Phase delay membranes, phase delay membrane segments, phase delay membrane assemblies, and methods for manufacturing lens assemblies or display systems.
Patent Information
- Authority / Receiving Office
- VN · VN
- Patent Type
- Applications
- Current Assignee / Owner
- NITTO DENKO CORP
- Filing Date
- 2024-08-30
- Publication Date
- 2026-06-15
Smart Images
Figure VN1202603243_0
Abstract
Description
Method for manufacturing retardation film, retardation film piece, retardation film set, or lens part or display system
[0001] The present invention relates to a method for manufacturing a retardation film, a retardation film strip, a retardation film set, or a lens section or display system.
[0002] Image display devices, such as liquid crystal display devices and electroluminescence (EL) display devices (e.g., organic EL display devices), are rapidly becoming popular. In image display devices, optical components such as polarizing components and phase difference components are generally used to realize image display and improve image display performance (see, for example, Patent Document 1).
[0003] In recent years, new applications of image display devices have been developed. For example, goggles with displays (VR goggles) for realizing virtual reality (VR) have begun to be commercialized. Since the use of VR goggles in various situations is being considered, there is a demand for lighter weight, improved visibility, and the like.
[0004] Japanese Patent Application Laid-Open No. 2021-103286
[0005] While the weight reduction of the VR goggles can be achieved by, for example, thinning the lenses used in the VR goggles, there is also a need for the development of optical components suitable for display systems using thin lenses.
[0006] In view of the above, the main object of the present invention is to provide a retardation film, a retardation film piece, a retardation film set, or a method for manufacturing a lens portion or a display system that can effectively achieve weight reduction of VR goggles while improving visibility.
[0007] [1] According to one aspect of the present invention, there is provided a method for manufacturing a display system for displaying an image to a user, the display system including: a display element having a display surface that emits light representing an image forward via a polarizing member; a reflective polarizing member disposed in front of the display element and reflecting the light emitted from the display element; a first lens unit disposed on an optical path between the display element and the reflective polarizing member and having a curved main surface; a half mirror disposed between the display element and the first lens unit, which transmits the light emitted from the display element and reflects the light reflected by the reflective polarizing member toward the reflective polarizing member; and a first λ / 4 member disposed on an optical path between the half mirror and the reflective polarizing element, and a second λ / 4 member disposed on an optical path between the half mirror and the reflective polarizing element, the second λ / 4 member being a retardation film having an in-plane retardation Re(550) of 100 nm to 190 nm and an absolute value of a retardation change value RS of 2.0 or less (wherein the retardation change value RS is the slope of an approximation line of the in-plane retardation Re(550) of the retardation film measured in a state where tensions of 0 kg, 0.5 kg, 1 kg, 1.5 kg, and 2 kg are applied). [2] The manufacturing method of [1] above may include preparing two of the retardation films, integrating one of the retardation films with the display element as the first λ / 4 member, and integrating the other of the retardation films with the first lens portion as the second λ / 4 member.[3] According to another aspect of the present invention, there is provided a method for manufacturing a lens unit used in a display system that displays an image to a user, the lens unit including: a reflective polarizing element that reflects light that is emitted forward from a display surface of a display element that displays an image and that has passed through a polarizing element and a first λ / 4 element; a first lens unit that is arranged on an optical path between the display element and the reflective polarizing element and has a curved main surface; and a second lens unit that is arranged between the display element and the first lens unit and transmits light that is emitted from the display element and reflects light reflected by the reflective polarizing element toward the reflective polarizing element. and a second λ / 4 member disposed on an optical path between the half mirror and the reflective polarizing member, wherein the retardation film has an in-plane retardation Re(550) of 100 nm to 190 nm and an absolute value of a retardation change value RS of 2.0 or less (here, the retardation change value RS is the slope of an approximation line of the in-plane retardation Re(550) of the retardation film measured in states in which tensions of 0 kg, 0.5 kg, 1 kg, 1.5 kg, and 2 kg are applied), and the retardation film includes the second λ / 4 member and is integrated with the first lens unit. [4] According to yet another aspect of the present invention, there is provided a retardation film having an in-plane retardation Re(550) of 100 nm to 190 nm, an absolute value of a retardation change value RS of 2.0 or less, and the retardation change value RS being the slope of an approximate straight line of the in-plane retardation Re(550) of the retardation film measured under tensions of 0 kg, 0.5 kg, 1 kg, 1.5 kg, and 2 kg. [5] In the retardation film according to [4] above, the in-plane retardations Re(450), Re(550), and Re(650) may satisfy the following relationships (i) to (iii): (i) 100 nm < Re(550) < 160 nm, (ii) Re(450) / Re(550) < 1.1, (iii) Re(650) / Re(550) > 0.9. [6] The retardation film according to the above [4] or [5] may have a dimensional change rate of 0.02% or less before and after heat treatment at 85° C. for 500 hours. [7] The retardation film according to any one of the above [4] to [6] may have an absolute value of a difference in in-plane retardation Re(550) before and after heat treatment at 85° C. for 500 hours of 3.5 nm or less.[8] The retardation film according to any one of [4] to [7] above may be integrated with a member having a curved surface. [9] In the retardation film according to [8] above, the radius of curvature of the curved surface may be 20 mm or more.
[10] In the retardation film according to any one of [4] to [9] above, when the retardation film is integrated with a member having a curved surface with a radius of curvature of 75 mm in a plan view, the absolute value of the difference between the in-plane retardation Re(550) of the central portion and the in-plane retardation Re(550) of the portion other than the central portion may be 10 nm or less.
[11] The retardation film according to any one of [4] to
[10] above may be used as the second λ / 4 member integrated with the first lens unit in a display system including: a display element having a display surface that emits light representing an image forward via a polarizing member; a reflective polarizing member that is arranged in front of the display element and reflects the light emitted from the display element; a first lens unit that is arranged on an optical path between the display element and the reflective polarizing member and has a curved main surface; a half mirror that is arranged between the display element and the first lens unit and transmits the light emitted from the display element and reflects the light reflected by the reflective polarizing member toward the reflective polarizing member; a first λ / 4 member that is arranged on the optical path between the display element and the half mirror; and a second λ / 4 member that is arranged on the optical path between the half mirror and the reflective polarizing member.
[12] According to yet another aspect of the present invention, there is provided a retardation film piece having a curved surface, wherein the absolute value of the difference between the in-plane retardation Re(550) of a central part of the curved surface and the in-plane retardation Re(550) of a part other than the central part is 10 nm or less.
[13] According to yet another aspect of the present invention, there is provided a display system including: a display element having a display surface that emits light representing an image forward via a polarizing member; a reflective polarizing member that is disposed in front of the display element and reflects the light emitted from the display element; a first lens unit that is disposed on an optical path between the display element and the reflective polarizing member and has a curved main surface; a half mirror that is disposed between the display element and the first lens unit and transmits the light emitted from the display element and reflects the light reflected by the reflective polarizing member toward the reflective polarizing member; a first λ / 4 member that is disposed on the optical path between the display element and the half mirror; and a second λ / 4 member that is disposed on the optical path between the half mirror and the reflective polarizing member, wherein the second λ / 4 member and the first lens unit are integrated. In the system, there is provided a set of a first retardation film for constituting the first λ / 4 member and a second retardation film for constituting the second λ / 4 member, wherein the first retardation film and the second retardation film each have an in-plane retardation Re(550) of 100 nm to 190 nm and an absolute value of a retardation change value RS of 2.0 or less (wherein the retardation change value RS is the slope of an approximate straight line of the in-plane retardation Re(550) of the retardation film measured in a state where tensions of 0 kg, 0.5 kg, 1 kg, 1.5 kg, and 2 kg are applied), and the absolute value of the difference between the in-plane retardation Re(550) of the first retardation film and the in-plane retardation Re(550) of the second retardation film is 5 nm or less.
[0008] According to the method for manufacturing a retardation film, a retardation film piece, a retardation film set, or a lens portion or a display system according to the embodiment of the present invention, it is possible to effectively achieve a reduction in the weight of VR goggles while improving visibility.
