly suitable. As for PVA resins, in addition to ethylene alcohol homopolymers obtained by saponifying polyvinyl acetate homopolymers, PVA copolymers obtained by saponifying copolymers of vinyl acetate and other monomers capable of copolymerizing with it, or modified PVA polymers obtained by partially modifying their hydroxyl groups, can also be used. Water-based adhesives may contain crosslinking agents such as aldehyde compounds (glyoxal, etc.), epoxy compounds, melamine compounds, hydroxymethyl compounds, isocyanate compounds, amine compounds, and polyvalent metal salts.

[0094] When using a water-based adhesive, it is preferable to perform a drying process to remove water contained in the water-based adhesive after bonding the polarizer 31 to the protective film 32. After the drying process, a curing process can be performed, for example, at a temperature of 20–45°C.

[0095] The aforementioned active energy ray curable adhesive refers to 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, preferably an ultraviolet curable adhesive.

[0096] The aforementioned curable compounds can be cationicly polymerizable or radically polymerizable. Examples of cationicly polymerizable curable compounds 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), or combinations thereof. Examples of radically polymerizable curable compounds include (meth)acrylic acid compounds (compounds having one or more (meth)acryloyloxy groups in the molecule), other vinyl compounds with radically polymerizable double bonds, or combinations thereof. Cationicly polymerizable and radically polymerizable curable compounds can also be used in combination. Active energy radiation-curable adhesives typically also contain cationic polymerization initiators and / or radical polymerization initiators for initiating the curing reaction of the aforementioned curable compounds.

[0097] When bonding the polarizer 31 to the protective film 32, surface activation treatment can be applied to the bonding surfaces of at least one of them to improve adhesion. Examples of surface activation treatments include dry treatments such as corona treatment, plasma treatment, discharge treatment (glow discharge treatment, etc.), flame treatment, ozone treatment, UV ozone treatment, and ionizing active ray treatment (ultraviolet treatment, electron beam treatment, etc.); and wet treatments such as ultrasonic treatment, saponification treatment, and anchor coating treatment using solvents such as water and acetone. These surface activation treatments can be performed individually or in combination of two or more.

[0098] When protective films 32 are attached to both sides of the polarizer 31, the adhesive used to attach these protective films 32 can be of the same type or different types.

[0099] The optical laminate 40 is disposed in the display device 100 on the polarizer 31 (in Figure 1 In the illustrated scheme, the linear polarizer 30 is positioned between the optical layer 10 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 arranged in the order of λ / 2 portion 41 and λ / 4 portion 42 from the observation side. In this embodiment, unless otherwise specified, the slow axis of the λ / 2 portion 41 and the λ / 4 portion is parallel to nx.

[0100] Figure 2 This is a schematic diagram showing the arrangement relationship between the slow axis 41a of the λ / 2 section 41, the slow axis 42a of the λ / 4 section 42, and the transmission axis 31a of the polarizer 31. (For example...) Figure 2 As shown, the λ / 2 section 41 and the λ / 4 section 42 are arranged such that the angle θ1 between the slow axis 41a of the λ / 2 section 41 and the slow axis 42a of the λ / 4 section 42 is approximately 60°. Approximately 60° refers to a range of 60° ± 5°. The λ / 2 section 41 is preferably arranged relative to the polarizer 31 such that the angle between the slow axis 41a of the λ / 2 section 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 section 42 is preferably arranged relative to the polarizer 31 such that the angle θ3 between the slow axis 42a of the λ / 4 section 42 and the transmission axis 31a of the polarizer 31 is approximately 75°. Approximately 75° refers to a range of 75° ± 5°.

[0101] The λ / 2 section 41 has the function of imparting a phase difference of λ / 2 to incident light of wavelength λ. The expected value of the Nz coefficient of the λ / 2 section 41 is approximately 0.5. An Nz coefficient value of approximately 0.5 means an Nz coefficient in the range of 0.5 ± 0.1. A suitable range for the Nz coefficient of the λ / 2 section 41 is 0.45 or higher and 0.55 or lower. Unless otherwise specified, the slow axis of the λ / 2 section 41 is parallel to nx.

[0102] The λ / 2 section 41 has two delay elements (first delay element) Q and two delay elements (second delay element) ZA. The λ / 2 section 41 consists of two delay elements Q and two delay elements ZA as shown below. Figure 1 The stack shown is formed by stacking delay element Q, delay element ZA, delay element ZA and delay element Q in that order.

[0103] [Delay chip element Q]

[0104] A retardation film element Q is a retardation film exhibiting inverse dispersion and imparting an in-plane phase difference of approximately λ / 4 to incident light of wavelength λ. Approximately λ / 4 refers to the range of one-sixth to one-third of the wavelength λ. The retardation film element Q can be a λ / 4 plate. Alternatively, the retardation film element Q can be a positive A-plate with an in-plane phase difference of approximately λ / 4 at a wavelength of 550 nm. The retardation film element Q can be obtained by curing a polymerizable liquid crystal compound, or by molding or further stretching molten resin.

[0105] [Delay chip element ZA]

[0106] The delay element ZA is a retardation film that imparts a phase difference in the thickness direction to the incident light. The delay element ZA can be a positive C-plate. The aforementioned positive C-plate refers to a positive C-plate whose thickness direction delay Reth(550) satisfies equation (14).

[0107] -30nm≥Reth(550)≥-120nm···(14)

[0108] The suitable range for the Reth (550) of the retardation film 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 retardation film element ZA can be obtained by curing a polymerizable liquid crystal compound, or by molding or further stretching molten resin. The in-plane retardation ReoZA (550) of the retardation film element ZA is expected to be substantially 0. "Substantially 0" means a range of 0 nm ± 5.

[0109] When the retardation film element Q and retardation film element ZA are layers obtained by curing polymeric liquid crystal, the retardation film element Q and retardation film element ZA are formed on an alignment film disposed on a substrate. The substrate may be a strip-shaped substrate that functions to support the alignment film. This substrate functions as a release support, capable of supporting the retardation film for transfer. Furthermore, it is preferable that its surface has adhesive strength sufficient for peeling. A resin film, exemplified as the material of the protective film 32, can be used as a substrate.

[0110] The thickness of the substrate is not particularly limited, but it is preferably set to a range of 20 μm or more and 200 μm or less. If the thickness of the substrate is 20 μm or more, it can impart strength. On the other hand, if the thickness is 200 μm or less, when the substrate is cut into a single sheet, the increase of processing chips and the wear of the cutting blade can be suppressed.

[0111] Various anti-adhesion treatments can be applied to the substrate. Examples of anti-adhesion treatments include easy-bonding treatments, treatments involving the incorporation of fillers, and embossing (knurling). By applying such anti-adhesion treatments to the substrate, adhesion between substrates during winding can be effectively prevented, enabling the high-productivity manufacturing of optical films.

[0112] A layer formed by curing a polymeric liquid crystal compound is formed on a substrate by an alignment film. That is, the layer formed by curing the polymeric liquid crystal compound is stacked on the alignment film in the order of substrate and alignment film.

[0113] The alignment film is not limited to a vertical alignment film; it can be an alignment film that aligns the molecular axes of the polymerizable liquid crystal compound horizontally or tilted. A horizontal alignment film can be used when fabricating a retardation film element Q, while a vertical alignment film can be used when fabricating a retardation film element ZA.

