Optical multilayer panels and display systems
Patent Information
- Authority / Receiving Office
- VN · VN
- Patent Type
- Applications
- Current Assignee / Owner
- NITTO DENKO CORP
- Filing Date
- 2024-08-14
- Publication Date
- 2026-06-15
Smart Images
Figure VN1202602842_0
Abstract
Description
Optical laminate and display system
[0001] The present invention relates to an optical stack and a 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.
[0004] Japanese Patent Application Laid-Open No. 2021-103286
[0005] In view of the above, a main object of the present invention is to provide an optical laminate that can contribute to improving the display characteristics of VR goggles.
[0006] 1. A display system according to an embodiment of the present invention is a display system for displaying an image to a user, comprising: a display element having a display surface that emits light representing an image forward via a polarizing element; a reflecting element disposed in front of the display element and including a reflective polarizing element and reflecting the light emitted from the display element; a first lens element disposed on an optical path between the display element and the reflecting element; a half mirror disposed between the display element and the first lens element and transmitting the light emitted from the display element and reflecting the light reflected by the reflecting element toward the reflecting element; a first phase difference element disposed on the optical path between the display element and the half mirror; and a second phase difference element disposed on the optical path between the half mirror and the reflecting element, the polarizing element and the first phase difference element constituting an optical stack, the optical stack comprising, in this order, a polarizing element, a layer functioning as a λ / 2 plate, and a layer functioning as a λ / 4 plate. 2. An optical stack according to an embodiment of the present invention comprises, in this order, a polarizing element, a layer functioning as a λ / 2 plate, and a layer functioning as a λ / 4 plate, and is used in the display system described above in 1. 3. In the optical laminate according to the above 2, the layer functioning as a λ / 2 plate may have an in-plane retardation Re(550) of 230 nm to 330 nm. 4. In the optical laminate according to the above 2 or 3, the layer functioning as a λ / 4 plate may have an in-plane retardation Re(550) of 100 nm to 200 nm. 5. In the optical laminate according to any one of the above 2 to 4, the angle between the slow axis of the layer functioning as a λ / 2 plate and the absorption axis of the polarizing member may be 5° to 35°. 6. In the optical laminate according to any one of the above 2 to 5, the angle between the slow axis of the layer functioning as a λ / 4 plate and the absorption axis of the polarizing member may be 55° to 85°. 7. In the optical laminate according to any one of the above 2 to 6, the layer functioning as a λ / 2 plate may exhibit reverse dispersion wavelength characteristics. 8. In the optical laminate according to any one of the above 2 to 7, the layer functioning as a λ / 4 plate may exhibit reverse dispersion wavelength characteristics.9. The optical laminate according to any one of the above 2 to 8 may further include a member having refractive index characteristics that satisfy the relationship nz > nx = ny, and the member having refractive index characteristics that satisfy the relationship nz > nx = ny may be disposed on the side of the layer functioning as the λ / 4 plate opposite the layer functioning as the λ / 2 plate. 10. The optical laminate according to any one of the above 2 to 9 may further include an anti-reflection protective member, and the anti-reflection protective member may be disposed on the outermost side opposite the polarizing member. 11. The optical laminate according to any one of the above 2 to 10 may have a value (1-DI) obtained by subtracting the depolarization index (DI) of transmitted light having a wavelength of 550 nm measured at a polar angle of 0° from 1, which is 99.5% or more. 12. The optical laminate according to any one of the above 2 to 11 may have a value (1-DI) obtained by subtracting the depolarization index (DI) of transmitted light having a wavelength of 550 nm measured at a polar angle of 30° and an azimuth angle of 0° to 360° from 1, which is 99.4% or more. 13. The optical laminate described in any one of 2 to 12 above may be used as the first phase difference member in a display method having the steps of: passing light representing an image emitted through a polarizing member through a first phase difference member; passing the light that has passed through the first phase difference member through a half mirror and a first lens unit; passing the light that has passed through the half mirror and the first lens unit through a second phase difference member; reflecting the light that has passed through the second phase difference member toward the half mirror with a reflective polarizing member; and making the light reflected by the reflective polarizing member and the half mirror transmit through the reflective polarizing member with the second phase difference member.
[0007] According to the present invention, an optical laminate that can contribute to improving the display characteristics of VR goggles can be provided.
[0008] 1 is a schematic diagram illustrating a general configuration of a display system according to an embodiment of the present invention; FIG. 2 is a schematic cross-sectional view of an optical laminate according to an embodiment of the present invention;
[0009] 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 duplicate explanations may be omitted.
[0010] (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) × 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 referred to in this specification, unless otherwise specified, the angle includes both clockwise and counterclockwise angles with respect to the reference direction. Therefore, for example, "45°" means ±45°. Furthermore, in this specification, "substantially parallel" includes the range of 0° ±10°, preferably within the range of 0° ±5°, more preferably within the range of 0° ±3°, and even more preferably within the range of 0° ±1°. "Approximately perpendicular" encompasses the range of 90°±10°, preferably within the range of 90°±5°, more preferably within the range of 90°±3°, and even more preferably within the range of 90°±1°.
[0011] A. Display System FIG. 1 is a schematic diagram showing the overall configuration of a display system according to one embodiment of the present invention. FIG. 1 schematically illustrates the arrangement and shape of each component of a display system 2. The display system 2 includes a display element 12, a reflector 14 including a reflective polarizing member, a first lens unit 16, a half mirror 18, a first phase difference member 20, a second phase difference member 22, and a second lens unit 24. The reflector 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 reflector 14, and the half mirror 18 is disposed between the display element 12 and the first lens unit 16. The first phase difference member 20 is disposed on the optical path between the display element 12 and the half mirror 18, and the second phase difference member 22 is disposed on the optical path between the half mirror 18 and the reflector 14. The components arranged in front of the half mirror (in the illustrated example, the half mirror 18, the first lens section 16, the second phase difference member 22, the reflecting section 14, and the second lens section 24) may be collectively referred to as the lens section (lens section 4).
[0012] 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 (typically, a polarizing film) that may be included in the display element 12, and is converted into first linearly polarized light.
[0013] The first phase difference member 20 can convert first linearly polarized light incident on the first phase difference member 20 into first circularly polarized light. The first phase difference member 20 can be provided integrally with the display element 12, as shown in FIG. 1 . Specifically, a polarizing member that can be included in the display element 12 and the first phase difference member 20 can be provided integrally to form the optical stacked body 200 described below. In other words, a stacked body including a layer 20a that functions as a λ / 2 plate and a layer 20b that functions as a λ / 4 plate in the optical stacked body 200 described below can be the first phase difference member 20 in the display system 2.
[0014] The half mirror 18 transmits light emitted from the display element 12 and reflects light reflected by the reflecting portion 14 toward the reflecting portion 14. The half mirror 18 is provided integrally with the first lens portion 16.
[0015] The second phase difference member 22 is a λ / 4 member that can transmit light reflected by the reflecting unit 14 and the half mirror 18 through the reflecting unit 14, which includes a reflective polarizing member (hereinafter, the second phase difference member may be referred to as a second λ / 4 member). Note that the second phase difference member 22 may be provided integrally with the first lens unit 16.
[0016] The first circularly polarized light emitted from the phase difference member (first phase difference member) 20 passes through the half mirror 18 and the first lens unit 16 and is converted into second linearly polarized light by the second λ / 4 member 22. The second linearly polarized light emitted from the second λ / 4 member 22 is reflected toward the half mirror 18 without passing through the reflective polarizing member included in the reflecting unit 14. At this time, the polarization direction of the second linearly polarized light incident on the reflective polarizing member included in the reflecting unit 14 is the same as the reflection axis of the reflective polarizing member. Therefore, the second linearly polarized light incident on the reflecting unit 14 is reflected by the reflective polarizing member.
[0017] The second linearly polarized light reflected by the reflecting unit 14 is converted into second circularly polarized light by the second λ / 4 member 22, and the second circularly polarized light emitted from the second λ / 4 member 22 passes through the first lens unit 16 and is reflected by the half mirror 18. The 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 member 22. The third linearly polarized light passes through the reflective polarizing member included in the reflecting unit 14. At this time, the polarization direction of the third linearly polarized light incident on the reflective polarizing member included in the reflecting unit 14 is the same direction as the transmission axis of the reflective polarizing member. Therefore, the third linearly polarized light incident on the reflecting unit 14 passes through the reflective polarizing member.
[0018] The light transmitted through the reflecting portion 14 passes through the second lens portion 24 and enters the user's eye 26 .