[0009] 1 is a schematic cross-sectional view illustrating an example of a method for integrating a retardation film with a member having a curved surface. FIG. 2 is a schematic cross-sectional view illustrating a method for measuring ellipticity in a state in which a retardation film and a member having a curved surface are integrated, and FIG. 3 is a schematic view illustrating the state of FIG. 2 when viewed from the retardation film side. FIG. 3 is a schematic view illustrating a general configuration of an example of a display system for VR goggles. FIG. 4 is a schematic cross-sectional view illustrating a configuration of an example of an integrated product of a retardation film and a member having a curved surface, and a partially enlarged cross-sectional view thereof. FIG. 4 is a schematic cross-sectional view illustrating a configuration of an example of an optical laminate including a retardation film. FIG. 5 is a view illustrating a method for measuring thickness variation. FIG. 6 is a view illustrating a method for measuring an ISC value.
[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments. In order to clarify the description, the drawings may schematically show the width, thickness, shape, etc. of each part compared to the embodiments, but these are merely examples and do not limit the interpretation of the present invention. Furthermore, in the drawings, the same or equivalent elements are given the same reference numerals, and redundant explanations may be omitted.
[0011] (Definition of Terms and Symbols) The definitions of terms and symbols used in this specification are as follows. (1) Refractive Index (nx, ny, nz) "nx" is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), "ny" is the refractive index in the in-plane direction perpendicular to the slow axis (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction. (2) In-Plane Retardation (Re) "Re(λ)" is the in-plane retardation measured with light having a wavelength of λ nm at 23°C. For example, "Re(550)" is the in-plane retardation measured with light having a wavelength of 550 nm at 23°C. Re(λ) is calculated by the formula: Re(λ) = (nx - ny) × d, where d (nm) is the thickness of the layer (film). (3) Thickness Direction Retardation (Rth) "Rth(λ)" is the retardation in the thickness direction measured with light having a wavelength of λ nm at 23°C. For example, "Rth(550)" is the retardation in the thickness direction measured with light having a wavelength of 550 nm at 23°C. Rth(λ) is calculated by the formula: Rth(λ) = (nx - nz) x d, where d (nm) is the thickness of the layer (film). (4) Nz coefficient The Nz coefficient is calculated by Nz = Rth / Re. (5) Angle When an angle is mentioned in this specification, the angle includes both clockwise and counterclockwise angles relative to the reference direction. Therefore, for example, "45°" means ±45°.
[0012] A. Retardation Film According to one aspect of the present invention, a retardation film is provided in which the absolute value of the retardation change value RS is 2.0 or less. The retardation film can be suitably used in a state where it is integrated with a member having a curved surface. The retardation change value "RS" is the slope of the approximate line of the in-plane retardation Re (550) of the retardation film measured under tensions of 0 kg, 0.5 kg, 1 kg, 1.5 kg, and 2 kg, and can be an index of the degree of change in the in-plane retardation when tension is applied to the retardation film. Specifically, a small absolute value of RS means that the in-plane retardation is unlikely to change when tension is applied to the retardation film. When integrated with a member having a curved surface, tension is applied to the retardation film, which can result in a change in retardation. However, if the absolute value of RS is within the above range, the change in retardation can be suppressed. In addition, dimensional changes and retardation changes caused by heating can also be suppressed. The absolute value of RS may be, for example, 1.80 or less or 1.50 or less, and may be, for example, 0.05 or more.
[0013] The retardation film preferably has a refractive index characteristic of nx>ny≧nz. Here, "ny=nz" includes not only the case where ny and nz are completely equal, but also the case where they are substantially equal. Therefore, there may be cases where ny<nz, as long as the effects of the present invention are not impaired. The Nz coefficient of the retardation film is preferably 0.9 to 3, more preferably 0.9 to 2.5, even more preferably 0.9 to 1.5, and particularly preferably 0.9 to 1.3.
[0014] The in-plane retardation Re(550) of the retardation film is, for example, 100 nm to 190 nm, or may be 110 nm to 180 nm, 130 nm to 160 nm, or 135 nm to 155 nm. In one embodiment, the retardation film satisfies the relationship 100 nm<Re(550)<160 nm.
[0015] The retardation film preferably exhibits an inverse dispersion wavelength characteristic in which the retardation value increases with the wavelength of the measurement light, or a flat wavelength dispersion characteristic in which the retardation value changes little with the wavelength of the measurement light. The Re(450) / Re(550) of the retardation film is, for example, less than 1.1, and may be 1 or less, or even 0.95 or less, less than 0.90, or even 0.85 or less. The Re(450) / Re(550) of the retardation film is, for example, 0.75 or more. The Re(650) / Re(550) of the retardation film may, for example, exceed 0.9, for example, exceed 1, or may be greater than 1 and 1.2 or less, or may be 1.01 to 1.15. A retardation film exhibiting an inverse dispersion wavelength characteristic or a flat wavelength dispersion characteristic can contribute to improved visibility when applied to display systems such as VR goggles.
[0016] When linearly polarized light whose polarization direction forms an angle of 45° with respect to the slow axis is incident on the retardation film from the normal direction, the ellipticity of transmitted light having a wavelength of 550 nm measured at a polar angle of 0° (normal direction) is, for example, 0.80 or more, preferably 0.85 or more, and more preferably 0.90 to 1. Ellipticity is the ratio of the minor axis to the major axis of circularly polarized light, and for example, the ellipticity for completely circularly polarized light is 1, and the ellipticity for completely linearly polarized light is 0. A retardation film exhibiting the above ellipticity can contribute to improved visibility when applied to display systems such as VR goggles.
[0017] When the retardation film is subjected to heat treatment at 85° C. for 500 hours, the dimensional change rate before and after the heat treatment ((dimension before heat treatment−dimension after heat treatment) / dimension before heat treatment×100) is, for example, 0.02% or less, and may be 0.015% or less, or 0.01% or less. A retardation film exhibiting the above dimensional change rate has the advantage that, when used as a laminate with other members, peeling due to heating is unlikely to occur.
[0018] When the retardation film is subjected to heat treatment at 85° C. for 500 hours, the difference in in-plane retardation Re(550) before and after the heat treatment (|Re(550) before heat treatment−Re(550) after heat treatment|) is, for example, 3.5 nm or less, and may be 3 nm or less, 2 nm or less, 1 nm or less, or 0.5 nm or less. When the retardation film exhibits the above-mentioned difference in in-plane retardation, deterioration in visibility due to heating can be suppressed when applied to a display system such as VR goggles.
[0019] The ISC value of the retardation film is, for example, 50 or less, preferably 40 or less, more preferably 30 or less, and even more preferably 20 or less. The ISC value can be an index of smoothness or unevenness. A retardation film that satisfies such an ISC value and also satisfies the absolute value of RS can suppress the occurrence of retardation unevenness when integrated with a member having a curved surface.
[0020] The thickness variation of the retardation film is preferably 1 μm or less, more preferably 0.8 μm or less, even more preferably 0.6 μm or less, and even more preferably 0.4 μm or less. With such thickness variation, for example, the ISC value can be satisfactorily achieved. Here, the thickness variation can be determined by measuring the thickness of a first portion located in the plane of the retardation film and the thickness at a position spaced a predetermined distance (e.g., 5 mm to 15 mm) from the first portion in any direction (e.g., upward, downward, leftward, and rightward) from the first portion.
[0021] The ISC value per unit thickness of the retardation film is preferably not more than 1, more preferably not more than 0.7, and even more preferably not more than 0.5. The ISC value per unit thickness can be determined, for example, by dividing the ISC value by the thickness (unit: μm).
[0022] As described above, the retardation film can be used in a state where it is integrated with a member having a curved surface. More specifically, the retardation film can be used in a state where it is integrated with the curved surface of a member having a curved surface. The curved surface may be a concave surface or a convex surface. The radius of curvature of the curved surface is, for example, 20 mm or more, for example, 25 mm or more, or for example, 30 mm or more, and for example, 150 mm or less, preferably 125 mm or less, more preferably 110 mm or less, and may be 90 mm or less. The diameter (major axis) of the member having a curved surface can be, for example, 20 mm to 80 mm, or for example, 30 mm to 70 mm. A preferred example of a member having a curved surface is a lens having a concave surface.
