Optical film piece and method for manufacturing same

Abstract

Provided is an optical film piece with which it is possible to satisfactorily achieve weight reduction in VR goggles while improving visibility. The optical film piece includes a retardation member and has a first principal surface and a second principal surface facing each other. The optical film piece has a first region in which the standard deviation of an in-plane retardation Re (550) at a wavelength of 550 nm is 5 nm or less from a first site located at a central portion to a second site located outside the first site on the first principal surface, and has a second region in which the standard deviation of an in-plane retardation Re (550) at a wavelength of 550 nm exceeds 5 nm from the first site to a third site located outside the second site on the first principal surface. The average value of the in-plane retardation Re (550) at a wavelength of 550 nm in the first region is 135 nm or more.

Description

Optical film piece and method for manufacturing the same

[0001] The present invention relates to optical film pieces and methods for making the same.

[0002] Image display devices, such as liquid crystal display devices and electroluminescence (EL) display devices (e.g., organic EL display devices), are rapidly becoming popular. In image display devices, optical components such as polarizing components and phase difference components are generally used to realize image display and improve image display performance (see, for example, Patent Document 1).

[0003] In recent years, new applications of image display devices have been developed. For example, goggles with displays (VR goggles) for realizing virtual reality (VR) have begun to be commercialized. Since the use of VR goggles in various situations is being considered, there is a demand for lighter weight, improved visibility, and the like.

[0004] Japanese Patent Application Laid-Open No. 2021-103286

[0005] While the weight reduction of the VR goggles can be achieved by, for example, thinning the lenses used in the VR goggles, there is also a need for the development of optical components suitable for display systems using thin lenses.

[0006] In view of the above, a main object of the present invention is to provide an optical film piece that can effectively achieve weight reduction of VR goggles while improving visibility.

[0007] 1. An optical film piece according to an embodiment of the present invention includes a retardation member and has first and second principal surfaces facing each other, the first principal surface having a first region extending from a first portion located in the center to a second portion located outside the first region, in which the standard deviation of in-plane retardation Re(550) at a wavelength of 550 nm is 5 nm or less, and the first principal surface has a second region extending from the first portion to a third portion located outside the second portion, in which the standard deviation of in-plane retardation Re(550) at a wavelength of 550 nm is greater than 5 nm, and the average in-plane retardation Re(550) at a wavelength of 550 nm in the first region is 135 nm or greater. 2. In the optical film piece described above in 1, the absolute value of the difference between the average in-plane retardation Re(550) at a wavelength of 550 nm in the first region and the average in-plane retardation Re(550) at a wavelength of 550 nm in the second region may be 5 nm or less. The optical film piece described in 1 or 2 above may have a substantially circular shape in a planar view, and the third portion may be located in a region radially inward from the edge of the first main surface in a planar view that is 40% or less of the radius of the first main surface.

[0008] 4. A method for manufacturing an optical film piece according to an embodiment of the present invention is the method for manufacturing an optical film piece described in any one of 1 to 3 above, and includes integrating a member including a phase difference member with a part having a curved surface portion, and the integration includes contacting the tip of a contact member with the member in a deformable state to deform the member and form a protrusion pointing toward the curved surface portion, and contacting the protrusion of the member with the curved surface portion. 5. In the method for manufacturing an optical film piece described in 4 above, the curved surface portion of the part may have a concave surface. 6. In the method for manufacturing an optical film piece described in 4 or 5 above, the tip of the contact member may have a curved shape. 7. In the method for manufacturing an optical film piece described in 5 or 6 above, the tip of the contact member may have a curved shape, and the ratio of the radius of curvature of the curved shape of the tip of the contact member to the radius of curvature of the curved surface portion of the part may be 0.65 or more. 8. In the method for manufacturing an optical film piece according to any one of the above items 4 to 7, a region in which a change in in-plane retardation Re(550) of the retarder at a wavelength of 550 nm due to the integration is 10 nm or less may be formed in a central portion of the optical film piece. 9. In the method for manufacturing an optical film piece according to the above item 8, the component may be a lens.

[0009] According to the optical film piece according to the embodiment of the present invention, it is possible to effectively achieve a reduction in the weight of VR goggles while improving visibility.