[0019] For example, the absorption axis of the polarizing member included in the display element 12 and the reflection axis of the reflective polarizing member included in the reflecting section 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 phase difference member 20, and the in-plane phase difference of the first phase difference member 20 are set so as to convert the first linearly polarized light into the first circularly polarized light. The above angle and in-plane phase difference will be described in detail in Section B. The angle between the absorption axis of the polarizing member included in the display element 12 and the slow axis of the second phase difference member 22 is, for example, 40° to 50°, may be 42° to 48°, or may be approximately 45°.
[0020] The in-plane retardation Re(550) of the second retardation member 22 is, for example, 100 nm to 190 nm, may be 110 nm to 180 nm, may be 130 nm to 160 nm, or may be 135 nm to 155 nm.
[0021] The second phase difference member 22 preferably exhibits an inverse dispersion wavelength characteristic in which the phase difference value increases according to the wavelength of the measurement light. The Re(450) / Re(550) of the second phase difference member 22 is, for example, less than 1 and may be 0.95 or less, or even less than 0.90, or even 0.85 or less. The Re(450) / Re(550) of the second phase difference member 22 is, for example, 0.75 or more.
[0022] In one embodiment, the second phase difference member 22 satisfies all of Re(400) / Re(550)<0.85, Re(650) / Re(550)>1.03, and Re(750) / Re(550)>1.05. The second phase difference member 22 preferably satisfies at least one selected from 0.65<Re(400) / Re(550)<0.80 (preferably, 0.7<Re(400) / Re(550)<0.75), 1.0<Re(650) / Re(550)<1.25 (preferably, 1.05<Re(650) / Re(550)<1.20), and 1.05<Re(750) / Re(550)<1.40 (preferably, 1.08<Re(750) / Re(550)<1.36), more preferably satisfies at least two, and even more preferably satisfies all.
[0023] The second phase difference member 22 preferably has a refractive index characteristic that satisfies the relationship 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 second phase difference member 22 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.
[0024] The surface smoothness of the second retardation member 22 is, for example, 0.50 arcmin or less, preferably 0.40 arcmin or less, more preferably 0.30 arcmin or less, and even more preferably 0.20 arcmin or less. When the second retardation member 22 satisfies such surface smoothness, a display system with excellent visibility can be realized. For example, when the second retardation member 22 satisfies such surface smoothness, the uniformity of the in-plane retardation can be improved, and as a result, light leakage in the reflective portion, which will be described later, can be suppressed. A method for measuring surface smoothness will be described later.
[0025] The variation in thickness of the second phase difference member 22 is preferably 1 μm or less, more preferably 0.8 μm or less, even more preferably 0.6 μm or less, and still more preferably 0.4 μm or less. Such a variation in thickness can, for example, favorably achieve the above-mentioned surface smoothness.
[0026] The second retardation member 22 is formed of any appropriate material that can satisfy the above characteristics. The second retardation member 22 can be, for example, a stretched resin film or an oriented and solidified layer of a liquid crystal compound. The same explanation as for the layer functioning as a λ / 4 plate that constitutes the first retardation member 20 described in Section B can be applied to the second retardation member 22. The layer functioning as a λ / 4 plate and the second retardation member 22 may be members of the same configuration (forming material, thickness, optical properties, etc.) or may be members of different configurations.
[0027] The thickness of the second retardation member 22 is preferably 100 μm or less. Specifically, the thickness of the second retardation member 22 made of a stretched resin film is, for example, 10 μm to 100 μm, preferably 10 μm to 70 μm, more preferably 10 μm to 60 μm, and even more preferably 20 μm to 50 μm. The thickness of the second retardation member 22 made of a liquid crystal alignment solidified layer is, for example, 1 μm to 10 μm, preferably 1 μm to 8 μm, more preferably 1 μm to 6 μm, and even more preferably 1 μm to 4 μm.
[0028] The reflective section 14 may include an absorptive polarizing element in addition to a reflective polarizing element. The absorptive polarizing element may be disposed in front of the reflective polarizing element. The reflection axis of the reflective polarizing element and the absorption axis of the absorptive polarizing element may be disposed approximately parallel to each other, and the transmission axis of the reflective polarizing element and the transmission axis of the absorptive polarizing element may be disposed approximately parallel to each other. When the reflective section 14 includes an absorptive polarizing element, the reflective section 14 may include a laminate having a reflective polarizing element and an absorptive polarizing element.
[0029] The reflective polarizing element can transmit light polarized parallel to its transmission axis (typically, linearly polarized light) while maintaining its polarization state, and reflect light polarized in other states (typically, light polarized perpendicular to its transmission axis). The orthogonal transmittance (Tc) of the reflective polarizing element can be, for example, 0.01% to 3%. The single transmittance (Ts) of the reflective polarizing element can be, for example, 43% to 49%, preferably 45% to 47%. The degree of polarization (P) of the reflective polarizing element can be, for example, 92% to 99.99%. The reflective polarizing element is typically composed of a film having a multilayer structure (sometimes referred to as a reflective polarizing film). Commercially available reflective polarizing films include, for example, "DBEF" and "APF" manufactured by 3M, and "APCF" manufactured by Nitto Denko Corporation.
[0030] The absorptive polarizing member may typically include a resin film containing a dichroic material (i.e., an absorptive polarizing film). The absorptive polarizing film may be the absorptive polarizing film described in Section B. The thickness of the absorptive polarizing film is, for example, 1 μm or more and 20 μm or less, and 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.
[0031] B. Optical Laminate FIG. 2 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. The optical laminate 200 includes a polarizing member 10, a layer 20a functioning as a λ / 2 plate, and a layer 20b functioning as a λ / 4 plate, in this order. The optical laminate 200 is preferably used so that the layer 20b functioning as a λ / 4 plate is on the viewing side. In one embodiment, the optical laminate can be used by being disposed on the display element side (for example, between the display element and the lens unit) in a display system such as VR goggles. As described above, in the display system, the polarizing member and the first phase difference member included in the display element can constitute the optical laminate. In other words, a laminate including the layer 20a functioning as a λ / 2 plate and the layer 20b functioning as a λ / 4 plate constitutes the first phase difference member 20.
[0032] By using the optical laminate having the above configuration, a display system with excellent display characteristics can be obtained. For example, in a display system including a lens unit, by arranging the optical laminate in the optical path before reaching the lens unit, light with high circular polarization can be introduced into the lens unit of the display system, thereby reducing the so-called ghost phenomenon in which displayed images are perceived as overlapping. In addition, light leakage can be suppressed, contributing to higher resolution. These effects become more pronounced by incorporating the optical laminate into the display system described in Section A.
[0033] In the optical laminate, the ellipticity of transmitted light at a wavelength of 550 nm measured at a polar angle of 30° and an azimuth angle of 0° to 360° is preferably 0.77 or more, more preferably 0.78 or more, even more preferably 0.80 or more, even more preferably 0.82 or more, and particularly preferably 0.84 or more. The use of an optical laminate exhibiting such ellipticity results in significant effects. One of the benefits of the optical laminate is that improved display characteristics can be achieved by precisely controlling the ellipticity of transmitted light in all directions. In the optical laminate, the higher the ellipticity of transmitted light at a wavelength of 550 nm measured at a polar angle of 30° and an azimuth angle of 0° to 360°, the better, with the upper limit being, for example, 0.90 (preferably 0.93, more preferably 0.95, and even more preferably 0.99). Ellipticity is the ratio of the minor axis to the major axis of circularly polarized light; for example, the ellipticity of completely circularly polarized light is 1, and the ellipticity of completely linearly polarized light is 0. In this specification, the term "ellipticity" refers to the absolute value of the ellipticity.
[0034] In this specification, the ellipticity of transmitted light measured at a polar angle of 30° and an azimuth angle of 0° to 360° refers to the ellipticity measured at every 11.25° azimuth angle in the range of 0° to 360° for light of a predetermined wavelength incident from the polarizing member side at a polar angle of 30° and the emitted light at a polar angle of 30°. Therefore, "the ellipticity is X or more" measured at an azimuth angle of 0° to 360° means that the minimum value of the 32 obtained measurements is X.