[0114] As an alignment film, it is preferable to have solvent resistance that prevents dissolution by coating of compositions containing polymeric liquid crystal compounds (described later), and heat resistance for solvent removal and heat treatment for aligning the liquid crystal compound. Examples of alignment films include alignment films containing oriented polymers, photo-alignment films, and grooved alignment films in which a plurality of grooves are formed and aligned on the surface. The thickness of the alignment film is typically in the range of 10 nm to 10000 nm, preferably in the range of 10 nm to 1000 nm, more preferably 500 nm or less, and even more preferably in the range of 10 nm to 200 nm.

[0115] The resin used in the alignment film is not particularly limited as long as it is a known material for alignment films. Cured products obtained by curing conventionally known monofunctional or polyfunctional (meth)acrylate monomers under a polymerization initiator can be used. Specifically, examples of (meth)acrylate monomers 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 carbamate acrylates. It should be noted that the resin can be one of these monomers or a mixture of two or more.

[0116] There is no particular limitation on the type of polymeric liquid crystal compound used in this embodiment, but based on its shape, it can be classified into rod-shaped type (rod-shaped liquid crystal compound) and disk-shaped type (disc-shaped liquid crystal compound, disc-shaped liquid crystal compound). Furthermore, there are low-molecular-weight type and high-molecular-weight type. It should be noted that high-molecular-weight compounds generally refer to molecules with a degree of polymerization of 100 or higher (Polymer Physics and Phase Transfer Kinetics, Masao Doi, p. 2, Iwanami Shoten, 1992).

[0117] In this embodiment, any polymerizable liquid crystal compound may be used. Furthermore, two or more rod-shaped liquid crystal compounds, two or more disc-shaped liquid crystal compounds, or a mixture of rod-shaped and disc-shaped liquid crystal compounds may be used.

[0118] As a rod-shaped liquid crystal compound, for example, the rod-shaped liquid crystal compound described in claim 1 of Japanese Patent Application Publication No. 11-513019, or in paragraphs

[0026] to

[0098] of Japanese Patent Application Publication No. 2005-289980, may be suitable. As a disc-shaped liquid crystal compound, for example, the disc-shaped liquid crystal compound described in paragraphs

[0020] to

[0067] of Japanese Patent Application Publication No. 2007-108732, or in paragraphs

[0013] to

[0108] of Japanese Patent Application Publication No. 2010-244038, may be suitable.

[0119] Two or more polymerizable liquid crystal compounds can be used in combination. In this case, at least one of them has two or more polymerizable groups within its molecule. That is, the layer formed by curing the above-mentioned polymerizable liquid crystal compounds is preferably a layer formed by fixing liquid crystal compounds having polymerizable groups through polymerization. In this case, it is no longer necessary to exhibit liquid crystal properties after forming the layer.

[0120] Polymerizable liquid crystal compounds possess polymerizable groups capable of undergoing polymerization reactions. Preferred polymerizable groups include, for example, polymerizable olefinic unsaturated groups, cyclic polymerizable groups, and other functional groups capable of addition polymerization reactions. More specifically, examples of polymerizable groups include (meth)acryloyl, vinyl, styrene, and allyl. Among these, (meth)acryloyl is preferred. It should be noted that (meth)acryloyl refers to a concept encompassing both methacryloyl and acryloyl groups.

[0121] A layer cured from a polymeric liquid crystal compound can be formed by coating a composition containing the polymeric liquid crystal compound onto, for example, an alignment film. The composition may contain components other than the polymeric liquid crystal compound. For example, the composition preferably contains a polymerization initiator. The polymerization initiator used is selected according to the form of the polymerization reaction, for example, a thermal polymerization initiator or a photopolymerization initiator. Examples of photopolymerization initiators include α-carbonyl compounds, azobin ethers, α-hydrocarbon-substituted aromatic azobin compounds, polynuclear quinone compounds, and combinations of triarylimidazolium dimers and p-aminophenyl ketones. The amount of polymerization initiator used relative to the total solids content in the coating solution is preferably 0.01% to 20% by mass, more preferably 0.5% to 5% by mass.

[0122] From the perspective of the uniformity and strength of the coated film, the above composition may contain a polymerizable monomer. Examples of polymerizable monomers include free radical polymerizable or cationic polymerizable compounds. Among these, multifunctional free radical polymerizable monomers are preferred.

[0123] As the polymerizable monomer, a polymerizable monomer capable of copolymerizing with the aforementioned polymerizable liquid crystal compound is preferred. Specific examples of polymerizable monomers include those described in paragraphs

[0018] to

[0020] of Japanese Patent Application Publication No. 2002-296423. The amount of polymerizable monomer used relative to the total mass of the polymerizable liquid crystal compound is preferably 1 to 50% by mass, more preferably 2 to 30% by mass.

[0124] From the perspective of the uniformity and strength of the coated film, the above composition may contain a surfactant. Conventionally known compounds can be cited as surfactants. Among them, fluorinated compounds are particularly preferred. Specific surfactants include, for example, the compounds described in paragraphs

[0028] to

[0056] of Japanese Patent Application Publication No. 2001-330725 and the compounds described in paragraphs

[0069] to

[0126] of Japanese Patent Application No. 2003-295212.

[0125] The above composition may contain a solvent, preferably an organic solvent. 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). Alkyl halides and ketones are preferred. Furthermore, two or more organic solvents may be used in combination.

[0126] The above composition may contain various orientation agents such as vertical orientation agents on the polarization film interface side and vertical orientation agents on the air interface side, as well as horizontal orientation agents such as horizontal orientation agents on the polarization film interface side and horizontal orientation agents on the air interface side. In addition to the components mentioned above, the above composition may also contain adhesion modifiers, plasticizers, polymers, etc.

[0127] The direction of the slow axis of the delay element Q in the λ / 2 section 41 can be approximately the same as the direction of the slow axis 41a of the λ / 2 section 41. Approximately the same means that the directions of the two slow axes can deviate from each other by about ±5° (the same applies below).

[0128] The retardation element Q in the λ / 2 section 41 can be a stack of multiple retardation films that function as a retardation element Q as a whole. The slow axis of the multiple retardation films constituting the retardation element Q is approximately aligned with the direction of the slow axis 41a. Similarly, the retardation element Z in the λ / 2 section 41 can be a stack of multiple retardation films that function as a retardation element Z as a whole.

[0129] The λ / 4 section 42 has a delay element Q. The delay element Q in the λ / 4 section 42 is an element with the same characteristics as the delay element Q in the λ / 2 section 41, therefore its description is omitted. The λ / 4 section 42 may also have a delay element (the third delay element) ZB. In this case, the λ / 4 section 42 is a stack of delay elements Q and ZB stacked from the λ / 2 section 41 side in the order of delay elements Q and ZB. Unless otherwise specified, the arrangement of the delay element ZB in the λ / 4 section 42 will be described. The slow axis of the delay element Q in the λ / 4 section 42 corresponds to the slow axis of the λ / 4 section 42. Therefore, the delay element Q in the λ / 4 section 42 is arranged relative to the λ / 2 section 41 such that the angle between its slow axis and the slow axis 41a of the λ / 2 section 41 is approximately 60°.

[0130] [Delay chip element ZB]

[0131] A retardation film element ZB is a retardation film that imparts a phase difference in the thickness direction to incident light of wavelength λ. The retardation film element ZB is either 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, and from more than 0 to less than +40 nm, preferably from -170 nm to less than 0 nm. The in-plane retardation ReoZB(550) is expected to be substantially 0. "Substantially 0" means a range of 0 nm ± 5. Similar to the case of retardation film element ZA, the retardation film element ZB can be obtained by curing a polymerizable liquid crystal, or by molding or further stretching molten resin. In the case where the retardation film element ZB is a layer obtained by curing a polymerizable liquid crystal, the retardation film element ZB can be formed on an alignment film disposed on a substrate, similar to the case of retardation film element Z.