[0010] 4A is a diagram showing an optical film piece according to an embodiment of the present invention as viewed from above; FIG. 4B is a schematic partially enlarged cross-sectional view showing the general configuration of the optical film piece shown in FIG. 1; FIG. 4C is a schematic cross-sectional view showing the optical film piece shown in FIG. 1 integrated with an optical component; FIG. 4D is a diagram showing an example of a method for manufacturing an optical film piece according to an embodiment of the present invention; FIG. 4A is a diagram continuing from FIG. 4B; FIG. 4C is a diagram continuing from FIG. 4D; FIG. 4D is a schematic diagram showing the general configuration of an example of a display system for VR goggles; FIG. 4B is a diagram explaining an evaluation area, showing an optical film piece as viewed from above; FIG. 4D is a diagram explaining an evaluation area, showing a cross-sectional view of a lens.

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments. In order to clarify the description, the drawings may schematically show the width, thickness, shape, etc. of each part compared to the embodiments, but these are merely examples and do not limit the interpretation of the present invention. Furthermore, in the drawings, the same or equivalent elements are given the same reference numerals, and redundant explanations may be omitted.

[0012] (Definition of Terms and Symbols) The definitions of terms and symbols used in this specification are as follows. (1) Refractive Index (nx, ny, nz) "nx" is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), "ny" is the refractive index in the in-plane direction perpendicular to the slow axis (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction. (2) In-Plane Retardation (Re) "Re(λ)" is the in-plane retardation measured with light having a wavelength of λ nm at 23°C. For example, "Re(550)" is the in-plane retardation measured with light having a wavelength of 550 nm at 23°C. Re(λ) is calculated by the formula: Re(λ) = (nx - ny) × d, where d (nm) is the thickness of the layer (film). (3) Thickness Direction Retardation (Rth) "Rth(λ)" is the retardation in the thickness direction measured with light having a wavelength of λ nm at 23°C. For example, "Rth(550)" is the retardation in the thickness direction measured with light having a wavelength of 550 nm at 23°C. Rth(λ) is calculated by the formula: Rth(λ) = (nx - nz) x d, where d (nm) is the thickness of the layer (film). (4) Nz coefficient The Nz coefficient is calculated by Nz = Rth / Re. (5) Angle When an angle is mentioned in this specification, the angle includes both clockwise and counterclockwise angles relative to the reference direction. Therefore, for example, "45°" means ±45°.

[0013] [Optical Film Piece] The optical film piece according to an embodiment of the present invention typically includes an optical element such as a retardation element or a polarizing element. In one embodiment, the optical film piece includes at least a retardation element such as a λ / 4 element, and may include other optical elements in addition to the retardation element. Specifically, the optical film piece may include a polarizing element. The optical film piece may also include other elements such as a protective element and an adhesive layer for integrating adjacent elements. The thickness of the optical film piece varies depending on, for example, the type and number of elements included, but is, for example, 50 μm to 400 μm.

[0014] Fig. 1 is a top view of an optical film piece according to one embodiment of the present invention, Fig. 2 is a schematic partially enlarged cross-sectional view showing the general configuration of the optical film piece shown in Fig. 1, and Fig. 3 is a schematic cross-sectional view showing the optical film piece shown in Fig. 1 integrated with an optical component. Note that in Fig. 3, hatching has been omitted from the cross sections of the optical component and the optical film piece to make the drawing easier to see. Also, details of the optical film piece have been omitted.

[0015] The optical film piece 1 includes a retardation member 23 and a pressure-sensitive adhesive layer 40. The retardation member 23 is typically composed of a λ / 4 member. In this case, the retardation member 23 may have other retardation layers in addition to the λ / 4 member. When the retardation member 23 does not have other retardation layers, the retardation member 23 may be substantially a λ / 4 member.

[0016] The optical film piece 1 has a substantially circular shape in plan view, but is not limited to this. For example, the optical film piece 1 may have a substantially elliptical shape or a rounded rectangular shape. The major axis of the optical film piece 1 in plan view is, for example, 10 mm to 100 mm. Here, the major axis in plan view is the distance between the two most distant points on the periphery of the optical film piece when viewed from above.

[0017] The optical film piece 1 has a first main surface 1a and a second main surface 1b facing each other. The first main surface 1a and the second main surface 1b of the optical film piece 1 have curved surfaces. In the illustrated example, the optical film piece 1 has a convex curvature toward the second main surface 1b, the first main surface 1a has a concave curved surface, and the second main surface 1b has a convex curved surface. In the example shown in FIG. 3, the optical film piece 1 is bonded to the concave surface of an optical component (e.g., a lens) L having a curved surface by its pressure-sensitive adhesive layer 40 (not shown in FIG. 3), and the phase difference member 23 has a convex curvature toward the pressure-sensitive adhesive layer 40, and the main surface of the phase difference member 23 has a curved surface. Unlike the illustrated example, the optical film piece 1 may be bonded to the convex surface of the optical component L. The radius of curvature of the main surface of the optical film piece 1 is, for example, 10 mm or more and 150 mm or less, preferably 100 mm or less, and more preferably 90 mm or less. The radius of curvature can be confirmed using, for example, a laser displacement meter.