[0035] In one embodiment, the optical laminate has an ellipticity of transmitted light at a wavelength of 450 nm, measured at a polar angle of 30° and an azimuth angle of 0° to 360°, of preferably 0.77 or more, more preferably 0.80 or more, even more preferably 0.82 or more, and particularly preferably 0.84 or more. Within these ranges, an optical laminate can be obtained that exhibits significant effects in reducing ghosting, suppressing light leakage, and increasing definition. In the optical laminate, the higher the ellipticity of transmitted light at a wavelength of 450 nm, measured at a polar angle of 30° and an azimuth angle of 0° to 360°, the better, with the upper limit being, for example, 0.90 (preferably 0.93, more preferably 0.95, and even more preferably 0.99).
[0036] In one embodiment, the optical laminate has an ellipticity of transmitted light at a wavelength of 650 nm, measured at a polar angle of 30° and an azimuth angle of 0° to 360°, of preferably 0.77 or more, more preferably 0.80 or more, and even more preferably 0.82 or more. Within these ranges, an optical laminate can be obtained that exhibits significant effects in reducing ghosting, suppressing light leakage, and increasing definition. In the optical laminate, the higher the ellipticity of transmitted light at a wavelength of 650 nm, measured at a polar angle of 30° and an azimuth angle of 0° to 360°, the better, with the upper limit being, for example, 0.90 (preferably 0.93, more preferably 0.95, and even more preferably 0.99).
[0037] In one embodiment, when the ellipticity of transmitted light having a wavelength of 550 nm is measured at an azimuth angle of 0° to 360° at intervals of 11.25° at a polar angle of 30°, the average ellipticity is 0.83 or more, preferably 0.84 or more, and more preferably 0.86 or more. Within such a range, an optical laminate having a significant effect of reducing ghosting, suppressing light leakage, and achieving high definition can be obtained. When the ellipticity of transmitted light having a wavelength of 550 nm is measured at an azimuth angle of 0° to 360° at an azimuth angle of 30° at intervals of 11.25° at a polar angle of 30°, the higher the average ellipticity, the better, with the upper limit being, for example, 0.90 (preferably 0.95). In this specification, the average ellipticity refers to the average of 32 measured values obtained by measuring the ellipticity as described above.
[0038] In one embodiment, when the ellipticity of transmitted light having a wavelength of 450 nm is measured at an azimuth angle of 11.25° in the range of 0° to 360° at a polar angle of 30°, the average ellipticity is 0.80 or more, preferably 0.84 or more, and more preferably 0.86 or more. Within such a range, an optical laminate can be obtained that exhibits significant effects in reducing ghosting, suppressing light leakage, and achieving high definition. When the ellipticity of transmitted light having a wavelength of 450 nm is measured at an azimuth angle of 11.25° in the range of 0° to 360° at a polar angle of 30° in the optical laminate, the higher the average ellipticity, the better, with the upper limit being, for example, 0.90 (preferably 0.95).
[0039] In one embodiment, when the ellipticity of transmitted light having a wavelength of 650 nm is measured at an azimuth angle of 11.25° in the range of 0° to 360° at a polar angle of 30°, the average ellipticity is 0.80 or more, preferably 0.84 or more, and more preferably 0.86 or more. Within such a range, an optical laminate can be obtained that exhibits significant effects in reducing ghosting, suppressing light leakage, and achieving high definition. When the ellipticity of transmitted light having a wavelength of 650 nm is measured at an azimuth angle of 11.25° in the range of 0° to 360° at a polar angle of 30° in the optical laminate, the higher the average ellipticity, the better, with the upper limit being, for example, 0.90 (preferably 0.95).
[0040] In one embodiment, when the ellipticity of transmitted light of a wavelength of 550 nm is measured at an azimuth angle of 11.25° in the range of 0° to 360° at a polar angle of 30°, the optical laminate has 10 or more data points for which the ellipticity is 0.85 or more, preferably 15 or more, more preferably 20 or more, even more preferably 25 or more, particularly preferably 30 or more, and most preferably 32. Within such a range, an optical laminate can be obtained that exhibits significant effects of reducing ghosting, suppressing light leakage, and achieving high definition.
[0041] In one embodiment, when the ellipticity of transmitted light of a wavelength of 450 nm is measured at an azimuth angle of 11.25° in the range of 0° to 360° at a polar angle of 30°, the optical laminate has 10 or more data points for which the ellipticity is 0.85 or more, preferably 15 or more, more preferably 20 or more, even more preferably 25 or more, particularly preferably 30 or more, and most preferably 32. Within such a range, an optical laminate can be obtained that exhibits significant effects of reducing ghost phenomena, suppressing light leakage, and achieving high definition.
[0042] In one embodiment, when the ellipticity of transmitted light of a wavelength of 650 nm is measured at an azimuth angle of 11.25° in the range of 0° to 360° at a polar angle of 30°, the optical laminate has 10 or more data points for which the ellipticity is 0.85 or more, preferably 15 or more, more preferably 20 or more, even more preferably 25 or more, particularly preferably 30 or more, and most preferably 32. Within such a range, an optical laminate can be obtained that exhibits significant effects of reducing ghosting, suppressing light leakage, and achieving high definition.
[0043] In one embodiment, the optical laminate has an ellipticity of transmitted light at a wavelength of 550 nm measured at a polar angle of 0° (front direction) of preferably 0.94 or more, more preferably 0.95 or more, and even more preferably 0.96 or more. Within such a range, an optical laminate can be obtained that exhibits significant effects in reducing ghost phenomena, suppressing light leakage, and increasing definition. The higher the ellipticity of the optical laminate at a wavelength of 550 nm measured at a polar angle of 0° (front direction), the better, with the upper limit being, for example, 0.99 (preferably 1).
[0044] In one embodiment, the optical laminate has an ellipticity of transmitted light at a wavelength of 450 nm measured at a polar angle of 0° (front direction) of preferably 0.94 or more, more preferably 0.95 or more, and even more preferably 0.96 or more. Within such a range, an optical laminate can be obtained that exhibits significant effects in reducing ghost phenomena, suppressing light leakage, and achieving high definition. The higher the ellipticity of the optical laminate at a wavelength of 450 nm measured at a polar angle of 0° (front direction), the better, but the upper limit is, for example, 0.99 (preferably 1).
[0045] In one embodiment, the optical laminate has an ellipticity of transmitted light at a wavelength of 650 nm measured at a polar angle of 0° (front direction) of preferably 0.94 or more, more preferably 0.95 or more, and even more preferably 0.96 or more. Within such ranges, an optical laminate can be obtained that exhibits significant effects in reducing ghost phenomena, suppressing light leakage, and increasing definition. The higher the ellipticity of the optical laminate at a wavelength of 650 nm measured at a polar angle of 0° (front direction), the better, with the upper limit being, for example, 0.99 (preferably 1).
[0046] In the optical laminate, the ratio (ellipticity B / ellipticity A) of "the average value of the ellipticity when the ellipticity of transmitted light having a wavelength of 550 nm is measured at an azimuth angle of 11.25° in the range of 0° to 360° at a polar angle of 30°" (the ellipticity A) to "the ellipticity of transmitted light having a wavelength of 550 nm measured at a polar angle of 0° (front direction)" (ellipticity B) is preferably 0.85 or more, more preferably 0.88 or more, and more preferably 0.9 or more. Within such a range, an optical laminate having a remarkable effect of reducing ghosting, suppressing light leakage, and achieving high definition can be obtained. The upper limit of ellipticity B / ellipticity A is, for example, 0.98 (preferably 0.99, more preferably 1).
[0047] In one embodiment, the value (1-DI) obtained by subtracting the depolarization index (DI) of the optical laminate from 1 is 60% or more. The depolarization index can be determined by measuring a Mueller matrix (the following (1)) representing the polarization effect and using the following formula (2). The Mueller matrix representing the polarization effect is measured, for example, using a Mueller matrix polarimeter (manufactured by Axometrics, product name "Axoscan") by irradiating light of a predetermined wavelength (for example, 550 nm) from the polarizing member side of the optical laminate at 23°C.
[0048] The optical laminate has a depolarization index (DI) of transmitted light having a wavelength of 550 nm measured at a polar angle of 30° and an azimuth angle of 0° to 360°, and the value (1-DI) obtained by subtracting the DI from 1 is preferably 99.4% or more, more preferably 99.5% or more, even more preferably 99.6% or more, and particularly preferably 99.68% or more. Within such a range, the effects of the present invention are remarkable. In this specification, the depolarization index (DI) of a predetermined wavelength measured at a polar angle of 30° and an azimuth angle of 0° to 360° is the average value of the depolarization index measured at every 11.25° azimuth angle in the range of 0° to 360° for light of a predetermined wavelength incident on the polarizing member side of the optical laminate at a polar angle of 30° and the emitted light at a polar angle of 30°.