[0132] The retardation element Q of the λ / 4 section 42 can be a stack of multiple retardation films that function as a retardation element Q as a whole. The slow axis of the multiple retardation films constituting the retardation element Q is approximately aligned with the direction of the slow axis 42a. Similarly, the retardation element ZB of the λ / 4 section 42 can be a stack of multiple retardation films that function as a retardation element ZB as a whole.

[0133] Further explanation of the conditions that the above-mentioned display device 100 should meet.

[0134] [ρ coefficient]

[0135] like Figure 3 As shown, the plane orthogonal to the direction D2 with an angle α relative to the thickness direction D1 of the image display layer 10 is called the projection plane VP. The in-plane delay of the image display layer 10 at a wavelength of 550 nm in the projection plane VP when the angle α is 45° is set as ReM45. The in-plane delay of the λ / 4 portion 42 is set as ReoQ. In this embodiment, ReoQ corresponds to the in-plane delay of the delay element Q. In this case, the ρ coefficient is defined by equation (A).

[0136] ρ=ReM45 / ReoQ···(A)

[0137] When the ρ coefficient is defined by equation (A), in the above-described display device 100, the Nz coefficient of the λ / 4 part 42 and the ρ coefficient satisfy the relationship shown in equation (B). In other words, the λ / 4 part 42 is designed such that the Nz coefficient satisfies equation (B).

[0138] 4.5ρ-0.160<Nz<4.5ρ+0.955···(B)

[0139] The Nz coefficient of λ / 4 in equation (B) is defined by equation (C).

[0140] Nz={(RethQ+RethZB) / (ReoQ+ReoZB)}+0.5···(C)

[0141] In equation (C), as described above, ReoQ is the in-plane delay of the delay element Q of the λ / 4 section 42, and ReoZB is the in-plane delay of the delay element ZB of the λ / 4 section 42.

[0142] In equation (C), RethQ is the thickness direction delay of the delay element Q of the λ / 4 section 42, and RethZB is the thickness direction delay of the delay element ZB of the λ / 4 section 42.

[0143] In Equation (B), when the value of the ρ coefficient is greater than -0.06 and less than -0.02, the value of the Nz coefficient of λ / 4 is greater than -0.43 and less than 0.87.

[0144] In Equation (B), when the value of the coefficient of ρ is greater than -0.02 and less than 0, the value of the coefficient of Nz of λ / 4 is greater than -0.25 and less than 0.96.

[0145] In Equation (B), when the value of the coefficient of ρ is greater than 0 and less than 0.04, the value of the coefficient of Nz of λ / 4 is greater than -0.16 and less than 1.14.

[0146] In Equation (B), when the value of the coefficient of ρ is greater than 0.04 and less than 0.08, the value of the coefficient of Nz of λ / 4 is greater than 0.02 and less than 1.32.

[0147] The relationship between the Nz coefficient and the ρ coefficient of λ / 4 is more preferably shown in Equation (D).

[0148] 4.5ρ-0.035≤Nz≤4.5ρ+0.690···(D)

[0149] In Equation (D), when the value of the ρ coefficient is greater than or equal to -0.06 and less than or equal to -0.02, the value of the Nz coefficient of λ / 4 is greater than or equal to -0.31 and less than or equal to 0.60.

[0150] In Equation (D), when the value of the coefficient of ρ is greater than or equal to -0.02 and less than 0, the value of the coefficient of Nz of λ / 4 is greater than or equal to -0.13 and less than 0.69.

[0151] In Equation (D), when the value of the coefficient of ρ is greater than 0 and less than 0.04, the value of the coefficient of Nz of λ / 4 is greater than -0.04 and less than 0.87.

[0152] In Equation (D), when the value of the coefficient of ρ is greater than or equal to 0.04 and less than or equal to 0.08, the value of the coefficient of Nz of λ / 4 is greater than or equal to 0.15 and less than or equal to 1.05.

[0153] The components constituting the linear polarizer 30, the optical laminate 40, and the display device 100 (including the delay film element Q, the delay film element ZA, and the delay film element ZB) can be laminated, for example, using an adhesive layer (not shown). When the image display layer 10 includes electrodes provided with an organic EL display element, the organic EL display element and the optical laminate 40 can be laminated using an adhesive layer.

[0154] The adhesive layer can be composed of an adhesive composition with resins such as (meth)acrylic, rubber, urethane, ester, silicone, and polyvinyl ether as the main components. Among these, adhesive compositions using (meth)acrylic resins, which exhibit excellent transparency, weather resistance, and heat resistance, as the base polymer are suitable. The adhesive composition can be of the active energy radiation curing type or the thermosetting type. The thickness of the adhesive layer is typically 3 μm to 30 μm, preferably 3 μm to 25 μm.

[0155] The (meth)acrylic resin (base polymer) used in the adhesive composition is, for example, a polymer or copolymer with one or more (meth)acrylate monomers such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. It is preferable to copolymerize the polar monomer with the base polymer. Examples of polar monomers include, for example, (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, and glycidyl (meth)acrylate, which have carboxyl, hydroxyl, amide, amino, or epoxy groups.

[0156] The adhesive composition may contain only the aforementioned base polymer, but typically also contains a crosslinking agent. Examples of crosslinking agents include crosslinking agents that are divalent or higher metal ions forming a carboxylic acid metal salt with a carboxyl group; crosslinking agents that are polyamine compounds forming an amide bond with a carboxyl group; crosslinking agents that are polyepoxide compounds or polyols forming an ester bond with a carboxyl group; and crosslinking agents that are polyisocyanate compounds forming an amide bond with a carboxyl group. Among these, polyisocyanate compounds are preferred.

[0157] [Manufacturing method of elliptic polarizing plate and display device]

[0158] The elliptic polarizer 20 is manufactured by laminating an optical laminate 40, comprising a λ / 2 portion 41 and a λ / 4 portion 42, with a polarizer 31 using an adhesive layer. For example, as... Figure 1 As shown, in the case of a linear polarizer 30 with protective films 32 laminated on both sides of a polarizer 31, the linear polarizer 30 is obtained by manufacturing a polarizer 31 and laminating protective films 32 on both sides of the polarizer 31. Then, an adhesive layer formed on a release film is laminated on the protective film 32 opposite to the optical laminate 40. The release film on the adhesive layer is peeled off, and the polarizer 31 is bonded to separately manufactured λ / 2 portions 41 and λ / 4 portions 42 by means of the exposed adhesive layer, thereby obtaining an elliptical polarizer 20. By laminating this elliptical polarizer 20, for example, on the image display layer 10 by means of an adhesive layer, a display device 100 can be obtained.

[0159] The display device 100 satisfies equations (A) and (B). In this case, the λ / 4 portion 42 of the elliptic polarizer 20 is designed with respect to the light reflectivity in the direction of the tilt angle 45° of the image display layer 10. Therefore, even when the display device 100 is tilted, external light reflection can be prevented, and good display performance can be achieved. In the configuration of the display device 100, the aforementioned good display performance can be achieved throughout the entire visible area.

[0160] This invention is not limited to the embodiments described above, and is intended to include all modifications within the scope and meaning of the claims.

[0161] Example

[0162] The present invention will now be specifically described through embodiments. Unless otherwise specified, "%" and "parts" in the following description refer to mass percentage and mass parts, respectively. The present invention is not limited to the following embodiments. In the following description, the positive C-plate that can be used in both delay film elements ZA and ZB is sometimes referred to as delay film element Z.