[0018] The in-plane retardation Re(550) of the λ / 4 component is, for example, 100 nm to 190 nm, or may be 110 nm to 180 nm, 130 nm to 160 nm, or 135 nm to 155 nm. For example, the λ / 4 component preferably exhibits an inverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light. In this case, the Re(450) / Re(550) of the λ / 4 component may be, for example, 0.75 or more and less than 1, or 0.8 or more and 0.95 or less.

[0019] The refractive index characteristics of the λ / 4 member preferably exhibit 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 λ / 4 member 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.

[0020] The optical film piece 1 may have different retardation values ​​(e.g., in-plane retardation Re) on its major surface. Specifically, the major surface of the optical film piece 1 may have a distribution of retardation values. For example, the optical film piece 1 may have a first region 71 extending from a first portion (e.g., center) 1c located in the center of the first major surface 1a of the optical film piece 1 to a second portion 1d located outside the first portion 1c, in which the standard deviation of the in-plane retardation Re(550) at a wavelength of 550 nm is 5 nm or less. In a plan view, the first region 71 may be a circular area centered on the first portion 1c and having a radius equal to the distance between the first portion 1c and the second portion 1d. The standard deviation of the in-plane retardation Re(550) of the first region 71 is preferably 4.5 nm or less, more preferably 4 nm or less, even more preferably 3 nm or less, and particularly preferably 2 nm or less. By having a first region 71 with small variations in retardation values ​​in the center of the optical film piece 1, for example, a display with excellent visibility can be obtained.

[0021] The optical film piece 1 has a second region 72 on the first major surface 1a, extending from the first region 1c to a third region 1e located outside the second region 1d, in which the standard deviation of the in-plane retardation Re(550) at a wavelength of 550 nm exceeds 5 nm. In a plan view, the second region 72 may be a circular area centered on the first region 1c and having a radius equal to the distance between the first region 1c and the third region 1e. The standard deviation of the in-plane retardation Re(550) of the second region 72 may be 5.5 nm or more, 6 nm or more, 7 nm or more, or 8 nm or more. Even if the variation in retardation value is relatively large in the second region 72, which includes the first region 71 and is wider than the first region 71, this does not significantly affect, for example, the visibility of the resulting display.

[0022] The average value of the in-plane retardation Re(550) in the first region 71 is, for example, 135 nm or more, preferably 135 nm or more and 155 nm or less, and more preferably 135 nm or more and 150 nm or less. The average value of the in-plane retardation Re(550) in the second region 72 is, for example, 135 nm or more, preferably 135 nm or more and 155 nm or less, and more preferably 135 nm or more and 150 nm or less. The absolute value of the difference between the average value of the in-plane retardation Re(550) in the first region 71 and the average value of the in-plane retardation Re(550) in the second region 72 is preferably 5 nm or less, more preferably 4 nm or less, even more preferably 3 nm or less, and particularly preferably 2 nm or less.

[0023] For example, in a plan view, the third portion 1e is preferably located radially inward from the end of the first principal surface 1a (optical film piece 1) in an area that is 40% or less of the radius of the first principal surface 1a, more preferably 30% or less of the radius of the first principal surface 1a, and even more preferably 20% or less of the radius of the first principal surface 1a. Furthermore, for example, the line connecting the point facing the first region 71 on the concave surface of the lens L and the focal point of the lens L preferably forms an angle of 5° or more with respect to the line connecting the center of the lens L and the focal point of the lens L, more preferably 10° or more, and even more preferably 15° or more. By satisfying such an angle, for example, a display with extremely excellent visibility can be obtained.

[0024] The in-plane retardation Re(550) in the third region 1e may be larger or smaller than the in-plane retardation Re(550) in the first region 1c. In one embodiment, the optical film piece 1 may have, in the peripheral portion of the first main surface 1a, a region where the in-plane retardation Re(550) is larger than the in-plane retardation Re(550) in the first region 1c and a region where the in-plane retardation Re(550) is smaller than the in-plane retardation Re(550) in the first region 1c.

[0025] The λ / 4 member may be, for example, a stretched resin film or an oriented and solidified layer of a liquid crystal compound.

[0026] 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. Examples of combination methods include blending and copolymerization. When the λ / 4 member 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.

[0027] Any suitable polycarbonate resin can be used as the polycarbonate resin. For example, the polycarbonate 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 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 resin may contain structural units derived from other dihydroxy compounds as needed. Details of polycarbonate-based resins that can be suitably used for λ / 4 members and methods for forming λ / 4 members 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.