[0023] The retardation film and the member having a curved surface can be integrated by any appropriate method. FIG. 1 is a schematic diagram illustrating an example of a method for integrating a retardation film and a member having a curved surface. In FIG. 1( a), the retardation film 1 is placed on the member L, which is an adherend, in the form of a pressure-sensitive adhesive layer-attached retardation film 3 having a pressure-sensitive adhesive layer 2 provided on one side thereof. The member L is circular in plan view and has a concave shape upward in cross-sectional view. The pressure-sensitive adhesive layer-attached retardation film 3 can be placed in a predetermined position by chucking its end into a fixing jig (not shown). The pressure-sensitive adhesive layer-attached retardation film 3 is placed in a position where the pressure-sensitive adhesive layer 2 contacts the edge of the concave surface of the member L, and is pressed into the concave surface using a jig or the like in a heated and softened state, thereby being bonded to the entire concave surface of the member L, as shown in FIG. 1( b). Thereafter, as shown in FIG. 1( c), unnecessary portions of the pressure-sensitive adhesive layer-attached retardation film 3 (for example, portions protruding from the member L in plan view) are removed to obtain an integrated product.
[0024] When integrated with the curved surface, typically, the retardation film can be stretched. For example, the retardation film can be stretched from a planar shape (circular shape) corresponding to the planar shape of the member L to a curved shape that follows the curved shape of the member L. In this way, tension can be applied to the retardation film when integrated with the curved surface, and since the absolute value of RS of the retardation film is small, a change in retardation due to the application of tension can be suppressed.
[0025] 2, when the retardation film 1 is integrated with a member L having a circular shape with a radius of 32.5 mm when viewed from the concave side and a concave curvature radius of 75 mm, and linearly polarized light whose polarization direction forms an angle of 45° with respect to the slow axis is incident from the convex side in the normal direction to the center C of the member L (in other words, the center 1c of the retardation film 1), the difference between the ellipticity of transmitted light with a wavelength of 550 nm measured on the concave side in the normal direction and the ellipticity at a portion corresponding to the center 1c of the retardation film 1 before integration (ellipticity before integration - ellipticity after integration) is, for example, 0.06 or less, preferably 0.05 or less, more preferably 0 to 0.04. Such a retardation film can contribute to improving display characteristics when used in a display system in a state where it is integrated with a member having a curved surface.
[0026] 2, when the retardation film 1 is integrated with the member L, the difference between Re(550) at the center 1c of the curved retardation film 1 after integration and Re(550) at a portion of the retardation film corresponding to the center 1c before integration (|Re(550) before integration−Re(550) after integration|) is, for example, 6 nm or less, preferably 5 nm or less, and more preferably 4 nm or less. Such a retardation film can contribute to improving display characteristics when used in a display system in a state where it is integrated with a member having a curved surface.
[0027] As shown in FIG. 2, when the retardation film 1 is integrated with the member L, the maximum absolute value of the difference between the Re (550) at the center 1c of the retardation film 1 and the Re (550) at the other portion (outer portion) can be, for example, 15 nm or less, 10 nm or less, or 6 nm or less, and can be, for example, 0.5 nm or more. When stretched during integration with the member L, variations in the in-plane retardation can occur within the plane (curved surface) of the retardation film. For example, in a curved retardation film after integration, the Re (550) of a portion spaced a large distance from the center may be significantly different from the Re (550) at the center. According to a retardation film having the above absolute value of RS, even when stretched during integration with the member L, variations in the in-plane retardation within the plane can be reduced.
[0028] 2 , when the retardation film 1 is integrated with the member L, linearly polarized light whose polarization direction forms an angle of 45° with respect to the slow axis is incident on the convex surface side normal to the member L, with respect to the ellipticity of transmitted light having a wavelength of 550 nm measured on the concave surface side normal to the member L, the maximum absolute value of the difference between the ellipticity at the center 1c of the retardation film 1 and the ellipticity at other portions (outer portions) is, for example, 0.07 or less, preferably 0.06 or less, more preferably 0 to 0.05. Such a retardation film can contribute to improving display characteristics when used in a display system in a state where it is integrated with a member having a curved surface.
[0029] The retardation film is formed of any appropriate material that can satisfy the above-mentioned properties. The retardation film may be, for example, a stretched resin film or an oriented and solidified layer of a liquid crystal compound.
[0030] Examples of resins contained in the resin film include polycarbonate resins, polyester carbonate resins, polyester resins, polyvinyl acetal resins, polyarylate resins, cycloolefin resins, cellulose resins, polyvinyl alcohol resins, polyamide resins, polyimide resins, polyether resins, polystyrene resins, and acrylic resins. These resins may be used alone or in combination (e.g., blended or copolymerized). Among these, resin films containing cycloolefin resins are preferred.
[0031] As the cycloolefin-based resin, for example, polynorbornene can be preferably used. Polynorbornene refers to a (co)polymer obtained by using norbornene-based monomers having a norbornene ring as part or all of the starting materials (monomers).
[0032] Various polynorbornene products are commercially available, including, for example, "ZEONEX" and "ZEONOR" manufactured by Zeon Corporation, "Arton" manufactured by JSR Corporation, "TOPUS" manufactured by TICONA, and "APEL" manufactured by Mitsui Chemicals, Inc.
[0033] When the retardation film is a stretched resin film, the thickness is, for example, 10 μm to 100 μm, preferably 10 μm to 70 μm, more preferably 10 μm to 60 μm, and still more preferably 20 μm to 50 μm.
[0034] The above-mentioned liquid crystal compound alignment solidified layer is a layer in which the liquid crystal compound is aligned in a predetermined direction within the layer and the alignment state is fixed. The "alignment solidified layer" is a concept that encompasses an alignment solidified layer obtained by curing a liquid crystal monomer, as described below. Typically, rod-shaped liquid crystal compounds are aligned in the slow axis direction of the retardation film (homogeneous alignment). Examples of rod-shaped liquid crystal compounds include liquid crystal polymers and liquid crystal monomers. The liquid crystal compound is preferably polymerizable. If the liquid crystal compound is polymerizable, the alignment state of the liquid crystal compound can be fixed by aligning the liquid crystal compound and then polymerizing it.
[0035] The alignment and solidification layer of the liquid crystal compound (liquid crystal alignment and solidification layer) can be formed by performing an alignment treatment on the surface of a predetermined substrate, applying a coating liquid containing a liquid crystal compound to the surface to align the liquid crystal compound in a direction corresponding to the alignment treatment, and fixing the alignment state. Any appropriate alignment treatment can be used as the alignment treatment. Specific examples include mechanical alignment treatment, physical alignment treatment, and chemical alignment treatment. Specific examples of mechanical alignment treatment include rubbing treatment and stretching treatment. Specific examples of physical alignment treatment include magnetic field alignment treatment and electric field alignment treatment. Specific examples of chemical alignment treatment include oblique vapor deposition and photoalignment treatment. Any appropriate treatment conditions can be used for the various alignment treatments depending on the purpose.
[0036] The alignment of liquid crystal compounds is achieved by treating them at a temperature at which they exhibit a liquid crystal phase depending on the type of liquid crystal compound. By performing such temperature treatment, the liquid crystal compounds assume a liquid crystal state and are aligned in accordance with the alignment treatment direction on the substrate surface.
[0037] In one embodiment, the alignment state is fixed by cooling the liquid crystal compound aligned as described above. When the liquid crystal compound is polymerizable or crosslinkable, the alignment state is fixed by subjecting the liquid crystal compound aligned as described above to a polymerization treatment or a crosslinking treatment.