[0163] [Determination Method]

[0164] • Methods for measuring membrane thickness

[0165] The thickness of the membrane was measured using a contact thickness gauge ("MH-15M", "Counter TC101", "MS-5C", manufactured by Nikon Corporation).

[0166] • Methods for determining delay

[0167] The thickness retardation of the λ / 2 and λ / 4 portions, as well as the in-plane retardation of the λ / 2, λ / 4 portions and the elliptic polarizer, were measured using a retardation measuring device (“KOBRA-WPR”, manufactured by Oji Measurement Equipment Co., Ltd.).

[0168] Methods for determining refractive index

[0169] The refractive index of films, layers, etc. was determined using a spectroscopic ellipsometer (“M-2000”, manufactured by JAWoollam).

[0170] • Visibility correction and hue calculation methods

[0171] The visibility-corrected single-unit transmittance Ty, single-unit transmittance hue a, single-unit transmittance hue b, and visibility-corrected polarization degree Py, as well as the visibility-corrected reflectance Ry10 and visibility-corrected reflectance Ry45, described later, are calculated using their respective spectral characteristics, namely single-unit spectral transmittance T, spectral polarization degree P, spectral reflectance R, color matching function, and standard light source.

[0172] The visibility correction value is obtained by dividing the tristimulus value Y of the corresponding spectroscopic 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 spectroscopic spectrum (see "Introduction to Color Engineering," by Hiroyuki Shinoda and Ichiro Fujieda, published by Morikita, pp. 106-107, 2007). The color matching function uses the recommendations of the International Commission on Illumination (CIE) (1931). The standard illuminant uses D65 (ISO 10526:1999 / CIES005 / E-1998).

[0173] Methods for determining the degree of polarization P, single-unit spectral transmittance T, and single-unit transmission hues a and b of a polarizer.

[0174] The transmittance along the transmission axis and the transmittance along the absorption axis of the polarizer were measured using a UV-Vis spectrophotometer (“V7100”, manufactured by Nippon Spectrophotometer Co., Ltd.), and the degree of polarization P, the transmittance of a single element T, the transmittance hue a, and the transmittance hue b of the single element were calculated.

[0175] The single-cell spectral transmittance T is the average of the spectral transmittance along the transmission axis and the spectral transmittance along the absorption axis.

[0176] The degree of spectral polarization P is obtained by dividing the difference between the spectral transmittance along the transmission axis and the spectral transmittance along the absorption axis by the sum of the spectral transmittance along the transmission axis and the spectral transmittance along the absorption axis.

[0177] The spectral transmittance along the transmission axis is the transmittance of linearly polarized light that vibrates parallel to the transmission axis of the polarizer at each wavelength.

[0178] The absorption axis spectral transmittance is the transmittance of linearly polarized light that vibrates parallel to the absorption axis of the polarizer at each wavelength.

[0179] The absorption axis of the polarizer is aligned with the stretching direction of the polyvinyl alcohol.

[0180] • Measurement of reflectance and reflected hue

[0181] The spectral reflectance R was measured using the SCI mode of a display measurement system (“DMS803”, Instrument Systems) with an ellipsoidal polarizer positioned on the light-reflecting layer, and the visibility-corrected reflectance Ry was calculated.

[0182] The spectral reflectance R for tilt angles θ = 10° and θ = 45° (the tilt angle will be described later) was measured with the reflectance of the light-reflecting layer without an ellipsoidal polarizer set to 100%. The measurement wavelengths ranged from 380 nm to 780 nm per 1 nm.

[0183] The direction perpendicular to the plane (hereinafter referred to as "plane p" for ease of explanation) subtended by the axis parallel to the refractive index nx and the axis parallel to the refractive index ny is (equivalent to) Figure 3 The direction D1 shown is set as the tilt angle θ = 0°. Taking the in-plane angle φ in plane p as the tilt center axis, the spectral reflectivity R of the tilt angle θ is determined in steps of 5° for tilt angles of 10° and 45°. Plane p is equivalent to the surface of delay film elements Q, ZA, ZB, the surface of ellipsoidal polarizer, etc., and is also a plane parallel to the image display surface 10a.

[0184] 0°≤φ<360°···(15)

[0185] The average value of the in-plane angular region of the visibility-corrected reflectance at an tilt angle of θ = 10° (the angular range shown in Equation (15), the same below) is set as Ry10. The average value of the in-plane angular region of the visibility-corrected reflectance at an tilt angle of θ = 45° is set as Ry45.

[0186] [Preparation of compositions for horizontally oriented film formation]

[0187] Five parts of a photo-aligning material with the following structure (weight average molecular weight: 30,000) and 95 parts of cyclopentanone (solvent) were mixed. The resulting mixture was stirred at 80°C for 1 hour to obtain a composition for forming horizontally aligned films.

[0188] [Chemical Formula 1]

[0189]

[0190] [Preparation of compositions for vertically oriented film formation]

[0191] Made by Nissan Chemical Industries, Ltd., SUNEVER SE610.

[0192] [Preparation of the composition for forming the Q-type delay element]

[0193] To form the retardation film element Q (inverse dispersion positive A plate), polymeric liquid crystal compound A and polymeric liquid crystal compound B were used. Polymeric liquid crystal compound A was manufactured according to the method described in Japanese Patent Application Publication No. 2010-31223. Polymeric liquid crystal compound B was manufactured according to the method described in Japanese Patent Application Publication No. 2009-173893. Their respective molecular structures are shown below.

[0194] [Polymerizable liquid crystal compound A]

[0195] [Chemical Formula 2]

[0196]

[0197] [Polymerizable liquid crystal compound B]

[0198] [Chemical Formula 3]

[0199]

[0200] Polymerizable liquid crystal compound A and polymerizable liquid crystal compound B were mixed at a mass ratio of 90:10. 1.0 part of a leveling agent (“Megaface F-556”, manufactured by DIC Corporation) and 6 parts of a polymerization initiator 2-dimethylamino-2-benzyl-1-(4-morpholinophenyl)butane-1-one (“Omnirad 369”, manufactured by IGM Resins BV) were added per 100 parts of the resulting mixture. Furthermore, N-methyl-2-pyrrolidone (NMP) was added at a solids concentration of 13%, and the mixture was stirred at 80°C for 1 hour to obtain a composition for forming a retardation film element Q.

[0201] [Preparation of the composition for forming a delay film element Z]

[0202] To form a retardation film element Z (positive C plate), a composition was prepared according to the following steps: 0.1 parts of F-556 as a leveling agent and 3 parts of Omnirad 369 as a polymerization initiator were added relative to 100 parts of a polymerizable liquid crystal compound (“Paliocolor LC242”, manufactured by BASF). Cyclopentanone was added at a solids concentration of 13% to obtain the composition for forming the retardation film element Z.

[0203] [Making of Polarizing Filters]

[0204] A polyvinyl alcohol (PVA) film with an average degree of polymerization of approximately 2400, a saponification degree of ≥99.9 mol%, 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 of iodine / potassium iodide / water at 30°C for iodine staining (iodine staining step). The iodine-stained PVA film was then immersed in an aqueous solution of potassium iodide / boric acid / water at 56.5°C for boric acid treatment (boric acid treatment step). The boric acid-treated PVA film was washed with pure water at 8°C and dried at 65°C to obtain a polarizing film with iodine adsorption oriented to polyvinyl alcohol. The stretching of the PVA film was performed during the iodine staining and boric acid treatment steps. The total stretching ratio of the PVA film was 5.3 times. The thickness of the obtained polarizing film was 10 μm.