[0028] The thickness of the λ / 4 member made of a stretched resin film is, for example, 10 μm to 100 μm, preferably 10 μm to 70 μm, and more preferably 20 μm to 60 μm.

[0029] The above-mentioned liquid crystal compound alignment solidified layer is a layer in which the liquid crystal compound is aligned in a predetermined direction within the layer and the alignment state is fixed. The term "alignment solidified layer" encompasses an alignment solidified layer obtained by curing a liquid crystal monomer, as described below. In a λ / 4 component, rod-shaped liquid crystal compounds are typically aligned in the slow axis direction of the λ / 4 component (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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] The thickness of the λ / 4 member formed of the 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.

[0035] As described above, the retardation member 23 may have another retardation layer in addition to the λ / 4 member. As the other retardation layer, for example, a layer that satisfies the relationship nz > nx ≥ ny may be used. The other retardation layer is typically laminated on the λ / 4 member via an adhesive layer.

[0036] The thickness direction retardation Rth(550) of the layer having the refractive index characteristics of nz>nx≧ny is preferably -260 nm to -10 nm, more preferably -230 nm to -15 nm, and even more preferably -215 nm to -20 nm. In one embodiment, the other retardation layer is a so-called positive C plate whose refractive index exhibits the relationship nx=ny. 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. For example, it also includes the case where Re(550) is less than 10 nm. In another embodiment, the refractive index of the other retardation layer exhibits the relationship nx>ny. In this case, the in-plane retardation Re(550) of the other retardation layer is preferably 10 nm to 150 nm, more preferably 10 nm to 80 nm.

[0037] The layer whose refractive index characteristics satisfy the relationship nz > nx ≥ ny can be formed from any appropriate material. Preferably, it is composed of a film containing a liquid crystal material fixed in homeotropic alignment. The liquid crystal material (liquid crystal compound) that can be homeotropically aligned may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of such liquid crystal compounds and methods for forming the film include the liquid crystal compounds and formation methods described in paragraphs

[0020] to

[0042] of JP 2002-333642 A. In this case, the thickness is preferably 0.1 μm to 5 μm, more preferably 0.5 μm to 4 μm.

[0038] As another preferred example, the layer having refractive index characteristics satisfying the relationship nz > nx ≥ ny may be a retardation film formed of a fumaric acid diester resin described in JP 2012-32784 A. In this case, the thickness is preferably 5 μm to 50 μm, more preferably 10 μm to 35 μm.

[0039] <Manufacturing Method> The optical film piece can be obtained by integrating a member containing at least a retardation member with a curved surface portion of an optical component (for example, lens L shown in FIG. 3). The integration can be typically performed by bonding the member containing the retardation member to the curved surface portion of the optical component (for example, lens L) using a pressure-sensitive adhesive layer. The obtained optical film piece can then include a pressure-sensitive adhesive layer (pressure-sensitive adhesive layer 40 shown in FIG. 2).

[0040] 4A to 4E are diagrams illustrating an example method for manufacturing an optical film piece according to one embodiment of the present invention.

[0041] FIG. 4A shows a state in which a workpiece 2 is prepared by providing an adhesive layer 40 on a phase difference member 23 or a laminated portion including the phase difference member 23, and the workpiece 2 is placed above a lens L, which is an adherend. Details of the workpiece 2 are omitted in FIGS. 4A to 4E . The lens L is, for example, circular in plan view and concave in cross section. The radius of curvature of the curved surface of the lens L is, for example, 10 mm to 150 mm, preferably 100 mm or less, and more preferably 90 mm or less. The workpiece 2 is placed at a predetermined distance from the concave surface (top surface) of the lens L. The lens L is placed on a holder 52 on a liftable holding table 51 housed in a lower chamber 50. The end 2a of the workpiece 2 is sandwiched between the upper chamber 60 and the lower chamber 50.

[0042] 4B shows a state in which the space in which the workpiece 2 is placed is depressurized and the workpiece 2 is heated. Specifically, the upper chamber 60 and the lower chamber 50 are depressurized using a vacuum device (not shown) or the like, and then the workpiece 2 is heated. The shape of the workpiece 2 may be easily deformed by heating. The heating temperature of the workpiece 2 is preferably 50°C or higher and 150°C or lower.

[0043] The space in which the workpiece 2 is placed is decompressed, and when the workpiece 2 becomes easily deformable, as shown in Fig. 4C, the contact member 61 provided in the upper chamber 60 is lowered, and the tip 61a of the contact member 61 is brought into contact with and pressed against the workpiece 2. By pressing, a portion of the workpiece 2 is deformed according to the shape of the tip 61a of the contact member 61, and a protrusion 2b shaped toward the lens L is formed. When contacting the workpiece 2, the contact member 61 may or may not be heated.