[0049] The optical laminate has a depolarization index (DI) of 450 nm transmitted light measured at a polar angle of 30° and an azimuth angle of 0° to 360°, and the value (1-DI) obtained by subtracting this DI from 1 is preferably 99.4% or more, more preferably 99.5% or more, and even more preferably 99.6% or more. Within such a range, the effects of the present invention become significant.
[0050] The optical laminate has a depolarization index (DI) of 650 nm wavelength transmitted light measured at a polar angle of 30° and an azimuth angle of 0° to 360°, which is preferably 99.4% or more, more preferably 99.5%, and even more preferably 99.6% or more, obtained by subtracting from 1 the DI (1-DI). Within such a range, the effects of the present invention become significant.
[0051] The optical laminate has a depolarization index (DI) of 550 nm wavelength transmitted light measured at a polar angle of 0° (front direction) minus 1 (1-DI), which is preferably 99.5% or more, more preferably 99.6% or more, even more preferably 99.7% or more, and particularly preferably 99.75% or more. Within such a range, the effects of the present invention become significant.
[0052] The optical laminate has a depolarization index (DI) of 450 nm wavelength transmitted light measured at a polar angle of 0° (front direction) minus 1 (1-DI), which is preferably 99.5% or more, more preferably 99.6% or more, and even more preferably 99.7% or more. Within such a range, the effects of the present invention become significant.
[0053] The optical laminate has a depolarization index (DI) of 1 minus the DI of transmitted light at a wavelength of 650 nm measured at a polar angle of 0° (front direction), which is preferably 99.4% or more, more preferably 99.5% or more, and even more preferably 99.6% or more. Within such a range, the effects of the present invention become significant.
[0054] (Retardation Member) As described above, the optical laminate includes, as retardation members, a layer functioning as a λ / 2 plate and a layer functioning as a λ / 4 plate, in this order from the polarizing member side.
[0055] The angle between the slow axis of the layer functioning as a λ / 2 plate and the absorption axis of the polarizing member is preferably 5° to 35°, more preferably 10° to 20°, even more preferably 12° to 18°, and particularly preferably about 15°. The angle between the slow axis of the layer functioning as a λ / 4 plate and the absorption axis of the polarizing member is preferably 55° to 85°, more preferably 70° to 80°, even more preferably 72° to 78°, and particularly preferably about 75°.
[0056] The in-plane retardation Re(550) of the layer functioning as a λ / 4 plate is, for example, 100 nm to 200 nm, or may be 110 nm to 180 nm, 130 nm to 160 nm, or 135 nm to 155 nm.
[0057] The in-plane retardation Re(550) of the layer functioning as a λ / 2 plate is, for example, 200 nm to 330 nm, may be 230 nm to 330 nm, may be 230 nm to 290 nm, or may be 250 nm to 280 nm.
[0058] The layer functioning as a λ / 4 plate 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 layer constituting the retardation member is, for example, less than 1 and may be 0.95 or less, or even less than 0.90, or even 0.85 or less. The Re(450) / Re(550) of the layer constituting the retardation member is, for example, 0.75 or more. The layer functioning as a λ / 2 plate 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 layer constituting the retardation member is, for example, less than 1 and may be 0.95 or less, or even less than 0.90, or even 0.85 or less. The Re(450) / Re(550) of the layer constituting the retardation member is, for example, 0.75 or more. Hereinafter, the layer functioning as a λ / 4 plate and the layer functioning as a λ / 2 plate may be collectively referred to as layers constituting the phase difference member.
[0059] In one embodiment, the layers constituting the retardation member satisfy all of Re(400) / Re(550)<0.85, Re(650) / Re(550)>1.03, and Re(750) / Re(550)>1.05. The layers constituting the phase difference member preferably satisfy at least one of the following conditions: 0.65<Re(400) / Re(550)<0.80 (preferably, 0.7<Re(400) / Re(550)<0.75), 1.0<Re(650) / Re(550)<1.25 (preferably, 1.05<Re(650) / Re(550)<1.20), and 1.05<Re(750) / Re(550)<1.40 (preferably, 1.08<Re(750) / Re(550)<1.36), more preferably at least two of them, and even more preferably all of them.
[0060] The layers constituting the retardation member in the optical laminate preferably have 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 layers constituting the retardation member in the optical laminate 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.
[0061] The surface smoothness of the layer constituting the retardation member in the optical laminate is, for example, 0.50 arcmin or less, preferably 0.40 arcmin or less, more preferably 0.30 arcmin or less, and even more preferably 0.20 arcmin or less. Within such a range, a display system with excellent visibility can be realized. For example, by satisfying such surface smoothness, the uniformity of the in-plane retardation can be improved, and as a result, a display system with excellent display characteristics can be obtained.
[0062] The thickness variation of the layers constituting the retardation member in the optical laminate 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. Such thickness variation can, for example, achieve the above-mentioned surface smoothness. Here, the thickness variation can be determined by measuring the thickness of a first portion located within the measurement surface 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.
[0063] The layers constituting the retardation member in the optical laminate are formed of any appropriate material that can satisfy the above characteristics. The retardation member can be, for example, a stretched resin film or an oriented and solidified layer of a liquid crystal compound. Note that a stretched resin film may also be referred to as a retardation film.
[0064] Examples of resins contained in the resin film include polycarbonate resins, polyester carbonate resins, polyester resins, polyvinyl acetal resins, polyarylate resins, cyclic olefin 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). When the layer constituting the retardation member in the optical laminate exhibits reverse dispersion wavelength characteristics, a resin film containing a polycarbonate resin or a polyester carbonate resin (hereinafter sometimes simply referred to as a polycarbonate resin) can be suitably used.
[0065] As the polycarbonate-based resin, any suitable polycarbonate-based resin can be used as long as the effects of the present invention can be obtained. For example, the polycarbonate-based resin contains structural units derived from a fluorene-based dihydroxy compound, structural units derived from an isosorbide-based dihydroxy compound, and structural units derived from at least one dihydroxy compound selected from the group consisting of alicyclic diols, alicyclic dimethanols, di-, tri-, or polyethylene glycols, and alkylene glycols or spiroglycols. Preferably, the polycarbonate-based resin contains structural units derived from a fluorene-based dihydroxy compound, structural units derived from an isosorbide-based dihydroxy compound, structural units derived from an alicyclic dimethanol and / or structural units derived from di-, tri-, or polyethylene glycol; more preferably, it contains structural units derived from a fluorene-based dihydroxy compound, structural units derived from an isosorbide-based dihydroxy compound, and structural units derived from di-, tri-, or polyethylene glycol. The polycarbonate-based resin may contain structural units derived from other dihydroxy compounds as needed. Details of polycarbonate resins that can be suitably used in the layers that constitute the first phase difference member and methods for forming the layers that constitute the first phase difference member are described in, for example, JP 2014-10291 A, JP 2014-26266 A, JP 2015-212816 A, JP 2015-212817 A, and JP 2015-212818 A, and the descriptions in these publications are incorporated herein by reference.
[0066] When a layer functioning as a λ / 4 plate is formed from a stretched film, the thickness thereof is, for example, 10 μm to 100 μm, preferably 10 μm to 70 μm, more preferably 10 μm to 60 μm, and even more preferably 20 μm to 50 μm. When a layer functioning as a λ / 2 plate is formed from a stretched film, the thickness thereof is, for example, 20 μm to 200 μm, preferably 20 μm to 140 μm, more preferably 20 μm to 120 μm, and even more preferably 40 μm to 100 μm.
[0067] The above-mentioned alignment-solidified layer of the liquid crystal compound 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 term "alignment-solidified layer" 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 layer (e.g., a layer functioning as a λ / 4 plate, a layer functioning as a λ / 2 plate, etc.) constituting the retardation member in the optical laminate (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.
[0068] 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.
[0069] 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.
[0070] 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.
[0071] 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.
[0072] When a layer functioning as a λ / 4 plate is formed from 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 even more preferably 1 μm to 4 μm. When a layer functioning as a λ / 2 plate is formed from an oriented and solidified layer of a liquid crystal compound, the thickness thereof is, for example, 2 μm to 20 μm, preferably 2 μm to 16 μm, more preferably 2 μm to 12 μm, and even more preferably 2 μm to 8 μm.