[0205] A polarizing film was bonded to a saponified triacetyl cellulose (TAC) film (KC4UYTAC, 40 μm thick, manufactured by Konica Minolta, Ltd.) using a water-based adhesive and a clamping roller. The resulting composite was dried at 60°C for 2 minutes while maintaining a tension of 430 N / m, resulting in a polarizing film with a TAC film as a protective film on one side. It should be noted that the water-based adhesive was prepared by adding 3 parts of carboxyl-modified polyvinyl alcohol (Kuraray, Ltd., "KurarayPOVAL KL318") and 1.5 parts of water-soluble polyamide epoxy resin (Sumirez Resin 650, 30% solids concentration aqueous solution, manufactured by Taoka Chemical Industry Co., Ltd.) to 100 parts of water.

[0206] The optical properties of the obtained polarizer were measured. The visibility-corrected single-cell transmittance Ty of the obtained polarizer was 41.9%, the visibility-corrected polarization degree Py was 99.962%, the single-cell transmission hue a was -1.5, and the single-cell transmission hue b was 3.6.

[0207] [Fabrication of delay film element Q (inverse dispersion positive A plate)]

[0208] Corona treatment was performed on a cyclic olefin resin (COP) film (ZF-14-50) manufactured by ZEON Corporation of Japan. The corona treatment was performed using a TEC-4AX manufactured by Ushio Electric Co., Ltd. The corona treatment was performed once at an output power of 0.78 kW and a processing speed of 10 m / min. A horizontally oriented film-forming composition was coated onto the COP film using a bar coater and dried at 80°C for 1 minute. For the coated film, a polarized UV irradiation device (“SPOT CURE SP-9”, manufactured by Ushio Electric Co., Ltd.) was used, with a cumulative light intensity of 100 mJ / cm at a wavelength of 313 nm. 2The method involves polarized UV exposure at an axial angle of 45°. The resulting horizontally oriented film has a thickness of 100 nm.

[0209] Next, the composition for forming the retardation film element Q (anti-dispersion positive A plate) was coated onto the horizontally aligned film using a bar coater and dried at 120°C for 1 minute. The coated film was then irradiated with ultraviolet light (cumulative light intensity at 365nm wavelength: 500mJ / cm² under nitrogen atmosphere) using a high-pressure mercury lamp (“Unicure VB-15201BY-A”, manufactured by Ushio Electric Co., Ltd.). 2 This forms the delay element Q. The film thickness of the delay element Q is 2.3 μm.

[0210] A film consisting of a COP film, an alignment film, and a horizontally aligned liquid crystal cured film was bonded to glass on the retardation element Q using an adhesive layer. The COP film was then peeled off to obtain a sample for retardation measurement. The in-plane retardation ReoQ(λ) of the retardation element Q at various wavelengths was measured, and the results are as follows:

[0211] ReoQ(450) = 121nm,

[0212] ReoQ(550) = 142nm,

[0213] ReoQ(650) = 146nm,

[0214] ReoQ(450) / ReoQ(550)=0.85,

[0215] ReoQ(650) / ReoQ(550)=1.03,

[0216] The delay element Q exhibits inverse wavelength dispersion.

[0217] The retardation element Q is a positive A-plate satisfying the relationship nx>ny≈nz. It should be noted that the thickness-direction retardation RethQ(λ) at various wavelengths was measured, and the results are as follows:

[0218] RethQ(450) = 61nm,

[0219] RethQ(550) = 72nm,

[0220] RethQ(650) = 73nm.

[0221] [Fabrication of delay film element Z (positive C-plate)]

[0222] The COP film was subjected to corona treatment. The corona treatment conditions were the same as described above. A vertically oriented film-forming composition was coated onto the COP film using a bar coater, and dried at 80°C for 1 minute to obtain a vertically oriented film. The thickness of the obtained vertically oriented film was 50 nm.

[0223] The composition for Z-forming of the delay film element was coated onto a vertically aligned film using a bar coater and dried at 90°C for 120 seconds. The coated film was then irradiated with ultraviolet light (cumulative light intensity at 365nm wavelength: 500mJ / cm²) under a nitrogen atmosphere using a high-pressure mercury lamp (“UnicureVB-15201BY-A”, manufactured by Ushio Electric Co., Ltd.). 2 Thus, a retardation element Z is formed. A film consisting of a COP film, a vertically aligned film, and retardation element Z is obtained. The film thickness of retardation element Z is 0.6 μm.

[0224] An adhesive layer was laminated onto the retardation element Z. Using this adhesive layer, the film formed by the COP film, the alignment film, and the retardation element Z was bonded to the glass. The COP film was peeled off to obtain a sample for retardation measurement. The thickness retardation RethZ(550) at a wavelength of 550 nm of the retardation element Z was measured, and the results are as follows:

[0225] RethZ(550) = -70nm.

[0226] The in-plane retardation ReoZ(550) of the retardation element Z at a wavelength of 550 nm was measured, and the results are as follows:

[0227] ReoZ(550) = 0.1 nm,

[0228] The in-plane delay of the delay element Z is essentially 0.

[0229] The delay element Z is a positive C-plate that satisfies the relationship nx≈ny<nz.

[0230] <Making a Negative C-Pad>

[0231] Two 60 μm thick TAC films (“FUJITAC TG60UL”, manufactured by FUJIFILM) were bonded together using an adhesive layer to obtain a TAC film laminate consisting of a TAC film, an adhesive layer, and another TAC film. Next, the TAC film laminate was attached to glass using the adhesive layer to obtain a sample for measuring the retardation. The thickness-direction retardation Reth(550) at a wavelength of 550 nm was measured, and the results are as follows:

[0232] Reth(550) = +40nm.

[0233] The TAC film stack is a negative C-plate that satisfies the relationship nx≈ny>nz. Therefore, the in-plane retardation of the TAC film stack is essentially 0.

[0234] [Delayed-time laminate 1]

[0235] The vertically oriented film formed on the COP film and the retardation element Z in the retardation element Z are bonded to the horizontally oriented film formed on the COP film and the retardation element Q in the retardation element Q in the retardation element Z by adhesive. Then, the COP film on the side of the retardation element Z is peeled off, resulting in a film in which the COP film and the retardation film laminate 1 are sequentially stacked. The arrangement relationship of the retardation element Q and the retardation element Z in the retardation film laminate 1 is as follows. The retardation element Z in the retardation film laminate 1 is a positive C-plate. To indicate the arrangement of the retardation element Q and the retardation element Z relative to the COP film, the COP film is indicated by parentheses in the following arrangement relationship. Therefore, the following notation indicates that the retardation element Z and the retardation element Q are arranged in the order of retardation element Q and retardation element Z from the COP film side. The same notation is sometimes used for the arrangement relationship between elements (or between layers).

[0236] (COP membrane) / Q / Z

[0237] [Delayed-time laminate 2]

[0238] The vertically oriented film formed on the COP film and the retardation element Z in the retardation element Z are bonded to the horizontally oriented film formed on the COP film and the retardation element Q in the retardation element Q using an adhesive. Then, the COP film on the side of the retardation element Q is peeled off, resulting in a film in which the COP film and the retardation film laminate 2 are sequentially stacked. The arrangement relationship between the retardation element Q and the retardation element Z in the retardation film laminate 2 is as follows. The retardation element Z in the retardation film laminate 2 is a positive C-plate.