[0044] The tip 61a of the contact member 61 preferably has a curved shape (for example, a part of a sphere). In this case, the radius of curvature of the tip 61a of the contact member 61 is, for example, 10 mm to 150 mm. The ratio of the radius of curvature of the tip 61a of the contact member 61 to the radius of curvature of the curved surface (concave surface) of the lens L (radius of curvature of the tip 61a of the contact member 61 / radius of curvature of the curved surface of the lens L) is, for example, 0.25 or more and 1 or less, preferably 0.5 or more and 0.99 or less, and more preferably 0.65 or more.

[0045] FIG. 4D shows the state where bonding of the workpiece 2 has begun. With the contact member 61 in contact with (pressed against) a portion of the workpiece 2, the holding table 51 is raised, and the workpiece 2 (protruding portion 2b) is brought into contact with at least the center of the lens L. After contact, the workpiece 2 can be bonded to the lens L over its entire surface, moving outward (e.g., radially) from the contact point between the lens L and the workpiece 2. For example, after contact, the air pressure in the upper chamber 60 is gradually increased. The air pressure in the upper chamber 60 becomes higher than the air pressure in the lower chamber 50, creating a pressure difference between the two spaces. This pressure difference gradually draws the workpiece 2 downward, and as shown in FIG. 4E, the workpiece 2 can be bonded over its entire surface to the lens L. Note that when bonding the workpiece 2 without using the contact member 61, raising the holding table 51 can bring the periphery of the lens L into contact with the workpiece 2, and the workpiece 2 can be bonded from the periphery toward the center of the lens L. After lamination, unnecessary portions of the workpiece 2 (for example, portions that do not overlap with the lens L in a plan view) are removed, and an optical film piece 1 as shown in FIG. 3 can be obtained.

[0046] The retardation member (workpiece) may be stretched during integration with the curved surface portion. The degree of stretching may vary depending on the shape of the curved surface portion, etc. The retardation value of the retardation member may change due to stretching. Furthermore, the degree of change in the retardation value may vary depending on the degree of stretching. As a result, the retardation value (e.g., in-plane retardation Re) may vary within the plane (first principal surface 1a) of the resulting optical film piece 1. Meanwhile, for example, as shown in Figures 4A to 4E, a contact member may be brought into contact with the retardation member (workpiece) in advance to deform the retardation member and form a protrusion toward the curved surface portion, and the retardation member may be integrated with the curved surface portion starting from this protrusion, thereby successfully manufacturing an optical film piece having the first region.

[0047] For example, it is preferable that the change in the retardation value of the retarder before and after integration into an optical component is small. A small change makes it possible to easily obtain an optical film piece having desired optical properties (e.g., retardation value). Specifically, the change in in-plane retardation Re(550) before and after integration into an optical component is preferably 10 nm or less, more preferably 9 nm or less, and even more preferably 8 nm or less. In one embodiment, the change in in-plane retardation Re(550) at the central portion of the obtained optical film piece 1 facing the central portion of the lens L is preferably 10 nm or less, more preferably 9 nm or less, and even more preferably 8 nm or less. The line connecting the focal point of the lens L and a point facing the central portion of the concave surface of the lens L that satisfies the above-mentioned change preferably forms an angle of 5° or more with the line connecting the center of the lens L and the focal point of the lens L, more preferably 10° or more, and even more preferably 15° or more.

[0048] The amount of change in the retardation value can be, for example, the difference between the average value of the retardation value in a predetermined region and the average value of the retardation value of the entire retardation member before integration.

[0049] The optical film piece according to the embodiment of the present invention may include any other suitable optical element in addition to the retardation element. The optical film piece may be used in any suitable display. For example, the optical film piece may be suitably used in VR goggles.

[0050] [Display System] Figure 5 is a schematic diagram showing the general configuration of an example of a display system for VR goggles, and schematically illustrates the arrangement and shape of each component of the display system. The display system 10 includes a display element 12, a reflective polarizing element 14, a first lens unit 16, a half mirror 18, a first λ / 4 element 20, a second λ / 4 element 22, and a second lens unit 24. The reflective polarizing element 14 is disposed in front of the display surface 12a of the display element 12 and can reflect light emitted from the display element 12. The first lens unit 16 is disposed on the optical path between the display element 12 and the reflective polarizing element 14, and the half mirror 18 is disposed between the display element 12 and the first lens unit 16. The first λ / 4 element 20 is disposed on the optical path between the display element 12 and the half mirror 18, and the second λ / 4 element 22 is disposed on the optical path between the half mirror 18 and the reflective polarizing element 14.