[0038] Any suitable liquid crystal polymer and / or liquid crystal monomer can be used as the liquid crystal compound. The liquid crystal polymer and the liquid crystal monomer can be used alone or in combination. Specific examples of liquid crystal compounds and methods for producing a liquid crystal alignment solidified layer are described in, for example, JP 2006-163343 A, JP 2006-178389 A, and WO 2018 / 123551 A. The descriptions in these publications are incorporated herein by reference.
[0039] When the retardation film is an oriented and solidified layer of a liquid crystal compound, the thickness thereof is, for example, 1 μm to 10 μm, preferably 1 μm to 8 μm, more preferably 1 μm to 6 μm, and still more preferably 1 μm to 4 μm.
[0040] In the production of the above-mentioned retardation film, the RS of the obtained retardation film can be changed by changing the forming material, production conditions, etc. For example, in a retardation film which is a stretched film of a resin film, the absolute value of RS tends to be small by reducing the stretching ratio, etc. On the other hand, the absolute value of RS of a retardation film which is a liquid crystal alignment solidified layer tends to be very small.
[0041] B. Display System FIG. 3 is a schematic diagram showing the overall configuration of a display system according to one embodiment of the present invention, illustrating the arrangement and shape of each component of the display system. The display system 10 includes a display element 12, a reflective polarizing element 14, a first lens unit 16 having a curved main surface, a half mirror 18, a first λ / 4 element 20, a second λ / 4 element 22, and a second lens unit 24. The reflective polarizing element 14 is disposed in front of the display surface 12a of the display element 12 and can reflect light emitted from the display element 12. The first lens unit 16 is disposed on the optical path between the display element 12 and the reflective polarizing element 14, and the half mirror 18 is disposed between the display element 12 and the first lens unit 16. The first λ / 4 element 20 is disposed on the optical path between the display element 12 and the half mirror 18, and the second λ / 4 element 22 is disposed on the optical path between the half mirror 18 and the reflective polarizing element 14. Although not shown, from the viewpoint of improving visibility, the display system 10 may further include an absorptive polarizing member. The absorptive polarizing member may be disposed in front of the reflective polarizing member 14 such that the reflection axis of the reflective polarizing member 14 and the absorption axis of the absorptive polarizing member are approximately parallel to each other.
[0042] The half mirror or the components arranged forward from the first lens unit (in the illustrated example, the half mirror 18, first lens unit 16, second λ / 4 member 22, reflective polarizing member 14, and second lens unit 24) may be collectively referred to as the lens unit (lens unit 4).
[0043] The display element 12 is, for example, a liquid crystal display or an organic EL display, and has a display surface 12 a for displaying an image. The light emitted from the display surface 12 a passes through, for example, a polarizing member that may be included in the display element 12, and is converted into first linearly polarized light.
[0044] The first λ / 4 member 20 can convert the first linearly polarized light incident on the first λ / 4 member 20 into the first circularly polarized light. The first λ / 4 member 20 may be provided integrally with the display element 12.
[0045] The half mirror 18 transmits the light emitted from the display element 12 and reflects the light reflected by the reflective polarizing member 14 back toward the reflective polarizing member 14. The half mirror 18 is provided integrally with the first lens portion 16.
[0046] The second λ / 4 member 22 can transmit light reflected by the reflective polarizing member 14 and the half mirror 18 through the reflective polarizing member 14. The second λ / 4 member 22 is provided integrally with the first lens portion 16.
[0047] The first circularly polarized light output from the first λ / 4 member 20 passes through the half mirror 18 and the first lens portion 16, and is converted into the second linearly polarized light by the second λ / 4 member 22. The second linearly polarized light output from the second λ / 4 member 22 is reflected toward the half mirror 18 without passing through the reflective polarizing member 14. At this time, the polarization direction of the second linearly polarized light incident on the reflective polarizing member 14 is the same as the reflection axis of the reflective polarizing member 14. Therefore, the second linearly polarized light incident on the reflective polarizing member 14 is reflected by the reflective polarizing member 14.
[0048] The second linearly polarized light reflected by the reflective polarizing element 14 is converted into second circularly polarized light by the second λ / 4 element 22, and the second circularly polarized light emitted from the second λ / 4 element 22 passes through the first lens unit 16 and is reflected by the half mirror 18. The second circularly polarized light reflected by the half mirror 18 passes through the first lens unit 16 and is converted into third linearly polarized light by the second λ / 4 element 22. The third linearly polarized light is transmitted through the reflective polarizing element 14. At this time, the polarization direction of the third linearly polarized light incident on the reflective polarizing element 14 is the same direction as the transmission axis of the reflective polarizing element 14. Therefore, the third linearly polarized light incident on the reflective polarizing element 14 is transmitted through the reflective polarizing element 14.
[0049] The light transmitted through the reflective polarizing member 14 passes through the second lens portion 24 (the absorptive polarizing member 28 and the second lens portion 24 ) and enters the eye 26 of the user.
[0050] The absorption axis of the polarizing member included in the display element 12 and the reflection axis of the reflective polarizing member 14 may be disposed approximately parallel to each other or approximately perpendicular to each other. The angle between the absorption axis of the polarizing member included in the display element 12 and the slow axis of the first λ / 4 member 20 is, for example, 40° to 50°, or may be 42° to 48°, or may be approximately 45°. The angle between the absorption axis of the polarizing member included in the display element 12 and the slow axis of the second λ / 4 member 22 is, for example, 40° to 50°, or may be 42° to 48°, or may be approximately 45°.
[0051] The in-plane retardation Re(550) of the first λ / 4 member 20 is, for example, 100 nm to 190 nm, or may be 110 nm to 180 nm, 130 nm to 160 nm, or 135 nm to 155 nm. The first λ / 4 member 20 preferably exhibits an inverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light. The Re(450) / Re(550) of the first λ / 4 member 20 may be, for example, 0.75 or more and less than 1, or 0.8 or more and 0.95 or less.
[0052] The in-plane retardation Re(550) of the second λ / 4 component 22 is, for example, 100 nm to 190 nm, or may be 110 nm to 180 nm, 130 nm to 160 nm, or 135 nm to 155 nm. The second λ / 4 component 22 preferably exhibits an inverse dispersion wavelength characteristic in which the retardation value increases with the wavelength of the measurement light. The Re(450) / Re(550) of the second λ / 4 component 22 may be, for example, 0.75 or greater but less than 1, or 0.8 or greater but less than 0.95. Unless otherwise specified, the in-plane retardation of the second λ / 4 component is the in-plane retardation measured at a portion corresponding to the center of the first lens component. The center of the first lens component may be a portion that is generally recognized as the center. For example, the center of the first lens component may be the center of a circumscribing circle of its planar shape.
[0053] In the display system 10, the second λ / 4 member 22 is composed of the retardation film described in Section A and is integrated with the curved first lens unit 16. The integration of the second λ / 4 member 22 and the first lens unit 16 can be achieved by integrating the above-mentioned retardation film as the second λ / 4 member 22 with the first lens unit. The second λ / 4 member (the retardation film described in Section A) 22 can be integrated with the first lens unit 16 as an optical laminate that optionally further includes other optical members and has an adhesive layer (e.g., a pressure-sensitive adhesive layer) as the outermost layer, for example.
[0054] The radius of curvature of the curved surface of the first lens portion 16 is, for example, 20 mm or more, for example, 25 mm or more, or for example, 30 mm or more, and is, for example, 150 mm or less, preferably 125 mm or less, more preferably 110 mm or less, and may be 90 mm or less. The diameter (major axis) of the first lens portion 16 may be, for example, 20 mm to 80 mm, or for example, 30 mm to 70 mm. In the illustrated example, the second λ / 4 member 22 is integrated with the concave surface of the first lens portion 16, but it may also be integrated with the convex surface. The method for integrating the second λ / 4 member or the optical laminate with the first lens portion is not particularly limited, and for example, the same method as the method for integrating the retardation film with a member having a curved surface described in Section A can be used.