[0239] (COP membrane) / Z / Q

[0240] [Delayed-time laminate 3]

[0241] The aforementioned TAC film laminate is bonded to the horizontally oriented film formed on the COP film and the retardation element Q in the retardation element Q using an adhesive. Then, the COP film on the side of the retardation element Q is peeled off to obtain the retardation film laminate 3. The TAC film laminate is a negative C-plate. Therefore, the retardation film laminate 3 is a laminate of the retardation element ZB, which serves as the negative C-plate, and the retardation element Q.

[0242] <Elliptical Polarizer EP1>

[0243] ·λ / 2 parts

[0244] Two films, formed from a COP film and a retarder laminate 1, are prepared by cutting them such that the slow axes of the two retarder elements Q are in the same direction while the Z-sides of the retarder elements are tightly bonded together. The Z-sides of the retarder elements are then bonded together with an adhesive. The COP film on the Q-side of one film is then peeled off, resulting in a film sequentially stacked with a COP film and a λ / 2 section (retarder element Q, adhesive layer, retarder element Z, adhesive layer, retarder element Z, adhesive layer, and retarder element Q). It should be noted that the λ / 2 section (retarder element Q, adhesive layer, retarder element Z, adhesive layer, retarder element Z, adhesive layer, and retarder element Q) refers to the λ / 2 section in which the retarder element Q, adhesive layer, retarder element Z, adhesive layer, retarder element Z, adhesive layer, and retarder element Q are sequentially arranged. The same notation is sometimes used for other components (e.g., the λ / 4 section). The retardation element Z in the λ / 2 section is the same retardation element Z in the retardation layer 1, and is therefore a positive C-plate. Therefore, the retardation element Z in the λ / 2 section is retardation element ZA, and thus, the retardation element Z of the elliptic polarizer EP1 will be referred to as retardation element ZA below.

[0245] ·λ / 4 parts

[0246] The delay film stack 2, which has a delay film element Z manufactured with a thickness direction delay of RethZ(550) = -70nm, is designated as the λ / 4 part. Hereinafter, when the delay film stack 2 is used in the λ / 4 part, the delay film element Z of the delay film stack 2 is referred to as the delay film element ZB, and the thickness direction delay of 550nm is referred to as RethZB(550).

[0247] Elliptic polarizer EP1

[0248] A polarizer with a TAC film stacked on top of each other is bonded to the side opposite to the TAC film, and to the Q side of the retardation film element formed by the COP film and the λ / 2 portion, using an adhesive layer. The COP film is then peeled off to obtain a laminate. At this point, the angle between the transmission axis of the polarizer and the slow axis of the λ / 2 portion is 15°. Next, the retardation film element Q side of the laminated structure is bonded to the Q side of the retardation film element formed by the COP film and the λ / 4 portion, using an adhesive layer. The COP film is then peeled off to obtain an elliptical polarizer EP1. At this point, the angle between the transmission axis of the polarizer and the slow axis of the λ / 4 portion is 75°. The Nz coefficient of both the λ / 2 and λ / 4 portions is 0.51.

[0249] The elliptical polarizer EP1 has a layer structure consisting of a TAC film, a polarizer, an adhesive layer, a λ / 2 section (delay film element Q, adhesive layer, delay film element ZA, adhesive layer, delay film element ZA, adhesive layer, delay film element Q), an adhesive layer, and a λ / 4 section (delay film element Q, adhesive layer, delay film element ZB).

[0250] <Elliptical Polarizer EP2>

[0251] The retardation film stack 2, having a retardation film element ZB (retardation film element Z) obtained by adjusting the thickness direction retardation to RethZB(550) = -70nm, is taken as the λ / 4 part. Otherwise, the same operation as with the ellipsoidal polarizer EP1 is performed to obtain the ellipsoidal polarizer EP2. The N of the λ / 4 part... Z The coefficient is 0.79.

[0252] <Elliptical Polarizing Plate EP3>

[0253] The retardation film stack 2, which has a retardation film element ZB (retardation film element Z) obtained by adjusting the thickness direction retardation to RethZB(550) = -100nm, is taken as the λ / 4 part. Otherwise, the same operation as the ellipsoidal polarizer EP1 is performed to obtain the ellipsoidal polarizer EP3. The Nz coefficient of the λ / 4 part is 0.30.

[0254] <Elliptical Polarizer EP4>

[0255] The retardation film stack 2, which has a retardation film element ZB (retardation film element Z) obtained by adjusting the thickness direction retardation to RethZB(550) = -170nm, is taken as the λ / 4 part. Otherwise, the same operation as the ellipsoidal polarizer EP1 is performed to obtain the ellipsoidal polarizer EP4. The Nz coefficient of the λ / 4 part is -0.20.

[0256] <Elliptical Polarizing Plate EP5>

[0257] The retardation film stack 2, which has a retardation film element ZB (retardation film element Z) obtained by adjusting the thickness direction retardation to RethZB(550) = -190nm, is taken as the λ / 4 part. Otherwise, the same operation as the ellipsoidal polarizer EP1 is performed to obtain the ellipsoidal polarizer EP5. The Nz coefficient of the λ / 4 part is -0.34.

[0258] <Elliptical Polarizing Plate EP6>

[0259] Except for omitting the delay element ZB, the same operation as ellipsoidal polarizer EP1 was used to obtain ellipsoidal polarizer EP6. The Nz coefficient of the λ / 4 part is 1.00.

[0260] <Elliptical Polarizer EP7>

[0261] The retardation film stack 2, which has a retardation film element ZB (retardation film element Z) obtained by adjusting the thickness direction retardation to RethZB(550) = -40nm, is taken as the λ / 4 part. Otherwise, the same operation as the ellipsoidal polarizer EP1 is performed to obtain the ellipsoidal polarizer EP7. The Nz coefficient of the λ / 4 part is 0.72.

[0262] <Elliptic Polarizer EP8>

[0263] The retardation film stack 2, which has a retardation film element ZB (retardation film element Z) obtained by adjusting the thickness direction retardation to RethZB(550) = -140nm, is taken as the λ / 4 part. Otherwise, the same operation as the ellipsoidal polarizer EP1 is performed to obtain the ellipsoidal polarizer EP8. The Nz coefficient of the λ / 4 part is 0.01.

[0264] <Elliptic Polarizer EP9>

[0265] The retardation film stack 2, which has a retardation film element ZB (retardation film element Z) obtained by adjusting the thickness direction retardation to RethZB(550) = -160nm, is taken as the λ / 4 part. Otherwise, the same operation as the ellipsoidal polarizer EP1 is performed to obtain the ellipsoidal polarizer EP9. The Nz coefficient of the λ / 4 part is -0.13.

[0266] <Elliptical Polarizing Plate EP10>

[0267] A polarizer with a TAC film stacked on top of itself is bonded to the Q side of a retardation film element formed by a COP film and a λ / 2 portion using an adhesive layer. The COP film is then peeled off to obtain a laminate. At this point, the angle between the transmission axis of the polarizer and the slow axis of the λ / 2 portion is 15°. Next, the Q side of the retardation film element of the above-mentioned laminate is bonded to the Q side of the retardation film element of the retardation film laminate 3 using an adhesive layer to obtain an elliptic polarizer EP10. At this point, the angle between the transmission axis of the polarizer and the slow axis of the λ / 4 portion is 75°. The Nz coefficient of the λ / 2 portion is 0.51, and the Nz coefficient of the λ / 4 portion is 1.28.