[0051] The half mirror or the components arranged forward from the first lens unit (in the illustrated example, the half mirror 18, first lens unit 16, second λ / 4 member 22, reflective polarizing member 14, and second lens unit 24) may be collectively referred to as the lens unit (lens unit 4).

[0052] The display element 12 is, for example, a liquid crystal display or an organic EL display, and has a display surface 12 a for displaying an image. The light emitted from the display surface 12 a passes through, for example, a polarizing member that may be included in the display element 12, and is converted into first linearly polarized light.

[0053] The first λ / 4 member 20 can convert the first linearly polarized light incident on the first λ / 4 member 20 into the first circularly polarized light. The first λ / 4 member 20 may be provided integrally with the display element 12.

[0054] The half mirror 18 transmits the light emitted from the display element 12 and reflects the light reflected by the reflective polarizing member 14 back toward the reflective polarizing member 14. The half mirror 18 is provided integrally with the first lens portion 16.

[0055] The second λ / 4 member 22 can transmit the light reflected by the reflective polarizing member 14 and the half mirror 18 through the reflective polarizing member 14. The second λ / 4 member 22 may be provided integrally with the first lens portion 16.

[0056] The first circularly polarized light output from the first λ / 4 member 20 passes through the half mirror 18 and the first lens portion 16, and is converted into the second linearly polarized light by the second λ / 4 member 22. The second linearly polarized light output from the second λ / 4 member 22 is reflected toward the half mirror 18 without passing through the reflective polarizing member 14. At this time, the polarization direction of the second linearly polarized light incident on the reflective polarizing member 14 is the same as the reflection axis of the reflective polarizing member 14. Therefore, the second linearly polarized light incident on the reflective polarizing member 14 is reflected by the reflective polarizing member 14.

[0057] The second linearly polarized light reflected by the reflective polarizing element 14 is converted into second circularly polarized light by the second λ / 4 element 22, and the second circularly polarized light emitted from the second λ / 4 element 22 passes through the first lens unit 16 and is reflected by the half mirror 18. The second circularly polarized light reflected by the half mirror 18 passes through the first lens unit 16 and is converted into third linearly polarized light by the second λ / 4 element 22. The third linearly polarized light is transmitted through the reflective polarizing element 14. At this time, the polarization direction of the third linearly polarized light incident on the reflective polarizing element 14 is the same direction as the transmission axis of the reflective polarizing element 14. Therefore, the third linearly polarized light incident on the reflective polarizing element 14 is transmitted through the reflective polarizing element 14.

[0058] The light transmitted through the reflective polarizing member 14 passes through the second lens portion 24 (the absorptive polarizing member 28 and the second lens portion 24 described below) and enters the eye 26 of the user.

[0059] The absorption axis of the polarizing member included in the display element 12 and the reflection axis of the reflective polarizing member 14 may be disposed approximately parallel to each other or approximately perpendicular to each other. The angle between the absorption axis of the polarizing member included in the display element 12 and the slow axis of the first λ / 4 member 20 is, for example, 40° to 50°, or may be 42° to 48°, or may be approximately 45°. The angle between the absorption axis of the polarizing member included in the display element 12 and the slow axis of the second λ / 4 member 22 is, for example, 40° to 50°, or may be 42° to 48°, or may be approximately 45°.

[0060] The optical characteristics (in-plane retardation Re(550) and Re(450) / Re(550)) of the first λ / 4 member 20 and the second λ / 4 member 22 are as described above.

[0061] The display system 10 may include an absorptive polarizing element 28. The absorptive polarizing element 28 may be disposed in front of the reflective polarizing element 14. The reflection axis of the reflective polarizing element 14 and the absorption axis of the absorptive polarizing element 28 may be disposed approximately parallel to each other, and the transmission axis of the reflective polarizing element 14 and the transmission axis of the absorptive polarizing element 28 may be disposed approximately parallel to each other. The reflective polarizing element 14 and the absorptive polarizing element 28 may be integrated together. The absorptive polarizing element 28 may be used in the above-described display system, for example, from the viewpoint of improving visibility.

[0062] In the display system 10, a space may be formed between the first lens portion 16 and the second lens portion 24. In this case, it is preferable that the member disposed between the first lens portion 16 and the second lens portion 24 is integrally formed with either the first lens portion 16 or the second lens portion 24. For example, the member disposed between the first lens portion 16 and the second lens portion 24 is integrated with either the first lens portion 16 or the second lens portion 24 via an adhesive layer. This configuration may provide, for example, excellent ease of handling of each member. The adhesive layer may be formed of an adhesive 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, 0.01 μm to 60 μm.