[0055] FIG. 4 is a schematic cross-sectional view and an enlarged view of a key portion illustrating an example of the configuration of an integrated product 100 in which an optical laminate 70 including a second λ / 4 member (the retardation film described in Section A) 22 and a first lens portion 16 are integrated. The optical laminate 70 includes a member (a so-called second positive C plate) 72 whose refractive index characteristics can exhibit the relationship nz > nx = ny, arranged on one side of the second λ / 4 member 22, and a second protective member 74 arranged on the other side. The second λ / 4 member 22, the second positive C plate 72, and the second protective member 74 are typically laminated via an adhesive layer (such as an adhesive layer or a pressure-sensitive adhesive layer). The optical laminate 70 further includes a second pressure-sensitive adhesive layer 76 on the side of the second positive C plate 72 opposite the side on which the second λ / 4 member 22 is arranged. The optical laminate 70 is bonded to the first lens portion 16 by a second adhesive layer 76 so as to conform to the concave surface 16 a of the first lens portion 16 .
[0056] The thickness direction retardation Rth(550) of the second positive C plate is preferably −20 nm to −200 nm, more preferably −30 nm to −180 nm, even more preferably −40 nm to −160 nm, and particularly preferably −50 nm to −140 nm. Here, "nx=ny" encompasses not only the case where nx and ny are strictly equal, but also the case where nx and ny are substantially equal. The in-plane retardation Re(550) of the second positive C plate is, for example, less than 10 nm.
[0057] The second positive C plate can be formed from any suitable material, but is preferably composed of a film containing a liquid crystal material fixed in homeotropic alignment. The liquid crystal material (liquid crystal compound) that can be homeotropically aligned may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of such liquid crystal compounds and methods for forming the second positive C plate include the liquid crystal compounds and methods for forming the retardation layer described in paragraphs
[0020] to
[0028] of JP-A-2002-333642. In this case, the thickness of the second positive C plate is preferably 0.5 μm to 5 μm.
[0058] The second protective member typically includes a substrate. The substrate may be composed of any appropriate film. Examples of materials that form the main component of the film constituting the substrate include cellulose-based resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, polysulfone-based, polystyrene-based, cycloolefin-based resins such as polynorbornene, polyolefin-based, (meth)acrylic, and acetate-based resins. The thickness of the substrate is preferably 5 μm to 80 μm, more preferably 10 μm to 40 μm, and even more preferably 15 μm to 35 μm.
[0059] The second protective member preferably has a substrate and a surface treatment layer formed on the substrate. The second protective member having the surface treatment layer can be disposed so that the surface treatment layer is located on the front side. The surface treatment layer can have any appropriate function. For example, from the viewpoint of improving visibility, the surface treatment layer preferably has an anti-reflection function. The surface treatment layer may also include a hard coat layer. The thickness of the surface treatment layer is preferably 1 μm to 20 μm, more preferably 2 μm to 15 μm, and even more preferably 3 μm to 10 μm.
[0060] The adhesive constituting the second adhesive layer typically contains a (meth)acrylic polymer, a urethane polymer, a silicone polymer, or a rubber polymer as a base polymer. Preferably, the adhesive is a (meth)acrylic adhesive containing a (meth)acrylic polymer as a main component. The thickness of the second adhesive layer is, for example, 12 μm or more, preferably 15 μm or more, and, for example, 100 μm or less, preferably 80 μm or less.
[0061] In the display system 10, the first λ / 4 member 20 may also be composed of the retardation film described in Section A. In this case, the first λ / 4 member (the retardation film described in Section A) 20 may be integrated with the display surface 12a of the display element 12. The display surface of the display element may be flat. As described above, the retardation film described in Section A has a small absolute value of RS, and changes in optical properties associated with integration with a curved member are small. Therefore, when the retardation film described in Section A is integrated as the first λ / 4 member and the second λ / 4 member along the flat display surface of the display element and the curved surface of the first lens portion, respectively, a display system with a small difference in in-plane retardation between the two members can be preferably obtained. In such a display system, the absolute value of the difference between the in-plane retardation Re(550) of the retardation film (first λ / 4 member) integrated with the display element and the in-plane retardation Re(550) of the retardation film (second λ / 4 member) integrated with the first lens portion is, for example, 6 nm or less, preferably 5 nm or less, more preferably 4 nm or less, and even more preferably 3.5 nm or less, and may be, for example, 3.0 nm or less, 2.5 nm or less, 2.0 nm or less, 1.5 nm or less, or 1.0 nm or less.
[0062] The first λ / 4 member (the retardation film described in Section A) 20 may be integrated with the display element 12 as an optical laminate that further includes, for example, any other appropriate optical member and has an adhesive layer (for example, a pressure-sensitive adhesive layer) as the outermost layer.
[0063] 5 is a schematic cross-sectional view illustrating an example of the configuration of an optical laminate 80 including a first λ / 4 member (the retardation film described in Section A) 20. The optical laminate 80 includes a polarizing member 82 arranged on one side of the first λ / 4 member 20, and a first positive C plate 84 and a first protective member 86 arranged in this order on the other side. The polarizing member 82 is a polarizing member that can be included in the display element 12. The optical laminate 80 further includes a first pressure-sensitive adhesive layer 88 on the side of the polarizing member 82 opposite to the side on which the first λ / 4 member 20 is arranged. The optical laminate 80 can be attached to the front side of the display element by the first pressure-sensitive adhesive layer 88.
[0064] The polarizing member is typically an absorptive polarizing member and may include a resin film containing a dichroic material (sometimes referred to as an absorptive polarizing film). The thickness of the absorptive polarizing film is, for example, 1 μm or more and 20 μm or less, or may be 2 μm or more and 15 μm or less, 12 μm or less, 10 μm or less, 8 μm or less, or 5 μm or less.
[0065] The absorptive polarizing film may be made from a single layer of resin film or may be made from a laminate of two or more layers.
[0066] When the absorptive polarizing film is produced from a single-layer resin film, for example, an absorptive polarizing film can be obtained by subjecting a hydrophilic polymer film such as a polyvinyl alcohol (PVA)-based film, a partially formalized PVA-based film, or a partially saponified ethylene-vinyl acetate copolymer-based film to a dyeing treatment with iodine or a dichroic substance such as a dichroic dye, a stretching treatment, etc. Among these, an absorptive polarizing film obtained by dyeing a PVA-based film with iodine and uniaxially stretching it is preferred.
[0067] The dyeing with iodine is carried out, for example, by immersing the PVA-based film in an aqueous iodine solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching may be carried out after the dyeing treatment or while dyeing. Alternatively, the PVA-based film may be dyed after stretching. If necessary, the PVA-based film may be subjected to a swelling treatment, a crosslinking treatment, a washing treatment, a drying treatment, or the like.
[0068] Examples of laminates produced using the two or more layer laminate include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, and a laminate of a resin substrate and a PVA-based resin layer formed by coating on the resin substrate. An absorptive polarizing film obtained using a laminate of a resin substrate and a PVA-based resin layer formed by coating on the resin substrate can be produced, for example, by applying a PVA-based resin solution to the resin substrate and drying the solution to form a PVA-based resin layer on the resin substrate, thereby obtaining a laminate of the resin substrate and the PVA-based resin layer, and then stretching and dyeing the laminate to convert the PVA-based resin layer into an absorptive polarizing film. In this embodiment, a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin is preferably formed on one side of the resin substrate. The stretching typically involves immersing the laminate in an aqueous boric acid solution to stretch it. Furthermore, the stretching may further include in-air stretching of the laminate at a high temperature (e.g., 95°C or higher) before stretching in the boric acid aqueous solution, as necessary. In addition, in this embodiment, the laminate is preferably subjected to a drying shrinkage treatment in which the laminate is heated while being transported in the longitudinal direction, thereby shrinking the laminate by 2% or more in the width direction. Typically, the manufacturing method of this embodiment includes subjecting the laminate to an auxiliary in-air stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment, in this order. By introducing auxiliary stretching, it is possible to increase the crystallinity of the PVA, even when the PVA is coated on a thermoplastic resin, thereby achieving high optical properties. Furthermore, by simultaneously increasing the orientation of the PVA in advance, problems such as a decrease in orientation or dissolution of the PVA when immersed in water in the subsequent dyeing or stretching steps can be prevented, thereby achieving high optical properties. Furthermore, when the PVA-based resin layer is immersed in a liquid, the disordering of the polyvinyl alcohol molecules and the decrease in orientation can be suppressed compared to when the PVA-based resin layer does not contain a halide. This can improve the optical properties of the absorptive polarizing film obtained through treatment steps in which the laminate is immersed in a liquid, such as a dyeing treatment and an underwater stretching treatment.Furthermore, the optical properties can be improved by shrinking the laminate in the width direction through a drying shrinkage treatment.The obtained resin substrate / absorptive polarizing film laminate may be used as is (i.e., the resin substrate may be used as a protective layer for the absorptive polarizing film), or any suitable protective layer may be laminated depending on the purpose on the surface obtained by peeling the resin substrate from the resin substrate / absorptive polarizing film laminate or on the surface opposite to the peeled surface. Details of such methods for producing an absorptive polarizing film are described in, for example, JP-A-2012-73580 and Japanese Patent No. 6,470,455. The entire disclosures of these publications are incorporated herein by reference.