[0268] <Elliptical Polarizing Plate EP11>

[0269] The retardation film stack 2, which has a retardation film element ZB (retardation film element Z) obtained by adjusting the thickness direction retardation to RethZB(550) = -120nm, is taken as the λ / 4 part. Otherwise, the same operation as the ellipsoidal polarizer EP1 is performed to obtain the ellipsoidal polarizer EP11. The Nz coefficient of the λ / 4 part is 0.15.

[0270] [Preparation of the light-reflecting layer]

[0271] The following three types of light-reflecting layers were used.

[0272] • Light reflective layer A: This is used after disassembling a commercially available Samsung Electronics OLED display device and installing it in a smartphone, the GALAXY Tab S8.4 SC-03G, and removing the cover glass and elliptical polarizing plate.

[0273] • Light reflective layer B: This is used after disassembling a commercially available Huawei Technologies OLED display device and installing it in a smartphone, such as the Mate 30 Pro, and removing the cover glass and elliptical polarizer.

[0274] • Light reflective layer C: This is used after disassembling a commercially available Apple Inc. OLED display device and installing it in a smartphone, the iPhone (registered trademark) X, and removing the cover glass and elliptical polarizer.

[0275] The projection surface of each light-reflecting layer at a tilt angle of 45° (using Figure 3 The in-plane retardation ReM45 of each reflective layer at a wavelength of 550 nm in the projection plane (VP) is shown in Table 1.

[0276] [Table 1]

[0277] Light reflector ReM45(nm) A -5.4 B 1.5 C 9.8

[0278] <Delay of elliptic polarizers EP1~EP5, EP7~EP11>

[0279] An adhesive layer was laminated onto the retardation element ZB of each of the ellipsoidal polarizers EP1–EP5 and EP7–EP11. The ellipsoidal polarizers EP1–EP5 and EP7–EP11 were then bonded to glass using this adhesive layer, resulting in samples for retardation measurement. The in-plane retardation Reo(λ) at each wavelength of the ellipsoidal polarizers EP1–EP5 and EP7–EP11 was measured, and the results were as follows:

[0280] Reo(450) = 112nm,

[0281] Reo(550) = 138nm,

[0282] Reo(650) = 162nm,

[0283] Reo(450) / Reo(550)=0.81,

[0284] Reo(650) / Reo(550)=1.17.

[0285] <Delay of Ellipsoidal Polarizer EP6>

[0286] An adhesive layer was laminated onto the retardation element Q of the ellipsoidal polarizer EP6, and the ellipsoidal polarizer EP6 was then bonded to glass using this adhesive layer, resulting in a sample for retardation measurement. The in-plane retardation Reo(λ) at various wavelengths was measured, and the results are as follows:

[0287] Reo(450) = 112nm,

[0288] Reo(550) = 138nm,

[0289] Reo(650) = 162nm,

[0290] Reo(450) / Reo(550)=0.81,

[0291] Reo(650) / Reo(550)=1.17.

[0292] <Visual verification of display performance>

[0293] When combining the prepared ellipsoidal polarizers EP1 to EP11 with light-reflecting layers A, B, and C, the display performance of the ellipsoidal polarizers EP1 to EP11 is visually confirmed as follows.

[0294] (Visual confirmation method)

[0295] The experiment was conducted in the field on a sunny day by five observers. Observations were made at an in-plane angle of 10° and 45°, covering the entire range of in-plane angles shown in Equation (15). If four or more of the five observers did not perceive any iridescent reflected light from the light-reflecting layer, the observation was evaluated as having good light-reflecting performance. Otherwise, the observation was evaluated as having impaired display performance.

[0296] <Reflectivity at a tilt angle of 10° when using light-reflecting layer A>

[0297] For samples obtained by bonding elliptic polarizers EP1 to EP5 to the light-reflecting layer A with adhesive, the visibility-corrected reflectivity at a tilt angle θ = 10° was measured and calculated, and the result was Ry10 = 4.7%. In addition, observation of reflected external light at a tilt angle θ = 10° confirmed that good display performance was achieved in all cases, effectively preventing reflected light.

[0298] <Reflectivity at a tilt angle of 10° when using light-reflecting layer B>

[0299] For samples obtained by bonding elliptic polarizers EP1, EP6-EP9 to the light-reflecting layer B with adhesive, the visibility-corrected reflectivity at a tilt angle θ = 10° was measured and calculated, and the result was Ry10 = 4.6%. Furthermore, visual observation of reflected external light at a tilt angle θ = 10° confirmed that, in all cases, good display performance was achieved by effectively preventing reflected light.

[0300] <Reflectivity at a tilt angle of 10° when using light-reflecting layer C>

[0301] For samples obtained by bonding elliptical polarizers EP2, EP3, EP6, EP10, and EP11 to the light-reflecting layer C using adhesive, the visibility-corrected reflectivity at a tilt angle θ = 10° was measured and calculated, with a result of Ry10 = 4.5% for all samples. Furthermore, visual observation of reflected external light at a tilt angle θ = 10° confirmed that, in all cases, good display performance was achieved by effectively preventing reflected light.

[0302] (1) Examples 1-3

[0303] For samples obtained by bonding elliptical polarizers EP1, EP3, and EP4 to the light-reflecting layer A using adhesive, the visibility-corrected reflectance Ry45 at a tilt angle θ = 45° was measured and calculated. The calculation results are as follows: Figure 4 (See Table 2). Furthermore, observation of external light reflection from the light-reflecting layer under sunlight at a tilt angle θ = 45° confirmed that, in both cases, it effectively prevented reflected light and provided good display performance.

[0304] (2) Examples 4-6

[0305] For samples obtained by bonding elliptical polarizers EP7, EP1, and EP8 to the light-reflecting layer B using adhesive, the visibility-corrected reflectance Ry45 at a tilt angle θ = 45° was measured and calculated. The calculation results are as follows: Figure 4 (See Table 2). Furthermore, observation of external light reflection from the light-reflecting layer under sunlight at a tilt angle θ = 45° confirmed that, in both cases, it effectively prevented reflected light and provided good display performance.

[0306] (3) Examples 7-9

[0307] For samples obtained by bonding elliptical polarizers EP6, EP2, and EP3 to the light-reflecting layer C using adhesive, the visibility-corrected reflectance Ry45 at a tilt angle θ = 45° was measured and calculated. The calculation results are as follows: Figure 4(See Table 2). Furthermore, observation of external light reflection from the light-reflecting layer under sunlight at a tilt angle θ = 45° confirmed that, in both cases, it effectively prevented reflected light and provided good display performance.

[0308] (4) Comparison of Examples 1 and 2

[0309] For samples obtained by bonding elliptical polarizers EP2 and EP5 to the light-reflecting layer A using adhesive, the visibility-corrected reflectance Ry45 at a tilt angle θ = 45° was measured and calculated. The calculation results are as follows: Figure 4 (See Table 2). Furthermore, observation of external light reflection from the light-reflecting layer under sunlight at a tilt angle θ = 45° confirmed that strong iridescent reflected light was observed in both cases, impairing display performance.

[0310] (5) Comparison of Examples 3 and 4

[0311] For samples obtained by bonding elliptical polarizers EP6 and EP9 to the light-reflecting layer B using adhesive, the visibility-corrected reflectance Ry45 at a tilt angle θ = 45° was measured and calculated. The calculation results are as follows: Figure 4 (See Table 2). Furthermore, observation of external light reflection from the light-reflecting layer under sunlight at a tilt angle θ = 45° confirmed that strong iridescent reflected light was observed in both cases, impairing display performance.