[0063] The optical film piece according to the embodiment of the present invention may include, for example, components provided in the display system. For example, the optical film piece according to the embodiment of the present invention may include a second λ / 4 component 22. Specifically, the retardation component 23 of the optical film piece 1 in the illustrated example may correspond to the second λ / 4 component 22. Furthermore, the optical film piece 1 may include a reflective polarizing component 14 in addition to the retardation component 23 (second λ / 4 component 22). Furthermore, the optical film piece 1 may include an absorptive polarizing component 28. The optical film piece may include other components, such as an adhesive layer, for integrating adjacent components.

[0064] The optical film piece 1 can be integrated with, for example, the first lens portion 16 or the second lens portion 24. Typically, it can be attached to the adherend, the first lens portion 16 or the second lens portion 24, via an adhesive layer. For example, the first lens portion 16 shown in FIG. 5 has a curved surface portion and can correspond to the optical component (lens L). By positioning the first region 71 of the optical film piece 1 in the center of the lens L (first lens portion 16), for example, it is possible to obtain a display with excellent visibility.

[0065] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The thickness values ​​are measured by the following measurement method. <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").

[0066] Example 1 (Preparation of λ / 4 Member) 55 parts of a compound represented by formula (I), 25 parts of a compound represented by formula (II), and 20 parts of a compound represented by formula (III) were added to 400 parts of cyclopentanone (CPN), heated to 60°C, and stirred to dissolve. After dissolution was confirmed, the mixture was returned to room temperature, and 3 parts of Irgacure 907 (manufactured by BASF Japan Ltd.), 0.2 parts of Megafac F-554 (manufactured by DIC Corporation), and 0.1 parts of p-methoxyphenol (MEHQ) were added, followed by further stirring to obtain a solution. The solution was transparent and homogeneous. The resulting solution was filtered through a 0.20 μm membrane filter to obtain a polymerizable composition. The polyimide solution for alignment film was applied to a 0.7 mm thick glass substrate using a spin coating method, dried at 100°C for 10 minutes, and then baked at 200°C for 60 minutes to obtain a coating film. The resulting coating film was subjected to a rubbing treatment using a commercially available rubbing device to form an alignment film. The polymerizable composition obtained above was applied to an alignment film (substrate) by spin coating and dried for 2 minutes at 100° C. After the obtained coating film was cooled to room temperature, it was irradiated with 30 mW / cm using a high-pressure mercury lamp. ２ The liquid crystal alignment solidified layer was irradiated with ultraviolet light at an intensity of 100 nm for 30 seconds to obtain a 3 μm thick liquid crystal alignment solidified layer. The obtained liquid crystal alignment solidified layer had an in-plane retardation Re(550) of 141 nm, an Re(450) / Re(550) of 0.851, and exhibited reverse dispersion wavelength characteristics. The in-plane retardation value was measured by cutting the obtained liquid crystal alignment solidified layer into a size of 100 mm x 100 mm and performing area analysis on the entire cut-out measurement sample using a two-dimensional birefringence evaluation device (manufactured by Photonic Lattice, product name "WPA-200"), and the average value (unit: nm) was obtained.

[0067]

[0068] (Production of Workpiece) An acrylic adhesive composition was applied to the λ / 4 member side and dried to form an adhesive layer with a thickness of 40 μm, thereby obtaining a workpiece.

[0069] (Preparation of Optical Film Piece) As shown in Figures 4A to 4E, the obtained workpiece was bonded to the curved surface (concave surface) of a lens having a diameter (major axis) of 50 mm and a curvature radius of 40 mm. For bonding, a contact member with a curved tip (curvature radius of 12.5 mm) was used. After bonding, the portion that did not overlap with the lens in a planar view was removed to obtain an optical film piece.

[0070] Example 2 An optical film piece was obtained in the same manner as in Example 1, except that a contact member having a curved tip with a radius of curvature of 25 mm was used for lamination.

[0071] Example 3 An optical film piece was obtained in the same manner as in Example 1, except that a contact member having a curved tip with a curvature radius of 35 mm was used for lamination.

[0072] Example 4 An optical film piece was obtained in the same manner as in Example 1, except that a contact member having a curved tip with a curvature radius of 38 mm was used for lamination.

[0073] Comparative Example 1 An optical film piece was obtained in the same manner as in Example 1, except that no contact member was used during lamination.

[0074] The retardation distribution of the optical film pieces of each of the Examples and Comparative Examples was evaluated by the following method. The evaluation results are summarized in Table 1.