[0069] The crossed transmittance (Tc) of the absorptive polarizing element (absorptive polarizing film) is preferably 0.5% or less, more preferably 0.1% or less, and even more preferably 0.05% or less. The single transmittance (Ts) of the absorptive polarizing element (absorptive polarizing film) is, for example, 41.0% to 45.0%, and preferably 42.0% or more. The polarization degree (P) of the absorptive polarizing element (absorptive polarizing film) is, for example, 99.0% to 99.997%, and preferably 99.9% or more.
[0070] The crossed transmittance, single transmittance, and degree of polarization can be measured, for example, using an ultraviolet-visible spectrophotometer. The degree of polarization P can be calculated from the obtained Tp and Tc by measuring the single transmittance Ts, parallel transmittance Tp, and crossed transmittance Tc using an ultraviolet-visible spectrophotometer, using the following formula: Ts, Tp, and Tc are Y values measured using a 2-degree visual field (C light source) according to JIS Z 8701 and corrected for visibility. Degree of polarization P (%) = {(Tp - Tc) / (Tp + Tc)} １／２ ×100
[0071] The same explanations as for the second positive C plate, second protective member, and second adhesive layer can be applied to the first positive C plate, first protective member, and first adhesive layer, respectively.
[0072] C. Set of Retardation Films According to another aspect of the present invention, there is provided a set of two retardation films, each independently having an in-plane retardation Re(550) of 100 nm to 190 nm and an absolute value of a retardation change value RS of 2.0 or less. The absolute value of the difference between the in-plane retardation Re(550) of the two retardation films included in the set is, for example, 10 nm or less, preferably 7 nm or less, more preferably 0 nm to 5 nm. Each of the two retardation films included in the set is preferably the retardation film described in Section A.
[0073] 3, the display system may include a planar first λ / 4 member and a curved second λ / 4 member. In such a display system, by using one of the retardation films to form the first λ / 4 member and the other to form the second λ / 4 member, even when the other retardation film is deformed to follow the curved surface of the first lens portion, the difference in in-plane retardation between the first λ / 4 member and the second λ / 4 member can be made small (for example, the absolute value of the difference in in-plane retardation Re(550) is 10 nm or less, preferably 7 nm or less, more preferably 5 nm or less, and even more preferably 0 nm to 3.5 nm). As a result, a display system with excellent visibility can be preferably obtained.
[0074] D. Retardation Film Pieces Retardation films having the absolute value of RS described in Section A can reduce the variation in in-plane retardation even when stretched from a flat surface to a curved surface by being integrated with a curved member. Therefore, according to another aspect of the present invention, a retardation film piece is provided, which has a curved surface, and the absolute value of the difference between the in-plane retardation Re(550) at the center of the curved surface and the in-plane retardation Re(550) at portions other than the central portion is, for example, 15 nm or less, 10 nm or less, or 6 nm or less. The radius of curvature of the curved surface of the retardation film piece is, for example, 20 mm or more, or, for example, 25 mm or more, or, for example, 30 mm or more, and may be, for example, 150 mm or less, preferably 125 mm or less, more preferably 110 mm or less, and may be, for example, 90 mm or less. The diameter (major axis) of the retardation film piece can be, for example, 20 mm to 80 mm, or, for example, 30 mm to 70 mm.
[0075] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The thickness and retardation are values measured by the following measurement methods. <Thickness> Thicknesses of 10 μm or less were measured using a scanning electron microscope (manufactured by JEOL Ltd., product name "JSM-7100F"). Thicknesses of more than 10 μm were measured using a digital micrometer (manufactured by Anritsu Corporation, product name "KC-351C"). <Retardation> In-plane retardation at 23°C was measured using a birefringence mapping measurement device (manufactured by Photoron Co., Ltd., product name "KAMAKIRI X stage".
[0076] Example 1 55 parts by weight of a compound represented by formula (I), 25 parts by weight of a compound represented by formula (II), and 20 parts by weight of a compound represented by formula (III) were added to 400 parts by weight of cyclopentanone (CPN), and then heated to 60°C and stirred to dissolve. The solution of the above compounds was then returned to room temperature, and 3 parts by weight of Irgacure 907 (manufactured by BASF Japan), 0.2 parts by weight of Megafac F-554 (manufactured by DIC), and 0.1 parts by weight of p-methoxyphenol (MEHQ) were added to the solution and further stirred. The solution after stirring was transparent and homogeneous. The resulting solution was filtered through a 0.20 μm membrane filter to obtain a polymerizable composition. In addition, a polyimide solution for an alignment film was applied to a 0.7 mm thick glass substrate using a spin coating method, dried at 100°C for 10 minutes, and then baked at 200°C for 60 minutes to obtain a coating film. The resulting coating film was rubbed using a commercially available rubbing device to form an alignment film. Next, the polymerizable composition obtained above was applied to the substrate (essentially the alignment film) using a spin coating method and dried at 100°C for 2 minutes. The resulting coating film was cooled to room temperature and then irradiated with ultraviolet light from a high-pressure mercury lamp at an intensity of 30 mW / cm2 for 30 seconds to obtain a retardation film 1 (thickness 3 μm) which was an aligned and solidified layer of the liquid crystal compound. The in-plane retardation Re(550) of the retardation film 1 was 140 nm. The Re(450) / Re(550) of the retardation film 1 was 0.851, demonstrating reverse dispersion wavelength characteristics.
[0077] [Example 2] A stretched film of a cycloolefin-based resin film (ZEON Corporation, Zeonorfilm ZD) was used as the retardation film 2. The retardation film 2 had a thickness of 22 μm and an in-plane retardation Re(550) of 141 nm. The retardation film 2 had an Re(450) / Re(550) of 1.00 and exhibited flat dispersion wavelength characteristics.