[0312] (6) Comparison of Examples 5 and 6

[0313] For samples obtained by bonding elliptical polarizers EP10 and EP11 to the light-reflecting layer C using adhesive, the visibility-corrected reflectance Ry45 at a tilt angle θ = 45° was measured and calculated. The calculation results are as follows: Figure 4 (See Table 2). Furthermore, observation of external light reflection from the light-reflecting layer under sunlight at a tilt angle θ = 45° confirmed that strong iridescent reflected light was observed in both cases, impairing display performance.

[0314] Figure 4 Table 2 shows the results of Examples 1-9 and Comparative Examples 1-6.

[0315] exist Figure 4 In the chart (Table 2), the "Type" column of "Light Reflecting Layer" corresponds to light reflecting layer A, light reflecting layer B, and light reflecting layer C.

[0316] The ρ coefficient in the column of "light reflection layer" is the value calculated by substituting the ReM45 of the light reflection layers A, B, and C shown in Table 1 and the in-plane delay ReoQ of the delay element Q of the λ / 4 part of the elliptic polarizer EP1 to EP11 combined with the light reflection layers A, B, and C into equation (A).

[0317] The “Nz coefficient” is a value calculated by substituting the in-plane delay and thickness direction delay of the delay elements Q and ZB in the λ / 4 section into equation (C).

[0318] In the "45° tilt angle for visual inspection" column, "〇" indicates "good display performance with good prevention of reflected light", while "×" as described later indicates "rainbow-colored reflected light was observed, which impaired display performance".

[0319] according to Figure 4 The results shown in Table 2 indicate that in Examples 1-9, the evaluation for "viewing at a tilt angle of 45°" was "0". That is, in Examples 1-9, even when the display device obtained by stacking an elliptical polarizer on the light-reflecting layer was viewed under sunlight at an angle, the external light reflection of the light-reflecting layer was well prevented, resulting in good display performance. On the other hand, in Comparative Examples 1-6, the evaluation for "viewing at a tilt angle of 45°" was "×". That is, in Comparative Examples 1-6, when the display device obtained by stacking an elliptical polarizer on the light-reflecting layer was viewed under sunlight at an angle, iridescent reflected light was observed, and the display performance was impaired. It should be noted that sunlight encompasses the entire visible area; therefore, the above evaluation of display performance is equivalent to the evaluation of the entire visible area. Figure 4 Table 2 shows the results for a tilt angle of 45°, but as mentioned above, the results are the same for a tilt angle of 10° as for a tilt angle of 45°.

[0320] Figure 5 It is relative to Figure 4 The ρ coefficients in Table 2 are used to plot the Nz coefficients. Figure 5 The horizontal axis represents the ρ coefficient, and the vertical axis represents the Nz coefficient. Figure 5 Lines L1, L2, L3, L4, and L5 in the diagram are represented by the following formula.

[0321] L1: Nz = 4.5ρ + 0.955

[0322] L2: Nz = 4.5ρ - 0.160

[0323] L3: Nz = 4.5ρ + 0.690

[0324] L4: Nz = 4.5ρ - 0.035

[0325] L5: Nz = 4.5ρ + 0.5

[0326] according to Figure 5 The relationship between lines L1 to L4 and the plotting points of the embodiments and comparative examples is shown. In embodiments 1 to 9, the relationship between the Nz coefficient and the ρ coefficient of the λ / 4 portion satisfies equation (B). In comparative examples 1 to 6, the relationship between the Nz coefficient and the ρ coefficient of the λ / 4 portion does not satisfy equation (B). Therefore, it can be understood that by satisfying equation (B) in the relationship between the Nz coefficient and the ρ coefficient of the λ / 4 portion, even when observing external light reflection from the light-reflecting layer in a tilted display device state, good display performance that effectively prevents reflected light throughout the visible area can be obtained. Furthermore, according to... Figure 5 The relationship between the lines L1 to L4 shown and the plotting points of the embodiment and the comparative example can be understood. Preferably, the relationship between the Nz coefficient and the ρ coefficient of the λ / 4 part satisfies equation (D).

[0327] according to Figure 4 The results for Ry45 shown in Table 2 are understandable; Ry is preferably below 8.1%.

[0328] Explanation of reference numerals in the attached figures

[0329] 20…elliptical polarizer, 31…polarizer, 41…λ / 2 part, 42…λ / 4 part, 100…display device, Q…retardation element (first retardation element), ZA…(second retardation element), ZB…retardation element (third retardation element).

Claims

1. A display device comprising: Light-reflective image display layer; and An elliptical polarizing plate is stacked on the image display surface of the light-reflective image display layer. The elliptical polarizing plate has a polarizing plate, a λ / 2 section, and a λ / 4 section. The polarizer, the λ / 2 portion, and the λ / 4 portion are arranged in the following order from the light-reflective image display layer side: the λ / 4 portion, the λ / 2 portion, and the polarizer. The λ / 2 section is a stack of a first retardation element, a second retardation element, a third retardation element, and a fourth retardation element, arranged in the order of the first retardation element, the second retardation element, the third retardation element, and the fourth retardation element. The first delay element has inverse wavelength dispersion and is a positive A-plate that imparts an in-plane phase difference of approximately λ / 4 as the wavelength of 550 nm. The second delay element is a positive C-plate that imparts a phase difference in the thickness direction. When the in-plane retardation of the light-reflective image display layer at a wavelength of 550 nm in a projection plane with a tilt angle of 45° relative to the thickness direction of the light-reflective image display layer is set to ReM45, the in-plane retardation at a wavelength of 550 nm in the λ / 4 portion is set to ReoQ, the thickness direction retardation at a wavelength of 550 nm in the λ / 4 portion is set to RethQ, the ρ coefficient ρ of the light-reflective image display layer is expressed by equation (A), and the Nz coefficient Nz of the λ / 4 portion is expressed by equation (C), the Nz coefficient Nz of the λ / 4 portion and the ρ coefficient ρ satisfy the relationship shown in equation (B). ρ=ReM45 / ReoQ ···(A) Nz=(RethQ / ReoQ)+0.5···(C) 4.5ρ-0.160<Nz<4.5ρ+0.955···(B).

2. The display device according to claim 1, wherein The first delay element satisfies equation (i), and the second delay element satisfies equation (ii). nx>ny≈nz ···(i) nx≈ny<nz ···(ii) In equation (i), nx represents the principal refractive index in the direction parallel to the plane of the first retardation element within the first refractive index ellipsoid formed by the first retardation element; ny represents the refractive index in the direction parallel to the plane of the first retardation element and orthogonal to the direction of nx within the first refractive index ellipsoid; and nz represents the refractive index in the direction perpendicular to the plane of the first retardation element within the first refractive index ellipsoid. In equation (ii), nx represents the principal refractive index in the direction parallel to the plane of the second retardation element in the second refractive index ellipsoid formed by the second retardation element, ny represents the refractive index in the direction parallel to the plane of the second retardation element and orthogonal to the direction of nx in the second refractive index ellipsoid, and nz represents the refractive index in the direction perpendicular to the plane of the second retardation element in the second refractive index ellipsoid.

3. The display device according to claim 1 or 2, wherein The λ / 4 section is a stack formed by layering the third delay film element and the first delay film element from the side of the light-reflective image display layer in the order of the third delay film element and the first delay film element. The first retardation element in the λ / 4 section has inverse wavelength dispersion, which is a positive A-plate that imparts an in-plane phase difference of approximately λ / 4 as the wavelength of 550 nm. The third delay element is an element that imparts a phase difference in the thickness direction.

4. The display device according to claim 3, wherein, The third delay element is a positive or negative C-plate that imparts a phase difference in the thickness direction.

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