[0073] (Polarizing Member) The polarizing member may typically include a resin film (sometimes referred to as an absorptive polarizing film) containing a dichroic material. The absorptive polarizing film has a thickness of, for example, 1 μm or more and 20 μm or less, or may be 2 μm or more and 15 μm or less, or may be 12 μm or less, or 10 μm or less, or may be 8 μm or less, or may be 5 μm or less.
[0074] The polarizing member may be made from a single layer of resin film, or may be made from a laminate of two or more layers.
[0075] When a polarizing member is produced from a single-layer resin film, for example, 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 can be dyed with iodine or a dichroic substance such as a dichroic dye, stretched, etc., to obtain a polarizing member. Among these, a polarizing member obtained by dyeing a PVA-based film with iodine and uniaxially stretching it is preferred.
[0076] 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.
[0077] 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.
[0078] The crossed transmittance (Tc) of the 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 film is, for example, 41.0% to 45.0%, and preferably 42.0% or more. The polarization degree (P) of the absorptive polarizing film is, for example, 99.0% to 99.997%, and preferably 99.9% or more.
[0079] (Other Components) Each component constituting the optical laminate can be laminated via any suitable adhesive layer. By laminating the components via an adhesive layer, an optical laminate with excellent smoothness can be obtained. For example, if the display system described in Section A is constructed using an optical laminate with excellent smoothness, it is possible to realize an image display with excellent display characteristics even when the image is enlarged by the lens unit.
[0080] In one embodiment, the retardation member in the optical laminate includes any suitable adhesive layer, and the layers constituting the retardation member in the optical laminate can be laminated via the adhesive layer. The retardation member and the polarizing member can be laminated via the adhesive layer. By integrating the retardation member and the polarizing member with the adhesive layer, an optical laminate that can contribute to preventing the ghost phenomenon can be obtained.
[0081] The adhesive layer may be formed of an adhesive agent or a pressure-sensitive adhesive. Specifically, the adhesive layer may be an adhesive layer or a pressure-sensitive adhesive layer. The thickness of the adhesive layer is, for example, 0.05 μm to 30 μm.
[0082] Specific examples of adhesives include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. By adjusting the type, number, combination, and compounding ratio of the monomers that form the base resin of the adhesive, as well as the amount of crosslinking agent, reaction temperature, reaction time, etc., it is possible to prepare an adhesive with desired properties according to the purpose. The base resin of the adhesive may be used alone or in combination of two or more. An acrylic resin is preferably used as the base resin.
[0083] The adhesive irreversibly changes its state from liquid to solid during the process of forming the adhesive layer, has fluidity when applied, and has the property of being hardened by a hardening treatment (for example, irradiation with active energy rays, heating). As the adhesive, a curable adhesive is preferably used. Specifically, the adhesive layer is preferably a cured layer of resin. As the hardening adhesive, an ultraviolet-curable adhesive is preferably used.
[0084] The ultraviolet-curable adhesive contains a curable monomer such as a compound having a (meth)acryloyl group or a compound having a vinyl group. Preferably, a compound having a (meth)acryloyl group is used. Here, the (meth)acryloyl group refers to an acryloyl group and / or a methacryloyl group.
[0085] The thickness of the adhesive layer included in the retardation member is, for example, 0.5 μm or more and 3 μm or less, preferably 2 μm or less, more preferably 1.3 μm or less, even more preferably 1.1 μm or less, and particularly preferably 0.9 μm or less. With such a thickness, an optical laminate having extremely excellent smoothness can be obtained.
[0086] The optical laminate may further include a member (a so-called positive C plate) whose refractive index characteristics can exhibit the relationship nz > nx = ny. The positive C plate may be disposed, for example, on the opposite side of the retardation member from the polarizing member (i.e., the opposite side of the layer functioning as a λ / 4 plate from the layer functioning as a λ / 2 plate). By disposing the positive C plate, an optical laminate having a higher ellipticity of emitted light can be obtained.
[0087] The thickness direction retardation Rth(550) of the 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" includes 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 positive C plate is, for example, less than 10 nm.
[0088] The positive C plate may be made of any suitable material that satisfies the above-mentioned characteristics, and may be, for example, a resin film or an oriented and solidified layer of a liquid crystal compound.
[0089] A typical example of a material for the resin film constituting the positive C plate is a resin material having negative birefringence. A resin having negative birefringence is a resin that exhibits the property that, when uniaxially stretched, the refractive index in the direction perpendicular to the stretching direction is maximized. Examples of resins having negative birefringence include resins in which chemical bonds or functional groups with large polarization anisotropy, such as aromatic rings or carbonyl groups, are introduced into the side chain. Specific examples of resins having negative birefringence include acrylic resins, styrene resins, maleimide resins, modified polyolefin resins, fumaric acid ester resins, etc., and specific examples thereof can be found in JP 2021-076759 A, JP 2008-544304 A, JP 2008-544317 A, etc., for example. The above resin materials can be used alone or in combination of two or more.
[0090] The resin film constituting the positive C plate may further contain any appropriate additives as necessary. Specific examples of additives include plasticizers, heat stabilizers, light stabilizers, lubricants, antioxidants, UV absorbers, flame retardants, colorants, antistatic agents, compatibilizers, crosslinking agents, thickeners, etc. The type and content of the additives may be appropriately determined depending on the purpose. The content of the additives in the resin film is, for example, about 3% to 10% by weight.
[0091] In one embodiment, the resin material can be formed into a film and then used as a positive C plate as is. Specifically, the formed film can be used as a positive C plate as is without stretching. For example, when a resin solution containing the resin material is applied to a support (by a solution casting method) to form a film, stress occurs due to volume shrinkage when the resin solution dries on the support, and the polymer molecular chains tend to be oriented in the in-plane direction. When a resin material with high birefringence expression and negative intrinsic birefringence is used, a coating film with large thickness-direction birefringence can be formed on the support due to shrinkage during drying. The formed coating film can then be used as a positive C plate as is.
[0092] The thickness of the positive C plate made of a resin film is, for example, 1 μm to 40 μm, preferably 3 μm to 35 μm, and more preferably 5 μm to 30 μm.
[0093] A preferred example of the alignment and solidification layer of a liquid crystal compound constituting the positive C plate is an alignment and solidification layer of 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 a 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.
[0094] The thickness of the positive C plate formed of an aligned and solidified layer of a liquid crystal compound is preferably 0.5 μm to 10 μm, more preferably 0.5 μm to 8 μm, and even more preferably 0.5 μm to 5 μm.
[0095] The optical laminate may include a protective member. The protective member may be disposed on the outermost side opposite to the polarizing member. In one embodiment, the protective member is an anti-reflection protective member.
[0096] The protective member is preferably composed of a laminated film having a substrate and a surface treatment layer formed on the substrate. The thickness of the laminated film is preferably 10 μm to 80 μm, more preferably 15 μm to 60 μm, and even more preferably 20 μm to 45 μm. The thickness of the surface treatment layer is preferably 0.5 μm to 10 μm, more preferably 1 μm to 7 μm, and even more preferably 2 μm to 5 μm.
[0097] The surface treatment layer typically includes a hard coat layer. The hard coat layer is typically formed by applying a hard coat layer-forming material to a substrate and curing the applied layer. The hard coat layer-forming material typically includes a curable compound as a layer-forming component. Examples of the curing mechanism of the curable compound include a thermosetting type and a photocurable type. Examples of the curable compound include a monomer, an oligomer, and a prepolymer. Preferably, a polyfunctional monomer or oligomer is used as the curable compound. Examples of the polyfunctional monomer or oligomer include a monomer or oligomer having two or more (meth)acryloyl groups, a urethane (meth)acrylate or a urethane (meth)acrylate oligomer, an epoxy-based monomer or oligomer, and a silicone-based monomer or oligomer.
[0098] The thickness of the hard coat layer is preferably 0.5 μm to 10 μm, more preferably 1 μm to 7 μm, and even more preferably 2 μm to 5 μm.
[0099] The surface treatment layer preferably includes a functional layer. The functional layer preferably functions as an antireflection layer. A protective member including an antireflection layer may be the antireflection protective member described above. In a preferred embodiment, the surface treatment layer includes, from the substrate side, the hard coat layer and the antireflection layer in this order. The thickness of the functional layer is preferably 0.05 μm to 10 μm, more preferably 0.1 μm to 5 μm, and even more preferably 0.1 μm to 2 μm.