[0078] Comparative Example 1 A batch polymerization apparatus consisting of two vertical reactors equipped with stirring blades and reflux condensers controlled to 100°C was charged with 29.60 parts by weight (0.046 mol) of bis[9-(2-phenoxycarbonylethyl)fluoren-9-yl]methane, 29.21 parts by weight (0.200 mol) of isosorbide (ISB), 42.28 parts by weight (0.139 mol) of spiroglycol (SPG), 63.77 parts by weight (0.298 mol) of diphenyl carbonate (DPC), and 1.19 × 10 mol of calcium acetate monohydrate as a catalyst. －２ Parts by weight (6.78 x 10 －５mol) was charged. After purging the reactor with nitrogen under reduced pressure, heating was performed with a heat medium, and stirring was initiated when the internal temperature reached 100°C. 40 minutes after the start of the temperature increase, the internal temperature reached 220°C, and while controlling to maintain this temperature, pressure reduction was initiated. 90 minutes after reaching 220°C, the pressure was reduced to 13.3 kPa. Phenol vapor by-produced during the polymerization reaction was introduced into a reflux condenser at 100°C, and a small amount of monomer components contained in the phenol vapor were returned to the reactor, while uncondensed phenol vapor was introduced into a condenser at 45°C and recovered. Nitrogen was introduced into the first reactor, and the pressure was temporarily restored to atmospheric pressure. The oligomerized reaction liquid in the first reactor was then transferred to the second reactor. Next, heating and pressure reduction in the second reactor were initiated, and the internal temperature reached 240°C and the pressure reached 0.2 kPa in 50 minutes. Polymerization was then allowed to proceed until the predetermined stirring power was achieved. When the predetermined power was reached, nitrogen was introduced into the reactor to restore the pressure, and the resulting polyester carbonate resin was extruded into water and cut into strands to obtain pellets. The obtained polyester carbonate resin (pellets) was vacuum-dried at 80 ° C for 5 hours, and then a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder setting temperature: 250 ° C), a T-die (width 200 mm, setting temperature: 250 ° C), a chill roll (setting temperature: 120-130 ° C) and a film-forming device equipped with a winder were used to produce a long resin film with a thickness of 130 μm. The obtained long resin film was stretched in the width direction at a stretching temperature of 140 ° C and a stretch ratio of 2.7 times, and wound into a roll. As a result, a retardation film C1 having a thickness of 47 μm, an Re (590) of 140 nm, and an Nz coefficient of 1.2 was obtained. The retardation film C1 had an Re(450) / Re(550) of 0.859, and exhibited reverse dispersion wavelength characteristics.
[0079] [Comparative Example 2] A retardation film C2 having a thickness of 57 μm, an Re(590) of 140 nm, and an Nz coefficient of 1.2 was obtained in the same manner as in Comparative Example 1, except that a long resin film having a thickness of 130 μm was stretched in the width direction at a stretching temperature of 137° C. and a stretching ratio of 2.1 times. The retardation film C2 had an Re(450) / Re(550) of 0.859, and exhibited reverse dispersion wavelength characteristics.
[0080] <Retardation change value RS> The retardation films obtained in the examples and comparative examples were attached to an acrylic film (Re(550) ≒ 0 nm) via an acrylic pressure-sensitive adhesive layer (thickness 5 μm) to obtain a laminate. The obtained laminate was cut into a length of 150 mm and a width of 15 mm so that the slow axis direction of the retardation film was the longitudinal direction, to obtain a sample. The acrylic film is a film that causes almost no retardation change when the following tension is applied. A tension meter (manufactured by MYCARBON, product name "Digital Luggage Scale") was used to apply tension to the obtained sample in the longitudinal direction. The in-plane retardation (Re(550)) was measured using a retardation measurement device (manufactured by Axometrics, product name: Axo Scan) at tensions of 0 kg, 0.5 kg, 1 kg, 1.5 kg, and 2 kg. Using an Excel function, the tension was plotted on the x-axis and Re(550) on the y-axis, and the Re(550) values measured at each tension were plotted to create an approximate straight line, and the slope of the approximate line was taken as the phase difference change value RS.
[0081] <Thickness Variation> The retardation films obtained in Examples and Comparative Examples were cut into a size of 100 mm × 100 mm to prepare measurement samples. As shown in Fig. 6, the thickness was measured at five points, including the center of the measurement sample and four points 10 mm apart from the center on each of the upper, lower, left, and right sides, and the difference between the maximum and minimum values was taken as the thickness variation.
[0082] <ISC Value> The ISC value of the retardation films obtained in the examples and comparative examples was measured using an EyeScale-4W manufactured by I-System Co., Ltd. Specifically, based on the specifications of the measurement device, in-plane unevenness was calculated as the ISC value in the ISC measurement mode of a 3CCD image sensor. FIG. 7 is a diagram for explaining the method for measuring the ISC value, and is a schematic diagram showing the arrangement of a light source, a retardation film, a screen, and a CCD camera as viewed from above. As shown in FIG. 7, the light source Ls, the retardation film M, and the screen S were arranged in this order, and the transmitted image projected onto the screen S was measured using the CCD camera C. The retardation film M was attached to an alkali-free glass plate (manufactured by Corning Incorporated, 1737) and was subjected to measurement in a state where the glass plate was positioned on the light source Ls side. The distance from the light source Ls to the retardation film M in the X-axis direction was 10 to 60 cm. The distance from the light source Ls to the screen S in the X-axis direction was 70 to 130 cm. The CCD camera C was positioned so that the distance from the CCD camera C to the retardation film M in the Y-axis direction was 3 to 30 cm. The CCD camera C was positioned so that the distance from the CCD camera C to the screen S in the X-axis direction was 70 to 130 cm.
[0083] <Preparation and evaluation of curved surface integrated product> 1. Preparation of lens with retardation film An acrylic adhesive layer (thickness 15 μm) was provided on one side of the retardation film obtained in Examples and Comparative Examples, and the adhesive layer was bonded to the concave surface of a lens having a circular shape in plan view with a diameter of 65 mm and a curvature radius of 75 mm. Specifically, as shown in Figure 1, the retardation film with adhesive layer was set so that the adhesive layer surface was in contact with the edge of the concave side of the lens, and in the state of being heated to 120 ° C and softened, it was pressed into the concave side to be bonded to the concave surface of the lens. Thus, a lens with retardation film, which is an integrated product of the retardation film and the lens, was obtained.
[0084] 2. Change in Retardation at the Center 1. For the lens with retardation film obtained in 1., the in-plane retardation Re (543) of the retardation film at the center ａ The Re(543) of the portion corresponding to the center of the retardation film before lamination was measured.ｂ and Re (543) ａ Difference with (Re(543) ｂ -Re (543) ａ The absolute value of the retardation change at the center due to lamination to the curved surface was calculated as the change in retardation at the center due to lamination to the curved surface. The retardation change due to lamination to the curved surface can be evaluated as "poor (×)" when the absolute value is 6.0 nm or more, and as "good (◯)" when the absolute value is less than 6.0 nm.
[0085] 3. In-plane retardation unevenness For the lens with retardation film obtained in 1, the in-plane retardation Re(543) was measured over the entire surface of the retardation film. In the in-plane retardation distribution obtained in this way, the difference in in-plane retardation Re(543) between the center and the other parts (outer parts) was detected, and the maximum value was taken as the in-plane retardation unevenness. Note that the in-plane retardation unevenness (|Re(543) 中心部 -Re (543) 外方部 |) can be evaluated as "poor (x)" if it exceeds 15 nm, "fair (△)" if it is more than 10 nm and up to 15 nm, and "good (◯)" if it is 10 nm or less.
[0086] 4. Ellipticity Unevenness Using a Mueller matrix polarimeter (manufactured by Axometrics, product name "Axoscan"), linearly polarized light with a wavelength of 550 nm was incident on the lens side of the lens with a retardation film at 23°C, and the ellipticity of the transmitted light (diffused light) was measured over the entire surface of the retardation film side. In the ellipticity distribution obtained in this way, the difference in ellipticity between the center and other parts (outer parts) was detected, and the maximum value was taken as the ellipticity unevenness. Note that the ellipticity unevenness (| ellipticity 中心部 - ellipticity 外方部 |) can be evaluated as "poor (x)" if it exceeds 0.15, "fair (△)" if it is more than 0.1 and 0.15 or less, and "good (◯)" if it is 0.1 or less.
[0087] 5. Peeling test The lens with the retardation film was placed in an oven at 80°C and 0% RH, and then removed after 120 hours. The appearance was visually inspected to evaluate whether or not the retardation film had peeled off.
[0088] <Preparation and evaluation of planar integrated product> 1. Preparation of glass plate with retardation film The retardation films obtained in Examples and Comparative Examples were cut into squares of 100 mm × 100 mm with the slow axis direction and width direction as side directions, and an acrylic pressure-sensitive adhesive layer (thickness 5 μm) was provided on one side of each square, and the squares were bonded to a flat glass plate (thickness 1.1 mm) via the pressure-sensitive adhesive layer. In this way, a glass plate with a retardation film, which is an integrated product of the retardation film and the glass plate, was obtained.