[0075] <Evaluation> The distribution of in-plane retardation of the optical film pieces obtained in the examples and comparative examples was evaluated using a two-dimensional birefringence evaluation device (manufactured by Photonic Lattice, product name "WPA-200"). Specifically, the in-plane retardation Re(550) of the optical film piece while it was still bonded to the lens was analyzed in each of areas A to D at a measurement wavelength of 550 nm, and the average value (unit: nm) and standard deviation σ for each area were determined. In Table 1, "Difference" indicates the difference between the average value and the value before bonding. Here, as shown in FIG. 6A , “Area A” refers to an area within a circle of a radius of 6.53 mm centered at a point facing the point through which the optical axis of the lens passes in a planar view; “Area B” refers to an area within a circle of a radius of 13.06 mm centered at a point facing the point through which the optical axis of the lens passes in a planar view; “Area C” refers to an area within a circle of a radius of 18.69 mm centered at a point facing the point through which the optical axis of the lens passes in a planar view; and “Area D” refers to an area within a circle of a radius of 24.06 mm centered at a point facing the point through which the optical axis of the lens passes in a planar view. The focal length of the lens used was 80 mm, and as shown in Figure 6B, the line connecting a point located within area A to the focal point of the lens forms an angle of 5° or less with the line connecting the center of the lens to the focal point of the lens, the line connecting a point located within area B to the focal point of the lens forms an angle of 10° or less with the line connecting the center of the lens to the focal point of the lens, the line connecting a point located within area C to the focal point of the lens forms an angle of 15° or less with the line connecting the center of the lens to the focal point of the lens, and the line connecting a point located within area D to the focal point forms an angle of 18° or less with the line connecting the center of the lens to the focal point of the lens.

[0076]

[0077] The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the configurations shown in the above-described embodiment can be replaced with configurations that are substantially the same as those shown in the above-described embodiment, that have the same effects, or that can achieve the same purpose.

[0078] Optical film pieces according to embodiments of the present invention can be used in displays such as VR goggles, for example.

[0079] REFERENCE SIGNS LIST 1 Optical film piece 2 Work 1a First main surface 1b Second main surface 1c First portion 1d Second portion 1e Third portion 10 Display system 12 Display element 14 Reflective polarizing member 16 First lens portion 18 Half mirror 20 First λ / 4 member 22 Second λ / 4 member 23 Phase difference member 24 Second lens portion 40 Pressure-sensitive adhesive layer 61 Contact member 71 First region 72 Second region L Lens

Claims

1. An optical film piece including a retardation member and having first and second principal surfaces opposed to each other, wherein the first principal surface has a first region from a first portion located at the center to a second portion located outside the first portion, in which the standard deviation of in-plane retardation Re(550) at a wavelength of 550 nm is 5 nm or less, and the first principal surface has a second region from the first portion to a third portion located outside the second portion, in which the standard deviation of in-plane retardation Re(550) at a wavelength of 550 nm exceeds 5 nm, and the average value of in-plane retardation Re(550) at a wavelength of 550 nm in the first region is 135 nm or more.

2. The optical film piece according to claim 1, wherein the absolute value of the difference between the average in-plane retardation Re(550) at a wavelength of 550 nm in the first region and the average in-plane retardation Re(550) at a wavelength of 550 nm in the second region is 5 nm or less.

3. The optical film piece according to claim 1, wherein the shape in a planar view is substantially circular, and the third portion is located in a region inwardly in a radial direction from an end of the first main surface, the region being 40% or less of a radius of the first main surface, in a planar view.

4. A method for manufacturing an optical film piece as described in claim 1, comprising integrating a member including a phase difference member with a part having a curved surface portion, said integration including: bringing a tip of a contact member into contact with the member, which has been made in a deformable state, to deform the member and form a protrusion pointing toward the curved surface portion; and bringing the protrusion of the member into contact with the curved surface portion.

5. The manufacturing method according to claim 4, wherein the curved portion of the part has a concave surface.

6. The manufacturing method according to claim 4, wherein the tip of the contact member has a curved shape.

7. The manufacturing method according to claim 5, wherein the tip of the contact member has a curved shape, and the ratio of the radius of curvature of the curved shape of the tip of the contact member to the radius of curvature of the curved portion of the part is 0.65 or more.

8. The manufacturing method according to claim 4, wherein a region in which the change in in-plane retardation Re(550) of the retardation member at a wavelength of 550 nm due to the integration is 10 nm or less is formed in a central portion of the optical film piece.

9. The method of claim 8, wherein the part is a lens.

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