[0100] The protective member having a surface treatment layer can be arranged so that the surface treatment layer is located on the front side. Specifically, the surface treatment layer can be located on the outermost surface of the optical laminate. In one embodiment, the surface of the protective member on the surface treatment layer side preferably has a maximum value of 2.0% or less in the 5° specular reflectance spectrum in the wavelength range of 420 nm to 680 nm, more preferably 1.2% or less, even more preferably 1.0% or less, and particularly preferably 0.8% or less. Here, the 5° specular reflectance can be measured, for example, by attaching the measurement object to a black acrylic plate using an adhesive to prepare a measurement sample, using a spectrophotometer (manufactured by Hitachi High-Technologies Corporation, product name "U-4100") as the measurement device, and setting the angle of incidence of light on the measurement sample to 5°.
[0101] The present invention will be specifically described below using examples, but the present invention is not limited to these examples. The test and evaluation methods used in the examples are as follows. The term "parts" means "parts by weight" unless otherwise specified, and the term "%" means "% by weight" unless otherwise specified.
[0102] (1) Thickness Thicknesses of 10 μm or less were measured using a scanning electron microscope (manufactured by JEOL Ltd., product name "JSM-7100F"). Thicknesses exceeding 10 μm were measured using a digital micrometer (manufactured by Anritsu Corporation, product name "KC-351C"). (2) In-plane retardation Re(λ) A sample was prepared by cutting a square shape of 50 mm in width and 50 mm in length from the center and both ends of the retardation film in the width direction, with one side parallel to the width direction of the film. The in-plane retardation of this sample at each wavelength at 23°C was measured using a Mueller matrix polarimeter (manufactured by Axometrics, product name "Axoscan"). (3) Single transmittance and polarization degree of polarizing film The single transmittance Ts, parallel transmittance Tp, and crossed transmittance Tc of the polarizing film were measured using a spectrophotometer (manufactured by Otsuka Electronics Co., Ltd., "LPF-200"). These Ts, Tp, and Tc are Y values measured using a 2-degree visual field (C light source) according to JIS Z8701 and corrected for visibility. The degree of polarization of the polarizing film was calculated from the obtained Tp and Tc using the following formula: Degree of polarization (%) = {(Tp - Tc) / (Tp + Tc)} １／２ × 100 (4) Surface Smoothness The smoothness of the retardation film was measured using a phase-shifting laser interferometer (manufactured by Zygo, product name "DynaFiz"). Specifically, the retardation film was laminated on a microslide glass (manufactured by Matsunami Glass Industry Co., Ltd., product name "S200200") to prevent the intrusion of foreign matter, bubbles, and deformation streaks. Next, in order to remove the influence of minute bubbles, degassing was performed using a pressurized degassing device (autoclave). The degassing conditions were 50 ° C, 0.5 MPa, and 30 minutes. After degassing, the sample was allowed to cool at room temperature for 30 minutes or more to obtain a measurement sample. The measurement sample was placed on a measurement table with a vibration-isolating table, and a single-wavelength (633 nm) laser was used to interfere with a standard with guaranteed flatness, and the relative displacement within a predetermined area (30 mm φ circle) was measured. For the analysis, the smoothness of the retardation film (unit: arcmin) was defined as doubling the angle index "Slope magnitude RMS" obtained by extracting frequency values of 0.1 / mm to 1 / mm (corresponding to 2σ).
[0103] [Production Example 1-1: Production of Retardation Film 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 Part 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 resulting 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. In this way, a retardation film 1 (λ / 4 plate) having a thickness of 47 μm, an Re (590) of 140 nm, and an Nz coefficient of 1.2 was obtained. The obtained retardation film 1 had an Re(450) / Re(550) of 0.856, exhibiting reverse dispersion wavelength characteristics, and the surface smoothness of the film was 0.25 arcmin.
[0104] [Production Example 1-2: Production of Retardation Film 2] In the same manner as in Production Example 1-1, a polyester carbonate resin (pellet) was obtained. The obtained polyester carbonate resin (pellet) was vacuum-dried at 80 ° C. for 5 hours, and then a film-forming device equipped with 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 to 130 ° C.) and a winder was used to produce a long resin film having a thickness of 260 μm. The obtained long resin film was stretched in the width direction at a stretching temperature of 140 ° C. and a stretching ratio of 2.7 times. In this way, a retardation film 2 (λ / 2 plate) having a thickness of 91 μm, an Re (590) of 270 nm, and an Nz coefficient of 1.2 was obtained. The obtained retardation film 2 had an Re(450) / Re(550) of 0.859, exhibiting reverse dispersion wavelength characteristics, and the surface smoothness of the film was 0.35 arcmin.
[0105] [Production Example 1-3: Preparation of Retardation Layer (Liquid Crystal Compound Alignment Solidification Layer) 3] 55 parts by weight of the compound represented by formula (I), 25 parts by weight of the compound represented by formula (II), and 20 parts by weight of the compound represented by formula (III) were added to 400 parts by weight of cyclopentanone (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 uniform. 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 glass substrate having a thickness of 0.7 mm by spin coating, dried at 100°C for 10 minutes, and then baked at 200°C for 60 minutes to obtain a coating film. The obtained coating film was subjected to a rubbing treatment using a commercially available rubbing device to form an alignment film. Next, the polymerizable composition obtained above was applied to the substrate (substantially the alignment film) by spin coating, and dried at 100°C for 2 minutes. The obtained coating film was cooled to room temperature, and then irradiated with 30 mW / cm using a high-pressure mercury lamp. ２The film was irradiated with ultraviolet light at an intensity of 1000 nm for 30 seconds to obtain a retardation layer (thickness: 3 μm) that was an alignment and solidification layer of the liquid crystal compound. The in-plane retardation Re(590) of the retardation layer was 140 nm. The Re(450) / Re(550) of the retardation layer was 0.851, showing reverse dispersion wavelength characteristics. This retardation layer can function as a λ / 4 plate. The surface smoothness of the retardation layer was 0.16 arcmin.
[0106]
[0107] [Production Example 1-4: Preparation of Retardation Layer (Liquid Crystal Compound Alignment Layer) 4] A retardation layer was obtained in the same manner as in Production Example 1-3, except that the thickness of the retardation layer was 6 μm. The in-plane retardation Re(590) of this retardation layer was 270 nm. Furthermore, the Re(450) / Re(550) of this retardation layer was 0.851, indicating reverse dispersion wavelength characteristics. This retardation layer can function as a λ / 2 plate. Furthermore, the surface smoothness of the retardation layer was 0.22 arcmin.
[0108] [Production Example 1-5: Preparation of Retardation Film 5] A long norbornene-based resin film (manufactured by Zeon Corporation, trade name Zeonor, thickness 40 μm) was stretched at a stretching ratio and stretching temperature so that the in-plane retardation Re (590) was 140 nm, and the free end was stretched longitudinally to prepare a retardation film 5 (λ / 4 plate) having a thickness of 33 μm. The retardation film 5 thus obtained had a refractive index of nx > ny = nz. The retardation layer had an Re (450) / Re (550) of 1.004, which showed approximately flat dispersion wavelength characteristics. The surface smoothness of the film was 0.32 arcmin.
[0109] [Production Example 1-6: Preparation of Retardation Film 6] A long norbornene-based resin film (manufactured by Zeon Corporation, trade name Zeonor, thickness 50 μm) was stretched at a stretching ratio and stretching temperature so that the in-plane retardation Re (590) was 270 nm, and the free end was stretched longitudinally to prepare a retardation film 6 (λ / 2 plate) having a thickness of 33 μm. The retardation film 6 thus obtained had a refractive index of nx > ny = nz. The retardation layer had an Re (450) / Re (550) of 1.004, which showed approximately flat dispersion wavelength characteristics. The surface smoothness of the film was 0.42 arcmin.
[0110] [Production Example 1-7: Preparation of Retardation Layer (Liquid Crystal Compound Alignment Solidification Layer) 7] 10 g of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (manufactured by BASF: trade name "Paliocolor LC242") and 3 g of a photopolymerization initiator for the polymerizable liquid crystal compound (manufactured by BASF: trade name "Irgacure 907") were dissolved in 40 g of toluene to prepare a liquid crystal composition (coating liquid). The surface of a polyethylene terephthalate (PET) film (thickness 38 μm) was rubbed with a rubbing cloth to perform an alignment treatment. The liquid crystal coating liquid was applied to this alignment-treated surface using a bar coater, and the liquid crystal compound was aligned by heating and drying at 90°C for 2 minutes. The liquid crystal layer thus formed was then irradiated with 1 mJ / cm using a metal halide lamp. ２ The liquid crystal layer was cured by irradiating the PET film with light, forming a retardation layer, which was a liquid crystal alignment solidified layer. The retardation layer had a thickness of 1.5 μm and an in-plane retardation Re(590) of 140 nm. Furthermore, the retardation layer exhibited a refractive index characteristic of nx>ny=nz. The retardation layer also had an Re(450) / Re(550) of 1.089, indicating positive dispersion wavelength characteristics. This retardation layer can function as a λ / 4 plate. The surface smoothness of the film was 0.18 arcmin.