[0089] The glass plate with the retardation film obtained in 1. was placed in an oven at 85°C and 0% RH and taken out after 500 hours. The dimensions of the retardation film on the glass plate were then measured, and the dimensional change rate in the slow axis direction before and after heating [(dimension before heating - dimension after heating) / dimension before heating x 100] was calculated as the dimensional change rate.
[0090] 3. Retardation Change Regarding the glass plate with retardation film obtained in 1., the in-plane retardation Re(543) of the retardation film was measured. Thereafter, the glass plate with retardation film was placed in an oven at 85°C and 0% RH, and after 500 hours, it was taken out and the in-plane retardation Re(543) of the retardation film was measured. Re(543) of the retardation film before heat treatment ｂ and Re(543) after heat treatment ａ Difference with (Re(543) ｂ -Re (543) ａ The absolute value of the difference (x) was calculated as the change in retardation due to heating. The retardation change due to heating can be evaluated as follows: 4.0 nm or more is "poor (x)", 3.5 nm or more and less than 4.0 nm is "fair (△)", 2.0 nm or more and less than 3.5 nm is "good (◯)", and less than 2.0 nm is "excellent (◎)".
[0091] The results are shown in Table 1.
[0092] The retardation films of the Examples, which have a small absolute value of RS, show small changes in retardation and ellipticity of transmitted light when bonded to a curved lens, and are also less susceptible to peeling due to heating. When such retardation films are applied to a display system as an integrated product with a curved lens, they can exhibit the desired optical properties and contribute to improving visibility.
[0093] The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the configurations shown in the above-described embodiment can be replaced with configurations that are substantially the same as those shown in the above-described embodiment, that have the same effects, or that can achieve the same purpose.
[0094] The manufacturing method of a display system according to an embodiment of the present invention can be suitably used for manufacturing a display system such as VR goggles, for example.
[0095] REFERENCE SIGNS LIST 1 retardation film 10 display system 12 display element 14 reflective polarizing member 16 first lens portion 18 half mirror 20 first λ / 4 member 22 second λ / 4 member 24 second lens portion
Claims
1. A method for manufacturing a display system for displaying an image to a user, the display system comprising: a display element having a display surface that emits light representing an image forward via a polarizing member; a reflective polarizing member arranged in front of the display element and reflecting the light emitted from the display element; a first lens portion arranged on an optical path between the display element and the reflective polarizing member and having a curved main surface; a half mirror arranged between the display element and the first lens portion, transmitting the light emitted from the display element and reflecting the light reflected by the reflective polarizing member towards the reflective polarizing member; a first λ / 4 member arranged on the optical path between the display element and the half mirror; and a second λ / 4 member arranged on the optical path between the half mirror and the reflective polarizing member, a retardation film having an in-plane retardation Re(550) of 100 nm to 190 nm and an absolute value of a retardation change value RS of 2.0 or less (wherein the retardation change value RS is a slope of an approximation line of the in-plane retardation Re(550) of the retardation film measured in a state where tensions of 0 kg, 0.5 kg, 1 kg, 1.5 kg, and 2 kg are applied) is integrated with the first lens portion as the second λ / 4 member.
2. The manufacturing method according to claim 1, comprising: preparing two of the retardation films; integrating one of the retardation films with the display element as the first λ / 4 member; and integrating the other of the retardation films with the first lens portion as the second λ / 4 member.
3. A method for manufacturing a lens unit used in a display system that displays an image to a user, the lens unit comprising: a reflective polarizing element that reflects light that is emitted forward from a display surface of a display element that displays an image and that has passed through a polarizing element and a first λ / 4 element; a first lens unit that is disposed on an optical path between the display element and the reflective polarizing element and has a curved main surface; a half mirror that is disposed between the display element and the first lens unit and transmits light emitted from the display element and reflects light reflected by the reflective polarizing element toward the reflective polarizing element; and a second λ / 4 element that is disposed on the optical path between the half mirror and the reflective polarizing element, a retardation film having an in-plane retardation Re(550) of 100 nm to 190 nm and an absolute value of a retardation change value RS of 2.0 or less (wherein the retardation change value RS is a slope of an approximation line of the in-plane retardation Re(550) of the retardation film measured in a state where tensions of 0 kg, 0.5 kg, 1 kg, 1.5 kg, and 2 kg are applied) is integrated with the first lens portion as the second λ / 4 member.
4. A retardation film having an in-plane retardation Re(550) of 100 nm to 190 nm, an absolute value of a retardation change value RS of 2.0 or less, and the retardation change value RS being a gradient of an approximation line of the in-plane retardation Re(550) of the retardation film measured under tensions of 0 kg, 0.5 kg, 1 kg, 1.5 kg, and 2 kg.
5. The retardation film according to claim 4, wherein the in-plane retardations Re(450), Re(550), and Re(650) satisfy the following relationships (i) to (iii): (i) 100 nm<Re(550)<160 nm, (ii) Re(450) / Re(550)<1.1, (iii) Re(650) / Re(550)>0.
9.
6. The retardation film according to claim 4, which has a dimensional change rate of 0.02% or less before and after heat treatment at 85° C. for 500 hours.
7. The retardation film according to claim 4, wherein the absolute value of the difference in in-plane retardation Re(550) before and after heat treatment at 85° C. for 500 hours is 3.5 nm or less.
8. The retardation film according to claim 4, which is integrated with a member having a curved surface.
9. The retardation film according to claim 8, wherein the radius of curvature of the curved surface is 20 mm or more.
10. The retardation film according to claim 4, wherein when the retardation film is integrated with a member having a curved surface with a radius of 32.5 mm in a plan view and a radius of curvature of 75 mm, the absolute value of the difference between the in-plane retardation Re(550) at the center and the in-plane retardation Re(550) at a portion other than the center is 10 nm or less.
11. A display system comprising: a display element having a display surface that emits light representing an image forward via a polarizing member; a reflective polarizing member arranged in front of the display element and reflecting the light emitted from the display element; a first lens section arranged on an optical path between the display element and the reflective polarizing member and having a curved main surface; a half mirror arranged between the display element and the first lens section, transmitting the light emitted from the display element and reflecting the light reflected by the reflective polarizing member toward the reflective polarizing member; a first λ / 4 member arranged on the optical path between the display element and the half mirror; and a second λ / 4 member arranged on the optical path between the half mirror and the reflective polarizing member, wherein the retardation film according to claim 4 is used integrally with the first lens section as the second λ / 4 member.
12. A piece of retardation film having a curved surface, wherein the absolute value of the difference between the in-plane retardation Re(550) of a central portion of the curved surface and the in-plane retardation Re(550) of a portion other than the central portion is 10 nm or less.
13. A display system comprising: a display element having a display surface that emits light representing an image forward via a polarizing member; a reflective polarizing member arranged in front of the display element and reflecting the light emitted from the display element; a first lens section arranged on an optical path between the display element and the reflective polarizing member and having a curved main surface; a half mirror arranged between the display element and the first lens section, transmitting the light emitted from the display element and reflecting the light reflected by the reflective polarizing member toward the reflective polarizing member; a first λ / 4 member arranged on the optical path between the display element and the half mirror; and a second λ / 4 member arranged on the optical path between the half mirror and the reflective polarizing member, wherein the second λ / 4 member and the first lens section are integrated, comprising a set of a first retardation film for constituting the first λ / 4 member and a second retardation film for constituting the second λ / 4 member, The first retardation film and the second retardation film each have an in-plane retardation Re(550) of 100 nm to 190 nm and an absolute value of a retardation change value RS of 2.0 or less (wherein the retardation change value RS is a slope of an approximation line of the in-plane retardation Re(550) of the retardation film measured under conditions of applying tensions of 0 kg, 0.5 kg, 1 kg, 1.5 kg, and 2 kg), and an absolute value of a difference between the in-plane retardation Re(550) of the first retardation film and the in-plane retardation Re(550) of the second retardation film is 5 nm or less.