[0111] [Production Example 1-8: Preparation of Retardation Layer (Liquid Crystal Compound Alignment Solidified Layer) 8] A retardation layer having an in-plane retardation Re(590) of 270 nm was obtained in the same manner as in Production Example 1-7, except that the thickness of the retardation layer was 2.5 μm. The retardation layer exhibited refractive index characteristics of nx>ny=nz. Furthermore, the retardation layer had an Re(450) / Re(550) of 1.089, indicating positive dispersion wavelength characteristics. This retardation layer can function as a λ / 2 plate.
[0112] [Production Example 1-9: Preparation of Retardation Film (Positive C Plate) 9] 48 parts by weight of hydroxypropyl methylcellulose (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: Metrose 60SH-50), 15,601 parts by weight of distilled water, 8,161 parts by weight of diisopropyl fumarate, 240 parts by weight of 3-ethyl-3-oxetanylmethyl acrylate, and 45 parts by weight of polymerization initiator t-butyl peroxypivalate were placed in an autoclave equipped with a stirrer, cooling tube, nitrogen inlet tube, and thermometer. Nitrogen bubbling was performed for 1 hour, and then the mixture was stirred at 49°C for 24 hours to carry out radical suspension polymerization. The mixture was then cooled to room temperature, and the suspension containing the resulting polymer particles was centrifuged. The resulting polymer was washed twice with distilled water and twice with methanol and then dried under reduced pressure. The resulting fumarate ester-based resin was dissolved in a toluene-methyl ethyl ketone mixed solution (toluene / methyl ethyl ketone 50% by weight / 50% by weight) to prepare a 20% solution. Furthermore, 5 parts by weight of tributyl trimellitate as a plasticizer was added to 100 parts by weight of the fumaric acid ester resin to prepare a dope. A biaxially stretched polyester (polyethylene terephthalate / isophthalate copolymer) film (75 μm thick) was used as the support film. The prepared dope was applied to the support film to a dry thickness of 20 μm and dried at 140°C. The dried coating film (positive C plate) had an Re(590) of approximately 0 nm and an Rth(590) of -83 nm. Furthermore, the Rth(450) / Rth(550) of the retardation layer was 1.012, demonstrating positive dispersion wavelength characteristics.
[0113] [Production Example 2: Preparation of Polarized Film] A long, amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) with a Tg of approximately 75°C was used as the thermoplastic resin substrate. One side of the resin substrate was subjected to a corona treatment. A PVA-based resin (100 parts by weight of a 9:1 mixture of polyvinyl alcohol (degree of polymerization: 4200, degree of saponification: 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Mitsubishi Chemical Corporation, trade name "GOHSENEX Z410") was prepared. 13 parts by weight of potassium iodide was added to 100 parts by weight of the resulting PVA-based resin, and the resulting solution was dissolved in water to prepare an aqueous PVA solution (coating solution). The PVA-based resin was applied to the corona-treated surface of the resin substrate and dried at 60°C to form a 13 μm-thick PVA-based resin layer, producing a laminate. The resulting laminate was uniaxially stretched 2.4 times in the longitudinal direction (longitudinal direction) in an oven at 130°C (in-air auxiliary stretching treatment). Next, the laminate was immersed for 30 seconds in an insolubilizing bath (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40°C (insolubilization treatment), then immersed for 60 seconds in a dyeing bath (an iodine aqueous solution obtained by blending iodine and potassium iodide in a weight ratio of 1:7 with 100 parts by weight of water) at a liquid temperature of 30°C while adjusting the concentration so that the single-unit transmittance (Ts) of the finally obtained absorptive polarizing film would have a desired value (dyeing treatment), then immersed for 30 seconds in a crosslinking bath (a boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40°C (crosslinking treatment). The laminate was then immersed in a boric acid aqueous solution (boric acid concentration: 4 wt %, potassium iodide concentration: 5 wt %) at a liquid temperature of 70°C and uniaxially stretched in the longitudinal direction (machine direction) between rolls operating at different peripheral speeds to a total stretch ratio of 5.5 (underwater stretching treatment). The laminate was then immersed in a cleaning bath (aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 20°C (washing treatment). The laminate was then dried in an oven maintained at approximately 90°C and brought into contact with a stainless steel heated roll maintained at a surface temperature of approximately 75°C (drying shrinkage treatment). The shrinkage rate of the laminate in the width direction due to the drying shrinkage treatment was 5.2%. In this manner, an absorptive polarizing film having a thickness of approximately 5 μm was formed on the resin substrate.A cycloolefin resin film (thickness: 25 μm) was attached as a protective layer to the surface of the obtained absorptive polarizing film (the surface opposite to the resin substrate) via a UV-curable adhesive. Specifically, the curable adhesive was applied so that the total thickness was approximately 1 μm, and the films were attached using a roller. The adhesive was then cured by irradiating it with UV light from the cycloolefin resin film side. The resin substrate was then peeled off. This resulted in a polarizing film having a cycloolefin resin film / absorptive polarizing film configuration. The polarizing film had a single transmittance (Ts) of 43.4% and a polarization degree of 99.993%.
[0114] [Example 1] The polarizing film obtained in Production Example 2, a retardation film 2 (λ / 2 plate), and a retardation film 1 (λ / 4 plate) were laminated in this order to obtain an optical laminate. Adjacent films were superposed via an acrylic pressure-sensitive adhesive layer (manufactured by Nitto Denko Corporation, thickness 5 μm). In the superposition, the relationship between the slow axis of each retardation film and the absorption axis of the polarizing film was such that, when the absorption axis direction of the polarizing film as viewed from the retardation film 1 (λ / 4 plate) was taken as the reference (0°), the angle of the slow axis direction of the retardation film 2 (λ / 2 plate) was 15°, and the angle of the slow axis direction of the retardation film 1 (λ / 4 plate) was 75°.
[0115] [Example 2] An optical laminate was obtained by laminating the polarizing film obtained in Production Example 2, a retardation layer 4 (λ / 2 plate), and a retardation layer 3 (λ / 4 plate). Adjacent elements were superposed via an acrylic pressure-sensitive adhesive layer (manufactured by Nitto Denko Corporation, thickness 5 μm). In the superposition, the relationship between the slow axis of each retardation film and the absorption axis of the polarizing film was such that, when the absorption axis direction of the polarizing film as viewed from the retardation layer 3 (λ / 4 plate) was taken as the reference (0°), the angle of the slow axis direction of the retardation layer 4 (λ / 2 plate) was 15°, and the angle of the slow axis direction of the retardation layer 3 (λ / 4 plate) was 75°.
[0116] [Example 3] An optical laminate was obtained by laminating the polarizing film obtained in Production Example 2, retardation film 2 (λ / 2 plate), retardation film 1 (λ / 4 plate), and retardation film 9. Adjacent elements were superposed via an acrylic pressure-sensitive adhesive layer (manufactured by Nitto Denko Corporation, thickness 5 μm). In the superposition, the relationship between the slow axis of each retardation film and the absorption axis of the polarizing film was such that, when the absorption axis direction of the polarizing film as viewed from retardation film 1 (λ / 4 plate) was taken as the reference (0°), the angle of the slow axis direction of retardation film 2 (λ / 2 plate) was 15°, and the angle of the slow axis direction of retardation film 1 (λ / 4 plate) was 75°.
[0117] [Example 4] An optical laminate was obtained by laminating the polarizing film obtained in Production Example 2, a retardation layer 4 (λ / 2 plate), a retardation layer 3 (λ / 4 plate), and a retardation film 9. Adjacent elements were superposed via an acrylic pressure-sensitive adhesive layer (manufactured by Nitto Denko Corporation, thickness 5 μm). In the superposition, the relationship between the slow axis of each retardation layer and the absorption axis of the polarizing film was such that, when the absorption axis direction of the polarizing film as viewed from the retardation layer 3 (λ / 4 plate) was taken as the reference (0°), the angle of the slow axis direction of the retardation layer 4 (λ / 2 plate) was 15°, and the angle of the slow axis direction of the retardation layer 3 (λ / 4 plate) was 75°.
[0118] [Experimental Example 1] The polarizing film obtained in Production Example 2, a retardation film 6 (λ / 2 plate), and a retardation film 5 (λ / 4 plate) were laminated to obtain an optical laminate. Adjacent films were overlapped via an acrylic pressure-sensitive adhesive layer (manufactured by Nitto Denko Corporation, thickness 5 μm). In the overlapping, the relationship between the slow axis of each retardation film and the absorption axis of the polarizing film was such that, when the absorption axis direction of the polarizing film as viewed from the retardation film 5 (λ / 4 plate) was taken as the reference (0°), the angle of the slow axis direction of the retardation film 6 (λ / 2 plate) was 15°, and the angle of the slow axis direction of the retardation film 5 (λ / 4 plate) was 75°.
[0119] [Experimental Example 2] An optical laminate was obtained by laminating the polarizing film obtained in Production Example 2, a retardation film 6 (λ / 2 plate), a retardation film 5 (λ / 4 plate), and a retardation film 9. Adjacent films were overlapped via an acrylic pressure-sensitive adhesive layer (manufactured by Nitto Denko Corporation, thickness 5 μm). In the overlapping, the relationship between the slow axis of each retardation film and the absorption axis of the polarizing film was such that, when the absorption axis direction of the polarizing film as viewed from the retardation film 5 (λ / 4 plate) was taken as the reference (0°), the angle of the slow axis direction of the retardation film 6 (λ / 2 plate) was 15°, and the angle of the slow axis direction of the retardation film 5 (λ / 4 plate) was 75°.
[0120] [Experimental Example 3] An optical laminate was obtained by laminating the polarizing film obtained in Production Example 2, a retardation layer 8 (λ / 2 plate), and a retardation layer 7 (λ / 4 plate). Adjacent elements were overlapped via an acrylic pressure-sensitive adhesive layer (manufactured by Nitto Denko Corporation, thickness 5 μm). In the overlapping, the relationship between the slow axis of each retardation film and the absorption axis of the polarizing film was such that, when the absorption axis direction of the polarizing film as viewed from the retardation layer 7 (λ / 4 plate) was taken as the reference (0°), the angle of the slow axis direction of the retardation layer 8 (λ / 2 plate) was 15°, and the angle of the slow axis direction of the retardation layer 7 (λ / 4 plate) was 75°.
[0121] [Experimental Example 4] An optical laminate was obtained by laminating the polarizing film obtained in Production Example 2, a retardation layer 8 (λ / 2 plate), a retardation layer 7 (λ / 4 plate), and a retardation film 9. Adjacent elements were superposed via an acrylic pressure-sensitive adhesive layer (manufactured by Nitto Denko Corporation, thickness 5 μm). In the superposition, the relationship between the slow axis of each retardation film and the absorption axis of the polarizing film was such that, when the absorption axis direction of the polarizing film as viewed from the retardation layer 7 (λ / 4 plate) was taken as the reference (0°), the angle of the slow axis direction of the retardation layer 8 (λ / 2 plate) was 15°, and the angle of the slow axis direction of the retardation layer 7 (λ / 4 plate) was 75°.
[0122] <Evaluation> The following evaluations were performed for each example. 1. Ellipticity Using a Mueller matrix polarimeter (manufactured by Axometrics, product name "Axoscan"), light of a predetermined wavelength (450 nm, 550 nm, 650 nm) was incident on the polarizing member side of the optical laminate at 23°C, and the ellipticity of the light emitted from the retardation member was measured. The incident angle and the exit angle were set to a polar angle of 30°, and the ellipticity was measured at azimuth angles of 11.25° in the range of azimuth angles from 0° to 360°. The minimum and average values of 32 measured values, as well as the number of data points with a value of 0.85 or greater, are shown in Table 1. The ellipticity was also measured with the incident angle and the exit angle set to a polar angle of 0. The measured values are shown in Table 1.
[0123]
[0124] 2. Depolarization Property Using a Mueller matrix polarimeter (manufactured by Axometrics, product name "Axoscan"), light of a predetermined wavelength (450 nm, 550 nm, 650 nm) was incident on the polarizing member side of the optical laminate at 23°C, and the depolarization index (DI) was calculated from the obtained Mueller matrix using the following formula. The depolarization property was evaluated using the value (1-DI) obtained by subtracting the depolarization index (DI) from 1. The depolarization index (DI) was calculated by measuring the depolarization index (DI) of transmitted light of a predetermined wavelength at a polar angle of 30° and an azimuth angle of 0° to 360°, and the depolarization index (DI) of transmitted light of a predetermined wavelength at a polar angle of 0° (front direction). The depolarization index (DI) of transmitted light of a predetermined wavelength measured at a polar angle of 30° and an azimuth angle of 0° to 360° was calculated as the average value of the depolarization indexes measured at azimuth angles of 11.25° for light emitted at a polar angle of 30° in the range of azimuth angles of 0° to 360°. The results are shown in Table 2.
[0125]
[0126] A display system according to an embodiment of the present invention can be used in a display such as VR goggles, for example.
[0127] 2 Display system 10 Polarizing member 12 Display element 14 Reflecting portion 16 First lens portion 18 Half mirror 20 First phase difference member 22 Second phase difference member 24 Second lens portion 200 Optical laminate
Claims
1. A display system for displaying an image to a user, comprising: a display element having a display surface that emits light representing an image forward via a polarizing member; a reflecting section arranged in front of the display element, including a reflective polarizing member, and reflecting the light emitted from the display element; a first lens section arranged on an optical path between the display element and the reflecting section; 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 reflecting section towards the reflecting section; a first phase difference member arranged on the optical path between the display element and the half mirror; and a second phase difference member arranged on the optical path between the half mirror and the reflecting section, wherein the polarizing member and the first phase difference member constitute an optical laminate, and the optical laminate comprises, in this order, a polarizing member, a layer functioning as a λ / 2 plate, and a layer functioning as a λ / 4 plate.
2. An optical laminate for use in the display system according to claim 1, comprising, in this order, a polarizing member, a layer functioning as a λ / 2 plate, and a layer functioning as a λ / 4 plate.
3. The optical laminate according to claim 2, wherein the layer functioning as a λ / 2 plate has an in-plane retardation Re(550) of 230 nm to 330 nm.
4. The optical laminate according to claim 2, wherein the layer functioning as a λ / 4 plate has an in-plane retardation Re(550) of 100 nm to 200 nm.
5. The optical laminate according to claim 2, wherein the angle between the slow axis of the layer functioning as a λ / 2 plate and the absorption axis of the polarizing member is 5° to 35°.
6. The optical laminate according to claim 2, wherein the angle between the slow axis of the layer functioning as the λ / 4 plate and the absorption axis of the polarizing member is 55° to 85°.
7. The optical laminate according to claim 2, wherein the layer functioning as a λ / 2 plate exhibits inverse dispersion wavelength characteristics.
8. The optical laminate according to claim 2, wherein the layer functioning as a λ / 4 plate exhibits inverse dispersion wavelength characteristics.
9. The optical laminate according to claim 2, further comprising a member whose refractive index characteristics exhibit the relationship nz>nx=ny, said member whose refractive index characteristics exhibit the relationship nz>nx=ny being disposed on the side of said layer functioning as a λ / 4 plate opposite to said layer functioning as a λ / 2 plate.
10. The optical laminate according to claim 2, further comprising an anti-reflection protective member, the anti-reflection protective member being disposed on the outermost side opposite the polarizing member.
11. The optical laminate according to claim 2, wherein the value (1-DI) obtained by subtracting the depolarization index (DI) of transmitted light having a wavelength of 550 nm measured at a polar angle of 0° from 1 is 99.5% or more.
12. The optical laminate according to claim 2, wherein the value (1-DI) obtained by subtracting the depolarization index (DI) of transmitted light having a wavelength of 550 nm measured at a polar angle of 30° and an azimuth angle of 0° to 360° from 1 is 99.4% or more.
13. The optical laminate according to claim 2, which is used as the first phase difference member in a display method comprising the steps of: passing light representing an image emitted through a polarizing member through a first phase difference member; passing the light that has passed through the first phase difference member through a half mirror and a first lens unit; passing the light that has passed through the half mirror and the first lens unit through the second phase difference member; reflecting the light that has passed through the second phase difference member towards the half mirror with a reflective polarizing member; and allowing the light reflected by the reflective polarizing member and the half mirror to pass through the reflective polarizing member by the second phase difference member.